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  1. 5 Blicharska B.

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1
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Nuclear Spin Relaxation in Periodically Perturbed Systems IV. The Relaxation in the Presence of Double Rotation and Pulse Sequence

100%
Blicharski J. S., Jasiński G., Klose G.
Acta Physica Polonica A
|
1994
|
vol. 86
|
issue 6
1001-1005
EN
The effective relaxation times are calculated in the weak collision case for the system of identical nuclear spins perturbed by double rotation, periodic sequences of r.f. pulses and spin interactions.
2
Content available remote

Influence of Sample Rotation on the Shape of the Free Induction Decay

100%
Blicharska B., Kruk D.
Acta Physica Polonica A
|
1993
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vol. 84
|
issue 2
321-325
EN
Free induction decay is calculated at the presence of rotation of a liquid sample in a static magnetic field with a constant gradient.
3
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Nuclear Spin Relaxation in Periodically Perturbed Systems

100%
Blicharski J. S., Wolak A.
Acta Physica Polonica A
|
1991
|
vol. 79
|
issue 4
591-598
EN
The effective relaxation time T_{2e} is calculated in the weak collision case for a system of identical nuclear spins perturbed by periodic sequences of r.f. pulses and dipole-dipole and quadrupole interactions.
4
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Nuclear Spin Relaxation in Periodically Perturbed Systems. II. Like and Unlike Spins

100%
Blicharski J., Wołak A.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 3
511-515
EN
The effective relaxation time T_{2e} is calculated in the weak collision case for a system consisting of resonant nuclear spins I and nonresonant spins S, perturbed by periodic sequences of r.f. pulses and dipole-dipole interactions.
5
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Nuclear SPin Relaxation in Periodically Perturbed Systems. III. The Relaxation in the Presence of Double Rotation

100%
Blicharski J., Jasiński G.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 6
993-997
EN
The effective spin relaxation times are calculated in the presence of double rotation in the weak collision case.
6
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Molecular Dynamics in Biological Systems Observed by NMR Relaxation in a Rotating Frame

63%
Wierzuchowska D., Skórski L., Blicharska B.
Acta Physica Polonica A
|
2012
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vol. 121
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issue 2
434-438
EN
NMR relaxation provides powerful tools for obtaining information on three-dimensional structures, dynamic properties and intermolecular interactions of biological macromolecules. One of these methods, called dispersion profile, is based on measuring the field dependence of spin-relaxation rates in the rotating frame, R_{1ρ} = 1/T_{1ρ}, in the presence of a low magnetic field B_1. In the presented study we use this method for investigation of molecular dynamics in protein samples. Dispersion profiles can be predicted theoretically and using two models, assuming either dipolar interaction between protons or power law dispersion, we have evaluated some molecular dynamic parameters of water adsorbed on protein surface. Our researches are focused on the connections of obtained parameters of molecular dynamics with conformation changes of protein. We have calculated the correlation times and power parameters for samples of lyophilized powder of albumins (egg white and bovine and rabbit blood serum) and lysozyme, as well as its aqueous solutions. Analysis of these parameters yields valuable information on the molecular nature of investigated biological systems. We also used this method to analyze experimental data of T_{1ρ} obtained by other authors for bovine serum albumin and we have found good accordance with their conclusions concerning molecular dynamics of proteins.
7
Content available remote

Alkali Intercalated C_{60}: NMR and Magnetic Susceptibility Studies

63%
Rachdi F., Goze C., Reichenbach J., Lukyanchuk J., Kirova N., Zimmer G., Mehring M., Molinié P.
Acta Physica Polonica A
|
1995
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vol. 87
|
issue 4-5
861-867
EN
We report on ^{13}C NMR measurements on potassium intercalated C_{60} compounds. By using high resolution NMR technique we were able to char­acterize the different thermodynamically stable phases. The effects of the intercalation on the molecular dynamics as well as on the electronic proper­ties will be discussed. We also performed the magnetic susceptibility mea­surements on Rb_{4}C_{60} compound, which reveal the activation temperature behavior with the activation energy about 1200 K. By comparison with the NMR and ESR data of the same sample we conclude that the additional electrons are localized on the C_{60} molecule and form the spin singlet ground state.
8
Content available remote

