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Tytuł:
The Evidence of Quasi-Free Positronium State in GiPS-AMOC Spectra of Glycerol
Autorzy:
Zvezhinskiy, D.
Butterling, M.
Wagner, A.
Krause-Rehberg, R.
Stepanov, S.
Powiązania:
https://bibliotekanauki.pl/articles/1196485.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
82.30.Gg
34.80.-i
34.80.Lx
Opis:
We present the results of processing of age-momentum correlation spectra that were measured for glycerol by the gamma-induced positron spectroscopy facility. Our research has shown that the shape of experimental s(t) curve cannot be explained without introduction of the intermediate state of positronium (Ps), called quasi-free Ps. This state yields the wide Doppler line near zero lifetimes. We discuss the possible properties of this intermediate Ps state from the viewpoint of developed model. The amount of annihilation events produced by quasi-free Ps is estimated to be less than 5% of total annihilations. In the proposed model, quasi-free Ps serves as a precursor for trapped Ps of para- and ortho-states.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 821-824
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Studies of Fractal Aspects of Cement
Autorzy:
Janik, J. A.
Kurdowski, W.
Podsiadły, R.
Samseth, J.
Powiązania:
https://bibliotekanauki.pl/articles/1952755.pdf
Data publikacji:
1996-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.12.Ex
82.70.Gg
Opis:
Small angle neutron scattering can be used to reveal the fractal nature of matter. The problems of fractal aspects of the structure of cement are related to those of fractal aspects of silica aerogels. Natural cement, when mixed with water, transforms after a series of chemical reactions (in a large part) into an amorphous phase called C-S-H. It is believed that the cationic sublattice composed of CaO$\text{}_{6}$ octahedrons constitutes the C-S-H structural basis, to which the SiO$\text{}_{4}$ tetrahedral chains are attached. It is a layer structure in which the cation sublattice determines the way of SiO$\text{}_{4}$ condensation. It is natural to expect that in this way one may obtain a really amorphous substance, since some tetrahedrons may be lacking, which leads to defects. We present here the results of a small angle neutron scattering and X-ray diffraction study of several samples with the pure C-S-H phase for which during the process of chemical synthesis various ratios of molar contents of CaO and SiO$\text{}_{2}$ were used (various C/S ratios). We obtained a gradual change of fractal characteristics with the change of C/S ratio.
Źródło:
Acta Physica Polonica A; 1996, 90, 6; 1179-1184
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sol-Gel Derived Lanthanide-Substituted Layered Double Hydroxides $Mg_3//Al_{1-x}Ln_{x}$
Autorzy:
Smalenskaite, A.
Şen, S.
Salak, A.
Ferreira, M.
Beganskiene, A.
Kareiva, A.
Powiązania:
https://bibliotekanauki.pl/articles/1398236.pdf
Data publikacji:
2018-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.66.Fd
82.70.Gg
82.33.Ln
71.20.Eh
78.55.Hx
Opis:
Mg/Al/Ln (Ln = Nd, Sm, Eu) layered double hydroxides (LDHs) were synthesized using sol-gel method for the first time to the best our knowledge. The obtained materials were characterized by X-ray diffraction analysis and fluorescence spectroscopy. The phase composition and luminescent properties of these LDHs were investigated and discussed. The Ln³⁺ substitution effects were investigated in the $Mg_3Al_{1-x}Ln_{x}$ LDHs by changing the Ln³⁺ concentration in the metal cation layers up to 10 mol%. It was demonstrated that only $Mg_3Al_{1-x}Eu_{x}$ LDHs showed luminescence properties, however, no any light emission was observed for the $Mg_3Al_{1-x}Nd_{x}$ and $Mg_3Al_{1-x}Sm_{x}$ LDH samples.
Źródło:
Acta Physica Polonica A; 2018, 133, 4; 884-886
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positrons and Positronium Atoms in a Condensed Phase Close to Its Melting Point
Autorzy:
Stepanov, S.
Zvezhinskiy, D.
Byakov, V.
Duplâtre, G.
Stepanov, P.
