Electrical behavior of PU/POMA blends

The incorporation of conducting polymer into a conventional polymer matrix has received attention because of the possibility of combining the good processability and mechanical performance of the conventional polymer with the electrical and optical properties of conducting polymer. In this work, flexible films of polyurethane (PU) and Poli(o-metoxyaniline)(POMA) blends were obtained by casting and investigated using thermally stimulated depolarisation current (TSDC) measurements. Two relaxation peaks were found in the range of-20°C to 90°C. The first one at T=24°C was attributed as α relaxation associated to the glass transition of PU/POMA blend and the second one located at T=60°C can be attributed to space charge.

Efeitos da abamectina na bioenergética de mitocôndrias isoladas de fígado de rato: Juliana Carla Castanha Zanoli. -

Pós-graduação em Ciência Animal - FMVA

Hopping-tunneling model to describe electric charge injection at metal/organic semiconductor heterojunctions

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

Synthesis, characterization, optical absorption, luminescence and defect centres in Er3+ and Yb3+ co-doped MgAl2O4 phosphors

The Er3+-Yb3+ co-doped MgAl2O4 phosphor powders have been prepared by the combustion method. The phosphor powders are well characterized by X-ray diffraction (XRD) and energy dispersive (EDX) techniques. The absorption spectrum of Er3+/Er3+-Yb3+ doped/co-doped phosphor powder has been recorded in the UV-Vis-NIR region of the electro-magnetic spectrum. The evidence for indirect pumping under 980 nm excitation of Er3+ from Yb3+ was observed in the MgAl2O4 matrix material. Electron spin resonance (ESR) studies were carried out to identify the defect centres responsible for the thermally stimulated luminescence (TSL) process in MgAl2O4:Er3+ phosphor. Three defect centres were identified in irradiated phosphor by ESR measurements which were carried out at room temperature and these were assigned to an O- ion and F+ centres. O- ion (hole centre) appears to correlate with the low temperature TSL peak at 210 A degrees C and one of the F+ centres (electron centre) is related to the high temperature peak at 460 A degrees C.

THERMORESPONSIVE PROPERTIES OF GOLD HYBRID NANOPARTICLES OF POLY(DI(ETHYLENE GLYCOL) METHYL ETHER METHACRYLATE) (PDEGMA) AND ITS BLOCK COPOLYMERS WITH DIFFERENT ANCHORING REGIMES

Thermo-responsive materials have been of interest for many years, and have been studied mostly as thermally stimulated drug delivery vehicles. Recently acrylate and methacrylates with pendant ethylene glycol methyl ethers been studied as thermo responsive materials. This work explores thermo response properties of hybrid nanoparticles of one of these methacrylates (DEGMA) and a block copolymer with one of the acrylates (OEGA), with gold nanoparticle cores of different sizes. We were interested in the effects of gold core size, number and type of end groups that anchored the chains to the gold cores, and location of bonding sites on the thermo-response of the polymer. To control the number and location of anchoring groups we using a type of controlled radical polymerization called Reversible Addition Fragmentation Transfer (RAFT) Polymerization. Smaller gold cores did not show the thermo responsive behavior of the polymer but the gold cores did seem to self-assemble. Polymer anchored to larger gold cores did show thermo responsivity. The anchoring end group did not alter the thermoresponsivity but thiol-modified polymers stabilized gold cores less well than chains anchored by dithioester groups, allowing gold cores to grow larger. Use of multiple bonding groups stabilized the gold core. Using block copolymers we tested the effects of number of thiol groups and the distance between them. We observed that the use of multiple anchoring groups on the block copolymer with a sufficiently large gold core did not prevent thermo responsive behavior of the polymer to be detected which allows a new type of thermo-responsive hybrid nanoparticle to be used and studied for new applications.

Caratterizzazione delle proprietà elettriche di nanocompositi a matrice epossidica additivata con Quantum Dots

Questo elaborato prevede la caratterizzazione delle proprietà elettriche di nanocompositi a matrice epossidica additivata con Quantum Dots. Inizialmente sono state presentate le caratteristiche fondamentali dei materiali polimerici con particolare attenzione alle proprietà elettriche. In seguito, sono stati descritti i temi pratici e teorici delle misure che permettono di ottenere i risultati utili alla caratterizzazione, nello specifico: Spettroscopia Dielettrica, metodo Pulsed Electro-Acustic (PEA), Prova di Conducibilità e metodo Thermally Simulated Depolarization Current (TSDC). Le misure sono state effettuate su dei provini di resina epossidica vergine e nanocompositi Epoxy/QDsCS. Sono stati esposti i processi fondamentali che portano alla realizzazione dei diversi provini e di seguito sono stati mostrati i risultati delle misure precedentemente elencate. L’analisi e l’elaborazione dei dati ha portato alla caratterizzazione finale e permette di concludere che l’inserzione di Quantum Dots Core-Shell non provoca variazioni della conducibilità del materiale ma ne modifica le proprietà dielettriche, quali profondità di trappola e carica di spazio.

