Control of Chenopodium album by soil application of Ascochyta caulina under greenhouse conditions

Effects of soil application of Ascochyta caulina spores on seedlings of Chenopodium album and five cultivated plant species were investigated under greenhouse conditions as a part of a study on biological control of C. album. Application of A. caulina spores to soils resulted in disease development on C. album and to a lesser degree on Spinacia oleracea seedlings, but not on Beta vulgaris subspecies vulgaris, Zea mays, Triticum aestivum and Pisum sativum seedlings. Affected C. album seedlings had an abnormal olive-green colour or necrotic spots on cotyledons and hypocotyls, and were stunted or died. Affected S. oleracea seedlings were pale in colour or had necrotic spots on the cotyledons, but did not die. Time courses of disease incidence and of mortality of C. album could be described by a monomolecular model. Effects of spore density, sowing depth, soil water content, soil type and time of sowing on disease development were examined. Disease incidence and mortality were influenced by spore density, soil water content and soil type, but not by sowing depth. Spores in a moist soil maintained infectivity at least 2 wk. Spore densities of 10⁹ to 10¹⁰ spores m^-2 were required for 50% mortality of emerged C. album plants. Aspects of the development of A. caulina into a soil-applied mycoherbicide are discussed.     

Differences between observed and predicted energy costs at rest and during exercise in three subsistence-level populations

Estimates of daily energy expenditure are important for many areas of research in human ecology and adaptability. The most common technique for estimating human energy expenditure under field conditions, the factorial method, generally relies on activity-specific energy costs derived from published sources, based largely on North American and European subjects. There is concern that such data may not be appropriate for non-Western populations because of differences in metabolic costs. The present study addresses this concern by comparing measured vs. predicted energy costs at rest and during sub-maximal exercise in 83 subjects (52 males, 31 females) from three subsistence-level populations (Siberian herders and high-land and coastal Ecuadorian farmers). Energy costs at rest (i.e., lying, sitting and standing) and while performing a standard stepping exercise did not significantly differ among the three groups. However, resting energy costs were significantly elevated over predicted levels (+16% in men, +11% in women), whereas exercising costs were comparable to predicted values (?6% in men, +3% in women). Elevations in resting energy needs appear to reflect responses to thermal stress. These results indicate that temperature adjustments of resting energy costs are critical for accurately predicting daily energy needs among traditionally living populations. o 1996 Wiley-Liss, Inc.     

Application of radiotelemetry to the survey of acorn dispersal byApodemus mice

We examined the applicability of radiotelemetry to studies of acorn dispersal byApodemus mice and compared its efficiency with the of this spool-and-line method. Installation of a transmitter (2.2 g) onto acorns did not interfere with the transporting and feeding behavior of the mice. We were able to detect all transmitter-installed acorns and follow the daily changes in the sites in which they were hoarded, while we missed 59% of the spool-tied acorns due to mice breaking the threads. Mice carried transmitter-installed acorns farther than spool-tied ones. The radiotelemetry method is superior to the spool-and-line method and useful for the study of hoarding behavior in rodents.     

An impedimetric method for rapid screening of cosmetic preservatives

An efficient impedance method was developed for rapid evaluation of cosmetic preservatives. The method used decimal reduction time or D-value to assess preservative efficacies. The D-value, which was calculated from the plot of Log CFU ml^–1 versus time by linear regression analysis, could be obtained within 48 h. Thus, the time required for the challenge test was reduced from 4–8 weeks with the standard procedures (eg US Pharmacopeia), to 2 days with the current method. A calibration curve (r=-0.95) was established by plotting the Log CFU ml^–1 versus capacitance detection time (DT) of 108 samples. With the calibration, CFU can be estimated directly from the impedance test without plating. Two commercial biocides and several other chemicals were evaluated in a shampoo by the impedance procedure againstPseudomonas aeruginosa. The D-values obtained from the impedance test were not significantly different from those produced by the conventional plate count method. The technique was found to be particularly useful when screening a large number of compounds to find novel preservatives and synergistic preservative combinations.     

血凝法的生物载体选择与处理

用ＨＢｓＡｇＲＰＨＡ做为模式,选用羊、火鸡、鹅、人Ｏ型血球为载体,醛化后分成致敏和不致敏两种,与异嗜性抗体、中国生物制品药品检定所的参比品等作凝集试验。结果表明,无论特异性还是灵敏度都以人Ｏ型血球为最佳。在此基础上,设计了五种醛化方法处理人Ｏ型血球,共得出１８个醛化样品,经７３种不同的比较试验,筛选出最佳醛化方法为改良丙酮醛──甲醛法,采用该法醛化后血球为褐色,阴性血清和空白对照背景清晰,血球沉集点致密,下滑程度好。致敏抗—ＨＢｓＭｃＡｂ后,使ＨＢｓＡｇ灵敏度达到１～２ｎｇ／ｍｌ。为制备高质量的血凝试剂提供了最佳载体。     

不同生境区稻田节肢动物群落相似性分析

根据不同生境区稻田节肢动物群落系统调查结果,应用组平均聚类分析法及主成分分析法,讨论节肢动物群落的相似（相异）性问题。结果表明：生境条件及管理措施的差异对群落的结构影响较为明显,不同生境区的稻田节肢动物群落,都能在一定距离取值时聚合成一类,而水稻品种对此影响较小。主成分分析结果由二维图表达已基本满足要求。结果说明大八镇生境区稻田节肢动物群落与岗列镇生境区稻田节肢动物群落差异较大,分别列于两个极端。海陵镇生境区稻田介于两者之间,而与岗列镇生境区稻田节肢动物群落重叠。与聚类分析结果有所差异。这可能与主成分分析法损失部分信息有关。     

Bifurcation analysis of periodic SEIR and SIR epidemic models

The bifurcations of the periodic solutions of SEIR and SIR epidemic models with sinusoidally varying contact rate are investigated. The analysis is carried out with respect to two parameters: the mean value and the degree of seasonality of the contact rate. The corresponding portraits in the two-parameter space are obtained by means of a numerical continuation method. Codimension two bifurcations (degenerate flips and cusps) are detected, and multiple stable modes of behavior are identified in various regions of the parameter space. Finally, it is shown how the parametric portrait of the SEIR model tends to that of the SIR model when the latent period tends to zero.     

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     

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.