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Wyszukujesz frazę "61.30.-v" wg kryterium: Temat


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:
Thermal Stability of Bent-Core Liquid Crystals Doped with Magnetic Nanoparticles
Autorzy:
Juríková, A.
Csach, K.
Miškuf, J.
Tomašovičová, N.
Mitróová, Z.
Závišová, V.
Koneracká, M.
Kopčanský, P.
Timko, M.
Éber, N.
Fodor-Csorba, K.
Vajda, A.
Powiązania:
https://bibliotekanauki.pl/articles/1387994.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
64.70.mj
65.80.-g
Opis:
In the work phase transitions in bent-core liquid crystals were studied using differential scanning calorimetry. For the binary mixture of bent-core molecules with 50 wt% of rod-shaped compound, the nematic to smectic transition occured below 40°C and the crystallization temperature shifted to sub-ambient temperatures. The influence of doping of the bent-core liquid crystals with magnetic nanoparticles on the kinetics of observed phase transitions was studied. The phase transition temperatures were shifted depending on the nanoparticle type and changed with varying cooling rate for all studied liquid crystal samples.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 638-640
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical Study of the Effect of Light on Nematic to Isotropic Phase Transition
Autorzy:
Suresha, B.
Radhakrishna, M.
Govind, A.
Powiązania:
https://bibliotekanauki.pl/articles/1493611.pdf
Data publikacji:
2011-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
64.70.M-
Opis:
Optical response of liquid crystals is very important from the point of view of applications of liquid crystals in display and data storage devices. Experiments have shown that UV rays incident on nematic liquid crystals doped with photoactive azo compounds lower the nematic isotropic transition temperature $(T_{NI})$. This is attributed to the transformation of photoactive trans isomer to cis isomer due to UV rays. We have earlier developed a mean field model involving molecular explanation for two lengths in which the mutual orientation of near neighbor molecules changes from an antiparallel to a parallel configuration as the temperature lowered. In this paper, this model is extended to include the length change from trans to cis isomer. The calculated values of change in $T_{NI}$ qualitatively agree with experimental trends.
Źródło:
Acta Physica Polonica A; 2011, 120, 3; 462-467
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical study of nematic to isotropic transition in porous media
Autorzy:
Govind, A.
Banerjee, Kumarii
Powiązania:
https://bibliotekanauki.pl/articles/1075553.pdf
Data publikacji:
2016-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
61.30.Cz
64.70.M-
61.30.Pq
Opis:
Experimental observations show that the N-I transition temperature (T_{NI}) for liquid crystals embedded in solid porous materials is lower compared to that of the bulk liquid crystals and T_{NI} is reduced linearly with the inverse pore diameter. To explain this, various theoretical studies have been proposed. We propose to use the mean field approach. We modify the Maier-Saupe mean field theory to include the disordering effects of porosity as a disordering surface potential. A molecule near the surface is assumed to feel the mean field potential (the Maier-Saupe type) and also the surface induced potential. We calculate the values of the nematic order parameter and hence find the T_{NI} for different pore diameters. The weighted average of the order parameter is calculated considering the cylindrical symmetry of the pores. Our calculations on the variation of T_{NI} with pore diameter agree with experimental data. Also, the calculated values of specific heat peak decrease with decrease in pore radius, in agreement with experimental trends.
Źródło:
Acta Physica Polonica A; 2016, 130, 3; 748-750
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical Explanations of the Optical Band Positions and Local Structure for $Cu^{2+}$ Centers in $ZnO-Bi_{2}O_{3}-B_{2}O_{3}-CuO$ Glasses
Autorzy:
Yuan, M.
Powiązania:
https://bibliotekanauki.pl/articles/1377767.pdf
Data publikacji:
2014-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.72.Bb
75.10.Dg
76.30.-v
76.30.Fc
Opis:
The local structure, two optical band positions and three electronic spin resonance parameters for $Cu^{2+}$ centers at the tetragonally-distorted octahedral sites in $ZnO-Bi_2O_3-B_2O_3-CuO$ glasses are calculated from the high-order perturbation method based on the two-spin-orbit-parameter model, where the contributions from both the spin-orbit coupling parameters of central $d^{n}$ ion and ligand ion are included. The theoretical results are in good agreement with the experimental values. The calculations show that the high-order perturbation method based on the two-spin-orbit-parameter model is effective in the explanations of optical spectra, electronic spin resonance parameters and local distortion structure for $d^{9}$ ions in glasses.
Źródło:
Acta Physica Polonica A; 2014, 126, 6; 1293-1295
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Role of Ferric(III) Oxide in Poly-(1,4-Phenylene Sulphide) Curing. EPR and X-ray Studies
Autorzy:
Wejchan-Judek, M.
Hoffmann, S. K.
Goslar, J.
Garbarczyk, J.
