7,388 research outputs found

    The Temperature Dependence of Solar Active Region Outflows

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    Spectroscopic observations with the EUV Imaging Spectrometer (EIS) on Hinode have revealed large areas of high speed outflows at the periphery of many solar active regions. These outflows are of interest because they may connect to the heliosphere and contribute to the solar wind. In this Letter we use slit rasters from EIS in combination with narrow band slot imaging to study the temperature dependence of an active region outflow and show that it is more complicated than previously thought. Outflows are observed primarily in emission lines from Fe XI - Fe XV. Observations at lower temperatures (Si VII), in contrast, show bright fan-like structures that are dominated by downflows. The morphology of the outflows is also different than that of the fans. This suggests that the fan loops, which often show apparent outflows in imaging data, are contained on closed field lines and are not directly related to the active region outflows.Comment: Movies are available online at: http://tcrb.nrl.navy.mil/~hwarren/temp/papers/flow_temperatures/ To be submitted to ApJ

    Technical efficiency of hybrid maize production in eastern terai of Nepal: A stochastic frontier approach

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    Maize is the second most important crop after rice in terms of area and production in Nepal. This article analyzes the technical efficiency and its determinants of hybrid maize production in eastern Nepal. Using a randomly selected data from 98 farmers (41 from Morang and 57 from Sunsari) in eastern Nepal, the study employed a stochastic frontier production model to find the production elasticity coefficients of inputs, determinants of efficiency and technical efficiency of hybrid maize farmers. The results showed that maize production responds positively to increase in amount of urea, DAP and the area planted, where as it is negative to seed quantity. The study indicate that farmers are not technically efficient with a mean technical efficiency 79 %. Socioeconomic variable age had a negative and significant while the household size had a positive and significant related to maize output. The younger farmers were observed more technically efficient than older farmers. Larger the members in the household higher the maize production. It is recommended that farmers should increase their fertilizer dose and farm size while they should decrease their seed rate for efficient production

    Spectroscopy of resonance decays in high-energy heavy-ion collisions

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    Invariant mass distributions of the hadronic decay products from resonances formed in relativistic heavy ion collision (RHIC) experiments are investigated with a view to disentangle the effects of thermal motion and the phase space of decay products from those of intrinsic changes in the structure of resonances at the freeze-out conditions. Analytic results of peak mass shifts for the cases of both equal and unequal mass decay products are derived. The shift is expressed in terms of the peak mass and width of the vacuum or medium-modified spectral functions and temperature. Examples of expected shifts in meson (e.g., rho, omega, and sigma) and baryon (e.g., Delta) resonances that are helpful to interpret recent RHIC measurements at BNL are provided. Although significant downward mass shifts are caused by widened widths of the ρ−\rho-meson in medium, a downward shift of at least 50 MeV in its intrinsic mass is required to account for the reported downward shift of 60-70 MeV in the peak of the rho-invariant mass distribution. An observed downward shift from the vacuum peak value of the Delta distinctively signals a significant downward shift in its intrinsic peak mass, since unlike for the rho-meson, phase space functions produce an upward shift for the Delta isobar.Comment: published version with slight change of title and some typos corrected, 12 pages, 5 figure

    Fetal MRI in management of complicated meconium ileus: Prenatal and surgical imaging

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    Objective To review fetal MRI cases surgically proven to have meconium ileus (MI) and obstruction, describe the common fetal MRI findings that distinguish cases of complicated MI, and to compare these findings with surgical images and perinatal outcomes. Method We performed a retrospective review of all fetal MRI examinations and the corresponding medical record from our tertiary care children's hospital over an 18‐month period. Postnatal management and outcomes were reviewed for these patients, and those patients with surgical or postmortem diagnosis of complicated MI were included in the study. Results Our analysis revealed 7 cases. In this cohort, 3 imaging features of the fetal bowel were repeatedly seen: gradient appearance of intraluminal bowel contents, abnormally localized meconium signal, and collapsed appearance of the colon on MRI. Surgical diagnoses confirmed MI. All live‐born infants underwent surgical repair. Conclusion Fetal MRI should be included in the diagnostic algorithm of any pregnancy where fetal bowel obstruction is suspected to better risk stratify patients

