Measurement of k(L)a by dynamic pressure method in pilot-plant fermentor

The dynamic pressure method (DPM) is used for measurement of k(L)a in a 1-m(3) pilot scale fermentor in coalescing (distilled water) and noncoalescing (0.3 M Na(2)SO(4) aqueous solution) batches. The method consists in recording oxygen concentration in a batch after a small pressure change (20 kPa) in the fermentor. The upward pressure change is brought about by temporary closing and subsequent throttling of outlet gas stream and the downward change by full reopening of the gas outlet. Absorption of pure oxygen yields the same k(L)a values as absorption of air. In noncoalescing batch, the downward k(L)a values are always higher than the upward values owing to spontaneous nucleation of bubbles. The experiments performed in a stirred cell confirm this behavior. Thus, only upward pressure change should be used for measurement. The correlation of k(L)a data measured in small (18-L) and large (1000-L) vessels based on power dissipated and superficial gas velocity are in a good agreement. Unlike the DPM, the classical dynamic methods yield, under the same conditions, excessively low values of k(L)a (the dynamic startup method) or fail to produce data at all (the dynamic method with interchange of air for N(2)). (c) 1994 John Wiley & Sons, Inc.     

The posterior probability distribution of alignments and its application to parameter estimation of evolutionary trees and to optimization of multiple alignments

How to sample alignments from their posterior probability distribution given two strings is shown. This is extended to sampling alignments of more than two strings. The result is first applied to the estimation of the edges of a given evolutionary tree over several strings. Second, when used in conjunction with simulated annealing, it gives a stochastic search method for an optimal multiple alignment.Correspondence to: L. Allison     

A comparative study of the distribution and density of stomata in the British flora

The distribution of stomata over both leaf surfaces may affect both the photosynthetic rate and water use efficiency of species, implying that species with different photosynthetic and water requirements may also have different stomatal distributions. A database containing data on the distribution of stomata on the leaves of 469 British plant species was used to look for relationships between stomatal distribution (including both location on the leaf and density) and both habitat and morphological variables. Statistical models were applied to the data that minimized any effects that phylogenetic constraints may have had on the data.
Hypostomaty is common in woody species, species which typically occur in shaded habitats and species with large or glabrous leaves. Amphistomaty, however, predominates in species which occur in non-shaded habitats, species with small, dissected or hairy leaves, and in annual species. Amphistomaty, therefore, tends to occur in species where CO₂ may be limiting photosynthesis (unshaded environments), or where there are structures to prevent water loss from the leaf (e.g. hairs). Hypostomaty, however, occurs in slow-growing species (e.g. trees), species with leaves which have large boundary layers (large or entire leaves) and in species where CO₂ is unlikely to limit photosynthesis (shaded habitats).     

New technique in optical resolutions

The present paper illustrates the development of an advanced technique in optical resolution. Both of the amphetamine enantiomers can be obtained by a two-step distillation in nearly quantitative yield without any loss of the resolving agent. It is proved that the second-order interactions (H-bond) are sufficient for separation of enantiomers by distillation. © 1994 Wiley-Liss, Inc.     

热带林茎流收集及计算方法探索

热带林茎流收集及计算方法探索周光益,吴仲民,李意德,陈步峰（中国林科院热带林业研究所,广州５１０５２０）ＣｏｌｌｅｃｔｉｏｎａｎｄＣａｌｃｕｌａｔｉｏｎＭｅｔｈｏｄｓｆｏｒＳｔｅｍｆｌｏｗｉｎＴｒｏｐｉｃａｌＦｏｒｅｓｔ．￥ＺｈｏｕＧｕａｎｇｙｉ;Ｗ...     

Analytical study of the effects of some soil and plant parameters on root growth due to absorption of one mobile ion: A free-boundary model

The object of our study is: a model for root growth through a free-boundary problem and the effects resulting from differences in nutrient availability and transport of only one mobile nutrient between the root surface and the rhizosphere produced by an absorption Michaelis-Menten for low and high concentrations. The model equations are solved by two methods: the quasi-stationary method and the balance integral method. The numerical solutions are used to compute radial root growth. Curves of nutrient concentration at the root-soil interface, curve as a function of root radius as well as curves representing root radius as a function of time are plotted. The parameters which are varied are the root absorption power, flux velocity at the root surface, efflux, rhizosphere radius, diffusion coefficient, buffer power, and maximum influx. The two methods show the theoretical results for radial root growth in the range of low and high concentrations. The balance integral method provides more detailed information.     

