CH3CH2SCH3+OH radicals: Temperature-dependent rate coefficient and product identification under atmospheric pressure of air

Relative rate coefficients have been determined for the gas-phase reaction of hydroxyl (OH) radicals with ethyl methyl sulfide (EMS) using isobutene as a reference compound. The experiments were performed in a 1080 L quartz glass photoreactor in the temperature range of 286-313 K at a total pressure of 760W10 Torr synthetic air using in situ FTIR absorption spectroscopy to monitor the concentration-time behaviors of reactants and products. OH radicals were produced by the 254nm photolysis of hydrogen peroxide (H2O 2). The kinetic data obtained were used to derive the following Arrhenius expression valid in the temperature range of 286-313 K (in units of cm3 molecule-1 s-1): k = (3.0±0:6) × 10-15 exp [(2457 ± 65)/=T]The rate coefficient displays a negative temperature dependence and low pre-exponential factor which supports the existence of an addition mechanism for the reaction involving reversible OH-adduct formation. The results are compared with previous data of other sulfides from the literature and are rationalized in terms of structure-reactivity relationships. Additionally, product identification of the title reaction was performed for the first time by the FTIR technique under atmospheric conditions. Sulfur dioxide, formaldehyde, and formic acid were observed as degradation products in agreement with the two possible reaction channels (addition/abstraction). Copyright © 2010 John Wiley and Sons, Ltd.Fil: Oksdath Mansilla, Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Peñeñory, Alicia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Albu, Mihaela. Bergische Universitaet Wuppertal. Physikalische Chemie/FBC; AlemaniaFil: Barnes, Ian. Bergische Universitaet Wuppertal. Physikalische Chemie/FBC; AlemaniaFil: Wiesen, Peter. Bergische Universitaet Wuppertal. Physikalische Chemie/FBC; Alemania; AlemaniaFil: Teruel, Mariano Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin

Gastrointestinal function in intensive care patients: terminology, definitions and management. Recommendations of the ESICM Working Group on Abdominal Problems

Acute gastrointestinal (GI) dysfunction and failure have been increasingly recognized in critically ill patients. The variety of definitions proposed in the past has led to confusion and difficulty in comparing one study to another. An international working group convened to standardize the definitions for acute GI failure and GI symptoms and to review the therapeutic options

The Road Opens: From Escape to New Truth on the Road in American Literature

Travel and relocation have been integral parts of the American experience from the first known journeys of Leif Ericson five hundred years before Columbus. Since then, Europeans moved about the continent as explorers, and eventually Americans moved westward as part of Manifest Destiny and in search of the American Dream. When they finally reached the west coast, the journey doubled back on itself, forcing the journeyers to search the already developed land for the disappearing American Dream. However, regardless of their reason for departing the land they were on, the characters of many of the works of American fiction (and in the case of Into the Wild, non-fiction) were altered by their time on the road, resulting in their finding a new truth at the end of their journey. By examining the journeys in Herman Melville’s Moby-Dick, Mark Twain’s Adventures of Huckleberry Finn, F. Scott Fitzgerald’s The Great Gatsby, John Steinbeck’s The Grapes of Wrath, Jack Kerouac’s On the Road, Arthur Miller’s Death of a Salesman, Barbara Kingsolver’s The Bean Trees, and Jon Krakauer’s Into the Wild, this paper examines the reasons for the journey or movement, the encounters with falsehood and hypocrisy, and the discovery of new understandings or truths at the end of their journeys

Assessing the need for critical minerals to shift the German energy system towards a high proportion of renewables

