Zero Modes in Electromagnetic Form Factors of the Nucleon in a Light-Cone Diquark Model

We use a diquark model of the nucleon to calculate the electromagnetic form factors of the nucleon described as a scalar and axialvector diquark bound state. We provide an analysis of the zero-mode contribution in the diquark model. We find there are zero-mode contributions to the form factors arising from the instantaneous part of the quark propagator, which cannot be neglected compared with the valence contribution but can be removed by the choice of wave function. We also find that the charge and magnetic radii and magnetic moment of the proton can be reproduced, while the magnetic moment of the neutron is too small. The dipole shape of the form factors, $G^p_M(Q^2)/\mu_p$ and $G^n_M(Q^2)/\mu_n,$ can be reproduced. The ratio $\mu G^p_E/G^p_M$ decreases with $Q^2,$ but too fast.Comment: 22 pages, 6 pages, accepted by J.Phys.

Modelling the Asymmetric Volatility in Hog Prices in Taiwan

Prices in the hog industry in Taiwan are determined according to an auction system. There are significant differences in hog prices before, during and after joining the World Trade Organization (WTO). The paper models growth rates and volatility in daily hog prices in Taiwan from 23 March 1999 to 30 June 2007, which enables an analysis of the effects of joining the WTO. The empirical results have significant implications for risk management and policy in the agricultural industry. The three sub-samples for the periods before, during and after joining the WTO display significantly different volatility persistence of symmetry, asymmetry and leverage, respectively

Atomic Distribution of Ptco/c Nanoparticles as Investigated by X-ray Absorption Spectroscopy

X-Ray Absorption Spectroscopy (XAS) was utilized to deduce the structural parameters that can provide information on atomic distribution and extent of alloying as well as the surface population of bimetallic nanoparticles (NPs). In this study, we focused on PtCo/C NPs treated by CO with various of time. XAS measurement showed that this experiment is related to the Case 3, which is JPt JPt, it appears that the core is rich in Pt atoms and shell is rich in Co atoms. On the contrary if JPt > JCo resulting in Co atoms are rich in the core and Pt atoms are rich in the shell. The XAS results reveal that the time of treatment influences the surface population hence the structure of the catalyst. Catalyst treated CO for 0, 3 and 5 hours leads to higher population of Pt on the core and Co was moved to the surface resulting to Pt rich in core Co rich in shell, while treated for 7 and 15 hours leads to higher population of Pt on the shell and Co on the core resulting to Pt rich in shell Co rich in core

Nonequilibrium Kondo Effect in a Multi-level Quantum Dot near singlet-triplet transition

The linear and nonlinear transport through a multi-level lateral quantum dot connected to two leads is investigated using a generalized finite-$U$ slave-boson mean field approach. For a two-level quantum dot, our calculation demonstrates a substantial conductance enhancement near the degeneracy point of the spin singlet and triplet states, a non-monotonic temperature-dependence of conductance and a sharp dip and nonzero bias maximum of the differential conductance. These agree well with recent experiment observations. This two-stage Kondo effect in an out-of-equilibrium situation is attributed to the interference between the two energy levels.Comment: 4 pages, 3 figure

Faint high-energy gamma-ray photon emission of GRB 081006A from Fermi observations

Since the launch of the Fermi gamma - ray Space Telescope on June 11, 2008, the LAT instrument has solidly detected more than 20 GRBs with high energy photon emission above 100 MeV. Using the matched filter technique, 3 more GRBs have also shown evidence of correlation with high energy photon emission as demonstrated by Akerlof et al. In this paper, we present another GRB unambiguously detected by the matched filter technique, GRB 081006A. This event is associated with more than 13 high energy photons above 100 MeV. The likelihood analysis code provided by the $Fermi$ Science Support Center (FSSC) generated an independent verification of this detection by comparison of the Test Statistics (TS) value with similar calculations for random LAT data fields. We have performed detailed temporal and spectral analysis of photons from 8 keV up to 0.8 GeV from the GBM and the LAT. The properties of GRB 081006A can be compared to the other two long duration GRBs detected at similar significance, GRB 080825C and GRB 090217A. We find that GRB 081006A is more similar to GRB 080825C with comparable appearances of late high energy photon emission. As demonstrated previously, there appears to be a surprising dearth of faint LAT GRBs, with only one additional GRB identified in a sample of 74 GRBs. In this unique period when both $Swift$ and $Fermi$ are operational, there is some urgency to explore this aspect of GRBs as fully as possible.Comment: ApJ, 745, 7

