Home About us Contact
|
Home About us Contact | ||
|
|
||
Gas Concentration (gas + concentration)
Selected AbstractsAdsorption of SO2 on Activated Carbon for Low Gas ConcentrationsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2007P. Zhang Abstract Adsorption experiments of SO2 on activated carbon has been carried out for low concentrations (about 100,ppm) at room temperature (15 to 33,°C) with varying humidity in the air. The breakthrough curves show that at high relative humidity or relative higher SO2 concentration, the load capacity increases with respect to temperature. The humidity of the air is also of benefit to the load capacity of SO2. When an adsorption process is interrupted and the activated carbon is kept closed for a while, the SO2 concentration at the exit of a fixed-bed adsorber is similar to that of the fresh activated carbon and begins at a very low value. It appears that the sorption potential has been refreshed after the storage period. Analysis of desorption experiments by simultaneous thermal analysis combined with mass spectrometry (MS) after loading, shows that the physisorbed SO2 and H2O are desorbed at low temperatures. At higher temperatures, the MS peak of SO2 and H2O occur at the same time. Compared with desorption immediately after loading, after one day, the desorption peak due to the physisorbed SO2 disappears. From this, it can be concluded that the refreshment of the loading capacity of the activated carbon after storage is mainly due to a change in the nature of the SO2 from a physisorbed state to a chemisorbed form. The same mechanism leads to a continuous refreshment of the sorption potential by means of a chemical reaction during the adsorption process. [source] Effectiveness of ozone against endodontopathogenic microorganisms in a root canal biofilm modelINTERNATIONAL ENDODONTIC JOURNAL, Issue 1 2009K. C. Huth Abstract Aim, To assess the antimicrobial efficacy of aqueous (1.25,20 ,g mL,1) and gaseous ozone (1,53 g m,3) as an alternative antiseptic against endodontic pathogens in suspension and a biofilm model. Methodology,Enterococcus faecalis, Candida albicans, Peptostreptococcus micros and Pseudomonas aeruginosa were grown in planctonic culture or in mono-species biofilms in root canals for 3 weeks. Cultures were exposed to ozone, sodium hypochlorite (NaOCl; 5.25%, 2.25%), chlorhexidine digluconate (CHX; 2%), hydrogen peroxide (H2O2; 3%) and phosphate buffered saline (control) for 1 min and the remaining colony forming units counted. Ozone gas was applied to the biofilms in two experimental settings, resembling canal areas either difficult (setting 1) or easy (setting 2) to reach. Time-course experiments up to 10 min were included. To compare the tested samples, data were analysed by one-way anova. Results, Concentrations of gaseous ozone down to 1 g m,3 almost and aqueous ozone down to 5 ,g mL,1 completely eliminated the suspended microorganisms as did NaOCl and CHX. Hydrogen peroxide and lower aqueous ozone concentrations were less effective. Aqueous and gaseous ozone were dose- and strain-dependently effective against the biofilm microorganisms. Total elimination was achieved by high-concentrated ozone gas (setting 2) and by NaOCl after 1 min or a lower gas concentration (4 g m,3) after at least 2.5 min. High-concentrated aqueous ozone (20 ,g mL,1) and CHX almost completely eliminated the biofilm cells, whilst H2O2 was less effective. Conclusion, High-concentrated gaseous and aqueous ozone was dose-, strain- and time-dependently effective against the tested microorganisms in suspension and the biofilm test model. [source] The impact of flow field pattern on concentration and performance in PEMFCINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2005A. Su Abstract In this study, we present a rigorous mathematical model, to treat prediction and analysis of proton exchange membrane fuel cells gas concentration and current density distribution in mass transfer area and chemical reaction area performed in 3-D geometry. The model is based on the solution of the conservation equations of mass, momentum, species, and electric current in a fully integrated finite-volume solver using the CFDRC commercial code. The influences of fuel cell performance with two kinds of flow channel pattern design are studied. The gas concentration of the straight flow pattern appears excessively non-uniform, resulting in a local concentration polarization. On the other hand, the gas concentration is well distributed for the serpentine flow pattern, creating a better mass transfer phenomena. The performance curves (polarization curves) are also well correlated with experimental data. Copyright © 2005 John Wiley & Sons, Ltd. [source] Mineralization improvement of phenol aqueous solutions through heterogeneous catalytic ozonationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2003Fernando J Beltrán Abstract To assess the mineralization level achieved, aqueous solutions of phenol have been treated with ozone in the presence of different solid catalysts. Activated carbon was the principal catalyst investigated, although some additional experiments were carried out by utilizing metal oxide-based catalysts (ie Ti, Co and Fe) supported onto alumina. Usage of Co/Al2O3 led to the highest values of phenol byproduct mineralization, nevertheless some metal leaching was experienced in the process. The operating variables studied when using activated carbon as the catalyst were ozone gas concentration, amount of catalyst added and temperature. Regardless of the catalyst type used, two