旋转摩擦挤压法制备CNTs/Mg复合材料的组织和力学性能

通过显微硬度和抗拉强度试验、X射线衍射仪、扫描电镜和金相显微镜观察,研究经旋转摩擦挤压法制备的CNTs/Mg复合材料的组织及性能。结果表明:CNTs/Mg复合材料的组织为细小等轴晶,且随着CNTs含量的增加,复合材料晶粒尺寸逐渐细化,当CNTs含量为5%时,晶粒尺寸最小,由63μm减小至3.79μm,为AZ91基材晶粒尺寸的6.01%。经过旋转摩擦挤压加工后基材内第二相β-Al12Mg17相的量减少,CNTs的加入使复合材料中出现了Al4C3相,且第二相β-Al12Mg17相网状结构消失。加工后的镁合金抗拉强度提高,最大值为330.9 MPa,较原基材提高了90.6%,当CNTs含量小于2%时,复合材料强度高于原基材。复合材料硬度随着CNTs含量的增加呈先增加后降低的趋势,当CNTs含量为2%时,硬度最高,达101.3HV,比AZ91基材提高了40.3%。     

铝合金厚板搅拌摩擦焊焊缝局部金属的塑性流动特征

以0.02mm厚铜箔为标示材料,采用带三角平面圆锥形搅拌针对20mm厚7075-T6铝板进行焊接。通过测试沿焊缝厚度方向上温度场分布及观察标示材料分布状态,分析焊缝局部金属塑性流动行为特征。结果表明,沿焊缝厚度方向上自上而下的金属温度逐渐降低;焊缝上、下表面温度差约为90℃;同一厚度上相对称的两点,位于前进边金属的温度高于返回边约15℃。位于焊核区上部的铜箔呈细小颗粒状均匀分布;下部铜箔则呈层片状分布,且向前进边偏移。焊核区由多个呈纹路状、有序排列的洋葱环结构相互层叠而成,这与焊缝塑化金属沿轴向迁移方式发生变化有关。     

Linkage map of Escherichia coli K-12, edition 10: the physical map

A physical map, EcoMap10, of the now completely sequenced Escherichia coli chromosome is presented. Calculated genomic positions for the eight restriction enzymes BamHI, HindIII, EcoRI, EcoRV, BglI, KpnI, PstI, and PvuII are depicted. Both sequenced and unsequenced Kohara/Isono miniset clones are aligned to this calculated restriction map. DNA sequence searches identify the precise locations of insertion sequence elements and repetitive extragenic palindrome clusters. EcoGene10, a revised set of genes and functionally uncharacterized open reading frames (ORFs), is also depicted on EcoMap10. The complete set of unnamed ORFs in EcoGene10 are assigned provisional names beginning with the letter "y" by using a systematic nomenclature.     

Serum from diabetic BB/W rats enhances calcium currents in primary sensory neurons

We examined the hypothesis that exposure of nondiabetic rat dorsal root ganglion (DRG) neurons to sera from diabetic BB/W rats would produce an increase in calcium currents associated with impaired regulation of the inhibitory G protein-calcium channel complex. Acutely dissociated rat DRGs were incubated for 18-24 h in medium supplemented with sera (10% vol/vol) from either diabetic rats with neuropathy or age-matched, nondiabetic controls. Exposure of DRG neurons to sera from diabetic BB/W rats resulted in a surface membrane immunofluorescence pattern when treated with an anti-rat light-chain antibody that was not observed in neurons exposed to control sera. Calcium current density (IDCa) was assessed with the use of the whole cell variation of the patch-clamp technique. IDCa in neurons exposed to diabetic sera was significantly increased compared with neurons exposed to control sera. Guanine nucleotide-binding (G) protein regulation of calcium channel function was examined with the use of a two-pulse "facilitation" or IDCa enhancement protocol in the presence of activators [guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S)] or antagonists [guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) and pertussis toxin (PTX)] of G protein function. Facilitation was significantly decreased in neurons exposed to diabetic sera. Intracellular diffusion of neurons with GDP beta s blocked facilitation, whereas dialysis with GTP gamma s increased facilitation to a similar magnitude in neurons exposed to either diabetic or control sera. Treatment with PTX resulted in a significant increase in IDCa and approximately 50% decrease in facilitation in neurons treated with control sera but no significant changes in neurons exposed to diabetic sera. We conclude that serum from diabetic BB/W rats with neuropathy contains an autoimmune immunoglobulin that impairs regulation of the inhibitory G protein-calcium channel complex, resulting in enhanced calcium influx. Regulation of the inhibitory G protein-calcium channel complex involves PTX-sensitive and -insensitive G proteins.     

Ecstasy--cool dope with long-lasting effects?

The amphetamine derivative MDMA (3,4-methylenedioxymethamphetamine) was first synthesised in 1914 as an appetite suppressant, but was never used as such. MDMA is commonly known as "ecstasy" and has become a popular recreational drug of abuse at dance-clubs and rave parties, where it is combined with all-night dancing, crowded conditions, poor hydration and loud sound. This combination is probably the main reason why we have seen an upsurge in toxicity problems at rave parties, since all these factors are thought to promote or increase the toxicity of MDMA. The desired effects of MDMA are euphoria, increased energy and enhanced communication with others. Adverse effects are hyperthermia, rhabdomyolysis, acute renal failure, hepatotoxicity, depression and psychosis.     

Profibus-DP在连铸辊道控制系统上的应用

介绍攀钢1#方坯连铸后区辊道控制的基本原理,概述西门子S7-400PLC与M440变频器通过现场总线Profibus-DP怎样连接起来,阐述PLC硬件组态如何进行、变频器相应参数如何设置,并提出PLC和变频器之间进行数据交换的方法。     

3σ规则和μ律阈值法在心音信号去噪中的应用

讨论小波包阈值法去噪的机理,提出基于小波包变换的3σ规则和μ律阈值法在心音信号预处理中的方法,该方法保留小波包变换去噪的优势,能够有效地突出心音的特征部分,在心杂音信号去噪中有较好的效果。实验结果表明,该方法在去除干扰和心杂音上有着一定的优势,在心音信号检测中有重要的应用价值。     

3G用户在WLANs间的快速认证方法

EAP-AKA协议可以实现用户和3G网络的双向认证,但缺乏对无线局域网(WLAN)接入网络的认证和用户主密钥的更新机制,并且3G用户在WLAN间漫游时代价较高。针对上述问题,利用身份加密技术和门票技术改进EAP-AKA协议,设计无需3G网络参与的WLAN间快速漫游协议,实现对WLAN接入网络的认证和主密钥更新。     

3σ规则和µ律阈值法在心音信号去噪中的应用

讨论小波包阈值法去噪的机理,提出基于小波包变换的3σ规则和µ律阈值法在心音信号预处理中的方法,该方法保留小波包变换去噪的优势,能够有效地突出心音的特征部分,在心杂音信号去噪中有较好的效果。实验结果表明,该方法在去除干扰和心杂音上有着一定的优势,在心音信号检测中有重要的应用价值。