Bayesian analysis of linkage between genetic markers and quantitative trait loci. I. Prior knowledge

Summary Prior information on gene effects at individual quantitative trait loci (QTL) and on recombination rates between marker loci and QTL is derived. The prior distribution of QTL gene effects is assumed to be exponential with major effects less likely than minor ones. The prior probability of linkage between a marker and another single locus is a function of the number and length of chromosomes, and of the map function relating recombination rate to genetic distance among loci. The prior probability of linkage between a marker locus and a quantitative trait depends additionally on the number of detectable QTL, which may be determined from total additive genetic variance and minimum detectable QTL effect. The use of this prior information should improve linkage tests and estimates of QTL effects.     

天花粉蛋白与FMP复合物的晶体结构

用浸泡法得到了天花粉蛋白（ＴＣＳ）与ＦＭＰ复合物的晶体,在ＳＩＭＥＮＮＳＸ－２００Ｂ面探测器系统上收集了一套２．０分辨率的Ｘ射线衍射数据。用同晶差值傅立叶法解析了复合物的结构,经Ｘ—ＰＬＯＲ程序修正得到了ＴＣＳ—ＦＭＰ复合物的分子结构并找出了１９７个水分子,最后的Ｒ因子为０．１７２,键长和键角的ＲＭＳ偏差分别为０．０１５和２．９２２度。ＴＣＳ—ＦＭＰ复合物中,ＦＭＰ与天花粉蛋白分子有较好的结合,其结合位置正处于根据三维结构和突变体信息推测的Ｎ一糖苷酶活性口袋之中。它的类嘌呤环夹在Ｙ７０和Ｙ１１１两个侧链环之间,与Ｙ７０环近乎平行,其Ｎ７和Ｎ６分别与ＴＣＳ分子的Ｇ１０９４羰基氧和Ｉ７１的Ｎ成氢键,Ｎ３靠近Ｒ１６３的侧链,其磷酸根则伸向活性口袋的底部,与Ｅ１８９、Ｅ１６０和Ｒ１６３等残基作用。     

工业固体废弃物的急性生物毒性研究

工业固体废弃物的急性生物毒性研究谢思琴,顾宗濂,周德智（中国科学院南京土壤研究所,南京２１０００８）Ａｃｕｔｅｂｉｏｔｏｘｉｃｉｔｙｏｆｉｎｄｕｓｔｒｉａｌｓｏｌｉｄｗａｓｔｅｓ￥．ＸｉｅＳｉｑｉｎ;ＧｕＺｏｎｇｌｉａｎａｎｄＺｈｏｕＤｅｚｈｉ（Ｉｎ...     

河南木兰属9种植物过氧化物同工酶分析

本文采用聚丙烯酰胺凝胶电泳系统,测定了河南木兰属8种、1变种50多份的成熟叶片材料的过氧化物同工酶酶谱。测定结果表明,该属植物9种、变种的酶谱均有差异性,每种、变种均有特征酶谱,种间酶谱显著大于种内酶谱,根据其酶谱差异性,可以进行生物种、变种的鉴别和良种的选择。为免除其酶带Rf单一指标,鉴别生物种、变种可能出现的问题,作者创立了"酶谱多指标综合判断距离法"分析技术,首次将该属植物种、变种酶谱的酶带数目、Rf、酶带宽度及其活性强弱4个因子的差异性,进行编码联机、电脑运算分析,其结果与该属玉兰亚属内的玉兰派和辛夷派的形态分类相吻合。但是,从酶学观点不支持椭圆叶玉兰作为独立种的存在,以作为河南玉兰的变种为宜,也不支持河南玉兰派和腋花玉兰派的成立,以并入辛夷派为佳。