Skocz do pozycji: 1.

Tytuł:

Understanding electron-positron momentum densities in solids : effect of the positron distribution

Autorzy:

Rubaszek, A.

Powiązania:

https://bibliotekanauki.pl/articles/147180.pdf

Data publikacji:

2015

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron annihilation
electronic band structure
positron states

Opis:

The influence of the positron distribution on the electron-positron (e-p) momentum densities (MDs) is studied in terms of the l (l = s, p, d, f) character of the initial electronic state. The effect of the positron is discussed for momenta in the extended and reduced zone scheme on the example of Al (simple metal), Cu (metal with almost filled d shell), and Cr (transition metal). Present result indicates a weak sensitivity of the e-p MD inside the central Fermi surface to the positron charge density for the delocalized s and p electrons. In the case of d states, the effect of the positron on the relevant contribution to the e-p MD directly reflects the degree of localization of d electrons in the electron density of states.

Źródło:

Nukleonika; 2015, 60, No. 4, part 1; 759-763
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 2.

Tytuł:

Some remarks on positron/positronium diffusion models

Autorzy:

Świątkowski, W.

Powiązania:

https://bibliotekanauki.pl/articles/148428.pdf

Data publikacji:

2003

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

diffusion
diffusion length
positron
positronium

Opis:

Positrons thermalized near the sample boundary (as well as Ps atoms formed in the sample) can reach the boundary as a result of diffusive movement. Observations of such effects as positron reemission or positron surface trapping as well as positronium emission allow one to calculate respective diffusion lengths. From the presented analysis it follows that some models used in such calculations give quite wrong results.

Źródło:

Nukleonika; 2003, 48, 3; 141-144
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 3.

Tytuł:

Slow positron beam at the JINR, Dubna

Autorzy:

Horodek, P.
Kobets, A. G.
Meshkov, I. N.
Sidorin, A. A.
Orlov, O. S.

Powiązania:

https://bibliotekanauki.pl/articles/147134.pdf

Data publikacji:

2015

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron beam
positron injector

Opis:

The Low Energy Positron Toroidal Accumulator (LEPTA) at the Joint Institute for Nuclear Research (JINR) proposed for generation of positronium in flight has been adopted for positron annihilation spectroscopy (PAS). The positron injector generates continuous slow positron beam with positron energy range between 50 eV and 35 keV. The radioactive 22Na isotope is used. In distinction to popular tungsten foil, here the solid neon is used as moderator. It allows to obtain the beam intensity of about 105 e+/s width energy spectrum characterized by full width at half maximum (FWHM) of 3.4 eV and a tail to lower energies of about 30 eV. The paper covers the characteristic of variable energy positron beam at the LEPTA facility: parameters, the rule of moderation, scheme of injector, and transportation of positrons into the sample chamber. Recent status of the project and its development in the field of PAS is discussed. As an example, the measurement of the positron diffusion length in pure iron is demonstrated.

Źródło:

Nukleonika; 2015, 60, No. 4, part 1; 725-728
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 4.

Tytuł:

Positron annihilation in liquid crystals

Autorzy:

Dryzek, E.
Juszyńska-Gałązka, E.

Powiązania:

https://bibliotekanauki.pl/articles/148118.pdf

Data publikacji:

2015

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

liquid crystals
positron annihilation
phase transitions

Opis:

Positron annihilation studies of liquid crystals are reviewed with particular reference to thermotropic liquid crystals with rod-like molecules. The studies of compounds exhibiting smectic A or smectic E phases indicate that local arrangement of dipole molecules play an important role because high electron density at the end group of molecules can influence substantially formation and annihilation of positronium. The obtained ortho-positronium lifetimes in these phases can be explained by antiparallel pairing of molecules in case of the smectic A phase or a structure with a nanosegregation of alkyl chains and others parts of molecules into sublayers and liquid-like state of alkyl chains in case of the smectic E phase.

Źródło:

Nukleonika; 2015, 60, No. 4, part 1; 703-708
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 5.

Tytuł:

Gamma Induced Positron Annihilation: History, Current, and Future Developments

Autorzy:

Selim, F.

Powiązania:

https://bibliotekanauki.pl/articles/1030020.pdf

Data publikacji:

2017-11

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

gamma induced positron spectroscopy
positron transient measurements
thermal neutron capture
proton capture
electron accelerator
Van de Graaff accelerator

Opis:

Positron annihilation spectroscopy is often performed using radioactive sources for bulk measurements or positron beams for depth resolved measurements. Both have many advantages and great capabilities for a variety of applications. In the recent history, we have shown that positron annihilation spectroscopy can be carried out directly using high energy photons without the need for positron source or positron beam. This approach brings unique capabilities for some specific applications and promotes the use of positron annihilation spectroscopy in new areas of materials science and probably in industrial applications. Some of the important applications include developing new nondestructive highly penetrating sensitive probe for structural and engineering materials. It can also greatly advance positron applications in bulk semiconductors, electronic and photonic materials as well as in polymers, ceramics, and liquids. The recently developed γ-induced positron spectroscopy in HZDR in Dresden provides an example of an excellent facility for many of these applications. When incorporated with pulsed accelerators, γ-induced positron annihilation spectroscopy may trigger novel studies of transient states in matter and explore several solid-state processes that take place on short time scale. In this article I will review the history and development of the technique and its incorporation in a wide range of accelerators including table top electron accelerators, pulsed electron accelerators, and Van de Graaff accelerators. Then I will introduce a design for a new γ-induced positron annihilation spectroscopy facility based on using small nuclear research reactors or neutron generators. The paper presents all the possible approaches for γ-induced positron annihilation spectroscopy and discusses its potential and limitations to guide the efforts in further development of the technique and illustrate the unique aspects that the technique can bring to positron science and applications.

Źródło:

Acta Physica Polonica A; 2017, 132, 5; 1450-1455
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 6.

Tytuł:

Principles of positron porosimetry

Autorzy:

Zaleski, R.

Powiązania:

https://bibliotekanauki.pl/articles/146520.pdf

Data publikacji:

2015

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

porous materials
positron annihilation lifetime spectroscopy (PALS)
positronium
extended Tao-Eldrup model

Opis:

The paper deals with positron porosimetry (PP), which is based on positron annihilation lifetime spectroscopy (PALS). The numerical analysis of positron lifetime spectra for PP is more demanding than in most of other applications of PALS. The resulting intensity distributions of ortho-positronium (o-Ps) lifetimes are interpreted in terms of the extended Tao-Eldrup (ETE) model, which provides the dependence between the o-Ps lifetime and pore size. Additionally, the relation between the intensity of an o-Ps component and the pore volume allows obtaining pore size distribution (PSD). The value of the empirical parameter Δ, which is dependent on material, can be estimated from the temperature dependence of an o-Ps lifetime. The most unique feature of PP among other techniques that allow determination of PSDs is its ability to perform measurements in almost any conditions. This makes this method suitable for various in situ studies. In this review article, both the capabilities and the limitations of PP are discussed. The methods to overcome some of the limitations are presented.

Źródło:

Nukleonika; 2015, 60, No. 4, part 1; 795-800
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 7.

Tytuł:

Momentum distributions in positron annihilation with tightly bound electrons in Al

Autorzy:

Boroński, E.

Powiązania:

https://bibliotekanauki.pl/articles/148016.pdf

Data publikacji:

2013

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron annihilation
electronic structure

Opis:

An approach based on Carbotte, Salvadori and Chiba two-body schemes for calculation of electron-positron (e-p) momentum densities ro(p) for core electrons in solids is developed. The approach allows to avoid such common approximations as the local density approximation (LDA) etc. in determination of ro(p) of deeper atomic shells and reduces the contribution to ro(p) for higher momenta. Thus, the final calculations of the Doppler spectra of annihilation radiation yield lower values for greater momenta than those obtained within the LDA scheme. The exemplary calculations for Al are presented.

Źródło:

Nukleonika; 2013, 58, 1; 211-214
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 8.

Tytuł:

Positron annihilation studies of mesoporous iron modified MCM-41 silica

Autorzy:

Wiertel, M.
Surowiec, Z.
Budzyński, M.
Gac, W.

Powiązania:

https://bibliotekanauki.pl/articles/147950.pdf

Data publikacji:

2013

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

iron
MCM-41 silica mesoporous materials
N2 sorption
positron annihilation
positron lifetime spectra

Opis:

MCM-41 silica materials modified by iron incorporation in the stage of its synthesis were investigated. The aim of the studies was determination of the nature of iron species and the influence of its content on the structural changes of materials and following the changes of their properties. For this purpose, the N2 sorption/desorption method and positron annihilation lifetime spectroscopy (PALS) were used. Disappearance of the longest-lived ortho-positronium (o-Ps) component (tau5) present in the PALS spectra of the initial MCM-41 material in the spectra of Fe-modified MCM-41 measured in vacuum is a result of a strong chemical o-Ps quenching and/or the Ps inhibition mechanism. Filling of pores by air or N2 at ambient pressure causes reappearance of the (tau5) component with lifetime shortened in comparison to that observed in vacuum for pure MCM-41 to the extent which can be explained by usual paramagnetic quenching in air. In contrary to the tendency observed for (tau5) lifetime which is practically independent of Fe content, the relevant intensity I5 monotonically decreases. This fact suggests that only inhibition of Ps formation occurs for the samples in air. Observed anti-quenching effect of air seems to be a result of competition of two processes : neutralization of surface active centres acting as inhibitors and considerably weaker paramagnetic quenching by O2 molecules.

Źródło:

Nukleonika; 2013, 58, 1; 245-250
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 9.

Tytuł:

Effect of electronelectron correlations on positron-electron momentum density distributions

Autorzy:

Boroński, E.

Powiązania:

https://bibliotekanauki.pl/articles/146328.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron annihilation
electronic structure
many-body physics

Opis:

The calculations of the influence of the self-energy effects on the electron-positron (e-p) enhancement factors and the e-p momentum distributions are presented. The approach bases on the novel formulation of the Bethe- -Goldstone (B-G) equation for the positron in an electron gas where the scattering of the electrons into the states below the Fermi surface due to the self-energy effects is allowed. This equation has been solved and the corresponding e-p enhancement factors and momentum distributions have been found. The agreement between the absolute values of the theoretical calculations and experimental data has improved noticeably.

Źródło:

Nukleonika; 2010, 55, 1; 3-8
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 10.

Tytuł:

Investigation of corrosion defects in titanium by positron annihilation

Autorzy:

Pietrzak, R.
Szatanik, R.

Powiązania:

https://bibliotekanauki.pl/articles/147338.pdf

Data publikacji:

2015

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron annihilation spectroscopy
corrosion defects

Opis:

The positron annihilation method was used to study the formation of defects in titanium samples during their corrosion in the vapor of a 3% HCl solution. In particular, the distribution of defects depending on the distance from the corroding surface and the impact of an external magnetic fi eld on the concentration of vacancies forming during the corrosion of titanium layers close to the surface were determined.

Źródło:

Nukleonika; 2015, 60, No. 4, part 1; 755-758
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 11.

Tytuł:

Positron lifetime calculations for some elements on the base of the GGAPHNC approximation

Autorzy:

Boroński, E.

Powiązania:

https://bibliotekanauki.pl/articles/146330.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron annihilation
electronic structure

Opis:

In studies of several interesting materials by positron annihilation technique the theoretical values of positron lifetimes in bulk and defected elements are useful. These lifetimes are often calculated within the GGA approximation. In this approximation the results of Arponen and Pajanne calculations for the positron in an electron gas are used. It is known, however, that when using the LDA approximation for the calculations of positron lifetime in real metals, Arponen and Pajanne values yield worse agreement with experimental data than the results obtained on the basis of PHNC formalism. Therefore, in this paper the appropriate PHNC formulas are incorporated into the GGA approximation and the calculations have been performed for some metals: bulk as well as containing monovacancies. The comparison of the lifetimes found in this way to the ones based on the previous method is promising for the applicability of the new algorithm.

Źródło:

Nukleonika; 2010, 55, 1; 9-12
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 12.

Tytuł:

Positron study of the structure of nonadecane-tricosane mixed solid

Autorzy:

Zgardzińska, B.
Goworek, T.

