On the Omori-Yau Maximum Principle and Geometric Applications

We introduce a version of the Omori-Yau maximum principle which generalizes the version obtained by Pigola-Rigoli-Setti 21. We apply our method to derive a non-trivial generalization Jorge-Koutrofiotis Theorem 15 for cylindrically bounded submanifolds due to Alias-Bessa-Montenegro 2, we extend results due to Alias-Dajczer 5, Alias-Bessa-Dajczer 1 and Alias-Impera-Rigoli 6

Mach Bands: How Many Models are Possible? Recent Experiemental Findings and Modeling Attempts

Mach bands are illusory bright and dark bands seen where a luminance plateau meets a ramp, as in half-shadows or penumbras. A tremendous amount of work has been devoted to studying the psychophysics and the potential underlying neural circuitry concerning this phenomenon. A number of theoretical models have also been proposed, originating in the seminal studies of Mach himself. The present article reviews the main experimental findings after 1965 and the main recent theories of early vision that have attempted to discount for the effect. It is shown that the different theories share working principles and can be grouped in three clsses: a) feature-based; b) rule-based; and c) filling-in. In order to evaluate individual proposals it is necessary to consider them in the larger picture of visual science and to determine how they contribute to the understanding of vision in general.Air Force Office of Scientific Research (F49620-92-J-0334); Office of Naval Research (N00014-J-4100); COPPE/UFRJ, Brazi

Mach Band Attenuation by Adjacent Stimuli

Mach bands are illusory bright and dark bands seen where a luminance plateau meets a ramp, as in half-shadows or penumbras. Ratliff, Milkman, and Kaufman (1983) showed that Mach bands are attenuated by placing stimuli, such as bars, nearby. An experiment comparing Mach band attenuation for bar and Craik-O'Brien stimuli shows that they are equally effective in attenuating Mach bands. The results suggest that the high-frequency components of a stimulus adjacent to a ramp are responsible for the attenuation. Thc findings are interpreted in terms of a recent filling-in model of brighness perception and the results of computer simulations of stimuli used by Ratliff et al and the present experiment are shown

Tourism and Regional Competitiveness: the Case of the Portuguese Douro Valley

Using a framework that articulates the most important factors of competitiveness to evaluate the regional economic strategies, and applying this framework to the Portuguese NUT III Douro, we show that this region is relatively weak in terms of internal linkages, subject to ageing and out-migration and lacking in innovation and entrepreneurship, apart from being isolated from mass markets. With these characteristics, to define only the priority to tourism is clearly insufficient for convergence. So, after assessing the results of such strategy, the paper ends with a conclusion that is extensive to other regions: the lagging regions, which are trying to converge with the more developed ones based on tourism, cannot only rely on a combination of environmental resources and marketing, but have to attend to other factors of competitiveness as well.Douro Valley, environmental resources, regional competitiveness, tourism

KUZNETS’S HYPOTHESIS AND THE DATA CONSTRAINT

Five decades ago, Simon Kuznets expressed an important hypothesis about the relationship between the degree of income inequality within a country and its level of economic development: the Kuznets’s inverted-U hypothesis. The lack of longitudinal data has forced the use of cross-section or pooled datasets in order to draw conclusions about that relationship. In the present note we highlight the lack of international comparability of surveys where the measures of inequality are based, and we show two main findings: 1) data comparability goes on constituting a problem, particularly in what respects to the different welfare indicators used in national surveys, and 2) the procedure usually used to minimize the problem of noncomparability is likely to enforce the bias rather than to solve it.Inequality, Kuznets’s hypothesis, economic development, income distribution

FDI and Host Country Productivity: A Review

This paper reviews arguments and empirical findings on positive effects of FDI on host country firms. With the exception of the only unambiguous result of microeconometric studies, which is the superior productivity of foreign firms, the main conclusion extracted from empirical studies is the diversity of results. This diversity suggests that FDI will have different effects depending on the ‘technological congruence’ and ‘social capability’ of the host economy, as well as the familiarity of indigenous firms to products and technology of a given multinational corporation.Economic Growth, Foreign Direct Investment, Multinational Corporations, Spillovers, Technology Transfer

Educational Reform in Developing Countries: Private Involvement and Partnerships

The paper looks at recent changes in the role of government in the provision of education in Developing Countries. It begins with a reflection about the concept of public-private partnership (PPP), discusses the rationale that inspires the ‘contracting out’ of educational services and describes several cases of private sector involvement in education. After looking at the conditions for building PPPs and the necessary requirements for assuring an effective regulatory framework, the paper closes concluding that while contracting out needs not be made a priority there is a large room for other forms of private sector involvement in education in developing countries.Contracting out, educational reform, market/government failure, NPM, public-private partnerships.

Natural resources and institutions: the “natural resources curse” revisited

The present paper deals with the role of political authorities and institutions in explaining growth failures. We aim to search answers for three related questions: is there a natural resources curse? Are all types of natural resources exposed to a curse? Can good institutions, measured by a single indicator, avoid this “curse”? Although the estimates presented are supportive of negative relation between growth and relative resources abundance, and of the idea that good institutions enhance growth, our investigation do not demonstrated that if the curse exists it only appears in countries with inferior institutions. So, the key conclusion is that there is no justification for the pessimistic conviction that certain countries will remain caught up in a low growth trap constrained with institutions that impede their growth. At the international level, the main policy implication is that, the support to countries with a high share of natural resources in its exports should be directed towards improving specific areas of control fault, such as public budget and improving organizational systems, rather than imposing on aid-recipient countries wide-ranging global governance measures, that are usually measured by a cross-section general used, but subjective, index.economic growth; institutions; natural resources curse; resource dependence; rent seeking