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Wyświetlanie 1-20 z 20
Tytuł:
FT-IR, Thermal and NLO Studies on Amino Acid (L-Arginine and L-Alanine) Doped KDP Crystals
Autorzy:
Muley, G.
Rode, M.
Pawar, B.
Powiązania:
https://bibliotekanauki.pl/articles/1585044.pdf
Data publikacji:
2009-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.66.Hq
Opis:
Single crystals of pure and amino acid (L-arginine and L-alanine) doped potassium dihydrogen phosphate (KDP) for second harmonic generation have been grown from low temperature solution growth method by employing slow evaporation of the solvent. FT-IR spectrum of pure and doped KDP crystals confirms qualitatively the doping of the L-arginine and L-alanine in the host crystals. UV-visible spectroscopy shows the improvement in the transparency. Crystal structure has been studied by powder X-ray diffraction. Modification in the lattice parameters has been observed. Improvement in the SHG efficiency was studied by the Kurtz and Perry method. Thermal analysis has been performed on the grown crystals.
Źródło:
Acta Physica Polonica A; 2009, 116, 6; 1033-1038
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Paramagnetic Centers in DOPA-Melanin-Dihydrostreptomycin Complexes
Autorzy:
Buszman, E.
Pilawa, B.
Zdybel, M.
Wrześniok, D.
Grzegorczyk, A.
Wilczok, T.
Powiązania:
https://bibliotekanauki.pl/articles/2043624.pdf
Data publikacji:
2005-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.66.Hq
76.30.Rn
Opis:
DOPA-melanin-dihydrostreptomycin complexes with drug concentrations 1×10$\text{}^{-4}$-1×10$\text{}^{-2}$ M were examined by the use of electron paramagnetic resonance spectroscopy at X-band (9.3 GHz). Dihydrostreptomycin was chosen for studies, because this aminoglycoside antibiotic causes strong toxic effects in organism. It was stated that dihydrostreptomycin generates o-semiquinone free radicals with g=2.0038 in melanin. Free radicals formation increases with increase in the antibiotic concentration. Changes of EPR lines with microwave powers pointed out that slow spin-lattice relaxation processes exist in DOPA-melanin and in its complexes with dihydrostreptomycin. The measured EPR lines were homogeneously broadened.
Źródło:
Acta Physica Polonica A; 2005, 108, 2; 353-356
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multi-Component EPR Spectra of Coals with Different Carbon Content
Autorzy:
Pilawa, B.
Więckowski, A. B.
Pietrzak, R.
Wachowska, H.
Powiązania:
https://bibliotekanauki.pl/articles/2043651.pdf
Data publikacji:
2005-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.66.Hq
76.30.Rn
Opis:
EPR spectra of lignite"Mequinenza" (Spain) (62.3 wt% C) and Polish orthocoking coal (87.8 wt% C) were compared. The spectra were superpositions of broad Gaussian, broad Lorentzian 1, and narrow Lorentzian 3 lines. Concentration of paramagnetic centers - mainly delocalizedπ electrons - responsible for narrow Lorentzian 3 lines increases with increase in carbon content in coal. Coal units with slow and fast spin-lattice relaxation processes exist in the two studied samples. Slow spin-lattice interactions occur in simple aromatic coal units with broad Gaussian and Lorentzian 1 lines. Fast spin-lattice relaxation processes are characteristic of large aromatic units with narrow Lorentzian 3 lines.
Źródło:
Acta Physica Polonica A; 2005, 108, 2; 403-407
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of pH on Paramagnetic Centers in Cladosporium cladosporioides Melanin
Autorzy:
Pilawa, B.
Buszman, E.
Gondzik, A.
Wilczyński, S.
Zdybel, M.
Witoszyńska, T.
Wilczok, T.
Powiązania:
https://bibliotekanauki.pl/articles/2043413.pdf
Data publikacji:
2005-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.66.Hq
76.30.Rn
Opis:
Paramagnetic centers in melanin existing in pigmented soil fungi Cladosporium cladosporioides cultured at acidic (4, 5, 6), neutral (7), and alkaline (8) pH were studied by EPR method. o-semiquinone free radicals (g: 2.0032-2.0040) concentration in melanin biopolymer increased for pH from 4 to 6, decreased at pH 7, and reached the maximum value at pH 8. It may be expected that melanin free radicals reactions with small molecules (metal ions, drugs) are the most effective at pH between 6 and 8. Slow spin-lattice relaxation processes exist in the all studied melanin samples.
