Biological Subject Research Articles

Computer-controlled vibrations of a biological subject in the nm range.

Computer-controlled vibrations of a biological subject in the nm range.

Early Fetal Growth and Development

Ed R H T Ward, S K Smith, D Donnai RCOG Press, £35, pp 456 ISBN 0-902331-64-7 It is surprising in this day and age to come across a biological subject which is so poorly understood and so comparatively little researched that it hardly impinges on our consciousness. Furthermore, it is equally refreshing to discover that it is one in which genetic mechanisms are not all powerful. Indeed, the underlying theme of Early Fetal Growth and Development is that it is environmental factors which have a …

Dynamic behavior classification of a model for a continuous bio-reactor subject to product inhibition

The dynamic behavior of the continuous biological reactor subject to product inhibition is analysed and classified in terms of multiplicity and stability of steady states and existence and stability character of limit cycles. Various boundary conditions are derived which delineate the parameter space into regions of dynamically different behavior. The predicted types of behavior are then illustrated by numerical computation of cells and product concentration trajectories.

O discurso da medicina mudou?

On occasion of a Historic Medico-Surgical Exhibition. The A. analyses the evolution of medical discourse: in the early phases considering the patient as an object of charity (humanistic concept); later as a biological subject (scientific concept) and, finally, in our days, as an object of analysis (technological concept forgetting the human being and his personality). The big scientific-technological advance in individual medicine contrasts, nevertheless, with its incapacity to solve the major social problems of our time (AIDS, drugs) and to maintain a reliable organization in regional wars (Yugoslavia, Africa). Keeping this background in mind, the A. comments on the evolution of Portuguese medicine and some of it traits.

Some conceptual problems in multivariable analyses of perinatal mortality

Summary Biostatisticians, epidemiologists and other researchers in maternal and child health have often used multivariable analysis to investigate associations with perinatal and infant mortality. A review of reports of such multivariable analyses published over the last 35 years revealed four problems that occur repeatedly. (1) Variables that are intermediate in the causal pathway between some study variables and perinatal death (‘intervening variables’) are controlled as though they were confounders. (2) When birthweight is analysed as an intervening variable, it is entered into the analysis in a few large categories, such as above and below 2500 g. This is not an adequate way of controlling for birthweight. (3) Social and demographic variables often interact statistically with birthweight in their effects on perinatal mortality, but these interactions have not been analysed in most multivariable studies. (4) Highly intercorrelated variables that represent similar theoretical constructs are entered simultaneously into one regression analysis. Solutions to these problems are suggested. Analytical approaches in which investigators use knowledge of biological and medical subject matter to make judgements about confounding and causal inference are encouraged.

Some conceptual problems in multivariable analyses of perinatal mortality

Biostatisticians, epidemiologists and other researchers in maternal and child health have often used multivariable analysis to investigate associations with perinatal and infant mortality. A review of reports of such multivariable analyses published over the last 35 years revealed four problems that occur repeatedly. (1) Variables that are intermediate in the causal pathway between some study variables and perinatal death ('intervening variables') are controlled as though they were confounders. (2) When birthweight is analysed as an intervening variable, it is entered into the analysis in a few large categories, such as above and below 2500 g. This is not an adequate way of controlling for birthweight. (3) Social and demographic variables often interact statistically with birthweight in their effects on perinatal mortality, but these interactions have not been analysed in most multivariable studies. (4) Highly intercorrelated variables that represent similar theoretical constructs are entered simultaneously into one regression analysis. Solutions to these problems are suggested. Analytical approaches in which investigators use knowledge of biological and medical subject matter to make judgements about confounding and causal inference are encouraged.

A topological model of cell division: Structure of the computer program

The general structure of a computer program (CD3D) simulating division in a sheet of cells is presented. The program is based on a topological representation of cell division previously developed by the authors, and the biological background to the model is discussed. The computer modelling of the various elements of the model (i.e. vertices, edges and meshes) is described, and an annotated description of the subroutines making up the program is given in an Appendix. Although the program and model are specifically designed to represent cell division processes, the graph framework may have applicability in other biological subject areas where dynamic relationships between elements are involved.

