533 research outputs found
The etiology of esophageal cancer in high- and low- risk areas of Jiangsu province, China
No full text [Background]Esophageal cancer (EC) remains one of the most common and fatal malignancies worldwide. The geographic variation in EC occurrence is striking, and China is an area with one of the highest incidences of EC. A number of epidemiological studies have been conducted toward EC in the past decades, results suggested that tobacco smoking, alcohol drinking, unhealthy dietary factors and chronic injuries of the esophageal mucosa are important in the development of this disease. Genetic polymorphisms in enzymes involved in metabolism of carcinogens may also influence individual susceptibility. However, the effects of major lifestyle and hereditary risk factors on the development of EC remain poorly understood in China. Moreover, little attention has been paid to the etiological heterogeneity between similar areas with great risk gradient. [Methods]From 2003 to 2007, a large population-based case-control study of EC has been conducted in a selected high-risk area and a selected low-risk area of Jiangsu Province, one of the highest cancer incidence areas in China. In total, 1,520 cases and 3,879 controls were recruited. In this thesis, we evaluated the role of major lifestyle factors such as tobacco smoking, alcohol drinking and dietary factors, as well as inherited determinants including family history of cancer and genetic polymorphisms of alcohol-metabolizing related genes on the risk of EC. In addition, we investigated how much of the risk gradient between two areas could be explained by variation in the distributions of major risk factors. [Results] Tobacco smoking and alcohol drinking moderately increased the risk of EC, while the positive associations were only found among men but not among women. Dietary factors were observed to play important roles in the development of EC. Specific dietary habits i.e., fast eating speed, and hot eating and/or drinking substantially elevated EC risk and could explain more than 20% of EC cases each. High intake of salty foods and fried foods, low consumption of raw garlic were also observed to increase the risk of EC. In addition to environmental and lifestyle factors, we confirmed that a positive family history can significantly increase EC risk, and found the inheritance may modify the effect of some unhealthy lifestyles. Moreover, we further explored the relationship between EC and single nucleotide polymorphismsof ADH1B, ADH1C and ALDH2 genes. Results showed that the slow metabolizing ADH1B G allele, ADH1C G allele and ALDH2 A allele significantly increased EC risk among moderate-to-heavy alcohol drinkers, and a significant interaction was observed between ALDH2 gene and alcohol consumption. Lastly, we found that more than 60% of EC cases could be attributable to major lifestyle risk factors in the study population; furthermore, dissimilar distribution of several lifestyle factors, together with variations of hereditary factors may be largely responsible for the incidence difference between two study areas. [Conclusion]The findings in this thesis confirm that unhealthy lifestyles including smoking, alcohol drinking and some dietary factors are the predominant risk factors of EC in China, and a large proportion of incidence difference between regions at varying risk could be attributed to the different prevalence of lifestyle factors. As most of the identified risk factors are modifiable, these could be translated into risk reduction prevention programs in China, and a substantial proportion of new EC cases are expected to be prevented by eliminating or avoiding these risk factors in the population. </p
What Does the Yield Curve Tell Us About Exchange Rate Predictability?
Get PDFThis paper uses information contained in the cross-country yield curves to test the asset-pricing approach to exchange rate determination, which models the nominal exchange rate as the discounted present value of its expected future fundamentals. Research on the term structure of interest rates has long argued that the yield curve contains information about future economic activity such as GDP growth and inflation. Bringing this lesson to the international context, we extract the Nelson-Siegel (1987) factors of relative level, slope, and curvature from cross-country yield differences to proxy expected movements in future exchange rate fundamentals. Using monthly data between 1985-2005 for the United Kingdom, Canada, Japan and the US, we show that the yield curve factors indeed can explain and predict bilateral exchange rate movements and excess currency returns one month to two years ahead. Out-of-sample analysis also shows the yield curve factors to outperform a random walk in forecasting short-term exchange rate returns.
