Riqueza de espécies, estrutura e composição florística de uma floresta secundária de 40 anos no leste da Amazônia.

A perda de florestas naturais devido a pressões antrópicas levou as florestas secundárias a ocupar uma grande proporção de áreas no leste da Amazônia. Com o objetivo de conhecer as características de uma comunidade arbórea e a estrutura populacional das espécies mais representativas, foram investigadas a riqueza de espécies, a estrutura e a composição florística de uma floresta secundária de 40 anos no município de Bragança (01°11'S e 46°40'W), Estado do Pará, Brasil. A amostragem contou com todos os indivíduos de espécies arbóreas (exceto Arecaceae) com DAP > 5 cm em 150 quadrados de 10×10 m. Foram registrados 2.934 indivíduos em 154 espécies, 101 gêneros e 40 famílias. A densidade foi de 1.956,00 ± 643,45 ind ha-1 e a área basal de 17,358 ± 7,952 m2 ha-1 com um índice de diversidade de Shannon de 4,030 nats. ind.-1. As espécies com a maior abundância de indivíduos foram Myrcia bracteata, Casearia arborea e Maprounea guianensis. As com maior área basal foram Tapirira guianensis, Croton matourensis e Maprounea guianensis. A riqueza de espécies adaptou-se ao modelo de distribuição lognormal apenas para área basal e não para número de indivíduos. Em 40 anos de sucessão, esta floresta mostra uma grande diversidade de espécies e baixa área basal

Self-Optimizing Photoelectrochemical Growth of Nanopatterned Se–Te Films in Response to the Spectral Distribution of Incident Illumination

Photoelectrochemical growth of Se–Te films spontaneously produces highly ordered, nanoscale lamellar morphologies with periodicities that can be tuned by varying the illumination wavelength during deposition. This phenomenon has been characterized further herein by determining the morphologies of photoelectrodeposited Se–Te films in response to tailored spectral illumination profiles. Se–Te films grown under illumination from four different sources, having similar average wavelengths but having spectral bandwidths that spanned several orders of magnitude, all nevertheless produced similar structures which had a single, common periodicity as quantitatively identified via Fourier analysis. Film deposition using simultaneous illumination from two narrowband sources, which differed in average wavelength by several hundred nanometers, resulted in a structure with only a single periodicity intermediate between the periods observed when either source alone was used. This single periodicity could be varied by manipulating the relative intensity of the two sources. An iterative model that combined full-wave electromagnetic effects with Monte Carlo growth simulations, and that considered only the fundamental light-material interactions during deposition, was in accord with the morphologies observed experimentally. Simulations of light absorption and concentration in idealized lamellar arrays, in conjunction with all of the available data, additionally indicated that a self-optimization of the periodicity of the nanoscale pattern, resulting in the maximization of the anisotropy of interfacial light absorption in the three-dimensional structure, is consistent with the observed growth process of such films

Optical and electrochemical effects of H₂ and O₂ bubbles at upward-facing Si photoelectrodes

The effects of the size, contact-angle, and coverage of gas bubbles on solar fuels devices were characterized at cm-scale, upward-facing planar and microwire-array Si photoelectrodes in stagnant electrolytes. Experimental measurements were supported by ray-tracing simulations of surface attached gas bubble films. A dilute, redox-active tracer allowed for the quantification of the mass-transport effects of bubble coverage during photoanodic O₂ (g) evolution at upward-facing photoanodes in 1.0 M KOH(aq.). Measurements of the gas coverage at upward-facing p-Si photocathodes in 0.50 M H₂SO₄ (aq.) allowed for the nucleation rate and contact angle of H₂ (g) bubbles to be evaluated for systems having various surface free energies. Under simulated solar illumination, the rapid departure of small O₂ (g) bubbles produced stable photocurrents at upward-facing oxygen-evolving Si photoanodes and yielded increased mass-transport velocities relative to a stagnant electrolyte, indicating that bubbles can provide a net benefit to the photoelectrochemical performance of an upward-facing photoanode in solar fuels devices

Inorganic Phototropism in Electrodeposition of Se-Te

Photoelectrochemical deposition of Se–Te on isolated Au islands using an unstructured, incoherent beam of light produces growth of Se–Te alloy toward the direction of the incident light beam. Full-wave electromagnetic simulations of light absorption indicated that the induced spatial growth anisotropy was a function of asymmetric absorption in the evolving deposit. Inorganic phototropic growth is analogous to biological systems such as palm trees that exhibit phototropic growth wherein physical extension of the plant guides the crown toward the time-averaged position of the sun, to maximize solar harvesting

