Effect of salt nature on structure and ionic conductivity of sodium-doped siloxane-PPO ormolytes

Siloxane-polyoxypropylene (PPO) hybrids obtained by the sol-gel process and containing short polymer chain have been doped with different sodium salts NaX (X = ClO4, BF4 or I). The effect of the counter-ion (X) on the chemical environment of the sodium ions and on the ionic conductivity of these hybrids was investigated by Na-23 NMR, small angle X-ray scattering (SAXS), complex impedance, Raman spectroscopy and differential scanning calorimetry (DSC). Results reveal that the different sodium salts have essentially the same effect on the nanoscopic structure of the hybrids. The formation of immobile Na+ cations involved in NaCl-like species could be minimized by using a low amount of HCl as hydrolytic catalyst. The differences in the ionic conductivity of hybrids doped with different sodium salts were correlated with the proportion of Na ions solvated by ether-type oxygen of the polymeric chains and by the carboxyl oxygen located in the urea groups of the PPO chain extremities. (c) 2005 Elsevier Ltd. All rights reserved.

Endothelial dysfunction in DOCA-salt hypertension - Possible involvement of prostaglandin endoperoxides

The effects of the arachidonic acid metabolism inhibitors on the acetylcholine responses of aortae from control (CR) and deoxycorticosterone acetate (DOCA)-salt hypertensive (HR) rats were investigated. The acetylcholine decreased response observed in HR [relaxation (%): CR 95.5 +/- 2.7, n = 4; HR 52.0 +/- 6.3, n = 5, p < 0.05] was restored by the cyclooxygenase inhibitor piroxicam [relaxation (%): CR 99.8 +/- 0.2, n = 4; HR 86.0 +/- 4.0, n = 5] and by the thromboxane synthetase inhibitor and the thrombox ane A(2)/prostaglandin H-2 receptor antagonist ridogrel [relaxation (%): CR 92.1 +/- 4.4, n = 7; HR 93.1 +/- 2.0, n = 7] but not by the inhibitors of thromboxane synthetase, prostacyclin synthetase, cytochrome P-450 monooxygenase, and lipoxygenase. So, endoperoxide intermediates seem to be involved in the decreased endothelium-dependent relaxation to acetylcholine in DOCA-salt hypertension. (C) 1999 Elsevier B.V. All rights reserved.

Role of endothelial cell apoptosis in regulation of skeletal muscle angiogenesis during high and low salt intake

Angiogenesis, under normal conditions, is a tightly regulated balance between pro- and antiangiogenic factors. The goal of this study was to investigate the mechanisms involved in the control of the skeletal muscle angiogenic response induced by electrical stimulation during the suppression of plasma renin activity (PRA) with a high-salt diet. Rats fed 0.4% or 4% salt diets were exposed to electrical stimulation for 7 days. The tibialis anterior ( TA) muscles from stimulated and unstimulated hindlimbs were removed and prepared for gene expression analysis, CD31-terminal deoxynucleotide transferase-mediated dUTP nick-end labeling ( TUNEL) double-staining assay, and Bcl-2 and Bax protein expression by Western blot. Rats fed a low-salt diet showed a dramatic angiogenesis response in the stimulated limb compared with the unstimulated limb. This angiogenesis response was significantly attenuated when rats were placed on a high-salt diet. Microarray analysis showed that in the stimulated limb of rats fed a low-salt diet many genes related to angiogenesis were upregulated. In contrast, in rats fed a high-salt diet most of the genes upregulated in the stimulated limb function in apoptosis and cell cycle arrest. Endothelial cell apoptosis, as analyzed by CD31-TUNEL staining, increased by fourfold in the stimulated limb compared with the unstimulated limb. There was also a 48% decrease in the Bcl-2-to-Bax ratio in stimulated compared with unstimulated limbs of rats fed a high-salt diet, confirming severe apoptosis. This study suggests that the increase in endothelial cell apoptosis in TA muscle might contribute to the attenuation of angiogenesis response observed in rats fed a high-salt diet.

