Electron Transport in Dye-Sensitized Solar Cells Based on ZnO Nanotubes: Evidence for Highly Efficient Charge Collection and Exceptionally Rapid Dynamics

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Improvement of the physical performance is associated with activation of NO/PGC-l alpha/mtTFA signaling pathway and increased protein expressions of electron transport chain in gastrocnemius muscle from rats supplemented with L-arginine

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

Responses of chlorophyll fluorescence parameters of the facultative halophyte and C-3-CAM intermediate species Mesembryanthemum crystallinum to salinity and high irradiance stress

Mesembryanthemum crystallinum L. (Aizoaceae) is a facultative annual halophyte and a C-3-photosynthesis/crassulacean acid metabolism intermediate species currently used as a model plant in stress physiology. Both salinity and high light irradiance stress are known to induce CAM in this species. The present study was performed to provide a diagnosis of alterations at the photosystem 11 level during salinity and irradiance stress. Plants were subjected for up to 13 days to either 0.4M NaCl salinity or high irradiance of 1000 mu mol m(-2) s(-1), as well as to both stress factors combined (LLSA = low light plus salt; HLCO = high light of 1000 mu mol m(-2)s(-1), no salt; HLSA = high light plus salt). A control of LLCO = low light of 200 mu mol m(-2) s(-1), no salt was used. Parameters of chlorophyll a fluorescence of photosystem 11 (PSII) were measured with a pulse amplitude modulated fluorometer. HLCO and LLSA conditions induced a weak degree of CAM with day/night changes of malate levels (Delta malate) of similar to 12 mM in the course of the experiment, while HLSA induced stronger CAM of Delta malate similar to 20mM. Effective quantum yield of PSII, Delta F/F'(m), was only slightly affected by LLSA, somewhat reduced during the course of the experiment by HLCO and clearly reduced by HLSA. Potential quantum efficiency of PSII, F-v/F-m, at predawn times was not affected by any of the conditions, always remaining at >= 0.8, showing that there was no acute photoinhibition. During the course of the days HL alone (HLCO) also did not elicit photoinhibition; salt alone (LLSA) caused acute photoinhibition which was amplified by the combination of the two stresses (HLSA). Non-photochemical, NPQ, quenching remained low (< 0.5) under LLCO, LLSA and HLCO and increased during the course of the experiment under HLSA to 1-2. Maximum apparent photosynthetic electron transport rates, ETRmax, declined during the daily courses and were reduced by LLSA and to a similar extent by HLSA. It is concluded that A crystallinum expresses effective stress tolerance mechanisms but photosynthetic capacity is reduced by the synergistic effects of salinity and tight irradiance stress combined. (c) 2006 Elsevier GmbH. All rights reserved.

Electrical properties of polymer/metal interface in polymer light-emitting devices: electron injection barrier suppression

The electrical characterization of a high efficient multilayer polymer light emitting diode using poly[(2-methoxy-5-hexyloxy)-p-phenylenevinylene] as the emissive layer and an anionic fluorinated surfactant as the electron transport layer was performed. For the sake of comparison, a conventional single layer device was fabricated. The density current vs. voltage measurements revealed that the conventional device has a higher threshold voltage and lower current compared to the surfactant modified device. The effective barrier height for electron injection was suppressed. The influence of the interfaces and bulk contributions to the dc and high frequencies conductivities of the devices was also discussed. (c) 2006 Springer Science + Business Media, Inc.

An Arabidopsis Mitochondrial Uncoupling Protein Confers Tolerance to Drought and Salt Stress in Transgenic Tobacco Plants

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Photoacclimation in a tropical population of Cladophora glomerata (L.) Kützing 1843 (Chlorophyta) from southeastern Brazil

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

Daily dynamics of photosynthesis of the freshwater red alga Sirodotia delicatula (Batrachospermales, Rhodophyta)

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

Chlorophyll fluorescence of tropical tree species in a semi-deciduous forest gap

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

Kinetic study of the plastoquinone pool availability correlated with H2O2 release in seawater and antioxidant responses in the red alga Kappaphycus alvarezii exposed to single or combined high light, chilling and chemical stresses

