9,593 research outputs found
Comparisons and Combinations of Reactor and Long-Baseline Neutrino Oscillation Measurements
We investigate how the data from various future neutrino oscillation
experiments will constrain the physics parameters for a three active neutrino
mixing model. The investigations properly account for the degeneracies and
ambiguities associated with the phenomenology as well as estimates of
experimental measurement errors. Combinations of various reactor measurements
with the expected J-PARC (T2K) and NuMI offaxis (Nova) data, both with and
without the increased flux associated with proton driver upgrades, are
considered. The studies show how combinations of reactor and offaxis data can
resolve degeneracies (e.g. the theta23 degeneracy) and give more precise
information on the oscillation parameters. A primary purpose of this
investigation is to establish the parameter space regions where CP violation
can be discovered and where the mass hierarchy can be determined. It is found
that such measurements, even with the augmented flux from proton driver
upgrades, demand sin^2 (2 theta13) be fairly large and in the range where it is
measurable by reactor experiments.Comment: 25 pages, 13 figures, fixed typos; 25 pages, 13 figures, updated
content, references; previous 22 pages, 12 figures, added references and
fixed reference display proble
Constraints on the sound speed of dark energy
We have studied constraints on the equation of state, , and speed of
sound, c_s, of the dark energy from a joint analysis of data from the cosmic
microwave background, large scale structure and type-Ia supernovae. We find
that current observations have no significant sensitivity to c_s. However,
there is a slight difference between models in which there are no dark energy
perturbations and models in which dark energy behaves as a fluid. Assuming that
there are no dark energy perturbations shifts the allowed region for to
slightly higher values. At present models with and without dark energy
perturbations provide roughly equally good fits to observations, but the
difference is potentially important for future parameter estimations. Finally,
we have also performed error forecasts for future measurements of c_s.Comment: 9 pages, 6 figures, Revte
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Trends in life cycle greenhouse gas emissions of future light duty electric vehicles
The majority of previous studies examining life cycle greenhouse gas (LCGHG) emissions of battery electric vehicles (BEVs) have focused on efficiency-oriented vehicle designs with limited battery capacities. However, two dominant trends in the US BEV market make these studies increasingly obsolete: sales show significant increases in battery capacity and attendant range and are increasingly dominated by large luxury or high-performance vehicles. In addition, an era of new use and ownership models may mean significant changes to vehicle utilization, and the carbon intensity of electricity is expected to decrease. Thus, the question is whether these trends significantly alter our expectations of future BEV LCGHG emissions. To answer this question, three archetypal vehicle designs for the year 2025 along with scenarios for increased range and different use models are simulated in an LCGHG model: an efficiency-oriented compact vehicle; a high performance luxury sedan; and a luxury sport utility vehicle. While production emissions are less than 10% of LCGHG emissions for today's gasoline vehicles, they account for about 40% for a BEV, and as much as two-thirds of a future BEV operated on a primarily renewable grid. Larger battery systems and low utilization do not outweigh expected reductions in emissions from electricity used for vehicle charging. These trends could be exacerbated by increasing BEV market shares for larger vehicles. However, larger battery systems could reduce per-mile emissions of BEVs in high mileage applications, like on-demand ride sharing or shared vehicle fleets, meaning that trends in use patterns may countervail those in BEV design
Development of UHF radiometer
A wideband multifrequency UHF radiometer was initially developed to operate in the 500 to 710 MHz frequency range for the remote measurement of ocean water salinity. However, radio-frequency interference required a reconfiguration to operate in the single-frequency radio astronomy band of 608 to 614 MHz. Details of the radiometer development and testing are described. Flight testing over variable terrain provided a performance comparison of the UHF radiometer with an L-band radiometer for remote sensing of geophysical parameters. Although theoretically more sensitive, the UHF radiometer was found to be less desirable in practice than the L-band radiometer
Optical measurements of phase steps in segmented mirrors - fundamental precision limits
Phase steps are an important type of wavefront aberrations generated by large
telescopes with segmented mirrors. In a closed-loop correction cycle these
phase steps have to be measured with the highest possible precision using
natural reference stars, that is with a small number of photons. In this paper
the classical Fisher information of statistics is used for calculating the
Cramer-Rao bound, which determines the limit to the precision with which the
height of the steps can be estimated in an unbiased fashion with a given number
of photons and a given measuring device. Four types of measurement devices are
discussed: a Shack-Hartmann sensor with one small cylindrical lenslet covering
a sub-aperture centred over a border, a modified Mach-Zehnder interferometer, a
Foucault test, and a curvature sensor. The Cramer-Rao bound is calculated for
all sensors under ideal conditions, that is narrowband measurements without
additional noise or disturbances apart from the photon shot noise. This limit
is compared with the ultimate quantum statistical limit for the estimate of
such a step which is independent of the measuring device. For the
Shack-Hartmann sensor, the effects on the Cramer-Rao bound of broadband
measurements, finite sampling, and disturbances such as atmospheric seeing and
detector readout noise are also investigated. The methods presented here can be
used to compare the precision limits of various devices for measuring phase
steps and for optimising the parameters of the devices. Under ideal conditions
the Shack-Hartmann and the Foucault devices nearly attain the ultimate quantum
statistical limits, whereas the Mach-Zehnder and the curvature devices each
require approximately twenty times as many photons in order to reach the same
precision.Comment: 23 pages, 19 figures, to be submitted to Journal of Modern Optic
MintHint: Automated Synthesis of Repair Hints
Being able to automatically repair programs is an extremely challenging task.