^{13}C High Resolution NMR Study of Methyl-Diethyl Sulfonium TCNQ 1:2 Complex

63%
Firlej L., Pęcherz J., Bernier P.
Acta Physica Polonica A
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1995
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vol. 87
|
issue 4-5
829-834
EN
Solid state high resolution ^{13}C NMR studies of a 1 : 2 charge transfer complex of TCNQ with diethyl-methyl sulfonium S + Et_{2}Me(TCNQ)_{2} are presented. The metallic shifts of TCNQ resonances are interpreted as due to the Pauli paramagnetism of conducting electrons and quantitatively con­nected with inhomogeneous spin density distribution over (TCNQ2)¯ dimer. A singularity of NMR parameters at T = 330 K is observed and described as a structural phase transition occurring in the S + Et_{2}Me cation sublattice.
9
Publication available in full text mode
Content available

A ^{55}Mn NMR Study of La_{0.33}Nd_{0.33}Ca_{0.34}Mn O_3 with ^{16}O and ^{18}O

63%
Rybicki D., Kapusta C., Riedi P., Oates C., Sikora M., Zając D., De Teresa J., Marquina C., Ibarra M.
Acta Physica Polonica A
|
2004
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vol. 105
|
issue 1-2
183-188
EN
A ^{55}Mn NMR study of ^{16}O and ^{18}O containing La_{0.33}Nd_{0.33}Ca_{0.34}Mn O_3 is reported. The spin-echo spectra measured at 4.2 K and zero field consist of a double exchange line corresponding to the ferromagnetic metallic regions. The line intensity is more than an order of magnitude lower for the ^{18}O compound, which indicates an order of magnitude lower content of the ferromagnetic metallic phase in this compound. The frequency dependence of the spin-spin relaxation time T_2 shows a pronounced minimum at the center of the double exchange line of both compounds due to the Suhl-Nakamura interaction, which indicates that the ferromagnetic metallic regions are at least 10~nm in size. The results are discussed in terms of the influence of oxygen isotopic substitution on phase segregation.
10
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Content available

An NMR study of Pr_{0.5}Ca_{0.5}Mn_{1-x}Ga_xO_3 (x=0 and 0.03)

63%
Oates C., Kapusta C., Riedi P., Sikora M., Zając D., Rybicki D., Martin C., Yaicle C., Maignan A.
Acta Physica Polonica A
|
2004
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vol. 105
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issue 1-2
189-195
EN
An NMR study of polycrystalline Pr_{0.5}Ca_{0.5}Mn_{1-x}Ga_xO_3 (x=0 and 0.03) at 3 K is presented. Zero field spin-echo spectra of the Ga doped compound consist of an overlapping ^{69,71}Ga signal at 74~MHz (hyperfine field of 5.3 T), a ^{55}Mn double exchange line at 375 MHz (35.5 T) and a weak Mn^{3+} signal between 400 and 550 MHz. Measurements in an applied field show a step-like increase in the double exchange line intensity, which corresponds to an increase in the amount of the ferromagnetic metallic phase. This coincides with a step-like feature in the bulk magnetization measurements. The effect is similar to that in the previous field dependent ^{55}Mn NMR measurements of Pr_{0.67}Ca _{0.33}MnO_3. At the demagnetized and remanent state, a variation of spin- spin relaxation time, T_2, across the ^{55}Mn line, due to the Suhl-Nakamura interaction is observed, which suggests that the ferromagnetic metallic double exchange regions, at liquid helium temperatures, are at least 4 nm in size.
11
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Hyperfine Field in YIG with Charged Substitution

63%
Kohout J., Štĕpánková H., Englich J., Novák P., Kučera M., Nitsch K.
Acta Physica Polonica A
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2000
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vol. 97
|
issue 3
519-522
EN
^{57}Fe NMR spectra were measured on thin films of yttrium iron garnet with divalent (Ca^{2+}) and tetravalent (Ge^{4+}) cation substitutions using the spin echo technique at 4.2 K. A series of Y_{3-x}Ca_{x}Fe_{5-x}Ge_{x}O_{12} samples with 0 ≤ x ≤ 0.0 5 was prepared by an epitaxial growth from BaO/B_{2}O_{3}/BaF_{2} flux on gadolinium gallium garnet substrate. Satellite lines corresponding to the iron ions having the Ge^{4+} and Ca^{2+} in their neighbourhood were identified. The sample with the germanium content of x(Ge) = 0.004 and (110) substrate orientation was used for a detailed study: NMR spectra of this sample were measured in an external magnetic field of 0.1 T applied along several directions in the plane of the film. The modification of the isotropic part and the anisotropy tensor of the hyperfine interaction caused by the Ge^{4+} substituent were obtained from the experimental data. The results were compared with those previously reported for trivalent substitution (Ga^{3+}).
12
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Proton and Deuteron Relaxation Study of Molecular Dynamics in Lysozyme Solutions

