Variação espacial e temporal da produtividade primária pelo fitoplâncton na represa de Jurumirim (Rio Paranapanema, SP)

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

Trocas gasosas e ciclo fotossintético da figueira 'Roxo de Valinhos'

No presente trabalho, determinaram-se as trocas gasosas de folhas de figueira 'Roxo de valinhos' e o ciclo fotossintético por meio da relação isotópica 12C/13C. Essas medidas foram realizadas sempre na região mediana das folhas, completamente expandidas e totalmente expostas à radiação solar, no período das 09h00min às 10h30min. As folhas fotossinteticamente ativas da figueira apresentaram área foliar em torno de 160cm², com uma assimilação de 14,38µmol m-2 s-1 de CO2, cujos valores isotópicos médios no ramo 1 e no 2 são -28,98±0,69 e -29,28±0,85 , respectivamente. Com base nos valores da fotossíntese máxima e na discriminação isotópica do 13C, evidenciou-se que a figueira pode ser considerada uma planta do ciclo fotossintético C3.

Simulação do saldo de radiação na Serra da Mantiqueira

A influência do desmatamento da Mata Atlântica sobre o microclima da Serra da Mantiqueira ainda não é totalmente compreendida. Para conhecer as consequências do desmatamento sobre o clima serrano é necessário realizar estudos sobre o balanço de radiação na superfície. A falta de dados possibilita conjugar imagens de satélite com dados meteorológicos em um Sistema de Informação Geográfica na determinação do balanço de radiação. O presente estudo teve por objetivo avaliar o modelo MTCLIM em dias de céu claro ou nublado para simular o balanço de radiação na Serra da Mantiqueira, divisa entre os estados de São Paulo, Minas Gerais e Rio de Janeiro, Brasil. Imagens diárias, semanais e dezesseis dias do sensor MODIS disponíveis em 2003 foram utilizadas em rotinas específicas do MTCLIM. Alvos específicos foram selecionados para avaliar o comportamento do balanço de radiação. Observou-se que o balanço de radiação acompanhou a topografia local e é influenciado pelo tipo de uso da terra. Conclui-se que a temperatura da superfície contribui para aumentar a temperatura do ar implicando em diminuição do balanço de radiação sobre pastagem. O modelo MTCLIM demonstrou boa correlação para a temperatura do ar (R² = 0,82) e para a radiação solar global (R² = 0,71).

Efeitos do estresse térmico nas concentrações plasmáticas de progesterona (P4) e estradiol 17-b (E2) e temperatura retal em cabras da raça Pardo Alpina

Seis cabras lactantes foram distribuídas aleatoriamente em um delineamento experimental em crossover, em dois grupos: sob condições termoneutras e estresse térmico. Um período de adaptação de 28 dias foi seguido por quatro períodos de 14 dias cada, quando os animais sob estresse térmico foram expostos à temperatura média de 33,84ºC; THI de 86,20; BGT de 36,18 e BT de 32,11ºC das 8 às 17 horas, incluindo radiação solar simulada das 10 às 15 horas. Não houve diferença entre as concentrações plasmáticas de progesterona, mas as fêmeas submetidas ao estresse térmico apresentaram diminuição nas concentrações plasmáticas de estradiol, quando comparados ao grupo termoneutro. A temperatura retal dos animais sob estresse térmico foi mais elevada quando foi comparada à do grupo de animais em condições de termoneutralidade. As cabras mantiveram as concentrações plasmáticas da progesterona, com diminuição na secreção de estradiol, quando expostas a um estresse repetido e intermitente, a despeito de ocorrer hipertermia durante o estresse pelo calor.