Powiązania:

https://bibliotekanauki.pl/articles/146297.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron annihilation
n-alkanes
binary mixture

Opis:

Positron annihilation lifetime and intensity were measured as a function of temperature for a binary mixture of two normal alkanes. The rotator phase is preceded by the range of about 7 K, in which one observes instability of spectrum parameters. In that range the mixed solid, being initially introduced into rotator phase, transforms to a rigid one in the time scale of several hours.

Źródło:

Nukleonika; 2010, 55, 1; 47-49
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 13.

Tytuł:

Influence of low temperature on the free volume in polyethylene by positron annihilation

Autorzy:

Osoba, W.

Powiązania:

https://bibliotekanauki.pl/articles/146305.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron annihilation
polymers
free volume

Opis:

Positron lifetime measurements were performed as a function of temperature in thermo-shrunken, modified polyethylene. Mean volume of free volume cavities in the investigated polymer was estimated from the results of the measurements. This mean volume turned out to be a smooth function of temperature (from room temperature to 8.5 K). The effect of trapping of free electrons, produced during positron irradiation, was observed at lowered temperature.

Źródło:

Nukleonika; 2010, 55, 1; 69-72
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 14.

Tytuł:

Positron annihilation in precious and common opals

Autorzy:

Chojcan, J.
Sachanbiński, M.
Idczak, R.
Konieczny, R.

Powiązania:

https://bibliotekanauki.pl/articles/148010.pdf

Data publikacji:

2013

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

opal-A
porosity
positron annihilation

Opis:

The nano-porosity structure of several non-crystalline opal samples of different origin was investigated with positronium atoms. The obtained data show that the structure depends on both the kind of opal (precious, common or hyalite) as well as the place of its creation (sedimentary or volcanic rocks). The sizes of the pores "seen" by positronium atoms are relatively small, not greater than about 1 nm for all studied samples which may suggest that the pores are located inside the silica matter from which the samples are made. Moreover, the pores detected in the "sedimentary" precious opals are smaller and have less diverse sizes than those found in 'sedimentary" common opals and "volcanic' precious opals.

Źródło:

Nukleonika; 2013, 58, 1; 225-228
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 15.

Tytuł:

Some Remarks on Diffusion Model of Positron Reemission and/or Positron Surface Trapping

Autorzy:

Dębowska, M.
Świątkowski, W.

Powiązania:

https://bibliotekanauki.pl/articles/2007963.pdf

Data publikacji:

1999-04

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

68.35.Wm

Opis:

The problem of a role of boundary conditions in a diffusion model of positron reemission is discussed. It was shown that a sink rate cannot change from zero up to infinity but has an upper limit equal to a half of a mean positron velocity. Some additional relations connected with this result are presented as well.

Źródło:

Acta Physica Polonica A; 1999, 95, 4; 515-520
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 16.

Tytuł:

Influence of neoplastic therapy on the investigated blood using positron annihilation lifetime spectroscopy

Autorzy:

Pietrzak, R.
Borbulak, S.
Szatanik, R.

Powiązania:

https://bibliotekanauki.pl/articles/147997.pdf

Data publikacji:

2013

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

blood
positron annihilation

Opis:

The influence of neoplastic radiotherapy and chemotherapy was investigated using annihilation lifetime spectroscopy in blood types 0 Rh+ -AB Rh+. Changes in the parameters of the longest lived component of the spectrum were analyzed depending on the time between the moment of taking the blood sample from a patient and that of taking measurements, and also the time passing from the cessation of radio- and chemotherapy.

Źródło:

Nukleonika; 2013, 58, 1; 199-202
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 17.

Tytuł:

Positron Irradiation Effects on Positronium Formation in Polycarbonate Sduring a Positron-Annihilation Experiment

Autorzy:

Suzuki, T.
Kondo, K.
Hamada, E.
Ito, Y.

Powiązania:

https://bibliotekanauki.pl/articles/2025767.pdf

Data publikacji:

2001

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

The positron-irradiation effect on polycarbonate during a positron-annihilation lifetime spectroscopy experiment was investigated using different intensities of $\text{}^{22}$Na positron sources andγ-irradiated samples. The decrease in I$\text{}_{3}$ was larger for a larger intensity of positron sources. In the case of a weak source (≈ 140 kBq), I$\text{}_{3}$ did not change with the elapsed time for non-irradiated samples. However, for 1 MGy irradiated samples, I$\text{}_{3}$ measured with the weak source increased with the elapsed time. This can be attributed to a decrease in the radicals induced in the irradiated samples by γ-irradiation. In order to explain the change in I$\text{}_{3}$ measured at room and liquid-nitrogen temperatures, several effects, such as radicals, cross-linking, structure change, and charging, need to be considered. Also, it is difficult to explain the change in I$\text{}_{3}$ using only one of these effects.

Źródło:

Acta Physica Polonica A; 2001, 99, 3-4; 515-521
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 18.

Tytuł:

Effect of magnetic field on the corrosion of iron as studied by positron annihilation

Autorzy:

Pietrzak, R.
Szatanik, R.

Powiązania:

https://bibliotekanauki.pl/articles/146285.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

corrosion
magnetic field
positron annihilation

Opis:

Lifetime spectra of positron annihilation in iron corroded in a water solution of HCl and in vapour above its surface have been investigated with emphasis on the effect of corrosion time and environment (solution or vapour) as well as of the presence and orientation of the magnetic field on the measured positron annihilation parameters. All the registered positron lifetime spectra consist of two components. For corroded samples, the intensities of the two components as well as the corresponding values of the mean positron lifetime, differ from those for uncorroded material. The corrosion-induced changes in the positron annihilation parameters depend on the corrosion environment (solution or vapour) and on the presence and direction of external magnetic field.

Źródło:

Nukleonika; 2010, 55, 1; 31-34
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 19.

Tytuł:

Positron annihilation studies of high-manganese steel deformed by rolling

Autorzy:

Dryzek, E.
Sarnek, M.
Wróbel, M.

Powiązania:

https://bibliotekanauki.pl/articles/146593.pdf

Data publikacji:

2015

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

plastic deformation
positron annihilation
high-manganese steel

Opis:

Positron annihilation spectroscopy (PAS) has been used to study the annealing behavior of cold rolled Fe – 21 wt% Mn steel with 0.05 wt% C. After the initial annealing of defects shown by Doppler broadening of the annihilation line, a slight increase in the annihilation line shape parameter, i.e., the so-called S parameter and then its decrease in the temperature range between 225◦C and 450◦C indicates generation of new defects and their subsequent annealing. This temperature range coincides with X-ray diffraction measurements, which indicate reversion of deformation-induced ε-martensite. However, for annealing in this temperature range with slow cooling of the sample, the formation of ferrite already starts. The results are compared with our previous results for deformed austenitic stainless steel 1.4301 (EN) where only reversion of deformation-induced α'-martensite was detected.

Źródło:

Nukleonika; 2015, 60, No. 4, part 1; 709-712
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 20.

Tytuł:

Monte Carlo calculations of positron implantation profiles and backscattering probabilities in gold

Autorzy:

Aydin, A.

Powiązania:

https://bibliotekanauki.pl/articles/147555.pdf

Data publikacji:

2001

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

backscattering
computer simulation
incoming angle
mean penetration depth
positron

Opis:

The transport of charged particles through matter is worth considering for various applications. In this work, backscattering probabilities and mean penetration depths were calculated from the implantation profiles for positrons of energies 1-75 keV entering normally at various angles into a semi-infinite gold target. The theoretical results of backscattering probability and mean penetration depth are compared with other published [1, 3, 4, 10, 11, 13]. Monte Carlo calculations and experimental results for the semi-infinite gold target. In general, good agreement is observed.

Źródło:

Nukleonika; 2001, 46, 3; 87-90
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 21.

Tytuł:

The POCOBIO Database for Computed Scattering Cross-Sections for Positron Collisions with Biomolecular Systems

Autorzy:

Franz, J.

Powiązania:

https://bibliotekanauki.pl/articles/1030032.pdf

Data publikacji:

2017-11

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

positron-molecule scattering
quantum calculations
molecular gases

Opis:

The design of a database for positron interactions with biomolecular systems is outlined. The database contains only scattering cross-sections, which are derived from theory. The data model is defined in a very flexible way, which facilitates the usage of weakly bound clusters of molecules and molecular systems with many tautomeric forms.

Źródło:

Acta Physica Polonica A; 2017, 132, 5; 1478-1481
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 22.

Tytuł:

Monte Carlo simulation of the positron implantation profiles in the layered samples

Autorzy:

Dryzek, J.
Horodek, P.

Powiązania:

https://bibliotekanauki.pl/articles/146332.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron implantation
implantation profile
GEANT4 tool kit

Opis:

Theoretical studies of the positron implantation profiles in the layered samples are presented. Simulations performed using a GEANT4 tool kit revealed accumulation of positrons in denser layer embedded by less dens environment. This effect is significant for implantation profiles of slow positrons formed in a beam. Nevertheless, it is also present in conventional experiments, where positrons are emitted from radioactive nuclei. In some cases the diffusion process, which follows the implantation and thermalization processes, can smear this effect. However, defects on the interfaces or differences in the positron affinity can sustain it.

Źródło:

Nukleonika; 2010, 55, 1; 13-16
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 23.

Tytuł:

Toward a European Network of Positron Laboratories

Autorzy:

Karwasz, G. P.
Brusa, R. S.
Egger, W.
Ogorodnikova, O. V.

Powiązania:

https://bibliotekanauki.pl/articles/146548.pdf

Data publikacji:

2015

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron beams
material science
thermonuclear reaction

Opis:

Some applications of controlled-energy positron beams in material studies are discussed. In porous organic polysilicates, measurements of 3γ annihilation by Doppler broadening (DB) method at the Trento University allowed to trace pore closing and filling by water vapor. In silicon coimplanted by He+ and H+, DB data combined with positron lifetime measurements at the München pulsed positron beam allowed to explain Si blistering. Presently measured samples of W for applications in thermonuclear reactors, irradiated by W+ and electrons, show vast changes of positron lifetimes, indicating complex dynamics of defects.

Źródło:

Nukleonika; 2015, 60, No. 4, part 1; 733-739
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 24.

Tytuł:

Positron-annihilation and photoluminescence studies of nanostructured ZrO2

Autorzy:

Fidelus, J. D.
Karbowski, A.
Mariazzi, S.
Brusa, R. S.
Karwasz, G.

Powiązania:

https://bibliotekanauki.pl/articles/146313.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron annihilation
zirconia nanopowders
photoluminescence

Opis:

In the present work, photoluminescence and Doppler broadening depth-resolved positron annihilation spectroscopy was performed on pure zirconia nanopowders. Zirconia nanopowders were grown by a hydrothermal microwave-driven process followed by annealing in oxygen atmosphere. Photoluminescence under 274 nm wavelength excitation from a 150 W high-pressure Xe exhibits similar spectra, in the region from 320 to 820 nm, although its intensity depends on the annealing. Positron annihilation Doppler-broadening spectra show low values of the normalized S-parameter, varying little with the depth, from 0.495 on the surface to 0.47-0.49 in bulk. Both high the annealing temperature and oxygen concentrations, lead to low bulk S-values. The ortho-positronium (o-Ps) fraction is about 10-11% for all samples on the surface, whereas it is reduced to 7-8% in the bulk for samples annealed at 700°C and 5-6% for samples annealed at 800°C. Both photoluminescence (PL) and positron studies show the presence of defects in all samples. The o-Ps signal suggests a high porosity of samples, particularly at a depth down to 10 nm.

Źródło:

Nukleonika; 2010, 55, 1; 85-89
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 25.

Tytuł:

Uniqueness of studies on electron densities in the extended momentum space

Autorzy:

Kontrym-Sznajd, G.

