Interaction between two Fuzzy Spheres

We have calculated interactions between two fuzzy spheres in 3 dimension. It depends on the distance r between the spheres and the radii rho_1, rho_2. There is no force between the spheres when they are far from each other (long distance case). We have also studied the interaction for r=0 case. We find that an attractive force exists between two fuzzy sphere surfaces.Comment: Latex file, 13 page

BRST approach to Lagrangian construction for bosonic continuous spin field

We formulate the conditions defining the irreducible continuous spin representation of the four-dimensional Poincar\'e group based on spin-tensor fields with dotted and undotted indices. Such a formulation simplifies analysis of the Bargmann-Wigner equations and reduces the number of equations from four to three. Using this formulation we develop the BRST approach and derive the covariant Lagrangian for the continuous spin fields.Comment: 10 pages, v2 references adde

Dipolar modes in luminous red giants

Lots of information on solar-like oscillations in red giants has been obtained thanks to observations with CoRoT and Kepler space telescopes. Data on dipolar modes appear most interesting. We study properties of dipolar oscillations in luminous red giants to explain mechanism of mode trapping in the convective envelope and to assess what may be learned from the new data. Equations for adiabatic oscillations are solved by numerical integration down to the bottom of convective envelope, where the boundary condition is applied. The condition is based on asymptotic decomposition of the fourth order system into components describing a running wave and a uniform shift of radiative core. If the luminosity of a red giant is sufficiently high, for instance at M = 2 Msun greater than about 100 Lsun, the dipolar modes become effectively trapped in the acoustic cavity, which covers the outer part of convective envelope. Energy loss caused by gravity wave emission at the envelope base is a secondary or negligible source of damping. Frequencies are insensitive to structure of the deep interior.Comment: 10 pages, 7 figures, accepted for publication in Astronomy and Astrophysic

Non-Coding RNA Features Critical to the Replication of HIV-1

The HIV-1 genome contains RNA sequences and structures that control many aspects of viral replication including, but not limited to transcription, splicing, nuclear export, translation, packaging and reverse transcription. Despite this extensive existing catalogue of RNA sequences that are critical to its replication, chemical probing and targeting mutagenesis studies suggest that the HIV-1 genome may contain many more RNA elements of unknown important function. To determine whether there are additional, undiscovered cis-acting RNA elements in the HIV-1 genome that are important for viral replication, we conducted a global synonymous mutagenesis experiment. Sixteen mutant proviruses containing clusters of ~50 to ~200 synonymous mutations covering nearly the entire HIV-1 protein coding sequence were designed and synthesized. Analyses of these mutant viruses resulted in their division into three phenotypic groups. Group 1 mutants exhibited near wild-type replication, Group 2 mutants exhibited replication defects accompanied by perturbed RNA splicing, and Group 3 mutants had replication defects in the absence of obvious splicing perturbation. The three phenotypes were caused by mutations that exhibited a clear regional bias in their distribution along the viral genome, and those that caused replication defects all caused reductions in the level of unspliced RNA. We characterized in detail the underlying defects for Group 2 mutants. Second-site revertants that enabled viral replication could be derived for Group 2 mutants, and generally contained point mutations that reduced the utilization of proximal splice sites. Mapping of the changes responsible for splicing perturbations in Group 2 viruses revealed the presence of several RNA sequences that apparently suppressed the use of cryptic or canonical splice sites. Some sequences that affected splicing were diffusely distributed, while others could be mapped to discrete elements, proximal or distal to the affected splice sites. This data from the Group 2 mutants indicates complex negative regulation of HIV-1 splicing by RNA elements in various regions of the HIV-1 genome that enable balanced splicing and viral replication. In silico analysis of the Group 3 mutants revealed that our mutagenesis had significantly increased the frequency of CG dinucleotides in sections of the viral genome to that of random sequence. This is important due to the remarkable CG suppression in both the HIV-1 and human genomes, and we had therefore disrupted the dinucleotide congruence that exists between HIV-1 and the genome of its host. We recoded these mutants to selectively remove either only the CG dinucleotides or only remove the mutations that did not encode a CG dinucleotide. Analysis of these mutants clearly demonstrated that the addition of CG dinucleotides were the causative mutations entirely responsible for the observed replication defects. qPCR analysis and smFISH microscopy revealed that the addition of CG dinucleotides to HIV-1 resulted in a depletion of the cytoplasmic mRNA molecules where the CG-dinucleotides were encoded as exons. A targeted siRNA screen for proteins that destabilize cytoplasmic RNA identified the Zinc-finger Antiviral Protein (ZAP) as responsible for the restriction of the CG-high HIV-1, specifically by targeting CGhigh viral RNA. CLIP-Seq experiments demonstrate that ZAP binds directly to CG dinucleotides in both cellular and viral RNA. Collectively these studies implicate ZAP as a cellular protein that can recognize CG-high viral RNA and is possibly a cellular mechanism for determining self from non-self RNA based on the CG composition. TRIM25 has previously been identified as a cofactor for two cytosolic RNA binding proteins that have antiviral functions, RIG-I where it is an essential cofactor, and ZAP where it functions as an enhancing cofactor. The mechanism by which TRIM25 enhances the antiviral activity of ZAP currently remains unclear. Through CLIP-Seq experiments in cells knocked out for TRIM25, we determined that ZAP does not require TRIM25 to recognize CG-high RNA. Using full length mutants of TRIM25 that are deficient for either RNA binding, E3 ligase activity, or formation of higher order multimers, our data suggest that the key biological activity required for TRIM25 to enhance ZAP is the formation of higher order multimers. Analyzing the replication of CG-high HIV-1 in different cell lines indicates that ZAP is not equally potent across all cell lines. The degree of potency ZAP possess against CG-high HIV-1 does not correlate with TRIM25 expression, suggesting the possibility of an additional ZAP cofactor that is heterogeneously expressed in varying cell lines. siRNA screens have been used in an attempt to identify a yet undiscovered cofactor, but so far these experiments have not yielded any such factor

