Pollutant dispersion in a developing valley cold-air pool

Pollutants are trapped and accumulate within cold-air pools, thereby affecting air quality. A numerical model is used to quantify the role of cold-air-pooling processes in the dispersion of air pollution in a developing cold-air pool within an alpine valley under decoupled stable conditions. Results indicate that the negatively buoyant downslope flows transport and mix pollutants into the valley to depths that depend on the temperature deficit of the flow and the ambient temperature structure inside the valley. Along the slopes, pollutants are generally entrained above the cold-air pool and detrained within the cold-air pool, largely above the ground-based inversion layer. The ability of the cold-air pool to dilute pollutants is quantified. The analysis shows that the downslope flows fill the valley with air from above, which is then largely trapped within the cold-air pool, and that dilution depends on where the pollutants are emitted with respect to the positions of the top of the ground-based inversion layer and cold-air pool, and on the slope wind speeds. Over the lower part of the slopes, the cold-air-pool-averaged concentrations are proportional to the slope wind speeds where the pollutants are emitted, and diminish as the cold-air pool deepens. Pollutants emitted within the ground-based inversion layer are largely trapped there. Pollutants emitted farther up the slopes detrain within the cold-air pool above the ground-based inversion layer, although some fraction, increasing with distance from the top of the slopes, penetrates into the ground-based inversion layer.Peer reviewe

Certification of butyltins and phenyltins in marine sediment certified reference material by species-specific isotope-dilution mass spectrometric analysis using synthesized (118)Sn-enriched organotin compounds

A new marine sediment certified reference material, NMIJ CRM 7306-a, for butyltin and phenyltin analysis has been prepared and certified by the National Metrological Institute of Japan at the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). Candidate sediment material was collected at a bay near industrial activity in Japan. After air-drying, sieving, and mixing the material was sterilized with γ-ray irradiation. The material was re-mixed and packaged into 250 glass bottles (15 g each) and these were stored in a freezer at −30 °C. Certification was performed by use of three different types of species-specific isotope-dilution mass spectrometry (SSID–MS)—SSID–GC–ICP–MS, SSID–GC–MS, and SSID–LC–ICP–MS, with (118)Sn-enriched organotin compounds synthesized from (118)Sn-enriched metal used as a spike. The (118)Sn-enriched mono-butyltin (MBT), dibutyltin (DBT), and tributyltin (TBT) were synthesized as a mixture whereas the (118)Sn-enriched di-phenyltin (DPhT) and triphenyltin (TPhT) were synthesized individually. Four different extraction methods, mechanical shaking, ultrasonic, microwave-assisted, and pressurized liquid extraction, were adopted to avoid possible analytical bias caused by non-quantitative extraction and degradation or inter-conversion of analytes in sample preparations. Tropolone was used as chelating agent in all the extraction methods. Certified values are given for TBT 44±3 μg kg(−1) as Sn, DBT 51 ± 2 μg kg(−1) as Sn, MBT 67 ± 3 μg kg(−1) as Sn, TPhT 6.9 ± 1.2 μg kg(−1) as Sn, and DPhT 3.4 ± 1.2 μg kg(−1) as Sn. These levels are lower than in other sediment CRMs currently available for analysis of organotin compounds

Temperature Dependence of Solar Light Assisted CO2 Reduction on Ni Based Photocatalyst

