Fretting corrosion and fatigue of gears

We describe the fretting and fatigue fracture of gears with guaranteed clearance. The results of a study of macro- and micro-reliefs of surfaces damaged by fretting and the results of X-ray analysis of products of wear and the oxide film are presented. The dependence of the joint operating conditions on the state of the working surfaces of slot teeth is analyzed.Chubar Institute of Mechanical Engineering, Zaporozh'e. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 29, No. 6, pp. 112–114, November–December, 1993.     

Fractal physiology

The nature of fractals and the use of fractals instead of classical scaling concepts to describe the irregular surfaces, structures, and processes exhibited by physiological systems are described. The mathematical development of fractals is reviewed, and examples of natural fractals are cited. Relationships among power laws, noise, and fractal time signals are examined     

Frequency-dependence of myocardial energetics in failing human myocardium as quantified by a new method for the measurement of oxygen consumption in muscle strip preparations

Diastolic dysfunction at high heart rates may be associated with increased myocardial energy consumption. Frequency-dependent changes of isometric force and oxygen consumption (MVO2) were investigated in strip preparations from endstage failing human hearts exhibiting various degrees of diastolic dysfunction. MVO2 was determined by a new method which was validated. When stimulation rate was increased from 40 to 200 min-1 (n=7), developed force decreased from 16.5+/-4.3 to 7.9+/-2.9 mN/mm2 (P<0.01), diastolic force increased from 15.9+/-3.2 to 22.0+/-3.0 mN/mm2 (P<0.01), and total MVO2 increased from 2.6+/-0.6 to 4.7+/-0.9 ml/min/100 g (P<0.025). Resting MVO2 and resting force were 1.8+/-0.4 ml/min/100 g and 15.9+/-3.0 mN/mm2, respectively. After addition of 30 mm 2,3-butanedione monoxime (BDM) to inhibit crossbridges, resting MVO2 and resting force decreased by 46% (P<0.05) and 15% (P<0.01), respectively, indicating the presence of active force generation in unstimulated failing human myocardium. In each muscle preparation, there was a significant correlation between force-time integral (FTI) and total MVO2 (r=0.96+/-0.01). The strength of these correlations did not vary with the contribution of diastolic FTI to total FTI. The ratio of activity related MVO2 to developed FTI, an inverse index of the economy of contraction, increased depending on the rise of diastolic FTI at higher stimulation rates. In conclusion, in failing human myocardium, diastolic force development is occurring at the same energy expenditure as systolic force generation. Therefore, in muscle preparations with disturbed diastolic function economy of contraction decreases with higher stimulation rates, depending on the rise of diastolic force.     

Disability management and occupational health

Disability costs have an enormous impact on a corporation's profits. Medical managed care techniques can improve outcomes in disability management and help a business to remain competitive.     

Derivative constrained optimum broad-band antenna arrays

The optimization problem corresponding to the design of a presteered broadband processor with maximally flat second-order spatial response in the look direction is discussed. The constraints corresponding to necessary and sufficient conditions for second-order flatness are presented. The nonlinearly constrained optimization approach is unable to consistently locate the global minimum. An approach to solving this problem that essentially converts the nonconvex optimization problem into a parameterized set of convex problems is presented. In the case of 2-D scenarios, the global optimum is determined by finding the roots of a cubic function. The characteristics of the constraints, including the minimum number required and the dependence on the choice of coordinate systems, are examined     

Indomethacin reduces contraction of isolated non-pregnant human uterine artery induced by prostaglandin F2 alpha

The purpose of this study was to explore whether cyclooxygenase products derived from endothelium or vascular smooth muscle participate in the response of human uterine artery to prostaglandin F2 alpha. Experiments were performed using human uterine arterial rings. Prostaglandin F2 alpha (0.4 nM-1 microM) induced contraction of human uterine arteries with both intact and denuded endothelium with similar potency and efficacy (pD2 values: 7.93 +/- 0.01 and 8.07 +/- 0.03 for vessels with and without endothelium respectively; maximal response values: 89.1 +/- 4.7% and 92.3 +/- 3.8% for vessels with and without endothelium respectively). Indomethacin (10 microM) significantly suppressed the maximum effects of prostaglandin F2 alpha and induced a shift towards the right of the prostaglandin F2 alpha concentration-response curves, regardless of the endothelial condition. On the other hand, in both types of preparations, OKY-046 (10 microM), an inhibitor of thromboxane synthesis, did not affect prostaglandin F2 alpha-induced contraction of human uterine arteries. It is concluded that in human uterine artery prostaglandin F2 alpha-induced contraction is mediated, at least in part, through constrictor prostanoid(s) of vascular smooth muscle origin that is not thromboxane A2.     

Eigenstates of polarization of elliptical single-mode fibers

The degree of polarization of radiation in an elliptical polarization-maintaining fiber and the polarization states of eigenpolarization modes of such fibers have been experimentally investigated in a wide spectral range. It has been shown that the elliptical fibers are uniform, homogeneously twisted fibers with elliptically polarized eigenpolarization modes. The ellipticity of the eigenpolarization mode is independent of fiber length and increases with wavelength, while the azimuth of the eigenpolarization mode is spectrally independent     

Determining the safe purge rate of flare tubes

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 5, pp. 5–7, May, 1993.     

Comparative study of the death during sea voyages among Polish seamen and deep-sea and boat fishermen

181 fatal cases of diseases and work-related accidents recorded in the years 1985-1994 among seamen and fishermen were analyzed. The highest mortality rate and fatal accident rate were noted in seamen. They were higher than those pertaining to workers employed on land. The respective rates for Polish fishermen were lower than those reported in other countries. The main causes of death at sea were sea catastrophes, injuries, drowning, poisoning and circulatory system diseases. The most frequent were deaths during the day and not on the watch, being alone in the cabin. Limited access to qualified medical assistance during the voyage and frequent occurrence of sudden deaths reduce substantially the efficacy of help. Therefore, prevention of diseases and accidents is of crucial importance.