Interaction of supramolecular aggregates and the enhanced optical torque on the director in a dye doped nematic liquid crystal.

There has been strong experimental evidence that molecules of some dyes in an anisotropic solvent, nematic liquid crystal, form aggregates. We present a detailed experimental analysis of the light-induced director reorientation (DR) in a dye-doped nematic liquid crystal (known as the Jánossy effect) and a theoretical model of its strong enhancement based on the aggregates' interaction. The DR transition is found to be very different from the Frederiks effect. If the light polarization is normal to the director, the transition is jump-like first order. Moreover, light polarization along the director also induces a DR which is a smooth second order transition with a very low threshold intensity. The theoretical model which explains these effects is based on the idea that dye molecules form rodlike supramolecular aggregates. The aggregates interact via the director distortions and their effective diameter gets certain field-dependence. As a result, the related entropy depletion depends on the light intensity and polarization and can be decreased by a certain DR along with the aggregate subsystem. This entropy gain is proportional to the square of light intensity which is a two-photon effect: the first resonance photon excites the dye molecule and the second photon polarizes the aggregate. This is in line with the experimental dependence of the critical intensity on the sample thickness. A special experiment shows that the effect is not connected with a possible heat-induced isotropic phase and hydrodynamic motion.

Effect of collective molecular reorientations on Brownian motion of colloids in nematic liquid crystal.

In the simplest realization of Brownian motion, a colloidal sphere moves randomly in an isotropic fluid; its mean squared displacement (MSD) grows linearly with time τ. Brownian motion in an orientationally ordered fluid--a nematic--is anisotropic, with the MSD being larger along the axis of molecular orientation, called the director. We found that at short time scales, the anisotropic diffusion in a nematic becomes anomalous, with the MSD growing slower or faster than τ; these states are respectively termed subdiffusion and superdiffusion. The anomalous diffusion occurs at time scales that correspond to the relaxation times of director deformations around the sphere. Once the nematic melts, the diffusion becomes normal and isotropic. Our experiment shows that the deformations and fluctuations of long-range orientational order profoundly influence diffusive regimes.

Elasticity of lyotropic chromonic liquid crystals probed by director reorientation in a magnetic field.

Using a magnetic Frederiks transition technique, we measure the temperature and concentration dependences of splay K1, twist K2, and bend K3 elastic constants for the lyotropic chromonic liquid crystal sunset yellow formed through noncovalent reversible aggregation of organic molecules in water. K1 and K3 are comparable to each other and are an order of magnitude higher than K2. At higher concentrations and lower temperatures, K1 and the ratios K1/K3 and K1/K2 increase, which is attributed to elongation of self-assembled lyotropic chromonic liquid crystal aggregates, a feature not found in conventional thermotropic and lyotropic liquid crystals formed by covalently bound units of a fixed length.

Square colloidal lattices and pair interaction in a binary system of quadrupolar nematic colloids.

Spherical colloidal particles with normal and tangential surface director alignment in a nematic liquid crystal induce elastic quadrupoles of opposite signs that attract one another along and perpendicular to the director. We utilize this unique angular profile of the mixed quadrupolar interaction to build 2D crystals with square lattices by laser tweezers.

Surface alignment and anchoring transitions in nematic lyotropic chromonic liquid crystal.

The surface alignment of lyotropic chromonic liquid crystals can not only be planar (tangential) but also homeotropic, with self-assembled aggregates perpendicular to the substrate, as demonstrated by mapping optical retardation and by three-dimensional imaging of the director field. With time, the homeotropic nematic undergoes a transition into a tangential state. The anchoring transition is discontinuous and can be described by a double-well anchoring potential with two minima corresponding to tangential and homeotropic orientation.

Coexistence of two colloidal crystals at the nematic-liquid-crystal-air interface.

Glycerol droplets at a nematic-liquid-crystal-air interface form two different lattices--hexagonal and dense quasihexagonal--which are separated by the energy barrier and can coexist. Director distortions around each droplet form an elastic dipole. The first order transition between the two lattices is driven by a reduction of the dipole-dipole repulsion through reorientation of these dipoles. The elastic-capillary attraction is essential for the both lattices. The effect has a many-body origin.

