Comparação entre metodologias de extração de HPAs em água utilizando um planejamento fatorial com quantificação no CG/EM

PAHs (Polycyclic Aromatic Hydrocarbons) are a group of organic substances which receive considerable attention because of the carcinogenic and mutagenic properties of some of them. It is therefore important to determine the PAHs in different environmental matrices. Several studies have shown the use of gas chromatography coupled to mass spectrometry as a technique for quantification of PAHs by presenting excellent detection limits. This study aimed to develop an analytical methodology for the determination of 16 PAHs listed by the USEPA, test two methods for extraction of PAHs in water from a 23 factorial design, quantify them through the analytical technique coupled to gas chromatography mass spectrometry (GC/MS) using the method developed, and finally apply the results in chemometrics. The sample was synthesized and subjected to tests of the 23 factorial design, which has the factors: the type of extraction technique (ultrasound and digester), the ratio solvent / sample (1:1 and 1:3) and the type of solvent (dichloromethane / hexane and acetone / dichloromethane). The responses of eight combinations of the factorial design were obtained from the quantification by external calibration in GC/MS. The quantification method was developed from an optimized adaptation of the USEPA Method 8270. We used the full scan mode as a way of acquiring the mass spectra of 16 PAHs. The time in which the samples were subjected to ultrasound was fixed at 10 min and held an investigation to establish the conditions of power and time in the digester. We had the best response in the investigation of the digester power of 100 watts and the time of six minutes. The factorial design of liquid-liquid extraction showed that the most representative factors were: the use of the digester as extraction technique, the ratio solvent / sample 1:1 and the use of a 1:1 mixture of dichloromethane / hexane as a solvent more suitable. These results showed that the 1:1 mixture of dichloromethane / hexane is an excellent mixture to recover the extraction of PAHs an aqueous sample using the microwave digester. The optimization of the method of separation, identification and quantification of PAHs in the GC/MS was valid for 16 PAHs present in each chromatogram of the samples

Efficacy of surgical versus conservative treatment in esophageal perforation: a systematic review of case series studies

PURPOSE: To evaluate the efficacy of surgical treatment for esophageal perforation. METHODS: A systematic review of the literature was performed. We conducted a search strategy in the main electronic databases such as PubMed, Embase and Lilacs to identify all case series. RESULTS: Thirty three case series met the inclusion criteria with a total of 1417 participants. The predominant etiology was iatrogenic (54.2%) followed by spontaneous cause (20.4%) and in 66.1% the localization was thoracic. In 65.4% and 33.4% surgical and conservative therapy, respectively, was considered the first choice. There was a statistically significance different with regards mortality rate favoring the surgical group (16.3%) versus conservative treatment (21.2%) (p<0.05). CONCLUSION: Surgical treatment was more effective and safe than conservative treatment concerning mortality rates, although the possibility of bias due to clinical and methodological heterogeneity among the included studies and the level of evidence that cannot be ruled out.

Padronização de um protocolo experimental de treinamento periodizado em natação utilizando ratos Wistar

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

New Species of Ischnocnema (Anura: Brachycephalidae) from the State of Minas Gerais, Southeastern Brazil, with Comments on the I. verrucosa Species Series

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

The Q-D algorithm for transforming series expansions into a corresponding continued fraction: an extension to cope with zero coefficients

An algorithm for deriving a continued fraction that corresponds to two series expansions simultaneously, when there are zero coefficients in one or both series, is given. It is based on using the Q-D algorithm to derive the corresponding fraction for two related series, and then transforming it into the required continued fraction. Two examples are given. (C) 2003 Elsevier B.V. All rights reserved.

Thermotropic phase behavior in aqueous mixtures of dioctadecyldimethylammonium bromide and alkyltrimethylammonium bromide surfactant series studied by differential scanning calorimetry

The effect of the micelle-forming surfactant series alkyltrimethylammonium bromide (C(n)TAB, n = 12, 14, 16 and 18) on the thermotropic phase behavior of dioctadecyldimethylammonium bromide (DODAB) vesicles in water was investigated by differential scanning calorimetry at constant 5.0 mM total surfactant concentration and varying individual surfactant concentrations. The pre-, post- and main transition temperatures (T-s, T-p and T-m), melting enthalpy (Delta H) and peak width of the main transition (Delta T-1/2) are reported as a function of the surfactant molar fraction. No clear dependence of these parameters on the C(n)TAB chain length was found. At 5 mM, neat DODAB in water exhibits two transition temperatures, T-s = 32.1 and T-m = 42.7 degrees C, as obtained from the DSC upscans, but not a clear T-p. For every n, except n = 12, T-s vanishes as CnTAB concentration increases and approaches CMC. T-m behaves differently for different n, the longer C(14)TAB and C(16)TAB decrease, while C(18)TAB increases T-m with increasing concentration. The data indicate that changes in T-m, T-s, T-p and Delta H of the transition are related not only to the extent of C(n)TAB affinity to DODAB but also to the surfactant chain length. Accordingly, C18TAB yields a more compact bilayer, thus increasing T-m, while C(14)TAB and C(1G)TAB yield a less organized bilayer and reduce T-m. C(12)TAB does not much affect T-s and T-m, although it yields T-p approximate to 51.6 degrees C. (C) 2008 Elsevier B.V. All rights reserved.

