甲烷氧化偶联制C2烃La2O3基催化剂的研究

本文的实验结果表明,具有开放型本征构型的La_2O_3对甲烷氧化偶联反应有相当好的活性和选择性,在750℃、原料气空速6.O×10~4ml.g~(-1).h~(-1),CH_4:O_2:N_2=3.7:l.0:9.0(V/V)的反应条件下,氧接近全部转化,甲烷转化率达25.4％,C_2烃选择性为43.6％,添加碱土金属(Ca、Sr、Ba)氧化物或碳酸盐能显著地改善催化剂的性能,在上述反应条件下,60mol％Ba-La_2O_3催化剂的C_2烃选择性达到58％。     

CD43, a molecule defective in Wiskott-Aldrich syndrome, binds ICAM-1.

THE protein CD43 (also known as sialophorin, leukosialin, large sialoglycoprotein or gp115) is expressed on the surface of T lymphocytes, monocytes, neutrophils, platelets and some B lymphocytes. Expression of CD43 is deficient and/or defective in the X-chromosome-linked immunodeficiency disorder Wiscott-Aldrich syndrome, suggesting that CD43 might have a role in T-cell activation. We have shown that expression of human CD43 in an HLA-DR-specific murine T-cell hybridoma enhances the antigen-specific response to stimulation by the human lymphoblastoid cell line Daudi, and that Daudi cells bind specifically to purified immobilized CD43. These data indicate that the specific interaction of CD43 with a ligand on the surface of Daudi cells might contribute to T-cell activation. Here we report evidence that intercellular adhesion molecule-1 (ICAM-1, or CD54), is a ligand for CD43.     

Structure of a nanobody-stabilized active state of the β(2) adrenoceptor

G protein coupled receptors (GPCRs) exhibit a spectrum of functional behaviours in response to natural and synthetic ligands. Recent crystal structures provide insights into inactive states of several GPCRs. Efforts to obtain an agonist-bound active-state GPCR structure have proven difficult due to the inherent instability of this state in the absence of a G protein. We generated a camelid antibody fragment (nanobody) to the human β(2) adrenergic receptor (β(2)AR) that exhibits G protein-like behaviour, and obtained an agonist-bound, active-state crystal structure of the receptor-nanobody complex. Comparison with the inactive β(2)AR structure reveals subtle changes in the binding pocket; however, these small changes are associated with an 11?? outward movement of the cytoplasmic end of transmembrane segment 6, and rearrangements of transmembrane segments 5 and 7 that are remarkably similar to those observed in opsin, an active form of rhodopsin. This structure provides insights into the process of agonist binding and activation.     

Cloning of a cDNA encoding a non-isopeptide-selective subtype of the endothelin receptor

Endothelin-1 was initially identified as a 21-residue potent vasoconstrictor peptide produced by vascular endothelial cells, but was subsequently found to have many effects on both vascular and non-vascular tissues. The discovery of three isopeptides of the endothelin family, ET-1, ET-2 and ET-3, each possessing a diverse set of pharmacological activities of different potency, suggested the existence of several different endothelin receptor subtypes. Endothelins may elicit biological responses by various signal-transduction mechanisms, including the G protein-coupled activation of phospholipase C and the activation of voltage-dependent Ca2+ channels. Thus, different subtypes of the endothelin receptor may use different signal-transduction mechanisms. Here we report the cloning of a complementary DNA encoding one subtype belonging to the superfamily of G protein-coupled receptors. COS-7 cells transfected with the cDNA express specific and high-affinity binding sites for endothelins, responding to binding by the production of inositol phosphates and a transient increase in the concentration of intracellular free Ca2+. The three endothelin isopeptides are roughly equipotent in displacing 125I-labelled ET-1 binding and causing Ca2+ mobilization. A messenger RNA corresponding to the cDNA is detected in many rat tissues including the brain, kidney and lung but not in vascular smooth muscle cells. These results indicate that this cDNA encodes a 'nonselective' subtype of the receptor which is different from the vascular smooth muscle receptor.     

线性统计模型中回归分位点的强相合性及渐近正态性(英文)

论证了线性模型中回归分位点估计量的强相合性及渐近正态性等大样本性质 ,这些结果推广了陈希孺等 ( 1 990 ,1 992 )的有关定理 ,改进了Koenker与Basstee( 1 978) ,Gutenburnner与Jurec∨kova( 1 992 ) ,以及Jurec∨kovo与Prochazka( 1 994)等人的有关成果。     

Fras1 deficiency results in cryptophthalmos,renal agenesis and blebbed phenotype in mice

Loss of tight association between epidermis and dermis underlies several blistering disorders and is frequently caused by impaired function of extracellular matrix (ECM) proteins. Here we describe a new protein in mouse, Fras1, that is specifically detected in a linear fashion underlying the epidermis and the basal surface of other epithelia in embryos. Loss of Fras1 function results in the formation of subepidermal hemorrhagic blisters as well as unilateral or bilateral renal agenesis during mouse embryogenesis. Postnatally, homozygous Fras1 mutants have fusion of the eyelids and digits and unilateral renal agenesis or dysplasia. The defects observed in Fras1-/- mice phenocopy those of the existing bl (blebbed) mouse mutants, which have been considered a model for the human genetic disorder Fraser syndrome. We show that bl/bl homozygous embryos are devoid of Fras1 protein, consistent with the finding that Fras1 is mutated in these mice. In sum, our data suggest that perturbations in the composition of the extracellular space underlying epithelia could account for the onset of the blebbed phenotype in mouse and Fraser syndrome manifestation in human.     

聚甲基乙撑碳酸酯的交联(英文)

利用过氧化物过氧化二异丙苯(DCP)和多官能团化合物三烯丙基异氰尿酸酯(TAIC),对聚甲基乙撑碳酸酯(PPC)进行了交联研究。研究发现, DCP和TAIC的用量对PPC的交联均有较大影响, PPC交联后,其凝胶含量、机械性能、弹性模量、玻璃化转变温度均有所增加, 1%的DCP和4%的TAIC用量可得到较理想的交联PPC材料。     

Multiple dynamic representations in the motor cortex during sensorimotor learning

The mechanisms linking sensation and action during learning are poorly understood. Layer 2/3 neurons in the motor cortex might participate in sensorimotor integration and learning; they receive input from sensory cortex and excite deep layer neurons, which control movement. Here we imaged activity in the same set of layer 2/3 neurons in the motor cortex over weeks, while mice learned to detect objects with their whiskers and report detection with licking. Spatially intermingled neurons represented sensory (touch) and motor behaviours (whisker movements and licking). With learning, the population-level representation of task-related licking strengthened. In trained mice, population-level representations were redundant and stable, despite dynamism of single-neuron representations. The activity of a subpopulation of neurons was consistent with touch driving licking behaviour. Our results suggest that ensembles of motor cortex neurons couple sensory input to multiple, related motor programs during learning.     

超音速火焰喷涂Cr_3C_2-NiCr涂层的冲蚀磨损特性

实验研究了燃气流量、氧气流量和喷涂距离对超音速火焰 (HVOF)喷涂Cr3C2 NiCr涂层冲蚀磨损性能的影响 ,在对不同角度冲蚀后涂层表面和横截面结构分析的基础上 ,探讨了其冲蚀磨损失效机制 .结果表明 :Cr3C2 NiCr涂层的冲蚀磨损呈现脆性材料的冲蚀磨损特征 ,在 90°冲蚀率最大 ;磨料冲击引起的裂纹沿涂层内粒子界面萌生、扩展并最终导致粒子剥落 ,是涂层主要的冲蚀磨损机制 .