Structures and characteristics of a neural network model for generating circadian rhythm

AbstractThe biological subject contains a circadian rhythm, which is considered as an autonomous phenomenon originating from its internal structure. the rhythm is known as a biological activity observed in any creature except for prochordata. In most animals, it is found that the circadian rhythm originates from the nervous system. We have discussed the neural network model based on the functions of the neural system, which generate the circadian rhythm. the aim of this paper is to clarify the network structure of the model and to discuss in detail the characteristics through analysis and simulation. It is shown first that the model is composed of two neural oscillators and a neural network with nonlinear transformation characteristics. Then each of the subnetworks is analyzed, describing their basic behaviors. By computer simulation, the entrainment and the change of period are discussed, comparing the result with that of analysis. Those results are compared further with the actual properties of the circadian rhythms of creatures.

A microwave interferometer system for the displacement measurements of biological subject

AbstractThe microwave displacement meter based on the principle of phase interferometer has a high sensitivity in detection. However, in the conventional system the measurable displacement width is limited to the order of one half‐wavelength of the microwave, and quantitative information cannot be obtained without calibration. In the system proposed in this paper, a twophase microwave Doppler sensor (10.525 GHz) is used for detecting the reflected signal from the object as a vector, and the displacement is measured directly from the phase. While the high sensitivity of the phase interferometric method is maintained, the measurable width is improved significantly and quantitative measurement is possible. However, in the present method, the offset caused by the existence of unwanted reflectors other than the object can be a problem. Since this is dependent on the measurement environment, the problem is especially severe for biological measurement. In this paper, this offset is calculated by estimation and is shown to be removable. Next, a recurrence formula is derived that is used for calculating the displacement from the phase of the signal vector. the prototype system can measure the displacement width of 36 cm with the resolution of 90 μm. As an example of biological measurement, two‐dimensional body movement measurement in the balancing function test is presented. Finally, the accuracy and resolution of the present method are studied.

Lens applicator for localized microwave hyperthermia

AbstractHyperthermia is now recognized as an effective means for cancer therapy, and many reports on the irradiation of biological subjects by electromagnetic waves to produce dielectric heating and hyperthermia have been reported. Although it is desirable in hyperthermia selectively to heat the cancer tissue, it is difficult to estimate the heat distribution in the subject owing to insufficient analysis of the electromagnetic field distribution in the irradiated subject. At present it is not yet possible to control the temperature distribution in the biological subject. In electromagnetic wave hyperthermia, microwaves are effective from the viewpoint of efficiency or selective heating. On the other hand, it is difficult to heat a cancer in deep tissue because of reduced penetration of the microwaves into the subject. This paper shows experimentally and by theoretical analysis, using a microwave lens geometrically designed to produce a focused cylindrical wave as the applicator, that selective heating is possible for tissue 10 to 40 percent deeper than with planar wave. It is shown that the microwave lens applicator is effective for the heating of biological tissues.

The Anthropological Concept of Race

The concept of has been a continuingly confused and controversial term despite its importance as social science and biological subject matter. Although the idea of may have existed in earliest writing, the word race first appeared in European languages during the sixteenth century. In the seventeenth century, the French phrase especes-ou-races d'homme was used to refer to family or breed. Around 1700, the German word Rasse, meaning something like generation, was introduced into the language by Leibnitz.I The word was not employed in its contemporary meaning, however, until Kant (1775) used the phrase races of to designate peoples who could be distinguished from others according to their physical attributes (Rose, 1968). The first anthropologists to actually classify mankind according to his physical attributes used words other than race to describe the same phenomena (e.g., stocks, varieties). Using facial and body forms as criteria, Francois Bernier, a seventeenth-century naturalist, grouped man into four stocks (1684). Later, Carol Von Linneaus, in his classic work, Systematic Naturae (1735), grouped man into four varieties: White, Red, Yellow, and Black. For purposes of classification, Linneaus used skin color and physiognomy as criteria and then correlated these traits with temperament or personality types.

