Cloud Atlas: Navigating the Multiphase Landscape of Tempestuous Galactic Winds

Galaxies comprise intricate networks of interdependent processes which together govern their evolution. Central among these are the multiplicity of feedback channels, which remain incompletely understood. One outstanding problem is the understanding and modeling of the multiphase nature of galactic winds, which play a crucial role in galaxy formation and evolution. We present the results of three dimensional magnetohydrodynamical tall box interstellar medium patch simulations with clustered supernova driven outflows. Fragmentation of the interstellar medium during superbubble breakout seeds the resulting hot outflow with a population of cool clouds. We focus on analyzing and modeling the origin and properties of these clouds. Their presence induces large scale turbulence, which in turn leads to complex cloud morphologies. Cloud sizes are well described by a power law distribution and mass growth rates can be modelled using turbulent radiative mixing layer theory. Turbulence provides significant pressure support in the clouds, while magnetic fields only play a minor role. We conclude that many of the physical insights and analytic scalings derived from idealized small scale simulations translate well to larger scale, more realistic turbulent magnetized winds, thus paving a path towards their necessary yet challenging inclusion in global-scale galaxy models.Comment: 34 pages, 37 figures; Accepted for publication in MNRA

State criminal justice telecommunications (STACOM). Volume 3: Requirements analysis and design of Texas criminal Justice Telecommunications Network

For abstract, see N78-16218

Behavioural changes in relation to risk perception and prevention of avian and human influenza in the general population of Hong Kong, 2006 to 2010

Conference Theme: Translating Health Research into Policy and Practice for Health of the PopulationPoster Presentation: abstract no. P84-Ab0047BACKGROUND: The Hong Kong government has introduced a series of progressive measures on importation, farming and retail of live poultry to minimize risk of A/H5N1 transmission since 1997. Perceived risk of A/H5N1 and related preventions could decline as these macro-level policies minimizing human-chicken contact. This may paradoxically increase population risk of other influenza and respiratory infection due to reduced preventive behaviors. OBJECTIVES: A follow-up survey in 2010 was conducted to investigate change of live poultry exposure, risk perception and prevention of A/H5N1 among respondents who participated in the random household telephone survey in 2006. METHODS: Totally, of 1,760 respondents who completed the 2006 survey, 680 could be traced and ...published_or_final_versio

Electron Paramagnetic Resonance Investigation of the Structure of Graphene Oxide: pH-Dependence of the Spectroscopic Response

The time-dependence of the electron paramagnetic resonance (EPR) signal arising from purified graphene oxide (GO) in various solvents has been investigated. The prepared GO was sequentially base and acid (ba) treated to remove manganese impurities. The EPR signal of ba-GO was found to be pH-dependent when exposed to different aqueous solutions, which is related to the decarboxylation process the material undergoes in solution. This process involves the fragmentation of the carbonaceous framework and occurs most rapidly in alkaline conditions. Under acidic conditions, fragmentation is much slower, leading to a gradual increase in the EPR signal from ba-GO in the presence of oxygen. Inferred structural changes were correlated with those deduced from X-ray photoelectron spectroscopy to explain the observed pH- and time-dependent effects. Comparative experiments showed that the oxygen molecule was the key to the increase of unpaired electron density. Exposure to superoxide anions in situ confirmed that the scavenging ability of ba-GO was related to the oxidation of the sp2-carbon structure, which led to an increase of the EPR signal. Overall, the results demonstrate changes of the structure and stability of GO at different pH values

In situ Electron Paramagnetic Resonance Spectroelectrochemical Study of Graphene-based Supercapacitors: Comparison between Chemically Reduced Graphene Oxide and Nitrogen-doped Reduced Graphene Oxide

