Urban or rural fragments: which soil use in forest surroundings induces greater litter deposition?

Urban Ecosystems - The soil use in surroundings of forest remnants, as well as, variations in seasonality and rainfall totals from each year might influence the composition, structure, and...     

A New Model for Multivariate Markov Chains

We propose a new model for multivariate Markov chains of order one or higher on the basis of the mixture transition distribution (MTD) model. We call it the MTD‐Probit. The proposed model presents two attractive features: it is completely free of constraints, thereby facilitating the estimation procedure, and it is more precise at estimating the transition probabilities of a multivariate or higher‐order Markov chain than the standard MTD model.     

Procedure to identify outliers through cumulative distribution of extremes in a Gamma response model

This work aimed at proposing a procedure based on the cumulative distribution of maximums and minimums to identify outliers in generalized Gamma-response models. In order to validate such method, we used simulations scenarios defined by the combination of different samples, contamination rate and distributions with different degrees of asymmetry. In this context, probabilities related to errors in classification and accuracy were obtained by carrying by Monte Carlo simulations. Using cumulative distribution of extremes to identify outliers in a Gamma-response model is recommended, since it is not likely to present errors and was highly accurate in all assessed scenarios.     

Racialisation and racial formation in urban spaces*

ABSTRACT

In this paper, I try to clarify the notions of racialisation and racial formation and how they operate in the framework of nation states like Brazil. My main argument is that these processes are always constrained by the formation of social classes and national cultural repertoires even if transnational forces are important in nurturing them. I conclude by making a preliminary effort to unravel mechanisms and institutions which allow these processes of racialisation and racial formation to form part of the daily lives of black Brazilians in the context of class-structured urban spaces.     

Data and projections of HIV/AIDS cases in Portugal: an unstoppable epidemic?

The size of the affected population with HIV/AIDS is a vital question asked by healthcare providers. A statistical procedure called Back-calculation has been the most widely used method to answer that question. Recent discussions suggest that this method is gradually becoming less appropriate for reliable incidence and prevalence estimates, as it does not take into account the effect of treatment. In spite of this, in the current paper that method and a worst-case scenario are used to assess the quality of previous projections and obtain new ones. The first problem faced was the need to account for reporting delays, no reporting and underreporting. The adjusted AIDS incidence data were then used to obtain lower bounds on the size of the AIDS epidemic, using the back-calculation methodology. A Weibull and Gamma distribution was considered for the latency period distribution. The EM algorithm was applied to obtain maximum likelihood estimates of the HIV incidence. The density of infection times was parameterized as a step function. The methodology is applied to AIDS incidence in Portugal for four different transmission categories (injecting drug users, heterosexual, homo/bisexual and other) to obtain short-term projections (2002–2005) and an estimate of the minimum size of the epidemic.     

Involvement of advanced glycation end products in the pathogenesis of diabetic complications: the protective role of regular physical activity

Advanced glycation end products (AGEs) may play an important role in the pathogenesis of chronic diabetic complications and in the natural process of biological aging. In fact, maintained hyperglycaemia favours the formation of AGEs at the tissue level in diabetic patients, which may influence the triggering of different chronic pathologies of diabetes such as retinopathy, nephropathy, neuropathy and macro- and micro-vascular diseases. Moreover, the literature has also demonstrated the involvement of AGEs in biological aging, which may explain the accelerated process of aging in diabetic patients. The practice of regular physical activity appears to positively influence glycaemic control, particularly in type 2 diabetes mellitus patients. This occurs through the diminution of fasting glycaemia, with a consequent reduction of glycation of plasmatic components suggested by the normalisation of HbA1c plasmatic levels. This exercise-induced positive effect is evident in the blood of diabetic patients and may also reach the endothelium and connective tissues of different organs, such as the kidneys and eyes, and systems, such as the cardiovascular and nervous systems, with a local reduction of AGEs production and further deceleration of organ dysfunction. The aim of this paper was to review the literature concerning this topic to coherently describe the harmful effects of AGEs in organ dysfunction induced by diabetes in advanced age as well as the mechanisms behind the apparent protection given by the practice of regular physical activity.     

Ordering Properties of Convolutions of Exponential Random Variables

Convolutions of independent random variables are usually compared. In this paper, after a synthetic comparison with respect to hazard rate ordering between sums of independent exponential random variables, we focus on the special case where one sum is identically distributed. So, for a given sum of n independent exponential random variables, we deduce the "best" Erlang-n bounds, with respect to each of the usual orderings: mean ordering, stochastic ordering, hazard rate ordering and likelihood ratio ordering.     

Lean-healthcare approach to reduce costs in a sterilization plant based on surgical tray rationalization

Abstract

Sterilization plants process all reusable materials used in hospitals during different stages of healthcare provision. Most items sterilized come from the surgical theater in the form of individual instruments, linen and surgical trays. Reducing the number of instruments in trays impacts on the performance of the sterilization process. Here, we propose a three-phase method, based on lean healthcare principles, cluster analysis and kaizen groups of experts to rationalize surgical trays, reducing sterilization processing costs. We innovate by proposing a strategy to approach tray rationalization prioritizing surgical specialties that are both complex and frequent, and by using group technology to cluster surgical trays expediting expert analyses carried out by kaizen groups. Our propositions were tested in a high complexity, tertiary care hospital, covering 12 surgical specialties, reducing the number of instruments by average 9.75%, and the time-to-assemble trays by average 9.68%, obtaining annual savings of US$285.756,00 in sterilization processing costs.     

A maximal domain of preferences for strategy-proof,efficient, and simple rules in the division problem

The division problem consists of allocating an amount M of a perfectly divisible good among a group of n agents. Sprumont (1991) showed that if agents have single-peaked preferences over their shares, the uniform rule is the unique strategy-proof, efficient, and anonymous rule. Ching and Serizawa (1998) extended this result by showing that the set of single-plateaued preferences is the largest domain, for all possible values of M, admitting a rule (the extended uniform rule) satisfying strategy-proofness, efficiency and symmetry. We identify, for each M and n, a maximal domain of preferences under which the extended uniform rule also satisfies the properties of strategy-proofness, efficiency, tops-onlyness, and continuity. These domains (called partially single-plateaued) are strictly larger than the set of single-plateaued preferences. However, their intersection, when M varies from zero to infinity, coincides with the set of single-plateaued preferences.An earlier version of this paper circulated under the title A maximal domain of preferences for tops-only rules in the division problem. We are grateful to an associate editor of this journal for comments that helped to improve the presentation of the paper and to Matt Jackson for suggesting us the interest of identifying a maximal domain of preferences for tops-only rules. We are also grateful to Dolors Berga, Flip Klijn, Howard Petith, and a referee for helpful comments. The work of Alejandro Neme is partially supported by Research Grant 319502 from the Universidad Nacional de San Luis. The work of Jordi Massó is partially supported by Research Grants BEC2002-02130 from the Spanish Ministerio de Ciencia y Tecnología and 2001SGR-00162 from the Generalitat de Catalunya, and by the Barcelona Economics Program of CREA from the Generalitat de Catalunya. The paper was partially written while Alejandro Neme was visiting the UAB unde r a sabbatical fellowship from the Generalitat de Catalunya.