Under biotic/abiotic stresses, the red alga Kappaphycus alvarezii reportedly releases massive amounts of H2O2 into the surrounding seawater. As an essential redox signal, the role of chloroplast-originated H2O2 in the orchestration of overall antioxidant responses in algal species has thus been questioned. This work purported to study the kinetic decay profiles of the redox-sensitive plastoquinone pool correlated to H2O2 release in seawater, parameters of oxidative lesions and antioxidant enzyme activities in the red alga Kappaphycus alvarezii under the single or combined effects of high light, low temperature, and sub-lethal doses of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), which are inhibitors of the thylakoid electron transport system. Within 24 h, high light and chilling stresses distinctly affected the availability of the PQ pool for photosynthesis, following Gaussian and exponential kinetic profiles, respectively, whereas combined stimuli were mostly reflected in exponential decays. No significant correlation was found in a comparison of the PQ pool levels after 24 h with either catalase (CAT) or ascorbate peroxidase (APX) activities, although the H2O2 concentration in seawater (R = 0.673), total superoxide dismutase activity (R = 0.689), and particularly indexes of protein (R = 0.869) and lipid oxidation (R = 0.864), were moderately correlated. These data suggest that the release of H2O2 from plastids into seawater possibly impaired efficient and immediate responses of pivotal H2O2-scavenging activities of CAT and APX in the red alga K. alvarezii, culminating in short-term exacerbated levels of protein and lipid oxidation. These facts provided a molecular basis for the recognized limited resistance of the red alga K. alvarezii under unfavorable conditions, especially under chilling stress. © 2006 Elsevier B.V. All rights reserved.

Respostas de curto período das características fotossintéticas da alga vermelha Batrachospermum delicatulum a temperatura e irradiância

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

Efeitos de lantadenos sobre a bioenergética em mitocôndrias isoladas de fígado de rato

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

Hybridization effects on the out-of-plane electron tunneling properties of monolayers: is h-BN more conductive than graphene?

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Técnica do Grupo de Renormalização Numérico (GRN) aplicada em quantum dots

Pós-graduação em Física - IGCE

Eficiência fotossintética e consumo de água de Ipomoea triloba após aplicação de herbicidas

Este trabalho foi desenvolvido com o objetivo de avaliar a fluorescência através da taxa de transporte de elétrons, consumo de água e intoxicação de plantas de Ipomoea triloba após aplicação de quatro herbicidas de diferentes mecanismos de ação. Os herbicidas aplicados foram: glyphosate, haloxyfop-methyl, diuron e amicarbazone. A aplicação foi feita com auxílio de um pulverizador estacionário instalado em laboratório; após a aplicação dos tratamentos, as plantas foram mantidas em casa de vegetação. Foi avaliada a taxa de transporte de elétrons (ETR), o consumo de água e a intoxicação das plantas em vários períodos após o início do experimento. Os dados de ETR e fitointoxicação foram expressos em porcentagem da testemunha e submetidos à análise de variância e à comparação das médias. Quanto ao consumo de água, os dados foram acumulados e ajustados por modelos de regressão. Assim, pode-se dizer que o fluorômetro é uma ferramenta adequada para verificar a intoxicação antecipada em plantas de I. triloba tratadas com os herbicidas amicarbazone e diuron, visto que a inibição da ETR foi verificada antes de qualquer intoxicação visual sofrida por essas plantas; o consumo de água está relacionado diretamente com o transporte de elétrons, com exceção das plantas submetidas ao haloxyfop-methyl, que não sofreram interferência no transporte de elétrons, mas reduziram o consumo de água.

Eficiência fotossintética de cultivares de cana-de-açúcar e de diferentes espécies de plantas daninhas após a aplicação do diuron

O objetivo deste trabalho foi avaliar a eficiência fotossintética, através da taxa de transporte de elétrons, de seis espécies de plantas daninhas e três cultivares de cana-de-açúcar após aplicação do herbicida diuron em pós-emergência inicial. Os cultivares utilizados (PO8862, SP80-3280 e RB83-5486) foram cortados em gemas e plantados em vasos com capacidade de 12 litros. A semeadura das seis espécies de plantas daninhas - Brachiaria decumbens, Digitaria horizontalis, Panicum maximum, Ipomoea grandifolia, Ipomoea hederifolia e Merremia cissoides - foi realizada para obter 25 plantas por vaso. A aplicação do herbicida diuron em pós-emergência inicial das plantas daninhas e dos cultivares de cana-de-açúcar foi realizada na dose de 3,0 kg ha-1, com adição de 0,2% de surfatante. As avaliações da taxa de transporte de elétrons no fotossistema (ETR) das plantas após a aplicação foram realizadas com auxílio de um fluorômetro portátil. Para as espécies de plantas daninhas, a ETR foi avaliada após intervalos de 2, 4, 24, 48, 72, 96 e 144 horas após a aplicação. Quanto aos cultivares de cana-de-açúcar, os intervalos avaliados foram de 2, 24, 48, 72, 120, 168 e 240 horas após a aplicação. de maneira geral, as reduções dos valores da ETR indicaram o nível de sensibilidade dos diferentes cultivares de cana-de-açúcar e das diferentes plantas daninhas ao diuron, e a intoxicação foi detectada antes ou mesmo sem a presença dos sintomas. A classificação da sensibilidade dos cultivares de cana-de-açúcar foi em ordem decrescente: PO-8862, SP80-3280 e RB83-5486; para as plantas daninhas, as espécies mais sensíveis foram M. cissoides, I. grandifolia e I. hederifolia, seguidas das gramíneas D. horizontalis, P. maximum e B. decumbens.