Reduction of mercury(II) by tropical river humic substances (Rio Negro) - A possible process of the mercury cycle in Brazil

The evolution of elemental Hg from its environmental compounds has already been supposed to be an important process within the global mercury cycle. The present study characterizes the abiotic reduction of Hg(II) ions by typical river humic substances (HS) conventionally pre-isolated by the adsorbent XAD 8 from the Rio Negro near Manaus, Brazil. For the investigation of this reduction process a special reaction and Hg(0) trapping unit combined with cold-vapor atomic absorption spectrometry (CVAAS) was developed. Preconcentration of traces of mercury(II), if required, was obtained by a home-made FIA system using microcolumns filled with the Hg(II)-selective collector CheliteS(R) (Serva Company). The effect of environmentally relevant parameters such as the pH value, the Hg(II)/HS ratio and the HS concentration on the I-IE;(II) reduction process was studied as a function of the time. The Hg(0) production was highest at pH 8.0 and in the case of decreasing HS amounts (0.5 mg) when about 65% of initially 1.0 mug Hg(H) was reduced within 50 h. Moreover, the reduction efficiency of HS towards HE;(II) strongly depended on the HS concentration but hardly on the Hg(II)/HS ratio. The reduction kinetics followed a relatively slow two-step first-order mechanism with formal rate constants of about 0.1 and 0.02 h(-1), respectively. Based on these findings the possible relevance of the abiotic evolution of mercury in humic-rich aquatic environments is considered. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Electrochemical Reduction as a Powerful Tool to Highlight the Possible Formation of By-Products More Toxic Than Sudan III Dye

The present work describes the electrochemical reduction of the azo dye Sudan III in methanol/0.01 mol l(-1) Bu4NBF4 at applied potential of -1.2V, which promotes 98% discoloration of the commercial sample. The reduction products were analyzed by high performance liquid chromatography, after optimized conditions for 20 aromatic amines with carcinogenic potentiality. The harmful compounds such as: aniline, benzidine, o-toluidine, 2,6-dimethylaniline, 4,4'-oxydianiline, 4,4'-metileno-bis-2-methylaniline and 4-aminobiphenyl are formed after azo bond cleavage. The electrochemical reduction is compared with chemical reduction by using sodium thiosulfate. Our findings illustrates that commercial Sudan III under reductive condition can forms a number of products, which some are known active genotoxins. The technique could be used to mimic important redox reactions in human metabolism or environment, highlighting the possible formation of by-products more toxic than the original dyes.

Prognosis of Atrial Fibrillation in Patients with Symptomatic Peripheral Arterial Disease: Data from the REduction of Atherothrombosis for Continued Health (REACH) Registry

BACKGROUND: Atrial fibrillation (AF) is a significant risk factor for cardiovascular (CV) mortality. This study aims to evaluate the prognostic implication of AF in patients with peripheral arterial disease (PAD). METHODS: The International Reduction of Atherothrombosis for Continued Health (REACH) Registry included 23,542 outpatients in Europe with established coronary artery disease, cerebrovascular disease (CVD), PAD and/or >/=3 risk factors. Of these, 3753 patients had symptomatic PAD. CV risk factors were determined at baseline. Study end point was a combination of cardiac death, non-fatal myocardial infarction (MI) and stroke (CV events) during 2 years of follow-up. Cox regression analysis adjusted for age, gender and other risk factors (i.e., congestive heart failure, coronary artery re-vascularisation, coronary artery bypass grafting (CABG), MI, hypertension, stroke, current smoking and diabetes) was used. RESULTS: Of 3753 PAD patients, 392 (10%) were known to have AF. Patients with AF were older and had a higher prevalence of CVD, diabetes and hypertension. Long-term CV mortality occurred in 5.6% of patients with AF and in 1.6% of those without AF (p<0.001). Multivariable analyses showed that AF was an independent predictor of late CV events (hazard ratio (HR): 1.5; 95% confidence interval (CI): 1.09-2.0). CONCLUSION: AF is common in European patients with symptomatic PAD and is independently associated with a worse 2-year CV outcome.

4D/3D reduction of dualities: mirrors on the circle

We engineer a brane picture for the reduction of Seiberg dualities from 4D to 3D, valid also in the presence of orientifold planes. We obtain effective 3D dualities on the circle by T-duality, geometrizing the non-perturbative superpotential which is an affine Toda potential. When reducing to pure 3D, we define a double-scaling limit which creates a sector of interacting singlets, giving a unified mechanism for the brane reduction of dualities.

