Solvation in Pure Liquids: What Can Be Learned from the Use of Pairs of Indicators?

The solvation of six solvatochromic probes in a large number of solvents (33-68) was examined at 25 degrees C. The probes employed were the following: 2,6-diphenyl-4-(2,4,6-triphenylpyridinium-1-yl) phenolate (RB); 4-[(E)2-(1-methylpyridinium-4-yl)ethenyl] phenolate, MePM; 1-methylquinolinium-8-olate, QB; 2-bromo-4-[(E)-2-(1-methylpyridinium-4-yl)ethenyl] phenolate, MePMBr, 2,6-dichloro-4-(2,4,6-triphenyl pyridinium-1-yl) phenolate (WB); and 2,6-dibromo-4-[(E)-2-(1-methylpyridinium-4-yl)ethenyl] phenolate, MePMBr(2), respectively. Of these, MePMBr is a novel compound. They can be grouped in three pairs, each with similar pK(a) in water but with different molecular properties, for example, lipophilicity and dipole moment. These pairs are formed by RB and MePM; QB and MePMBr; WB and MePMBr(2), respectively. Theoretical calculations were carried out in order to calculate their physicochemical properties including bond lengths, dihedral angles, dipole moments, and wavelength of absorption of the intramolecular charge-transfer band in four solvents, water, methanol, acetone, and DMSO, respectively. The data calculated were in excellent agreement with available experimental data, for example, bond length and dihedral angles. This gives credence to the use of the calculated properties in explaining the solvatochromic behaviors observed. The dependence of an empirical solvent polarity scale E(T)(probe) in kcal/mol on the physicochemical properties of the solvent (acidity, basicity, and dipolarity/polarizability) and those of the probes (pK(a), and dipole moment) was analyzed by using known multiparameter solvation equations. For each pair of probes, values of E(T)(probe) (for example, E(T)(MePM) versus E(T)(RB)) were found to be linearly correlated with correlation coefficients, r, between 0.9548 and 0.9860. For the mercyanine series, the values of E(T)(probe) also correlated linearly, with (r) of 0.9772 (MePMBr versus MePM) and 0.9919 (MePMBr(2) versus MePM). The response of each pair of probes (of similar pK(a)) to solvent acidity is the same, provided that solute-solvent hydrogen-bonding is not seriously affected by steric crowding (as in case of RB). We show, for the first time, that the response to solvent dipolarity/polarizability is linearly correlated to the dipole moment of the probes. The successive introduction of bromine atoms in MePM (to give MePMBr, then MePMBr(2)) leads to the following linear decrease: pK(a) in water, length of the phenolate oxygen-carbon bond, length of the central ethylenic bond, susceptibility to solvent acidity, and susceptibility to solvent dipolarity/polarizability. Thus studying the solvation of probes whose molecular structures are varied systematically produces a wealth of information on the effect of solute structure on its solvation. The results of solvation of the present probes were employed in order to test the goodness of fit of two independent sets of solvent solvatochromic parameters.

Probing the dependence of the properties of cellulose acetates and their films on the degree of biopolymer substitution: use of solvatochromic indicators and thermal analysis

Although cellulose acetates, CAs, are extensively employed there is scant information about the systematic dependence of their properties on their degree of substitution, DS; this is the subject of the present work. Nine CAs samples, DS from 0.83 to 3.0 were synthesized; their films were prepared. The following solvatochromic probes have been employed in order to determine the empirical polarity, E (T)(33); ""acidity, alpha""; ""basicity, beta"", and ""dipolarity/polarizability, pi*"" of the casted films: 2,6-dichloro-4-(2,4,6-triphenyl-pyridinium-1-yl) phenolate, WB; 4-nitroaniline; 4-nitroanisole; 4-nitro-N,N-dimethylaniline; 2,6-diphenyl-4-(2,4,6-triphenyl-pyridinium-1-yl)phenolate, RB. Additionally, two systems, ethanol plus ethyl acetate (EtOH-EtAc), and cellulose plus cellulose triacetate, CTA, were employed as models for CAs of different DS. Regarding the model systems, the following was observed: (i) For EtOH-EtAc, the dependence of all solvatochromic parameters on the ""equivalent-DS"" of the binary mixture was non-linear because of preferential solvation; (ii) The dependence of E (T)(33) on equivalent DS of the cellulose-CTA films is linear, but the slope is smaller than that of the corresponding plot for CAs. This is attributed to the more efficient hydrogen bonding in the model system, a conclusion corroborated by IR measurements. The dependence of solvatochromic parameters of CAs on their DS is described by the simple equations; a consequence of the substitution of the OH by the ester group. The thermal properties of bulk CAs samples were investigated by DSC and TGA; their dependence on DS is described by simple equations. The relevance of these data to the processing and applications of CAs is briefly discussed.

