Improving the GNSS positioning stochastic model in the presence of ionospheric scintillation

Ionospheric scintillations are caused by time-varying electron density irregularities in the ionosphere, occurring more often at equatorial and high latitudes. This paper focuses exclusively on experiments undertaken in Europe, at geographic latitudes between similar to 50 degrees N and similar to 80 degrees N, where a network of GPS receivers capable of monitoring Total Electron Content and ionospheric scintillation parameters was deployed. The widely used ionospheric scintillation indices S4 and sigma(phi) represent a practical measure of the intensity of amplitude and phase scintillation affecting GNSS receivers. However, they do not provide sufficient information regarding the actual tracking errors that degrade GNSS receiver performance. Suitable receiver tracking models, sensitive to ionospheric scintillation, allow the computation of the variance of the output error of the receiver PLL (Phase Locked Loop) and DLL (Delay Locked Loop), which expresses the quality of the range measurements used by the receiver to calculate user position. The ability of such models of incorporating phase and amplitude scintillation effects into the variance of these tracking errors underpins our proposed method of applying relative weights to measurements from different satellites. That gives the least squares stochastic model used for position computation a more realistic representation, vis-a-vis the otherwise 'equal weights' model. For pseudorange processing, relative weights were computed, so that a 'scintillation-mitigated' solution could be performed and compared to the (non-mitigated) 'equal weights' solution. An improvement between 17 and 38% in height accuracy was achieved when an epoch by epoch differential solution was computed over baselines ranging from 1 to 750 km. The method was then compared with alternative approaches that can be used to improve the least squares stochastic model such as weighting according to satellite elevation angle and by the inverse of the square of the standard deviation of the code/carrier divergence (sigma CCDiv). The influence of multipath effects on the proposed mitigation approach is also discussed. With the use of high rate scintillation data in addition to the scintillation indices a carrier phase based mitigated solution was also implemented and compared with the conventional solution. During a period of occurrence of high phase scintillation it was observed that problems related to ambiguity resolution can be reduced by the use of the proposed mitigated solution.

Changes of metabolic and inflammatory markers in HIV infection: glucose, lipids, serum Hs-CRP and myeloperoxidase

Objective: HIV infection is exacerbated through additional pro-atherogenic mechanisms related to the processes of immune activation, inflammation, coagulation, and the modification of lipoproteins (e.g., particles of high density lipoprotein), contributing to increased cardiovascular risk. The aim of this study was to analyze the serum concentrations of myeloperoxidase (MPO) and other laboratory parameters in HIV-infected patients treated or not with antiretroviral drugs compared to non-infected individuals.Materials/Methods: The study included 154 volunteers: 47 non-infected individuals (control group - CON), 27 infected and untreated individuals (NTARv group) and 80 treated individuals (TARV group). We analyzed the counts of CD4+ lymphocytes and the viral load of the infected patients, along with the blood count, fasting glucose, total serum cholesterol (CHOL), HDL cholesterol, LDL cholesterol, triglycerides, MPO and high-sensitivity C-reactive protein (CRP) of all study participants.Results: There were significant increases in glucose, CHOL, LDL cholesterol, and triglycerides in the TARV group and significant reductions in the levels of HDL cholesterol for the TARV and NTARV groups. Significantly elevated levels of Hs-CRP were observed only in the TARV group, while levels of MPO were significantly higher in the TARV and NTARV groups compared to the control group. A correlation of MPO with Hs-CRP (r = 0.21, p = 0.032) was observed for HIV-infected patients, but MPO did not correlate significantly with the other analyzed parameters.Conclusions: The investigation of early biomarkers for cardiovascular risk evaluation, such as MPO, contributes to the clinical monitoring of HIV-infected individuals. The serum levels of MPO correlated with Hs-CRP and were high in HIV-infected individuals, indicating a possible predictor of cardiovascular events in these patients. (c) 2012 Elsevier B.V. All rights reserved.

Synthesis and Characterization of Ordered Intermetallic Nanostructured PtSn/C and PtSb/C and Evaluation as Electrodes for Alcohol Oxidation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Stability and convergence analysis of a neural model applied in nonlinear systems optimization

A neural model for solving nonlinear optimization problems is presented in this paper. More specifically, a modified Hopfield network is developed and its internal parameters are computed using the valid-subspace technique. These parameters guarantee the convergence of the network to the equilibrium points that represent an optimal feasible solution. The network is shown to be completely stable and globally convergent to the solutions of nonlinear optimization problems. A study of the modified Hopfield model is also developed to analyze its stability and convergence. Simulation results are presented to validate the developed methodology.

