Co-occurrences of tropical trees in eastern South America : disentangling abiotic and biotic forces

Species co-occurrences in local communities can arise independent or dependent on species' niches. However, the role of niche-dependent processes has not been thoroughly deciphered when generalized to biogeographical scales, probably due to combined shortcomings of data and methodology. Here, we explored the influence of environmental filtering and limiting similarity, as well as biogeographical processes that relate to the assembly of species' communities and co-occurrences. We modelled jointly the occurrences and co-occurrences of 1016 tropical tree species with abundance data from inventories of 574 localities in eastern South America. We estimated species co-occurrences as raw and residual associations with models that excluded and included the environmental effects on the species' co-occurrences, respectively. Raw associations indicate co-occurrence of species, whereas residual associations indicate co-occurrence of species after accounting for shared responses to environment. Generally, the influence of environmental filtering exceeded that of limiting similarity in shaping species' co-occurrences. The number of raw associations was generally higher than that of the residual associations due to the shared responses of tree species to the environmental covariates. Contrary to what was expected from assuming limiting similarity, phylogenetic relatedness or functional similarity did not limit tree co-occurrences. The proportions of positive and negative residual associations varied greatly across the study area, and we found a significant tendency of some biogeographical regions having higher proportions of negative associations between them, suggesting that large-scale biogeographical processes limit the establishment of trees and consequently their co-occurrences.Peer reviewe

Structural, morphological, and magnetic characterizations of (FexMn1-x)2O3 nanocrystals: A comprehensive stoichiometric determination

Iron manganese trioxide (FexMn1-x)2O3 nanocrystals were synthesized by the sol-gel method. The 80 K Mossbauer spectrum was well-fitted using two doublets representing the 8b and 24d crystallographic sites of the (FexMn1-x)2O3 phase and two weak extra sextets which were attributed to crystalline and amorphous hematite. Our findings showed formation of a bixbyite primary phase. The Raman spectrum exhibits six Raman active modes, typical of (Fe,Mn)2O3, and two extra Raman modes associated with the secondary hematite phase. X-ray photoelectron spectroscopy analysis confirmed the presence of oxygen vacancy onto the (FexMn1-x)2O3 particle surface, with varying oxidation states. X-band magnetic resonance data revealed a single broad resonance line in the whole temperature range (3.8 K - 300 K). The temperature dependence of both resonance field and resonance linewidth shows a remarkable change in the range of 40 - 50 K, herein credited to surface spin glass behavior. The model picture used assumes (FexMn1-x)2O3 nanoparticles with a core-shell structure. Results indicate that below about 50 K the spin system of shell reveals a paramagnetic to spin glass-like transition upon cooling, with a critical temperature estimated at 43 K. In the higher temperature range, the superparamagnetic hematite (secondary) phase contributes remarkably to the temperature dependence of the resonance linewidth. Zero-field-cooled (ZFC) and fieldcooled (FC) data show strong irreversibility and a peak in the ZFC curve at 33 K, attributed to a paramagnetic-ferrimagnetic transition of the main phase. Hysteresis curve at 5 K shows a low coercive field of 4 kOe, with the magnetization not reaching saturation at 70 kOe, suggesting the occurrence of a ferrimagnetic core with a magnetic disorder at surface, characteristic of core-shell spin-glass-like behavior

Prevention of hypertension in patients with pre-hypertension: protocol for the PREVER-prevention trial