Powiązania:
https://bibliotekanauki.pl/articles/1196038.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
34.80.Lx
78.70.Bj
82.30.Gg
Opis:
Investigation of the local heating effect at the terminal part of a fast positron track sheds light on the accumulation of defects in a frozen medium close to its melting point. Estimations of the formation energies of the structural defects which may trap the Ps atom as well as a contribution of these defects to the enthalpy of fusion are obtained.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 691-695
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positronium Formation in Organic Liquids
Autorzy:
Karbowski, A.
Fedus, K.
Służewski, K.
Bruzdowska, J.
Karwasz, G.
Powiązania:
https://bibliotekanauki.pl/articles/1030028.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
82.30.Gg
36.10.Dr
Opis:
This paper reports on the results of positron annihilation lifetime measurements of three organic liquids: benzene (C₆H₆), cyclohexane (C₆H₁₂), and methanol (CH₃OH). The lifetime spectra are acquired at different temperatures for non-degassed, degassed, and oxygen-saturated samples, at temperatures between 5°C and 25°C. The spectra are analyzed using a standard three-exponential model. The influence of oxygen on each lifetime and intensity component is discussed.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1466-1469
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation Lifetime Analysis of Left- and Right-Handed Alanine Single Crystals
Autorzy:
Eren, B.
Wu, F.
Eren, E.
Jean, Y.
Van Horn, J.
Powiązania:
https://bibliotekanauki.pl/articles/1030024.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
82.30.Gg
34.80.-i
87.15.B-
Opis:
Studies of the interaction of polarized light or particles (including electrons, e¯, or positrons, e⁺) with asymmetric forms of matter has been of interest to scientists since the discovery of chirality and the subsequent development of particle physics. Researchers have been interested in e⁺ interactions with chiral molecules for decades, but with mixed and indecisive results. After reviewing the field, we speculated that the e⁺ or positronium (Ps) might interact differently with chiral pairs of large single crystals, i.e., the left-handed or right-handed asymmetric forms of the crystals - and subsequently observed significant differences in "free positron" annihilation and intensities in the evaluation of left-handed or right-handed quartz single crystals. This result may be understood to be a "particle stereorecognition" phenomenon. To extend this line of inquiry we crystallized mm scale L- or D-alanine crystals and performed positron annihilation lifetime spectroscopy measurements using a ²²Na positron source. Alanine crystals were obtained via slow evaporation of water in a Dewar, or from water/acetone solvent in a temperature-controlled environment. These methods resulted in small ( ≈0.5 cm/side) or large ( ≥1.0 cm/side) crystals, respectively. While some intensity (I₂) results from left-handed and right-handed crystals varied in positron annihilation lifetime spectroscopy analysis, the errors associated with the measurements do not indicate a stereorecognition of alanine via positron interactions.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1456-1460
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron and Positronium Annihilation in Polymers Studied by Age-Momentum Correlation Spectroscopy
Autorzy:
Sato, K.
Murakami, H.
Ito, K.
Hirata, K.
Kobayashi, Y.
Powiązania:
https://bibliotekanauki.pl/articles/1812549.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
78.70.Bj
82.30.Gg
42.70.jk
Opis:
Positron (e⁺) and positronium (Ps) annihilation processes in polymers are studied by positron age-momentum correlation spectroscopy, which can sensitively probe momentum distributions of e⁺, p-Ps, and o-Ps. For polyether sulfone and ethylene tetrafluoroethylene copolymer belonging to oxygen-containing polymers (O group) and fluorine-containing polymers (F group), respectively, significant effects of positron trapping by polar element are observed. The Doppler profile of o-Ps pick-off annihilation is strongly influenced by F atoms, giving rise to anomalous broadening. The results are discussed together with our previous data of the S-I₃ correlation in order to explore the feasibility of chemical analysis around the free volumes by age-momentum correlation spectroscopy.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1511-1516
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Microstructure and Dynamics of Magnetic Iron Nanoparticles Aggregates in Protein Gels
Autorzy:
Konik, K.
Fornal, P.
Okła, D.
Stanek, J.
