9,393 research outputs found
Estimations of the Distances of Stellar Collapses in the Galaxy by Analyzing the Energy Spectrum of Neutrino Bursts
The neutrino telescopes of the present generation, depending on their
specific features, can reconstruct the neutrino spectra from a galactic burst.
Since the optical counterpart could be not available, it is desirable to have
at hand alternative methods to estimate the distance of the supernova explosion
using only the neutrino data. In this work we present preliminary results on
the method we are proposing to estimate the distance from a galactic supernova
based only on the spectral shape of the neutrino burst and assumptions on the
gravitational binding energy released an a typical supernova explosion due to
stellar collapses.Comment: Proceedings of the Second International Symposium on Strong
Electromagnetic Fields and Neutron Stars (SMFNS 2011) Instituto de
Cibern\'etica, Matem\'atica y F\'isica (ICIMAF) Sociedad Cubana de F\'isica
(SCF) Varadero, Cuba, 5-7 May 201
THE ECONOMIC THRESHOLD FOR GRASSHOPPER CONTROL ON PUBLIC RANGELANDS
The U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS) is responsible for controlling grasshopper populations on public rangelands. Under current guidelines, control of grasshoppers on rangeland should occur if grasshopper densities are at least eight per square yard. This article evaluates the concept of an economic threshold relative to the value of forage saved from destruction during a grasshopper outbreak. It is shown that financial justification for treating grasshopper outbreaks depends upon grasshopper density, rangeland productivity, climate factors, livestock cost and return relationships, and the efficacy of treatment options.Resource /Energy Economics and Policy, Land Economics/Use,
Advances in the corporate governance practices of Johannesburg Stock Exchange companies
Since the 20th century, corporate governance mechanisms haveĀ been developed globally to curb the negative effects of the agencyĀ problem. South Africa was a pioneer with the publication of the firstĀ King Report on corporate governance in 1994. Given the paucity ofĀ research on corporate governance in the country, the researchers setĀ out to investigate the corporate governance practices of 230 companiesĀ listed on the Johannesburg Stock Exchange over the period 2002 toĀ 2010. Annual corporate governance scores were compiled by meansĀ of content analysis of the sample companiesā annual reports. TheĀ empirical findings revealed an increasing compliance trend towardsĀ 2010. Although the sample companies tended to improve the disclosureĀ of their corporate governance practices over time, their practices wereĀ not per se acceptable (where acceptability implies meeting the King IIĀ recommendations). Inexperienced directors and managers might benefitĀ from more training to enhance their understanding of the application ofĀ corporate governance principles.Keywords: corporate governance, King II Report, South Africa, compliance, disclosur
Laser-heated rocket studies
CW laser heated rocket propulsion was investigated in both the flowing core and stationary core configurations. The laser radiation considered was 10.6 micrometers, and the working gas was unseeded hydrogen. The areas investigated included initiation of a hydrogen plasma capable of absorbing laser radiation, the radiation emission properties of hot, ionized hydrogen, the flow of hot hydrogen while absorbing and radiating, the heat losses from the gas and the rocket performance. The stationary core configuration was investigated qualitatively and semi-quantitatively. It was found that the flowing core rockets can have specific impulses between 1,500 and 3,300 sec. They are small devices, whose heating zone is only a millimeter to a few centimeters long, and millimeters to centimeters in radius, for laser power levels varying from 10 to 5,000 kW, and pressure levels of 3 to 10 atm. Heat protection of the walls is a vital necessity, though the fraction of laser power lost to the walls can be as low as 10% for larger powers, making the rockets thermally efficient
Fit for work? Health, employability and challenges for the UK welfare reform agenda