An in situ electrochemical electron paramagnetic resonance (EPR) spectroscopic study of N-doped reduced graphene oxide (N-rGO) is reported with the aim of understanding the properties of this material when employed as an electrical double-layer capacitor. N-rGO shows a capacitance of 100 F g−1 in 6 M KOH, which is twice that found for reduced graphene oxide (rGO). The temperature dependence of the rGO EPR signal revealed two different components: a narrow component, following the Curie law, was related to defects; and a broad curve with a stronger Pauli law component was attributed to the spin interaction between mobile electrons and localised π electrons trapped at a more extended aromatic structure. The N-rGO sample presented broader EPR signals, indicative of additional contributions to the resonance width. In situ EPR electrochemical spectroscopy was applied to both samples to relate changes in unpaired electron density to the enhanced capacitance. The narrow and broad components increased and diminished reversibly with potential. The potential-dependent narrow feature was related to the generated radical species from corresponding functional groups: e.g. O- and N-centred radicals. Improved capacitance seen for the N-modified basal graphene planes can be accordingly suggested to underlie the enhanced capacitance of N-rGO in basic electrolytes

Plasmoid Instability in the Multiphase Interstellar Medium

The processes controlling the complex clump structure, phase distribution, and magnetic field geometry that develops across a broad range of scales in the turbulent interstellar medium remains unclear. Using unprecedentedly high resolution three-dimensional magnetohydrodynamic simulations of thermally unstable turbulent systems, we show that large current sheets unstable to plasmoid-mediated reconnection form regularly throughout the volume. The plasmoids form in three distinct environments: (i) within cold clumps, (ii) at the asymmetric interface of the cold and warm phases, and (iii) within the warm, volume-filling phase. We then show that the complex magneto-thermal phase structure is characterized by a predominantly highly magnetized cold phase, but that regions of high magnetic curvature, which are the sites of reconnection, span a broad range in temperature. Furthermore, we show that thermal instabilities change the scale dependent anisotropy of the turbulent magnetic field, reducing the increase in eddy elongation at smaller scales. Finally, we show that most of the mass is contained in one contiguous cold structure surrounded by smaller clumps that follow a scale free mass distribution. These clumps tend to be highly elongated and exhibit a size versus internal velocity relation consistent with supersonic turbulence, and a relative clump distance-velocity scaling consistent with subsonic motion. We discuss the striking similarity of cold plasmoids to observed tiny scale atomic and ionized structures and HI fibers, and consider how the prevalence of plasmoids will modify the motion of charged particles thereby impacting cosmic ray transport and thermal conduction in the ISM and other similar systems.Comment: 19 pages, 10 figures. For associated movies, see https://dfielding14.github.io/movies

The Anatomy of a Turbulent Radiative Mixing Layer: Insights from an Analytic Model with Turbulent Conduction and Viscosity

Turbulent Radiative Mixing Layers (TRMLs) form at the interface of cold, dense gas and hot, diffuse gas in motion with each other. TRMLs are ubiquitous in and around galaxies on a variety of scales, including galactic winds and the circumgalactic medium. They host the intermediate temperature gases that are efficient in radiative cooling, thus play a crucial role in controlling the cold gas supply, phase structure, and spectral features of galaxies. In this work, we introduce a simple parameterization of the effective turbulent conductivity and viscosity that enables us to develop a simple and intuitive analytic 1.5 dimensional model for TRMLs. Our analytic model reproduces the mass flux, total cooling, and phase structure of 3D simulations of TRMLs at a fraction of the computational cost. It also reveals essential insights into the physics of TRMLs, particularly the importance of the viscous dissipation of relative kinetic energy in balancing radiative cooling. This dissipation takes place both in the intermediate temperature phase, which offsets the enthalpy flux from the hot phase, and in the cold phase, which enhances radiative cooling. Additionally, our model provides a fast and easy way of computing the column density and surface brightness of TRMLs, which can be directly linked to observations.Comment: 32 pages, 22 figures. Submitted to Ap

Searching Data: A Review of Observational Data Retrieval Practices in Selected Disciplines

A cross-disciplinary examination of the user behaviours involved in seeking and evaluating data is surprisingly absent from the research data discussion. This review explores the data retrieval literature to identify commonalities in how users search for and evaluate observational research data. Two analytical frameworks rooted in information retrieval and science technology studies are used to identify key similarities in practices as a first step toward developing a model describing data retrieval