Powiązania:

https://bibliotekanauki.pl/articles/148018.pdf

Data publikacji:

2013

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

electron-positron momentum densities
Compton scattering
extended momentum space
positron annihilation

Opis:

This work draws attention to the fact that by measuring electronic structure via angular correlation of positron radiation (ACAR) and Compton scattering experiments one probes electron densities in the extended momentum space, directly related to the electron Bloch wave functions. Presenting some examples of electron densities in the extended and reduced momentum spaces, it is demonstrated what kind of information concerning the electronic structure can be obtained depending on the considered space. It is also shown how the knowledge of the symmetry selection rules allows to separate various Fermi surfaces and establish Fermi momenta.

Źródło:

Nukleonika; 2013, 58, 1; 203-206
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 26.

Tytuł:

Effect of the Positron Distribution on the Electron-Positron Momentum Density Calculated for SiC

Autorzy:

Rubaszek, A.

Powiązania:

https://bibliotekanauki.pl/articles/1812547.pdf

Data publikacji:

2008-05

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj
71.15.Ap
71.20.Mq

Opis:

To interpret positron annihilation data in solids in terms of the electron momentum density, both the electron-positron interaction and positron distribution have to be considered explicitly. In the present work the influence of the shape of the positron wave function on the calculated electron-positron momentum density in elemental SiC is discussed. It is shown that the form of the positron distribution in the Wigner-Seitz cell has a considerable effect on the resulting annihilation characteristics. Calculations were performed for SiC of 3C diamond structure within the linear muffin-tin orbital-atomic spheres approximation method.

Źródło:

Acta Physica Polonica A; 2008, 113, 5; 1501-1506
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 27.

Tytuł:

The influence of hydrogen concentration on positron lifetime and electrical resistivity in vanadium-hydrogen systems

Autorzy:

Pietrzak, R.
Szatanik, R.

Powiązania:

https://bibliotekanauki.pl/articles/146289.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron lifetime
resistivity
V-H system
annihilation parameters

Opis:

Positron lifetime spectra and electrical resistivity of the vanadium-hydrogen systems with hydrogen concentration ranging from 0 to 0.29 at.H/at.V have been investigated. The range of hydrogen concentrations under investigation included the single alfa phase and a mixture of the alfa and beta phases of V-H system. The registered positron lifetime spectra were analysed by decomposition into two components. A distinct change in the annihilation parameters has been found after exceeding the boundary concentration of hydrogen in vanadium corresponding to the phase transition alfa (alfa+ beta). Correlation of changes in the parameters of the positron lifetime spectrum and in the electrical resistivity resulting from the changes in hydrogen concentration, has been revealed.

Źródło:

Nukleonika; 2010, 55, 1; 35-39
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 28.

Tytuł:

Gas filling of SBA - 15 silica micropores probed by positron annihilation lifetime spectroscopy (PALS)

Autorzy:

Gorgol, M.
Zaleski, R.
Kierys, A.

Powiązania:

https://bibliotekanauki.pl/articles/147961.pdf

Data publikacji:

2013

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

SBA-15 porous silica
positron annihilation

Opis:

Positron annihilation lifetime measurements were conducted in situ while two gasses (nitrogen and oxygen, respectively) were introduced into the SBA-15 porous silica sample. Slow changes in lifetime spectra were observed during a long lasting gas interaction with the sample. Introduced gases slowly filled the free volumes, starting from the smallest ones, especially small micropores. In the presence of a gas, the rate of change of ortho-positronium (o-Ps) and unbound positron intensity was larger than the rate of change of lifetime. This suggests the existence of an additional process, which reduces the number of ortho-positronium atoms due to the interaction with the gas. Moreover, the process of filling pores with gas was slower than the process of emptying them while the gas was pumped out.

Źródło:

Nukleonika; 2013, 58, 1; 229-233
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 29.

Tytuł:

Annealing behaviour of plastically deformed stainless steel 1.4307 studied by positron annihilation methods

Autorzy:

Dryzek, E.
Sarnek, M.
Siemek, K.

Powiązania:

https://bibliotekanauki.pl/articles/148014.pdf

Data publikacji:

2013

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

plastic deformation
positron annihilation
stainless steel

Opis:

Isochronal and isothermal annealing of stainless steel 1.4307 samples deformed by compression were investigated using Doppler broadening measurements of the annihilation line. We made an attempt to describe the obtained dependencies in terms of vacancy migration and sinking to the grain boundaries. The model assumed spherical grains with a homogeneous initial distribution of vacancies. The model was capable of following the isochronal annealing data quite accurately. However, the obtained activation energy of vacancy migration equal to 0.44 plus or minus 0.05 eV seemed too low. The isothermal annealing dependency was reproduced less precisely. The reason for this may be the presence of the alfa'-martensite particles in the samples, which can introduce additional defects seen by positrons in the temperature range in which the martensite reversion takes place.

Źródło:

Nukleonika; 2013, 58, 1; 215-219
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 30.

Tytuł:

Spektroskopia anihilacji pozytonow w Zjednoczonym Instytucie Badań Jądrowych w Dubnej
Positron Annihilation Spectroscopy at Joint Institute for Nuclear Research in Dubna

Autorzy:

Horodek, P.

Powiązania:

https://bibliotekanauki.pl/articles/214281.pdf

Data publikacji:

2016

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

spektroskopia anihilacji pozytonów
defekty struktury krystalicznej
wiązka powolnych pozytonów
przykłady zastosowań
positron annihilation spectroscopy
lattice defects
slow positron beam
examples of application

Opis:

W artykule przedstawiono spektroskopię anihilacji pozytonów, jako metodę dedykowaną do badań defektów struktury krystalicznej. Omówiono jej podstawy fizyczne i zaprezentowano technikę dopplerowskiego poszerzenia linii anihilacyjnej. Wskazano zakres stosowalności odnosząc się do najnowszych rozwiązań opartych na tzw. wiązkach powolnych pozytonów. Idea takiej wiązki, działającej w Laboratorium Problemów Jądrowych im. Dzhelepova w Zjednoczonym Instytucie Badań Jądrowych w Dubnej, została szerzej zaprezentowana. Przedstawiono zasadę działania oraz przykłady zastosowań z podstawami analizy otrzymywanych wyników.
Positron annihilation spectroscopy (PAS) as a method dedicated to study structural defects was presented. Physical basics of PAS and the Doppler broadening of annihilation line technique were discussed. Application range based on the newest technology, namely slow positron beams was presented. The idea of the beam, working at Dzhelepov Laboratory of Nuclear Problems at Joint Institute for Nuclear Research, along with the basic analysis of the results were described in details.

Źródło:

Postępy Techniki Jądrowej; 2016, 2; 18-23
0551-6846

Pojawia się w:

Postępy Techniki Jądrowej

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 31.

Tytuł:

Positron annihilation in bioactive glass/poly(glycolide-co-L-lactide) composites

Autorzy:

Dryzek, E.
Cholewa-Kowalska, K.
Pamuła, E.

Powiązania:

https://bibliotekanauki.pl/articles/146311.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

poly(glycolide-co-L-lactide)
bioglass
composites
positron annihilation

Opis:

Composites made of bioactive glasses and resorbable polymers are promising biomaterials for bone tissue regeneration. In this study several types of composites produced from bioactive glasses, differing in chemical composition (A2 and S2) and poly(glycolide-co-lactide) (PGLA) were obtained. The resulting composite materials were investigated with positron lifetime spectroscopy and Doppler broadening of annihilation line. It was found that for the composites made of S2 bioglass the intensity of the third positron lifetime component coming from the positronium (Ps) annihilation decreased with increasing in volume fraction of bioglass particles exhibiting behaviour characteristic of microcomposites. For the composites produced from A2 bioglass, such a dependence was not found. The differences obtained may be connected with chemical composition of the bioglass and/or its crystallinity.

Źródło:

Nukleonika; 2010, 55, 1; 79-83
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 32.

Tytuł:

The detection of reverse accumulation effect in the positron annihilation profile of stack of aluminum and silver foils

Autorzy:

Dryzek, J.
Siemek, K.

Powiązania:

https://bibliotekanauki.pl/articles/148620.pdf

Data publikacji:

2015

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron implantation profile
stack of foils

Opis:

The implantation profile of positrons emitted from 22Na into a stack of aluminum and silver foils is the subject of the presented report. The characteristic dimple in the profile behind the Ag foil was detected. This effect arises from the differences in the linear absorption coefficient of aluminum and silver. The good agreement between the theoretical profile obtained within the multiscattering model and experimental one was achieved. The observed phenomenon can affect the positron annihilation characteristics measured for the inhomogeneous samples.

Źródło:

Nukleonika; 2015, 60, No. 4, part 1; 713-716
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 33.

Tytuł:

80 Years of Positron Annihilation Radiation

Autorzy:

Goworek, T.

Powiązania:

https://bibliotekanauki.pl/articles/1339289.pdf

Data publikacji:

2014-03

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

01.65.+g

Opis:

Short history of the investigations of annihilation radiation is presented, from early experiments with ThC" to the introduction of two main methods: angular correlation of annihilation quanta and positron lifetime spectroscopy.

Źródło:

Acta Physica Polonica A; 2014, 125, 3; 685-687
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 34.

Tytuł:

Positron annihilation and speed of sound in the systems containing beta-cyclodextrin

Autorzy:

Jerie, K.
Baranowski, A.
Burakowski, A.
Gliński, J.

Powiązania:

https://bibliotekanauki.pl/articles/146303.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

sound speed
compressibility
positron annihilation
cyclodextrin
alcohol
inclusion compounds

Opis:

Positron annihilation measurements were performed in aqueous solutions of beta-cyclodextrin, as well as in solid mixtures of this sugar with a long-chained alcohol, n-nonanol. Additionally, acoustic (sound speed, density and compressibility) experiments were done in aqueous beta-cyclodextrin and tert-butanol systems and in a three-component water-beta-cyclodextrin-tert-butanol system. The results show that in aqueous solution cyclodextrin does not form inclusive complexes with alcohol, while solid sugar-alcohol mixtures undergo slow changes in time, most probably caused by exchange of guest between interior and exterior of the host molecule.

Źródło:

Nukleonika; 2010, 55, 1; 65-68
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 35.

Tytuł:

The implantation profile of positrons emitted in beta plus decay of 48V in water

Autorzy:

Dryzek, J.
Horodek, P.
Dryzek, E.

Powiązania:

https://bibliotekanauki.pl/articles/148130.pdf

Data publikacji:

2009

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron implantation range in water
V-48 positron emitter

Opis:

The experimental technique based on scanning of positron implantation profile, hereafter referred to as the DSIP is used for the determination of linear absorption coefficient for positrons emitted from a 48V source into water. This coefficient is equal to 1/(299š62) mi m–1. The determined value is in agreement with the one obtained from the computer simulations using the well known EGS nrc 4.0 and GEANT4 codes. The experimental technique was used for the determination of linear absorption coefficients for 48V positrons in materials of biological origin. The presented data can be useful for PET studies because of similarities of the 18F and 48V positron implantation profiles.

Źródło:

Nukleonika; 2009, 54, 4; 223-226
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 36.

Tytuł:

Umklapp Components of the Positron Momentum Density Depending on Different Models for the Positron Wave Function

Autorzy:

Kontrym-Sznajd, G.
Sormann, H.

Powiązania:

https://bibliotekanauki.pl/articles/1933519.pdf

Data publikacji:

1995-07

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

71.25.Pi
71.60.+z
78.70.Bj

Opis:

In this paper, we present a numerical investigation about the question how sensitively Fourier coefficients of the positron wave function ψ$\text{}_{+}$ react to different (and not too strong) changes of ψ$\text{}_{+}$. In order to obtain general information about this problem, we studied this sensitivity for several bcc and fcc metals and for different models of the positron wave function. Summarizing our results, we can say that this sensitivity is generally small (or at least moderate) for Fourier coefficients belonging to reciprocal lattice vectors G which lie nearest to the centre of the momentum space. For the outer vectors G, the amount of this sensitivity is strongly dependent on the crystal structure of the metal and on the special like of the change of the positron wave function.

Źródło:

Acta Physica Polonica A; 1995, 88, 1; 185-192
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 37.

Tytuł:

Positron Trapping Model in Fine Grained Sample

Autorzy:

Dryzek, J.