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

A NuSTAR Observation of the Gamma-ray Emitting Millisecond Pulsar PSR J1723-2837

We report on the first NuSTAR observation of the gamma-ray emitting millisecond pulsar binary PSR J1723-2837. X-ray radiation up to 79 keV is clearly detected and the simultaneous NuSTAR and Swift spectrum is well described by an absorbed power-law with a photon index of ~1.3. We also find X-ray modulations in the 3-10 keV, 10-20 keV, 20-79 keV, and 3-79 keV bands at the 14.8-hr binary orbital period. All these are entirely consistent with previous X-ray observations below 10 keV. This new hard X-ray observation of PSR J1723-2837 provides strong evidence that the X-rays are from the intrabinary shock via an interaction between the pulsar wind and the outflow from the companion star. We discuss how the NuSTAR observation constrains the physical parameters of the intrabinary shock model.Comment: Accepted for publication in ApJ. 5 pages, 3 figure

Strong valence fluctuation in the quantum critical heavy fermion superconductor beta-YbAlB4: A hard x-ray photoemission study

Electronic structures of the quantum critical superconductor beta-YbAlB4 and its polymorph alpha-YbAlB4 are investigated by using bulk-sensitive hard x-ray photoemission spectroscopy. From the Yb 3d core level spectra, the values of the Yb valence are estimated to be ~2.73 and ~2.75 for alpha- and beta-YbAlB4, respectively, thus providing clear evidence for valence fluctuations. The valence band spectra of these compounds also show Yb2+ peaks at the Fermi level. These observations establish an unambiguous case of a strong mixed valence at quantum criticality for the first time among heavy fermion systems, calling for a novel scheme for a quantum critical model beyond the conventional Doniach picture in beta-YbAlB4.Comment: 4 pages, 3 figures, revised version accepted for publication in PR

Swift, XMM-Newton, and NuSTAR observations of PSR J2032+4127/MT91 213

We report our recent Swift, NuSTAR, and XMM-Newton X-ray and Lijiang optical observations on PSR J2032+4127/MT91 213, the gamma-ray binary candidate with a period of 45-50 years. The coming periastron of the system was predicted to be in November 2017, around which high-energy flares from keV to TeV are expected. Recent studies with Chandra and Swift X-ray observations taken in 2015/16 showed that its X-ray emission has been brighter by a factors of ~10 than that before 2013, probably revealing some on-going activities between the pulsar wind and the stellar wind. Our new Swift/XRT lightcurve shows no strong evidence of a single vigorous brightening trend, but rather several strong X-ray flares on weekly to monthly timescales with a slowly brightening baseline, namely the low state. The NuSTAR and XMM-Newton observations taken during the flaring and the low states, respectively, show a denser environment and a softer power-law index during the flaring state, implying that the pulsar wind interacted with stronger stellar winds of the companion to produce the flares. These precursors would be crucial in studying the predicted giant outburst from this extreme gamma-ray binary during the periastron passage in late 2017.Comment: 6 pages, including 3 figures and 2 tables. Accepted for publication in Ap