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    Wyświetlanie 1-45 z 45
    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:
    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:
    Induced Smectic A Phase through Intermolecular Hydrogen Bonding: Part XVIII: Influence of p-n-Alkyl Benzoic Acids on Thermal and Phase Behavior οf Hydrogen-Bonded Liquid Crystals
    Autorzy:
    Vijayalakshmi, K.
    Sreehari Sastry, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1808111.pdf
    Data publikacji:
    2009-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.30.-v
    61.30.Cz
    Opis:
    A novel series of intermolecular hydrogen bonded liquid crystals was synthesized with the mesogens of p-n-alkyl benzoic acids (nBA where n =5 to 10) and p-(p'-octyloxy benzylidene)-cyano aniline (OBCA) moieties. The thermal and phase behaviors of these mesogens (nBA:OBCA) are studied by thermal polarizing optical microscopy and differential scanning calorimetry techniques. Induced smectic A phase with focal conic fan texture is observed in all the synthesized compounds. Moreover, the nematic phase present in all the pure p-n-alkyl benzoic acids (nBA where n =6 to 10) is quenched in all the hydrogen bonded compounds (nBA:OBCA) and smectic A phase is induced. But, in the compound 5BA:OBCA the nematic phase is also present along with the induced smectic A phase. The structural elucidation pertaining to the formation and stabilization of intermolecular hydrogen bonding is carried out by a detailed IR spectral investigation.
    Źródło:
    Acta Physica Polonica A; 2009, 115, 3; 690-693
    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:
    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:
    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:
    Enhancement of Nematic Order of Liquid Crystals in Thin Cells
    Autorzy:
    Aswini, P.
    Govind, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1489838.pdf
    Data publikacji:
    2012-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.30.Gd
    61.30.-v
    64.70.mf
    Opis:
    Experimental observations show that the nematic order parameter is significantly enhanced as the thickness of the cell is reduced. Calculations of earlier theories do not agree well with the experimental data. We propose a simple extension of Maier-Saupe theory to account for the enhancement. A molecule near the surface is assumed to feel the mean field potential (the Maier-Saupe type) and also the surface induced potential. This is included in the Maier-Saupe theory. Our calculations are in better agreement with the experimental data.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 3; 625-627
    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:
    First Order Hyperpolarizabilities, NPA and Fukui Functions of Cyclohexanone by Density Functional Theory Method
    Autorzy:
    Gangadharan, Rubarani
    Sampath Krishnan, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1398896.pdf
    Data publikacji:
    2015-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.30.-v
    78.30.Jw
    31.15.Ew
    Opis:
    The molecular structure of cyclohexanone was calculated by the B3LYP density functional model with 6-311++G(d,p) basis set by Gaussian program. The results from natural bond orbital analysis have been analyzed in terms of the hybridization of atoms and the electronic structure of the title molecule. The formation of hydrogen bond was investigated using natural bond orbital calculation. The electron density based local reactivity descriptors such as Fukui functions were calculated. The dipole moment (μ) and polarizability (α), anisotropy polarizability (Δα) and first order hyperpolarizability ($β_\text{tot}$) of the molecule have been reported. Thermodynamic properties of the title compound were calculated at different temperatures.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 3; 748-752
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Density Functional Theory Studies on Ir Spectra of the Triphenylene Derivatives. A Scaled Quantum Mechanical Force Field Approach
    Autorzy:
    Merkel, K.
    Kocot, A.
    Wrzalik, R.
    Orgasińska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/2014386.pdf
    Data publikacji:
    2000-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.30.-v
    31.15.Ew
    78.30.Jw
    Opis:
    Density functional theory, B3-LYP with the 6-31G$\text{}^{*}$ basis set was applied to study the structures and vibrational infrared spectra of triphenylene and the hexasubstituted triphenylene derivatives. The calculated force fields were scaled using the scaled quantum mechanical force field method. The predicted vibrational frequencies were compared with the experimental IR spectra (500-4000cm$\text{}^{-1}$). The spectra were interpreted and vibrational assignments were reported. This study shows that the scaled density functional force field approach enables, through the transferability of scale factors, good interpretation of vibrational spectra of large molecules.
    Źródło:
    Acta Physica Polonica A; 2000, 98, 5; 525-531
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Determination of Orientational Order Parameters of Two Tri-Component Mixtures from Optical Birefringence and X-Ray Diffraction Measurements
    Autorzy:
    Basak, S.
    Dasgupta, P.
