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A few hepatitis B virus (HBV) infections are characterized by the presence of HBV DNA in serum or liver tissue, or both, in the absence of detectable hepatitis B surface antigen (HBsAg) in serum. However, such infections have rarely been described previously in North American patients. In the present study, 31 hepatocellular carcinoma (HCC) patients from the United States and Canada who had no detectable HBsAg in their serum were studied. In these 31 HBsAg-negative HCC patients, HBV DNA was detected in HCC and/or in adjacent nontumorous liver tissue using nested polymerase chain reaction (PCR) in 5/9 (56%) patients from the United States and in 12/22 (55%) from Canada. The 17 HBV DNA-positive/HBsAg-negative patients from the United States and Canada included 9 without any serological markers for HBV and 8 with detectable antibodies to hepatitis B core antigen. In these patients, HBV genotype C was the most prevalent genotype (11/17; 64%). HBV genotypes have not been previously reported in HCC patients from North America. Replicative intermediate forms of HBV (covalently closed circular HBV DNA) were detected in 2/17 (12%) HBV DNA-positive/HBsAg-negative patients, indicating that at least two of these patients had actively replicating HBV infections. The use of tests to detect HBV DNA permitted the identification of HBV infections in HBsAg-negative HCC patients from North America. Among these patients, those with antibody to hepatitis C virus (HCV) would otherwise have been designated “HCV-associated HCCs” based on serological tests alone. These findings provide a new perspective on determining the possible viral etiologies of HCCs in North America. J. Med. Virol. 70: 20–26, 2003. © 2003 Wiley-Liss, Inc.

Determination of 129I activity of low-level waste has become important from the standpoint of radiation safety and environmental concern. The 129I generated from power plants could be released into the environment through the subsequent fuel reprocessing and waste disposal. In order to minimize this impact, the concentrations of 129I and some affiliated radionuclides in the wastes to be disposed of should be determined and put in compliance with the stipulated regulations. In this work, neutron activation analysis is proposed to determine 129I/127I and 129I in radwastes. The long-lived 126I, activated from 127I, is selected to replace 128I as an indicator of stable iodine. Long-term neutron irradiation and γ-ray counting are permitted and the related detection limit can be improved. In addition, the proposed method has related advantages of low-counting interferences and convenience for chemical operation over traditional methods; these make it a practical alternative for analyzing 129I in radwastes in a facility near a research reactor.

Modelling methodologies including a dynamic stress evolution are proposed in this work to characterize the relative stress-induced voiding (SIV) probability inside via of various Cu/low k interconnects. Seven patterns being representative of versatile IC design units are selected. It is demonstrated that our modelling approach can serve as a good method identifying the most troublesome layout units to inside-via SIV, and the results aligned well with the experimental data. From our studies, two kinds of layout styles when designed together are found detrimental: (1) the layout units with via(s) subjected to significant upper-metal edge confinement and (2) the one with via close to big vacancy sources.

Stress migration (SM) behavior found on various Cu/Low k interconnects is analyzed in this article. The simulation results demonstrate that the minimum stresses always occur on/near via bottom, which makes the dummy via insertion an effect way relieving SM induced circuit failure. A numerical index reflecting the bulk vacancy density evolution is developed from the simulated stress distribution and aimed at predicting the destination of the migrating vacancies driven by the thermally generated stress gradient of the interconnect system. Though still in its burgeoning stage, the simulated SM behavior using the index compared well against those experimentally collected data.

Integration of hepatitis B virus is thought to be an essential step in hepatitis B virus associated hepatocarcinogenesis. Mutations at nucleotides 1762 and 1764 in the hepatitis B virus, within a sequence encoding both the core promoter gene and the X gene, have been found frequently in patients with hepatocellular carcinoma. However, integration of these mutant sequences has not been reported to date. Methods. A 228-base pair segment of the hepatitis B virus core promoter gene was amplified from hepatocellular carcinomas and adjacent non-tumourous liver tissue by nested PCR and sequenced. Integration of hepatitis B virus into human genomic DNA was investigated using the ‘genome walking’ method. Results. Point mutations were found in both hepatitis B virus nucleotides 1762 and 1764 in 8 of 14 hepatocellular carcinoma tissues (57%) and in 11 of 14 adjacent non-tumourous liver tissues (79%). Three patients were evaluated using the ‘genome walking’ method; all were found to have hepatitis B virus DNA integrated in their hepatocellular carcinoma (two patients) and/or in their non-tumourous liver tissue (three patients). Integration occurred in all tissues near host genomic sites that are prone to integration. Hepatitis B virus was integrated at or near the hepatitis B virus DR1 site in all samples, and all contained truncated X gene sequences that have been reported to be capable of producing fusion transcripts with transactivation potential. Conclusions. Integrated hepatitis B virus DNA containing core promoter mutations at nucleotides 1762 and 1764 was found in hepatocellular carcinoma and/or adjacent non-tumourous liver tissue of three patients. These findings leave open the possibility that insertional mutagenesis or transactivation by fusion transcripts resulting from hepatitis B virus integration could play a role in hepatocarcinogenesis in some patients.

A complete set of test structures was developed to monitor the compounding effects of UV exposure, ion bombardment, electron shading and plasma charging in a HDP poly etcher. Electron shading-enhanced ion bombardment damage was observed in our experiments. We also found that UV exposure does enhance plasma charging damage.

From electrical simulations, the best performance dual damascene Cu/FSG integration scheme has been defined to be via first without etching stop layer and with thinnest possible sealing nitride layer. To realize this process, 0.16 /spl mu/m and 0.27 /spl mu/m (local and global interconnect) borderless via chains (100 K) with minimum 0.36 /spl mu/m pitched metal lines (10 cm) were used as test vehicles. Sacrificial layer filled process was then defined with its process window carefully studied. From good electrical results with clearly defined process window, it is concluded that the proposed integration scheme is suitable for sub-0.13 /spl mu/m technology node applications.