Energy balance in the interaction of intense high-temperature plasma flows with solid targets

The energy balance in the interaction of intense (W≈7 MW/cm², Q≈130 J/cm²) flows of a high-temperature (T _e+T _i≈0.7 keV deuterium plasma with targets made of different materials (graphite, tungsten, copper, etc.) is studied experimentally. It is shown that radiation plays a decisive role in the interaction energy balance: a plasma layer arising near the surface of the eroded target reemits most of the plasma-flow energy into the surrounding space. No more than 50 J/cm² reaches the surface. Then, this energy is expended primarily on the target heating and only a small fraction (less than 3 J/cm²) is spent on the evaporation of the target surface layer. It is shown that, for targets made of high-Z materials, the energy reaching the surface is transferred predominantly by radiation.     

Histochemical localization of oxidized glutathione-catalysing enzymes in human term placenta

Summary This paper reports a new cytochemical affinity technique for detecting oxidized-glutathione-binding enzymes by light microscopy and for carrying out fine structural analyses by means of oxidized glutathione labelled with colloidal gold. Albumin-colloidal gold particles were prepared. Oxidized glutathione, added to the solution, replaced albumin on the surface of the gold, thus forming a new histochemical reagent. In human placenta, oxidized-glutathione-catalysing activity was detected on the brush border of the placental villi, over the foldings of endothelial membranes, and in the ground substance of connective tissue in the villous core. Every process of the cell membrane demonstrated enhanced oxidized-glutathione-catalysing activity. This new reagent is a unique example of a low-molecular-weight compound labelled with colloidal gold, and it permits direct measurement of oxidized-glutathione-binding activity in tissue sections.     

Mechanical characteristics of synthetic polyelectrolyte gel as a physical model of the cytoskeleton

A physical model of the cytoskeleton based on synthetic polyelectrolyte hydrogel of polymethacrylic acid has been proposed. From the physicochemical point of view, the structures of polyelectrolyte gel and the cytoskeleton show a high degree of similarity. It has been shown that polyelectrolyte gel can shorten and produce mechanical stress in response to changes in the composition of the surrounding solution. The mechanical properties of the model gel have been evaluated: Young modulus (2–6 kPa), stress relaxation time (0.1–1 s), and apparent viscosity (0.3–3 kPa s). The viscoelastic properties of the gel depend on the degree of its swelling. It has been demonstrated that the mechanical properties of gels of polymethacrylic acid are close to those of biological objects.     

Ecology of the Siberian Lemming (Lemmus sibiricus) and the Distribution History of the Collared Lemming (Dicrostonyx torquatus) (Rodentia,Cricetidae) on the New Siberian Islands

Biology Bulletin - One hundred twenty Siberian lemmings (Lemmus sibiricus) were studied from Kotelnyi Island in the eastern sector of the Polar basin. The main habitats, abundance, nutrition,...     

The effect of darkness on knee-jerk reflexes

In considering the processes that regulate motor functions in darkness, the following factors should be taken into account: the fear of losing spatial orientation, daily processes in the circadian system, stimulating influence of the light, and a mechanism that induces anxiety, probably of rudimentary origin, serving as a sentinel center monitoring the probable aggressiveness of the environment, which increases in the dark. The results of published studies suggest that the anxiety response to darkness induces emotional stress, and, consequently, an increase in the background supraspinal excitatory influence mediated by the corticospinal tract and leading to decreased α-motoneuron thresholds.     

Chaotic and ordered processes mediating the knee-jerk reflex

In nerve chains that mediate tendon reflexes one can distinguish structured activity that represents the development of reflex excitation in response to muscle stretch and stochastic activity which is the result of fluctuations emerging in nerve structures. In analyzing neuron processes, one should consider also the factor of information whose carriers in nerve chains are structured and stochastic activities. A putative generator of fluctuations of muscle responses (possibly the main one) are cortex levels. Stochastic processes in neuron chains cause instability of the motor system at rest and in movement. Stochastic activity maintains the tone of skeletal muscles and affects the sensitivity of sensory systems via the mechanism of stochastic resonance.