Characterization of must and wine of six varieties of grapes by direct infusion electrospray ionization mass spectrometry

Samples of must derived from six different varieties of grapes taken during the fermentation process, as well as the respective wine samples directly after the end of the malolactic fermentation, were analyzed by direct infusion negative ion mode electrospray ionization mass spectrometry (ESI-MS). Diagnostic ions for must were different from those of wine samples, although small variations for each of the grape varieties were also detected. The addition of unfermented must or sugar to wine could also be clearly detected. The spectra were acquired in a few minutes per sample, indicating that ESI-MS can be used for high-throughput analysis of samples and should prove useful for quality control during and after the fermentation process.     

Suzuki-Miyaura cross-coupling reactions of aryl tellurides with potassium aryltrifluoroborate salts

[reaction: see text] Palladium(0)-catalyzed cross-coupling between potassium aryltrifluoroborate salts and aryl tellurides proceeds readily to afford the desired biaryls in good to excellent yield. The reaction seems to be unaffected by the presence of electron-withdrawing or electron-donating substituents in both the potassium aryltrifluoroborate salts and aryl tellurides partners. Biaryls containing a variety of functional groups can be prepared. A chemoselectivity study was also carried out using aryl tellurides bearing halogen atoms in the same compound. In addition, this new version of the Suzuki-Miyaura cross-coupling reaction was monitored by electrospray ionization mass spectrometry where some reaction intermediates were detected and analyzed.     

Quantum Vacuum Fluctuations in a Chromomagnetic-Like Background

In this paper, we study the effects associated to quantum vacuum fluctuations of vectorial perturbations of the Abelian SU(2) Yang-Mills field in a static and homogeneous chromomagnetic-like background field, at zero temperature. We use periodic and antiperiodic boundary conditions in order to calculate the Casimir energy by means of the frequency sum technique and of the regularization method based on zeta functions, analyzing its behavior in the weak and strong coupling regimes. We compare the obtained results with the similar ones found for scalar and spinor fields placed in an ordinary magnetic field background. We show that only in the weak coupling regime the non-trivial topology of the system encoded in the antiperiodic boundary conditions changes the nature of the Casimir force with respect to the periodic ones. Considering the weak coupling scenario, we show that the introduction of a third polarization state in the perturbations makes manifest the effects on the Casimir energy due to the coupling with the chromomagnetic-like background field, for both the boundary conditions. Finally, in the strong coupling regime, in which the quantum vacuum is not stable due to the Nielsen-Olesen instabilities, we evaluate the effects of a compact extra dimension on its stabilization.     

RP-HPLC method for estimation of sesamin in two Zanthoxylum species

Zanthoxylum naranjillo and Z. tingoassuiba (Rutaceae) are traditional herbal medicines with various biological activities including anti-inflammatory, analgesic, and antimalarial action. In this work, we have developed a simple HPLC-DAD method to quantify sesamin, a bioactive lignan present in Z. naranjillo and Z. tingoassuiba; egonol was the internal standard. According to the developed method, 11.07 ± 1.66, 8.69 ± 0.95, and 15.11 ± 0.72 µg/mL sesamin was present in the ethanol extract of Z. naranjillo leaves, in the methanol extract of Z. naranjillo leaves, and in the methanol extract of Z. tingoassuiba bark, respectively. The limits of detection and quantification were 0.32 and 1.06 µg/mL, respectively. The developed method can be easily applied during routine analysis of sesamin in these medicinal plants.     

A new minor dimmeric ester from seeds of Cassia fistula L. (Leguminosae)

Bioactivity-guided fractionation of n-hexane phase from MeOH extract of the seeds of Cassia fistula L. (Leguminosae) yielded two bioactive substances against Cladosporium cladosporioides and C. sphaerospermum. After spectroscopic analysis, these compounds were characterised as the known benzyl 2-hydroxy-3,6-dimethoxybenzoate and its dimer dibenzyl 2,2'-dihydroxy-3,6,3″,6″-tetramethoxy-biphenyl-1,1'-dicarboxylate, which showed a new structural arrangement.     

Lectin from Canavalia brasiliensis seeds (ConBr) is a valuable biotechnological tool to stimulate the growth of Rhizobium tropici in vitro

To study the interactions between a Rhizobium tropici strain and lectins isolated from the seeds of Canavalia ensiformis (ConA) and Canavalia brasiliensis (ConBr), a lectin fluorescence assay was performed. In addition, an experiment was designed to evaluate the effect of the two lectins on bacterial growth. Both lectins were found to bind to R. tropici cells, but the interactions were inhibited by D-mannose. Interestingly, only ConBr stimulated bacterial growth in proportion to the concentrations used (15.6-500 μg/mL), and the bacterial growth stimulation was inhibited by D-mannose as well. Structure/Function analyses by bioinformatics were carried out to evaluate the volume and carbohydrate recognition domain (CRD) configuration of ConA and ConBr. The difference of spatial arrangement and volume of CRD may indicate the variation between biological activities of both lectins. The results suggest that ConBr could be a promising tool for studies focusing on the interactions between rhizobia and host plants.     

The Moduli Space of Complex Geodesics in the Complex Hyperbolic Plane

We consider the space M\mathcal{M} of ordered m-tuples of distinct complex geodesics in complex hyperbolic 2-space, H_\mathbbC²{\rm\bf H}_{\mathbb{C}}^{2}, up to its holomorphic isometry group PU(2,1). One of the important problems in complex hyperbolic geometry is to construct and describe the moduli space for M\mathcal{M}. This is motivated by the study of the deformation space of groups generated by reflections in complex geodesics. In the present paper, we give the complete solution to this problem.     

Analysis of 210Pb and 210Po in Brazilian foods and diets

Radiochemical procedures for the analysis of ²¹⁰ Pb and ²¹⁰ Po in foods and diets are presented. Because of the low beta energy of ²¹⁰ Pb, its analysis was based on a separation of the daughter radionuclide ²¹⁰ Bi by precipitation of lead sulphate, ²¹⁰ Bi ingrowing and beta counting of this nuclide. ²¹⁰ Po analysis was based on wet dissolution of the sample, deposition onto silver disc and counting by alpha-spectrometry. Levels of these radionuclides in individual items and diets of selected university students were determined in order to evaluate the intakes of ²¹⁰ Pb and ²¹⁰ Po as well as the dose due to ingestion of foods and diets in São Paulo city.     

Identification of stiffness properties of composite tubes from dynamic tests

The identification of the stiffness properties of typical laminated composite tubes from dynamic tests is presented. Unknown coefficients are identified by a technique of model updating. The fomulation is based on the minimization of the eigensolution residuals (sensitivity method). Errors of generalized masses are considered. The technique allows for the simultaneous identification of several properties from a single test. Stiffness properties of extension, bending/twisting and transverse shear are identified. Important points of the model updating of tubes in dynamics are addressed: potential energy evaluation, placement of sensors and the problem of multiple eigenvalues. Results obtained by numerical simulation show the efficiency of the proposed method.