Top quark forward-backward asymmetry and charge asymmetry in left-right twin Higgs model

In order to explain the Tevatron anomaly of the top quark forward-backward asymmetry $A_{FB}^t$ in the left-right twin Higgs model, we choose to give up the lightest neutral particle of $\hat{h}$ field as a stable dark matter candidate. Then a new Yukawa interaction for $\hat{h}$ is allowed, which can be free from the constraint of same-sign top pair production and contribute sizably to $A_{FB}^t$. Considering the constraints from the production rates of the top pair ($t\bar t$), the top decay rates and $t\bar{t}$ invariant mass distribution, we find that this model with such new Yukawa interaction can explain $A_{FB}^t$ measured at the Tevatron while satisfying the charge asymmetry $A_{C}^t$ measured at the LHC.Moreover, this model predicts a strongly correlation between $A_{C}^t$ at the LHC and $A_{FB}^t$ at the Tevatron, i.e., $A_{C}^t$ increases as $A_{FB}^t$ increases.Comment: 17 pages, 9 figures; matches the published versio

Quantum transport of two-dimensional Dirac fermions in SrMnBi2

We report two-dimensional quantum transport in SrMnBi$_2$ single crystals. The linear energy dispersion leads to the unusual nonsaturated linear magnetoresistance since all Dirac fermions occupy the lowest Landau level in the quantum limit. The transverse magnetoresistance exhibits a crossover at a critical field $B^*$ from semiclassical weak-field $B^2$ dependence to the high-field linear-field dependence. With increase in the temperature, the critical field $B^*$ increases and the temperature dependence of $B^*$ satisfies quadratic behavior which is attributed to the Landau level splitting of the linear energy dispersion. The effective magnetoresistant mobility $\mu_{MR}\sim 3400$ cm$^2$/Vs is derived. Angular dependent magnetoresistance and quantum oscillations suggest dominant two-dimensional (2D) Fermi surfaces. Our results illustrate the dominant 2D Dirac fermion states in SrMnBi$_2$ and imply that bulk crystals with Bi square nets can be used to study low dimensional electronic transport commonly found in 2D materials like graphene.Comment: 5 papges, 4 figure

Effect of the Kondo correlation on thermopower in a Quantum Dot

In this paper we study the thermopower of a quantum dot connected to two leads in the presence of Kondo correlation by employing a modified second-order perturbation scheme at nonequilibrium. A simple scheme, Ng's ansatz [Phys. Rev. Lett. {\bf 76}, 487 (1996)], is adopted to calculate nonequilibrium distribution Green's function and its validity is further checked with regard to the Onsager relation. Numerical results demonstrate that the sign of the thermopower can be changed by tuning the energy level of the quantum dot, leading to a oscillatory behavior with a suppressed magnitude due to the Kondo effect. We also calculate the thermal conductance of the system, and find that the Wiedemann-Franz law is obeyed at low temperature but violated with increasing temperature, corresponding to emerging and quenching of the Kondo effect.Comment: 6 pages, 4 figures; accepted for publication in J Phys.: Condensed Matte

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

Comment on ``Measurement of the 3^3He mass diffusion coefficient in superfluid 4^4He over the 0.45--0.95 K temperature range

The role of 3He-3He collisions in our diffusion experiment is addressed and shown to not be relevant to the measurement of 3He diffusion against phonons in superfluid helium.Comment: Two pages, in Europhysics Letters forma

Nuclear pairing reduction due to rotation and blocking

Nuclear pairing gaps of normally deformed and superdeformed nuclei are investigated using the particle-number conserving (PNC) formalism for the cranked shell model, in which the blocking effects are treated exactly. Both rotational frequency $\omega$-dependence and seniority (number of unpaired particles) $\nu$-dependence of the pairing gap $\tilde{\Delta}$ are investigated. For the ground-state bands of even-even nuclei, PNC calculations show that in general $\tilde{\Delta}$ decreases with increasing $\omega$, but the $\omega$-dependence is much weaker than that calculated by the number-projected Hartree-Fock-Bogolyubov approach. For the multiquasiparticle bands (seniority $\nu> 2$), the pairing gaps keep almost $\omega$-independent. As a function of the seniority $\nu$, the bandhead pairing gaps $\tilde{\Delta}(\nu,\omega=0)$ decrease slowly with increasing $\nu$. Even for the highest seniority $\nu$ bands identified so far, $\tilde{\Delta}(\nu,\omega=0)$ remains greater than 70% of $\tilde{\Delta}(\nu=0,\omega=0)$.Comment: 15 pages, 5 figure

