The X-ray and radio emission from SN 2002ap: The importance of Compton scattering

The radio and X-ray observations of the Type Ic supernova SN 2002ap are modeled. We find that inverse Compton cooling by photospheric photons explains the observed steep radio spectrum, and also the X-ray flux observed by XMM. Thermal emission from the shock is insufficient to explain the X-ray flux. The radio emitting region expands with a velocity of, roughly, 70,000 km/s. From the ratio of X-ray to radio emission we find that the energy densities of magnetic fields and relativistic electrons are close to equipartion.Comment: 15 pages, 2 figures, ApJ accepte

Multiple synchrotron self-Compton modeling of gamma-ray flares in 3C 279

The correlation often observed in blazars between optical-to-radio outbursts and gamma-ray flares suggests that the high-energy emission region shall be co-spatial with the radio knots, several parsecs away from the central engine. This would prevent the important contribution at high-energies from the Compton scattering of seed photons from the accretion disk and the broad-line region that is generally used to model the spectral energy distribution of low-frequency peaking blazars. While a pure synchrotron self-Compton model has so far failed to explain the observed gamma-ray emission of a flat spectrum radio quasar like 3C 279, the inclusion of the effect of multiple inverse-Compton scattering might solve the apparent paradox. Here, we present for the first time a physical, self-consistent SSC modeling of a series of shock-waves in the jet of 3C 279. We show that the analytic description of the high-energy emission from multiple inverse-Compton scatterings in the Klein-Nishina limit can fairly well account for the observed gamma-ray spectrum of 3C 279 in flaring states.Comment: 6 pages, 3 figures, proceedings of "Beamed and Unbeamed Gamma-rays from Galaxies", 11-15 April 2011, Finland. To be published in the Journal of Physics: Conference Serie

Using the Uncharged Kerr Black Hole as a Gravitational Mirror

We extend the study of the possibility to use the Schwarzschild black hole as a gravitational mirror to the more general case of an uncharged Kerr black hole. We use the null geodesic equation in the equatorial plane to prove a theorem concerning the conditions the impact parameter has to satisfy if there shall exist boomerang photons. We derive an equation for these boomerang photons and an equation for the emission angle. Finally, the radial null geodesic equation is integrated numerically in order to illustrate boomerang photons.Comment: 11 pages Latex, 3 Postscript figures, uufiles to compres

Limits on O VI Emission from the Shocked Circumstellar Gas of SN 1987A

The Far Ultraviolet Spectroscopic Explorer (FUSE) was used to search for emission from the shock interaction of the ejecta of SN 1987A with its circumstellar material. FUSE observations of SN 1987A between 2000 and 2007 did not detect broad OVI emission. However, OVI emission was detected in 2000-2001 with a narrow line width (FWHM <35 kms t ) and a heliocentric radial velocity of +280 km/s. This places the emitting gas at rest relative to the supernova and is interpreted as emission from unshocked circumstellar gas. This narrow emission had disappeared in 2007 (and possibly earlier) as a result of the advancing shock overtaking the H II region that was flash ionized by the supernova explosion in 1987

Detecting a Light Stop from Top Decays at the Tevatron

We study the possibility of discovering or excluding a light top squark (stop) based on top quark decays in the t-tbar events produced at the Fermilab Tevatron. In particular, we consider the Minimal Supersymmetric Standard Model with the sparticle spectrum m_{chi^+_1}+m_b, M_W+m_{chi^0_1}+m_b > m_{stop} > m_{chi^0_1}+m_c, where chi^0_1 is the lightest neutralino and chi^+_1 is the lightest chargino, so that t -> stop chi^0_1 and stop -> c chi^0_1. All other sparticle masses are assumed to be heavier than m_t. Such a spectrum seeks to explain the experimental values of alpha_s(M_Z^2), R_b and A_{LR} obtained from LEP/SLC data. We find that the prospect to observe a light stop via this channel at the Tevatron is very promising.Comment: 12 pages with 1 Postscript figure using psfig.sty. Postscript file available at http://sgi2.hep.anl.gov:8001/index.htm

Investigating the trade-off between the effectiveness and efficiency of process modeling

