Search for photon-linelike signatures from dark matter annihilations with H.E.S.S.

Gamma-ray line signatures can be expected in the very-high-energy (E(γ)>100 GeV) domain due to self-annihilation or decay of dark matter (DM) particles in space. Such a signal would be readily distinguishable from astrophysical γ-ray sources that in most cases produce continuous spectra that span over several orders of magnitude in energy. Using data collected with the H.

Search for a dark matter annihilation signal from the galactic center halo with H.E.S.S.

A search for a very-high-energy (VHE; ≥100  GeV) γ-ray signal from self-annihilating particle dark matter (DM) is performed towards a region of projected distance r∼45-150  pc from the Galactic center. The background-subtracted γ-ray spectrum measured with the High Energy Stereoscopic System (H.E.

Detection of gamma rays from a starburst galaxy.

Starburst galaxies exhibit in their central regions a highly increased rate of supernovae, the remnants of which are thought to accelerate energetic cosmic rays up to energies of approximately 10(15) electron volts. We report the detection of gamma rays--tracers of such cosmic rays--from the starburst galaxy NGC 253 using the High Energy Stereoscopic System (H.E.

Radio imaging of the very-high-energy gamma-ray emission region in the central engine of a radio galaxy.

The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles to energies exceeding 10(12) electron volts and are bright sources of very-high-energy (VHE) gamma-ray emission, it is not yet known where the VHE emission originates. Here we report on radio and VHE observations of the radio galaxy Messier 87, revealing a period of extremely strong VHE gamma-ray flares accompanied by a strong increase of the radio flux from its nucleus.

Energy spectrum of cosmic-ray electrons at TeV energies.

The very large collection area of ground-based gamma-ray telescopes gives them a substantial advantage over balloon or satellite based instruments in the detection of very-high-energy (>600 GeV) cosmic-ray electrons. Here we present the electron spectrum derived from data taken with the High Energy Stereoscopic System (H.E.

Limits on an energy dependence of the speed of light from a flare of the active galaxy PKS 2155-304.

In the past few decades, several models have predicted an energy dependence of the speed of light in the context of quantum gravity. For cosmological sources such as active galaxies, this minuscule effect can add up to measurable photon-energy dependent time lags. In this Letter a search for such time lags during the High Energy Stereoscopic System observations of the exceptional very high energy flare of the active galaxy PKS 2155-304 on 28 July 2006 is presented.

Effects of surface treatment on orthodontic bonding to amalgam.

Aim: This study aimed to compare the shear bond strengths of metal brackets bonded to amalgam surfaces.

Methods: One hundred and fifty amalgam samples were fabricated and either polished, roughened with a diamond bur or sandblasted with 50 mm aluminium oxide. Following thermocycling the shear bond strengths were tested and compared with control samples bonded to etched enamel.

Life quality and psychological morbidity with an ileostomy.

The recent introduction of restorative proctocolectomy for the treatment of ulcerative colitis has reopened the debate about the effects of ileostomy on quality of life. This study analysed life quality and psychological morbidity in 113 patients with an ileostomy using a postal questionnaire which included questions about their opinion of the pouch operation. Of the questionnaires, 73 per cent were suitable for analysis.

Place of Achilles tenotomy in the treatment of severe intermittent claudication.

Achilles tenotomy was performed on 66 limbs in 60 patients with severe intermittent claudication and the results were assessed two years later. Early improvement occurred in half of them but decreased to 17% two years postoperatively. Sympathectomy did not influence the result.