Powiązania:

https://bibliotekanauki.pl/articles/2007999.pdf

Data publikacji:

1999-04

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

In the paper we consider the positron trapping model in the sample where the spherical particles were immersed in the medium. The radius of the particles was small enough to take into account the diffusion of positrons. We present the exact solutions of the model for two cases, when transition of the positrons from the particle to the medium was neglected and when it was taken into consideration. The theoretical calculations were applied to description of the positron annihilation in the copper sample where the recrystallization process took place.

Źródło:

Acta Physica Polonica A; 1999, 95, 4; 539-545
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 38.

Tytuł:

Positron annihilation lifetime spectroscopy study of roller burnished magnesium alloy

Autorzy:

Zaleski, R.
Zaleski, K.
Gorgol, M.

Powiązania:

https://bibliotekanauki.pl/articles/146650.pdf

Data publikacji:

2015

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

AZ91HP magnesium alloy
defects
positron lifetime annihilation spectroscopy (PALS)
roller burnishing
Vickers hardness test

Opis:

The effect of roller burnishing on Vickers’ hardness and positron lifetimes in the AZ91HP magnesium alloy was studied. The microhardness increases with an increase in the burnishing force and with a decrease in the feed. The comparison of various methods of analysis of positron annihilation lifetime (PAL) spectra allowed identification of two components, which are related to solute-vacancy complexes and vacancy clusters, respectively. It was found that the increase in microhardness was related to the increase in the concentration of vacancy clusters.

Źródło:

Nukleonika; 2015, 60, No. 4, part 1; 789-794
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 39.

Tytuł:

New Porosimetric Method Based on the 3γ Annihilation Rate. Applications to Materials Science and Medical Imaging

Autorzy:

Jasińska, B.
Zgardzińska, B.

Powiązania:

https://bibliotekanauki.pl/articles/1033228.pdf

Data publikacji:

2017-11

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

positron annihilation
positronium
3γ annihilation
porosity
positron emission tomography
medical imaging

Opis:

A new parameter δ based on 3γ annihilation is proposed. It describes the porosity of the materials containing small intermolecular voids below 1 nm. It can be applied to material investigation to compare changes in the material porosity depending on temperature or pressure as well as to study of ageing or manufacturing processes. Particularly it is dedicated to prepare the new imaging method and can be used during positron emission tomography diagnosis allowing determination the kind or stage of pathogenic alteration.

Źródło:

Acta Physica Polonica A; 2017, 132, 5; 1616-1619
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 40.

Tytuł:

Biodegradable polyester blend and copolyesters studied by positron annihilation and other methods

Autorzy:

Dębowska, M.
Rudzińska-Girulska, J.
Serwadczak, M.
Kiersnowski, A.
Pigłowski, J.

Powiązania:

https://bibliotekanauki.pl/articles/146301.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

mixing of polymers
polyesters
transesterification
positron annihilation
positronium
free volume

Opis:

Two polyesters, i.e. an aromatic one: poly(butylene terephthalate) – PBT and an aliphatic one: poly(ĺ- -caprolactone) – PCL were mixed in melt to obtain a biodegradable product. DSC, 1H NMR, SEM, WAXS, SAXS, BOD and PALS measurements were performed to study the homopolymers as well as their physical blend and copolyesters. The latter were obtained due to the transesterification reaction. Ortho-positronium (o-Ps) annihilation lifetimes were used to create the distributions of free volume. The progressive changes in probability density function of free volume, i.e. increase in large free volume holes contribution to the total free volume, appearing when going from the homopolymers to the blend and then to the copolyesters reflect the influence of: the addition of aliphatic polyester, the weight fraction of it in the composition and transesterification. The higher contribution of larger free volume holes corresponds well with the reduced crystallinity of compositions revealed in X-ray diffraction and the worsening of the regularity of structure of the macromolecules involved in formation of crystals, deduced from the 1H NMR.

Źródło:

Nukleonika; 2010, 55, 1; 57-64
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 41.

Tytuł:

Positron annihilation lifetime spectroscopy study of thermal processing and rehydration of dry leek (Allium porrum L.)

Autorzy:

Zaleski, R.
Wawryszczuk, J.
Sobczak, K.

Powiązania:

https://bibliotekanauki.pl/articles/146309.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron annihilation
lifetime spectroscopy
food processing
rehydration
leek (Allium porrum L.)

Opis:

New application of positron annihilation lifetime spectroscopy (PALS) to development of food processing techniques is tested. Dehydrated leeks were an object of the study. Three experiments were performed consisting of evacuating air and volatile compounds from the sample, applying thermal treatment and rehydrating the sample. Distinct changes in positron lifetime spectra allowed the monitoring of alterations in the sample structure. The most likely origin of the particular components present in the spectra was able to be proposed from these data. Changes of the components were ascribed to the various processes occurring in the samples.

Źródło:

Nukleonika; 2010, 55, 1; 73-78
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 42.

Tytuł:

Positron Implantation Profile in Kapton

Autorzy:

Dryzek, J.
Dryzek, E.

Powiązania:

https://bibliotekanauki.pl/articles/2047124.pdf

Data publikacji:

2006-11

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.-g

Opis:

The discussion presented in the paper focuses on processes accompanying positron implantation in condensed matter. They finally constitute the positron implantation profile which generally does not exhibit the exponential behavior as it is concluded from the Monte Carlo simulation made using the EGSnrc 4.0 code. The simulation was performed for the kapton and two commonly used positron sources $\text{}^{22}$Na and $\text{}^{68}$Ge/g$\text{}^{68}$Ga. New formula for the implantation profile was proposed.

Źródło:

Acta Physica Polonica A; 2006, 110, 5; 577-582
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 43.

Tytuł:

Algorithm for Shifting Positron Annihilation Spectra

Autorzy:

Dryzek, J.
Polak, A.

Powiązania:

https://bibliotekanauki.pl/articles/2024230.pdf

Data publikacji:

2001

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

We present a simple procedure which allows us to shift the positron annihilation spectra, e.g., the Doppler broadening spectrum of the annihilation line. That is especially required when we wish to compare different spectra obtained with a spectrometer with the reduction of background. As an application of the obtained algorithm we present the studies of positron annihilation in carbon material samples.

Źródło:

Acta Physica Polonica A; 2001, 99, 3-4; 355-361
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 44.

Tytuł:

Positron annihilation study of iron oxide nanoparticles in mesoporous silica MCM-41 template

Autorzy:

Surowiec, Z.
Wiertel, M.
Zaleski, R.
Budzyński, M.
Goworek, J.

Powiązania:

https://bibliotekanauki.pl/articles/148449.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron annihilation
Mössbauer effect
MCM-41 porous silica
superparamagnetic nanoparticles

Opis:

The subject of investigation were the samples obtained by impregnation of MCM-41 template with an aqueous solution prepared from Fe(NO3)3ź9H2O. As a result of such a procedure, iron oxides deposits on MCM-41 were formed. The Mössbauer studies revealed an occurrence of Fe3O4 nanocrystallites in the both ferri- and superparamagnetic states. Almost 80% small particles exist in a paramagnetic state. The positron annihilation lifetime spectroscopy (PALS) spectra were measured in air or in vacuum. The long-lived ortho-positronium (o-Ps) components and their intensities are time dependent due to air molecules interaction with iron oxide nanocrystallites and silica walls surfaces. The adsorption of air on the nanocrystallites surface causes a total screening of their surface and a raise of the o-Ps lifetime values. Observed anti-quenching effect is a result of competition of two phenomena: practically switching off a pick-off mechanism related to interaction of o-Ps with magnetite nanoparticles and considerably weaker usual quenching by paramagnetic oxygen molecules.

Źródło:

Nukleonika; 2010, 55, 1; 91-96
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 45.

Tytuł:

Positron Annihilation in Medical Substances of Insulin

Autorzy:

Pietrzak, R.
Szatanik, R.

Powiązania:

https://bibliotekanauki.pl/articles/2043341.pdf

Data publikacji:

2005-05

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

Positrons lifetimes were measured in medical substances of insulin (human and animal), differing as far as the degree of purity and time of their activity in the organism are concerned. In all of the cases the spectrum of positron lifetime was distributed into three components, with the long-life component ranging from 1.8 to 2.08 ns and the intensity taking on values from 18 to 24%. Making use of Tao-Eldrup model, the average radius of the free volume, in which o-Ps annihilated, and the degree of filling in the volume were determined. It was found that the value of the long-life component for human insulin is higher than that of animal insulin. Moreover, the value of this component clearly depends on the manner of purification of the insulin. It was also noticed that there occurs a correlation between the value of this component and the time after which it begins to be active in the organism, as well as the total time of its activity.

Źródło:

Acta Physica Polonica A; 2005, 107, 5; 852-856
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 46.

Tytuł:

Photo-oxidative Aging Behaviors of Acrylic Coatings during UV Irradiation Investigated by Positron Annihilation Spectroscopy

Autorzy:

Zhao, Xipo
Cai, Xiaolin
Liu, Chang
Chen, Ting
He, Chunqing
Fang, Pengfei
Peng, Shaoxian

Powiązania:

https://bibliotekanauki.pl/articles/1033253.pdf

Data publikacji:

2017-11

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

Acrylic coating
UV irradiation
positron annihilation spectroscopy

Opis:

Slow positron annihilation spectroscopy, contact angle and scanning electron microscope (SEM) were employed to investigate the surface polarity and morphologies as functions of aging time in acrylic coatings during UV-a irradiation. The S parameter plots of each exposed sample are lower than that of the virgin sample in the whole range of E. The S parameter plots become lower as the exposing longer time, indicated that the irradiation generated more polar groups and increased the oxidation layer depth. Combined with surface morphology and the surface energy of acrylic coating, the variation of contact angle, and surface energy, polar component and dispersive component is related with surface polarity and morphologies.

Źródło:

Acta Physica Polonica A; 2017, 132, 5; 1527-1530
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 47.

Tytuł:

Photoluminescence and positron annihilation lifetime studies on pellets of ZnO nanocrystals

Autorzy:

Karbowski, A.
Fedus, K.
Patyk, J.
Bujak, Ł.
Służewski, K.
Karwasz, G.

Powiązania:

https://bibliotekanauki.pl/articles/148001.pdf

Data publikacji:

2013

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

photoluminescence (PL)
positron annihilation lifetime spectroscopy (PALS)
X-ray diffraction (XRD)
ZnO nanocrystals

Opis:

We explore the interrelationships between the X-ray diffraction patterns, the photoluminescence spectra and the positron lifetimes obtained from circular pellets composed of commercial ZnO nanoparticles. The experimental results are studied as a function of thermal treatment at different temperatures. X-ray diffractograms reveal the temperature- independent wurtzite phase structure of nanocrystals and show huge enlargement of ZnO grains after annealing at temperatures higher than 700 centigrade. Photoluminescence measurements exhibit two emission bands : a near band edge emission in UV (small tilde 378 nm) and a defect-related broad visible peak with a maximum in the green region ( small tilde 502 nm). The significant enhancement of the green emission at the expense of UV luminescence is observed after sample sintering at 800 and 1000 centigrade. The positron annihilation lifetime spectroscopy (PALS) is applied in order to study the thermally induced evolution of defects. The lifetime components show a step-like dependence on the thermal treatment, but do not follow exactly the variation in crystallographic phases and only vaguely follow differences in photoluminescence. The positron data indicate therefore some additional structural and/or defect changes. The possible origin of green luminescence from ZnO pellets is discussed.

Źródło:

Nukleonika; 2013, 58, 1; 189-194
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 48.

Tytuł:

Positron Annihilation in Obsidians

Autorzy:

Chojcan, J.
Sachanbiński, M.

Powiązania:

https://bibliotekanauki.pl/articles/1933482.pdf

Data publikacji:

1995-07

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

61.43.Fs
78.70.Bj

Opis:

Positron lifetime spectra as well as one-dimensional angular correlations of positron annihilation radiation were measured at room temperature for samples of rhyolitic obsidian coming from Iceland, Italy and Armenia. The samples were of different age. One specimen (originating from Iceland) was relatively young, formed in 1980. The others were much older, collected during the 19th century. It was found that the linear dimensions of pores trapping the positronium atoms before their decay as well as the pore concentration in all old obsidians are almost the same independently of the place of their formation. Simultaneously the concentration of the pores in the young sample is about five times lower than in the old specimens. Basing on the result it is suggested to extend the study in order to find out if positron annihilation can be used for the investigation of the age of the volcanic accumulations containing obsidian.

