13,839 research outputs found
Recording from two neurons: second order stimulus reconstruction from spike trains and population coding
We study the reconstruction of visual stimuli from spike trains, recording
simultaneously from the two H1 neurons located in the lobula plate of the fly
Chrysomya megacephala. The fly views two types of stimuli, corresponding to
rotational and translational displacements. If the reconstructed stimulus is to
be represented by a Volterra series and correlations between spikes are to be
taken into account, first order expansions are insufficient and we have to go
to second order, at least. In this case higher order correlation functions have
to be manipulated, whose size may become prohibitively large. We therefore
develop a Gaussian-like representation for fourth order correlation functions,
which works exceedingly well in the case of the fly. The reconstructions using
this Gaussian-like representation are very similar to the reconstructions using
the experimental correlation functions. The overall contribution to rotational
stimulus reconstruction of the second order kernels - measured by a chi-squared
averaged over the whole experiment - is only about 8% of the first order
contribution. Yet if we introduce an instant-dependent chi-square to measure
the contribution of second order kernels at special events, we observe an up to
100% improvement. As may be expected, for translational stimuli the
reconstructions are rather poor. The Gaussian-like representation could be a
valuable aid in population coding with large number of neurons
Risk Premium: Insights Over The Threshold
The aim of this paper is twofold: First to test the adequacy of Pareto distributions to describe the tail of financial returns in emerging and developed markets, and second to study the possible correlation between stock market indices observed returns and returnâs extreme distributional characteristics measured by Value at Risk and Expected Shortfall. We test the empirical model using daily data from 41 countries, in the period from 1995 to 2005. The findings support the adequacy of Pareto distributions and the use of a log linear regression estimation of their parameters, as an alternative for the usually employed Hillâs estimator. We also report a significant relationship between extreme distributional characteristics and observed returns, especially for developed countries.
RISK PREMIUM: INSIGHTS OVER THE THRESHOLD
The aim of this paper is twofold: First to test the adequacy of Pareto distributions to describe the tail of financial returns in emerging and developed markets, and second to study the possible correlation between stock market indices observed returns and returnâs extreme distributional characteristics measured by Value at Risk and Expected Shortfall. We test the empirical model using daily data from 41 countries, in the period from 1995 to 2005. The findings support the adequacy of Pareto distributions and the use of a log linear regression estimation of their parameters, as an alternative for the usually employed Hillâs estimator. We also report a significant relationship between extreme distributional characteristics and observed returns, especially for developed countries.
Risk premium: insights over the threshold
The aim of this paper is twofold: First to test the adequacy of Pareto distributions to describe the tail of financial returns in emerging and developed markets, and second to study the possible correlation between stock market indices observed returns and return's extreme distributional characteristics measured by Value at Risk and Expected Shortfall. We test the empirical model using daily data from 41 countries, in the period from 1995 to 2005. The findings support the adequacy of Pareto distributions and the use of a log linear regression estimation of their parameters, as an alternative for the usually employed Hill's estimator. We also report a significant relationship between extreme distributional characteristics and observed returns, especially for developed countries
Myopic Loss Aversion and House-Money Effect Overseas: an experimental approach
Recent literature has found two behavioral effects - house-money and myopic loss aversion (MLA) - in several experimental designs. We show that although we can find a house-money effect using survey methods this evidence disappears when we study investment decision within a multi-period investment experiment. Loss aversion is found to govern the risk-taking behavior of subjects in dynamic settings, overcoming the house-money effect. These results are robust to experiments conducted in two different countries, Spain and Brazil.
Variação da produtividade do arroz de terras altas influenciados pela seca meteorológica em Goiås.
A seca Ă© um fenĂŽmeno meteorolĂłgico caracterizado pela falta de precipitação pluvial, que pode causar grandes prejuĂzos Ă produção agrĂcola. O presente trabalho tem como objetivo caracterizar a ocorrĂȘncia de seca, utilizando o Ăndice Padronizado de Precipitação (SPI) em cinco microrregiĂ”es do estado de GoiĂĄs e sua influencia na produtividade de arroz de terras altas. As cinco microrregiĂ”es estudadas foram: AnĂĄpolis, Ceres, IporĂĄ, Anicuns e GoiĂąnia. A sĂ©rie de dados histĂłricos de precipitação foi disponibilizada pela AgĂȘncia Nacional de Ăguas (ANA), coletados em um municĂpio pertencente Ă microrregiĂŁo analisada. O perĂodo de estudo foi de 1975 a 2005. Os dados de produtividade, para o mesmo perĂodo foi disponibilizado pela AGROTEC. Os valores do SPI foram caracterizados pela a ocorrĂȘncia dos eventos de seca, frequĂȘncia relativa, comparação com os dados de produtividade do arroz de terras altas e o percentual de acerto do Ăndice. Foi possĂvel observar que o SPI nĂŁo acompanhou totalmente a variação da produtividade do arroz de terras altas. O SPI apresentou percentuais de acerto baixos, em todas as microrregiĂ”es, ficando prĂłximo a 51%
AnĂĄlise de solos: finalidade e procedimentos de amostragem.
A anĂĄlise de solos Ă© o Ășnico mĂ©todo que permite, antes do plantio, conhecer a capacidade de um determinado solo suprir nutrientes para as plantas. Ă a forma mais simples, econĂŽmica e eficiente de diagnose da fertilidade das terras e constitui base imprescindĂvel para a recomendação de quantidades adequadas de corretivos e fertilizantes para aumentar a produtividade das culturas e, como consequĂȘncia a produção e a lucratividade das lavouras.bitstream/CPAP-2010/57309/1/COT79.pd
Soil carbon and nitrogen stocks under natural forested savannah and cultivated pasture in the Pantanal, Mato Grosso do Sul, Brazil.
The goal of this study was to estimate the soil C and N stocks under Urochloa spp.pasture with a natural forested savannah as a reference.(Embrapa Gado de Corte. Documentos, 216). Coordenador Roberto Giolo de Almeida. II SIGEE. DisponĂvel em: . Acesso em: 30 nov. 2016
Digital tourism marketing: Case study of the campaign Canât Skip Portugal
The theme of this study is the analysis of the advertising campaign "Canât Skip Portugal" launched in 2017 by Tourism of Portugal, which the main objective was to show all the regions of the country, covering not only the most known areas but also to promote other areas of the country, showcasing Portugal as a potential destination for tourists. The objective of the study is to understand how this kind of Digital Marketing can be sufficiently appealing and arouse in-terest in the viewers. To reach the proposed objective, a qualitative research of descriptive type was carried out. Throughout this study it was possible to have a better understanding of the benefits of Digital Marketing. It could be con-cluded that the advertising campaign âCanât Skip Portugalâ achieved its pro-posed goals, involving and influencing the target audience in the choice of Portugal as a touristic destination.info:eu-repo/semantics/acceptedVersio
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