4,608 research outputs found
A Three-Term Conjugate Gradient Method with Sufficient Descent Property for Unconstrained Optimization
Conjugate gradient methods are widely used for solving large-scale unconstrained optimization problems, because they do not need the storage of matrices. In this paper, we propose a general form of three-term conjugate gradient methods which always generate a sufficient descent direction. We give a sufficient condition for the global convergence of the proposed general method. Moreover, we present a specific three-term conjugate gradient method based on the multi-step quasi-Newton method. Finally, some numerical results of the proposed method are given
Thermal switching rate of a ferromagnetic material with uniaxial anisotropy
The field dependence of the thermal switching rate of a ferromagnetic
material with uniaxial anisotropy was studied by solving the Fokker-Planck
equation. We derived the analytical expression of the thermal switching rate
using the mean first-passage time approach, and found that Brown's formula
[Phys. Rev. 130, 1677 (1963)] is applicable even in the low barrier limit by
replacing the attempt frequency with the proper factor which is expressed by
the error function.Comment: 5 pages, 2 figure
A requirement for PARP-1 for the assembly or stability of XRCC1 nuclear foci at sites of oxidative DNA damage
The molecular role of poly (ADP-ribose) polymerase-1 in DNA repair is unclear. Here, we show that the single-strand break repair protein XRCC1 is rapidly assembled into discrete nuclear foci after oxidative DNA damage at sites of poly (ADP-ribose) synthesis. Poly (ADP-ribose) synthesis peaks during a 10 min treatment with H2O2 and the appearance of XRCC1 foci peaks shortly afterwards. Both sites of poly (ADP-ribose) and XRCC1 foci decrease to background levels during subsequent incubation in drug-free medium, consistent with the rapidity of the single-strand break repair process. The formation of XRCC1 foci at sites of poly (ADP-ribose) was greatly reduced by mutation of the XRCC1 BRCT I domain that physically interacts with PARP-1. Moreover, we failed to detect XRCC1 foci in Adprt1¿/¿ MEFs after treatment with H2O2. These data demonstrate that PARP-1 is required for the assembly or stability of XRCC1 nuclear foci after oxidative DNA damage and suggest that the formation of these foci is mediated via interaction with poly (ADP-ribose). These results support a model in which the rapid activation of PARP-1 at sites of DNA strand breakage facilitates DNA repair by recruiting the molecular scaffold protein, XRCC1
Reduced Dynamics from the Unitary Group to Some Flag Manifolds : Interacting Matrix Riccati Equations
In this paper we treat the time evolution of unitary elements in the N level
system and consider the reduced dynamics from the unitary group U(N) to flag
manifolds of the second type (in our terminology). Then we derive a set of
differential equations of matrix Riccati types interacting with one another and
present an important problem on a nonlinear superposition formula that the
Riccati equation satisfies.
Our result is a natural generalization of the paper {\bf Chaturvedi et al}
(arXiv : 0706.0964 [quant-ph]).Comment: Latex ; 13 pages ; no figur
Reflection asymmetric relativistic mean field approach and its application to the octupole deformed nucleus Ra
A Reflection ASymmetric Relativistic Mean Field (RAS-RMF) approach is
developed by expanding the equations of motion for both the nucleons and the
mesons on the eigenfunctions of the two-center harmonic-oscillator potential.
The efficiency and reliability of the RAS-RMF approach are demonstrated in its
application to the well-known octupole deformed nucleus Ra and the
available data, including the binding energy and the deformation parameters,
are well reproduced.Comment: 4 pages, 2 figures, and 2 tables, to appear in Chinese Physics
Letter
Possible effects of tilt order on phase transitions of a fixed connectivity surface model
We study the phase structure of a phantom tethered surface model shedding
light on the internal degrees of freedom (IDOF), which correspond to the
three-dimensional rod like structure of the lipid molecules. The so-called tilt
order is assumed as IDOF on the surface model. The model is defined by
combining the conventional spherical surface model and the XY model, which
describes not only the interaction between lipids but also the interaction
between the lipids and the surface. The interaction strength between IDOF and
the surface varies depending on the interaction strength between the variables
of IDOF. We know that the model without IDOF undergoes a first-order transition
of surface fluctuations and a first-order collapsing transition. We observe in
this paper that the order of the surface fluctuation transition changes from
first-order to second-order and to higher-order with increasing strength of the
interaction between IDOF variables. On the contrary, the order of collapsing
transition remains first-order and is not influenced by the presence of IDOF.Comment: 20 pages, 14 figure
Possible Charge-Exchange X-Ray Emission in the Cygnus Loop Detected with Suzaku
X-ray spectroscopic measurements of the Cygnus Loop supernova remnant
indicate that metal abundances throughout most of the remnant's rim are
depleted to about 0.2 times the solar value. However, recent X-ray studies have
revealed in some narrow regions along the outermost rim anomalously "enhanced"
abundances (up to about 1 solar). The reason for these anomalous abundances is
not understood. Here, we examine X-ray spectra in annular sectors covering
nearly the entire rim of the Cygnus Loop using Suzaku (21 pointings) and
XMM-Newton (1 pointing). We find that spectra in the "enhanced" abundance
regions commonly show a strong emission feature at about 0.7 keV. This feature
is likely a complex of He-like O K(gamma + delta + epsilon), although other
possibilities cannot be fully excluded. The intensity of this emission relative
to He-like O Kalpha appears to be too high to be explained as thermal emission.
This fact, as well as the spatial concentration of the anomalous abundances in
the outermost rim, leads us to propose an origin from charge-exchange processes
between neutrals and H-like O. We show that the presence of charge-exchange
emission could lead to the inference of apparently "enhanced" metal abundances
using pure thermal emission models. Accounting for charge-exchange emission,
the actual abundances could be uniformly low throughout the rim. The overall
abundance depletion remains an open question.Comment: Published in Ap
Incommensurate Matrix Product State for Quantum Spin Systems
We introduce a matrix product state (MPS) with an incommensurate periodicity
by applying the spin-rotation operator of each site to a uniform MPS in the
thermodynamic limit. The spin rotations decrease the variational energy with
accompanying translational symmetry breaking and the rotational symmetry
breaking in the spin space even if the Hamiltonian has the both symmetries. The
optimized pitch of rotational operator reflects the commensurate/incommensurate
properties of spin-spin correlation functions in the Heisenberg chain
and the ferro-antiferro zigzag chain.Comment: 6 pages, 5 figure
Noise-Induced Synchronization of a Large Population of Globally Coupled Nonidentical Oscillators
We study a large population of globally coupled phase oscillators subject to
common white Gaussian noise and find analytically that the critical coupling
strength between oscillators for synchronization transition decreases with an
increase in the intensity of common noise. Thus, common noise promotes the
onset of synchronization. Our prediction is confirmed by numerical simulations
of the phase oscillators as well as of limit-cycle oscillators
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