An application of neural network technique to correct the dome temperature effects on pyrgeometer measurements

This work describes an application of a multilayer perceptron neural network technique to correct dome emission effects on longwave atmospheric radiation measurements carried out using an Eppley Precision Infrared Radiometer (PIR) pyrgeometer. It is shown that approximately 7-month-long measurements of dome and case temperatures and meteorological variables available in regular surface stations (global solar radiation, air temperature, and air relative humidity) are enough to train the neural network algorithm and correct the observed longwave radiation for dome temperature effects in surface stations with climates similar to that of the city of São Paulo, Brazil. The network was trained using data from 15 October 2003 to 7 January 2004 and verified using data, not present during the network-training period, from 8 January to 30 April 2004. The longwave radiation values generated by the neural network technique were very similar to the values obtained by Fairall et al., assumed here as the reference approach to correct dome emission effects in PIR pyrgeometers. Compared to the empirical approach the neural network technique is less limited to sensor type and time of day (allows nighttime corrections).

A note on the horseshoe confinement model: the Poynting-Robertson effect

In the present work we numerically simulated the motion of particles coorbital to a small satellite under the Poynting-Robertson light drag effect in order to verify the symmetry suggested by Dermott et al. (1979, 1980) on their ring confinement model. The results reveal a more complex scenario, especially for very small particles (micrometer sizes), which present chaotic motion. Despite the complexity of the trajectories the particles remain confined inside the coorbital region. However, the dissipative force caused by the solar radiation also includes the radiation pressure component which can change this configuration. Our results show that the inclusion of the radiation pressure, which is not present in the original confinement model, can destroy the configuration in a time much shorter than the survival time predicted for a dust particle in a horseshoe orbit with a satellite.

Non-isothermal kinetic applied to thermal decomposition of commercial alkyd varnish

Samples of commercial alkyd resin varnish were spread in a film form on slides, dried at room temperature and exposed to solar radiation from one day up to seven months.Thermogravimetric measurements have been done. Based on the TG data, the Flynn-Wall isoconversional method was applied. The activation energy varied between 176-154 kJ mol(-1) and logA was between 15.5-12.9 min(-1) for A, B and C samples at 95% confidence level.

Concentrações plasmáticas de cortisol, hormônios tiroídeanos, metabólitos lipídicos e temperatura corporal de cabras alpinas submetidas ao estresse térmico

The objective of this work was to determine the plasma concentrations of cortisol, thyroid hormone, lipids metabolites and corporal temperature or lactating Alpine goats submitted to heat stress. Six lactating Alpine goats were allotted randomly in a crossover experimental design for two groups: thermoneutral conditions or thermal stress. An adaptation period of 28 days was followed by Four-periods of 14 days each, when the animals submitted to thermal stress were exposed to the average temperature of 33.84 degrees C; THI of 86.20; BGT of 36.18 and BT of 32.11 degrees C from 8:00 am to 5:00 pm, including simulated solar radiation from 10:00 am to 3:00 pm. There were no differences between the groups in the plasma concentrations of cortisol, thyroid hormones (T-3-triiodothyronine and T-(4) tiroxine), and lipid metabolites (cholesterol and HDL). Rectal temperature was higher during thermal stress when compared to the group of animals in thermoneutral conditions. The goats maintained the thyroid plasma hormone concentrations, when exposed to repealed and intermittent stress, in spite of the occurrence of hypertermia during heat stress.

Modelling short-term temporal changes of bare soil CO2 emissions in a tropical agrosystem by using meteorological data

Determining the variability of carbon dioxide emission from soils is an important task as soils are among the largest sources of carbon in biosphere. In this work the temporal variability of bare soil CO2 emissions was measured over a 3-week period. Temporal changes in soil CO2 emission were modelled in terms of the changes that occurred in solar radiation (SR), air temperature (T-air), air humidity (AR), evaporation (EVAP) and atmospheric pressure (ATM) registered during the time period that the experiment was conducted. The multiple regression analysis (backward elimination procedure) includes almost all the meteorological variables and their interactions into the final model (R-2 = 0.98), but solar radiation showed to be the one of the most relevant variables. The present study indicates that meteorological data could be taken into account as the main forces driving the temporal variability of carbon dioxide emission from bare soils, where microbial activity is the sole source of carbon dioxide emitted. (C) 2003 Elsevier B.V. All rights reserved.

