Diffuse Gamma Rays: Galactic and Extragalactic Diffuse Emission

"Diffuse" gamma rays consist of several components: truly diffuse emission from the interstellar medium, the extragalactic background, whose origin is not firmly established yet, and the contribution from unresolved and faint Galactic point sources. One approach to unravel these components is to study the diffuse emission from the interstellar medium, which traces the interactions of high energy particles with interstellar gas and radiation fields. Because of its origin such emission is potentially able to reveal much about the sources and propagation of cosmic rays. The extragalactic background, if reliably determined, can be used in cosmological and blazar studies. Studying the derived "average" spectrum of faint Galactic sources may be able to give a clue to the nature of the emitting objects.Comment: 32 pages, 28 figures, kapproc.cls. Chapter to the book "Cosmic Gamma-Ray Sources," to be published by Kluwer ASSL Series, Edited by K. S. Cheng and G. E. Romero. More details can be found at http://www.gamma.mpe-garching.mpg.de/~aws/aws.htm

Parameterizing the interstellar dust temperature

The temperature of interstellar dust particles is of great importance to astronomers. It plays a crucial role in the thermodynamics of interstellar clouds, because of the gas-dust collisional coupling. It is also a key parameter in astrochemical studies that governs the rate at which molecules form on dust. In 3D (magneto)hydrodynamic simulations often a simple expression for the dust temperature is adopted, because of computational constraints, while astrochemical modelers tend to keep the dust temperature constant over a large range of parameter space. Our aim is to provide an easy-to-use parametric expression for the dust temperature as a function of visual extinction ($A_{\rm V}$) and to shed light on the critical dependencies of the dust temperature on the grain composition. We obtain an expression for the dust temperature by semi-analytically solving the dust thermal balance for different types of grains and compare to a collection of recent observational measurements. We also explore the effect of ices on the dust temperature. Our results show that a mixed carbonaceous-silicate type dust with a high carbon volume fraction matches the observations best. We find that ice formation allows the dust to be warmer by up to 15% at high optical depths ($A_{\rm V}> 20$ mag) in the interstellar medium. Our parametric expression for the dust temperature is presented as $T_{\rm d} = \left[ 11 + 5.7\times \tanh\bigl( 0.61 - \log_{10}(A_{\rm V})\bigr) \right] \, \chi_{\rm uv}^{1/5.9}$, where $\chi_{\rm uv}$ is in units of the Draine (1978) UV fieldComment: 16 pages, 17 figures, 4 tables. Accepted for publication in A&A. Version 2: the omission of factor 0.921 in equation 4 is correcte

Quasi-classical approximation in vortex filament dynamics. Integrable systems, gradient catastrophe and flutter

Quasiclassical approximation in the intrinsic description of the vortex filament dynamics is discussed. Within this approximation the governing equations are given by elliptic system of quasi-linear PDEs of the first order. Dispersionless Da Rios system and dispersionless Hirota equation are among them. They describe motion of vortex filament with slow varying curvature and torsion without or with axial flow. Gradient catastrophe for governing equations is studied. It is shown that geometrically this catastrophe manifests as a fast oscillation of a filament curve around the rectifying plane which resembles the flutter of airfoils. Analytically it is the elliptic umbilic singularity in the terminology of the catastrophe theory. It is demonstrated that its double scaling regularization is governed by the Painleve' I equation.Comment: 25 pages, 5 figures, minor typos correcte

Decaying Dark Matter in Supersymmetric Model and Cosmic-Ray Observations

We study cosmic-rays in decaying dark matter scenario, assuming that the dark matter is the lightest superparticle and it decays through a R-parity violating operator. We calculate the fluxes of cosmic-rays from the decay of the dark matter and those from the standard astrophysical phenomena in the same propagation model using the GALPROP package. We reevaluate the preferred parameters characterizing standard astrophysical cosmic-ray sources with taking account of the effects of dark matter decay. We show that, if energetic leptons are produced by the decay of the dark matter, the fluxes of cosmic-ray positron and electron can be in good agreements with both PAMELA and Fermi-LAT data in wide parameter region. It is also discussed that, in the case where sizable number of hadrons are also produced by the decay of the dark matter, the mass of the dark matter is constrained to be less than 200-300 GeV in order to avoid the overproduction of anti-proton. We also show that the cosmic gamma-ray flux can be consistent with the results of Fermi-LAT observation if the mass of the dark matter is smaller than nearly 4 TeV.Comment: 24 pages, 5 figure

The rapid assembly of an elliptical galaxy of 400 billion solar masses at a redshift of 2.3