different ozonation kinetic regimes were observed: (I) an initial period, corresponding to the presence of phenol in solution, characterized by small amounts of dissolved ozone and no improvement of the mineralization degree if comparing catalytic and non-catalytic runs; (II) a second period, free of phenol, in which dissolved ozone accumulated in water and the beneficial effects of catalysts on mineralization were noticed. Experimental data also demonstrated the improvement in oxalic acid elimination in the presence of heterogeneous catalysts. Finally, consumption of ozone per mass of carbon removed, reaction factors and Hatta numbers were also calculated. Copyright © 2003 Society of Chemical Industry [source] Quality Changes of Highbush Blueberries Fruit Stored in CA with Different CO2 LevelsJOURNAL OF FOOD SCIENCE, Issue 4 2009Carolina Duarte ABSTRACT:, Quality changes of blueberries (Vacccinium corymbosum L. cv Brigitta) were evaluated during CA storage (0 °C) with different concentrations of CO2 (5%, 10%, and 15%) combined with 5% O2, respectively. Atmospheric air (20.9% O2+ 0.03% CO2) was used as control. From samples taken at 0, 24, and 48 d of storage, unmarketable fruits and weight loss were recorded as well as color (h), firmness (g), soluble solid content (%), titratable acidity (% citric acid), ratio, and the monomeric anthocyanin content (ppm). At each sampling time, additional units were kept for 3 d at 10 °C to simulate retail holding conditions. Irrespective of gas concentration, 0.9% of the initial fresh weight was lost after 48 d at 0 °C. CA fruit had better quality than control at the 24 d sampling but due to the high number of unmarketable fruits, this advantage was not observed at 48 d at 0 °C. After 24 d of storage, fruits for CA treatments were more firm and had better color, with higher anthocyanin and acidity levels. Soluble solid content showed no significant differences throughout the cold storage period. Residual effect of CA storage was observed at the retail holding condition yielding better firmness, acidity, and ratio. However, the CO2 level tested increased the number of unmarketable fruit in long-term storage (48 d). Response of "Brigitta" blueberries to the different CO2 levels studied was moderate and could be related to the high storage potential of this cultivar. [source] Response Surface Modeling for the Inactivation of Escherichia coli O157:H7 on Green Peppers (Capsicum annuum) by Ozone Gas TreatmentJOURNAL OF FOOD SCIENCE, Issue 3 2002Y. Han ABSTRACT: : The effects of ozone gas concentration (2 to 8 mg/l), relative humidity (RH) (60 to 90%), and treatment time (10 to 40 min) on inactivation of E. coli O157:H7 on green peppers were studied using response surface methodology. A 3-factor Box-Behnken experimental plan was designed and microbial log reduction was measured as a response. The statistical analysis of developed predictive model suggested that ozone gas concentration, RH, and treatment time all significantly (P < 0.01) increased the rate of log reduction of E. coli O157:H7. Among the 3 factors, the effect of ozone gas concentration on bacterial inactivation was the greatest, while the effect of RH was the least. The interaction between ozone gas concentration and RH exhibited a significant and synergistic effect (P < 0.05). [source] Influence of Storage Atmosphere and Temperature on Quality Evolution of Cut Belgian EndivesJOURNAL OF FOOD SCIENCE, Issue 8 2001M.D. Van de Velde ABSTRACT: An optimal combination of O2, CO2, and N2 for storage of cut Belgian Endive was defined, investigating visual quality aspects. In the experimental design, principles of mixture theory were used. The acceptability of cut endives stored under different gas combinations, selected in the range where both CO2 and O2 were varied between 2% and 18%, was evaluated by a consumer panel at different time intervals during storage. The response was modeled with a second-degree polynomial, the response surface pointed in the direction of a gas mixture 10% CO2, 10% O2, and 80% N2 for maximum acceptability or best quality during storage. Repeated experiments, including different varieties from 2 different growers, confirmed the optimal gas concentration, (10% CO2, 10% O2, and 80% N2). In a second step, the effect of temperature on quality degradation of cut endives stored under optimal atmosphere conditions, was quantified using the Arrhenius equation. An activation energy of 16.3 kcal/mol was obtained. [source] Evaluation of different varieties of cauliflower for minimal processingJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 2 2007Susana Sanz Abstract The impact of minimal processing technology on the sensory quality and the growth of micro-organisms in eight varieties of cauliflower packaged in four different films (one PVC and three P-Plus) was measured and quantified during more than 25 days of storage at 4 °C. Other important parameters such as weight loss and gas concentration in the packages were also determined. The composition of the atmosphere in the packages of minimally processed cauliflower depended on both the permeability of the film used for the packaging and the variety of cauliflower. When establishing shelf-life, loss of sensory quality was the deciding factor rather than loss of microbiological quality. The initial microbial load proved more important than the composition of the atmosphere inside the packages. In sensory evaluation the most important aspect was colour. In instrumental evaluation, coordinate b* was the main means of estimating shelf-life. The combination