| Strona główna |
| Zespół |
| Badania |
| Aparatura |
| Seminaria |
| Publikacje |
|
Nasze konferencje |
|
Aktywność konferencyjna |
| Projekty |
| Programy |
|
Najbliższe wydarzenia |
| Linki |
| Kontakt |
|
|
|
od 2020-09-20 |
|
|
|
|
|
1. |
|||
|
Effect of addition of pore expanding agent on changes of structure characteristics of ordered mesoporous silicas A series of mesoporous silica materials were synthesized by applying two types of Pluronic copolymers as pore creating agents. Differentiation of pore structure of the obtained sorbents was attained by changing the amount of trimethylbenzene as pore expander introduced to a reacting mixture. The parameters characterizing porous structure were estimated from nitrogen adsorption/desorption isotherms. The changes of pore arrangement in the synthesized materials were investigated by using X-ray diffraction. The structural transformations were found at the TMB/polymer ratio of 0.8 and 1. Correlations between the values of structure parameters and the content of TMB were found.
(C) 2008 Published by Elsevier B.V. |
|||
|
Applied Surface Science, 255(5), 2851-2858, (2008) |
|||
|
|
|||
|
|
|||
|
2. |
|||
|
Effective and accurate single-shot NMR diffusion experiments based on magnetization grating Current single-shot diffusion methods based on magnetization gratings suffer from low sensitivity due to small rf tip angles and, consequently, from inefficient use of the total equilibrium magnetization. Here, we propose and illustrate the use of a slightly modified form of the magnetization encoding scheme OUFIS for single-shot diffusion experiments. In a detailed theoretical and experimental analysis, we compare the performance of the proposed method to other encoding schemes such as the one-phase or two-phase DANTE and conclude that the OUFIS-based experiment is a superior one. The primary reason is that this scheme allows one to use a larger total pulse area. Hence, one can encode a far larger portion of the initial magnetization into a frequency grating before the onset of various nonlinear effects. In the experimental illustration, we present a single-shot measurement of multicomponent diffusion.
(C) 2008 Elsevier Inc. All rights reserved. |
|||
|
Journal of Magnetic Resonance, 195(2), 123-128, (2008) |
|||
|
|
|||
|
|
|||
|
3. |
|||
|
Magnetic anisotropy study of triangular-shaped Co nanostructures Atomic force microscopy (AFM), X-ray magnetic circular dichroism (XMCD), magnetic force microscopy (MFM) and vibrating sample magnetometry (VSM) have been used to measure the magnetic and geometrical characteristics of triangular-shaped Co structures of lateral size 730 nm and thickness 32 nm, prepared by nanosphere lithography (NSL). Evidence of in-plane six-fold magnetic anisotropy induced by the symmetry of the structure has been found. By means of XMCD measurements, performed at remanence after applying a pulsed field, a structure rotation angle-dependent oscillation of about 15% with a periodicity of 601 has been observed for both the orbital and spin moments. Furthermore, the system exhibits the angular hysteresis effect. The magnetic measurements performed by MFM show a reduction of the magnetic configurations to only two states, one quasi-single domain Y state and second, a combination of vortex and Y state.
