80,115 research outputs found
Quakes in Solid Quark Stars
A starquake mechanism for pulsar glitches is developed in the solid quark
star model. It is found that the general glitch natures (i.e., the glitch
amplitudes and the time intervals) could be reproduced if solid quark matter,
with high baryon density but low temperature, has properties of shear modulus
\mu = 10^{30~34} erg/cm^3 and critical stress \sigma_c = 10^{18~24} erg/cm^3.
The post-glitch behavior may represent a kind of damped oscillations.Comment: 11 pages, 4 figures (but Fig.3 is lost), a complete version can be
obtained by http://vega.bac.pku.edu.cn/~rxxu/publications/index_P.htm, a new
version to be published on Astroparticle Physic
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Fighting coal — Effectiveness of coal-replacement programs for residential heating in China: Empirical findings from a household survey
Household fuel substitution has been a crucial step for controlling air pollution in China, but the performance evaluation of household fuel substitution policies is overlooked. This study capitalized on the opportunity to use data collected during the household coal-replacement program in North China to evaluate the effect of a mandatory policy on fuel substitution at the micro-level. The results indicate that there is a significant effect of the coal-replacement program on fuel substitution, as we expected. The coal-to-electricity policy is effective in achieving the goal of a clean winter but not a warm winter due to the decline of delivered energy, while the high-quality coal replacement policy results in better performance in delivered energy but no improvement in indoor air quality. It is recommended to prioritize supporting measures on both the supply and demand sides before implementation, along with undertaking differential measures during the implementation phase to better address energy inequality
Generation of high-energy monoenergetic heavy ion beams by radiation pressure acceleration of ultra-intense laser pulses
A novel radiation pressure acceleration (RPA) regime of heavy ion beams from
laser-irradiated ultrathin foils is proposed by self-consistently taking into
account the ionization dynamics. In this regime, the laser intensity is
required to match with the large ionization energy gap when the successive
ionization of high-Z atoms passing the noble gas configurations [such as
removing an electron from the helium-like charge state to
]. While the target ions in the laser wing region are ionized
to low charge states and undergo rapid dispersions due to instabilities, a
self-organized, stable RPA of highly-charged heavy ion beam near the laser axis
is achieved. It is also found that a large supplement of electrons produced
from ionization helps preserving stable acceleration. Two-dimensional
particle-in-cell simulations show that a monoenergetic beam
with peak energy and energy spread of is obtained by
lasers at intensity .Comment: 5 pages, 4 figure
Applying mesh conformation on shape analysis with missing data
A mesh conformation approach that makes use of deformable generic meshes has been applied to establishing correspondences between 3D shapes with missing data. Given a group of shapes with correspondences, we can build up a statistical shape model by applying principal component analysis (PCA). The conformation at first globally maps the generic mesh to the 3D shape based on manually located corresponding landmarks, and then locally deforms the generic mesh to clone the 3D shape. The local deformation is constrained by minimizing the energy of an elastic model. An algorithm was also embedded in the conformation process to fill missing surface data of the shapes. Using synthetic data, we demonstrate that the conformation preserves the configuration of the generic mesh and hence it helps to establish good correspondences for shape analysis. Case studies of the principal component analysis of shapes were presented to illustrate the successes and advantages of our approach
Infrared spectroscopy of the charge ordering transition in NaCoO
We report infrared spectra of a NaCoO single crystal which
exhibits a sharp metal-insulator transition near 50 K due to the formation of
charge ordering. In comparison with x=0.7 and 0.85 compounds, we found that the
spectral weight associated with the conducting carriers at high temperature
increases systematically with decreasing Na contents. The charge ordering
transition only affects the optical spectra below 1000 cm. A hump near
800 cm develops below 100 K, which is accompanied by the appearance of
new lattice modes as well as the strong anti-resonance feature of phonon
spectra. At lower temperature , an optical gap develops at the
magnitude of 2, evidencing an insulating charge
density wave ground state. Our experimental results and analysis unequivocally
point towards the importance of charge ordering instability and strong
electron-phonon interaction in NaCoO system.Comment: 4 pages, 3 figure
OM Theory and V-duality
We show that the (M5, M2, M2, MW) bound state solution of eleven
dimensional supergravity recently constructed in hep-th/0009147 is related to
the (M5, M2) bound state one by a finite Lorentz boost along a M5-brane
direction perpendicular to the M2-brane. Given the (M5, M2) bound state as a
defining system for OM theory and the above relation between this system and
the (M5, M2, M2', MW) bound state, we test the recently proposed V-duality
conjecture in OM theory. Insisting to have a decoupled OM theory, we find that
the allowed Lorentz boost has to be infinitesimally small, therefore resulting
in a family of OM theories related by Galilean boosts. We argue that such
related OM theories are equivalent to each other. In other words, V-duality
holds for OM theory as well. Upon compactification on either an electric or a
`magnetic' circle (plus T-dualities as well), the V-duality for OM theory gives
the known one for either noncommutative open string theories or noncommutative
Yang-Mills theories. This further implies that V-duality holds in general for
the little m-theory without gravity.Comment: 17 pages, typos corrected and references adde
Comprehensive Characterization of the Transmitted/Founder env Genes From a Single MSM Cohort in China
Background: The men having sex with men (MSM) population has become one of the major risk groups for HIV-1 infection in China. However, the epidemiological patterns, function of the env genes, and autologous and heterologous neutralization activity in the same MSM population have not been systematically characterized. Methods: The env gene sequences were obtained by the single genome amplification. The time to the most recent common ancestor was estimated for each genotype using the Bayesian Markov Chain Monte Carlo approach. Coreceptor usage was determined in NP-2 cells. Neutralization was analyzed using Env pseudoviruses in TZM-bl cells. Results: We have obtained 547 full-length env gene sequences by single genome amplification from 30 acute/early HIV-1–infected individuals in the Beijing MSM cohort. Three genotypes (subtype B, CRF01_AE, and CRF07_BC) were identified and 20% of the individuals were infected with multiple transmitted/founder (T/F) viruses. The tight clusters of the MSM sequences regardless of geographic origins indicated nearly exclusive transmission within the MSM population and limited number of introductions. The time to the most recent common ancestor for each genotype was 10–15 years after each was first introduced in China. Disparate preferences for coreceptor usages among 3 genotypes might lead to the changes in percentage of different genotypes in the MSM population over time. The genotype-matched and genotype-mismatched neutralization activity varied among the 3 genotypes. Conclusions: The identification of unique characteristics for transmission, coreceptor usage, neutralization profile, and epidemic patterns of HIV-1 is critical for the better understanding of transmission mechanisms, development of preventive strategies, and evaluation of vaccine efficacy in the MSM population in China
Observation of orbital ordering and origin of the nematic order in FeSe
To elucidate the origin of nematic order in FeSe, we performed
field-dependent 77Se-NMR measurements on single crystals of FeSe. We observed
orbital ordering from the splitting of the NMR spectra and Knight shift and a
suppression of it with magnetic field B0 up to 16 T applied parallel to the
Fe-planes. There is a significant change in the distribution and magnitude of
the internal magnetic field across the orbital ordering temperature Torb while
stripe-type antiferromagnetism is absent. Giant antiferromagnetic (AFM) spin
fluctuations measured by the NMR spin-lattice relaxation are gradually
developed starting at ~ 40 K, which is far below the nematic ordering
temperature Tnem. These results demonstrate that orbital ordering is the origin
of the nematic order, and the AFM spin fluctuation is the driving mechanism of
superconductivity in FeSe under the presence of the nematic order.Comment: 6 pages, 4 figure
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