of P-Plus 120 film and varieties of cauliflower of large size and great vigour allowed the atmosphere inside the packages to have an O2 level below 10% and a CO2 level above 10%. That atmosphere composition proved essential for maintaining the sensory quality of minimally processed cauliflower. In these conditions, samples attained a shelf-life of more than 25 days. However, the different behaviours of the cauliflower varieties make it necessary to establish particular packaging conditions. The use of less permeable films than those used in this study, or the use of actively modified atmospheres, could be an alternative for those varieties that require special packaging conditions when processed using this technology. Copyright © 2006 Society of Chemical Industry [source] Metallocene-Catalyzed Gas-Phase Ethylene Copolymerization: Kinetics and Polymer PropertiesMACROMOLECULAR REACTION ENGINEERING, Issue 8 2009Michiel F. Bergstra Abstract The influence of 1-hexene is examined on the kinetics of ethylene copolymerization with a metallocene catalyst in gas phase. A model is derived, which is able to describe a large reaction rate increase due to a small amount of incorporated comonomer. This complexation model describes the measured reaction rates for ethylene and 1-hexene, and the co-monomer incorporation. Polymer properties were analyzed, such as comonomer weight fraction. The density, melting point, and molecular weight of the produced polymer decreased with increase in 1-hexene gas concentration. The in situ 1-hexene sorption is estimated and follows Henry's law, but seems much higher than reported in the literature. [source] Delivery characteristics of a combined nitric oxide nasal continuous positive airway pressure systemPEDIATRIC ANESTHESIA, Issue 6 2002DEAA, R. Lindwall MD Summary Background: Nitric oxide (NO), when inhaled, has a synergistic effect with airway recruitment strategies such as positive endexpiratory pressure (PEEP) or continuous positive airway pressure (CPAP) in improving oxygenation in lung injury. Methods: We modified a commercially available nasal CPAP (nCPAP) system to enable the concomitant delivery of inhaled NO (iNO) and nCPAP to neonates and term babies. Oxygen, NO and nitrogen dioxide (NO2) concentrations were measured, comparing the effects of using 50 or 1000 parts per million (p.p.m.) NO stock gas cylinders. Results: Stable and accurate delivery of iNO was found for both stock gas concentrations. Using a 50 p.p.m. NO stock gas resulted in limited NO2 formation, with a maximum inspired NO2 concentration of , 0.3 p.p.m. (dose range up to 37 p.p.m. iNO), which was interpreted as the result of progressive dilution with nitrogen. In contrast, using a 1000 p.p.m. NO stock gas cylinder, inspired NO2 levels increased nonlinearly as expected with an increasing inspired concentration of NO. Conclusions: Inhaled NO can be safely and reliably delivered by the system we describe. The NO2 levels generated by the system are low, at least up to a dose of 37 p.p.m. NO, regardless of a stock gas concentration of 50 or 1000 p.p.m. NO. Using a 50 p.p.m. NO stock gas concentration, up to 80% oxygen can be given at 10 p.p.m. iNO. [source] Sorption of sulfuryl fluoride by food commoditiesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 8 2008Venkata-rao Sriranjini Abstract BACKGROUND: The use of sulfuryl fluoride, a structural fumigant for termite and woodborer control, has recently been expanded to treating stored food commodities and food facilities. There is, however, a lack of data on the sorption of sulfuryl fluoride by food commodities. Knowledge about sorption is important in the context of effective treatment and residues. RESULTS: When sulfuryl fluoride was applied at a dose of 50 g m,3 to various food commodities (total 68) with 300 g per replicate in 0.75 L gas wash bottles (fumigation chambers) at 25 ± 1 °C, in most cases (81%) the gas concentrations in the free space of the commodities exceeded 50 g m,3 (range 51,80 g m,3) at the end of 24 h exposure. In chambers without the substrate, an average concentration of 49.7 g m,3 was recorded. About 54% of the commodities showed low-level ( , 25%) sorption of sulfuryl fluoride, 34% showed medium-level (26,50%) sorption and only 12% were highly sorptive (>50%). The latter include white oats (terminal gas concentration 17.8 g m,3), some of the decorticated split pulses (24.0,29.3 g m,3), chickpea flour (26.3 g m,3), dried ginger (29.0 g m,3), refined wheat flour (30.3 g m,3) and coriander powder (40.5 g m,3). In unfumigated control commodities, owing to interfering volatiles, Fumiscope® readings in the range 0,13 were noted. CONCLUSION: Sulfuryl fluoride has the advantage of a low or moderate level of sorption with the majority of the food commodities. Copyright © 2008 Society of Chemical Industry [source] GaN-based Schottky diodes for hydrogen sensing in transformer oilPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2006Peter Sandvik Abstract We report the demonstration of robust, GaN-based hydrogen sensors for use directly in transformer oil. These 1 mm2 Schottky diodes were immersed in a closed loop with Voltesso insulating oil for 21 months of continuous testing. They showed good reproducibility in response to hydrogen gases, while exposed to varying temperatures. We will briefly discuss the transformer monitoring application, the device design and fabrication process, and the sensor performance from 21-months of testing. Transfer functions from oil temperature and dissolved gas concentration have been quantified, and those will be briefly discussed. These new sensors offer a novel alternative to electrochemical cell-based sensors for various applications. