Prospects for Observing the low-density Cosmic Web in Lyman-alpha Emission

Mapping the intergalactic medium (IGM) in Lyman-$\alpha$ emission would yield unprecedented tomographic information on the large-scale distribution of baryons and potentially provide new constraints on the UV background and various feedback processes relevant to galaxy formation. Here, we use a cosmological hydrodynamical simulation to examine the Lyman-$\alpha$ emission of the IGM due to collisional excitations and recombinations in the presence of a UV background. We focus on gas in large-scale-structure filaments in which Lyman-$\alpha$ radiative transfer effects are expected to be moderate. At low density the emission is primarily due to fluorescent re-emission of the ionising UV background due to recombinations, while collisional excitations dominate at higher densities. We discuss prospects of current and future observational facilities to detect this emission and find that the emission of filaments of the cosmic web will typically be dominated by the halos and galaxies embedded in them, rather than by the lower density filament gas outside halos. Detecting filament gas directly would require a very long exposure with a MUSE-like instrument on the ELT. Our most robust predictions that act as lower limits indicate this would be slightly less challenging at lower redshifts ($z \lesssim 4$). We also find that there is a large amount of variance between fields in our mock observations. High-redshift protoclusters appear to be the most promising environment to observe the filamentary IGM in Lyman-$\alpha$ emission.Comment: 20 pages, 13 figures. Accepted for publication in Astronomy & Astrophysics. Accepted version contains several revisions following suggestions made in the review proces

Simulating Induced Interdigitation in Membranes

AbstractIn this study we introduce a mesoscopic lipid-water-alcohol model. Dissipative particle dynamics (DPD) simulations have been used to investigate the induced interdigitation of bilayers consisting of double-tail lipids by adding alcohol molecules to the bilayer. Our simulations nicely reproduce the experimental phase diagrams. We find that alcohol can induce an interdigitated structure where the common bilayer structure changes into monolayer in which the alcohol molecules screen the hydrophobic tails from the water phase. At low concentrations of alcohol the membrane has domains of the interdigitated phase that are in coexistence with the common membrane phase. We compute the effect of the chain length of the alcohol on the phase behavior of the membrane and show that the stability of the interdigitated phase depends on the length of the alcohol. We show that we can reproduce the experimental hydrophobic thickness of the bilayer for various combinations of lipids and alcohols. We use our model to clarify some of the experimental questions related to the structure of the interdigitated phase and put forward a simple model that explains the alcohol chain length dependence of the stability of this interdigitated phase

Urban Agriculture and Community Food Security in the United States: Farming from the City Center To the Urban Fringe

Urban Agriculture and Community Food Security in the United States: Farming from the City Center To the Urban Fringe is prepared by the Urban Agriculture Committee of the Community Food Security Coalition to raise awareness of the ways that urban agriculture can respond to food insecurity. The document advocates for policies that promote small-scale urban and peri-urban farming, and thereby prepare the next generation of urban farming leaders

Evaluating The Effect of Fair Value Adjustments to Investment Property Based on Profitability Ratios

Research aims: The aim of the study was to determine whether fair value adjustments to investment property affect the profitability ratios of listed companies. Design/Methodology/Approach: To investigate the problem, a brief literature overview of performance analysis through ratio calculations, as well as fair value measurement are discussed. These discussions are based on the International Financial Reporting Standards (IFRS), IFRS 13 and International Accounting Standards (IAS), IAS 40. IAS 40 addresses how the value of investment property may be recognised through the fair value model. To determine whether the recognition of fair value adjustments affect the profitability ratios of sampled companies, the Wilcoxon rank test and Cohen’s d-value were used as statistical measures to fulfil this objective. The Top 40 companies as listed on the Johannesburg Stock Exchange (JSE) in South Africa were populated, and judgment sampling was applied to calculate the sampling frame.Research findings: The results demonstrate that 50% to 75% of the sampled companies had profitability ratios, which were impacted by the recognition of fair value adjustments. These findings are relevant to potential investors who need to interpret financial ratios to improve investment decisions. Finally, the study recommends that the prospective investor eliminate fair value adjustments when profitability ratios are calculated.Theoretical contribution/Originality: The contribution of the study is that fair value adjustments (favourable or unfavourable) relating to IAS 40 affect the decisions taken by users of the financial statements. Substantial changes to profit or loss and/or investment property significantly impact ratio analysis outcomes and, therefore, investor decision making. The research contributes to the use of fair value adjustments and its impact on profitability ratios. Practitioner/Policy implications: Regulators may benefit from the findings when considering regulatory reforms of accounting practices as well as the disclosures required that assist the users of financial statements

O cidadão e o legislador na ética e política de Aristóteles.

O cidadão e o legislador são conceitos de grande importância tanto na Ética a Nicômacos quanto na Política. É dos dois que depende a autossuficiência da cidade e a felicidade de seus habitantes, ou seja, a realização da finalidade da ciência política e da ética. A partir disso, este trabalho se propõe a elaborar a relação entre essas duas figuras, considerando o que é necessário para que alguém seja um bom cidadão e, no caso do legislador, o que o torna capaz de instituir uma boa constituição, e aquilo em que ela consiste. Nessas questões, delineiase mais claramente a relação entre os dois: o bom cidadão depende de boas leis (em sua formação e em sua convivência com outros cidadãos), elaboradas por bons legisladores, assim como o trabalho desses legisladores só alcança de fato sua finalidade se as leis são respeitadas e promovidas por cidadãos virtuosos

The self-referential method combined with thermodynamic integration

The self-referential method [M. B. Sweatman, Phys. Rev. E 72, 016711 (2005)] for calculating the free energy of crystalline solids via molecular simulation is combined with thermodynamic integration to produce a technique that is convenient and efficient. Results are presented for the chemical potential of hard sphere and Lennard-Jones face centered cubic crystals that agree well with this previous work. For the small system sizes studied, this technique is about 100 times more efficient than the parameter hopping technique used previously

Chemical transport model ozone simulations for spring 2001 over the western Pacific: Regional ozone production and its global impacts

The spatial and temporal variation in ozone production over major source regions in East Asia during the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) measurement campaign in spring 2001 is assessed using a global chemical transport model. There is a strong latitudinal gradient in ozone production in springtime, driven by regional photochemistry, which rapidly diminishes as the season progresses. The great variability in meteorological conditions characteristic of East Asia in springtime leads to large daily variability in regional ozone formation, but we find that it has relatively little impact on the total global production. We note that transport processes effectively modulate and thus stabilize total ozone production through their influence over its location. However, the impact on the global ozone burden, important for assessing the effects of precursor emissions on tropospheric oxidizing capacity and climate, is sensitive to local meteorology through the effects of location on chemical lifetime. Stagnant, anticyclonic conditions conducive to substantial boundary layer ozone production typically allow little lifting of precursors into the free troposphere where greater ozone production could occur, and the consequent shorter chemical lifetime for ozone leads to relatively small impacts on global ozone. Conversely, cyclonic conditions with heavy cloud cover suppressing regional ozone production are often associated with substantial cloud convection, enhancing subsequent production in the free troposphere where chemical lifetimes are longer, and the impacts on global ozone are correspondingly greater. We find that ozone formation in the boundary layer and free troposphere outside the region of precursor emissions dominates total gross production from these sources in springtime, and that it makes a big contribution to the long range transport of ozone, which is greatest in this season