4,754 research outputs found

    Vibrational Branching Ratios From The Dissociation Of The NeIBr Van Der Waals Molecule

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    The degree of vibrational excitation in the IBr fragment from the vibrational predissociation of NeIBr (A (3)PI(1)) has been measured using two-color pump-probe laser-induced fluorescence spectroscopy. We find that for the lowest initial vibrational states examined, DELTA-upsilon = -1 dissociation pathways dominate the dynamics, while this channel is closed for upsilon greater-than-or-equal-to 17. From this result, the A state binding energy (D0) of the complex is determined to be 67 +/- 4 cm-1, while that in the X electronic state is found to be 73 +/- 4 cm-1. The X state binding energy is identical to that for NeI2 and NeBr2, suggesting that the potential energy surface for NeIBr can be constructed from a summation of atom-atom pair potentials; we present such a model potential energy surface. The variations in the vibrational branching ratios, when combined with the trends in the predissociation rates, point to the importance of fragment rotational excitation in the dynamics of the dissociation

    The emergence of product certification systems as trade barriers: forecasting changes in the automotive sector based on an analysis of key drivers

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    This paper addresses the growing difficulties automobile manufacturers face within their after sales business: an increasing number of trade obstacles set up by import countries discriminates against the foreign suppliers and impedes the international sales of genuine parts. The purpose of the study is to explore the emergence of trade restrictive product certification systems, which affect spare parts exports of automobile manufacturers. The methodology used includes review of the literature and an empirical study based on qualitative interviews with representatives of major stakeholders of the automotive after sales business. Relevant key drivers, which initiate the introduction of technical regulations in importing countries, are identified and analysed to evaluate their effect on the emerging trade policy. The analysis of the key drivers outlines that several interacting components, such as the global competitiveness of the country, macroeconomic and microeconomic factors, and certain country-specific variables induce trade restrictive product certification systems. The findings allow for an early detection of the emergence of product certification systems and provide a means to early recognise the risks and opportunities for the sales of automotive spare parts in the automakers’ target markets. This allows the manufacturers to react immediately and adapt in time to the upcoming changes

    Collisional stripping of planetary crusts

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    Geochemical studies of planetary accretion and evolution have invoked various degrees of collisional erosion to explain differences in bulk composition between planets and chondrites. Here we undertake a full, dynamical evaluation of 'crustal stripping' during accretion and its key geochemical consequences. We present smoothed particle hydrodynamics simulations of collisions between differentiated rocky planetesimals and planetary embryos. We find that the crust is preferentially lost relative to the mantle during impacts, and we have developed a scaling law that approximates the mass of crust that remains in the largest remnant. Using this scaling law and a recent set of N-body simulations, we have estimated the maximum effect of crustal stripping on incompatible element abundances during the accretion of planetary embryos. We find that on average one third of the initial crust is stripped from embryos as they accrete, which leads to a reduction of ~20% in the budgets of the heat producing elements if the stripped crust does not reaccrete. Erosion of crusts can lead to non-chondritic ratios of incompatible elements, but the magnitude of this effect depends sensitively on the details of the crust-forming melting process. The Lu/Hf system is fractionated for a wide range of crustal formation scenarios. Using eucrites (the products of planetesimal silicate melting, thought to represent the crust of Vesta) as a guide to the Lu/Hf of planetesimal crust partially lost during accretion, we predict the Earth could evolve to a superchondritic 176-Hf/177-Hf (3-5 parts per ten thousand) at present day. Such values are in keeping with compositional estimates of the bulk Earth. Stripping of planetary crusts during accretion can lead to detectable changes in bulk composition of lithophile elements, but the fractionation is relatively subtle, and sensitive to the efficiency of reaccretion.Comment: 15 pages, 9 figures. Accepted for publication in EPSL. Abstract shortened. Accompanying animations can be found at http://www.star.bris.ac.uk/pcarter/crust_strip