Despite recent efforts to improve the quality of process models, we still observe a significant dissimilarity in quality between models. This paper focuses on the syntactic condition of process models, and how it is achieved. To this end, a dataset of 121 modeling sessions was investigated. By going through each of these sessions step by step, a separate ‘revision’ phase was identified for 81 of them. Next, by cutting the modeling process off at the start of the revision phase, a partial process model was exported for these modeling sessions. Finally, each partial model was compared with its corresponding final model, in terms of time, effort, and the number of syntactic errors made or solved, in search for a possible trade-off between the effectiveness and efficiency of process modeling. Based on the findings, we give a provisional explanation for the difference in syntactic quality of process models

A comparative study on the efficacy of four anthelmintics on some important reindeer parasites

Four anthelmintic preparations were tested against some of the most important parasites of reindeer, i.e. warble fly (Oedemagena tarandi), nostril fly (Cephenemyia trompe), brainworm (Elaphostrongylus rangiferi), and lungworm (Dictyocaulus viviparus). Their efficacy against intestinal nematodes was also registered. Test drugs were Fenthion (Bayer), Fenbendazole (Hoechst), Mebendazole (Janssen), and Ivermectin (Merk Sharp &amp; Dohme). Against O. tarandi and C. trompe Ivermectin was 100% effective and Fenthion 86 and 100% respectively. The efficacy of Fen- and Mebendazole against these parasites was not significant. Against E. rangiferi the benzimidazole compounds were highly effective, with Mebendazole a bit ahead. Ivermectin had a moderate effect and Fenthion had no effect on this parasite. Against D. viviparus Fenbendazole, Mebendazole and Ivermectin were of equal, moderate-high effectiveness. No drug had a complete effect on the &laquo;arrested&raquo; larvae of D. viviparus. Fenthion had no effect at all. Fenbendazole and Ivermectin were both 100% effective against intestinal nematodes. Mebendazole was less effective and Fenthion had no effects. Ivermectin is considered to be the overall most effective anthelmintic in this test.En jamforande studie av effekten av fyra anthelmintika mot n&aring;gra betydelsesfulla parasiter hos ren.Abstract in Swedish / Sammandrag: Fyra antiparasitmedel har pr&ocirc;vats mot n&aring;gra av renens viktigaste parasiter, n&agrave;mligen hudkorm (Oedemagena tarandi), svalgkorm (Cephenemyia trompe), hj&aring;rnmask (Elaphostrongylus rangiferi) och lungmask (Dictyocaulus viviparus). Vidare har medlens effekt p&aring; mag- tarmnematoder (Trichostongylider) ocks&aring; noterats. De pr&ocirc;vade medicinerna var Fenthion (Bayer), Mebendazole (Leo/Janssen), Fenbendazole (Hoechst) och Ivermectin (Merck Sharp &amp; Dohme). Mot hud- och svalgkorm var Ivermectin 100% effektivt medan for Fenthion effekten var 86 resp 100%. Effekten av Fen- och Mebendazole mot de b&aring;da parasiterna var inte signifikant. Mot hj&aring;rnmask noterades mycket h&ocirc;g effekt av Mebendazole och aven Fenbendazole medan Ivermectin hade n&aring;got s&aring;mre effekt med den valda doseringen. Fenthion hade ingen effekt p&aring; denna parasit. Mot lungmask visade Fenbendazole och Ivermectin god effekt medan Mebendazole visade n&aring;got lagre effekt. Inget av preparaten hade dock fullgod verkan p&aring; de vilande inaktiva 5:te stadiets larverna av denna parasit. Fenthion hade ingen effekt. Mot mag-tarmnematoder var Fenbendazole och Ivermectin 100% effektiva medan Mebendazole hade en n&aring;got l&agrave;gre, delvis undertryckande effekt. Fenthion hade ingen effekt. Ivermectin f&aring;r anses vara det allm&aring;nt sett effektivaste maskmedlet i denna undersokning.Vertailevatutkielma neljan loislaakeaineen vaikutuksesta muutamia tarkeita porojen loisia vastaan.Abstract in Finnish / Yhteenveto: On kokeiltu neljaa loislaakeainetta muutamia porojen tarkeinpia loisia vastaan, nimittain kurmua (Oedemagena tarandi), saulakkaa (Cephenemyia trompe), aivomatoa (Elaphostrongylus rangiferi) ja keuhkomatoa (Dictyocaulus viviparus). Edelleen on laakeaineiden vaikutus maha- ja suolistomatoihin (Trichostrongyliidit) myoskin pantu merkille. Kokeillut laakeaineet olivat Fenthion (Bayer), Mebendazole (Leo/Janssen), Fenbendazole (Hoechst) ja Ivermectin (Merck - Sharp and Dohme). Kurmua ja saulakkaa vastaan oli Ivermectin 100% tehokas, kun taas Fenthionin vaikutus oli toisessa 86 ja toisessa 100%. Fen- ja Mebendazolen vaikutus molempia loisia vastaan ei ollut merkittava. Mebendazolen ja myos Fenbendazolen vaikutus aivomatoa vastaan havaittiin hyvin korkeaksi, kun taas Ivermectinilla oli jonkin verran huonompi vaikutus valitulla annostuksella. Fenthionilla ei ollut mitaan vaikutusta tata loista vastaan. Keuhkomatoa vastaan osoitti Fenbendazole ja Ivermectin hyvan vaikutuksen, kun taas Mebendazolella oli jonkin verran heikompi vaikutus. Kuitenkaan ei millaan laakevalmisteista ollut taystehokasta vaikutusta taman loisen lepaaviin tehottomiin 5:asteen toukkiin. Fenthionilla ei ollut mitaan vaikutusta. Fenbendazole ja Ivermectin maha- ja suolistomatoja vastaan olivat 100% tehokkaita, kun taas Mebendazolella oli jonkin verran alhaisempi, osittain vaimentava vaikutus. Fenthionilla ei ollut mitaan vaikutusta