Powiązania:
https://bibliotekanauki.pl/articles/2043404.pdf
Data publikacji:
2005-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.30.-v
61.41.+e
Opis:
Commercially available poly-(1,4-phenylene sulfide) = PPS with trade names TEDUR and RYTON contain a great amount of Fe(III) (order of 10$\text{}^{20}$ Fe/gram) as shown by electron spin resonance spectra. The curing of the pure and Fe-doped (0.2% Fe$\text{}_{2}$O$\text{}_{3}$) PPS polymers proves that Fe(III) can be used for improvement of the PPS strength by increasing the polymer cross-linking and a decrease in the polymer crystallinity degree as shown by X-ray diffraction.
Źródło:
Acta Physica Polonica A; 2005, 108, 1; 107-112
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin Hamiltonian parameters for Co²⁺ ions in PbMoO₄ crystal - interplay between the fictitious spin S=1/2 and the effective spin S̃ =3/2
Autorzy:
Piwowarska, D.
Kaczmarek, S.
Gnutek, P.
Rudowicz, C.
Powiązania:
https://bibliotekanauki.pl/articles/1055009.pdf
Data publikacji:
2017-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Dg
71.70.Ch
61.50.Ah
61.72.Hh
76.30.-v
76.30.Fc
Opis:
The interplay between the fictitious spin S' = 1/2 and the effective spin S̃=3/2 for Co²⁺(3d⁷) ions is considered. The available experimental data on the Ze g_{i}' factors for the two Co²⁺ complexes in PbMoO₄ obtained using the fictitious "spin" S'=1/2 description serve for determination of the Zeeman g_{i} factors corresponding to the effective spin S̃ =3/2. The second-rank zero-field splitting parameters D and E (S̃ = 3/2) are also indirectly determined from the experimental EMR data by employing the formulas arising from projection of the g_{i}(S̃=3/2) factors onto the g_{i}'(S' = 1/2) factors. The so-determined second-rank zero-field splitting parameters and g_{i}(S̃ = 3/2) factors will enable comparison with the respective quantities obtained in a subsequent paper using a combined modeling approach.
Źródło:
Acta Physica Polonica A; 2017, 132, 1; 73-76
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Singular Elastic Properties of Mixtures with the Re-entrant Nematic Phase
Autorzy:
Czechowski, G.
Jadżyn, J.
Powiązania:
https://bibliotekanauki.pl/articles/2038376.pdf
Data publikacji:
2004-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.70.Md
62.20.Dc
61.30.-v
Opis:
The paper presents temperature behavior of the splay and bend elastic constants measured for n-hexyloxycyanobiphenyl and n-octyloxycyanobiphenyl mixtures - a system exhibiting the re-entrant nematic phase. It was shown that singularities in the elastic properties of the system concern not only the nematic phase (the well-known pre-smectic effects) but first of all - the smectic A phase, in which the splay and bend deformations, normally not allowed for the layered structures, can be induced.
Źródło:
Acta Physica Polonica A; 2004, 106, 4; 475-485
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Refractive Indices, Order Parameter and Optical Transmittance Studies of a Nematic Liquid Crystal Mixture
Autorzy:
Singh, A. K.
Manohar, R.
Shukla, J. P.
Biradar, A. M.
Powiązania:
https://bibliotekanauki.pl/articles/2047089.pdf
Data publikacji:
2006-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
42.70.Df
Opis:
Measurements of ordinary refractive index, birefringence, density, and order parameter were made on a technologically important nematogen and the data obtained for its nematic and isotropic phase were reported. A modified wedge method was used for the measurement of the birefringence (δ n). The nematic-isotropic phase transition temperature matches very well as is exhibited from the value of refractive indices and densities obtained using different techniques. The optical anisotropy and density data were used to determine the order parameter and principal polarizability of the nematic mixture using the Vuks approach and their temperature dependence was discussed. The macroscopic order parameter was obtained and compared with microscopic order parameter. These two values agree very well.
Źródło:
Acta Physica Polonica A; 2006, 110, 4; 485-493
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Physical Studies of Cyclohexane Derivatives
Autorzy:
Murthy, Y. N.
Ramanaiah, M. V.
Murthy, V. R.
Powiązania:
https://bibliotekanauki.pl/articles/2012947.pdf
Data publikacji:
2000-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
Opis:
Mean molecular polarizabilities, polarizability anisotropies and order parameters of two homologous series of cyclohexane derivatives namely trans-4-alkyl cyclohexyl 4'-cyanophenyl ester and trans-4-alkyl cyclohexyl 4'-n-pentyloxy phenyl ester are evaluated using molecular vibration approach. The variation of polarizability and polarizability anisotropy with a number of carbon atoms in the alkyl chain is studied. In addition, the dependence of order parameter on temperature is reported and discussed.
Źródło:
Acta Physica Polonica A; 2000, 97, 2; 315-322
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Physical Studies of Binary Mesophase Mixtures Containing N-(p-Propoxy Benzylidene)-p-Pentylaniline
Autorzy:
Ranga Reddy, R. N. V.
Reddy, K. C.
Murthy, V. R.
Powiązania:
https://bibliotekanauki.pl/articles/1931627.pdf
Data publikacji:
1994-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
35.20.My
61.30.-v
Opis:
The applicability of the modified Lippincott δ-function model method is tested for binary mesophase mixtures. Using this method, the polarizabilities, polarizability anisotropies and order parameters of binary mesophase mixtures containing N-(p-propoxy-benzylidene)-p-pentylaniline are evaluated and compared with the reported values. A close agreement is observed between the estimated values and reported values.