Powiązania:
https://bibliotekanauki.pl/articles/1490101.pdf
Data publikacji:
2012-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.75.Jn
83.60.Np
61.25.H-
82.70.Gg
Opis:
The 60 nm metallic iron nanoparticles and its aggregates in gelatine gel were studied by means of optical microscopy, X-ray microtomography, atomic force scanning microscopy and the Mössbauer spectroscopy. The isolated nanoparticles in gel exhibit fast bounded diffusion described by Brownian movement. In the external magnetic field these magnetic particles form spectacular linear aggregates whose local dynamical and magnetic properties were determined from the Mössbauer spectra.
Źródło:
Acta Physica Polonica A; 2012, 121, 2; 457-463
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Is a Molecular Adiabatic Approximation Appropriate to Positronic Atoms and Molecules?
Autorzy:
Mohallem, J.
Powiązania:
https://bibliotekanauki.pl/articles/1812542.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.-k
36.10.Dr
78.70.Bj
82.30.Gg
Opis:
The adiabatic approximation to positronic atoms and molecules was considered as an option to the computationally unfeasible methods that treat all particles in a common footing, in two different approaches communicated in the 37th PSPA. Here we present further assessment and comparison of the two approaches as a way of evaluating the potential of adiabatic or, as we found preferable, molecular approaches.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1465-1469
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
IR and Raman Investigation of Some Poly(acrylic) Acid Gels in Aqueous and Neutralized State
Autorzy:
Todica, M.
Stefan, R.
Pop, C.
Olar, L.
Powiązania:
https://bibliotekanauki.pl/articles/1402342.pdf
Data publikacji:
2015-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
82.70.Dd
82.70.Gg
82.70.Kj
Opis:
The modification of local polymeric conformation of poly(acrylic) acid (PAA), induced by hydration and neutralization with triethanol amine (TEA), was investigated by IR and Raman spectroscopy. The effect of water is the perturbation of hydrogen bonds established between different polymeric chains and the modification of the local conformation of the polymer. The neutralization with TEA affects the carboxylic groups and modifies the local conformation of the polymer. These modifications are correlated with the shift and the modification of the characteristics of IR and Raman spectra.
Źródło:
Acta Physica Polonica A; 2015, 128, 1; 128-135
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hydrodynamic Memory in the Motion of Charged Brownian Particles across the Magnetic Field
Autorzy:
Tóthová, J.
Lisý, V.
Powiązania:
https://bibliotekanauki.pl/articles/1535477.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.40.Jc
05.10.Gg
75.47.-m
82.70.Dd
Opis:
An exact solution of the Langevin equation is given for a charged Brownian particle driven in an incompressible fluid by the magnetic field, taking into account the hydrodynamic aftereffect. The stochastic integro-differential Langevin equation is converted to a deterministic equation for the particle mean square displacement. We have found the mean square displacement and other time correlation functions describing the particle motion. For the motion along the field the known results from the theory of the hydrodynamic motion of a free Brownian particle are recovered. The correlation functions across the field contain at long times the familiar Einstein terms and additional algebraic tails. The longest-lived tail in the mean square displacement is proportional to $t^{1//2}$. At short times the motion is ballistic and independent of the magnetic field.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 1051-1053
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hydration of Hydroxypropylmethyl Cellulose: Effects of pH and Molecular Mass
Autorzy:
Tritt-Goc, J.
Kowalczuk, J.
Piślewski, N.
Powiązania:
https://bibliotekanauki.pl/articles/2043541.pdf
Data publikacji:
2005-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
82.70.Gg
76.60.Pc
Opis:
Magnetic resonance imaging was used to study the diffusion of a water solution of hydrochloric acid (HCl) and sodium hydrochloride (NaOH) into hydroxypropylmethyl cellulose matrices. Polymer in the form of a cylinder was hydrated in a water solvent of pH = 2, 7, and 12 at 37ºC and monitored at equal intervals with a 300 MHz Bruker AVANCE. The spatially resolved spin-spin relaxations times and spin densities, along with a change in the dimension of the glass core of the polymer were determined for hydroxypropylmethyl cellulose tablets as a function of hydration times. The data showed the effects of the pH solvent and of the molecular mass of the polymer on the swelling process, spin-spin relaxation time, and diffusion of solvent molecules into hydroxypropylmethyl cellulose matrices. The time dependence of the diffusion front, effective T$\text{}_{2}$, and proton-density ρ analysis clearly indicate a case II diffusion mechanism in the system composed of a water solution of hydrochloric acid (pH = 2) and hydroxypropylmethyl cellulose, whereas in the case of water solutions with pH = 7 and 12 the anomalous and case I diffusion are observed, respectively.