    Das, B.
    Das, M.
    Dabrowski, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1492775.pdf
    Data publikacji:
    2011-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.05.cp
    61.30.-v
    42.70.Df
    Opis:
    Two tri-component mixtures as base mixtures for vertically aligned mode LCD's were prepared. The eutectic compositions were theoretically estimated and experimentally verified from differential scanning calorimetry studies. A room temperature nematic mixture with fairly broad operating range emerged from each of the tri-component mixtures. The optical birefringence of these mixtures at the eutectic composition was measured as a function of temperature. X-ray diffraction measurements were done on these mixtures to obtain the orientational order parameters as a function of temperature. The order parameter values were also determined from birefringence measurements and the results were compared with mean field theory. Structural parameters like intermolecular distance and apparent molecular length have also been determined.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 6; 1037-1042
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Correlation Length in PBnA Liquid Crystal Family
    Autorzy:
    El Guermai, K.
    Ayadi, M.
    El Boussiri, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1992845.pdf
    Data publikacji:
    1998-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.30.-v
    61.10.-i
    64.70.Md
    61.30.Gd
    Opis:
    We present a study of the range molecular interactions inside layers in smectic phases A and I of PBnA (phenyl-4 benzylidene 4'-alkylaniline) liquid crystals family. The purpose of this work is to determine the correlation length of the molecules' gravity centers in existing domain of smectic phases and at the transition between them. We used X-rays in-plane peaks of the pattern diffraction of aligned sample by a magnetic field.
    Źródło:
    Acta Physica Polonica A; 1998, 94, 5-6; 779-784
    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:
    Equimolecular Mixture of Calamitic and Bent-Core Thiobenzoates
    Autorzy:
    Chruściel, J.
    Wantusiak, B.
    Ossowska-Chruściel, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1419573.pdf
    Data publikacji:
    2012-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.30.-v
    64.70.M-
    78.15.+e
    Opis:
    This article reports on the new results on phase transitions, mesomorphic and electro-optical properties of new equimolecular mixture of calamitic and bent-core thiobenzoates. Two following liquid crystals were the components of the binary mixture: (S)-(+)-4-(1-methylheptyloxy)biphenyl 4'-octylthiobenzoate (MHOBS8) having rode-like, calamitic-chiral molecules possessing among others ferroelectric smectic C (SmC*) and bis [4-(4'-octylphenylthiocarbonyl)phenyl] isophtalates from a homologous series of banana-shaped thioesters, referred to as IFOS8, where n = 8 denoted the number of carbon atoms in terminal alkyl chains in both mesogens, synthesized by us. The IFOS8 compound has two enantiotropic phases: B2 with antiferroelectric order and B6. The mesomorphic properties were investigated by means of three complementary methods: differential scanning calorimetry, polarized light optical microscopy, and transmitted light intensity. Electro-optical measurements were also carried out.
    Źródło:
    Acta Physica Polonica A; 2012, 122, 2; 375-377
    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:
    Dielectric and Conductivity Anisotropy in Liquid Crystalline Phases of Strongly Polar Thioesters
    Autorzy:
    Mikułko, A.
    Fraś, M.
    Marzec, M.
    Wróbel, S.
    Ossowska-Chruściel, M.
    Chruściel, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1813171.pdf
    Data publikacji:
    2008-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.30.-v
    61.30.Eb
    77.22.-d
    66.10.Ed
    Opis:
    The main objective of this paper is to study dielectric properties of two compounds of acronyms 5OSCl and 6OSCl having strongly polar bond (C-Cl) at para position. Dielectric measurements were done in the frequency range from 40 Hz to 15 MHz. The dielectric spectra were measured for two principal alignments. For homeotropic alignment, the reorientation of molecule around the short molecular axis was observed. Both substances studied exhibit large positive dielectric anisotropy and the anisotropy of conductivity was obtained in smectic A as well as nematic phase.
    Źródło:
    Acta Physica Polonica A; 2008, 113, 4; 1155-1160
    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
    Tytuł:
    Dielectric Properties of Compounds Creating Dual-Frequency Nematic Liquid Crystals
    Autorzy:
    Mrukiewicz, M.
    Perkowski, P.
    Garbat, K.
    Dąbrowski, R.
