Alkaloids ofBerberis laurina Billb. II. Two new phenolic biscoclaurine alkaloids

Zusammenfassung Die Isolierung von zwei neuen dauricinartigen AlkaloÏden, Espinin and Espinidin, ausBerberis laurina, und deren Strukturaufklärung durch Spektroskopie und Degradation werden beschrieben.     

Continuous deep sea salt layer along North Atlantic margins related to early phase of rifting

Deep seismic reflexion surveys have revealed diapiric structures in deep water off Labrador, Newfoundland, Mauritania, Morocco, Portugal, Spain and Ireland as well as in the Mediterranean. Many of these diapirs are similar to the Gulf of Mexico salt domes, and it is suggested that there is a continuous deep sea salt layer, off the continental margin, which is related to the early phase of rifting.     

Characterization of the estrogen receptors in the uterine and blood eosinophil leukocytes

Summary Estrogen receptors are found in the rat uterine and in the eosinophil-rich human blood leukocyte 24,000g fractions, but not in the low-eosinophil count human blood leukocyte 24,000g fraction. The total number of binding sites per blood eosinophil leukocyte is 7,400 sites per cell, and theK _d =5.6×10^–10 M.Acknowledgments. This work was supported in part by funds from the Unité de Recherches sur le Métabolisme Moléculaire et la Physio-Pathologie des Stéroïdes de l'INSERM, Hôpital de Bicetre, France, and by grant No. 2015 from the Oficina Técnica de Desarrollo Científico y Creación Artística of the University of Chile.     

藏东类乌齐地区始新世钾玄质侵入岩特征及构造环境

往过同岩体位于藏东类乌齐地区往过同,岩石类型为斑状中粒黑云母二长花岗岩,黑云母K-Ar同位素年龄为35 Ma,时代为始新世。往过同花岗岩富硅、铝、碱,高钾贫钛,低铁、镁、钙,在SiO2-K2O和K2O-Na2O图解中样品均落在钾玄岩系列区,岩石系列为钾玄质花岗岩。岩石富集大离子亲石元素和轻稀土元素,负Eu异常;在原始地幔蛛网图上Th强烈富集,Sr呈现低谷负异常,高场强元素Nb、Ta、Ti亏损,表现出钾玄岩的地球化学特征。经分析,并应用构造环境判别图解,往过同花岗岩形成于后碰撞的构造环境。     

老采区及地表残余变形对建筑物的影响

浅部开采条件下地表残余变形分析是岩层移动领域的一个棘手问题．通过老采空区影响下地表残余变形和地基承载能力变化对地面新建建筑物的影响分析,提出了老采区上方新建建筑物地基稳定性计算公式、岩层移动参数、评价方法．应用鹤岗市和谐花园小区建筑物实例进行了验证．     

Superconductivity in doped cubic silicon

Although the local resistivity of semiconducting silicon in its standard crystalline form can be changed by many orders of magnitude by doping with elements, superconductivity has so far never been achieved. Hybrid devices combining silicon's semiconducting properties and superconductivity have therefore remained largely underdeveloped. Here we report that superconductivity can be induced when boron is locally introduced into silicon at concentrations above its equilibrium solubility. For sufficiently high boron doping (typically 100 p.p.m.) silicon becomes metallic. We find that at a higher boron concentration of several per cent, achieved by gas immersion laser doping, silicon becomes superconducting. Electrical resistivity and magnetic susceptibility measurements show that boron-doped silicon (Si:B) made in this way is a superconductor below a transition temperature T(c) approximately 0.35 K, with a critical field of about 0.4 T. Ab initio calculations, corroborated by Raman measurements, strongly suggest that doping is substitutional. The calculated electron-phonon coupling strength is found to be consistent with a conventional phonon-mediated coupling mechanism. Our findings will facilitate the fabrication of new silicon-based superconducting nanostructures and mesoscopic devices with high-quality interfaces.     

NMDA receptors mediate calcium accumulation in myelin during chemical ischaemia

Central nervous system myelin is a specialized structure produced by oligodendrocytes that ensheaths axons, allowing rapid and efficient saltatory conduction of action potentials. Many disorders promote damage to and eventual loss of the myelin sheath, which often results in significant neurological morbidity. However, little is known about the fundamental mechanisms that initiate myelin damage, with the assumption being that its fate follows that of the parent oligodendrocyte. Here we show that NMDA (N-methyl-d-aspartate) glutamate receptors mediate Ca2+ accumulation in central myelin in response to chemical ischaemia in vitro. Using two-photon microscopy, we imaged fluorescence of the Ca2+ indicator X-rhod-1 loaded into oligodendrocytes and the cytoplasmic compartment of the myelin sheath in adult rat optic nerves. The AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid)/kainate receptor antagonist NBQX completely blocked the ischaemic Ca2+ increase in oligodendroglial cell bodies, but only modestly reduced the Ca2+ increase in myelin. In contrast, the Ca2+ increase in myelin was abolished by broad-spectrum NMDA receptor antagonists (MK-801, 7-chlorokynurenic acid, d-AP5), but not by more selective blockers of NR2A and NR2B subunit-containing receptors (NVP-AAM077 and ifenprodil). In vitro ischaemia causes ultrastructural damage to both axon cylinders and myelin. NMDA receptor antagonism greatly reduced the damage to myelin. NR1, NR2 and NR3 subunits were detected in myelin by immunohistochemistry and immunoprecipitation, indicating that all necessary subunits are present for the formation of functional NMDA receptors. Our data show that the mature myelin sheath can respond independently to injurious stimuli. Given that axons are known to release glutamate, our finding that the Ca2+ increase was mediated in large part by activation of myelinic NMDA receptors suggests a new mechanism of axo-myelinic signalling. Such a mechanism may represent a potentially important therapeutic target in disorders in which demyelination is a prominent feature, such as multiple sclerosis, neurotrauma, infections (for example, HIV encephalomyelopathy) and aspects of ischaemic brain injury.