(Table 2) Concentrations and D/L values for three amino acids in bulk foraminifera from ODP Sites 182-1126 and 182-1127

A number of studies have shown that methanogens are active in the presence of sulfate under some conditions. This phenomenon is especially exemplified in carbonate sediments of the southern Australian continental margin. Three sites cored during Ocean Drilling Program (ODP) Leg 182 in the Great Australian Bight have high concentrations of microbially-generated methane and hydrogen sulfide throughout almost 500 m of sediments. In these cores, the sulfate-reducing and methanogenic zones overlap completely; that is, the usual sulfate-methane transition zone is absent. Amino acid racemization data show that the gassy sediments consist of younger carbonates than the low-gas sites. High concentrations of the reduced gases also occur in two ODP sites on the margin of the Bahamas platform, both of which have similar sedimentary conditions to those of the high-gas sites of Leg 182. Co-generation of these reduced gases results from an unusual combination of conditions, including: (1) a thick Quaternary sequence of iron-poor carbonate sediments, (2) a sub-seafloor brine, and (3) moderate amounts of organic carbon. The probable explanation for the co-generation of hydrogen sulfide and methane in all these sites, as well as in other reported environments, is that methanogens are utilizing non-competitive substrates to produce methane within the sulfate-reducing zone. Taken together, these results form the basis of a new model for sulfate reduction and methanogenesis in marine sediments. The biogeochemical end-members of the model are: (1) minimal sulfate reduction, (2) complete sulfate reduction followed by methanogenesis, and (3) overlapping sulfate reduction and methanogenesis with no transition zone.

Aestivation in the South American lungfish, Lepidosiren paradoxa: Effects on cardiovascular function, blood gases, osmolality and leptin levels

The African (Protopterus sp.) and South American lungfish (Lepidosiren paradoxa) inhabit shallow waters, that seasonally dry out, which induces aestivation and cocoon formation in Protopterus. Differently, L. paradoxa has no cocoon, and it aestivates in a simple burrow. In water PaCO(2) is 21.8 +/- 0.4 mmHg (mean values +/- S.E.M.; n = 5), whereas aestivation for 20 days increased PaCO(2) to as much as 37.6 +/- 2.1 mmHg, which remained the same after 40 days (35.8 +/- 3.3 mmHg). Concomitantly. the plasma [HCO(3)(-)]-values for animals in water were 22.5 +/- 0.5 mM, which after 20 days increased to 40.2 +/- 2.3 mM and after 40 days to 35.8 +/- 3.3 mM. Initially in water, PaO(2) was 87.7 +/- 2.0 mmHg, but 20 days in aestivation reduced the value to 80.5 +/- 2.2 and later (40 days) to 77.1 +/- 3.0 mmHg. Meanwhile, aestivation had no effect on pHa and hematocrit. The blood pressures were equal for animals in the water or in the burrow (P(mean) similar to 30 mmHg), and cardiac frequency (f(H)) fell from 31 beats min(-1) to 22 beats min(-1) during 40 days of aestivation. The osmolality (mOsm kg H(2)O(-1)) was elevated after 20 and 40 days of aestivation but declined upon return to water. The transition front activity to aestivation involves new set-points for the variables that determine the acid-base status and PaO(2) of the animals, along with a reduction of cardiac frequency. (C) 2008 Elsevier B.V. All rights reserved.

Blood gases and cardiovascular shunt in the South American lungfish (Lepidosiren paradoxa) during normoxia and hyperoxia

The South American lungfish (Lepidosiren paradoxa) has an arterial P(O2), (Pa(O2)) as high as 70-100 mm Hg, corresponding to Hb-O(2) saturations from 90% to 95%, which indicates a moderate cardiovascular right to left (R-L) shunt. In hyperoxia (50% O(2)), we studied animals in: (1) aerated water combined with aerial hyperoxia, which increased Pa(O2) from 78 +/- 2 to 114 +/- 3 mm Hg and (2) and aquatic hyperoxia (50% O(2)) combined room air, which gradually increased Pa(O2) from 75 +/- 4 mm Hg to as much as 146 +/- 10 mm Hg. Further, the hyperoxia (50%) depressed pulmonary ventilation from 58 +/- 13 to 5.5 +/- 3.0 mLBTPS kg h(-1), and Pa(CO2) increased from 20 +/- 2 to 31 +/- 4 mm Hg, while pHa became reduced from 7.56 +/- 0.03 to 7.31 +/- 0.09. At the same time, venous P(O2) (Pv(O2)) rose from 40.0 +/- 2.3 to 46.4 +/- 1.2 mm Hg and, concomitantly, Pvco, increased from 23.2 +/- 1.1 to 32.2 +/- 0.5 mm Hg. R-L shunts were estimated to about 19%, which is moderate when compared to most amphibians. (C) 2010 Elsevier B.V. All rights reserved.

