Occupation time of exclusion processes with conductances

Em publicação em "Journal of statistical physics". ISSN 0022-4715.We obtain the fluctuations for the occupation time of one-dimensional symmetric exclusion processes with speed change, where the transition rates ({\em conductances}) are driven by a general function $W$. The approach does not require sharp bounds on the spectral gap of the system nor the jump rates to be bounded from above or below. We present some examples and for one of them, we observe that the fluctuations of the current are trivial, but the fluctuations of the occupation time are given by a fractional Brownian Motion. This shows that, in general, the fluctuations of the current and of the occupation time are not of same order.CAPESFundação para a Ciência e a Tecnologia (FCT)CNP

Homopolymer tract length dependent enrichments in functional regions of 27 eukaryotes and their novel dependence on the organism DNA (G+C)% composition

BACKGROUND: DNA homopolymer tracts, poly(dA).poly(dT) and poly(dG).poly(dC), are the simplest of simple sequence repeats. Homopolymer tracts have been systematically examined in the coding, intron and flanking regions of a limited number of eukaryotes. As the number of DNA sequences publicly available increases, the representation (over and under) of homopolymer tracts of different lengths in these regions of different genomes can be compared. RESULTS: We carried out a survey of the extent of homopolymer tract over-representation (enrichment) and over-proportional length distribution (above expected length) primarily in the single gene documents, but including some whole chromosomes of 27 eukaryotics across the (G+C)% composition range from 20 – 60%. A total of 5.2 × 10(7 )bases from 15,560 cleaned (redundancy removed) sequence documents were analyzed. Calculated frequencies of non-overlapping long homopolymer tracts were found over-represented in non-coding sequences of eukaryotes. Long poly(dA).poly(dT) tracts demonstrated an exponential increase with tract length compared to predicted frequencies. A novel negative slope was observed for all eukaryotes between their (G+C)% composition and the threshold length N where poly(dA).poly(dT) tracts exhibited over-representation and a corresponding positive slope was observed for poly(dG).poly(dC) tracts. Tract size thresholds where over-representation of tracts in different eukaryotes began to occur was between 4 – 11 bp depending upon the organism (G+C)% composition. The higher the GC%, the lower the threshold N value was for poly(dA).poly(dT) tracts, meaning that the over-representation happens at relatively lower tract length in more GC-rich surrounding sequence. We also observed a novel relationship between the highest over-representations, as well as lengths of homopolymer tracts in excess of their random occurrence expected maximum lengths. CONCLUSIONS: We discuss how our novel tract over-representation observations can be accounted for by a few models. A likely model for poly(dA).poly(dT) tract over-representation involves the known insertion into genomes of DNA synthesized from retroviral mRNAs containing 3' polyA tails. A proposed model that can account for a number of our observed results, concerns the origin of the isochore nature of eukaryotic genomes via a non-equilibrium GC% dependent mutation rate mechanism. Our data also suggest that tract lengthening via slip strand replication is not governed by a simple thermodynamic loop energy model

Photovoltaic powered irrigation system applied to familiary agriculture

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel SuperiorA presente dissertaÃÃo tem como objetivo principal analisar a viabilidade tÃcnica e financeira de um sistema fotovoltaico autÃnomo para bombeamento de Ãgua aplicado na irrigaÃÃo de uma unidade de produÃÃo agrÃcola familiar. A unidade agrÃcola pesquisada està instalada no NÃcleo de Ensino e Pesquisa em Agricultura Urbana (NEPAU), que atua em parceria com o LaboratÃrio de Energias Alternativas (LEA), situados no Campus do PICI da Universidade Federal do CearÃ. A unidade ocupa uma Ãrea Ãtil de 43 m2, com um reservatÃrio de Ãgua que simula um aÃude, lago ou poÃo com capacidade de 3.534 litros, um motor bomba de 12 VDC e um mÃdulo fotovoltaico de 135 Wp. O sistema de irrigaÃÃo à constituÃdo por 12 micro-aspersores com pressÃo de trabalho de 7 psi, com raio de alcance de 1,2 m e vazÃo de 0,6 l/min. A unidade de produÃÃo consumiu 31.592 litros de Ãgua e demandou 5,2 kWh de energia elÃtrica ao longo de 44 dias de produÃÃo do coentro. Um sensor de umidade do solo foi utilizado para controlar a umidade do solo o que permitiu economizar 3.608 litros de Ãgua e 0,6 kWh de energia elÃtrica na produÃÃo de 23 kg de coentro. O custo de implantaÃÃo do sistema fotovoltaico de bombeamento desenvolvido foi de R$1.694,00. As eficiÃncias do mÃdulo fotovoltaico, conjunto motobomba e global foram de 8,4$ 1,694.00. The efficiencies of photovoltaic module, pump and global set were 8.4%, 42% and 3.5%, respectively. The return on capital invested time is 10 years without regard to any allowance and 8.4 years for a 20% allowance on capital invested in the acquisition of equipment