Surface Properties of Calcinated Titanium Dioxide Probed by Solvatochromic Indicators: Relevance to Catalytic Applications

Titanium dioxide was obtained by hydrolysis of the corresponding ethoxide, followed by washing, drying, and calcination at 80, 160, 240, 320, 400, and 700 C, respectively. The following surface properties of the solids obtained were determined as a function of the calcinations temperature: T(Calcn); area by the BET method; BrOnsted acidity by titration with sodium hydroxide; empirical polarity, ET(30); Lewis acidity, alpha(Surf); Lewis basicity, beta(Surf); and dipolarity/polarizability pi*(Sturf), by use of solvatochromic indicators. Except for le surf whose value increased slightly, heating the samples resulted in a decrease of all of the above-mentioned surface properties, due to the decrease of surface hydroxyl groups. This conclusion has been corroborated by FTIR. Values of E(T)(30), alpha(Surf), and pi*(Surf) are higher than those of water and alcohols; the BrOnsted and Lewis acidities of the samples correlate linearly. The advantages of using solvatochromic indicators to probe the surface properties and relevance of the results to the applications of TiO(2) are discussed.

A New Indirect Electroanalytical Method to Monitor the Contamination of Natural Waters with 4-Nitrophenol Using Multiwall Carbon Nanotubes

The electrochemical detection of the hazardous pollutant 4-nitrophenol (4-NP) at low potentials, in order to avoid matrix interferences, is an important research challenge. This study describes the development, electrochemical characterization and utilization of a multiwall carbon nanotube (MWCNT) film electrode for the quantitative determination of 4-NP in natural water. Electrochemical impedence spectroscopy measurements showed that the modified surface exhibits a decrease of ca. 13 times in the charge transfer resistance when compared with a bare glassy carbon (GC) surface. Voltammetric experiments showed the possibility to oxidize a hydroxylamine layer (produced by the electrochemical reduction of 4-NP on the GC/MWNCT surface) in a potential region which is approximately 700 mV less positive than that needed to oxidize 4-NP, thus minimizing the interference of matrix components. The limit of detection for 4-NP obtained using square-wave voltammetry (0.12 mu mol L(-1)) was lower than the value advised by EPA. A natural water sample from a dam located in Sao Carlos (Brazil) was spiked with 4-NP and analyzed by the standard addition method using thee GC/MWCNT electrode, without any further purification step. the recovery procedure yielded a value of 96.5% for such sample, thus confirming the suitability of the developed method to determine 4-NP in natural water samples. The electrochemical determination was compared with that obtained by HPLC with UV-vis detection.

The role of HBF(4) in electro-catalysis: Arsenic contamination and anion adsorption

We present in this work a comprehensive investigation of the role played by dissolved tetrafluoroboric acid on the electrochemical response of a polycrystalline platinum electrode in acidic media. HBF(4) from two different suppliers was employed and characterized in terms of the amount of arsenic contamination by Inductively Coupled Plasma-Optical Emission Spectroscopy. The effect of different amounts of HBF(4) on the voltammetric profile of the Pt vertical bar HClO(4)(aq) interface was investigated by means of electrochemical quartz crystal nanobalance (EQCN). Despite the comparable cyclic voltammograms, the presence of arsenic in one of the two HBF(4) used resulted in dramatic variations in the mass change profile, which evidences the deposition/dissolution of arsenic prior to the surface oxidation. For the arsenic-free HBF(4), its effect on the mass change profile was mainly associated to anion adsorption. The impact of dissolved HBF(4) on the electro-oxidation of formic acid was rationalized in terms of two contributions: current enhancement at low potentials due to the arsenic-assisted formic acid electro-oxidation and inhibition at high potentials due to anion adsorption. (C) 2011 Elsevier B.V. All rights reserved.

Temporal indicators of language dominance in bilingual children

In the field of bilingualism it is of particular interest to stablish which, if any, of a speaker’s languages is dominant. Earlier research has shown that immigrants who acquire a new language tend to use elements of the timing patterns of the new language in their native language. It is shown here that measurements of timing in the two languages spoken by bilingual children can give information about the relative dominance of the languages for the individual speaker.

