Thermodiffusion in a multicomponent lyotropic mixture in the vicinity of the critical micellar concentration by using the Z-scan technique

Thermodiffusion in a lyotropic mixture of water and potassium laurate is investigated by means of an optical technique (Z scan) distinguishing the index variations due to the temperature gradient and the mass gradients. A phenomenological framework allowing for coupled diffusion is developed in order to analyze thermodiffusion in multicomponent systems. An observable parameter relating to the mass gradients is found to exhibit a sharp change around the critical micellar concentration, and thus may be used to detect it. The change in the slope is due to the markedly different values of the Soret coefficients of the surfactant and the micelles. The difference in the Soret coefficients is due to the fact that the micellization process reduces the energy of interaction of the ball of amphiphilic molecules with the solvent.

Thermo-optical characteristics and concentration quenching effects in Nd(3+)doped yttrium calcium borate glasses

In this work we present a comprehensive study of the spectroscopic and thermo-optical properties of a set of samples with composition xNd(2)O(3)-(5-x)Y(2)O(3-)40CaO-55B(2)O(3) (0 <= x <= 1.0 mol%). Their fluorescence quantum efficiency (eta) values were determined using the thermal lens technique and the dependence on the ionic concentration was analyzed in terms of energy transfer processes, based on the Forster-Dexter model of multipolar ion-ion interactions. A maximum eta = 0.54 was found to be substantially higher than for yttrium aluminoborate crystals and glasses with comparable Nd(3+) content. As for the thermo-optical properties of yttrium calcium borate, they are comparable to other well-known laser glasses. The obtained energy transfer microparameters and the weak dependence of. on the Nd(3+) concentration with a high optimum Nd(3+) concentration put this system as a strong candidate for photonics applications. (C) 2011 American Institute of Physics. [doi:10.1063/1.3567091]

Effect of Mn concentration and atomic structure on the magnetic properties of Ge thin films

This work reports on the magnetic properties of Ge(100-x)Mn(x) (x=0-24 at. %) films prepared by cosputtering a Ge+Mn target and submitted to cumulative thermal annealing treatments up to 500 degrees C. Both as-deposited and annealed films were investigated by means of compositional analysis, Raman scattering spectroscopy, magnetic force microscopy, superconducting quantum interference device magnetometry, and electrical resistivity measurements. All as-deposited films (either pure or containing Mn) exhibit an amorphous structure, which changes to crystalline as the annealing treatments are performed at increasing temperatures. In fact, the magnetic properties of the present Ge(100-x)Mn(x) films are very sensitive to the Mn content and whether their atomic structure is amorphous or crystalline. More specifically: whereas the amorphous Ge(100-x)Mn(x) films (with high x) present a characteristic spin glass behavior at low temperature; after crystallization, the films (with moderate Mn contents) are ferromagnetic at room temperature. Moreover, the magnetic behavior of the films scales with their Mn concentration and tends to be more pronounced after crystallization. Finally, the semiconducting behavior of the films, experienced by previous optical studies, was confirmed through electrical measurements, which also indicate the dependence of the resistivity with the atomic composition of the films. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3520661]

Hypervalent organochalcogenanes as inhibitors of protein tyrosine phosphatases

A series of organochalcogenanes was synthesized and evaluated as protein tyrosine phosphatases (PTPs) inhibitors. The results indicate that organochalcogenanes inactivate the PTPs in a time- and concentration-dependent fashion, most likely through covalent modification of the active site sulfur-moiety by the chalcogen atom. Consequently, organochalcogenanes represent a new class of mechanism-based probes to modulate the PTP-mediated cellular processes.

The electronic states of SeF: A reinterpretation of the chemiluminescent emission of the reaction of selenium with fluorine

