Film Thickness and Shape Evaluation in a Cam-Follower Line Contact with Digital Image Processing

Film thickness is the most important parameter of a lubricated contact. Its evaluation in a cam-follower contact is not easy due to the continuous variations of speed, load and geometry during the camshaft rotation. In this work, experimental apparatus with a system for film thickness and shape estimation using optical interferometry, is described. The basic principles of the interferometric techniques and the color spaces used to describe the color components of the fringes of the interference images are reported. Programs for calibration and image analysis, previously developed for point contacts, have been improved and specifically modified for line contacts. The essential steps of the calibration procedure are illustrated. Some experimental interference images obtained with both Hertzian and elastohydrodynamic lubricated cam-follower line contacts are analyzed. The results show program is capable of being used in very different conditions. The methodology developed seems to be promising for a quasi-automatic analysis of large numbers of interference images recorded during camshaft rotation.

Early development of nematode embryos: differences and similarities

To determine whether embryogenesis of Caenorhabditis elegans is typical for nematodes in general, we started to analyse in comparison several aspects of development in various nematode species. The differences we observed can be subdivided into two classes, those visible in the intact embryo and those requiring experimental interference. Particularly obvious differences of both types were revealed between C. elegans (Rhabditidae) and Acrobeloides nanus (Cephalobidae). Not only does the spatial and temporal pattern of early events differ but also that of intercellular communication and cell specification. Our data suggest that some developmental variations are characteristic for certain nematode groups and therefore may be useful as phylogenetic markers. In contrast, we detected little evidence so far for environmental influence on early developmental processes. Pour déterminer dans quelle mesure l’embryogenèse de Caenorhabditis elegans est une caractéristique générale des nématodes, nous avons commencé l’analyse de plusieurs aspects du développement chez différentes espèces de nématodes. Les différences observées peuvent être divisées en deux catégories: celles observables chez l’embryon intact et celles nécessitant une intervention expérimentale. En particulier, des différences nettes entre les deux catégories ont été mises en évidence chez C. elegans (Rhabditidae) et Acrobeloides nanus (Cephalobidae). Diffèrent non seulement le schéma spatio-temporel des évènements précoces, mais également la communication intercellulaire et la différenciation cellulaire. Nos données suggèrent que certaines variations du développement sont caractéristiques de certains groupes de nématodes et pourraient donc être utiles comme marqueurs phylogénétiques. A contrario, une influence de l’environnement sur les processus précoces du développement n’a pas, jusqu’à présent, été détectée.

Pressure diuresis and autonomic function in conscious dogs

Pressure diuresis is thought to be a major long-term regulator of arterial blood pressure (AP). Previously, pressure diuresis has been characterized using pharmacological or surgical blockade of other mechanisms known to affect renal function. This study evaluated pressure diuresis in conscious dogs with minimal experimental interference. Dogs were chronically instrumented under pentobarbital anesthesia with aortic and urinary bladder catheters. AP was increased by 10% in resting dogs by exposure to increased light and sound intensity (arousal) for 90 min. During arousal, urine flow (UV) and Na+ excretion (UNa+ V) correlated with AP (UV vs. AP, r = 0.12, P less than 0.05; UNa+ V vs. AP, r = 0.19, P less than 0.005; 17 trials in 7 dogs). Arousal did not affect the plasma concentration of atrial natriuretic factor, suggesting that this hormone did not contribute to the correlations between UV or UNa+ V and AP. Because arousal may induce an autonomically mediated antidiuresis, studies were repeated during autonomic ganglionic blockade with hexamethonium. During autonomic blockade, the correlations between UV or UNa+ V and AP were increased (UV vs. AP, r = 0.72; UNa+ V vs. AP, r = 0.72, P less than 0.001; 6 trials in 4 dogs). We conclude that the effect of pressure diuresis on UV and UNa+ V can be detected in the intact animal, during normal operation of all the mechanisms that control renal function. Furthermore, when autonomic reflexes are blocked, the pressure-diuresis mechanism is a major determinant of UV and UNa+ V.

Antarctic marine ecosystem management

ABSTRACTThis article describes a framework within which an initial strategy could be developed for managing commercial exploitation of marine living resources of the Southern Ocean, particularly of krill and fish, in accordance with Article II of the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR). Quantitative predictions involving multi–species models are needed to assess any indirect impacts of fish or krill exploitation, and also for management to restore depleted populations. This article recommends research to provide the knowledge necessary for the models (identifying key species, estimating their demographic status, and experimental interference), and suggests interim management action to delimit management areas, agree target levels for stock–size, and monitor stocks. Early efforts to model the fishing operation are particularly recommended.

Mycobacterium tuberculosis in a closed colony of baboons (Papio ursinus)

An outbreak of tuberculosis in a nonhuman primate colony involved 11 of 91 (12·1%) baboons ( Papio ursinus). Tuberculin tests identified 80%, X-ray screening 10% and throat swab bacteriology 30% of diseased animals. Cough was a misleading indicator of tuberculosis. Stress resulting from experimental interference with animals was unrelated to disease development. Twice as many females as males were attacked. Screening and prophylactic, therapeutic and preventive measures are discussed.