Rate constants for the reaction of NO and HO2 with peroxy radicals formed from the reaction of OH, Cl or NO3 with alkenes, dienes and α,β-unsaturated carbonyls

Rate constants for the gas-phase reaction of NO and HO2 radicals with 33 peroxy radicals are presented. The peroxy radicals are derived from the addition of either OH, Cl, or NO3 radicals, followed by addition of O2, to a series of alkenes: tetrachloroethene, ethene, 2,3-dimethyl but-2-ene, butadiene, 2,3,4,5-tetramethyl hexa-2,4-diene, 1,1,2,3,4,4-hexachlorobutadiene, but-1-ene-3-one (methyl vinyl ketone) and 2,3-dimethylpen-2-ene-4-one. The rate constants were predicted using a correlation between the singly occupied molecular orbital (SOMO) energy of the peroxy radical and the logarithm of the rate constant for reaction with NO or HO2. A discussion of the accuracy of the method and the trends in the reactivity of the titled peroxy radicals is given. Peroxy radicals derived from halogenated alkenes have larger values of rate constants for reaction with NO relative to reaction with HO2, indicating that they are more likely to react with NO, rather than HO2, in the atmosphere. The reverse is true for peroxy radicals derived from alkylated alkenes

Exploring NOy chemistry in levitated aqueous aerosol droplets

Chemistry of reactive nitrogen oxides, NOy, is crucial for our understanding of composition and properties of the Earth’s atmosphere. The proof-of-principle experiments demonstrated that we are able to study the atmospheric fate of nitrogen oxides that has significant impact on global climate and hydrological cycle, thus affecting the likelihood of local floods and acid rain

Oxidation of biogenic and water-soluble compounds in aqueous and organic aerosol droplets by ozone: a kinetic and product analysis approach using laser Raman tweezers

The results of an experimental study into the oxidative degradation of proxies for atmospheric aerosol are presented. We demonstrate that the laser Raman tweezers method can be used successfully to obtain uptake coeffcients for gaseous oxidants on individual aqueous and organic droplets, whilst the size and composition of the droplets is simultaneously followed. A laser tweezers system was used to trap individual droplets containing an unsaturated organic compound in either an aqueous or organic ( alkane) solvent. The droplet was exposed to gas- phase ozone and the reaction kinetics and products followed using Raman spectroscopy. The reactions of three different organic compounds with ozone were studied: fumarate anions, benzoate anions and alpha pinene. The fumarate and benzoate anions in aqueous solution were used to represent components of humic- like substances, HULIS; a alpha- pinene in an alkane solvent was studied as a proxy for biogenic aerosol. The kinetic analysis shows that for these systems the diffusive transport and mass accommodation of ozone is relatively fast, and that liquid- phase di. ffusion and reaction are the rate determining steps. Uptake coe. ffcients, g, were found to be ( 1.1 +/- 0.7) x 10(-5), ( 1.5 +/- 0.7) x 10 (-5) and ( 3.0 - 7.5) x 10 (-3) for the reactions of ozone with the fumarate, benzoate and a- pinene containing droplets, respectively. Liquid- phase bimolecular rate coe. cients for reactions of dissolved ozone molecules with fumarate, benzoate and a- pinene were also obtained: k(fumarate) = ( 2.7 +/- 2) x 10 (5), k(benzoate) = ( 3.5 +/- 3) x 10 (5) and k(alpha-pinene) = ( 1-3) x 10(7) dm(3) mol (-1) s (- 1). The droplet size was found to remain stable over the course of the oxidation process for the HULIS- proxies and for the oxidation of a- pinene in pentadecane. The study of the alpha- pinene/ ozone system is the first using organic seed particles to show that the hygroscopicity of the particle does not increase dramatically over the course of the oxidation. No products were detected by Raman spectroscopy for the reaction of benzoate ions with ozone. One product peak, consistent with aqueous carbonate anions, was observed when following the oxidation of fumarate ions by ozone. Product peaks observed in the reaction of ozone with alpha- pinene suggest the formation of new species containing carbonyl groups

