Sorption and preconcentration of metal ions in ethanol solution with a silica gel surface chemically modified with benzimidazole

The adsorption isotherms of MCl(2) (M = Mn, Ni, Cu, Zn and Cd) and FeCl3 by silica gel chemically modified with benzimidazole molecules (= SI(CH2)(3)-NC7H5N) were studied in ethanol solution at 298 K. A column made of modified silica was used to adsorb and preconcentrate the above metal ions from ethanol solution. Elution was done with 0.1 M hydrochloric acid in an ethanol/water mixture having a mole fraction of water of 0.8. The material was applied in the preconcentration of metal ions from commercial ethanol normally used as engine fuel.

Sorption and preconcentration of metal ions on silica gel modified with 2,5-dimercapto-1,3,4-thiadiazole

Silica gel, chemically modified with 2,5-dimercapto-1,3,4-thiadiazole [=Si(CH2)(3)-NC2HNS3], abbreviated as SiB, was used to adsorb metal ions from ethanol by both batch and column techniques. Elution of Cu(II) was done with a solvent mixture of acetone and hydrochloric acid (9:1 v/v). Zn(II), Cd(II), Ni(II), Pb(II), Co(II) and Fe(III) were eluted with 0.5 mol l(-1) HC1 in ethanol solution. The modified silica was applied in the preconcentration of metal ions from commercial ethanol, normally used as engine fuel. The method is suitable for quantifying these metals at low mu g l(-1) levels.

Plasmodium vivax infection among Duffy antigen-negative individuals from the Brazilian Amazon region: an exception?

We present evidence for Plasmodium vivax infection among Duffy blood group-negative inhabitants of Brazil. The P. vivax identification was determined by both genotypic and non-genotypic screening tests. The Duffy blood group was genotyped by PCR/RFLP and phenotyped using a microtyping kit. We detected two homozygous FY*B-33 carriers infected by P vivax, whose circumsporozoite protein genotypes were VK210 and/or P. vivax-like. Additional efforts are necessary in order to clarify the evidence that P. vivax is being transmitted among Duffy blood group-negative patients from the Brazilian Amazon region. (C) 2007 Published by Elsevier Ltd on behalf of Royal Society of Tropical Medicine and Hygiene.

4f-4f intensities of the Tm3+ ions in fluoroindate glasses: the influence of third-order effects through odd intensity parameters

In this work an analysis of the phenomenological Omega(lambda) intensity parameters for the Tm3+ ion in fluoroindate glass is made using the standard Judd-Ofelt theory, and a modified oscillator strength taking into account odd-order contributions is utilized. Different sets of phenomenological intensity parameters Omega(lambda) (lambda=1,2,3,4,5,6) are discussed. The set of better quality is used to analyze the influence of third-order effects through odd intensity parameters in the new approximation. Fluoroindate glasses of compositions (40-x)InF3-20ZnF(2)-20SrF(2)-16BaF(2)-2GdF(3)-2NaF-xTmF(3) with x=1, 2 and 3 mol% were prepared, and the absorption spectra at room temperature in the spectral range from 300 to 2500 nm were obtained. The experimental oscillator strengths determined from the area under the absorption band are compared to the calculated ones. (C) 1998 Elsevier B.V. S.A.

Synthesis, characterisation and thermal behaviour of solid state compounds of 4-methylbenzylidenepyruvate with some bivalent metal ions

Solid state M-4-Me-BP compounds, where M stands for bivalent Mn, Fe, Co, Ni, Cu, Zn, Pb and 4-Me-BP is 4-methylbenzylidenepyruvate, have been synthesized. Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, elemental analysis, and complexometry were used to characterise and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, thermal stability and thermal decomposition of the isolated complexes. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Effects of the magnesium and chloride ions and shikimate on the structure of shikimate kinase from Mycobacterium tuberculosis

Bacteria, fungi and plants can convert carbohydrate and phosphoenolpyruvate into chorismate, which is the precursor of various aromatic compounds. The seven enzymes of the shikimate pathway are responsible for this conversion. Shikimate kinase (SK) is the fifth enzyme in this pathway and converts shikimate to shikimate-3-phosphate. In this work, the conformational changes that occur on binding of shikimate, magnesium and chloride ions to SK from Mycobacterium tuberculosis (MtSK) are described. It was observed that both ions and shikimate influence the conformation of residues of the active site of MtSK. Magnesium influences the conformation of the shikimate hydroxyl groups and the position of the side chains of some of the residues of the active site. Chloride seems to influence the affinity of ADP and its position in the active site and the opening length of the LID domain. Shikimate binding causes a closing of the LID domain and also seems to influence the crystallographic packing of SK. The results shown here could be useful for understanding the catalytic mechanism of SK and the role of ions in the activity of this protein.