Vasopressin-stimulated CFTR Cl- currents are increased in the renal collecting duct cells of a mouse model of Liddle's syndrome.

Liddle's syndrome is a genetic form of hypertension linked to Na(+) retention caused by activating mutations in the COOH terminus of the beta or gamma subunit of the epithelial sodium channel (ENaC). In this study, we used the short-circuit current (I(sc)) method to investigate the effects of deamino-8-d-arginine vasopressin (dDAVP) on Na(+) and Cl(-) fluxes in primary cultures of cortical collecting ducts (CCDs) microdissected from the kidneys of mice with Liddle's syndrome carrying a stop codon mutation, corresponding to the beta-ENaC R(566) stop mutation (L) found in the original pedigree. Compared to wild-type (+/+) CCD cells, untreated L/+ and L/L CCD cells exhibited 2.7- and 4.2-fold increases, respectively, in amiloride-sensitive (Ams) I(sc), reflecting ENaC-dependent Na(+) absorption. Short-term incubation with dDAVP caused a rapid and significant increase (approximately 2-fold) in Ams I(sc) in +/+, but not in L/+ or L/L CCD cells. In sharp contrast, dDAVP induced a greater increase in 5-nitro-2-(3-phenylpropamino)benzoate (NPPB)-inhibited apical Cl(-) currents in amiloride-treated L/L and L/+ cells than in their +/+ counterparts. I(sc) recordings performed under apical ion substituted conditions revealed that the dDAVP-stimulated apical secretion of Cl(-), which was absent in cultured CCDs lacking CFTR, was 1.8-fold greater in L/+ and 3.7-fold greater in L/L CCD cells than in their +/+ CCD counterparts. After the basal membrane had been permeabilized with nystatin and a basal-to-apical Cl(-) gradient had been imposed, dDAVP also stimulated larger Cl(-) currents across L/L and L/+ CCD layers than +/+ CCD layers. These findings demonstrate that vasopressin stimulates greater apical CFTR Cl(-) conductance in the renal CCD cells of mice with Liddle's syndrome than in wild-type mice. This effect could contribute to the enhanced NaCl reabsorption observed in the distal nephron of patients with Liddle's syndrome.

Odorant-induced currents in intact patches from rat olfactory receptor neurons: Theory and experiment

Odorant-induced currents in mammalian olfactory receptor neurons have proved difficult to obtain reliably using conventional whole-cell recording. By using a mathematical model of the electrical circuit of the patch and rest-of-cell, we demonstrate how cell-attached patch measurements can be used to quantitatively analyze responses to odorants or a high (100 mM) K+ solution. High K+ induced an immediate current flux from cell to pipette, which was modeled as a depolarization of similar to 52 mV, close to that expected from the Nernst equation (56 mV), and no change in the patch conductance. By contrast, a cocktail of cAMP-stimulating odorants induced a current flux from pipette into cell following a significant (4-10 s) delay. This was modeled as an average patch conductance increase of 36 pS and a depolarization of 13 mV, Odorant-induced single channels had a conductance of 16 pS. In cells bathed with no Mg2+ and 0.25 mM Ca2+, odorants induced a current flow from cell to pipette, which was modeled as a patch conductance increase of similar to 115 pS and depolarization of similar to 32 mV, All these results are consistent with cAMP-gated cation channels dominating the odorant response, This approach, which provides useful estimates of odorant-induced voltage and conductance changes, is applicable to similar measurements in any small cells.

Separate neuronal and glial Na+,K+-ATPase isoforms regulate glucose utilization in response to membrane depolarization and elevated extracellular potassium.