    Parka, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399014.pdf
    Data publikacji:
    2013-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    77.22.Gm
    77.84.Nh
    61.30.-v
    Opis:
    In this paper we report how dielectric spectroscopy can help in creating of dual-frequency nematic liquid crystals. Dual-frequency nematic liquid crystals is new class of liquid crystal materials. Such mixture is usually formed by a combination of many components (even more than 10), which can be split into two groups: molecules having large transverse dipole moment and molecules with a large longitudinal dipole moment. The behavior of a base (parent) mixture, functional admixtures and final dual-frequency nematic liquid crystals mixture is investigated by dielectric spectroscopy in wide frequency (100 Hz-10 MHz) and temperature ranges. This allows us to find out why the dual-frequency liquid crystal has an important feature: positive and negative dielectric anisotropy at different frequencies. We present parameters of molecular motions around short (S-mode) and long (L-mode) molecular axes observed in investigated materials and discuss how the creation of final dual-frequency nematic liquid crystals mixture can modify molecular relaxations.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 6; 940-945
    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:
    Blocking of Phase Transitions in Liquid Crystal 5*CB (Isopentylcyanobiphenyl) as a Result of Surface Interactions in the Nanomembranes
    Autorzy:
    Bąk, A.
    Chłędowska, K.
    Inglot, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1402554.pdf
    Data publikacji:
    2015-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.30.-v
    64.70.pp
    68.08.-p
    77.22.Gm
    Opis:
    In this paper we present the results of dielectric measurements of liquid crystal (LC) 5*CB arranged in porous matrices with a pore diameter of 100 and 20 nm. We analyse the effect of the surface interactions on the dynamics of the molecules. The results are compared with the results for bulk 5*CB. The most important observation is the blocking of the phase transition of 5*CB into the solid phase in the matrix with pore diameter of 20 nm.
    Źródło:
    Acta Physica Polonica A; 2015, 128, 2; 147-149
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dielectric Permittivity and Viscoelastic Measurements οf Two Tricomponent Mixtures Consisting οf Laterally Fluorinated Terphenyl Derivatives
    Autorzy:
    Basak, S.
    Dasgupta, P.
    Das, B.
    Das, M.
    Dabrowski, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1400143.pdf
    Data publikacji:
    2013-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.30.-v
    78.20.Fm
    87.19.rd
    87.19.rf
    83.60.Bc
    Opis:
    Two tricomponent room temperature nematic eutectic mixtures ABC and ABD with laterally fluorinated constituents A and B were prepared as base mixtures for vertically aligned mode LCD's. The physical properties of these mixtures viz. birefringence, dielectric anisotropy, bend elastic constant, relaxation time and rotational viscosities were determined in order to compare with the optimum values required to achieve the target specifications of VA mode materials. The dielectric anisotropy, Δ ε, and optical birefringence, Δ n, of these mixtures were found to be in the range of (-1.3 to -1.4) and (0.13 and 0.14), respectively, at around 20°C. The figure of merit for the ABD mixture has been found to be higher than that of ABC mixture throughout the entire temperature range. The pretilt angle effect in the physical parameters has also been studied. At T=20°C, the response time decreases to 25% and 35% for mixture ABC for 2° and 5° pretilt respectively in comparison to zero pretilt. On the other hand, at the same temperature for the ABD mixture these values are reduced by 16% and 35%, respectively.
    Źródło:
    Acta Physica Polonica A; 2013, 123, 4; 714-719
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Investigations of Phase Transitions in (NH$\text{}_{4}$)$\text{}_{3}$H(SO$\text{}_{4}$)$\text{}_{2}$ Crystal by Means of Mn$\text{}^{2+}$ EPR Spectra
    Autorzy:
    Bednarski, W.
    Waplak, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1952756.pdf
    Data publikacji:
    1996-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.50.-f
    76.30.-v
    Opis:
    EPR of Mn$\text{}^{2+}$ impurity ion in the (NH$\text{}_{4}$)$\text{}_{3}$H(SO$\text{}_{4}$)$\text{}_{2}$ crystal is studied in the temperature range 80-420 K. It is shown that Mn$\text{}^{2+}$ substitutes NH$\text{}_{4}^{+}$(I) ion and is coordinated in deformed oxygen octahedron in which takes two "off-center" positions. Its spin-Hamiltonian parameters and direction cosines of crystal field are determined. The successive EPR line splitting for three phase transitions is discussed.
