Biomedical subjects

V I Ponomarenko

Publications and source records attributed to V I Ponomarenko.

18 recordsLinked to original sources

PubMed2005

Estimation of coupling between time-delay systems from time series.

We propose a method for estimation of coupling between the systems governed by scalar time-delay differential equations of the Mackey-Glass type from the observed time series data. The method allows one to detect the presence of certain types of linear coupling between two time-delay systems, to define the type, strength, and direction of coupling, and to recover the model equations of coupled time-delay systems from chaotic time series corrupted by noise. We verify our method using both numerical and experimental data.

Journal Article↗

PubMed2003

Synchronization between main rhythmic processes in the human cardiovascular system.

For the cases of spontaneous respiration and paced respiration with a fixed frequency and linearly increasing frequency, we investigate synchronization between three main rhythmic processes governing the cardiovascular dynamics in humans, namely, the main heart rhythm, respiration, and the process whose fundamental frequency is close to 0.1 Hz. The analysis of the experimental records reveals synchronous regimes of different orders n:m between all the three main rhythms. The influence of the regime of breathing and the magnitude of heart rate variability on the degree of synchronization is considered.

Adult↗

PubMed2002

Extracting information masked by the chaotic signal of a time-delay system.

We further develop the method proposed by Bezruchko et al. [Phys. Rev. E 64, 056216 (2001)] for the estimation of the parameters of time-delay systems from time series. Using this method we demonstrate a possibility of message extraction for a communication system with nonlinear mixing of information signal and chaotic signal of the time-delay system. The message extraction procedure is illustrated using both numerical and experimental data and different kinds of information signals.

Journal Article↗

PubMed2001

Reconstruction of time-delay systems from chaotic time series.

We propose a method that allows one to estimate the parameters of model scalar time-delay differential equations from time series. The method is based on a statistical analysis of time intervals between extrema in the time series. We verify our method by using it for the reconstruction of time-delay differential equations from their chaotic solutions and for modeling experimental systems with delay-induced dynamics from their chaotic time series.

Journal Article↗

PubMed2001

Mandelbrot set in coupled logistic maps and in an electronic experiment.

We suggest an approach to constructing physical systems with dynamical characteristics of the complex analytic iterative maps. The idea follows from a simple notion that the complex quadratic map by a variable change may be transformed into a set of two identical real one-dimensional quadratic maps with a particular coupling. Hence, dynamical behavior of similar nature may occur in coupled dissipative nonlinear systems, which relate to the Feigenbaum universality class. To substantiate the feasibility of this concept, we consider an electronic system, which exhibits dynamical phenomena intrinsic to complex analytic maps. Experimental results are presented, providing the Mandelbrot set in the parameter plane of this physical system.

Journal Article↗

PubMed1980

[Obtaining mutants that yield tobramycin in a culture of the producer of a complex of aminoglycoside antibiotics, Streptomyces cremeus var. tobramycini var. nov. 2242].

The organism producing an aminoglycoside antibiotic complex was subjected to selection with a purpose of obtaining a strain producing tobramycin. Spontaneous and gamma-radiation-induced variation of the strains obtained as a result of a step-wise selection of the tobramycin-producing organism was studied. Correlation between the antibiotic activity levels and morphological features of these strains was shown. 8 physiological groups of mutants were differentiated and characterized as dependent on the ratio of the components in the aminoglycoside antibiotic complex produced by them. A highly productive strain 3406 was selected. The level of tobramycin synthesis by this strain is 10 times higher than that of the initial culture.

Aminoglycosides↗

PubMed1978

[Selection of active strains of Actinomadura carminata, the producer of carminomycin].

The method of selecting active strains among a definite group of analogue-resistant mutants was used on the basis of studying the dependence of the carminomycin-producing organism growth and the antibiotic synthesis level on some metabolites. As a result, gamma-ray induced mutants 4 times more active than the parent strains were obtained.

Antibiotics, Antineoplastic↗

PubMed1977

[Relationship between the quality of the inoculum material and carminomycin biosynthesis by a culture of Actinomadura carminata].

The effect of the inoculum mycelium quality on carminomycin biosynthesis by Actinomadura carminata was studied. The time of the organism growth on the culture medium containing cornsteep liquor continued for 6 hours without losing by the inoculum of its seeding qualities during that period. The mycelium growth in the inoculum was more intensive under conditions of moderate aeration, i.e. 0.98-2.64 mg O2H1-min. Anincrease in the aeration rate up to 18.56 mg O2/1-min resulted in the growth suppression up to 40 per cent. No correlation between the aeration rate during the inoculum growth and the culture capacity for carminomycin biosynthesis and of the content of the complex in active components the fermentation medium were observed, when a 5-10 per cent of inoculum was used.

Actinomycetales↗

PubMed1977

[Physico-chemical characteristics of the new antitumor antibiotic virenomycin].

Virenomycin, a new crystalline antitumor antibiotic was isolated from the mycelium of Streptomyces virens. The antibiotic contained: C 64.87 per cent, H 5.66 per cent, methoxylic groups 9.5 per cent. The melting temperature was 255-260 degrees (dec.), [alpha]20D=-17 (c 0.142, chloroform). Virenomycin had a complex UV spectrum with lambdamax. 245 (677), 265 (453), 275 (542), 287 (507), 395 (222) nm. A chromofor fragment and carbohydrate (C7H14O5) were found in the methanolysis products. Virenomycin was close to antibiotic c B-21085 BY THe physico-chemical properties and differed from it in the character of the UV spectrum and the values of the specific absorption, as well as by the optic rotation in dimethyl sulphoxide and acetic acid.

Antibiotics, Antineoplastic↗

PubMed1977

[Effect of the pH of the medium on the growth of a carminomycin producer and on the biosynthesis of the carminomycin complex].

The effect of the nutrient medium acidity on the growth of the carminomycin-producing organism and formation of the carminomycin complex with its aid was studied. Satisfactory development of the organism was observed when pH of the nutrient medium on the culture inoculation was 4.9 to 8.5. A shift in the alkaline and acid values of pH to 6.3--6.4 was registered during the first 24 hours of the culture growth. The biosynthesis of carminomycin depended on the culture growth time and pH value of the nutrient medium and culture fluid during the fermentation process. Maximum production of the carminomycin complex and its active components was observed on the 7th--8th day of the culture growth. The medium reaction close to the neutral one was optimal for biosynthesis of the carminomycin complex and its active components. Under acid, as well as alkaline conditions the antibiotic production was markedly lower.

Actinomycetales↗

PubMed1976

[Effect of aeration conditions on the biosynthesis of carminomycin by an actinomadura carminata culture].

The effect of the aeration rate on biosynthesis of carminomycin by Actinomadura carminata and biochemical changes in the fermentation broth on the use of 3 complex media of different composition was studied. The carminomycin-producing organism can grow and produce the antibiotic within the ranges of the aeration changes from 0.98 to 18.56 mgO2/1-min. A decrease in the maximum rate of oxygen dissolution up to 0.98 mgO2/1-min resulted in some decrease in the activity level. Intensive aeration, i.e. 18.56 mgO2/1-min induced suppression of the antibiotic production by 25 per cent.

Aerobiosis↗

PubMed1975