Crytallization and high-resolution X-ray diffraction data collection of an Asp49 PLA(2) from Bothrops jararacussu venom both in the presence and absence of Ca2+ ions

Snake venom PLA(2)s have been extensively studied due to their role in mediating and disrupting physiological processes such as coagulation, platelet aggregation and myotoxicity. The Ca2+ ion bound to the putative calcium-binding loop is essential for hydrolytic activity. We report the crystallization in the presence and absence of Ca2+ and X-ray diffraction data collection at 1.60 Angstrom (with Ca2+) and 1.36 Angstrom (without Ca2+) of an Asp49 PLA(2) from Bothrops jararacussu venom. The crystals belong to orthorhombic space group C222(1). Initial refinement and electron density analysis indicate significant conformational. changes upon Ca2+ binding. (C) 2004 Elsevier B.V. All fights reserved.

Solubilization profiles of metal ions from bioleaching of sewage sludge as a function of pH

Two patterns of solubilization of metal ions resulting from bioleaching of sewage sludge by sulphur-oxidizing Thiobacillus spp. were established as a function of pH. Chromium and copper ions required a pH of 2-3 to initiate their solubilization, whereas nickel and zinc ions had their solubilization initiated at pH 6-6.5. The patterns obtained were independent of the sludge solids concentrations investigated (10, 17, 25, 32.5 and 40 g l(-1)).

Determination of the local site occupancy of Eu3+ ions in ZnAl2O4 nanocrystalline powders

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Thermal behaviour of malonic acid, sodium malonate and its compounds with some bivalent transition metal ions

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

Observational study on efficacy of negative expiratory pressure test proposed as screening for obstructive sleep apnea syndrome among commercial interstate bus drivers - protocol study

Background: Obstructive sleep apnea (OSA) is a respiratory disease characterized by the collapse of the extrathoracic airway and has important social implications related to accidents and cardiovascular risk. The main objective of the present study was to investigate whether the drop in expiratory flow and the volume expired in 0.2 s during the application of negative expiratory pressure (NEP) are associated with the presence and severity of OSA in a population of professional interstate bus drivers who travel medium and long distances.Methods/Design: An observational, analytic study will be carried out involving adult male subjects of an interstate bus company. Those who agree to participate will undergo a detailed patient history, physical examination involving determination of blood pressure, anthropometric data, circumference measurements (hips, waist and neck), tonsils and Mallampati index. Moreover, specific questionnaires addressing sleep apnea and excessive daytime sleepiness will be administered. Data acquisition will be completely anonymous. Following the medical examination, the participants will perform a spirometry, NEP test and standard overnight polysomnography. The NEP test is performed through the administration of negative pressure at the mouth during expiration. This is a practical test performed while awake and requires little cooperation from the subject. In the absence of expiratory flow limitation, the increase in the pressure gradient between the alveoli and open upper airway caused by NEP results in an increase in expiratory flow.Discussion: Despite the abundance of scientific evidence, OSA is still underdiagnosed in the general population. In addition, diagnostic procedures are expensive, and predictive criteria are still unsatisfactory. Because increased upper airway collapsibility is one of the main determinants of OSA, the response to the application of NEP could be a predictor of this disorder. With the enrollment of this study protocol, the expectation is to encounter predictive NEP values for different degrees of OSA in order to contribute toward an early diagnosis of this condition and reduce its impact and complications among commercial interstate bus drivers.

Anthropogenic influences on annual flux of cations and anions at meio stream basin, São Paulo State, Brazil

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

Wet deposition of major ions in a rural area impacted by biomass burning emissions

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

Thermal investigation of solid 2-methoxycinnamylidenepyruvate of some bivalent transition metal ions

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

The correlation between subordinate fish eye colour and received attacks: a negative social feedback mechanism for the reduction of aggression during the formation of dominance hierarchies

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)