ATP-sensitive K+ channel in the mitochondrial inner membrane.

Mitochondria take up and extrude various inorganic and organic ions, as well as larger substances such as proteins. The technique of patch clamping should provide real-time information on such transport and on energy transduction in oxidative phosphorylation. It has been applied to detect microscopic currents from mitochondrial membranes and conductances of ion channels in the 5-1,000 pS range in the outer and inner membranes. These pores are not, however, selective for particular ions. Here we use fused giant mitoplasts prepared from rat liver mitochondria to identify a small conductance channel highly selective for K+ in the inner mitochondrial membrane. This channel can be reversibly inactivated by ATP applied to the matrix side under inside-out patch configuration; it is also inhibited by 4-aminopyridine and by glybenclamide. The slope conductance of the unitary currents measured at negative membrane potentials was 9.7 +/- 1.0 pS (mean +/- s.d., n = 6) when the pipette solution contained 100 mM K+ and the bathing solution 33.3 mM K+. Our results indicate that mitochondria depolarize by generating a K+ conductance when ATP in the matrix is deficient.     

Phosphatidylglycerol is involved in protein translocation across Escherichia coli inner membranes

Newly synthesized proteins to be exported out of the cytoplasm of bacterial cells have to pass across the inner membrane. In Gram-negative bacteria ATP, a membrane potential, the products of the sec genes and leader peptidases (enzymes which cleave the N-terminal signal peptides of the precursor proteins) are required. The mechanism of translocation, however, remains elusive. Important additional roles for membrane lipids have been repeatedly suggested both on theoretical grounds and on the basis of experiments with model systems but no direct evidence had been obtained. We demonstrate here, using mutants of Escherichia coli defective in the synthesis of the major anionic membrane phospholipids, that phosphatidylglycerol is involved in the translocation of newly synthesized outer-membrane proteins across the inner membrane.     

Patch-clamping of the inner mitochondrial membrane reveals a voltage-dependent ion channel

The prime function of mitochondria is to provide the cell with adenosine triphosphate (ATP). ATP synthesis is driven by the protonmotive force (delta p), which is generated and maintained across the inner mitochondrial membrane (IMM) by the activity of the respiratory chain. It is widely believed that the IMM is unlikely to contain ion channels like those present in the plasma membrane, because the high rates of ion transport characteristic of open channels would be expected to dissipate the delta p. Although the small size of the organelle has prevented the use of classical electrophysiological methods, the recent introduction of the patch-clamp technique, which allows currents to be recorded from very small cells, has enabled us to test this hypothesis. By patch-clamping the IMM, we have identified a slightly anion-selective channel, which is voltage-dependent and has a mean conductance of 107 pS in the presence of symmetrical 150 mM KCl.     

In vitro synthesized bacterial outer membrane protein is integrated into bacterial inner membranes but translocated across microsomal membranes

The LamB protein is an integral membrane protein of the outer membrane of Escherichia coli. We have now found that, when synthesized in an E. coli cell-free translation system supplemented with inverted vesicles derived from the E. coli inner membrane, LamB protein is integrated into the vesicle membrane as assayed by its resistance to extraction at alkaline pH. These data suggest that the inner membrane is the primary site for integration of LamB protein prior to subsequent sorting to the outer membrane. When synthesized in a wheat germ cell-free translation system supplemented with canine microsomal membranes, LamB protein is glycosylated at one or two cryptic sites, and surprisingly, it is translocated across instead of being integrated into the vesicle membrane. We suggest that the translocation machinery of the microsomal membrane, although able to recognize the signal sequence(s) of LamB, is unable to recognize its stop-transfer sequence(s), thereby yielding translocation instead of integration.     

A forty-kilodalton protein of the inner membrane is the mitochondrial calcium uniporter

Mitochondrial Ca(2+) homeostasis has a key role in the regulation of aerobic metabolism and cell survival, but the molecular identity of the Ca(2+) channel, the mitochondrial calcium uniporter, is still unknown. Here we have identified in silico a protein (named MCU) that shares tissue distribution with MICU1 (also known as CBARA1), a recently characterized uniporter regulator, is present in organisms in which mitochondrial Ca(2+) uptake was demonstrated and whose sequence includes two transmembrane domains. Short interfering RNA (siRNA) silencing of MCU in HeLa cells markedly reduced mitochondrial Ca(2+) uptake. MCU overexpression doubled the matrix Ca(2+) concentration increase evoked by inositol 1,4,5-trisphosphate-generating agonists, thus significantly buffering the cytosolic elevation. The purified MCU protein showed channel activity in planar lipid bilayers, with electrophysiological properties and inhibitor sensitivity of the uniporter. A mutant MCU, in which two negatively charged residues of the putative pore-forming region were replaced, had no channel activity and reduced agonist-dependent matrix Ca(2+) concentration transients when overexpressed in HeLa cells. Overall, these data demonstrate that the 40-kDa protein identified is the channel responsible for ruthenium-red-sensitive mitochondrial Ca(2+) uptake, thus providing a molecular basis for this process of utmost physiological and pathological relevance.     

Bcl-2 is an inner mitochondrial membrane protein that blocks programmed cell death

The t(14; 18) chromosomal translocation of human follicular B-cell lymphoma juxtaposes the bcl-2 gene with the immunoglobulin heavy chain locus. The bcl-2 immunoglobulin fusion gene is markedly deregulated resulting in inappropriately elevated levels of bcl-2 RNA and protein. Transgenic mice bearing a bcl-2 immunoglobulin minigene demonstrate a polyclonal expansion of resting yet responsive IgM-IgD B cells which display prolonged cell survival but no increase in cell cycling. Moreover, deregulated bcl-2 extends the survival of certain haematopoietic cell lines following growth-factor deprivation. By using immunolocalization studies we now demonstrate that Bcl-2 is an integral inner mitochondrial membrane protein of relative molecular mass 25,000 (25k). Overexpression of Bcl-2 blocks the apoptotic death of a pro-B-lymphocyte cell line. Thus, Bcl-2 is unique among proto-oncogenes, being localized to mitochondria and interfering with programmed cell death independent of promoting cell division.     