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Nanofibrous polyaniline thin film prepared by plasma-induced polymerization technique for detection of NO2 gasPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2010Ashutosh Tiwari Abstract A nanofibrous polyaniline (PANI) thin film was fabricated using plasma-induced polymerization method and explored its application in the fabrication of NO2 gas sensor. The effects of substrate position, pressure, and the number of plasma pulses on the PANI film growth rate were monitored and an optimum condition for the PANI thin film preparation was established. The resulting PANI film was characterized with UV,visible spectrophotometer, FTIR, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The PANI thin film possessed nanofibers with a diameter ranging from 15 to 20 nm. The NO2 gas sensing behavior was studied by measuring the change in electrical conductivity of PANI film with respect to NO2 gas concentration and exposure time. The optimized sensor exhibited a sensitivity factor of 206 with a response time of 23 sec. The NO2 gas sensor using nanofibrous PANI thin film as sensing probe showed a linear current response to the NO2 gas concentration in the range of 10,100 ppm. Copyright © 2009 John Wiley & Sons, Ltd. [source] Influence of Iron Ore Indirect Reduction on the Transfer Process in Porous MediaASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2006Ming-Chun Li The solid material used in most metallurgical reactions can be considered as porous media consisting of the accumulated pellets. When the fluid flows through the porous media, various chemical reactions may occur between the fluid and solid matrix which have a significant effect on the transfer process in the porous media. Based on derivation of the overall rate formulation of the representative elementary volume (REV), a mathematical model describing the transfer process in the porous media was established. The model was tested numerically by applying the implicit formulation finite volume method. The predictions were validated by comparison with the experimental results and literature data. For the indirect reduction of iron ores, the influence of the flow rate, the particle size, reaction rate, the dimension of the reactor, and the ratio of the Thielet number to the Peclet number on the distribution of gas concentration and the solid conversion degree were analyzed. [source] Accuracy of flow and sensors of indirect calorimetry for neonates and infants: Using mass spectrometry and a pneumotachogramCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue S4 2002Teruyoshi Amagai Summary 1.,The accuracy of measurements of flow rate and concentrations of O2 and CO2 in expiratory gas by indirect calorimetry (IC) using paediatric and adult circuits were assessed by mass spectrometry and a pneumotachogram, which have been proven as the most reliable instruments for these purposes. 2.,In the paediatric circuit, all measurements were demonstrated to be reliable: error rates for flow rate, O2 concentration and CO2 concentration were +3.13, +2.66 and ,6.63%, respectively. All were within the 10%, which is acceptable as a biological error. 3.,However, in the adult circuit of IC, all measurements were reliable except for measurements of CO2 concentration: error rates for flow rate, O2 concentration and CO2 concentration were +2.82, +1.64 and +11.42%, respectively. 4.,A fluctuation phenomenon of expiratory gas concentration was observed only in IC. Mass spectrometry did not show this phenomenon. This phenomenon seems to be derived from the IC machine itself. [source] Pilot scale SO2 control by dry sodium bicarbonate injection and an electrostatic precipitatorENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2007Michael J. Pilat Abstract A 500 actual cubic feet gas per minute (acfm) pilot-scale SO2 control study was undertaken to investigate flue gas desulfurization (FGD) by dry sodium sorbents in 400°F (204.5°C) flue gases emitted from a coal fired boiler with flue gas concentrations between 350 and 2500 ppm SO2. Powdered sodium alkaline reagents were injected into the hot flue gas downstream of the air preheater and the spent reagents were collected using an electrostatic precipitator. Three different sorbents were used: processed sodium bicarbonate of two particle sizes; solution mined sodium bicarbonate, and processed sodium sesquicarbonate. SO2 concentrations were measured upstream of the reagent injection, 25-ft (7.62 m) downstream of the injection point, and downstream of the electrostatic precipitator. SO2 collection efficiencies ranged from 40 to 80% using sodium bicarbonate stoichiometric ratios from 0.5 to 3.0. Much of the in-duct SO2 removal occurred during the first second of reagent reaction time, indicating that the sulfur dioxide,sodium reaction rates may be faster than have been measured for fixed bed measurements reported in the literature. © 2007 American Institute of Chemical Engineers Environ Prog, 2007 [source] Predicting toxic gas concentrations resulting from enclosure fires using local equivalence ratio concept linked to fire field modelsFIRE AND MATERIALS, Issue 1 2007Z. Wang Abstract A practical CFD method is presented in this study to predict the generation of toxic gases in enclosure fires. The model makes use of local combustion conditions to determine the yield of carbon monoxide, carbon dioxide, hydrocarbon, soot and oxygen. The local