A Characterization of the Bivariate Exponential Distribution

In this article a characterisation of the Gumbel's Bivariate Exponential Distribution is established on the basis of the properties of the conditional expectation of the component variables. The characterising property is proposed as the definition of lack of memory in the bivariate case.     

Characterizations of the Exponential Distribution by Local Maximum Random Variables

Let {X_n, n≧1} be a sequence of independent and identically distributed random variables. Suppose n(K)=min n for which X_n>X_k, with K fixed and n>K. We will characterize the exponential distribution by considering the distributional properties of X_k and X_k and X_n(k).     

Randomized Blocks Analysis for the Exponential Distribution

A procedure for analyzing randomized blocks experiments for uncensored exponential random variables is presented. Its small sample behavior is studied in several simulations. Sample size requirements are given.     

Exponential Size Distribution of von Willebrand Factor

Von Willebrand Factor (VWF) is a multimeric protein crucial for hemostasis. Under shear flow, it acts as a mechanosensor responding with a size-dependent globule-stretch transition to increasing shear rates. Here, we quantify for the first time, to our knowledge, the size distribution of recombinant VWF and VWF-eGFP using a multilateral approach that involves quantitative gel analysis, fluorescence correlation spectroscopy, and total internal reflection fluorescence microscopy. We find an exponentially decaying size distribution of multimers for recombinant VWF as well as for VWF derived from blood samples in accordance with the notion of a step-growth polymerization process during VWF biosynthesis. The distribution is solely described by the extent of polymerization, which was found to be reduced in the case of the pathologically relevant mutant VWF-IIC. The VWF-specific protease ADAMTS13 systematically shifts the VWF size distribution toward smaller sizes. This dynamic evolution is monitored using fluorescence correlation spectroscopy and compared to a computer simulation of a random cleavage process relating ADAMTS13 concentration to the degree of VWF breakdown. Quantitative assessment of VWF size distribution in terms of an exponential might prove to be useful both as a valuable biophysical characterization and as a possible disease indicator for clinical applications.     

Exponential Size Distribution of von Willebrand Factor

Von Willebrand Factor (VWF) is a multimeric protein crucial for hemostasis. Under shear flow, it acts as a mechanosensor responding with a size-dependent globule-stretch transition to increasing shear rates. Here, we quantify for the first time, to our knowledge, the size distribution of recombinant VWF and VWF-eGFP using a multilateral approach that involves quantitative gel analysis, fluorescence correlation spectroscopy, and total internal reflection fluorescence microscopy. We find an exponentially decaying size distribution of multimers for recombinant VWF as well as for VWF derived from blood samples in accordance with the notion of a step-growth polymerization process during VWF biosynthesis. The distribution is solely described by the extent of polymerization, which was found to be reduced in the case of the pathologically relevant mutant VWF-IIC. The VWF-specific protease ADAMTS13 systematically shifts the VWF size distribution toward smaller sizes. This dynamic evolution is monitored using fluorescence correlation spectroscopy and compared to a computer simulation of a random cleavage process relating ADAMTS13 concentration to the degree of VWF breakdown. Quantitative assessment of VWF size distribution in terms of an exponential might prove to be useful both as a valuable biophysical characterization and as a possible disease indicator for clinical applications.     

福建省被子植物分布新记录

在闽东地区的植被调查中,发现福建省被子植物地理分布新记录属1个:虉草属(Phalaris Linn.);新记录种4个,分别是虉草(Phalaris arundinacea Linn.)、浙江虎耳草(Saxifraga zhejiangensis Z. Wei. et Y. B. Chang)、莼菜(Brasenia schreberi J. P. Gmel.)和斑地锦(Euphorbia maculate Linn.)。标本存放于宁德师范学院植物标本室(NDTC)。     

福建被子植物分布新记录Ⅰ

在福建省药用植物资源调查中,陆续发现了福建省被子植物地理新分布记录属及种多个,经整理鉴定,本文报道新分布记录属：八宝属（Hylotelephium）、假奓包叶属（Discocleidion）;新分布记录种：浙江蜡梅（Chimonanthus zhejiangensis）、柳叶蜡梅（Chimonanthus salicifolius）、紫花八宝（Hylotelephium mingjinianum）、冷饭藤（Kadsura oblongifolia）、假奓包叶（Discocleidion rufescens）。凭证标本暂存于福建中医药大学药用植物标本室。     

Characterization of the WEIBULL Distribution by Properties of Order Statistics

Let X_1:n, X_2:n, X_3:n…, X_n:n be the order statistics of n independent random variables with the common (absolutely continuous strictly increasing) distribution function F. The main results given in this article are:

• 1 For any fixed r and two distinct numbers s₁ and s₂ (1<r<s₁<s₂≦n) the distributions of V_i and W_i (defined in (1.11) and (1.12) are identical for i = 1,2 iff F(x) is WEIBULL (1.2).
• 2 The statistics D₁ and D₂ (as in (1.8) and (1.9)) are independent iff F(x) is WEIBULL (1.2).
• 3 The statistics U_i (1≦j≦n?1) and X_i:n (i ≦ j) are independent iff F(x) is WEIBULL (1.2).
• 4 Let X, X₁, X₂, …, X_k be random variables such that

These conditions are necessary and sufficient for F(x) to be WEIBULL .     