Źródło:
Acta Physica Polonica A; 2005, 108, 1; 147-150
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Geometry of the Excited Charge Transfer States: Flattening or Twisting?
Autorzy:
Dobkowski, J.
Sazanovich, I.
Powiązania:
https://bibliotekanauki.pl/articles/1813988.pdf
Data publikacji:
2007-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.50.-j
61.66.Hq
Opis:
Numerous molecules built of an electron acceptor and electron donor units linked together by single bond exhibit a peculiar behavior in their low-lying electronically excited states. N,N-diethylaminoacetophenone and 4-acetyl-4'-dimethylamino-biphenyl, having acetophenone as the acceptor and differentiated by the donors groups $N(CH_3)_2$ and dimethylaniline, respectively, were selected as the subject of study. To recognize the excited state relaxation paths the stationary and time-resolved spectroscopy in absorption and emission was applied. Experimental results indicate that after excitation in polar solvents N,N-diethylaminoacetophenone reduces to minimum the overlap between π-electron systems of the donor and acceptor groups relaxing to the twisted internal charge-transfer state; contrary to that, flattening of the 4-acetyl-4'-dimethylamino-biphenyl skeleton generates increase in the overlap of the π-electron systems.
Źródło:
Acta Physica Polonica A; 2007, 112, S; S-127-S-142
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
EPR Studies of Carbonized Cellulose - Oxygen Interactions
Autorzy:
Pilawa, B.
Pietrzak, R.
Wachowska, H.
Babeł, K.
Powiązania:
https://bibliotekanauki.pl/articles/2043418.pdf
Data publikacji:
2005-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.66.Hq
76.30.Rn
Opis:
EPR examination of cellulose carbonized at 400ºC and 600ºC has been performed. The aim of this work was to search a sample useful as the oximetric probe in biology and medicine. The higher paramagnetic centers concentration characterizes cellulose carbonized at 600ºC, which was found as the sensitive oximetric probe. Quasi-chemical bonds between cellulose molecules and paramagnetic O$\text{}_{2}$ molecules decrease paramagnetic centers concentration. A linear increase in paramagnetic centers concentration and a linear decrease in EPR linewidth with increasing time of sample evacuation were observed for cellulose carbonized at 600ºC. Oxygen affects spin-lattice interactions in carbonized cellulose.
Źródło:
Acta Physica Polonica A; 2005, 108, 1; 151-154
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal Development of Free Volumes in Nafion Membrane
Autorzy:
Melikhova, O.
Čížek, J.
Košinová, L.
Hruška, P.
Powiązania:
https://bibliotekanauki.pl/articles/1033913.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
61.66.Hq
82.35.Lr
Opis:
In this work we employed positron lifetime spectroscopy for investigation of the thermal development of free volumes in H⁺ Nafion membrane over a broad range of temperatures from -150 to 150°C. Positron lifetime studies were combined with differential scanning calorimetry. Size distribution of free volumes was determined from ortho-positronium contribution to positron lifetime spectra. Our investigations revealed that the mean size of free volume holes strongly increases with temperature. On the other hand, the width of the size distribution and the positronium yield decreases with temperature. Transition temperatures corresponding to a change in the slope of the temperature dependence of ortho-positronium lifetime were identified. Results of positron lifetime spectroscopy agree well with the curve obtained by differential scanning calorimetry.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1538-1542
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
EPR Evidence for Thermally Excited Triplet States in Exinite, Vitrinite and Inertinite Separated from Bituminous Coal
Autorzy:
Słowik, G. P.
Wojtowicz, W.
Więckowski, A. B.
