Comment on "Spin-1 aggregation model in one dimension"

M. Girardi and W. Figueiredo have proposed a simple model of aggregation in one dimension to mimic the self-assembly of amphiphiles in aqueous solution [Phys. Rev. E 62, 8344 (2000)]. We point out that interesting results can be obtained if a different set of interactions is considered, instead of their choice (the s=1 Ising model).Comment: Accepted for publication in Phys. Rev.

An exact master equation for the system-reservoir dynamics under the strong coupling regime and non-Markovian dynamics

In this paper we present a method to derive an exact master equation for a bosonic system coupled to a set of other bosonic systems, which plays the role of the reservoir, under the strong coupling regime, i.e., without resorting to either the rotating-wave or secular approximations. Working with phase-space distribution functions, we verify that the dynamics are separated in the evolution of its center, which follows classical mechanics, and its shape, which becomes distorted. This is the generalization of a result by Glauber, who stated that coherent states remain coherent under certain circumstances, specifically when the rotating-wave approximation and a zero-temperature reservoir are used. We show that the counter-rotating terms generate fluctuations that distort the vacuum state, much the same as thermal fluctuations.Finally, we discuss conditions for non-Markovian dynamics

Electronic properties of curved graphene sheets

A model is proposed to study the electronic structure of slightly curved graphene sheets with an arbitrary number of pentagon-heptagon pairs and Stone-Wales defects based on a cosmological analogy. The disorder induced by curvature produces characteristic patterns in the local density of states that can be observed in scanning tunnel and transmission electron microscopy.Comment: Corrected versio

Throughfall and temporal trends of rainfall redistribution in an open tropical rainforest, south-western Amazonia (Rondônia, Brazil)

International audienceThroughfall volumes and incident rainfall were measured between 23 August and 2 December 2004 as well as from 6 January to 15 April 2005 for individual rain events of differing intensities and magnitudes in an open tropical rainforest in Rondônia, Brazil. Temporal patterns of throughfall spatial variability were examined. Estimated interception was compared to modeled interception obtained by applying the revised Gash model in order to identify sources of throughfall variability in open tropical rainforests. Gross precipitation of 97 events amounted to 1309 mm, 89±5.6% (S.E.) of which reached the forest floor as throughfall. The redistribution of water within the canopy was highly variable in time, which we attribute to the high density of babassu palms (Orbignya phalerata), their seasonal leaf growth, and their conducive morphology. We identified a 10-min rainfall intensity threshold of 30 mmh-1 above which interception was highly variable. This variability is amplified by funneling and shading effects of palms. This interaction between a rainfall variable and vegetation characteristics is relevant for understanding the hydrology of all tropical rainforests with a high palm density

Fungos associados a sementes de açaí: efeito da temperatura e do teor de água das sementes durante o armazenamento.

O trabalho teve como objetivo verificar os efeitos do teor de água e da temperatura do ambiente de armazenamento na incidência de fungos e na germinação de sementes de açaí (Euterpe oleracea Mart.). Foram utilizadas sementes da cultivar BRS Pará, com teores de água de 43%, 37%, 30%, 26%, 21% e 12%, que foram acondicionadas em sacos de polietileno, armazenadas sob temperaturas de 20 ºC, 15 ºC e 10 ºC, durante 360 dias e submetidas a avaliações bimensais do teor de água, da germinação e da incidência de Penicillium sp., Aspergillus sp., Fusarium solani e Fusarium verticillioides. Foi adotado o delineamento experimental inteiramente casualizado com quatro repetições para o teste de germinação e cinco repetições para os testes de sanidade. Foi observada maior ocorrência de Penicillium sp., e Aspergillus sp em sementes com teores de água abaixo de 30% e mantidas nas temperaturas de 15 ºC e 20 ºC. Enquanto, as maiores incidências de fungos do gênero Fusarium foram encontradas em sementes armazenadas com graus de umidade de 43% e 37% e mantidas em temperatura de 10 ºC

Rainfall Erosivity in Apeú River Watershed, Northeastern State of Pará, in the Brazilian Amazon Region.

Resumo em português: Erosividade das Chuvas na Bacia Hidrográfica do Rio Apeú, Região Nordeste do Estado do Pará

Bacillus thuringiensis production using cassava liquid waste (manipueira) as a fermentation substrate.

In developing countries the search for inexpensive substrates to grow useful microorganisms is a desirable way to get new and safe products to protect man against insect pest losses. Bacillus thuringiensis is an entomopathogenic bacteria, which by fermentation produces endo- or exotoxins to be used against Lepidoptera or Diptera, resp. These are insect pests of economic importance in developing countries, mainly in Brazil, where 60% losses in agriculture are caused by this type of pest. Our research group has been working with B. thuringiensis since 1970; and many papers have been published on the processes, culture media composition and available substrates, culture and operational conditions, equipment and so on. Many residues and waste waters were tried forthe fermentation culture medium. This paper reports the possibility of using manipueira, a residual waste water from cassava processing as a substrate to produce B. thuringiensis by fermentation. The culture medium was composed of 75% manipueira & 25% water. Operational conditions considered agitation and aeration rate, as well as initial pH and optimum growing temperature. Microbial growth and sporulation behavior were accomplished by optical density determination, pH variation and sugar consumption. Results are promising