Physiologically-Based Pharmacokinetic Modeling of a Mixture of Toluene and Xylene in Humans

A physiologically-based pharmacokinetic (PBPK) model for a mixture of toluene (TOL) and xylene (XYL), developed and validated in the rat, was used to predict the uptake and disposition kinetics of TOL/XYL mixture in humans. This was accomplished by substituting the rat physiological parameters and the blood:air partition coefficient with those of humans, scaling the maximal velocity for hepatic metabolism on the basis of body weight^0.75, and keeping all other model parameters species-invariant. The human TOL/XYL mixture PBPK model, developed based on the quantitative biochemical mechanism of interaction elucidated in the rat (i.e., competitive metabolic inhibition), simulated adequately the kinetics of TOL and XYL during combined exposures in humans. The simulations with this PBPK model indicate that an eight hour co-exposure to concentrations that remain within the current threshold limit values of TOL (50 ppm) and XYL (100 ppm) would not result in significant pharmacokinetic interferences, thus implying that data on biological monitoring of worker exposure to these solvents would be unaffected during co-exposures.     

The World Wide Web as a public relations medium: the use of research, planning, and evaluation in web site development

The World Wide Web is viewed as a desirable medium for public relations by many organizations. Given the evolving nature of the Web and the mixed findings about commercial successes of Web sites, little is known about the managerial aspects of Web site research, planning, and evaluation. This study found that, in many cases, Web site planning is done by trial and error based on subjective knowledge and intuition, with little or no formal research and evaluation.Interviews with persons responsible for making Web site decisions for organizations revealed that competition and the desire to establish an Internet presence were the driving forces in deciding to develop a Web site. Very little research about present effectiveness is done, but there is a strong belief that Web site communication will be increasingly important in the future.Candace White is assistant professor of public relations in the School of Journalism at The University of Tennessee in Knoxville. Niranjan Raman works for The Burke Institute in Cincinnati, Ohio.     

Catching‐up or Leapfrogging in the Indian IT Service Sector: Windows of Opportunity,Path‐creating,and Moving up the Value Chain

Indian IT service firms are successfully competing with world leaders and research on the industry is emerging. Providing analysis at firm rather than industry level, this article identifies the windows of opportunity open to Indian firms, with the following findings: (i) the catching‐up process by Indian IT firms can be classified as a three‐stage ‘body shopping–offshoring–global delivery model’, comparable with the three steps in original equipment, own‐design and own‐brand manufacturing; (ii) the window of opportunity for Indian firms was primarily the techno‐economic paradigm shift, and secondarily the government's regulation and support of the industry; and (iii) Indian firms initially partially re‐invented their own path by offshoring and created their own global delivery model, gradually moving to higher value‐added services.     

DYNAMIC DISAGGREGATE CHOICE MODELS,WITH AN APPLICATION IN TRANSPORTATION

A standard assumption of disaggregate mode-choice models is that an individual faced with a choice among several available alternative transportation modes compares their utilities. These utilities are almost always expressed as a linear composite measure of various perceived benefits which are assumed constant. However, the individual's perceptions change as he learns, acquires new habits, or adapts to different physical, economic, and social circumstances. In order to account for these changes, two dynamic models of model-choice behavior are developed herein. These two models are based on two common postulates. (1) One alternative is preferred over another only if the absolute difference in their utilities exceeds a positive constant; otherwise, the decision maker is indifferent toward the two alternatives. (2) If an alternative is preferred, it will be chosen with certainty. In the indifference state, the individual is postulated to randomly choose one of the two alternatives (Model 1) or choose the same alternative as was most recently chosen (Model 2). Choice probabilities derived from these two models are shown to differ from those obtained using the conventional logit model. If there is a strong loyalty toward a mode, the logit model underestimates its choice probability when that mode is less attractive than the competing mode. The results are illustrated using numerical examples.     

Calibration approach for estimating population total with subsampling of non respondents under single- and two-phase sampling

ABSTRACT

Using the calibration approach, the Hansen and Hurwitz (1946 Hansen, M.H., Hurwitz, W.N. (1946). The problem of non response in sample surveys. J. Am. Stat. Assoc. 46:147–190.[Taylor & Francis Online] , [Google Scholar]) technique-based estimator is developed for the situation where the information on auxiliary variable is assumed known for the entire population units. The double-sampling case has also been dealt with. Expressions for the estimator of population total, its variance, and variance estimator are developed. The theoretical results are illustrated with the help of simulation studies. Simulation results show that the proposed calibration approach-based estimator outperforms the Hansen and Hurwitz estimator.     

The Accessibility of Public Spaces for People with Dementia: a new priority for the 'open city'

The social model of disability de-medicalises disability and politicises it as an issue of universal rights. However, the rights of people with dementia have been less strongly advocated than those of people with physical disabilities. This is particularly the case with environmental planning and design. The needs of people with dementia are now informing the design of residential homes and day centres, but the issue of accessibility to public spaces and amenities has been almost completely neglected. Many outdoor environments such as shopping centres or parks may be inhospitable for people with dementia because they are disorientating, difficult to interpret and navigate, threatening or distressing. The article reviews the literature on indoor design for dementia, reports on research investigating the accessibility of outdoor environments, and describes a new approach using virtual reality technology to enable people with dementia to identify and test outdoor design and planning improvements themselves.     

Quality upgrading and restrictive hiring practices in unionized jobs

Most previous work has suggested that unionized employers upgrade labor quality of new hires, but has been silent on the behavior of unions when they control hiring. In this paper, it is argued that unions also have the incentive to upgrade quality, but to an extent less than or equal to upgrading by employers. Empirical support for this argument is provided using data from the National Longitudinal Surveys of young men and young women, in conjunction with an industry measure of union control over hiring. Years of schooling and worker IQ measure labor quality. The author may be contacted at 9271-B Jamison Avenue, Philadelphia, PA 19115. She thanks her dissertation committee members Masanori Hashimoto, Patricia Reagan, and especially Donald Parsons, for their detailed comments, and seminar participants at the Ohio State University for helpful suggestions on previous drafts.     

The noncentral bivariate chisquared distribution and extensions

The distribution of certain correlated noncentral chisquared variates P, Q, is termed the noncentral bivariate chisquared distribution. Moment generating functions of the distributions of (P, Q), (P+Q) and other quadratic forms have been obtained. A relationship to the linear case of the noncentral Wishart distribution is indicated. Convolution properties and applications are presented.     

Operations Management Opportunities in Technology Commercialization and Entrepreneurship

The field of Production and Operations Management (POM) is increasingly perceived as a rigorous but narrow field, antiquated and not very relevant to the current challenges and concerns of managers in job‐creating growth companies vital to our economies. I argue that a narrower positioning of POM in the past is responsible for its perceived limited utility to growth firms and global economies. POM at its core is about “doing more with less,” which is very well aligned with the context and needs of resource‐constrained entrepreneurial companies. My discussion is focused on how the research paradigm of POM is and can be relevant to meeting the emerging challenges of growth companies of tomorrow. Specifically, I examine how POM can help meet the needs of these organizations to become scalable and sustainable. The objective is to stimulate thought and discussion and encourage early‐stage POM scholars to seriously consider the contexts of technology commercialization, entrepreneurship, and growth companies as avenues for future research.     

Toward a prediction of third-world immigrants into Canada, 1973-1985

The author examines trends in migratory movements to Canada between 1949 and 1972 in an attempt to determine the statistical regularity of immigration from developing countries and to predict the probable number of third world immigrants to Canada for the period 1973-1985. The effects on migration of political factors and of variables associated with the area of origin are studied (SUMMARY IN FRE, SPA)