The role of cell type-specific Na+,K+-ATPase isozymes in function-related glucose metabolism was studied using differentiated rat brain cell aggregate cultures. In mixed neuron-glia cultures, glucose utilization, determined by measuring the rate of radiolabeled 2-deoxyglucose accumulation, was markedly stimulated by the voltage-dependent sodium channel agonist veratridine (0.75 micromol/L), as well as by glutamate (100 micromol/L) and the ionotropic glutamate receptor agonist N-methyl-D-aspartate (NMDA) (10 micromol/L). Significant stimulation also was elicited by elevated extracellular potassium (12 mmol/L KCl), which was even more pronounced at 30 mmol/L KCl. In neuron-enriched cultures, a similar stimulation of glucose utilization was obtained with veratridine, specific ionotropic glutamate receptor agonists, and 30 mmol/L but not 12 mmol/L KCl. The effects of veratridine, glutamate, and NMDA were blocked by specific antagonists (tetrodotoxin, CNQX, or MK801, respectively). Low concentrations of ouabain (10(-6) mol/L) prevented stimulation by the depolarizing agents but reduced only partially the response to 12 mmol/L KCl. Together with previous data showing cell type-specific expression of Na+,K+-ATPase subunit isoforms in these cultures, the current results support the view that distinct isoforms of Na+,K+-ATPase regulate glucose utilization in neurons in response to membrane depolarization, and in glial cells in response to elevated extracellular potassium.

A CALORIMETRIC STUDY OF THE ULTRASOUND-STIMULATED HYDROLYSIS OF SOLVENTLESS TEOS-WATER MIXTURES

The kinetics of ultrasound-stimulated and HCl-catalyzed hydrolysis of solventless TEOS-water mixtures was studied as a function of temperature ranging from 10 degrees C up to 65 degrees C by means of flux calorimetry measurements. A specially designed device was utilized for this purpose. The exothermic peak arising few minutes after sonication began has been attributed mainly to the hydrolysis reaction. The overall hydrolysis process, which was measured through the irradiation time up to the hydrolysis peak, was found to be thermally activated, with an apparent activation energy Delta E = 36.4 kJ/mol. The alcohol produced at the early hydrolysis due to sonication seems to further enhance the reaction, via a parallel autocatalytic path, which is controlled by a faster pseudo second order rate constant (k'). Our modeling yielded k' = 6.3 x 10(-2) M(-1) min(-1) at 20 degrees C, which is in a reasonable agreement with the literature, and an activation energy Delta E = 40.4 kJ/mol for the specific process of hydrolysis in presence of alcohol.

Use of recent geoid models to estimate mean dynamic topography and geostrophic currents in South Atlantic and Brazil Malvinas confluence

The use of geoid models to estimate the Mean Dynamic Topography was stimulated with the launching of the GRACE satellite system, since its models present unprecedented precision and space-time resolution. In the present study, besides the DNSC08 mean sea level model, the following geoid models were used with the objective of computing the MDTs: EGM96, EIGEN-5C and EGM2008. In the method adopted, geostrophic currents for the South Atlantic were computed based on the MDTs. In this study it was found that the degree and order of the geoid models affect the determination of TDM and currents directly. The presence of noise in the MDT requires the use of efficient filtering techniques, such as the filter based on Singular Spectrum Analysis, which presents significant advantages in relation to conventional filters. Geostrophic currents resulting from geoid models were compared with the HYCOM hydrodynamic numerical model. In conclusion, results show that MDTs and respective geostrophic currents calculated with EIGEN-5C and EGM2008 models are similar to the results of the numerical model, especially regarding the main large scale features such as boundary currents and the retroflection at the Brazil-Malvinas Confluence.

Use of recent geoid models to estimate mean dynamic topography and geostrophic currents in South Atlantic and Brazil Malvinas confluence

The use of geoid models to estimate the Mean Dynamic Topography was stimulated with the launching of the GRACE satellite system, since its models present unprecedented precision and space-time resolution. In the present study, besides the DNSC08 mean sea level model, the following geoid models were used with the objective of computing the MDTs: EGM96, EIGEN-5C and EGM2008. In the method adopted, geostrophic currents for the South Atlantic were computed based on the MDTs. In this study it was found that the degree and order of the geoid models affect the determination of TDM and currents directly. The presence of noise in the MDT requires the use of efficient filtering techniques, such as the filter based on Singular Spectrum Analysis, which presents significant advantages in relation to conventional filters. Geostrophic currents resulting from geoid models were compared with the HYCOM hydrodynamic numerical model. In conclusion, results show that MDTs and respective geostrophic currents calculated with EIGEN-5C and EGM2008 models are similar to the results of the numerical model, especially regarding the main large scale features such as boundary currents and the retroflection at the Brazil-Malvinas Confluence.

