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Biomedical subjects

V G Nazarenko

Publications and source records attributed to V G Nazarenko.

At least 19 recordsLinked to original sources
PubMed2004

Ordered droplet structures at the liquid crystal surface and elastic-capillary colloidal interactions.

We demonstrate a variety of ordered patterns, including hexagonal structures and chains, formed by colloidal particles (droplets) at the free surface of a nematic liquid crystal (LC). The surface placement introduces a new type of particle interaction as compared to particles entirely in the LC bulk. Namely, director deformations caused by the particles lead to distortions of the interface and thus to capillary attraction. The elastic-capillary coupling is strong enough to remain relevant even at the micron-scale when its buoyancy-capillary counterpart becomes irrelevant.

Adsorption↗
PubMed2001

Crystal structure in nematic emulsion.

We describe the experimental observation of a crystal structure formed by glycerol droplets suspended in a nematic liquid crystal. The structure exhibits a high density hexagonal ordering. We have experimentally observed a noticeable interaction between droplets with tangential boundary conditions. Within the scope of known models we discuss the nature of appropriate mechanisms of the interaction.

Journal Article↗
PubMed2001

Deformation of liquid crystal droplets under the action of an external ac electric field.

Deformation of liquid crystal droplets suspended in liquid polymer matrix under the action of external electric field was observed in dependence of ion concentration in such system. Experimental dependence of droplet elongation vs electric field demonstrates nonmonotonous character with increase of ion concentration. The theory that provides the basic agreement with experimental observation is developed.

Journal Article↗
PubMed1999

Non-Debye screening of a surface charge and a bulk-ion-controlled anchoring transition in a nematic liquid crystal.

We study the anchoring mechanism due to substrate-adsorbed ions by examining a related anchoring transition. An analytical solution to the Poisson equation shows that, as their number suffices for a non-negligible anchoring contribution, the surface field is screened over some characteristic microscopic distance. It is shown both theoretically and experimentally that the critical temperature of the transition can be controlled by bulk ion density through its relation to the density of adsorbed ions.

Journal Article↗
PubMed1996

Quantal Ca2+ release and inactivation in a model of the inositol 1,4,5-trisphosphate receptor involving transformation of the ligand by the receptor.

A model explaining quantal Ca2+ release as an intrinsic property of the inositol 1,4,5-triphosphate (IP3) receptor has been put forward. The model is based on the hypothesis that the IP3 receptor can catalyze a transformation of the IP3 molecule differing from its conventional metabolism. A simple kinetic mechanism is considered, in which IP3-induced Ca2+ channel opening is followed by the step of IP3 conversion and channel closure. Examination of the resulting mathematical model shows that it can reproduce well both partial release of stored Ca2+ and the same responsiveness to subsequent IP3 additions. On incorporation of an additional closed state of the channel, the model describes also a time-dependent channel inactivation at a high IP3 dose. Temperature sensitivity of the catalytic step accounts for the reported elimination of quantal responses and inactivation at low temperature. The transformation product is surmised to be a positional or stereo isomer of IP3.

Calcium↗
PubMed1993

[Immunogenetic similarity and the distance between Swiss brown cattle and 86 other bovine populations].

By using the frequencies of 43-46 antigens of 9-11 genetic blood group systems in 108145 animals the immunogenetic similarity (r +/- m(r)) and the distance (d) between a Swiss brown cattle and other 86 representatives of the Bovinae subfamily were calculated. The position of Swiss brown cattle on a linear model of the Bovinae family was determined. The position has following indexes: r = 0.7816 +/- 0.0197; d = 0.2181. Phylogenesis of 16 cattle breeds reared with participation of the Swiss brown breed was studied. On the dendrogram these breeds formed two clusters and three branches. The clusters at the bottom of the dendrogram (Swiss brown x brown carpathian) and in the middle (ala-tau x caucasian brown) included breeds reared in the foothills and highlands, and the top of the dendrogram is formed by the lebedin, kostroma breeds and the Tajik type of Swiss brown zebu cattle reared in the flat country.

Animals↗
PubMed1992

[A clinico-diagnostic evaluation of the sequelae of craniocerebral trauma by using computed tomography].

The authors analyzed sequelae of head injuries in persons of call-up age (16-23 years) using computer tomography. Neurological, psychopathological, clinico-laboratory methods, electroencephalography, rheoencephalography, echoencephalography and lumbar puncture were also carried out. The obtained data indicate that these subjects who sustained head injuries showed pronounced polymorphous posttraumatic disorders in the nervous system. These data should be considered in the examination of call-up age persons.

Adolescent↗
PubMed1992

[Disordered blood supply of the brain in bradyarrhythmia patients].

Results are reported of a study of the blood flow in patients (age: 18-70) with different grades of bradyarrhythmia due to atrioventricular block with weakness of the sinus node. Examined were: CBF rheoencephalographically, ultrasound dopplerography, products of lipid peroxidation in the blood. Bradyarrhythmia was found to occupy a major place in the pathogenesis of cerebrovascular disorders. Adequate therapy allows to achieve good rehabilitation of this category of patients.

Adult↗
PubMed1990

[Psychomotor disorders in patients with autonomic dystonia].

The authors used an original device to examine the psychomotor function: rate of information processing, mean reaction time to light stimuli, number of errors in these events and changes of the functional state of the vegetative nervous system by fixation of electrical resistance of the skin before and after work. A study of 120 patients and 20 healthy subjects revealed a close relationship of psychomotor and vegetative functions, worsening of psychomotor reaction in hyperactivation of one of the links of the vegetative nervous system.

Adolescent↗
PubMed1990

[Autonomic dysfunction in diabetics].

The authors examined 120 patients with diabetes mellitus of the first and second types. Vegetative dysfunction was revealed in 84 patients (70%) that was manifested in disorders of the vegetative tone, vegetative reactivity. Different tests for assessment of the vegetative status and method of treatment of vegetative dysfunction are described.

Adolescent↗
PubMed1990

[The initial manifestations of cerebral circulatory failure in coal mine workers of the Don Basin].

The authors examined 354 workers of Donbass coal mines with initial manifestations of cerebral circulation insufficiency. It was established that the onset of the disease is in workers over 30 years of age and gradually its frequency increases. Cerebrovascular pathology is more pronounced in miners working at evening and night hours, in particular, in case of unfavourable working conditions. An important place in the development of cerebrovascular pathology belongs to dysfunction of the vegetative nervous system. Prophylactic and therapeutic measures are outlined.

Adult↗
PubMed1984

Theoretical study of oscillatory and resonance phenomena in an open system with induction of enzyme by substrate.

A simple mathematical model of an open metabolic system is constructed in which the metabolism of a substrate is enhanced by induction of the catalyzing enzyme. It is demonstrated that the steady-state in such a system may be approached by damped oscillations of substrate and enzyme levels. If the input rate of substrate into the system has periodic fluctuations, the phenomenon of resonance is observed. Numerical analysis reveals the non-linear character of the resonance.

Enzyme Induction↗