The German government has set itself the target of reducing the country's GHG emissions by between 80 and 95% by 2050 compared to 1990 levels. Alongside energy efficiency, renewable energy sources are set to play the main role in this transition. However, the large-scale deployment of renewable energies is expected to cause increased demand for critical mineral resources. The aim of this article is therefore to determine whether the transformation of the German energy system by 2050 ("Energiewende") may possibly be restricted by a lack of critical minerals, focusing primarily on the power sector (generating, transporting and storing electricity from renewable sources). For the relevant technologies, we create roadmaps describing a number of conceivable quantitative market developments in Germany. Estimating the current and future specific material demand of the options selected and projecting them along a range of long-term energy scenarios allows us to assess potential medium- or long-term mineral resource restrictions. The main conclusion we draw is that the shift towards an energy system based on renewable sources that is currently being pursued is principally compatible with the geological availability and supply of mineral resources. In fact, we identified certain sub-technologies as being critical with regard to potential supply risks, owing to dependencies on a small number of supplier countries and competing uses. These sub-technologies are certain wind power plants requiring neodymium and dysprosium, thin-film CIGS photovoltaic cells using indium and selenium, and large-scale redox flow batteries using vanadium. However, non-critical alternatives to these technologies do indeed exist. The likelihood of supplies being restricted can be decreased further by cooperating even more closely with companies in the supplier countries and their governments, and by establishing greater resource efficiency and recyclability as key elements of technology development

Kinetic investigation of the OH radical and Cl atom initiated degradation of unsaturated ketones at atmospheric pressure and 298 K

Rate coefficients for the reactions of hydroxyl radicals and chlorine atoms with 4-hexen-3-one, 5-hexen-2-one, and 3-penten-2-one have been determined at 298 ± 2 K and atmospheric pressure of air. Rate coefficients for the compounds were determined using a relative kinetic technique with different reference compounds. The experiments were performed in a large photoreactor (480 L) using in situ FTIR spectroscopy to monitor the decay of reactants. From the different measurements the following rate coefficients (in units of cm 3 molecule -1 s -1) have been determined: k 1(OH + 4-hexen-3-one) = (9.04 ± 2.12) × 10 -11, k 2(OH + 5-hexen-2-one) = (5.18 ± 1.27) × 10 -11, k 3(OH + 3-penten-2-one) = (7.22 ± 1.74) × 10 -11, k 4(Cl + 4-hexen-3-one) = (3.00 ± 0.58) × 10 -10, k 5(Cl + 5-hexen-2-one) = (3.15 ± 0.50) × 10 -10 and k 6(Cl + 3-penten-2-one) = (2.53 ± 0.54) × 10 -10. The reactivity of the double bond in alkenes and unsaturated ketones at 298 K toward addition of OH radicals and Cl atoms are compared and discussed. In addition, a correlation between the reactivity of the unsaturated ketones toward OH radicals and the HOMO of the compounds is presented. On the basis of the kinetic measurements, the tropospheric lifetimes of 4-hexen-3-one, 5-hexen-2-one, and 3-penten-2-one with respect to their reaction with hydroxyl radicals are estimated to be between 2 and 3 h. © 2012 American Chemical Society.Fil: Blanco, Maria Belen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina. Bergische Universität Wuppertal; AlemaniaFil: Barnes, Ian. Bergische Universität Wuppertal; AlemaniaFil: Wiesen, Peter. Bergische Universität Wuppertal; Alemani

Secondary Organic Aerosol Formation from Nitrophenols Photolysis under Atmospheric Conditions

Nitrophenols are important products of the aromatic compounds photooxidation and play a considerable role in urban chemistry. Nitrophenols are important components of agricultural biomass burning that could influence the climate. The formation of secondary organic aerosol from the direct photolysis of nitrophenols was investigated for the first time in a quartz glass simulation chamber under simulated solar radiation. The results from these experiments indicate rapid SOA formation. The proposed mechanism for the gas-phase degradation of nitrophenols through photolysis shows the formation of biradicals that could react further in the presence of oxygen to form low volatile highly oxygenated compounds responsible for secondary organic aerosol formation. The inhibiting effect of NOx and the presence of an OH radical scavenger on the aerosol formation were also studied. For 2-nitrophenol, significant aerosol formation yields were observed in the absence of an OH radical scavenger and NOx, varying in the range of 18%–24%. A gas-phase/aerosol partitioning model was applied assuming the presence of only one compound in both phases. A degradation mechanism is proposed to explain the aerosol formation observed in the photolysis of nitrophenols. The atmospheric impact of nitrophenol photolysis is discussed and the importance for atmospheric chemical models is assessed