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排序方式： 共有175条查询结果，搜索用时 15 毫秒
41.
It has been postulated that mitochondrially derived reactive oxygen species (ROS) play a major causative role in aging processes. The primary sources of these oxidants are believed to be complexes I and III of the electron transport chain, with little evidence supporting oxidant formation at complex II (succinate dehydrogenase). Mutation of a complex II protein has, however, been shown to cause increased oxidative stress and decreased life expectancy in the Caenorhabditis elegans mutant mev-1. A recent study by Yankovskaya and colleagues, in which the structure of Escherichia coli succinate dehydrogenase was determined, provides an explanation for these observations. Furthermore, these results suggest possible mechanisms by which electron leakage might occur at this site in the aged organism. 相似文献
42.
Murat Erkoc Haresh Gurnani Saibal Ray Mingzhu Jin 《Production and Operations Management》2023,32(1):207-226
This paper studies the interaction between two key quality management decisions—input conformance quality and inspection policy—and related wholesale and retail prices in a two echelon supply chain. Market demand depends on the retail price as well as the end-product conformance quality, which itself depends on the input quality and the inspection scheme. Consistent with previous empirical findings in the literature, we show that an increase in quality does not always result in higher prices for consumers due to the cost-lowering effect of better quality. We also show that a lower input quality may still result in higher end-product quality because of how it might incentivize more and/or better inspection. Any interaction between input quality and inspection policy becomes more pronounced in the decentralized system due to incentive asymmetry between the channel partners. This makes the adoption of a full-inspection policy more likely there compared to an integrated system. Indeed, while vertical competition due to decentralization results in higher prices for customers, it can also result in better quality of end products. Another interesting finding in the decentralized setting is that, somewhat counterintuitively, a player may indeed opt to bear a higher share of the penalty for defective products sold to consumers resulting in higher profits for the player. 相似文献
43.
Asim K. Dey Cuneyt G. Akcora Yulia R. Gel Murat Kantarcioglu 《Revue canadienne de statistique》2020,48(3):561-581
Cryptocurrencies and the underpinning blockchain technology have gained unprecedented public attention recently. In contrast to fiat currencies, transactions of cryptocurrencies, such as Bitcoin and Litecoin, are permanently recorded on distributed ledgers to be seen by the public. As a result, public availability of all cryptocurrency transactions allows us to create a complex network of financial interactions that can be used to study not only the blockchain graph, but also the relationship between various blockchain network features and cryptocurrency risk investment. We introduce a novel concept of chainlets, or blockchain motifs, to utilize this information. Chainlets allow us to evaluate the role of local topological structure of the blockchain on the joint Bitcoin and Litecoin price formation and dynamics. We investigate the predictive Granger causality of chainlets and identify certain types of chainlets that exhibit the highest predictive influence on cryptocurrency price and investment risk. More generally, while statistical aspects of blockchain data analytics remain virtually unexplored, the paper aims to highlight various emerging theoretical, methodological and applied research challenges of blockchain data analysis that will be of interest to the broad statistical community. The Canadian Journal of Statistics 48: 561–581; 2020 © 2020 Statistical Society of Canada 相似文献
44.
45.
Sukru Anıl Toygar Derya Kara Mehmet Kırlıoğlu 《Journal of social service research》2020,46(2):264-272
AbstractThe aim of this article is to examine the health care employees’ attitudes toward women in health care organizations in Turkey. It was measured using a 25-item scale by Spence, Helmreich, and Stapp (1973). The study was conducted on 541 employees: 279 males and 262 females. Structural equation model (SEM) was applied to analyze the relationship between gender, marital status, and income and attitudes toward woman. The result of this analysis showed that the relations between gender, marital status, and income and attitudes toward woman were statistically significant. All three hypotheses were statistically supported. This result indicated that employees’ marital status and (monthly) income significantly predicted their scores of attitudes toward woman in a positive direction. Besides, employees’ gender significantly predicted their scores of attitudes toward woman in an inverse direction. Future research can focus on investigating the effects of the attitudes toward women on other elements (e.g., performance, motivation, job satisfaction) or a wider sample to reach more generalized results. 相似文献
46.
