Phase transition in a sexual age-structured model of learning foreign languages

The understanding of language competition helps us to predict extinction and survival of languages spoken by minorities. A simple agent-based model of a sexual population, based on the Penna model, is built in order to find out under which circumstances one language dominates other ones. This model considers that only young people learn foreign languages. The simulations show a first order phase transition where the ratio between the number of speakers of different languages is the order parameter and the mutation rate is the control one.Comment: preliminary version, to be submitted to Int. J. Mod. Phys.

The mechanism for the electrooxidation of procarbazine pharmaceutical preparation in alkaline media and its mathematical description

The mechanism for the electrooxidation of procarbazine in alkaline media has been proposed. The process is realized completely on the electrode surface and is adsorption-controlled. The oscillatory behavior in this case is more probable, than for neutral media and may be caused by influences of electrochemical oxidation and salt dissolution from the electrode surface

Chaos and a Resonance Mechanism for Structure Formation in Inflationary Models

We exhibit a resonance mechanism of amplification of density perturbations in inflationary mo-dels, using a minimal set of ingredients (an effective cosmological constant, a scalar field minimally coupled to the gravitational field and matter), common to most models in the literature of inflation. This mechanism is based on the structure of homoclinic cylinders, emanating from an unstable periodic orbit in the neighborhood of a saddle-center critical point, present in the phase space of the model. The cylindrical structure induces oscillatory motions of the scales of the universe whenever the orbit visits the neighborhood of the saddle-center, before the universe enters a period of exponential expansion. The oscillations of the scale functions produce, by a resonance mechanism, the amplification of a selected wave number spectrum of density perturbations, and can explain the hierarchy of scales observed in the actual universe. The transversal crossings of the homoclinic cylinders induce chaos in the dynamics of the model, a fact intimately connected to the resonance mechanism occuring immediately before the exit to inflation.Comment: 4 pages. This essay received an Honorable Mention from the Gravity Research Foundation, 1998-Ed. To appear in Mod. Phys. Lett.

Simulation for competition of languages with an ageing sexual population

Recently, individual-based models originally used for biological purposes revealed interesting insights into processes of the competition of languages. Within this new field of population dynamics a model considering sexual populations with ageing is presented. The agents are situated on a lattice and each one speaks one of two languages or both. The stability and quantitative structure of an interface between two regions, initially speaking different languages, is studied. We find that individuals speaking both languages do not prefer any of these regions and have a different age structure than individuals speaking only one language.Comment: submitted to International Journal of Modern Physics

Estimativa do custo de produção de café agroecológico no Município de Alto Paraíso - Rondônia.

Considerando a necessidade de se gerar informações socioeconômicas que contribuam para o delineamento de agroecossistemas sustentáveis, objetivo deste trabalho é a determinação do custo de produção do café robusta em sistema agroecológico no Município de Alto Paraíso, Rondônia. Pretende-se ainda determinar a renda auferida por uma unidade de produção típica do sistema café-mel-madeira.bitstream/item/24715/1/cot317-cafeagroecologico.pd

ESO 603-G21: A strange polar-ring galaxy

We present the results of B, V, R surface photometry of ESO603-G21 - a galaxy with a possible polar ring. The morphological and photometric features of this galaxy are discussed. The central round object of the galaxy is rather red and presents a nearly exponential surface brightness distribution. This central structure is surrounded by a blue warped ring or disk. The totality of the observed characteristics (optical and NIR colors, strong color gradients, HI and H_2 content, FIR luminosity and star-formation rate, rotation-curve shape, global mass-to-luminosity ratio, the agreement with the Tully-Fisher relation, etc.) shows that ESO603-G21 is similar to late-type spiral galaxies. We suppose that morphological peculiarities and the possible existence of two large-scale kinematically-decoupled subsystems in ESO603-G21 can be explained as being a result of dissipative merging of two spiral galaxies or as a consequence of a companion accretion onto a pre-existing spiral host.Comment: 8 pages, Astron. Astrophys, accepte