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排序方式: 共有417条查询结果,搜索用时 31 毫秒
331.
Gopannagari Madhusudana Muniraj Vedi Kuyil Azhagan Kwon Ki Young Kim Yujin Reddy D. Amaranatha Kim Tae Kyu Yoo Hyun Deog 《Journal of Applied Electrochemistry》2022,52(10):1449-1458
Journal of Applied Electrochemistry - Improving the reversible capacity, fast chargeability, and cyclability of cathode materials are the primary challenges in the development of advanced... 相似文献
332.
Zainab Ibrahim S G Adiya Valerie Dupont Tariq Mahmud 《International Journal of Hydrogen Energy》2018,43(14):6904-6917
The catalytic steam reforming of shale gas was examined over NiO on Al2O3 and NiO on CaO/Al2O3 in the double role of catalysts and oxygen carrier (OC) when operating in chemical looping in a packed bed reactor at 1 bar pressure and S:C 3. The effects of gas hourly space velocity GHSV (h?1), reforming temperatures (600–750 °C) and catalyst type on conventional steam reforming (C-SR) was first evaluated. The feasibility of chemical looping steam reforming (CL-SR) of shale gas at 750 °C with NiO on CaO/Al2O3 was then assessed and demonstrated a significant deterioration after about 9 successive reduction-oxidation cycles. But, fuel conversion was high over 80% approximately prior to deterioration of the catalyst/OC, that can be strongly attributed to the high operating temperature in favour of the steam reforming process. 相似文献
333.
Catalysis Letters - Allylic oxidation of cycloalkenes is a promising route to generate α,β-unsaturated ketones but encounters difficulties in selectivity control. Here, it is demonstrated... 相似文献
334.
Ferney Osorio Laurent Dupont Mauricio Camargo Pedro Palominos Jos Ismael Pea Miguel Alfaro 《Creativity & Innovation Management》2019,28(1):82-100
There is a strong emergence of new spaces to foster innovation all over the world (Fablabs, Living Labs and Design Factories, among others). Past experiences have shown these types of projects involving “innovation laboratories” are at risk of not succeeding in their goals. Although several studies have tackled the problem of design, development and sustainability of innovation laboratories, there is still a gap in understanding how the capabilities and performance of these environments are affected by the strategic intentions at the early stages of design and functioning. Throughout this work, eight frameworks from the literature that analyze innovation laboratories are identified and compared. Then, based on both literature and the authors' experience, an updated framework is proposed as the basis for a guidance tool for researchers and practitioners aiming to assess or to adapt an existing project. As part of the operationalization process of the framework, a maturity grid‐based assessment tool is proposed to evaluate the maturity degree of an innovation laboratory. Afterwards, to evaluate the viability and to integrate the perception of innovation laboratory managers, an exploratory study with answers from fifteen laboratories from five different countries is performed. Insights and implications for emerging and already existent projects of innovation laboratories are then discussed. 相似文献
335.
Simultaneous maximum a posteriori reconstruction of attenuation andactivity distributions from emission sinograms 总被引:1,自引:0,他引:1
Nuyts J. Dupont P. Stroobants S. Benninck R. Mortelmans L. Suetens P. 《IEEE transactions on medical imaging》1999,18(5):393-403
In order to perform attenuation correction in emission tomography an attenuation map is required. We propose a new method to compute this map directly from the emission sinogram, eliminating the transmission scan from the acquisition protocol. The problem is formulated as an optimization task where the objective function is a combination of the likelihood and an a priori probability. The latter uses a Gibbs prior distribution to encourage local smoothness and a multimodal distribution for the attenuation coefficients. Since the attenuation process is different in positron emission tomography (PET) and single photon emission tomography (SPECT), a separate algorithm for each case is derived. The method has been tested on mathematical phantoms and on a few clinical studies. For PET, good agreement was found between the images obtained with transmission measurements and those produced by the new algorithm in an abdominal study. For SPECT, promising simulation results have been obtained for nonhomogeneous attenuation due to the presence of the lungs. 相似文献
336.