(C) 2008 Elsevier B. V. All rights reserved. |
|||
|
Journal of Magnetism and Magnetic Materials, 320(21), 2682-2687, (2008) |
|||
|
|
|||
|
|
|||
|
4. |
|||
|
PEO/fatty acid blends for thermal energy storage materials. Structural/morphological teatures and hydrogen interactions Application of poly(ethylene oxide)-based materials as efficient thermal energy storage systems requires understanding of structural and morphological issues that govern the thermal transitions of the blends. Poly(ethylene oxide)/lauric acid and poly(ethylene oxide)/stearic acid blends show high values of heat of melting and heat of crystallisation which exceed theoretically determined values - it is a synergistic effect that is advantageous in terms of energy storage. The PEO blends were investigated by PLM, SEM, AFM, WAXD, SAXS and H-1 NMR techniques - PLM, SEM and AFM allows to observe regions, in which parallelly-packed crystals of fatty acid are present. WAXD results of PEO/fatty acid blends confirmed hindered crystallization of PEO in PEO/fatty acid blends and, finally, lower degree of polymer crystallinity. The NMR study shows that mixing of PEO and lauric acid results in an increase of PEO amorphous phase content in blends as compared to the pure PEO. From FTIR spectra, taken during melting and crystallization, it can be seen that for both investigated blends in the solid state there is only one maximum of band from v(C=O) (in position indicating that C=O groups are engaged in formation of hydrogen bonds), while in the liquid state there are two maxima - position of the first maximum is characteristic for v(C=O) vibrations of C=O groups that do not participate in formation of hydrogen bond, whereas position of the second maximum in the liquid state proves the presence of C=O groups involved in formation of hydrogen bonds. Solid state NMR analysis reveals no esterification reactions between PEO and fatty acid.
(C) 2008 Elsevier Ltd. All rights reserved. |
|||
|
European Polymer Journal, 44(10), 3344-3360, (2008) |
|||
|
|
|||
|
|
|||
|
5. |
|||
|
Redetermination of the structure and dielectric properties of bis-thiourea pyridinium ioide a new ferroelectric inclusion compounds The crystal structure of bis(thiourea) pyridinium iodide (T(2)PyI) was previously determined at 295 and 110 K [Prout, Heyes, Dobson, McDaid, Maris, Mueller & Seaman (2000). Chem. Mater. 12, 3561-3569] and the two phases were described in the space groups Cmcm and P2(1)cn, respectively. Because differential scanning calorimetry revealed two phase transitions, at 161 and 141 K, a redetermination of the structure of T(2)pyI at 295, 155 and 110 K has been undertaken, and the following sequence of space groups obtained: Cmcm (I) -> C2cm (II) -> P2(1)cn (III). The high- (I) and low- temperature (III) phases confirmed the results reported in the previous study. In the new intermediate phase II, the mirror plane perpendicular to the x axis vanishes and the crystal structure loses the centre of symmetry. In phases I and II the pyridinium cations are strongly dynamically disordered, while in the low-temperature phase III the cations are well ordered. In all three phases the thiourea-iodine hydrogen-bonded sublattice is very well ordered. Dielectric measurements show that the intermediate and low-temperature phases are ferroelectric and that 161 K is the Curie point of a new ferroelectric crystal.
|
|||
|
Acta Crystallographica - Section B, Structural Science, B64(5), 567-572, (2008) |
|||
|
|
|||
|
|
|||
|
6. |
|||
|
|
|||
|
Crystallography Open Database, (2008) |
|||
|
|
|||
|
|
|||
|
7. |
|||
|
Alternating multiblock copolymers exhibiting protein-like transitions in selective solvents: A Monte Carlo study We present a lattice Monte Carlo study of a series of block copolymer chains in selective solvents of varying quality, first using a diblock chain of the length of N = 32 with a 16-16 microarchitecture, and then - two multiblock chains of N = 64 and N = 128, with (8-8)(4) and (16-16)(4) microarchitectures, respectively. We report a variety of thermodynamic and structural properties, such as energy, specific heat, end-to-end distance and radius of gyration both for the whole chain and for individual blocks. The simulations have demonstrated that a multiblock copolymer in a selective solvent exhibits protein-like behavior undergoing a two-step transition, first from a swollen state to a secondary 'pearl-necklace' state and then to a tertiary super-globular state as the solvent quality decreases, i.e. upon cooling. We have found that mean-squared end-to-end distances of multiblock chains decrease as the temperature is reduced, as expected.