Keratocystic odontogenic tumour masquerading as a mucosal antral cyst

Keratocystic odontogenic tumour (KCOT) is of clinical importance because of its pronounced tendency to recur. Among the factors that complicate KCOT management are its protean radiological presentations. KCOT showing involvement of the maxillary antrum in the absence of an associated impacted tooth is exceptionally rare. In these instances an odontogenic source of the lesion is often not suspected and the clinico-radiological features may be misinterpreted. We report such a case and highlight pertinent clinical and radiological features of antral KCOT.http://www.sada.co.zaam201

The Influence of Structure and Processing on the Behavior of TiO_2 Protective Layers for Stabilization of n-Si/TiO_2/Ni Photoanodes for Water Oxidation

Light absorbers with moderate band gaps (1–2 eV) are required for high-efficiency solar fuels devices, but most semiconducting photoanodes undergo photocorrosion or passivation in aqueous solution. Amorphous TiO_2 deposited by atomic-layer deposition (ALD) onto various n-type semiconductors (Si, GaAs, GaP, and CdTe) and coated with thin films or islands of Ni produces efficient, stable photoanodes for water oxidation, with the TiO_2 films protecting the underlying semiconductor from photocorrosion in pH = 14 KOH(aq). The links between the electronic properties of the TiO_2 in these electrodes and the structure and energetic defect states of the material are not yet well-elucidated. We show herein that TiO_2 films with a variety of crystal structures and midgap defect state distributions, deposited using both ALD and sputtering, form rectifying junctions with n-Si and are highly conductive toward photogenerated carriers in n-Si/TiO_2/Ni photoanodes. Moreover, the photovoltage of these electrodes can be modified by annealing the TiO_2 in reducing or oxidizing environments. All of the polycrystalline TiO_2 films with compact grain boundaries investigated herein protected the n-Si photoanodes against photocorrosion in pH = 14 KOH(aq). Hence, in these devices, conduction through the TiO_2 layer is neither specific to a particular amorphous or crystalline structure nor determined wholly by a particular extrinsic dopant impurity. The coupled structural and energetic properties of TiO_2, and potentially other protective oxides, can therefore be controlled to yield optimized photoelectrode performance

Estudos físico-químicos de mesocarpo e endocarpo de urucuri (Attalea pharelata Mart. ex Spreng.).

O urucurizeiro é uma palmeira que se encontra também distribuída no Estado do Amapá, entre outros estados, tendo sua principal utilização como fonte de óleo que é extraído tanto da polpa quanto da semente, assim como da ingestão de sua polpa na forma in natura ou cozida, mas poucos estudos sobre a composição nutricional dessa espécie. existem. O Amapá possui uma grande biodiversidade e a preocupação com sua conservação, enfrentando também problemas de isolamento de muitas comunidades. Entende-se que o uso sustentável de sua biodiversidade pode ser realizado através da investigação de modo científico do conhecimento tradicional das espécies locais, como o urucuri e deste modo pretendeu-se disponibilizar com este trabalho alguns dados sobre as características intrínsecas desta espécie, nas condições do Amapá. Amostras de urucuri foram coletadas nos município de Mazagão e Laranjal do Jari em 2005 c 2006, sendo avaliadas as características físico-químicas do mesocarpo (polpa) e do endocarpo (semente). Observou-se que o teor de matéria seca apresentou média de 16,29% com variações entre locais. O teor de proteína das polpas variaram entre 7,42% a 8,07%, representando uma média considerável (7,75%) para uma utilização alimentar, assim como o conteúdo na semente ou endocarpo (5,35%) para alimentação animal. O pH do mesocarpo mostrou-se ácido (5,37), com um reduzido teor de acidez total titulável (4,59mL NaOHIN) e teor de sacarose de 9,13°Brix. A relação SST/ATT da polpa indicou valor muito baixo (1,99), podendo indicar um comprometimento com o sabor da mesma. O teor de lipídeos das polpas não foi expressivo no mesocarpo (média de 2,83%), enquanto que no endocarpo a média foi de 7,48%, superior ao valor encontrado na polpa. Nas condições do Amapá, o urucuri pode ser considerado uma matéria-prima alternativa como componente para produção de energia, principalmente para comunidades isoladas, assim como sua polpa pode ter um aproveitamento potencial na alimentação humana e animalEditado por Pedro Castro Neto, Antônio Carlos Fraga