Primary anthropogenic aerosol emission trends for China, 1990–2005

An inventory of anthropogenic primary aerosol emissions in China was developed for 1990–2005 using a technology-based approach. Taking into account changes in the technology penetration within industry sectors and improvements in emission controls driven by stricter emission standards, a dynamic methodology was derived and implemented to estimate inter-annual emission factors. Emission factors of PM<sub>2.5</sub> decreased by 7%–69% from 1990 to 2005 in different industry sectors of China, and emission factors of TSP decreased by 18%–80% as well, with the measures of controlling PM emissions implemented. As a result, emissions of PM<sub>2.5</sub> and TSP in 2005 were 11.0 Tg and 29.7 Tg, respectively, less than what they would have been without the adoption of these measures. Emissions of PM<sub>2.5</sub>, PM<sub>10</sub> and TSP presented similar trends: they increased in the first six years of 1990s and decreased until 2000, then increased again in the following years. Emissions of TSP peaked (35.5 Tg) in 1996, while the peak of PM<sub>10</sub> (18.8 Tg) and PM<sub>2.5</sub> (12.7 Tg) emissions occurred in 2005. Although various emission trends were identified across sectors, the cement industry and biofuel combustion in the residential sector were consistently the largest sources of PM<sub>2.5</sub> emissions, accounting for 53%–62% of emissions over the study period. The non-metallic mineral product industry, including the cement, lime and brick industries, accounted for 54%–63% of national TSP emissions. There were no significant trends of BC and OC emissions until 2000, but the increase after 2000 brought the peaks of BC (1.51 Tg) and OC (3.19 Tg) emissions in 2005. Although significant improvements in the estimation of primary aerosols are presented here, there still exist large uncertainties. More accurate and detailed activity information and emission factors based on local tests are essential to further improve emission estimates, this especially being so for the brick and coke industries, as well as for coal-burning stoves and biofuel usage in the residential sector

Improved preservation effects of litchi fruit by combining chitosan coating with ascorbic acid treatment during postharvest storage

Pericarp browning and aril decay of litchi fruits shorten post-harvest storage and thus reduce market value. Effects of chitosan coating and ascorbic acid (AsA) on litchi fruits storage were investigated in this paper. Based on the fact that AsA increases anti-oxidation capacity and chitosan inhibitsdehydration and microbial attack, the novel strategies of combining chitosan with AsA treatment were developed to improve litchi storability. By treating harvest fruits with 40 mmol/l AsA and 1.0% (w/v) chitosan solution, parameters of browning index and relative leakage rate and activities of polyphenol oxidase (PPO) and peroxidase (POD) in pericarp were markedly lowered in treated fruits. Moreover, increased activities of super oxide dismutase (SOD) and catalase (CAT) and contents of AsA andglutathione were observed in pulp of treated fruit, thus leading to lowered contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA). Correspondingly, total soluble solids, soluble sugar and titratable acidity were significantly increased and thus lowered decay rate was achieved. It was suggested that chitosan and AsA play active roles in inhibiting pericarp browning, dehydration and microbial attack and maintaining membrane integrity, thus improved litchi storability being achieved

η\eta-meson in nuclear matter

The $\eta$-nucleon ($\eta$N) interactions are deduced from the heavy baryon chiral perturbation theory up to the next-to-leading-order terms. Combining the relativistic mean-field theory for nucleon system, we have studied the in-medium properties of $\eta$-meson. We find that all the elastic scattering $\eta$N interactions come from the next-to-leading-order terms. The $\eta$N sigma term is found to be about 280$\pm$130 MeV. The off-shell terms are also important to the in-medium properties of $\eta$-meson. On application of the latest determination of the $\eta$N scattering length, the ratio of $\eta$-meson effective mass to its vacuum value is near $0.84\pm0.015$, while the optical potential is about $-(83\pm5)$ MeV, at the normal nuclear density.Comment: 8 pages, 3 figures, to appear in PRC, many modification