Powiązania:
https://bibliotekanauki.pl/articles/2043436.pdf
Data publikacji:
2005-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.66.Hq
76.30.Rn
87.64.Hd
Opis:
In this work we have made an electron spin resonance (EPR) study of macerals obtained from the lithotype clarain separated from Polish medium-rank coal (85.6 wt.% C). For three macerals:~exinite, vitrinite, and inertinite, the temperature dependence of intensity of EPR spectra in the temperature range of 100-373 K was investigated. The experimentally obtained EPR spectra of macerals were fitted by curves of the derivatives of the Gaussian and Lorentzian functions. The best fitting was obtained, when the experimental EPR spectra were assumed to be a superposition of three lines, for exinite and vitrinite - a broad Gaussian (G), a broad Lorentzian (L1) and a narrow Lorentzian (L3) line, but for inertinite of two lines - a narrow Lorentzian (L2) and a narrow Lorentzian (L3) line. The computer-assisted fitting has shown that each individual component line has similar values of resonance field, but different linewidths and amplitudes. The temperature dependence of line intensity I of the broad Gaussian (G) and narrow Lorentzian (L2 and L3) lines fulfils the Curie law in the form I=C/T or IT=C, whereas the broad Lorentzian (L1) line does not fulfil the Curie law. In the last case the temperature dependence of the Lorentzian (L1) component was fitted by the relation I=C/T+B/[T(3+exp(J/kT))] or IT=C+B/[3+exp(J/kT))], valid for thermally excited triplet states (S=1). For exinite and vitrinite the curves presenting the temperature dependence of the product IT versus temperature T were resolved into two curves, one for paramagnetic centres in the doublet state (S=1/2), and the other for paramagnetic centres in the thermally excited triplet state (S=1).
Źródło:
Acta Physica Polonica A; 2005, 108, 1; 171-176
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Time Differential Perturbed Angular γγ-Correlation Studies of Diethylenetriaminepentaacetic Acid Complexes with $\text{}^{111}$In and $\text{}^{111m}$Cd
Autorzy:
Shpinkova, L. G.
Carbonari, A. W.
Nikitin, S. M.
Mestnik-Filho, J.
Powiązania:
https://bibliotekanauki.pl/articles/2029030.pdf
Data publikacji:
2001-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
23.20.En
23.40.-s
61.66.Hq
Opis:
Static and dynamic electric quadrupole interactions of $\text{}^{111}$Cd in complexes with diethylenetriaminepentaacetic acid were studied by the time differential perturbed angular γγ-correlation technique using two parent isotopes, $\text{}^{111}$In(EC)$\text{}^{111}$Cd and $\text{}^{111 m}$Cd. The measurements were carried out using neutral aqueous solutions of the diethylenetriaminepentaacetic- acid-complexes with initial isotopes at 293 K and 77 K. It was shown that the $\text{}^{111}$Cd-diethylenetriaminepentaacetic-acid-complex in aqueous solutions at pH = 7.0 is characterised by the re-orientational correlation time of 7.7×10$\text{}^{-11}$ s and an electric field gradient V$\text{}_{zz}$=6.7(2)×10$\text{}^{21}$ V/m$\text{}^{2}$ with an asymmetry parameter η=0.75(5). A direct comparison of the electric quadrupole interaction parameters for diethylenetriaminepentaacetic- acid-complexes with $\text{}^{111}$In and $\text{}^{111m}$Cd confirmed the proposal about the fragmentation of the complexes caused by the after-effects of electron capture in $\text{}^{111}$In. An observed difference in the electric quadrupole interaction parameters obtained for the solutions with $\text{}^{111}$In and $\text{}^{111m}$Cd complexes reflects a process of a chemical rearrangement of the complex structure after the In decay into Cd
Źródło:
Acta Physica Polonica A; 2001, 100, 5; 799-805
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Paramagnetic Centres in Coal Macerals
Autorzy:
Słowik, G.
Więckowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1536501.pdf
Data publikacji:
2010-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.66.Hq
76.30.Rn
89.30.ag
Opis:
The electron paramagnetic resonance (EPR) study of coal macerals: exinite, vitrinite and inertinite separated from clarain of the Polish medium-rank coal with carbon content of 85.6 wt% C, were performed. Using the continuous microwave saturation technique (measurements at 223 K and 291 K), as a result of numerical analysis of recorded EPR spectra of exinite, vitrinite and inertinite, their multi-component structure was shown. The EPR spectra of exinite and vitrinite consist of three component lines: one Gaussian G and two Lorentzians: L1 and L3. The EPR spectra of inertinite consist of two narrow lines with Lorentzian line shape L2 and L3. Temperature measurements of studied coal macerals in the range 100-373 K were done. It was evidenced that, in group of paramagnetic centres responsible for Lorentzian L1 component line, paramagnetic centres with thermally excited triplet states (S = 1) exist. Existence of paramagnetic centres with thermally excited triplet states was not observed in inertinite.
