14,554 research outputs found
Rich variety of defects in ZnO via an attractive interaction between O-vacancies and Zn-interstitials
As the concentration of intrinsic defects becomes sufficiently high in
O-deficient ZnO, interactions between defects lead to a significant reduction
in their formation energies. We show that the formation of both O-vacancies and
Zn-interstitials becomes significantly enhanced by a strong attractive
interaction between them, making these defects an important source of n-type
conductivity in ZnO.Comment: 12 pages, 4 figure
Stochastic Reinforcement Learning
In reinforcement learning episodes, the rewards and punishments are often
non-deterministic, and there are invariably stochastic elements governing the
underlying situation. Such stochastic elements are often numerous and cannot be
known in advance, and they have a tendency to obscure the underlying rewards
and punishments patterns. Indeed, if stochastic elements were absent, the same
outcome would occur every time and the learning problems involved could be
greatly simplified. In addition, in most practical situations, the cost of an
observation to receive either a reward or punishment can be significant, and
one would wish to arrive at the correct learning conclusion by incurring
minimum cost. In this paper, we present a stochastic approach to reinforcement
learning which explicitly models the variability present in the learning
environment and the cost of observation. Criteria and rules for learning
success are quantitatively analyzed, and probabilities of exceeding the
observation cost bounds are also obtained.Comment: AIKE 201
Spectroscopic Evidence for Anisotropic S-Wave Pairing Symmetry in MgB2
Scanning tunneling spectroscopy of superconducting MgB ( K)
were studied on high-density pellets and c-axis oriented films. The sample
surfaces were chemically etched to remove surface carbonates and hydroxides,
and the data were compared with calculated spectra for all symmetry-allowed
pairing channels. The pairing potential () is best described by an
anisotropic s-wave pairing model, with , where is the angle relative to the
crystalline c-axis, meV, and meV.Comment: 4 pages and 3 figures. Submitted to Physical Review Letters.
Corresponding author: Nai-Chang Yeh (e-mail: [email protected]
Dynamic Release of Bending Stress in Short dsDNA by Formation of a Kink and Forks
Bending with high curvature is one of the major mechanical properties of double-stranded DNA (dsDNA) that is essential for its biological functions. The emergence of a kink arising from local melting in the middle of dsDNA has been suggested as a mechanism of releasing the energy cost of bending. Herein, we report that strong bending induces two types of short dsDNA deformations, induced by two types of local melting, namely, a kink in the middle and forks at the ends, which we demonstrate using D-shaped DNA nanostructures. The two types of deformed dsDNA structures dynamically interconvert on a millisecond timescale. The transition from a fork to a kink is dominated by entropic contribution (anti-Arrhenius behavior), while the transition from a kink to a fork is dominated by enthalpic contributions. The presence of mismatches in dsDNA accelerates kink formation, and the transition from a kink to a fork is removed when the mismatch size is three base pairs.1157Ysciescopu
"Dark" Z implications for Parity Violation, Rare Meson Decays, and Higgs Physics
General consequences of mass mixing between the ordinary Z boson and a
relatively light Z_d boson, the "dark" Z, arising from a U(1)_d gauge symmetry,
associated with a hidden sector such as dark matter, are examined. New effects
beyond kinetic mixing are emphasized. Z-Z_d mixing introduces a new source of
low energy parity violation well explored by possible future atomic parity
violation and planned polarized electron scattering experiments. Rare K (B)
meson decays into pi (K) l^+ l^- (l = e, mu) and pi (K) nu anti-nu are found to
already place tight constraints on the size of Z-Z_d mixing. Those
sensitivities can be further improved with future dedicated searches at K and B
factories as well as binned studies of existing data. Z-Z_d mixing can also
lead to the Higgs decay H -> Z Z_d, followed by Z -> l_1^+ l_1^- and Z_d ->
l_2^+ l_2^- or "missing energy", providing a potential hidden sector discovery
channel at the LHC. An illustrative realization of these effects in a 2 Higgs
doublet model is presented.Comment: Version to appear in PR
Effect of sintering temperature under high pressure in the uperconductivity for MgB2
We report the effect of the sintering temperature on the superconductivity of
MgB2 pellets prepared under a high pressure of 3 GPa. The superconducting
properties of the non-heated MgB2 in this high pressure were poor. However, as
the sintering temperature increased, the superconducting properties were vastly
enhanced, which was shown by the narrow transition width for the resistivity
and the low-field magnetizations. This shows that heat treatment under high
pressure is essential to improve superconducting properties. These changes were
found to be closely related to changes in the surface morphology observed using
scanning electron microscopy.Comment: 3 Pages including 3 figure
- …