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od 2020-09-20 |
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1. |
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The effect of aging temperature on structure characteristics of ordered mesoporous silicas A series of mesoporous silica materials were synthesized by applying Pluronic type polymers as pore creating agents. In order to differentiate the characteristics of porous structure of the obtained sorbents the temperature of aging process was changed in the synthesis. The parameters characterizing the pore structure were estimated from nitrogen adsorption/desorption isotherms. The changes of pore arrangement of the obtained materials being a result of different synthesis conditions were investigated by using a small angle X-ray scattering method. Correlations between the values of structure parameters and aging temperature were found.
(C) 2005 Elsevier B.V. All rights reserved. |
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Applied Surface Science, 252(3), 625-632, (2005) |
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2. |
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Direct comparison of the crystal and solution structure of glucose/xylose isomerase from Streptomyces rubiginosus Glucose isomerase (D-xylose ketol-isomerase, EC 5.3.1.5.) catalyses the isomerization reaction of glucose and xylose. The small angle X-ray scattering (SAXS) data of glucose/xylose isomerase from Streptomyces rubiginosus were recorded for protein solution using synchrotron radiation. The experimental data were compared with theoretical scattering calculated on the basis of the known crystal structure (PDB code: 10AD). The radius of gyration measured by SAXS (R-G=3.30 nm) was almost identical and the maximum dimension in the distance distribution function was by about 2.5 % lower than the corresponding values calculated on the basis of the crystal structure.
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Protein and Peptide Letters, 12(6), 547-550, (2005) |
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3. |
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Molecular dynamics of tert-butyl chloride confined to CPG (7.4, 15.6 nm) The paper complements our earlier NMR investigation of molecular dynamics of tert-butyl chloride restricted by geometries of the type MCM-41 and CPG by the new sizes of CPG and by differential scanning calorimetry method. We report proton and deuteron NMR lineshapes and the spin-lattice relaxation results of tert-butyl chloride in CPG of the 15.6 nm and 7.4 nm pore diameter in the temperature range 70 K
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Acta Physica Polonica A, 108(2), 357-370, (2005) |
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4. |
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Molecular dynamics in cyclic olefin copolymer Nuclear magnetic resonance, broadband dielectric spectroscopy and dynamic-mechanical thermal analysis were employed to study molecular dynamics of ethylene-norbornene copolymer. The analysis of experimental data indicates existence of three motional processes denoted as α, β, and γ in order of decreasing temperature. The α relaxation is related to the dynamic glass transition, while the beta relaxation, observed only for the untreated sample, is assigned to short range segmental motions involving norbornene units. The γ relaxation is due to very local motions of ethylene units e.g. trans-gauche isomerization, similar to those responsible for γ relaxation in polyethylene. The rate of motion accountable for γ process, follows the Vogel-Fulcher-Tammann equation, similarly to alpha transition, indicating cooperative nature of the motion.
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Acta Physica Polonica A, 108(2), 385, (2005) |
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5. |
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Polski Przegląd Nauk o Zdrowiu, 5, 58-62, (2005) |
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6. |
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1H NMR and rheological studies of the calcium induced gelation process in aqueous low methoxyl pectin solutions The H-1 NMR relaxometry in combination with water proton spin-spin relaxation time measurements and rheometry have been applied to study the ionic gelation of 1% w/w aqueous low methoxyl pectin solution induced by divalent Ca2+ cations from a calcium chloride solution. The model-free approach to the analysis of H-1 NMR relaxometry data has been used to separate the information on the static (β) and dynamic (<τ(c)>) behaviour of the systems tested. The H-1 NMR results confirm that the average mobility of both water and the pectin molecules is largely dependent on the concentration of the cross-linking agent. The character of this dependency (β, <τ(c)> and T-2 vs. CaCl2 concentration) is consistent with the two-stage gelation process of low methoxyl pectin, in which the formation of strongly linked dimer associations (in the range of 0-2.5 mM CaCl2) is followed by the appearance of weak inter-dimer aggregations (for CaCl2 >= 3.5 mM). The presence of the weak gel structure for the sample with 3.5 mM CaCl2 has been confirmed by rheological measurements. Apart from that, the T1 and T2 relaxation times have been found to be highly sensitive to the syneresis phenomenon, which can be useful to monitor the low methoxyl pectin gel network stability.