    Źródło:
    Acta Physica Polonica A; 1996, 90, 6; 1185-1192
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    EPR Application in the Study of K$\text{}_{3}$H(SO$\text{}_{4}$)$\text{}_{2}$ Proton Conductor Doped with Mn$\text{}^{2+}$ or VO$\text{}^{2+}$ Ions
    Autorzy:
    Waplak, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1931810.pdf
    Data publikacji:
    1994-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.50.-f
    76.30.-v
    Opis:
    The EPR of Mn$\text{}^{2+}$- or VO$\text{}^{2+}$-doped superprotonic conductor K$\text{}_{3}$H(SO$\text{}_{4}$)$\text{}_{2}$ is studied in the 80-471 K temperature range. VO$\text{}^{2+}$ EPR spectrum reveals diffusion induced merging of proton transferred superhyperfine structure above 380 K. Line width anomaly is observed in Mn$\text{}^{2+}$ EPR spectrum which is attributed to the intrabond and interbond proton motions, these lead to high protonic conductivity. It is shown that paramagnetic centers namely of electronic spin greater than 1, with excess charge compensated by the protonic vacancy, are good probes to monitor the protonic conductivity on molecular level.
    Źródło:
    Acta Physica Polonica A; 1994, 86, 6; 939-945
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    EPR Study of Cu$\text{}^{2+}$ Doped Fast-Proton Conductor K$\text{}_{3}$H(SO$\text{}_{4}$)$\text{}_{2}$ in the Temperature Range 100-450 K
    Autorzy:
    Ostrowski, A.
    Bednarski, W.
    Waplak, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/2037037.pdf
    Data publikacji:
    2003-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.50.-f
    76.30.-v
    Opis:
    The K$\text{}_{3}$H(SO$\text{}_{4}$)$\text{}_{2}$ doped with Cu$\text{}^{2+}$ ion was studied in detail by X-band CW EPR. Two kinds of Cu$\text{}^{2+}$ complexes (magnetically and structurally nonequivalent) denoted as Cu$\text{}^{2+}$(I) and Cu$\text{}^{2+}$(II) were found. Spin-Hamiltonian parameters, direction cosines, and coordination of Cu$\text{}^{2+}$ ion were determined at room temperature. The superhyperfine structure was observed below 250 K as a result of interacting of Cu$\text{}^{2+}$ ion with four equivalent protons (I=1/2). Temperature studies of K$\text{}_{3}$H(SO$\text{}_{4}$)$\text{}_{2}$ crystal show that interbond motion as a precursor of superprotonic phase transition occurs at above≈250 K.
    Źródło:
    Acta Physica Polonica A; 2003, 104, 6; 549-558
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electron Spin Resonance Spectra of Fe$\text{}^{3+}$ Ions in SrLaAlO$\text{}_{4}$ and SrLaGaO$\text{}_{4}$ High-T$\text{}_{c}$ Substrates
    Autorzy:
    Jabłoński, R.
    Pajączkowska, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1964358.pdf
    Data publikacji:
    1997-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    76.30.-v
    61.72.Hh
    Opis:
    New results concerning paramagnetic defects in SrLaAlO$\text{}_{4}$ and SrLaGaO$\text{}_{4}$ high-T$\text{}_{c}$ substrates connected with unavoidable impurity Fe$\text{}^{3+}$ are reported. The identification was checked by measuring the spectra in SrLaAlO$\text{}_{4}$ crystals intentionally doped with 0.5 at.% Fe. Angular dependences of three lines were distinguished at X-band frequency in the temperature range from 4 K to 300 K. We attribute these lines to the transitions inside the doublets ±1/2, and "forbidden" doublets ±3/2, ±5/2, respectively. By diagonalization of spin-Hamiltonian, parameters |D| > 1.2 cm$\text{}^{-1}$, |E| ≈ 0.1 cm$\text{}^{-1}$ and g$\text{}_{x}$=g$\text{}_{y}$=g$\text{}_{z}$= 1.987(13) for SrLaAlO$\text{}_{4}$ and SrLaGaO$\text{}_{4}$ were calculated and within the margin of error they were of the same value.
    Źródło:
    Acta Physica Polonica A; 1997, 92, 1; 173-176
    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:
    EPR Study of VO$\text{}^{2+}$ Center in Fast Proton Conductor K$\text{}_{3}$H(SO$\text{}_{4}$)$\text{}_{2}$
    Autorzy:
    Ostrowski, A.
    Waplak, S.
