以辉锑矿为原料放电等离子烧结快速制备黝铜矿Cu_(12)Sb_4S_(13)及反应机理

采用辉锑矿为原料成功制备出Cu_(12)Sb_4S_(13)块体。研究以Sb_2S_3矿物为原料时烧结工艺对Cu_(12)Sb_4S_(13)合成的影响。在400 ～ 440℃温度区间内均可快速合成Cu_(12)Sb_4S_(13)块体且二次烧结能够进一步减小中间相CuSbS_2和Cu_3SbS_3。第二相Cu_3SbS_4和残留相CuS随着烧结时间的延长而降低。二次烧结前进行机械化球磨处理,干磨比湿磨更容易减小残留相。初次烧结块体的断面SEM和EDS能谱分析表明内部存在Cu或Cu_2S颗粒团聚现象。适当降低Cu或CuS摩尔量(化学计量比0.1 mol)能促进烧结块表面反应进行。烧结过程中,硫磺蒸汽压的导致烧结块表面成分和内部粉末的成分不同。     

MyoD and Myf-5 differentially regulate the development of limb versus trunk skeletal muscle

The myogenic progenitors of epaxial (paraspinal and intercostal) and hypaxial (limb and abdominal wall) musculature are believed to originate in dorsal-medial and ventral-lateral domains, respectively, of the developing somite. To investigate the hypothesis that Myf-5 and MyoD have different roles in the development of epaxial and hypaxial musculature, we further characterized myogenesis in Myf-5- and MyoD-deficient embryos by several approaches. We examined expression of a MyoD-lacZ transgene in Myf-5 and MyoD mutant embryos to characterize the temporal-spatial patterns of myogenesis in mutant embryos. In addition, we performed immunohistochemistry on sectioned Myf-5 and MyoD mutant embryos with antibodies reactive with desmin, nestin, myosin heavy chain, sarcomeric actin, Myf-5, MyoD and myogenin. While MyoD(-/-) embryos displayed normal development of paraspinal and intercostal muscles in the body proper, muscle development in limb buds and brachial arches was delayed by about 2.5 days. By contrast, Myf-5(-/-) embryos displayed normal muscle development in limb buds and brachial arches, and markedly delayed development of paraspinal and intercostal muscles. Although MyoD mutant embryos exhibited delayed development of limb musculature, normal migration of Pax-3-expressing cells into the limb buds and normal subsequent induction of Myf-5 in myogenic precursors was observed. These results suggest that Myf-5 expression in the limb is insufficient for the normal progression of myogenic development. Taken together, these observations strongly support the hypothesis that Myf-5 and MyoD play unique roles in the development of epaxial and hypaxial muscle, respectively.     

Effects of macrophage colony-stimulating factor (M-CSF) on lipopolysaccharide (LPS)-induced mediator production from monocytes in vitro

M-CSF is a macrophage-lineage-specific growth factor that causes proliferation and differentiation of progenitor cells in the bone marrow. To investigate the effects of M-CSF on more matured cells, human monocytes were cultured in the presence or absence of M-CSF for 6 days. Addition of M-CSF at more than 10(2) U/ml resulted in higher viability and caused morphological differentiation to large macrophage-like cells. LPS-induced mediator production was also compared between M-CSF-treated and control cell. Monocytes were incubated with or without M-CSF for 3 days, and were stimulated with 1 microgram/ml of LPS for 2 days. IL-1 beta was not detected in the both culture supernatants, and PGE2 production was not influenced by M-CSF. However, amounts of G-CSF, GM-CSF, IL-6, and TNF-alpha produced in response to 1 microgram/ml of LPS were 1.5 to 2 times greater from monocytes treated with 10(4) U/ml of M-CSF than from control cells. The priming effect of M-CSF on LPS-induced cytokine production was found to require 3-day preincubation, and reached a maximum at the concentration of 10(4) U/ml. M-CSF-treated cells responded to a 10 times lower concentration of LPS than control cells in terms of cytokine production. M-CSF was also shown by flowcytometric analysis to influence the expression of CD14, a receptor for LPS, which might render monocytes more sensitive to LPS.     

基于RD算法的星载SAR斜视成像

本文研究了用距离一多普勒（ＲＤ）算法来实现星载 ＳＡＲ的斜视成像处理。给出了星载 ＳＡＲ斜视时的空间几何模型和回波信号模型，详细分析了地球自转和斜视产生的多普勒质心所引起的距离走动差异，及时域和频域校正对成像的影响，并研究了一种改进的ＲＤ算法进行距离走动的校正，此算法能适应大的斜视距离走动和地球自转距离走动。针对不同的距离走动校正进行了计算机仿真，理论分析和仿真结果表明：这种改进的ＲＤ算法是有效的。     

REM sleep deprivation potentiates the effects of imipramine and desipramine but not that of clomipramine in the forced swimming test

The human amnestic syndrome associated with lesions of the hippocampus and amygdala is characterized by a selective impairment of recent (explicit, episodic) memory. Benzodiazepine (BZ) treated normal subjects demonstrate similar, marked impairments in episodic memory, but in addition, BZ also induces sedation and inattention. Thus, the amnestic effects of BZ may be secondary to drug-induced sedation. However, when subjects were pretreated with the specific BZ receptor antagonist, flumazenil, the sedative and attentional effects of diazepam were blocked, but a marked impairment in episodic memory still occurred. This demonstrates that, using neuropharmacological methods, it is possible to produce a dissociation of memory impairment from inattention and sedation. Such distinct patterns of cognitive dysfunction may serve as models for clinical cognitive syndromes.     

Micro-computerized tomographic observation of the spinning apparatus in Bombyx mori silkworms

Silkworms and spiders have evolved complex spinning apparatus thought to use highly controlled conditions to optimize protein folding and crystallization to provide a tough fiber. Accordingly, the structure and function of the natural spinning apparatus has been studied with great attention as an interesting piece of biological engineering with potential for mimicry in an industrial process. However it is still not well understood. Here we used Micro-Computerized Tomographic equipment (mCT) to visualize the three-dimensional structure of the spinning apparatus in Bombyx mori silkworms. Multidirectional tomograms obtained by X-ray radioscopy provided valuable information on the detailed arrangement of each muscle of the silk press. It is suggested that the duct in the silk press part plays a part as an extrusion die whose cross-sectional area can be controlled by muscles to optimize applied stresses in the partially gelled silk within its lumen.     

一种PN码自适应捕获门限的改进算法

文献[1]提出了一种用于直扩系统的PN码自适应门限算法。但该文献也指出,此算法对门限总数十分敏感。当门限总数设置不当时,系统的平均捕获时间将显著增加。这限制了该算法在实际中的应用。本文就此提出了改进,给出了算法及电路框图。仿真结果表明,与原方案相比,改进算法改善了对门限总数的敏感性,降低了PN码平均捕获时间。