Źródło:

Acta Physica Polonica A; 1995, 88, 1; 103-110
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 49.

Tytuł:

Positron Annihilation in Helium Charged Ni Samples

Autorzy:

Pająk, J.
Rozenfeld, B.

Powiązania:

https://bibliotekanauki.pl/articles/1929108.pdf

Data publikacji:

1993-03

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

The angular correlation curves of annihilation quanta and isochronal annealing curves for the plastically deformed nickel samples charged with helium have been measured. The results indicate that helium is effectively trapped at crystal lattice defects and is released from them at the temperature below 350 K.

Źródło:

Acta Physica Polonica A; 1993, 83, 3; 371-374
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 50.

Tytuł:

Remarks on Reconstruction of Defects Distribution by Positron Lifetime Measurements

Autorzy:

Dryzek, J.

Powiązania:

https://bibliotekanauki.pl/articles/1933485.pdf

Data publikacji:

1995-07

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

It is well known that the positron trapping rate obtained from positron lifetime measurements depends upon defect concentrations and trapping efficiency. If a distribution of open volume defects exists, a distribution of trapping efficiency also could be present. As an example, the calculation of trapping efficiency as a function of radius of defects in Al is presented. The correct explanation of defect size distribution obtained by positron lifetime measurements needs to introduce some additional assumptions about trapping efficiency.

Źródło:

Acta Physica Polonica A; 1995, 88, 1; 125-128
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 51.

Tytuł:

Ortho-positronium in liquid alkanes

Autorzy:

Zgardzińska, B.

Powiązania:

https://bibliotekanauki.pl/articles/146291.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron annihilation
liquid alkanes
bubble model
surface tension

Opis:

Positron lifetime spectra were measured for a series of odd-numbered liquid n-alkanes (C7H16, C9H20, C13H28 and C19H40) in a broad range of temperature. According to the “bubble model” the ortho-positronium (o-Ps) lifetime is determined by surface tension. Bubble radius was calculated using the Tao-Eldrup model and compared to the radius expected from the surface tension of liquid. The radii are not identical, their difference rises with temperature. If one assumes the difference of radii as constant, the o-Ps lifetime calculated from the Tao-Eldrup model rises faster than the experimental one. The distinct rise of the difference of radii has no physical explanation in the accepted o-Ps annihilation model. This effect can be the result of radiation chemistry processes not taken into account so far in the bubble model.

Źródło:

Nukleonika; 2010, 55, 1; 41-46
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 52.

Tytuł:

Positron Annihilation Studies of the Free Volumes in Nylon12/PVA Films Treated by Supercritical Carbon Dioxide

Autorzy:

Li, Jingjing
Yin, Chongshan
Zhou, Yawei
Li, Gang
Yeh, Jen-taut
He, Chunqing

Powiązania:

https://bibliotekanauki.pl/articles/1033920.pdf

Data publikacji:

2017-11

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

Nylon12/PVA
ScCO₂
positron annihilation
free volume
relaxation

Opis:

Free volume variations of Nylon12/Polyvinyl alcohol (Nylon12/PVA) blends treated in supercritical carbon dioxide (ScCO₂) were investigated using positron annihilation lifetime spectroscopy. It is found that o-Ps lifetime τ₃ and the corresponding intensity I₃ in Nylon12/PVA decrease with increase of the PVA content. Being treated in ScCO₂ at 50°C and 20 MPa for 1 h, the free volume holes in Nylon12/PVA blends expand to different extents depending on the weight ratio of PVA. After releasing of CO₂, the free volume size decreases as a function of the elapsed time due to the molecular relaxation, and the relaxation time constant depends on the content of PVA in the blends.

Źródło:

Acta Physica Polonica A; 2017, 132, 5; 1552-1555
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 53.

Tytuł:

Positron Annihilation Methods by Use of LSO Scintillators

Autorzy:

Hirade, T.
Oka, T.

Powiązania:

https://bibliotekanauki.pl/articles/1339992.pdf

Data publikacji:

2014-03

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

$Lu_2SiO_5$:Ce (LSO) scintillator is one of the scintillators used for positron emission tomography because of its high efficiency of gamma-ray detection. We tried to use LSO for positron annihilation lifetime and age-momentum correlation measurements because the high efficiency is needed to reduce the positron irradiation effect during measurements. The high efficiency with reasonable time resolution was successfully obtained by use of the dynode signals from photomultiplier tubes.

Źródło:

Acta Physica Polonica A; 2014, 125, 3; 825-828
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 54.

Tytuł:

Positron Annihilation in Internally Oxidized Copper

Autorzy:

Misheva, M.
Nancheva, N.
Feschiev, N.

Powiązania:

https://bibliotekanauki.pl/articles/1929106.pdf

Data publikacji:

1993-03

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

The positron lifetimes in internally oxidized polycrystalline copper, annealed at different temperatures, were measured. It was found that the dispersed alumina particles act as positron traps. Estimation of concentration of defects was made in the frames of the trapping model.

Źródło:

Acta Physica Polonica A; 1993, 83, 3; 365-369
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 55.

Tytuł:

Positron annihilation study of structural relaxation and crystallization of glassified milk fat

Autorzy:

Rashevskaya, T.
Guly, I.
Pryadko, M.
Nishchenko, M.
Likhtorovich, S.

Powiązania:

https://bibliotekanauki.pl/articles/25394.pdf

Data publikacji:

2000

Wydawca:

Polska Akademia Nauk. Instytut Agrofizyki PAN

Tematy:

positron annihilation technique
milk fat
physical property
plasticity
consistency
crystallization
nutrition product
butter
amorphism
consistence zob.consistency
crystalline
elasticity

Źródło:

International Agrophysics; 2000, 14, 2
0236-8722

Pojawia się w:

International Agrophysics

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 56.

Tytuł:

Effect of Ultraviolet Absorber on Photo-Degradation of Epoxy Coating Studied by Slow Positron Beam

Autorzy:

Wang, Zheng
Liu, Fuwei
Li, Jingjing
He, Chunqing
Peng, Xiangyang
Huang, Zhen
Fang, Pengfei

Powiązania:

https://bibliotekanauki.pl/articles/1033239.pdf

Data publikacji:

2017-11

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

epoxy coating
photo-degradation
ultraviolet absorber
slow positron beam
microstructure

Opis:

The photo-degradation progress of epoxy coating and the effect of ultraviolet absorber under UV-B irradiation have been investigated in slow positron beam and by the Fourier transform infrared spectrometer. After 120 h of irradiation, the value of S parameter in sample bulk is reduced while compared with the virgin sample. The result is mostly due to post-cure process happening in this initial irradiation stage. As the irradiation time increases to 360 h, the S parameter decreases sharply. This is due to the growth of carbonyl group and the generation of free radical. After 528 h or longer time of irradiation, a very low S value was obtained near sample surface, indicating the formation of a dead surface layer. Positron results also reveal that the addition of ultraviolet absorber suppresses the development of the dead layer after long-term UV-B irradiation. Ultraviolet absorber has a suppressing effect on generation of polar groups towards sample bulk. The addition of ultraviolet absorber is a key factor that affects the photo-degradation of epoxy coating.

Źródło:

Acta Physica Polonica A; 2017, 132, 5; 1523-1526
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 57.

Tytuł:

Positron Annihilation Study of Defects in the Cage-Type Uranium Compound

Autorzy:

Rubaszek, A.

Powiązania:

https://bibliotekanauki.pl/articles/1336614.pdf

Data publikacji:

2014-03

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

The electron and positron properties of the $UIr_2Zn_{20}$ compound of the Fd-3m cage-type crystal structure are studied. The characteristics for the perfect crystal are compared with their counterparts in the elements containing Ir and Zn vacancy. The presence of the vacancy hardly influences the electron charge density around individual atoms. In contrast to electrons, the positron is strongly localized inside the vacancy and the transfer of positron charge is observed. The positron lifetime, τ, appears to be strongly sensitive to the presence and type of the vacancy. Furthermore, this parameter calculated for the perfect crystal is very close to the experimental value for Zn. Here the theoretical values of τ depend on the approach applied to the electron positron (e-p) correlations.

Źródło:

Acta Physica Polonica A; 2014, 125, 3; 737-740
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 58.

Tytuł:

Positron Annihilation in Tektite and Hyalite

Autorzy:

Chojcan, J.
Sachanbiński, M.

Powiązania:

https://bibliotekanauki.pl/articles/1928968.pdf

Data publikacji:

1993-03

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

61.43.Fs
78.70.Bj

Opis:

Positron lifetime spectra as well as one-dimensional angular distributions of photons coming from the two-photon annihilation of an electron-positron pair were measured at room temperature for samples of natural tektite and hyalite. The data were used for estimation of positronium characteristics in the specimens. The characteristics were analysed in terms of parameters of pores trapping the positronium atoms before their decay. In the analysis two models of the traps were taken into account, i.e. the square potential wells of spherical symmetry with barriers of finite and infinite heights. It was found that the linear dimensions of the pores resulting from these two-trap models are almost the same and they are of the order of 1 nm.

Źródło:

Acta Physica Polonica A; 1993, 83, 3; 267-271
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 59.

Tytuł:

Detection of Positron Implantation Profile in Different Materials

Autorzy:

Dryzek, J.

Powiązania:

https://bibliotekanauki.pl/articles/2042176.pdf

Data publikacji:

2005-04

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

61.72.Ji
78.70.Bj

Opis:

The objective of this paper is experimental studies of the linear absorption coefficient, or mean penetration depth of positrons emitted from $\text{}^{22}$Na isotope in different materials. For this purpose we constructed a new experimental setup which allows us to scan the depth implantation profile of positrons. For the studied metals: Mg, Al, the obtained values of mean penetration depth coincide well with those which can be calculated using the mathematical formula commonly used but for Si and S the discrepancy has been observed similarly like for polymers.

Źródło:

Acta Physica Polonica A; 2005, 107, 4; 598-607
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 60.

Tytuł:

Screening of a Positron in An Inhomogeneous Electron Gas

Autorzy:

Stachowiak, H.

Powiązania:

https://bibliotekanauki.pl/articles/2008186.pdf

Data publikacji:

1999-04

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj
71.60.+z

Opis:

Calculations of the local annihilation rate of positrons in inhomogeneous media have been recently performed. However, the problem was solved only for the positron at the center of the inhomogeneity. This allowed to benefit of the spherical symmetry of the problem. Since the positron is usually an itinerant particle, it is necessary in practical applications to perform computations for every possible coordinates of this particle. In the present work local annihilation rates were obtained for noncentral coordinates of the positron.

Źródło:

Acta Physica Polonica A; 1999, 95, 4; 663-670
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 61.

Tytuł:

Positron Annihilation in Cotton Cellulose

Autorzy:

Golonka, P.
Mayer, J.
Dryzek, E.

Powiązania:

https://bibliotekanauki.pl/articles/2024232.pdf

Data publikacji:

2001

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj
42.70.Jk

Opis:

The changes of the cotton fibre microstructure as a result of annealing at temperatures from 20ºC to 300ºC were investigated by positron lifetime spectroscopy and differential scanning calorimetry. The aim of the paper was to examine the cotton cellulose thermal degradation process.

Źródło:

Acta Physica Polonica A; 2001, 99, 3-4; 363-367
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 62.

Tytuł:

A Comparison of Different Theoretical Models of Positron Lifetime Spectra for Polymers

Autorzy:

Kansy, J.

Powiązania:

https://bibliotekanauki.pl/articles/1812531.pdf

Data publikacji:

2008-05

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

The same reference positron lifetime spectra of polyurethane, measured in temperature range 112 to 390 K, were analyzed with three theoretical models: the "conventional" model with three exponential decay component of discrete values of lifetimes, a model with one discrete exponential component and two "packages" of exponentials with log-normal distribution of annihilation rates, and a model considering positronium slow localization, positronium internal relaxation as well as "delayed" formation of positronium. It turns out that the two latter models fit to the experimental data with the same excellent quality, in spite of the fact that in both models the ratio of intensities related to para-positronium and ortho-positronium was constrained to be as 1:3.

