Inibição da mineralização de compostos nitrogenados de lixiviado de macrófita aquática: Adequação metodológica

This study aimed to establish the adequate concentrations of nitrapyrin for the effective inhibition of oxygen demand required for the oxidation of nitrogen compounds during aerobic mineralization of leachate. The aquatic macrophyte Myriophyllum aquaticum was used as a source of dissolved organic matter (DOM). The leachate was incubated in several chambers, containing different composition and treatments: (i) treatment with leachate (DOM), (ii) treatment with DOM plus nitrapyrin in different concentrations (10; 25 and 50 mg L-1), aiming at finding the right concentration that inhibits the nitrification process, (iii) treatment with DOM plus NH4SO 2, (iv) treatment containing DOM and nitrapyrin plus NH 4SO2, and (v) treatment with DOM plus azide. The dissolved oxygen amount in each incubation treatment was periodically measured. The results indicated that the ratio of 10 mg L-1 of nitrapyrin for each 10 mg C of leachate is efficient in inhibiting the oxidation of nitrogen compounds from aquatic macrophytes.

In vitro assessment of pulp chamber temperature of different teeth submitted to dental bleaching associated with LED/laser and halogen lamp appliances

This study sought to assess the pulp chamber temperature in different groups of human teeth that had been bleached using hydrogen peroxide gel activated with halogen lamps or hybrid LED/laser appliances. Four groups of ten teeth (maxillary central incisors, mandibular incisors, mandibular canines, and maxillary canines) were used. A digital thermometer with a K-type thermocouple was placed inside pulp chambers that had been filled with thermal paste. A 35% hydrogen peroxide-based red bleaching gel was applied to all teeth and photocured for a total of three minutes and 20 seconds (five activations of 40 seconds each), using light from an LED/laser device and a halogen lamp. The temperatures were gauged every 40 seconds and the data were analyzed by three-way ANOVA, followed by Tukey's test. Regardless of the light source, statistically significant differences were observed between the groups of teeth. The mean temperature values (±SD) were highest for maxillary central incisors and lowest for mandibular canines. The halogen lamp appliance produced more pulp chamber heating than the LED/laser appliance. The increase in irradiation time led to a significant increase in temperature.

Permanent Magnet Hall Thruster for satellite orbit raising with low power energy consumption

Electric propulsion is now a succeful method for primary propulsion of deep space long duration missions and for geosyncronous satellite attitude control. Closed Drift Thruster, so called Hall Thruster or SPT (Stationary Plasma Thruster), was primarily conceived in USSR (the ancient Soviet Union) and, since then, it has been developed by space agencies, space research institutes and industries in several countries such as France, USA, Israel, Russian Federation and Brazil. In this work we present the main features of the Permanent Magnet Hall Thruster (PMHT) developed at the Plasma Laboratory of the University of Brasilia. The idea of using an array of permanent magnets, instead of an electromagnet, to produce a radial magnetic field inside the plasma channel of the thruster is very significant. It allows the development of a Hall Thruster with power consumption low enough to be used in small and medium size satellites. Description of a new vacuum chamber used to test the second prototype of the PMHT (PHALL II) will be given. PHALL II has an aluminum plasma chamber and is smaller with 15 cm diameter and will contain rare earth magnets. We will show plasma density and temperature space profiles inside and outside the thruster channel. Ion temperature measurements based on Doppler broadening of spectral lines and ion energy measurements are also shown. Based on the measured plasma parameters we constructed an aptitude figure of the PMHT. It contains the specific impulse, total thrust, propellant flow rate and power consumption necessary for orbit raising of satellites. Based on previous studies of geosyncronous satellite orbit positioning we perform numerical simulations of satellite orbit raising from an altitude of 700 km to 36000 km using a PMHT operating in the 100 mN - 500 mN thrust range. In order to perform these calculations integration techniques were used. The main simulation paraters were orbit raising time, fuel mass, total satellite mass, thrust and exaust velocity. We conclude comparing our results with results obtainned with known space missions performed with Hall Thrusters. © 2008 by the American Institute of Aeronautics and Astronautics, Inc.