An Evaluation on How General Aviaton Pilots Learn Basic Meteorology

An Evaluation on How General Aviation Pilots Learn Basic Meteorology Jayde M. King, Jessica Cruit, M.S., Beth Blickensderfer, PhD. Introduction. As General Aviation (GA) accidents continue to occur each year, industry officials as well as researchers search for insights into possible causes to these accidents. Weather, in particular degraded weather poses a threat to general aviation. In fact, according to Jarboe (2005), “weather-related airplane accidents led to 240 fatalities in the United States (U.S) and Puerto Rico”(pp.3-11). Considering these facts, questions rise to the degree to which GA pilots actually understand aviation weather knowledge. Currently, the Federal Aviation Administration (FAA) requires private pilots to pass the FAA Knowledge exam with a 70% or above. Although this exam includes weather-related questions to test pilots\u27 knowledge of these concepts, pilots can fail the weather portion of the knowledge exam while passing the entire exam, thus receiving their private pilot\u27s license without fully understanding the extent of weather products and weather phenomenon. Therefore, the purpose of this study was to gain a deeper understanding into how pilots learn basic meteorology. Method. In order to assess how pilots learn about weather phenomenon, products, and sources before and/or during their training, we conducted 30 semi-structured interviews with ERAU and non ERAU affiliated pilots. The interview included questions such as, where pilots receive their weather training, how they receive their training, which phase of flight was the most important in terms of weather awareness, and what courses provided the most beneficial weather-related material. Results. The results of the interview reveal several interesting points. 1) Pilots learn weather-related material better when instructed by their flight instructor over any other form of instruction. 2) Pilots stated that the preflight phase of flight was the most crucial for understanding weather products and basic meteorological concepts. 3) As for which courses provided the most beneficial weather-related information, pilots claimed that the introductory weather course (WX201) gave students a better understanding of weather phenomenology over the more advanced weather course (WX301). Pilots stated that the material learned in WX301 was too specific and unnecessary. And although confessing that they did not fully understand or conceptualize the weather information presented in their meteorology courses, pilots explained that they felt comfortable with the breadth of weather-related knowledge learned. Ultimately, pilots agreed that weather plays an important role in flight and general aviation. Discussion. The information obtained from these interviews helps emphasize the importance of improving the quality and scope of weather-related questions on the FAA written exam. The results of the data seek to provide insights into how to better prepare student pilots during their training for possible weather-related hazards during their flight. Ultimately, the goal of this study is to train student pilots with a greater depth of weather knowledge in order to increase certainty in decision making during weather-related events. References Jarboe, J. (2005). U.S. Aviation Weather-Related Crashes and Fatalities in 2004. NOAA’sNational Weather Service, 4(2), 3-11. Retrieved February 17, 2015, from http://www.nws.noaa.gov/os/aviation/front/05june-front.pd

Influence of frustration on a d=3 diluted antiferromagnet: FexZn1−xF2Fe_{x}Zn_{1-x}F_{2}

The influence of a frustrated bond on the magnetic properties of a d=3 uniaxial (Ising) b.c.c. diluted antiferromagnet, with emphasis in the compound $Fe_{x}Zn_{1-x}F_{2}$, is investigated by a local mean-field numerical simulation. In particular we find that the initial drop of the saturation staggered magnetization ($M_{S}$) with concentration follows a percolation-like phenomenon characterized by an exponent $\beta_{p}$. For the frustrated samples, however, this regime is followed by a second one identified by a ``long tail" effect such that $M_{S}$ is zero only at the percolation threshold. Our numerical data also confirms a spin-glass phase near this threshold.Comment: 11 pages (Latex) with 3 uuencoded postscript figure

Air-snow transfer of nitrate on the East Antarctic plateau – Part 2: An isotopic model for the interpretation of deep ice-core records

Unraveling the modern budget of reactive nitrogen on the Antarctic plateau is critical for the interpretation of ice core records of nitrate. This requires accounting for nitrate recycling processes occurring in near surface snow and the overlying atmospheric boundary layer. Not only concentration measurements, but also isotopic ratios of nitrogen and oxygen in nitrate, provide constraints on the processes at play. However, due to the large number of intertwined chemical and physical phenomena involved, numerical modelling is required to test hypotheses in a~quantitative manner. Here we introduce the model "TRansfer of Atmospheric Nitrate Stable Isotopes To the Snow" (TRANSITS), a~novel conceptual, multi-layer and one-dimensional model representing the impact of processes operating on nitrate at the air–snow interface on the East Antarctic plateau, in terms of concentrations (mass fraction) and the nitrogen (δ15N) and oxygen isotopic composition (17O}-excess, Δ17O) in nitrate. At the air–snow interface at Dome C (DC, 75°06' S, 123°19' E), the model reproduces well the values of δ15N in atmospheric and surface snow (skin layer) nitrate as well as in the δ15N profile in DC snow including the observed extraordinary high positive values (around +300 ‰) below 20 \unit{cm}. The model also captures the observed variability in nitrate mass fraction in the snow. While oxygen data are qualitatively reproduced at the air–snow interface at DC and in East Antarctica, the simulated Δ17O values underestimate the observed Δ17O values by a~few~‰. This is explained by the simplifications made in the description of the atmospheric cycling and oxidation of NO2. The model reproduces well the sensitivity of δ15N, Δ17O and the apparent fractionation constants (15ϵapp, 17Eapp) to the snow accumulation rate. Building on this development, we propose a~framework for the interpretation of nitrate records measured from ice cores. Measurement of nitrate mass fractions and δ15N in the nitrate archived in an ice core, may be used to derive information about past variations in the total ozone column and/or the primary inputs of nitrate above Antarctica as well as in nitrate trapping efficiency (defined as the ratio between the archived nitrate flux and the primary nitrate input flux). The Δ17O of nitrate could then be corrected from the impact of cage recombination effects associated with the photolysis of nitrate in snow. Past changes in the relative contributions of the Δ17O in the primary inputs of nitrate and the Δ17O in the locally cycled NO2 could then be determined. Therefore, information about the past variations in the local and long range processes operating on reactive nitrogen species could be obtained from ice cores collected in low accumulation regions such as the Antarctic plateau