Źródło:

Acta Physica Polonica A; 2008, 113, 5; 1397-1407
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 63.

Tytuł:

Positron Annihilation Studies of the Subsurface Zone in Aluminium Alloys

Autorzy:

Dryzek, E.
Dryzek, J.

Powiązania:

https://bibliotekanauki.pl/articles/2047123.pdf

Data publikacji:

2006-11

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

The paper presents positron lifetime studies of the subsurface region of the aluminium cast AK64 alloy containing silicon as a main alloying element after sliding against stainless steel in the pin-on-disc tester. The subsurface zone of the depth exceeding 150μm has been detected. The scanning electron microscopy revealed only the plastically deformed region occurring at the depth up to ca. 50μm and cracks at the depth less than 30μm. The comparison with the results obtained for the AK12 alloy containing almost a twice higher amount of silicon demonstrates the influence of the hard silicon rich particles on the total depth of the subsurface zone. A higher amount of hard particle prevents to some extend the propagation of defects inside the material.

Źródło:

Acta Physica Polonica A; 2006, 110, 5; 569-575
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 64.

Tytuł:

Positron Annihilation in p-Terphenyl Doped with Benzofluorene

Autorzy:

Goworek, T.
Rybka, C.

Powiązania:

https://bibliotekanauki.pl/articles/2024234.pdf

Data publikacji:

2001

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj
31.70.Ks

Opis:

In earlier measurements of momentum distribution of annihilating e$\text{}^{+}$e$\text{}^{-}$ pairs the intensity of o-Ps component seemed to be much higher than that expected from the lifetime data. In this paper we show that such a deviation disappears if one assumes that the pick-off component of angular correlation of annihilation radiation is narrower by 10% than the component related to free annihilation.

Źródło:

Acta Physica Polonica A; 2001, 99, 3-4; 369-371
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 65.

Tytuł:

Relativistic Phenomena in Two-Quantum Annihilation of Electron-Positron Pairs

Autorzy:

Baranowski, A.

Powiązania:

https://bibliotekanauki.pl/articles/2047121.pdf

Data publikacji:

2006-11

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj
03.30.+p

Opis:

The kinematics of e$\text{}^{+}$e$\text{}^{-}$ pair and annihilation quanta momentum vectors have been presented basing on ellipse and spheroid properties. Using the formulae resulting from the Lorentz transformation of momentum and energy there was pointed out that the aberration and the longitudinal and transversal Doppler effects are inseparably associated.

Źródło:

Acta Physica Polonica A; 2006, 110, 5; 551-558
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 66.

Tytuł:

Performance of a High-Resolution Digital Positron-Lifetime Spectrometer

Autorzy:

Bečvář, F.
Čížek, J.
Procházka, I.

Powiązania:

https://bibliotekanauki.pl/articles/1812465.pdf

Data publikacji:

2008-05

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

This work describes a digital positron-lifetime spectrometer based on two ultrafast digitizers. Performance of the digital spectrometer in conditions of a routine measurement is compared with an analogue setup connected to the same detectors. It was found that engagement of the digital setup leads to an improvement of timing resolution (FWHM for $\text{}^{22}Na$) from 169 ps for the traditional analogue setup to 146 ps for the digital setup. The coincidence count rate for 1.2 MBq $\text{}^{22}Na$ source is 75-80 coinc./s for both configurations. These results clearly demonstrate the advantages of the digital timing over the traditional analogue setup.

Źródło:

Acta Physica Polonica A; 2008, 113, 5; 1279-1284
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 67.

Tytuł:

Positron Scattering at Thermal Energies

Autorzy:

Fedus, K.
Karwasz, G.

Powiązania:

https://bibliotekanauki.pl/articles/1340032.pdf

Data publikacji:

2014-03

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

34.80.-i
34.80.Bm
34.80.Uv

Opis:

Modified effective range theory in analytical form is used to extrapolate elastic cross-sections down to thermal energies for positron scattering from five atomic and molecular targets including Ar, $H_2$, $N_2$, $C_6H_6$ (benzene) and $C_6H_{12}$ (c-hexane). The derived scattering parameters are then used to estimate the annihilation rates for chosen elements using a simple formula by Gribakin. We show that a combination of two simple models has a potential for accurate parameterization of coefficients describing the interaction of thermal positrons with non-polar targets of low polarizability such as Ar and $N_2$.

Źródło:

Acta Physica Polonica A; 2014, 125, 3; 829-832
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 68.

Tytuł:

Electron traps in long-chain alkanes

Autorzy:

Pietrow, M.
Wawryszczuk, J.

Powiązania:

https://bibliotekanauki.pl/articles/146299.pdf

Data publikacji:

2010

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

PALS
positron annihilation
electron traps
quenching by light

Opis:

Positron lifetime spectra in long-chain alkanes were measured at various wavelengths of light illuminating the samples as a function of temperature, storage time. It was found that in n-alkanes with carbon chain longer than 30 atoms two kinds of electron traps exist; the depth of shallower of them is less than 0.52 eV. They are discharged already at a temperature of 120 K.

Źródło:

Nukleonika; 2010, 55, 1; 51-55
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 69.

Tytuł:

Modern radiation techniques for treatment of head and neck cancers

Autorzy:

Kiprian, Dorota

Powiązania:

https://bibliotekanauki.pl/articles/1401820.pdf

Data publikacji:

2015

Wydawca:

Index Copernicus International

Tematy:

positron emission tomography
radiotherapy
throat
apoptosis

Opis:

Alongside surgery, radiation therapy remains the mainstay of treatment for head and neck cancers.  Because the head and neck contain a number of critically important structures, it is crucial to try to curtail the adverse effects of radiation therapy by increasing its precision. Such precise radiation techniques include the three-dimensional conformal as well as highly conformal radiotherapy. The latter includes, for instance, intensity modulated radiation therapy (IMRT), stereotactic radiation, and proton-beam therapy. All of the above-mentioned techniques are available in Poland and give the opportunity of a more aggressive treatment that lead to improved outcomes, curtailment of adverse effects, and by that, a better quality of life.

Źródło:

Polski Przegląd Otorynolaryngologiczny; 2015, 4, 4; 1-10
2084-5308
2300-7338

Pojawia się w:

Polski Przegląd Otorynolaryngologiczny

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 70.

Tytuł:

Compact cyclotrons for the production of tracers and radiopharmaceuticals

Autorzy:

Paans, A.

Powiązania:

https://bibliotekanauki.pl/articles/146155.pdf

Data publikacji:

2003

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

positron emission tomography (PET)
cyclotron
radionuclide production

Opis:

Positron Emission Tomography (PET) is a method for determining biochemical and physiological processes in vivo in a quantitative manner. The most commonly used radionuclides are 11C, 13N, 15O and 18F, with respective half-lives of approximately 20 min, 10 min, 2 min, and 110 min. 18F labeled FDG (fluoro-2-deoxy-D-glucose) is now the most frequently used radiopharmaceutical and finds its application prominently in the field of oncology. Originally, the production of these radionuclides was performed with the existing accelerators, designed for nuclear physics, but with increasing interest in the PET methodology specially designed PET-production cyclotrons became available. The nuclear reactions involved are (p,n), (d,n), (p,a) and (d,a) and the thresholds for the nuclear reactions involved are 5 to 6 MeV. Based on these values and on other parameters, a proton 15 to 20 MeV cyclotron is often chosen. Since the half-life of a radionuclide limits the production time, the maximum beam current is an important parameter, together with the target construction, for the ultimate yield obtainable. In the development of special PET production cyclotrons, attention has also been paid to improve the extraction efficiency and the possibility of multiple extractions by designing negative ion cyclotrons. Commercial cyclotrons can often be acquired as an easy to operate integrated radionuclide production unit including targetry and some units. Regional FDG factories are nowadays being created to fulfil the demand for PET radiopharmaceutics. The possible choices in commercially available cyclotrons for the production of PET radionuclides will be discussed.

Źródło:

Nukleonika; 2003, 48,suppl.2; 169-172
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 71.

Tytuł:

Electroni-Positron Scattering in Real Metals

Autorzy:

Boroński, E.
Daniuk, S.
Stachowiak, H.

Powiązania:

https://bibliotekanauki.pl/articles/1928926.pdf

Data publikacji:

1993-03

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj
71.60.+z

Opis:

The purpose of the paper is to point at the importance of some detailed studies of electron-positron scattering in real metals using wave functions obtained from band structure calculations. In this work some preliminary investigations of the matrix elements of electron-positron scattering, e.g. the transitions from occupied to non-occupied states close to the Fermi surface are presented. One can observe that for s → s transitions of the positron (s, p are orbital quantum numbers) electrons do not change their orbital quantum numbers but for s → p transitions of the positron, electron quantum numbers change by unity.

Źródło:

Acta Physica Polonica A; 1993, 83, 3; 255-260
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 72.

Tytuł:

Electron-Positron Interaction in Metals. Theory and Experiment

Autorzy:

Stachowiak, H.
Boroński, E.

Powiązania:

https://bibliotekanauki.pl/articles/2042125.pdf

Data publikacji:

2005-04

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

71.60.+z
78.70.Bj

Opis:

The electron-positron interaction greatly complicates the interpretation of positron annihilation data. The two-detector Doppler measurements of Mijnarends et al. as well as our theoretical calculations point at the conclusion that the local density approximation to e$\text{}^{+}$-e$\text{}^{-}$ interaction is a good way of treating this problem in real metals, at least the simplest ones. This shows that e$\text{}^{+}$-e$\text{}^{-}$ interaction in an electron gas is the key to understanding this phenomenon also in inhomogeneous systems. On the basis of dozens of experiments one comes to the conclusion that the well known formula of Boroński and Nieminen for the electron accumulation on the positron in jellium describes the best the positron lifetimes in metals. However, it is based on the calculations of Lantto which start from a physically oversimplified trial function. The results of Arponen and Pajanne, of Rubaszek and Stachowiak, and of Stachowiak and Lach lead to too short positron lifetimes in spite of using less controversial assumptions. The discrepancy is of the order of 8 to 15% for r$\text{}_{s}$=2. This shows that we still do not fully understand e$\text{}^{+}$-e$\text{}^{-}$ interaction even in an electron gas.

Źródło:

Acta Physica Polonica A; 2005, 107, 4; 541-553
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 73.

Tytuł:

Positron Annihilation in Defected Monocrystalline Gold Samples

Autorzy:

Pająk, J.
Rudzińska, W.
Szuszkiewicz, M.
Garłowska, M.

Powiązania:

https://bibliotekanauki.pl/articles/2043340.pdf

Data publikacji:

2005-05

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

Angular distribution of the positron annihilation quanta was measured for monocrystalline gold samples, oriented in (110) and (111) directions. The samples were deformed by elongation for different deformation degrees. The S and W parameters as a function of deformation degree of the sample were determined. It was found that the dynamics of the dislocations and vacancy generation during the sliding of some crystallographic planes, depends on the crystallographic direction.

Źródło:

Acta Physica Polonica A; 2005, 107, 5; 848-851
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 74.

Tytuł:

Positron Annihilation Studies of the Ni-H Systems Containing Thermally Induced Crystal Lattice Defects

Autorzy:

Pająk, J.

Powiązania:

https://bibliotekanauki.pl/articles/1933538.pdf

Data publikacji:

1995-07

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

The interaction between hydrogen and thermally induced defects has been studied in nickel samples using the positron annihilation technique. From measurements further evidence has been found for agglomeration of vacancies and small vacancy complexes into large-size three-dimensional void-like defects in the plastically deformed and electron beam irradiated samples containing hydrogen.

Źródło:

Acta Physica Polonica A; 1995, 88, 1; 219-223
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 75.

Tytuł:

Does the Dielectric-Dielectric Interface Affect the Positron Diffusion Current?

Autorzy:

Beliczyński, J.
Dębowska, E.
Świątkowski, W.

