On electron transport in 3D quantum waveguides of variable cross-sections

We consider three-dimensional axially symmetric quantum wires with circular cross-sections whose radius may vary along the axis of the waveguide. In the narrows, there arise barriers to the longitudinal motion of an electron. Varying the radius, one can create barriers and provide conditions for resonant tunnelling of electrons. We suggest a method for numerically studying such phenomena. The method can be applied to wires not possessing axial symmetry as well. Besides this, we discuss some possible applications.     

Microcapillary waves on liquid electrodes in high electric fields

The initiation and sustaining of field emission processes from a liquid surface are based mainly on the effect of field amplification at the surface microtips. Such microtips form under different types of hydrodynamic instabilities. However, the threshold field of such instabilities has a very high value. At the same time, there are some situations when one needs to excite the emission using an arbitrary low amplitude of the external voltage. In this paper, in order to solve this problem, the process of preliminary excitation of the surface by an ultrasonic field on the liquid emitter surface has been studied. The theory developed has shown that, as a result of parametric instability, the formation of surface microstructures is possible. Such structures can be produced at very low levels of ultrasonic power. This fact is of particular importance for large surface area cathodes. The dependence of the geometric parameters of the surface structures both on frequency and power of the ultrasonic field is determined theoretically. Experiments with field pulses in the nanosecond range confirm the decrease of the explosive emission mechanism when preliminary ultrasonic excitation is used     

Antigen responsiveness of an established human B-lymphoid cell line. II. Loss of Candida antigen responsiveness following exposure of cells to specific anti-human immunoglobulin antisera

Metabolism of D-glucose by Bacteroides ruminicola subsp. brevis, strain B14, has been examined. Growth yield studies gave molar growth yields, corrected for storage polysaccharide, of approximately 66 g (dry weight)/mol of glucose fermented. The storage polysaccharide amounted to about 14% of the total dry weight, or 55% of the total cellular carbohydrate, at full growth. After correcting glucose utilization for incorporation into cellular carbohydrate, measurement of product formation showed that 1.1 succinate, 0.8 acetate, and 0.35 formate are produced and 0.5 CO2 net is taken up during the fermentation of 1 glucose under the conditions used. The implication of these results with respect to adenosine 5'-triphosphate (ATP) molar growth yield calculations is discussed. If substrate-level phosphorylation reactions alone are responsible for ATP generation, then the ATP molar growth yield must be about 23 g (dry weight)/mol of ATP. Alternatively, if anaerobic electron transfer-linked phosphorylation also occurs, the ATP molar growth yield will be lower.     

Semi-artificial Fluorescent Molecular Machine for DNA Damage Detection

The design of artificial molecular machines is complicated because the mechanics used in macromachines is not readily adaptable for nano environments. We constructed a semi-artificial molecular device, which contains a naturally occurring molecular machine-a vaccinia virus encoded protein-linked with an artificial part. The self-assembled construct makes two fluorescently labeled detector units. It is the first sensor capable of selectively detecting different types of DNA breaks, exemplifying a practical approach to the design of molecular devices.     

Neuroanatomical changes in the rat bladder after bladder outlet obstruction

OBJECTIVE: To evaluate the perinatal and 2-year outcomes in pregnancies complicated by preterm premature rupture of membranes (PROM) during the second trimester. METHODS: Fifty-three consecutive singleton pregnancies with PROM at 14 to 28 weeks of gestation were studied retrospectively. Management goals were to prolong the pregnancies to 32 weeks through expectant management and to avoid fetal compromise through closer monitoring and active intervention, when necessary, after 23 weeks. Outcome of the surviving infants was based on neurologic, audiometric, and ophthalmologic examinations at 2 years of corrected age. RESULTS: Rupture of membranes occurred at 14-19 weeks (mean 17.4 weeks) in 10 women, at 20-25 weeks (mean 24.0 weeks) in 24, and at 26-28 weeks (mean 27.6 weeks) in 19. The median latency periods to delivery were 72 days, 12 days, and 10 days when rupture of membranes occurred at 14-19 weeks, 20-25 weeks, and 26-28 weeks, respectively. The overall incidence of chorioamnionitis was 28%. There were no fetal deaths and nine neonatal deaths. When rupture of membranes occurred at 14-19 weeks, 20-25 weeks, and 26-28 weeks, the perinatal survival rates were 40%, 92%, and, 100%, respectively. Pulmonary hypoplasia accounted for seven deaths. Of the live-born infants, 81% were alive at 2 years of corrected age. Survival without major impairment was observed in 75%, 80%, and 100% of the survivors when rupture of membranes occurred at 14-19 weeks, 20-25 weeks, and 26-28 weeks, respectively. CONCLUSION: Expectant management of second-trimester PROM offers better perinatal and long-term survival than previously thought.     