conditions used in the determination of these species are the local equivalence ratio (LER) and the local temperature. The heat released from combustion is calculated using the volumetric heat source model or the eddy dissipation model (EDM). The model is then used to simulate a range of reduced-scale and full-scale fire experiments. The model predictions for most of the predicted species are then shown to be in good agreement with the test results. Copyright © 2006 John Wiley & Sons, Ltd. [source] Evaluation of Noble Gas Recharge Temperatures in a Shallow Unconfined AquiferGROUND WATER, Issue 5 2009Bradley D. Cey Water table temperatures inferred from dissolved noble gas concentrations (noble gas temperatures, NGT) are useful as a quantitative proxy for air temperature change since the last glacial maximum. Despite their importance in paleoclimate research, few studies have investigated the relationship between NGT and actual recharge temperatures in field settings. This study presents dissolved noble gas data from a shallow unconfined aquifer heavily impacted by agriculture. Considering samples unaffected by degassing, NGT calculated from common physically based interpretive gas dissolution models that correct measured noble gas concentrations for "excess air" agreed with measured water table temperatures (WTT). The ability to fit data to multiple interpretive models indicates that model goodness-of-fit does not necessarily mean that the model reflects actual gas dissolution processes. Although NGT are useful in that they reflect WTT, caution is recommended when using these interpretive models. There was no measurable difference in excess air characteristics (amount and degree of fractionation) between two recharge regimes studied (higher flux recharge primarily during spring and summer vs. continuous, low flux recharge). Approximately 20% of samples had dissolved gas concentrations below equilibrium concentration with respect to atmospheric pressure, indicating degassing. Geochemical and dissolved gas data indicate that saturated zone denitrification caused degassing by gas stripping. Modeling indicates that minor degassing (<10% ,Ne) may cause underestimation of ground water recharge temperature by up to 2°C. Such errors are problematic because degassing may not be apparent and degassed samples may be fit by a model with a high degree of certainty. [source] A review of recent climate variability and climate change in southeastern AustraliaINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2008Bradley F. Murphy Abstract Southeastern Australia (SEA) has suffered from 10 years of low rainfall from 1997 to 2006. A protracted dry spell of this severity has been recorded once before during the 20th century, but current drought conditions are exacerbated by increasing temperatures. Impacts of this dry decade are wide-ranging, so a major research effort is being directed to better understand the region's recent climate, its variability and climate change. This review summarizes the conditions of these 10 years and the main mechanisms that affect the climate. Most of the rainfall decline (61%) has occurred in autumn (March,May). Daily maximum temperatures are rising, as are minimum temperatures, except for cooler nights in autumn in the southwest of SEA closely related to lower rainfall. A similar rainfall decline occurred in the southwest of western Australia around 1970 that has many common features with the SEA decline. SEA rainfall is produced by mid-latitude storms and fronts, interactions with the tropics through continental-scale cloudbands and cut-off lows. El Niño-Southern Oscillation impacts on SEA rainfall, as does the Indian Ocean, but neither has a direct influence in autumn. Trends have been found in both hemispheric (the southern annular mode) and local (sub-tropical ridge) circulation features that may have played a role in reducing the number and impact of mid-latitude systems around SEA, and thus reducing rainfall. The role of many of these mechanisms needs to be clarified, but there is likely to be an influence of enhanced greenhouse gas concentrations on SEA climate, at least on temperature. Copyright © 2007 Royal Meteorological Society [source] An Arctic and antarctic perspective on recent climate changeINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 3 2007John Turner Abstract We contrast recent climatic and environmental changes and their causes in the Arctic and the Antarctic. There are continuing increases in surface temperatures, losses of sea ice and tundra, and warming of permafrost over broad areas of the Arctic, while most of the major increase in Antarctic temperatures is on the Antarctic Peninsula associated with sea ice loss in the Bellingshausen,Amundsen Seas sector. While both natural atmospheric and oceanic variability, and changes in external forcing including increased greenhouse gas concentrations, must be considered in the quest for understanding such changes, the interactions and feedbacks between system components are particularly strong at high latitudes. For the 1950s to date in the Arctic and for 1957 to date in the Antarctic, positive trends in large-scale atmospheric circulation represented by the Arctic oscillation (AO) and Antarctic oscillations (AAO) and the Pacific North American (PNA) pattern contribute to the long-term temperature trends. However, continuing Arctic trends during the last decade of near neutral AO will require alternate explanations. The trend in the AAO since 1950 is larger than expected from natural variability and may be associated