Homogeneous Strain Introduction Using Reciprocation Technique in High-Pressure Sliding

Metallurgical and Materials Transactions A - This study examines strain distribution occurring in the high-pressure sliding (HPS) processing for rods of pure Al and an AZ61 alloy. The strain...     

Dose-dependent induction of both pepsinogen-altered pyloric glands and adenocarcinomas in the glandular stomach of C3H mice treated with N-methyl-N-nitrosourea

BACKGROUND: Cigarette smoking has been shown to increase oxidative DNA damage in human sperm cells. Assessment of the role of cigarette smoking in the etiology of childhood cancer has focused primarily on the effect of maternal smoking. Similar studies in relation to paternal smoking, however, have been inconclusive. Few studies have evaluated the effect of paternal smoking in the preconception period, and most of these could not disentangle the effects of paternal from maternal smoking. PURPOSE: We investigated the relationship of paternal smoking, particularly in the preconception period, with childhood cancer among offspring of the nonsmoking mothers. METHODS: We conducted a population-based, case-control study in Shanghai, People's Republic of China, where the prevalence of smoking is high among men but extremely low among women. The study included 642 childhood cancer case patients (<15 years of age) and their individually matched control subjects. Information concerning parental smoking, alcohol drinking, and other exposures of the index child was obtained by direct interview of both parents of the study subjects. Odds ratios (ORs), derived from conditional logistic regression models, were used to measure the association between paternal smoking and risk of childhood cancers. RESULTS AND CONCLUSIONS: Paternal preconception smoking was related to a significantly elevated risk of childhood cancers, particularly acute leukemia and lymphoma. The risks rose with increasing pack-years of paternal preconception smoking for acute lymphocytic leukemia (ALL) (P for trend = .01), lymphoma (P for trend = .07), and total cancer (P for trend = .006). Compared with children whose fathers had never smoked cigarettes, children whose fathers smoked more than five pack-years prior to their conception had adjusted ORs of 3.8 (95% confidence interval [CI] = 1.3-12.3) for ALL, 4.5 (95% CI = 1.2-16.8) for lymphoma, 2.7 (95% CI = 0.8-9.9) for brain tumors, and 1.7 (95% CI = 1.2-2.5) for all cancers combined. Statistically significant increased risks of cancer were restricted to children under the age of 5 years at diagnosis or those whose fathers had smoked during all of the 5 years prior to conception. IMPLICATIONS: Further studies are needed to confirm the association of paternal smoking with increased risk of cancer in offspring, to clarify the pattern of risks in relation to the timing of cigarette smoking, and to elucidate the biologic mechanism involved in predisposing the offspring to cancer. For example, it may be that paternal smoking induces prezygotic genetic damage that, in turn, acts as the predisposing factor.     

Monoclonal development of squamous cell carcinomas from polyclonal papillary or nodular hyperplasias in the forestomach of C3H/HeN<-->BALB/c chimeric mice treated with N-methyl-N-nitrosourea or diethylnitrosamine

The clonality of epithelial proliferative lesions of forestomach carcinogenesis was immunohistochemically investigated in C3H/HeN<-->BALB/c chimeric mice using a specific antibody to C3H strain specific antigen (CSA) and as well as in terms of microsatellite DNA polymorphism patterns. The C3H/HeN<-->BALB/c chimeric mice were produced by an aggregation procedure. Male chimeric, C3H/HeN, and BALB/c animals were given N-methyl-N-nitrosourea (MNU) 0.5 mg/mouse once a week for a total of 10 times by intragastric intubation or 30 p.p.m. diethylnitrosamine (DEN) in their drinking water for 20 weeks. Those treated with MNU were killed at weeks 11, 25 and 45 and with DEN at week 35. Normal chimeric forestomach epithelium was found to demonstrate mixtures of epithelial cell groups composed of either CSA positive or negative cells. The same was the case for all simple hyperplasias. Papillary and nodular (PN) hyperplasias increased with time even after cessation of MNU treatment and many of them consisted of both CSA positive and negative cell groups. In one case, a CSA positive and a negative cancer were observed to have developed independently in the same PN-hyperplasia consisting of both parental cell types. In 28 tumor bearing chimeric mice, all squamous cell carcinomas (SCCs) were composed entirely of either CSA positive or negative tumor cells. However, in two animals with advanced CSA positive cancers and negative cancers, tiny cancer nests composed of both parental type cells were found in association. Microsatellite DNA polymorphism patterns of DNAs sampled from histological sections completely conformed with the outcomes of immunohistochemical staining. The results suggest that PN-hyperplasias are aggregates (polyclonal) of preneoplastic changes from which monoclonal SCCs are derived. Polyclonal cancers may also arise secondarily at low incidence during progression, due to two or more lesions coalescing.     

Surface-borehole electric potential survey in layered media and its applications

The method in which a source is set on the surface and electric potential is received in the borehole is called surface-borehole electric potential technique. Technique of surface-borehole electric potential was employed to study electric response of layered formation. The electric potential was obtained by solving Poisson equation with finite difference method. In the course of calculation, forward modeling with finite difference method was realized by adopting bandwidth non-zero storage technique and the incomplete Cholesky conjugate gradient method. The results show that method of surface-borehole can acquire anomalous electric potential corresponding to geo-electric layers. In addition, application of appropriate mathematical operator can improve the resolution. Moreover, overburden low resistivity layers have severe influence on measuring results of surface-borehole electric potential. However, bottom low resistivity layers play a positive role in the measurement.     

