The kinetics of diffusion processes in the nickel-aluminum composition

The kinetics of diffusion processes on interlayer boundaries of the three-layered composites aluminum (AD1) + nickel (NP1) + aluminum (AD1) obtained by explosion welding with subsequent cold rolling is investigated. The phase composition of the diffusion region is established.     

A randomized, controlled trial of aminophylline in ventilatory weaning of premature infants

OBJECTIVES: To determine whether maximal inspiratory force predicts successful neonatal extubation, and whether aminophylline affects maximal inspiratory force or the success rate of extubation. DESIGN: Double-blind, prospective, randomized, placebo-controlled trial. SETTING: Tertiary level neonatal intensive care unit. PATIENTS: A total of 20 ventilated, preterm, newborn infants: birth weight < 2.5 kg; gestation < 35 wks. INTERVENTIONS: Intravenous aminophylline 4 mg/kg bolus followed by 2.5 mg/kg every 6 hrs x three doses, then 1.5 mg/kg every 6 hrs; or placebo. Drug administration began when infants were receiving an FIO2 of < 0.4 and were progressively weaning from assisted mechanical ventilation. A standardized weaning protocol was instituted, and patients were extubated when they were able to tolerate a mechanical ventilatory rate of < 5 cycles/min. MEASUREMENTS AND MAIN RESULTS: Occlusion pressures, including maximal inspiratory force, were measured before aminophylline and daily until endotracheal extubation. Arterial blood gases were measured every 3 hrs, and 24-hr cardiac and respiratory recordings were performed postextubation. Three of ten aminophylline-treated patients failed extubation compared with two of ten placebo infants (p = nonsignificant). Mean apnea frequency postextubation was 0.02/hr in the aminophylline group compared with 0.3/hr in the placebo group (p < .05). Aminophylline had no effect on successful extubation or on maximal inspiratory force. Maximal inspiratory force was not correlated with the success of extubation. Apnea frequency postextubation was significantly reduced by aminophylline. CONCLUSIONS: Aminophylline is an effective prophylaxis for postextubation apnea in the preterm infant but does not affect maximal inspiratory force or increase the success rate of extubation in this patient population.     

Influence of superstoichiometric boron on the synthesis of cubic boron nitride

Initiators of the synthesis of cubic boron nitride in the Mg-B-N and Li-B-N-O systems are compared. The influence of boron not bound in metal boronitrides and metal borates is investigated. It is proposed to distinguish “excess” boron introduced in the elemental form from “active excess” boron formed in the course of chemical transformations of initiators.     

13C enrichment of fullerenes

It is shown experimentally that fullerenes can be enriched with ¹³C as a constituent of CO₂ gas molecules. A qualitative model of the processes that correctly reflects the experimental laws is proposed. Center for Laser Technology, Scientific-Research Institute for Electrophysical Apparatus Pis’ma Zh. Tekh. Fiz. 25, 12–18 (September 26, 1999)     

The Burch procedure: a comprehensive review

The relationship of timing of early parental separation to psychosocial development of daughters was examined in 77 girls, 6-9 years of age over a four-year period. Disruptive behavior across contexts was prevalent in girls separated between birth and two years of age. Girls separated between three and five years of age showed more externalizing behavior problems, but only in school. Results suggest that early parental separation has more pervasive and stable negative effects on psychosocial adjustment of girls in this age group in single-parent families. Implications of the findings and directions for research are discussed.     

Channeling radiation from relativistic electrons in a thin LiF crystal: When is a classical description valid?

Calculation of channeling radiation from relativistic electrons under (1 1 1) planar channeling conditions in a LiF crystal is performed using both classical and quantum methods. The complicated shape of the periodic (1 1 1) planar potential allows the existence of a different number of discrete energy levels (quantum states) in the potential well formed by planes consisting of only Li atoms and the potential well consisting of only F atoms is large enough to apply the classical method. With increasing electrons energy, the classical method becomes valid to describe CR from under-barrier electrons in a deeper potential well, while one should still apply the quantum method to calculate CR from electrons in neighboring planes. Thus, the quantum feature of a CR spectrum from relativistic electrons maintains its quantum characteristics up to relativistic factors 1000.     

Conversion of Diesel Engines to a Gas and Gas–Diesel Cycle

Russian Engineering Research - The conversion of diesel engines to gas and gas–diesel cycles during the production process is analyzed. The requirements for conversion to natural-gas...     

Classification of unifloral honeys with an MS-based electronic nose using different sampling modes: SHS,SPME and INDEX

An electronic nose based on mass spectrometry has been applied to the control of the authenticity of the botanical origin of honey. PCA and DFA models were built based on groups of samples identified as typical unifloral honey by a classical method, i.e. a combination of sensory, pollen and physicochemical analysis. Swiss unifloral honeys of the following types were analysed: acacia, chestnut, dandelion, lime, fir and rape. Three different sampling modes were tested: static headspace (SHS), solid-phase micro-extraction (SPME) and inside-needle dynamic extraction (INDEX). The last two showed interesting abilities to extract volatile components in a higher concentration and, most important, heavier compounds than SHS. The best classification, under the sampling conditions used, was provided by the SPME sampling mode. This method proved to be fast, reliable and powerful for this type of task. A good correlation was found between the present approach and the classical one for the determination of the botanical origin of honey.