Local solvability for a class of evolution equations

Motivated by the celebrated example of Y. Kannai of a linear partial differential operator which is hypoelliptic but not locally solvable, we consider it class of evolution operators with real-analytic coefficients and study their local solvability both in L(2) and in the weak sense. In order to do so we are led to propose a generalization of the Nirenberg-Treves condition (psi) which is suitable to our study. (C) 2009 Published by Elsevier Inc.

Crossed products by twisted partial actions and graded algebras

For a twisted partial action e of a group G on an (associative non-necessarily unital) algebra A over a commutative unital ring k, the crossed product A x(Theta) G is proved to be associative. Given a G-graded k-algebra B = circle plus(g is an element of G) B-g with the mild restriction of homogeneous non-degeneracy, a criteria is established for B to be isomorphic to the crossed product B-1 x(Theta) G for some twisted partial action of G on B-1. The equality BgBg-1 B-g = B-g (for all g is an element of G) is one of the ingredients of the criteria, and if it holds and, moreover, B has enough local units, then it is shown that B is stably isomorphic to a crossed product by a twisted partial action of G. (c) 2008 Elsevier Inc. All rights reserved.

CONTINUITY OF GLOBAL ATTRACTORS FOR A CLASS OF NON LOCAL EVOLUTION EQUATIONS

In this work we prove that the global attractors for the flow of the equation partial derivative m(r, t)/partial derivative t = -m(r, t) + g(beta J * m(r, t) + beta h), h, beta >= 0, are continuous with respect to the parameters h and beta if one assumes a property implying normal hyperbolicity for its (families of) equilibria.

An algebraic theory for generalized Jordan chains and partial signatures in the Lagrangian Grassmannian

We discuss an algebraic theory for generalized Jordan chains and partial signatures, that are invariants associated to sequences of symmetric bilinear forms on a vector space. We introduce an intrinsic notion of partial signatures in the Lagrangian Grassmannian of a symplectic space that does not use local coordinates, and we give a formula for the Maslov index of arbitrary real analytic paths in terms of partial signatures.

DIAGNOSTIC TECHNIQUES OF LOCAL INFLUENCE IN SPATIAL ANALYSIS OF SOYBEAN YIELD

Modeling of spatial dependence structure, concerning geoestatistics approach, is an indispensable tool for fixing parameters that define this structure, applied on interpolation of values in places that are not sampled, by kriging techniques. However, the estimation of parameters can be greatly affected by the presence of atypical observations on sampled data. Thus, this trial aimed at using diagnostics techniques of local influence in spatial linear Gaussians models, applied at geoestatistics in order to evaluate sensitivity of maximum likelihood estimators and restrict maximum likelihood to small perturbations in these data. So, studies with simulated and experimental data were performed. Those results, obtained from the study of real data, allowed us to conclude that the presence of atypical values among the sampled data can have a strong influence on thematic maps, changing, therefore, the spatial dependence. The application of diagnostics techniques of local influence should be part of any geoestatistic analysis, ensuring that the information from thematic maps has better quality and can be used with greater security by farmers.

Local power of some tests in exponential family nonlinear models

In this paper we obtain asymptotic expansions up to order n(-1/2) for the nonnull distribution functions of the likelihood ratio, Wald, score and gradient test statistics in exponential family nonlinear models (Cordeiro and Paula, 1989), under a sequence of Pitman alternatives. The asymptotic distributions of all four statistics are obtained for testing a subset of regression parameters and for testing the dispersion parameter, thus generalising the results given in Cordeiro et al. (1994) and Ferrari et al. (1997). We also present Monte Carlo simulations in order to compare the finite-sample performance of these tests. (C) 2010 Elsevier B.V. All rights reserved.

On the statistical estimation of diffusion processes - a partial survey

Data available on continuous-time diffusions are always sampled discretely in time. In most cases, the likelihood function of the observations is not directly computable. This survey covers a sample of the statistical methods that have been developed to solve this problem. We concentrate on some recent contributions to the literature based on three di§erent approaches to the problem: an improvement of the Euler-Maruyama discretization scheme, the employment of Martingale Estimating Functions, and the application of Generalized Method of Moments (GMM).