Powiązania:

https://bibliotekanauki.pl/articles/1928879.pdf

Data publikacji:

1993-03

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

68.35.Wm

Opis:

The angular correlations of annihilation radiation have been measured for NaI, NaF and (NaI)$\text{}_{0.65}$(NaF)$\text{}_{0.35}$ alloy. The angular correlations of annihilation radiation for the alloy appeared to be more similar to the one for NaI than it should be expected from the content of NaI in the alloy. The result can be easily explained by assuming that NaI/NaF interface acts directionally on positron diffusion movement.

Źródło:

Acta Physica Polonica A; 1993, 83, 3; 251-254
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 76.

Tytuł:

The Effective Electron-Positron Potential in Jellium

Autorzy:

Stachowiak, H.
Boroński, E.
Lach, J.

Powiązania:

https://bibliotekanauki.pl/articles/1929114.pdf

Data publikacji:

1993-03

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj
71.60.+z

Opis:

One of the methods of determining theoretical annihilation characteristics in real metals is the approximation called Bloch modified ladder approach. In this approach a Bethe-Goldstone type equation is solved with an effective electron-positron potential obtained previously for jellium of the corresponding electron density. If one wishes to include the dependence on the local electron density of the e$\text{}^{+}$-e$\text{}^{-}$ effective potential in this formalism, it is necessary to know this potential for jellium, for metallic and above metallic densities. A review of different proposed e$\text{}^{+}$-e$\text{}^{-}$ potentials is presented and their correctness is evaluated from the point of view of their application in a Bethe-Goldstone type formalism which is the jellium analogue of Bloch modified ladder approach.

Źródło:

Acta Physica Polonica A; 1993, 83, 3; 391-394
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 77.

Tytuł:

Positron Annihilation in Deformed and Hydrogenated Pd-23%atcu Alloy

Autorzy:

Pająk, J.
Szatanik, R.
Szuszkiewicz, M.

Powiązania:

https://bibliotekanauki.pl/articles/2008180.pdf

Data publikacji:

1999-04

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

Peak coincidence counting rate and positron lifetime spectra for deformed by cold-rolling, and annealed by four hours in the temperature 973 K, hydrogen free and hydrogenated PdCu with 23% Cu samples, in the temperature range from room temperature to about 720 K were measured. It was found that hydrogen improved to tempered samples creates defects that are annealed to the temperature about 525 K. In the cold-rolled up to deformation degree of 50% samples, hydrogen is trapped at defects, probably vacancies, forming H-V complexes, that become disappearing in the vicinity of the temperature at 350 K.

Źródło:

Acta Physica Polonica A; 1999, 95, 4; 637-640
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 78.

Tytuł:

Positron Affinities and Deformation Potentials in Cubic Semiconductors

Autorzy:

Panda, B. K.
Brauer, G.

Powiązania:

https://bibliotekanauki.pl/articles/2008145.pdf

Data publikacji:

1999-04

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

79.20.Mb
73.30.+y

Opis:

Positron affinities and deformation potentials are calculated in cubic bulk semiconductors using the density functional theory with the electron and positron energies in the local density approximation and generalized gradient approximation, respectively. In order to estimate these quantities, two different forms of the electron-positron correlation potential are used. Positron affinities calculated using these two correlation potentials differ by about 0.3 eV. Our calculated affinities in 3C-SiC are in better agreement with experiments than those obtained previously by another first principles method. In the present work the positron affinity in BN is found to be quite close to the one in diamond.

Źródło:

Acta Physica Polonica A; 1999, 95, 4; 641-646
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 79.

Tytuł:

Positron Trapping Rate Coefficient for Thermalized Positrons at Metal-Dielectric Interface

Autorzy:

Baranowski, A.
Ewertowski, R.
Świątkowski, W.

Powiązania:

https://bibliotekanauki.pl/articles/1887383.pdf

Data publikacji:

1991-04

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

68.35.Wn

Opis:

On the basis of experimental positron lifetime spectra it was shown that positrons can be trapped at metal-dielectric interface. The coefficient indicating the trapping possibility of the AgŃa$\text{}_{3}$AlF$\text{}_{6}$ interface has been evaluated.

Źródło:

Acta Physica Polonica A; 1991, 79, 4; 517-523
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 80.

Tytuł:

Estimate of the Crystallite Size for Nanocrystalline AISI 316L Stainless Steel and Armco Iron Processed by Hydrostatic Extrusion Using Variable Energy Positron Beam

Autorzy:

Sarnek, M.
Dryzek, E.
Horodek, P.
Pachla, W.

Powiązania:

https://bibliotekanauki.pl/articles/1033950.pdf

Data publikacji:

2017-11

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

stainless steel
Armco iron
plastic deformation
hydrostatic extrusion
variable energy positron beam
X-ray diffraction

Opis:

The paper presents the results of research of nanocrystalline AISI 316L type stainless steel and nanocrystalline Armco pure iron processed by severe plastic deformation using hydrostatic extrusion method. Surface and subsurface of the steel samples extruded at different pressure were investigated using variable energy positron beam. It enabled us to determine the positron diffusion length and compare its values with those for annealed AISI 304 stainless steel. Furthermore positron lifetime and microhardness were measured for all the samples and X-ray diffraction was used to estimate the crystallite size.

Źródło:

Acta Physica Polonica A; 2017, 132, 5; 1598-1601
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 81.

Tytuł:

Synthesis of Endogenous Compounds Labeled with $\text{}^{11}C$ for Positron Emission Tomography

Autorzy:

Kilian, K.
Pękal, A.

Powiązania:

https://bibliotekanauki.pl/articles/1402613.pdf

Data publikacji:

2015-05

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

87.57.un

Opis:

Among the β⁺ emitting isotopes, produced in medical cyclotrons, carbon-11 is promising radionuclide for labeling of biologically active compounds and tracking their distribution in living organism. Therefore aminoacids, carboxylic acids, fatty acids and amines have been widely used in assessing and staging of brain tumors ($\text{}^{11}C$-methionine), prostate cancer ($\text{}^{11}C$-choline, $\text{}^{11}C$-acetate) and neurological disorders ($\text{}^{11}C$-labeled neurotransmitters). This paper reviews recent achievements in synthesis of endogenous substances labeled with $\text{}^{11}C$ and presents our experience in $\text{}^{11}C$-methionine synthesis. Proposed protocol is a reliable tool for routine manufacturing in clinical applications and animal studies.

Źródło:

Acta Physica Polonica A; 2015, 127, 5; 1475-1478
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 82.

Tytuł:

New Experimental Approach to the Detection of Positron Annihilation in Flight Process

Autorzy:

Dryzek, J.

Powiązania:

https://bibliotekanauki.pl/articles/1812488.pdf

Data publikacji:

2008-05

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj
07.85.-m

Opis:

Positron annihilation in flight, when mainly positron contributes to the energy and momentum of the annihilating pair, is rarely observed in condensed matter due to its small probability. Additionally, this process does not manifest itself by any characteristic features, which would help in observation. Hence, our knowledge about that process is poor. In the paper we propose the new experimental method which allows us to detect this process. We applied the conventional positron lifetime spectrometer, which after changing photon energy ranges and layout of detectors was suitable for that detection. The first measurements allow us to estimate that in pure aluminum almost 4.76% of all implanted positrons from isotope source ^{22}Na annihilate in flight.

Źródło:

Acta Physica Polonica A; 2008, 113, 5; 1339-1346
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 83.

Tytuł:

Positron Annihilation in Steel Samples Deformed by Uniaxial Tension

Autorzy:

Rudzińska, W.
Szuszkiewicz, M.
Bujnarowski, G.
Kluza, A.

Powiązania:

https://bibliotekanauki.pl/articles/1812548.pdf

Data publikacji:

2008-05

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

Angular distributions of the positron annihilation quanta were measured for steel ST2 SAL samples deformed by uniaxial tension up to different deformation degrees. The dependences of the S parameter on the relative elongation of the samples are presented. The positron annihilation data for steel are compared with the results obtained previously for polycrystalline iron samples deformed by uniaxial tension up to different deformation degrees in the proportionality and limited proportionality regions.

Źródło:

Acta Physica Polonica A; 2008, 113, 5; 1507-1510
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 84.

Tytuł:

Polymerization of Epoxy Resins Studied by Positron Annihilation

Autorzy:

Suzuki, T.
Hayashi, T.
Ito, Y.

Powiązania:

https://bibliotekanauki.pl/articles/2007966.pdf

Data publikacji:

1999-04

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj
83.80.Cq

Opis:

The polymerization process of epoxy resins (bisphenol-A dicyanate) was studied using positron-annihilation lifetime spectroscopy. The polymerization from monomer to polymer through a polymerization reaction was followed by positron-annihilation lifetime spectroscopy measurements. Resins kept at curing temperatures (120, 150, and 200°C) changed form from a powder to a solid through a liquid. The size of the intermolecular spaces of the solid samples increased along with the progress of polymerization.

Źródło:

Acta Physica Polonica A; 1999, 95, 4; 671-676
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 85.

Tytuł:

Preferential Positron Annihilation in Binary Alloys

Autorzy:

Kuriplach, J.
Dryzek, E.
Dryzek, J.
Šob, M.

Powiązania:

https://bibliotekanauki.pl/articles/2008109.pdf

Data publikacji:

1999-04

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj
71.60.+z

Opis:

The effect of preferential positron annihilation at individual constituent atoms in binary alloys is examined theoretically and experimentally. In particular, the results of recently studied alloys Fe-Al and Mg-Cd together with new preliminary results for the Sn-In system are discussed and summarised. In the case of the Sn-In system, the concentration dependencies of positron annihilation rates and Doppler broadening spectra are analysed.

Źródło:

Acta Physica Polonica A; 1999, 95, 4; 605-611
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 86.

Tytuł:

Positron Lifetime Studies of the Subsurface Zones Created under Dry and Lubrication Conditions

Autorzy:

Dryzek, J.
Dryzek, E.

Powiązania:

https://bibliotekanauki.pl/articles/2024223.pdf

Data publikacji:

2001

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

We present the measurement of the positron lifetime spectra in the subsurface zones in copper samples with surfaces damaged in dry and lubrication conditions. We observe that close to the damaged surface the single vacancies were present, but deeper in the sample treated in the dry condition the vacancy clusters were detected. A zone with dislocations was located deeper than the zone with the vacancies and their clusters.

Źródło:

Acta Physica Polonica A; 2001, 99, 3-4; 351-354
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 87.

Tytuł:

Investigation of Electron-Positron Correlations by Monte Carlo Simulation

Autorzy:

Boroński, E.

Powiązania:

https://bibliotekanauki.pl/articles/2042170.pdf

Data publikacji:

2005-04

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

71.60.+z
78.70.Bj
02.70.Ss

Opis:

Earlier theoretical studies, as well as recent calculations of positron annihilation rates in metals, show that some basic problems concerning electron-positron (e-p) interaction have not been solved satisfactorily, even for homogeneous media (the electron gas). In turn, the "computer experiments" e.g. quantum Monte Carlo simulations applied to these problems by several authors yielded only fragmentary, inaccurate and even incorrect results for smaller electron densities. It is shown in the present paper that the quantum Monte Carlo method may be useful in investigations of positron interactions with electrons. Reasonable annihilation rates have been obtained owing to appropriate construction of the trial function and taking into account the 3-particle correlations (i.e. dependence of the electron-electron (e-e) interaction on the distance from the positron). Moreover, the method of "exact determination" (without any fitting) of positron annihilation rates on the basis of the variational trial function was proposed. One also found the way of calculating the momentum dependent enhancement factors, the quantities not achievable within the Monte Carlo method until now.

Źródło:

Acta Physica Polonica A; 2005, 107, 4; 576-585
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 88.

Tytuł:

Elastic Positron Scattering from Zinc and Cadmium in the Relativistic Polarized Orbital Approximation

Autorzy:

Szmytkowski, Radosław

Powiązania:

https://bibliotekanauki.pl/articles/1929814.pdf

Data publikacji:

1993-12

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

34.80.Bw
34.90.+q

Opis:

Results of relativistic calculations on the elastic positron scattering from zinc and cadmium atoms are presented in the low-energy region. The ab initio calculated polarization potentials applied in these calculations were obtained by solving the coupled Dirac-Hartree-Fock equations. It is shown that the indirect relativistic effects play an important role in the description of the scattering process. Particularly, relativity has a great influence on values of scattering lengths.