Źródło:
Acta Physica Polonica A; 2005, 108, 1; 197-205
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Gelation Process of Toluene-Based bis-Urea in Cyclohexane Studied with Magnetic Resonance Imaging
Autorzy:
Tritt-Goc, J.
Boguszyńska, J.
Szwaj, M.
Boutellier, L.
Jadżyn, J.
Powiązania:
https://bibliotekanauki.pl/articles/2043392.pdf
Data publikacji:
2005-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
82.70.Gg
76.60.Pc
82.56.Lz
82.56.Na
Opis:
Magnetic resonance imaging was used for studies of the gelation and swelling processes of toluene-based bis-urea prepared in a form of cylindrical tablet and immersed in cyclohexane. The processes were investigated with the use of Bruker AVANCE (300 MHz) spectrometer equipped with a micro imaging probe head. The images were taken for cyclohexane protons within the bis-urea gel formed around the sample dry core at different intervals of the immersion. The mobility of the solvent molecules was estimated from the spatially resolved distribution of the spin-spin relaxation time T$\text{}_{2}$ and the spin densitiesρ, calculated on the basis of the images obtained. It was shown that the time-evolution of the thickness of the gel layer can be well described by the power equation with an exponent equal to 0.47 (±0.04), indicating the Fickian nature of the diffusion of cyclohexane molecules.
Źródło:
Acta Physica Polonica A; 2005, 108, 1; 81-87
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Free-Volume Studies in Polycaprolactone/Poly(propylene oxide) Urethane/Urea Membranes by Positron Lifetime Spectroscopy
Autorzy:
Ferreira Marques, M.
Gordo, P.
de Lima, A.
Queiroz, D.
Norberta de Pinho, M.
Major, P.
Kajcsos, Zs.
Powiązania:
https://bibliotekanauki.pl/articles/1812490.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.41.+e
78.70.Bj
82.30.Gg
Opis:
Positron annihilation lifetime spectroscopy was used to study the free volume parameters in polypropylene oxide-based tri-isocyanate terminated prepolymer/polycaprolactone diol bi-soft urethane/urea membranes (PU/PCL) with PCL content from 5 up to 25 wt%. Positron annihilation lifetime spectroscopy measurements carried out in the temperature range 298-324 K mirrored the phase separation of the various soft and hard segments present in the membranes. The size and amount of free volume holes determined by positron annihilation lifetime spectroscopy appear to be correlated with the $CO_2$ gas permeability through the membranes.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1359-1364
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fractal Structure of C-S-H and Tobermorite Phases
Autorzy:
Janik, J. A.
Kurdowski, W.
Podsiadły, R.
Samseth, J.
Powiązania:
https://bibliotekanauki.pl/articles/2028897.pdf
Data publikacji:
2001-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.12.Ex
82.70.Gg
Opis:
The C-S-H I phase is the main component of the cement paste, which is a near-amorphous, highly porous gel. Due to high porosity of the sample in this phase we can observe a fractal nature of the volume pores distribution, similar to that observed for silica aerogels. The C-S-H I phase is thermodynamically unstable and crystallize to a tobermorite phase, forming crystal aggregates on the surface of the amorphous paste. The mixture of these two phases, formed in this way, have irregular volume and surface structures, both of which may exhibit the fractal nature. To study the fractal nature of the matter the small angle neutron scattering method is frequently used. We present here the results of small angle neutron scattering studies supported by the X-ray diffraction and scanning electron microscope observations of several samples with the common molar C/S ratio equal to 1. Some of the samples were autoclaved during various time periods to accelerate transformation of the C-S-H I phase to tobermorite. We observed the fractal properties of the volume structure of all samples under study. Moreover, we observed also the fractal behaviors of the surfaces of the samples which were autoclaved.
Źródło:
Acta Physica Polonica A; 2001, 100, 4; 529-537
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 24

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