Stellar archeology shows that massive elliptical galaxies today formed rapidly about ten billion years ago with star formation rates above several hundreds solar masses per year (M_sun/yr). Their progenitors are likely the sub-millimeter-bright galaxies (SMGs) at redshifts (z) greater than 2. While SMGs' mean molecular gas mass of 5x10^10 M_sun can explain the formation of typical elliptical galaxies, it is inadequate to form ellipticals that already have stellar masses above 2x10^11 M_sun at z ~ 2. Here we report multi-wavelength high-resolution observations of a rare merger of two massive SMGs at z = 2.3. The system is currently forming stars at a tremendous rate of 2,000 M_sun/yr. With a star formation efficiency an order-of-magnitude greater than that of normal galaxies, it will quench the star formation by exhausting the gas reservoir in only ~200 million years. At a projected separation of 19 kiloparsecs, the two massive starbursts are about to merge and form a passive elliptical galaxy with a stellar mass of ~4x10^11 M_sun. Our observations show that gas-rich major galaxy mergers, concurrent with intense star formation, can form the most massive elliptical galaxies by z ~ 1.5.Comment: Appearing in Nature online on May 22 and in print on May 30. Submitted here is the accepted version (including the Supplementary Information), see nature.com for the final versio

The Chitin Connection

Chitin, a polymer of N-acetylglucosamine, is an essential component of the fungal cell wall. Chitosan, a deacetylated form of chitin, is also important in maintaining cell wall integrity and is essential for Cryptococcus neoformans virulence. In their article, Gilbert et al. [N. M. Gilbert, L. G. Baker, C. A. Specht, and J. K. Lodge, mBio 3(1):e00007-12, 2012] demonstrate that the enzyme responsible for chitosan synthesis, chitin deacetylase (CDA), is differentially attached to the cell membrane and wall. Bioactivity is localized to the cell membrane, where it is covalently linked via a glycosylphosphatidylinositol (GPI) anchor. Findings from this study significantly enhance our understanding of cryptococcal cell wall biology. Besides the role of chitin in supporting structural stability, chitin and host enzymes with chitinase activity have an important role in host defense and modifying the inflammatory response. Thus, chitin appears to provide a link between the fungus and host that involves both innate and adaptive immune responses. Recently, there has been increased attention to the role of chitinases in the pathogenesis of allergic inflammation, especially asthma. We review these findings and explore the possible connection between fungal infections, the induction of chitinases, and asthma

Surfactant protein D modulates HIV infection of both T-cells and dendritic cells

Surfactant Protein D (SP-D) is an oligomerized C-type lectin molecule with immunomodulatory properties and involvement in lung surfactant homeostasis in the respiratory tract. SP-D binds to the enveloped viruses, influenza A virus and respiratory syncytial virus and inhibits their replication in vitro and in vivo. SP-D has been shown to bind to HIV via the HIV envelope protein gp120 and inhibit infectivity in vitro. Here we show that SP-D binds to different strains of HIV (BaL and IIIB) and the binding occurs at both pH 7.4 and 5.0 resembling physiological relevant pH values found in the body and the female urogenital tract, respectively. The binding of SP-D to HIV particles and gp120 was inhibited by the presence of several hexoses with mannose found to be the strongest inhibitor. Competition studies showed that soluble CD4 and CVN did not interfere with the interaction between SP-D and gp120. However, soluble recombinant DC-SIGN was shown to inhibit the binding between SP-D and gp120. SP-D agglutinated HIV and gp120 in a calcium dependent manner. SP-D inhibited the infectivity of HIV strains at both pH values of 7.4 and 5.0 in a concentration dependent manner. The inhibition of the infectivity was abolished by the presence of mannose. SP-D enhanced the binding of HIV to immature monocyte derived dendritic cells (iMDDCs) and was also found to enhance HIV capture and transfer to the T-cell like line PM1. These results suggest that SP-D can bind to and inhibit direct infection of T-cells by HIV but also enhance the transfer of infectious HIV particles from DCs to T-cells in vivo

Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS) experiment: design, execution and science overview