Methanation of CO2 by H-2 can be in the future an important reaction to store the surplus of renewable electricity during production peaks. The catalytic thermal CO2 methanation (the Sabatier reaction) can be carried out at temperatures above 250 degrees C using Ni supported on silica-alumina (Ni/SiO2-Al2O3). Recently it has been observed that this exothermic reaction can be promoted by solar light irradiation of Ni/SiO2-Al2O3 at initial near ambient temperatures. In the present work we provide a study of the influence of the initial temperature on the photoassisted Ni/SiO2-Al2O3 methanation of CO2, under conditions in which the dark reaction is not observed. An increase of the photoassisted methanation rate with the initial temperature in the range from ambient to 150 degrees C has been observed. The reaction kinetics for lower initial temperatures exhibited an induction period not observed for reactions performed at higher temperatures. The results are discussed in terms of the operation of plasmon photo activation in which the energy of photons is thermalised in a confined space of the active nanoparticles leading to locally high temperatures and the simultaneous photogeneration of electrons and positive holes.Albero Sancho, J.; García Gómez, H.; Corma Canós, A. (2016). Temperature Dependence of Solar Light Assisted CO2 Reduction on Ni Based Photocatalyst. Topics in Catalysis. 59(8-9):787-791. doi:10.1007/s11244-016-0550-xS787791598-9Hammarstrom L, Hammes-Schiffer S (2009) Artificial photosynthesis and solar fuels. Acc Chem Res 42:1859–1860Schlögl R (2015) The revolution continues: energiewende 2.0. Angew Chem Int Ed 54:4436–4439Herron JA, Kim J, Upadhye AA, Huber GW, Maravelias CT (2015) A general framework for the assessment of solar fuel technologies. Energy Environ Sci 8:126–157Hoekman SK, Broch A, Robbins C, Purcell R (2010) CO2 recycling by reaction with renewably-generated hydrogen. Int J Greenh Gas Control 4:44–50Hoch LB, Wood TE, O’Brien PG, Liao K, Reyes LM, Mims CA, Ozin GA (2014) The rational design of a single-component photocatalyst for gas-phase CO2 reduction using both UV and visible light. Adv Sci 1:1400010–1400013Sastre F, Puga AV, Liu L, Corma A, Garcia H (2014) Complete photocatalytic reduction of CO2 to methane by H2 under solar light irradiation. J Am Chem Soc 136:6798–6801Melsheimer J, Guo W, Ziegler D, Wesemann M, Schlögl R (1991) Methanation of carbon dioxide over Ru/titania at room temperature: explorations for a photoassisted catalytic reaction. Catal Lett 11:157–168O’Brien PG, Sandhel A, Wood TE, Jelle AA, Hoch LB, Perovic DD, Mims CA, Ozin GA (2014) Photomethanation of gaseous CO2 over Ru/silicon nanowire catalysts with visible and near-infrared photons. Adv Sci 1:1400001–1400007Ghuman KK, Wood TE, Hoch LB, Mims CA, Ozin GA, Singh CV (2015) Illuminating CO2 reduction on frustrated Lewis pair surfaces: investigating the role of surface hydroxides and oxygen vacancies on nanocrystalline In2O3−x(OH)y. Phys Chem Chem Phys 17:14623–14635Wei W, Jinlong G (2011) Methanation of carbon dioxide: an overview. Front Chem Sci Eng 5:2–10Scaiano JC, Stamplecoskie K (2013) Can surface plasmon fields provide a new way to photosensitize organic photoreactions? Custom applications. J Phys Chem Lett 4:1177–1187Fasciani C, Alejo CJB, Grenier M, Netto-Ferreira JC, Scaiano JC (2011) High-temperature organic reactions at room temperature using plasmon excitation: decomposition of dicumyl peroxide. Org Lett 13:204–207Leadbeater NE (2010) Microwave heating as a tool for sustainable chemistry. CRC Press, Boca Rato

Measurement of the B+ and B-0 lifetimes and search for CP(T) violation using reconstructed secondary vertices

The lifetimes of the B+ and B-0 mesons, and their ratio, have been measured in the OPAL experiment using 2.4 million hadronic Z(0) decays recorded at LEP. Z(0) --> b (b) over bar decays were tagged using displaced secondary vertices and high momentum electrons and muons. The lifetimes were then measured using well-reconstructed charged and neutral secondary vertices selected in this tagged data sample. The results aretau(B+) = 1.643 +/- 0.037 +/- 0.025 pstau(Bo) = 1.523 +/- 0.057 +/- 0.053 pstau(B+)/tau(Bo) = 1.079 +/- 0.064 +/- 0.041,where in each case the first error is statistical and the second systematic.A larger data sample of 3.1 million hadronic Z(o) decays has been used to search for CP and CPT violating effects by comparison of inclusive b and (b) over bar hadron decays, No evidence fur such effects is seen. The CP violation parameter Re(epsilon(B)) is measured to be Re(epsilon(B)) = 0.001 +/- 0.014 +/- 0.003and the fractional difference between b and (b) over bar hadron lifetimes is measured to(Delta tau/tau)(b) = tau(b hadron) - tau((b) over bar hadron)/tau(average) = -0.001 +/- 0.012 +/- 0.008

Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV

The performance of muon reconstruction, identification, and triggering in CMS has been studied using 40 inverse picobarns of data collected in pp collisions at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection criteria covering a wide range of physics analysis needs have been examined. For all considered selections, the efficiency to reconstruct and identify a muon with a transverse momentum pT larger than a few GeV is above 95% over the whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4, while the probability to misidentify a hadron as a muon is well below 1%. The efficiency to trigger on single muons with pT above a few GeV is higher than 90% over the full eta range, and typically substantially better. The overall momentum scale is measured to a precision of 0.2% with muons from Z decays. The transverse momentum resolution varies from 1% to 6% depending on pseudorapidity for muons with pT below 100 GeV and, using cosmic rays, it is shown to be better than 10% in the central region up to pT = 1 TeV. Observed distributions of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO

Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV

The performance of muon reconstruction, identification, and triggering in CMS has been studied using 40 inverse picobarns of data collected in pp collisions at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection criteria covering a wide range of physics analysis needs have been examined. For all considered selections, the efficiency to reconstruct and identify a muon with a transverse momentum pT larger than a few GeV is above 95% over the whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4, while the probability to misidentify a hadron as a muon is well below 1%. The efficiency to trigger on single muons with pT above a few GeV is higher than 90% over the full eta range, and typically substantially better. The overall momentum scale is measured to a precision of 0.2% with muons from Z decays. The transverse momentum resolution varies from 1% to 6% depending on pseudorapidity for muons with pT below 100 GeV and, using cosmic rays, it is shown to be better than 10% in the central region up to pT = 1 TeV. Observed distributions of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO

