1,577 research outputs found
The morphology of anomalous cosmic rays in the outer heliosphere
The well established cosmic ray transport equation describes the physics of cosmic ray modulation in the heliosphere and is thought to be complete. Its solution for anomalous cosmic rays has special characteristics due to the local acceleration of these particles at the solar wind termination shock. Some of these characteristics are demonstrated here, namely effects by the strength of the shock, shock drift, the cutoff in the spectrum at the shock, species scaling, drift, and ionization
HotGrid: Graduated Access to Grid-based Science Gateways
We describe the idea of a Science Gateway, an application-specific task wrapped as a web service, and some examples of these that are being implemented on the US TeraGrid cyberinfrastructure. We also describe HotGrid, a means of providing simple, immediate access to the Grid through one of these gateways, which we hope will broaden the use of the Grid, drawing in a wide community of users. The secondary purpose of HotGrid is to acclimate a science community to the concepts of certificate use. Our system provides these weakly authenticated users with immediate power to use the Grid resources for science, but without the dangerous power of running arbitrary code. We describe the implementation of these Science Gateways with the Clarens secure web server
SOAP Services with Clarens: Guide for Developers and Administrators
The Clarens application server enables secure, asynchronous SOAP services to run on a Grid cluster such as one of those of the TeraGrid. There is a Client, who wants to use the service and understands the application domain enough to form a reasonable service request; a Developer, who is a power-user of the TeraGrid, who understands both Clarens and the application domain, and creates and deploys a service on a TeraGrid head node; and there is a Root system administrator, who controls the Clarens installation and the cluster on which it runs. The purpose of this document is to provide all of the information a service developer needs to know in order to deploy a Clarens service, with information also provided for the system administrator of the Clarens installation. First we discuss how each of the three roles see the service
The Cosmic Origins Spectrograph and the Future of Ultraviolet Astronomy
I describe the capabilities of the Cosmic Origins Spectrograph, scheduled for
May 2009 installation on the Hubble Space Telescope. With a factor-of-ten
increase in far-UV throughput for moderate resolution spectroscopy, COS will
enable a range of scientific programs that study hot stars, AGN, and gas in the
interstellar medium, intergalactic medium, and galactic halos. We also plan a
large-scale HST Spectroscopic Legacy Project for QSO absorption lines, galactic
halos, and AGN outflows. Studies of next-generation telescopes for UV/O
astronomy are now underway, including small, medium, and large missions to fill
the imminent ten-year gap between the end of Hubble and a plausible launch of
the next large mission. Selecting a strategy for achieving these goals will
involve hard choices and tradeoffs in aperture, wavelength, and capability.Comment: To appear in Future Directions in Ultraviolet Astronomy (AIP Conf
Proc
Opportunities for integrated pest management to control the poultry red mite, Dermanyssus gallinae
Dermanyssus gallinae is the most economically important ectoparasite of laying hens in Europe. Control of D. gallinae is already hampered by issues of pesticide resistance and product withdrawal and, with the prohibition of conventional cages in 2012 and the resulting switch to more structurally complex housing which favours red mite, the importance of managing this pest will increase. Integrated Pest Management (IPM), as often employed in agricultural pest control, may be a way to address these issues where a combination of different novel control methods could be used with/without conventional management techniques to provide a synergistic and more efficacious effect. Work at in our laboratory has shown that essential oils including thyme and garlic may act as effective D. gallinae repellents and acaricides, whilst preliminary vaccine studies have demonstrated a significant increase in mite mortality in vitro using concealed antigens. Work elsewhere 27 has considered predators and fungi for D. gallinae control and other husbandry techniques such as manipulating temperature and lighting regimes in poultry units. This paper will review the available and emerging techniques for D. gallinae control and discuss which techniques might be suitable for inclusion in an integrated management programme (e.g. synthetic acaricides and diatomaceous earths)
The Clarens web services architecture
Clarens is a uniquely flexible web services infrastructure providing a
unified access protocol to a diverse set of functions useful to the HEP
community. It uses the standard HTTP protocol combined with application layer,
certificate based authentication to provide single sign-on to individuals,
organizations and hosts, with fine-grained access control to services, files
and virtual organization (VO) management. This contribution describes the
server functionality, while client applications are described in a subsequent
talk.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 6 pages, LaTeX, 4 figures, PSN
MONT00
Intergalactic Baryons in the Local Universe
Simulations predict that shocks from large-scale structure formation and
galactic winds have reduced the fraction of baryons in the warm, photoionized
phase (the Lya forest) from nearly 100% in the early universe to less than 50%
today. Some of the remaining baryons are predicted to lie in the warm-hot
ionized medium (WHIM) phase at T=10^5-10^7 K, but the quantity remains a highly
tunable parameter of the models. Modern UV spectrographs have provided
unprecedented access to both the Lya forest and potential WHIM tracers at z~0,
and several independent groups have constructed large catalogs of far-UV IGM
absorbers along ~30 AGN sight lines. There is general agreement between the
surveys that the warm, photoionized phase makes up ~30% of the baryon budget at
z~0. Another ~10% can be accounted for in collapsed structures (stars,
galaxies, etc.). However, interpretation of the ~100 high-ion (OVI, etc)
absorbers at z<0.5 is more controversial. These species are readily created in
the shocks expected to exist in the IGM, but they can also be created by
photoionization and thus not represent WHIM material. Given several pieces of
observational evidence and theoretical expectations, I argue that most of the
observed OVI absorbers represent shocked gas at T~300,000 K rather than
photoionized gas at T<30,000 K, and they are consequently valid tracers of the
WHIM phase. Under this assumption, enriched gas at T=10^5-10^6 K can account
for ~10% of the baryon budget at z<0.5, but this value may increase when bias
and incompleteness are taken into account and help close the gap on the 50% of
the baryons still "missing".Comment: Invited review to appear in "Future Directions in Ultraviolet
Spectroscopy", Oct 20-22, 2008, Annapolis, MD, M. E. Van Steenberg, ed.