Electrospun Polyaniline-Reduced Graphene Oxide Composite Nanofibers Based High Sensitive Ammonia Gas Sensor

Ammonia is an important gas in many power plants and industrial processes so its detection is of extreme importance in environmental monitoring and process control due to its high toxicity. Ammonia’s threshold limit is 25 ppm and the exposure time limit is 8 h, however exposure to 35 ppm is only secure for 10 min. In this work a brief introduction to ammonia aspects are presented, like its physical and chemical properties, the dangers in its manipulation, its ways of production and its sources. The application areas in which ammonia gas detection is important and needed are also referred: environmental gas analysis (e.g. intense farming), automotive-, chemical- and medical industries. In order to monitor ammonia gas in these different areas there are some requirements that must be attended. These requirements determine the choice of sensor and, therefore, several types of sensors with different characteristics were developed, like metal oxides, surface acoustic wave-, catalytic-, and optical sensors, indirect gas analyzers, and conducting polymers. All the sensors types are described, but more attention will be given to polyaniline (PANI), particularly to its characteristics, syntheses, chemical doping processes, deposition methods, transduction modes, and its adhesion to inorganic materials. Besides this, short descriptions of PANI nanostructures, the use of electrospinning in the formation of nanofibers/microfibers, and graphene and its characteristics are included. The created sensor is an instrument that tries to achieve a goal of the medical community in the control of the breath’s ammonia levels being an easy and non-invasive method for diagnostic of kidney malfunction and/or gastric ulcers. For that the device should be capable to detect different levels of ammonia gas concentrations. So, in the present work an ammonia gas sensor was developed using a conductive polymer composite which was immobilized on a carbon transducer surface. The experiments were targeted to ammonia measurements at ppb level. Ammonia gas measurements were carried out in the concentration range from 1 ppb to 500 ppb. A commercial substrate was used; screen-printed carbon electrodes. After adequate surface pre-treatment of the substrate, its electrodes were covered by a nanofibrous polymeric composite. The conducting polyaniline doped with sulfuric acid (H2SO4) was blended with reduced graphene oxide (RGO) obtained by wet chemical synthesis. This composite formed the basis for the formation of nanofibers by electrospinning. Nanofibers will increase the sensitivity of the sensing material. The electrospun PANI-RGO fibers were placed on the substrate and then dried at ambient temperature. Amperometric measurements were performed at different ammonia gas concentrations (1 to 500 ppb). The I-V characteristics were registered and some interfering gases were studied (NO2, ethanol, and acetone). The gas samples were prepared in a custom setup and were diluted with dry nitrogen gas. Electrospun nanofibers of PANI-RGO composite demonstrated an enhancement in NH3 gas detection when comparing with only electrospun PANI nanofibers. Was visible higher range of resistance at concentrations from 1 to 500 ppb. It was also observed that the sensor had stable, reproducible and recoverable properties. Moreover, it had better response and recovery times. The new sensing material of the developed sensor demonstrated to be a good candidate for ammonia gas determination.

On modified simple reacting spheres kinetic model for chemically reactive gases

Versão dos autores para esta publicação.

Understanding land-sea warming contrast in response to increasing greenhouse gases. Part I: Transient adjustment

Climate model simulations consistently show that surface temperature over land increases more rapidly than over sea in response to greenhouse gas forcing. The enhanced warming over land is not simply a transient effect caused by the land–sea contrast in heat capacities, since it is also present in equilibrium conditions. This paper elucidates the transient adjustment processes over time scales of days to weeks of the surface and tropospheric climate in response to a doubling of CO2 and to changes in sea surface temperature (SST), imposed separately and together, using ensembles of experiments with an atmospheric general circulation model. These adjustment processes can be grouped into three stages: immediate response of the troposphere and surface processes (day 1), fast adjustment of surface processes (days 2–5), and adjustment of the whole troposphere (days 6–20). Some land surface warming in response to doubled CO2 (with unchanged SSTs) occurs immediately because of increased downward longwave radiation. Increased CO2 also leads to reduced plant stomatal resistance and hence restricted evaporation, which increases land surface warming in the first day. Rapid reductions in cloud amount lead in the next few days to increased downward shortwave radiation and further warming, which spreads upward from the surface, and by day 5 the surface and tropospheric response is statistically consistent with the equilibrium value. Land surface warming in response to imposed SST change (with unchanged CO2) is slower. Tropospheric warming is advected inland from the sea, and over land it occurs at all levels together rather than spreading upward from the surface. The atmospheric response to prescribed SST change in about 20 days is statistically consistent with the equilibrium value, and the warming is largest in the upper troposphere over both land and sea. The land surface warming involves reduction of cloud cover and increased downward shortwave radiation, as in the experiment with CO2 change, but in this case it is due to the restriction of moisture supply to the land (indicated by reduced soil moisture), whereas in the CO2 forcing experiment it is due to restricted evaporation despite increased moisture supply (indicated by increased soil moisture). The warming over land in response to SST change is greater than over the sea and is the dominant contribution to the land–sea warming contrast under enhanced CO2 forcing.

