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Wyświetlanie 1-15 z 286
Tytuł:
Zastosowanie PET/CT w neurologii
PET/CT in neurology
Autorzy:
Cegła, Paulina
Chrapko, Beata
Pietrasz, Katarzyna
Cholewiński, Witold
Powiązania:
https://bibliotekanauki.pl/articles/986633.pdf
Data publikacji:
2019
Wydawca:
Indygo Zahir Media
Tematy:
pozytonowa tomografia emisyjna
neurologia
obrazowanie molekularne
positron emission tomography
neurology
molecular imaging
Opis:
Pozytonowa tomografia emisyjna w połączeniu z tomografią komputerową (positron emission tomography/computed tomography, PET/CT) jest techniką dostarczającą informacji na temat różnych procesów zachodzących w ośrodkowym układzie nerwowym (OUN). Pozwala na ocenę metabolizmu glukozy (18F-fluorodeoksyglukoza, 18F-FDG), układu dopaminergicznego (18F-DOPA) czy wychwytu aminokwasów (18F-fluoroetylotyrozyna, 18F-FET). Celem niniejszej pracy jest omówienie zastosowania techniki PET/CT w zaburzeniach neurologicznych w oparciu o analizę piśmiennictwa.
Positron emission tomography/computed tomography (PET/ CT) is an imaging technique used for assessment of different metabolic processes of central nervous system (CNS). Allows to evaluate glucose metabolism (18F-Fluorodeoxyglucose, 18F-FDG), dopaminergic pathway integrity (18F-dihydroxyphenylalanine, 18F-DOPA) and amino acid uptake (18F-fluoroethylo-thyrosine, 18F-FET). The aim of this review is to discuss the usefulness of the PET/CT method in the neurological disorders based on literature review.
Źródło:
Inżynier i Fizyk Medyczny; 2019, 8, 2; 79-83
2300-1410
Pojawia się w:
Inżynier i Fizyk Medyczny
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Water-Sorption Effects near Grain Boundaries in Modified MgO-Al₂O₃ Ceramics Tested with Positron-Positronium Trapping Algorithm
Autorzy:
Klym, H.
Ingram, A.
Shpotyuk, O.
Hadzaman, I.
Chalyy, D.
Powiązania:
https://bibliotekanauki.pl/articles/1030933.pdf
Data publikacji:
2018-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Je
07.07.Df
Opis:
Water-sorption processes near grain boundaries in the MgO-Al₂O₃ ceramics prepared at different temperatures were studied using positron annihilation lifetime spectroscopy. Numerical values of three- and four-component treatment of spectra were used for study of physical- and chemical-sorption processes in the MgO-Al₂O₃ ceramics. To apply mathematical approach in the form of positron-positronium trapping algorithm into three-component treatment of positron annihilation lifetime spectra it was shown that physical-adsorbed water did not modify positron trapping sites near grain boundaries in water-immersed MgO-Al₂O₃ ceramics and localized mainly in nanopores. The chemically-adsorbed water modifies structural extended defects located near grain boundaries that accompanied them by void fragmentation at water desorption.
Źródło:
Acta Physica Polonica A; 2018, 133, 4; 864-868
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Water Sorption and Dessiccation in a Portland Cement Paste: Positron Annihilation Results
Autorzy:
Consolati, G.
Dotelli, G.
Quasso, F.
Powiązania:
https://bibliotekanauki.pl/articles/2024222.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
71.60.+z
81.05.Rm
Opis:
Positron annihilation experiments were carried out on a Portland cement paste one year aged, which was subjected to cycles of dessiccation and subsequent water resaturation, in order to study possible changes of the porosity. Analysis of the annihilation time spectra suggests that drying and rewetting treatments do not induce irreversible modifications in the configuration of the finest gel pores.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 345-349
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vickers Hardness and Positron Annihilation Study of Eurofer97 and ODS Eurofer
Autorzy:
Bartošová, I.
Čížek, J.
Lukáč, F.
Slugeň, V.
Powiązania:
https://bibliotekanauki.pl/articles/1196045.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
28.52.Fa
Opis:
This paper describes investigations of Eurofer97 and oxide dispersion strengthened version of this steel, in as received state and after annealing. Vickers hardness test was performed on the as received specimens and after annealing at various temperatures to obtain information about development of the strength of studied materials. After identifying the temperature region where significant changes of the strength take place we applied positron annihilation spectroscopy to probe the microstructural changes in ferritic/martensitic steels. An observation of phase transformation was observed in both steels at various temperatures indicating different behaviour of the base material and its strengthened version. All applied methods proved the importance of strengthening by oxides to improve properties of steels.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 702-705
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
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
Artykuł
Tytuł:
Vacancy Cluster Distributions in He Implanted Silicon Studied by Slow Positron Annihilation Spectroscopy
Autorzy:
Brusa, R. S.
Powiązania:
https://bibliotekanauki.pl/articles/2007921.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
78.70.Bj
71.55.Cn
Opis:
Doppler broadening measurements performed by a slow positron beam on p-type Si samples implanted with He at 20 keV and at a fluence of 5×10$\text{}^{15}$ and 2×10$\text{}^{16}$ cm$\text{}^{-2}$ are reviewed and discussed. The evolution of the open volume defects distribution was studied as a function of isochronal and isothermal annealing of the samples. In the as implanted samples the majority of the open volume defects produced by implantation was passivated by He. The open volume defects density decreases, reaching a minimum at 250°C. In the 250-650°C temperature range there is an increase in defects due to the appearance of vacancy clusters. At the higher annealing temperatures (700-900°C) the vacancy clusters disappear only in the samples implanted at 5×10$\text{}^{15}$ cm$\text{}^{-2}$.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 474-478
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Using a Bent Tube as an Energy Filter for a Positron Beam. Simulations on Determining the Optimum Angle of the Bend
Autorzy:
Dinescu, D.
