Chalcogenide glass planar MIR couplers for future chip based Bracewell interferometers

Photonic integrated circuits are established as the technique of choice for a number of astronomical processing functions due to their compactness, high level of integration, low losses, and stability. Temperature control, mechanical vibration and acoustic noise become controllable for such a device enabling much more complex processing than can realistically be considered with bulk optics. To date the benefits have mainly been at wavelengths around 1550 nm but in the important Mid-Infrared region, standard photonic chips absorb light strongly. Chalcogenide glasses are well known for their transparency to beyond 10000 nm, and the first results from coupler devices intended for use in an interferometric nuller for exoplanetary observation in the Mid-Infrared L band (3800-4200 nm) are presented here showing that suitable performance can be obtained both theoretically and experimentally for the first fabricated devices operating at 4000 nm.Comment: in Proc. SPIE 9907, Optical and Infrared Interferometry and Imaging V, 990730 (August 4, 2016

BMQ

BMQ: Boston Medical Quarterly was published from 1950-1966 by the Boston University School of Medicine and the Massachusetts Memorial Hospitals

Transport Coefficients for Granular Media from Molecular Dynamics Simulations

Under many conditions, macroscopic grains flow like a fluid; kinetic theory pred icts continuum equations of motion for this granular fluid. In order to test the theory, we perform event driven molecular simulations of a two-dimensional gas of inelastic hard disks, driven by contact with a heat bath. Even for strong dissipation, high densities, and small numbers of particles, we find that continuum theory describes the system well. With a bath that heats the gas homogeneously, strong velocity correlations produce a slightly smaller energy loss due to inelastic collisions than that predicted by kinetic theory. With an inhomogeneous heat bath, thermal or velocity gradients are induced. Determination of the resulting fluxes allows calculation of the thermal conductivity and shear viscosity, which are compared to the predictions of granular kinetic theory, and which can be used in continuum modeling of granular flows. The shear viscosity is close to the prediction of kinetic theory, while the thermal conductivity can be overestimated by a factor of 2; in each case, transport is lowered with increasing inelasticity.Comment: 14 pages, 17 figures, 39 references, submitted to PRE feb 199

BMQ

BMQ: Boston Medical Quarterly was published from 1950-1966 by the Boston University School of Medicine and the Massachusetts Memorial Hospitals

A New Approach to the Treatment of Alzheimer's Disease: the Need for a Controlled Study

Abstract. It has been widely believed that decreased cerebral blood flow (CBF), known to occur in Alzheimer's disease (AD), is the result of neuronal degeneration that causes a decrease in the need for adequate CBF. There is new interest in the idea, however, that it is not neuronal degeneration that leads to decreased CBF to critical neurons, but it is the decrease in CBF which is the cause of the neuronal deterioration seen in AD patients. In order to increase CBF to the AD brain, an operation called omental transposition has been developed in which an intact elongated omental pedicle, when placed directly on the brain, provides additional CBF and other biological nutrients to the brain. It is understandable that AD patients are awaiting a method to control their disease, but this may take years to become available. Placing the omentum on the AD brain has demonstrated increased CBF which may be the reason that several studies have shown that omental transposition to the brain can improve the cognitive ability of AD patients who have undergone the operation. What is needed is a prospective controlled study that could scientifically establish the benefit of the procedure