1,892 research outputs found
Heterogeneous embedding propagation for large-scale e-commerce user alignment
National Research Foundation (NRF) Singapore CREATE; Alibaba Innovative Researc
Constraining large scale HI bias using redshifted 21-cm signal from the post-reionization epoch
In the absence of complex astrophysical processes that characterize the
reionization era, the 21-cm emission from neutral hydrogen (HI) in the
post-reionization epoch is believed to be an excellent tracer of the underlying
dark matter distribution. Assuming a background cosmology, it is modelled
through (i) a bias function b(k,z), which relates HI to the dark matter
distribution and (ii) a mean neutral fraction (x_{HI}) which sets its
amplitude. In this paper, we investigate the nature of large scale HI bias. The
post-reionization HI is modelled using gravity only N-Body simulations and a
suitable prescription for assigning gas to the dark matter halos. Using the
simulated bias as the fiducial model for HI distribution at z\leq 4, we have
generated a hypothetical data set for the 21-cm angular power spectrum (C_{l})
using a noise model based on parameters of an extended version of the GMRT. The
binned C_{l} is assumed to be measured with SNR \gtrsim 4 in the range 400 \leq
l \leq 8000 at a fiducial redshift z=2.5. We explore the possibility of
constraining b(k) using the Principal Component Analysis (PCA) on this
simulated data. Our analysis shows that in the range 0.2 < k < 2 Mpc^{-1}, the
simulated data set cannot distinguish between models exhibiting different k
dependences, provided 1 \lesssim b(k) \lesssim 2 which sets the 2-sigma limits.
This justifies the use of linear bias model on large scales. The largely
uncertain x_{HI} is treated as a free parameter resulting in degradation of the
bias reconstruction. The given simulated data is found to constrain the
fiducial x_{HI} with an accuracy of \sim 4% (2-sigma error). The method
outlined here, could be successfully implemented on future observational data
sets to constrain b(k,z) and x_{HI} and thereby enhance our understanding of
the low redshift Universe.Comment: 10 pages, 11 figures, 2 tables. Accepted in MNRAS. Revised to match
the accepted versio
The regional differences in prevalence, medical expenditures and risk factors for injury in Taiwanese teenagers
BACKGROUND: Injury is the leading cause of death in teenagers worldwide. In Taiwan, people in mountainous areas have a 4 to 8 years shorter life span than the general population. Injury among teenagers is likely a major cause. The objective of this study was to investigate the regional differences in the prevalence, the risk factors, and the medical expenditures for injury among Taiwanese teenagers. METHOD: An equal probability national sample was used. In addition, representative samples from mountainous areas and offshore islands were used. Only those who aged between 12 and 21 years, and signed the consent form permitting us to link their National Health Insurance (NHI) claim data were included in the analysis. Injury-related visits and expenditures in outpatient services were extracted from the NHI data. Logistic regression was used to examine the factors associated with injury. For those who had injury related outpatient visits, mixed model was used to examine the factors associated with medical expenditures accounting for multiple visits by the same individual. RESULTS: The prevalence of nonfatal injury was around 30% of teenagers in Taiwan. It was 10% higher in mountainous areas. Factors associated with injury were those who lived in mountainous areas (adjusted odds ratio [OR]: 1.7; 95%; confidence interval [CI]: 1.3–2.3), males (OR: 1.3; 95%; CI: 1.1–1.6), older teens (18–21 years old), and those with risk behavior were positively associated with injury. These factors were also associated with the number of injury-related outpatient visits. However, teenagers in mountainous areas did not spend more on medical care than those who lived in metropolitan Taiwan. CONCLUSION: Around 30% of the teenagers were injured in a year, not including the dead. Each of the injured spent at least 851.4NTD (~27USD) for outpatient visits. The scope of the problem was not trivial. Hazardous environments and high-risk behaviors were the universal causes. In remote areas, lack of medical resources was another possibility. Empowering local people to design prevention programs according to their needs is recommended
Direct Measurement of the Pseudoscalar Decay Constant fD+
The absolute branching fraction of has been directly
measured by an analysis of a data sample of about 33 collected
around GeV with the BES-II at the BEPC. At these energies,
meson is produced in pair as . A total of mesons are reconstructed from this data set. In the
recoil side of the tagged mesons, purely leptonic decay
events of are observed. This yields a branching fraction of
, and a
corresponding pseudoscalar decay constant
MeV.Comment: 7 pages, 8 figures, Submitted to Physics Letters B in October, 200
Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta
Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector,
the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are
measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and
(7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure
Measurements of the Mass and Full-Width of the Meson
In a sample of 58 million events collected with the BES II detector,
the process J/ is observed in five different decay
channels: , , (with ), (with
) and . From a combined fit of all five
channels, we determine the mass and full-width of to be
MeV/ and
MeV/.Comment: 9 pages, 2 figures and 4 table. Submitted to Phys. Lett.
Search for the Lepton Flavor Violation Processes and
The lepton flavor violation processes and are
searched for using a sample of 5.8 events collected with
the BESII detector. Zero and one candidate events, consistent with the
estimated background, are observed in and
decays, respectively. Upper limits on the branching ratios are determined to be
and at the 90% confidence level (C.L.).Comment: 9 pages, 2 figure
Asymmetric effects of volatility risk on stock returns:evidence from VIX and VIX futures
First, to separate different market conditions, this study focuses on how VIX spot (VIX), VIX futures (VXF), and their basis (VIX-VXF) perform different roles in asset pricing. Secondly, this study decomposes the VIX index into two parts, volatility calculated from out-of-the-money call options and volatility calculated from out-of-the-money put options. The analysis shows that out-of-the-money put options capture more useful information in predicting future stock returns
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
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