12,287 research outputs found
"Virus hunting" using radial distance weighted discrimination
Motivated by the challenge of using DNA-seq data to identify viruses in human
blood samples, we propose a novel classification algorithm called "Radial
Distance Weighted Discrimination" (or Radial DWD). This classifier is designed
for binary classification, assuming one class is surrounded by the other class
in very diverse radial directions, which is seen to be typical for our virus
detection data. This separation of the 2 classes in multiple radial directions
naturally motivates the development of Radial DWD. While classical machine
learning methods such as the Support Vector Machine and linear Distance
Weighted Discrimination can sometimes give reasonable answers for a given data
set, their generalizability is severely compromised because of the linear
separating boundary. Radial DWD addresses this challenge by using a more
appropriate (in this particular case) spherical separating boundary.
Simulations show that for appropriate radial contexts, this gives much better
generalizability than linear methods, and also much better than conventional
kernel based (nonlinear) Support Vector Machines, because the latter methods
essentially use much of the information in the data for determining the shape
of the separating boundary. The effectiveness of Radial DWD is demonstrated for
real virus detection.Comment: Published at http://dx.doi.org/10.1214/15-AOAS869 in the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Gravitational Lensing by Dark Matter Halos with Non-universal Density Profiles
The statistics of gravitational lensing can provide us with a very powerful
probe of the mass distribution of matter in the universe. By comparing
predicted strong lensing probabilities with observations, we can test the mass
distribution of dark matter halos, in particular, the inner density slope. In
this letter, unlike previous work that directly models the density profiles of
dark matter halos semi-analytically, we generalize the density profiles of dark
matter halos from high-resolution N-body simulations by means of generalized
Navarro-Frenk-White (GNFW) models of three populations with slopes, ,
of about -1.5, -1.3 and -1.1 for galaxies, groups and clusters, respectively.
This approach is an alternative and independent way to examine the slopes of
mass density profiles of halos. We present calculations of lensing
probabilities using these GNFW profiles for three populations in various
spatially flat cosmological models with a cosmological constant . It
is shown that the compound model of density profiles does not match well with
the observed lensing probabilities derived from the Jodrell-Bank VLA
Astrometric Survey data in combination with the Cosmic Lens All-Sky Survey
data. Together with the previous work on lensing probability, our results
suggest that a singular isothermal sphere mass model of less than about
10^{13}h^{-1}M_{\sun} can predict strong lensing probabilities that are
consistent with observations of small splitting angles.Comment: 11 pages, 2 figures, Accepted by ApJL for publication (February 10
issue 2004
Regulating the adaptive immune response to respiratory virus infection
This article is made available for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.Recent years have seen several advances in our understanding of immunity to virus infection of the lower respiratory tract, including to influenza virus infection. Here, we review the cellular targets of viruses and the features of the host immune response that are unique to the lungs. We describe the interplay between innate and adaptive immune cells in the induction, expression and control of antiviral immunity, and discuss the impact of the infected lung milieu on moulding the response of antiviral effector T cells. Recent findings on the mechanisms that underlie the increased frequency of severe pulmonary bacterial infections following respiratory virus infection are also discussed
Local vertical measurements and violation of Bell inequality
For two qubits belonging to Alice and Bob, we derive an approach to setup the
bound of Bell operator in the condition that Alice and Bob continue to perform
local vertical measurements. For pure states we find that if the entanglement
of the two qubits is less than 0.2644 (measured with von Neumann entropy) the
violation of the Bell inequality will never be realized, and only when the
entanglement is equal to 1 the maximal violation () can occur. For
specific form of mixed states, we prove that the bound of the Bell inequality
depends on the concurrence. Only when the concurrence is greater than 0.6 the
violation of the Bell inequality can occur, and the maximal violation can never
be achieved. We suggest that the bound of the Bell operator in the condition of
local vertical measurements may be used as a measure of the entanglement.Comment: 4 pages, 3 figure
T Cell Responses during Acute Respiratory Virus Infection
This article is made available for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.The T cell response is an integral and essential part of the host immune response to acute virus infection. Each viral pathogen has unique, frequently nuanced, aspects to its replication, which affects the host response and as a consequence the capacity of the virus to produce disease. There are, however, common features to the T cell response to viruses, which produce acute limited infection. This is true whether virus replication is restricted to a single site, for example, the respiratory tract (RT), CNS etc., or replication is in multiple sites throughout the body. In describing below the acute T cell response to virus infection, we employ acute virus infection of the RT as a convenient model to explore this process of virus infection and the host response. We divide the process into three phases: the induction (initiation) of the response, the expression of antiviral effector activity resulting in virus elimination, and the resolution of inflammation with restoration of tissue homeostasis
Correlation Between the Halo Concentration (c) and the Virial Mass (Mvir) Determined from X-ray Clusters
Numerical simulations of structure formation have suggested that there exists
a good correlation between the halo concentration c (or the characteristic
density delta_c) and the virial mass Mvir for any virialized dark halo
described by the Navarro, Frenk & White (1995) density profile. In this Letter,
we present an observational determination of the c-Mvir (or delta_c-Mvir)
relation in the mass range of 10^14< Mvir <10^16 (solar mass) using a sample of
63 X-ray luminous clusters. The best-fit power law relation, which is roughly
independent of the values of Omega_M and Lambda, is c propto Mvir^(-0.5) or
delta_c propto Mvir^(-1.2), indicating n=-0.7 for a scale-free power spectrum
of the primordial density fluctuations. We discuss the possible reasons for the
conflict with the predictions by typical CDM models such as SCDM, LCDM and
OCDM.Comment: 13 pages, 1 figure, two tables. Accepted for publication in ApJ
Electromagnetically controlled multiferroic thermal diode
We propose an electromagnetically tunable thermal diode based on a two phase
multiferroics composite. Analytical and full numerical calculations for
prototypical heterojunction composed of Iron on Barium titanate in the
tetragonal phase demonstrate a strong heat rectification effect that can be
controlled externally by a moderate electric field. This finding is of an
importance for thermally based information processing and sensing and can also
be integrated in (spin)electronic circuits for heat management and recycling.Comment: Accepted in Phys. Rev.
Quantum phase transition in easy-axis antiferromagnetic Heisenberg spin-1 chain
The fidelity and entropy in an easy-axis antiferromagnetic Heisenberg spin-1
chain are studied numerically. By using the method of density-matrix
renormalization group, the effects of anisotropy on fidelity and entanglement
entropy are investigated. Their relations with quantum phase transition are
analyzed. It is found that the quantum phase transition from the Haldane spin
liquid to N\'eel spin solid can be well characterized by the fidelity. The
phase transition can be hardly detected by the entropy but it can be
successfully detected by the first deviation of the entropy.Comment: 3 figure
Quantum discord dynamical behaviors due to initial system-cavity correlations
We analyze the roles of initial correlations between the two-qubit system and
a dissipative cavity on quantum discord dynamics of two qubits. Considering two
initial system-cavity states, we show that the initial system-cavity
correlations not only can initially increase the two-qubit quantum discord but
also would lead to a larger long-time quantum discord asymptotic value.
Moreover, quantum discord due to initial correlations is more robust than the
case of the initial factorized state. Finally, we show the initial
correlations' importance for dynamics behaviors of mutual information and
classical correlation
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