978 resultados para propagating in the slant path


Relevância:

100.00% 100.00%

Publicador:

Resumo:

Several competing hypotheses attempt to explain how environmental conditions affect mass-independent basal metabolic rate (BMR) in mammals. One of the most inclusive and yet debatable hypotheses is the one that associates BMR with food habits, including habitat productivity. These effects have been widely investigated at the interspecific level under the assumption that for any given species all traits are fixed. Consequently, the variation among individuals is largely ignored. Intraspecific analysis of physiological traits has the potential to compensate for many of the pitfalls associated with interspecific analyses and, thus, to be a useful approach for evaluating hypotheses regarding metabolic adaptation. In this study, we investigated the effects of food quality, availability, and predictability on the BMR of the leaf-eared mouse Phyllotis darwini. BMR was measured on freshly caught animals from the field, since they experience natural seasonal variations in environmental factors ( and, hence, variations in habitat productivity) and diet quality. BMR was significantly correlated with the proportion of dietary plants and seeds. In addition, BMR was significantly correlated with monthly habitat productivity. Path analysis indicated that, in our study, habitat productivity was responsible for the observed changes in BMR, while diet per se had no effect on this variable.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

We prove the equivalence of many-gluon Green's functions in the Duffin-Kemmer-Petieu and Klein-Gordon-Fock statistical quantum field theories. The proof is based on the functional integral formulation for the statistical generating functional in a finite-temperature quantum field theory. As an illustration, we calculate one-loop polarization operators in both theories and show that their expressions indeed coincide.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The effects of a temperature dependent viscosity in surface nonlinear waves propagating in a shallow fluid heated from below are investigated. It is shown that the (2+1)-dimensional Burgers equation may appear as the equation governing the upper free surface perturbations of a Bénard system, even when the viscosity is assumed to depend on temperature. The critical Rayleigh number for the appearance of waves governed by the Kadomtsev-Petviashvili equation, however, will be smaller than R=30, which is the critical number obtained for a constant viscosity. © 1992.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

We observed Crested caracaras (Caracara plancus) consuming and dispersing fruits of the palm Attalea phalerata at Pantanal, Brazil. We reviewed the literature of seed dispersal by raptors and suggest that raptors may affect seed dispersal by three different paths: secondary seed dispersal by preying on frugivorous birds, primary seed dispersal of ornithocoric fruits and primary seed dispersal of large, lipid-rich fruits. The latter path may be an important long-distance seed dispersal mechanism for large seeds.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Includes bibliography

Relevância:

100.00% 100.00%

Publicador:

Resumo:

In this work, a new approach for supervised pattern recognition is presented which improves the learning algorithm of the Optimum-Path Forest classifier (OPF), centered on detection and elimination of outliers in the training set. Identification of outliers is based on a penalty computed for each sample in the training set from the corresponding number of imputable false positive and false negative classification of samples. This approach enhances the accuracy of OPF while still gaining in classification time, at the expense of a slight increase in training time. © 2010 Springer-Verlag.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

As predicted in the first bulletin, produced jointly by the Economic Commission for Latin America and the Caribbean (ECLAC) and the International Labour Organization (ILO), the impact of the economic crisis continued to be felt in Latin America and the Caribbean during the second quarter of 2009. Regional exports of goods and services contracted in response to sluggish demand on international markets, while remittances and foreign direct investment flows continued to fall, credit lost its buoyancy and the total wage bill diminished, owing mainly to job losses. As a result, the growth forecasts of many countries had to be adjusted downwards. Since the end of 2008, the countries of the region had started to implement countercyclical policies —albeit with significant differences— in an effort to use public spending to counter flagging investment and consumer-spending levels and boost aggregate demand. In this second bulletin, ECLAC and ILO show how the impact of the crisis has deepened in labour markets in the region in the first half of the year and examine existing options and the outcome of public-infrastructure and emergency employment programmes designed to mitigate the impact of the crisis on the labour market. The unemployment rate has risen in practically all countries compared with the previous year and this situation worsened further in the second quarter, when urban unemployment exceeded the rate of the corresponding period in 2008 by 1 percentage point (to stand at 8.5%, up from 7.5%), while in the first quarter, the variation was 0.6 of a percentage point. Labour indicators also point to an increase in informality, a decline in employment with social protection and a decrease in full-time employment. Labour-market trends observed in the first half-year, together with the forecast for a 1.9% decline in regional GDP in 2009, suggest that the average annual rate of urban unemployment in the region will be close to 8.5%. This forecast is slightly less pessimistic than the estimate given in the first bulletin; this is attributable to the fall in the participation rate in the first half-year to levels that are expected to remain low for the rest of the year. Without this reduction in the labour supply, due largely to the “discouragement effect”, the annual average urban unemployment rate would stand at between 8.8% and 8.9%. Thus, the open urban unemployment figure would increase by 2.5 million and if the “discouraged job-seekers” are included, then the number of additional persons not finding a niche in the urban labour market would climb to 3.2 million. In the region, as in the rest of the world, there are signs that the crisis may have reached bottom in the middle of the year. In many countries, production levels have ceased their decline and there are indications of an incipient recovery leading to cautious optimism that there may be a moderate upturn in labour markets in the fourth quarter. The pace of recovery will vary from one country to the next and is expected to be gradual at best. Even with the return to a growth path, there should be no illusion that the labour problems will immediately disappear. First, the recovery in employment is expected to lag behind the upturn in economic activity. Second, since economic growth is likely to remain moderate in the short term and well below the rates recorded between late 2003 and mid-2008, demand for labour and consequently the generation of good-quality jobs will continue to be weak. Thus, countries should not relax their efforts to defend and create decent jobs, but rather should take steps to improve the effectiveness and efficiency of available instruments. In this way, the region will be in a better position not only to confront the challenges of economic recovery, but also to strengthen the foundations for social inclusion and for advancing under more favourable conditions towards fulfilment of the Millennium Development Goals.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

