Tribute to R.G. Boutilier: Skin colour and body temperature changes in basking Bokermannohyla alvarengai (Bokermann 1956)

In amphibians solar basking far from water sources is relatively uncommon since the highly permeable amphibian skin does not represent a significant barrier to the accompanying risk of losing water by evaporation. A South American frog, Bokermannohyla alvarengai (Bokermann 1956), however, spends a significant amount of the day exposed to full sun and relatively high temperatures. The means by which this frog copes with potentially high rates of evaporative water loss and high body temperatures are unknown. Thus, in this study, skin colour changes, body surface temperature, and evaporative water loss rates were examined under a mixture of field and laboratory conditions to ascertain whether changes in skin reflectivity play an important role in this animal's thermal and hydric balance. Field data demonstrated a tight correlation between the lightness of skin colour and frog temperature, with lighter frogs being captured possessing higher body temperatures. Laboratory experiments supported this relationship, revealing that frogs kept in the dark or at lower temperatures (20 degrees C) had darker skin colours, whereas frogs kept in the light or higher temperatures (30 degrees C) had skin colours of a lighter hue. Light exhibited a stronger influence on skin colour than temperature alone, suggesting that colour change is triggered by the increase in incident solar energy and in anticipation of changes in body temperature. This conclusion is corroborated by the observation that cold, darkly coloured frogs placed in the sun rapidly became lighter in colour during the initial warming up period (over the first 5 min), after which they warmed up more slowly and underwent a further, albeit slower, lightening of skin colour. Surprisingly, despite its natural disposition to bask in the sun, this species does not possess a 'waterproof' skin, since its rates of evaporative water loss were not dissimilar from many hylid species that live in arboreal or semi-aquatic environments. The natural history of B. alvarengai is largely unknown and, therefore, it is likely that the herein reported colour change and basking behaviour represent a complex interaction between thermoregulation and water balance with other ecologically relevant functions, such as crypsis.

Alterações no Código Florestal Brasileiro: impactos potenciais sobre a ictiofauna

É apresentada uma análise dos possíveis impactos que a diminuição da vegetação nativa, notadamente das florestas ripárias, pode causar sobre a ictiofauna. Três conjuntos de aspectos funcionais primordiais desempenhados pelas florestas ripárias são discutidos: transferência de energia solar ao ambiente aquático, interceptação de nutrientes e sedimentos que adentram nos rios e trocas de material orgânico entre o sistema terrestre e aquático. Conclui-se que qualquer alteração que se traduza em mais perdas de vegetação nativa, seja em áreas de preservação permanente ou em reservas legais, pode gerar perdas de espécies, homogeneização faunística e diminuição de biomassa íctica.

Fundamental Limits on Wavelength, Efficiency and Yield of the Charge Separation Triad

In an attempt to optimize a high yield, high efficiency artificial photosynthetic protein we have discovered unique energy and spatial architecture limits which apply to all light-activated photosynthetic systems. We have generated an analytical solution for the time behavior of the core three cofactor charge separation element in photosynthesis, the photosynthetic cofactor triad, and explored the functional consequences of its makeup including its architecture, the reduction potentials of its components, and the absorption energy of the light absorbing primary-donor cofactor. Our primary findings are two: First, that a high efficiency, high yield triad will have an absorption frequency more than twice the reorganization energy of the first electron transfer, and second, that the relative distance of the acceptor and the donor from the primary-donor plays an important role in determining the yields, with the highest efficiency, highest yield architecture having the light absorbing cofactor closest to the acceptor. Surprisingly, despite the increased complexity found in natural solar energy conversion proteins, we find that the construction of this central triad in natural systems matches these predictions. Our analysis thus not only suggests explanations for some aspects of the makeup of natural photosynthetic systems, it also provides specific design criteria necessary to create high efficiency, high yield artificial protein-based triads.

Utilização de reações foto-Fenton na prevenção de contaminações agrícolas

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

Chlorophyll fluorescence as a marker for herbicide mechanisms of action

Photosynthesis is the single most important source of 02 and organic chemical energy necessary to support all non-autotrophic life forms. Plants compartmentalize this elaborate biochemical process within chloroplasts in order to safely harness the power of solar energy and convert it into usable chemical units. Stresses (biotic or abiotic) that challenge the integrity of the plant cell are likely to affect photosynthesis and alter chlorophyll fluorescence. A simple three-step assay was developed to test selected herbicides representative of the known herbicide mechanisms of action and a number of natural phytotoxins to determine their effect on photosynthesis as measured by chlorophyll fluorescence. The most active compounds were those interacting directly with photosynthesis (inhibitors of photosystem I and II), those inhibiting carotenoid synthesis, and those with mechanisms of action generating reactive oxygen species and lipid peroxidation (uncouplers and inhibitors of protoporphyrinogen oxidase). Other active compounds targeted lipids (very-long-chain fatty acid synthase and removal of cuticular waxes). Therefore, induced chlorophyll fluorescence is a good biomarker to help identify certain herbicide modes of action and their dependence on light for bioactivity. Published by Elsevier B.V.

