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Biomedical subjects

V N Chikhman

Publications and source records attributed to V N Chikhman.

17 recordsLinked to original sources
PubMed2000

[Blocking of cold paralysis of physiological functions].

For more than 100-year history of studying hypothermia a rewarming of a cooled organism was always considered as the only method of restoring the cold-paralysed physiological functions and the vital activity of an overcooled organism of homoiothermal animals and humans. The paper gives the results of applying the method developed at our Laboratory, of restoring the cold-paralysed important physiological functions after a continuous cooling of rats, without rewarming the animals.

Animals↗
PubMed2000

[Innervation of the humerus metaepiphysis in newborn and one year old children].

Analysis of home and foreign literature on metaepiphyseal cartilage innervation and blood supply was presented, data on these organ diseases substantiate theoretical and clinical significance of the study was performed. Using macro-microscopic preparation, histological study, automatic image analyzer branches of humerus proximal metaepiphysis were shown to originate from axillary and subscapulary nerves. Nerves and vessels penetrating in the cartilaginous canals form neurovascular complexes. Cartilaginous canals are located unevenly. Nervous structures were found in the canals and their characteristics was given.

Growth Plate↗
PubMed1999

[The structure of the white pulp of the spleen and the peripheral blood indices in rats under increased muscle activity].

The white pulp structure was studied in rat spleen white pulp in conditions of increased muscle activity as well as certain parameters of peripheral blood. 36 male outbred albino rats were involved. Experimental rats were subjected to the increased physical load (everyday swimming seances lasting from 10 to 40 hrs during 4 weeks). The number of erythrocytes, leukocytes and level of hemoglobin were determined in peripheral blood. Perimeter squares and density of lymphoid nodules (LN) and marginal zone (MZ) as well as LN minimal and maximal diameter and MZ minimal and maximal width were determined in histological sections prepared at the level of the organ portae using TV-computer set. Besides, marginal sinuses width were measured in nine sites in every LN as well as the capsule thickness in three sites and at the level of portae. The data obtained indicate that increased muscle activity causes reorganization of red and white pulp in the direction of growth of the red pulp square which is associated with the increase of erythropoietic function. The appearance of lymphoid nodules with germination centres indicates lymphocytopoietic function intensification while the significant increase of marginal zone morphometric parameters witnesses its participant in primary immune response. High correlation between certain blood indexes and the parameters of lymphoid nodules and marginal zones supports these data.

Adaptation, Physiological↗
PubMed1998

[The model of adaptive primary image processing].

A computer model of adaptive segmentation of the 2D visual objects was developed. Primary image descriptions are realised via spatial frequency filters and feature detectors performing as self-organised mechanisms. Simulation of the control processes related to attention, lateral, frequency-selective and cross-orientation inhibition, determines the adaptive image processing.

Models, Neurological↗
PubMed1981

[Principles of temporal processing of spectral information during vowel perception].

Pairs of "one-formant pulses" with 10 ms onset-to-onset interval and highly different F values for the first and the second pulse (LH and HL pairs) were used in vowel identification experiment. Response distributions corresponding to these stimuli and to "stationary" two-formant and one-formant pulse pairs were compared to calculate the phonetic distance between stimuli. The results are in favour of low-pass filtering of excitation pattern with sampling at the stimulus offset.

Computers↗
PubMed1980

[Perception of voiceless plosive consonants in syllables of the "vowel--consonant" type].

Bursts were the determining cue for perception of stops in VC syllables in Russian material under conditions of partial exclusion of information and in conflict combinations; the transitional part of vowels also contained certain information. If the information was reduced, /p/--answers predominated, but in conflict combination /p/ was suppressed by competing cues. The distribution of answers for a conflict combination cannot be described as a sum of distributions of answers for its parts.

Computers↗
PubMedDate not supplied

A model of adaptive visual processes of primary image processing.

A computer model of adaptive segmentation of two-dimensional visual objects was developed, based on neurophysiological and psychophysiological principles. The model imitates several stages of visual information processing. At the first stage, a preliminary assessment of the image is performed using a brightness pattern analyzer. At the second stage, control parameters are formed on the bases of the initial assessment. A defined control vector is synthesized for each type of starting image, which allows adaptive processing; this initiates two parallel mechanisms of primary image description: one contains the outlines of images and the sharp boundaries between their fragments, and the second contains areas of uniform intensity. The control parameter vector is applied to these two descriptions to analyze their brightnesses and spatial characteristics, and this is used as the basis for forming the regime for subsequent processing, which includes a set of processing operators whose parameters are tuned for each fragment of the image. The primary phasic and tonic descriptions are then used to extract individual fragments of the image (i.e., discrimination of figures from the background) and to form the final presentation. The resulting descriptions complement each other, creating a basis for quantitative measurements of image characteristics and allowing various signs needed for image classification to be formed. The computer program for adaptive image segmentation was tested using a large number of different two-dimensional half-tone objects, the purposes of these exercises including segmentation and measurement of objects in morphometric and cytometric studies.

Adaptation, Physiological↗
PubMedDate not supplied

Effect of electrode dimensions on motor unit potentials.

Different effects of longitudinal and transversal electrode dimensions on nerve or muscle single fibre action potentials detected monopolarly, were reported in the literature. The results were contradictory. We studied motor unit potentials (MUPs) detected at a large distance (typical of surface recording) on the basis of a mathematical model without source simplification. The MUPs were calculated as a single convolution of the first temporal derivative of a realistic intracellular action potential and MU impulse response. The spatial averaging of the MUPs by rectangular plate electrodes was performed through analytical integration of the MU impulse response over the electrode area. The effects of longitudinal dimension of the electrode were stronger than those of a transversal one. The effects were distance dependent. The longitudinal dimension of the electrode influenced the main phases (that reflected the excitation origin and propagation) more than the terminal phases (that reflected the excitation extinction at the muscle fibers' ends). This was due to differences in the character of the potential fields (quadrupole or dipole) during generation of individual MUP phases. It was shown that the relative weight of the individual MUP phases could be stressed or suppressed by a proper choice of electrode dimensions, position and orientation.

Action Potentials↗