Abstract  OBJECTIVE: This article reviews panel studies of air pollution on children's respiratory health and proposes future research directions.

METHODS: The PubMed electronic database was used to search published original epidemiological studies in peer-reviewed journals from 2000 to November 2011. Children's age was limited to ≤18 years old. A total of 33 relevant articles were obtained, with 20 articles relating to lung function, 21 articles relating to respiratory symptoms, and 8 articles examining both.

RESULTS: Most studies suggested the adverse effects of air pollution on children's lung function and respiratory symptoms. Particles and NO(2) showed more significant results, whereas effects of SO(2) were not consistent. A few studies indicated that O(3) interacted with temperature and sometimes seemed to be a protective factor for children's respiratory health. Negative associations between air pollutants and pulmonary health were more serious in asthmatic children than in healthy subjects. However, many outcomes depended on the number of lag days. Peak expiratory flow (PEF) was the most usual measurement for children's lung function, followed by forced expiratory volume in 1 second (FEV(1)).

CONCLUSIONS: There are significant adverse effects of air pollution on children's pulmonary health, especially for asthmatics. Future studies need to examine the lag effects of air pollution on children's lung function and respiratory symptoms. Ambient temperature is predicted to change worldwide due to climate change, which will threaten population health. Further research is needed to examine the effects of ambient temperature and the interactive effects between air pollution and ambient temperature on children's lung function and respiratory symptoms.

Abstract  Injection pressure and hydraulic nozzle flow rate are significant parameters that influence mixture formation and combustion in the direct injection (DI) diesel combustion process. An injection pressure increase enhances mixture formation as well as combustion. Decreasing the hydraulic flow rate, by means of reducing spray hole orifice diameter, affects mixture formation primarily through improved gas entrainment processes. Both injection pressure increase and hydraulic flow rate decrease therefore benefit mixture formation and combustion, which cause less soot emissions. Thus, the application of higher exhaust gas recirculation rates to decrease nitrogen oxide emissions is possible. The objective of this paper is to determine the effects of hydraulic flow rate variation in combination with very high injection pressures.

Engine tests are carried out using a single-cylinder research engine, which is based on a light-duty DI diesel engine. With a displacement of 755 cm(3) per cylinder, the engines range between typical passenger car (approximate to 500 cm(3)) and medium-sized heavy-duty (approximate to 1000 cm(3)) engines. The engine is equipped with a prototype common rail fuel injection system that is capable of delivering system pressures larger than 250MPa. Four different hydraulic nozzle layouts are tested. The effects are presented for one part load and one full load operating condition. For each engine operating point, exhaust gas recirculation variations with different injection pressure levels and boost conditions are conducted. Evaluation of engine test results is performed at a constant soot/nitrogen oxide emission ratio of 1:10, which is relevant in engine calibration. Hydraulic measurements and the application of an empirical spray model support the interpretation of the engine test results.

It is observed that a reduced hydraulic flow rate is beneficial for part load emission performance. It was found that a lower hydraulic flow rate causes a higher mean relative air/fuel ratio within the fuel spray and thus induces less soot formation. Moreover, the premixed fraction of combustion is enhanced through both injection pressure and hydraulic flow rate increases. In full load operation, the beneficial effect of reduced flow rates by means of smaller nozzle orifices cannot be detected. Parameters such as injection duration, combustion duration and spray momentum during spray/wall interaction are identified as more important. Boost pressure variation has only a minor effect on part load, whereas full load results are greatly influenced. In part load and full load operation, a limitation of the potential to reduce emissions is not observed within the investigated injection pressure range.

