Non-linear generalization of the sl(2) algebra

We present a generalization of the sl(2) algebra where the algebraic relations are constructed with the help of a general function of one of the generators. When this function is linear this algebra is a deformed sl(2) algebra. In the non-linear case, the finite dimensional representations are constructed in two different ways. In the first case, which provides finite dimensional representations only for the non-linear case, these representations come from solutions to a dynamical equation and we show how to construct explicitly these representations for a general quadratic non-linear function. The other type of finite dimensional representation comes from solutions to a cut condition equation. We give examples of solutions of this type in the non-linear case as well.Comment: 13 pages, 3 EPS figures, Late

Some boundary effects in quantum field theory

We have constructed a quantum field theory in a finite box, with periodic boundary conditions, using the hypothesis that particles living in a finite box are created and/or annihilated by the creation and/or annihilation operators, respectively, of a quantum harmonic oscillator on a circle. An expression for the effective coupling constant is obtained showing explicitly its dependence on the dimension of the box.Comment: 12 pages, Late

Hortas comunitárias de Teresina : agricultura urbana e perspectiva de desenvolvimento local

Esse artigo analisa se as Hortas Comunitárias de Teresina apresentam-se como alternativa de geração de trabalho e renda e de melhoria sócio-econômica, sem degradar o meio ambiente. O procedimento metodológico embasa-se em levantamento de dados primários e na realização de pesquisa de campo nas 43 hortas urbanas de Teresina. Detectou-se que a maioria dos horticultores é do sexo feminino, possui mais de 45 anos; tem até o ensino fundamental incompleto; aufere até um salário mínimo; procede do interior do Estado; trabalhava na agricultura antes das hortas; e exerce a função em família. Além disso, constatou-se que a maior parte dos produtores não participou de treinamentos desde sua inserção no Programa; utiliza recursos próprios na produção; 70,08% do produzido centram-se em coentro, cebolinha e alface; e comercializam a produção, primordialmente, na própria horta. Ademais, observou-se que usam majoritariamente esterco para adubação do solo com pouca utilização de adubos químicos, bem como apenas 36,81% dos horticultores utilizam agrotóxicos no cultivo. Conclui-se que, a baixa remuneração percebida pelos horticultores, decorrente da pouca diversidade do cultivo, da precária organização e da falta de financiamento, conduziu alguns membros da família a buscarem ocupação alternativa com vista à complementação da renda.This article analyses if The Community Gardens from Teresina are really an alternative source of employment and income, and if they can improve the local socio-economical status, without depleting the environment. The methodological approach was a primary data survey and a research carried out in 43 urban gardens located in Teresina. The research detected that the majority of the gardeners were females, over 45 years old and had not completed elementary school; these female gardeners earn one minimal salary or less; are from the countryside of Piauí, were agriculturist before cultivating the gardens and work with their children and partner. Also, since the insertion to the program, the majority of the producers has not joined courses or lectures related to this activity; they use self funds, 70,08% of the production is coriander, onions and lettuce; and sell them at the garden. Furthermore, this study observed that to fertilize the soil they mostly use manure and a minority uses chemical fertilizer. From this picture, the study concludes that the low remuneration, witch comes from the little diversity of the products cultivated, the precarious organization and lack of financings, has driven some members of the family to search alternative occupations to complement the family income

Construction of a non-standard quantum field theory through a generalized Heisenberg algebra

We construct a Heisenberg-like algebra for the one dimensional quantum free Klein-Gordon equation defined on the interval of the real line of length $L$. Using the realization of the ladder operators of this type Heisenberg algebra in terms of physical operators we build a 3+1 dimensional free quantum field theory based on this algebra. We introduce fields written in terms of the ladder operators of this type Heisenberg algebra and a free quantum Hamiltonian in terms of these fields. The mass spectrum of the physical excitations of this quantum field theory are given by $\sqrt{n^2 \pi^2/L^2+m_q^2}$, where $n= 1,2,...$ denotes the level of the particle with mass $m_q$ in an infinite square-well potential of width $L$.Comment: Latex, 16 page

Hortas comunitárias de Teresina : agricultura urbana e perspectiva de desenvolvimento local

