Description of spatial patterns of radionuclide deposition by lognormal distribution and hot spots.

Spatial distributions of activity density (kBq/m(2)) and activity concentration (Bq/kg) are studied on sites with non-cultivated soils. Fitting datasets with lognormal, Weibull and normal distributions with sampling size n ≥ 60 showed that radionuclide deposition ((90)Sr, (137)Cs, (238)Pu, (239+240)Pu, (241)Am) due to Chernobyl fallout no more than in 10% of cases are described by Weibull distribution, and in the rest of the cases--by lognormal distribution. However asymptotics of "righthand tail" of empirical (sample) distribution quite often differs from the right-hand tail asymptotics of lognormal distribution.

[Radioanatomy of cerebral perfusion in single-photon emission-computed tomography using 99mTc-labelled amines].

A study was made of the cerebral hemodynamics by assessing the distribution in single-photon emission computerized tomography with 99mTc-hexamethyl-propyleneminoxyne in health using a Testascan in 9 standard slices. The whole set of tomographic slices was conventionally divided into 3 levels. For better orientation in gamma-tomographic images, pictures were presented where in addition to scintigrams a morphological scheme of the cerebral parts with the marked parts perfused by cerebral arteries, was given.

[Interdependence of mycelial dehydrogenase activity in Streptomyces aureofaciens and its capacity for tetracycline biosynthesis].

The maximum dehydrogenase (oxidation-reduction) activity of the vegetative inoculum of S. aureofaciens is the criterion of its availability for transfer to the fermentation medium. The activity is determined by the rate of the methylen blue reduction and the growth characteristics of the seed culture.

[Possibility of the spectral analysis of heterogeneous biological systems. The determination of the mycelium concentration of Actinomyces aureofaciens, a producer of tetracycline, cultured on a medium with corn meal].

A possibility of using spectroscopy of attenuated total reflection in the IR region for analysis of the heterogenic system consisting of the microorganisms and plant cells is discussed. The method of spectroscopy is proposed for estimating the mycelium concentration of Act. aureofaciens producing tetracycline in the presence of corn meal in the medium.

[Morphofunctional study of the development of Actinomyces aureofaciens under conditions of regulated and unregulated fermentation].

Actinomyces aureofaciens producing tetracycline and its inactive proactinomyces-like variant were studied by electron microscopy during their growth under conditions of regulated and non-regulated fermentation. The ultrastructure of the active variant changed: the cell wall and ribosomes underwent modification, amorphous electron-transparent structures appeared, and tubular membrane structures were formed. No changes were found in the inactive variant.

[Macrokinetic equations of pH effect on the growth of Actinomyces aureofaciens and biosynthesis of tetracycline].

The effect of pH on the culture respiration rate at different concentrations of glucose in the medium was studied. It was found that the hydrogen ions showed their effect irrespective of the subsrate concentration in the medium. In this connection a type of macrokinetic equations of the effect of pH on the growth and antibiotic biosynthesis was chosen.

[Effect of dissolved carbon dioxide on tetracycline biosynthesis].

The paper presents data on the effect of CO2 dissolved in the fermentation broth on biosynthesis of tetracycline. It was shown that there was optimal concentration of CO2 for the tetracyline-producing organism. As a result of the experiments the ranges of the optimal concentrations within 2 to 8 ml of CO2 per 100 ml of the fermentation broth were determined.

[Mathematical model of the effect of inorganic phosphorus on the tetracycline biosynthesis process].

A special apparatus with continuous dosing of substrates to flasks was used for experiments on the effect of inorganic phosphorus concentrations on the growth process of Act. aureofaciens and tetracycline biosynthesis. The experimental data showed that the character of the orthophosphorus effect on the mycellium growth and antibiotic biosynthesis was different.

[Regulation of tetracycline biosynthesis by controlling the growth of the producer].

Regulation of the rate growth of Act. aureofaciens in batch fermentation by maintaining the concentrations of phosphorus, ammonium nitrogen, glucose and pH values at the levels favourable for intensive growth at the beginning of the process and after accumulation of the biomass at the levels optimal for retarded growth of the organism resulted in significant prolongation of the period of intensive antibiotic production, i.e.

[Effect of orthophosphate on the growth rate and biosynthesis of tetracycline by an Actinomyces aureofaciens culture].

A low initial rate of the culture growth is an obligatory condition for intensive biosynthesis of tetracycline by Act. aureofaciens in batch fermentations. The mineral phosphorus concentration is a factor limiting the growth rate.