Three essays on local demand for public services

Local provision of public services has the positive effect of increasing the efficiency because each locality has its idiosyncrasies that determine a particular demand for public services. This dissertation addresses different aspects of the local demand for public goods and services and their relationship with political incentives. The text is divided in three essays. The first essay aims to test the existence of yardstick competition in education spending using panel data from Brazilian municipalities. The essay estimates two-regime spatial Durbin models with time and spatial fixed effects using maximum likelihood, where the regimes represent different electoral and educational accountability institutional settings. First, it is investigated whether the lame duck incumbents tend to engage in less strategic interaction as a result of the impossibility of reelection, which lowers the incentives for them to signal their type (good or bad) to the voters by mimicking their neighbors’ expenditures. Additionally, it is evaluated whether the lack of electorate support faced by the minority governments causes the incumbents to mimic the neighbors’ spending to a greater extent to increase their odds of reelection. Next, the essay estimates the effects of the institutional change introduced by the disclosure on April 2007 of the Basic Education Development Index (known as IDEB) and its goals on the strategic interaction at the municipality level. This institutional change potentially increased the incentives for incumbents to follow the national best practices in an attempt to signal their type to voters, thus reducing the importance of local information spillover. The same model is also tested using school inputs that are believed to improve students’ performance in place of education spending. The results show evidence for yardstick competition in education spending. Spatial auto-correlation is lower among the lame ducks and higher among the incumbents with minority support (a smaller vote margin). In addition, the institutional change introduced by the IDEB reduced the spatial interaction in education spending and input-setting, thus diminishing the importance of local information spillover. The second essay investigates the role played by the geographic distance between the poor and non-poor in the local demand for income redistribution. In particular, the study provides an empirical test of the geographically limited altruism model proposed in Pauly (1973), incorporating the possibility of participation costs associated with the provision of transfers (Van de Wale, 1998). First, the discussion is motivated by allowing for an “iceberg cost” of participation in the programs for the poor individuals in Pauly’s original model. Next, using data from the 2000 Brazilian Census and a panel of municipalities based on the National Household Sample Survey (PNAD) from 2001 to 2007, all the distance-related explanatory variables indicate that an increased proximity between poor and non-poor is associated with better targeting of the programs (demand for redistribution). For instance, a 1-hour increase in the time spent commuting by the poor reduces the targeting by 3.158 percentage points. This result is similar to that of Ashworth, Heyndels and Smolders (2002) but is definitely not due to the program leakages. To empirically disentangle participation costs and spatially restricted altruism effects, an additional test is conducted using unique panel data based on the 2004 and 2006 PNAD, which assess the number of benefits and the average benefit value received by beneficiaries. The estimates suggest that both cost and altruism play important roles in targeting determination in Brazil, and thus, in the determination of the demand for redistribution. Lastly, the results indicate that ‘size matters’; i.e., the budget for redistribution has a positive impact on targeting. The third essay aims to empirically test the validity of the median voter model for the Brazilian case. Information on municipalities are obtained from the Population Census and the Brazilian Supreme Electoral Court for the year 2000. First, the median voter demand for local public services is estimated. The bundles of services offered by reelection candidates are identified as the expenditures realized during incumbents’ first term in office. The assumption of perfect information of candidates concerning the median demand is relaxed and a weaker hypothesis, of rational expectation, is imposed. Thus, incumbents make mistakes about the median demand that are referred to as misperception errors. Thus, at a given point in time, incumbents can provide a bundle (given by the amount of expenditures per capita) that differs from median voter’s demand for public services by a multiplicative error term, which is included in the residuals of the demand equation. Next, it is estimated the impact of the module of this misperception error on the electoral performance of incumbents using a selection models. The result suggests that the median voter model is valid for the case of Brazilian municipalities.

Cálculo do Value at Risk (VaR) para o Ibovespa, pós crise de 2008, por meio dos modelos de heterocedasticidade condicional (GARCH) e de volatilidade estocástica (Local Scale Model - LSM)

O objetivo deste estudo é propor a implementação de um modelo estatístico para cálculo da volatilidade, não difundido na literatura brasileira, o modelo de escala local (LSM), apresentando suas vantagens e desvantagens em relação aos modelos habitualmente utilizados para mensuração de risco. Para estimação dos parâmetros serão usadas as cotações diárias do Ibovespa, no período de janeiro de 2009 a dezembro de 2014, e para a aferição da acurácia empírica dos modelos serão realizados testes fora da amostra, comparando os VaR obtidos para o período de janeiro a dezembro de 2014. Foram introduzidas variáveis explicativas na tentativa de aprimorar os modelos e optou-se pelo correspondente americano do Ibovespa, o índice Dow Jones, por ter apresentado propriedades como: alta correlação, causalidade no sentido de Granger, e razão de log-verossimilhança significativa. Uma das inovações do modelo de escala local é não utilizar diretamente a variância, mas sim a sua recíproca, chamada de “precisão” da série, que segue uma espécie de passeio aleatório multiplicativo. O LSM captou todos os fatos estilizados das séries financeiras, e os resultados foram favoráveis a sua utilização, logo, o modelo torna-se uma alternativa de especificação eficiente e parcimoniosa para estimar e prever volatilidade, na medida em que possui apenas um parâmetro a ser estimado, o que representa uma mudança de paradigma em relação aos modelos de heterocedasticidade condicional.