The low-lying doublet and quartet electronic states of the species SeF correlating with the first dissociation channel are investigated theoretically at a high-level of electronic correlation treatment, namely, the complete active space self-consistent field/multireference single and double excitations configuration interaction (CASSCF/MRSDCI) using a quintuple-zeta quality basis set including a relativistic effective core potential for the selenium atom. Potential energy curves for (Lambda+S) states and the corresponding spectroscopic properties are derived that allows for an unambiguous assignment of the only spectrum known experimentally as due to a spin-forbidden X (2)Pi-a (4)Sigma(-) transition, and not a A (2)Pi-X (2)Pi transition as assumed so far. For the bound excited doublets, yet unknown experimentally, this study is the first theoretical characterization of their spectroscopic properties. Also the spin-orbit coupling constant function for the X (2)Pi state is derived as well as the spin-orbit coupling matrix element between the X (2)Pi and a (4)Sigma(-) states. Dipole moment functions and vibrationally averaged dipole moments show SeF to be a very polar species. An overview of the lowest-lying spin-orbit (Omega) states completes this description. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3426315]

omega-Transaminases as efficient biocatalysts to obtain novel chiral selenium-amine ligands for Pd-catalysis

omega-Transaminases have been evaluated as biocatalysts in the reductive amination of organoselenium acetophenones to the corresponding amines, and in the kinetic resolution of racemic organoselenium amines. Kinetic resolution proved to be more efficient than the asymmetric reductive amination. By using these methodologies we were able to obtain both amine enantiomers in high enantiomeric excess (up to 99%). Derivatives of the obtained optically pure o-selenium 1-phenylethyl amine were evaluated as ligands in the palladium-catalyzed asymmetric alkylation, giving the alkylated product in up to 99% ee.

Method for cadmium and lead longitudinal profiles determination in hair by solid sampling graphite furnace atomic absorption spectrometry

This paper describes methods for the direct determination of Cd and Pb in hair segments (c.a. 5 mm similar to 80 mu g) by solid sampling graphite furnace atomic absorption spectrometry, becoming possible longitudinal profiles in a single strand of hair. To distinguish endogenous and exogenous content. strands of hair were washed by using two different procedures: IAEA protocol (acetone + water + acetone) and the combination of IAEA protocol with HCl washing (acetone + water + acetone + 0.1 mol l(-1) HCl). The concentration of Cd and Pb increased from the root Until the tip of hair washed according to IAEA protocol. However, when the strand of hair was washed using the combination of IAEA protocol and 0.1 mol l(-1) HCl, Cd concentrations decreased in all segments, and Pb concentrations decreased drastically near to the root (5 to 12 mm) and was systematically higher ill the end. The proposed method showed to be useful to assess the temporal variation to Cd and Pb exposure and call be Used for toxicological and environmental investigations. The limits of detection were 2.8 ng g(-1) for Cd and 40 ng g(-1) for Pb. The characteristic masses based oil integrated absorbance were 2.4 pg for Cd and 22 pg for Pb.

Discharge-calcium concentration relationships in streams of the Amazon and Cerrado of Brazil: soil or land use controlled

Stream discharge-concentration relationships are indicators of terrestrial ecosystem function. Throughout the Amazon and Cerrado regions of Brazil rapid changes in land use and land cover may be altering these hydrochemical relationships. The current analysis focuses on factors controlling the discharge-calcium (Ca) concentration relationship since previous research in these regions has demonstrated both positive and negative slopes in linear log(10)discharge-log(10)Ca concentration regressions. The objective of the current study was to evaluate factors controlling stream discharge-Ca concentration relationships including year, season, stream order, vegetation cover, land use, and soil classification. It was hypothesized that land use and soil class are the most critical attributes controlling discharge-Ca concentration relationships. A multilevel, linear regression approach was utilized with data from 28 streams throughout Brazil. These streams come from three distinct regions and varied broadly in watershed size (< 1 to > 10(6) ha) and discharge (10(-5.7)-10(3.2) m(3) s(-1)). Linear regressions of log(10)Ca versus log(10)discharge in 13 streams have a preponderance of negative slopes with only two streams having significant positive slopes. An ANOVA decomposition suggests the effect of discharge on Ca concentration is large but variable. Vegetation cover, which incorporates aspects of land use, explains the largest proportion of the variance in the effect of discharge on Ca followed by season and year. In contrast, stream order, land use, and soil class explain most of the variation in stream Ca concentration. In the current data set, soil class, which is related to lithology, has an important effect on Ca concentration but land use, likely through its effect on runoff concentration and hydrology, has a greater effect on discharge-concentration relationships.

