Study of the Ion Composition of the Diffuse Vacuum Arc on a Hot Cathode by the Time-of-Flight Method

Plasma Physics Reports - The study of a diffuse vacuum arc (DVA) is of interest in connection with the developing methods of plasma processing of the spent nuclear fuel (SNF). This type of...     

On the Feasibility of Plasma Separation of Spent Nuclear Fuel Components in a Nonuniform Magnetic Field

Plasma Physics Reports - A new concept of plasma separation of spent nuclear fuel components in a variable-cross-section chamber with a nonuniform magnetic field is proposed. Numerical simulation...     

Stable Levitation of Superconducting Myxines of Galathea Plasma Traps

Plasma Physics Reports - Designing magnetic systems of Galathea plasma traps on the basis of levitating superconducting magnetic coils requires searching for their stable levitating states. For...     

A model of direction selectivity in the starburst amacrine cell network

Displaced starburst amacrine cells (SACs) are retinal interneurons that exhibit GABA _A receptor-mediated and Cl ^? cotransporter-mediated, directionally selective (DS) light responses in the rabbit retina. They depolarize to stimuli that move centrifugally through the receptive field surround and hyperpolarize to stimuli that move centripetally through the surround (Gavrikov et al, PNAS 100(26):16047–16052, 2003, PNAS 103(49):18793–18798, 2006). They also play a key role in the activity of DS ganglion cells (DS GC; Amthor et al, Vis Neurosci 19:495–509 2002; Euler et al, Nature 418:845–852, 2002; Fried et al, Nature 420:411– 414, 2002; Gavrikov et al, PNAS 100(26):16047–16052, 2003, PNAS 103(49):18793–18798, 2006; Lee and Zhou, Neuron 51:787–799 2006; Yoshida et al, Neuron 30:771–780, 2001). In this paper we present a model of strong DS behavior of SACs which relies on the GABA-mediated communication within a tightly interconnected network of these cells and on the glutamate signal that the SACs receive from bipolar cells (a presynaptic cell that receives input from cones). We describe how a moving light stimulus can produce a large, sustained depolarization of the SAC dendritic tips that point in the direction that the stimulus moves (i.e., centrifugal motion), but produce a minimal depolarization of the dendritic tips that point in the opposite direction (i.e., centripetal motion). This DS behavior, which is quantified based on the relative size and duration of the depolarizations evoked by stimulus motion at dendritic tips pointing in opposite directions, is robust to changes of many different parameter values and consistent with experimental data. In addition, the DS behavior is strengthened under the assumptions that the Cl^? cotransporters Na^?+?-K^?+?-Cl^?? and K^?+?-Cl^?? are located in different regions of the SAC dendritic tree (Gavrikov et al, PNAS 103(49):18793–18798, 2006) and that GABA evokes a long-lasting response (Gavrikov et al, PNAS 100(26):16047–16052, 2003, PNAS 103(49):18793–18798, 2006; Lee and Zhou, Neuron 51:787–799, 2006). A possible mechanism is discussed based on the generation of waves of local glutamate and GABA secretion, and their postsynaptic interplay as the waves travel between cell compartments.     

The seasonal variability of Drosophila population according to the individual asymmetry

The natural Drosophila population is characterized by the presence of directional (DA) and fluctuating (FA) asymmetry of individuals. It was found that genotype has an effect on DA-level. FA evaluated in spring, summer and autumn periods had its maximum value in summer period. Genetically determined seasonal decrease in size of individuals was accompanied with increase in their FA. The structure of FA population variability is defined by genotypes of individuals. The phenotype and genotype structures of Drosophila population were investigated by FA of the individuals. There was regrouping of lineages number within of each frequency class in period from spring to autumn. Investigating central frequency class with least FA values in spring to summer period we observed the decrease in number of lineages for all traits with the exception of sternoupleral bristles (SB). At the same time the increase in number of lineages in the central and extreme frequency class with maximal FA values of sternoupleral bristles (SB). At the same time the increase in number of lineages in the central and extreme frequency class with maximal FA values of lines is observed. The number of lineages in the central frequency class of genotype structure is prevailing to all traits, without dependence on season. Individuals with rather high FA value acquire advantages in summer period whereas the individuals with low FA--in spring and autumn periods. Annual dynamics of FA is defined by this population parameters reorganization. The reasons of seasonal change of FA are discussed.     

