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  • 1
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract MoO3/Al2O3 восстанавливается хотя бы частично серой, образующейся в сульфидировании смесью H2S/N2. Образование SO2 в ходе ТПД на MoO3/Al2O3, подвергнутом пресорбции H2S, свидетельствует о справедливости предложенной схемы.
    Notes: Abstract MoO3/Al2O3 is reduced at least partly by sulfur which is formed from H2S in sulfidation with H2S/N2 mixture. SO2 formation during TPD of MoO3/Al2O3 with presorbed H2S provides evidence for the explanation.
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  • 2
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention variation ; Effect of sample composition on retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The variation of the retention index of a solute due to the presence of a closely neighboring peak is discussed. The neighboring peak is likely to modify the original stationary liquid by forming a temporary “mixed” stationary phase. The extent of the retention index variation is influenced by many experimental parameters and becomes pronounced when the stationary phase is overloaded by the neighboring peak and the film thickness of the stationary phase is not very large. However, the exact extent of this variation is rather unpredictable. The practical significance of this finding is also discussed.
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  • 3
    ISSN: 1612-1112
    Keywords: Gas Chromatography ; Fused-Silica Capillaries ; Deactivation ; Temperature dependance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Uncoated fused-silica capillary tubing has found widespread use in GC and GC/MS, e. g., in splitless and oncolumn injection, in the open-split interface used in GC/MS, and in hybrid fused-silica/glass capillary columns. As the uncoated capillary is usually more active than the coated one, it is very important to pay sufficient attention to the deactivation of the uncoated capillary. Otherwise the uncoated portion used as column inlet and/or outlet may become the main source of column activity and of analytical error. This case is especially serious under temperature-programmed runs. The effect of film thickness and temperature program on column activity is also discussed.
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  • 4
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Fused-silica columns ; Static coating ; Sealing method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In this paper a new sealing method for the static coating of capillary columns is described. When one end of the fully filled capillary was immersed into liquid nitrogen in a Dewar flask, the coating solution at this end would be frozen and became a temporary seal, and an air-free solvent/seal interface was obtained. No bumping has ever been found at the interface, even when butane was used as solvent. By applying this sealing method, several capillary columns, including some narrow bore capillary, had been successfully coated.
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  • 5
    ISSN: 1612-1112
    Keywords: Gas Chromatography ; GC/MS ; Temperature-Programmed Retention Indices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It has been found that the ratio $$\frac{{r \cdot t_0 }}{\beta }$$ , where r is the heating rate, t0 is the gas hold-up time of the column and β is the phase ratio of the column used, is a most explicit and convenient parameter in linear temperatur-programmed gas chromatography for reproducing temperature-programmed retention indices, ITP. For two columns of different sizes (length, inner diamter), working under different heating rates with the same or different carrier gases at different gas flow-rates, as long as the initial oven temperature, T0, phase ratio, β, and their r·t0/β ratios are kept unchanged, the ITP value of a solute can be reproduced within 1–2 i.u. on either OV-101 or PEG-20M columns. When a combined gas chromatography-mass spectrometry technique is used applying vacuum at the column outlet reduces t0. Nevertheless, r·t0/β can still be kept unchanged by a proper choice of the oven heating rate, and thus a total ion chromatogram (TIC), quite similar to the corresponding gas chromatogram in shape, can be obtained.
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  • 6
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Micellar electrokinetic capillary chromatography ; (MECC) ; Instrumentation ; Sample introduction ; Analytical performance ; Separation parameters ; Reproducibility of retention and response data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A self-designed capillary electrophoresis instrument is described in detail. It has been constructed in a modular mode for systematical studies on CE and related techniques. The instrument is characterized by the following features: -alternative modes of automated sample introduction, -liquid cooling and adequate temperature control of the separation capillary, -computer controlled adjustment of voltage and voltage gradients, -automated aquisition, handling and evaluation of analytical data. The reproducibility of data which characterize the performance of the instrumentation (“efficiency”, migration times) has been investigated by a large number of repetitive measurements. Quantitative data such as absolute and relative peak areas have also been measured and evaluated. The results of these investigations show that the apparatus is well suited for reproducible measurements. The influence of significant parameters such as temperature, buffer pH or the concentration of organic modifier in the buffer on the separation performance were studied. A particular kind of peak tailing which may arise due to poor sample introduction can be avoided by inclusion of a rinsing step of the outside of the capillary inlet. The rinsing is achieved by dipping the column inlet into another vial with buffer before the actual separation is initiated. A four step procedure of sample introduction is proposed. Typical capillary electrophoretic separations are shown.