Correlation between the photocatalysed oxidation of methylene blue in solution and the reduction of resazurin in a photocatalyst activity indicator ink (Rz Paii)

Analysis of the nano-surface of a modified glassy carbon electrode by pseudo phase plane method

This paper presents the Pseudo phase plane (PPP) method for detecting the existence of a nanofilm on the nitroazobenzene-modified glassy carbon electrode (NAB-GC) system. This modified electrode systems and nitroazobenze-nanofilm were prepared by the electrochemical reduction of diazonium salt of NAB at the glassy carbon electrodes (GCE) in nonaqueous media. The IR spectra of the bare glassy carbon electrodes (GCE), the NAB-GC electrode system and the organic NAB film were recorded. The IR data of the bare GC, NAB-GC and NAB film were categorized into five series consisting of FILM1, GC-NAB1, GC1; FILM2, GC-NAB2, GC2; FILM3, GC-NAB3, GC3 and FILM4, GC-NAB4, GC4 respectively. The PPP approach was applied to each group of the data of unmodified and modified electrode systems with nanofilm. The results provided by PPP method show the existence of the NAB film on the modified GC electrode.

The effects of glutamine-supplemented diet on the intestinal mucosa of the malnourished growing rat

Glutamine is the most abundant amino acid in the blood and plays a key role in the response of the small intestine to systemic injuries. Mucosal atrophy is an important phenomenon that occurs in some types of clinical injury, such as states of severe undernutrition. Glutamine has been shown to exert powerful trophic effects on the gastrointestinal mucosa after small bowel resection or transplant, radiation injury, surgical trauma, ischemic injury and administration of cytotoxic drugs. Since no study has been performed on the malnourished animal, we examined whether glutamine exerts a trophic effect on the intestinal mucosa of the malnourished growing rat. Thirty-five growing female rats (aged 21 days) were divided into 4 groups: control - chow diet; malnutrition diet; malnutrition+chow diet; and malnutrition+glutamine-enriched chow diet (2%). For the first 15 days of the experiment, animals in the test groups received a malnutrition diet, which was a lactose-enriched diet designed to induce diarrhea and malnutrition. For the next 15 days, these animals received either the lactose-enriched diet, a regular chow diet or a glutamine-enriched chow diet. After 30 days, the animals were weighed, sacrificed, and a section of the jejunum was taken and prepared for histological examination. All the animals had similar weights on day 1 of experiment, and feeding with the lactose-enriched diet promoted a significant decrease in body weight in comparison to the control group. Feeding with both experimental chow-based diets promoted significant body weight gains, although the glutamine-enriched diet was more effective. RESULTS: The morphological and morphometric analyses demonstrated that small intestinal villous height was significantly decreased in the malnourished group, and this change was partially corrected by the two types of chow-based diet. Crypt depth was significantly increased by malnutrition, and this parameter was partially corrected by the two types of chow-based diet. The glutamine-enriched diet resulted in the greatest reduction of crypt depth, and this reduction was also statistically significant when compared with control animals. CONCLUSIONS: Enteral glutamine has some positive effects on body weight gain and trophism of the jejunal mucosa in the malnourished growing rat.

The molluscicidal activity of the latex of Euphorbia splendens var. hislopii on Melanoides tuberculata (Thiaridae), a snail associated with habitats of Biomphalaria glabrata (Planorbidae)

The use of the latex of Euphorbia splendens var. hislopii was considered as an effective control method for Biomphalaria glabrata in Sumidouro, Rio de Janeiro. However, the appearance and expansion of the snail Melanoides tuberculata since August 1997, with the concomitant reduction of the population of B. glabrata suggest that competitive exclusion might be taking place. Depending on the susceptibility of the thiarid to the E. splendens toxin, the natural control that is occurring could be interrupted by the employment of the latex if the planorbid were less susceptible to the toxin. The aim of this study is to investigate the molluscicidal activity of the latex on M. tuberculata. We used 420 M. tuberculata, from Sumidouro. Fourteen different latex concentrations were tested using World Health Organization general methodology. Probit analysis was used for LD90 and LD50 determination. The LD50 was 3.57 mg/l and LD90 was 6.22 mg/l. At the highest concentration (10 mg/l) there was no survival. No significant differences among replicas (chi2 = 8.31; gl = 13; p > 0.05) were found. The LD90 dose for M. tuberculata was 13.8 times greater than that for B. glabrata, so that the molluscicide in the presence of the thiarid may have a synergic effect on reduction of Biomphalaria populations.