with the decrease in stratospheric ozone over Antarctic. The persistence shown in many Arctic and Antarctic Peninsula components of climate and their influence through possible feedback supports continuation of current trends over the next decade. One can expect large spatial and temporal differences, however, from the relative contributions of intrinsic variability, external forcing, and internal feedback/amplifications. It is particularly important to resolve regional feedback processes in future projections based on modeling scenarios. Copyright © 2006 Royal Meteorological Society. [source] Transient climate simulation forced by natural and anthropogenic climate forcingsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 6 2002Cédric Bertrand Abstract Numerical experiments have been carried out with a two-dimensional sector-averaged global climate model coupled to a diffusive ocean in order to assess the potential impact of four hypothesized mechanisms of decadal to century-scale climate variability, both natural and anthropogenically induced: (1) solar variability; (2) variability in volcanic aerosol loading of the atmosphere; (3) anthropogenic increase of sulphate aerosols' concentration; (4) anthropogenic increase of greenhouse gas concentrations. Our results suggest that neither the individual responses nor the combined natural or anthropogenic forcings allow one to reproduce all of the recorded major temperature fluctuations since the latter half of the 19th century. They show that these temperature variations are the result of both naturally driven climate fluctuations and the effects of industrialization. By contrast, the dominant cause of decade-to-century-scale variability of the 21st century is likely to be changes in atmospheric trace-gas concentrations. Indeed, when the solar, volcanic, and tropospheric aerosols forcings used in our experiments are extended into the future, they are unable to counter the expected greenhouse warming. Copyright © 2002 Royal Meteorological Society. [source] Exposure to anaesthetic trace gases during general anaesthesia: CobraPLA vs.ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 7 2010LMA classic Background: To prospectively investigate the performance, sealing capacity and operating room (OR) staff exposure to waste anaesthetic gases during the use of the Cobra perilaryngeal airway (CobraPLA) compared with the laryngeal mask airway classic (LMA). Methods: Sixty patients were randomly assigned to the CobraPLA or the LMA group. Insertion time, number of insertion attempts and airway leak pressures were assessed after induction of anaesthesia. Occupational exposure to nitrous oxide (N2O) and Sevoflurane (SEV) was measured at the anaesthetists' breathing zone and the patients' mouth using a photoacoustic infrared spectrometer. Results: N2O waste gas concentrations differed significantly in the anaesthetist's breathing zone (11.7±7.2 p.p.m. in CobraPLA vs. 4.1±4.3 p.p.m. in LMA, P=0.03), whereas no difference could be shown in SEV concentrations. Correct CobraPLA positioning was possible in 28 out of 30 patients (more than one attempt necessary in five patients). Correct positioning of the LMA classic was possible in all 30 patients (more than one attempt in three patients). Peak airway pressure was higher in the CobraPLA group (16±3 vs. 14±2 cmH2O, P=0.01). The average leak pressure of the CobraPLA was 24±4 cmH2O, compared with 20±4 cmH2O of the LMA classic (P<0.001; all values means±SD). Conclusion: Despite higher airway seal pressures, the CobraPLA caused higher intraoperative N2O trace concentrations in the anaesthetists' breathing zone. [source] Impact of dietary crude protein and amino acids status on performance and some excreta characteristics of broiler chicks during 10,28 days of ageJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 3 2010N. F. Namroud Summary A study was conducted in a completely randomised design to evaluate the effects of providing almost all important essential amino acids (EAA) in low-crude protein (CP) diets equal to that of higher CP diets in broiler chickens. Also the effects of additional mixture of glycine (Gly) and glutamic acid (Glu) or supplementation of excess EAA to low-CP diets on the live performance and excreta characteristics including pH, moisture, nitrogen, uric acid and ammonia concentration were measured to ascertain the optimum CP concentration for the maximum performance and reduced excreta ammonia concentration. Male, broiler chickens growing from 10 to 28 days of age were fed eight experimental diets. Reducing dietary CP below 19% negatively affected performance. Adding the Gly and Glu mixtures to 17% CP diets improved live performance. Reducing CP to 19% with a normal amino acids status declined N, ammonia, uric acid, moisture and pH of excreta significantly. These findings suggest that diminishing dietary CP from 23% to 19% while maintaining adequate EAA levels during 10,28 days of age results in not only a significant decline in N emission, but also a probable reduction in the NH3 volatilisation because of reduction in pH and moisture. Contrary to expectations, reduction of dietary CP below the minimum level (19%) resulted in more ammonia. All these factors may improve on litter and air quality within the housing facility and reduce the ventilation rate required to emit the elevated ammonia gas concentrations. [source] Carbon-based stock feed additives: a research methodology that explores ecologically delivered C biosequestration, alongside live weights, feed use efficiency, soil nutrient