Variation in the Distribution of Trace Elements in Renal Cell Carcinoma

The development of cancer is a complex, multistage process during which a normal cell undergoes genetic changes that result in phenotypic alterations and in the acquisition of the ability to invade other sites. Inductively coupled plasma optical emission spectroscopy was used to estimate the contents of Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, P, Pb, and Zn in healthy kidney and renal cell carcinoma (RCC), and significant differences were found for all elements. Along with the progression of the malignant disease, a progressive decrease of Cd and K was observed. In fact, for Cd, the concentration in stage T4 was 263.9 times lower than in stage T1, and for K, the concentration in stage T4 was 1.73 times lower than in stage T1. Progressive accumulation was detected for P, Pb, and Zn in stage T4. For P, the concentration in stage T4 was 11.1 times higher than in stage T1; for Pb, the concentration in stage T4 was 232.7 times higher than in T1; and for Zn, the concentration in T4 was 8.452 times higher than in T1. This study highlights the marked differences in the concentrations of selected trace metals in different malignant tumor stages. These findings indicate that some trace metals may play important roles in the pathogenesis of RCC.

Cloud point extraction and concentration of carbaryl from natural waters

An improved procedure is proposed for determination of the pesticide carbaryl in natural waters based on double cloud point extraction. The clean up step was carried out only with Triton X-114 in alkaline medium in order to avoid the use of toxic organic solvents as well as to minimise waste generation. Cloud point preconcentration of the product of the reaction of the analyte with p-aminophenol and cetyltrimethylammonium bromide was explored to increase sensitivity and improve the detection limit. Linear response was achieved within 10 and 500 mu g L-1 and the apparent molar absorptivity was estimated as 4.6 x 105 L mol-1 cm-1. The detection limit was estimated as 7 mu g L-1 at the 99.7% confidence level and the coefficient of variation was 3.4% (n = 8). Recoveries within 91 and 99% were estimated for carbaryl spiked water samples. The results obtained for natural water samples were in agreement with those achieved by the batch of spectrophotometric procedure at the 95% confidence level. The proposed procedure is then a simple, fast, inexpensive and greener alternative for carbaryl determination.

A comparison between the concentration of mast cells in squamous cell carcinomas of the skin and oral cavity

FUNDAMENTS: The lethality of squamous cell carcinomas (SCC) of the skin is considered low. SCC in the mouth is usually associated with poor prognosis. Current evidence suggests that mast cells in the normal tissue contribute to the tumorigenesis of SCC, probably by promoting angiogenesis. OBJECTIVE: The aim of this study was to compare the concentration of mast cells in SCC of the mouth and skin and evaluate whether there is a correlation with the degree of differentiation of these tumors. MATERIAL AND METHODS: Thirty cases of SCC of the skin and 34 of the mouth were investigated. Toluidine blue staining was used to identify mast cells in blocks containing the central portion of the neoplasm. RESULTS: A concentration of between 0 and 10 mast cells was found in one single case of SCC of the skin and there were no cases of SCC of the mouth with concentrations of mast cells in the tumor >201. In the majority of cases of SCC of the mouth (47%; n=16), mast cell concentration was between 0 and 10, with a concentration >51 mast cells in 80% of cases of SCC of the skin. All the cases of SCC of the mouth with a concentration of mast cells between 100 and 200 and 80% of those with a concentration of 51-99 were located on the lip. The concentration of mast cells was unrelated to the degree of differentiation of the tumor. CONCLUSION: The concentration of mast cells is lower in SCC of the mouth except when the tumor is located on the lip. This may reflect a lower need for cell activation in the microenvironment to improve vascularization in oral cancer.

The effect of Sao Paulo`s smoke-free legislation on carbon monoxide concentration in hospitality venues and their workers

Background Studies have shown that there is no safe level of secondhand smoke (SHS) exposure and there is a close link between SHS and the risk of coronary heart disease and stroke. Carbon monoxide (CO) is one of the most important components present in SHS. Objective To evaluate the impact of the smoking ban law in the city of Sao Paulo, Brazil, on the CO concentration in restaurants, bars, night clubs and similar venues and in their workers. Methods In the present study we measured CO concentration in 585 hospitality venues. CO concentration was measured in different environments (indoor, semi-open and open areas) from visited venues, as well as, in the exhaled air from approximately 627 workers of such venues. Measurements were performed twice, before and 12 weeks after the law implementation. In addition, the quality of the air in the city during the same period of our study was verified. Results The CO concentration pre-ban and pot-ban in hospitality venues was indoor area 4.57 (3.70) ppm vs 1.35 (1.66) ppm (p<0.0001); semi-open 3.79 (2.49) ppm vs 1.16 (1.14) ppm (p<0.0001); open area 3.31 (2.2) ppm vs 1.31 (1.39) ppm (p<0.0001); smoking employees 15.78 (9.76) ppm vs 11.50 (7.53) ppm (p<0.0001) and non-smoking employees 6.88 (5.32) ppm vs 3.50 (2.21) ppm (p<0.0001). The average CO concentration measured in the city was lower than 1 ppm during both pre-ban and post-ban periods. Conclusion Sao Paulos smoking-free legislation reduced significantly the CO concentration in hospitality venues and in their workers, whether they smoke or not.

