Espectroscopia de impedância eletroquímica aplicada ao estudo das reações heterogêneas em ânodos dimensionalmente estáveis

This paper discusses different aspects related to the application of electrochemical impedance spectroscopy (EIS) in the study of heterogeneous electrochemical reactions occurring on Dimensionally Stable anodes (DSA®). The most relevant aspects of the semiconductor/electrolyte interface, the application of the EIS classical equivalent circuit approach and the ac porous model in DSA are presented. The paper shows that DSA type electrodes can be consistently investigated by using the ac porous model and an analysis is presented showing the advantage of applying this kind of approach to study heterogeneous reactions on DSA electrodes. Furthermore, some preliminary results on Ti/Ru0,3Ti(0,7-x)Sn x O2 based electrodes are presented to exemplify the use of the ac porous model analysis.

Characteristics of pyridine adsorption on Au(111) and Au(210) by EIS parameters fitting procedure

Some aspects of the application of electrochemical impedance spectroscopy to studies of solid electrode / solution interface, in the absence of faradaic processes, are analysed. In order to perform this analysis, gold electrodes with (111) and (210) crystallographic orientations in an aqueous solution containing 10 mmol dm-3 KF, as supporting electrolyte, and a pyridine concentration varying from 0.01 to 4.6 mmol dm-3, were used. The experimental data was analysed by using EQUIVCRT software, which utilises non-linear least squares routines, attributing to the solid electrode / solution interface behaviour described by an equivalent circuit with a resistance in series with a constant phase element. The results of this fitting procedure were analysed by the dependence on the electrode potential on two parameters: the pre-exponential factor, Y0, and the exponent n f, related with the phase angle shift. By this analysis it was possible to observe that the pyridine adsorption is strongly affected by the crystallographic orientation of the electrode surface and that the extent of deviation from ideal capacitive behaviour is mainly of interfacial origin.

Low transformation growth factor-β1 production and collagen synthesis correlate with the lack of hepatic periportal fibrosis development in undernourished mice infected with Schistosoma mansoni

Undernourished mice infected (UI) submitted to low and long-lasting infections by Schistosoma mansoni are unable to develop the hepatic periportal fibrosis that is equivalent to Symmers’ fibrosis in humans. In this report, the effects of the host’s nutritional status on parasite (worm load, egg viability and maturation) and host (growth curves, biology, collagen synthesis and characteristics of the immunological response) were studied and these are considered as interdependent factors influencing the amount and distribution of fibrous tissue in hepatic periovular granulomas and portal spaces. The nutritional status of the host influenced the low body weight and low parasite burden detected in UI mice as well as the number, viability and maturation of released eggs. The reduced oviposition and increased number of degenerated or dead eggs were associated with low protein synthesis detected in deficient hosts, which likely induced the observed decrease in transformation growth factor (TGF)-β1 and liver collagen. Despite the reduced number of mature eggs in UI mice, the activation of TGF-β1 and hepatic stellate cells occurred regardless of the unviability of most miracidia, due to stimulation by fibrogenic proteins and eggshell glycoproteins. However, changes in the repair mechanisms influenced by the nutritional status in deficient animals may account for the decreased liver collagen detected in the present study.

Synthesis, characterization, DFT and Td-dfT study of the [Fe(mnt)(L)(t-BuNC) 2] octahedral complex (L = phen, bipy)

FeBr2 has reacted with an equivalent of mnt2- (mnt = cis-1,2-dicyanoethylene-1,2-dithiolate) and the α-diimine L (L = 1,10'-phenantroline, 2,2'-bipyridine) in THF solution, and followed by adding of t-butyl-isocyanide to give [Fe(mnt)(L)(t-BuNC)2] neutral compound. The products were characterized by infrared, UV-visible and Mössbauer spectroscopy, besides thermogravimetric and conductivity data. The geometry in the equilibrium was calculated by the density functional theory and the electronic spectrum by the time-dependent. The experimental and theoretical results in good agreement have defined an octahedral geometry with two isocyanide neighbours. The π→π* intraligand electronic transition was not observed for cis-isomers in the near-IR spectral region.

Economic viability of the third milking in systems of production using closed-circuit mechanical milking

This study aimed to analyze the economic viability of the third milking in production systems using mechanical milking in a closed circuit, aiming to provide technicians and farmers with information to assist them in decision-making. Specifically, it intended: (a) to estimate the cost of one milking; (b) to estimate the cost of the third milking; (c) to develop a mathematical equation to estimate the minimum amount of milk produced with two milkings, from which it would be economically feasible to do the third milking. Data were collected from three dairy farms, from November 2010 to March 2011, keeping a twice-a-day milking frequency, with three data collections in each farm, totalizing nine collections. Considering the average data, it would be feasible to do the third milking if the average milk yield per day of lactating cows in a twice-a-day milking frequency was greater than or equal to 24.43 kg of milk.

