ABSTRACT
We report the detection of pulsed gamma rays from the Crab pulsar at energies above 100 giga-electron volts (GeV) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) array of atmospheric Cherenkov telescopes. The detection cannot be explained on the basis of current pulsar models. The photon spectrum of pulsed emission between 100 mega-electron volts and 400 GeV is described by a broken power law that is statistically preferred over a power law with an exponential cutoff. It is unlikely that the observation can be explained by invoking curvature radiation as the origin of the observed gamma rays above 100 GeV. Our findings require that these gamma rays be produced more than 10 stellar radii from the neutron star.
ABSTRACT
The 1999 practice guideline 'Acne vulgaris' from the Dutch College of General Practitioners has been revised. Benzoyl peroxide and local retinoids are first choice in local treatment of acne. When treatment with oral antibiotics is indicated, doxycycline is first choice. Use of minocycline is not recommended in general practice. It is recommended that both local and oral antibiotics are always combined with local benzoyl peroxide or a local retinoid. Oral contraceptives are only recommended in women with acne who also desire contraception. Use of oral contraceptives containing cyproterone acetate is no longer recommended in women with acne, because they are not more effective than other oral contraceptives. Treatment with oral isotretinoin may be given by the general practitioner, as long as the treatment guidelines are carefully followed.