573 research outputs found
Quantum dynamics of the Li+HF-->H+LiF reaction at ultralow temperatures
Quantum mechanical calculations are reported for the
Li+HF(v=0,1,j=0)-->H+LiF(v',j') bimolecular scattering process at low and
ultralow temperatures. Calculations have been performed for zero total angular
momentum using a recent high accuracy potential energy surface for the X 2A'
electronic ground state. For Li+HF(v=0,j=0), the reaction is dominated by
resonances due to the decay of metastable states of the Li...F-H van der Waals
complex. Assignment of these resonances has been carried out by calculating the
eigenenergies of the quasibound states. We also find that while chemical
reactivity is greatly enhanced by vibrational excitation the resonances get
mostly washed out in the reaction of vibrationally excited HF with Li atoms. In
addition, we find that at low energies, the reaction is significantly
suppressed due to the formation of rather deeply bound van der Waals complexes
and the less efficient tunneling of the relatively heavy fluorine atom.Comment: 24 pages, 8 figures, 1 table, submitted to J. Chem. Phy
The rovibrational spectrum of BeH, MgH and CaH at high temperatures in the state: a theoretical study
Accurate line lists for three molecules, BeH, MgH and CaH, in their ground
electronic states are presented. These line lists are suitable for temperatures
relevant to exoplanetary atmospheres and cool stars (up to 2000K). A
combination of empirical and \textit{ab initio} methods is used. The
rovibrational energy levels of BeH, MgH and CaH are computed using the programs
Level and DPotFit in conjunction with `spectroscopic' potential energy curves
(PECs). The PEC of BeH is taken from the literature, while the PECs of CaH and
MgH are generated by fitting to the experimental transition energy levels. Both
spin-rotation interactions (except for BeH, for which it is negligible) and
non-adiabatic corrections are explicitly taken into account. Accurate line
intensities are generated using newly computed \textit{ab initio} dipole moment
curves for each molecule using high levels of theory. Full line lists of
rotation-vibration transitions for BeH, MgH, MgH, MgH
and CaH are made available in an electronic form as supplementary data
to this article and at \url{www.exomol.com}.Comment: MNRAS (in press
Variation in survival after diagnosis of breast cancer in Switzerland
Background: Survival after diagnosis of cancer is a key criterion for cancer control. Major survival differences between time periods and countries have been reported by the EUROCARE studies. We investigated whether similar differences by period and region existed in Switzerland. Methods: Survival of 11 376 cases of primary invasive female breast cancer diagnosed between 1988 and 1997 and registered in seven Swiss cancer registries covering a population of 3.5 million was analysed. Results: Comparing the two periods 1988-1992 and 1993-1997, age-standardized 5 year relative survival improved globally from 77% to 81%. Furthermore, multivariate analysis adjusting for age, tumour size and nodal involvement identified regional survival differences. Survival was lowest in the rural parts of German-speaking eastern Switzerland and highest in urbanised regions of the Latin- and German-speaking northwestern parts of the country. Conclusions: This study confirms that survival differences are present even in a small and affluent, but culturally diverse, country like Switzerland, raising the issue of heterogeneity in access to care and quality of treatmen
Chemical reactivity of ultracold polar molecules: investigation of H + HCl and H + DCl collisions
Quantum scattering calculations are reported for the H+HCl(v,j=0) and
H+DCl(v,j=0) collisions for vibrational levels v=0-2 of the diatoms.
Calculations were performed for incident kinetic energies in the range 10-7 to
10-1 eV, for total angular momentum J=0 and s-wave scattering in the entrance
channel of the collisions. Cross sections and rate coefficients are
characterized by resonance structures due to quasibound states associated with
the formation of the H...HCl and H...DCl van der Waals complexes in the
incident channel. For the H+HCl(v,j=0) collision for v=1,2, reactive scattering
leading to H_2 formation is found to dominate over non-reactive vibrational
quenching in the ultracold regime. Vibrational excitation of HCl from v=0 to
v=2 increases the zero-temperature limiting rate coefficient by about 8 orders
of magnitude.Comment: 9 pages, 6 figures, submitted to Euro. Phys. J. topical issue on
"Ultracold Polar Molecules: Formation and Collisions
Design of a five-axis ultra-precision micro-milling machine—UltraMill. Part 1: Holistic design approach, design considerations and specifications
High-accuracy three-dimensional miniature components and microstructures are increasingly in demand in the sector of electro-optics, automotive, biotechnology, aerospace and information-technology industries. A rational approach to mechanical micro machining is to develop ultra-precision machines with small footprints. In part 1 of this two-part paper, the-state-of-the-art of ultra-precision machines with micro-machining capability is critically reviewed. The design considerations and specifications of a five-axis ultra-precision micro-milling machine—UltraMill—are discussed. Three prioritised design issues: motion accuracy, dynamic stiffness and thermal stability, formulate the holistic design approach for UltraMill. This approach has been applied to the development of key machine components and their integration so as to achieve high accuracy and nanometer surface finish
Virtual manufacturing: prediction of work piece geometric quality by considering machine and set-up accuracy
Primeval very low-mass stars and brown dwarfs - III. The halo transitional brown dwarfs
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We report the discovery of an esdL3 subdwarf, ULAS J020858.62+020657.0 and a usdL4.5 subdwarf, ULAS J230711.01+014447.1. They were identified as L subdwarfs by optical spectra obtained with the Gran Telescopio Canarias, and followed up by optical to near infrared spectroscopy with the Very Large Telescope. We also obtained an optical to near infrared spectrum of a previously known L subdwarf, ULAS J135058.85+081506.8, and re-classified it as a usdL3 subdwarf. These three objects all have typical halo kinematics. They have around 2050-2250 K, 1.8 [Fe/H] 1.5, and mass around 0.0822-0.0833 M, according to model spectral fitting and evolutionary models. These sources are likely halo transitional brown dwarfs with unsteady hydrogen fusions, as their masses are just below the hydrogen-burning minimum mass, which is 0.0845 M at [Fe/H] = 1.6 and 0.0855 M at [Fe/H] = 1.8. Including these, there are now nine objects in the `halo brown dwarf transition zone', which is a `substellar subdwarf gap' spans a wide temperature range within a narrow mass range of the substellar population.Peer reviewedFinal Accepted Versio
Women and Illegal Activities: Gender Differences and Women's Willingness to Comply Over Time
In recent years the topics of illegal activities such as corruption or tax evasion have attracted a great deal of attention. However, there is still a lack of substantial empirical evidence about the determinants of compliance. The aim of this paper is to investigate empirically whether women are more willing to be compliant than men and whether we observe (among women and in general) differences in attitudes among similar age groups in different time periods (cohort effect) or changing attitudes of the same cohorts over time (age effect) using data from eight Western European countries from the World Values Survey and the European Values Survey that span the period from 1981 to 1999. The results reveal higher willingness to comply among women and an age rather than a cohort effect. Working Paper 06-5
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