Effect of plasma surface modification on electrical conduction in polyethylene

High-density polyethylene films 50 μm thick were exposed to the downstream plasma flow of RF glow discharges in argon, hydrogen, or oxygen. It was found that many transvinylene and unreacted radicals remain after the argon or hydrogen plasma treatment, and that carbonyl groups are formed in the oxygen plasma treatment. The conduction current was smaller in the hydrogen-plasma treated samples and the samples exposed to oxygen or ozone after hydrogen-plasma treatment than in the untreated samples. Thermal pulse current measurements indicate that the treated surface layer traps electrons or holes and reduces the field strength at the electrode surface, thus suppressing further injection of electrons or holes.     

Relationship between grade and stage of renal pelvic and/or ureteral tumor and associated bladder tumor

The use of proxy respondents in surveys designed to provide population estimates of smoking prevalence offers an inexpensive way to obtain these data. The accuracy of this information is examined in analyzing data from tobacco use surveys of adults conducted in 22 North American communities as part of the National Cancer Institute's Community Intervention Trial for Smoking Cessation. Proxy-reported smoking status was obtained in a cross-sectional telephone survey conducted from August 1993 to January 1994 (n = 99,682). Self-reported smoking status was obtained from an in-depth interview of a sample of the respondents aged 25-64 years enumerated from the telephone survey (n = 31,417). Discrepancy rates were calculated by comparing the proxy-reported and self-reported smoking statuses of a given individual (n = 10,226). In both surveys, respondents were categorized as current smokers (those who currently smoke and have smoked at least 100 cigarettes in their lifetime), recent quitters (< or = 8 years since cessation), long-term quitters (> 8 years since cessation), and never smokers. The overall discrepancy rate between the self-report and the proxy report was 5.4%. Self-respondents who were black, Hispanic, Asian, recent quitters, or aged 25-34 years were more likely to have inconsistent proxy reports. The authors estimate that the screener interview underestimated the true smoking prevalence by 0.1% when they corrected for smoking status discrepancies. These results confirm that proxy-reported smoking status is an accurate and effective means to monitor populationwide smoking prevalence of adults.     

Differences of resected hepatocellular carcinoma with hepatitis B or C virus

BACKGROUND/AIMS: The purpose of this study was to clarify the clinicopathologic differences of hepatocellular carcinoma associated with the hepatitis B versus the hepatitis C virus. METHODOLOGY: One hundred and sixty-eight patients with resected hepatocellular carcinoma were tested for viral hepatitis. Ten (6%) had both the hepatitis B surface antigen and antibodies to the hepatitis C virus. Thirty-three (20%) had neither marker. Sixteen (9%) had only the hepatitis B surface antigen (group B), and 109 (65%) had only antibodies to the hepatitis C virus (group C). We compared groups B and C clinicopathologically. RESULTS: The mean tumor diameter was larger in group B than in group C (6.3 cm vs 3.4 cm), while group B patients were younger than group C (48 yrs vs 62 yrs, p<0.0001). Poor liver function, histologic cirrhosis and chronic active hepatitis were frequently found in group C. The 1- and 2-year tumor-free survival rates following surgery in group B were 67% and 33%, and those in group C were 73% and 49%. The 1-, 2-, and 3-year survival rates following surgery in group B were 78%, 68%, and 0%, while those in group C were 92%, 83%, and 76% (p=0.0189). CONCLUSIONS: Hepatocellular carcinoma with concomitant hepatitis B viral infection was found to present as larger tumors in younger patients with less severe liver dysfunction. Hepatocellular carcinoma with concomitant hepatitis C viral infection was often detected in follow-up studies when it was small.     

Pulsed laser focusing for triggering arc discharge in an arc welding system

In tungsten inert gas (TIG) arc welding systems, arc plasma is generated between the cathode (tungsten rod) and anode (workpiece).¹ Availability of a dependable technique for triggering arc discharge is indispensable for production processes using arc welding. Typical conventional triggering techniques include the high-frequency, high-voltage and touch-start methods. The high-frequency and high-voltage methods involve arc discharge being triggered through ionization of the gas present between the electrodes by means of a conventional high-frequency generator or high-voltage DC generator.² The high-frequency method, however, may possibly disrupt operation of peripheral computer systems, whereas the high-voltage method involves suitable electric circuits being arranged inside the power source to prevent high voltage-related accidents.^{2, 3} After the rod is lowered to make contact with the workpiece in the touch-start method, it is quickly withdrawn to trigger the arc. This method obviates the need for any power source other than the arc welding power source. An important advantage of the touch-start method therefore is its simplicity. When the rod is withdrawn, however, part of it (tungsten) may sustain melt-through to the workpiece in a way that adversely affects weld quality. This is a disadvantage of the touch-start method.₃     

The Potential of Fast Ignition and Related Experiments with a Petawatt Laser Facility

A model of energy gain induced by fast ignition of thermonuclear burn in compressed deuterium-tritium fuel, is used to show the potential for 300× gain with a driver energy of 1 MJ, if the National Ignition Facility (NIF) were to be adapted for fast ignition. The physics of fast ignition has been studied using a petawatt laser facility at the Lawrence Livermore National Laboratory. Laser plasma interaction in a preformed plasma on a solid target leads to relativistic self-focusing evidenced by x-ray images. Absorption of the laser radiation transfers energy to an intense source of relativistic electrons. Good conversion efficiency into a wide angular distribution is reported. Heating by the electrons in solid density CD₂ produces 0.5 to 1 keV temperature, inferred from the D-D thermo-nuclear neutron yield.