Sensitive VLBI Studies of the OH Megamaser Emission from IRAS 17208-0014

We present phase-referenced VLBI results on the radio continuum and the OH 18 cm megamaser emission from the Ultra-Luminous Infrared Galaxy, IRAS 17208--0014. The observations were carried out at 1599 MHz using the Very Long Baseline Array, the phased VLA, and the Green Bank Telescope. The highest resolution radio continuum results show several compact sources with brightness temperatures on the order of $10^{6}$ K. These sources are more likely to be clustered supernova remnants and/or luminous radio supernovae. However, the agreement between the number of observed and expected compact sources above the 5 $\sigma$ level supports the possibility that each one of the compact sources could be dominated by a recently detonated luminous radio supernova. The continuum results suggest that there is no radio-loud AGN in the nuclear region of this galaxy. The OH 18 cm megamaser emission in IRAS 17208--0014 is detected at various angular resolutions. It has an extent of $170 \times 110$ pc, and is mostly localized in two regions separated by 61 pc. The structure and dynamics of the maser emission seem to be consistent with a clumpy, rotating, ring-like geometry, with the two dominant maser regions marking the tangential points of the proposed rotating-ring distribution. Assuming Keplerian motion for the rotating maser ring, the enclosed dynamical mass and the mass density within a radius of 30.5 pc, are about {$3 \times 10^7 ({\rm sin}^{-2}i) M{_\odot}$}, and $281 ({\rm sin}^{-2} i) M{_\odot} {\rm pc}^{-3}$, respectively.Comment: 8 pages, 5 figures. ApJ Accepte

Thermoelastic Damping in Micro- and Nano-Mechanical Systems

The importance of thermoelastic damping as a fundamental dissipation mechanism for small-scale mechanical resonators is evaluated in light of recent efforts to design high-Q micrometer- and nanometer-scale electro-mechanical systems (MEMS and NEMS). The equations of linear thermoelasticity are used to give a simple derivation for thermoelastic damping of small flexural vibrations in thin beams. It is shown that Zener's well-known approximation by a Lorentzian with a single thermal relaxation time slightly deviates from the exact expression.Comment: 10 pages. Submitted to Phys. Rev.

The electric double layer has a life of its own

Using molecular dynamics simulations with recently developed importance sampling methods, we show that the differential capacitance of a model ionic liquid based double-layer capacitor exhibits an anomalous dependence on the applied electrical potential. Such behavior is qualitatively incompatible with standard mean-field theories of the electrical double layer, but is consistent with observations made in experiment. The anomalous response results from structural changes induced in the interfacial region of the ionic liquid as it develops a charge density to screen the charge induced on the electrode surface. These structural changes are strongly influenced by the out-of-plane layering of the electrolyte and are multifaceted, including an abrupt local ordering of the ions adsorbed in the plane of the electrode surface, reorientation of molecular ions, and the spontaneous exchange of ions between different layers of the electrolyte close to the electrode surface. The local ordering exhibits signatures of a first-order phase transition, which would indicate a singular charge-density transition in a macroscopic limit

A field study of team working in a new human supervisory control system

This paper presents a case study of an investigation into team behaviour in an energy distribution company. The main aim was to investigate the impact of major changes in the company on system performance, comprising human and technical elements. A socio-technical systems approach was adopted. There were main differences between the teams investigated in the study: the time of year each control room was studied (i.e. summer or winter),the stage of development each team was in (i.e. 10 months), and the team structure (i.e. hierarchical or heterarchical). In all other respects the control rooms were the same: employing the same technology and within the same organization. The main findings were: the teams studied in the winter months were engaged in more `planning’ and `awareness’ type of activities than those studies in the summer months. Newer teams seem to be engaged in more sharing of information than older teams, which maybe indicative of the development process. One of the hierarchical teams was engaged in more `system-driven’ activities than the heterarchical team studied at the same time of year. Finally, in general, the heterarchical team perceived a greater degree of team working culture than its hierarchical counterparts. This applied research project confirms findings from laboratory research and emphasizes the importance of involving ergonomics in the design of team working in human supervisory control

