Photon-meson transition form factors of light pseudoscalar mesons

The photon-meson transition form factors of light pseudoscalar mesons $\pi ^{0}$, $\eta$, and $\eta ^{\prime}$ are systematically calculated in a light-cone framework, which is applicable as a light-cone quark model at low $Q^{2}$ and is also physically in accordance with the light-cone pQCD approach at large $Q^{2}$. The calculated results agree with the available experimental data at high energy scale. We also predict the low $Q^{2}$ behaviors of the photon-meson transition form factors of $\pi ^{0}$, $\eta$ and $\eta ^{\prime }$, which are measurable in $e+A({Nucleus})\to e+A+M$ process via Primakoff effect at JLab and DESY.Comment: 22 Latex pages, 7 figures, Version to appear in PR

Abell 1201: a Minor merger at second core passage

We present an analysis of the structures and dynamics of the merging cluster Abell~1201, which has two sloshing cold fronts around a cooling core, and an offset gas core approximately 500kpc northwest of the center. New Chandra and XMM-Newton data reveal a region of enhanced brightness east of the offset core, with breaks in surface brightness along its boundary to the north and east. This is interpreted as a tail of gas stripped from the offset core. Gas in the offset core and the tail is distinguished from other gas at the same distance from the cluster center chiefly by having higher density, hence lower entropy. In addition, the offset core shows marginally lower temperature and metallicity than the surrounding area. The metallicity in the cool core is high and there is an abrupt drop in metallicity across the southern cold front. We interpret the observed properties of the system, including the placement of the cold fronts, the offset core and its tail in terms of a simple merger scenario. The offset core is the remnant of a merging subcluster, which first passed pericenter southeast of the center of the primary cluster and is now close to its second pericenter passage, moving at ~1000 km/s. Sloshing excited by the merger gave rise to the two cold fronts and the disposition of the cold fronts reveals that we view the merger from close to the plane of the orbit of the offset core.Comment: accepted by Ap

The Quark/Antiquark Asymmetry of the Nucleon Sea

Although the distributions of sea quarks and antiquarks generated by leading-twist QCD evolution through gluon splitting $g \rightarrow \bar q q$ are necessarily CP symmetric, the distributions of nonvalence quarks and antiquarks which are intrinsic to the nucleon's bound state wavefunction need not be identical. In this paper we investigate the sea quark/antiquark asymmetries in the nucleon wavefunction which are generated by a light-cone model of energetically-favored meson-baryon fluctuations. The model predicts striking quark/antiquark asymmetries in the momentum and helicity distributions for the down and strange contributions to the proton structure function: the intrinsic $d$ and $s$ quarks in the proton sea are predicted to be negatively polarized, whereas the intrinsic $\bar d$ and $\bar s$ antiquarks give zero contributions to the proton spin. Such a picture is supported by experimental phenomena related to the proton spin problem and the violation of the Ellis-Jaffe sum rule. The light-cone meson-baryon fluctuation model also suggests a structured momentum distribution asymmetry for strange quarks and antiquarks which could be relevant to an outstanding conflict between two different determinations of the strange quark sea in the nucleon. The model predicts an excess of intrinsic $d \bar d$ pairs over $u \bar u$ pairs, as supported by the Gottfried sum rule violation. We also predict that the intrinsic charm and anticharm helicity and momentum distributions are not identical.Comment: LaTex 18 pages, 4 figures. To obtain a copy, send e-mail to [email protected]

Unified nonequilibrium dynamical theory for exchange bias and training effects

We investigate the exchange bias and training effects in the FM/AF heterostructures using a unified Monte Carlo dynamical approach. This real dynamical method has been proved reliable and effective in simulating dynamical magnetization of nanoscale magnetic systems. The magnetization of the uncompensated AF layer is still open after the first field cycling is finished. Our simulated results show obvious shift of hysteresis loops (exchange bias) and cycling dependence of exchange bias (training effect) when the temperature is below 45 K. The exchange bias fields decrease with decreasing the cooling rate or increasing the temperature and the number of the field cycling. With the simulations, we show the exchange bias can be manipulated by controlling the cooling rate, the distributive width of the anisotropy energy, or the magnetic coupling constants. Essentially, these two effects can be explained on the basis of the microscopical coexistence of both reversible and irreversible moment reversals of the AF domains. Our simulated results are useful to really understand the magnetization dynamics of such magnetic heterostructures. This unified nonequilibrium dynamical method should be applicable to other exchange bias systems.Comment: Chin. Phys. B, in pres

