The origin of power-law distributions in deterministic walks: the influence of landscape geometry

We investigate the properties of a deterministic walk, whose locomotion rule is always to travel to the nearest site. Initially the sites are randomly distributed in a closed rectangular ($A/L \times L)$ landscape and, once reached, they become unavailable for future visits. As expected, the walker step lengths present characteristic scales in one ($L \to 0$) and two ($A/L \sim L$) dimensions. However, we find scale invariance for an intermediate geometry, when the landscape is a thin strip-like region. This result is induced geometrically by a dynamical trapping mechanism, leading to a power law distribution for the step lengths. The relevance of our findings in broader contexts -- of both deterministic and random walks -- is also briefly discussed.Comment: 7 pages, 11 figures. To appear in Phys. Rev.

BRS Novaera: cultivar de feijão-caupi de porte semi-ereto.

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Adaptabilidade e estabilidade da produtividade em grãos de genótipos de feijão-caupi de porte semi-ereto na região Nordeste.

Foram avaliadas a adaptabilidade e a estabilidade da produtividade de grãos de 20 genótipos de feijão-caupi de porte semi-ereto, utilizando o modelo de efeitos aditivos principais e interação multiplicativa. Os ensaios foram realizados em 16 ambientes, locais e anos, da região Meio-Norte do Brasil, Estados do Maranhão (MA), Piauí (PI), Pernambuco (PE), Sergipe (SE), Bahia (BA) e Paraíba (PB), no período de 2002 a 2004. Os efeitos de ambiente e da interação genótipos x ambientes, e os dois primeiros eixos da análise de componentes principais da interação foram significativos (P < 0,01). A análise de componentes principais explicou 55,11% da soma de quadrados da interação genótipos x ambientes. Os genótipos TE-97-411-1F-16, EVX-92-49E e EVX-63-10E reúnem adaptabilidade e estabilidade e podem ser cultivados em todos os ambientes estudados, enquanto que os genótipos TE-BRS Guariba e EVX-91-2E-1 expressam melhor potencial genético em ambientes de alta produtividade. Os ambientes mais favoráveis para a produtividade de grãos foram Bom Jesus 2003, Nossa senhora das Dores 2003, São Raimundo das Mangabeiras 2003 e Teresina 2002

Salicornia as a fermented product: development of an optimised procedure for a controlled process

[PORT] Com o intuito de desenvolver um produto fermentado à base de rebentos de salicórnia conduziu-se esta experiência para monitorizar o processo fermentativo. Os dados inicialmente obtidos por caracterização fenotípica revelaram a inexistência de bactérias do ácido láctico na flora indígena da planta. Consequentemente, optou-se pela utilização de culturas de arranque, tendo-se monitorizado as condições de pH, acidez titulável e salinidade em soro de couve estéril, com e sem salicórnia, quando expostas a diferentes bactérias fermentativas: Lactobacillus plantarum, Leuconostoc mesenteroides e Pediococcus acidilactici. Apenas se verificaram alterações significativas no processo fermentativo com a introdução da salicórnia no caso da fermentação com L. plantarum, tendo-se observado um aumento significativo na variação do pH e da % de ácido láctico, no decorrer do processo, e comparativamente com as restantes estirpes. Os resultados obtidos para a acidez titulável são satisfatórios já que foi detectado, aproximadamente, 1 % de ácido láctico como resultado da actividade fermentativa nas diferentes culturas de arranque. A espécie predominante no final da fermentação foi L. Plantarum, sendo esta a que produziu maior percentagem de ácido láctico. [ENG] In order to develop a fermented product with young stems of salicornia/pickleweed, an experiment was worked out and the fermentative process was studied. Initial data on the bacterial fauna of the plants revealed the existence of no lactic acid bacteria. Therefore, we chose to use of starting cultures. Sterile “heart cabbage” juice was the base for different fermentative bacteria: Lactobacillus plantarum, Leuconostoc mesenteroides, Pediococcus acidilactici, and pH, titrated acidity and salinity were evaluated. The same experiment was undertaken with and without the glasswort or salicornia. Significant differences were observed only with L. plantarum: pH variation and percentage of lactic acid suffered a significant increase during the fermentative process, specially when salicornia was introduced in the juice. Results obtained for the titrated acidity were also good, since approximately 1% lactic acid was detected, as a result of the fermentative activity in the different starting cultures. Predominant species by the end of the fermentation was L. plantarum, being the one that produced higher quantities of lactic acid.Este trabalho foi financiado pelo Programa Ideia - Prime, ADI 13-02-04-FDR-01269 – Desenvolvimento de aplicações para a planta halófila Salicornia. Os autores agradecem à Necton, Belamandil, Portugal, o fornecimento de semestes de Salicornia

Salicornia as a fermented product: development of an optimised procedure for a controlled process

In order to develop a fermented product with young stems of salicornia/pickleweed, an experiment was worked out and the fermentative process was studied. Initial data on the bacterial fauna of the plants revealed the existence of no lactic acid bacteria. Therefore, we chose to use of starting cultures. Sterile “heart cabbage” juice was the base for different fermentative bacteria: Lactobacillus plantarum, Leuconostoc mesenteroides, Pediococcus acidilactici, and pH, titrated acidity and salinity were evaluated. The same experiment was undertaken with and without the glasswort or salicornia. Significant differences were observed only with L. plantarum: pH variation and percentage of lactic acid suffered a significant increase during the fermentative process, specially when salicornia was introduced in the juice. Results obtained for the titrated acidity were also good, since approximately 1% lactic acid was detected, as a result of the fermentative activity in the different starting cultures. Predominant species by the end of the fermentation was L. plantarum, being the one that produced higher quantities of lactic acid

Local mean-field study of capillary condensation in silica aerogels

We apply local mean-field (i.e. density functional) theory to a lattice model of a fluid in contact with a dilute, disordered gel network. The gel structure is described by a diffusion-limited cluster aggregation model. We focus on the influence of porosity on both the hysteretic and the equilibrium behavior of the fluid as one varies the chemical potential at low temperature. We show that the shape of the hysteresis loop changes from smooth to rectangular as the porosity increases and that this change is associated to disorder-induced out-of-equilibrium phase transitions that differ on adsorption and on desorption. Our results provide insight in the behavior of $^4$He in silica aerogels.Comment: 19 figure

Ferroelectric nanofibers with an embedded optically nonlinear benzothiazole derivative

We report measurements of the molecular first hyperpolarizability, thermal stability, photophysical, piezoelectric and ferroelectric properties of a benzothiazole derivative bearing an arylthiophene π-conjugated bridge both in solution and when embedded into a poly (L-lactic acid) (PLLA) matrix in the form of electrospun fibers with an average diameter of roughly 500 nm. The embedded nanocrystalline phenylthienyl-benzothiazole derivative, with crystal sizes of about 1.4 nm resulted in a good piezoelectric response from these functionalized electrospun fibers, indicative of a polar crystalline structure.Fundação para a Ciência e a Tecnologia (FCT