1,008 research outputs found
Star formation in Chamaeleon I and III: a molecular line study of the starless core population
The Chamaeleon clouds are excellent targets for low-mass star formation
studies. Cha I and II are actively forming stars while Cha III shows no sign of
ongoing star formation. We aim to determine the driving factors that have led
to the very different levels of star formation activity in Cha I and III and
examine the dynamical state and possible evolution of the starless cores within
them. Observations were performed in various molecular transitions with APEX
and Mopra. Five cores are gravitationally bound in Cha I and one in Cha III.
The infall signature is seen toward 8-17 cores in Cha I and 2-5 cores in Cha
III, which leads to a range of 13-28% of the cores in Cha I and 10-25% of the
cores in Cha III that are contracting and may become prestellar. Future
dynamical interactions between the cores will not be dynamically significant in
either Cha I or III, but the subregion Cha I North may experience collisions
between cores within ~0.7 Myr. Turbulence dissipation in the cores of both
clouds is seen in the high-density tracers N2H+ 1-0 and HC3N 10-9. Evidence of
depletion in the Cha I core interiors is seen in the abundance distributions of
C17O, C18O, and C34S. Both contraction and static chemical models indicate that
the HC3N to N2H+ abundance ratio is a good evolutionary indicator in the
prestellar phase for both gravitationally bound and unbound cores. In the
framework of these models, we find that the cores in Cha III and the southern
part of Cha I are in a similar evolutionary stage and are less chemically
evolved than the central region of Cha I. The measured HC3N/N2H+ abundance
ratio and the evidence for contraction motions seen towards the Cha III
starless cores suggest that Cha III is younger than Cha I Centre and that some
of its cores may form stars in the future. The cores in Cha I South may on the
other hand be transient structures. (abridged)Comment: Accepted for publication in A&A. The resolution of Figure 2 has been
degraded and the abstract in the metadata has been shortened to fit within
the limits set by arXi
Finite temperature bosonization
Finite temperature properties of a non-Fermi liquid system is one of the most
challenging probelms in current understanding of strongly correlated electron
systems. The paradigmatic arena for studying non-Fermi liquids is in one
dimension, where the concept of a Luttinger liquid has arisen. The existence of
a critical point at zero temperature in one dimensional systems, and the fact
that experiments are all undertaken at finite temperature, implies a need for
these one dimensional systems to be examined at finite temperature.
Accordingly, we extended the well-known bosonization method of one dimensional
electron systems to finite temperatures. We have used this new bosonization
method to calculate finite temperature asymptotic correlation functions for
linear fermions, the Tomonaga-Luttinger model, and the Hubbard model.Comment: REVTex, 48 page
The impact of constructive operating lease capitalisation on key accounting ratios
Current UK lease accounting regulation does not require operating leases to be capitalised in the accounts of lessees, although this is likely to change with the publication of FRS 5. This study conducts a prospective analysis of the effects of such a change. The potential magnitude of the impact of lease capitalisation upon individual users' decisions, market valuations, company cash flows, and managers' behaviour can be indicated by the effect on key accounting ratios, which are employed in decision-making and in financial contracts. The capitalised value of operating leases is estimated using a method similar to that suggested by Imhoff, Lipe and Wright (1991), adapted for the UK accounting and tax environment, and developed to incorporate company-specific assumptions. Results for 1994 for a random sample of 300 listed UK companies show that, on average, the unrecorded long-term liability represented 39% of reported long-term debt, while the unrecorded asset represented 6% of total assets. Capitalisation had a significant impact (at the 1% level) on six of the nine selected ratios (profit margin, return on assets, asset turnover, and three measures of gearing). Moreover, the Spearman rank correlation between each ratio before and after capitalisation revealed that the ranking of companies changed markedly for gearing measures in particular. There were significant inter-industry variations, with the services sector experiencing the greatest impact. An analysis of the impact of capitalisation over the five-year period from 1990 to 1994 showed that capitalisation had the greatest impact during the trough of the recession. Results were shown to be robust with respect to key assumptions of the capitalisation method. These findings contribute to the assessment of the economic consequences of a policy change requiring operating lease capitalisation. Significant changes in the magnitude of key accounting ratios and a major shift in company performance rankings suggest that interested parties' decisions and company cash flows are likely to be affected
Differences in the processing of anaphoric reference between closely related languages: neurophysiological evidence
Contains fulltext :
67857.pdf ( ) (Open Access)1 p
Introducing willingness-to-pay for noise changes into transport appraisal: an application of benefit transfer.
Numerous research studies have elicited willingness-to-pay values for transport-related noise, however, in many industrialised countries including the UK, noise costs and benefits are still not incorporated into appraisals for most transport projects and policy changes (Odgaard et al, 2005; Grant-Muller et al, 2001). This paper describes the actions recently taken in the UK to address this issue, comprising: primary research based on the city of Birmingham; an international review of willingness-to-pay evidence; development of values using benefit transfers over time and locations; and integration with appraisal methods. Amongst the main findings are: that the willingness-to-pay estimates derived for the UK are broadly comparable with those used in appraisal elsewhere in Europe; that there is a case for a lower threshold at
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45dB(A)Leq,18hr1 rather than the more conventional 55dB(A); and that values per dB(A) increase with the noise level above this threshold. There are significant issues over the valuation of rail versus road noise, the neglect of non-residential noise and the valuation of high noise levels in different countries. Conclusions are drawn regarding the feasibility of noise valuation based on benefit transfers in the UK and elsewhere, and future research needs in this field are discussed
Derivation of the Blackbody Radiation Spectrum from a Natural Maximum-Entropy Principle Involving Casimir Energies and Zero-Point Radiation
By numerical calculation, the Planck spectrum with zero-point radiation is
shown to satisfy a natural maximum-entropy principle whereas alternative
choices of spectra do not. Specifically, if we consider a set of
conducting-walled boxes, each with a partition placed at a different location
in the box, so that across the collection of boxes the partitions are uniformly
spaced across the volume, then the Planck spectrum correspond to that spectrum
of random radiation (having constant energy kT per normal mode at low
frequencies and zero-point energy (1/2)hw per normal mode at high frequencies)
which gives maximum uniformity across the collection of boxes for the radiation
energy per box. The analysis involves Casimir energies and zero-point radiation
which do not usually appear in thermodynamic analyses. For simplicity, the
analysis is presented for waves in one space dimension.Comment: 11 page
Grain Surface Models and Data for Astrochemistry
AbstractThe cross-disciplinary field of astrochemistry exists to understand the formation, destruction, and survival of molecules in astrophysical environments. Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. A broad consensus has been reached in the astrochemistry community on how to suitably treat gas-phase processes in models, and also on how to present the necessary reaction data in databases; however, no such consensus has yet been reached for grain-surface processes. A team of ∼25 experts covering observational, laboratory and theoretical (astro)chemistry met in summer of 2014 at the Lorentz Center in Leiden with the aim to provide solutions for this problem and to review the current state-of-the-art of grain surface models, both in terms of technical implementation into models as well as the most up-to-date information available from experiments and chemical computations. This review builds on the results of this workshop and gives an outlook for future directions
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