The Effect of 53 micron IR Radiation on 18 cm OH Megamaser Emission

OH megamasers (OHMs) emit primarily in the main lines at 1667 and 1665 MHz, and differ from their Galactic counterparts due to their immense luminosities, large linewidths and 1667/1665 MHz flux ratios, which are always greater than one. We find that these maser properties result from strong 53 micron radiative pumping combined with line overlap effects caused by turbulent linewidths of about 20 km/s; pumping calculations that do not include line overlap are unreliable. A minimum dust temperature of about 45 K is needed for inversion, and maximum maser efficiency occurs for dust temperatures in the range 80 - 140 K. We find that warmer dust can support inversion at lower IR luminosities, in agreement with observations. Our results are in good agreement with a clumpy model of OHMs, with clouds sizes about 1 pc and OH column densities about 5e16 cm^2, that is able to explain both the diffuse and compact emission observed for OHMs. We suggest that all OH main line masers may be pumped by far-IR radiation, with the major differences between OHMs and Galactic OH masers caused by differences in linewidth produced by line overlap. Small Galactic maser linewidths tend to produce stronger 1665 MHz emission. The large OHM linewidths lead to inverted ground state transitions having approximately the same excitation temperature, producing 1667/1665 MHz flux ratios greater than one and weak satellite line emission. Finally, the small observed ratio of pumping radiation to dense molecular gas, as traced by HCN and HCO$^+$, is a possible reason for the lack of OH megamaser emission in NGC 6240.Comment: Accepted to ApJ, 26 pages including 1 table and 7 figure

A system approach for modelling additive manufacturing in defence acquisition programs

Defence Contractors and NATOMinistry of Defences (MoDs) are currently exploiting Additive Manufacturing (AM) Technology to improve availability of defence platforms and support soldiers deployed in remote Area of Operations (AO). Additive Manufacturing is considered a disruptive technology when employed in a military context to reduce the reliance on supply chains and improve the responsiveness to Operation Tempo (OT). This papers aims at presenting a novel system approach to model the end-to-end process of delivering a product printed with AM and estimate accurately the time and costs of AM. Understanding better the time and costs of AM will allow the MoDs and Defence Contractors to perform comparison with current practices and support their decision making in AM technology acquisition

Religion, Partisanship, and Attitudes Toward Science Policy

We examine issues involving science which have been contested in recent public debate. These “contested science” issues include human evolution, stem-cell research, and climate change. We find that few respondents evince consistently skeptical attitudes toward science issues, and that religious variables are generally strong predictors of attitudes toward individual issues. Furthermore, and contrary to analyses of elite discourse, partisan identification is not generally predictive of attitudes toward contested scientific issues

SRAO CO Observation of 11 Supernova Remnants in l = 70 to 190 deg

We present the results of 12CO J = 1-0 line observations of eleven Galactic supernova remnants (SNRs) obtained using the Seoul Radio Astronomy Observatory (SRAO) 6-m radio telescope. The observation was made as a part of the SRAO CO survey of SNRs between l = 70 and 190 deg, which is intended to identify SNRs interacting with molecular clouds. The mapping areas for the individual SNRs are determined to cover their full extent in the radio continuum. We used halfbeam grid spacing (60") for 9 SNRs and full-beam grid spacing (120") for the rest. We detected CO emission towards most of the remnants. In six SNRs, molecular clouds showed a good spatial relation with their radio morphology, although no direct evidence for the interaction was detected. Two SNRs are particularly interesting: G85.4+0.7, where there is a filamentary molecular cloud along the radio shell, and 3C434.1, where a large molecular cloud appears to block the western half of the remnant. We briefly summarize the results obtained for individual SNRs.Comment: Accepted for publication in Astrophysics & Space Science. 12 pages, 12 figures, and 3 table