Associação entre manometria ano-retal e neuropatia pudenda em pacientes com incontinência fecal

A incontinência fecal é a incapacidade de manter o controle da eliminação do conteúdo intestinal em local e tempo socialmente adequados, resultando em escape de gases e fezes. Esta condição acarreta grande prejuízo na vida social dos acometidos. A causa conhecida mais comum é o trauma perineal, porém em uma grande proporcão a incontinência é idiopática. A avaliação da função esfincteriana anal é fundamental para o diagnóstico e para a conduta terapêutica na incontinência fecal. Para o entendimento da fisiopatologia desta condição desenvolveram-se vários exames de investigação. A manometria ano-retal é considerado imprescindível na avaliação. A correlação dos dados da manometria com a gravidade da doença e com estudos eletrofisiológicos ainda não estão bem estabelecidos. O objetivo deste estudo é correlacionar os dados da manometria ano-retal e o estudo do tempo de latência motora terminal do nervo pudendo com a incontinência fecal e comorbidades. Foram estudados prospectivamente todos os pacientes com queixa clínica de incontinência fecal atendidos no ambulatório de Serviço de Coloproctologia do Hospital Nossa Senhora da Conceição, de Porto Alegre (RS), entre março de 1997 e junho de 2000. De todos os pacientes foram coletados dados da anamnese que os classificaram segundo escore de incontinência proposto por JORGE & WEXNER (1993). Todos foram submetidos a manometria ano-retal, estudo do tempo de latência motora terminal do nervo pudendo bilateralmente e exame proctológico. Foram excluídos os pacientes que não concluíram toda a investigação, com cirurgias colo-retais baixas prévias ou neoplasia de reto e canal anal. Para análise estatística, os pacientes foram separados em grupos segundo a manometria normal ou alterada (hipotonia), presença ou não de neuropatia de nervo pudendo, por idade e por sexo. Foram estudados 39 pacientes, 85,6% do sexo feminino com idade média de 60,1 anos (±12,89). A média do escore de incontinência fecal foi de 9,30±4,93. À manometria ano-retal, vinte e três pacientes (59%) apresentaram pressões reduzidas. As pressões foram significativamente mais elevadas nos pacientes do sexo masculino. O tempo de latência motora terminal do nervo pudendo (neuropatia) foi prolongado em 14 doentes (35,9%). A idade e o tempo de latência motora terminal do nervo pudendo correlacionaram-se significativamente, r=0,422, (P=0,007). A demais correlações entre idade, pressões da manometria, tempo de latência motora terminal do nervo pudendo e escore de incontinência não foram estatisticamente significativas.

On the contamination of confidence

Contaminação da confiança é um caso especial de incerteza Knightiana ou ambiguidade na qual o tomador de decisões está diante de não apenas uma única distribuição de probabilidades, mas sim de um conjunto de distribuições de probabilidades. A primeira parte desta tese tem o propósito de fornecer uma caracterização da contaminação da confiança e então apresentar um conjunto de axiomas comportamentais simples sob os quais as preferências de um tomador de decisões é representada pela utilidade esperada de Choquet com contaminação da confiança. A segunda parte desta tese apresenta duas aplicações econômicas de contaminação da confiança: a primeira delas generaliza o teorema de existência de equilíbrio de Nash de Dow e Werlang (o que permite apresentar uma solução explícita para o paradoxo segundo o qual os jogadores de um jogo do dilema dos prisioneiros com um número infinito de repetições não agem de acordo com o esperado pelo procedimento da indução retroativa) e a outra estuda o impacto da contaminação da confiança na escolha de portfolio.

Fecal androgen levels in common marmoset (Callithrix jacchus) males living in captive family groups

In captive common marmoset groups, the reproductive inhibition observed in subordinate female seems to be a result of olfactory, visual and behavioral cues from the dominant female. However, few studies have examined the relationship among adult males living in the same social group. These studies have shown that reproductive failure among peer males seems to be based on hormonal and behavioral mechanisms. New insights on sexual strategies in primates have been shown using fecal steroids, but so far no information is available for common marmoset males. In the present study, we evaluated the influence of light-dark cycle, age and reproductive condition on the profile of fecal androgens in males living in the same family group. Feces were collected from six fathers and six sons for androgen determination during the light phase of the 24-h cycle for eight days randomly distributed over a 4-week period. Androgen levels were determined by enzyme immunoassay technique. Adult sons showed higher androgen levels (166.97 ± 22.95 ng/g) than fathers (80.69 ± 44.38 ng/g) and juveniles (49.06 ± 23.15 ng/g; P < 0.05). No diurnal variation (P > 0.05) in fecal androgen profile was observed in adults or juveniles. No indication of androgen-mediated social competition between fathers and adult sons was demonstrable. These results provide basic information on fecal androgen profile useful to investigate the socioendocrinology of free-ranging common marmoset males and verify that, in contrast to daughters, the reproductive suppression of sons is not based on physiological inhibition of their gonads