Kinetic parameters obtained for thermal decomposition of acrylic resins present in commercial paint emulsions

Samples of water based commercial acrylic resin paints were spread in a film form on slides, dried at room temperature and exposed to solar radiation for up to eight months.The characterization and quantification of resins and charges in the white paint emulsion were carried out for the thermal decomposition. Besides this, X-ray diffractometry was used to identify CaCO3 as charge and TiO2 (rutile phase) as pigment.It was observed through thermal techniques similar behavior to the samples even though with varied exposure time.Kinetic studies of the samples allowed to obtain the activation energy (Ea) and Arrhenius parameters (A) to the thermal decomposition of acrylic resin to three different commercial emulsion (called P-1, P-2, P-3) through non-isothermal procedures. The values of E. varied regarding the exposition time (eight months) and solar radiation from 173 to 197 U mol(-1) (P-1 sample), from 175 to 226 W mol(-1) (P-2 sample) and 206 to 197 kJ mol(-1) (P-3 sample).Kinetic Compensation Effect (KCE) observed for samples P-2 and P-3 indicate acrylic resin s present in these may be similar in nature. This aspect could be observed by a small difference in the thermal behavior of the TG curves from P I to P-2 and P-3 sample.The simulated kinetic model to all the samples was the autocatalytic estdk Berggreen.

Radiative properties of the skin and haircoat of cattle and other animals

Radiative properties (reflectance rho, transmittance tau, and absorptance alpha) were determined for wavelengths from 300 to 850 nm in the haircoat and the skin of water buffalo, deer (Pantanal deer, Blastocerus dichotomus), and cattle of the Holstein, Simmental, Canchim, Brangus, and Nelore breeds. The results showed that white hairs have higher rho (0.60 to 0.67) than the other coat colors, but the gray coats (mixed white and dark hair) of the Nelore cattle presented higher rho than that of the white coats of the European breeds at wavelengths lower than 600 nm. The light gray colored skin of the Canchim cattle had higher rho (0. 66) than the non-pigmented skin of Holstein (0.53). Red skins presented rho values higher than those of dark gray and black skins. Buffalo skin (dark gray) presented an average rho of 0.23+/-0.02 and alpha of 0.77+/-0.02. The red haircoat of the deer presented rho lower (0.37) than that of cattle of the same color (0.58). However, there was little difference between deer and cattle with respect to reflectance and absorptance of the skin. As for the spectral transmittance of the skin, it was very low and about the same for both species, until 600 nm. In the range 600 to 850 nm, the tau values for cattle rose to 0. 17, while those for deer increased only to 0.12.

Thermoregulatory responses of Alpine goats during thermal stress

Eight non-lactating Alpine goats, averaging 57kg, were paired according to weight and assigned randomly to 2 groups of 4 animals, control (CG) and treatment (TG) with feed and water ad libitum. An adjustment period of 7 days with all animals at thermoneutral conditions was followed by a 28-day period when TG was exposed to air temperatures averaging 35.0 degrees C, from 0800 to 1700h, including simulated solar radiation, and thermoneutral conditions from 2700 to 0800h. CG remained under thermoneutral conditions. Respiratory frequency was greater, tidal volume lower, and respiratory minute volume greater for TG than CG (176 vs 30 breaths/min, P<.001, 105 vs 293ml, P<.01; 18.4 vs 9.21, P<.05). Respiratory evaporation and sweating rate as well as rectal and skin temperatures were greater for TG than CG (14.59 vs 6.32 kcal h(-1), P<.01; 43.97 vs.00 g m(-2) h(-1), P<.001; 40.0 vs 38.9 degrees C, P<.001; 39.3 vs 35.8 degrees C, P<.01). There was no difference between groups for hematocrit and feed intake, but water consumption was greater for stressed goats than control ones (28.3 vs 29.7%; 1.44 vs 1.49 kg/day; 3.07 vs 1.26 I/day, P<.05), Final body weights of both groups were similar to initial ones. It was concluded that non-lactating goats tolerated well a 35 degrees C day temperature which is 5 degrees C above the upper critical temperature, with a black-globe temperature of 39.1 degrees C and a Botsball temperature of 28.3 degrees C, though a certain degree of hyperthermia may occur, as long as thermoneutral conditions have prevailed during the night.