Flavour Changing Neutral Currents, Weak-Scale Scalars and Rare Top Decays

We examine the decays $t\rightarrow c\gamma$ and $c Z^0$ in the Standard Model with an extra scalar doublet and no discrete symmetry preventing tree-level flavour changing neutral currents. The Yukawa couplings of the new scalars are assumed to be proportional to fermion masses, evading bounds on FCNC's from the light quark sector. These rare top decays may be visible at the SSC.Comment: (some wording changed, and several references added) 13 pages, 2 figures included, uses harvmac.tex and epsf.tex, UCSD/PTH 93-0

Heterogeneously integrated impedance measuring system with disposable thin-film electrodes

We propose a novel integrated impedance measurement system with disposable thin-film electrodes. Most modern CMOS-based biosensors use on-chip electrodes to interface between the electronics and biosamples, which forces disposal of the CMOS chip after a few measurements, since most biological reactions are non-reversible. The sensor performance is also limited by the design of on-chip electrodes due to the physical dimensions and the CMOS design rules restrictions. In this work, we extract the electrodes from the silicon chip for relocation onto a low-cost, disposable substrate. This enables reusability of the high-performance CMOS chip, at the same time providing a low-cost route for manufacture of the active thin-film electrodes using large-area processing. The use of disposable thin-film chip also enables customised designed electrodes for different applications, such as extra high sensitivity concentration sensors. In this work, DNA concentration measurements are performed, and it shows a doubling of sensitivity over the previously reported system.This work is partially supported by Isaac Newton Trust.This is the accepted manuscript of a paper published in Sensors and Actuators B (Ma H, Li J, Cheng X, Nathan A, Sensors and Actuators B 2015, 21, 77–82, doi:10.1016/j.snb.2015.01.044)

How external stakeholders drive the green public procurement practice? An organizational learning perspective

Purpose - This study aims to uncover the black box of the influence mechanism between external stakeholder drivers and green public procurement practice, and meanwhile to explore the moderating role of administrative level in this process. Green public procurement (GPP) has been widely implemented. Existing literature has found that external stakeholder drivers can affect public sectors' GPP practice, however, the definition of its connotation is still unclear, and how external stakeholders affect GPP practice has remained a black box.Design/methodology/approach - After defining the major external stakeholders, this study develops a multiple mediation theoretical model using survey data from 142 Chinese local public sectors. It aims to uncover the black box of the influence mechanism between external stakeholder drivers and GPP practice and meanwhile explore the moderating effect of administrative levels in this process.Findings - The results show that external stakeholder drivers have a positive relationship with GPP practices. The knowledge of GPP implementation policies and the knowledge of GPP benefits can both mediate this relationship. This study also finds that the administrative level of public sectors can positively moderate the mediating effect produced by the knowledge of GPP implementation policies and negatively moderate the mediation effect produced by the knowledge of GPP benefits.Social implications - Local governments need to better encourage public sectors to implement GPP. Managers of public sectors need to pay attention to organizational learning to acquire relevant knowledge on GPP.Originality/value - This study makes a theoretical contribution to a better understanding of the influence mechanism for GPP practice. This study also provides comparisons of GPP implementation policies between China and European Union

Effects of rumen-protected tryptophan on performance, nutrient utilization and plasma tryptophan in cashmere goats

Thirty-six Liaoning cashmere goat wethers (28.72 ± 0.59 kg) were used to  determine the effects of rumen-protected tryptophan (RPT) on performance, nutrient utilization and plasma tryptophan (Trp) during the cashmere fast-growing period. The goats were randomly assigned to the following treatments: Control (without RPT), LRPT (RPT – low), MRPT (RPT– medium) and HRPT (RPT – high) at RPT levels of 0, 2.0, 4.0 and 6.0 g per goat per day, respectively. RPT-medium supplementation improved average daily gain and feed efficiency (P < 0.05) when compared with the control and HRPT. RPT supplementation increased (P < 0.05) the length and growth rate of cashmere fiber, whereas no differences were observed among the LRPT, MRPT and HRPT treatment groups (P > 0.05). RPT-medium supplementation decreased urinary nitrogen (N) excretion and increased N retention when compared with other groups (P < 0.05). Plasma Trp concentration was higher for HRPT treatment group when compared with other treatments (P < 0.05). In conclusion, RPT supplementation potentially improved growth performance, N utilization and cashmere fibre growth in Liaoning cashmere goats. In the experimental conditions of the current trial, the optimum RPT supplementation level was 4.0 g per goat per day during the cashmere fast-growing period.Key words: Rumen-protected tryptophan, growth performance, fibre characteristics, nutrient utilization, plasma tryptophan, cashmere goats