Influence of vegetable oil in the viscosity of biodiesel-a review

Viscosity is a measure fluid resistance to flowing, affecting the fuel spray in the combustion chamber and, by this way, thus the formation of carbon deposits. The analysis of the influence of vegetable oil viscosity in biodiesel seems appropriate, because biodiesel viscosity is a function of vegetable oil. The increase of the fuel viscosity, promoted by biodiesel, has a major impact on the dynamics of jet fuel, increasing its speed and distance of penetration, obtaining therefore an increase in the amount of turbulent movement of the jet and thus an increase in the rate of preparation of the mixture, air-fuel, when adding biodiesel to diesel oil. The negative effect of this higher fuel viscosity is the increase of the wear of the train of gears, cam shaft, and valve push rod of all the injection pumps due to the higher pressure of injection. The viscosity of biodiesel is influenced by the size of its molecule and by the increase of molecule insaturations, is directly related with its origin vegetable oil or fat. This study is a review of the influence of vegetable oils in viscosity of biodiesel. Copyright © 2008 SAE International.

Indirect cytotoxicity of a 35% hydrogen peroxide bleaching gel on cultured odontoblast-like cells

The aim of this study was to evaluate the trans-enamel and trans-dentinal effects of a 35% hydrogen peroxide (H2O2) bleaching gel on odontoblast-like cells. Enamel/dentin discs obtained from bovine incisors were mounted in artificial pulp chambers (APCs). Three groups were formed: G1- 35% H2O2; G2- 35% H2O2 + halogen light application; G3- control. The treatments were repeated 5 times and the APCs were incubated for 12 h. Then, the extract was collected and applied for 24 h on the cells. Cell metabolism, total protein dosage and cell morphology were evaluated. Cell metabolism decreased by 62.09% and 61.83% in G1 and G2, respectively. The depression of cell metabolism was statistically significant when G1 and G2 were compared to G3. Total protein dosage decreased by 93.13% and 91.80% in G1 and G2, respectively. The cells in G1 and G2 exhibited significant morphological alterations after contact with the extracts. Regardless of halogen light application, the extracts caused significantly more intense cytopathic effects compared to the control group. After 5 consecutive applications of a 35% H2O2 bleaching agent, either catalyzed or not by halogen light, products of gel degradation were capable to diffuse through enamel and dentin causing toxic effects to the cells.

Spatial and temporal variability in soil CO2-C emissions and relation to soil temperature at King George Island, maritime Antarctica

Few studies have examined the effects of temperature on spatial and temporal trends in soil CO2-C emissions in Antarctica. In this work, we present in situ measurements of CO2-C emissions and assess their relation with soil temperature, using dynamic chambers. We found an exponential relation between CO2 emissions and soil temperature, with the value of Q10 being close to 2.1. Mean emission rates were as low as 0.026 and 0.072 g of CO2-C m-2 h-1 for bare soil and soil covered with moss, respectively, and as high as 0.162 g of CO2-C m-2 h-1 for soil covered with grass, Deschampsia antarctica Desv. (Poaceae). A spatial variability analysis conducted using a 60-point grid, for an area with mosses (Sannionia uncianata) and D. antarctica, yielded a spherical semivariogram model for CO2-C emissions with a range of 1 m. The results suggest that soil temperature is a controlling factor on temporal variations in soil CO2-C emissions, although spatial variations appear to be more strongly related to the distribution of vegetation types. © 2010 Elsevier B.V. and NIPR.

Precise mapping of the magnetic field in the CMS barrel yoke using cosmic rays

The CMS detector is designed around a large 4 T superconducting solenoid, enclosed in a 12 000-tonne steel return yoke. A detailed map of the magnetic field is required for the accurate simulation and reconstruction of physics events in the CMS detector, not only in the inner tracking region inside the solenoid but also in the large and complex structure of the steel yoke, which is instrumented with muon chambers. Using a large sample of cosmic muon events collected by CMS in 2008, the field in the steel of the barrel yoke has been determined with a precision of 3 to 8% depending on the location. © 2010 IOP Publishing Ltd and SISSA.