侧条跳树蛙的分布新纪录及其分布区域分析

2008年5月30日,在广东黑石顶自然保护区采集到5只侧条跳树蛙(Chirixalus vittatus),为广东省两栖动物新纪录.通过对侧条跳树蛙分布区域分析,认为十万大山至云开大山之间的山区是侧条跳树蛙在中国大陆的主要分布区,侧条跳树蛙的现代分布属中印半岛-中国南部热湿型.     

On the Frequency Distribution of a Product

Biometric interest often attaches to the product of two directly determined variables. In sugar production, for example, the yield of the desired commodity is the product of the total weight of cane or beet from unit area and the sugar content per unit weight. In crop and animal production, there are many analogous situations where experimental or other information may come from field plots or individual animals and the success of inferences or decisions is related to the frequency distribution of such a product. The voluminous published literature relating to frequency distributions appears to contain little that is directly relevant. It therefore seems worth placing on record results recently obtained for the third and fourth moments of a product in the simple case of both variables being Normally distributed.     

Measurement of the Cytoplasmic pH in Nitella translucens: Comparison of Values Obtained by Microelectrode and Weak Acid Methods

A comparison has been made between the use of two types of pH microelectrode and the weak acid method for determining the cytoplasmic pH of Nitella translucens at an external pH of 6. There was good agreement between the value obtained with glass pH microelectrodes (7.54 +/- 0.15 se) and that obtained using the weak acid 5,5-dimethyloxazolidine-2,4-dione (7.42 +/- 0.07 se). Plastic-insulated antimony microelectrodes gave a significantly lower value (6.74 +/- 0.15 se) possibly due to disruption of the insulation by the cell wall. The addition of 1 mM NaN(3) rapidly reduced the pH recorded by the glass pH microelectrodes to about 5.3. A smaller change was observed using the weak acid method. The relevance of this observation to recent work on indoleacetic acid transport is discussed.     

中国裸伞属已知种的分布及1个大陆新记录种

对我国22个省区的裸伞属(GymnopilusP.Karst.)27个已知名称进行了整理和修订,并描述了1个中国大陆新记录种———藏花黄褶裸伞[Gymnopilus crociphyllus(Cooke&Massee)Pegler]。     

福建被子植物分布新记录Ⅷ

在福建省中药资源普查及本土植物全覆盖调查过程中,发现福建植物2个新记录属——金瓜属(Gymnopetalum Arn.)、穿心草属(Canscora Lam.),4个新记录种——金瓜[Gymnopetalum chinense(Lour.)Merr.]、罗星草(Canscora andrographioides Griff.ex C.B.Clarke)、长毛野扁豆[Dunbaria crinita(Dunn)Maesen]、针齿铁仔(Myrsine semiserrata Wall.)。4种均为华东地区新记录。凭证标本存放于福建中医药大学标本馆和上海辰山植物标本馆(CSH)。     

眼镜蛇毒中一个弱纤维蛋白原水解活性金属蛋白酶的纯化和性质研究

通过蛋白层析从中华眼镜蛇毒中分离纯化出一个新的纤维蛋白原水解酶atrase A. Atrase A是一个分子量为64.6 kD,等电点为pH 9.6和中性糖含量为4.16%的碱性单链糖蛋白.它具有弱的纤维蛋白原α链水解活性.该活性能被金属螯合剂EDTA, EGTA,1,10 phenanthroline和还原剂DTT完全抑制,而PMSF只能部分抑制该活性,大豆胰蛋白酶抑制剂对其没有影响, 表明atrase A属于金属蛋白酶. Atrase A具有水肿活性和金黄色葡萄球菌抑制活性.它对A549 和K562 细胞没有细胞毒性,但能使贴壁生长的A549细胞解离悬浮. Atrase A没有纤维蛋白、azocasein 、BAEE水解活性,对ADP、胶原诱导的血小板聚集没有明确的抑制作用. 经小鼠皮下注射后没有发现其有出血毒活性.     

Characterization of the Formation and Distribution of Photosynthetic Products by Sedum praealtum Chloroplasts

Photoassimilation of ¹⁴CO₂ by intact chloroplasts from the Crassulacean acid metabolism plant Sedum praealtum was investigated. The main water-soluble, photosynthetic products were dihydroxyacetone phosphate (DHAP), glycerate 3-phosphate (PGA), and a neutral saccharide fraction. Only a minor amount of glycolate was produced. A portion of neutral saccharide synthesis was shown to result from extrachloroplastic contamination, and the nature of this contamination was investigated with light and electron microscopy. The amount of photoassimilated carbon partitioned into starch increased at both very low and high concentrations of orthophosphate. High concentrations of exogenous PGA also stimulated starch synthesis.

DHAP and PGA were the preferred forms of carbon exported to the medium, although indirect evidence suported hexose monophosphate export. The export of PGA and DHAP to the medium was stimulated by high exogenous orthophosphate, but depletion of chloroplastic reductive pentose phosphate intermediates did not occur. As a result only a relatively small inhibition in the rate of CO₂ assimilation occurred.

The rate of photoassimilation was stimulated by exogenous PGA, ribose 5-phosphate, fructose 1,6-bisphosphate, fructose 6-phosphate, and glucose 6-phosphate. Inhibition occurred with phosphoenolpyruvate and high concentrations of PGA and ribose 5-phosphate. PGA inhibition did not result from depletion of chloroplastic orthophosphate or from inhibition of ribulose 1,5-bisphosphate carboxylase. Exogenous PGA and phosphoenolpyruvate were shown to interact with the orthophosphate translocator.