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  • 7
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract An investigation has been made of blood interactions with plasticized poly(vinyl chloride) (PVC) biomaterials in tubular form, taking into account the influence on the blood response of the polymer, antithrombotic agent, blood condition and test procedure. In vitro and ex vivo procedures were used to achieve a comparison between PVC plasticized with di- (2-ethylhexyl)phthalate (DEHP) and with tri-(2-ethylhexyl)trimellitate (TEHTM). The blood response was monitored in terms of the measurement of fibrinogen adsorption capacity, thrombin–antithrombin III complex (TAT) and the complement component C3a. Surface characterization of the polymers was performed by X-ray photoelectron spectroscopy (XPS). The data obtained indicate that in comparison with DEHP-PVC, there is a higher reactivity for TEHTM-PVC, which correlates with the plasticizer distribution at the polymer surface. © 1999 Kluwer Academic Publishers
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  • 8
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper deals with a variational approach of the displacement discontinuity method. This method is an indirect boundary element technique which uses the double layer potential representation of displacements and stresses. The variational approach presented here is based upon the theorem of minimum potential energy in elasticity. In the numerical procedure, the global shape function used to approximate the displacement discontinuity distribution is the continuous piecewise linear function. Regular displacements and resultant force expressions are obtained from these shape functions and these expressions are used to build the system of linear equations. The method is applied to crack problems in both infinite and finite bodies. The stress intensity factors are then calculated and high accurate numerical results are obtained.
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  • 9
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of (001)-oriented Sr2FeMoO6 have been epitaxially deposited on LaAlO3 and SrTiO3 (001) substrates. Comparison of their transport and magnetic properties with those of polycrystalline ceramic samples shows a metallic versus semiconductor temperature dependence and a saturation magnetization Ms at 10 K of 3.2 μB/f.u. in the film as against 3.0 for a tetragonal polycrystalline sample. However, the Curie temperature TC(approximate)389 K is reduced from 415 K found for the tetragonal ceramic, which lowers Ms at 300 K in the thin films to 2.0 μB/f.u. compared to 2.2 μB/f.u. in the ceramics. A Wheatstone bridge arrangement straddling a bicrystal boundary has been used to verify that spin-dependent electron transfer through a grain boundary is responsible for the low-field magnetoresistance found in polycrystalline samples below TC. © 1999 American Institute of Physics.
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  • 10
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Adenosine and colchicine have antagonistic effects on cell shape. When Chinese Hamster lung fibroblasts (CHE36-6) or SV40 transformed 3T3 (SV3T3) cells are incubated with colchicine (1 μM) for one hour at 37°C, they round up into spheres with short spikes. Cells treated with adenosine (1 μM-4 mM) for one hour become refractile and develop spindly processes. However, when the two compounds are added simultaneously, the characteristic responses to either drug are abolished and the cells appear normal. The counteraction is specific for adenine and its derivatives, adenosine being the most effective of the compounds we tested. Accumulation of colchicine or adenosine is not altered significantly by the presence of the other drug, ruling out decreases in uptake as the basis of the mutual antagonism. The morphological changes can be observed under conditions where there are no changes in intracellular cAMP levels (such as incubation with low concentrations of adenosine or cordycepin, an adenosine analog that cannot be directly converted to cAMP). Colchicine does not alter cAMP content of control or adenosine-treated cells. These data show that adenine compounds have potent effects on cell shape, and the antagonistic effects of adenosine and colchicine on cell shape are not mediated through changes in intracellular cAMP levels.
    Additional Material: 2 Ill.
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