Unital quantum operators on the Bloch ball and Bloch region

For one qubit systems, we present a short, elementary argument characterizing unital quantum operators in terms of their action on Bloch vectors. We then show how our approach generalizes to multi-qubit systems, obtaining inequalities that govern when a ``diagonal'' superoperator on the Bloch region is a quantum operator. These inequalities are the n-qubit analogue of the Algoet-Fujiwara conditions. Our work is facilitated by an analysis of operator-sum decompositions in which negative summands are allowed.Comment: Revised and corrected, to appear in Physical Review

Inequalities in the dental health needs and access to dental services among looked after children in Scotland: a population data linkage study

Background: There is limited evidence on the health needs and service access among children and young people who are looked after by the state. The aim of this study was to compare dental treatment needs and access to dental services (as an exemplar of wider health and well-being concerns) among children and young people who are looked after with the general child population. Methods: Population data linkage study utilising national datasets of social work referrals for ‘looked after’ placements, the Scottish census of children in local authority schools, and national health service’s dental health and service datasets. Results: 633 204 children in publicly funded schools in Scotland during the academic year 2011/2012, of whom 10 927 (1.7%) were known to be looked after during that or a previous year (from 2007–2008). The children in the looked after children (LAC) group were more likely to have urgent dental treatment need at 5 years of age: 23%vs10% (n=209/16533), adjusted (for age, sex and area socioeconomic deprivation) OR 2.65 (95% CI 2.30 to 3.05); were less likely to attend a dentist regularly: 51%vs63% (n=5519/388934), 0.55 (0.53 to 0.58) and more likely to have teeth extracted under general anaesthesia: 9%vs5% (n=967/30253), 1.91 (1.78 to 2.04). Conclusions: LAC are more likely to have dental treatment needs and less likely to access dental services even when accounting for sociodemographic factors. Greater efforts are required to integrate child social and healthcare for LAC and to develop preventive care pathways on entering and throughout their time in the care system

Evidence for complementary effects of code- and knowledge-focused reading instruction

There is growing recognition of the need to end the debate regarding reading instruction in favor of an approach that provides a solid foundation in phonics and other underlying language skills to become expert readers. We advance this agenda by providing evidence of specific effects of instruction focused primarily on the written code or on developing knowledge. In a grade 1 program evaluation study, an inclusive and comprehensive program with a greater code-based focus called Reading for All (RfA) was compared to a knowledge-focused program involving Dialogic Reading. Phonological awareness, letter word recognition, nonsense word decoding, listening comprehension, reading comprehension, written expression and vocabulary were measured at the beginning and end of the school year, and one year after in one school only. Results revealed improvements in all measures except listening comprehension and vocabulary for the RfA program at the end of the first school year. These gains were maintained for all measures one year later with the exception of an improvement in written expression. The Dialogic Reading group was associated with a specific improvement in vocabulary in schools from lower socioeconomic contexts. Higher scores were observed for RfA than Dialogic Reading groups at the end of the first year on nonsense word decoding, phonological awareness and written expression, with the differences in the latter two remaining significant one year later. The results provide evidence of the need for interventions to support both word recognition and linguistic comprehension to better reading comprehension

Reconstruction of superoperators from incomplete measurements

We present strategies how to reconstruct (estimate) properties of a quantum channel described by the map E based on incomplete measurements. In a particular case of a qubit channel a complete reconstruction of the map E can be performed via complete tomography of four output states E[rho_j ] that originate from a set of four linearly independent test states j (j = 1, 2, 3, 4) at the input of the channel. We study the situation when less than four linearly independent states are transmitted via the channel and measured at the output. We present strategies how to reconstruct the channel when just one, two or three states are transmitted via the channel. In particular, we show that if just one state is transmitted via the channel then the best reconstruction can be achieved when this state is a total mixture described by the density operator rho = I/2. To improve the reconstruction procedure one has to send via the channel more states. The best strategy is to complement the total mixture with pure states that are mutually orthogonal in the sense of the Bloch-sphere representation. We show that unitary transformations (channels) can be uniquely reconstructed (determined) based on the information of how three properly chosen input states are transformed under the action of the channel.Comment: 13 pages, 6 figure