Central sleep apnea

A central sleep apnea is the absence of respiratory effect, and, thus, the absence of airflow during sleep. Central hypopnea, a related disorder, is also discussed. The sensory component of central sleep apnea; defects involving the integrative and executive neurons; non-neurologic causes of central sleep apneas, including chronic obstructive pulmonary disease and congestive heart failure; diagnosis; treatment; and other topics are reviewed in detail.     

Extinction of dispersed heterogeneous systems

We consider extinction of various dispersed systems. Isolated boron particles and boron particles in gases are studied. Stability analysis of steady-state thermal regimes of reacting heterogeneous systems for the case of two parallel reactions on the reaction surface using the Frank-Kamenetskii method gives extinction conditions in oxygen-containing media. Curves of the extinction particle size versus the ambient temperature, oxidizer concentration, and, for particles in gases, also versus the oxidizer-to-fuel ratio are plotted. Approximate analytical calculations showed that the extinction process can be most actively controlled by varying the combustion temperature: a decrease in the latter increases the extinction particle size and decreases the completeness of fuel combustion. It is shown that at low ambient temperatures the extinction particle size for suspensions is larger than that for isolated particles. This effect is caused by a decrease in the oxidizer concentration during combustion of suspensions. At high temperatures, the role of this factor weakens.Translated from Fizika Goreniya i Vzryva, Vol. 32, No. 6, pp. 12–19, November–December, 1996.     

Autonomous vehicles

There are various kinds of autonomous vehicles (AV's) which can operate with varying levels of autonomy. This paper is concerned with underwater, ground and aerial vehicles operating in a fully autonomous (nonteleoperated) mode. Further this paper deals with AV's as a special kind of device, rather than full-scale manned vehicles operating unmanned. The distinction is one in which the AV is likely to be designed for autonomous operation rather than being adapted for it as would be the case for manned vehicles. We provide a survey of the technological progress that has been made in AV's, the current research issues and approaches that are continuing that progress, and the applications which motivate this work. It should be noted that issues of control are pervasive regardless of the kind of AV being considered, but that there are special considerations in the design and operation of AV's depending on whether the focus is on vehicles underwater on the ground, or in the air. We have separated the discussion into sections treating each of these categories     

Cyclobutanones as markers for irradiated samples of Brie and Camembert cheese

The feasibility of applying a chemical method based on the formation of 2-alkylcyclobutanone to samples of irradiated soft cheese (Brie and Camembert) was investigated. Significant quantities of 2-dodecylcyclobutanone (DCB) and 2-tetradecylcyclobutanone (TCB) were detected in both types of irradiated cheese and are proposed as qualitative markers. Other members of the cyclobutanone family (decyl- and tetradecenyl-) are also thought to be present but could not be substantiated due to a lack of authentic standards. These compounds were absent from the unirradiated samples. Results also show a significant linear relationship between the irradiation dose (1 to 8 kGy) and the amount of DCB and TCB detected in the cheese.     

Evaluation of factors influencing platelet aggregation in patients with chronic glomerulonephritis (CGN)

Platelets (PLT) play an important role in hemostasis, modulation of immunological and inflammatory processes. There is also evidence that PLT takes part in the development of atherosclerosis and glomerulosclerosis. The aim of presented study was to determine morphological and functional changes of platelets and their relation to the lipid, protein and coagulation factors disturbances in patients with chronic glomerulonephritis (CGN). The studies were carried out in 60 patients with CGN diagnosed by renal biopsy: 30 patients without nephrotic syndrome (NS)-CGN and 30 patients with NS-CGN+NS. Protein and lipid disturbances, coagulation factors were estimated using routine laboratory methods. Platelet count (PLT), mean platelet volume (MPV) and modal platelet volume (PLT-Mode) were measured using Technicon H1 hematological autoanalyser. Platelet function was assessed by aggregometry using turbidimetric method (inductors: ADP 1-3 microM, collagen 50g/ml, epinephrine 0.25-5 microM). Spontaneous platelet aggregation (SPA) was measured in platelet rich plasma (PRP) without inductors for 15 min, in 1-2 hours after venesection. SPA was observed in 9 of 30 patients with CGN and in 19 of 30 patients with CGN+NS. MPV and PLT Mode were significantly higher in patient showing SPA compared with those without. Significant correlations between SPA and the concentration of plasma albumin (r = -0,70; p < 0.02) TG and CH-LDL (r = 0,61; p < 0.05) were found in CGN+NS patients. APTT was significantly shorter in patients showing SPA compared with those without and negative significant correlation between SPA and APTT was found. Platelet aggregation to inductors in CGN and CGN+NS patients was diminished compared with control group. Lack of second phase aggregation in response to aggregation inducers was observed in patients with SPA. Conclusions. 1. Platelet hyperaggregation play an important role in hypercoagulation state in CGN patients. 2. SPA in vitro was observed in majority of CGN+NS patients and in some without NS. 3. Pathomechanism of SPA is probably multifactorial (hypoalbuminemia, dyslipidemia, changes in concentration of coagulation parameters).     

Dependence of attenuation in a vegetation canopy on frequency andplant water content

Theory is presented to provide insight into the observation that attenuation through vegetation is proportional to vegetation water content. In this analysis, the canopy is modeled as a sparse layer of randomly oriented particles (leaves, stalks, etc.) over a flat, homogeneous ground plane (soil) and an expression is obtained for the “optical depth”. The formulas developed by Ulaby and El Rayes are used to relate this expression to the water content of the canopy. In the low frequency extreme (Rayleigh scatterers), the attenuation varies almost linearly with water content and inversely with wavelength. In contrast, in the high frequency limit, the attenuation is independent of both water content and frequency, in between, geometry dependent “resonances” occur even at the low frequency end of the microwave spectrum (e.g. L-band) making the dependence of attenuation on frequency and water content specific to canopy architecture     

Nickel/microcapsules composite electrocoatings; the synthesis of water-containing microcapsules and preparation of the coatings

Composite coatings, the product of electrolytic codeposition of solid particles in a metallic matrix have been developed and utilized in industry as wear resistant coatings. The work described in this paper concerns the development of water-containing metallic coatings prepared by the electrolytic codeposition of water-containing microcapsules from nickel Watts plating baths under pulse reversed current conditions. The water-containing polystyrene microcapsules employed in the codeposition experiments were produced by the complex emulsion/solvent evaporation technique. The influence of the use of two types of stabilizers on the size and the surface chemistry of the microcapsules is discussed. The microcapsules prepared in both cases are rigid spheres with compact walls and a smooth surface. The different stabilizers showed a significant influence on the dispersability of the capsules in the plating solution and their codeposition behaviour. The codeposition experiments carried out with the use of a rotating disc electrode revealed the influence of the plating parameters on the incorporation procedure and on the quality of the composite electrodeposits.     

Melt-extracted oxide ceramic fibres — the fundamentals

A melt-extraction technique, using a sharpened molybdenum wheel, has been used to produce fine oxide ceramic fibres. Wetting of the molybdenum wheel by molten ceramic is a key parameter in the melt-extraction process. Two types of fibre are generally obtained, depending on the extraction speed. At very low wheel speed, fine and uniform fibres of high quality are produced. However, when the wheel speed exceeds a critical velocity, Rayleigh waves are formed on the free surface of the fibres. Moreover, the average fibre thickness first increases with the wheel velocity, then passes through a maximum, decreasing at high velocity. This thickness variation is discussed in terms of both surface tension and viscosity of the liquid ceramics.