    Bednarski, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043409.pdf
    Data publikacji:
    2005-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.50.-f
    76.30.-v
    Opis:
    The pretransitional phenomena of superprotonic phase transition (T$\text{}_{sp}$=471 K) were studied in detail by X-band continuous wave EPR spectra of K$\text{}_{3}$H(SO$\text{}_{4}$)$\text{}_{2}$ crystal doped with VO$\text{}^{2+}$ ions. Three kinds of VO$\text{}^{2+}$ complexes (magnetically equivalent but structurally non-equivalent) denoted as VO$\text{}^{2+}$(I), VO$\text{}^{2+}$(II), and VO$\text{}^{2+}$(III) were found. "Smearing out" of the superhyperfine structure was observed as a result of interbond proton motion. VO$\text{}^{2+}$ impurity replaces K$\text{}^{+}$ ion and experiences the same average crystal field gradient at T$\text{}_{sp}$=471 K for I- and II-type complexes. The increase in interbond proton frequency hopping above 360 K is a reason of significant line broadening.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 1; 127-135
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electron Spin-Lattice Relaxation in Polymers and Crystals Related to Disorder and Structure Defects
    Autorzy:
    Hoffmann, S. K.
    Hilczer, W.
    Radczyk, T.
    Polus, I.
    Powiązania:
    https://bibliotekanauki.pl/articles/2035737.pdf
    Data publikacji:
    2003-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.41.+e
    61.80.-x
    76.30.-v
    Opis:
    Temperature dependences (4-300 K) of the electron spin-lattice relaxation have been determined by electron spin echo technique for free radicals in two polymeric systems: phenol-formaldehyde resin and polyhydrazodisulphide. The dependences are described in terms of dynamics specific for amorphous systems involving two-level tunnelling states at low temperatures, exchange-coupled clusters of paramagnetic centres and local oscillators. Some universal temperature behaviour of the spin-lattice relaxation of amorphous systems is suggested, with a strong increase in relaxation rate with temperature at low temperatures and much weaker increase above 50 K with characteristic linear temperature dependence in a broad temperature range and cosech(Δ/kT) -type behaviour. It is also shown that the amorphous-type behaviour appears in low temperatures relaxation studies of single crystals but it is due to a non-uniform distribution of doped paramagnetic ions. Such behaviour we have found in Tutton salt crystals doped with Cu$\text{}^{2+}$, as well as for free radical centres produced by ionising irradiation in (NH$\text{}_{4}$)$\text{}_{3}$H(SeO$\text{}_{4}$)$\text{}_{2}$ and Li(N$\text{}_{2}$H$\text{}_{5}$)SO$\text{}_{4}$ single crystals, where extended phonons are suppressed around radiation damage centres suggesting a local amorphisation of the crystal structure.zapisz i p
    Źródło:
    Acta Physica Polonica A; 2003, 103, 4; 373-385
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electron Spin Resonance Study of Thermal Defects in SrLaAlO$\text{}_{4}$ and SrLaGaO$\text{}_{4}$ High-T$\text{}_{c}$ Substrates
    Autorzy:
    Jabłoński, R.
    Gloubokov, A.
    Pajączkowska, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1964356.pdf
    Data publikacji:
    1997-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    76.30.-v
    61.72.Hh
    61.72.Ji
    Opis:
    The effect of annealing SrLaAlO$\text{}_{4}$ (SLA) and SrLaGaO$\text{}_{4}$ (SLG) crystals in oxidizing and reducing atmospheres in the temperature range of 950°C-1300°C was investigated. Three kinds of anisotropic defects D$\text{}_{1}$, D$\text{}_{2}$, and E at the temperature range of 4-300 K were found. By diagonalization of orthorhombic spin-Hamiltonian parameters: |D|=0.0541(10) cm$\text{}^{-1}$, |E|=0.0108(10) cm$\text{}^{-1}$, g$\text{}_{∥}$=0.883(5), and g$\text{}_{⊥ }$=1.922(5) for D$\text{}_{1}$ defects for SLG and SLA were calculated and they had the same values within the margin of error.
    Źródło:
    Acta Physica Polonica A; 1997, 92, 1; 169-172
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Crystal structure and EPR investigation of pyrazinamide containing copper (II) 2-nitrobenzoate single crystal
    Autorzy:
    Çelik, Y.
    Bozkurt, E.
    Karabulut, B.
    Dege, N.
