High energy gamma-ray astronomy has recently made significant progresss through ground-based instruments like the H.E.S.S. array of imaging atmospheric Cherenkov telescopes. The unprecedented angular resolution and the large field of view has allowed to spatially resolve for the first time the morphology of gamma-ray sources in the TeV energy range. The experimental technique is described and t...

Recent results, the present status and the perspectives of high energy gamma-ray astronomy are described. Since the satellite observations by the Compton Gamma Ray Observatory and its precursor missions have been reviewed extensively, emphasis is on the results from the ground-based gamma-ray telescopes. They concern the physics of Pulsar Nebulae, Supernova Remnants in their assumed role as the...

Electrical recording studies in humans and monkeys have shown attentional enhancement of evoked responses and gamma synchrony in ventral stream cortical areas, but it is unknown if synchrony results from intrinsic activity in visual cortex or from inputs from other structures. Based on paired-recordings in the frontal eye field and area V4, we find that attention to a stimulus in their joint re...

A non-destructive, gamma-spectrometric method for verifying the plutonium content of Pu-Be neutron sources has been developed. It is also shown that the isotopic composition and the age of plutonium (Pu) can be determined in the intensive neutron field of these sources by the “Multi-Group Analysis” method. Gamma spectra were taken in the far-field of the sample, which was assumed to be cylindri...

The feasibility of the generation of bright ultrashort gamma-ray pulses is demonstrated in the interaction of a relativistic electron bunch with a counterpropagating tightly focused superstrong laser beam in the radiation-dominated regime. The Compton scattering spectra of gamma radiation are investigated using a semiclassical description for the electron dynamics in the laser field and a quant...

In candidate Kitaev materials, the off-diagonal $\Gamma$ and $\Gamma'$ interactions are identified to come from spin-orbit coupling trigonal distortion, respectively. They have generated intense research efforts because of their intimate relation field-induced magnetically disordered state reported in $\alpha$-RuCl$_3$. Theoretically, while a plethora phases has been proposed honeycomb lattice,...

I briefly review magnetic effects in accretion physics, and then go on to discuss a possible central engine for gamma–ray bursts. A rotating black hole immersed in a non–axisymmetric magnetic field experiences a torque trying to align spin and field. I suggest that gamma–ray burst hosts may provide conditions where this effect allows rapid extraction of a significant fraction of the hole’s rota...

We investigated confinement effects on the resistive anisotropy of a superconducting niobium strip with a rectangular cross section. When its transverse dimensions are comparable to the superconducting coherence length, the angle dependent magnetoresistances at a fixed temperature can be scaled as R(theta,H) = R(H/Hctheta) where Hctheta =Hc0(cos2theta + gamma(-2)sin2theta)(-1/2) is the angular ...

We determine the local galactic extinction towards the field of gamma-ray burst GRB970228 using a variety of methods. We develop a maximum likelihood method for measuring the extinction by comparing galaxy counts in the field of interest to those in a field of known extinction, and apply this method to the GRB970228 field. We also measure the extinction by comparing the observed stellar spectra...