Quebra de dormência em sementes de Sesbania virgata (Cav.) Pers

Forest species with hard seeds often pose considerable problems to nursery managers because their hard and impermeable seed coats hinder and delay germination. Therefore, this work aimed to determine the most efficient, practical and low cost methodology to overcome dormancy in Sesbania virgata (Cav.) Pers. Seed, a specie with potential for recovery of degraded areas. The seeds were submitted to chemical scarification by immersion in sulfuric acid during a period of 5, 10, 20 and 30 minutes, mechanical scarification and heat treatment. After the scarification the seeds were submitted to germ test in germination chambers at 25oC and photoperiod of 14 h. Treatment with mechanical scarification showed the highest germination percentage (98%), followed by chemical scarification for 30 minutes (57%). The heat treatment in spite of obtaining a higher germination percentage than the controls had abnormal development of seedlings and is not therefore recommended for seeds of S. virgata. From the parameters utilized in this study, we recommend the use of the mechanical scarification to overcome dormancy of S. virgata seeds.

Echocardiographic predictors of ventricular remodeling after acute myocardial infarction in rats

Background: The prediction of the ventricular remodeling process after acute myocardial infarction (AMI) may have important clinical implications. Objetive: To analyze echocardiographic variables predictors of remodeling in the infarction model in rats. Methods: The animals underwent echocardiography in two moments, five days and three months after infarction (AMI group) or sham surgery (control group). Linear regression was used to identify the echocardiographic variables on the fifth day after the infarction, which were predictive of remodeling after three months of coronary occlusion. We considered as a criterion of remodeling in this study, the values of left ventricular diastolic diameter (LVDD) after three months of infarction. Results: The infarction induced increase in the left chambers, associated with changes in systolic and diastolic functions. The variables body weight, left ventricular wall stress index (LVWSI), systolic area (SA), diastolic area (DA), LVDD, left ventricular systolic diameter (LVSD), fractional area change (FAC), ejection fraction (EF), fractional shortening (%Short), posterior wall shortening velocity (PWSV) and infarct size assessed five days after infarction were predictors of LVDD after three months. At the multivariate regression analysis, we included the size of infarction, the LVWSI and PWSV. The LVWSI (coefficient: 4.402, standard error: 2.221, p = 0.05), but not the size of infarction and PWSV, was a predictor of remodeling after three months of infarction. Conclusion: LVPSI was an independent predictor of remodeling three months after the myocardial infarction and could be included in the clinical stratification after the coronary occlusion.

Ammonia volatilization losses from surface-applied urea with urease and nitrification inhibitors

Urease inhibitor (UI) and nitrification inhibitor (NI) have the potential to improve N-use efficiency of applied urea and minimize N losses via gaseous emissions of ammonia (NH 3) to the atmosphere and nitrate (NO3-) leaching into surface and ground water bodies. There is a growing interest in the formulations of coating chemical fertilizers with both UI and NI. However, limited information is available on the combined use of UI and NI applied with urea fertilizer. Therefore the aim of this study was to investigate the effects of treating urea with both UI and NI to minimize NH 3 volatilization. Two experiments were set up in volatilization chambers under controlled conditions to examine this process. In the first experiment, UR was treated with the urease inhibitor NBPT [N-(n-butyl) thiophosphoric acid triamide] at a rate of 1060 mg kg -1 urea and/or with the nitrification inhibitor DCD (dicyandiamide) at rates equivalent to 5 or 10% of the urea N. A randomized experimental design with five treatments and five replicates was used: 1) UR, 2) UR + NBPT, 3) UR + DCD 10%, 4) UR + NBPT + DCD 5%, and 5) UR + NBPT + DCD 10%. The fertilizer treatments were applied to the surface of an acidic Red Latosol soil moistened to 60% of the maximum water retention and placed inside volatilization chambers. Controls chambers were added to allow for NH 3 volatilized from unfertilized soil or contained in the air that swept over the soil surface. The second experiment had an additional treatment with surface-applied DCD. The chambers were glass vessels (1.5 L) fit with air inlet and outlet tubings to allow air to pass over the soil. Ammonia volatilized was swept and carried to a flask containing a boric acid solution to trap the gas and then measured daily by titration with a standardized H 2SO 4 solution. Continuous measurements were recorded for 19 and 23 days for the first and second experiment, respectively. The soil samples were then analyzed for UR-, NH4+-, and NO3--N. Losses of NH 3 by volatilization with unamended UR ranged from 28 to 37% of the applied N, with peak of losses observed the third day after fertilization. NBPT delayed the peak of NH 3 losses due to urease inhibition and reduced NH 3 volatilization between 54 and 78% when compared with untreated UR. Up to 10 days after the fertilizer application, NH 3 losses had not been affected by DCD in the UR or the UR + NBPT treatments; thereafter, NH 3 volatilization tended to decrease, but not when DCD was present. As a consequence, the addition of DCD caused a 5-16% increase in NH 3 volatilization losses of the fertilizer N applied as UR from both the UR and the UR + NBPT treatments. Because the effectiveness of NBPT to inhibit soil urease activity was strong only in the first week, it could be concluded that DCD did not affect the action of NBPT but rather, enhanced volatilization losses by maintaining higher soil NH4+ concentration and pH for a longer time. Depending on the combination of factors influencing NH 3 volatilization, DCD could even offset the beneficial effect of NBPT in reducing NH 3 volatilization losses. © 2012 Elsevier Ltd.