retention, and perennial fodder plantationsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 2 2010Mark P McHenry Abstract There is considerable interest in reliable and practical methods to sequester carbon (C) into agricultural soils to both reduce atmospheric greenhouse gas concentrations and improve conventional productivity. This article outlines a research methodology to refine the efficacy and economics of using long-lived C species (biochars) as stock feed additives, produced from farm waste biomass, for ecologically delivered soil biosequestration, while generating renewable bioenergy. This article also draws attention to potential parallel outputs including annual feed use efficiency, fodder species expansion, soil nutrient retention, aquatic habitat protection, and forestry revegetation, using nitrogen-fixing perennial fodder plant species. A methodology to generate parallel results including standing fodder tree C sequestration, optimised production of Acacia spp. biochar, animal growth on high-tannin fodder with biochar feed additives, soil nutrient and stable C fractions, and economics of Acacia spp. bioenergy production. This form of research is contextually dependent on the regional agricultural production system, legislation, and surrounding ecosystem. Therefore, this article suggests the use of a scenario approach to include regionally specific levels of biochar integration with respect to the local prices for C, fossil fuels, meat and livestock, fertilisers, fodder, feed additives, water, renewable energy, revegetation and capital. Copyright © 2009 Society of Chemical Industry [source] Control of internal browning and quality improvement of ,Fuji' apples by stepwise increase of CO2 level during controlled atmosphere storageJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 5 2005Hun-Sik Chung Abstract To control internal browning injury and to reduce quality loss in ,Fuji' apples during storage, a stepwise controlled atmosphere (CA) method was applied in this study. Both non-bagged and bagged apples during maturation were stored at 0 °C under 1% O2 + 1% CO2, 1% O2 + 3% CO2 or air for 10 months, and 1% O2 + 1% CO2 for 2 months followed by 1% O2 + 3% CO2 for 8 months (stepwise CA). The concentrations of internal ethylene and carbon dioxide in apples kept for 24 h at 20 °C after storage under CA conditions were maintained at low level, but there was no effect of stepwise CO2 increase on internal gas concentrations. The non-bagged and bagged apples stored under stepwise CA were not significantly different from those stored under 1% O2 + 3% CO2 continuously for 10 months in term of flesh firmness, titratable acidity and yellowing index. However, the apples stored under stepwise CA were firmer, more acid and greener than those stored under 1% O2 + 1% CO2 continuously for 10 months. Internal browning injury occurred in apples stored under 1% O2 + 3% CO2 continuously for 10 months, but it was suppressed completely by stepwise CA storage. The stepwise CA, increasing of CO2 level after holding at 1% CO2 for the first 2 months of storage, was effective in maintaining the quality and controlling the internal browning injury in non-bagged and bagged ,Fuji' apples. Copyright © 2005 Society of Chemical Industry [source] A research on determination of explosive gases utilizing cataluminescence sensor arrayLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 4-5 2005Xiaoan Cao Abstract In this paper, we propose a model of a sensor array system, which consists of three cataluminescence sensors based on nanosized SrCO3, , -Al2O3 and BaCO3 as catalysts, for quantitative analysis of the explosive gases of propane, n -butane and iso-butane in a mixture. Six linear regression equations of the cataluminescence intensity vs. the gas concentrations in the range 2000,10 000 ppm were established from the sensor array system at two working temperatures, as the explosive gases show different sensitivity to the three sensors. The least squares method was employed for solving the simultaneous equations and quantifying the concentrations of the three components. The detection limits (3,) of propane, n -butane and iso-butane on SrCO3, , -Al2O3 and BaCO3 sensors are 50, 40 and 20 ppm, 80, 60 and 40 ppm, and 20, 10 and 5 ppm, respectively. The concentrations of two artificial samples containing the tertiary mixture were analysed with satisfactory results. Copyright © 2005 John Wiley & Sons, Ltd. [source] Petrology and chemistry of the new shergottite Dar al Gani 476METEORITICS & PLANETARY SCIENCE, Issue 1 2000J. ZIPFEL The meteorite is classified as a basaltic shergottite and is only the 13th martian meteorite known to date. It has a porphyritic texture consisting of a fine-grained groundmass and larger olivines. The groundmass consists of pyroxene and feldspathic glass. Minor phases are oxides and sulfides as well as phosphates. The presence of olivine, orthopyroxene, and chromite is a feature that DaG 476 has in common with lithology A of Elephant Moraine (EET) A79001. However, in DaG 476, these phases appear to be early phenocrysts rather than xenocrysts. Shock features, such as twinning, mosaicism, and impact-melt pockets, are ubiquitous. Terrestrial weathering was severe and led to formation of carbonate veins following grain boundaries and cracks. With a molar MgO/(MgO + FeO) of 0.68, DaG 476 is the most magnesian member among the basaltic shergottites. Compositions of augite and pigeonite and some of the bulk element concentrations are intermediate between those of lherzolitic and basaltic shergottites. However, major