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Acta Physica Polonica A, 108(1), 33, (2005) |
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7. |
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Spectroscopic studies of poly(epsilon-caprolactone)/sodium montmorillonite nanocomposites Polymer-layered silicate nanocomposites belong to a new class of hybrid materials consisting of organic-synthetic polymer matrix and inorganic filler-layered structure clay minerals. The paper presents the results of FTIR, NMR, and SAXS studies of poly( epsilon -caprolactone)/sodium montmorillonite nanocomposites. We observed a correlation between the concentration of poly( epsilon -caprolactone) in nanocomposite samples and structural changes both of the clay mineral and the intercalated polymer. Stiffening of the clay structure appears as a result of poly(epsilon -caprolactone) intercalation into a clay structure. 27Al NMR studies indicated in nanocomposites two non-equivalent sites of aluminium ions, i.e. in octahedral and tetrahedral coordination, whereas in the montmorillonite clay structure the aluminium ions are located in the interlayer space too. We found also that the temperatures of structural changes and softening process of poly( epsilon-caprolactone) chains in the nanocomposites depend on the concentration of poly( epsilon -caprolactone).
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Acta Physica Polonica A, 108(1), 187-196, (2005) |
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8. |
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Glucose isomerase from Streptomyces Rubiginosus - potential molecular weight standard for small-angle X-ray scattering Stability of solutions of glucose isomerase from Streptomyces rubiginosus on long-term storage and on exposure to synchrotron radiation has been studied by the small-angle X-ray scattering (SAXS) method. The values of the radii of gyration and forward scattering do not change significantly on storage and on exposure to synchrotron radiation. The mean value of the radius of gyration characterizing glucose isomerase is R-G = 3.27 ± 0.02 nm. For comparison, a SAXS study of monodispersive and aggregated bovine serum albumin (BSA) has been carried out. The results show that glucose isomerase could be a more stable molecular weight standard for SAXS than BSA.
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Journal of Applied Crystallography, 38(3), 555-558, (2005) |
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9. |
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Structure of multicomponent SiO2-Al2O3-Fe2O3-CaO-MgO glasses for the preparation of fibrous insulating materials Glasses used for the fabrication of fibrous insulating materials are made from natural raw materials, mainly basalts. Basalt alloys, however, show relatively high crystallization capability, which is disadvantageous for throwing and durability of the fibres prepared.
In the work new raw materials, such as melaphyres and diabase from the Silesia region of Poland were applied for the preparation of aluminosilicate alloys. In order to study their crystallization ability the glasses were heated in an electric furnace at various temperatures for various time periods. Depending on the raw material used as well as the temperature of heat-treatment amorphous or crystalline materials were obtained. Crystalline phases were identified based on X-ray diffraction studies. It was found that magnetite/titanomagnetite crystallized in the first step. Then pyroxenes phases of diopsides or augite type appeared in the systems.
Spectroscopic investigations in the mid IR region were carried out for all the glasses. This made it possible to determine the influence of thermal treatment on the structural changes of glasses (changes in the spectra shapes). Locations of the bands due to Al-O-Si and Si-O-Si bridges vibrations suggested that in most cases the augite-type phases were present in the systems (aluminium coordination number equal to 4 and 6). Appearance of aluminium in coordination 4 and 6 was confirmed by NMR investigations (two clear bands in the spectra).