    Powiązania:
    https://bibliotekanauki.pl/articles/1070369.pdf
    Data publikacji:
    2016-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.05.cp
    75.10.Dg
    76.30.-v
    78.30.-j
    Opis:
    The crystal structure and paramagnetism in the pyrazinamide containing copper(II) 2-nitrobenzoate single crystal were investigated using X-ray diffraction, Fourier-transform infrared spectroscopy, and electron paramagnetic resonance techniques. X-ray diffraction analysis shows that the complex crystallizes in monoclinic system having two molecules in the unit cell. After using curve fitting method to the electron paramagnetic resonance spectra, anisotropic g and hyperfine A tensors were obtained. The local symmetry, spin Hamiltonian parameters, and molecular bonding coefficients of the paramagnetic Cu²⁺ ion were determined. Perturbation approach was applied to the spin Hamiltonian to calculate the g and A values.
    Źródło:
    Acta Physica Polonica A; 2016, 130, 1; 163-166
    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:
    EPR Investigations of Electrons and Neutrons Irradiated Cubic Boron Nitride
    Autorzy:
    Azarko, I.
    Ignatenko, O.
    Karpovich, I.
    Odzhaev, V.
    Kozlova, E.
    Zhukowski, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1400479.pdf
    Data publikacji:
    2013-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    76.30.-v
    81.05.Ea
    61.72.J-
    Opis:
    Microcrystals of cubic boron nitride powders synthesised under different conditions and further irradiated with neutrons and electrons have been investigated. It was found that some changes of the samples' paramagnetic properties depend on the electron irradiation dose. It was also shown that the initial boron type defects growth occurs under thermal neutron, as well as under fast neutrons irradiation. The nitrogen-containing defects concentration changes in a threshold manner.
    Źródło:
    Acta Physica Polonica A; 2013, 123, 5; 923-925
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electron Spin Resonance Study of Nd$\text{}^{3+}$ and Er$\text{}^{3+}$ Ions in YAlO$\text{}_{3}$
    Autorzy:
    Jabłoński, R.
    Frukacz, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/1945633.pdf
    Data publikacji:
    1996-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    76.30.-v
    61.72.-y
    42.70.Hj
    Opis:
    In this paper we present the results of ESR and photo-ESR measurements on YAlO$\text{}_{3}$(YAP) single crystals and powder samples doped purposely with about 1 at.% Nd$\text{}^{3+}$ and undoped crystals in which Er$\text{}^{3+}$ was observed as residual dopant. The ESR measurements were carried out at X-band spectrometer in 4-300 K temperature range. The photo-ESR was performed at 5 K using a mercury arc lamp. For the Nd$\text{}^{3+}$ doped crystals the intensity of ESR signal decreased about 2 times during illumination conditions. Moreover, the calculations of the g tensor and A hyperfine structure parameters for Nd$\text{}^{3+}$ and Er$\text{}^{3+}$ were carried out.
    Źródło:
    Acta Physica Polonica A; 1996, 90, 2; 339-343
    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:
    Groups of Paramagnetic Centres in Reduced and Methylated Low Rank Coal
    Autorzy:
    Pilawa, B.
    Wachowska, H.
    Kozłowski, M.
    Więckowski, A.
    Najder-Kozdrowska, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1401865.pdf
    Data publikacji:
    2015-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    33.35.+r
    61.66.Hq
    76.30.-v
    76.30.Rn
    89.30.ag
    Opis:
    Low rank Illinois No. 6 coal was studied by electron paramagnetic resonance EPR spectroscopy. The parameters of EPR spectra (spectroscopic splitting factors g, linewidths $\DeltaB_{pp}$, concentrations of paramagnetic centres N) were measured for row and chemically treated coal (demineralized, reduced and methylated samples). The multi-component structure of experimental spectra of this coal was proved. Two groups of paramagnetic centres responsible for broad Lorentzian 1 and narrow Lorentzian 2 lines exist in studied samples. Paramagnetic centres connected with component lines revealed different behaviour during chemical treatments.
    Źródło:
    Acta Physica Polonica A; 2015, 128, 3; 264-267
    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:
    Creep Deformation of Intermetallic TiAl-Based Alloy
    Autorzy:
    Lapin, J.
    Staneková, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/1418436.pdf
    Data publikacji:
    2012-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.72.-y
    62.20.F-
    81.30.Mh
    83.50.-v
    Opis:
    In the present work, the creep deformation behaviour of a new cast intermetallic Ti-46Al-8Ta [at.%] alloy is analysed. Constant load tensile creep tests were performed at initial applied stresses ranging from 200 to 400 MPa in the temperature range from 973 to 1073 K. The measured creep deformation curves are analysed and the observed deviations from calculated curves are discussed based on microstructural changes observed in the studied alloy during creep. The kinetics of creep deformation are evaluated in terms of the true activation energy for creep and the stress exponent. Creep damage initiation and propagation leading to the fracture of the creep specimens are characterized as functions of the applied stress and temperature.
