Effect of cobalt(II) oxide and manganese(IV) oxide on sintering of tin(IV) oxide

Additions of 0.5 to 2.0 mol% of CoO or MnO2 onto SnO, promote densification of this oxide up to 99% of theoretical density. The temperature of the maximum shrinkage rate (TM) and the relative density in the maximum densification rate (p*) during constant sintering heating rate depend on the dopant concentration. Thus, dopant concentration controls the densifying and nondensifying mechanisms during sintering. The densification of SnO2 witih addition of CoO or MnO, is explained in terms of the creation of oxygen vacancies.

Activity of Mo(II) allylic complexes supported in MCM-41 as oxidation catalysts precursors

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

Interaction between supraoptic nucleus and septal area in the control of water, sodium intake and arterial blood pressure induced by injection of angiotensin II

We investigated the effects of injection into the supraoptic nucleus (SON) of losartanand PD 123319 (nonpeptide AT(1) and AT(2)- angiotensin II [ANG II] receptor antagonists, respectively); d(CH2)(5)-Tyr(Me)-AVP (AVPA; an arginine-vasopressin [AVP] V-1 receptor antagonist), FK 409 (a nitric oxide [NO] donor), and N-W-mtro-(L)-arginine methyl ester ((L)-NAME; an NO synthase inhibitor) oil water intake, sodium chloride 3% (NaCl) intake and arterial blood pressure induced by injection of ANG 11 into the lateral septal area (LSA). Mate Holtzman rats (250-300 g) were implanted with cannulae into SON and LSA unilaterally. The drugs were injected in 0.5 mul over 30-60 s. Controls were injected with a similar volume of 0.15 M NaCl. ANG II was injected at a dose of 10 pmol. ANG II antagonists and AVPA were injected at doses of 80 nmol. FK 409 and (L)-NAME were injected at doses of 20 and 40 mug, respectively. Water and NaCl intake was measured over a 2-h period. Prior administration of losartan into the SON decreased water and NaCl intake induced by injection of ANG II. While there was a decrease in water intake, ANG II-induced NaCl intake was significantly increased following injection of AVPA. FK 409 injection decreased water intake and sodium intake induced by ANG II. L-NAME alone increased water and sodium intake and induced a pressor effect. (L)-NAME-potentiated water and sodium intake induced by ANG II. PD 123319 produced no changes in water or sodium intake induced by ANG II. The prior administration of losartan or AVPA decreased mean arterial pressure (MAP) induced by ANG II. PD 123319 decreased the pressor effect of ANG II to a lesser degree than losartan. FK 409 decreased the pressor effect of ANG II while (L)-NAME potentiated it. These results suggest that both ANG II AT, and AVP V, receptors and NO within the SON may be involved in water intake, NaCl intake and the pressor response were induced by activation of ANG II receptors within the LSA. These results do not support the involvement of LSA AT(2) receptors in the mediation of water and NaCl intake responses induced by ANG II, but influence the pressor response. (C) 2004 Elsevier B.V. All rights reserved.

Spectroscopic studies on glassy Ni(II) and Co(II) polyphosphate coacervates

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

Factors affecting Hg (II) adsorption in soils from the Rio Negro basin (Amazon)

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

Sintering and crystallite growth of nanocrystalline copper doped tin oxide

The effect of Cu2+ contents and of firing temperature on sintering and crystallite growth of nanocrystalline SnO2 xerogels was analyzed by thermoanalysis (mass loss (TG), linear shrinkage, and differential thermal analysis (DTA)), X-ray powder diffraction (XRPD), and EXAFS (extended X-ray absorption fine structures) measurements. Samples were prepared by two methods: (a) coprecipitation of a colloidal suspension from aqueous solution containing both Sn(IV) and Cu(II) ions and (b) grafting copper(II) species on the surface of tin pride gel. The thermoanalysis has shown that the shrinkage associated with the mass loss decreases by increasing the amount of copper. The EXAFS measurements carried out at the Cu K edge have evidenced the presence of copper in substitutional solid solution for the dried xerogel prepared with 0.7 mol % of copper, while for higher concentration of doping, copper has been observed also at the external surface of crystallites. The solid solution is metastable and copper migrates toward the surface during firing. The XRPD and DTA results have shown a recrystallization process near 320 degrees C, which leads to crystallite growth. The presence of copper segregated near the crystallite surface controls its growth.

Speciation analysis of Sn(II) and Sn(IV) using baker's yeast and inductively coupled plasma optical emission spectrometry

The use of Saccharomyces cerevisiae as a substrate to selectively retain Sn(II) and Sn(IV) has been investigated. Several factors affecting the retention of the analytes by yeast, such as pH, amount of biomass, temperature and time of contact were evaluated. Based on this study, a method for determination of Sn(II) and Sn(IV) combining inductively coupled plasma optical emission spectrometry (ICP OES) and solid phase extraction using Saccharomyces cerevisiae is proposed. The procedure consists of the selective retention of Sn(IV) by yeast at pH = 2.0 while Sn(II) remains in solution. Determination of tin in the solid phase was easily carried out by submitting a slurry of the yeast (0.5 g/40 mL) directly to ICP OES. The precision of the extraction procedure was characterized by an RSD lower than 4%. The detection limits of tin (3 sigma) in the solid phase and the liquid phase were 1.1 and 0.7 mu g L-1, respectively. The proposed approach was evaluated for determination of Sn(II) and Sn(IV) in spiked river water and real samples of industrial waste water (untreated and treated). For all samples, recoveries of spiked Sn(II) and Sn(IV) were between 85 and 112%.

