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  • 1
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Фракции кислых центров не цеолитах HNaY, активных в крекинге, изомеризации и дегидогенизации метилциклогексана не увеличиваются линейно с увеличением степени обмена. Реакции изомеризации и дегидрогенизации протекают через образование одинакового активированного комплекса, а крекинт через другой активированный комплекс и нуждается в более сильных кислых центрах. Энергия активации не зависит от степени обмена.
    Notes: Abstract On HNaY zeolites the fractions of acid sites which are active for cracking, isomerization and dehydrogenation of methylcyclohexane do not increase linearly with increasing degree of exchange. Isomerization and dehydrogenation seem to involve a similar activated complex, while cracking proceeds through a different one and requires stronger acid sites. Activation energies are independent of exchange degree.
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  • 2
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Было исследовано разложение метилциклогексана на цеолитах H−NaY и PtH−NaY. Было найдено, что присутствие или отсутствие H2 не только влияет на активность этих катализаторов, но также и на селективность образования продуктов дегидрогенизации и изомеризации.
    Notes: Abstract The decomposition of methylcyclohexane on H−NaY and PtH−NaY zeolites has been studied. It has been found that the presence or abscence of H2 affects not only the activity of these catalysts but also their selectivity to dehydrogenation and isomerization products.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 13 (1997), S. 0 
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Analysis of little-known manuscripts revealed that there have been at least two pre-Linnean descriptions of the South American freshwater dolphin Inia geoffrensis (Blainville, 1817). The earliest one that we found was made by Frei Cristóvâo de Lisboa in a manuscript written around 1627. The second one was by Pehr Löfling, a disciple of Linnaeus, who wrote a very detailed and accurate description of this mammal in 1755. He used the binomial system to designate this species, and his description was much more complete and sophisticated than the ones used by Linnaeus in the 10th edition of System Naturae for other cetaceans. This and other zoological work by Löfling remains almost completely unexamined to date. Like the outcome of other field work carried out by many Spanish scientists in America, failure to publish the findings of the expeditions resulted in scientific information being largely lost.
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  • 4
    ISSN: 0167-4943
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
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  • 5
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Chemisorption of CO at temperatures below 100°C has been used to evaluate the dispersion of NiO in a series of NiO/γ-Al2O3 catalysts. CO adsorption measurements were supplemented by i.r. spectroscopy to establish the CO/NiO stoichiometry. From monolayer coverage data derived from Freundlich's equation, the percentage of NiO dispersion and the average NiO crystallite size were calculated. The crystallite size of supported NiO was found to be practically constant for NiO loadings from 1 to 8 wt%, experimenting an abrupt increase for higher NiO contents. These results were consistent with additional information on the surface structure of the catalysts obtained by IR spectroscopy, X-ray diffraction, magnetic susceptibility, and reduction with H2.
    Additional Material: 6 Ill.
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  • 6
    ISSN: 1572-879X
    Keywords: phosphorus-containing catalysts ; tungsten disulfide ; high-resolution electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A series of WS2/Al2O3 catalysts containing a varied amount of phosphorus (0.0,2.5 and 6.0 wt% P2O5), sulfided at two different temperatures (873 and 1073 K), were studied by means of high-resolution transmission electron microscopy (HRTEM). The stacking of (002) layers in the WS2-2H crystallites of the “rag” structure increases with the addition of phosphorus, whereas its length is kept almost constant. At high sulfidation temperatures phosphorus shows a stabilizing effect on the catalysts by retarding the stacking growth of WS2 crystallites. Additionally, an aluminum phosphate crystalline phase is identified in the phosphorus promoted catalysts.
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  • 7
    ISSN: 1572-879X
    Keywords: Zeolites ; hydrodesulfurization ; sulfide catalysts ; cobalt/zeolite ; molybdenum/zeolite ; cobalt-molybdenum/zeolite ; gas oil hydrotreating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Three series of Co/NaY, Mo/NaY and CoMo/NaY zeolite catalysts with variable metal content, prepared by a conventional impregnation method, were characterized by XRD, IR spectroscopy (oxide state) and acidity measurements (sulfide state), and tested in hydrodesulfurization (HDS) of gas oil at high pressure in the temperature range 275–350°C. The combined results of surface area, XRD and IR showed that in the catalysts with high metal loading a small loss in crystallinity and a partial blockage of the zeolite supercages were produced by Mo oxide species. The number of acid sites, which was lower for the Co/NaY than for the Mo/NaY catalysts, increased with increasing Co or Mo loading, but the strength of the acid sites was stronger for the Co/NaY series. HDS specific activities of the Co/NaY and Mo/NaY monometallic catalysts reached a maximum at very low loadings of Co (∼ 0.10 at. nm−2) or Mo (∼ 0.16 at. nm−2) by the double action of the metal sulfide species and the strong acid sites generated on the zeolite by the Co or Mo incorporation. In the binary CoMo/NaY catalysts, the synergy between Co and Mo species was significant for high Mo contents only.