Abstract  Kinetics and products of the interaction of HONO with solid films of Al2O3 were investigated under dark and UV irradiation conditions using a low pressure flow reactor (1-10 Torr) combined with a modulated molecular beam mass spectrometer for monitoring of the gaseous species involved. The reactive uptake of HONO to Al2O3 was studied as a function of HONO concentration ([HONO](0)=(0.6-3.5) x 10(12) molecule cm(-3)), relative humidity (RH=1.4 x 10(-4) to 35.4%), temperature (T=275-320 K) and UV irradiation intensity (J(NO2)=0.002-0.012s(-1)). The measured reactive uptake coefficient was independent of the HONO concentration and temperature. In contrast, the relative humidity (RH) was found to have a strong impact on the uptake coefficient: gamma=4.8 x 10(-6) (RH)(-6.61) and gamma=1.7 x 10(-5) (RH)(-0.44) under dark conditions and on irradiated surface (J(NO2)=0.012 s(-1)), respectively (gamma calculated with BET surface area, 30% conservative uncertainty). NO2 and NO were observed as products of the HONO reaction with Al2O3 surface with yields of 40 +/- 6 and 60 +/- 9%, respectively, independent of relative humidity, temperature, concentration of HONO and UV irradiation intensity under experimental conditions used. The HONO uptake on mineral aerosol (calculated with uptake data for HONO on Al2O3 surface) appears to be of minor importance compared with other HONO loss processes in the boundary layer of the earth atmosphere. (C) 2012 Elsevier B.V. All rights reserved.

Abstract  The objective of this work was to evaluate the potential of using reflectance and fluorescence sensors to assess the levels of N-NO3- in the petiole, plant biomass production and yield of cotton. A randomized complete block design was used in a 3x4 factorial arrangement, with four replicates. Treatments consisted of three cotton varieties (ST- 4288-B2RF, ST-4498-B2RF and DP-164-B2RF) and of four N rates (0, 45, 90 and 135 kg ha(-1)). At 120 days after sowing, readings were done with optical sensors for canopy fluorescence and reflectance. There were no significant correlations for N-NO3- in the petiole with the reflectance sensor indices; however, there was correlation to biomass production (0.39) and yield (0.32 to 0.41). The fluorescence sensor indices were significantly correlated to N-NO3- in the petiole (0.34 to 0.61), biomass production (0.30 to 0.53) and yield (0.34). Compared to the reflectance indices, the fluorescence ones have a greater ability to assess the levels of N-NO3- in the petiole, a similar ability to detect variation of plant biomass, and a lower ability to detect the variation in cotton yield when increasing rates of nitrogen are applied.

Abstract  ROUKOS, Ch., C. PAPANIKOLAOU, I. MOUNTOUSIS, S. KANDRELIS and F. CHATZITHEODORIDIS, 2011. Soil property variations in relation to plant community and altitudinal zone in the rangelands of Epirus, Greece. Bulg. J. Agric. Sci., 17: 806-815 Epirus is a mountainous area in northwest Greece. Most of the rangelands extended there are overgrazed and eroded. This study was performed in order to assess soil property variations along with the dominant plant communities, the altitudinal zone and their interaction in the Preveza Prefecture grasslands in Epirus. Forty-eight field sites, with a west-southwest aspect divided into three different altitudinal zones, representing the typical rangeland conditions of this area were selected. These rangelands, based on the dominant species, were grouped into six plant communities (Bromus - Hordeum, Festuca - Lotus, Asphodelus, Pteridium, Phlomis, and Quercus). Therefore, four representative soil samples from the surface layer were collected from each plant community area for the purposes of the experiment. Soil texture, organic matter, electrical conductivity, pH, active Ca, NO3-N, available P, exchangeable K, Cd, and Pb were analyzed and estimated. Soil texture showed significant differences among altitudinal zones, while soil organic matter, electrical conductivity, pH, active Ca, NO3-N, available P, exchangeable K, Cd, and Pb presented significant differences among plant communities. The results of this study showed that the soil's physical and chemical properties are significantly affected by the altitudinal zone, although plant communities significantly affected mostly the soil's chemical properties, indicating that each plant community created its own soil micro environmental conditions.