Weakened tropical circulation and reduced precipitation in response to geoengineering

Geoengineering by injection of reflective aerosols into the stratosphere has been proposed as a way to counteract the warming effect of greenhouse gases by reducing the intensity of solar radiation reaching the surface. Here, climate model simulations are used to examine the effect of geoengineering on the tropical overturning circulation. The strength of the circulation is related to the atmospheric static stability and has implications for tropical rainfall. The tropical circulation is projected to weaken under anthropogenic global warming. Geoengineering with stratospheric sulfate aerosol does not mitigate this weakening of the circulation. This response is due to a fast adjustment of the troposphere to radiative heating from the aerosol layer. This effect is not captured when geoengineering is modelled as a reduction in total solar irradiance, suggesting caution is required when interpreting model results from solar dimming experiments as analogues for stratospheric aerosol geoengineering.

Análise estatística das emissões de CO e HC produzidas por gases da exaustão veicular oriundos de gasolina, GNV e mistura álcool/gasolina

The vehicles are the main mobile sources of carbon monoxide (CO) and unburned hydrocarbons (HC) released into the atmosphere. In the last years the increment of the fleet of vehicles in the municipal district of Natal-RN it is contributing to the increase of the emissions of those pollutants. The study consisted of a statistical analysis of the emissions of CO and HC of a composed sample for 384 vehicles with mechanization Gasoline/CNG or Alcohol/Gasoline/CNG of the municipal district of Natal-RN. The tests were accomplished in vehicles submitted to Vehicular Safety's Inspection, in the facilities of INSPETRANS, Organism of Vehicular Inspection. An partial gases analyzer allowed to measure, for each vehicle, the levels of CO and HC in two conditions of rotation of the motor (900 and 2500 rpm). The statistical analysis accomplished through the STATISTICA software revealed a sensitive reduction in the efficiency of the converters catalytic after 6 years of use with emission average it is of 0,78% of CO and 156 (ppm) of HC, Which represents approximately 4 (four) times the amount of CO and the double of HC in comparison with the newest vehicles. The result of a Student s t-test, suggests strongly that the average of the emissions of HC (152 ppm), at 900 rpm, is 40% larger than at 2500 rpm, for the motor without load. This result reveals that the efficiency of the catalytic conversion is limited kinetically in low engine speeds. The Study also ends that when comparing the emissions of CO and HC considering the influence of the fuels, it was verified that although the emissions of CO starting from CNG are 62% smaller than arising from the gasoline, there are not significant differences among the emissions of HC originating from of CNG and of the gasoline. In synthesis, the results place the current criteria of vehicular inspection, for exhaust gases, in doubt, leading the creation of emission limits of pollutant more rigorous, because the efficiency of the converters catalytic is sensibly reduced starting from 6 years of use. It is also raised the possibility of modifications in the test conditions adopted by the current norms, specifically in the speed engine, have seen that in the condition without load the largest emission indexes were registered in slow march. That fact that allows to suggest the dismissal of the tests in high speed engine, reducing the time of inspection in half and generating economy of fuel

Effects of temperature on lung and blood gases in the South American rattlesnake Crotalus durissus terrificus

The effects of temperature on lung and blood gases were measured in the South American rattlesnake (Crotalus durissus terrificus). Arterial blood and lung gas samples were obtained from chronically cannulated animals at 15, 25, and 35 degrees C. As expected for reptiles, arterial pH fell with increased temperature (0.018 U degrees C-1 between 15 and 25 degrees C and 0.011 U degrees C-1 between 25 and 35 degrees C) while lung gas PCO2 rose from 5.8 mmHg at 15 degrees C to 13.2 mmHg at 35 degrees C. Concurrently, lung gas PO2 declined from 132 mmHg at 15 degrees C to 120 mmHg at 35 degrees C, and arterial PO2 increased from 33 to 76 mmHg in that temperature range. Arterial haemoglobin O-2 saturation rose from 0.53 at 15 degrees C to 0.83 at 25 degrees C but became slightly reduced (0.77) with a further elevation of temperature to 35 degrees C. Arterial haemoglobin concentration increased from 1.96 to 2.53 mM between 15 and 35 degrees C, consistent with higher demands on oxygen delivery to tissues at elevated temperatures. Moreover, the substantial increase of haemoglobin O-2 saturation between 15 and 25 degrees C conforms to the idea that reduction of the central vascular right-to-left shunt (pulmonary bypass of systemic venous return) is associated with high metabolic demands. (C) 1998 Elsevier B.V. All rights reserved.

Balanço de gases de efeito estufa em áreas de cana-de-açúcar sob diferentes cenários de manejo, considerando-se mitigações

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Inventário dos gases de efeito estufa associado ao manejo da cana-de-açúcar na localidade de Barretos-SP, Brasil

Pós-graduação em Agronomia (Produção Vegetal) - FCAV

Uso de aeradores e substratos no cultivo semi-intensivo do camarão-da-amazônia Macrobrachium amazonicum: análise técnica, econômica e emissão de gases do efeito estufa

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Processo combinado químico-bacteriano para a remoção de H2S de gases

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

Emissão de gases de efeito estufa nos sistemas de colheita crua e queimada no estado de São Paulo, Brasil

Pós-graduação em Agronomia (Produção Vegetal) - FCAV