Źródło:
Acta Physica Polonica A; 2010, 118, 3; 507-510
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stabilized 1D Metal in TTF(Ni(dmit)$\text{}_{2}$)$\text{}_{2}$ through Very Weak Coupling between Phonons and Weakly Correlated Fermions
Autorzy:
Doublet, M. L.
Malfant, I.
Hebrard, S.
Canadell, E.
Gaultier, J.
Chasseau, D.
Legros, J. P.
Brossard, L.
Powiązania:
https://bibliotekanauki.pl/articles/1933351.pdf
Data publikacji:
1995-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Hk
71.45.Lr
61.66.Hq
Opis:
Extended Hückel band structure calculations derived from low temperature X-ray structural data, provide evidence, as temperature decreases, for an increasing 1D character of the multiparallel bands of the TTF(Ni(dmit)$\text{}_{2}$)$\text{}_{2}$ compound. This result is discussed within the monotonous metallic behaviour of the weakly correlated fermions gas, despite condensations of charge density wave instabilities.
Źródło:
Acta Physica Polonica A; 1995, 87, 4-5; 781-784
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigations of Resorcinol under High Pressure
Autorzy:
Tydda, M.
Jasińska, B.
Powiązania:
https://bibliotekanauki.pl/articles/1196480.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
36.10.Dr
61.66.Hq
Opis:
The investigation of intermolecular free volumes in resorcinol was conducted under high pressure, hydraulic pressure and gas (argon or nitrogen) atmosphere. The sizes of free volumes were estimated basing on the mean lifetime of ortho-positronium (o-Ps). In the first case, a monotonous change of lifetime and intensity was observed for the o-Ps component while the range of pressure was 0-477 MPa. On the other case, the samples were put into the pressure chamber filled with argon or nitrogen in the range of pressure from 0 to 450 MPa. When the pressure chamber was filled with a gas, the appearance of an additional o-Ps component has been found. In the nitrogen atmosphere, the material crushed when the gas pressure reached about 200 MPa, and the mean lifetime of the longest o-Ps component increased.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 812-815
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Structure and Vibrational Spectra of 1,3,5-Trimethoxybenzene
Autorzy:
Pawlukojć, A.
Bator, G.
Sobczyk, L.
Powiązania:
https://bibliotekanauki.pl/articles/1813991.pdf
Data publikacji:
2007-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.30.-j
78.70.Nx
61.66.Hq
Opis:
Inelastic neutron scattering infrared and Raman spectra of the crystalline 1,3,5-trimethoxybenzene were measured and compared with simulated ones by using the Gaussian 98 and DMol3 programs at density functional theory methods. Application of the double numerical plus polarization basis set for the crystalline state within the local density Perdew and Wang (PWC functionals) approximation quite well reproduces the low frequency bands related to the methyl group librational modes, which are very sensitive to molecular interactions. Infrared spectra for the crystalline sample and $CCl_4$ solution show spectacularly the change of low frequency modes by going from the symmetric $D_{3h}$ molecules in the gas phase to asymmetric ones in the crystal.
Źródło:
Acta Physica Polonica A; 2007, 112, S; S-171-S-181
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Triplet States in DOPA-Melanin and in Its Complexes with Kanamycin and Copper Cu(II) Ions
Autorzy:
Najder-Kozdrowska, L.
Pilawa, B.
Buszman, E.
Więckowski, A.
Świątkowska, L.
Wrześniok, D.
Wojtowicz, W.
Powiązania:
https://bibliotekanauki.pl/articles/1535688.pdf
Data publikacji:
2010-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.66.Hq
76.30.Rn
87.64.kh
Opis:
The mono- and biradical forms of DOPA-melanin (DOPA-eumelanin) were studied by EPR spectroscopy in 100-300 K temperature range. The existence of triplet states in DOPA-melanin was proved. The analysis of EPR spectra has shown that in DOPA-melanin and its complexes with kanamycin and $Cu^{2+}$ ions, two kinds of paramagnetic centres exist. The first of them are in doublet ground state with spin S = 1/2 and they obey the Curie law. The paramagnetic centres of the second group are in thermally excited triplet state with spin S = 1 and in this case the Curie law is not fulfilled.
Źródło:
Acta Physica Polonica A; 2010, 118, 4; 613-618
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Paramagnetic Centres in Oxidised Coal
Autorzy:
Najder-Kozdrowska, L.