    Źródło:
    Acta Physica Polonica A; 2012, 122, 3; 453-456
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    EPR characteristics of activated carbon for hydrogen production by the thermo-catalytic decomposition of methane
    Autorzy:
    Więckowski, A.
    Najder-Kozdrowska, L.
    Rechnia, P.
    Malaika, A.
    Krzyżyńska, B.
    Kozłowski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1158900.pdf
    Data publikacji:
    2016-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    33.35.+r
    61.66.Hq
    76.30.-v
    82.30.Lp
    82.65.+r
    88.30.ej
    Opis:
    The electron paramagnetic resonance (EPR) method was used to characterize samples of activated coal before and after reactions of the catalytic decomposition of methane and ethanol at temperatures of 1023 K (750°C), 1123 K (850°C) and 1223 K (950°C). The EPR parameters: spectroscopic splitting factor g, peak-to-peak linewidth ΔBₚₚ, and spin concentration c were measured. During the ethanol-assisted catalytic decomposition of methane carbon-located-spin radicals are partially transformed into oxygen-located-spin radicals.
    Źródło:
    Acta Physica Polonica A; 2016, 130, 3; 701-704
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Characterization of New U-Ni-X₂ Splats and Study of their Physical Properties
    Autorzy:
    Molčanová, Z.
    Mihalik, M.
    Reiffers, M.
    Džubinská, A.
    Huráková, M.
    Kavečanský, V.
    Paukov, M.
    Havela, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1032182.pdf
    Data publikacji:
    2017-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.82.Bg
    75.50.Kj
    75.30.-m
    72.15.-v
    Opis:
    We explored the crystal structure, magnetic, and transport properties of UNiX₂ (X = Ge, Si) materials, which were prepared by a conventional metallurgical technique and by rapid solidification - splat cooling. The UNiSi₂ splat is mostly single phase, containing only small traces of a minority phase. Magnetic and electrical properties of the splat resemble properties of samples, which were prepared by conventional methods, exhibiting a ferromagnetic transition at about 91 K and similar temperature dependence of resistivity. The coercive field of μ₀H_c=4.25 T is much enhanced due to the magnetic anisotropy introduced by the sample preparation technique. The Barkhausen jumps were observed on the hysteresis loop. Magnetization of the sample does not saturate in fields up to μ₀H=9 T. The phase structure of UNiGe₂ splat is not completely solved and will be subject of our study in future. Our preliminary results indicate the presence of completely new phase with tetragonal crystal structure and antiferromagnetic ordering below 54 K.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 4; 994-996
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    EPR and Optical Spectroscopy of Iron Doped Mixed Alkali Cadmium Phosphate Glasses
    Autorzy:
    Giridhar, G.
    Punyaseshudu, D.
    Srinivas Prasad, M.
    Venkateswarlu, M.
    Srinivas, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/1400155.pdf
    Data publikacji:
    2013-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    71.55.Jv
    61.43.Fs
    76.30.-v
    78.20.-e
    Opis:
    Iron doped mixed alkali cadmium phosphate (LiNaCdP) glasses of the following chemical composition $xLi_2O + (20-x)Na_2O + 20CdO + 59.5P_2O_5 + 0.5Fe_2O_3$ (5
    Źródło:
    Acta Physica Polonica A; 2013, 123, 4; 761-765
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Investigation of Sol-Gel Glasses Doped with Lanthanide Ions by Spectroscopic, Acoustic, and Positron Annihilation Methods
    Autorzy:
    Jerie, K.
    Baranowski, A.
    Legendziewicz, J.
    Guzik, M.
    Burakowski, A.
    Gliński, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047126.pdf
    Data publikacji:
    2006-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    32.30.Jc
    43.35.Cg
    61.20.Qg
    61.25.Em
    62.60.+v
    78.70.Bj
    Opis:
    The results of optical spectroscopic (UV-Vis, absorption, and emission), acoustic (sound velocity of precursor solutions, the solvation numbers of ions in these solutions), and positron annihilation of glasses are presented and discussed for silica glasses obtained by the alcoholic sol-gel technique, doped with selected lanthanides and with some addition of ethylene glycol. The aim of these investigations was the determination of the local structure of glass close to lanthanide ions and its influence on the optical properties of the material. The results show that the existence of alcohol-glycol solvates in glasses decrease the number of empty voids in its structure as well as the size of the remaining ones. One can suppose that this is caused by cooperative interactions of glycol molecules with the network of hydrogen bonds of the glass.