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  • 8
    ISSN: 1572-879X
    Keywords: HDN ; carbon-supported catalysts ; NiMo catalysts ; sulfided catalysts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrodenitrogenation (HDN) of pyridine over activated carbon-supported Mo and NiMo sulfided catalysts was studied. Without H2S in the feed the catalysts showed a high conversion of pyridine and of piperidine to C5 hydrocarbons at the beginning of reaction, followed by a strong deactivation. A large increase in the conversion of pyridine was observed when H2S was added to the feed at H2S/H2⩾0.006. The conversion of piperidine to C5 hydrocarbons was enhanced by H2S and it increased as the H2S pressure increases up to H2S/H2⩾0.006. The promotion effect of Ni was operative only when H2S was present and it increased with the H2S/H2 ratio. Without H2S, the degree of surface oxidation of the support affected the deactivation of the catalysts. When H2S was added to the feed, the conversion of pyridine was stable and independent of the acid treatment of the support. A more oxidized support enhanced the C-N bond breaking reaction.
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  • 9
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Raman spectroscopy has been used to characterize various MoO3/γ-Al2O3 and CoO (or NiO)-MoO3/γ-Al2O3 catalysts containing 12 wt% MoO3 and 3 wt% CoO (or NiO) prepared by different methods. No significant differences between samples prepared by the wet impregnation and the pore volume method could be observed in molybdena-supported catalysts; in these samples the majority of Mo is present as isolated distorted MoO42- tetrahedra due probably to a low coverage of the alumina surface (SBET=240 m2 g-1). Addition of NiO to the molybdena-supported catalysts seems to cause only a slight increase in the distortion and interaction between MoO42- species. In contrast, CoO addition to the molybdena-supported catalysts changes considerably the spectra features, suggesting that the Mo species are highly distorted, presumably in different surroundings on the alumina surface, due to the strong interaction of Co with Mo species. However, simultaneous impregnation of both MoO3 and CoO or NiO results in a more regular arrangement of Mo species and an increase in formation of polymeric Mo species, particularly with Co-containing catalyst, where a relative higher degree of polymeric aggregation may occur.
    Additional Material: 3 Ill.
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  • 10
    Publication Date: 2018-11-16
    Description: Purpose: Renal cell carcinoma (RCC) has the potential for cure with surgery when diagnosed at an early stage. Kidney injury molecule-1 (KIM-1) has been shown to be elevated in the plasma of RCC patients. We aimed to test whether plasma KIM-1 could represent a means of detecting RCC prior to clinical diagnosis. Experimental Design: KIM-1 concentrations were measured in prediagnostic plasma from 190 RCC cases and 190 controls nested within a population-based prospective cohort study. Cases had entered the cohort up to 5 years before diagnosis, and controls were matched on cases for date of birth, date at blood donation, sex, and country. We applied conditional logistic regression and flexible parametric survival models to evaluate the association between plasma KIM-1 concentrations and RCC risk and survival. Results: The incidence rate ratio (IRR) of RCC for a doubling in KIM-1 concentration was 1.71 [95% confidence interval (CI), 1.44–2.03, P = 4.1 x 10 –23 ], corresponding to an IRR of 63.3 (95% CI, 16.2–246.9) comparing the 80th to the 20th percentiles of the KIM-1 distribution in this sample. Compared with a risk model including known risk factors of RCC (age, sex, country, body mass index, and tobacco smoking status), a risk model additionally including KIM-1 substantially improved discrimination between cases and controls (area under the receiver-operating characteristic curve of 0.8 compared with 0.7). High plasma KIM-1 concentrations were also associated with poorer survival ( P = 0.0053). Conclusions: Plasma KIM-1 concentrations could predict RCC incidence up to 5 years prior to diagnosis and were associated with poorer survival. Clin Cancer Res; 24(22); 5594–601. ©2018 AACR .
    Print ISSN: 1078-0432
    Electronic ISSN: 1557-3265
    Topics: Medicine
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