(C) 2008 Elsevier B.V. All rights reserved. |
|||
|
Journal of Non-Crystalline Solids, 354(35-39), 4138-4142, (2008) |
|||
|
|
|||
|
|
|||
|
8. |
|||
|
The SAXS and rheological studies of HEWL amyloid formation We performed small angle X-ray scattering and rheological experiments in order to analyze the aggregation and denaturation processes of hen egg white lysozyme initiated by the presence of ethanol molecule. At low ethanol concentrations (below 60% (v/v)) we did not observe any change of the radius of gyration of lysozyme and no drastic changes in viscosity of the protein solution. With the increase in ethanol concentration up to the final concentration of 85% (v/v) the viscosity of protein solution dramatically increased. For high ethanol concentration a pseudoplastic behavior of lysozyme solution was observed, indicating a process of aggregation and reorientation of the protein molecules. Similar effects were observed in small angle X-ray scattering experiments. We assume that the analysis of the aggregation processes of the hen egg white lysozyme could contribute to our understanding of the mechanism of lysozyme amyloid formation.
|
|||
|
Acta Physica Polonica A, 114(2), 447-454, (2008) |
|||
|
|
|||
|
|
|||
|
9. |
|||
|
A comparative study of water distribution and dehydrin protein localization in maturing pea seeds n this study, the distribution of water in pea seeds after harvesting at different seed stages was traced by magnetic resonance imaging (MRI). MRI visualized the process of water toss in maturing pea seeds. MR images showed local inhomogeneities of water distribution inside seeds. The intensity of the signal coming from water declined from the inner to the outer part of cotyledon tissue. This spatial inhomogeneity of water signals inside cotyledons may be correlated with the gradient of storage substances accumulation within cotyledons. Tissue localization of dehydrins showed the presence of dehydrin protein in the area of protovascular tissue of both the embryo axis and cotyledons. The temporal accumulation of two dehydrin proteins with molecular masses of 30 and 35 kDa correlated welt with seed desiccation. The pattern of dehydrin localization reflected the pattern of water distribution in the protovascular bundles region of maturing pea embryos, suggesting the involvement of these proteins in promoting water influx into the vascular bundles.
(C) 2008 Elsevier GmbH. All rights reserved. |
|||
|
Journal of Plant Physiology, 165(18), 1940-1946, (2008) |
|||
|
|
|||
|
|
|||
|
10. |
|||
|
Monte Carlo phase diagram of symmetric diblock copolymer in selective solvent With a lattice Monte Carlo method, we investigate 16-16 symmetric diblock in selective solvent, A-b-B/A, at 10 volume fractions from 1.0 to 0.1, and for each volume fraction, we perform simulations at up to 54 temperatures, using simulation boxes of different sizes. We report temperature dependencies for a number of quantities such as energy, specific heat, and mean-squared end-to-end distances and construct a phase diagram using the thermodynamic and structural quantities as well as snapshots of the selected configurations. The simulated phase diagram is compared with the experimental data of Lodge and co-workers for nearly symmetric poly(styrene-b-isoprene) mixed with dimethyl phthalate.
|
|||
|
Macromolecules, 41(15), 5945-5951, (2008) |
|||
|
|
|||
|
|
|||
|
11. |
|||
|
Acid induced gelation of low methoxyl pectins studied by 1H NMR and rheological methods The various 1H NMR techniques (1H NMRD, water proton spin-spin relaxation time and diffusion measurements) in combination with rheological measurements were applied to the analysis of the acid induced gelation of 3% w/w aqueous LM pectin solutions at 279 K. A decrease of the pH value of solutions from 5 to 2.6 leads to a slowdown in the dynamics of the water molecules and to a substantial modification in the structure of the system studied. The most significant changes in the 1H NMRD and T2 measurements were observed when the pH was varied from 5 to 3, which reflected an increase in the stiffness of the pectin chains caused by non-ionic associations and by an increase of water molecules that were trapped between the pectin chains in the gelled ste. The results obtained by the rheological method are consistent with those of 1H NMR, indicating a solution-like mechanical response for the sample at pH 5 and a gel-like response at pH 3. Results of 1H NMR measurements have also shown an important role for aggregation processes of the LM pectin molecules in the acid-induced gel network formation.
