The metabolism of tryptophan in rats and in man

Thesis (Ph.D.)--Boston UniversityTryptoPhan and its metabolites have been implicated in various mental disorders including schizopnrenia. This serious disease of unknown etiology has become an increasingly important subject of biochemical investigation. In order to understand more fully the metabolism of tryptopnan in schizophrenia, an investigation of urinary metabolites was undertaken, utilizing radioactivity as a marker. Bats were studied to perfect the techniques and to provide possible indications of the metabolites to be looked for in man. TryptoPhan was administered to humans orally, to duplicate the normal route of intake, and intravenously, to obtain indications of tissue activity without the tryptopnan having been acted on by intestinal bacteria. The techniques employed were a combination of two-dimensional ascending paper chromatography and radioautography. The latter was useful in the visual identification of the urinary metabolites of radioactive C14-labelled tryptophan. Through the use of extraction procedures with various solvents, selective separation and identification were made possible. Concentration of the extracts provided for the detection of substances present in only minute quantities [TRUNCATED

Sealed Nickel-Metal Hydride Batteries for Small Satellite Applications

Sealed, nickel-metal hydride cells are being developed for aerospace applications by Eagle-Picher Industries, Inc. Sizes ranging from 3.5 ampere-hours to 20 ampere-hours are targeted for the small satellite program. The nickel-metal hydride system offers nearly twice the energy density of aerospace nickel-cadmium cells with no memory effect. The cells contain no cadmium, mercury or other toxic materials. The system operates at low pressure and offers significant cost advantages over the nickel-hydrogen system. The cells exhibit excellent overcharge and overdischarge capability with cycle life similar to that of nickel-cadmium. Cells are also being assembled and tested in a number of sizes and designs for use in terrestrial applications

New Thin-Film Tunnel Triode Using Amorphous Semiconductors

A new thin‐film tunnel triode is discussed which uses a p‐type amorphous film to achieve amplification of injected current from a tunnel cathode. It is not only the basis for a new semiconductor device but also suggests a novel method for measuring electrical properties of semiconductors

On-chip photonic memory elements employing phase-change materials

Open Access Article - Wiley OnlineOpenPhase-change materials integrated into nanophotonic circuits provide a flexible way to realize tunable optical components. Relying on the enormous refractive-index contrast between the amorphous and crystalline states, such materials are promising candidates for on-chip photonic memories. Nonvolatile memory operation employing arrays of microring resonators is demonstrated as a route toward all-photonic chipscale information processing...Deutsche Forschungsgemeinschaft (DFG)Engineering and Physical Sciences Research Council (EPSRC)NSF Materials World Networ

Master-equation approach to the study of phase-change processes in data storage media

We study the dynamics of crystallization in phase-change materials using a master-equation approach in which the state of the crystallizing material is described by a cluster size distribution function. A model is developed using the thermodynamics of the processes involved and representing the clusters of size two and greater as a continuum but clusters of size one (monomers) as a separate equation. We present some partial analytical results for the isothermal case and for large cluster sizes, but principally we use numerical simulations to investigate the model. We obtain results that are in good agreement with experimental data and the model appears to be useful for the fast simulation of reading and writing processes in phase-change optical and electrical memories

Ovonic nickel metal hydride batteries for space applications

Ovonic nickel-metal hydride (NiMH) rechargeable batteries are easily adaptable to a variety of applications. Small consumer NiMH cells were developed and are now being manufactured by licensees throughout the world. This technology was successfully scaled up in larger prismatic cells aimed at electric vehicle applications. Sealed cells aimed at satellite power applications were also built and cycle tested by OBC and other outside agencies. Prototype batteries with high specific energy (over 80 Wh/kg), high energy density (245 Wh/L), and excellent power capability (400 W/kg) were produced. Ovonic NiMH batteries demonstrated an excellent cycle life of over 10,000 cycles at 30 percent DOD. Presently, Ovonic Battery Company is working on an advanced version of this battery for space applications as part of an SBIR contract from NASA

Models for Metal Hydride Particle Shape, Packing, and Heat Transfer

A multiphysics modeling approach for heat conduction in metal hydride powders is presented, including particle shape distribution, size distribution, granular packing structure, and effective thermal conductivity. A statistical geometric model is presented that replicates features of particle size and shape distributions observed experimentally that result from cyclic hydride decreptitation. The quasi-static dense packing of a sample set of these particles is simulated via energy-based structural optimization methods. These particles jam (i.e., solidify) at a density (solid volume fraction) of 0.665+/-0.015 - higher than prior experimental estimates. Effective thermal conductivity of the jammed system is simulated and found to follow the behavior predicted by granular effective medium theory. Finally, a theory is presented that links the properties of bi-porous cohesive powders to the present systems based on recent experimental observations of jammed packings of fine powder. This theory produces quantitative experimental agreement with metal hydride powders of various compositions.Comment: 12 pages, 12 figures, 2 table

Photoplastic effects in chalcogenide glasses: A review

A synopsis of the various photoinduced changes of rheological, mechanical and elastic properties is presented in the first part of the article. After a critical appraisal of a large body of experimental data it suggested that the photoviscous effect, that is, the athermal decrease of viscosity of a non-crystalline chalcogenide upon illumination is the key for a plethora of photoinduced effects reported so far in the literature under different names. Morphic effects (shape or surface morphology) may ap-pear either in the presence or absence of external mechanical stimuli leading to the fabrication of a variety of technologically important photoprocessed structures. A few representative examples of photoplastic effects are described, in the second part of the paper, in some detail based on information provided by in situ Raman scattering and nanoindentation experiments.Comment: 12 pages, 10 figure

Breakdown of Stokes-Einstein relation in the supercooled liquid state of phase change materials

The application of amorphous chalcogenide alloys as data-storage media relies on their ability to undergo an extremely fast (10-100 ns) crystallisation once heated at sufficiently high temperature. However, the peculiar features that make these materials so attractive for memory devices still lack a comprehensive microscopic understanding. By means of large scale molecular dynamics simulations, we demonstrate that the supercooled liquid of the prototypical compound GeTe shows a very high atomic mobility (D \sim 10^(-6) cm2/s) down to temperatures close to the glass transition temperatures. This behaviour leads to a breakdown of the Stokes-Einstein relation between the self- diffusion coefficient and the viscosity in the supercooled liquid. The results suggest that the fragility of the supercooled liquid is the key to understand the fast crystallisation process in this class of materials.Comment: 6 pages, 4 figure