5,971 research outputs found
Non-Thermal Dark Matter from Cosmic Strings
Cosmic strings can be created in the early universe during symmetry-breaking
phase transitions, such as might arise if the gauge structure of the standard
model is extended by additional U(1) factors at high energies. Cosmic strings
present in the early universe form a network of long horizon-length segments,
as well as a population of closed string loops. The closed loops are unstable
against decay, and can be a source of non-thermal particle production. In this
work we compute the density of WIMP dark matter formed by the decay of gauge
theory cosmic string loops derived from a network of long strings in the
scaling regime or under the influence of frictional forces. We find that for
symmetry breaking scales larger than 10^10 GeV, this mechanism has the
potential to account for the observed relic density of dark matter. For
symmetry breaking scales lower than this, the density of dark matter created by
loop decays from a scaling string network lies below the observed value. In
particular, the cosmic strings originating from a U(1) gauge symmetry broken
near the electroweak scale, that could lead to a massive Z' gauge boson
observable at the LHC, produce a negligibly small dark matter relic density by
this mechanism.Comment: 22 pages, 4 figures, added discussion about boosted decay products
from loop cusp
Is Administration of Marijuana Effective in Reducing Pain?
Objective: The objective of this selective EBM review is to determine whether or not “Is administration of marijuana effective in reducing pain”
Study Design: Systematic review of 2 randomized, double-blind placebo controlled trials (RCTs) and 1 cohort study published after July 2016.
Data Sources: Both RCTs and the cohort study were found through the PubMed database Outcome(s) measured: All 3 studies utilized the 11-point numerical rating scale to measure pain intensity.
Results: Wilsey et. al showed a notable improvement in pain intensity when participants inhaled both 2.9% delta 9-THC and 6.7% delta 9-THC concentrations when compared to visually matched placebo with no significant distinction between the lower and higher concentrations of delta 9-THC at the end of 7 hours. Although Schimrigk et. al did show pain reduction with administration of both dronabinol (PO form of THC) and placebo after 16 weeks, the results between the two were not significant when compared to each other. Lastly, the cohort study performed by Vigil et al. did reflect a significant change in pain intensity reduction after selfadministrated use of marijuana after 12 months.
Conclusion: This EBM review demonstrated that marijuana is an safe, effective treatment option for chronic pain patients looking to reduce their pain intensity. Although marijuana should not replace current conventional medical therapies, it may serve as an alternative for patients willing to try other options for pain relief
Cosmic Archaeology with Gravitational Waves from Cosmic Strings
Cosmic strings are generic cosmological predictions of many extensions of the
Standard Model of particle physics, such as a symmetry breaking
phase transition in the early universe or remnants of superstring theory.
Unlike other topological defects, cosmic strings can reach a scaling regime
that maintains a small fixed fraction of the total energy density of the
universe from a very early epoch until today. If present, they will oscillate
and generate gravitational waves with a frequency spectrum that imprints the
dominant sources of total cosmic energy density throughout the history of the
universe. We demonstrate that current and future gravitational wave detectors,
such as LIGO and LISA, could be capable of measuring the frequency spectrum of
gravitational waves from cosmic strings and discerning the energy composition
of the universe at times well before primordial nucleosynthesis and the cosmic
microwave background where standard cosmology has yet to be tested. This work
establishes a benchmark case that gravitational waves may provide an
unprecedented, powerful tool for probing the evolutionary history of the very
early universe.Comment: 6 pages, 3 figure
Effects of Heparin and Enoxaparin on APP Processing and Aβ Production in Primary Cortical Neurons from Tg2576 Mice
BACKGROUND Alzheimer's disease (AD) is caused by accumulation of Aβ, which is produced through sequential cleavage of β-amyloid precursor protein (APP) by the β-site APP cleaving enzyme (BACE1) and γ-secretase. Enoxaparin, a low molecular weight form of the glycosaminoglycan (GAG) heparin, has been reported to lower Aβ plaque deposition and improve cognitive function in AD transgenic mice. METHODOLOGY/PRINCIPAL FINDINGS We examined whether heparin and enoxaparin influence APP processing and inhibit Aβ production in primary cortical cell cultures. Heparin and enoxaparin were incubated with primary cortical cells derived from Tg2576 mice, and the level of APP and proteolytic products of APP (sAPPα, C99, C83 and Aβ) was measured by western blotting. Treatment of the cells with heparin or enoxaparin had no significant effect on the level of total APP. However, both GAGs decreased the level of C99 and C83, and inhibited sAPPα and Aβ secretion. Heparin also decreased the level of β-secretase (BACE1) and α-secretase (ADAM10). In contrast, heparin had no effect on the level of ADAM17. CONCLUSIONS/SIGNIFICANCE The data indicate that heparin and enoxaparin decrease APP processing via both α- and β-secretase pathways. The possibility that GAGs may be beneficial for the treatment of AD needs further study.This work was funded by a project grant (490031) from the National Health and Medical Research Council of Australia (http://www.nhmrc.gov.au). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Link-based Full Cost Analysis of Travel
This paper develops a link-based full cost model, which identifies the key cost components of travel, including both internal and external versions of cost, and gives a link-based cost estimate. The key cost components for travelers are categorized as time cost, emission cost, crash cost, user monetary cost, and infrastructure cost. Selecting the Minneapolis - St. Paul (Twin Cities) Metropolitan region as the study area, the estimates show that the average full cost of travel is $0.68/veh-km, in which the time and user monetary costs account for approximately 85% of the total. Except for the infrastructure cost, highways are more cost-effective than other surface road- ways considering all the other cost components, as well as the internal and full costs
Map Generation from Large Scale Incomplete and Inaccurate Data Labels
Accurately and globally mapping human infrastructure is an important and
challenging task with applications in routing, regulation compliance
monitoring, and natural disaster response management etc.. In this paper we
present progress in developing an algorithmic pipeline and distributed compute
system that automates the process of map creation using high resolution aerial
images. Unlike previous studies, most of which use datasets that are available
only in a few cities across the world, we utilizes publicly available imagery
and map data, both of which cover the contiguous United States (CONUS). We
approach the technical challenge of inaccurate and incomplete training data
adopting state-of-the-art convolutional neural network architectures such as
the U-Net and the CycleGAN to incrementally generate maps with increasingly
more accurate and more complete labels of man-made infrastructure such as roads
and houses. Since scaling the mapping task to CONUS calls for parallelization,
we then adopted an asynchronous distributed stochastic parallel gradient
descent training scheme to distribute the computational workload onto a cluster
of GPUs with nearly linear speed-up.Comment: This paper is accepted by KDD 202
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