28,261 research outputs found
Possible discovery of the r-process characteristics in the abundances of metal-rich barium stars
We study the abundance distributions of a sample of metal-rich barium stars
provided by Pereira et al. (2011) to investigate the s- and r-process
nucleosynthesis in the metal-rich environment. We compared the theoretical
results predicted by a parametric model with the observed abundances of the
metal-rich barium stars. We found that six barium stars have a significant
r-process characteristic, and we divided the barium stars into two groups: the
r-rich barium stars (, [La/Nd]\,) and normal barium stars. The
behavior of the r-rich barium stars seems more like that of the metal-poor
r-rich and CEMP-r/s stars. We suggest that the most possible formation
mechanism for these stars is the s-process pollution, although their abundance
patterns can be fitted very well when the pre-enrichment hypothesis is
included. The fact that we can not explain them well using the s-process
nucleosynthesis alone may be due to our incomplete knowledge on the production
of Nd, Eu, and other relevant elements by the s-process in metal-rich and super
metal-rich environments (see details in Pereira et al. 2011).Comment: 5 pages, 5 figures, accepted for publication in A&
Multiparticle Entanglement in the Lipkin-Meshkov-Glick Model
The multiparticle entanglement in the Lipkin-Meshkov-Glick model has been
discussed extensively in this paper. Measured by the global entanglement and
its generalization, our calculation shows that the multiparticle entanglement
can faithfully detect quantum phase transitions. For an antiferromagnetic case
the multiparticle entanglement reaches the maximum at the transition point,
whereas for ferromagnetic coupling, two different behaviors of multiparticle
entanglement can be identified, dependent on the anisotropic parameter in the
coupling.Comment: 7 pages and 5 figure
Compensation of Effective Field in the Field-Induced Superconductor k-(BETS)2FeBr4 Observed by 77Se NMR
We report results of 77Se NMR frequency shift in the normal state of the
organic charge-transfer-salt k-(BETS)2FeBr4 which shows magnetic field-induced
superconductivity (FISC). From a simple mean field analysis, we determined the
field and the temperature dependences of the magnetization m_{pi} of the \pi
conduction electrons on BETS molecules. We found that the Fe spins are
antiferromagnetically coupled to the pi electrons and determined the exchange
field to be J = -2.3T/mu_B. The exchange field from the fully saturated Fe
moments (5 mu_B) is compensated by an external field of 12T. This is close to
the central field of the FISC phase, consistent with the Jaccarino-Peter local
field-compensation mechanism for FISC (Phys. Rev. Lett. 9, 290 (1962))
Entropy and specific heat for open systems in steady states
The fundamental assumption of statistical mechanics is that the system is
equally likely in any of the accessible microstates. Based on this assumption,
the Boltzmann distribution is derived and the full theory of statistical
thermodynamics can be built. In this paper, we show that the Boltzmann
distribution in general can not describe the steady state of open system. Based
on the effective Hamiltonian approach, we calculate the specific heat, the free
energy and the entropy for an open system in steady states. Examples are
illustrated and discussed.Comment: 4 pages, 7 figure
Hydrodynamic interaction in quasi-two-dimensional suspensions
Confinement between two parallel surfaces is found, theoretically and
experimentally, to drastically affect the hydrodynamic interaction between
colloid particles, changing the sign of the coupling, its decay with distance
and its concentration dependence. In particular, we show that three-body
effects do not modify the coupling at large distances as would be expected from
hydrodynamic screening.Comment: 8 pages, 2 figure
Mesoscopic Kondo effect of a quantum dot embedded in an Aharonov-Bohm ring with intradot spin-flip scattering
We study the Kondo effect in a quantum dot embedded in a mesoscopic ring
taking into account intradot spin-flip scattering . Based on the finite-
slave-boson mean-field approach, we find that the Kondo peak in the density of
states is split into two peaks by this coherent spin-flip transition, which is
responsible for some interesting features of the Kondo-assisted persistent
current circulating the ring: (1) strong suppression and crossover to a sine
function form with increasing ; (2) appearance of a "hump" in the
-dependent behavior for odd parity. -induced reverse of the persistent
current direction is also observed for odd parity.Comment: 7 pages,6 figures, to be published by Europhys. Let
Mold Fabrication for 3D Dual Damascene Imprinting
Previously, a damascene process based on nanoimprint lithography has been proposed (Schmid G M, et al. in J Vac Sci Technol B 24(3) 1283, 2006) to greatly reduce the fabrication steps of metal interconnection in integrated circuit. For such a process to become a viable technique, a mold having two pattern levels with precise alignment between them must be fabricated first. To this end, this work demonstrates a “self-aligned” fabrication process where the two pattern levels would be perfectly aligned if ignoring the noise during e-beam writing. The process is based on one EBL on a bi-layer resist stack, with the sensitivity for the top layer much higher than that of the bottom layer, which enables separate pattern transfer of the two pattern levels. Using ZEP-520A and poly(dimethylglutarimide) (PMGI) resists, we fabricated pillars having a diameter of 150 nm sitting on ridges having a width of 1.5 μm, which can be used to create via-holes and trenches for IC interconnect by nanoimprint lithography. The current process can also find applications in other areas that require two-level patterning with precise alignment between them
- …