Design and analysis of an efficient neural network model for solving nonlinear optimization problems

This paper presents an efficient approach based on a recurrent neural network for solving constrained nonlinear optimization. More specifically, a modified Hopfield network is developed, and its internal parameters are computed using the valid-subspace technique. These parameters guarantee the convergence of the network to the equilibrium points that represent an optimal feasible solution. The main advantage of the developed network is that it handles optimization and constraint terms in different stages with no interference from each other. Moreover, the proposed approach does not require specification for penalty and weighting parameters for its initialization. A study of the modified Hopfield model is also developed to analyse its stability and convergence. Simulation results are provided to demonstrate the performance of the proposed neural network.

A neural system to robust Nonlinear optimization subject to disjoint and constrained sets

The ability of neural networks to realize some complex nonlinear function makes them attractive for system identification. This paper describes a novel method using artificial neural networks to solve robust parameter estimation problems for nonlinear models with unknown-but-bounded errors and uncertainties. More specifically, a modified Hopfield network is developed and its internal parameters are computed using the valid-subspace technique. These parameters guarantee the network convergence to the equilibrium points. A solution for the robust estimation problem with unknown-but-bounded error corresponds to an equilibrium point of the network. Simulation results are presented as an illustration of the proposed approach.

Implementation of two-stage Hopfield model and its application in nonlinear systems

This paper presents an efficient neural network for solving constrained nonlinear optimization problems. More specifically, a two-stage neural network architecture is developed and its internal parameters are computed using the valid-subspace technique. The main advantage of the developed network is that it treats optimization and constraint terms in different stages with no interference with each other. Moreover, the proposed approach does not require specification of penalty or weighting parameters for its initialization.

Waveshapes of continuing currents and properties of M-components in natural positive cloud-to-ground lightning

This work analyses the waveshapes of continuing currents and parameters of M-components in positive cloud-to-ground (CG) flashes through high-speed GPS synchronized videos. The dataset is composed of only long continuing currents (with duration longer than 40 ms) and was selected from more than 800 flashes recorded in Sao Jose dos Campos (45.864 degrees W, 23.215 degrees S) and Uruguaiana (29.806 degrees W, 57.005 degrees S) in Southeast and South of Brazil, respectively, during 2003 to 2007 summers. The videos are compared with data obtained by the Brazilian Lightning Location System (BrasilDAT) in order to determine the polarity of each flash and select only positive cases. There are only two studies of waveshapes of continuing currents in the literature. One is based on direct current measurements of triggered lightning, in which four different types of waveshapes were observed; and the other is based on measurements of luminosity variations in high-speed videos of CG negative lightning, in which besides the four types above mentioned two additional types were observed. The present work is an extension of the latter, using the same method but now applied to obtain the waveshapes of positive CG lightning. As far as the authors know, this is the first report on M-components in positive continuing currents. We also have used the luminosity-versus-time graphs to observe their occurrence and measure some parameters (duration, elapsed time and time between two successive M-components), whose statistics are presented and compared in detail to the data for negative flashes. We have plotted a histogram of the M-components elapsed time over the total duration of the continuing current for positive flashes, which presented an exponential decay (correlation coefficient: 0.83), similar to what has been observed for negative flashes. (C) 2008 Elsevier B.V. All rights reserved.

Adsorption of Cu(II) and Co(II) complexes on a silica gel surface chemically modified with 2-mercaptoimidazole

The isotherms of adsorption of MeX2 (Me = Cu2+, Co2+; X = Cl-, Br-, ClO4-) by silica gel chemically modified with 2-mercaptoimidazole (SiMI) were studied in acetone and ethanol solutions, at 25 degrees C. Covalently attached 2-mercaptoimidazole molecule to silica gel surface adsorbs MeX2 from solvent by forming a surface complex. The metal is bonded to the surface through the nitrogen atom of attached 2-mercaptoimidazole. At low loading, the electronic and ESR spectral parameters indicated that the Cu2+ complexes are in a distorted-tetragonal symmetry field. The d-d electronic transition spectra showed that for Cu(ClO4)(2) complex, the peak of absorption did not change for any degree of metal loading and for Cl- and Br- complexes, the peak maxima shifted to higher energy with lower metal loading. The CoX2(X = Cl-, Br-, ClO4-) analogues possess a distorted-tetrahedral field.

