79 research outputs found
The role of normally hyperbolic invariant manifolds (NHIMS) in the context of the phase space setting for chemical reaction dynamics
Molecular excitation in the Interstellar Medium: recent advances in collisional, radiative and chemical processes
We review the different excitation processes in the interstellar mediumComment: Accepted in Chem. Re
Teaching: Natural or Cultural?
In this chapter I argue that teaching, as we now understand the term, is historically and cross-culturally very rare. It appears to be unnecessary to transmit culture or to socialize children. Children are, on the other hand, primed by evolution to be avid observers, imitators, players and helpersâroles that reveal the profoundly autonomous and self-directed nature of culture acquisition (Lancy in press a). And yet, teaching is ubiquitous throughout the modern worldâat least among the middle to upper class segment of the population. This ubiquity has led numerous scholars to argue for the universality and uniqueness of teaching as a characteristically human behavior. The theme of this chapter is that this proposition is unsustainable. Teaching is largely a result of recent cultural changes and the emergence of modern economies, not evolution
Nfs Version 4 Protocol
NFS (Network File System) version 4 is a distributed file system protocol which owes heritage to NFS protocol versions 2 [RFC1094] and 3 [RFC1813]. Unlike earlier versions, the NFS version 4 protocol supports traditional file access while integrating support for file locking and the mount protocol. In addition, support for strong security (and its negotiation), compound operations, client caching, and internationalization have been added. Of course, attention has been applied to making NFS version 4 operate well in an Internet environment. Key Words The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. Table of Contents 1
Low energy H+CO scattering revisited
Context.A recent modeling study of brightness ratios for CO rotational transitions in
gas typical of the diffuse ISM by Liszt found the role of H collisions to
be more important than previously assumed. This conclusion
was based on recent quantum scattering calculations using the so-called WKS
potential energy surface (PES) which reported a large cross section for
the important 01 rotational transition. This result is in contradiction to
one obtained using the earlier BBH PES for which the cross section is quite
small and which is consistent with an expected homonuclear-like
propensity for even transitions.
Aims.We revisit this contradiction with new scattering
calculations using two new ab initio PESs
that focus on the important long-range behavior and explore the
validity of the apparent departure from the expected
even propensity
in H-CO rotational excitation obtained with the WKS PES.
Methods.Close-coupling (CC) rigid-rotor calculations for CO(v = 0, J = 0) excitation
by H are performed on four different PESs. Two of the PESs are obtained
in this work using state-of-the-art quantum chemistry techniques at the
CCSD(T) and MRCI levels of theory.
Results.Cross sections for the J = 01, as well as other odd ,
transitions are significantly suppressed compared to even  transitions in thermal energy CC calculations using the CCSD(T) and MRCI
surfaces. This is consistent with the expected even  propensity
and in contrast to CC calculations using the WKS PES which predict a
dominating 01 transition.
Conclusions.Inelastic collision cross section calculations are sensitive to fine
details in the anisotropic components of the PES and its long-range
behavior. The current results
obtained with new surfaces for H-CO scattering suggest that the original
astrophysical assumption that excitation of CO by H2 dominates the kinetics
of CO in diffuse ISM gas is likely to remain valid
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