Turgay Ayer Mehmet U. S. Ayvaci Zeynal Karaca Jan Vlachy 《Production and Operations Management》2019,28(3):740-758
Health information exchanges (HIEs) are expected to improve poor information coordination in emergency departments (EDs); however, whether and when HIEs are associated with better operational outcomes remains poorly understood. In this work, we study HIE and length of stay (LOS) relationship using a large dataset from the Healthcare Cost and Utilization Project consisting of about 7.4 million treat‐and‐release visits made to 63 EDs in Massachusetts. Overall, we find that HIE adoption is associated with a 10.2% reduction in LOS and the percentage reduction increases to 14.8% when the hospital is part of an integrated health system or to 21.0% when a patient has a previous visit to an HIE‐carrying hospital. We further find that (i) teaching hospitals benefit more from HIE adoption compared with non‐teaching hospitals, (ii) patients with severe or multiple comorbid conditions spend less time in the ED under HIE presence. Together, these results imply that (i) HIE adoption reduces overall ED LOS, (ii) wider HIE adoption would scale up the benefits for individual hospitals, (iii) magnitude of the association between HIE and LOS is higher when financial incentives for HIE adoption are stronger (e.g., integrated health systems), and (iv) the size of the reduction depends on certain contextual moderating factors. Given that HIEs are a key component of healthcare delivery and ongoing reforms, we believe that our findings have important implications and may inform policymakers regarding the nationwide HIE adoption. 相似文献
47.
This paper develops a dyadic supply chain model with one buyer who contracts the manufacturing of a new product to a supplier. Due to the lack of experience in manufacturing, the extent of supply risk is unknown to both the buyer and supplier before the time of contract. However, after the contract is accepted, the supplier may invest in a diagnostic test to acquire information about his true reliability, and use this information when deciding on a process improvement effort. Using this setting, we identify both operational and strategic benefits and costs of the diagnostic test. Operationally, it helps the supplier to take the first‐best level of improvement effort, which would increase efficiency of the total supply chain. Strategically, it enables the buyer to reduce the agency costs associated with implementing process improvement on the supplier. Besides these benefits, diagnostic test increases the degree of information asymmetry along the supply chain. This in turn provides the supplier with proprietary information, whose rent would be demanded from the buyer in equilibrium. Benefit‐cost analysis reveals two key factors in determining the value of diagnostic test: (i) degree of endogenous information asymmetry between supply chain firms, and (ii) the relative cost of a diagnostic test with respect to process improvement cost. Our results indicate that when both are high, the mere presence of a diagnostic test can result in less reliable supply chain. This implies that when incentives are not properly aligned, information asymmetry amplified due to diagnostic test neutralizes all its benefits. 相似文献
48.
Murat Demirci 《Economic inquiry》2019,57(3):1367-1391
I analyze how visa policies affect international students' transition to the U.S. labor market. The Optional Practical Training (OPT) program permits international students to work via a student visa for a limited period after graduation before obtaining a work visa—an uncertain process due to the binding visa cap. I find that the extension in the length of OPT terms for students in science, technology, engineering, and mathematics (STEM) increases their likelihood of initially staying in the United States and using OPT. This result suggests that uncertainties about obtaining work visas hinder international STEM students' participation in the U.S. labor market. (JEL J61, K37, I23). 相似文献
49.
In this study, new unbiased and nonlinear estimators based on order statistics are proposed for the family of symmetric location-scale distributions and these estimators can be computed from both uncensored and symmetric doubly Type II censored samples. In addition, other relevant unbiased estimators are proposed to estimate standard deviations of these new estimators. A simulation study has been performed to evaluate the performance of the new estimators compared to BLU estimators for small sample sizes. As a result of the simulation study, the new estimators proposed for the location-scale family in general performed nearly as good as BLU estimators. Furthermore, the computational advantage of the proposed estimators over BLU and ML estimators are worthy of notice. In addition, these new estimators have been applied to real data, and the estimation results obtained have been compatible with those of BLUE methods. 相似文献
50.
Most of today’s complex systems and processes involve several stages through which input or the raw material has to go before the final product is obtained. Also in many cases factors at different stages interact. Therefore, a holistic approach for experimentation that considers all stages at the same time will be more efficient. However, there have been only a few attempts in the literature to provide an adequate and easy-to-use approach for this problem. In this paper, we present a novel methodology for constructing two-level split-plot and multistage experiments. The methodology is based on the Kronecker product representation of orthogonal designs and can be used for any number of stages, for various numbers of subplots and for different number of subplots for each stage. The procedure is demonstrated on both regular and nonregular designs and provides the maximum number of factors that can be accommodated in each stage. Furthermore, split-plot designs for multistage experiments with good projective properties are also provided. 相似文献