(C) 2004 Elsevier B.V. All rights reserved. |
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Journal of Molecular Structure, 744-747, 615-619, (2005) |
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10. |
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Spectroscopic studies of glassy phospho-silicate materials The aim of the work is to determine the internal structure of bioactive glasses based on structural studies. Due to the absence of the long-range order, the X-ray methods usually applied in the studies of crystalline materials are of low applicability in the investigations of glasses. Therefore, spectroscopic methods, such as IR and NMR, which make it possible to 'see' the short- and the middle-range order are extremely suitable in their studies. IR investigations have shown that the glasses studied exhibit non-uniform domain composition, which should facilitate their transformation into glass-crystalline state. Additionally, detailed NMR measurements have been carried out in order to determine the influence of glass structure on the course of its crystallization. These studies make it possible to verify the common opinions on the middle-range order (domains) in the glasses studied. The results obtained for Al-27 and P-31 are particularly promising. Changes in the environment Of [SiO4](4-) tetrahedra, which can be spatially connected with various numbers Of [PO4](3-) and [AlO4](5-) tetrahedra cause the presence of various types of bridging bonds, such as Si-O-Si, Si-O-Al and Si-O-P. This in turn has significant impact on the number and the shape of the bands occurring in the spectra.
(C) 2005 Elsevier B.V. All rights reserved. |
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Journal of Molecular Structure, 744-747, 621-626, (2005) |
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11. |
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ICP, IR, Raman, NMR investigations of beryls from pegmatites of the Sudety Mts Detailed ICP, IR, Raman and NMR investigation were performed for more than 50 samples of beryls from pegmatites in the Sudety Mts. MIR spectra were measured at room (293 K), low up to 22 K and high up to 1273 K temperatures. The absorption bands for studied samples of beryl are correlated with chemical composition and structural parameters. The samples represent both alkali-poor (potassium-bearing, sodium-potassium-bearing) and alkali-rich (sodic and sodic-lithian) members of the beryl group. Two types of H2O molecules are discerned in all studied beryls. The I-type is not connected with alkali with bands at 3697/3690 cm(-1), 3647/3630/3610 cm(-1) (3606 cm(-1) in Raman spectra) and 1602/1550 cm(-1) dominates over the II-type (hydrated anions of alkali) with bands at 3660 cm(-1), 3592/3590 cm(-1) (3597 cm(-1) in Raman spectra) and 1637/1630cm(-1). CO2 molecules (2360 cm(-1) in MIR spectra, 1386 cm(-1), 1240 cm(-1) in Raman spectra) and hydroxyl groups in subordinate quantities occur in structural channels of beryls, except for mentioned above. Main bands in the range of 1200-400 cm(-1) are diagnostic in discerning of the three types of beryls according to lattice parameter classification. Studied beryls, in the most cases, belong to normal-type. Some samples are octahedral-type, and do not occur tetrahedral beryls in the Sudety Mts.
(C) 2005 Elsevier B.V. All rights reserved. |
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Journal of Molecular Structure, 744-747, 1005-1015, (2005) |
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12. |
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Nanomechanical properties of silica-coated multiwall carbon nanotubes-poly(methyl methacrylate) composites Nanomechanical properties of polymer composites, reinforced with silica coated multiwall carbon nanotubes (MWNT), have been studied using the nanoindentation technique. The nanohardness and the Young's modulus have been found to increase strongly with the increasing content of these nanotubes in the polymer matrix. Similar experiments conducted on thin films containing MWNT, but without silica shell, revealed that the presence of these nanotubes does not affect nanomechanical properties of the composites. While carbon nanotubes (CNT) have a very high tensile strength due to small nanotube stiffness, composites fabricated with CNT may exhibit inferior toughness. The silica shell on the surface of a nanotube enhances its stiffness and rigidity. Our composites, at 4wt% of the silica coated MWNT, display maximum hardness of 120±20 Mpa, and the Young's modulus of 9±1 GPa. These are respectively 2 and 3 times higher than those for the polymeric matrix.