Cardiac remodeling induced by smoking: Concepts, relevance, and potential mechanisms

Cardiac or ventricular remodeling is characterized by molecular, cellular, and interstitial alterations that lead to changes in heart size, mass, geometry and function in response to a given insult. Currently, tobacco smoke exposure is recognized as one of these insults. Indeed, tobacco smoke exposure induces the enlargement of the left-sided cardiac chambers, myocardial hypertrophy, and ventricular dysfunction. Potential mechanisms for these alterations include hemodynamic and neurohormonal changes, oxidative stress, inflammation, nitric oxide bioavailability, matrix metalloproteinases and mitogen-activated protein kinase activation. This review will focus on the concepts, relevance, and potential mechanisms of cardiac remodeling induced by tobacco smoke. © 2012 Bentham Science Publishers.

Efficacy and cytotoxicity of a bleaching gel after short application times on dental enamel

Objectives: This study aimed to evaluate and correlate the efficacy and cytotoxicity of a 35 % hydrogen peroxide (HP) bleaching gel after different application times on dental enamel. Materials and methods: Enamel/dentin disks in artificial pulp chambers were placed in wells containing culture medium. The following groups were formed: G1, control (no bleaching); G2 and G3, three or one 15-min bleaching applications, respectively; and G4 and G5, three or one 5-min bleaching applications, respectively. Extracts (culture medium with bleaching gel components) were applied for 60 min on cultured odontoblast-like MDPC-23 cells. Cell metabolism (methyl tetrazolium assay) (Kruskal-Wallis/Mann-Whitney; α = 5 %) and cell morphology (scanning electron microscopy) were analyzed immediately after the bleaching procedures and the trans-enamel and trans-dentinal HP diffusion quantified (one-way analysis of variance/Tukey's test; α = 5 %). The alkaline phosphatase (ALP) activity was evaluated 24 h after the contact time of the extracts with the cells (Kruskal-Wallis/Mann-Whitney; α = 5 %). Tooth color was analyzed before and 24 h after bleaching using a spectrophotometer according to the Commission Internationale de l'Eclairage L*a*b* system (Kruskal-Wallis/Mann-Whitney; α = 0.05). Results: Significant difference (p < 0.05) in cell metabolism occurred only between G1 (control, 100 %) and G2 (60.6 %). A significant decrease (p < 0.05) in ALP activity was observed between G2, G3, and G4 in comparison with G1. Alterations on cell morphology were observed in all bleached groups. The highest values of HP diffusion and color alterations were observed for G2, with significant difference among all experimental groups (p < 0.05). G3 and G4 presented intermediate color change and HP diffusion values with no statistically significant differences between them (p > 0.05). The lowest amount of HP diffusion was observed in G5 (p < 0.05), which also exhibited no significant color alteration compared to the control group (p > 0.05). Conclusions: HP diffusion through dental tissues and its cytotoxic effects were proportional to the contact time of the bleaching gel with enamel. However, shorter bleaching times reduced bleaching efficacy. Clinical relevance: Shortening the in-office tooth bleaching time could be an alternative to minimize the cytotoxic effects of this clinical procedure to pulp tissue. However, the reduced time of bleaching agent application on enamel may not provide adequate esthetic outcome. © 2012 Springer-Verlag Berlin Heidelberg.