Homoclinic chaos and energy condition violation

In this letter we discuss the connection between so-called homoclinic chaos and the violation of energy conditions in locally rotationally symmetric Bianchi type IX models, where the matter is assumed to be non-tilted dust and a positive cosmological constant. We show that homoclinic chaos in these models is an artifact of unphysical assumptions: it requires that there exist solutions with positive matter energy density $\rho>0$ that evolve through the singularity and beyond as solutions with negative matter energy density $\rho<0$. Homoclinic chaos is absent when it is assumed that the dust particles always retain their positive mass.In addition, we discuss more general models: for solutions that are not locally rotionally symmetric we demonstrate that the construction of extensions through the singularity, which is required for homoclinic chaos, is not possible in general.Comment: 4 pages, RevTe

How Advanced Change Patterns Impact the Process of Process Modeling

Process model quality has been an area of considerable research efforts. In this context, correctness-by-construction as enabled by change patterns provides promising perspectives. While the process of process modeling (PPM) based on change primitives has been thoroughly investigated, only little is known about the PPM based on change patterns. In particular, it is unclear what set of change patterns should be provided and how the available change pattern set impacts the PPM. To obtain a better understanding of the latter as well as the (subjective) perceptions of process modelers, the arising challenges, and the pros and cons of different change pattern sets we conduct a controlled experiment. Our results indicate that process modelers face similar challenges irrespective of the used change pattern set (core pattern set versus extended pattern set, which adds two advanced change patterns to the core patterns set). An extended change pattern set, however, is perceived as more difficult to use, yielding a higher mental effort. Moreover, our results indicate that more advanced patterns were only used to a limited extent and frequently applied incorrectly, thus, lowering the potential benefits of an extended pattern set

Matter and dynamics in closed cosmologies

To systematically analyze the dynamical implications of the matter content in cosmology, we generalize earlier dynamical systems approaches so that perfect fluids with a general barotropic equation of state can be treated. We focus on locally rotationally symmetric Bianchi type IX and Kantowski-Sachs orthogonal perfect fluid models, since such models exhibit a particularly rich dynamical structure and also illustrate typical features of more general cases. For these models, we recast Einstein's field equations into a regular system on a compact state space, which is the basis for our analysis. We prove that models expand from a singularity and recollapse to a singularity when the perfect fluid satisfies the strong energy condition. When the matter source admits Einstein's static model, we present a comprehensive dynamical description, which includes asymptotic behavior, of models in the neighborhood of the Einstein model; these results make earlier claims about ``homoclinic phenomena and chaos'' highly questionable. We also discuss aspects of the global asymptotic dynamics, in particular, we give criteria for the collapse to a singularity, and we describe when models expand forever to a state of infinite dilution; possible initial and final states are analyzed. Numerical investigations complement the analytical results.Comment: 23 pages, 24 figures (compressed), LaTe