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.

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.

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.

[The characteristics of the bioelectrical excitation of the muscles of the lower extremities during the evocation of knee-jerk reflexes in patients with lumbar osteochondrosis]. / Osobennosti bioélektricheskogo vozbuzhdeniia myshts nizhnykh konechnostei pri vyzyvanii kolennykh refleksov u bol'nykh poiasnichnym osteokhondrozom.

While provoking a knee-jerk reflex in patients with lumber osteochondrosis one can observe irradiation of excitation going on to the muscles of both feet. Augmentation of kinetic response of a knee-jerk reflex on the side of pain in this patient population is deemed to be a major cause of relief of the reflex ability of spinal centres. The above-described way in which the bioelectric excitation of muscles of the lower extremities makes itself evident in eliciting knee-jerk reflexes indicates some change(s) in reflex excitation of spinal centres in patients with lumbar osteochondrosis, which fact suggests to us an involvement of these structures into the pathological process.

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.

[Dynamic interphase tensiometry of the cerebrospinal fluid and blood serum in nervous system tumors]. / Dinamicheskaia mezhfaznaia tenziometriia spinnomozgovoi zhidkosti i syvorotki krovi pri opukholiakh nervnoi sistemy.

Dynamic superficial tension (ST) of spinal fluid (SF) and blood serum in patients with CNS tumors was investigated. The maximum bubble tension was measured by a MPT2 computer tensiometer (LAUDA). There were decreases in ST of blood serum at t = 1 and t-->infinity, increases in ST at t = 0.01 and decreases in the angle on SF tensiograms. The parameters of interphasic tensiometry of the biological fluids depend on content of biologically active substances severity of the neurological symptomatology and duration of disease. Successive surgical treatment is followed by normalization of SF and blood serum ST.

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.

[Bettolepsy as a variant of transient ischemic attacks]. / Bettolepsiia kak variant tranzitornykh ishemicheskikh atak.

Bettolepsy (B) refers to episodes of fainting of abrupt onset in patients with nonspecific pulmonary diseases, occurring at the paroxysm of coughing. The authors conducted a comprehensive evaluation in 12 patients liable to B attacks, that incorporated study of the state of the vegetative nervous system, EEG, REG, ultrasonic dopplerography of major vessels of the brain, computerized tomography to the brain, echocardioscopy, roentgenography of the spinal column. The data obtained allow B episodes to be regarded as an acute disturbance in cerebral bloodflow in vascular beds of the vertebrobasilar system of transient ischemic attacks type, which fact leads to derangement in the ascending impacts of the reticular formation, and is a syncopal state.

[Immunogenetic similarity and the distance between Swiss brown cattle and 86 other bovine populations]. / Immunogeneticheskoe skhodstvo i distantsiia shvitskogo skota s 86 drugimi populiatsiiami bych'ikh.

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.

[The clinical picture, diagnosis and treatment of thoracalgias]. / Klinika, diagnostika i lechenie torakalgii.

The clinical picture of 260 patients with thoracalgia was characterized by chest pain, thoracic spine pain, subcostal and epigastric pain. In several patients treatment (traditional) failed. Different diseases of the digestive organs were found: chronic cholecystitis, biliary dyskinesia, gastric and duodenal ulcers which significantly contributed to the painful syndrome. Cooperation of the neurologist, gastroenterologist and surgeon favoured adequate rehabilitation of this category of patients.

[Disordered blood supply of the brain in bradyarrhythmia patients]. / Narushenie krovosnabzheniia mozga u bol'nykh s bradiaritmiiami.

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.

[A clinico-diagnostic evaluation of the sequelae of craniocerebral trauma by using computed tomography]. / Kliniko-diagnosticheskaia otsenka posledstvii cherepno-mozgovoi travmy s primeneniem metoda komp'iuternoi tomografii.

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.

[Psychomotor disorders in patients with autonomic dystonia]. / Psikhomotornye narusheniia u bol'nykh vegetativnoi distoniei.

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.