Ethyl-14C-acetoacetate was used to trace oxidation and metabolism of acetoacetate when rats were fed a high fat diet (80% of total
calories from beef tallow or corn oil, carbohydrate free), a high carbohydrate diet (2% corn oil) or a high carbohydrate diet
with restriction of calories to one half of ad lib. consumption for two weeks. The rate of expiration of14CO2 in all groups of animals did not differ significantly and was not related to plasma concentration of acetoacetate. The high
fat diets slightly enhanced the oxidation of acetoacetate to14CO2 over a 3 hr period compared to other diets. Incorporation of acetoacetate into fatty acids did not differ significantly among
groups. Rats fed the high carbohydrate diet ad lib. incorporated into liver cholesterol more acetoacetate than did any other
group, but dietary unsaturated fat resulted in greater incorporation of acetoacetate into cholesterol than saturated fat.
High calorie and high beef tallow groups were ketonemic but the low concentration of plasma acetoacetate in rats fed a high
corn oil diet indicates that unsaturated fatty acids are not ketogenic. The data show that utilization of acetoacetate is
not significantly reduced in a ketonemic condition and support the premise that overproduction of ketone bodies is the cause
of ketonemia. Rats appeared to be normal during the two-week period when no carbohydrate was included in the diet.
Presented at the AOCS Meeting, Chicago, October, 1967. 相似文献
337.
Male and female rats were fed diets containing 2% of calories as corn oil or that plus 40% of calories as beef tallow or corn
oil. After 3, 6, 12 and 18 months groups were given 4-14C-cholesterol ip, and feces were collected for 9 days. Just prior to necropsy3H-acetate was administered ip. Samples of serum, liver, heart and carcass were obtained for analysis. Concentrations of fatty
acids and cholesterol, synthesis of those and recovery of ring-labeled steroid are reported. Mortality from acute respiratory
disease was very high in male rats fed beef tallow or low fat diets and very low in those fed the corn oil diet. In females,
only beef tallow diet resulted in a high mortality rate, and this was lower and at a later age than in males. The most notable
effects of age were in relation to fatty acid synthesis and presence of14C-acidic steroid in the carcass. In 3-month-old rats both fats depressed fatty acid synthesis in comparison to the low fat
diet. At later ages beef fat ceased to depress fatty acid synthesis in both sexes. Corn oil continued to depress fatty acid
synthesis up to 12 months in males and 18 months in females. The presence of14C-acidic steroid in carcass was substantial in 6-month-old rats and constituted ca. 40% of recovered14C in 18-month-old rats. The possibility that the increase in acetate incorporation into fatty acids with age in fat feeding
is related to chain elongation rather than de novo synthesis is discussed. Both the presence and amount of acidic steroid
in the carcass are notable and may be of importance in constructing models of cholesterol turnover.
Presented in part at the AOCS Sterol Symposium, April 1970, and the Federation of American Societies for Experimental Biology,
April 1971.
Scientific Series Paper No. 1536, Colorado Agricultural Experiment Station. 相似文献
338.