Heat transfer in dust structures in an RF discharge plasma

Results are presented from experimental studies of heat transfer in liquid-like plasma-dust structures. The experiments were performed with aluminum oxide grains ～3–5 μm in size in an RF discharge plasma. The heat capacity of the dust grains in plasma is measured. The thermal conductivity and thermal diffusivity of liquid-like plasma-dust structures are deduced under the assumption that the observed temperature gradients and the propagation of a thermal perturbation in a dusty plasma are related to heat conduction within the dust component. The measured temperature dependences of the thermal conductivity and thermal diffusivity are in qualitative agreement with the results of numerical simulations performed in the model of a simple single-atom liquid. It is shown that quantitative discrepancy between the experimental and numerical results is related to the energy loss of dust grains in their collisions with the neutral particles of the ambient gas.     

Phenomenological model of carbon-sequestering forest management

The key aspects of a new “carbon-sequestering forest” management practice have been discussed. Carbon-sequestering forest management is a cross-disciplinary issue touching on both ecology and economics. A qualitative scheme has been proposed for the dynamics of economic and ecological components of this type of management.     

Trunk-Top Relations in a Siberian Pine Forest

In this paper we study relations between trunks and tops of pines in natural Siberian forests. By statistical methods we show that the tops tend to deviate in the direction away from the nearest neighbour tree or from a summary of the trees in a given neighbourhood. In an alternative approach we show that the tops deviate into the direction of the empty space near the trunk position defined by the corresponding Voronoi polygon.     

Treacle and TOPBP1 control replication stress response in the nucleolus

Replication stress is one of the main sources of genome instability. Although the replication stress response in eukaryotic cells has been extensively studied, almost nothing is known about the replication stress response in nucleoli. Here, we demonstrate that initial replication stress–response factors, such as RPA, TOPBP1, and ATR, are recruited inside the nucleolus in response to drug-induced replication stress. The role of TOPBP1 goes beyond the typical replication stress response; it interacts with the low-complexity nucleolar protein Treacle (also referred to as TCOF1) and forms large Treacle–TOPBP1 foci inside the nucleolus. In response to replication stress, Treacle and TOPBP1 facilitate ATR signaling at stalled replication forks, reinforce ATR-mediated checkpoint activation inside the nucleolus, and promote the recruitment of downstream replication stress response proteins inside the nucleolus without forming nucleolar caps. Characterization of the Treacle–TOPBP1 interaction mode leads us to propose that these factors can form a molecular platform for efficient stress response in the nucleolus.     

The variability characteristics of the arterial pressure in man and animals

The development of computer monitoring methods over haemodynamic parameters has made possible on objective quantitative estimation of blood pressure (BP) variability in humans and animals which can have both periodic and aperiodic feachers. The spectral analysis of spontaneous BP fluctuations reveals presence of several power peaks main of which, as well as in heart rate variability, reflect sympathetic and parasympathetic activity. Both in hypertensive patients and animal models of arterial hyper tension BP variability is higher, but its relationship with BP level is not realized in a simple causal scheme. Observations in prehypertensive period demonstrate an opportunity of dissociation between rates of BP level and variability increase. The pharmacological analysis permisses to suggest the sympathetic activation as the main cause of BP destabilization. Despite a leading role of baroreceptor reflex (BR) in damping of evoked BP fluctuations, its role in regulation of spontaneous variability seems to be ambiguous. The studies excluding episodes of locomotor and other activities from the curve analysis do not confirm a correlation between BP variability and BR gain. The spectral analysis of BP lability in animals with denervated mechanoreceptor zones has revealed BR effective control only of a low and superlow frequency areas (less than 0.07 Hz). The study of the regional blood flows in sinoartic denervated rats has concluded that the increase of their autonomy is the main reason of BP lability. The offset of BR efferent limb by ganglionic blocking agents or desympathization leads to analogical BP lability. Thus, BP variability seems to be a reflection of functional efficiency of BP stabilization mechanisms. Considering that on its origin, connections with other haemodynamic parameters, amplitude and frequency characteristics is a complex phenomenon, no one of mechanisms is an universal instrument of its regulation.