3,966 research outputs found
Mobile Computing in Physics Analysis - An Indicator for eScience
This paper presents the design and implementation of a Grid-enabled physics
analysis environment for handheld and other resource-limited computing devices
as one example of the use of mobile devices in eScience. Handheld devices offer
great potential because they provide ubiquitous access to data and
round-the-clock connectivity over wireless links. Our solution aims to provide
users of handheld devices the capability to launch heavy computational tasks on
computational and data Grids, monitor the jobs status during execution, and
retrieve results after job completion. Users carry their jobs on their handheld
devices in the form of executables (and associated libraries). Users can
transparently view the status of their jobs and get back their outputs without
having to know where they are being executed. In this way, our system is able
to act as a high-throughput computing environment where devices ranging from
powerful desktop machines to small handhelds can employ the power of the Grid.
The results shown in this paper are readily applicable to the wider eScience
community.Comment: 8 pages, 7 figures. Presented at the 3rd Int Conf on Mobile Computing
& Ubiquitous Networking (ICMU06. London October 200
The galaxy cluster X-ray luminosity--gravitational mass relation in the light of the WMAP 3rd year data
The 3rd year WMAP results mark a shift in best fit values of cosmological
parameters compared to the 1st year data and the concordance cosmological
model. We test the consistency of the new results with previous constraints on
cosmological parameters from the HIFLUGCS galaxy cluster sample and the impact
of this shift on the X-ray luminosity-gravitational mass relation. The measured
X-ray luminosity function combined with the observed luminosity-mass relation
are compared to mass functions predicted for given cosmological parameter
values. The luminosity function and luminosity-mass relation derived previously
from HIFLUGCS are in perfect agreement with mass functions predicted using the
best fit parameter values from the 3rd year WMAP data (OmegaM=0.238,
sigma8=0.74) and inconsistent with the concordance cosmological model
(OmegaM=0.3, sigma8=0.9), assuming a flat Universe. Trying to force consistency
with the concordance model requires artificially decreasing the normalization
of the luminosity-mass relation by a factor of 2. The shift in best fit values
for OmegaM and sigma8 has a significant impact on predictions of cluster
abundances. The new WMAP results are now in perfect agreement with previous
results on the OmegaM-sigma8 relation determined from the mass function of
HIFLUGCS clusters and other X-ray cluster samples (the ``low cluster
normalization''). We conclude that - unless the true values of OmegaM and
sigma8 differ significantly from the 3rd year WMAP results - the
luminosity-mass relation is well described by their previous determination from
X-ray observations of clusters, with a conservative upper limit on the bias
factor of 1.5. These conclusions are currently being tested in a complete
follow-up program of all HIFLUGCS clusters with Chandra and XMM-Newton.Comment: 4 pages; A&A Letters, in press; replaced to match accepted version;
also available at http://www.reiprich.ne
Detectability of Microwave Background Polarization
[NOTE: Previous versions of this paper (both on astro-ph and published in
Phys. Rev. D) contain results that are in error. The power spectra C_l were
normalized incorrectly by a factor of 2 pi. All observing times in
detector-years in those versions are too large by a factor of 2 pi. The main
place these numbers appear is on the vertical axes of Figures 4 and 5. Note
that because all calculations were based on the same power spectra, all
conclusions pertaining to comparisons of different techniques remain unchanged.
This error has been corrected in the present version of the paper. An erratum
is being sent to Phys. Rev. D. I apologize for the error.]
Using a Fisher-matrix formalism, we calculate the required sensitivities and
observing times for an experiment to measure the amplitudes of both E and B
components as a function of sky coverage, taking full account of the fact that
the two components cannot be perfectly separated in an incomplete sky map. We
also present a simple approximation scheme that accounts for mixing of E and B
components in computing predicted errors in the E-component power spectrum
amplitude. In an experiment with small sky coverage, mixing of the two
components increases the difficulty of detecting the subdominant B component by
a factor of two or more in observing time; however, for larger survey sizes the
effect of mixing is less pronounced. Surprisingly, mixing of E and B components
can enhance the detectability of the E component by increasing the effective
number of independent modes that probe this componentComment: Previous versions of this paper contained results that were in error.