A fluorescence probe study of gemini surfactants in aqueous solution: a comparison between n-2-n and n-6-n series of the alkanediyl-a,w-bis (dimethylalkylammonium bromides)

Two series of alkanediyl-a,w-bis (dimethylalkylammonium bromide (n-2-n and n-6-n; n=8, 10,12, and 16) have been synthesized and their micelles properties studied in aqueous solution using pyrene, pyrenecarboxaldehyde (PCA) and 1,8 anilinonaphtalene sulfonic acid sodium salt (ANS) as fluorescent probes. The micelles from these surfactants have been characterized on the basis of the information provided by micelle-solubilized fluorescent probes. The obtained results indicated that the surfactant concentration at which a marked decrease in l max parameter of pyrenecarboxaldehyde (PCA) occurs corresponds to the CMC determined by conductimetric measurements. Changes in the emission spectra of ANS and PCA observed in the submicellar range for both surfactants series (n-2-n and n-6-n) were interpreted as formation of pre-aggregates. It was found that the dimeric surfactants with long spacer (s= 6) form more hydrated aggregates when compared with those formed by the n-2-n and CnTAB surfactants series. This was attributed to a more difficult packing of n-6-n surfactant molecules to form micelles.

Time series analysis for minority game simulations of financial markets

The minority game (MG) model introduced recently provides promising insights into the understanding of the evolution of prices, indices and rates in the financial markets. In this paper we perform a time series analysis of the model employing tools from statistics, dynamical systems theory and stochastic processes. Using benchmark systems and a financial index for comparison, several conclusions are obtained about the generating mechanism for this kind of evolution. The motion is deterministic, driven by occasional random external perturbation. When the interval between two successive perturbations is sufficiently large, one can find low dimensional chaos in this regime. However, the full motion of the MG model is found to be similar to that of the first differences of the SP500 index: stochastic, nonlinear and (unit root) stationary. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Synthesis and characterization of a novel series of meso (nitrophenyl) and meso (carboxyphenyl) substituted porphyrins

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

Thermal decomposition and stability in a series of heterobimetallic carbonyl compounds of the type [Fe(CO)4(HgX)2] (X=Cl, Br, I)

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

Comparison between the complete Bayesian method and empirical Bayesian method for ARCH models using Brazilian financial time series

In this work we compared the estimates of the parameters of ARCH models using a complete Bayesian method and an empirical Bayesian method in which we adopted a non-informative prior distribution and informative prior distribution, respectively. We also considered a reparameterization of those models in order to map the space of the parameters into real space. This procedure permits choosing prior normal distributions for the transformed parameters. The posterior summaries were obtained using Monte Carlo Markov chain methods (MCMC). The methodology was evaluated by considering the Telebras series from the Brazilian financial market. The results show that the two methods are able to adjust ARCH models with different numbers of parameters. The empirical Bayesian method provided a more parsimonious model to the data and better adjustment than the complete Bayesian method.

Correlation of reactivity with structural factors in a series of Fe(II) substituted cobalt ferrites

A series of powdered cobalt ferrites, CoxFe3-xO4 with 0.66 <= x< 1.00 containing different amounts of Fe-II, were synthesized by a mild procedure, and their Fe and Co site occupancies and structural characteristics were explored using X-ray anomalous scattering and the Rietveld refinement method. The dissolution kinetics, measured in 0.1 M oxalic acid aqueous solution at 70 degrees C, indicate in all cases the operation of a contracting volume rate law. The specific rates increased with the Fell content following approximately a second-order polynomial expression. This result suggests that the transfer of Fe-III controls the dissolution rate, and that the leaching of a first layer of ions Co-II and Fe-II leaves exposed a surface enriched in slower dissolving octahedral Fe-III ions. Within this model, inner vicinal lattice Fe-II accelerates the rate of Fe-III transfer via internal electron hopping. A chain mechanism, involving successive electron transfers, fits the data very well. (C) 2006 Elsevier B.V. All rights reserved.

Structural study of a series of synthetic goethites obtained in aqueous solutions containing cadmium(II) ions

The capacity of goethite for Cd-II substitution has been explored in a series of synthetic samples prepared from Fe-III and Cd-II nitrate solutions aged 21 days in alkaline media. The total metal content ([ Fe] + [ Cd]) was 0.071 M in all preparations. The samples have been characterized by chemical and X-ray diffraction analysis; the morphology of the solids is described. The cell parameters for all samples were obtained by the Rietveld fits to the X-ray diffraction data. Refined structures show that for samples prepared at the final molar ratio mu(Cd)less than or equal to5.50 (expressed as mu(Cd) = 100X[Cd]/[Cd] + [Fe]), a (Cd, Fe)-goethite is the only crystalline product. In these samples, the unit cell parameters increased as a function of Cd concentration, indicating Cd incorporation in the structural frame. At the preparative ratio, mu(Cd)=7.03, the incorporation of Cd in the goethite structure is drastically reduced and a probable Cd-substituted hematite is formed together with the Fe,Cd-goethite. (C) 2003 International Centre for Diffraction Data.