Protons with energies up to ~ 10 15 eV are the main component 1 of cosmic rays, but evidence for the specific locations where they could have been accelerated to these energies has been lacking 2 . Electrons are known to be accelerated to cosmic-ray energies in supernova remnants 3,4 , and the shock waves associated with such remnants, when they hit the surrounding interstellar medium, could also provide the energy to accelerate protons. The signature of such a process would be the decay of pions (π 0 ), which are generated when the protons collide with atoms and molecules in an interstellar cloud: pion decay results in γ-rays with a particular spectral-energy distribution 5,6 . Here we report the observation of cascade showers of optical photons resulting fromγ-rays at energies of ~ 10 12 eV hitting Earth's upper atmosphere, in the direction of the supernova remnant RX J1713.7-3946. The spectrum is a good match to that predicted by pion decay, and cannot be explained by other mechanisms.
Observations of the PSR B1259À63/SS 2883 binary system using the CANGAROO-II Cerenkov telescope are reported. This nearby binary consists of a 48 ms radio pulsar in a highly eccentric orbit around a Be star and offers a unique laboratory to investigate the interactions between the outflows of the pulsar and Be star at various distances. It has been pointed out that the relativistic pulsar wind and the dense mass outflow of the Be star may result in the emission of gamma rays up to TeV energies. We have observed the binary in 2000 and 2001, $47 and $157 days after the 2000 October periastron. Upper limits at the 0.13-0.54 crab level are obtained. A new model calculation for high-energy gamma-ray emission from the Be star outflow is introduced, and the estimated gammaray flux, considering bremsstrahlung, inverse Compton scattering, and the decay of neutral pions produced in proton-proton interactions, is found to be comparable to the upper limits of these observations. Comparing our results with these model calculations, we constrain the mass-outflow parameters of the Be star.
Ling Zhi-8 (LZ-8), a novel and recently discovered immunomodulatory protein having in vivo immuno-suppressive activity, was tested for in vivo effect against Type 1 (insulin-dependent) diabetes mellitus in the nonobese diabetic mouse, the disease having immunologically mediated aetiology in this animal. LZ-8 had mitogenic activity in vitro towards spleen cells of the non-obese diabetic mice as previously shown towards those of DBA/2 mice. Intraperitoneal administration of LZ-8 twice weekly into the mice (10.3-12.6 mg/kg body weight) from 4 weeks of age prevented insulitis and an almost normal number of insulin producing cells were observed. Extreme insulitis and reduction of the number of insulin producing cells were observed in the pancreata of the untreated non-obese diabetic mouse. No cumulative incidence of diabetes mellitus was observed in the LZ-8 treated group, while cumulative incidences of 70% and 60% were observed in an untreated group followed up to 42 weeks of age when the incidence of diabetes was defined as a plasma glucose level of greater than 11 mmol/l and as a urine glucose level of greater than 2+, respectively. T cell subset population analysis was performed to further investigate the action of LZ-8 on the non-obese diabetic mouse which revealed that LZ-8 treatment increased in L3T4'/Lyt-2+ ratio.
Abstract. TeV gamma-rays were recently detected from the nearby normal spiral galaxy NGC 253 (Itoh et al. 2002). Observations to detect the Cherenkov light images initiated by gamma-rays from the direction of NGC 253 were carried out in 2000 and 2001 over a total period of ∼150 hours. The orientation of images in gamma-ray-like events is not consistent with emission from a point source, and the emission region corresponds to a size greater than 10 kpc in radius. Here, detailed descriptions of the analysis procedures and techniques are given.
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