Djourelov, N.
Powiązania:
https://bibliotekanauki.pl/articles/1033242.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
41.75.Fr
78.70.Bj
Opis:
One way to perform lifetime measurements at a DC positron beam is to pass positrons through a pulsing device. The compressed e⁺ bunches are accelerated to a desired energy for depth profiling of the studied sample. A fraction of the e⁺ that are backscattered from the sample surface can travel back through the uniform magnetic field that is generated along the central axis of the beam transport lines and reach the accelerator. The backscattered e⁺ that reach the accelerator can be re-accelerated towards the sample and re-implant in it with a delay from the initial implanted e⁺ bunch. These e⁺ that are re-implanted into the sample with a delay cause distortions in the lifetime spectra. A setup which uses a bent tube to act as an energy filter to reduce the effect of the backscattered e⁺ is studied by simulations. The simulations are performed in order to find the optimum geometry for minimum distortions.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1624-1627
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
Tytuł:
Ultramarine, Lazurite and Sodalite Studied by Positron Annihilation and EPR Methods
Autorzy:
Baranowski, A.
Dębowska, M.
Jerie, K.
Jezierski, A.
Sachanbiński, M.
Powiązania:
https://bibliotekanauki.pl/articles/1933463.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
78.70.-g
61.90.+d
76.30.-v
Opis:
Studies of positron annihilation accompanied by EPR technique were undertaken for sodalite and lazurite and their synthetic counterparts (synthetic sodalite and ultramarines). Results of measurements performed by two techniques of positron annihilation spectroscopy (angular correlation of annihilation radiation, ACAR, and positron annihilation lifetime) revealed the undoubted influence of free radicals on positron annihilation mechanism but both inhibition of positronium formation by them and the effect of filling cages ought to be taken into account. The distinct differences between ACAR curves for sodalites, lazurites and ultramarines probably reflect the presence of different radicals in their cages and chemical heterogeneity as well as the disorder in Al, Si-site ordering in case of ultramarines. Comparison of the results of ACAR measurements with the ones of the EPR studies indicates that there is correspondence between them. Similarly to three families of the ACAR curves, different likes of EPR lines were obtained for three groups of samples; sodalites, lazurites and ultramarines. It is possible that the annihilation of positrons takes place mainly with unpaired electrons recorded by the EPR technique.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 29-41
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultra Fine-Grained Metals Prepared by Severe Plastic Deformation: A Positron Annihilation Study
Autorzy:
Čížek, J.
Procházka, I.
Kužel, R.
Matĕj, Z.
Cherkaska, V.
Cieslar, M.
Smola, B.
Stulíková, I.
Brauer, G.
Anwand, W.
Islamgaliev, R. K.
Kulyasova, O.
Powiązania:
https://bibliotekanauki.pl/articles/2043303.pdf
Data publikacji:
2005-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
79.60.Jv
Opis:
Recent investigations of ultra fine-grained metals (Cu, Fe, Ni) performed within a Prague-Rossendorf-Ufa collaboration will be reviewed. The specimens were prepared by severe plastic deformation: the high-pressure torsion and equal channel angular pressing. Positron annihilation spectroscopy was used as the main method including (i) the conventional lifetime and the Doppler broadening measurements with $\text{}^{22}$Na and (ii) the slow-positron implantation spectroscopy with the Doppler broadening measurement. Other methods were also involved: transmission electron microscopy, X-ray diffraction, and microhardness. First, the mean grain size was determined and defects were identified in the as-deformed materials. Defects concentration and spatial distribution were studied in detail. Dislocations situated in distorted regions along grain boundaries, and a few-vacancy clusters distributed homogeneously inside dislocations-free grains, were observed in the ultra fine-grained Cu, Fe, and Ni. Subsequently, the thermal evolution of the ultra fine-grained structures during isochronal annealing was studied.
Źródło:
Acta Physica Polonica A; 2005, 107, 5; 745-752
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Two-Component Density Functional Study of Positron-Vacancy Interaction in Metals and Semiconductors
Autorzy:
Ishibashi, S.
Powiązania:
https://bibliotekanauki.pl/articles/1033953.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
78.70.Bj
61.72.jd
Opis:
The positron-vacancy interaction in metals and semiconductors has been studied by the two-component density-functional-theory formalism. If a positron is not trapped at the vacancy, atoms surrounding the vacancy show inward relaxation for most cases except for nitrides, where outward relaxation is observed. The presence of positron suppresses the inward relaxation. Positron lifetimes have been calculated with and without the positron effect. The difference between two lifetime values is investigated in relation to the bulk modulus.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1602-1605
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Track Effects in Positronium Formation
Autorzy:
Stepanov, S.
Byakov, V.
Duplâtre, G.
Stepanov, P.
Bokov, A.
Powiązania:
https://bibliotekanauki.pl/articles/1030026.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
positron
positronium
annihilation
ion-electron recombination
solvation
mobility
external electric field
track effects
polar and nonpolar liquids
Opis:
We discuss some aspects important for interpretation of the Ps formation process in liquids and molecular media: (1) inhomogeneity of intratrack reactions and parameters of the e⁺ track, (2) final states of e⁺, its solvation in polar and nonpolar liquids, relation to e⁺ mobility, (3) quasi-neutrality of the e⁺ blob and its ambipolar outdiffusion, (4) appearance of the "in-blob" and "out-of-the-blob" positron fractions, and (5) electric field effect on Ps formation.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1461-1465
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 286

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