<p>Abstract</p> <p>Background</p> <p>Blood pressure (BP) within pre-hypertensive levels confers higher cardiovascular risk and is an intermediate stage for full hypertension, which develops in an annual rate of 7 out of 100 individuals with 40 to 50 years of age. Non-drug interventions to prevent hypertension have had low effectiveness. In individuals with previous cardiovascular disease or diabetes, the use of BP-lowering agents reduces the incidence of major cardiovascular events. In the absence of higher baseline risk, the use of BP agents reduces the incidence of hypertension. The PREVER-prevention trial aims to investigate the efficacy, safety and feasibility of a population-based intervention to prevent the incidence of hypertension and the development of target-organ damage.</p> <p>Methods</p> <p>This is a randomized, double-blind, placebo-controlled clinical trial, with participants aged 30 to 70 years, with pre-hypertension. The trial arms will be chlorthalidone 12.5 mg plus amiloride 2.5 mg or identical placebo. The primary outcomes will be the incidence of hypertension, adverse events and development or worsening of microalbuminuria and of left ventricular hypertrophy in the EKG. The secondary outcomes will be fatal or non-fatal cardiovascular events: myocardial infarction, stroke, heart failure, evidence of new sub-clinical atherosclerosis, and sudden death. The study will last 18 months. The sample size was calculated on the basis of an incidence of hypertension of 14% in the control group, a size effect of 40%, power of 85% and P alpha of 5%, resulting in 625 participants per group. The project was approved by the Ethics committee of each participating institution.</p> <p>Discussion</p> <p>The early use of blood pressure-lowering drugs, particularly diuretics, which act on the main mechanism of blood pressure rising with age, may prevent cardiovascular events and the incidence of hypertension in individuals with hypertension. If this intervention shows to be effective and safe in a population-based perspective, it could be the basis for an innovative public health program to prevent hypertension in Brazil.</p> <p>Trial Registration</p> <p>Clinical Trials <a href="http://www.clinicaltrials.gov/ct2/show/NCT00970931">NCT00970931</a>.</p

O Programa de Cidades Históricas : por uma política integrada de preservação do patrimônio cultural urbano

O Programa de Cidades Históricas (PCH), implementado a partir de 1973, foi o primeiro programa federal que investiu recursos para a recuperação do patrimônio cultural urbano. Implementado pelo Ministério do Planejamento, buscava o desenvolvimento econômico das cidades históricas e dialogava com outros assuntos em pauta naquele momento, como o desenvolvimento urbano e regional e o turismo cultural. Tinha em sua concepção uma mudança na maneira de abordar as cidades históricas: a partir do entendimento da cidade como produtora de capital, o patrimônio cultural geraria desenvolvimento econômico pelo seu consumo para a atividade turística. De 1973 a 1979, foram investidos 17,3 milhões de dólares, realizando-se 143 obras em monumentos (85% dos investimentos); 8 cursos de qualificação de mão de obra nos três níveis (superior, intermediário e operário); 7 planos urbanísticos; 6 obras em espaços públicos (urbanos); e 10 ações de tipos diversos. Nossa análise busca entender essa política a partir do seu processo de formulação e implementação, no período de 1972 a 1979. Pretende, nesse sentido: a) avaliar as relações de poder em jogo durante a construção e a implementação do programa; b) compreender o grau de sucesso que o programa obteve na construção de um Sistema Nacional de Patrimônio Cultural, analisando sua articulação junto aos estados e outros órgãos federais; e c) avaliar o papel do programa enquanto indutor de novas práticas institucionais no campo da preservação do patrimônio cultural, especialmente com relação ao Iphan e aos estados federativos brasileiros.The Historic Cities Program (PCH: 1973-1979) was the first federal program that has invested resources to the recovery of the urban cultural heritage. Implemented by the Ministry of Planning, sought economic development of historic towns and dialogued with other items on the agenda at the time, such as urban and regional development and cultural tourism. It brought a change in the way of approach the historic towns: from the understanding of the city as a producer of capital, heritage would generate economic development through its consume by the tourism. From 1973 to 1979 it was invested 17.3 million dollars, performing 143 works on monuments (85% of investments); 8 hand-to-work training courses in three levels (top, middle and working class); 7 urban plans; 6 works in public spaces (urban); and 10 shares of various types. Our analysis seeks to understand this policy from its formulation and implementation in the period from 1972 to 1979. The aim, in this sense, is: a) to assess the power relations at play during construction and implementation of the Program; b) to understand the degree of success that the program achieved in building a national system, analyzing its relationship with states and other federal agencies; and c) to evaluate the role of Program while inducing new institutional practices in the field of preservation of cultural heritage, especially with regard to Iphan