Organophosphate resistance in the maize weevil Sitophilus zeamais: Magnitude and behavior

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Hematologic, serum biochemistry and urinary values for captive Crab-eating Fox (Cerdocyon thous) in São Paulo state, Brazil

A importância do estudo dos valores hematológicos, de bioquímica sérica e urinários de Cachorro-do-mato (Cerdocyon thous) baseia-se na necessidade de cuidados e manutenção da sanidade destas populações. Este estudo visou investigar os parâmetros fisiológicos hematológicos, de bioquímica sérica e urinários dos Cachorros-do-mato de cativeiro, comparando as possíveis diferenças sexuais e de faixa etária. Foram colhidas amostras de sangue de 52 animais, pertencentes a diversos Zoológicos do Estado de São Paulo, Brasil. Foram colhidos cerca de 7mL de sangue, que foram utilizados para se obter os valores hematológicos e o perfil de bioquímica sérica. Também foram colhidos 5mL de urina para realização da urinálise. Não se encontraram diferenças entre os valores obtidos para machos e fêmeas tanto na hematologia, quanto na bioquímica sérica. Alguns parâmetros hematológicos e de bioquímica sérica foram afetados pela idade, mostrando diferenças significativas. Os resultados da urinálise foram demonstrados apenas em forma descritiva. Os principais valores encontrados foram, hemácias 4,35+0,73 x 106 células /µL, leucócitos totais 7,72+3,66 x 103 células /µL (predomínio de neutrófilos segmentados), plaquetas 227,06+111,58 x 103 células /µL, ureia 43,06+14,28mg/dL e creatinina 1,03+0,24mg/dL. Os valores hematológicos, de bioquímica sérica e urinários obtidos neste estudo podem ser utilizados como valores fisiológicos de Cachorros-do-mato de cativeiro. Pode-se concluir que as espécies silvestres necessitam de seus próprios valores de referência com necessidade de se diferenciar animais em cativeiro de animais de vida livre.

Effect of soluble fiber on hypertriglyceridemia and immune profile in HIV-positive individuals undergoing highly active antiretroviral therapy

The advent of highly active antiretroviral therapy (HAART), since 1996, represented a profound impact on the natural history of HIV-infection by promoting important and sustainable viral replication suppression and increasing survival and quality of life among seropositive patients. Nonetheless, antiretroviral therapy has been observed to be accompanied by metabolic alterations such as dyslipidemia, especially hypertriglyceridemia, insulin resistance, hyperglycemia and lipodystrophy (body fat redistribution). Epidemiological studies have demonstrated a correlation between high triglyceride (TG) levels and higher incidence of coronary artery disease (CAD). Some investigators suggest dietary intervention as part of hyperlipidemia treatment, including an increase in soluble fiber intake (10-25g/day). Whereas some studies have demonstrated that both cholesterol and serum triglyceride levels decrease with the use of food fiber, others have shown just a serum triglyceride decrease, and others failed to observe any alteration in lipid metabolism. The purpose of this study was to assess the effect of soluble fiber (R) (partially hydrolyzed guar gum) supplementation on hypertriglyceridemia and immune profile in HIVpositive individuals on HAART. Nineteen HIV-positive individuals with hypertriglyceridemia (serum levels >= 150 to < 500mg/dl) were studied. of these individuals, 63.16% were males and 36.84% females, with mean age of 43.52 +/- 9.22 years. These individuals had been on the same HAART regimen for at least six months, had no change in therapy during the study and received 20g/day of soluble fiber for four months at pre-established times. Clinical-nutritional, biochemical (total proteins, albumin, globulin, total cholesterol, LDL-c, HDL-c, TG, TG/HDL-c and LDLc/HDL-c), hematimetric (hemoglobin, hematocrit and total lymphocytes), and immunologic (lymphocytes T CD4(+), T CD8(+); T CD4(+)/CD8(+) ratio, viral load, TNF-alpha and IL-6) parameters were assessed in all patients at three time points (M0: pretreatment, M1: 30 days, and M2: four months after intervention). Significance level was set at 5% for all data statistically analyzed. Serum TG and TG/HDL-c ratio reduction was observed at all time points, but statistical significance was found just at M0 and M2. The remaining biochemical, hematimetric and immunologic parameters (lymphocytes T CD4(+), T CD8(+); T CD4(+)/ CD8(+) ratio, and viral load) showed no significant difference at all times. Regarding serum cytokines, TNF-alpha and IL-6 significantly decreased between M0 and M2, and only IL-6 reduced between M1 and M2. The data collected show that dietary and anthropometric parameters remained unchanged excluding potential confounding factors related with the effect of fiber supplementation on serum TG, TNF-alpha and IL-6. Thus, soluble fiber (R) contributed to an important reduction in hypertriglyceridemia and in the serum levels of the proinflammatory cytokines TNF-alpha and IL-6 in HIV-seropositive individuals on HAART. In addition, soluble fiber (R) might have minimized the process of atherosclerosis in these individuals, given that elevated serum levels of TG, TNF-alpha and IL-6 have been associated with the development of these lesions.