Źródło:

Acta Physica Polonica A; 1993, 84, 6; 1035-1040
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 89.

Tytuł:

Antihydrogen Formation in Low Energy Collision of Positron with Antiproton

Autorzy:

Bhattacharyya, S.

Powiązania:

https://bibliotekanauki.pl/articles/1931542.pdf

Data publikacji:

1994-05

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

34.50.+a
34.70.+e
39.10.+x

Opis:

In the present paper two-body radiative recombination rate for the production of antihydrogen (H̅) in a merged beam of slow positrons (e$\text{}^{+}$) and antiprotons (p¯) is studied in the light of a two-step process, which consists of capture in an excited state of H̅ with subsequent decay to the ground state and emission of a photon. Computation is done using the field theory and the Coulomb gauge. Importance of the two-step radiative recombination process relative to the well-known spontaneous photorecombination process, on the two-body radiative recombination rate for antihydrogen formation, is discussed. The present result predicts higher contribution from the two-step radiative recombination process as compared to the spontaneous photorecombination process to the rate of cold antihydrogen formation with the relative collision energy below 0.01 Rydberg, near which experiments are being conducted. However, above 0.1 Rydberg the spontaneous photorecombination process dominates over the two-step radiative recombination process. The present result is valid, as well, for the formation of hydrogen atom due to collision between slow electron and proton.

Źródło:

Acta Physica Polonica A; 1994, 86, 3; 297-308
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 90.

Tytuł:

Elastic Positron Scattering from Krypton and Xenon in the Relativistic Polarized Orbital Approximation

Autorzy:

Szmytkowski, R.

Powiązania:

https://bibliotekanauki.pl/articles/1931546.pdf

Data publikacji:

1994-05

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

34.80.Bm
34.90.+q

Opis:

We present results of ab initio relativistic calculations on the elastic positron scattering from Kr and Ye atoms in the energy region below 10 eV. The approach employed was the relativistic polarized orbital approximation in which we tried to keep correctly orders of various contributions to positron-atom interaction potentials. In view of the serious disagreement between the present results and experimental data we conclude that the polarized orbital approximation even in its relativistic version is not able to provide reliable values of positron scattering cross-sections.

Źródło:

Acta Physica Polonica A; 1994, 86, 3; 309-314
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 91.

Tytuł:

A Magnetically Guided Slow Positron Beam for Defect Studies

Autorzy:

Anwand, W.
Kissener, H.
Brauer, G.

Powiązania:

https://bibliotekanauki.pl/articles/1933460.pdf

Data publikacji:

1995-07

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

06.90.+v
07.90.+c

Opis:

The design and construction of a compact, magnetically guided slow positron beam is discussed. The system uses a 30 mCi $\text{}^{22}$Νa source. It consists of three main parts: (i) the source chamber with a tungsten foil transmission moderator and the extraction optics, (ii) the beam line with magnetic beam guidance, a bent tube for the separation of the fast positrons and the accelerator stage, (iii) the target chamber with the sample holder and the detector electronics. The energy of the incident positrons can be varied from 30 eV up to 50 keV. Furthermore source geometries, pre-acceleration, main acceleration sections and various magnetic induction profiles have been considered, such as (i) rectangular, conical and bent Wehnelt electrodes, (iii) pre-accelerator voltage shared over several electrodes, (iii) weak, strong, constant and z-dependent B-profiles, (iv) geometric options in the main accelerator region, (v) purely electrostatic and combined electric/magnetic fields. The beam is mainly designed for defect profile studies in ultra high vacuum conditions.

Źródło:

Acta Physica Polonica A; 1995, 88, 1; 7-11
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 92.

Tytuł:

Investigation of the Free Volume Changes in Thermally Treated Polyethylene by Positron Annihilation

Autorzy:

Osoba, W.

Powiązania:

https://bibliotekanauki.pl/articles/2008147.pdf

Data publikacji:

1999-04

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

71.60.+z
78.70.Bj

Opis:

Positron lifetimes measurements in polyethylene were performed. Samples of the polyethylene were heated in the temperature range from 320 to 570 K. After cooling, the samples were used for the lifetime measurements in air at room temperature. A conventional fast-slow coincidence lifetime spectrometer was used for the measurements. Mean free volumes radii were calculated from the lifetime data.

Źródło:

Acta Physica Polonica A; 1999, 95, 4; 632-636
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 93.

Tytuł:

Positron Lifetime Measurements of Subsurface Region in Aluminium Alloy and Aluminium Alloy Composite after Dry Sliding

Autorzy:

Dryzek, E.

Powiązania:

https://bibliotekanauki.pl/articles/2043305.pdf

Data publikacji:

2005-05

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

This paper presents positron lifetime studies of the subsurface region of AK12 aluminium alloy and Al$\text{}_{2}$O$\text{}_{3}$-particle-reinforced AK12 aluminium alloy composite after sliding against steel in the pin-on-disc machine. The defect depth profile detected in the AK12 alloy extended up to 300μm but for the composite AK12 the range of this profile was significantly shortened to less than 90μm. The positron lifetime dependence on depth evidences a steep gradient of defect concentration near the surface. The subsurface zones have been also examined using scanning electron microscopy.

Źródło:

Acta Physica Polonica A; 2005, 107, 5; 753-760
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 94.

Tytuł:

Calculation of Positron Response from Embedded Nanoparticles

Autorzy:

Kuriplach, J.

Powiązania:

https://bibliotekanauki.pl/articles/2043318.pdf

Data publikacji:

2005-05

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj
71.60.+z
61.46.+w
81.40.Np

Opis:

Nanoparticles embedded in a matrix can trap positrons under certain conditions. In such cases nanoparticles can be effectively studied by means of positron annihilation because positron annihilation characteristics contain information related to nanoparticles' electronic and atomic structure. Of great importance is to calculate the positron response from such nanoparticles. Then, nanoparticles can, in principle, be identified by comparing the measured and calculated positron annihilation response. For this purpose we present an efficient computational method based on the well-known atomic superposition technique. This method is explained in detail, justified on the basis of first principles calculations, and applied to Cu nanoparticles embedded in the Fe matrix.

Źródło:

Acta Physica Polonica A; 2005, 107, 5; 784-791
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 95.

Tytuł:

Monte Carlo calculations of low energy positrons in silicon

Autorzy:

Aydin, A.

Powiązania:

https://bibliotekanauki.pl/articles/148795.pdf

Data publikacji:

2005

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

Monte Carlo method
positron transmission
backscattering
angular distribution
energy distribution

Opis:

Theoretical data for positron scattering from a thin silicon film and semi-infinite silicon are presented as a function of incident and outgoing angles and energies. These theoretical data of the scattering processes of low energy positrons penetrating into silicon were performed by Monte Carlo simulation. The simulation is based on the use of different types of differential cross sections for individual elastic and inelastic scattering i) inelastic scattering; Gryzinski's excitation function to simulate the energy loss and Liljequist's model to calculate the inelastic scattering cross section, ii) elastic scattering; the screened Rutherford differential cross section with the spin-relativistic factor. In calculations on positron traversing matter, it is important to know the transmission through medium, their path lengths, and their energy and angular distribution through matter. The simulation results are well agreed with experiments.

Źródło:

Nukleonika; 2005, 50, 1; 37-42
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 96.

Tytuł:

Studies of stainless steel exposed to sandblasting

Autorzy:

Horodek, P.
Eseev, M. K.
Kobets, A. G.

Powiązania:

https://bibliotekanauki.pl/articles/147075.pdf

Data publikacji:

2015

Wydawca:

Instytut Chemii i Techniki Jądrowej

Tematy:

stainless steel
sandblasting
defects
positron beam

Opis:

The influence of sandblasting on surface and subsurface of stainless steel is investigated using variable energy positron beam (VEP), positron annihilation spectroscopy (PAS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Samples of stainless steel were blasted using 110 μm particles of Al2O3 under different pressure and time duration. In the case of sandblasting for 90 s, the reduction of positron diffusion length depending on the applied pressure was observed. Sandblasting during 30 s leads only to the reduction of positron diffusion length to about 60 nm for all samples. Positron lifetimes close to 170 ps measured using positrons emitted directly from the source point to the presence of vacancies on the dislocation lines. SEM and AFM images show that surface roughness depends rather on pressure of sandblasting than time of exposition.

Źródło:

Nukleonika; 2015, 60, No. 4, part 1; 721-724
0029-5922
1508-5791

Pojawia się w:

Nukleonika

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 97.

Tytuł:

Electron-Positron Momentum Densities for Electrons from Individual Core Levels

Autorzy:

Rubaszek, A.

Powiązania:

https://bibliotekanauki.pl/articles/2043363.pdf

Data publikacji:

2005-05

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj
71.20.-b
71.60.+z

Opis:

In the present contribution I focus on various effects affecting the slope of calculated electron-positron momentum densities for electrons from individual core shells. In particular, I discuss the influence of positron distribution, of approximation used for the electron-positron correlation functions, as well as of finite apparatus resolution on the resulting spectra.

Źródło:

Acta Physica Polonica A; 2005, 107, 5; 864-867
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 98.

Tytuł:

Methods of Extracting Electron-Positron Enhancement Factors from Experimental ACAR Data

Autorzy:

Kontrym-Sznajd, G.
Rubaszek, A.

Powiązania:

https://bibliotekanauki.pl/articles/1929100.pdf

Data publikacji:

1993-03

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj
71.20.-b

Opis:

Methods of extracting the full shape of the electron-positron momentum density from experimental angular correlation of positron annihilation radiation curves are discussed. The proposed analysis of experimental data allows more reliable verification of the form of electron-positron enhancement factors near the Fermi surface in simple metals.

Źródło:

Acta Physica Polonica A; 1993, 83, 3; 339-344
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 99.

Tytuł:

Use of Energy Summing for Selection of Coincidence Events in Positron-Lifetime Spectroscopy

Autorzy:

Bec̆vár̆, F.
C̆iz̆ek, J.
Procházka, I.

Powiązania:

https://bibliotekanauki.pl/articles/2007883.pdf

Data publikacji:

1999-04

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj

Opis:

A BaF$\text{}_{2}$ positron-lifetime spectrometer equipped with a coincidence system that represents a compromise between the traditional fast-fast and fast-slow arrangements is described. The main difference of the present configuration from both the fast-slow and fast-fast ones consists in use of a sum of the energy signals from the start and stop detectors to select the coincidence events. Quality of the spectrometer response function (≈ 150 ps FWHM for $\text{}^{22}$Na) is very close to that observed for our fast-slow configuration with the equivalent detectors but throughput of the present apparatus is increased almost by a factor of two. Moreover, the electronic scheme becomes less complicated, which has also a positive impact on its cost.

Źródło:

Acta Physica Polonica A; 1999, 95, 4; 448-454
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce

Skocz do pozycji: 100.

Tytuł:

Variable-Energy Positron Annihilation as Highly Sensitive Nanoporosimetry for Porous Thin Films

Autorzy:

Ito, K.
Kobayashi, Y.

Powiązania:

https://bibliotekanauki.pl/articles/2042214.pdf

Data publikacji:

2005-05

Wydawca:

Polska Akademia Nauk. Instytut Fizyki PAN

Tematy:

78.70.Bj
78.55.Mb

Opis:

Positron annihilation was applied to measuring critical pore sizes in various materials. In recent years, positron annihilation with a variable-energy positron beam has emerged as a powerful tool for the investigation of porous thin films synthesized as low-k dielectrics, high performance gas sensor materials, and so on. This paper is a brief overview of recent progress in nanopore characterization of thin films by means of positron annihilation with a description of several important issues relevant to positron annihilation.

Źródło:

Acta Physica Polonica A; 2005, 107, 5; 717-723
0587-4246
1898-794X

Pojawia się w:

Acta Physica Polonica A

Dostawca treści:

Biblioteka Nauki

/5

Artykuł

Zmień widok

• na półce