人工挖孔桩桩孔稳定性分析

在设计人工挖孔桩时，设计人员往往忽视桩孔稳定性分析，而在施工人工挖孔桩时，又存在许多不安全的施工方法，致使人身事故经常发生，桩孔不能顺利施工。本文先分析了桩孔周围的土压力计算和护壁的设计问题，然后根据人工挖孔桩扩大头以上土体的自重与土体表面摩擦力的平衡，推导出 能够判断桩孔整体稳定性的临界深度公式，本文的分析对指导桩孔设计和施工具有一定的作用。     

RBF函数的孔洞修复技术研究

提出了一种利用RBF函数对具有“孔洞”的散乱点云进行修复的算法,该算法是通过给散乱点云数据建立隐式曲面方程,隐式曲面方程是通过一个连续的函数来描述重建的实体模型,在曲面重建的过程中可以自动实现数据缺损处的孔洞修补.通过编程实现了孔洞的修复,该算法在MATLAB 7.0上进行实验.实验的结果表明,该算法在孔洞修复方面具有很好的效果.     

Injection Flow Researh Through Discrete Holes

本文给出在不同的加热条件下,确定壁面温度场并得到孔内、孔壁和孔口附近裸表面的的传热传质系数和膜冷却系数的方法,对膜冷却孔周围及流体的数学模型的建立有很大帮助     

廊道型孔口的应力集中

本文为“标准廊道附近的应力集中”一文的继续和补充.首先采用改进的梅林契耶夫法求解映象函数,然后应用穆斯海里什维里方法求解无限平面域内廊道型孔口在五种应力场(σ_x~∞=1,σ_y~∞=1,τ=_(xy)~∞=1,σ_x~∞=-(M/J)y,σ_y~∞=(M/J)x)中的孔边应力.从而把原来求映象函数的绘图、计算交叉循环解法改为纯数解法,并与应力计算一气呵成,便于应用计算机求解.编制了 PC-1500微型计算机的程序,并算出了四种孔型的孔边应力,计算结果与有关文献结果一致,因而可以提供设计部门应用参考.     

基于RGB-D图像的深度图空洞修复

提出一种基于RGB-D的深度图像空洞修复算法。通过改进的双边滤波对深度图进行滤波处理,填充了空洞而且保持了图像的边缘;再利用复合型中值滤波对深度图进行处理消除孤立点的影响,平滑了深度图像。实验结果表明,这一方法能够有效地对深度图进行空洞修复且图像边缘清晰。     

直通式探放水钻孔在白洞煤矿的应用

针对我国煤炭生产中防治水存在的问题,依据多年来从事煤矿水文地质技术和管理的经验,探索出直通式探放水研究理论,并在同煤集团白洞煤业有限责任公司实施,效果很好。就大同煤田地质水文条件来讲,该法推广具有广泛的实用性。     

含地下孔洞层状半空间中瞬态波的传播

针对任意层数层状半空间的波动问题,采用相应介质域基本解在时域中建立了层状半空间的边界积分方程,系统地给出其离散求解的基本公式及数值化实施的计算技术.给出的边界元算法可以直接求解含孔洞任意层数层状半空间介质的波动问题而无需对各层交接面离散和设立自由度,从根本上克服了这类问题传统边界元法分区算法的弊端,大幅度减少了离散自由度,提高了求解效率.数值实例验证了上述方法的可行性及可靠性.     

蒸发黑洞量子热效应中的tortoise坐标

本文取Ｖａｉｄｙａ－ｄｅ ｓｉｔｔｅｒ黑洞，证明了广义ｔｏｒｔｏｉｓｅ坐标变换中Ｋ只能是关于Ｖ的常数。     

1129回采工作面高位孔瓦斯抽放技术应用

为解决低瓦斯矿井中瓦斯涌出异常区域的瓦斯涌出量大,时常发生瓦斯超限事故的隐患,在林南仓矿1129工作面采取高位孔抽放等安全技术措施,收到了很好的成效。     

结构洞综合评价指标的构建与应用

针对描述结构洞特性的单一性指标有效规模系数(ES)、效率(EF)和凝聚约束系数(AC)的不足性问题,提出了综合评价结构洞特性指标——有效凝聚约束系数EFAC。应用于小世界网络中,可以清晰地揭示小世界网络的结构特性与其结构洞分布规律的一致性。     

带双周期裂缝与孔洞的弹性平面基本问题

本文讨论了双周期基本胞腔中既含若干个任意形状孔洞,又具若干条任意形状裂缝的平面弹性基本问题。将寻求复应力函数的问题归结为求解正则型的奇异积分方程,并证明了其解存在且唯一。     

n型掺杂GaAs中电子与空穴的超快弛豫特性

研究了n型重掺杂GaAs中的光生电子与空穴的超快弛豫特性.在n型重掺杂情况下,由于费米面已进入导带之中,抑制了费米面附近光激发电子的弛豫过程对泵浦探测信号的贡献,而突出了空穴弛豫在饱和吸收谱中的地位.理论计算表明空穴通过吸收光声子在～300fs时间内达到与晶格热平衡,并由此所导出的材料光学形变势常数d0=31eV.计算值与实验测量结果相符合.