Mood's test for dispersion as a counting of triplets

The well-known equivalence of Wilcoxon and Mann-Whitney location statistics is herein extended to dispersion tests. Mood (1954) statistic is related to a statistic based on “triplets”. The triplet version of Mood statistic is useful for proving the asymptotic normality (under alternatives) of the test.     

Foreign Scientists at the National Institutes of Health: Ramifications of U.S. Immigration and Labor Policies1

This article describes the findings of a study undertaken to shed light on some of the factors that determine the employment of foreign biomedical scientists in the United States by examining their presence at the National Institutes of Health (NIH). NIH was selected as the focus of the study for its unique combination of characteristics. It is a federal agency with the ambiance of academe that carries out biomedical research and training internally while supporting like activities externally through grant‐ and contract‐based linkages with a host of academic institutions and biotechnology firms in the United States and abroad. Over a two‐year period, in‐depth interviews were conducted with more than 200 stakeholders at the NIH campus and elsewhere, as well as ethnographic observations. The study identified several hitherto unreported important functions that NIH plays in facilitating the inflow of talented foreign scientists to meet its manpower needs and those of the broader national economy.     

Optimal Maintenance Time for Repairable Systems Under Two Types of Failures

Determination of preventive maintenance is an important issue for systems under degradation. A typical maintenance policy calls for complete preventive repair actions at pre-scheduled times and minimal repair actions whenever a failure occurs. Under minimal repair, failures are modeled according to a non homogeneous Poisson process. A perfect preventive maintenance restores the system to the as good as new condition. The motivation for this article was a maintenance data set related to power switch disconnectors. Two different types of failures could be observed for these systems according to their causes. The major difference between these types of failures is their costs. Assuming that the system will be in operation for an infinite time, we find the expected cost per unit of time for each preventive maintenance policy and hence obtain the optimal strategy as a function of the processes intensities. Assuming a parametrical form for the intensity function, large sample estimates for the optimal maintenance check points are obtained and discussed.     

Emergy Measures of Carrying Capacity to Evaluate Economic Investments

This paper outlines a method for determining carrying capacity for economic investments based on an emergy evaluation of the environmental resources of a region. Using data from tourism development in Mexico and Papua New Guinea, the concept of carrying capacity is related to intensity of development, environmental support area, and the fit of economic development in local environments and economies.Emergy, a unit of resource use and work potential, is used to quantitatively evaluate intensity of development. Emergy evaluation is briefly described and the evaluations of tourism used to further explain the methodology. The total annual resource use for the tourist resorts and the economies in which they are embedded (including inputs of renewable and nonrenewable resources and purchased goods and services) was calculated and converted to emergy units. The renewable resource base and an Environmental Loading Ratio (ELR), are proposed as a means for determining both long term and short term carrying capacity respectively. The concept of sustainable development is related to the net emergy benefits that result from development. Expressed as a ratio of the amount of emergy received by the local economy to the amount that is exported (embodied in tourists), sustainability is suggested to result from a positive emergy trade balance.     

The Sonoran Desert’s Domestic Bracero Programme: Institutional Actors and the Creation of Labour Migration Streams

This paper traces the journeys of male migrants to Empalme, Sonora, Mexico to uncover the development of the often overlooked domestic bracero programme that operated in conjunction with its well‐known international equivalent. Drawing on interviews and observations with ex‐braceros who met at a park near the Mexico‐US border, I examine their experiences and participation in Mexico’s domestic bracero program, an unintended and unexplored consequence of its international counterpart. The study shows how regulation and control were constantly reinvented at every step of the selection process by state actors and their affiliates in Mexico. The paper reveals how the oversupply of labour and modernization of agriculture in Sonora resulted in the development of a migration industry where local municipal leaders, coyotes, the state, and Mexican agribusiness capitalized from men’s displacement. The migration industry during the bracero selection process controlled who gained access to the United States labour market by capturing migrant labour en route to the United States in the process fueling a thriving cotton industry in the otherwise stagnant Sonoran Desert economy. The study concludes by taking the lessons from the historic domestic bracero programme to show one instance in which internal and international labour markets were closely interwoven. In the end, I call for more research that examines the relationship between markets on both sides of the border that uncovers how networks are not only structured by personal ties but also by state and market relations.     

Inapproximability results for the lateral gene transfer problem

This paper concerns the Lateral Gene Transfer Problem. This minimization problem, defined by Hallett and Lagergren (2001), is that of finding the most parsimonious lateral gene transfer scenario for a given pair of gene and species trees. Our main results are the following:

Special pension schemes for workers in arduous and hazardous jobs: Functions and conditions to ensure equal treatment

Most jurisdictions grant differentiated and more beneficial treatment – usually in the form of early retirement, and commonly under special pension schemes – to workers in arduous or hazardous jobs. Several justifications for such treatment have been advanced, including i) compensating the worker for the hardship, ii) protecting the worker from the hazard, and iii) realizing the principle of equality in the distribution of costs and benefits in the social security system. This article analyses these functions from a socioeconomic perspective and explains how early retirement for workers in arduous and hazardous jobs is necessary to ensure equality by treating “unequals unequally”, and in proportion to their inequality. Moreover, this article presents a precise formula to calculate when a worker should be allowed to retire, so that workers in occupational domains with a shorter life expectancy do not systematically enjoy lower expected benefits from the pension system while having contributed the same amount. Implications for the design and desirability of special pension benefits are discussed.