Avaliação das principais t́cnicas para obtenção de MPPT de paińis fotovoltaicos

Electrical energy from photovoltaic panels (PV) has became an increasing viable alternative because of the great concern for environmental preservation and the possibility of the reduction of the conventional fuels, and this natural energy source is free, abundant and clean. In addition, Brazil is a privileged country because of the high levels of irradiation throughout its territory all over the year. Thus the exploitation of the energy from PV is one of the best alternatives to overcome the supply electrical energy issues. However, nowadays the energy conversion efficiency is low and the initial costs are high for these energy systems. Therefore, in order to increase the efficiency of these systems the extraction of the maximum power point (MPP) from PV is extremely necessary, and it is done using the maximum power point tracking (MPPT) techniques. The MPP of the PV varies non linearly with the environmental conditions and several MPPT techniques are available in literature, and this paper presents a careful comparison among the most usual techniques, doing meaningful comparisons with respect to the amount of energy extracted, PV voltage ripple, dynamic response and use of sensors, considering that the models are implemented via MatLab/Simulink®. © 2010 IEEE.

Evaluation of integrated inverter topologies for low power PV systems

This work presents the stage integration in power electronics converters as a suitable solution for solar photovoltaic inverters. The rated voltages available in Photovoltaic (PV) modules have usually low values for applications such as regulated output voltages in stand-alone or grid-connected configurations. In these cases, a boost stage or a transformer will be necessary. Transformers have low efficiencies, heavy weights and have been used only when galvanic isolation is mandatory. Furthermore, high-frequency transformers increase the converter complexity. Therefore, the most usual topologies use a boost stage and one inverter stage cascaded. However, the complexity, size, weight, cost and lifetime might be improved considering the integration of both stages. These are the expected features to turn attractive this kind of integrated structures. Therefore, some integrated converters are analyzed and compared in this paper in order to support future evaluations and trends for low power single-phase inverters for PV systems. © 2011 IEEE.

Entransy and its utilization in problems of thermodynamics and heat transfer

The concept of entransy was recently proposed in terms of the analogy to the electric energy stored in a capacitor. The entransy of a system describes its heat transfer ability, as the exergy of a system quantifies its work production potential. Hence, the concept of entransy can be useful in problems where the heat transfer is the main objective, as for example, in systems collecting solar energy. This concept is quite recent and there are only a few works related to this topic. It is expected, however, that this approach will soon be used more often in the analysis of problems in thermodynamics and heat transfer. The objective of this work is to present a review of the concept of entransy in a systematic way, beginning with its definition, balance equations and a few examples of simple applications. It is hoped that this concept of entransy becomes a useful tool in the analysis and design of more efficient thermal systems. © 2012 Praise Worthy Prize S.r.l.- All rights reserved.

Estimates of hourly diffuse radiation on tilted surfaces in southeast of brazil

The global radiation incident on a tilted surfaces consists of components direct, diffuse and reflected from the ground. On a hourly database, the direct radiation can be calculated by geometric projections (ratio of the incidence angle to the solar zenith angle). The reflected radiation has a small effect on calculations and may be calculated with an isotropic model. Both components presents dependence of measures in incidence or horizontal surface. The great difficulty is to evaluate the diffuse radiation by variations of circumsolar, brightness horizontal, isotropic and anisotropic subcomponents. This study evaluated twenty models to estimate hourly diffuse radiation incident on tilted surfaces at 12.85° (latitude - 10°), 22.85° (latitude) and 32.85° (latitude + 10°) facing to North, under different cloudiness sky conditions, in Botucatu, São Paulo State, Brazil (22°53' S, 48°26' W and 786 m above the mean sea level). In contrast, models for estimating the diffuse component show major differences, which justify the validation for local calibrations. There is a decrease of the maximum total radiation scattered with increasing atmospheric transmissivity and inclination angle. The best results are obtained by anisotropic models: Ma and Iqbal, Hay, Reindl et al. and Willmott; isotropic: Badescu and Koronakis, and the Circumsolar model. The increase of the inclination angle allows for a reduction in the performance of statistical parametric models for estimating the hourly diffuse radiation.

Estimativas das radiações direta e difusa em superfícies inclinadas com base na razáo de insolação

Statistical equations were obtained and evaluated with annual, seasonal and monthly data groupings for estimates of direct and diffuse components of solar radiation based on the sunshine duration (ratio of sunshine and photoperiod) incident on horizontal and inclined surfaces to 12.85, 22.85 and 32.85° with facing to North, in Botucatu, SP. The ratios between the two components and radiation at the top of the atmosphere were used, in a database whose inclinations were measured in three different periods (22.85°: 04/1998 to 07/2001; 12.85°: 08/2011 to 02/2003; and 32.85°: 03/2003 to 12/2007) and concomitant with horizontal measures and sunshine duration. The correlations showed a linear and second degree polynomial behavior for the direct and diffuse radiation, with higher coefficients of determination in periods of low variation in the coverage of the sky (cloudiness). The highest values of the direct and diffuse radiation were found in winter and summer, respectively for all surfaces evaluated. The increase in the inclination angle decreased the performance of equations in all groups of data with increase in scattering and decrease in index of the adjustment, however, the monthly equations allowed better performance for the two components.

Sistema de geração fotovoltaico multifuncional

Pós-graduação em Engenharia Elétrica - FEB

Distribuição de frequência das condições de céu em função das variações climáticas em Botucatu-SP

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação do desempenho hidro-energético de sistemas fotovoltaicos utilizados no bombeamento de água

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

A comercialização da energia elétrica cogerada pelo setor sucroalcooleiro em regiões do estado de São Paulo

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Estudo comparativo de coletores solares sem cobertura utilizados para aquecimento de piscinas

Pós-graduação em Engenharia Mecânica - FEB