Lateral parabrachial nucleus serotonergic mechanisms and salt appetite induced by sodium depletion

This study investigated the effects of bilateral injections of a serotonin (5-HT) receptor agonist into the lateral parabrachial nucleus (LPBN) on the intake of NaCl and water induced by 24-h water deprivation or by sodium depletion followed by 24 h of sodium deprivation (injection of the diuretic furosemide plus 24 h of sodium-deficient diet). Rats had stainless steel cannulas implanted bilaterally into the LPBN. Bilateral LPBN injections of the serotonergic 5-HT1/2 receptor antagonist methysergide (4 mu g/200 nl at each site) increased hypertonic NaCl intake when tested 24 h after sodium depletion and after 24 h of water deprivation. Water intake also increased after bilateral injections of methysergide into the LPBN. In contrast, the intake of a palatable solution (0.06 M sucrose) under body fluid-replete conditions was not changed after bilateral LPBN methysergide injections. The results show that serotonergic mechanisms in the LPBN modulate water and sodium intake induced by volume depletion and sodium loss. The finding that sucrose intake was not affected by LPBN serotonergic blockade suggests that the effects of the methysergide treatment on the intakes of water and NaCl are not due to a mechanism producing a nonspecific enhancement of all ingestive behaviors.

Electrical percolation during gelation of lithium doped siloxane-poly(oxyethylene) hybrids

Gelation mechanisms of lithium-doped Siloxane-Poly(oxyethylene) (PEO) hybrids containing polymer of two different molecular weight (500 and 1900 g/mol) were investigated through the evolution of the electrical properties during the solgel transition. The results of electrical measurements, performed by in-situ complex impedance spectroscopy, were correlated with the coordination and the dynamical properties of the lithium ions during the process as shown by Li-7 NMR measurements. For both hybrids sols, a decrease of the conductivity is observed at the initial gelation stage, due to the existence of an inverted percolation process consisting of the progressive separation of solvent molecules containing conducting species in isolated islands during the solid network formation. An increase of conductivity occurs at more advanced stages of gelation and aging, attributed to the increasing connectivity between PEO chains promoted by the formation of crosslinks of siloxane particles at their extremities, favoring hopping motions of lithium ions along the chains.

EFFECT OF CHOLINERGIC STIMULATION OF THE AMYGDALOID COMPLEX ON WATER AND SALT INTAKE

The effect of carbachol (80 nmol/mul) injection into the amygdaloid nuclear complex (AMG) on sodium appetite and water intake was studied in male Holtzman rats weighing 240-270 g. Twenty-five satiated rats and 38 water-deprived rats were used in the experiment on water intake. In the experiment on sodium intake, 19 rats were injected with atropine + carbachol and 9 rats with hexamethonium + carbachol. After carbachol injection into the AMG, water intake decreased in rats submitted to 30 h of water deprivation (10.28 +/- 1.04 ml/120 min vs 0.69 +/- 0.22 ml/120 min). The decrease in water intake was blocked by prior local injection of a tropine (20 nmol/1 mul)(11.66 +/- 1.46 ml/120 min vs 0.69 +/- 0.22 ml/120 min), but not of hexamethonium (30 nmol/1 mul), into the AMG. In water-deprived animals, carbachol injection into the AMG caused a decrease in sodium chloride intake (6.16 +/- 1.82 ml/h vs 0.88 +/- 0.54 ml/h) which was blocked by previous injection of hexamethonium but not of a tropine. These results suggest that the cholinergic system of the AMG plays a role in the control of water and salt intake.

Thermodynamic aspects of ion intercalation in KhFek[Fe(CN)(6)](l)center dot mH(2)O compounds: Application to the Everit's salt/Prussian Blue transition

The K+ reversible processes for ion exchange in KhFek[Fe(CN)(6)](l)center dot mH(2)O host compounds (Prussian Blue) were thermodynamically analyzed. A thermodynamic approach was established and developed based on the consideration of a lattice-gas model where the electronic contribution to the chemical potential is neglected and the ion-host interaction is not considered. The occupation fraction of the intercalation process was calculated from the kinetic parameters obtained through ac-electrogravimetry in a previous paper. In this way, the mass potential transfer function introduces a new way to evaluate the thermodynamic aspect of intercalation. Finally, based on the thermodynamic approach, the energy used to put each K+ ion into the host material was calculated. The values were shown to be in good agreement with the values obtained through transient techniques, for example, cyclic voltammetry. As a result, this agreement between theory and experimental data validates the thermodynamic approach considered here, and for the first time, the thermodynamic aspects of insertion were considered for mixed valence materials.