Kondo effect and anti-ferromagnetic correlation in transport through tunneling-coupled double quantum dots

We propose to study the transport through tunneling-coupled double quantum dots (DQDs) connected in series to leads, using the finite-$U$ slave-boson mean field approach developed initially by Kotliar and Ruckenstein [Phys. Rev. Lett. {\bf 57}, 1362 (1986)]. This approach treats the dot-lead coupling and the inter-dot tunnelling $t$ nonperturbatively at arbitrary Coulomb correlation $U$, thus allows the anti-ferromagnetic exchange coupling parameter $J=4t^2/U$ to appear naturally. We find that, with increasing the inter-dot hopping, the DQDs manifest three distinct physical scenarios: the Kondo singlet state of each dot with its adjacent lead, the spin singlet state consisting of local spins on each dot and the doubly occupied bonding orbital of the coupled dots. The three states exhibit remarkably distinct behavior in transmission spectrum, linear and differential conductance and their magnetic-field dependence. Theoretical predictions agree with numerical renormalization group and Lanczos calculations, and some of them have been observed in recent experiments.Comment: 5 pages, 5 figures. Physics Review B (Rapid Communication) (in press

PSR 0943+10: a bare strange star?

Recent work by Rankin & Deshpande strongly suggests that there exist strong ``micro-storms'' rotating around the magnetic axis of the 1.1s pulsar PSR 0943+10. Such a feature hints that most probably the large-voltage vacuum gap proposed by Ruderman & Sutherland (RS) does exist in the pulsar polar cap. However, there are severe arguments against the formation of the RS-type gap in pulsars, since the binding energies of both the Fe ions and the electrons in a neutron star's surface layer is too small to prevent thermionic ejection of the particles from the surface. Here we propose that PSR 0943+10 (probably also most of the other ``drifting'' pulsars) might be bare strange stars rather than normal neutron stars, in which the ``binding energy'' at the surface is merely infinity either for the case of ``pulsar'' or ``anti-pulsar''. It is further proposed that identifying a drifting pulsar as an anti-pulsar is the key criterion to distinguish strange stars from neutron stars.Comment: 4 pages, no figures, LaTeX, accepted 1999 July 9 by ApJ Letter

Subcellular localization of Bombyx mori ribosomal protein S3a and effect of its over-expression on BmNPV infection

In the present study, using a BV/PH-Bms3a-EGFP, we found that Bombyx mori ribosomal protein S3a (BmS3a) with EGFP fused to its C-terminal, was predominantly localized in the cytoplasm of B. mori cells. Subsequently, to investigate the effect of BmS3a over-expression on BmNPV infection both at the cellular level and in vivo, a transgenic BmN cell line expressing BmS3a was constructed using a piggybac-A3-EGFP and recombinant baculovirues expressing BmS3a-EGFP fusion protein (BV/IE1-Bms3a-EGFP) or EGFP (BV/EGFP) were produced using BmNPV/Bac-to-Bac expression system. Results showed that the number of polyhedral in the transgenic cells of BmS3a was much smaller than that in non-transgenic cells, and that silkworms injected with BV/IE1-Bms3a-EGFP survived much longer than those injected with BV/EGFP. Taken together, we speculated that BmS3a might be capable of inhibiting BmNPV replication through its activities in the cytoplasm

Jet Breaks in Short Gamma-Ray Bursts. I: The Uncollimated Afterglow of GRB 050724

We report the results of the \chandra observations of the \swift-discovered short Gamma-Ray Burst GRB 050724. \chandra observed this burst twice, about two days after the burst and a second time three weeks later. The first \chandra pointing occurred at the end of a strong late-time flare. About 150 photons were detected during this 49.3 ks observation in the 0.4-10.0 keV range. The spectral fit is in good agreement with spectral analysis of earlier \swift XRT data. In the second \chandra pointing the afterglow was clearly detected with 8 background-subtracted photons in 44.6 ks. From the combined \swift XRT and \chandra-ACIS-S light curve we find significant flaring superposed on an underlying power-law decay slope of $\alpha$=0.98$^{+0.11}_{-0.09}$. There is no evidence for a break between about 1 ks after the burst and the last \chandra pointing about three weeks after the burst. The non-detection of a jet break places a lower limit of 25$^{\circ}$ on the jet opening angle, indicating that the outflow is less strongly collimated than most previously-reported long GRBs. This implies that the beaming corrected energy of GRB 050724 is at least $4\times 10^{49}$ ergs.Comment: 7 pages, ApJ acceped, scheduled for December 20, 2006, ApJ, 65