Mathematical Model of the Accelerated Cooling of Metal in Thick-Plate Hot Rolling

Metallurgist - The paper describes the issues in predicting the consumer properties of thick-plate pipe products manufactured at the hot rolling mill 5000 of the Magnitogorsk Iron and Steel Works....     

The role of occupational medicine in the development of current and future legal documents on women's work safety and women's health

The article covers legal documents of general and specific measures for women's work safety and health care. Legal basis for work safety and health care in women of childbearing age in this country corresponds with international legal norms. Preservation of social and biologic prosperity for women in this country should be guaranteed by "On protection of maternity" law including medical, social, economic and legal measures.     

Mechanisms of neuronal calcium homeostasis destabilization caused by hyperstimulation of glutamate receptors

The present paper summarizes the data obtained in studying the mechanisms of glutamate-induced deterioration of neuronal Ca2+ homeostasis. In the cultured mammalian central neurons, a short-term (< 1 min) glutamate (GLU, 100 mu) challenge is known to induce a readily reversible (transient) neuronal [Ca2+]i increase. In contrast, a long-term (15-30 min) GLU exposure leads to the appearance of high [Ca2+]i plateau or to the partial recovery of the increased [Ca2+]i. Experiments show that impaired [Ca2+]i recovery in the postglutamate period cannot be explained by the increased [Ca2+]i permeability of the neuronal membrane, as earlier considered. Moreover, a sustained elevation of [Ca2+]i during and after chronic GLU application is associated with a progressive decrease in Ca2+ permeability. The major cause of GLU-induced Ca2+ overload is the mitochondrial depolarization resulted from excessive Ca2+ influx into the mitochondria, the generation of free radicals and the opening of a "giant pore" in the inner mitochondrial membrane. This in turn suppresses both ATP synthesis and Ca2+ electrophoretic uptake into the mitochondrial matrix. In combination with [Ca2+]i-dependent acidification, this leads to the suppression of Ca2+ release from the cell via Na+/Ca2+ exchanger and Ca2+/H+ pump of the neuronal membrane. Therefore, [Ca2+]i recovery following a long-term GLU treatment becomes strongly or even irreversibly compromised.     

Design, fabrication, and testing of a bistable electromagneticallyactuated microvalve

A bistable electromagnetically actuated microvalve was designed, processed, and tested. The valve was designed to control a water flow of 0.05-0.5 μs from a reservoir at a pressure of 1-2000 Pa. The two valve components were fabricated in silicon, the upper piece comprises an electroplated gold coil, and the lower piece is an Ni/Fe alloy beam. The bistable capability was achieved by balancing the elastic forces on the beam with the magnetic forces due to a 46-μm-thick rolled magnetic foil. The design includes the flow through the orifice, squeeze film damping due to beam motion, beam elasticity, and electromagnetics. The microvalve was tested for power consumption, flow rate, time response, Ni/Fe alloy composition, and magnetic foil properties. The valve operates at 1-2 V in both air and water     

A microfabricated electrochemical actuator for large displacements

A large-displacement electrochemical actuator was designed, fabricated, and tested. The large displacement is obtained by using a corrugated membrane made by physical vapor deposition of Parylene sandwiched with an intermediate layer of sputtered platinum. The layered structure is approximately 8-μm thick, with 26 grooves approximately 120-μm deep, and with a radial period of 350 μm. The electrochemical cell consists of platinum electrodes with a 1 M H₂ SO₄ solution. Hydrogen and oxygen gas is generated to displace the membrane. Although the actuator can operate at a voltage as low as 1.23 V, the experimentally determined efficiency of converting electrical energy to mechanical work is only 0.37%. The governing equations for the conservation of mass, momentum (equilibrium), energy, and the entropy generation rate were formulated assuming that the gas bubbles either nucleate without growth or grow without nucleation. For the nucleation case, simulations were performed for constant pressure isothermal actuation, and the average experimental efficiency was bounded by simulations with gas bubble radii between 1×10^-6 m and 1×10^-6 m. The predicted ratio of the power dissipated to the electrical power supplied is 1.37 for isothermal actuation     

Human oogenesis in organ culture

The authors compared the extent of development of the germ cells of the human fetus ovaries developing in the organ culture and of control ovaries obtained of fetuses of "equivalent" age. The capacity to enter the meiosis prophase under conditions of the organ culture was expressed by the germ cells of fetuses of 8-9 week of gestation, and older; only individual oocytes reached the leptotene stage in the explants of the ovaries of 7-8 week fetuses. The oocytes at the leptotene, zygotene and pachitene stage appeared in the culture at the same periods as in the organism. However, the percentage of cells of these stages in the explant was as a rule lower than in control ovaries. In case of pulse administration of thymidine-3H into the culture labeled oocytes at the zygotene stage appeared in 4, and at the pachitene stage - in 14 days.     

Comparison of Operant Escape and Innate Reflex Responses to Nociceptive Skin Temperatures Produced by Heat and Cold Stimulation of Rats.

In behavioral tests, rats performed learned escape responses to thermal stimulation of the paws by 44.0. 47.0. or 0.3 degrees C. Licking, guarding, and jumping reflexes were evaluated at these temperatures. The frequency, latency, and duration of escape and reflex responses were compared and were related to hind-paw skin temperatures measured during stimulation of awake and anesthetized rats. The duration and latency of escape from heat were appropriately related to stimulus intensity. Escape occurred reliably for each intensity. Reflexes occurred unreliably and at long latency to 44.0 or 0.3 degrees C and were not appropriately related to heat intensity. The reflexes were relatively insensitive to thermal nociceptive stimulation other than heating of the skin at a high rate. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preparation of an exponentially rising optical pulse for efficient excitation of single atoms in free space

We report on a simple method to prepare optical pulses with exponentially rising envelope on the time scale of a few ns. The scheme is based on the exponential transfer function of a fast transistor, which generates an exponentially rising envelope that is transferred first on a radio frequency carrier, and then on a coherent cw laser beam with an electro-optical phase modulator. The temporally shaped sideband is then extracted with an optical resonator and can be used to efficiently excite a single (87)Rb atom.     

A preclinical study of the effect of the animal polysaccharide chonsurid on reparative osteogenesis of the jaws

Experimental studies making use of morphological and x-ray methods demonstrated that in comparison with control (filling of mandibular bone defects with blood clots) chonsuride, an animal polysaccharide, promoted earlier filling of postoperative bone cavities with connective tissue replacement of this tissue with coarse-fiber bone tissue. Secondary restructuring and mineralization of bone regenerate were enhanced as well.