974 resultados para Stretch-break


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Item 1005-C

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Deficiencies in DNA repair have been hypothesized to increase cancer risk and excess cancer incidence is a feature of inherited diseases caused by defects in DNA damage recognition and repair. We investigated, using a case-control design, whether the double-strand break repair gene polymorphisms RAD51 5' untranslated region -135 G > C, XRCC2 R188H G > A, and XRCC3 T241M C > T were associated with risk of breast or ovarian cancer in Australian women. Sample sets included 1,456 breast cancer cases and 793 age-matched controls ages under 60 years of age, 549 incident ovarian cancer cases, and 335 controls of similar age distribution. For the total sample and the subsample of Caucasian women, there were no significant differences in genotype distribution between breast cancer cases and controls or between ovarian cancer cases and combined control groups. The crude odds ratios (OR) and 95% confidence intervals (95% CI) associated with the RAD51 GC/CC genotype frequency was OR, 1.10; 95% CI, 0.80-1.41 for breast cancer and OR, 1.22; 95% CI, 0.92-1.62 for ovarian cancer. Similarly, there were no increased risks associated with the XRCC2 GA/AA genotype (OR, 0.98; 95% CI, 0.76-1.26 for breast cancer and OR, 0.93; 95% CI, 0.69-1.25 for ovarian cancer) or the XRCC3 CT/TT genotype (OR, 0.92; 95% Cl, 0.77-1.10 for breast cancer and OR, 0.87; 95% CI, 0.71-1.08 for ovarian cancer). Results were little changed after adjustment for age and other measured risk factors. Although there was little statistical power to detect modest increases in risk for the homozygote variant genotypes, particularly for the rare RAD51 and XRCC2 variants, the data suggest that none of these variants play a major role in the etiology of breast or ovarian cancer.

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The initial disturbance amplitude has an effect on stretching jets that is not observed for capillary jet instability where gravitational acceleration is not significant. For inviscid and viscous fluids, gravity diminishes the effect that the initial amplitude has on jet length and its ability to prevent satellite formation. In stretching jets, not only the dimensionless frequency of the disturbance but also its initial amplitude must be known to properly study their satellite forming nature. Indirect methods of relating the applied disturbance energy to an initial velocity perturbation are not simple when the gravity parameter G is changing. When G A 0, the optimum disturbance frequency Omega(opt) and the initial disturbance amplitude are related, with Omega(opt) proportional to f (G) x In(1 /epsilon(nu)). Results from numerical simulations and experiments are presented here. (c) 2005 Elsevier Ltd. All rights reserved.

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Thixotropy is the characteristic of a fluid to form a gelled structure over time when it is not subjected to shearing, and to liquefy when agitated. Thixotropic fluids are commonly used in the construction industry (e.g., liquid concrete and drilling fluids), and related applications include some forms of mud flows and debris flows. This paper describes a basic study of dam break wave with thixotropic fluid. Theoretical considerations were developed based upon a kinematic wave approximation of the Saint-Venant equations down a prismatic sloping channel. A very simple thixotropic model, which predicts the basic theological trends of such fluids, was used. It describes the instantaneous state of fluid structure by a single parameter. The analytical solution of the basic flow motion and theology equations predicts three basic flow regimes depending upon the fluid properties and flow conditions, including the initial degree of jamming of the fluid (related to its time of restructuration at rest). These findings were successfully compared with systematic bentonite suspension experiments. The present work is the first theoretical analysis combining the basic principles of unsteady flow motion with a thixotropic fluid model and systematic laboratory experiments.

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Many tests of financial contagion require a definition of the dates separating calm from crisis periods. We propose to use a battery of break search procedures for individual time series to objectively identify potential break dates in relationships between countries. Applied to the biggest European stock markets and combined with two well established tests for financial contagion, this approach results in break dates which correctly identify the timing of changes in cross-country transmission mechanisms. Application of break search procedures breathes new life into the established contagion tests, allowing for an objective, data-driven timing of crisis periods.

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This paper demonstrates that the conventional approach of using official liberalisation dates as the only existing breakdates could lead to inaccurate conclusions as to the effect of the underlying liberalisation policies. It also proposes an alternative paradigm for obtaining more robust estimates of volatility changes around official liberalisation dates and/or other important market events. By focusing on five East Asian emerging markets, all of which liberalised their financial markets in the late, and by using recent advances in the econometrics of structural change, it shows that (i) the detected breakdates in the volatility of stock market returns can be dramatically different to official liberalisation dates and (ii) the use of official liberalisation dates as breakdates can readily entail inaccurate inference. In contrast, the use of data-driven techniques for the detection of multiple structural changes leads to a richer and inevitably more accurate pattern of volatility evolution emerges in comparison with focussing on official liberalisation dates.