Low nanomolar concentration of mercury chloride increases vascular reactivity to phenylephrine and local angiotensin production in rats

Exposure to mercury at nanomolar level affects cardiac function but its effects on vascular reactivity have yet to be investigated. Pressor responses to phenylephrine (PHE) were investigated in perfused rat tail arteries before and after treatment with 6 nM HgCl2 during 1 h,,in the presence (E+) and absence (E-) of endothelium, after L-NAME (10(-4) M), indomethacin (10(-5) M), enalaprilate (1 mu M), tempol (1 mu M) and deferoxamine (300 mu M) treatments. HgCl2 increased sensitivity (pD(2)) without modifying the maximum response (Em) to PHE, but the pD(2) increase was abolished after endothelial damage. L-NAME treatment increased pD(2) and Emax. However, in the presence of HgCl2, this increase was smaller, and it did not modify Emax. After indomethacin treatment, the increase of pD(2) induced by HgCl2 was maintained. Enalaprilate, tempol and deferoxamine reversed the increase of pD(2) evoked by HgCl2. HgCl2 increased the angiotensin converting enzyme (ACE) activity explaining the result obtained with enalaprilate. Results suggest that at nanomolar concentrations HgCl2 increase the vascular reactivity to PHE. This response is endothelium mediated and involves the reduction of NO bioavailability and the action of reactive oxygen species. The local ACE participates in mercury actions and depends on the angiotensin 11 generation. (c) 2007 Elsevier Inc. All rights reserved.

The effect of agitation speed, enzyme loading and substrate concentration on enzymatic hydrolysis of cellulose from brewer`s spent grain

Brewer`s spent grain components (cellulose, hemicellulose and lignin) were fractionated in a two-step chemical pretreatment process using dilute sulfuric acid and sodium hydroxide solutions. The cellulose pulp produced was hydrolyzed with a cellulolytic complex, Celluclast 1.5 L, at 45 degrees C to convert the cellulose into glucose. Several conditions were examined: agitation speed (100, 150 and 200 rpm), enzyme loading (5, 25 and 45 FPU/g substrate), and substrate concentration (2, 5 and 8% w/v), according to a 2(3) full factorial design aiming to maximize the glucose yield. The obtained results were interpreted by analysis of variance and response surface methodology. The optimal conditions for enzymatic hydrolysis of brewer`s spent grain were identified as 100 rpm, 45 FPU/g and 2% w/v substrate. Under these conditions, a glucose yield of 93.1% and a cellulose conversion (into glucose and cellobiose) of 99.4% was achieved. The easiness of glucose release from BSG makes this substrate a raw material with great potential to be used in bioconversion processes.

Establishment of the optimum initial xylose concentration and nutritional supplementation of brewer`s spent grain hydrolysate for xylitol production by Candida guilliermondii

The effects of initial xylose concentration and nutritional supplementation of brewer`s spent grain hydrolysate on xylitol production by Candida guilliermondii were evaluated using experimental design methodology. The hydrolysate containing 55, 75 or 95 g/l xylose, supplemented or not with nutrients (calcium chloride, ammonium sulfate and rice bran extract), was used as fermentation medium. The increase in xylitol yield and productivity was related to the increase of initial xylose concentration, but up to a certain limit. above of which the yeast performance was not improved. The hydrolysate supplementation with nutrients did not interfere with xylose-to-xylitol conversion. By using the statistic tool the best conditions for maximum xylitol production were found. which consisted in using the non-supplemented hydrolysate containing 70 g/l initial xylose concentration. Under these conditions, a xylitol yield of 0.78 g/g and productivity of 0.58 g/(l h) were achieved. (C) 2008 Elsevier Ltd. All rights reserved.