Estimation of genetic parameters for partial egg production periods by means of random regression models

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Partial HELLP Syndrome: maternal and perinatal outcome

CONTEXTO: A síndrome HELLP é uma grave complicação da gestação caracterizada por hemólise, elevação das enzimas hepáticas e plaquetopenia. Algumas gestantes desenvolvem somente uma ou duas dessas características da síndrome HELLP. Esse quadro é denominado de síndrome HELLP parcial (SHP). OBJETIVO: O objetivo deste estudo foi avaliar as repercussões maternas e perinatais das mulheres que desenvolveram SHP e comparar os resultados com mulheres que tiveram hipertensão gestacional ou pré-eclâmpsia sem alterações dos exames laboratoriais para síndrome HELLP. TIPO DE ESTUDO: Observacional, retrospectivo e analítico. LOCAL: Maternidade do Hospital das Clínicas da Faculdade de Medicina de Botucatu, Universidade Estadual Paulista, Botucatu, São Paulo, Brasil. AMOSTRA: Foram selecionadas gestantes ou puérperas que tiveram elevação dos níveis pressóricos detectada pela primeira vez após a primeira metade da gestação com ou sem proteinúria entre janeiro/1990 a dezembro/1995. As mulheres foram divididas em dois grupos: Grupo SHP quando as mulheres com hipertensão arterial tinham pelo menos uma, mas não todas as alterações de exames que demonstravam hemólise, elevação das enzimas hepáticas ou plaquetopenia e Grupo Hipertensas pacientes com hipertensão sem alterações nos exames laboratoriais para síndrome HELLP. PRINCIPAIS VARIÁVEIS: Analisamos idade materna, raça, paridade, classificação da hipertensão, idade gestacional no diagnóstico da SHP, alterações nos exames laboratoriais para síndrome HELLP, tempo de permanência no hospital, complicações maternas, via de parto, incidência de prematuridade, restrição de crescimento intra-uterino, natimortos e neomortos. RESULTADOS: 318 mulheres foram selecionadas, das quais 41 (12,9%) tiveram SHP e 277 (87,1%) não desenvolveram alterações dos exames laboratoriais que compõem o diagnóstico da síndrome HELLP. A pré-eclâmpsia foi um tipo de hipertensão mais freqüente no grupo SHP que no grupo hipertensas. Não houve pacientes com hipertensão crônica isolada que desenvolveram SHP. A taxa de cesárea, eclâmpsia e de partos prematuros foi significativamente mais freqüente no grupo SHP que no grupo hipertensas. CONCLUSÃO: Observamos uma conduta agressiva nas pacientes com SHP, que resultou na interrupção imediata da gestação, com elevada taxa de cesárea e de recém-nascido pré-termo. Esta conduta deve ser revista para a redução desses índices.

Microsatellite loci isolation from river buffalo using enriched partial genomic libraries

The extensive use of buffalo in agriculture, especially in developing countries, begs for genetic resources to evaluate and improve traits important to local and regional economies. Brazil presents the largest water buffalo populations in the New World, with 1 1 million heads including swamp and river types. To design rational breeding strategies for optimum utilization and conservation of available genetic variability in the Brazilian buffalo's population, it is essential to understand their genetic architecture and relationship among various breeds. This depends, in part, on the knowledge of their genetic structure based on molecular markers like microsatellites. In the present study, we developed six enriched partial genomic libraries for river buffalo using selective hybridization methods. Genomic DNA was hybridized with six different arrays of repeat motif, 5' biotinylated - (CA)(15), (CT)(15), (AGG)(8), (GAAA)(8), (GATA)(8), (AAAAC)(8) - and bound to streptavidin coated beads. The cloning process generated a total of 1920 recombinant clones. Up to date, 487 were directly sequenced for the presence of repeats, from which 13 have been positive for presence of repeats as follows: 9 for di-nucleotide repeats, 3 for tri-nucleotide repeats and 1 for tetra-nucleotide repeat. PCR primer pairs for the isolated microsatellites are under construction to determine optimum annealing temperature. These microsatellites will be useful for studies involving phylogenetic relationships, genome mapping and genetic diversity analysis within buffalo populations worldwide.