63%
Kakule J. F., Węglarz W. P., Shenoy R. K., Sharp A. R., Peemoeller H.
Acta Physica Polonica A
|
2000
|
vol. 98
|
issue 1-2
131-152
EN
A nuclear magnetic resonance spin-lattice relaxation dispersion study of the relaxation of several magnetization components in both natural and deuterated lysozyme solutions was undertaken at 20°C. Proton and deuteron resonances were employed. The two-dimensional time evolution of the magnetization and the spin-spin relaxation were analyzed. In addition, an isotopic dilution study was performed at 5 and 30.6MHz. The results indicate that the water proton spin-lattice relaxation rate which arises from intermolecular relaxation between the water protons and the lysozyme protons represents a relatively strong relaxation mechanism. A model for the dynamics of the water molecules, consistent with the proton and deuteron dispersions as well as with the isotopic dilution results, is presented.
13
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Content available

^1H NMR Study of Molecular Dynamics of 4-apyH Cation under High Hydrostatic Pressure

63%
Medycki W., Świergiel J., Jakubas R., Hołderna-Natkaniec K.
Acta Physica Polonica A
|
2005
|
vol. 108
|
issue 1
161-164
EN
Polycrystalline [4-NH_2C_5H_4NH] SbCl_4 and [4-NH_2C_5H_4NH] SbCl_6 have been investigated by proton NMR methods between 120 K and 370 K under hydrostatic pressure of 0.1 and 520 MPa. Reduction in the dipolar second moment is interpreted in terms of cation reorientation. Activation energies characterizing the motion increase with increasing pressure.
14
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Molecular Dynamics of Proteins Investigated by NMR Relaxation Methods

63%
Wierzuchowska D., Blicharska B.
Acta Physica Polonica A
|
2014
|
vol. 125
|
issue 4
907-910
EN
The nuclear magnetic resonance relaxation times of solvent water nuclei are known to decrease upon addition of diamagnetic solute protein. For this reason NMR relaxation methods are able to provide information on molecular dynamics changes of water protons and their interaction with macromolecules' surfaces. We present results of measurements of relaxation rates R_1 = 1/T_1, R_2 = 1/T_2 and R_{1ρ} = 1/T_{1ρ} in the rotating frame for three proteins: chicken egg white lysozyme, egg white albumin, and bovine serum albumin, obtained at proton resonant frequency of 60 MHz. Besides the relaxation rates dependences on concentration in the 4-23% (g/100 g solution) range, the analysis of the Carr-Purcell-Meiboom-Gill CPMG multi-echo T_2 experiments with variable pulse rate τ was performed. The dependences of relaxation rates on protein concentration are linear at low concentration. When protein concentration increases the slope of the straight line rapidly changes at so-called "critical" concentration which depends on MW of the diluted protein. Investigated dispersion of T_2, obtained using the CPMG method with a variable pulse rate, for concentrations higher and lower than the "critical" one, exhibits unequal behavior. At high concentration one-exponential curves and at low concentration two-exponential curves correspond closely with experimental data. The obtained parameters of exponents allow an estimation of the ratio of the amount of water with the determined motion freedom, that is free and bounded water, in solution. We showed that the CPMG dispersion method applied to aqueous protein solutions may widen the current understanding of the nature of molecular dynamics of hydrated water protons in non-perturbed environment.
15
Content available remote

^{57}Fe Hyperfine Field Anisotropy in Ferrites and its Relation to the Non-Uniformity of the Ionic Surrounding

63%
Štepánková H., Englich J., Kohout J.
Acta Physica Polonica A
|
2000
|
vol. 97
|
issue 5
757-760
EN
The hyperfine field anisotropy tensors, obtained from analysis of ^{57}Fe NMR spectra for iron sites in various magnetic oxides (barium hexaferrite, lithium spinel, magnetite and yttrium-iron garnet) were used to investigate the relation between the hf anisotropy and surrounding ionic arrangement. While a reasonable correlation has been found when the distribution of the nearest cations was considered, no correlation was obtained between the hyperfine field anisotropy and the positions of the nearest oxygen anions.
16
Content available remote

NMR Study of Ion Motions in [C(NH_{2})_{3}]_{3}GaF_{6}

63%
Kozak A., Grottel M., Pająk Z.
Acta Physica Polonica A
|
1993
|
vol. 83
|
issue 2
219-225
EN
Proton and fluorine spin-lattice relaxation times as well as second moments were measured in guanidinium hexafluorogallate over a wide range of temperature. The analysis of all cross-relaxation effects occurring in the four unlike spin system revealed two cation motions and yielded their activation parameters. It was found that the anion size did not influence C_{3} reorientation of cation nor isotropic reorientation of anion.
17
Publication available in full text mode
Content available