Abstract  This paper aims to advance regional worldwide source receptor relationships, providing fate factors for acidifying and eutrophying air emissions (NOx, HNO3, SO2, SO4 and NH3) to be used within life cycle impact assessment. A simulation for the reference year 2005 of the three-dimensional global scale tropospheric GEOS-Chem model was used as the basis of a novel methodological approach to derive source receptor matrices (SRMs) whose elements are fate factors at a global 2 degrees x 2.5 degrees grid. This new approach makes it possible to assess the impact of transboundary emissions while maintaining regional scale emission differentiation. These 2 degrees x 2.5 degrees grid resolution fate factors were later aggregated at continental and country resolutions using emission weighting. Continental fate factor results showed that 50-70% of nitrogen oxides (NOx, HNO3) and sulfur oxides (SO2, SO4) and approximately 80% of ammonia (NH3) emissions will deposit on the same continent. Results showed that the developed fate factor derivation approach was within a +/-10% agreement with GEOS-Chem simulations in which fate factors were determined by withdrawing the regional emission inventory over Canada and in +/-50% agreement with current state-of-the-art LCIA fate factors (calculated with the European Monitoring and Evaluation Programme (EMEP) model). The SRMs outlined in this paper facilitate further modeling developments without having to run the underlying tropospheric model, thus opening the door to the assessment of the regional life cycle inventories of a global economy. (C) 2012 Elsevier Ltd. All rights reserved.

Abstract  Carbon nanotubes (CNTs) have excellent mechanical and electrical properties than conventional materials (carbon black and glass fibers), and are promising candidates as reinforcement material for composites. Formation of electrical conductive with effective dispersion of filler remains a main challenge in the polymer matrix and fillers in order to achieve a good electrical conductivity. Therefore, one of the solutions is to functionalize through wet oxidation of the CNTs besides adding surfactants or assisted liquids. Functionalization of CNTs involves the generation of chemical moieties on their surface that can improve the solubility and processibility. Any functionalization that is undertaken must preferably not influence other key properties such as strength and electrical conductivity of the nano-composite. The matrix used in this study was epoxy and reinforcement filler was multi-walled carbon nanotubes (MWCNTs). MWCNTs were treated with sulfuric acid and nitric acid at 3:1 (v/v) ratio. The present of functional groups on CNTS were investigated using Fourier Transform Infrared (FT-IR). Different weight percentages of MWCNTs (functionalized and as produced) / epoxy composite were prepared. The electrical conductivity of fiinctionalized MWCNTs nanocomposites and as produced MWCNTs nanocomposites were measured by the four point probe. Dispersion state of CNTs in epoxy matrix was observed on fractured surface by scanning electron microscopic. Functionalized CNTs gave better dispersion stability in solvents than non-functionalized CNTs. As expected, non- functionalized CNTs (as produced MWCNTs) are not dispersed at all in all the solvents. However, functionalized CNTs composites give low electrical conductivity. Defects from acid treatment are assumed will damage the original chirality of as produced CNTs and give unbalance polarization on the CNTs, which are the reasons for no formation of conductive pathway networks of acid treated CNTs under electric field.

Abstract  Nitroxyl, or HNO, is involved in a number of important physiological processes, such as vascular relaxation and neuroregulation. Effective imaging tools are required in order to gain a deeper understanding of the in vivo mechanisms of these processes and to identify the endogenous sources of HNO. Here, we further investigate the physical properties of our previously reported fluorescent nitroxyl sensor, [Cu(BOT1)Cl]Cl (J. Am. Chem. Soc. 2010, 132,5536; BOT1 = BODIPY. triazole, a tetradentate ligand). A new high-yielding synthetic procedure for BOT1 is reported. The X-ray crystal structures of two Cu(II) complexes of BOT1 are described. These structural studies show that the BOT1 ligand can form Cu(II) coordination complexes of both square-pyramidal and trigonal-bipyramidal geometries. Cyclic voltammograms of [Cu(BOT1)Cl]Cl were acquired, revealing the presence of a quasi-reversible feature at 130 mV (vs the ferrocene/ferrocenium couple) in MeCN and at -40 mV (vs Ag/AgCl) in aqueous buffer, which is assigned to the Cu-II/Cu-I couple. The reactivity of [Cu(BOT1)Cl]Cl with Angeli's salt, a stable source of HNO, was further investigated. A 1000-fold excess of Angeli's salt elicits an immediate 10-fold emission turn-on response of the sensor, consistent with our previous report. A new observation, reported here, is that the intensity of this turn-on emission diminishes at longer incubation times. Fluorescent imaging of nitroxyl by [Cu(BOT1)Cl]Cl in HeLa cells was carried out Upon treatment of the cells with Angeli's salt, there was a modest 2-fold intracellular turn-on in emission intensity. (C) 2012 Elsevier Inc. All rights reserved.

