The and molecular emission spectra are frequently observed simultaneously in plasmas containing nitrogen. Relative band intensities of these systems are very sensitive to a variation of the ratio and ...temperature. The spectrum, emitted between 3800 and 4000 A, has been used to measure rotational and vibrational temperatures, and to estimate the ratio when the electron temperature is known, in different plasma sources (Glidarc, ac discharge between tips). The proposed method is based on a point-to-point comparison of an experimentally measured spectrum with the computer-simulated one.
The present in vivo study was undertaken to evaluate the patency rate and histological appearance of 30 venous anastomoses and 30 carotid anastomoses in Wistar rats using a laser. An argon laser was ...used with the following parameters: power, 100 mW; time, 3 seconds; continuous mode; spot, 200 microns (fluence, 950 J/cm2; irradiance. 320 W/cm2). The macroscopic appearance and patency rate were evaluated at different postoperative intervals (30 days and 60 days). In the venous group, the patency rate was 100% with no saccular pseudo-aneurysm. In the arterial group, the patency rate was 93% with three saccular pseudo-aneurysms and two thromboses. Histological studies noted slight and transitory modifications of the media in the arterial group. In the venous group, the modifications appeared under the endothelium. Since the procedure was similar in both groups, the lack of pseudo-aneurysm formation in the venous group can be explained by a lower intravascular pressure.
Experimental investigations of the arc in MIG-MAG welding Zieliriska, S; Musiol, K; Pellerin, N ...
Trends in welding research : proceedings of the 7th International Conference, May 16-20, 2005, Callaway Gardens Resort, Pine Mountain, Georgia, USA,
01/2006
Journal Article
Shielding gases have a strong influence on the stability of the welding process. In particular, increase of carbon dioxide percentage in argon mixtures induces a shift of the transition current ...threshold between globular mode and spray mode. Observed effects on the arc shape are linked to the microstructural modifications of the anode tip during the MIG-MAG welding process as a function of the gas composition, and especially to the appearance or disappearance of a thick insulating oxide layer at the wire tip. Spectroscopic diagnostics of the welding arc are also necessary to understand the observed modifications of the metal transfer mode. An original diagnostic method allows to estimate the temperature and the electronic density distributions into the arc plasma with no particular hypothesis on its equilibrium state.
The present experiment was designed to assess daily fluctuations of visual discriminability, a function reflecting the resolution power of the visual sensitivity by measure of a differential ...threshold. Sixteen subjects underwent a visual discrimination threshold task (using the constant method) in a protocol allowing one point every 2h over the 24h period. The results show that the visual discrimination threshold is low in the morning and increases progressively over the day, reaching a first peak at 22:00. During the night, the same pattern occurs, with low threshold levels at the beginning of the night and high levels at the end. This profile is quite different from that of detection threshold variations, suggesting that the two visual functions are under the control of different underlying mechanisms. Two interpretations could account for this discrepancy. The first relates to different oscillators in the eye for detection and discrimination. The second refers to a possible linkage of visual discriminability with the sleep-wake cycle since threshold measures were systematically low (i.e., high resolution power) after long sleep periods. (Chronobiology International, 17(12), 187-195, 2000)
A circadian rhythm for visual sensitivity has been intensively assessed in animals. This rhythm may be due to the existence of a circadian clock in the mammalian eye, which could account for ...fluctuating sensitivity to light over the day in certain species. However, very few studies have been devoted to the human visual system. The present experiment was designed to assess a possible rhythm of visual sensitivity using a psychophysical method over the whole 24h period. Twelve subjects underwent visual detection threshold measures in a protocol that allowed one point every 2h. The results show that the visual detection threshold changes over the 24h period, with high thresholds in the morning, a progressive decrease over the day and the early night, and an increase during the last part of the night. These data suggest that a circadian rhythm influences visual sensitivity to mesopic luminance in humans. (Chronobiology International, 17(6), 795-805, 2000)
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