    The perception and management of risk in UK office property development

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    Risk is an ever-present aspect of business, and risk taking is necessary for profit and economic progress. Speculative property development is popularly perceived as a 'risky business' yet, like other entrepreneurs, developers have opportunities to manage the risks they face; techniques include phasing and joint ventures. The associated areas of investment portfolio risk, development risk analysis and construction risk management have all been addressed by research. This article presents new knowledge about how developers perceive risks and the means they subsequently adopt to manage them. The developers of office projects across the UK were sent questionnaires by post. Respondents were asked about their perceptions of risks at the first appraisal stage and currently and about the risk management techniques that they had adopted. In-depth interviews with a selection of respondents were then used to discuss and augment the findings. Developers were most concerned about market-based risks at both stages. Concern about production-orientated risks was lower and fell significantly between the two stages. A fixed price contract was the most common risk management technique. Risk management techniques were used more often outside London and the South East. Developer type affects both the perception and management of risk. While developers do manage risk, decisions are made on the basis of professional and business experience. These findings should help development companies manage risk in a more objective and analytical way

    Technical Efficiency of Hybrid Maize Production in Eastern Terai of Nepal: a Stochastic Frontier Approach

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    Maize is the second most important crop after rice in terms of area and production in Nepal. This article analyzes the technical efficiency and its determinants of hybrid maize production in eastern Nepal. Using a randomly selected data from 98 farmers (41 from Morang and 57 from Sunsari) in eastern Nepal, the study employed a stochastic frontier production model to find the production elasticity coefficients of inputs, determinants of efficiency and technical efficiency of hybrid maize farmers. The results showed that maize production responds positively to increase in amount of urea, DAP and the area planted, where as it is negative to seed quantity. The study indicate that farmers are not technically efficient with a mean technical efficiency 79 %. Socioeconomic variable age had a negative and significant while the household size had a positive and significant related to maize output. The younger farmers were observed more technically efficient than older farmers. Larger the members in the household higher the maize production. It is recommended that farmers should increase their fertilizer dose and farm size while they should decrease their seed rate for efficient production

    The asymptotic dynamics of three-dimensional Einstein gravity with a negative cosmological constant

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    Liouville theory is shown to describe the asymptotic dynamics of three-dimensional Einstein gravity with a negative cosmological constant. This is because (i) Chern-Simons theory with a gauge group SL(2,R)×SL(2,R)SL(2,R) \times SL(2,R) on a space-time with a cylindrical boundary is equivalent to the non-chiral SL(2,R)SL(2,R) WZW model; and (ii) the anti-de Sitter boundary conditions implement the constraints that reduce the WZW model to the Liouville theory.Comment: 10 pages in LaTeX, LaTeX problem fixe

    Early Ultraviolet, Optical and X-Ray Observations of the Type IIP SN 2005cs in M51 with Swift

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    We report early photospheric-phase observations of the Type IIP Supernova (SN) 2005cs obtained by Swift's Ultraviolet-Optical and X-Ray Telescopes. Observations started within two days of discovery and continued regularly for three weeks. During this time the V-band magnitude remained essentially constant, while the UV was initially bright but steadily faded until below the brightness of an underlying UV-bright HII region. This UV decay is similar to SNe II observed by the International Ultraviolet Explorer. UV grism spectra show the P-Cygni absorption of MgII 2798A, indicating a photospheric origin of the UV flux. Based on non-LTE model atmosphere calculations with the CMFGEN code, we associate the rapid evolution of the UV flux with the cooling of the ejecta, the peak of the spectral energy distribution (SED) shifting from ~700A on June 30th to ~1200A on July 5th. Furthermore, the corresponding recombination of the ejecta, e.g., the transition from FeIII to FeII, induces considerable strengthening of metal line-blanketing at and above the photosphere, blocking more effectively this fading UV flux. SN2005cs was not detected in X-rays, and the upper limit to the X-ray luminosity yields a limit to the mass loss rate of the progenitor of about 10^-5 solar masses per year. Overall, Swift presents a unique opportunity to capture the early and fast evolution of Type II SNe in the UV, providing additional constraints on the reddening, the SED shortward of 4000A, and the ionization state and temperature of the photon-decoupling regions.Comment: 15 pages, 6 figures. Accepted for publication by Astrophysical Journa

    The Effect of Air on Granular Size Separation in a Vibrated Granular Bed

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    Using high-speed video and magnetic resonance imaging (MRI) we study the motion of a large sphere in a vertically vibrated bed of smaller grains. As previously reported we find a non-monotonic density dependence of the rise and sink time of the large sphere. We find that this density dependence is solely due to air drag. We investigate in detail how the motion of the intruder sphere is influenced by size of the background particles, initial vertical position in the bed, ambient pressure and convection. We explain our results in the framework of a simple model and find quantitative agreement in key aspects with numerical simulations to the model equations.Comment: 14 pages, 16 figures, submitted to PRE, corrected typos, slight change
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