Źródło:
Acta Physica Polonica A; 1994, 86, 3; 385-391
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimization of Antioxidant Properties of Creams with Berry Extracts by Artificial Neural Networks
Autorzy:
Makarova, K.
Zawada, K.
Wagner, D.
Skowyra, J.
Powiązania:
https://bibliotekanauki.pl/articles/1030222.pdf
Data publikacji:
2017-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
07.05.Mh
33.35.+r
61.72.Hh
76.30.-v
87.64.kh
87.80.Lg
Opis:
Oxidative stress and the excess of free radicals accelerate the ageing process of human skin. The application of skin cream with antioxidant compounds could reduce the damage caused by free radicals. In this work we studied two types of skin creams with extracts from aronia (Aronia melanocarpa), elderberry (Sambucus nigra) and bilberry (Vaccinium myrtillus) because of their high content of anthocyanins, i.e. strong natural antioxidants. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability of the skin creams with berry extracts were studied with ESR spectroscopy. The artificial neural networks were applied to optimize the berry extract concentration and storage time for oil-in-water and water-in-oil creams. Based on experimental results chokeberry and elderberry extracts in oil-in-water cream base revealed higher DPPH radical scavenging ability than in the corresponding water-in-oil. Artificial neural networks predicts maxima of DPPH radical scavenging for 1-week stored elderberry (2.23 mg DPPH/g) and 1-week stored chokeberry (5.84 mg DPPH/g) and bilberry (5.26 mg DPPH/g) 0.76% extracts in oil-in-water creams. The maxima of DPPH radical scavenging for water-in-oil creams were predicted for 6-week stored 0.8% aronia extract, freshly prepared 0.76% bilberry extract and 1-week stored 0.56% elderberry extract. The artificial neural networks predicted values are in good agreement with the experimental values. DPPH-EPR could be combined with artificial neural networks to optimize the extract concentration, and the type of cream base as well as to predict the effect of storage based on a limited number of experiments and samples.
Źródło:
Acta Physica Polonica A; 2017, 132, 1; 44-51
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Molecular Vibration Approach to Polarizabilities of Methyl Cinnamate Liquid Crystal Compounds
Autorzy:
Murthy, Y. N.
Murthy, V. R.
Ranga Reddy, R. N. V.
Powiązania:
https://bibliotekanauki.pl/articles/1964211.pdf
Data publikacji:
1997-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
Opis:
A new theoretical method of evaluating polarizabilities of liquid crystals is presented and applied to the liquid crystalline compounds, namely n-alkyl-p-(4-ethoxy benzylidene amino)-α-methyl cinnamates, which exhibit smectic A and nematic phases. In the present method, vibrational frequencies are used to evaluate force constants, mean amplitude of vibration and hence bond polarizabilities. From mean polarizabilities, polarizability anisotropies and mean diamagnetic susceptibilities are also estimated. A close agreement is found between the values estimated from the present molecular vibration method and the reported data, which confirms the applicability of this method to the liquid crystals exhibiting smectic A and nematic phases. In addition, the variation of the order parameter with temperature is also studied.
Źródło:
Acta Physica Polonica A; 1997, 91, 6; 1069-1079
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Liquid Crystal Nonlinear Optics
Autorzy:
Khoo, I. C.
Powiązania:
https://bibliotekanauki.pl/articles/1931533.pdf
Data publikacji:
1994-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
42.65.-k
42.65.Vh
42.65.Hw
Opis:
A review of liquid crystal nonlinearities and nonlinear optical phenomena observed in all phases of liquid crystals is presented. Recent observation of self-starting optical phase conjugation in nematic liquid crystal is specifically discussed as an example of a novel nonlinear optical phenomenon.
Źródło:
Acta Physica Polonica A; 1994, 86, 1; 267-278
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kinetics of Nematic to Isotropic Phase Transition in Liquid Crystal Doped with Magnetic Nanoparticles
Autorzy:
Csach, K.
Juríková, A.
Miškuf, J.
Tomašovičová, N.
Gdovinová, V.
Závišová, V.
Kopčanský, P.
Éber, N.
Fodor-Csorba, K.
Vajda, A.
Powiązania:
https://bibliotekanauki.pl/articles/1032719.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
64.70.mj
65.80.-g
Opis:
A binary mixture of bent-core and rod-shaped liquid crystals was chosen as a model substance combining the properties of both types of liquid crystals. The mixture was doped with a small amount of spherical and rod-like magnetic nanoparticles. Differential scanning calorimetry experiments were performed for the pure as well as for the doped mixture at different heating rates ranging from 1 to 16°C/min. The addition of the magnetic nanoparticles lowered the phase transition temperature. This effect is more intensive in the case of the rod-like magnetic nanoparticles. The kinetics of the nematic to isotropic phase transition was evaluated in the framework of the differential isoconversional method. The calculated apparent activation energy showed non-monotonic behaviour and a sensitivity on the shape of added magnetic nanoparticles.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 949-951
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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