Abstract  Hantavirus pulmonary syndrome (HPS), also referred to as hantavirus cardiopulmonary syndrome (HCPS), is a rare but frequently fatal disease caused by New World hantaviruses. In humans HPS is associated with severe pulmonary edema and cardiogenic shock; however, the pathogenesis of this disease remains unclear largely due to a lack of suitable animal models for the study of disease progression. In this study we monitored clinical, virological, pathophysiological parameters and host immunological responses to decipher pathological factors and events in the lethal Syrian hamster model of HPS following intranasal inoculation of Andes virus. Transcriptional profiling of the host gene responses demonstrated a suppression of innate immune responses in most organs analyzed during the early stage of infection, except for in the lung which had low level activation of several pro-inflammatory genes. During this phase Andes virus established a systemic infection in hamsters, with viral antigen readily detectable in the endothelium of the majority of tissues analyzed by 7-8 days post-inoculation. Despite wide-spread infection, histological analysis confirmed pathological abnormalities were almost exclusively found in the lungs. Immediately preceding clinical signs of disease, intense activation of pro-inflammatory and Th1/Th2 responses were observed in the lungs as well as the heart, but not in peripheral organs, suggesting that localized immune-modulations by infection is paramount to pathogenesis. Throughout the course of infection a strong suppression of regulatory T-cell responses was noted and is hypothesized to be the basis of the aberrant immune activations. The unique and comprehensive monitoring of host immune responses to hantavirus infection increases our understanding of the immuno-pathogenesis of HPS and will facilitate the development of treatment strategies targeting deleterious host immunological responses.

Abstract  The fossil fuel and bio-fuel burning in a developing country like India can have a significant impact on global climate. In the current work, we have set-up a more realistic, accurate and spatially distributed, all India, NOx emissions from different fuel combustion and industrial activities at 1 degrees x1 degrees grid resolution by incorporating the most recently available micro-level activity data as well as country specific emission factors (EFs) at high resolution. The emission scenarios and their trends are studied in a comprehensive way for approximately 593 districts (sub-region) in India. We have developed three scenarios to construct the possible range of past and present NOx emissions using Geographical Information System (GIS) based methodology. The total NOx emissions are estimated to be 2 952 Giga gram (Gg)/yr, 4 487 Gg/yr and 7 583 Gg/yr for three different base years, i.e., 1991, 2001 and 2011. NOx emission trends in India during 1990s and 2000s due to different major anthropogenic activities are estimated and their growth is discussed. A strong growth of NOx is found during 2000s as compared to 1990s. All major cities remain as top emitters of NOx. The present work depicts that the contribution of fossil fuel will gradually increase in coming years and will be around 91% by 2011. The present new gridded emission inventory will be very useful as an input to Chemical Transport Modeling study over Indian geography. (c) Author(s) 2012. This work is distributed under the Creative Commons Attribution 3.0 License.

Abstract  The solution behavior of dopants, Si, La, and N, in HfO2 polymorphs, monoclinic, tetragonal, and cubic was investigated by using a first principles calculation based on density functional theory within the local density approximation. It was found that the Si and La solutions are more preferable under oxidization atmosphere than reduction atmosphere, and the most efficient nitridation condition for the HfO2 is NO/NO2 atmosphere. By comparing the energy difference between the monoclinic and the tetragonal phases, it was found that the energy difference is decreased by the Si or La doping, whereas influence of the N doping is small, indicating that the phase transition from the monoclinic to tetragonal phase would be enhanced by the Si or La doping. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4755797]

