12,200 research outputs found
Adaptive just-in-time code diversification
We present a method to regenerate diversified code dynamically in a Java bytecode JIT compiler, and to update the diversification frequently during the execution of the program. This way, we can significantly reduce the time frame in which attackers can let a program leak useful address space information and subsequently use the leaked information in memory exploits. A proof of concept implementation is evaluated, showing that even though code is recompiled frequently, we can achieved smaller overheads than the previous state of the art, which generated diversity only once during the whole execution of a program
-decay half-lives of neutron-rich nuclei and matter flow in the -process
The -decay half-lives of neutron-rich nuclei with are systematically investigated using the newly developed fully
self-consistent proton-neutron quasiparticle random phase approximation (QRPA),
based on the spherical relativistic Hartree-Fock-Bogoliubov (RHFB) framework.
Available data are reproduced by including an isospin-dependent proton-neutron
pairing interaction in the isoscalar channel of the RHFB+QRPA model. With the
calculated -decay half-lives of neutron-rich nuclei a remarkable
speeding up of -matter flow is predicted. This leads to enhanced -process
abundances of elements with , an important result for the
understanding of the origin of heavy elements in the universe.Comment: 14 pages, 4 figure
Vanishing viscosity limits for the degenerate lake equations with Navier boundary conditions
The paper is concerned with the vanishing viscosity limit of the
two-dimensional degenerate viscous lake equations when the Navier slip
conditions are prescribed on the impermeable boundary of a simply connected
bounded regular domain. When the initial vorticity is in the Lebesgue space
with , we show the degenerate viscous lake equations
possess a unique global solution and the solution converges to a corresponding
weak solution of the inviscid lake equations. In the special case when the
vorticity is in , an explicit convergence rate is obtained
Isolation and purification of alkaline keratinase from Bacillus sp. 50-3
A new alkaline keratinase extracted from Bacillus sp. 50-3 was isolated and purified in this study. Solid ammonium sulfate was selected to precipitate the enzyme. Its proper adding mass was also determined.Through solid ammonium sulfate precipitation and liquid chromatography via the DEAE-Sephadex-A50 column using with azokeratin as a substrate, 17.7-fold purification with a yield of 46.5% was obtained. The purification effect was determined through SDS-PAGE, and the molecular weight of the enzyme was found at 27 423 Da by the MALDI-TOF-MS. Its simple purification step and high yield using a cheap medium attest to the great biotechnological potential of keratinase, especially in environmentprotection and in recycling valuable materials from wastes
Control of atomic currents using a quantum stirring device
We propose a BEC stirring device which can be regarded as the incorporation
of a quantum pump into a closed circuit: it produces a DC circulating current
in response to a cyclic adiabatic change of two control parameters of an
optical trap. We demonstrate the feasibility of this concept and point out that
such device can be utilized in order to probe the interatomic interactions.Comment: 5 pages, 4 figures, uses epl2.cls, revised versio
More on volume dependence of spectral weight function
Spectral weight functions are easily obtained from two-point correlation
functions and they might be used to distinguish single-particle from
multi-particle states in a finite-volume lattice calculation, a problem crucial
for many lattice QCD simulations. In previous studies, it is shown that the
spectral weight function for a broad resonance shares the typical volume
dependence of a two-particle scattering state i.e. proportional to in a
large cubic box of size while the narrow resonance case requires further
investigation. In this paper, a generalized formula is found for the spectral
weight function which incorporates both narrow and broad resonance cases.
Within L\"uscher's formalism, it is shown that the volume dependence of the
spectral weight function exhibits a single-particle behavior for a extremely
narrow resonance and a two-particle behavior for a broad resonance. The
corresponding formulas for both and channels are derived. The
potential application of these formulas in the extraction of resonance
parameters are also discussed
Weak Field Phase Diagram for an Integer Quantum Hall Liquid
We study the localization properties in the transition from a two-dimensional
electron gas at zero magnetic field into an integer quantum Hall (QH) liquid.
By carrying out a direct calculation of the localization length for a finite
size sample using a transfer matrix technique, we systematically investigate
the field and disorder dependences of the metal-insulator transition in the
weak field QH regime. We obtain a different phase diagram from the one
conjectured in previous theoretical studies. In particular, we find that: (1)
the extended state energy for each Landau level (LL) is {\it always}
linear in magnetic field; (2) for a given Landau level and disorder
configuration there exists a critical magnetic field below which the
extended state disappears; (3) the lower LLs are more robust to the
metal-insulator transition with smaller . We attribute the above results
to strong LL coupling effect. Experimental implications of our work are
discussed.Comment: 4 pages, ReVTeX 3.0, 4 figures (available upon request
Berry phase correction to electron density of states in solids
Liouville's theorem on the conservation of phase space volume is violated by
Berry phase in the semiclassical dynamics of Bloch electrons. This leads to a
modification of the phase space density of states, whose significance is
discussed in a number of examples: field modification of the Fermi-sea volume,
connection to the anomalous Hall effect, and a general formula for orbital
magnetization. The effective quantum mechanics of Bloch electrons is also
sketched, where the modified density of states plays an essential role.Comment: Minor revision. Journal info updat
- …