The present version on astro-ph has been corrected, and an erratum is being
submitted. See abstract for detail
High-Latitude Tree Growth and Satellite Vegetation Indices: Correlations and Trends in Russia and Canada (1982-2008)
Vegetation in northern high latitudes affects regional and global climate through energy partitioning and carbon storage. Spaceborne observations of vegetation, largely based on the normalized difference vegetation index (NDVI), suggest decreased productivity during recent decades in many regions of the Eurasian and North American boreal forests. To improve interpretation of NDVI trends over forest regions, we examined the relationship between NDVI from the advanced very high resolution radiometers and tree ring width measurements, a proxy of tree productivity. We collected tree core samples from spruce, pine, and larch at 22 sites in northeast Russia and northwest Canada. Annual growth rings were measured and used to generate site-level ring width index (RWI) chronologies. Correlation analysis was used to assess the association between RWI and summer NDVI from 1982 to 2008, while linear regression was used to examine trends in both measurements. The correlation between NDVI and RWI was highly variable across sites, though consistently positive (r = 0.43, SD = 0.19, n = 27). We observed significant temporal autocorrelation in both NDVI and RWI measurements at sites with evergreen conifers (spruce and pine), though weak autocorrelation at sites with deciduous conifers (larch). No sites exhibited a positive trend in both NDVI and RWI, although five sites showed negative trends in both measurements. While there are technological and physiological limitations to this approach, these findings demonstrate a positive association between NDVI and tree ring measurements, as well as the importance of considering lagged effects when modeling vegetation productivity using satellite data
Observational constraints on an inflation model with a running mass
We explore a model of inflation where the inflaton mass-squared is generated
at a high scale by gravity-mediated soft supersymmetry breaking, and runs at
lower scales to the small value required for slow-roll inflation. The running
is supposed to come from the coupling of the inflaton to a non-Abelian gauge
field. In contrast with earlier work, we do not constrain the magnitude of the
supersymmetry breaking scale, and we find that the model might work even if
squark and slepton masses come from gauge-mediated supersymmetry breaking. With
the inflaton and gaugino masses in the expected range, and
in the range to (all at the high scale) the model can give
the observed cosmic microwave anisotropy, and a spectral index in the observed
range. The latter has significant variation with scale, which can confirm or
rule out the model in the forseeable future.Comment: Latex, 19 pages, 14 figures, uses epsf.st
Community seismic network and localized earthquake situational awareness
Community-hosted seismic networks are a solution to the need for large numbers of sensors to operate over a seismically active region in order to accurately measure the size and location of an earthquake, assess resulting damage, and provide alerts. The Community Seismic Network is one such strong-motion network, currently comprising hundreds of elements located in California. It consists of low-cost, three-component, MEMS accelerometers capable of recording accelerations up to twice the level of gravity. The primary product of the network is to produce measurements of shaking of the ground and multiple locations of every upper floor in buildings, in the seconds during and following a major earthquake. Each sensor uses a small, dedicated ARM processor computer running Linux, and analyzes time series data in real time at hundreds of samples per second. The network reports on shaking parameters that indicate intensity of the structural response levels such as maximum floor acceleration and velocity, displacement of a floor in a building, as well as data products that depend on the response time histories. To do this, Cloud computing has been expanded through the use of statically defined subsets of sensors called cloudlets. These are smaller subsets of similar sensors that carry out customized calculations for those locations. The measurements are reported as rapidly as possible following an earthquake so that they may be incorporated into structural diagnosis and prognosis applications that can be used by first responders to prioritize their initial disaster management efforts. The cloudlet displays are customized for specific buildings and they show in real time: instantaneous displacement, inter-story drift, and resonant frequency and mode shapes using system identification software tools. The real-time display products are useful for decision-making about whether the potential for damage exists, what level of damage may have occurred and where, and whether total business disruption is necessary. City-wide dense monitoring makes it possible for emergency response managers to prioritize the target locations requiring first response on a block-by-block scale based on reports of shaking intensity
Frequentist Estimation of Cosmological Parameters from the MAXIMA-1 Cosmic Microwave Background Anisotropy Data
We use a frequentist statistical approach to set confidence intervals on the
values of cosmological parameters using the MAXIMA-1 and COBE measurements of
the angular power spectrum of the cosmic microwave background. We define a
statistic, simulate the measurements of MAXIMA-1 and COBE,
determine the probability distribution of the statistic, and use it and the
data to set confidence intervals on several cosmological parameters. We compare
the frequentist confidence intervals to Bayesian credible regions. The
frequentist and Bayesian approaches give best estimates for the parameters that
agree within 15%, and confidence interval-widths that agree within 30%. The
results also suggest that a frequentist analysis gives slightly broader
confidence intervals than a Bayesian analysis. The frequentist analysis gives
values of \Omega=0.89{+0.26\atop -0.19}, \Omega_{\rm B}h^2=0.026{+0.020\atop
-0.011} and n=1.02{+0.31\atop -0.10}, and the Bayesian analysis gives values of
\Omega=0.98{+0.14\atop -0.19}, \Omega_{\rm B}h^2=0.0.029{+0.015\atop-0.010},
and , all at the 95% confidence level.Comment: 10 pages, 9 Postscript figures, changes made to reflect published
versio
Earliest Porotic Hyperostosis on a 1.5-Million-year-old Hominin, olduvai gorge, Tanzania.
Meat-eating was an important factor affecting early hominin brain expansion, social organization and geographic movement. Stone tool butchery marks on ungulate fossils in several African archaeological assemblages demonstrate a significant level of carnivory by Pleistocene hominins, but the discovery at Olduvai Gorge of a child's pathological cranial fragments indicates that some hominins probably experienced scarcity of animal foods during various stages of their life histories. The child's parietal fragments, excavated from 1.5-million-year-old sediments, show porotic hyperostosis, a pathology associated with anemia. Nutritional deficiencies, including anemia, are most common at weaning, when children lose passive immunity received through their mothers' milk. Our results suggest, alternatively, that (1) the developmentally disruptive potential of weaning reached far beyond sedentary Holocene food-producing societies and into the early Pleistocene, or that (2) a hominin mother's meat-deficient diet negatively altered the nutritional content of her breast milk to the extent that her nursing child ultimately died from malnourishment. Either way, this discovery highlights that by at least 1.5 million years ago early human physiology was already adapted to a diet that included the regular consumption of meat
Assessing the Effects of the Uncertainty in Reheating Energy Scale on Primordial Spectrum and CMB
The details of reheating energy scale is largely uncertain
today, independent of inflation models. This would induce uncertainty in
predicting primordial spectrum. Such uncertainty could be very large,
especially for spectra with large running . We find that for some
inflation models with a large , could be
highly restricted by current CMB observations.Comment: 8 pages, 6 figure
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