Modelling Epsilon Aurigae without solid particles

Three components can be expected to contribute to the emission of epsilon Aurigae. There is a primary F star. There is an opaque disk which occults it, and there is a gas stream which is observed to produce absorption lines. Evidence that the disk is not responsible for the gas stream lines comes both from the radial velocities, which are too small, and from the IR energy distribution out of eclipse, which shows free-free emission that would produce inadequate optical depth in electron scattering. The color temperature of the IR excess can give misleading indications of low temperature material. Free-free emission at 10,000 K between 10 and 20 microns has a color temperature of 350 K. Attempts to mold the system are discussed

A design study for an optimal non-linear receiver/demodulator Final report

Design study for optimal nonlinear receiver demodulato

Modelling the multi-wavelength emissions from PSR B1259-63/LS 2883: the effects of the stellar disc on shock radiations

PSR B1259-63/LS 2883 is an elliptical pulsar/Be star binary and emits broadband emissions from radio to TeV $\gamma$-rays. The massive star possesses an equatorial disc, which is inclined with the orbital plane of the pulsar. The non-thermal emission from the system is believed to be produced by the pulsar wind shock and the double-peak profiles in the X-ray and TeV $\gamma$-ray light curves are related to the phases of the pulsar passing through the disc region of the star. In this paper, we investigate the interactions between the pulsar wind and stellar outflows, especially with the presence of the disc, and present a multi-wavelength modelling of the emission from this system. We show that the double-peak profiles of X-ray and TeV $\gamma$-ray light curves are caused by the enhancements of the magnetic field and the soft photons at the shock during the disc passages. As the pulsar is passing through the equatorial disc, the additional pressure of the disc pushes the shock surface closer to the pulsar, which causes the enhancement of magnetic field in the shock, and thus increases the synchrotron luminosity. The TeV $\gamma$-rays due to the inverse-Compton (IC) scattering of shocked electrons with seed photons from the star is expected to peak around periastron which is inconsistent with observations. However, the shock heating of the stellar disc could provide additional seed photons for IC scattering during the disc passages, and thus produces the double-peak profiles as observed in the TeV $\gamma$-ray light curve. Our model can possibly be examined and applied to other similar gamma-ray binaries, such as PSR J2032+4127/MT91 213, HESS J0632+057, and LS I+61$^{\circ}$303.Comment: 14 pages, 6 figure

|V_ub| and |V_cb|, Charm Counting and Lifetime Differences in Inclusive Bottom Hadron Decays

Inclusive bottom hadron decays are analyzed based on the heavy quark effective field theory (HQEFT). Special attentions in this paper are paid to the b\to u transitions and nonspectator effects. As a consequence, the CKM quark mixing matrix elements |V_ub| and |V_cb| are reliably extracted from the inclusive semileptonic decays B\to X_u e \nu and B\to X_c e \nu. Various observables, such as the semileptonic branch ratio B_SL, the lifetime differences among B^-, B^0, B_s and \Lambda_b hadrons, the charm counting n_c, are predicted and found to be consistent with the present experimental data.Comment: 20 pages, Revtex, 4 figures and 2 table

Chiral transition and deconfinement transition in QCD with the highly improved staggered quark (HISQ) action

We report preliminary results on the chiral and deconfinement aspects of the QCD transition at finite temperature using the Highly Improved Staggered Quark (HISQ) action on lattices with temporal extent of N_{\tau}=6 and 8. The chiral aspects of the transition are studied in terms of quark condensates and the disconnected chiral susceptibility. We study the deconfinement transition in terms of the strange quark number susceptibility and the renormalized Polyakov loop. We made continuum estimates for some quantities and find reasonably good agreement between our results and the recent continuum extrapolated results obtained with the stout staggered quark action.Comment: Talk presented by P. Petreczky at workshop Dense Matter 2010, April 6-9, Stellenbosch, South Africa, to be published in the proceeding

Role of Dicer Enzyme in the Regulation of Store Operated Calcium Entry (SOCE) in CD4+ T Cells

Background/Aims: Activation of T cell receptors (TCRs) in CD4+ T cells leads to a cascade of signalling reactions including increase of intracellular calcium (Ca2+) levels with subsequent Ca2+ dependent stimulation of gene expression, proliferation, cell motility and cytokine release. The increase of cytosolic Ca2+ results from intracellular Ca2+ release with subsequent activation of store-operated Ca2+ entry (SOCE). Previous studies suggested miRNAs are required for the development and functions of CD4+ T cells. An enzyme called Dicer is required during the process of manufacturing mature miRNAs from the precursor miRNAs. In this study, we explored whether loss of Dicer in CD4+ T cells affects SOCE and thus Ca2+ dependent regulation of cellular functions. Methods: We tested the expression of Orai1 by q-RT-PCR and flow cytometry. Further, we measured SOCE by an inverted phase-contrast microscope with the Incident-light fluorescence illumination system using Fura-2. Intracellular Ca2+ was also measured by flow cytometry using Ca2+ sensitive dye Fluo-4. Results: We found that in Dicer deficient (DicerΔ/Δ) mice Orai1 was downregulated at mRNA and protein level in CD4+ T cells. Further, SOCE was significantly smaller in DicerΔ/Δ CD4+ T cells than in CD4+ T cells isolated from wild-type (Dicerfl/fl) mice. Conclusion: Our data suggest that miRNAs are required for adequate Ca2+ entry into CD4+ T cells and thus triggering of Ca2+ sensitive immune functions