|
|||
|
Applied Magnetic Resonance, 34(1-2), 71-81, (2008) |
|||
|
|
|||
|
|
|||
|
12. |
|||
|
Molecular motion in the biocopolymer sequence of glycolide and lactide studied by solid state NMR This paper reports a nuclear magnetic resonance study of the molecular motion in copolymers derived from glycolide and L-lactide in the solid state. Variation of T-1 relaxation times with temperature reflects a local disorder and the fast segment conformational motions which can be quantified in terms of correlation times predicted by the Bloembergen-Purcell-Pound and Davidson-Cole models. At low temperatures, spin relaxation is dominated by the axial methyl rotation in lactide units described by an asymmetry parameter of the correlation time delta which takes a value of about 0.45 for all systems. Above the devitrification points the trans and gauche isomerization in glycolide segments occurs. In addition to the chemical structure characterization, solid-state magic-angle spinning spectroscopy gives an insight into the role of glycol segments in the chain mobility.
|
|||
|
Applied Magnetic Resonance, 34(1-2), 193-203, (2008) |
|||
|
|
|||
|
|
|||
|
13. |
|||
|
Temperature dependence of spontaneous polarization in order-disorder pyridinium periodate extracted from 2H NMR data On the basis of occupancy factor data for nitrogen atoms in the pyridinium cation obtained from the structural study of PyHIO4 by neutron diffraction,(4) the shape of the potential for cation reorientation about the axis perpendicular to its plane was found. The H-2 NMR spectra of d(5)PyHIO(4) taken over a wide range of temperatures have allowed the determination of potential minima populations. These data were used to obtain the temperature dependence of spontaneous polarization. The agreement between the spontaneous polarization calculated in this way and the measured values is very good and indicates that the ferroelectric crystal is of the order-disorder type.
|
|||
|
Journal of Physical Chemistry C, 112(19), 7503-7508, (2008) |
|||
|
|
|||
|
|
|||
|
14. |
|||
|
Scaffold-aided repair of articular cartilage studied by MRI Objective The objective of the study was to evaluate the ability of the noninvasive magnetic resonance techniques to monitor the scaffold-aided process of articular cartilage repair.
Materials and methods Defects of 4 mm in diameter and 3 mm in depth were created in right knees of 30 adolescent white New Zealand rabbits. Fourteen rabbits were implanted with poly(lactide-co-glycolic acid) (PLGA) scaffold trimmed to match the size and the shape of the defect (PLGA+ group). No procedure was applied to the remaining 16 animals (PLGA- group). Animals were sacrificed sequentially at 4, 12, and 24 weeks after the surgery and magnetic resonance T(2)-weighted images (400 MHz) of the dissected bone plugs at eight different echo times were taken to derive T(2) relaxation time. The images and the T(2) time dependencies versus the tissue depth were statistically analyzed. Histological results of bone plugs were evaluated using semiquantitative histological scales. Results The results obtained for PLGA repair tissue were evaluated versus the PLGA- group and the healthy tissue harvested from the opposite knee (reference group), and compared with histological results (hematoxylin and eosin staining). The magnetic resonance images and T(2) relaxation time profiles taken 4 weeks after surgery for both the PLGA- and PLGA+ group did not reveal the tissue reconstruction. After 12 weeks of treatment T(2) time dependence indicates a slight reconstruction for PLGA+ group. The T(2) time dependence obtained for PLGA+ samples taken after 24 weeks of treatment resembled the one observed for the healthy cartilage, indicating tissue reconstruction in the form of fibrous cartilage. The tissue reconstruction was not observed for PLGA-samples. Conclusion The study revealed correlation between magnetic resonance and histology data, indicating the potential value of using MRI and spatial variation of T (2) as the noninvasive tools to evaluate the process of articular cartilage repair. It also suggested, that the PLGA scaffold-aided treatment could help to restore the proper architecture of collagen fibrils. |
|||
|
Magnetic Resonance Materials in Physics, Biology and Medicine, 21(3), 177-185, (2008) |