In this paper, we present MintHint, a novel technique for program repair that
is a departure from most of today's approaches. Instead of trying to fully
automate program repair, which is often an unachievable goal, MintHint performs
statistical correlation analysis to identify expressions that are likely to
occur in the repaired code and generates, using pattern-matching based
synthesis, repair hints from these expressions. Intuitively, these hints
suggest how to rectify a faulty statement and help developers find a complete,
actual repair. MintHint can address a variety of common faults, including
incorrect, spurious, and missing expressions.
We present a user study that shows that developers' productivity can improve
manyfold with the use of repair hints generated by MintHint -- compared to
having only traditional fault localization information. We also apply MintHint
to several faults of a widely used Unix utility program to further assess the
effectiveness of the approach. Our results show that MintHint performs well
even in situations where (1) the repair space searched does not contain the
exact repair, and (2) the operational specification obtained from the test
cases for repair is incomplete or even imprecise
Human Performance Assessments in Cadet Populations
This study assessed potential physiological differences between the Ranger Challenge (RC) Competition team and junior year cadets in an Army Reserve Officer Training Corps (ROTC) program. The method included: RC (m = 11, f = 2) and junior year cadets (m = 7, f = 3) were assessed in the following areas: 1) quickness and agility (5-10-5 shuttle run), 2) total-body power (standing broad jump), and 3) grip strength (hand grip dynamometry) assessed. The 5-10-5 shuttle run was performed twice (opening once to the left and once to the right). The standing broad jump required that cadets stand with their toes behind a line, perform a maximum of three preparatory movements, triple extend their knees, hips, and ankles while using their upper body to propel them as far forward as possible. After the jump the distanced reached was measured from the line to the heel of the nearest foot. Hand grip dynamometry was performed once on each hand. The cadet held the dynamometer out to his or her side and squeezed it as they lowered it to their hip. The results were that there were no significant differences between groups for the 5-10-5 shuttle run (p = 0.91), standing broad jump (p = 0.49), or grip strength (p = 0.31). RC did not outperform
The potential therapeutic effects of creatine supplementation on body composition and muscle function in cancer
Low muscle mass in individuals with cancer has a profound impact on quality of life and independence and is associated with greater treatment toxicity and poorer prognosis. Exercise interventions are regularly being investigated as a means to ameliorate treatment-related adverse effects, and nutritional/supplementation strategies to augment adaptations to exercise are highly valuable. Creatine (Cr) is a naturally-occurring substance in the human body that plays a critical role in energy provision during muscle contraction. Given the beneficial effects of Cr supplementation on lean body mass, strength, and physical function in a variety of clinical populations, there is therapeutic potential in individuals with cancer at heightened risk for muscle loss. Here, we provide an overview of Cr physiology, summarize the evidence on the use of Cr supplementation in various aging/clinical populations, explore mechanisms of action, and provide perspectives on the potential therapeutic role of Cr in the exercise oncology setting
Concepts of microdosimetry
This is the first part of an investigation of microdosimetric concepts relevant to numerical calculations. The definitions of the microdosimetric quantities are reviewed and formalized, and some additional conventions are adopted. The common interpretation of the quantities in terms of energy imparted to spherical sites is contrasted with their interpretation as the result of a diffusion process applied to the initial spatial pattern of energy transfers in the irradiated medium
Robust Inference of Trees
This paper is concerned with the reliable inference of optimal
tree-approximations to the dependency structure of an unknown distribution
generating data. The traditional approach to the problem measures the
dependency strength between random variables by the index called mutual
information. In this paper reliability is achieved by Walley's imprecise
Dirichlet model, which generalizes Bayesian learning with Dirichlet priors.
Adopting the imprecise Dirichlet model results in posterior interval
expectation for mutual information, and in a set of plausible trees consistent
with the data. Reliable inference about the actual tree is achieved by focusing
on the substructure common to all the plausible trees. We develop an exact
algorithm that infers the substructure in time O(m^4), m being the number of
random variables. The new algorithm is applied to a set of data sampled from a
known distribution. The method is shown to reliably infer edges of the actual
tree even when the data are very scarce, unlike the traditional approach.
Finally, we provide lower and upper credibility limits for mutual information
under the imprecise Dirichlet model. These enable the previous developments to
be extended to a full inferential method for trees.Comment: 26 pages, 7 figure
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