The genetic diversity and geographical separation study of Oncomelania hupensis populations in mainland China using microsatellite loci
Get PDF© 2016 Guan et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. The attached file is the published version of the article.NHM Repositor
Some sequential estimation problems in logistic regression models
No full textLet ({\bf X}\sb{i},Y\sb{i}), i = 1,2,\cdots, be a random sample satisfying a logistic regression model; that is, for each i, log(P(Y\sb{i} = 1\vert{\bf X}\sb{i})/P(Y\sb{i} = 0\vert{\bf X}\sb{i})\rbrack = {\bf X}\sbsp{i}{T}\beta\sb0, where Y\sb{i}\in\{0,1 {\bf X}\sb{i}\in{\bf R}\sp{p} and \beta\sb0\in{\bf R}\sp{p} is the unknown parameter vector of the logistic regression model. It is known that \sqrt{n}(\\beta\sb n-\beta\sb0){\buildrel{\cal L}\over{\longrightarrow}} N(0\sb p,\Sigma\sp{-1}), where \\beta\sb n is a MLE of \beta\sb0 and \Sigma\sp{-1} is the Fisher information matrix. If is known then R\sb d=\{Z\in{\bf R}\sp p:n(Z-\\beta\sb n)\sp T\Sigma(Z-\\beta\sb n) \le n\lambda d\sp2\} defines a confidence ellipsoid for \beta\sb0, with maximum axis and P(\beta\sb0\in R\sb d)\approx 1 - \alpha provided n\ge a\sp2/(\lambda d\sp2), where is the smallest eigenvalue of and a satisfies P(\chi\sp2(p)\le a\sp2) = . If is unknown then usually will be unknown. Hence, there is no fixed sample size that can be used to construct a confidence ellipsoid with prescribed accuracy and confidence level. In this work, a sequential procedure is proposed to overcome this difficulty. The procedure is shown to be asymptotically consistent and efficient. That is to say, as d approaches 0 the coverage probability converges to the required confidence level and the ratio of the expected sample size to the unknown best fixed sample size converges to 1. Similar asymptotic properties for fixed proportional accuracy problems and for two stage procedures have also been obtained.Made available in DSpace on 2011-05-07T13:09:32Z (GMT). No. of bitstreams: 2
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Some sequential estimation problems in logistic regression models
No full textLet ({\bf X}\sb{i},Y\sb{i}), i = 1,2,\cdots, be a random sample satisfying a logistic regression model; that is, for each i, log(P(Y\sb{i} = 1\vert{\bf X}\sb{i})/P(Y\sb{i} = 0\vert{\bf X}\sb{i})\rbrack = {\bf X}\sbsp{i}{T}\beta\sb0, where Y\sb{i}\in\{0,1 {\bf X}\sb{i}\in{\bf R}\sp{p} and \beta\sb0\in{\bf R}\sp{p} is the unknown parameter vector of the logistic regression model. It is known that \sqrt{n}(\\beta\sb n-\beta\sb0){\buildrel{\cal L}\over{\longrightarrow}} N(0\sb p,\Sigma\sp{-1}), where \\beta\sb n is a MLE of \beta\sb0 and \Sigma\sp{-1} is the Fisher information matrix. If is known then R\sb d=\{Z\in{\bf R}\sp p:n(Z-\\beta\sb n)\sp T\Sigma(Z-\\beta\sb n) \le n\lambda d\sp2\} defines a confidence ellipsoid for \beta\sb0, with maximum axis and P(\beta\sb0\in R\sb d)\approx 1 - \alpha provided n\ge a\sp2/(\lambda d\sp2), where is the smallest eigenvalue of and a satisfies P(\chi\sp2(p)\le a\sp2) = . If is unknown then usually will be unknown. Hence, there is no fixed sample size that can be used to construct a confidence ellipsoid with prescribed accuracy and confidence level. In this work, a sequential procedure is proposed to overcome this difficulty. The procedure is shown to be asymptotically consistent and efficient. That is to say, as d approaches 0 the coverage probability converges to the required confidence level and the ratio of the expected sample size to the unknown best fixed sample size converges to 1. Similar asymptotic properties for fixed proportional accuracy problems and for two stage procedures have also been obtained.U of I OnlyETDs are only available to UIUC Users without author permissio
A new look at the pathogenesis of asthma