We describe the design and execution of the BORTAS (Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites) experiment, which has the overarching objective of understanding the chemical aging of air masses that contain the emission products from seasonal boreal wildfires and how these air masses subsequently impact downwind atmospheric composition. The central focus of the experiment was a two-week deployment of the UK BAe-146-301 Atmospheric Research Aircraft (ARA) over eastern Canada, based out of Halifax, Nova Scotia. Atmospheric ground-based and sonde measurements over Canada and the Azores associated with the planned July 2010 deployment of the ARA, which was postponed by 12 months due to UK-based flights related to the dispersal of material emitted by the Eyjafjallajökull volcano, went ahead and constituted phase A of the experiment. Phase B of BORTAS in July 2011 involved the same atmospheric measurements, but included the ARA, special satellite observations and a more comprehensive ground-based measurement suite. The high-frequency aircraft data provided a comprehensive chemical snapshot of pyrogenic plumes from wildfires, corresponding to photochemical (and physical) ages ranging from 45 sr 10 days, largely by virtue of widespread fires over Northwestern Ontario. Airborne measurements reported a large number of emitted gases including semi-volatile species, some of which have not been been previously reported in pyrogenic plumes, with the corresponding emission ratios agreeing with previous work for common gases. Analysis of the NOy data shows evidence of net ozone production in pyrogenic plumes, controlled by aerosol abundance, which increases as a function of photochemical age. The coordinated ground-based and sonde data provided detailed but spatially limited information that put the aircraft data into context of the longer burning season in the boundary layer. Ground-based measurements of particulate matter smaller than 2.5 μm (PM2.5) over Halifax show that forest fires can on an episodic basis represent a substantial contribution to total surface PM2.5

Site use and connectivity of female grey seals (Halichoerus grypus) around Wales

The UK Natural Environment Research Council (NERC) provided core funding to the Sea Mammal Research Unit during this work and NERC Grant No. NE/G008930/1 to PP and LH to develop photo-ID use for grey seals. The Esmée Fairbairn Foundation provided additional funding to PP and LH for photo-ID work with grey seals. NRW funded survey work by MB, LM, SW and PS; contracted LH for survey design, software development and data management; IL and PP for work related to the production of this manuscript.Grey seals (Halichoerus grypus) are a qualifying feature of three special areas of conservation (SACs) in Wales, yet relatively little is known of their site use along this coastline. Since 1992, many individuals and organisations have contributed to a grey seal photographic identification database held by Natural Resources Wales, which is one of the largest and oldest of its kind, providing key information from grey seal haul-out sites around the Celtic and Irish Seas. Here, we investigated spatial connectivity of haul-out sites and fidelity of adult females to breeding sites. The minimum number of adult female grey seals using the area between 1992 and 2016 was 2688. Individual capture histories and relative spatial transition probabilities (Pij) between pairs of location groups were calculated. Adjacent locations were highly connected (e.g. Lleyn Peninsula and Bardsey, Pij = 0.7) but connections spanned the entire region, up to 230 km apart (e.g. Skomer and Dee Estuary, Pij = 0.004). Resights were recorded within SACs (e.g. Lleyn Peninsula and Bardsey [Lleyn Peninsula and the Sarnau SAC], Pij = 0.7), between SACs (e.g. Bardsey and Skomer [Pembrokeshire Marine], Pij = 0.03), between SACs and non-designated areas (e.g. Skerries and Bardsey, Pij = 0.09) and between sites outside any protected area (e.g. Dee Estuary and Anglesey, Pij = 0.5). While inter-annual fidelity to breeding sites was high (Pij = 0.82–1), individual female grey seals moved throughout the region. This evidence of extensive site use beyond protected areas is important for the management and conservation of grey seals around Wales.Publisher PDFPeer reviewe

Effects of MDM2, MDM4 and TP53 Codon 72 Polymorphisms on Cancer Risk in a Cohort Study of Carriers of TP53 Germline Mutations

Previous studies have shown that MDM2 SNP309 and p53 codon 72 have modifier effects on germline P53 mutations, but those studies relied on case-only studies with small sample sizes. The impact of MDM4 polymorphism on tumor onset in germline mutation carriers has not previously been studied.We analyzed 213 p53 germline mutation carriers including 168(78.9%) affected with cancer and 174 who had genotypic data. We analyzed time to first cancer using Kaplan-Meier and Cox proportional hazards methods, comparing risks according to polymorphism genotypes. For MDM2 SNP309, a significant difference of 9.0 years in the average age of cancer diagnosis was observed between GG/GT and TT carriers (18.6 versus 27.6 years, P = 0.0087). The hazards ratio was 1.58 (P = 0.03) comparing risks among individuals with GG/GT to risk among TT, but this effect was only significant in females (HR = 1.60, P = 0.02). Compared to other genotypes, P53 codon 72 PP homozygotes had a 2.24 times (P = 0.03) higher rate for time to develop cancer. We observed a multiplicative joint effect of MDM2 and p53 codon72 polymorphism on risk. The MDM4 polymorphism had no significant effects.Our results suggest that the MDM2 SNP309 G allele is associated with cancer risk in p53 germline mutation carriers and accelerates time to cancer onset with a pronounced effect in females. A multiplicative joint effect exists between the MDM2 SNP309 G allele and the p53 codon 72 G allele in the risk of cancer development. Our results further define cancer risk in carriers of germline p53 mutations