This article introduces a special issue of Policy Studies entitled āFit for work? Health, employability and challenges for the UK welfare reform agendaā. Growing from a shared concern over the need to expand the evidence base around the processes that led to large numbers of people claiming disability benefits in the UK, it brings together contributions from leading labour market and social policy researchers providing evidence and commentary on major reforms to Incapacity Benefit (IB) in the UK. This special issue address three key questions: what are the main causes of the long-term rise in the number of people claiming IBs; what will reduce the number of claimants; and what is likely to deliver policy effectively and efficiently? This introduction first explains and examines the challenges to reforms to IB in the UK, and then, in conclusion, highlights the answers to the previous three questions ā first, labour market restructuring and marginalisation have driven the rise in numbers claiming IBs. Second, economic regeneration in the Britainās less prosperous areas coupled with intensive and sustained supply-side support measures will bring numbers down. Third, delivery need to be flexible and tailored to individual needs and needs to be able to access local and expert knowledge in a range of organisations, including Job Centre Plus, the NHS as well as the private and voluntary sectors
High-resolution provenance of desert dust deposited on Mt. Elbrus, Caucasus in 2009ā2012 using snow pit and firn core records
The ļ¬rst record of dust deposition events on
Mt. Elbrus, Caucasus Mountains derived from a snow pit
and a shallow ļ¬rn core is presented for the 2009ā2012 period. A combination of isotopic analysis, SEVIRI red-greenblue composite imagery, MODIS atmospheric optical depth
ļ¬elds derived using the Deep Blue algorithm, air mass trajectories derived using the HYSPLIT model and analyses of
meteorological data enabled identiļ¬cation of dust source regions with high temporal (hours) and spatial (ca. 20ā100 km)
resolution. Seventeen dust deposition events were detected;
fourteen occurred in MarchāJune, one in February and two
in October. Four events originated in the Sahara, predominantly in northeastern Libya and eastern Algeria. Thirteen
events originated in the Middle East, in the Syrian Desert
and northern Mesopotamia, from a mixture of natural and
anthropogenic sources. Dust transportation from Sahara was
associated with vigorous Saharan depressions, strong surface
winds in the source region and mid-tropospheric southwesterly ļ¬ow with daily winds speeds of 20ā30 m sā1
at 700 hPa
level. Although these events were less frequent than those
originating in the Middle East, they resulted in higher dust
concentrations in snow. Dust transportation from the Middle
East was associated with weaker depressions forming over
the source region, high pressure centred over or extending towards the Caspian Sea and a weaker southerly or southeasterly ļ¬ow towards the Caucasus Mountains with daily wind
speeds of 12ā18 m sā1
at 700 hPa level. Higher concentrations of nitrates and ammonium characterised dust from the
Middle East deposited on Mt. Elbrus in 2009 indicating contribution of anthropogenic sources. The modal values of particle size distributions ranged between 1.98 Āµm and 4.16 Āµm.
Most samples were characterised by modal values of 2.0ā
2.8 Āµm with an average of 2.6 Āµm and there was no signiļ¬-
cant difference between dust from the Sahara and the Middle
East
How much dark matter is there inside early-type galaxies?
We study the luminous mass as a function of the dynamical mass inside the
effective radius (r_e) of early-type galaxies (ETGs) to search for differences
between these masses. We assume Newtonian dynamics and that any difference
between these masses is due to the presence of dark matter. We use several
samples of ETGs -ranging from 19 000 to 98 000 objects- from the ninth data
release of the Sloan Digital Sky Survey. We perform Monte Carlo (MC)
simulations of galaxy samples and compare them with real samples. The main
results are: i) MC simulations show that the distribution of the dynamical vs.
luminous mass depends on the mass range where the ETGs are distributed
(geometric effect). This dependence is caused by selection effects and
intrinsic properties of the ETGs. ii) The amount of dark matter inside r_e is
approximately 7% +- 22%. iii) This amount of dark matter is lower than the
minimum estimate (10%) found in the literature and four times lower than the
average (30%) of literature estimates. However, if we consider the associated
error, our estimate is of the order of the literature average.Comment: 24 pages, 12 figures. MNRAS accepte
- ā¦