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排序方式: 共有1111条查询结果,搜索用时 15 毫秒
61.
Sergei Vlassov Sven Oras Martin Timusk Veronika Zadin Tauno Tiirats Ilya M. Sosnin Rünno Lhmus Artis Linarts Andreas Kyritsakis Leonid M. Dorogin 《Materials》2022,15(5)
Polydimethylsiloxane (PDMS) is the most widely used silicon-based polymer due to its versatility and its various attractive properties. The fabrication of PDMS involves liquid phase cross-linking to obtain hydrophobic and mechanically flexible material in the final solid form. This allows to add various fillers to affect the properties of the resulting material. PDMS has a relatively low Thermal Conductivity (TC), in the order of 0.2 W/mK, which makes it attractive for thermal insulation applications such as sealing in construction. Although a further decrease in the TC of PDMS can be highly beneficial for such applications, most research on the thermal properties of PDMS composites have focused on fillers that increase the TC rather than decrease it. In the present work, we propose a simple and reliable method for making a PDMS-based composite material with significantly improved thermal insulation properties, by adding hollow glass microspheres (HGMs) to the mixture of the liquid base and the cross-linker (10:1 ratio), followed by degassing and heat-assisted crosslinking. We obtained a 31% reduction of thermal conductivity and a 60% increase in the elastic modulus of samples with HGM content of 17% by weight. At the same time, the sound insulation capacity of the PDMS-HGM composite is slightly decreased in comparison to pure PDMS, as a result of its lower density. Finally, the wettability of the samples had no dependence on HGM content. 相似文献
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63.
The evidence for a mutual dependence between convulsive activity and duration of the paradoxical sleep (PS) can be found from the literature. Convulsions diminish the PS time, on the other hand, PS restriction increases the sensitivity to convulsion-inducing stimuli. In epilepsy, the operation of this positive feedback loop mechanism is possibly promoted by elevated levels of enkephalin and norepinephrine that are characteristic of epileptics. The above supports the convulsions–PS interplay representing a relevant therapeutic target in epilepsy. In this connection, usage of PS duration increasing hypnotics like thalidomide, in combination with enkephalin and norepinephrine antagonists is thought to be of special importance. 相似文献
64.
Tabak S Broday DM Tabak I Manor G 《Applied occupational and environmental hygiene》2002,17(2):121-130
Air samples were collected at breathing height in the hulling-separation department of a modern cottonseed oil mill in Uzbekistan. The average elutriated mass concentration measured by standard cotton dust samplers was 4.6 mg/m3, much lower than the average total dust concentration measured by stationary personal samplers, 12.49 mg/m3, and by personal samplers attached to workers, 14.53 mg/m3. Differences in readings among the vertical elutriators, stationary personal samplers, and roving personal samplers are attributed to the distinct sampling nature and dynamics of these samplers. The data suggest that most of the dust consisted of particles larger than 15 microm, the particle size cutoff of the vertical elutriator. Differences in readings among stationary and roving personal samplers are statistically significant, presumably representing biased sampling by the roving personal samplers of regions characterized by high dust concentration (due to machines malfunctioning), the nonstatic nature of the sampling, and the interaction between the sampler and the worker (the personal cloud). Cotton dust concentrations in the hulling-separation room were nonuniform, peaking in front of and between the huller-separator pairs. The high total mass readings show that workers were exposed to very high levels of nonthoracic airborne dust, which upon inhalation tends to deposit in the extrathoracic airways. The high elutriated mass concentrations suggest that workers were exposed to respirable cotton dust at levels higher than 1 mg/m3 mean concentration, the current Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) for cotton dust. Regressions between dust concentrations measured by stationary vertical elutriators and by personal samplers attached to workers serve for estimating the potential occupational exposure to cotton dust of workers in the hulling-separation room. 相似文献
65.
66.
Kelmanson IV Shagin DA Usman N Matz MV Lukyanov SA Panchin YV 《The European journal of neuroscience》2002,16(12):2475-2476
Neurons can communicate with each other either via exchange of specific molecules at synapses or by direct electrical connections between the cytoplasm of either cell [for review see Bruzzone et al. (1996) Eur. J. Biochem., 238, 1-27]. Although electrical connections are abundant in many nervous systems, little is known about the mechanisms which govern the specificity of their formation. Recent cloning of the innexins--gap junction proteins responsible for electrical coupling in invertebrates (Phelan et al. (1998) Trends Genet., 14, 348-349], has made it possible to study the molecular mechanisms of patterning of the electrical connections between individual neurons in model systems. Here we demonstrate that intracellular injection of mRNA encoding the molluscan innexin Panx1 (Panchin et al. 2000 Curr. Biol., 10, R473-R474) drastically alters the specificity of electrical coupling between identified neurons of the pteropod mollusc Clione limacina. 相似文献
67.
68.
Andrei P Kozlov Yuri P Galachyants Ilya V Dukhovlinov Nickolai A Samusik Ancha V Baranova Dmitry E Polev Larisa L Krukovskaya 《Infectious agents and cancer》2006,1(1):8-10
Background
Earlier we suggested the concept of the positive evolutionary role of tumors. According to this concept, tumors provide conditions for the expression of evolutionarily new and/or sleeping genes in their cells. Thus, tumors are considered as evolutionary proving ground or reservoir of expression. To support this concept we have previously characterized in silico and experimentally a new class of human tumor-related transcribed sequences. 相似文献69.
Lee EJ Mircean C Shmulevich I Wang H Liu J Niemistö A Kavanagh JJ Lee JH Zhang W 《Molecular cancer》2005,4(1):7
Background
Insulin-like growth factor binding protein 2 (IGFBP2) is overexpressed in ovarian malignant tissues and in the serum and cystic fluid of ovarian cancer patients, suggesting an important role of IGFBP2 in the biology of ovarian cancer. The purpose of this study was to assess the role of increased IGFBP2 in ovarian cancer cells. 相似文献70.
Partial thickness articular cartilage defects in the knee are commonly encountered clinical problems. Recently, use of radiofrequency-based devices for performing arthroscopic chondroplasty has gained popularity. However, published experimental studies using different methods for evaluating the histologic effects of radiofrequency-chondroplasty on surrounding cartilage offer contradictory results. To date, few clinical findings after radiofrequency-based chondroplasty have been reported. We present four patients where follow-up arthroscopy documented partial thickness articular defects treated previously with radiofrequency-based chondroplasty to be completely filled with stable repair tissue. No attempt was made to stimulate cartilage regeneration (ie, abrasion or microfracture) in any of these cases. 相似文献