Dynamic Disorder in Perovskites: Local Symmetry Breaking at the Sr Site in SrTiO_3

63%
Blinc R., Zalar B., Laguta V., Zidanšek A.
Acta Physica Polonica A
|
2005
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vol. 108
|
issue 1
7-11
EN
A-site symmetry breaking in the macroscopically cubic paraelectric phase of SrTiO_3 was observed by quadrupole perturbed ^{87}Sr NMR. The local symmetry breaking at the A (Sr) site is connected with slow and biased disorder dynamics similarly as at the B (Ti) site.
18
Publication available in full text mode
Content available

Local Magnetic and Electronic Properties of the A2FeM'O6 (A = Ba, Sr, Ca, M' = Mo, Re) Double Perovskites

51%
Zając D., Sikora M., Prochazka V., Borowiec M., Stępień J., Kapusta C., Riedi P., Marquina C., De Teresa J., Ibarra M.
Acta Physica Polonica A
|
2007
|
vol. 111
|
issue 6
797-820
EN
The results of a combined NMR, X-ray absorption spectroscopy and X-ray magnetic cirrcular dichroism study of the AA'FeMoO_6 and AA'FeReO_6 double perovskites are presented. They revealed a dependence of electronic and magnetic properties, including a d-electron transfer between Fe and Mo sites, on the structural tolerance factor. The maximum value of the 4d Mo electron occupation and the corresponding Mo moment is obtained for the tolerance factor of unity. This corresponds to the maximum strength of the magnetic interaction and, respectively, to the Curie temperature. The dominant T^{5/2} type temperature dependence of the Mo hyperfine field reveals the half-metallicity of the AA'FeMoO_6 compounds. Antisite defects and antiphase boundaries have been identified in NMR measurements and the strength of their magnetic coupling have been determined. A considerable orbital contribution to the Re and Fe magnetic moments were found in the NMR and X-MCD measurements on the AA'FeReO_6 compounds. Its magnitude decreases with increasing structural tolerance factor and is correlated with their magnetic anisotropy.
19
Content available remote

Observation of Antioxidants Activity using NMR Relaxation Measurements

51%
Wierzuchowska D., Witek M., Blicharska B.
Acta Physica Polonica A
|
2018
|
vol. 133
|
issue 2
289-291
EN
Formation of free radicals in biological solutions leads to the changes in water protons relaxation times. Therefore, NMR relaxation measurements were used to investigate kinetics of oxidation processes induced by the addition, in low amounts, of hydrogen peroxide (H_2O_2) to aqueous protein solution and to blood serum. The measured relaxation times were not stable over time because of the progressive formation of free radicals and their damaging action to the protein structure. The addition of antioxidants (ascorbic acid, gallic acid etc.) changed the relaxation time courses due to free radical scavenging. Similar time courses, thus anti-oxidant actions, were observed in various blood serum without antioxidant additive. Moreover, the observed kinetics of spin-lattice relaxation time (T_1) depended on several factors, such as: structure and concentration of protein solutions and activity and concentration of the added antioxidants.
20
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Estimation of the Degree of Crystallinity of Partially Crystalline Polypropylenes Using ^{13}C NMR

51%
Hronský V., Koval'aková M., Vrábel P., Uhrínová M., Olčák D.
Acta Physica Polonica A
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2014
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vol. 126
|
issue 1
409-410
EN
The paper deals with a method for the estimation of the degree of crystallinity for partially-crystalline isotactic-polypropylenes (i-PP) using high-resolution solid-state ^{13}C NMR. For this purpose direct polarization ^{13}C MAS NMR spectra were measured for i-PP samples with different degrees of crystallinity at 98°C. The areas beneath the resonance lines in these spectra correspond to the number of carbons in particular functional groups, while the widths and shapes of the lines reflect the degree of crystallinity, crystalline modifications, distribution of chain conformations and the chain mobility. The ^{13}C MAS NMR spectra, measured using appropriate combination of delay time and high proton decoupling field, made it possible to detect only amorphous domains in the sample. This enabled identification of the lines associated with the amorphous domains in the complete ^{13}C MAS NMR spectra and provided sufficient information for reliable estimation of the degree of crystallinity. The heteronuclear Overhauser enhancement of the ^{13}C NMR signals due to short delay time was taken into account in our calculations.
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