Paintings and Numbers: An Econometric Investigation of Sales Rates, Prices and Returns in Latin American Art Auctions

This paper uses a unique data set of Latin American paintings auctioned by Sotheby's between 1995 and 2002 to investigate several puzzles from the recent auctions literature. Our results suggest that: (1) the reputation of an artist and the provenance of the artwork, omitted variables in most previous studies, seem to be more important determinants of the sale price of a painting than standard factors, such as medium and size, (2) the opinion of art experts seems to be of limited use in predicting whether or not an artwork sells at auction, (3) there is little supporting evidence for the widespread notion that the best or more expensive artworks tend to generate above average returns (the “masterpiece effect”), although (4) there is strong evidence in our data for the declining price anomaly, or “afternoon effect.”art auctions, masterpiece effect, Latin American art, declining price anomaly

Insights into channel function via channel dysfunction

The nicotinic synapse has been a touchstone for advances in neuroscience ever since Jean Nicot, the French ambassador to Portugal, sent some tobacco seeds home to Paris in 1550 with a note that the New World plant had interesting effects when smoked. Now the muscle nicotinic acetylcholine receptor (nAChR) is a well-studied example of ligand-gated ion channels. After a motor neuron is stimulated, the nerve impulse reaches the presynaptic terminal, where it evokes release of acetylcholine (ACh) into the synapse. The nAChR depolarizes the postsynaptic muscle and triggers muscle action potentials; muscle contraction follows. To date, several nAChR subtypes have been successfully isolated, purified, imaged, and expressed, and unitary currents have been recorded from these channels (1). Researchers continue to unravel the molecular mechanisms of these macromolecules that are embedded in membranes at vertebrate nerve-muscle synapses, at invertebrate nicotinic synapses (which explains why nicotine-producing tobacco plants have a select advantage against invertebrate pests), and in the vertebrate central system (which explains Jean Nicot’s fascination with those leaves). However, the precise structural events that trigger channel opening or "gating" remain mostly unknown

Adipocytes and immune cells cross-talk: the role of catecholamines

Background Obesity is reaching epidemic proportions worldwide, being characterised by long-term, low-grade inflammation with detrimental effects on virtually all physiological systems. Adipocyte dysfunction has been recently regarded as the instigator of the main metabolic disturbances observed in obesity and obesity-related comorbidities. Thus, the impact of this dysfunction upon major organic systems involved in obesity clearly needs to be determined. Given the intimate cross-talk between adipocytes and immune cells, and the recent discovery that immune cells are a source of cathecolamines (CA), we propose that these amines constitute an important link between neuroendocrine and immune networks. Consequently, we need to better understand the role of CA in modulation of the immune response in inflammatory-associated diseases such as obesity. Immune cell-derived CA alter a wide array of cell functions, including proliferation, differentiation, apoptosis and the pattern of cytokine expression, suggesting a crucial role in the inflammatory outcome. However, the exact mechanisms controlling the release of CA in obesity are not fully understood

Variação funcional em espécies de Rubiaceae em um gradiente ambiental na Floresta Atlântica

A coexistência de espécies relacionadas é um importante componente para o entendimento da diversidade e distribuição de plantas em florestas tropicais. Entre os fatores que influenciam na coexistência e distribuição de plantas, a luz se destaca por exercer forte influência na sobrevivência, crescimento e distribuição de espécies vegetais. Para avaliar os efeitos do gradiente de luz sobre uma comunidade de Rubiaceae que apresenta distribuição gregária, foi realizado o levantamento de indivíduos organizados de forma gregária, ao longo de um gradiente topográfico (dividido em baixada, relevo inclinado e topo de morro) e de luz. Dez atributos relacionados à luz foram avaliados em 85 indivíduos pertencentes a nove espécies de Rubiaceae. Os baixos valores das taxas de fotossíntese líquida, respiração no escuro, ponto de compensação e saturação encontrados evidenciam a condição de alta tolerância à sombra das espécies avaliadas. A baixa amplitude de variação dos atributos relacionados à luz se deve, possivelmente, à pouca possibilidade de expressão de estratégias fotossintéticas variadas para sobrevivência em um ambiente de sombra

Matéria orgânica do solo.

Compartimentos da matéria orgânica do solo; Fatores que regulam a dinâmica de matéria orgânica no solo; A modifica¢ão do ambiente solo;Manipulacão da quantidade e qualidade dos aportes orgânicos; Manipulacão da fauna do solo (agentes de decomposicão) via preparo, cobertura morta ou uso de pesticidas; Modelagem da dinâmica da matéria orgânica do solo.bitstream/item/36210/1/Doc97.pd