Nerve excitability changes in critical illness polyneuropathy

Patients in intensive care units frequently suffer muscle weakness and atrophy due to critical illness polyneuropathy (CIP), an axonal neuropathy associated with systemic inflammatory response syndrome and multiple organ failure. CIP is a frequent and serious complication of intensive care that delays weaning from mechanical ventilation and increases mortality. The pathogenesis of CIP is not well understood and no specific therapy is available. The aim of this project was to use nerve excitability testing to investigate the changes in axonal membrane properties occurring in CIP. Ten patients (aged 37-76 years; 7 males, 3 females) were studied with electrophysiologically proven CIP. The median nerve was stimulated at the wrist and compound action potentials were recorded from abductor pollicis brevis muscle. Strength-duration time constant, threshold electrotonus, current-threshold relationship and recovery cycle (refractoriness, superexcitability and late subexcitability) were recorded using a recently described protocol. In eight patients a follow-up investigation was performed. All patients underwent clinical examination and laboratory investigations. Compared with age-matched normal controls (20 subjects; aged 38-79 years; 7 males, 13 females), CIP patients exhibited reduced superexcitability at 7 ms, from -22.3 +/- 1.6% to -7.6 +/- 3.1% (mean +/- SE, P approximately 0.0001) and increased accommodation to depolarizing (P < 0.01) and hyperpolarizing currents (P < 0.01), indicating membrane depolarization. Superexcitability was reduced both in patients with renal failure and without renal failure. In the former, superexcitability correlated with serum potassium (R = 0.88), and late subexcitability was also reduced (as also occurs owing to hyperkalaemia in patients with chronic renal failure). In patients without renal failure, late subexcitability was normal, and the signs of membrane depolarization correlated with raised serum bicarbonate and base excess, indicating compensated respiratory acidosis. It is inferred that motor axons in these CIP patients are depolarized, in part because of raised extracellular potassium, and in part because of hypoperfusion. The chronic membrane depolarization may contribute to the development of neuropathy.

Optical recording of calcium currents during impulse conduction in cardiac tissue

We explore the feasibility of obtaining a spatially resolved picture of Ca2+Ca2+ inward currents (ICaICa) in multicellular cardiac tissue by differentiating optically recorded Ca2+Ca2+ transients that accompany propagating action potentials. Patterned growth strands of neonatal rat ventricular cardiomyocytes were stained with the Ca2+Ca2+ indicators Fluo-4 or Fluo-4FF. Preparations were stimulated at 1 Hz, and Ca2+Ca2+ transients were recorded with high spatiotemporal resolution (50  μm50  μm, 2 kHz analog bandwidth) with a photodiode array. Signals were differentiated after appropriate digital filtering. Differentiation of Ca2+Ca2+ transients resulted in optically recorded calcium currents (ORCCs) that carried the temporal and pharmacological signatures of L-type Ca2+Ca2+ inward currents: the time to peak amounted to ∼2.1  ms∼2.1  ms (Fluo-4FF) and ∼2.4  ms∼2.4  ms (Fluo-4), full-width at half-maximum was ∼8  ms∼8  ms, and ORCCs were completely suppressed by 50  μmol/L50  μmol/LCdCl2CdCl2. Also, and as reported before from patch-clamp studies, caffeine reversibly depressed the amplitude of ORCCs. The results demonstrate that the differentiation of Ca2+Ca2+ transients can be used to obtain a spatially resolved picture of the initial phase of ICaICa in cardiac tissue and to assess relative changes of activation/fast inactivation of ICaICa following pharmacological interventions.

Ascorbic acid acts as an inhibitory transmitter in the hypothalamus to inhibit stimulated luteinizing hormone-releasing hormone release by scavenging nitric oxide

Because ascorbic acid (AA) is concentrated in synaptic vesicles containing glutamic acid, we hypothesized that AA might act as a neurotransmitter. Because AA is an antioxidant, it might therefore inhibit nitric oxidergic (NOergic) activation of luteinizing hormone-releasing hormone (LH-RH) release from medial basal hypothalamic explants by chemically reducing NO. Cell membrane depolarization induced by increased potassium concentration [K+] increased medium concentrations of both AA and LH-RH. An inhibitor of NO synthase (NOS), NG-monomethyl-l-arginine (NMMA), prevented the increase in medium concentrations of AA and LH-RH induced by high [K+], suggesting that NO mediates release of both AA and LH-RH. Calcium-free medium blocked not only the increase in AA in the medium but also the release of LH-RH. Sodium nitroprusside, which releases NO, stimulated LH-RH release and decreased the concentration of AA in the incubation medium, presumably because the NO released oxidized AA to dehydro-AA. AA (10−5 to 10−3 M) had no effect on basal LH-RH release but completely blocked high [K+]- and nitroprusside-induced LH-RH release. N-Methyl-d-aspartic acid (NMDA), which mimics the action of the excitatory amino acid neurotransmitter glutamic acid, releases LH-RH by releasing NO. AA (10−5 to 10−3 M) inhibited the LH-RH-releasing action of NMDA. AA may be an inhibitory neurotransmitter that blocks NOergic stimulation of LH-RH release by chemically reducing the NO released by the NOergic neurons.