Ventricular shunt removal: the ultimate treatment of the slit ventricle syndrome

Atropine is known to impede the acquisition of conditioned responses by neurons of the motor cortex. Does atropine exert influence (and of what kind) on acquisition of local movements controlled by neurons of the motor cortex? In the present study we examined the influence of atropine microinjections on acquisition of reaching movement in freely moving rats. The intracortical pressure injections of atropine (5 mcg and 15 mcg/0,6 mcl/40 s) were made unilaterally into the forearm area of the motor cortex in adult mongrel rats. Hungry rats learned to reach sunflower seeds form a horizontal tube by using the forelimb contralateral to the injected site. Atropine exerted dose-dependent influence of the acquisition of the motor skill. All the tested doses depressed the inhibition of concurrent movements during learning. In addition, the higher dose of atropine inhibited the initiation of the reaching movements. A hypothesis was proposed to explain these differences.     

Specificity of leptin action on elevated blood glucose levels and hypothalamic neuropeptide Y gene expression in ob/ob mice

Correction of the obese state induced by genetic leptin deficiency reduces elevated levels of both blood glucose and hypothalamic neuropeptide Y (NPY) mRNA in ob/ob mice. To determine whether these responses are due to a specific action of leptin or to the reversal of the obese state, we investigated the specificity of the effect of systemic leptin administration to ob/ob mice (n = 8) on levels of plasma glucose and insulin and on hypothalamic expression of NPY mRNA. Saline-treated controls were either fed ad libitum (n = 8) or pair-fed to the intake of the leptin-treated group (n = 8) to control for changes of food intake induced by leptin. The specificity of the effect of leptin was further assessed by 1) measuring NPY gene expression in db/db mice (n = 6) that are resistant to leptin, 2) measuring NPY gene expression in brain areas outside the hypothalamus, and 3) measuring the effect of leptin administration on hypothalamic expression of corticotropin-releasing hormone (CRH) mRNA. Five daily intraperitoneal injections of recombinant mouse leptin (150 micrograms) in ob/ob mice lowered food intake by 56% (P < 0.05), body weight by 4.1% (P < 0.05), and levels of NPY mRNA in the hypothalamic arcuate nucleus by 42.3% (P < 0.05) as compared with saline-treated controls. Pair-feeding of ob/ob mice to the intake of leptin-treated animals produced equivalent weight loss, but did not alter expression of NPY mRNA in the arcuate nucleus. Leptin administration was also without effect on food intake, body weight, or NPY mRNA levels in the arcuate nucleus of db/db mice. In ob/ob mice, leptin did not alter NPY mRNA levels in cerebral cortex or hippocampus or the expression of CRH mRNA in the hypothalamic paraventricular nucleus (PVN). Leptin administration to ob/ob mice also markedly reduced serum glucose (8.3 +/- 1.2 vs. 24.5 +/- 3.8 mmol/l; P < 0.01) and insulin levels (7,263 +/- 1,309 vs. 3,150 +/- 780 pmol/l), but was ineffective in db/db mice. Pair-fed mice experienced reductions of glucose and insulin levels that were < 60% of the reduction induced by leptin. The results suggest that in ob/ob mice, systemic administration of leptin inhibits NPY gene overexpression through a specific action in the arcuate nucleus and exerts a hypoglycemic action that is partly independent of its weight-reducing effects. Furthermore, both effects occur before reversal of the obesity syndrome. Defective leptin signaling due to either leptin deficiency (in ob/ob mice) or leptin resistance (in db/db mice) therefore leads directly to hyperglycemia and the overexpression of hypothalamic NPY that is implicated in the pathogenesis of the obesity syndrome.     

Evidence that galanin is a parasympathetic, rather than a sympathetic, neurotransmitter in the baboon pancreas

Various cortical dysplasias, such as agyria-lissencephalia, pachygyria, micropolygyria, neuronal heterotopia and so on, have become relatively common neuropathological findings among the children with intactable epilepsy and mental and/or physical handicap. Together with various environmental factors, gene abnormalities are recently increasing as a cause in various cortical dysplasias. However, details of the pathogenesis still remain unknown. Experimental studies using animal models indicated that inhibition of neuron production, disorders of neuron-glia and neuron-neuron contact, and plastic and unbalanced synaptogenesis subsequent to abnormal neuron production play an important role either separately or in combination in the pathogenesis of various cortical dysplasias.     

Dynamic methods for calibration and verification of the metrological characteristics of instruments intended for gas analysis (generalized approach)

A systematic approach to the metrological provision (MP) of gas-analytical measurements in the range of microconcentrations (trace analysis) using dynamic and static control facilities is described. Results of investigations and development of the methods and facilities for continuous preparation of reference gas mixtures (RGMs) for the MP of commercial chromatographs, chemical sensors, and other instruments and devices for gas analysis are presented, including data on the capacity of adsorbents, parameters of sampling adsorption tubes, regimes of sorption and desorption, creation and maintenance of gas mixtures with preset compositions in testing chambers for toxicological investigations. Methodological and technical problems of MP in the field of trace analysis are considered. The main dynamic methods of preparation of the RGMs by flow mixing, diffusion leak, and exponential dilution of initial gases are described. Examples of the new generation of new “smart” systems of the Mikrogaz-F type intended for the RGM preparation in the range of microconcentrations are presented.