2,519 research outputs found
Effects of acceleration on the collision of particles in the rotating black hole spacetime
We study the collision of two geodesic particles in the accelerating and
rotating black hole spacetime and probe the effects of the acceleration of
black hole on the center-of-mass energy of the colliding particles and on the
high-velocity collision belts. We find that the dependence of the
center-of-mass energy on the acceleration in the near event-horizon collision
is different from that in the near acceleration-horizon case. Moreover, the
presence of the acceleration changes the shape and position of the
high-velocity collision belts. Our results show that the acceleration of black
holes brings richer physics for the collision of particles.Comment: 7 pages, 2 figures, The corrected version accepted for publication in
EPJ
Spin-dependent (magneto)transport through a ring due to spin-orbit interaction
Electron transport through a one-dimensional ring connected with two external
leads, in the presence of spin-orbit interaction (SOI) of strength \alpha and a
perpendicular magnetic field is studied. Applying Griffith's boundary
conditions we derive analytic expressions for the reflection and transmission
coefficients of the corresponding one-electron scattering problem. We
generalize earlier conductance results by Nitta et al. [Appl. Phys. Lett. 75,
695 (1999)] and investigate the influence of \alpha, temperature, and a weak
magnetic field on the conductance. Varying \alpha and temperature changes the
position of the minima and maxima of the magnetic-field dependent conductance,
and it may even convert a maximum into a minimum and vice versa.Comment: 19 pages, 9 figure
One-Loop MHV Amplitudes in Supersymmetric Gauge Theories
Using CSW rules for constructing scalar Feynman diagrams from MHV vertices,
we compute the contribution of chiral multiplet to one-loop
MHV gluon amplitude. The result agrees with the one obtained previously using
unitarity-based methods, thereby demonstrating the validity of the MHV-diagram
technique, in the case of one-loop MHV amplitudes, for all massless
supersymmetric theories.Comment: 20 pages, 5 figure
Quantum and classical criticalities in the frustrated two-leg Heisenberg ladder
This talk was about the frustration-induced criticality in the
antiferromagnetic Heisenberg model on the two-leg ladder with exchange
interactions along the chains, rungs, and diagonals, and also about the effect
of thermal fluctuations on this criticlity. The method used is the bond
mean-field theory, which is based on the Jordan-Wigner transformation in
dimensions higher than one. In this paper, we will summarize the main results
presented in this talk, and report on new results about the couplings and
temperature dependences of the spin susceptibility.Comment: 6 pages, 4 figures, talk presented at the Theory Canada 3 conference
in 2007, submitted to the Canadian Journal of Physic
Recursion relations, Helicity Amplitudes and Dimensional Regularization
Using the method of on-shell recursion relations we compute tree level
amplitudes including D-dimensional scalars and fermions. These tree level
amplitudes are needed for calculations of one-loop amplitudes in QCD involving
external quarks and gluons.Comment: 28 pages, 6 figures, clarifications adde
Scalar diagrammatic rules for Born amplitudes in QCD
We show that all Born amplitudes in QCD can be calculated from scalar
propagators and a set of three- and four-valent vertices. In particular, our
approach includes amplitudes with any number of quark pairs. The quarks may be
massless or massive. The proof of the formalism is given entirely within
quantum field theory.Comment: 20 pages, references adde
Statistical significance of fine structure in the frequency spectrum of Aharonov-Bohm conductance oscillations
We discuss a statistical analysis of Aharonov-Bohm conductance oscillations
measured in a two-dimensional ring, in the presence of Rashba spin-orbit
interaction. Measurements performed at different values of gate voltage are
used to calculate the ensemble-averaged modulus of the Fourier spectrum and, at
each frequency, the standard deviation associated to the average. This allows
us to prove the statistical significance of a splitting that we observe in the
h/e peak of the averaged spectrum. Our work illustrates in detail the role of
sample specific effects on the frequency spectrum of Aharonov-Bohm conductance
oscillations and it demonstrates how fine structures of a different physical
origin can be discriminated from sample specific features.Comment: accepted for publication in PR
Constrained estimation of intracranial aneurysm surface deformation using 4D-CTA
Background and objective
Intracranial aneurysms are relatively common life-threatening diseases, and assessing aneurysm rupture risk and identifying the associated risk factors is essential. Parameters such as the Oscillatory Shear Index, Pressure Loss Coefficient, and Wall Shear Stress are reliable indicators of intracranial aneurysm development and rupture risk, but aneurysm surface irregular pulsation has also received attention in aneurysm rupture risk assessment.
Methods
The present paper proposed a new approach to estimate aneurysm surface deformation. This method transforms the estimation of aneurysm surface deformation into a constrained optimization problem, which minimizes the error between the displacement estimated by the model and the sparse data point displacements from the four-dimensional CT angiography (4D-CTA) imaging data.
Results
The effect of the number of sparse data points on the results has been discussed in both simulation and experimental results, and it shows that the proposed method can accurately estimate the surface deformation of intracranial aneurysms when using sufficient sparse data points.
Conclusions
Due to a potential association between aneurysm rupture and surface irregular pulsation, the estimation of aneurysm surface deformation is needed. This paper proposed a method based on 4D-CTA imaging data, offering a novel solution for the estimation of intracranial aneurysm surface deformation
Near-infrared-actuated devices for remotely controlled drug delivery
A reservoir that could be remotely triggered to release a drug would enable the patient or physician to achieve on-demand, reproducible, repeated, and tunable dosing. Such a device would allow precise adjustment of dosage to desired effect, with a consequent minimization of toxicity, and could obviate repeated drug administrations or device implantations, enhancing patient compliance. It should exhibit low off-state leakage to minimize basal effects, and tunable on-state release profiles that could be adjusted from pulsatile to sustained in real time. Despite the clear clinical need for a device that meets these criteria, none has been reported to date to our knowledge. To address this deficiency, we developed an implantable reservoir capped by a nanocomposite membrane whose permeability was modulated by irradiation with a near-infrared laser. Irradiated devices could exhibit sustained on-state drug release for at least 3 h, and could reproducibly deliver short pulses over at least 10 cycles, with an on/off ratio of 30. Devices containing aspart, a fast-acting insulin analog, could achieve glycemic control after s.c. implantation in diabetic rats, with reproducible dosing controlled by the intensity and timing of irradiation over a 2-wk period. These devices can be loaded with a wide range of drug types, and therefore represent a platform technology that might be used to address a wide variety of clinical indications
Does accelerating universe indicates Brans-Dicke theory
The evolution of universe in Brans-Dicke (BD) theory is discussed in this
paper.
Considering a parameterized scenario for BD scalar field
which plays the role of gravitational "constant" ,
we apply the Markov Chain Monte Carlo method to investigate a global
constraints on BD theory with a self-interacting potential according to the
current observational data: Union2 dataset of type supernovae Ia (SNIa),
high-redshift Gamma-Ray Bursts (GRBs) data, observational Hubble data (OHD),
the cluster X-ray gas mass fraction, the baryon acoustic oscillation (BAO), and
the cosmic microwave background (CMB) data. It is shown that an expanded
universe from deceleration to acceleration is given in this theory, and the
constraint results of dimensionless matter density and parameter
are, and
which is consistent with the
result of current experiment exploration, . In
addition, we use the geometrical diagnostic method, jerk parameter , to
distinguish the BD theory and cosmological constant model in Einstein's theory
of general relativity.Comment: 16 pages, 3 figure
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