Samoilova, R.
Kappl, R.
Hüttermann, J.
Więckowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1536451.pdf
Data publikacji:
2010-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.35.+r
61.66.Hq
76.30.Rn
89.30.ag
Opis:
This paper comprises the results obtained by continuous wave (cw)/pulse electron paramagnetic resonance spectroscopy for oxidised coals. The values of EPR linewidths are different for samples of coal treated by different chemical agents. The asymmetric EPR line shape indicates to complex composition of paramagnetic centres in coal. In coal oxidised by $HNO_3$ big changes of linewidth with temperature were observed. For all samples the spin-lattice relaxation time $T_1$ was determined by pulse EPR method. The correlation between used chemical agents and the value of $T_1$ was established.
Źródło:
Acta Physica Polonica A; 2010, 118, 3; 475-479
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Orientation of Single Dibenzanthanthrene Molecules in Solid Xenon
Autorzy:
Sepioł, J.
Kołos, R.
Jasny, J.
Powiązania:
https://bibliotekanauki.pl/articles/1814017.pdf
Data publikacji:
2007-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.50.-j
61.66.Bi
61.66.Hq
61.72.Ww
Opis:
The spatial distributions of individual dibenzanthanthrene electronic transition dipole moments in solid Xe was investigated at the single molecule level, with the high-resolution fluorescence spectroscopy. Samples were prepared by the co-deposition of dibenzanthanthrene/Xe vapours onto the 50 K surface. The results indicate that the orientation of planar aromatic molecules is preferentially parallel to the trapping surface.
Źródło:
Acta Physica Polonica A; 2007, 112, S; S-121-S-126
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Studies of the Bacterial Surfaces by XPS and SEM Methods
Autorzy:
Płoszaj-Pyrek, J.
Talik, E.
Piotrowska-Seget, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1197681.pdf
Data publikacji:
2014-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
87.64.-t
71.20.Rv
61.66.Hq
31.50.Gh
Opis:
This work presents the results of studies on bacteria Bacillus subtilis which was grown at different temperatures. The experiments were carried out using X-ray photoelectron spectroscopy and scanning electron microscope equipped with "cryo-chamber", which gives the possibility of testing biological samples in a frozen state. These methods enabled receiving images of surface topography of the bacteria and demarcated their chemical composition. After deconvolution of the lines C 1s and O 1s information concerning the intensity of the various functional groups in the bindings presented in the cell walls surface of tested strain and reallocation in relation to the temperature of incubation was obtained. These changes are visible in the form of an additional peak in both the C 1s and O 1s in bacteria cultured in suboptimum temperature.
Źródło:
Acta Physica Polonica A; 2014, 125, 4; 929-931
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric and X-ray Studies of Eleventh and Twelfth Members of Two Isothiocyanato Mesogenic Compounds
Autorzy:
Jasiurkowska, M.
Budziak, A.
Czub, J.
Urban, S.
Powiązania:
https://bibliotekanauki.pl/articles/2047170.pdf
Data publikacji:
2006-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.10.Eq
61.66.Hq
64.70.Md
77.22.-d
77.22.Gm
Opis:
Results of the dielectric and X-ray studies of the long-alkyl-chain members (n=11, 12) of two homologous series: nBT (4-n-alkyl-4'-isothiocyanato-biphenyl) and nCHBT (4-trans-4'-n-alkyl-cyclohexyl-isothiocyanato-benzene) in their liquid crystalline phases are presented. These compounds exhibit different polymorphisms: the nematic phase for $n$CHBTs and the smectic E and smectic A phases for nBTs. The dielectric measurements were performed in a wide frequency range of 1 kHz-3 GHz. The layer thickness in the smectic E and smectic A phases and the orthorhombic unit cell parameters of the smectic E phase were determined using the small angle X-ray diffraction method. In the smectic E phase the layer-thickness-to-molecular-length ratios are found to be close to 1. The corresponding ratios observed for the smectic A phase of $n$BTs are considerably higher (≈1.24), which indicates that an alternating head-to-tail arrangement of molecules in the layers is favored. The rotational dynamics of molecules in the smectic E phases is discussed in relation to their packing in a unit cell.
Źródło:
Acta Physica Polonica A; 2006, 110, 6; 795-805
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:
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
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