Non-local interactions and the dynamics of dispersal in immature insects

A simple mathematical model is developed to explain the appearance of oscillations in the dispersal of larvae from the food source in experimental populations of certain species of blowflies. The life history of the immature stage in these flies, and in a number of other insects, is a system with two populations, one of larvae dispersing on the soil and the other of larvae that burrow in the soil to pupate. The observed oscillations in the horizontal distribution of buried pupae at the end of the dispersal process are hypothesized to be a consequence of larval crowding at a given point in the pupation substrate. It is assumed that dispersing larvae are capable of perceiving variations in density of larvae buried at a given point in the substrate of pupation, and that pupal density may influence pupation of dispersing larvae. The assumed interaction between dispersing larvae and the larvae that are burrowing to pupate is modeled using the concept of non-local effects. Numerical solutions of integro-partial differential equations developed to model density-dependent immature dispersal demonstrate that variation in the parameter that governs the non-local interaction between dispersing and buried larvae induces oscillations in the final horizontal distribution of pupae. (C) 1997 Academic Press Limited.

Avaliação experimental dos efeitos do anestésico local ropivacaína em nervos ciáticos

This study was undertaken to investigate the effects of ropivacaine after intrafascicular injection into the sciatic nerves of albino rabbits. Twenty adult albine rabbits were used, following sedation with intramuscular ketamine (50 mg/kg) for nerve exposure by lateral incision. We considered three experimental groups: Group I:sciatic nerve control; Group II: intrafascicular injection with 0.2 mL of physiologic saline solution in the left nerves and intrafascicular injection with 0.2 mL of local anesthetic ropivacaine into the rigth nerves. The specimens were colected at 48 h after drugs administration; Group III. intrafascicular injection with 0.2 mL of physiologic saline solution in the left nerves and intrafascicular injection with 0.2 mL of local anesthetic ropivacaine in the rigth nerves. The specimens were colected at 7 days after drugs administration. The sciatic nerves were removed from these animals and fixed in Karnowisky solution for 24 hours. After partial dehydration up to 95% ethanol, they were embedded in historesin (Leica). The tissue was then sectioned at 1-2μm. Sections were stained with haematoxylin-eosin (HE); toluidine blue (TB) or picrosirius-haematoxylin (PSH). Comparing with control group the histological evidence of inflammatory reaction (migration of macrophagic cells and eosinophils-appeared soon after injection, with intense proliferation of perineurial cells. The results show that after 7 days of intrafascicular injection there was a severe fibrosis and an increase on perineurial vascularization. In group 2 the inflammatory reaction was noted near the local of the injection. Furthermore in this experiment we observed an increase on the number of epineurial lipoblasts and adipocytes. This study demonstrated that the toxic effects of ropivacaine are transient. In many cases there was an initial fascicular recover and axonal regeneration after 7 days of the injection.

Puncture wounds by driftwood catfish during bucket baths: Local habits of riverside people and fish natural history in the Amazon

Objective. - To assess the prevalence of stings by small spiny driftwood catfish (carataí) of the genus Centromochlus (Auchenipteridae) accidentally caught in buckets during bucket bathing by riverside people along the Brazilian Amazon and to determine the probability of catching specimens of these fish during random throws of a bucket into the river. Methods. - We interviewed 27 adult residents living at the confluence of the Negro and Solimões rivers in Brazil regarding whether or not they had ever been stung by driftwood catfish while bucket bathing. To assess the likelihood of catching catfish in bathing buckets, we randomly threw a typical plastic bucket used for bathing in 4 series of 10 throws into the river at dusk or night around a floating house. Results. - Seventeen of the 27 subjects (63%) reported being injured by driftwood catfish during bucket bathing. Three individuals (17.6%) had been injured 2 to 3 times, totaling 23 puncture accidents. All stings occurred at dusk or early night. In the 4 series of 10 bucket throws, we caught 3 driftwood catfish (in 1 series we did not catch any fish). Thus, the chance of catching a driftwood catfish in a single bucket throw at dusk was slightly less than 10%. Conclusions. - The prevalence of stings by driftwood catfish to people bucket bathing in this section of the Brazilian Amazon is high, partly because of the relatively high chances of catching these small catfish during random throws of a bathing bucket into the river.