Use of linear free energy related and other parameters in the study of fungicidal selectivity

AbstractThe modulation of fungicidal activity in a congeneric series of compounds is dependent on several processes taking place in the biological object which may be influenced by the different hydrophobic, electronic and steric properties of the members of the series. These possible influences can be studied in a quantitative way with multiple regression analysis using substituent constants for the properties mentioned. The comparative study of the resulting regression equations for the activity on different fungi or on a fungus and another biological subject may contribute to an understanding of fungicidal selectivity. This is illustrated in studies on the fungitoxicity of isophthalonitriles, 2‐chlorobenzonitriles, arylsulphonyl‐ and arylsulphinyl‐alkylthio‐cyanates, acetylenic sulphones, methyl benzimidazol‐2‐ylcarbamates and phosphorus compounds derived from 3‐amino‐1,2,4‐triazole. In these studies new steric parameters were used, which have been introduced recently.

New approaches to restructuring school biology

Two structuring principles are discussed which both drop the old ‘systematic’ (taxonomic as well as subdiscipline-bound) way of structuring biological subject matter. They lead to a biology curriculum with great social and inter-disciplinary impact.

Soviet Cellular Biophysics 1950-1960

The Soviet biophysical literature has been the subject of an extensive and critical review. The subject matter has been subdivided into sections on techniques, effect sof ionizing radiation, effects of light radiation, photosynthesis, effects of ultrasonics, paramagnetic resonance, microorganisms, viruses, cell structure, proteins, nucleic acids, and muscle, nerve, vision and taste. A bibliography of 520 entries is included. The work which has been reviewed covers the best and worst in Soviet science. In general those experiments and concepts in fields that are close to physics are excellent. Examples are the work in paramagnetic resonance, energy transfer mechanism in photosynthesis systems, the properties of structural proteins such as procollagen, and the coding properties of DNA. The average paper concerned with more biological subject matter, such as microorganisms, viruses, and proteins, seems outdated in concept and lacking in controlled experiments or adequate data. Recent reviews (which contain mostly references to Western literature) indicate that Soviet scientists are well acquainted with in Western countries and that the role of DNA as a carrier of genetic information is now fully appreciated.

Diploma in Animal Genetics at Edinburgh

THE University of Edinburgh has recently instituted a diploma in animal genetics. The course lasts one year, during which students spend about half their time attending lectures and practical work, and during the remainder undertake directed research or attend other suitable courses in the University. Candidates should be honours graduates in a biological subject or in mathematics, or must otherwise satisfy the University of their fitness to enter the diploma course. It is expected that, during the coming year, Prof. Sewall Wright of Chicago will be in Edinburgh as a Fulbright visiting professor and will take part in the course.

The Neglect of Biological Subjects in Education

THE resolution of the Headmasters' Conference and Headmasters' Association, referred to in NATURE of January 9 (p. 379), that school instruction in natural science should include biology as well as chemistry and physics, reminds me of an impression which has been with me for some time that a similar reform is needed in our higher education. Arising, I suppose, from the curious notion that chemistry and physics are more exact and educative and of more general moment in the lives of animals than are botany and zoology, it is laid down at Oxford, for example, that a student who proposes to take a biological subject for his final school must pass an elementary examination in chemistry and physics, while if he specialises in chemistry or physics he is exempt from any preliminary course in biology. Something similar is, I believe, a pretty general regulation in all the universities in this country—and if not a regulation, at any rate a habit. The result is that a number of chemists are produced who are fearfully ignorant of the simplest truths of biology; they do not even know what biology is about or the general methods whereby a biologist will seek to solve his problems.