11,024 research outputs found
Single and Double Photoionization and Photodissociation of Toluene by Soft X-rays in Circumstellar Environment
The formation of polycyclic aromatic hydrocarbons (PAHs) and their methyl
derivatives occurs mainly in the dust shells of asymptotic giant branch (AGB)
stars. The bands at 3.3 and 3.4 m, observed in infrared emission spectra
of several objects, are attributed C-H vibrational modes in aromatic and
aliphatic structures, respectively. In general, the feature at 3.3 m is
more intense than the 3.4 m. Photoionization and photodissociation
processes of toluene, the precursor of methylated PAHs, were studied using
synchrotron radiation at soft X-ray energies around the carbon K edge with
time-of-flight mass spectrometry. Partial ion yields of a large number of ionic
fragments were extracted from single and 2D-spectra, where electron-ion
coincidences have revealed the doubly charged parent-molecule and several
doubly charged fragments containing seven carbon atoms with considerable
abundance. \textit{Ab initio} calculations based on density functional theory
were performed to elucidate the chemical structure of these stable dicationic
species. The survival of the dications subjected to hard inner shell ionization
suggests that they could be observed in the interstellar medium, especially in
regions where PAHs are detected. The ionization and destruction of toluene
induced by X-rays were examined in the T Dra conditions, a carbon-rich AGB
star. In this context, a minimum photodissociation radius and the half-life of
toluene subjected to the incidence of the soft X-ray flux emitted from a
companion white dwarf star were determined.Comment: 11 pages, 4 figures, accept for publication in Ap
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Learning From Coalitions' Efforts to Promote Equity and Justice.
Coalitions and collaboratives are working to address many of the most pressing contemporary health and social issues. The articles in this special issue provide numerous insights into these complex collaborative processes across different contexts and focal issues. All emphasize and scrutinize the strategies that groups are using in their work. These strategies seek to navigate not only conventional notions of effectiveness but also the challenges of pursuing greater equity and justice. In this concluding article, we distill some of the key insights from these articles as a collective. This special issue on collaborating for equity and justice can serve as a launching point for new efforts by coalitions and researchers pursuing policy, systems, and structural changes, particularly those intent on addressing root causes of health and social disparities
Multi-Component Dosing in Membrane Reactors Including an Internal Reactant Recycling
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The Finite Field Kakeya Problem
A Besicovitch set in AG(n,q) is a set of points containing a line in every
direction. The Kakeya problem is to determine the minimal size of such a set.
We solve the Kakeya problem in the plane, and substantially improve the known
bounds for n greater than 4.Comment: 13 page
Direct Synthesis of Propene Using Supported Bifunctional Nickel Catalysts: Preparation and Potential
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Kinetic Analysis of the Hydrocarbon Total Oxidation Using Individually Measured Adsorption Isotherms
Dedicated to Prof. Dr.-Ing. Andreas Seidel-Morgenstern on the occasion of his 60th birthda
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