Local electronic structure near oxygen dopants in BSCCO-2212: a window on the high-Tc pair mechanism?

The cuprate material BSCCO-2212 is believed to be doped by a combination of cation switching and excess oxygen. The interstitial oxygen dopants are of particular interest because scanning tunnelling microscopy (STM) experiments have shown that they are positively correlated with the local value of the superconducting gap, and calculations suggest that the fundamental attraction between electrons is modulated locally. In this work, we use density functional theory to try to ascertain which locations in the crystal are energetically most favorable for the O dopant atoms, and how the surrounding cage of atoms deforms. Our results provide support for the identification of STM resonances at -1eV with dopant interstitial O atoms, and show how the local electronic structure is modified nearby.Comment: 5 pages, 3 figure

The Origin of Gamma-Rays from Globular Clusters

Fermi has detected gamma-ray emission from eight globular clusters. We suggest that the gamma-ray emission from globular clusters may result from the inverse Compton scattering between relativistic electrons/positrons in the pulsar wind of MSPs in the globular clusters and background soft photons including cosmic microwave/relic photons, background star lights in the clusters, the galactic infrared photons and the galactic star lights. We show that the gamma-ray spectrum from 47 Tuc can be explained equally well by upward scattering of either the relic photons, the galactic infrared photons or the galactic star lights whereas the gamma-ray spectra from other seven globular clusters are best fitted by the upward scattering of either the galactic infrared photons or the galactic star lights. We also find that the observed gamma-ray luminosity is correlated better with the combined factor of the encounter rate and the background soft photon energy density. Therefore the inverse Compton scattering may also contribute to the observed gamma-ray emission from globular clusters detected by Fermi in addition to the standard curvature radiation process. Furthermore, we find that the emission region of high energy photons from globular cluster produced by inverse Compton scattering is substantially larger than the core of globular cluster with a radius >10pc. The diffuse radio and X-rays emitted from globular clusters can also be produced by synchrotron radiation and inverse Compton scattering respectively. We suggest that future observations including radio, X-rays, and gamma-rays with energy higher than 10 GeV and better angular resolution can provide better constraints for the models.Comment: Accepted by ApJ, Comments may send to Prof. K.S. Cheng: [email protected]

Field study on adaptive thermal comfort in typical air conditioned classrooms

This study investigates adaptive thermal comfort in air conditioned classrooms in Hong Kong. A field survey was conducted in several typical classrooms at the City University of Hong Kong. This survey covered objective measurement of thermal environment parameters and subjective human thermal responses. A total of 982 student volunteers participated in the investigation. The results indicate that students in light clothing (0.42 clo) have adapted to the cooler classroom environments. The neutral temperature is very close to the preferred temperature of approximately 24 °C. Based on the MTSV ranging between −0.5 and + 0.5, the comfort range is between 21.56 °C and 26.75 °C. The lower limit is below that of the ASHRAE standard. Of the predicted mean vote (PMV) and the University of California, Berkeley (UCB) model, the UCB model predictions agree better with the mean thermal sensation vote (MTSV). Also, the respective fit regression models of the MTSV versus each of the following: operative temperature (Top), PMV, and UCB were obtained. This study provides a better understanding of acceptable classroom temperatures

Multiple Reggeon Exchange from Summing QCD Feynman Diagrams

Multiple reggeon exchange supplies subleading logs that may be used to restore unitarity to the Low-Nussinov Pomeron, provided it can be proven that the sum of Feynman diagrams to all orders gives rise to such multiple regge exchanges. This question cannot be easily tackled in the usual way except for very low-order diagrams, on account of delicate cancellations present in the sum which necessitate individual Feynman diagrams to be computed to subleading orders. Moreover, it is not clear that sums of high-order Feynman diagrams with complicated criss-crossing of lines can lead to factorization implied by the multi-regge scenario. Both of these difficulties can be overcome by using the recently developed nonabelian cut diagrams. We are then able to show that the sum of $s$-channel-ladder diagrams to all orders does lead to such multiple reggeon exchanges.Comment: uu-encoded latex file with 11 postscript figures (20 pages