Esse artigo analisa se as Hortas Comunitárias de Teresina apresentam-se como alternativa de geração de trabalho e renda e de melhoria sócio-econômica, sem degradar o meio ambiente. O procedimento metodológico embasa-se em levantamento de dados primários e na realização de pesquisa de campo nas 43 hortas urbanas de Teresina. Detectou-se que a maioria dos horticultores é do sexo feminino, possui mais de 45 anos; tem até o ensino fundamental incompleto; aufere até um salário mínimo; procede do interior do Estado; trabalhava na agricultura antes das hortas; e exerce a função em família. Além disso, constatou-se que a maior parte dos produtores não participou de treinamentos desde sua inserção no Programa; utiliza recursos próprios na produção; 70,08% do produzido centram-se em coentro, cebolinha e alface; e comercializam a produção, primordialmente, na própria horta. Ademais, observou-se que usam majoritariamente esterco para adubação do solo com pouca utilização de adubos químicos, bem como apenas 36,81% dos horticultores utilizam agrotóxicos no cultivo. Conclui-se que, a baixa remuneração percebida pelos horticultores, decorrente da pouca diversidade do cultivo, da precária organização e da falta de financiamento, conduziu alguns membros da família a buscarem ocupação alternativa com vista à complementação da renda.This article analyses if The Community Gardens from Teresina are really an alternative source of employment and income, and if they can improve the local socio-economical status, without depleting the environment. The methodological approach was a primary data survey and a research carried out in 43 urban gardens located in Teresina. The research detected that the majority of the gardeners were females, over 45 years old and had not completed elementary school; these female gardeners earn one minimal salary or less; are from the countryside of Piauí, were agriculturist before cultivating the gardens and work with their children and partner. Also, since the insertion to the program, the majority of the producers has not joined courses or lectures related to this activity; they use self funds, 70,08% of the production is coriander, onions and lettuce; and sell them at the garden. Furthermore, this study observed that to fertilize the soil they mostly use manure and a minority uses chemical fertilizer. From this picture, the study concludes that the low remuneration, witch comes from the little diversity of the products cultivated, the precarious organization and lack of financings, has driven some members of the family to search alternative occupations to complement the family income

Development of biomanipulation strategies for the remediation of eutrophication problems in an urban reservoir, Lago Paranoa, Brazil

The feasibility of improving water quality by food web manipulation in an urban eutrophic tropical reservoir, Lago Paranoa (Brasilia, Brazil) was investigated. The potential of promising biomanipulation strategies was experimentally tested in limnocorrals: reduction of internal nutrient loading by controlling tilapia overpopulation, and suppression of nuisance cyanobacteria by stocking non reproducing filter-feeding silver carp. A four-month test in two large littoral isolated areas of the reservoir (1,000 m2 each) stocked with high vs. low tilapia biomass revealed that fish over-population promoted blooms of Microcystis and decreased water clarity by supplying phytoplankton with additional nutrients (mainly phosphorus, "P"). Since reduction of tilapia biomass from 150 to 40 g/m3 resulted in significant water quality improvements, the release of commercial fisheries using cast-nets was recommended. Field experiments III floating net-cages (10 m3) were conducted to evaluate silver carp adaptation to Lago Paranoa and to determine fish growth rates when maintained feeding exclusively on the abundant plankton in the reservoir. High growth rates (up to 6 g/day) and survivorship (> 90%) of young-of-the-year (72 g), juveniles (300 g) and adult silver carp (1100 g) during both dry and rainy season were observed. Efficient ingestion of nuisance algae was evidenced by the dominant presence of Microcystis aeruginosa and Botryococcus braunii colonies in the fore-intestine of experimental fishes. Results indicate the great potential for silver carp cage culture as a low-cost and environmentally beneficial economic activity. Following indications from literature and previous studies in Lago Paranoa, the optimum range of silver carp biomass which maximize phytoplankton control was determined in ten large replicated limnocorrals (50 m3 ). Although a significant decrease in Microcystis abundance was achieved by stocking silver carp at all biomass levels, net-phytoplankton biomass was only significantly suppressed at moderate fish stocking densities of 40 and 60 g/m3 . Two additional limnocorral experiments during dry and rainy seasons were performed to test the effectiveness of both biomanipulation strategies when adopted separately or simultaneously. Water quality improvements through control of tilapia abundance (from 100 to 40 g/m3) and stocking with silver carp (at moderate stocking rates of 40-50 g/m3) induced significant decreases in total phosphorus (21- 31 %), cyanobacteria density (40-44%) and phytoplankton biomass (22-38%). As those strategies were found to act independently, the combination of both enhanced water quality benefits by reducing total phosphorus by 38%, cyanobacteria density by 75% and phytoplankton biomass by 60%. To predict the internal P-loading reduction that could be achieved by implementing both biomanipulation strategies on a whole-reservoir scale, P excretion rates were quantified in indoor tanks for 16 and 40 g tilapia (0.527-1.576 ug SRP/g ww/h) and silver carp (0.391-0.737 ug SRP/g ww/h). It was estimated that the tilapia contribution to internal P-Ioading (5.4 mg TP/m2/day for 1,300 kg/ha) is equivalent to external P input to the Bananal Branch (6.0 mg TP/m2/day). A 60% reduction in tilapia biomass plus stocking of silver carp at densities of up to 60 g/m3 after three years would not change internal P-Ioading (5.6 mg TP/m2/day) but would (1) reduce by 60% the input of "new" phosphorus to the water column from tilapia bottom feeding, and (2) increase grazing on phytoplankton following silver carp introduction

Generalized quantum field theory: perturbative computation and perspectives

We analyze some consequences of two possible interpretations of the action of the ladder operators emerging from generalized Heisenberg algebras in the framework of the second quantized formalism. Within the first interpretation we construct a quantum field theory that creates at any space-time point particles described by a q-deformed Heisenberg algebra and we compute the propagator and a specific first order scattering process. Concerning the second one, we draw attention to the possibility of constructing this theory where each state of a generalized Heisenberg algebra is interpreted as a particle with different mass.Comment: 19 page