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排序方式: 共有1174条查询结果,搜索用时 15 毫秒
21.
Derek Hodson Gila Hanna Jacques Désautels 《Canadian Journal of Science, Mathematics, & Technology Education》2013,13(1):1-4
Abstract This article investigates some of the specific features involved in accommodating the idea of actual infinity as it appears in set theory. It focuses on the conceptions of two individuals with sophisticated mathematics background, as manifested in their engagement with variations of a well-known paradox: the ping-pong ball conundrum. The APOS theory is used as a framework to interpret participants’ efforts to resolve the paradoxes. The cases discussed focus on how transfinite subtraction may be conceptualized, and they suggest that there is more to accommodating the idea of actual infinity than the ability to act on a completed object—rather, it is the manner in which objects are acted upon that is also significant. 相似文献
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Hanna Mannell Petra Kameritsch Heike Beck Alexander Pfeifer Ulrich Pohl Kristin Pogoda 《International journal of molecular sciences》2022,23(1)
The gap junction protein connexin 43 (Cx43) is associated with increased cell migration and to related changes of the actin cytoskeleton, which is mediated via its C-terminal cytoplasmic tail and is independent of its channel function. Cx43 has been shown to possess an angiogenic potential, however, the role of Cx43 in endothelial cell migration has not yet been investigated. Here, we found that the knock-down of Cx43 by siRNA in human microvascular endothelial cells (HMEC) reduces migration, as assessed by a wound assay in vitro and impaired aortic vessel sprouting ex vivo. Immunoprecipitation of Cx43 revealed an interaction with the tyrosine phosphatase SHP-2, which enhanced its phosphatase activity, as observed in Cx43 expressing HeLa cells compared to cells treated with an empty vector. Interestingly, the expression of a dominant negative substrate trapping mutant SHP-2 (CS) in HMEC, via lentiviral transduction, also impaired endothelial migration to a similar extent as Cx43 siRNA compared to SHP-2 WT. Moreover, the reduction in endothelial migration upon Cx43 siRNA could not be rescued by the introduction of a constitutively active SHP-2 construct (EA). Our data demonstrate that Cx43 and SHP-2 mediate endothelial cell migration, revealing a novel interaction between Cx43 and SHP-2, which is essential for this process. 相似文献
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Viscosities are given of aqueous solutions of α-D-glucose, sucrose, apple pectin and Arabic gum, as well as of various binary mixtures of these solutions. Aqueous mixtures of α-D-glucose and sucrose exhibit a small increase in viscosity. The addition of apple pectin to the binary mixtures gives solutions of a viscosity of Arabic gum. 相似文献
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The review outlines the rationale behind starch polymer based thermoplastic resin production using reactive extrusion processing techniques, as well as characterization of these polymers. 相似文献
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Sajith Thottathil Abdulrahman Zakiah Ahmad Sabu Thomas Hanna J. Maria Azerai Ali Rahman 《应用聚合物科学杂志》2020,137(44):49372
The influence of boric acid (BA) and borax (BO) neutron-absorbing fillers on thermal stability and viscoelastic behavior of natural rubber (NR) low-density polyethylene composites has been studied. The thermal degradation and dynamic mechanical properties of the composites have been analyzed as a function of temperature. The results revealed the enhancement of thermal stability of the composites by the addition of BA and BO fillers. The flame resistance of the material was improved by the addition of both the fillers. The storage modulus was found to be dependent upon the temperature and nature of the filler. The amount of NR chains immobilized by filler particles has been quantified from dynamic mechanical analysis and secondary filler/filler interactions have been verified by the Payne effect analysis. Finally, the experimental results have been compared with theoretical predictions. 相似文献
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Kamil Cebulski Katarzyna Nowiska Karolina Jabloska Hanna Romanowicz Beata Smolarz Piotr Dzigiel Marzenna Podhorska-Okow 《International journal of molecular sciences》2022,23(7)
Irisin is a myokine formed from fibronectin type III domain-containing protein 5 (FNDC5), which can be found in various cancer tissues. FNDC5 and irisin levels have been poorly studied in the tumor tissues of breast cancer (BC). The aim of this study was to determine the levels of irisin expression in BC tissues and compare them to clinicopathological factors and Ki-67 and PGC-1α expression levels. Tissue microarrays (TMAs) with 541 BC tissues and 61 samples of non-malignant breast disease (NMBD; control) were used to perform immunohistochemical reactions. FNDC5 gene expression was measured in 40 BC tissue samples, 40 samples from the cancer margin, and 16 NMBD samples. RT-PCR was performed for the detection of FNDC5 gene expression. Higher irisin expression was found in BC patients compared to normal breast tissue. FNDC5/irisin expression was higher in patients without lymph node metastases. Longer overall survival was observed in patients with higher irisin expression levels. FNDC5/irisin expression was increased in BC tissues and its high level was a good prognostic factor for survival in BC patients. 相似文献
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Yubin Lan Qi Fang M. F. Kocher M. A. Hanna 《International Journal of Food Properties》2013,16(1):105-116
Thermal properties of native tapioca starch, including thermal conductivity, specific heat, and thermal diffusivity at 4, 15, and 30% moisture contents, and 25, 50, and 75°C temperature levels were studied. Thermal conductivity was measured using a line‐heat source thermal probe equipped with a computerized data acquisition system; specific heat was measured using Differential Scanning Calorimetry (DSC) and thermal diffusivity was calculated from the thermal conductivity, density, and specific heat. Thermal conductivity, specific heat, and thermal diffusivity increased with the increase of temperature and/or moisture content. Prediction models for the thermal properties of tapioca starch were developed for practical applications. 相似文献