Persistence of epoxy-based sealer residues in dentin treated with different chemical removal protocols

The presence of residual endodontic sealer in the pulp chamber may cause discoloration of the dental crown and interfere with the adhesion of restorative materials. The aim of this study was to compare the efficacy of different solvents in removing residues of an epoxy resin-based sealer (AH Plus) from the dentin walls of the pulp chamber, by scanning electron microscopy (SEM). Forty-four bovine incisor dental crown fragments were treated with 17% EDTA and 2.5% NaOCl. Specimens received a coating of AH Plus and were left undisturbed for 5 min. Then, specimens were divided in four groups (n = 10) and cleaned with one of the following solutions: isopropyl alcohol, 95% ethanol, acetone solution, or amyl acetate solution. Negative controls (n = 2) did not receive AH Plus, while in positive controls (n = 2) the sealer was not removed. AH Plus removal was evaluated by SEM, and a score system was applied. Data were analyzed by Kruskal-Wallis and Dunn tests. None of the solutions tested was able to completely remove AH Plus from the dentin of the pulp chamber. Amyl acetate performed better than 95% ethanol and isopropyl alcohol (p < 0.05), but not better than acetone (p > 0.05) in removing the sealer from dentin. No significant differences were observed between acetone, 95% ethanol, and isopropyl alcohol (p > 0.05). It was concluded that amyl acetate and acetone may be good options for cleaning the pulp chamber after obturation with AH Plus. SCANNING 35:17-21, 2013. © 2012 Wiley Periodicals, Inc. © Wiley Periodicals, Inc.

Queen lipid content and nest growth in the leaf cutting ant (Atta sexdens rubropilosa) (Hymenoptera: Formicidae)

The relationship between the queens' lipid content and nest growth (population size, biomass and nest architecture) was studied from founding up to 1 year. Nests aged 3, 4, 5, 6, 9 and 12 months were dug in the field, and their dimensions were measured. The ant nest population and fungus garden was also collected. The sample was taken to the laboratory where we counted the worker population and weighed the biomass (fungus plus offspring) and queens. Queens were separated for the determination of lipids. The lipid content in the bodies of queens decreased in the first months, then stabilized (at 4-6 months) before increasing in months 9 and 12. Nest biomass (symbiotic fungus and offspring) and worker population increased over time. The structural growth of the nests was observed by excavating around them. Initially nests (3 months old) had one chamber at an average depth of 15 cm. By 1 year, the nests had three or four deep chambers, and were about 3-4 m deep. Our study contributes to knowledge of the dynamics of the energy-reserve expenditure by queens during colony founding and colony development for up to 1 year. © 2013 Copyright Taylor and Francis Group, LLC.

Controlled route to the fabrication of carbon and boron nitride nanoscrolls: A molecular dynamics investigation

Carbon nanoscrolls (graphene layers rolled up into papyrus-like tubular structures) are nanostructures with unique and interesting characteristics that could be exploited to build several new nanodevices. However, an efficient and controlled synthesis of these structures was not achieved yet, making its large scale production a challenge to materials scientists. Also, the formation process and detailed mechanisms that occur during its synthesis are not completely known. In this work, using fully atomistic molecular dynamics simulations, we discuss a possible route to nanoscrolls made from graphene layers deposited over silicon oxide substrates containing chambers/pits. The scrolling mechanism is triggered by carbon nanotubes deposited on the layers. The process is completely general and can be used to produce scrolls from other lamellar materials, like boron nitride, for instance. © 2013 American Institute of Physics.