14,853 research outputs found
Direct analysis of hydrogen/deuterium mixtures: A concept
Fraction of deuterium/hydrogen mixture is isolated by column chromatography, ionized, and the HD+1-0 band absorption measured with conventional high-resolution infrared spectrophotometer
PACS and SPIRE photometer maps of M 33: First results of the HERschel M 33 Extended Survey (HERM33ES)
Context. Within the framework of the HERM33ES key program, we are studying the star forming interstellar medium in the nearby, metal-poor spiral galaxy M 33, exploiting the high resolution and sensitivity of Herschel.
Aims. We use PACS and SPIRE maps at 100, 160, 250, 350, and 500 μm wavelength, to study the variation of the spectral energy distributions (SEDs) with galacto-centric distance.
Methods. Detailed SED modeling is performed using azimuthally averaged fluxes in elliptical rings of 2 kpc width, out to 8 kpc galacto-centric distance. Simple isothermal and two-component grey body models, with fixed dust emissivity index, are fitted to the SEDs between 24 μm and 500 μm using also MIPS/Spitzer  data, to derive first estimates of the dust physical conditions.
Results. The far-infrared and submillimeter maps reveal the branched, knotted spiral structure of M 33. An underlying diffuse disk is seen in all SPIRE maps (250–500 μm). Two component fits to the SEDs agree better than isothermal models with the observed, total and radially averaged flux densities. The two component model, with β fixed at 1.5, best fits the global and the radial SEDs. The cold dust component clearly dominates; the relative mass of the warm component is less than 0.3% for all the fits. The temperature of the warm component is not well constrained and is found to be about 60 K ± 10 K. The temperature of the cold component drops significantly from ~24 K in the inner 2 kpc radius to 13 K beyond 6 kpc radial distance, for the best fitting model. The gas-to-dust ratio for β = 1.5, averaged over the galaxy, is higher than the solar value by a factor of 1.5 and is roughly in agreement with the subsolar metallicity of M 33
Measurements of mass and momentum flux in non-ideal molecular beams
Momentum transfer and mass determinations for nonideal molecular beam - fluid mechanic
BASIS RISK FOR RICE
The objective of this paper is to develop a cross hedging model for rice that minimizes basis risk and accounts for the existence of the nonstationary nature of basis. Basis is treated as an endogenous variable and model for basis risk are developed.Financial Economics, Risk and Uncertainty,
The Flowers of Extinction: An Ecocritical <i>Flâneur</i> in London, April 2019 to April 2020
How does one do ‘ecocritical Walter Benjamin’ in the city of London? As a professional flâneur between April 2019 and April 2020, I enlisted the support of Benjamin’s 1940 writings ‘Some Motifs in Baudelaire’ and ‘On the Concept of History’, and four poems from Charles Baudelaire’s Les Fleurs du Mal. These lyrics explore entangled spaces between the human and nonhuman world. Benjamin developed two concepts – ‘shock’ and ‘shock experience’ (Chockerlebnis), the latter through his engagement with Baudelaire’s work. Therefore, ecopoetic analyses of Baudelaire’s ‘Correspondances’, ‘Obsession’ (1857), ‘Le Soleil’ and ‘Le Squelette Laboureur’ (1861) aided my analysis of four London sites: Lewisham’s train tracks, Sky Garden, Oxford Circus, and the Charterhouse Museum. Reading the four sites with the aid of Baudelaire’s lyrics allowed an unearthing and creation of dialectical images as they relate to the climate emergency
Anti-Fall: A Non-intrusive and Real-time Fall Detector Leveraging CSI from Commodity WiFi Devices
Fall is one of the major health threats and obstacles to independent living
for elders, timely and reliable fall detection is crucial for mitigating the
effects of falls. In this paper, leveraging the fine-grained Channel State
Information (CSI) and multi-antenna setting in commodity WiFi devices, we
design and implement a real-time, non-intrusive, and low-cost indoor fall
detector, called Anti-Fall. For the first time, the CSI phase difference over
two antennas is identified as the salient feature to reliably segment the fall
and fall-like activities, both phase and amplitude information of CSI is then
exploited to accurately separate the fall from other fall-like activities.
Experimental results in two indoor scenarios demonstrate that Anti-Fall
consistently outperforms the state-of-the-art approach WiFall, with 10% higher
detection rate and 10% less false alarm rate on average.Comment: 13 pages,8 figures,corrected version, ICOST conferenc
Gas morphology and energetics at the surface of PDRs: New insights with Herschel observations of NGC 7023
Context. We investigate the physics and chemistry of the gas and dust in dense photon-dominated regions (PDRs), along with their dependence on the illuminating UV field.
Aims. Using Herschel/HIFI observations, we study the gas energetics in NGC 7023 in relation to the morphology of this nebula. NGC 7023 is the prototype of a PDR illuminated by a B2V star and is one of the key targets of Herschel.
Methods. Our approach consists in determining the energetics of the region by combining the information carried by the mid-IR spectrum (extinction by classical grains, emission from very small dust particles) with that of the main gas coolant lines. In this letter, we discuss more specifically the intensity and line profile of the 158 μm (1901 GHz) [C ii] line measured by HIFI and provide information on the emitting gas.
Results. We show that both the [C ii] emission and the mid-IR emission from polycyclic aromatic hydrocarbons (PAHs) arise from the regions located in the transition zone between atomic and molecular gas. Using the Meudon PDR code and a simple transfer model, we find good agreement between the calculated and observed [C ii] intensities.
Conclusions. HIFI observations of NGC 7023 provide the opportunity to constrain the energetics at the surface of PDRs. Future work will include analysis of the main coolant line [O i] and use of a new PDR model that includes PAH-related species
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