(April 2009). 8 pages, five figure
Flow tilt angles near forest edges - Part 1: Sonic anemometry
An analysis of flow tilt angles from a fetch-limited beech forest site with clearings is presented in the context of vertical advection of carbon dioxide. Flow angles and vertical velocities from two sonic anemometers by different manufacturers were analyzed. Instead of using rotations, where zero-flow angles were assumed for neutral flow, the data was interpreted in relation to upstream and downstream forest edges. <br><br> Uncertainties caused by flow distortion, vertical misalignment and limited sampling time (statistical uncertainty) were evaluated and found to be highly significant. Since the attack angle distribution of the wind on the sonic anemometer is a function of atmospheric stratification, an instrumental error caused by imperfect flow distortion correction is also a function of the atmospheric stratification. In addition, it is discussed that the sonic anemometers have temperature dependent off-sets. These features of the investigated sonic anemometers make them unsuitable for measuring vertical velocities over highly turbulent forested terrain. By comparing the sonic anemometer results to that of a conically scanning Doppler lidar (Dellwik et al., 2010b), sonic anemometer accuracy for measuring mean flow tilt angles was estimated to between 2° and 3°. Use of planar fit algorithms, where the mean vertical velocity is calculated as the difference between the neutral and non-neutral flow, does not solve this problem of low accuracy and is not recommended. <br><br> Because of the large uncertainties caused by flow distortion and vertical alignment, it was only possible to a limited extent to relate sonic anemometer flow tilt angles to upwind forest edges, but the results by the lidar indicated that an internal boundary layer affect flow tilt angles at 21m above the forest. This is in accordance with earlier studies at the site. <br><br> Since the mean flow tilt angles do not follow the terrain, an estimate of the vertical advection term for near-neutral conditions was calculated using profile measurements of carbon dioxide. The estimated advection term is large, but it is not recommended to include it in the surface carbon balance, unless all terms in the carbon dioxide conservation equation can be precisely estimated
Highly Ionized Envelopes of High Velocity Clouds
We present recent results on highly ionized gas in Galactic High-Velocity
Clouds (HVCs), originally surveyed in OVI (Sembach et al. 2003). In a new
FUSE/HST survey of SiII/III/IV (Shull et al. 2009) toward 37 AGN, we detected
SiIII (lambda 1206.500 A) absorption with a sky coverage fraction 81 +/- 5% (61
HVCs along 30 of 37 high-latitude sight lines). The SiIII (lambda 1206.500 A)
line is typically 4-5 times stronger than OVI (lambda 1031.926 A). The mean HVC
column density of perhaps 10^19 cm^-2 of low-metallicity (0.1 - 0.2 Z_sun)
ionized gas in the low halo. Recent determinations of HVC distances allow us to
estimate a total reservoir of ~10^8 M_sun. Estimates of infall velocities
indicate an infall rate of around 1 M_sun yr^-1, comparable to the
replenishment rate for star formation in the disk. HVCs appear to be sheathed
by intermediate-temperature gas (10^4.0 - 10^4.5 K) detectable in SiIII and
SiIV, as well as hotter gas seen in OVI and other high ions. To prepare for HST
observations of 10 HVC-selected sight lines with the Cosmic Origins
Spectrograph (COS), we compile FUSE/STIS spectra of these ions, plus FeIII,
CIII, CIV, and SIV. Better constraints on the physical properties of HVC
envelopes and careful treatment of HVC kinematics and infall rates should come
from high-quality (S/N ~ 30-40) COS data.Comment: 3 pages, 1 figure, published in Future Directions in Ultraviolet
Spectroscopy, Proceedings of the AIP Conference held October 20-22, 2008 in
Annapolis, Marylan
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