Abstract  Dairy slurry is an important plant nutrient source. However, mismanagement (e.g. high application rate) can lead to nutrient losses to the wider environment. There are few data on slurry management and its effect on nitrogen (N) losses specific to Southern Chile, although existing studies suggest that N leaching on volcanic Chilean soils might be expected to be low. The objective of this study was to evaluate the effect of heavy dairy slurry application on N leaching losses and compare it with an inorganic fertiliser on a volcanic soil of Southern Chile. A field experiment was carried out at the Agricultural Research Institute, Remehue Research Centre, on a volcanic soil of Southern Chile (40 degrees 35'S, 73 degrees 12'W) from March 2008 to March 2010. There were two N application treatments, with a target application rate of 400 kg N ha(-1) yr(-1) as either dairy slurry (S) or urea (U) split into four even applications over the year. Additionally, a control (C) treatment with no N addition was included. N leaching was measured using ceramic suction cups (3 per plot), with samples taken every 100 mm of drainage during the drainage season. Despite the high N rate and application time, N leaching losses were small with no significant differences between treatments in either year (P>0.05). Concentrations of NO3--N for each sampling period never exceeded c. 5.5 mg L-1 and annual mean values were below 0.5 mg L-1 for all treatments. Cumulative N leaching losses were small at 1.4 and 1.2 kg ha(-1) yr(-1) (C), 2.8 and 4.2 kg ha(-1) yr(-1) (S) and 2.4 and 3.3 kg ha(-1) yr(-1) (U) for 2008 and 2009, respectively. We suggest that this could be explained mainly by the unique N retention properties of volcanic soils in Southern Chile and/or gaseous N losses. (C) 2012 Elsevier B.V. All rights reserved.

Abstract  Acetohydroxamic acid (AHA) is an important complexant/reductant for Pu(IV) in the UREX process. It decomposes in the presence of nitric acid. In literature, its decomposition kinetics in nitric acid is traditionally reported as pseudo-first order reaction. In this study, new experimental data were reported for kinetics experiments under wide consecration conditions. It was found that the decomposition reaction was first order with respect to both the components hence overall second order.

Abstract  Sulfate and nitrate records from 5 ice cores spread across Svalbard were compared and revealed strong temporal similarities with previously published global estimates of SO2 and NOx anthropogenic emissions during the 20th century. A significant departure from the early century sulfate and nitrate levels was evident at all drilling sites starting from the mid-1940s. A steady increase was observed in both sulfate and nitrate profiles at most sites until the late 1960s, when the annual concentrations started to increase at a higher rate. This peak activity lasted for about a decade, and was observed to decrease steadily from the early 1980s on, when sulfate levels declined significantly and when nitrate levels finally reached sulfate levels for the first time in 20th century. The timing of these trends in Svalbard with global SO2 and NOx concentration profiles was best appraised when considering composite concentration profiles of all Svalbard ice cores for sulfate and nitrate, respectively. Composite profiles were also found to provide a convenient mean for distinguishing between the most important world source regions. Based on correlation analysis, the major pollutant sources appeared to be Western Europe and North America for both sulfate and nitrate, followed by Central Europe and former U.S.S.R. in generally similar proportions.

Abstract  In this investigation, the Tai-Chi swirl generator (TCSG) was utilized to modulate the flame behaviors behind a traditional nozzle. This novel TCSG nozzle significantly increases combustion intensity, saves energy, and reduces carbon production. The TCSG was installed at the exit of a traditional combustor. The axial momentum of the central fuel-jet is transformed to the radial momentum when the fuel jet passes through the TCSG and then the turbulence intensity is increased. The flame modes, flame length, temperature distribution, combustion intensity, and concentrations of exhausted gases are determined using the direct photography, thermal couple, and gas-concentration analyzer. The experimental results indicate that the flame fields include six flame modes-jet-flame, flickering-flame, recirculated-flame, lazy-eight flame, swirling-flame, and lifted flame modes. The normalized flame height of 4.38 behind the TCSG is approximately 56% lower than that of 10 behind the pure-jet nozzle. The total combustion intensity behind the TCSG is 38% higher than that behind the pure-jet nozzle. The peak concentrations of exhausted nitric-oxide (61 ppm) and propane (0.4%) behind the TCSG are about 67% and 95% lower than those of 190 ppm and 8.7% behind the pure-jet nozzle. Namely, the higher turbulence intensity behind the TCSG results in a higher air/fuel ratio behind the TCSG, and therefore a higher combustion intensity is carried out.

