Ultrahigh-quality silicon carbide single crystals

Silicon carbide (SiC) has a range of useful physical, mechanical and electronic properties that make it a promising material for next-generation electronic devices. Careful consideration of the thermal conditions in which SiC [0001] is grown has resulted in improvements in crystal diameter and quality: the quantity of macroscopic defects such as hollow core dislocations (micropipes), inclusions, small-angle boundaries and long-range lattice warp has been reduced. But some macroscopic defects (about 1-10 cm(-2)) and a large density of elementary dislocations (approximately 10(4) cm(-2)), such as edge, basal plane and screw dislocations, remain within the crystal, and have so far prevented the realization of high-efficiency, reliable electronic devices in SiC (refs 12-16). Here we report a method, inspired by the dislocation structure of SiC grown perpendicular to the c-axis (a-face growth), to reduce the number of dislocations in SiC single crystals by two to three orders of magnitude, rendering them virtually dislocation-free. These substrates will promote the development of high-power SiC devices and reduce energy losses of the resulting electrical systems.     

Genetic visualization of notch signaling in mammalian neurogenesis

Notch signaling plays crucial roles in fate determination and the differentiation of neural stem cells in embryonic and adult brains. It is now clear that the notch pathway is under more complex and dynamic regulation than previously thought. To understand the functional details of notch signaling more precisely, it is important to reveal when, where, and how notch signaling is dynamically communicated between cells, for which the visualization of notch signaling is essential. In this review, we introduce recent technical advances in the visualization of notch signaling during neural development and in the adult brain, and we discuss the physiological significance of dynamic regulation of notch signaling.     

Roberts syndrome is caused by mutations in ESCO2, a human homolog of yeast ECO1 that is essential for the establishment of sister chromatid cohesion

Roberts syndrome is an autosomal recessive disorder characterized by craniofacial anomalies, tetraphocomelia and loss of cohesion at heterochromatic regions of centromeres and the Y chromosome. We identified mutations in a new human gene, ESCO2, associated with Roberts syndrome in 15 kindreds. The ESCO2 protein product is a member of a conserved protein family that is required for the establishment of sister chromatid cohesion during S phase and has putative acetyltransferase activity.     

Klotho converts canonical FGF receptor into a specific receptor for FGF23

FGF23 is a unique member of the fibroblast growth factor (FGF) family because it acts as a hormone that derives from bone and regulates kidney functions, whereas most other family members are thought to regulate various cell functions at a local level. The renotropic activity of circulating FGF23 indicates the possible presence of an FGF23-specific receptor in the kidney. Here we show that a previously undescribed receptor conversion by Klotho, a senescence-related molecule, generates the FGF23 receptor. Using a renal homogenate, we found that Klotho binds to FGF23. Forced expression of Klotho enabled the high-affinity binding of FGF23 to the cell surface and restored the ability of a renal cell line to respond to FGF23 treatment. Moreover, FGF23 incompetence was induced by injecting wild-type mice with an anti-Klotho monoclonal antibody. Thus, Klotho is essential for endogenous FGF23 function. Because Klotho alone seemed to be incapable of intracellular signalling, we searched for other components of the FGF23 receptor and found FGFR1(IIIc), which was directly converted by Klotho into the FGF23 receptor. Thus, the concerted action of Klotho and FGFR1(IIIc) reconstitutes the FGF23 receptor. These findings provide insights into the diversity and specificity of interactions between FGF and FGF receptors.     

Occurrence of perfluoroalkyl acids in precipitation from Shenyang, China

Perfluorosulfonates （PFSAs） and perfluorocarboxylates （PFCAs） in precipitation collected from Shenyang, China were determined. Snow samples were collected in the snow event on March 4, 2007 from 34 sites involving both the urban and suburban areas in Shenyang. The snowmelt was preconcentrated by solid phase extraction and analyzed using LC-MS method. Measurable amounts of perfluoroalkyl acids （PFAS） were found in precipitation samples from Shenyang, demonstrating that wet deposition is one possible pathway for the removing of the selected PFAS chemicals from atmosphere. Major PFAS detected were PFOS （〈0.38-51 ng/L）, PFOA （0.82-13 ng/L） and PFHpA （0.76-11 ng/L）, with their mean concentration of 5.4, 3.3 and 2.9 ng/L, respectively. Other PFSAs and PFCAs were detected at much lower frequency or below the limit of detection in all the samples. The work presented here offers some basis for the investigation on the environmental behavior and the evaluation of human exposure to PFAS.     

距骨多糖（APS）和距骨类黄酮（AF）对活体外正常老鼠细胞和瘤变老鼠细胞的淋巴细胞繁殖及T—淋巴细胞亚群的影响

作者研究了距骨多糖（APS）和距骨类黄酮（AF）对外活体老鼠细胞和瘤变老鼠细胞的淋巴繁殖和T-淋巴细胞亚群的影响，结果表明：在正常的老鼠细胞中，单独加入APS能诱导非活性的淋巴细胞进行繁殖，而且对于由Con A（伴刀豆球蛋A）激活的淋巴细胞，在加入APS后，繁殖速率加快；单独加入AF不能诱导非活性的淋巴细胞进行繁殖，但是AF能加速的Con A激活的淋巴细胞进行繁殖，在瘤变的老鼠细胞中，由Con A激活的淋巴细胞繁殖速率下降，但当分别加入APS和AF后，繁殖速率得到提高，因此作者认为：不论是正常的老鼠细胞中还是在瘤变的老鼠细胞中，单独使用APS或是一起使用APS与Con A，都能引起T-淋巴细胞总数的增加，并且能使不稳定CD4^ /CD8^ 比率趋于正常化；一起使用AF与Con A时，也具有相同的效应。