A study of the main oxidation products of natural pyrite by voltammetric and photoelectrochemical responses

(Photo)electrochemical experiments on pyrite electrodes in acetic acid-acetate buffer (pH = 4.5) are conducted to clarify the main oxidation reactions and the nature of the products. Electrochemical reactions in the -0.40 to 1.25 V (SHE) potential range are studied, and the production of iron (III) polysulfide from anodically formed iron oxides and polysulfides is discussed. Charges experimentally obtained are considered for the estimation of the most likely stoichiometry of the metallic polysulfide. The photoselectivity of the pyrite corrosion process indicates that the oxidation reactions of Fe2+ and S-2(2-) an not consecutive. The changes in stoichiometry and/or annihilation of crystalline structure defects are responsible for the observed photosensitivity of pyrite. A description of light effects on the interfacial behaviour and stability of pyrite is presented in terms of conduction and valence band energies, and thermodynamic potentials. (C) 2001 Elsevier Science B.V. All rights reserved.

Reproductive biology and pollination mechanisms of Epidendrum secundum (Orchidaceae). Floral variation: a consequence of natural hybridization?

The phenology, flower morphology, pollination mechanism and reproductive biology of Epidendrum secundum were studied in a semi-deciduous forest at the Serra do Japi (SJ), and in the Atlantic rain forest of Picinguaba, both natural reserves in the State of Sao Paulo, southeastern Brazil. E. secundum flowers all year round, with a flowering peak between September and January. This species is either a lithophytic or terrestrial herb in the SJ, whereas, in Picinguaba, it grows mainly in disturbed areas along roadsides. E. secundum is pollinated by several species of diurnal Lepidoptera at both study sites. In Picinguaba, where E. secundum is sympatric with E. fulgens and both share the same pollinators, pollen transference between these two species was recorded. E. secundum is self-compatible but pollinator-dependent. It is inter-compatible with E. fulgens, producing fertile seeds. In contrast to the population of the SJ, in the Picinguaba region, floral morphology is quite variable among plants and some individuals present flowers with characteristics in-between both sympatric species, suggesting that natural hybridization occasionally occurs. The anthropogenic perturbation is probably the cause of the occurrence of E. secundum in the Picinguaba region, enabling its contact with E. fulgens.

Chemical Characterization and Antimicrobial Activity Evaluation of Natural Oil Nanostructured Emulsions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Allelopathic potential and survey of natural seed bank under the canopy of Copaifera Langsdorffii Desf

The aim of this study was to evaluate the allelopathic effect of soil samples collected under the canopies of three specimens of Copaifera langsdorffii the germination of Lactuca sativa and survey the natural seed bank according to seasonality. To test the allelopathic effect was carried experiments of pre and post-emergence with seeds of L. sativa and to quantify the stock of seeds, soil samples were collected from three specimens at three distances from the stem (1, 2 and 3 m) and at three depths (0-5, 5-10 and 10-15cm) in the region of savanna in the dry and wet seasons. The samples tested in bioassay of pre-emergence no significant influence on germinability, mean germination time and mean germination speed, but showed a difference in the synchronism of germination, these data were independent of sampling station. In test for post-emergence was observed statistical difference in the parameters evaluate (length of primary roots and hypocotyls) in both seasons. To quantify the natural seed bank were macroscopic analysis of each soil sample with the help of stereoscopic microscope. The analysis of the natural seed bank showed a larger number of seeds in the 0-5cm and in distance of 2m for both seasons. The results suggest the presence of allelochemical substances in soil samples collected under the canopy of Copaifera langsdorffii.

Balancing immunity and tolerance: genetic footprint of natural selection in the transcriptional regulatory region of HLA-G

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Electrical, mechanical, and thermal analysis of natural rubber/polyaniline-DBSA composite

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Studies of natural killer cells in patients with paracoccidioidomycosis

The number and activity of natural killer (NK) cells were studied in 34 untreated patients with paracoccidioidomycosis, 20 with the chronic form of the disease and 14 with the acute form. NK cells were detected with monoclonal antibody Leu-11c and the cytotoxic activity was measured using a single cell assay against K562 target cells. Both groups of patients had an increased number of circulating NK cells, their cytotoxic activity being significantly lower than in the healthy controls. These findings may be of importance in the immunological disturbances associated with paracoccidioidomycosis since NK cells exert important immune effector functions and may play a role in resistance against Paracoccidioides brasiliensis.

Extraction of natural red colorants from the fermented broth of Penicillium purpurogenum using aqueous two-phase polymer systems

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

Formação de professores das séries iniciais: o pedagogo em questão

Pós-graduação em Educação para a Ciência - FC

Medium and large-sized mammals in a private reserve of natural heritage in the municipality of Jaú, São Paulo, Brazil

Medium and large-sized mammals control invertebrate and vertebrate populations and are important seed dispersers. These animals are losing their territory and living range due to deforestation and the fragmentation of natural areas, particularly in the Atlantic Forest and Cerrado. The Private Reserve of Natural Heritage (PRNH) Amadeu Botelho is isolated from other forest fragments and is thus a wildlife refuge in the region of Jaú, central-western region of state of São Paulo, southeastem Brazil. Animals as such as the puma (Puma concolor), ocelot (Leopardus pardalis) and jaguarundi (Puma yagouaroundi) have been sighted in the reserve by wildlife guards and residents. This reserve, which belongs to “Santo Antônio dos Ipês” farm, is surrounded by several plantations, and is very close to the center of the city of Jaú. In addition to surveying the mammal species in the reserve, this study diagnosed the influence of the farm’s activities and the proximity to the center of the municipality of Jaú on the fauna under study

Effect of natural antimicrobials on microbiological and sensorial quality of fresh-cut cantaloupe melon

The effect of different natural antimicrobials on the microbiological and sensorial quality of fresh-cut Cantaloupe melons stored up to 10 days at 5°C was examined. Pieces of melon were washed for 1 min at 5ºC in water (control), vanillin (1000 mg/L and 2000 mg/L) or cinnamic acid (148.16 mg/L and 296.32 mg/L). Other antimicrobial treatments consisted of packaging the pieces of melon with an antimicrobial pad which contained cinnamic acid (148.16 mg/L and 296.32 mg/L). After 10 days of storage, significant differences among antimicrobials treatments and water treatment were found. In water treatment, the psychrotroph load was 3.63 ± 0.09 log cfu g-1 meanwhile on all antimicrobial treatments the values ranged from 3.04 ±0.13 log cfu g-1 to 3.28±0.1 log cfu g-1. Mesophilic growth in the control treatment averaged 6.79±0.06 log cfu g-1 meanwhile on antimicrobial treatments the counts were from 5.15±0.01 log cfu g-1 to 5.30±0.03 log cfu g-1. Total coliform levels were 7.8±0.1 log cfu g-1 when melon was washed in water, followed by washing with cinnamon (296.32 mg/L) at 6.5 log cfu g-1 and for the rest of the treatments were around 5.5 log cfu g-1. The treatments did not display differences among mould and yeast growth after 10 days of storage. The sensorial quality decreased throughout storage. However, at the end of storage, the scores ranged between 6.5 and 7, above the minimum level for marketability (level 5). Sensorial panelist noted a ‘sweet’ taste when vanillin was used as sanitizer. In all antimicrobial treatments, no relation was found between a higher dose and a higher microbial reduction. So, vanillin at 1000 mg/L in water or cinnamic acid at 148.16 mg/L provided in water dip or as a pad inside the trays could be optimal natural sanitizers to substitute the use of chlorine in fresh-cut products as Cantaloupe melon.