Abstract  Papain is employed to pre-digest and homogenize fish slurries which are directly placed on a tungsten coil atomizer and digested in situ with an oxidizing mixture of HNO3 and H2O2. Both Cs and Sr are determined in different fish samples by tungsten coil atomic emission spectrometry (WCAES) with limits of detection of 0.07 and 0.15 mu g l(-1), respectively. Sample aliquots of 50 mu l are dried, digested/pyrolyzed and atomized using a 400 W miniature solid-state constant current power supply and a Visual Basic temperature control program. The portable WCAES instrumental setup is composed of a small metallic atomization cell, a 2.54 cm diameter fused silica lens and a hand-held charge coupled device-based spectrometer. Tungsten filaments extracted from 24 V, 250 W commercially available light bulbs are used as atomizers. The method accuracy is demonstrated by comparing WCAES results with values obtained by ICP OES. No statistically significant differences are observed between the results from each different method at a 95% confidence level. Recovery tests are also carried out for Cs and values between 100 and 110% are obtained. The method precision is calculated to be 6.8 and 7.3% for 2.5 mu g l(-1) of Cs and 100 mu g l(-1) of Sr (n = 10), respectively. The method described is simple, fast and efficient, offering an interesting alternative for applications in food safety control and determinations in the field.

Abstract  Effect of nitric oxide (NO) in mitigating stress induced by arsenic (As) was assessed in Pistia stratiotes, with NO supplied in the form of SNP. Plants were exposed to four treatments: control, SNP (0.1 mg L-1), As (1.5 mg L-1) and As + SNP (1.5 and 0.1 mg L-1, respectively), for 24 h. The absorption of As triggered various changes, as the increased production of reactive oxygen intermediates and the damage to cell membranes. These effects were attenuated by SNP, which participated directly as an antioxidant, eliminating the superoxide anion, and as signaling, inducing an increase in the concentration of antioxidant enzymatic.

Abstract  This article presents the synthesis, physico-chemical, in particular voltammetric, characteristics of two iron(III) complexes with pyridoxal aminoguanidine (PLAG), [Fe(PLAG)Cl-2(H2O)]Cl (1) and [Fe(PLAG)(2)](NO3)(3) (2). As expected, the zwitterion of the chelate ligand is coordinated tridentate through oxygen of phenol and nitrogen atoms of azomethine and imino groups of the aminoguanidine fragment. In both complexes, Fe(III) is distorted octahedral. [Fe(PLAG)(2)](NO3)(3) (2) is the first bis(ligand) complex with this ligand. Cyclic voltammetric characteristics of the ligand and complexes were studied in DMF in the presence of TBAP or LiCl as supporting electrolytes. The complexes are unstable in this solvent, especially in the presence of an excess of chloride, thus forming several reducible species whose stabilities and behaviors were characterized.

Abstract  An optically accessible combustion rig was constructed to study the combustion characteristics of a reactive jet in a vitiated crossflow. The rig features two staged combustion zones. The main combustion zone is a swirl stabilized dump combustor. The second combustion zone, which is axially downstream from the main combustion zone, is formed by a transverse jet injecting either fuel or a premixed fuel/air mixture into the vitiated stream. The rig was designed to investigate the transverse jet conditions, equivalence ratio, and momentum ratios that produce low NOx and give an adequate temperature rise before the simulated high pressure turbine. A water-cooled sampling probe extracts exhaust gas downstream for emission measurements. As a baseline, the main combustion zone was fired without the transverse jet and the results compare closely to the work of previous researchers. The emission survey with the transverse jet found several conditions that show a benefit of staging compared to the baseline of firing only the main combustion zone. The flame structure from the transverse jet was captured using high speed CH* chemiluminescence, which shows the extent of the flame front and its penetration depth into the vitiated stream. The chemiluminescence images were averaged and compared to the Holdeman correlation, which showed good agreement for injection with fuel only but poorer agreement when premixed. [DOI: 10.1115/1.4006604]