Towards a global criteria based framework for the sustainability assessment of bioethanol supply chains: application to the Swiss dilemma : is local produced bioethanol more sustainable than bioethanol imported from Brazil?

Biofuels are considered as a promising substitute for fossil fuels when considering the possible reduction of greenhouse gases emissions. However limiting their impacts on potential benefits for reducing climate change is shortsighted. Global sustainability assessments are necessary to determine the sustainability of supply chains. We propose a new global criterion based framework enabling a comprehensive international comparison of bioethanol supply chains. The interest of this framework is that the selection of the sustainability indicators is qualified on three criterions: relevance, reliability and adaptability to the local context. Sustainability issues have been handled along environmental, social and economical issues. This new framework has been applied for a specific issue: from a Swiss perspective, is locally produced bioethanol in Switzerland more sustainable than imported from Brazil? Thanks to this framework integrating local context in its indicator definition, Brazilian production of bioethanol is shown as energy efficient and economically interesting for Brazil. From a strictly economic point of view, bioethanol production within Switzerland is not justified for Swiss consumption and questionable for the environmental issue. The social dimension is delicate to assess due to the lack of reliable data and is strongly linked to the agricultural policy in both countries. There is a need of establishing minimum sustainability criteria for imported bioethanol to avoid unwanted negative or leakage effects.

Diastereoselective Synthesis of Planar Chiral N-Substituted Ferrocenes Derived from Epimeric Imidazolones and their Application to Asymmetric Hydrogenation of Quinolines

This thesis describes the synthesis and use of an N-substituted ferrocene bearing a proline-derived chiral directing group and diastereoselective lithiation-electrophile quench of the pro-Sp hydrogen of the ferrocene to give planar chiral products in >95:5 dr. The auxiliary group is found to be stable to lithium bases of types RLi and R2NLi giving the same diastereoselectivity. The anti- epimer of the previously mentioned syn auxiliary induces lithiation of pro Rp rather than pro Sp hydrogen in >95:5 dr. Upon electrophile quench and elimination, the enantiomer of the syn-derived planar chiral imidazolone is obtained. Hence, this method provides a practical way to prepare planar chiral enantiomers in this series without the use of a more expensive D-proline derived starting material. The syn and anti epimers have β, γ-stereogenic centers and the origin of stereoselectivity in lithiation appears to be driven by the conformational bias exerted by the β-silyloxy moiety in each chiral auxiliary. In the thesis, this conclusion is supported using insensitivity of lithiation selectivity to the bulkiness of the base, comparison of enantiomers, deuteration experiments, nOe difference studies and computational modeling of the ground states and lithiation transition states for both substrates. The products are then converted to ligand precursors to make iridium and rhodium complexes. Among them, one of the cationic iridium complex is found to be effective in the asymmetric hydrogenation of 2-substituted quinolines with enantioselectivities up to 80% at pressures as low as 5 atm.

Bad reduction of genus three curves with complex multiplication

Let C be a smooth, absolutely irreducible genus 3 curve over a number field M. Suppose that the Jacobian of C has complex multiplication by a sextic CM-field K. Suppose further that K contains no imaginary quadratic subfield. We give a bound on the primes p of M such that the stable reduction of C at p contains three irreducible components of genus 1.

Bioreduction of alpha-chloroacetophenone by whole cells of marine fungi

The asymmetric reduction of 2-chloro-1-phenylethanone (1) by seven strains of marine fungi was evaluated and afforded (S)-(-)-2-chloro-1-phenylethanol with, in the best case, an enantiomeric excess of 50% and an isolated yield of 60%. The ability of marine fungi to catalyse the reduction was directly dependent on growth in artificial sea water-based medium containing a high concentration of Cl(-) (1.2 M). When fungi were grown in the absence of artificial sea water, no reduction of 1 by whole cells was observed. The biocatalytic reduction of 1 was more efficient at neutral rather than acidic pH values and in the absence of glucose as co-substrate.

Supersymmetry flows, semi-symmetric space sine-Gordon models and the Pohlmeyer reduction

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A note on the attenuation of the sommerfeld effect of a non-ideal system taking into account a MR damper and the complete model of a DC motor

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electrochemical reduction of disperse orange 1 textile dye at a boron-doped diamond electrode

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