ANTIFUNGAL ACTIVITY OF SILVER NANOPARTICLES OBTAINED BY GREEN SYNTHESIS

Silver nanoparticles (AgNPs) are metal structures at the nanoscale. AgNPs have exhibited antimicrobial activities against fungi and bacteria; however synthesis of AgNPs can generate toxic waste during the reaction process. Accordingly, new routes using non-toxic compounds have been researched. The proposal of the present study was to synthesize AgNPs using ribose as a reducing agent and sodium dodecyl sulfate (SDS) as a stabilizer. The antifungal activity of these particles against C. albicans and C. tropicalis was also evaluated. Stable nanoparticles 12.5 ± 4.9 nm (mean ± SD) in size were obtained, which showed high activity against Candida spp. and could represent an alternative for fungal infection treatment.

Evaluation of intrathecal synthesis of specific IgG antibodies against Toxoplasma gondii in the diagnosis assessment of presumptive toxoplasma encephalitis in aids patients

The diagnosis of neurotoxoplasmosis in patients with acquired immunodeficiency syndrome is mainly based on tomographic or magnetic resonance findings and on the response to specific treatment. We studied 55 patients with AIDS and neurotoxoplasmosis according to these diagnostic criteria (group 1), 37 patients with AIDS and neurological involvement of other etiology (group 2), and 16 anti-HIV-negative individuals with neurological manifestations (group 3). Serum and cerebrospinal fluid were examined for the presence of anti-T. gondii IgG, by indirect immunofluorescence. In 72 of them, the total amounts of these antibodies were determined in order to assess local production of anti-T. gondii antibodies in the central nervous system and to correlate their titers with infection activity in patients with AIDS and neurotoxoplasmosis. IgG titers > 1/64 in cerebrospinal fluid reached 100% specificity for the diagnosis of neurotoxoplasmosis in AIDS. Evidence of local synthesis of these antibodies was detected in 42.8% of patients of group 1, in 29.1% of patients of group 2 and in no patient of group 3. The test showed 70.8% specificity and therefore was not useful in our study for the differential diagnosis of neurotoxoplasmosis in patients with AIDS.

Liver synthesis function in chronic asymptomatic or oligosymptomatic alcoholics: correlation with other liver tests

Liver function and its correlation with bilirubin and hepatic enzymes were evaluated in 30 male chronic asymptomatic or oligosymptomatic alcoholics admitted into the psychiatric hospital for detoxification and treatment of alcoholism. Hypoalbuminemia, lowered prothrombin activity, hypotransferrinemia and hypofibrinogenemia were detected in 32 %, 32 %, 28 %, and 24 % of patients, respectively. Transferrin was elevated in 8 %. Greater prevalence of hyperbilirubinemia was found in patients with lowered prothrombin activity, hypofibrinogenemia, or hypotransferrinemia. No correlation was found between serum bilirubin or aminotransferase levels and normal or elevated albumin levels, time or activity of prothrombin, and fibrinogen levels. Serum alkaline phosphatase was elevated in normoalbuminemics and gamma-glutamyltransferase in patients with lowered prothrombin activity. Hypoalbuminemia was associated with hypofibrinogenemia, hypotransferrinemia with elevated aspartate aminotransferase or gamma-glutamyltransferase, and hypertransferrinemia with elevation of alanine aminotransferase. These data indicated the occurrence of hepatic dysfunction due to liver damage caused directly by alcohol or by alcoholism-associated nutritional deficiencies.

Synthesis and antibiotic activity of some β-Carboline alkaloids

Nine β-carboline alkaloids were synthetized and screened for antibiotic activity. Six of the compounds testes showed inhibitory activity against one or more of the microorganisms assayed.

Time-variations of equivalent water heights'from Grace Mission and in-situ river stages in the Amazon basin

Gravity Recovery and Climate Experiment (GRACE) mission is dedicated to measuring temporal variations of the Earth's gravity field. In this study, the Stokes coefficients made available by Groupe de Recherche en Géodésie Spatiale (GRGS) at a 10-day interval were converted into equivalent water height (EWH) for a ~4-year period in the Amazon basin (from July-2002 to May-2006). The seasonal amplitudes of EWH signal are the largest on the surface of Earth and reach ~ 1250mm at that basin's center. Error budget represents ~130 mm of EWH, including formal errors on Stokes coefficient, leakage errors (12 ~ 21 mm) and spectrum truncation (10 ~ 15 mm). Comparison between in situ river level time series measured at 233 ground-based hydrometric stations (HS) in the Amazon basin and vertically-integrated EWH derived from GRACE is carried out in this paper. Although EWH and HS measure different water bodies, in most of the cases a high correlation (up to ~80%) is detected between the HS series and EWH series at the same site. This correlation allows adjusting linear relationships between in situ and GRACE-based series for the major tributaries of the Amazon river. The regression coefficients decrease from up to down stream along the rivers reaching the theoretical value 1 at the Amazon's mouth in the Atlantic Ocean. The variation of the regression coefficients versus the distance from estuary is analysed for the largest rivers in the basin. In a second step, a classification of the proportionality between in situ and GRACE time-series is proposed.