Synthesis and structural characterization of dichlorobis (1-phenyl-3-methylpyrazole) palladium(II) and diazidobis (1-phenyl-3-methylpyrazole) palladiium(II)

Mononuclear pyrazolyl Pd(II) complexes of the type [PdX2(phmPz)(2)] (X = Cl-, N-3(-)) have been prepared. The 1-phenyl-3-methylpyrazole displaces acetonitrile from [PdCl2(CH3CN)(2)] to form [PdCl2(PhMPz)(2)] (phmPz = 1-phenyl-3-methylpyrazole) (1). [Pd(N-3)(2)(PhmPz)(2)] (2) could be obtained by metathesis from [PdCl2(CH3CN)(2)] or by substitution of the chloride in (1) by the azide ion. Both complexes were characterized by elemental analysis, infrared spectroscopy, H-1 and C-13 NMR and by single crystal X-ray diffraction. The coordination geometry around Pd(II) in these complexes is nearly square-planar, with the ligands in a trans configuration.

Electrochemical decomposition of cyanides on tin dioxide electrodes in alkaline media

The electrochemical oxidation of cyanide in alkaline media was studied at different pH levels on SnO2 doped with Sb supported on titanium, at 25 degrees C, the electrooxidation of CN- at constant current follows a first-order rate law with a half life of t(1/2) = 35 min on SnO2-SbOx electrodes and t(1/2) = 69 min on SnO2-SbOx-RuO2 electrodes, in K2SO4(aq), pH 12, the reaction rate increases with the applied current and tends to reach a plateau when j > 20 mA cm(-2), In the pH range 10-13.5 the reaction rate diminishes as pH is increased owing to an increasing competition between CN- and OH- ions for the electrode surface. Addition of chloride to the solution does not alter the rate law but increases the reaction rate, A mechanism is proposed to explain the observed behaviour.

A Chloro-Bridged Linear Chain Imine-Copper(II) Complex and Its Application as an Enzyme-Free Amperometric Biosensor for Hydrogen Peroxide

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

From tin oxalate to (Fe, Co, Nb)-doped SnO(2): Sintering behavior, microstructural and electrical features

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

Electronic spectra, ESR and crystal structure of tetrahedral halocuprates(II). The existence of cations (2tbpo·H+) with a very short hydrogen bond

Two compounds [2tbpo·H+)2[CuCl4]= (yellow) and (2tbpo·H+)2[CuBr4]= (dark purple) (tbpo = tribenzylphosphine oxide) have been prepared and investigated by means of crystal structure, electronic, vibrational and ESR spectra. The crystal structure of the (2tbpo·H+)2[CuCl4]= complex was determined by three-dimensional X-ray diffraction. The compound crystallizes in the space group P42/n with unit-cell dimensions a = 19.585(2), c = 9.883(1)Å, V = 3790 (1)Å3, Z = 2, Dm = 1.303 (flotation) Dx = 1.302 Mg m-3. The structure was solved by direct methods and refined by blocked full-matrix least-squares to R = 0.053 for 2583 observed reflections. Cu(II) is coordinated to four chlorides in a tetrahedral arrangement. Tribenzylphosphine oxide molecules, related by a centre of inversion, are connected by a short hydrogen bridge. Chemical analysis, electronic and vibrational spectra showed that the bromide compound is similar to the chloride one and can be formulated as (2tbpo·H+)2[CuBr4]=. The position of the dd transition bands, the charge transfer bands, the ESR and the vibrational spectra of both complexes are discussed. The results are compared with analogous complexes cited in the literature. © 1983.

Effects of the alpha antagonists and agonists injected into the lateral hypothalamus on the water and sodium intake induced by angiotensin II injection into the subfornical organ

The subfornical organ (SFO) and the lateral hypothalamus (LH) have been shown to be important for the central action of angiotensin II (ANG II) on water and salt regulation. Several anatomical findings have demonstrated neural connections between the SFO and the LH. The present experiments were conducted to investigate the role of the α-adrenergic antagonists and agonists injected into the LH on the water and salt intake elicited by injections of ANG II into the SFO. Prazosin (an α1-adrenergic antagonist) injected into the LH increased the salt ingestion, whereas yohimbine (an α2-adrenergic antagonist) and propranolol (a β-adrenergic antagonist) antagonized the salt ingestion induced by administration of ANG II into the SFO. Previous administration of clonidine (an α2-adrenergic agonist) or noradrenaline into the LH increased, whereas pretreatment with phenylephrine decreased the sodium intake induced by injection of ANG II into the SFO. Previous treatment with prazosin and propranolol reduced the water intake induced by ANG II. Phenylephrine increased the dipsogenic responses produced by ANG II, whereas previous treatment with clonidine injected into the LH reduced the water intake induced by ANG II administration into the SFO. The LH involvement with SFO on the excitatory and inhibitory mechanisms related to water and sodium intake is suggested.