Abstract  The purpose of this study is to analyze a long term database of the chemical composition of precipitation at three African dry savanna sites in the Sahel. The precipitation samples were collected during the monsoon season at Agoufou (15 degrees 20'N, 01 degrees 29'W, Mali) from 2004 to 2006, Banizoumbou (13 degrees 31'N, 02 degrees 38'E, Niger) from 1994 to 2009 and Katibougou (12 degrees 56'N, 07 degrees 32' W, Mali) from 1997 to 2008. pH and major inorganic and organic ions in precipitation were analyzed by ionic chromatography. A characterization of mean precipitation chemistry with the associated wet deposition fluxes for each species is presented. The first important result is that interannual variability of all volume-weighted mean (VWM) concentrations is low, ranging between +/- 5% and +/- 25%. Acidity in dry savannas is low and indicates the strong alkaline nature of the precipitation. The average annual pH at Agoufou is 6.28, 5.75 at Banizoumbou and 5.54 at Katibougou. This result is correlated with the important terrigenous contribution measured in the chemical content of precipitation, implying acidity neutralization by mineral species such as Ca2+ and NH4+. Mg2+ and K+ are found to play a minor role in neutralization. Enrichment factor calculations for Ca2+, SO42-, K+ and Mg2+ with respect to the sea reference reveal a significant influence of Saharan and Sahelian crustal sources. VWM concentrations of these species dominate the composition of measured precipitation. An estimation of the potential particulate and gas contribution to the total precipitation composition is given for each site: At Agoufou, the mean relative contribution in rainwater is 80% for particles and 20% for gases, while at the Banizoumbou and Katibougou sites, results indicate 70% for particles and 30% for gases. The high particulate phase contribution to precipitation emphasizes the importance of multiphase processes between gases and particles in the atmospheric chemistry typical of African semi-arid savanna ecosystems. The second highest contribution is nitrogenous, with high VWM concentrations of NO3- and NH4+ measured at the three sites. Monthly evolution of NO3- and NH4+ concentrations are studied in relation to gaseous emission sources in the Sahelian region, i.e. biogenic soil emission and ammonia sources from animals. The calculated wet nitrogen deposition flux presents a regular increase throughout the wet season at the three sites. Results suggest total mean nitrogen deposition fluxes of 1.80 kg N ha(-1) yr(-1) at Agoufou, 2.10 kg N ha(-1) yr(-1) at Banizoumbou, and 3.30 kg N ha(-1) yr(-1) at Katibougou. The marine contribution is lower, 23% at Agoufou, 17% at Banizoumbou and 13% at Katibougou. The last contribution concerns organic acidity, which ranges from 5% at Agoufou, 10% at Banizoumbou to 14% at Katibougou. Terrigenous and marine contributions present a negative gradient, whereas nitrogenous and organic contributions a positive gradient along the Sahelian transect defined by Agoufou-Banizoumbou-Katibougou. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract  Electron-impact vibrational-excitation cross sections, involving rovibrationally excited N-2 and NO molecules, are calculated for collisions occurring through the nitrogen resonant electronic state N-2(-) (X (2)Pi(g)), and the three resonant states of nitric oxide NO-( (3)Sigma(-), (1)Delta, (1)Sigma(+)). Complete sets of cross sections have been obtained for all possible transitions involving 68 vibrational levels of N-2 (X (1)Sigma(+) (g)) and 55 levels of NO(X (2)Pi), for incident electron energy between 0.1 and 10 eV. In order to study the rotational motion in the resonant processes, cross sections have also been computed for rotationally elastic transitions characterized by the rotational quantum number J running from 0 to 150. The calculations are performed within the framework of the local complex potential model, using potential energies and widths optimized to reproduce the experimental cross sections available in the literature. Rate coefficients are calculated for transitions between all vibrational levels by assuming a Maxwellian electron energy distribution function in the temperature range from 0.1 to 100 eV. All numerical data are available at http://users.ba.cnr.it/imip/cscpal38/phys4entry/database.html

