20,723 research outputs found
The Top Quark Production Asymmetries and
A large forward-backward asymmetry is seen in both the top quark rapidity
distribution and in the rapidity distribution of charged leptons
from top quarks produced at the Tevatron. We study the kinematic
and dynamic aspects of the relationship of the two observables arising from the
spin correlation between the charged lepton and the top quark with different
polarization states. We emphasize the value of both measurements, and we
conclude that a new physics model which produces more right-handed than
left-handed top quarks is favored by the present data.Comment: accepted for publication in Physical Review Letter
BOOST: A fast approach to detecting gene-gene interactions in genome-wide case-control studies
Gene-gene interactions have long been recognized to be fundamentally
important to understand genetic causes of complex disease traits. At present,
identifying gene-gene interactions from genome-wide case-control studies is
computationally and methodologically challenging. In this paper, we introduce a
simple but powerful method, named `BOolean Operation based Screening and
Testing'(BOOST). To discover unknown gene-gene interactions that underlie
complex diseases, BOOST allows examining all pairwise interactions in
genome-wide case-control studies in a remarkably fast manner. We have carried
out interaction analyses on seven data sets from the Wellcome Trust Case
Control Consortium (WTCCC). Each analysis took less than 60 hours on a standard
3.0 GHz desktop with 4G memory running Windows XP system. The interaction
patterns identified from the type 1 diabetes data set display significant
difference from those identified from the rheumatoid arthritis data set, while
both data sets share a very similar hit region in the WTCCC report. BOOST has
also identified many undiscovered interactions between genes in the major
histocompatibility complex (MHC) region in the type 1 diabetes data set. In the
coming era of large-scale interaction mapping in genome-wide case-control
studies, our method can serve as a computationally and statistically useful
tool.Comment: Submitte
Direct tunneling through high- amorphous HfO: effects of chemical modification
We report first principles modeling of quantum tunneling through amorphous
HfO dielectric layer of metal-oxide-semiconductor (MOS) nanostructures in
the form of n-Si/HfO/Al. In particular we predict that chemically modifying
the amorphous HfO barrier by doping N and Al atoms in the middle region -
far from the two interfaces of the MOS structure, can reduce the
gate-to-channel tunnel leakage by more than one order of magnitude. Several
other types of modification are found to enhance tunneling or induce
substantial band bending in the Si, both are not desired from leakage point of
view. By analyzing transmission coefficients and projected density of states,
the microscopic physics of electron traversing the tunnel barrier with or
without impurity atoms in the high- dielectric is revealed.Comment: 5 pages, 5 figure
Impurity resonance states in electron-doped high T_c superconductors
Two scenarios, i.e., the anisotropic s-wave pairing (the s-wave scenario) and
the d-wave pairing coexisting with antiferromagnetism (the coexisting scenario)
have been introduced to understand some of seemingly s-wave like behaviors in
electron doped cuprates. We considered the electronic structure in the presence
of a nonmagnetic impurity in the coexistence scenario. We found that even if
the AF order opens a full gap in quasi-particle excitation spectra, the mid-gap
resonant peaks in local density of states (LDoS) around an impurity can still
be observed in the presence of a d-wave pairing gap. The features of the
impurity states in the coexisting phase are markedly different from the pure AF
or pure d-wave pairing phases, showing the unique role of the coexisting AF and
d-wave pairing orders. On the other hand, it is known that in the pure s-wave
case no mid-gap states can be induced by a nonmagnetic impurity. Therefore we
proposed that the response to a nonmagnetic impurity can be used to
differentiate the two scenarios.Comment: 5 pages, two-column revtex4, 5 figures, author list correcte
Field Effect Transistor Nanosensor for Breast Cancer Diagnostics
Silicon nanochannel field effect transistor (FET) biosensors are one of the most promising technologies in the development of highly sensitive and label-free analyte detection for cancer diagnostics. With their exceptional electrical properties and small dimensions, silicon nanochannels are ideally suited for extraordinarily high sensitivity. In fact, the high surface-to-volume ratios of these systems make single molecule detection possible. Further, FET biosensors offer the benefits of high speed, low cost, and high yield manufacturing, without sacrificing the sensitivity typical for traditional optical methods in diagnostics. Top down manufacturing methods leverage advantages in Complementary Metal Oxide Semiconductor (CMOS) technologies, making richly multiplexed sensor arrays a reality. Here, we discuss the fabrication and use of silicon nanochannel FET devices as biosensors for breast cancer diagnosis and monitoring
Effect of electron interactions on the conductivity and exchange coupling energy of disordered metallic magnetic multilayer
We consider the effect of electron-electron interactions on the
current-in-plane (CIP) conductivity and exchange coupling energy of a
disordered metallic magnetic multilayer. We analyze its dependence on the value
of ferromagnetic splitting of conducting electrons and ferromagnetic layers
relative magnetizations orientation. We show that contribution to the CIP
conductivity and exchange coupling energy as a periodic function of the angle
of magnetizations relative orientation experience transition
depending on the characteristic energies: ferromagnetic splitting of the
conducting electrons and the Thouless energy of paramagnetic layer.Comment: 6 pages, 1 figur
Empirical study on clique-degree distribution of networks
The community structure and motif-modular-network hierarchy are of great
importance for understanding the relationship between structures and functions.
In this paper, we investigate the distribution of clique-degree, which is an
extension of degree and can be used to measure the density of cliques in
networks. The empirical studies indicate the extensive existence of power-law
clique-degree distributions in various real networks, and the power-law
exponent decreases with the increasing of clique size.Comment: 9 figures, 4 page
Phase transition and hysteresis in scale-free network traffic
We model information traffic on scale-free networks by introducing the node
queue length L proportional to the node degree and its delivering ability C
proportional to L. The simulation gives the overall capacity of the traffic
system, which is quantified by a phase transition from free flow to congestion.
It is found that the maximal capacity of the system results from the case of
the local routing coefficient \phi slightly larger than zero, and we provide an
analysis for the optimal value of \phi. In addition, we report for the first
time the fundamental diagram of flow against density, in which hysteresis is
found, and thus we can classify the traffic flow with four states: free flow,
saturated flow, bistable, and jammed.Comment: 5 pages, 4 figure
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