Myocardial repair with long-term and low-dose administration of a nitric oxide synthesis inhibitor. Myofibroblasts, type III collagen and fibronectin

OBJECTIVE: To study the healing process of the myocardium in hypertensive rats undergoing inhibition of nitric oxide synthesis. METHODS: Two groups of animals were studied: one received L-NAME, 12mg/kg/day, and the other was a control group. The presence of type III collagen, fibronectin, and alpha-smooth muscle actin-positive cells was assessed by immunohistochemistry. RESULTS: Fibronectin was seen in both early and late lesions, while type III collagen was seen mainly in areas of incomplete healing, situated among myocytes and around the intramyocardial branches of the coronary arteries. Areas representing early and late lesions showed a population of spindle-shaped cells. Immunohistochemistry showed that these cells were positive for alpha-smooth muscle actin. CONCLUSION: In the myocardium of hypertensive rats, the alpha-smooth muscle actin-positive cells are related to the accumulation of type III collagen and fibronectin in the areas of myocardial damage.

Quantitative study of myocardial microcirculation in arterial hypertension due to progressive inhibition of NO synthesis

OBJECTIVE: To study the quantitative changes in intramyocardial blood vessels in rats in whom nitric oxide synthesis was inhibited. METHODS: Four groups of 10 rats were studied: control (C25 and C40) and L-NAME (L25 and L40). The animals L25 and L40 received L-NAME in the dosage of 50mg/kg/day for 25 and 40 days, respectively. On days 26 and 41 the animals in groups 25 and 40 were sacrificed. Analysis of the myocardium was performed using light microscopy and stereology. RESULTS: Arterial blood pressure and heart weight increased 74.5 and 57.8% after 25 days and 90.2 and 34.6% after 40 days, respectively. Comparing the L-NAME rats with the respective controls revealed that vessel volume density decreased 31.3% after 40 days, and the vessel length-density decreased 53.5% after 25 days and 25.7% after 40 days. The mean cross-sectional area of the vessels showed an important reduction of 154.6% after 25 days. The intramyocardial vessels decreased significantly in length- density in the L-NAME animals. The mean cross-sectional area of the vessels, which normally increases during heart growth between 25 and 40 days, showed a precocious increase by the 25th day in the L-NAME rats. This suggests an increase of the size of the heart, including blood vessels. CONCLUSION: The inhibition of the NO synthesis provokes rarefaction in the intramyocardial vessels that progresses with the time of administration of L-NAME.

Fixação do dióxido de carbono por bactérias nitrificantes

During the oxidation of the substrate, both Nitrosomonas and Nitrobacter have part of the energy made available as high energy phosphate, mamely ADP and ATP. This chemical energy is used to fix CO2. The nature of the reducing power is unknown at present. Active cells of Nitrobacter were shown to fix CO2 along the same pathway as found in higher plant photosynthesis. Sonic extracts of Nitrosomonas and Nitrobacter when incubated with NaH14CO3 and cofactors showed two ports of entry of CO2 into organic compounds one being, as expected, the carboxidismutase reaction. On protein basis an equivalent amount of CO2 was, however, incorporated via the oxaloacetic carboxylase reation. It is clear then that both micoorganisms possess typical autotrophic and heterotrophic mechanisms for the fixation of CO2 which is required for the primary synthesis of cell material.

Effect of cAMP on macromolecule synthesis in the pathogenic protozoa Trypanosoma cruzi

Macromolecule synthesis of Trypanosoma cruzi in culture was monitored using radioactive tracers. Cells of different days in culture displayed a preferential incorporation of precursors as follows: 1 day for (³H)-thymidine cells; 3 days for (³H)-uridine cells, and 4 days for (³H)-leucine cells. Autoradiographic studies showed that (³H)-thymidine was incorporated in the DNA of both kinetoplast and nucleus in this order. Shifts in the intracellular content of cAMP either by addition of dibutyryl-cAMP or by stimulation of the adenylcyclase by isoproterenol, caused an inhibition in the synthesis of DNA, RNA and proteins. Addition to the T. cruzi cultures of these agents which elevate the intracellular content ofcAMP provoked an interruption of cell proliferation as a result of the impairment of macromolecule synthesis. A discrimination was observed among the stereoisomers of isoproterenol, the L configuration showing to be most active.