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排序方式: 共有998条查询结果,搜索用时 8 毫秒
1.
Christian P. Romero Jonathan I. Avila Edgardo Cisternas Guerau B. Cabrera Alejandro L. Cabrera Kristiaan Temst Margriet J. Van Bael 《Journal of Materials Science》2007,42(18):7667-7672
Hydrogen desorption curves were obtained from a sample composed of a square arrangement of Co dots with average diameter of
4.4 μm, separated by a distance of 11.6 μm. A macroscopic sample of Co dots grown on a 2.5 × 2.5 cm Si substrate was made
by standard lithographic techniques and used in these experiments. Thermal programmed desorption (TPD) was performed under
ultra-high vacuum conditions. Hydrogen TPD curves were obtained from a 1 × 1 cm Co dots samples displaying a maximum of intensity
at 425 K. Hydrogen TPD curve was also obtained from 1 cm× 1 cm samples of Co films and Co foils for comparison. The hydrogen
TPD curves have decreasing intensity from the Co foils to the Co dots and finally to the Co films. This indicates that there
are more sites for hydrogen adsorption on the Co dots than in the Co films. This is a surprising result because there is approximately
8.7 times less Co atoms exposed in the Co dots that in the Co film sample. A desorption energy of 27 kcal/mol was obtained
for the Co dots suggesting that hydrogen is adsorbed on an hcp hollow site of the Co dot crystalline structure. 相似文献
2.
Vanesa Rodríguez-Amor Juan P. Fernández-Blázquez Antonio Bello Ernesto Pérez María L. Cerrada 《Polymer Bulletin》2008,60(1):89-96
Summary The effect of molecular weight on the uniaxial orientation process has been analyzed in two samples of thermotropic poly(diethylene
glycol p,p′-bibenzoate), evaluating the influence of that parameter on the type of orientation obtained. Several strain rates and deformation
temperatures have been tested in order to map out the conditions for obtaining the two different kinds of orientation. The
results show that in the lower molecular weight PDEB sample (Mw=31200) it is rather easy to get exclusively perpendicular “anomalous” orientation, with the molecular axes aligned transversely
to the stretching direction. However, it is extremely difficult to obtain 100% parallel “normal” orientation. On the contrary,
either type of orientation or a mixture of them can be easily developed for the higher molecular weight PDEB sample (Mw=102900). 相似文献
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Two actin isoforms, gamma and beta, are contained within neuroblastoma cells. However, the relative amount and distribution of both isoforms within the cells are differentially regulated during neurite extension. The proportion of gamma-actin isoform became about four times greater than that of beta actin during neuroblastoma cell differentiation. Additionally, whereas beta actin appears to be concentrated in the cell cortex, gamma actin is also present throughout the cell body. Upon differentiation, neuroblastoma cells reorganize their actin cytoskeleton and gamma actin is induced to polymerize whereas beta actin polymers are partially disassembled. Moreover, both actin isoforms are differentially distributed within differentiated cells. Thus, gamma actin polymers are located both in the soma and proximal regions of extended neurites, whereas beta actin is enriched in the terminal tip of the neurites. Our results strongly suggest that both actin isoforms are involved in a different way in neuroblastoma cell differentiation. 相似文献
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Laboratory studies indicate that capsaicin, the hot-tasting component of chili peppers, may be carcinogenic. A population-based case-control study was conducted in Mexico City during 1989-1990 to evaluate the relation between chili pepper consumption and gastric cancer risk. The study included 220 incident cases and 752 controls randomly selected from the general population. Information was collected by interview. Chili pepper consumers were at high risk for gastric cancer compared with nonconsumers (age- and sex-adjusted odds ratio = 5.49, 95% confidence interval (CI) 2.72-11.06). Among consumers, there was a highly significant trend of increasing risk with increasing self-rated level of consumption (low, medium, and high) (p = 2 x 10(-7). The odds ratio for high-level consumers compared with nonconsumers was 17.11 (95% CI 7.78-37.59). However, when consumption was measured as frequency per day, a significant trend among consumers was not observed. Multivariable adjustment increased the magnitude of the chili pepper-gastric cancer association, but a significant trend among consumers (measured as frequency per day) was still not observed. Chili pepper consumption may be a strong risk factor for gastric cancer, but further studies are needed to test this hypothesis. 相似文献
8.
Chen Jiaoyan Hu Pan Jimenez-Ruiz Ernesto Holter Ole Magnus Antonyrajah Denvar Horrocks Ian 《Machine Learning》2021,110(7):1813-1845
Machine Learning - Semantic embedding of knowledge graphs has been widely studied and used for prediction and statistical analysis tasks across various domains such as Natural Language Processing... 相似文献
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The incorporation of [1-14C] acetate into fatty acids by cultured epimastigotes ofTrypanosoma cruzi was studied. After 8, 24, and 48 hr incubation with labeled precursor, up to 2.8% of the initial radioactivity added to the
medium was found in theT. cruzi long chain fatty acids. Saturated (16∶0 and 18∶0), monounsaturated (18∶1ω9), and diunsaturated (18∶2ω6) fatty acids were
synthesized. Both the pattern of incorporation of labeled acetate into the fatty acids and the decarboxylation ratios found
suggest that de novo synthesis of fatty acids has taken place. 相似文献