19,299 research outputs found
Why is the nuclear symmetry energy so uncertain at supra-saturation densities?
Within the interacting Fermi gas model for isospin asymmetric nuclear matter,
effects of the in-medium three-body interaction and the two-body short-range
tensor force due to the meson exchange as well as the short-range
nucleon correlation on the high-density behavior of the nuclear symmetry energy
are demonstrated respectively in a transparent way. Possible physics origins of
the extremely uncertain nuclear symmetry energy at supra-saturation densities
are discussed.Comment: Added discussions and revised format. Version to appear in Phys. Rev.
C (2010
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Mechanistic Study Of Plasma Damage Of Low k Dielectric Surfaces
Plasma damage to low k dielectric materials was investigated from a mechanistic point of view. Low k dielectric films were treated by plasma Ar, O-2, N-2/H-2, N-2 and H-2 in a standard RIE chamber and the damage was characterized by Angle Resolved X-ray Photoelectron Spectroscopy (ARXPS), X-Ray Reflectivity (XRR), Fourier Transform Infrared Spectroscopy (FTIR) and Contact Angle measurements. Both carbon depletion and surface densification were observed on the top surface of damaged low k materials while the bulk remained largely unaffected. Plasma damage was found to be a complicated phenomenon involving both chemical and physical effects, depending on chemical reactivity and the energy and mass of the plasma species. A downstream hybrid plasma source with separate ions and atomic radicals was employed to study their respective roles in the plasma damage process. Ions were found to play a more important role in the plasma damage process. The dielectric constant of low k materials can increase up to 20% due to plasma damage and we attributed this to the removal of the methyl group making the low k surface hydrophilic. Annealing was generally effective in mitigating moisture uptake to restore the k value but the recovery was less complete for higher energy plasmas. Quantum chemistry calculation confirmed that physisorbed water in low k materials induces the largest increase of dipole moments in comparison with changes of surface bonding configurations, and is primarily responsible for the dielectric constant increase.Microelectronics Research Cente
Incommensurate magnetic structure of CeRhIn5
The magnetic structure of the heavy fermion antiferromagnet CeRhIn5 is
determined using neutron diffraction. We find a magnetic wave vector
q_M=(1/2,1/2,0.297), which is temperature independent up to T_N=3.8K. A
staggered moment of 0.374(5) Bohr magneton at 1.4K, residing on the Ce ion,
spirals transversely along the c axis. The nearest neighbor moments on the
tetragonal basal plane are aligned antiferromagnetically.Comment: 4 pages, 4 figures There was an extra factor of 2 in Eq (2). This
affects the value of staggered moment. The correct staggered moment is
0.374(5) Bohr magneton at 1.4
Anisakis infection in allis shad, Alosa alosa (Linnaeus, 1758), and twaite shad, Alosa fallax (Lacépède, 1803), from Western Iberian Peninsula Rivers : zoonotic and ecological implications
Acknowledgments The authors would like to thank M. N. Cueto and J.M. Antonio (ECOBIOMAR) for their excellent technical support and also Rodrigo López for making the map of the study area. We also thank the personal of the Vigo IEO, for providing information about shad captures at sea collected on the basis of national program (AMDES) included in the European Data Collection Framework (DCF) project. We are also grateful to Comandancia Naval de Tui for providing fishing data. M. Bao is supported by a PhD grant from the University of Aberdeen and also by financial support of the contract from the EU Project PARASITE (grant number 312068). This study was partially supported by a PhD grant from the Portuguese Foundation for Science and Technology (FCT) SFRH/BD/44892/2008) and partially supported by the European Regional Development Fund (ERDF) through the COMPETE—Operational Competitiveness Programme and national funds through Foundation for Science and Technology (FCT), under the project BPEst-C/MAR/ LA0015/2013. The authors thank the staff of the Station of Hydrobiology of the USC BEncoro do Con^ due their participation in the surveys. This work has been partially supported by the project 10PXIB2111059PR of the Xunta de Galicia and the project MIGRANET of the Interreg IV BSUDOE (South-West Europe) Territorial Cooperation Programme (SOE2/P2/E288). D.J. Nachón is supported by a PhD grant from the Xunta de Galicia (PRE/2011/198)Peer reviewedPostprin
Improved Simulation of the Mass Charging for ASTROD I
The electrostatic charging of the test mass in ASTROD I (Astrodynamical Space
Test of Relativity using Optical Devices I) mission can affect the quality of
the science data as a result of spurious Coulomb and Lorentz forces. To
estimate the size of the resultant disturbances, credible predictions of
charging rates and the charging noise are required. Using the GEANT4 software
toolkit, we present a detailed Monte Carlo simulation of the ASTROD I test mass
charging due to exposure of the spacecraft to galactic cosmic-ray (GCR) protons
and alpha particles (3He, 4He) in the space environment. A positive charging
rate of 33.3 e+/s at solar minimum is obtained. This figure reduces by 50% at
solar maximum. Based on this charging rate and factoring in the contribution of
minor cosmic-ray components, we calculate the acceleration noise and stiffness
associated with charging. We conclude that the acceleration noise arising from
Coulomb and Lorentz effects are well below the ASTROD I acceleration noise
limit at 0.1 mHz both at solar minimum and maximum. The coherent Fourier
components due to charging are investigated, it needs to be studied carefully
in order to ensure that these do not compromise the quality of science data in
the ASTROD I mission.Comment: 20 pages, 14 figures, submitted to International Journal of Modern
Physics
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A review of microgrid development in the United States – A decade of progress on policies, demonstrations, controls, and software tools
Microgrids have become increasingly popular in the United States. Supported by favorable federal and local policies, microgrid projects can provide greater energy stability and resilience within a project site or community. This paper reviews major federal, state, and utility-level policies driving microgrid development in the United States. Representative U.S. demonstration projects are selected and their technical characteristics and non-technical features are introduced. The paper discusses trends in the technology development of microgrid systems as well as microgrid control methods and interactions within the electricity market. Software tools for microgrid design, planning, and performance analysis are illustrated with each tool's core capability. Finally, the paper summarizes the successes and lessons learned during the recent expansion of the U.S. microgrid industry that may serve as a reference for other countries developing their own microgrid industries
Three Dimensional Simulation of Jet Formation in Collapsing Condensates
We numerically study the behavior of collapsing and exploding condensates
using the parameters of the experiments by E.A. Donley et al. [Nature,
412, 295, (2001)]. Our studies are based on a full three-dimensional
numerical solution of the Gross-Pitaevskii equation (GPE) including three body
loss. We determine the three body loss rate from the number of remnant
condensate atoms and collapse times and obtain only one possible value which
fits with the experimental results. We then study the formation of jet atoms by
interrupting the collapse and find very good agreement with the experiment.
Furthermore we investigate the sensitivity of the jets to the initial
conditions. According to our analysis the dynamics of the burst atoms is not
described by the GPE with three body loss incorporated.Comment: 9 pages, 10 figure
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