Splashing of tungsten-based anode during arc discharge.

A unique mechanism of splashing from a tungsten-based anode was identified during arc discharge. Splashing occurred by breakoff of a liquid metal column, which elongates after a local concavity formed on the molten anode surface. Blue-violet luminescence, emitted by cerium ions originating from additives in the tungsten-based anode, was captured before the concavity formation. The surface temperature exceeded the boiling point of the additives at the time of splashing. The measured droplet speeds suggested that an electromagnetic force contributes the high-speed ejections. Energy dispersive spectrometry mapping also exhibited a remnant of the additives on the longitudinal cross-section of the anode after arc discharge. Based on these experimental facts, the mechanism of anode splashing in arc discharge was deduced as follows: bubble formation of additives at temperatures above their boiling point, bubble bursting at the surface, micro-plasma jet generation, liquid-column elongation and breakoff under an electromagnetic force, and consequent high-speed droplet ejection.

Identification of the Dominant Factor for Droplet Ejection from a Tungsten Electrode during AC Tungsten Inert Gas Welding by Visualisation of Electrode Phenomena.

Droplet ejections from a molten tungsten electrode during alternating current tungsten inert gas (AC TIG) welding were observed successfully by a high-speed video captured at 75,000 fps. The welding conditions and timings that were likely to occur were investigated. The electrode surface temperature was also measured. A crater was formed on the surface of the electrode, and a droplet ejection occurred following the separation of the tip of the ridge growing from the centre of the crater. A series of droplet ejections occurred on a time scale of approximately 0.4 ms. Our results showed that the high temperature of the electrode surface was the common factor for droplet ejections. The dominant force for droplet ejection was discussed by estimating the balance of forces acting on the molten electrode surface. The pressure due to surface tension was the largest pressure at any time during the AC cycle, which decreased in the second half of the EP period. Our findings suggest that the surface tension was the dominant force for changing the electrode shape and that droplet ejections occurred when the surface tension decreased due to the increase in the electrode surface temperature.

Distribution of mycobacterial antigen based on differences of histological characteristics in pulmonary Mycobacterium avium infectious diseases--consideration of the extent of surgical resection from the pathological standpoint.

Quantitative assessment of mycobacterial antigens is very important to determine the surgical indication, as well as the area of resection for pulmonary Mycobacterium avium complex (MAC) infectious disease. However, at present, pathological assessment is only possible as a postoperative examination. We performed quantitative evaluation of mycobacterial antigens using lung tissues with MAC pulmonary infection obtained from surgical resection. The distribution of mycobacterial antigens was evaluated by immunohistochemical staining with monoclonal antibody for mycobacteria. In exudative reactions, many monocyte-lineage cells containing mycobacterial antigens were observed in alveoli, whereas the quantity of mycobacterial antigens was extremely decreased in proliferative reactions. Epithelioid cells or multinucleated giant cells contained mycobacterial antigens in necrotic granulomas. In solitary nodules with central necrosis, mycobacterial antigens were frequently observed, whereas they were rarely observed in solitary nodules without caseous necrosis. Mycobacterial antigens were not observed in the epithelial layer of bronchioles in any cases, although proliferative granulomas were notably observed in the developed lymphoid follicles in subepithelial lesions of bronchiole. Thus, exudative reactions or nodules with caseous necrosis indicate the possibility of numerous mycobacteria remaining in the pulmonary focus. Therefore, intraoperative histological assessment may help in the determination of the area of surgical resection. This is the first study to quantitatively evaluate mycobacterial antigens according to histological characteristics in MAC pulmonary disease.

Applicability of allele/genotype frequency from documented controls for case-control studies on genotypes among Japanese: MTHFR C677T as an example.

In a case-control study, controls have to be selected from the population where cases are identified. However, there is an idea to make common controls applicable for different case-control studies, which could reduce study costs. This study compared methylenetetrahydrofolate reductase C677T among subjects from different studies, to examine the applicability of combined subjects as controls. Case-control studies and cross-sectional studies with more than 100 Japanese controls or subjects were selected from PubMed in December 2008. Between 1996 and 2008, 31 eligible studies with 14,510 subjects in total were published; the 677T allele frequency varied from 0.300 to 0.438. The genotype frequencies were all in Hardy-Weinberg equilibrium. The average weighted with the number of subjects was 0.385. The 95% confidence interval (95%CI) of 10 studies did not include the weighted average. The study whose proximal limit of 95%CI was furthest from the weighted average was removed, and then the weighted average was recalculated. Through the process, 7 studies were excluded, resulting in the remaining 24 studies having a 95%CI including the weighted average (0.391) with 10,854 subjects. Of the 7 excuded studies, one was from patients enrolled in a clinical study (0.431), two were relatively isolated (0.300 and 0.438), two were published ten years ago (0.315 and 0.334), one was from a study whose allele frequency of female subjects was 0.382 (0.436), and one had a large sample size (0.360). This example demonstrated that the allele frequency of MTHFR 677T was in common among 24 out of 31 Japanese studies, suggesting that the calculated allele frequency could be used for Japanese case-control studies, whose cases are sampled in a general population.