    Moment tensor inversions of icequakes on Gornergletscher, Switzerland

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    We have determined seismic source mechanisms for shallow and intermediate-depth icequake clusters recorded on the glacier Gornergletscher, Switzerland, during the summers of 2004 and 2006. The selected seismic events are part of a large data set of over 80,000 seismic events acquired with a dense seismic network deployed in order to study the yearly rapid drainage of Gornersee lake, a nearby ice-marginal lake. Using simple frequency and distance scaling and Green’s functions for a homogeneous half-space, we calculated moment tensor solutions for icequakes with M_w-1.5 using a full-waveform inversion method usually applied to moderate seismic events (M_w>4) recorded at local to regional distances (≈50–700 km). Inversions from typical shallow events are shown to represent tensile crack openings. This explains well the dominating Rayleigh waves and compressive first motions observed at all recording seismograms. As these characteristics can be observed in most icequake signals, we believe that the vast majority of icequakes recorded in the 2 yr is due to tensile faulting, most likely caused by surface crevasse openings. We also identified a shallow cluster with somewhat atypical waveforms in that they show less dominant Rayleigh waves and quadrantal radiation patterns of first motions. Their moment tensors are dominated by a large double-couple component, which is strong evidence for shear faulting. Although less than a dozen such icequakes have been identified, this is a substantial result as it shows that shear faulting in glacier ice is generally possible even in the absence of extreme flow changes such as during glacier surges. A third source of icequakes was located at 100 m depth. These sources can be represented by tensile crack openings. Because of the high-hydrostatic pressure within the ice at these depths, these events are most likely related to the presence of water lenses that reduce the effective stress to allow for tensile faulting

    The Precarious State of Family Balance Sheets

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    This report seeks to develop a clear picture of the current state of household financial security. It begins by exploring three components of family balance sheets -- income, expenditures, and wealth -- and how they have changed over the past several decades, and concludes with an examination of how these pieces interrelate and why understanding family finances requires that they be examined holistically. The data tell a powerful story about the state of household economic security and opportunity: Despite the national recovery, most families feel vulnerable and stressed, and could not withstand a serious financial emergency. This reality must begin to change if the American Dream is to remain alive and well for future generations

    National Board-certified Teachers: Can They Make a Difference in Maine Schools?

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    The National Board for Professional Teaching Standards (NBPTS) was created in an effort to improve the status of teaching as a career. In 2006, the Maine legislature authorized a salary supplement for Maine teachers who were certified by the NBPTS. Sarah Mackenzie and Walter Harris describe their study focused on the value of NBPTS certification in professional development and teacher leadership; teacher motivation for seeking certification; barriers to certification; and how Maine teachers might be encouraged to seek certification. They point out that National Board certification is one among many ways to support and improve the quality of teaching in Maine

    Predictors of School Counselors’ Intent to Use Online Counseling

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    As technological advancements provide increased access to mental health resources and online counseling practices continue to grow, it is essential to gain insights into the school counselors\u27 use of integrating technology in practice. The purpose of this quantitative survey study was to examine the predictor variables and their relationship to the school counselors’ intent to use online counseling. Participants in this study included ASCA members serving as school counselors (N = 273). The multiple regression analysis yielded a significant relationship between the independent variables of school counselors\u27 confidence to use online counseling and the school counselors\u27 educational experience, and the dependent variable, school counselors’ intent to use online counseling. The results of this study may be useful to inform counselors\u27 education, training, and preparation programs

    Neighborhood Poverty and Household Financial Security

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    In a previous study, The Pew Charitable Trusts examined the effects of neighborhood context on American families' economic mobility. That analysis found that neighborhood poverty is associated with downward mobility, reinforcing other research that has shown a link between high-poverty neighborhoods and unemployment, poorer performing schools, and increased violence, all of which pose risks to residents' economic security.This chartbook draws on data from the Survey of American Family Finances, commissioned by Pew in November 2014, to illustrate the health of family balance sheets in high- and low-poverty communities across the United States and to examine how neighborhood context influences people's attitudes toward the economy

    NASA Advanced Explorations Systems: 2017 Advancements in Life Support Systems

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    The NASA Advanced Exploration Systems (AES) Life Support Systems (LSS) project strives to develop reliable, energy-efficient, and low-mass spacecraft systems to provide environmental control and life support systems (ECLSS) critical to enabling long duration human missions beyond low Earth orbit (LEO). Highly reliable, closed-loop life support systems are among the capabilities required for the longer duration human space exploration missions planned in the mid-2020s and beyond. The LSS Project is focused on four are-as-architecture and systems engineering for life support systems, environmental monitoring, air revitalization, and wastewater processing and water management. Starting with the International Space Station (ISS) LSS systems as a point of departure where applicable, the three-fold mission of the LSS Project is to address discrete LSS technology gaps, to improve the reliability of LSS systems, and to advance LSS systems toward integrated testing aboard the ISS. This paper is a follow on to the AES LSS development status reported in 2016 and provides additional details on the progress made since that paper was published with specific attention to the status of the Aerosol Sampler ISS Flight Experiment, the Spacecraft Atmosphere Monitor (SAM) Flight Experiment, the Brine Processor Assembly (BPA) Flight Experiment, the CO2 removal technology development tasks, and the work investigating the impacts of dormancy on LSS systems
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