A new HCN maser in IRAS 15082-4808

We have identified a new vibrational HCN maser at 89.087 GHz in the asymptotic giant branch (AGB) star IRAS 15082-4808, a maser which is thought to trace the innermost region of an AGB envelope. The observations of this maser at three epochs are presented: two positive detections and one null detection. The line profile has varied between the positive detections, as has the intensity of the maser. The major component of the maser is found to be offset by -2.0+/-0.9 km/s with respect to the systemic velocity of the envelope, as derived from the 88.631 GHz transition of HCN. Similar blueshifts are measured in the other 9 sources where this maser has been detected. Maser variability with pulsation phase has been investigated for the first time using the 10 stars now available. Comparisons with AGB model atmospheres constrain the position of the formation region of the maser to the region between the pulsation shocks and the onset of dust acceleration, between 2 and 4 stellar radii.Comment: 11 pages, 10 figures, accepted MNRAS, minor correction to equation

Free-free and H42alpha emission from the dusty starburst within NGC 4945 as observed by ALMA

We present observations of the 85.69 GHz continuum emission and H42alpha line emission from the central 30 arcsec within NGC 4945. Both sources of emission originate from nearly identical structures that can be modelled as exponential discs with a scale length of ~2.1 arcsec (or ~40 pc). An analysis of the spectral energy distribution based on combining these data with archival data imply that 84% +/- 10% of the 85.69 GHz continuum emission originates from free-free emission. The electron temperature is 5400 +/- 600 K, which is comparable to what has been measured near the centre of the Milky Way Galaxy. The star formation rate (SFR) based on the H42alpha and 85.69 GHz free-free emission (and using a distance of 3.8 Mpc) is 4.35 +/- 0.25 M/yr. This is consistent with the SFR from the total infrared flux and with previous measurements based on recombination line emission, and it is within a factor of ~2 of SFRs derived from radio data. The Spitzer Space Telescope 24 micron data and Wide-field Infrared Survey Explorer 22 micron data yield SFRs ~10x lower than the ALMA measurements, most likely because the mid-infrared data are strongly affected by dust attenuation equivalent to A_V=150. These results indicate that SFRs based on mid-infrared emission may be highly inaccurate for dusty, compact circumnuclear starbursts.Comment: 19 pages, 9 figures, accepted for publication in MNRA

An Active-Sterile Neutrino Transformation Solution for r-Process Nucleosynthesis

We discuss how matter-enhanced active-sterile neutrino transformation in both neutrino and antineutrino channels could enable the production of the rapid neutron capture (r-process) nuclei in neutrino-heated supernova ejecta. In this scheme the lightest sterile neutrino would be heavier than the electron neutrino and split from it by a vacuum mass-squared difference roughly between 3 and 70 eV$^2$ and vacuum mixing angle given by $\sin^2 2\theta_{es} > 10^{-4}$.Comment: 27 pages plus twelve figures. Submitted to Phys. Rev.

Comment on "Elasticity Model of a Supercoiled DNA Molecule"

We perform simulations to numerically study the writhe distribution of a stiff polymer. We compare with analytic results of Bouchiat and Mezard (PRL 80 1556- (1998); cond-mat/9706050).Comment: 1 page, 1 figure revtex

Solvatochromism in Perylene Diimides; Experiment and Theory

We report an experimental and computational investigation into the solvatochromism of a perylene diimide derivative. The alkyl swallowtail substituents allowed solubility in many solvents of widely differing polarity, with a complicated resultant behaviour, illustrating both negative and positive solvatochromism as a function of dielectric constant. Luminescence quantum yield and optical absorption linewidth displayed an inverse correlation, indicating varying degrees of intermolecular aggregation, and a remarkably similar trend was found between the peak absorption wavelength and the solvent boiling point, illustrating the dependency of aggregation on the solvent interactions. These outline trends may be parameterised by an empirically derived dimensionless quantity, as a tool to be used in more sophisticated future models of solvatochromism in small molecule chromophoresPeer reviewe

Neutrino energy transport in weak decoupling and big bang nucleosynthesis

We calculate the evolution of the early universe through the epochs of weak decoupling, weak freeze-out and big bang nucleosynthesis (BBN) by simultaneously coupling a full strong, electromagnetic, and weak nuclear reaction network with a multi-energy group Boltzmann neutrino energy transport scheme. The modular structure of our code provides the ability to dissect the relative contributions of each process responsible for evolving the dynamics of the early universe in the absence of neutrino flavor oscillations. Such an approach allows a detailed accounting of the evolution of the $\nu_e$, $\bar\nu_e$, $\nu_\mu$, $\bar\nu_\mu$, $\nu_\tau$, $\bar\nu_\tau$ energy distribution functions alongside and self-consistently with the nuclear reactions and entropy/heat generation and flow between the neutrino and photon/electron/positron/baryon plasma components. This calculation reveals nonlinear feedback in the time evolution of neutrino distribution functions and plasma thermodynamic conditions (e.g., electron-positron pair densities), with implications for: the phasing between scale factor and plasma temperature; the neutron-to-proton ratio; light-element abundance histories; and the cosmological parameter \neff. We find that our approach of following the time development of neutrino spectral distortions and concomitant entropy production and extraction from the plasma results in changes in the computed value of the BBN deuterium yield. For example, for particular implementations of quantum corrections in plasma thermodynamics, our calculations show a $0.4\%$ increase in deuterium. These changes are potentially significant in the context of anticipated improvements in observational and nuclear physics uncertainties.Comment: 37 pages, 12 Figures, 6 Table

Space Station Centrifuge: A Requirement for Life Science Research

A centrifuge with the largest diameter that can be accommodated on Space Station Freedom is required to conduct life science research in the microgravity environment of space. (This was one of the findings of a group of life scientists convened at the University of California, Davis, by Ames Research Center.) The centrifuge will be used as a research tool to understand how gravity affects biological processes; to provide an on-orbit one-g control; and to assess the efficacy of using artificial gravity to counteract the deleterious biological effect of space flight. The rationale for the recommendation and examples of using ground-based centrifugation for animal and plant acceleration studies are presented. Included are four appendixes and an extensive bibliography of hypergravity studies

Operations Research And Operations Management: From Selective Optimization To System Optimization

The focus of this research paper is to discuss the development of Operations Management (OM) and Operations Research (OR) with respect to their use within the organization’s decision-making structure.  In addition, the difference in the tools and techniques of the two fields is addressed.  The question is raised as to how distinct the two academic fields have become in light of the application of their models to the service industry.  Suggestions are made regarding the possibility of incorporating OM/OR models and their output into the decision making structure of the organization towards the goal of “system optimization”