No full textAsthma is an inflammatory disorder of the conducting airways that has strong association with allergic sensitization. The disease is characterized by a polarized Th-2 (T-helper-2)-type T-cell response, but in general targeting this component of the disease with selective therapies has been disappointing and most therapy still relies on bronchodilators and corticosteroids rather than treating underlying disease mechanisms. With the disappointing outcomes of targeting individual Th-2 cytokines or manipulating T-cells, the time has come to re-evaluate the direction of research in this disease. A case is made that asthma has its origins in the airways themselves involving defective structural and functional behaviour of the epithelium in relation to environmental insults. Specifically, a defect in barrier function and an impaired innate immune response to viral infection may provide the substrate upon which allergic sensitization takes place. Once sensitized, the repeated allergen exposure will lead to disease persistence. These mechanisms could also be used to explain airway wall remodelling and the susceptibility of the asthmatic lung to exacerbations provoked by respiratory viruses, air pollution episodes and exposure to biologically active allergens. Variable activation of this epithelial-mesenchymal trophic unit could also lead to the emergence of different asthma phenotypes and a more targeted approach to the treatment of these. It also raises the possibility of developing treatments that increase the lung's resistance to the inhaled environment rather than concentrating all efforts on trying to suppress inflammation once it has become established.<br/
The systems silicon-aluminum - oxygen-nitrogen - yttrium(3) aluminum(5) oxygen(12) and silicon-aluminum - oxygen-nitrogen-cordierite: Sintering and grain growth.
No full textA complete study on sintering and grain growth has been conducted in the two silicon nitride systems: SiAlON-YAG (UAlO) and SiAlON-cordierite (MgAlSiO). SiAlON in this study is a solid solution of SiN with AlO. Extensive kinetic characterization on densification, \\alpha \o \\beta phase transformation and grain growth has been obtained with respect to sintering temperature and time, SiAlON composition, and liquid viscosity and content. Excellent sinterability has been demonstrated in both SiAlON-YAG and SiAlON-cordierite systems, especially in the former system. Full densification can be attained at 1500C, which is 150C lower than most contemporary cases. The result is consistent with the relatively low liquid forming temperature in the system, 1300C, measured by dilatometer. Phase transformation, which is always completed behind densification, is not entirely required to achieve full density. The lag between the two reactions depends strongly on the liquid content and the liquid viscosity in the system. Because of the solution reprecipitation characteristics, phase transformation can lead microstructural refinement in the early stage of grain growth. The extent of refinement, however, is very sensitive to the phase content in the starting SiN powders. A growth exponent, n, of 3 has been observed for the growth in (001) (length) and (210) (width) directions of the elongated grains. The growth rate constants measured in the length direction is about two order of magnitude higher than that in the width direction. This is the first result which quantifies the growth anisotropy. The growth anisotropy is believed to be introduced by the significant differences in structure and solute diffusivity at the growth front in the two directions. The aspect ratio of grains increases initially with increasing grain size. It approaches a plateau when the grain size is near 0.8 m and remains basically unchanged with further grain size increase. The plateau value of the aspect ratio increases with increasing liquid viscosity and liquid content of the system. Solute diffusion in the liquid is the rate controlling mechanism during sintering of silicon nitride ceramics. The conclusion is supported by the kinetic characteristics, the measured activation energies (586-753 KJ/mol), and repeated consistent correlation with the model prediction based on diffusion mechanism. (Abstract shortened with permission of author.)PhDMaterials scienceUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/161808/1/8812912.pd
El uso del software HistCite para identificar artículos significativos en búsquedas por materias en la Web of Science
Get PDFHistCiteTM is a large-scale computer tool for mapping science. Its power of visualization combines
the production of historiographs on the basis of the analysis of co-citations of documents, with the
use of bibliometrics specific indicators. The objective of this article is, to present the advantages of
the new bibliometrics configuration of HistCiteTM (2004) when identifying articles to analyze the
histograms that produces HistCiteTM, in terms of cumulative advantage and aging of the citations
to do a comparative study of the results of HistCiteTM, in its indicators of amplitude and recognition.