elements, such as Fe and Ti, as well as LREE concentrations are considerably lower than in other shergottites. Noble gas concentrations are low and dominated by the mantle component previously found in Chassigny. A component, similar to that representing martian atmosphere, is virtually absent. The ejection age of 1.35 ± 0.10 Ma is older than that of EETA79001 and could possibly mark a distinct ejection. Dar al Gani 476 is classified as a basaltic shergottite based on its mineralogy. It has a fine-grained groundmass consisting of clinopyroxene, pigeonite and augite, feldspathic glass and chromite, Ti-chromite, ilmenite, sulfides, and whitlockite. Isolated olivine and single chromite grains occur in the groundmass. Orthopyroxene forms cores of some pigeonite grains. Shock-features, such as shock-twinning, mosaicism, cracks, and impact-melt pockets, are abundant. Severe weathering in the Sahara led to significant formation of carbonate veins crosscutting the entire meteorite. Dar al Gani 476 is distinct from other known shergottites. Chemically, it is the most magnesian member among known basaltic shergottites and intermediate in composition for most trace and major elements between Iherzolitic and basaltic shergottites. Unique are the very low bulk REE element abundances. The CI-normalized abundances of LREEs are even lower than those of Iherzolitic shergottites. The overall abundance pattern, however, is similar to that of QUE 94201. Textural evidence indicates that orthopyroxene, as well as olivine and chromite, crystallized as phenocrysts from a magma similar in composition to that of bulk DaG 476. Whether such a magma composition can be a shergottite parent melt or was formed by impact melting needs to be explored further. At this time, it cannot entirely be ruled out that these phases represent relics of disaggregated xenoliths that were incorporated and partially assimilated by a basaltic melt, although the texture does not support this possibility. Trapped noble gas concentrations are low and dominated by a Chassigny-like mantle component. Virtually no martian atmosphere was trapped in DaG 476 whole-rock splits. The exposure age of 1.26 ± 0.09 Ma is younger than that of most shergottites and closer to that of EETA79001. The ejection age of 1.35 ± 0.1 Ma could mark another distinct impact event. [source] Delivery characteristics of a combined nitric oxide nasal continuous positive airway pressure systemPEDIATRIC ANESTHESIA, Issue 6 2002DEAA, R. Lindwall MD Summary Background: Nitric oxide (NO), when inhaled, has a synergistic effect with airway recruitment strategies such as positive endexpiratory pressure (PEEP) or continuous positive airway pressure (CPAP) in improving oxygenation in lung injury. Methods: We modified a commercially available nasal CPAP (nCPAP) system to enable the concomitant delivery of inhaled NO (iNO) and nCPAP to neonates and term babies. Oxygen, NO and nitrogen dioxide (NO2) concentrations were measured, comparing the effects of using 50 or 1000 parts per million (p.p.m.) NO stock gas cylinders. Results: Stable and accurate delivery of iNO was found for both stock gas concentrations. Using a 50 p.p.m. NO stock gas resulted in limited NO2 formation, with a maximum inspired NO2 concentration of , 0.3 p.p.m. (dose range up to 37 p.p.m. iNO), which was interpreted as the result of progressive dilution with nitrogen. In contrast, using a 1000 p.p.m. NO stock gas cylinder, inspired NO2 levels increased nonlinearly as expected with an increasing inspired concentration of NO. Conclusions: Inhaled NO can be safely and reliably delivered by the system we describe. The NO2 levels generated by the system are low, at least up to a dose of 37 p.p.m. NO, regardless of a stock gas concentration of 50 or 1000 p.p.m. NO. Using a 50 p.p.m. NO stock gas concentration, up to 80% oxygen can be given at 10 p.p.m. iNO. [source] Sorption of sulfuryl fluoride by food commoditiesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 8 2008Venkata-rao Sriranjini Abstract BACKGROUND: The use of sulfuryl fluoride, a structural fumigant for termite and woodborer control, has recently been expanded to treating stored food commodities and food facilities. There is, however, a lack of data on the sorption of sulfuryl fluoride by food commodities. Knowledge about sorption is important in the context of effective treatment and residues. RESULTS: When sulfuryl fluoride was applied at a dose of 50 g m,3 to various food commodities (total 68) with 300 g per replicate in 0.75 L gas wash bottles (fumigation chambers) at 25 ± 1 °C, in most cases (81%) the gas concentrations in the free space of the commodities exceeded 50 g m,3 (range 51,80 g m,3) at the end of 24 h exposure. In chambers without the substrate, an average concentration of 49.7 g m,3 was recorded. About 54% of the commodities showed low-level ( , 25%) sorption of sulfuryl fluoride, 34% showed medium-level (26,50%) sorption and only 12% were highly sorptive (>50%). The latter include white oats (terminal gas concentration 17.8 g m,3), some of the decorticated split pulses (24.0,29.3 g m,3), chickpea flour (26.3 g m,3), dried ginger (29.0 g m,3), refined wheat flour (30.3 g m,3) and coriander powder (40.5 g m,3). In unfumigated control commodities, owing to interfering volatiles, Fumiscope® readings in the range 0,13 were noted. CONCLUSION: Sulfuryl fluoride has the advantage of a low or moderate level of sorption with the majority of the food commodities. Copyright © 2008 Society of Chemical Industry [source] | ||||||||||||||||||||||||||||||||||