    Źródło:
    Acta Physica Polonica A; 2006, 110, 5; 583-591
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Controlling Mechanisms of Creep Deformation of New Air-Hardenable TiAl-Based Alloy
    Autorzy:
    Staneková, H.
    Lapin, J.
    Pelachová, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/1418511.pdf
    Data publikacji:
    2012-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.72.-y
    62.20.F-
    62.40.+i
    81.30.Mh
    83.50.-v
    Opis:
    In the present work, controlling mechanisms of creep deformation of a new cast air-hardenable Ti-46Al-8Ta [at.%] alloy was studied. Long-term constant load tensile creep tests combined with an abrupt change of the applied stress were performed at 700°C. The response of the alloy to a stress reduction is analyzed. Transient behaviour with zero creep before recommencing creep at a reduced load is related to possible creep deformation mechanisms. The dislocation microstructures are analysed for creep strains corresponding to the minimum creep rate by transmission electron microscopy. The controlling mechanisms of creep deformation are identified from the transient creep behaviour of the alloy during stress reduction, the stress exponent and dislocation microstructures observed after creep testing.
    Źródło:
    Acta Physica Polonica A; 2012, 122, 3; 512-515
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    EPR Study of Gamma Irradiated Cholestanone Single Crystal
    Autorzy:
    Caliskan, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1206732.pdf
    Data publikacji:
    2014-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    87.64.kh
    87.80.Lg
    61.72.Hh
    33.35.+r
    76.30.Rn
    32.10.Fn
    33.15.Pw
    71.18.+y
    76.30.-v
    61.82.Pv
    61.72.-y
    Opis:
    Cholestanone ($C_{27}H_{46}O$) single crystals were irradiated with ⁶⁰Co-γ rays at room temperature. The spectra were recorded for different orientations of the crystal in the magnetic field at 120 K using the EPR technique. Radiation damage center was attributed to $CHCH_2CH_2$ radical. The principal values of the hyperfine coupling tensor of the unpaired electron with the protons and the principal values of the g tensor were determined. The results were found to be in good agreement with the existing literature.
    Źródło:
    Acta Physica Polonica A; 2014, 125, 1; 135-138
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    At the Tip of an MeV Beam: Provoking Cells and Performing Tomographic Imaging
    Autorzy:
    Pallon, J.
    Arteaga-Marrero, N.
    Nilsson, Ch.
    Elfman, M.
    Kristiansson, P.
    Nilsson, C.
    Wegdén, M.
    Olsson, M.
    Åkerström, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1808531.pdf
    Data publikacji:
    2009-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    07.79.-v
    29.40.Wk
    87.53.-j
    87.53.Ay
    25.40.Cm
    29.30.Ep
    29.30.Kv
    61.43.Gt
    Opis:
    Biological applications of ion beams have recently become a new important research field using single ion hit facilities to study individual living cells and their response to the hit of a counted number of ions. One motivation is the search for a better understanding of the fundamental processes taking place in cells and organs as a result of irradiation. Another comes from the increasing interest in using high energy protons and heavy ions as a modality for radiotherapy of deep seated tumours. In the view of treatment efficiency, study of cell culture behaviour under controlled radiation experiments, and in different chemical environments at single ion hit facilities, is a first step towards a better understanding of the processes. Tomographic techniques are applicable to situations where you need information of the inside of an object but do not want to section it into thin slices or cannot do it. Using focused MeV ion beams for tomography restricts the sample size to the order of 10-100 μm, depending of the initial energy. On the other hand, the ability to focus at a sub-micrometer level makes ion beams well suited for analyses of small sized objects as cells, spores, etc. The scanning transmission ion microscopy mode of tomography gives the mass density and corresponding morphological structure of holes and pores. It can then be used to correct the results from the other mode, particle induced X-ray emission tomography. Here is discussed a porosity analysis of bentonite clay that is planned to form an important buffer zone around canisters filled with spent nuclear reactor fuel waste deposited 500 m underground in Sweden.
    Źródło:
    Acta Physica Polonica A; 2009, 115, 2; 501-506
    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
      Wyświetlanie 1-45 z 45

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