Abstract  The isothermal bulk modulus of compressibility is, together with viscosity, and density, one of the properties affecting diesel injection processes. This property was measured by means of a specific apparatus that compresses a fuel sample in a high-pressure closed bottom capillary tube (a pycnometer) and by observing the height change in the column of fluid as pressure is increased over a range of pressures from 3 to 33 MPa. The bulk modulus of a conventional diesel fuel, a soybean oil derived biodiesel, and a hydrotreated soybean oil diesel fuel, together with that of their ternary blends, was measured. Water served as the calibration fluid, and measurements were made at 38 degrees C. All the fuels tested displayed substantially lower isothermal bulk modulus than water. There are observed differences between these fuel samples, with biodiesel displaying much lower compressibility than both the conventional diesel fuel and the hydrotreated oil. Although most of the blends showed bulk modulus values proportional to their volume fractions, some nonlinear effects were found when diesel fuel was involved in the blends, and particularly, a synergistic effect was found in blends with diesel and hydrotreated oil. An optimized correlation has been obtained to predict bulk modulus from the volume proportions of the three fuels tested.

Abstract  We demonstrated graphene-based flexible NO2 chemical sensors on polyethylene terephthalate substrate where graphene was grown on Cu-foil by chemical vapor deposition technique. Introduction of NO2 molecules to graphene caused a rapid increase in the currents due to the charge transfer between NO2 molecules and graphene under both relaxed and strained conditions. However, the recovery was delayed due to slow desorption of NO2 molecules from defective sites in graphene. Also, strain in graphene increased the resistance of graphene layer where the change in conductance was reversible. Our graphene-based NO2 chemical sensors showed a great sensitivity and reproducibility under both strained and relaxed conditions. (C) 2012 Elsevier B.V. All rights reserved.

Abstract  This study describes the effects of diesel-biodiesel-bioethanol blending fuels on the combustion and emission characteristics of a compression ignition engine. The experiments were investigated for various blending ratios and various fuel injection parameters. In this study, biodiesel fuel was blended not only to prevent phase separation between bioethanol and diesel but also to compensate for the low viscosity of bioethanol. The bioethanol blending ratio is restricted up to 30 vol. % to maintain the ignition characteristics. The results showed that the ignition delay was extended and that the fuel consumption and the maximum rate of pressure rise deteriorated with increasing bioethanol blending ratio. In addition, the diesel-biodiesel-bioethanol fuel reduced the indicated specific soot emissions. As the bioethanol blending ratio is increased, the indicated specific carbon monoxide (CO), the indicated specific unburned hydrocarbon, and the indicated specific nitrogen oxide emissions increased slightly.

Abstract  Dimethyl ether (DME) continues to be considered as an alternative fuel to conventional hydrocarbon fuels. Specifically, DME has been considered as a substitute fuel for liquefied petroleum gas (LPG) because the physical and chemical characteristics of DME are similar to those of LPG. However, the combustion performance for DME has not yet been established. In this study, the combustion and NOx-emission characteristics of LPG, DME, and an LPG/DME-blended fuel were experimentally investigated in a counterflow nonpremixed flame. The flame structure, flame temperature, NOx concentration, and distribution of OH radicals are reported. In this experimental study, the types of LPG used were butane 100%, butane 80% + propane 20%, and butane 75% + propane 25% by mass with DME mole fraction varied from 0 to 100 mole%. The experimental results indicated that the combustion and NOx emission characteristics of LPG fuels varied with the DME mole fraction. As the DME mole fraction increased, the flame thickness increased, but the flame length decreased. Also, the flame became wider, and its origin moved closer to the oxidizer nozzle with increasing DME mole fraction. In addition, as the DME mole fraction increased, the maximum flame temperature increased due to fast pyrolysis of DME as a result of the high oxygen content (similar to 35% by mass) in DME. Moreover, NOx concentration decreased with increasing DME mole fraction in all LPGs.