Hepatoprotective and anti-inflammatory effects of silibinin on experimental preeclampsia induced by 1-NAME in rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Valor e variações da freqüência fundamental no choro de dor de recém-nascidos

OBJETIVO: estudar o valor da freqüência fundamental e suas variações presentes no choro de dor de recém-nascidos. MÉTODOS: foram gravadas as emissões de 111 recém-nascidos de termo e saudáveis, com idade de 24 a 72 horas durante procedimento da punção venosa periférica. A análise acústica foi realizada por meio dos softwares VOXMETRIA 1.1 com extração do valor da freqüência fundamental e GRAM 5.7 para verificar a ocorrência de variações da freqüência fundamental como quebras, bitonalidade e freqüência hiperaguda. A escala de dor NIPS foi realizada no momento da punção. A análise estatística é descritiva com extração dos valores de média, desvio-padrão e freqüência de ocorrência dos eventos. RESULTADOS: os recém-nascidos apresentaram 100% de suas emissões com variações de freqüência, ou seja, quebras e bitonalidade. A freqüência hiperaguda foi encontrada em 34,2% dos recém-nascidos. CONCLUSÃO: por meio do choro, o recém-nascido comunica sua dor. A emissão de dor do recém-nascido é tensa e estridente, com freqüência fundamental aguda e variações encontradas no traçado espectrográfico, como quebras, bitonalidade e freqüência hiperaguda. Tais características são importantes para chamar a atenção do adulto no pronto atendimento ao recém-nascido e auxiliar na avaliação de dor durante um procedimento.

Constituents and antiulcer effect of Alchornea glandulosa: Activation of cell proliferation in gastric mucosa during the healing process

Alchornea glandulosa (Euphorbiaceae) is a plant used in folk medicine as an antiulcer agent. Rats pretreated with methanolic extract obtained from the leaves of A. glandulosa (AG) showed a dose-dependent effect and significant reduction of gastric ulcers induced by absolute ethanol at the doses of 500 (57%) and 1000 mg/kg (35%) in relation to the control group. Pretreatment of mice with AG (500, 1000 mg/kg, p.o.) showed dose-dependent activity and significantly decreased the severity of lesions caused by HCl/ethanol and by non steroidal anti inflammatory drug-induced gastric lesions. Pretreatment with AG also induced antisecretory action via local and systemic routes and a significant decrease in the total gastric acid content. The gastroprotective effects of AG involved the participation of nitric oxide and increased levels of endogenous sulfhydryl compounds, which are defensive mechanisms of the gastrointestinal mucosa against aggressive factors. The ability of AG to heal gastric ulcers was evaluated after 14 consecutive days of treatment. The results showed that single oral administrations of AG (250 mg/kg/once daily) potently stimulates gastric epithelial cell proliferation that contributes to the accelerated healing of gastric ulcers induced by acetic acid. In addition, no subacute toxicity (body weight gain, vital organs, and serum biochemical parameters) was observed during treatment with AG. Phytochemical investigation of AG led to the isolation of myricetin-3-O-alpha-L-rhamnopyranoside, quercetin-3-O-alpha-L-arabinopyranoside, quercetin-3-O-beta-D-galactopyranoside, quercetin, amentoflavone, methyl gallate, gallic acid, and pterogynidine. We also established the phytochemical profile of AG with the quantification of total phenolic compounds. These compounds may contribute to the observed antiulcerogenic effects of AG.