Also is examined its treatment of the sampling problems, by formalizing the question of
Kendall
Thermal Modelling of the Ventilation and Cooling inside Axial Flux Permanent Magnet Generators
Get PDFAxial flux permanent magnet generators are of particular interest for power generation in harsh and confined conditions. Due to their compactness and high power density, the ventilation and cooling inside axial flux permanent magnet generators have becoming increasingly important for further performance improvement. This thesis describes the developments of a lumped parameter, thermal modelling technique for axial flux permanent magnet generators. The main aim of this research is to develop a fast and accurate thermal modelling tool which can be used for rapid machine design and ultimately, to replace complex and time consuming CFD analyses in the machine design process.
The thesis illustrates the construction of a generic thermal equivalent circuit, which comprises of conductive and convective sub-circuits, to model the conduction and convection heat transfers and temperature distributions in the radial and axial directions, within these machines. The conduction heat transfer between the solid components of these electrical machines is modelled by an annulus conductive thermal circuit derived from previous researchers; whereas, for convection heat transfer between the working fluid (air) and solids, the author has developed two convective thermal circuits, which are demonstrated as the Temperature Passing Method (TPM) and Heat Pick-up method in (HPM) in the thesis. Several case studies were designed to investigate the validity and accuracy of these thermal sub-circuits with both steady and transient boundary conditions. Since all the thermal impedances and capacitances used in the thermal circuits are in dimensionless form, the developed generic thermal equivalent circuit is capable of performing thermal simulations for axial flux generators of different sizes and topologies. Furthermore, special correction factors were introduced into the developed generic thermal equivalent circuit, to take into account the heat transfer in the circumferential direction in axial flux machines.
The thesis also demonstrates how the heat transfer in the stator windings is modelled in the generic thermal equivalent circuit. Two analytical models, which are the Simple Concentric Model (SCM) and Concentric-annulus Layer Model (CLM) were developed, for the evaluation of the thermal resistances of the stator windings. The results evaluated from these analytical models were validated by several numerical models and experimental results of two-phase materials published by previous researchers.
Lastly, experimental validation of the lumped parameter thermal equivalent circuit model and CFD simulations was conducted. Heat transfer coefficient measurements were carried out on two separate test rigs, which were a simplified single-sided axial flux machine test rig and a large-scale low speed axial flux machine. The experimental results were compared with the numerical results obtained from both the lumped parameter and CFD models. Good agreement between the experimental, lumped parameter model and CFD results were found. These indicate that the developed generic thermal circuit is potentially capable of replacing CFD analyses in the axial flux machines design process
The Google Book search settlement: A law and economics analysis
Get PDFBeginning in December 2004 Google has pursued a new project to create a book search engine (Google Book Search). The project has released a storm of controversy around the globe. While the supporters of Google Book Search conceive the project as a first reasonable step towards unlimited access to knowledge in the information age, its opponents fear profound negative effects due to an erosion of copyright law. Our law and economics analysis of the Book Search Project suggests that – from a copyright perspective – the proposed settlement may be beneficial to right holders, consumers, and Google. For instance, it may provide a solution to the still unsolved dilemma of orphan works. From a competition policy perspective, we stress the important aspect that Google’s pricing algorithm for orphan and unclaimed works effectively replicates a competitive Nash-Bertrand market outcome under post-settlement, third-party oversight.Book Rights Registry; Competition Policy; Copyright; Fair Use; Google Book Search; Library Program; Orphan Works
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