Effect of epicuticular waxes of fruits on the photodegradation of fenthion

After treatment lipophilic pesticides tend to diffuse by penetrating the epicuticular wax of fruits. In this way, solar radiation only acts on pesticide molecules after passing through the waxes. The effect of epicuticular waxes of three fruits (orange, nectarine, and olive) on the photodegradation of fenthion was studied. The waxes affected the photodegradation process of fenthion. The decay rate of fenthion increased in the presence of orange and nectarine waxes, while it decreased when olive wax was used. In all waxes, the transformation of fenthion produced mainly fenthion sulfoxide and low amounts of fenthion sulfone. In orange wax, 50% of the initial fenthion was transformed into unknown compounds. In nectarine wax, fenthion was degraded stoichiometrically into fenthion sulfoxide and fenthion sulfone. In olive wax, the photodegradation of fenthion yielded about 80% of fenthion sulfoxide.

Numerical study of low-cost alternative orbits around the Moon

In this paper, we have investigated a region of direct stable orbits around the Moon, whose stability is related to the H2 Family of periodic orbits and to the quasi-periodic orbits that oscillate around them. The stability criteria adopted was that the path did not escape from the Moon during an integration period of 1000 days (remaining with negative two-body Moon-probe orbital energy during this period). Considering the three-dimensional four-body Sun-Earth-Moon-probe problem, we investigated the evolution of the size of the stability region, taking into account the eccentricity of the Earth's orbit, the eccentricity and inclination of the Moon's orbit, and the solar radiation pressure on the probe. We also investigated the evolution of the region's size and its location by varying the inclination of the probe's initial osculating orbit relative to the Moon's orbital plane between 0 degrees and 180 degrees. The size of the stability region diminishes; nevertheless, it remains significant for 0 <= i <= 25 degrees and 35 degrees <= i <= 45 degrees. The orbits of this region could be useful for missions by space vehicles that must remain in orbit around the Moon for periods of up to 1000 days, requiring low maintenance costs. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

Amino Acids on Mango Yield and Fruit Quality at Submedio Sao Francisco Region, Brazil

Farmers of the Submedio Sao Francisco Region (Brazil) have been spraying amino acids on mango trees with the objective of increasing panicle length and improving fruit retention and quality. This study, done in two experiments, tested the effect of amino acids sprayings at concentrations of 0.0%; 0.02%; 0.04% and 0.06%, on mango plants, 'Tommy Atkins', on the budding phase (panicles with 5 cm), fruit set and fruit growth (5 cm diameter). They were carried out from June to October in 2003, that is the natural period for harvest in the region, and from January to May, in 2004. There were no statistical differences in the first experiment among treatments regarding panicle length and fruit production, probably due to an appropriate management of nutrition, water and plant growth regulators, besides climatic conditions, mainly temperature and solar radiation. In the second experiment, significant increments in the panicle length of 13.37%, 11.70% and 21.4% were observed with amino acids concentrations, compared to the control. Increasing amino acids doses also enhanced the number of fruits per plant, thirty days before the harvest, in 16.17%, 45.32% and 37.38%, respectively, compared to the control, but there were no significant statistical differences. Characteristics of fruit quality during storage, as weight loss, total soluble solids, total titratable acidity and pulp firmness were not significantly affected by amino acids spraying. Changes on those variables were registered as a consequence of fruit ripening. Amino acids sprays lightly delayed the evolution of skin luminosity and Hue of pulp, but the differences could not be visually identified. The concentrations of amino acids were not efficient for improving the natural concentrations of these substances in the leaves, which could be the reason for the non significant effects on the variables analyzed.