Durham University

About: Durham University is a education organization based out in Durham, United Kingdom. It is known for research contribution in the topics: Population & Galaxy. The organization has 39385 authors who have published 82311 publications receiving 3110994 citations. The organization is also known as: University of Durham & Gallery of Durham University.

Buffer structure between silicon carbide and gallium nitride and resulting semiconductor devices

Abstract: A transition crystal structure is disclosed for providing a good lattice and thermal match between a layer of single crystal silicon carbide (25) and a layer of single crystal gallium nitride (24). The transition structure comprises a buffer formed of a first layer of gallium nitride and aluminum nitride (22), and a second layer of gallium nitride and aluminum nitride (23) adjacent to the first layer. The mole percentage of aluminum nitride in the second layer (23) is substantially different from the mole percentage of aluminum nitride in the first layer (22). A layer of single crystal gallium nitride (24) is formed upon the second layer of gallium nitride and aluminum nitride. In preferred embodiments, the buffer further comprises an epitaxial layer of aluminum nitride upon a silicon carbide substrate.

Dark matter haloes within clusters

Abstract: We examine the properties of dark matter haloes within a rich galaxy cluster using a high-resolution simulation that captures the cosmological context of a cold dark matter universe. The mass and force resolution permit the resolution of 150 haloes with circular velocities larger than 80 km s−1 within the cluster virial radius of 2 Mpc (with Hubble constant H0 = 50 km s−1 Mpc−1). This enables an unprecedented study of the statistical properties of a large sample of dark matter haloes evolving in a dense environment. The cumulative fraction of mass attached to these haloes varies from close to zero per cent at 200 kpc to 13 per cent at the virial radius. Even at this resolution the overmerging problem persists; haloes that pass within 100–200 kpc of the cluster centre are tidally disrupted. Additional substructure is lost at earlier epochs within the massive progenitor haloes. The median ratio of apocentric to pericentric radii is 6:1, so that the orbital distribution is close to isotropic, circular orbits are rare and radial orbits are common. The orbits of haloes are unbiased with respect to both position within the cluster and the orbits of the smooth dark matter background, and no velocity bias is detected. The tidal radii of surviving haloes are generally well-fitted using the simple analytic prediction applied to their orbital pericentres. Haloes within clusters have higher concentrations than those in the field. Within the cluster, halo density profiles can be modified by tidal forces and individual encounters with other haloes that cause significant mass loss —‘galaxy harassment’. Mergers between haloes do not occur inside the cluster virial radius.

A model for the geometries of Van der Waals complexes

Abstract: Structures of Van der Waals complexes are predicted by a simple model based on electrostatic interaction between the monomers. Point multipoles are assigned to the atoms and embedded in hard sphere...