4,100 research outputs found

    Photodissociation of NO2 in the (2)B-2(2) state: A slice imaging study and reinterpretation of previous results

    Get PDF
    The photodissociation dynamics of nitrogen dioxide have been probed above the second dissociation limit at photolysis wavelengths close to 226 nm. The O(3PJ)+NO(2) product channel has been examined using direct current slice velocity map imaging of the O(3PJ) and NO(2) fragments. Mass-resolved resonantly enhanced multiphoton ionization spectroscopy and velocity map imaging have been used to probe directly the rovibrational population distributions of the NO fragments. We also examine possible interference from the dissociation of N2O4 by investigating the effect of the sample temperature on the O(3PJ) fragment energy distributions. The O(3PJ)+NO(2) dissociation channel has been found to favor the production of vibrationally cold, highly rotationally excited NO(2) products with all three oxygen spin-orbit components. Other minor dissociation channels which produce O(3PJ) atoms have also been identified. We discuss the significance of these dissociation channels and present a reinterpretation of previous studies of NO2 dissociation on excitation to the (2)2B2 state

    Seafood from Norway : food safety

    Get PDF
    Since Norway is a major supplier of seafood worldwide, monitoring the food safety of Norwegian fish products is a priority. This commentary gives a brief overview of the food safety of seafood from Norwegian waters. Several preventative measures during harvest/catch, processing and distribution have been established and are implemented regularly. Furthermore, comprehensive monitoring programmes to detect and quantify undesirable substances, such as heavy metals and polychlorinated biphenyls (PCBs), in Norwegian seafood are carried out. Substances with health benefits, such as omega-3 fatty acids, are also analysed. In general, evidence shows the level of undesirable substances in seafood from Norway to be low. In fact, in the majority of samples analysed, levels of undesirable substances were reported to be below the maximum limit set by the European Union (EU). This leads to the conclusion that consumption of seafood originating from Norway involves a low risk of negative health effects and that consumers can have confidence in the products they purchase.peer-reviewe

    Exploring Gifted Pedagogy: Evaluating Teacher Knowledge and Implementation of Common Core Professional Learning

    Get PDF
    The purpose of this quantitative study was to determine the effectiveness of professional learning with teachers on the Core Six Essential Strategies (CSES) within a gifted multicultural context. Criterion sampling was employed to identify the participants for the study. All participants were teachers of gifted and talented students within a large southeastern urban district. All participants met the gifted endorsement state credentialing criteria. A pre-experimental, single-group pretest-posttest design was constructed. Instruments employed in the study were the Association of Supervision and Curriculum Development’s Core Six Pre-Post Assessment (ASCD, 2012) and a modified participant reaction questionnaire. Four research questions were explored in the study. Guskey and Spark’s Model of Relationship between Professional Development and Improvements in Student Learning was the research paradigm employed to analyze the results of the study. A dependent samples t-test was used to find if there was a significant difference between the pre and posttest means of teacher knowledge on the Core Six Essential Strategies. To explore implementation, a dependent samples t-test was used to find if there was a significant difference between the index of intended frequency of use and the actual use of strategies. Descriptive statistics including the count and mean were examined to show which aspects of the professional learning have most value. Descriptive statistics indicating the count, mean, and variance were used to examine to what extent the professional learning prepared teachers to instruct within a multicultural gifted urban context. Findings indicated a significant difference in knowledge of the CSES; the participants intended to implement the strategies significantly more than they did; and several aspects of the professional learning were valuable and prepared them to teach in a multicultural gifted urban context. In summary, the research was significant to the field of gifted education because the results will inform future professional learning decisions, curriculum writing, and program implementation designed to improve student learning outcomes

    Spatial solitons under competing linear and nonlinear diffractions

    Full text link
    We introduce a general model which augments the one-dimensional nonlinear Schr\"{o}dinger (NLS) equation by nonlinear-diffraction terms competing with the linear diffraction. The new terms contain two irreducible parameters and admit a Hamiltonian representation in a form natural for optical media. The equation serves as a model for spatial solitons near the supercollimation point in nonlinear photonic crystals. In the framework of this model, a detailed analysis of the fundamental solitary waves is reported, including the variational approximation (VA), exact analytical results, and systematic numerical computations. The Vakhitov-Kolokolov (VK) criterion is used to precisely predict the stability border for the solitons, which is found in an exact analytical form, along with the largest total power (norm) that the waves may possess. Past a critical point, collapse effects are observed, caused by suitable perturbations. Interactions between two identical parallel solitary beams are explored by dint of direct numerical simulations. It is found that in-phase solitons merge into robust or collapsing pulsons, depending on the strength of the nonlinear diffraction

    The Arizona Summit: Tough Times in a Tough Land

    Get PDF
    Western repositories have much to gain and little to lose from statewide initiatives that promote cooperative collection management policies. The region\u27s topography, demographics, boom-bust cycles, and flood of new residents threaten their missions and their very existence. Add competition, backlogs, duplication, and fragmented collections to this volatile mix and it renders the collecting environment untenable

    Time-dependent photoionization of azulene: Competition between ionization and relaxation in highly excited states

    Get PDF
    Pump-probe photoionization has been used to map the relaxation processes taking place from highly vibrationally excited levels of the S2 state of azulene, populated directly or via internal conversion from the S4 state. Photoelectron spectra obtained by 1+2’ two-color time-resolved photoelectron imaging are invariant (apart from in intensity) to the pump-probe time delay and to pump wavelength. This reveals a photoionization process which is driven by an unstable electronic state (e.g. doubly excited state) lying below the ionization potential. This state is postulated to be populated by a probe transition from S2 and to rapidly relax via an Auger like process onto highly vibrationally excited Rydberg states. This accounts for the time invariance of the photoelectron spectrum. The intensity of the photoelectron spectrum is proportional to the population in S2. An exponential energy gap law is used to describe the internal conversion rate from S2 to S0. The vibronic coupling strength is found to be larger than 60±5 ÎŒeV

    A Bayesian approach for determining player abilities in football

    Get PDF
    We consider the task of determining a football player’s ability for a given event type, for example, scoring a goal. We propose an interpretable Bayesian model which is fit using variational inference methods. We implement a Poisson model to capture occurrences of event types, from which we infer player abilities. Our approach also allows the visualisation of differences between players, for a specific ability, through the marginal posterior variational densities. We then use these inferred player abilities to extend the Bayesian hierarchical model of Baio and Blangiardo (2010, Journal of Applied Statistics, 37(2), 253–264) which captures a team’s scoring rate (the rate at which they score goals). We apply the resulting scheme to the English Premier League, capturing player abilities over the 2013/2014 season, before using output from the hierarchical model to predict whether over or under 2.5 goals will be scored in a given game in the 2014/2015 season. This validates our model as a way of providing insights into team formation and the individual success of sports teams
    • 

    corecore