A diffusive-convective model for the dynamics of population-toxicant interactions: some analytical and numerical results

In this paper we consider a diffusive-convective model for the dynamics of a population living in a polluted environment. Threshold results are given concerning the effect of the toxicant on the living population. Some analytic results are proved and numerical experiments give suggestions in more general cases.     

Pitfalls in immunocytochemistry with special reference to the specificity problems in the localization of neuropeptides

In this review, the different types of specificity in immunocytochemistry (ICC) are discussed. Some examples of misinterpretations on the basis of ICC results are given. A strategy is proposed to assess the specificity of antisera and to test them again after purification.     

Preliminary study of organochlorine residues in human milk and cord blood

A large collection of human milk samples and cord blood from various hospitals of Tunis is studied for organochlorine residues. Some results obtained by ECD-GC are given.     

Serological studies on the taxonomy of planorbid snails

Techniques in the application of serological studies to the family Planorbidae are described. Some results obtained using hyperimmune rabbit sera are given and reasons are outlined for the final decision to use egg albumen antigens for future taxonomic work.     

Serological studies on the taxonomy of planorbid snails

Techniques in the application of serological studies to the family Planorbidae are described. Some results obtained using hyperimmune rabbit sera are given and reasons are outlined for the final decision to use egg albumen antigens for future taxonomic work.     

Low temperature column chromatography: application to microsomal hydroxylating system.

A chromatography device working at subzero temperature is described. Some results concerning resolution of microsomal hydroxylating system are given, after solubilisation and chromatography at ?20°C.     

On the Detection of Unusual Points in Regression

Some procedures, based on studentized residuals and the diagonal elements of the ‘hat’ matrix, for the detection of unusual points in regression are discussed. These procedures are quite simple but effective to uncover unusual structure of the data. Some examples are given.     

Pattern separability in a random neural net with inhibitory connections

Some interesting properties on pattern separation have been shown through researches by neural models of cerebellar cortex. It seems to us that those results are a part of the properties of pattern separation. A two layer random nerve net with inhibitory connections is given as a model of the cerebellar cortex. The model is composed of threshold elements there. A more general theory of pattern separation than those studied earlier is given, and the pattern separability of the model is considered. It is revealed that the standard deviation of threshold values of threshold elements has a great effect on the pattern separability and the control of the firing rate. The present study is also intended to investigate the pattern separability in such a case that the firing rate of input patterns are not equal, and a pattern includes the other pattern. It is assumed there that the standard deviation is small. Some properties of the degree of pattern separation are cleaned up.     

一个具暂时免疫且总人数可变的传染病动力学模型

建立了一个具常恢复率和接触率依赖于总人数的SIRS传染病动力学模型，讨论了系统平衡点的存在性和稳定性，对双线性传染率的特殊情形，给出了传染病平衡点的全局稳定性结论，推广和改进了已有的相应结果。     

An analysis of the phototactic behaviour of Daphnia magna clones and their sexual descendants

Daphnia magna clones, isolated from different natural populations, were inbred and crossbred. Some aspects of the heredity of the phototactic behaviour, quantified by an index, were analysed. Heritability in the broad sense was determined for several assemblages of clones through calculation of the clonal repeatability. Heritability sensu strictu was determined by offspring-parent regressions. Frequency distributions of a phototactic index of several inbred and crossbred families are given.The results indicate a significant contribution of additive genetic variance to the total phenotypic variance. Comparison of heritability estimates suggests an important genetic interaction component.Some implications of these results on the variability of vertical migration patterns in natural populations are discussed.     

R.B. Merrifield: European footnotes to his life and work.

Some reflections on the life and work of RB Merrifield in the European context are given.     

DEVELOPMENTAL BIOLOGY AND THE STUDY OF MALFORMATIONS

1. The scientific approach to malformations began with experimental work on abnormal conditions of incubation in the chick. 2. More precise experiments on causing abnormalities had a common origin with experimental embryology. 3. Progress in experimental teratology during the last fifty years is reviewed in a commentary on the four principles formulated by Stockard in 1921. 4. Some relationships are traced between the results of cytogenetical studies in man and in other organisms. 5. An account is given of present knowledge concerning malformations of the neural tube originating either experimentally, spontaneously, or phenotypically. 6. The teratological implications of some recent theories on the expression of the genotype are discussed, particularly in relation to problems of hormones as teratogens. 7. Some account is given of the implication of carbohydrate metabolism and terato-genesis. 8. Teratogenesis is possibly related to cationic balance in early development. 9. It is suggested that one factor retarding progress in the understanding of malformations is the tendency towards the development of teratology in an insufficiently close relationship with other branches of cell biology.     

The melanoidin-containing preparation MIGI-K from mussels and its characteristics]

The physico-chemical properties of preparation MIGI-K from mussels are given. Some characteristics of melanoidin fractions of MIGI-K are presented, their similarity to standard melanoidin is revealed. The given data on biological activity of the preparation permit to consider MIGI-K as immunomodulator.     

Dynamical aspects of P systems

A dynamical analysis of P systems is given that is focused on basic phenomena of biological relevance. After a short presentation of a new kind of P systems (PB systems), membrane systems with environment, called PBE systems, are introduced that are more suitable for modeling complex membrane interactions. Some types of periodicity and non-periodicity are considered for PBE systems by showing some "minimal" examples of systems that exhibit these properties. In particular, a discrete formulation of the Belousov-Zhabotinsky (BZ) reaction is given in terms of PBE systems. Some questions and open problems for future research are indicated.     

具有毒素影响的二维Kolmogorov模型的持续生存和绝灭

研究了具有毒素影响的二维Kolmogorov模型,给出了该系统持续生存与绝灭的充分条件.     

Large deformation analysis of some basic problems in biophysics

This study is concerned with the application of a possible form of a strain-energy function suitable for soft biological tissues. Two problems considered here are related to simultaneous extension and inflation of cylindrical arteries, and inflation of the left ventricle under a given internal pressure. The values of the material constants are obtained via comparison of theoretical results with experimental findings. Some details concerning the wall stresses and the elastic stiffness are also given in the paper. For each case, it is seen that experiment and theory are in good agreement.     

Note on the interpretation of tracer experiments in biological systems

It is shown that the results of C. W. Sheppard and A. S. Householder (1951) can be modified to include open systems which may or may not be in the steady state. Some conditions are given under which simple chemical reactions can be included.