On imitative behavior

It is shown that the linear equations of the formal theory of mass behavior proposed by the author in 1939 are first-order approximations of the biophysical theory proposed later. The second approximation contains cubic terms. It permits the expression of the time course of the change of behavior in terms of a quadrature.     

Contribution to the mathematical biophysics of automobile driving

Traffic in one direction on a multilane highway is considered, and a general expression for the number of cars which pass a car travelling at a given velocity, as well as the number of cars which the given car passes, is derived for the case when the speeds of different cars are distributed in some arbitrary manner. Closed expressions are derived and discussed for a rectangular distribution. Each passing by another car or of another car is considered as a distracting stimulus which affects the reaction times of the driver. Using previously derived expressions for the safe speed as a function of reaction times, expressions for the safe average speed are derived, in terms of the volume of traffic and of the spread of the distribution of speeds.     

A note on the cybernetics of segregation

The results of a preceding paper (Progress in Biocybernetics,2, Elsevier, 1965) are generalized to express the intensity of anti-Negro feelings, and of the segregation index as functions of the percentage of Negroes in the population. Previous results are applied to effects of migration of Negroes from regions of strong racial prejudice to regions of lesser racial prejudice.     

Production of mosquito larvicidal Bacillus thuringiensis serotype H-14 on raw material media from Nigeria

Bacillus thuringiensis serotype H-14 de Barjac, a potent larvicide of many mosquito and blackfly species, was grown on various media compounded from fermented cassava ( Mannihot esculenta ), ground and whole maize ( Zea mays ) grains and whole cowpeas ( Vigna unguiculata ) in shake flask fermentations. The liquors obtained from 100g/l of the whole cowpea and maize grains as well as combinations of these were used for further fermentations in 1 and 5 1 fermenters. The final whole cultures obtained were bioassayed against L11/111 of Aedes aegypti and the concentration-effects estimated. The potency of the preparations (estimated as LC₅₀, strength that showed 50% mortality of the mosquito larvae) ranged from 10.5 mg/l for the 1:3 combination of cowpea steep liquor:maize steep liquor to 90 mg/l for the 2:1 combination at 95% confidence limits. The LC₅₀ of a standard nutrient broth-yeast extract medium was 18 mg/l. The juice of Citrus aurantifolia and an extract from Elaeis guiniensis were used as acid and alkali respectively while bleached deodorized palm olein was used as antifoam.     

Streaming potential of intact wet bone

The conversion of mechanical loads to bioelectrical signals in bone have been suggested to control repair and remodeling. These signals in wet bone are attributed to the electrokinetic behavior where mechanical forces cause electrical signals due to motion of an ion carrying extracellular fluid in the bone matrix (streaming potentials). Streaming potential experiments were performed on control and chemically treated intact wet bone plugs in aphosphate and phosphate buffers to examine the contribution of bone constituents to the electrokinetic behavior of bone tissue. Data indicate that the organic constituents of bone dominate streaming potentials. Slopes of streaming potential vs pressure are related to the electrokinetic (zeta) potential. The slopes should be analyzed in the low pressure region where data is mainly linear. Comparisons of estimated zeta potentials from streaming potentials with existing data obtained by particle electrophoresis showed similar trends.     

Structural-functional organization of the par region of the ColN plasmid

In the 679 b.p. SalI-KpnI-fragment of the small colicinogenic plasmid Co1N, the par-region has been localized, functioning at the expense of resolution of plasmid DNA multimer forms. It has been shown that the replication process of the monomeric form of the recombinant plasmid containing the Co1N par-region do not result in formation of a considerable number of multimers. Gene xer A product is necessary for the functioning of the multimer resolution mechanism of Co1N as well as Co1E1. Nucleotide sequence analysis of the Co1N par-region revealed the presence of essential homology with the par-locus of plasmid Co1E1. Results obtained in this work and data from literature indicate that par-regions of the Co1E1-type plasmids possess considerable homology, function according to a similar mechanism and represent the universal stability module of multicopy colicinogenic plasmids.     

Hydrodynamic and optical behavior of DNA molecule in the range of high ionic strength

The hydrodynamic and optical properties (intrinsic viscosity and optical anisotropy of DNA) have been studied at the high ionic strength mu greater than or equal to 1 M. It has been shown that the effective volume of DNA molecule doesn't depend of mu when mu greater than or equal to 1 M. In these conditions the electrostatical interactions in DNA disappear. But thermodynamic excluded volume effects do not depend on mu and play also an important role in this range of mu (mu greater than or equal to 1 M). It has been concluded that the condensation of DNA in solutions of high salt concentration is the result of local denaturation of DNA. It has been shown that the optical anisotropy of DNA increases drastically at mu congruent to 2 M but the persistence length of DNA does not change under these conditions.