X-ray emission from the Sombrero galaxy: discrete sources

We present a study of discrete X-ray sources in and around the bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and archival Chandra observations with a total exposure of ~200 ks. With a detection limit of L_X = 1E37 erg/s and a field of view covering a galactocentric radius of ~30 kpc (11.5 arcminute), 383 sources are detected. Cross-correlation with Spitler et al.'s catalogue of Sombrero globular clusters (GCs) identified from HST/ACS observations reveals 41 X-rays sources in GCs, presumably low-mass X-ray binaries (LMXBs). We quantify the differential luminosity functions (LFs) for both the detected GC and field LMXBs, whose power-low indices (~1.1 for the GC-LF and ~1.6 for field-LF) are consistent with previous studies for elliptical galaxies. With precise sky positions of the GCs without a detected X-ray source, we further quantify, through a fluctuation analysis, the GC LF at fainter luminosities down to 1E35 erg/s. The derived index rules out a faint-end slope flatter than 1.1 at a 2 sigma significance, contrary to recent findings in several elliptical galaxies and the bulge of M31. On the other hand, the 2-6 keV unresolved emission places a tight constraint on the field LF, implying a flattened index of ~1.0 below 1E37 erg/s. We also detect 101 sources in the halo of Sombrero. The presence of these sources cannot be interpreted as galactic LMXBs whose spatial distribution empirically follows the starlight. Their number is also higher than the expected number of cosmic AGNs (52+/-11 [1 sigma]) whose surface density is constrained by deep X-ray surveys. We suggest that either the cosmic X-ray background is unusually high in the direction of Sombrero, or a distinct population of X-ray sources is present in the halo of Sombrero.Comment: 11 figures, 5 tables, ApJ in pres

Performance of the CMS Cathode Strip Chambers with Cosmic Rays

The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device in the CMS endcaps. Their performance has been evaluated using data taken during a cosmic ray run in fall 2008. Measured noise levels are low, with the number of noisy channels well below 1%. Coordinate resolution was measured for all types of chambers, and fall in the range 47 microns to 243 microns. The efficiencies for local charged track triggers, for hit and for segments reconstruction were measured, and are above 99%. The timing resolution per layer is approximately 5 ns

Light-Promoted Hydrogenation of Carbon Dioxide¿An Overview

[EN] Hydrogenation of carbon dioxide is considered as a viable strategy to generate fuels while closing the carbon cycle (heavily disrupted by the abuse in the exploitation of fossil resources) and reducing greenhouse gas emissions. The process can be performed by heat-powered catalytic processes, albeit conversion and selectivity tend to be reduced at increasing temperatures owing to thermodynamic constraints. Recent investigations, as summarised in this overview, have proven that light activation is a distinct possibility for the promotion of CO2 hydrogenation to fuels. This effect is particularly beneficial in methanation processes, which can be enhanced under simulated solar irradiation using materials based on metallic nanoparticles as catalysts. The use of nickel, ruthenium and rhodium has led to substantial efficiencies. Light-promoted processes entail performances on a par with (or even superior to) those of thermally-induced, industrially-relevant, commercial technologies.The author thanks the Spanish Government (Ministerio de Economía y Competitividad, MINECO) for financial support via a project for young researchers (CTQ2015-74138-JIN), and the ‘‘Severo Ochoa’’ programme (SEV 2012-0267). The European Union is also acknowledged for the SynCatMatch project (ERCAdG-2014-671093)Puga Vaca, A. (2016). Light-Promoted Hydrogenation of Carbon Dioxide¿An Overview. Topics in Catalysis. 59(15-16):1268-1278. https://doi.org/10.1007/s11244-016-0658-zS126812785915-16Centi G, Perathoner S (2009) Opportunities and prospects in the chemical recycling of carbon dioxide to fuels. Catal Today 148:191–205Aresta M, Dibenedetto A, Angelini A (2014) Catalysis for the valorization of exhaust carbon: from CO2 to chemicals, materials, and fuels. technological use of CO2. 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Inhibition of Lassa Virus Glycoprotein Cleavage and Multicycle Replication by Site 1 Protease-Adapted α1-Antitrypsin Variants

The virus family Arenaviridae includes several hemorrhagic fever causing agents such as Lassa, Guanarito, Junin, Machupo, and Sabia virus that pose a major public health concern to the human population in West African and South American countries. Current treatment options to control fatal outcome of disease are limited to the ribonucleoside analogue ribavirin, although its use has some significant limitations. The lack of effective treatment alternatives emphasizes the need for novel antiviral therapeutics to counteract these life-threatening infections. Maturation cleavage of the viral envelope glycoprotein by the host cell proprotein convertase site 1 protease (S1P) is critical for infectious virion production of several pathogenic arenaviruses. This finding makes this protease an attractive target for the development of novel anti-arenaviral therapeutics. We demonstrate here that highly selective S1P-adapted α1-antitrypsins have the potential to efficiently inhibit glycoprotein processing, which resulted in reduced Lassa virus replication. Our findings suggest that S1P should be considered as an antiviral target and that further optimization of modified α1-antitrypsins could lead to potent and specific S1P inhibitors with the potential for treatment of certain viral hemorrhagic fevers