In mammals, adiponectin and its receptors (AdipoR1 and AdipoR2) mRNAs are expressed in various tissues. However, the cellular expression and the role of adiponectin system have never been investigated in rat ovary. Here, we report the presence of adiponectin, AdipoR1 and AdipoR2 in rat ovaries, and we have investigated its role in granulosa cells. Using RT-PCR and western blot, we show that the mRNAs and proteins for adiponectin, AdipoR1 and AdipoR2 are found in the ovaries. Immunohistochemistry localized adiponectin, AdipoR1 and AdipoR2 in theca-interstitial T-I cells, corpus luteum, oocyte and less abundantly in granulosa cells. In the KGN human granulosa cell line, adiponectin mRNA and protein were undetectable; AdipoR2 was weakly expressed, whereas AdipoR1 was clearly present. Human chorionic gonadotrophin (hCG) injection (48 h) after pregnant mare serum gonadotrophin (PMSG) injection (24 h) in immature rats increased the level of adiponectin (protein) by about threefold (P < 0.05) and those of AdipoR1 by threefold (mRNA, P < 0.05) and 1.5-fold (protein, P < 0.05) in ovary, whereas the mRNA and protein levels of AdipoR2 were unchanged. Interestingly, hCG injection (48 h) after the PMSG treatment (24 h) decreased plasma adiponectin levels and increased insulin plasma levels. In vitro in primary rat granulosa cells, human adiponectin recombinant (5 microg/ml) in the presence or absence of follicle-stimulating hormone (10(-8) M, 48 h) had no effect on the steroidogenesis. However, it increased progesterone secretion (P < 0.05) by about twofold and oestradiol production (P < 0.05) by about 1.6-fold in response to insulin-like growth factor-I (IGF-I) (10(-8) M). Furthermore, it improved IGF-I-induced IGF-I receptor-beta subunit tyrosine phosphorylation and ERK1/2 phosphorylation. In basal state, human adiponectin recombinant also increased rapidly but transiently the ERK1/2, p38 and Akt phosphorylations, whereas it increased more lately the adenosine 5'-monophosphate-activated protein kinase (AMPK) phosphorylation. Thus, AdipoR1 and AdipoR2 are regulated by hCG treatment in rat ovary and adiponectin enhances IGF-I-induced steroidogenesis in granulosa cells. 相似文献
339.
The kinetic parameters of the lean oxidation of CH4 over alumina and ceria-alumina supported platinum catalysts in the presence of H2S and SO2 were derived in a stagnation point flow reactor at atmospheric pressure and at temperatures up to . A novel methodology similar to that of plug-flow reactors was devised to calculate the best-fit values for frequency factors and activation energies for the proposed heterogeneous gas-solid reactions of oxidation. Doping the N2-diluted CH4/air reactant flow with H2S or SO2 concentrations between 30 and had a significant promotional effect on the methane combustion rate. Al2O3 and CeO2/Al2O3 were shown to be inert with respect to the oxidation of CH4 to CO2, and also in the oxidation of SO2 to SO3 in air. Pt catalysed the oxidation of CH4, SO2 and that of H2S. A temperature window of conversion of SO2 to SO3 on the Pt-supported catalysts was found experimentally, and could be of practical use in combustion exhaust clean-up techniques. The repeated use of the foil resulted in a slight ageing effect for Pt/Al2O3. The presence of ceria in the washcoat helped prevent the loss of activity in CH4 oxidation by mitigating the extent of sintering of the Pt particles upon ageing. One-step and two-step chemical reaction mechanisms are proposed for the CH4 and the SO2 lean oxidations, respectively. 相似文献
340.
Liane M. Rossi Giovanna Machado Paulo F. P. Fichtner Sergio R. Teixeira Jairton Dupont 《Catalysis Letters》2004,92(3-4):149-155
The H2 reduction of RuO2 hydrate “dissolved” in 1-n-butyl-3-methylimidazolium ionic liquids with different counterions, hexafluorophosphate (BMI ? PF6), tetrafluoroborate (BMI ? BF4) and trifluoromethane sulfonate (BMI ? SO3CF3), is a simple and reproducible method for the preparation of ruthenium nanoparticles of 2.0–2.5?nm diameter size and with a narrow size distribution. The Ru nanoparticles were characterized by TEM and XRD. The isolated Ru nanoparticles are reoxidized in air, whereas they are less prone to oxidation when imbibed in the ionic liquids. These nanoparticles are active catalysts for the solventless or liquid–liquid biphasic hydrogenation of olefins under mild reaction conditions (4 atm, 75°C). The catalytic system composed of nanoparticles dispersed in BMI ? PF6 ionic liquid is very stable and can be reused several times without any significant loss in the catalytic activity. Total turnover numbers greater than 110 000 (based on total Ru) or 320 000 (corrected for exposed Ru atoms) were attained within 80?h for the hydrogenation of 1-hexene. 相似文献