95 research outputs found
Merged-beams Reaction Studies of O + H_3^+
We have measured the reaction of O + H3+ forming OH+ and H2O+. This is one of
the key gas-phase astrochemical processes initiating the formation of water
molecules in dense molecular clouds. For this work, we have used a novel merged
fast-beams apparatus which overlaps a beam of H3+ onto a beam of ground-term
neutral O. Here, we present cross section data for forming OH+ and H2O+ at
relative energies from \approx 3.5 meV to \approx 15.5 and 0.13 eV,
respectively. Measurements were performed for statistically populated O(3PJ) in
the ground term reacting with hot H3+ (with an internal temperature of \approx
2500-3000 K). From these data, we have derived rate coefficients for
translational temperatures from \approx 25 K to \approx 10^5 and 10^3 K,
respectively. Using state-of-the-art theoretical methods as a guide, we have
converted these results to a thermal rate coefficient for forming either OH+ or
H2O+, thereby accounting for the temperature dependence of the O fine-structure
levels. Our results are in good agreement with two independent flowing
afterglow measurements at a temperature of \approx 300 K, and with a
corresponding level of H3+ internal excitation. This good agreement strongly
suggests that the internal excitation of the H3+ does not play a significant
role in this reaction. The Langevin rate coefficient is in reasonable agreement
with the experimental results at 10 K but a factor of \approx 2 larger at 300
K. The two published classical trajectory studies using quantum mechanical
potential energy surfaces lie a factor of \approx 1.5 above our experimental
results over this 10-300 K range.Comment: 43 pages, 11 figures. Submitted to the Astrophysical Journa
Recommended Thermal Rate Coefficients for the C + H Reaction and Some Astrochemical Implications
We have incorporated our experimentally derived thermal rate coefficients for
C + H forming CH and CH into a commonly used astrochemical
model. We find that the Arrhenius-Kooij equation typically used in chemical
models does not accurately fit our data and use instead a more versatile
fitting formula. At a temperature of 10 K and a density of 10 cm, we
find no significant differences in the predicted chemical abundances, but at
higher temperatures of 50, 100, and 300 K we find up to factor of 2 changes.
Additionally, we find that the relatively small error on our thermal rate
coefficients, , significantly reduces the uncertainties on the
predicted abundances compared to those obtained using the currently implemented
Langevin rate coefficient with its estimated factor of 2 uncertainty.Comment: 19 pages, 5 figures. Accepted for publication in Ap
Expatriation and Incapacity created by a Multitude of Hidden Inequalities
The ability of UK based Academics to function within collaborative partnerships is becoming an important part of the UK Universities internationalisation agenda. This chapter offers an auto-ethnographical academic expatriate experience detailing some of the challenges faced when moving to work in a ‘UK environment positioned abroad’, specifically in China. It will provide HR personnel with alternative understandings of possible support strategies that could assist individuals in dealing with a variety of hidden inequalities that surface. These hidden inequalities can contribute to a possible shortening of the assignment due to cultural contexts in which they are operating (Foster 1997; Wang and Varma 2017)
The Effect of Intraocular Pressure on the Outcome of Myopic Photorefractive Keratectomy: A Numerical Approach
How Trade-Restrictive Is Standardized Packaging? Economic and Legal Implications of the WTO Panel Reports in Australia-Tobacco Plain Packaging
Published by Cambridge University Press. The lengthy and long-awaited WTO Panel Reports in Australia-Tobacco Plain Packaging contain a host of material for reflection, particularly in relation to the Agreement on Technical Barriers to Trade (TBT) and the Agreement on Trade-Related Aspects of Intellectual Property Rights. While two of the Panel Reports proceed to appeal, we consider with respect to the two adopted Panel Reports the Panel's reasoning in relation to Article 2.2 of the TBT, focusing on the meaning of trade-restrictiveness. This concept central to WTO law has been under-examined to date, and these Panel Reports demonstrate some of the complexities in identifying trade-restrictive measures, particularly where they are non-discriminatory. The Panel found that Australia's measures restrict trade because they contribute to their objective of reducing tobacco consumption. Therefore, any equally effective alternative will similarly restrict trade. This curious result under TBT Article 2.2 may be particular to non-discriminatory measures that target 'socially bad' products such as tobacco
A microstructural model of cross-link interaction between collagen fibrils in the human cornea
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