Colite de derivação fecal

A colite de derivação fecal (CD) é um processo inflamatório que ocorre no segmento colorretal desfuncionalizado, após uma cirurgia de desvio do trânsito intestinal. As principais características dessa entidade clínica são: apresenta-se na desfuncionalização do cólon ou reto; não há doença inflamatória intestinal preexistente; nunca acomete o sítio proximal à colostomia e ocorre resolução do processo após a restauração do trânsito intestinal. Diversas são as hipóteses postuladas para explicar o seu aparecimento; todavia, a deficiência nutricional do epitélio colônico, pela ausência dos ácidos graxos de cadeia curta (AGCC), no segmento desfuncionalizado, é a mais aceita na atualidade. Os autores fazem uma revisão da literatura enfocando os aspectos clínicos, histopatológicos e terapêuticos desta doença

Frequência da infecção por Toxoplasma gondii em galinhas caipira e frangos de corte em regiões dos Estados do Rio Grande do Norte e Paraíba

Toxoplasmosis is a zoonosis caused by Toxoplasma gondii, a protozoan that has a cosmopolitan geographic distribution and low host specificity. Usually a benign and selflimiting, infection can manifest itself in a severe systemic becoming overwhelming in fetuses and patients with immunosuppression. Domestic fowl are considered one of the most important hosts in the epidemiology of toxoplasmosis, since they are potential sources of infection for humans, in addition to playing the role of important indicators of environmental contamination by oocysts of T. gondii. We studied the prevalence of infection by the protozoan in chickens of different breeding systems mesoregions from the states of Rio Grande do Norte and Paraiba: broilers from commercial farms (200/PB) and free-range chickens of small farms (322/RN and PB). Were standardized IFAT and ELISA techniques for detecting specific antibodies in blood samples of birds, and commercial kit was used to determine the prevalence by IHAT. There was no seropositive reaction by T. gondii in the samples of broilers tested, indicating that the particularities of intensive management limit the chances of infection for these animals. Among the hens, the frequency of IgG anti-T. gondii diagnosed by the techniques of IHAT, IFAT and ELISA, respectively, were 3.73% (12/322), 37.88% (122/322) and 40.37% (130/322), for both young and adult animals. Amongst the seropositive samples by IFAT, 33 (27.05%) were positive at a dilution of 1:16, in 1:32, 31 (25.41%), in 1:64, 24 (19.67%), 15 (12.29%) in 1:128, and 19 presented titer greater than or equal to 1:256 (15.57%). The evaluation of the presence of anti-T. gondii should be careful, and reagents IHAT provided erratic results in this measure for the specie studied. This suggests the need for own standardization of the kit before the use in epidemiological studies in animal species. On the other hand, substantial agreement observed between IFAT and ELISA techniques (Kappa = 0.62) enables these methods as effective methodologies for the diagnosis of toxoplasmosis in chickens. The high prevalence of specific antibodies among poultry in the region studied attempts to the potential risk of transmission of toxoplasmosis to humans

Avaliação das condições higiênico-sanitárias da produção de refeições à base de carne da alimentação escolar no município de Natal-RN

The National School Nutrition Program is the oldest program in the country directed at food and nutrition safety. Its aims are to offer nutritional food as a supplement to students of public and philanthropic schools. Studying school nutrition transcends the investigation as a purely social program, given that it reaches the fields of public health, nutrition and food, using a wide variety of approaches. Thus, it is characterized by a multidisciplinary study, where the disciplines work side by side in distinct aspects of a single problem. Aim: This study aims to assess hygiene practices during the preparation of meat-based meals in public schools in the city of Natal, Brazil. Methods: A list was applied at 27 schools to identify the procedures of good food preparation practices. In addition, cooking and meal distribution temperature were measured and a microbiological analysis of the final preparation and of the water used in preparing it was performed. For microbiological analyses of the food, we analyzed coliforms at 45°C, coliforms at 35°C and Enterococcus, and for the water, we analyzed thermotolerant coliforms and total coliforms, using the methods recommended by APHA, 1995. Results: Most of the schools did not meet the required standards in all the variables related to good food preparation practices, except for the time spent preparing the meat, in which 89% were within the norm. Cooking temperature of the meals was within the standard; however, the temperature at distribution and the time spent dispensing the meals were inadequate. Of the 27 schools, 22 (81.5%) showed the presence of coliforms at 35° C in at least one meal sample and 18 (66.7%) had values above the recommended limit for coliforms at 45°C. The presence of E. coli was identified in 6.1% of the samples analyzed. The presence of Enterococcus was not found at any of the schools. With respect to the water, the North district of the city was the only one that did not meet the standards for the two indicators evaluated. The contamination found was not associated with the hygiene or food storage problems observed. Conclusions: The results show that the hygiene-sanitary conditions of meat-based public school meals were unsatisfactory, demonstrating the need for improvements in the production process to preserve the health of the student population. Multidisciplinarity: Researchers from the areas of food microbiology, nutrition, public health and statistics took part in this study, a decisive factor for characterizing the research as multidisciplinary