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2005 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2005, 167-170, (2005) |
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13. |
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Fabrication of nanoscale rings, dots, and rods by combining shadow nanosphere lithography and annealed polystyrene nanosphere masks The application of shadow nanosphere lithography for the preparation of large-area, two-dimensional, metallic nanostructures of different shape is described. Through changing the mask morphology by temperature processing and varying the evaporation conditions, particles with morphologies such as rings, rods, and dots have been produced. This process allot-vs outstanding control of the size and morphology of the particles. The efficient technique is shown to scale down the size of metallic nano-particles from 200 to 30 nm, while preserving the original nanosphere spacing and order. The 150-nm-diameter Fe rings produced by this method show ferromagnetic behavior, which was predicted by theoretical simulation. All the experimental results were confirmed by computer simulations, which also showed the possibility of creating periodic arrays of any other geometrical shape.
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Small, 1(4), 439-444, (2005) |
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14. |
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Nanomechanical properties of silica-coated multiwall carbon nanotubes-poly(methyl methacrylate) composites The mechanical properties of polymer composites, reinforced with silica-coated multiwall carbon nanotubes (MWNTs), have been studied using the nanoindentation technique. The hardness and the Young's modulus have been found to increase strongly with the increasing content of these nanotubes in the polymer matrix. Similar experiments conducted on thin films containing MWNTs, but without a silica shell, revealed that the presence of these nanotubes does not affect the nanomechanical properties of the composites. While carbon nanotubes (CNTs) have a very high tensile strength due to the nanotube stiffness, composites fabricated with CNTs may exhibit inferior toughness. The silica shell on the surface of a nanotube enhances its stiffness and rigidity. Our composites, at 4 wt % of the silica-coated MWNTs, display a maximum hardness of 120 ± 20 MPa, and a Young's modulus of 9 ± 1 GPa. These are respectively 2 and 3 times higher than those for the polymeric matrix. Here, we describe a method for the silica coating of MWNTs. This is a simple and efficient technique, adaptable to large-scale production, and might lead to new advanced polymer based materials, with very high axial and bending strength.
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Langmuir, 21(7), 3146-3152, (2005) |
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15. |
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SAXS study of lipid bilayer model systems. The phase diagram of n-undecylammonium chloride/water system Alkylammonium halides belong to cationic surfactants. In water solutions they can form bilayer systems whose properties mimic those of the lipid membranes. The n-undecylammonium chloride (C11H23NH3Cl; UDACl)/water system was studied by small angle X-ray scattering (SAXS) at the concentrations of UDACl from 15 to 70% and in temperature range from 20 to 70 ºC. The results permitted our drawing a fragment of phase diagram for this system. Three main phases: isotropic, lamellar and hexagonal were observed and characterized
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Fibres and Textiles in Eastern Europe, 13(5), 93-95, (2005) |
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16. |
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Generation of iron active species in MCM-41 materials A new method, the immobilisation or ferroceneacetic acid (FAA) on various MCM-41 mesoporous molecular sieves (containing Si or Si+Al) followed by calcination at 773 K has been applied for the formation of iron active species. The structural, surface and catalytic properties of these materials, characterised by N-2 adsorption/desorption, XRD, Al-27 NMR, ESR, and Mossbauer spectroscopy as well as test reactions, were compared with those of materials prepared via commonly used impregnation methods. Contrary to Fe-impregnated samples, Fe oxides species were only slightly detected in the solids modified by FAA followed by calcination. It is evidenced that the new technique applied for Fe-modification gives rise to the significantly higher activity (in isopropanol decomposition and acetonylacetone cyclization) reached thanks to a better isolation and/or dispersion of Fe3+ species. The presence of Al in the sample influences the Fe3+ reduction under vacuum.
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Studies in Surface Science and Catalysis A, 158 A, 829-836, (2005) |
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Zaktualizowano: podstrony 2021-06-21 / bazę danych: 2024-11-28 by Webmaster: Zbigniew Fojud