|||
|
|
|||
|
|
|||
|
15. |
|||
|
Electric-field gradient tensor and charge densities in LaB6: 11B NMR single-crystal investigations and first-principles calculations B-11 nuclear-magnetic-resonance measurements on a B-11 enriched single crystal of LaB6 have been performed at room temperature at a frequency of 128.4 MHz. The electric-field-gradient (EFG) tensor components have been determined from the angle dependence of the quadrupole splittings associated with (-3/2 <->-1/2) and (3/2 <-> 1/2) satellite transitions. These EFG components have been calculated using first-principles methods. Very satisfactory agreement with the experimental values has been obtained. The calculations show that the largest component of the EFG tensor mainly comes from the pp part of the so-called sphere component. The principal axis for the most negative EFG component is oriented in direction of the shortest and strongest bond between neighboring B atoms, which belong to two different B-6 units (interoctahedral B-B bonds). The fact that these interoctahedral B-B bonds are aligned in three different directions is responsible for the observation of up to three satellite pairs, although all boron atoms are crystallographically equivalent and there exists only one EFG tensor. Apart from the EFG investigations, chemical bonding in LaB6 is analyzed from densities of states and electron-density plots.
(C) 2008 American Institute of Physics. |
|||
|
Journal of Applied Physics, 103(8), 083534-7, (2008) |
|||
|
|
|||
|
|
|||
|
16. |
|||
|
The influence of radiation sterilization on thiamphenicol The effect of ionising radiation, applied in the form of an electron beam, in the doses of 25, 100 and 400kGy on the physical and chemical properties of thiamphenicol in solid phase has been studied by organoleptic analysis (form, colour, smell, solubility, clarity) and spectroscopic methods (UV, IR, EPR), chromatography (TLC), SEM observations, X-ray diffraction, polarimetry and thermal method (DSC).
The above-discussed results have proved that on irradiation with a dose of 25 kGy no significant changes appear in thiamphenicol, apart from the formation of free radicals of the lifetime of over 352 days. On irradiation with much higher doses (100 and 400 kGy) no changes were observed in the IR spectra but the UV line intensities slightly increased at lambda(max) = 266 and 273 nm, the colour of the powder changed, the radiolysis products appeared as detected by TLC, changes were also observed in the XRD, SEM pictures, the melting point values (DSC) and optical rotation. On the basis of DSC results a linear relation was found between the irradiation dose and the decrease in the melting point and increase in the enthalpy of melting, characterised by high correlation coefficients of r = 0.9839 and 0.9622, respectively. Moreover, a linear relation was established between the optical rotation angle and the irradiation dose, alpha(D) (degrees) =f(dose), characterised by the correlation coefficient r = 0.9874. The results obtained indicate that thiamphenicol can be safely subjected to radiation sterilization by the standard dose of 25 kGy. (C) 2007 Elsevier B.V. All rights reserved. |
|||
|
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy, 69(3) , 865-870, (2008) |
|||
|
|
|||
|
|
|||
|
17. |
|||
|
Polarisation and energy barriers in ferroelectric pyridinium perchlorate Polycrystalline sample of pyridinium perchlorate was studied by NMR method in the temperature range from 133 to 313 K. Assuming a reorientation of pyridinium cations over inequivalent potential energy barriers in the low-temperature and intermediate phases a temperature dependence of an asymmetry parameter was determined from analysis of 2H line shape. By using the known potential shape and population of its minima, a temperature dependence of the spontaneous polarisation was calculated. The polarisation determined in this way compared with that measured by the pyroelectric effect revealed the mixed type of ferroelectricity in the crystal studied: the order-disorder and displacive one.
|
|||
|
Ferroelectrics, 368(1p2), 63-71, (2008) |
|||
|
|
|||
|
|
|||
Zaktualizowano: podstrony 2025-01-24 / bazę danych: 2025-01-22 by Webmaster: Zbigniew Fojud