EQCM study during lithium insertion/deinsertion processes in Nb2O5 films prepared by polymeric precursor method

The electrochemical quartz crystal microbalance (EQCM) technique was used to study two chemically distinct Nb2O5 electrochromic thin films (one pure and the other lithium-doped) during the lithium electroinsertion reaction. In the initial cycles, the electrode showed an irreversible mass variation greater than expected for Li+ insertion/deinsertion processes, which was attributed to the wettability effect (allied to the porous morphology) that emerged as the dominant process in apparent electrode mass changes. As the cycles progressed, the mass variation stabilized and the changes in apparent mass became reversible, showing a good correlation with the charge variations.The results generally indicated that the Li+ insertion/deinsertion process occurred more easily in the Nb2O5-doped film, which also displayed a greater capacity for Li+ insertion. However, a total mass/charge balance analysis revealed that the stoichiometry of the Li+ solid state insertion/deinsertion reaction was similar in the two electrodes under study. © 2005 Elsevier B.V. All rights reserved.

First-order-like transition in salt-induced macroion-polyelectrolyte desorption

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Intercalation processes and diffusion paths of lithium ions in spinel-type structured Li(1+x)Ti(2)O(4): Density functional theory study

Intercalation processes and corresponding diffusion paths of Li ions into spinel-type structured Li(1+x)Ti(2)O(4) (0 <= x <= 0.375) are systematically studied by means of periodic density functional theory calculations for different compositions and arrangements. An analysis of the site preference for intercalation processes is carried out, while energy barriers for the diffusion paths have been computed in detail. Our results indicate that the Li insertion is thermodynamically favorable at octahedral sites 16c in the studied composition range, and Li migration from tetrahedral sites 8a to octahedral sites 16c stabilizes the structure and becomes favorable for compositions x >= 0.25. Diffusion paths from less stable arrangements involving Li migrations between tetrahedral and octahedral sites exhibit the lowest energy barrier since the corresponding trajectories and energy profiles take place across a triangle made by three neighboring oxygen anions without structural modification. Theoretical and experimental diffusion coefficients are in reasonable agreement.

Culture of Candida in vinasse and molasses: Effect of acid and salt addition on biomass and raw protein production

Species of the genera Candida grown in vinasse and molasses were studied under the following conditions: agitation of containers, pH 4.6, culture time of 24 hours at 30°C. The greatest biomass production of C. krusei grown in vinasse was obtained with the addition of 0.1% H3PO4, and of C. guilliermondii and C. utilis with the addition 0.02% urea plus 0.03% H3PO4. Protein levels near 50% were found in C. utilis in vinasse supplemented either with molasses, with 0.05% MgSO4, or with 0.02% urea plus 0.03% H3PO4. © 1982 Springer-Verlag.

Lithium-lanthanum double chromates

Synthesis and crystallographic data are reported for low and high temperature forms of LiLa(CrO4)2. The compounds are closely related to lamellar rare earth phosphates and arsenates of sodium and to RbLu(CrO4)2. Lattice parameters of the orthorhombic (low temperature) and monoclinic (high temperature) forms are given. The low temperature form is moisture sensitive and Li+ ions are easily displaced by protons. Thermal decomposition takes place at 250 °C and results in the formation of LiCrO2, LaCrO4, LaCrO3 and Cr2O3. © 1993.

Phonons in binary BCC lithium-sodium alloys

The dispersion relations along the principal symmetry directions in BCC lithium-sodium alloys are calculated using second-order perturbation theory. The local modified Hoshino-Youngmodel potential was used for the lithium and the local Harrison model potential for sodium. The phonon density of states, the root mean square displacements and (Θ-T) curves are also calculated. In the absence of experimental data, just the theoretical predictions are presented here.

Preoptic-periventricular tissue (AV3V): central cholinergic-induced hydromineral and cardiovascular responses, and salt intake.

The periventricular tissue of the anterior ventral portion of the third ventricle (AV3V) is an important area for the control of hydromineral balance and of cardiovascular function. The present work discusses the importance of the integrity of the AV3V for multiple responses to central cholinergic activation (water intake, hypertension, natriuresis, salivation) and for the control of salt intake.

Lanthanum-lithium-sodium double chromates as ionic conductors

Lanthanum-lithium-sodium double chromates Li1-xNaxLa(CrO4)2 were prepared and analysed by means of admittance spectroscopy. Their a.c. conductivity parameters are correlated with structural details of high and low temperature forms of pure lanthanum-lithium double chromates. Lithium compounds show the lowest conductivity values and the highest activation energy for ion motion, while the sample Li0.5Na0.5La(CrO4)2 exhibits the highest conductivity 10-5 S cm-1 and the lowest activation energy 0.58 eV.