This paper analyses public debt in the most indebted Caribbean countries – i.e. Barbados, Belize, Guyana, Jamaica, Antigua and Barbuda, Dominica, Grenada, and St. Kitts and Nevis – from the standpoint of its sustainability. A level of debt is deemed to be sustainable when the debt-to-GDP ratio remains constant or declines. The concept of sustainability is closely linked to that of solvency. A government is solvent if the net present value of its future primary balances (i.e. that excludes interest payments) is equal to or greater than the present value of public debt stock. It can be demonstrated that if the debt-to-GDP ratio is not on an explosive path, that it either stable or decreasing, the solvency condition holds. It is worth noting that the concept of fiscal sustainability addressed in this paper differs from that of optimality of public debt. The analysis that follows is intended to determine whether the service of the current debt levels is consistent with the fiscal stance. Therefore, it does not set out to identify the target debt level based on any optimality criteria. The next section presents the main features of different theoretical approaches to analyse public debt sustainability.1 Section II discusses the situation of public debt in the Caribbean countries showing different indicators; Section III analyses debt sustainability in countries with access to market financing; Section IV does the same in Guyana – a country dependent on concessional financing and, as such, included in the Highly Indebted Poor Countries (HIPC) Initiative – and the countries of the Eastern Caribbean Currency Union (ECCU). Sections V and VI go beyond debt levels as determinants of fiscal sustainability, highlighting the importance of the currency composition of debt and the variability of fiscal revenue. The last section concludes.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

In general, pattern recognition techniques require a high computational burden for learning the discriminating functions that are responsible to separate samples from distinct classes. As such, there are several studies that make effort to employ machine learning algorithms in the context of big data classification problems. The research on this area ranges from Graphics Processing Units-based implementations to mathematical optimizations, being the main drawback of the former approaches to be dependent on the graphic video card. Here, we propose an architecture-independent optimization approach for the optimum-path forest (OPF) classifier, that is designed using a theoretical formulation that relates the minimum spanning tree with the minimum spanning forest generated by the OPF over the training dataset. The experiments have shown that the approach proposed can be faster than the traditional one in five public datasets, being also as accurate as the original OPF. (C) 2014 Elsevier B. V. All rights reserved.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relevância:

100.00% 100.00%

Publicador:

Resumo:

There is compelling evidence that Planet Earth is on the path to an era of global warming that has serious implications for the well-being of both people and nature. This three-volume synthesis of literature will be a marvelous place for both the public and new scholars interested in global warming to begin their pursuit of the subject. The author captures the best of the scientific literature and press materials appearing in recent years. The utility of these volumes as a resource for gaining a broad background or pursuing a particular aspect of global warming is enhanced by Johansen's talent for explaining with clarity a vast and rapidly growing subject.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

ADOLESCENCE AND DRUG USE THROUGH THE LENS OF PSYCHOANALYSIS: SUFFERING AND ECSTASY IN THE PASSAGE The purpose of this study is to reflect upon the psychological factors of adolescent drug addiction according to a psychoanalytic perspective. First we consider adolescence as a social-historical category and then we discuss the psychoanalytic understanding of the adolescent transition. This theoretical path builds the approach that considers drug use as a phenomenon that serves as a passage ritual to contemporary adolescence. This phenomenon is modulated by the drive organization, which determines how the individual will take ownership of the use of psychoactive substances. We conclude that the substance use may function as a buffer-object, activated to deal with the structural fragility of the contemporary affective bonds.