1,680 research outputs found
Liquid pair correlations in four spatial dimensions: Theory versus simulation
Using liquid integral equation theory, we calculate the pair correlations of
particles that interact via a smooth repulsive pair potential in d = 4 spatial
dimensions. We discuss the performance of different closures for the
Ornstein-Zernike equation, by comparing the results to computer simulation
data. Our results are of relevance to understand crystal and glass formation in
high-dimensional systems
Electrokinetic and hydrodynamic properties of charged-particles systems: From small electrolyte ions to large colloids
Dynamic processes in dispersions of charged spherical particles are of
importance both in fundamental science, and in technical and bio-medical
applications. There exists a large variety of charged-particles systems,
ranging from nanometer-sized electrolyte ions to micron-sized charge-stabilized
colloids. We review recent advances in theoretical methods for the calculation
of linear transport coefficients in concentrated particulate systems, with the
focus on hydrodynamic interactions and electrokinetic effects. Considered
transport properties are the dispersion viscosity, self- and collective
diffusion coefficients, sedimentation coefficients, and electrophoretic
mobilities and conductivities of ionic particle species in an external electric
field. Advances by our group are also discussed, including a novel
mode-coupling-theory method for conduction-diffusion and viscoelastic
properties of strong electrolyte solutions. Furthermore, results are presented
for dispersions of solvent-permeable particles, and particles with non-zero
hydrodynamic surface slip. The concentration-dependent swelling of ionic
microgels is discussed, as well as a far-reaching dynamic scaling behavior
relating colloidal long- to short-time dynamics
High temperature superconducting thin film microwave circuits: Fabrication, characterization, and applications
Epitaxial YBa2Cu3O7 films were grown on several microwave substrates. Surface resistance and penetration depth measurements were performed to determine the quality of these films. Here the properties of these films on key microwave substrates are described. The fabrication and characterization of a microwave ring resonator circuit to determine transmission line losses are presented. Lower losses than those observed in gold resonator circuits were observed at temperatures lower than critical transition temperature. Based on these results, potential applications of microwave superconducting circuits such as filters, resonators, oscillators, phase shifters, and antenna elements in space communication systems are identified
NASA Space applications of high-temperature superconductors
The application of superconducting technology in space has been limited by the requirement of cooling to near liquid helium temperatures. The only means of obtaining these temperatures has been with cryogenic fluids which severely limit mission lifetime. The development of materials with superconducting transition temperatures above 77 K has made superconducting technology more attractive and feasible for employment in aerospace systems. Here, potential applications of high temperature superconducting technology in cryocoolers, remote sensing, communications, and power systems are discussed
Tolerance without clonal expansion: Self-antigen-expressing B cells program self-reactive T cells for future deletion
B cells have been shown in various animal models to induce immunological tolerance leading to reduced immune responses and protection from autoimmunity. We show that interaction of B cells with naive T cells results in T cell triggering accompanied by the expression of negative costimulatory molecules such as PD-1, CTLA-4, B and T lymphocyte attenuator, and CD5. Following interaction with B cells, T cells were not induced to proliferate, in a process that was dependent on their expression of PD-1 and CTLA-4, but not CD5. In contrast, the T cells became sensitive to Ag-induced cell death. Our results demonstrate that B cells participate in the homeostasis of the immune system by ablation of conventional self-reactive T cells
Heating and Trapping of Electrons in ECRIS from Scratch to Afterglow
Plasmas in Electron Cyclotron Resonance Ion Sources (ECRIS) are collisionless and can therefore be simulated by just following the motion of electrons in the confining static magnetic and oscillating microwave (MW) electric field of ECRIS. With a powerful algorithm the three-dimensional trajectories of 104 ECR-heated and confined electrons are calculated in a standard ECRIS with a deep minimum of |B| and a new ECRIS with a very flat minimum of |B|. The spatial electron (plasma) densities and electron energy densities deduced from these trajectories yield new and surprising insight in the performance of ECRIS. With computer animation we plan to present: The energy increase of certain electrons on extremely stable trajectories, the power dependence of the electron energy density up to the X-ray collapse, the time dependent build up of the electron density and energy density distributions, and the time evolution of these electron distributions under afterglow conditions
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