Experimental observation of creep damage evolution in seam-welded elbows of mod. 9Cr-1Mo steel

Seam-welded elbows and straight pipe of the same size as actual high temperature reheat piping for boiler applications were manufactured, and internal pressure creep testing was conducted. Uniaxial creep testing was also performed in order to compare creep damage behaviours. Comparing the observed creep damage evolution and stress analysis results, a creep damage estimation method was discussed. Creep damage distribution varied depending on ovality in the cross sections of the seam-welded elbows. It is important that FEM models for creep analysis incorporate measurement results for the cross-sectional shape of seam-welded elbows. Using the nominal stress of the specimens and the average creep rupture data from small size uniaxial welded joint tests, a simplified prediction method was discussed, which is applicable to creep rupture time prediction for both large creep specimens and seam-welded elbows.     

Developing the geothermal resources map of Iran

Geothermal exploration involves a high degree of uncertainty and financial risk, and requires reliable exploration data to constrain development decisions. The paper describes a geothermal exploration and resource identification method that is based on building a map of potential geothermal resource areas by combining geological, geochemical and geophysical datasets; it is a powerful tool for visualizing new and existing data during decision-making processes. By performing suitability analysis and geothermal area identification, and by establishing criteria to define geothermal resources with development potential, a map of Iran was constructed highlighting 18 promising areas.     

Development of aberrant crypt foci involves a fission mechanism as revealed by isolation of aberrant crypts

Morphological analysis of isolated colonic crypts in rats, postnatally, indicated that the crypts reproduce themselves by a fission mechanism, the division beginning at the crypt base and proceeding upwards until there are two separate crypts. Occasionally, before the separation is complete, a second fission process starts on one or both sides of a bifurcating crypt and a triple-branched or quadruple-branched crypt results. Analysis of isolated aberrant crypt foci (ACF) in rats treated with 1,2-dimethylhydrazine revealed that the development of ACF consisting of multiple crypts is also due to a fission mechanism. Initially, an indentation appears at the base of a single ACF crypt, with subsequent formation of a bifurcation and eventual crypt division.     

Growth characteristics in the initial stage of micrometastasis formation by bacterial LacZ gene-tagged rat prostatic adenocarcinoma cells

In a previous study we observed that protein tyrosine phosphorylation was significantly diminished in the focal adhesions of human fibroblasts attached on a hydrophobic surface in comparison with hydrophilic glass. This result raises the possibility that the tyrosine phosphorylation pathway may be involved in the regulation of cell-biomaterial interaction. To learn more about the interaction of anchorage-dependent cells with biomaterials, four different materials with wettability ranging from hydrophilic (water contact angle 25 degrees) to hydrophobic (water contact angle 111 degrees) were investigated, i.e. clean glass (glass), aminopropylsilane (APS), octadecylsilane (ODS) and silicone (SI). Immunofluorescence microscopy revealed increased stress formation and fibronectin (FN) receptor-rich focal adhesions for fibroblasts attached on more hydrophilic surfaces (glass and APS) in comparison to the relatively hydrophobic materials (ODS and SI). Phosphorylation of tyrosine residues, also studied by immunofluorescence microscopy, was considerably higher on glass and APS, lower for ODS, negligible for SI, and was found to colocalize with FN receptor-rich focal adhesions. Preadsorption of FN tended to restore cell adhesion and spreading on the hydrophobic ODS and SI. Quantitative data on cell proliferation and tyrosine phosphorylation showed moderate wettable material maximum values for APS, followed by glass. ODS and SI, demonstrating a non-linearity of these parameters with the wettability of materials. Interestingly, the preadsorption of FN increased both parameters, particularly for the hydrophobic materials ODS and SI. Phosphorylation of tyrosine on FN-coated substrata was corroborated by the accessibility of binding sites estimated by ELISA using polyclonal and monoclonal FN antibodies. Our results suggest that measurement of the phosphotyrosine activity of cells may be a sensitive parameter for the ability of biomaterials to support the attachment and proliferation of cells.     

Creep degradation in welds of Mod.9Cr-1Mo steel

Creep life assessment technology has not yet been developed for Mod.9Cr-1Mo steel welded joints due to the unique degradation and failure mechanisms in the heat affected zone. Nevertheless, there is strong demand from power plant operators for the development of nondestructive damage detection and life assessment technology for weldments of this steel. In this study creep rupture testing using a large-size welded joint was conducted, and creep and damage detection tests were carried out to elucidate the degradation mechanism. Also the microstructure and hardness changes in the heat affected zones of the welds were investigated to clarify the degradation mechanisms of such welds in comparison with base metal during creep. In general, the changes in hardness distribution along the welds were difficult to correlate with the life consumption, although degradation in welds due to creep was successfully detected. Accordingly, a new approach to degradation evaluation and creep life assessment by hardness measurement method for Mod.9Cr-1Mo steel welds is proposed.