State of the art and prospects for developing calculation methods and experimental investigations of radiative heat transfer and for practical application of their results

This article gives an overview of domestic theoretical and experimental investigations of radiative and combined heat transfer performed in recent years and formulates prospective lines of their development.I. I. Polzunov Central Boiler and Turbine Institute, St. Petersburg; Krasnoyarsk Institute of Non-Ferrous Metals; the Academic Scientific Complex A. V. Luikov Institute of Heat and Mass Transfer of the Academy of Sciences of Belarus, Minsk; Moscow Technological Institute of the Food Industry; G. M. Krzhizhanovskii Moscow Institute of Power Engineering. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 64, No. 6, pp. 698–717, June, 1993.     

Micromechanical digital-to-analog converter for out-of-plane motion

This paper describes a novel micromechanical digital-to-analog converter (MDAC) for out-of-plane motion using electrostatic parallel-plate actuators. The proposed mechanism converts an N-bit digital signal to a mechanical out-of-plane displacement that is proportional to the analog value represented by the N-bit binary word. The mechanism is analogous to that of an electrical binary-weighted-input digital-to-analog converter (DAC). It consists of a movable platform, an array of parallel-plate microactuators each operating in an ON/OFF mode and a set of connection springs that connect the actuators to the platform. The spring constants of the connection springs are weighted so that the stiffness of successive springs is related by a factor of 2. A 4-bit mechanism has been fabricated using the Poly-MUMPS process, achieving a total stroke of 675 nm (full-scale output) and step size (LSB) of 45 nm in a highly repeatable and stable manner. The linearity error (LE) of the device is within /spl plusmn/0.28 LSB, and the differential linearity error (DLE) is within /spl plusmn/0.25 LSB. This mechanism can be configured for many promising applications, particularly in optical devices and systems such as tunable external cavity diode laser, tunable VCSELs, adaptive micromirror array and tunable wavelength filter.     

Thermal heating regimes during first-order homogeneous reactions

Qualitative features of self-heating regimes for first-order homogeneous reactions are considered by analyzing the structure of the phase trajectories. Consideration of the temperature dependence of the heating rate makes it possible to extend the main results of Semenov’s theory of thermal explosion and pass to a two-dimensional parameter diagram, which allows the determination of the critical ignition conditions taking into account kinetic inhibition. It is found that the diagram of the Todes criterion versus the reciprocal of the Semenov criterion has four characteristic regions with different kinetics, two of which are limiting and two transitional ones. The boundaries of the regions are calculated, and the classical theory of thermal explosion is shown to be a special case of the projections of these boundaries on the range of the Semenov criterion.     

Composition and Tribological Properties of Hardened Cutting Blades of Tillage Machines under Abrasive Deterioration

The article presents the results of metallographic study of low-carbon 20 steel grade and high-carbon 70 and 65G steel grades upon carburizing, heat treatment, and laser hardening. The change in the microhardness through the depth of the surface layer of steels and their abrasion resistance upon hardening under different conditions has been measured. Optimal hardening conditions have been proposed for steels for cutting blades of tillage machines that enable the durability of the blades to be improved.     

Photoresponse recovery in silicon photodiodes upon VUV irradiation

The spatial homogeneity of the photoresponse is studied for silicon photodiodes based on p-n and n-p junctions a year after their irradiation at a wavelength of 121.6 nm and those based on n-p junctions four years after their irradiation with soft X-rays. It is demonstrated that silicon photodiodes based on p-n junctions exhibit a photoresponse recovery effect on being irradiated at a wavelength of 121.6 nm. No recovery effect is observed for silicon photodiodes based on n-p structures.     

Kaiser Effect in Rock Salt

Using the results of experiments with rock salt samples under various loading regimes as an example, the regularities of the Kaiser effect formation and manifestation in rocks with plastic properties are investigated.     

The effect of intravenous and oral fluconazole on the pharmacokinetics and pharmacodynamics of intravenous alfentanil

The growth-promoting activity of PDGF-BB was studied on the adult osteoclasts in the present study. The PDGF receptor beta was detected on the osteoclast membrane through immunohistochemistry (LSAB method) and immunomicroscopy. The PDGF-BB was exerted on the osteoclasts that adhered to the bone slice at concentrations of 0, 10, 20, 30, and 40 ng/ml. The volume of Howship's lacuna augmented significantly and the number of resorption pits also increased with its dose (p < 0.01). The activity of both total acid phosphatase (ACP) and tartrate-resistant acid phosphatase (TRAP) increased significantly. These results suggest that PDGF-BB promotes adult osteoclastic bone resorption directly through PDGF receptor beta and is believed to play important roles in the bone healing process and reconstruction.     

Clenbuterol and anabolic steroids: a previously unreported cause of myocardial infarction with normal coronary arteriograms

During the last 10 years, several cases of myocardial infarction associated with anabolic steroid use have been reported. Postulated mechanisms to explain this association have included changes in lipid levels, the fibrinolytic system, and platelet aggregation. Clenbuterol is a beta 2-agonist with anabolic properties that has not been seen previously with myocardial infarction. We report a case of myocardial infarction in an otherwise healthy 26-year-old body-builder who recently used clenbuterol and anabolic steroids. In this case, synergistic effects of the two agents seem likely to have played a role in the infarct. The normal coronary arteriograms before any anticoagulant or thrombolytic therapy strongly suggest coronary spasm as the mechanism of the infarct.     

Research and the cumulation of knowledge in Physical Therapy

BACKGROUND AND PURPOSE: Published research contributes to the knowledge base that distinguishes one discipline from another. More research is now published in the physical therapy journals, but concerns with the profession's knowledge base continue. SUBJECTS: The study examined citations from 78 clinical articles published and indexed on three thematic areas in Physical Therapy between 1951 and 1990. METHODS: Unique items and multiple-cited items were identified and counted and their sources ascertained. Linkages among multiple-cited items in each thematic area were identified and described. RESULTS: Most cited items were unique and not from the physical therapy literature. Few linkages were identified among the clinical articles. CONCLUSION AND DISCUSSION: The lack of evidence of cumulation or of coherence among the articles examined and the extent of reliance on non-physical therapy sources suggest that concerns with the knowledge base of the profession are well founded.