Precombustion Cleaning of Coal By Triboelectric Separation of Minerals

In one method of electrostatic beneficiation, pulverized coal is tribocharged by contact with electrically grounded copper. Coal maceral and mineral particles charge with positive and negative polarities, respectively. The charged particles are passed through a separator consisting of two plate electrodes, across which a high voltage is applied, and the positively charged coal particles are separated from the negatively charged mineral particles. The efficiency of separation is dependent upon coal bulk and surface composition, and fineness of grind. Analyses of total sulfur and ash content of the charge-separated particles were used to evaluate beneficiation success of the Illinois No. 6 and Pittsburgh No. 8 coals studied. Two-stage beneficiation demonstrated improved separation. Exposing coal powders to chemical vapors of SO 2 , NH 3 , or acetone prior to beneficiation did not enhance beneficiation.     

Test-case generation with IOGen

The IOGen static-analysis tool for a subset of Ada addresses part of the problem of verification of software reliability. It uses a technique based on symbolic execution and produces a set of I/O pairs that represent execution paths through a program. The authors present IOGen's design and demonstrate how to use it to test programs and validate Ada software interfaces. Although IOGen is specific to an Ada subset, the same technique can be applied to any language with a grammar that uses a left-to-right scan with one look-ahead token producing a leftmost derivation (an LL(1) grammar)     

EVAC: a virtual environment for control of remote imaginginstrumentation

The objective of this project, called the Experimentalist's Virtual Acquisition Console (EVAC), was to demonstrate a prototype system for using virtual environments that would allow a researcher access the hardware in a remote experimental laboratory over high-speed networks, in order to control remote instrumentation. We wanted to give the researcher tools that would not only allow for complete control of the imaging system but also provide the potential for collaboration with researchers at distant sites. We targeted three imaging instruments, all located at the Beckman Institute for Advanced and Technology: a magnetic resonance imaging system, a transmission electron microscope and a scanning tunneling microscope. Our goal was not to control all three instruments simultaneously but rather to demonstrate that our unified virtual environment interface could be adapted to these widely different imaging devices. In building this demonstration, we faced many problems commonly encountered in developing a remote interface to a new instrument. These included the lack of any standard interface to the devices, the necessity of dealing with proprietary software, and the problem of developing a distributed model so that the instruments could be controlled over the network. The EVAC project has illustrated the potential of a virtual laboratory over a high-speed network     

A complete parameterization of all positive rational extensions ofa covariance sequence

In this paper we formalize the observation that filtering and interpolation induce complementary, or “dual,” decompositions of the space of positive real rational functions of degree less than or equal to n. From this basic result about the geometry of the space of positive real functions, we are able to deduce two complementary sets of conclusions about positive rational extensions of a given partial covariance sequence. On the one hand, by viewing a certain fast filtering algorithm as a nonlinear dynamical system defined on this space, we are able to develop estimates on the asymptotic behavior of the Schur parameters (1918) of positive rational extensions. On the other hand we are also able to provide a characterization of all positive rational extensions of a given partial covariance sequence. Indeed, motivated by its application to signal processing, speech processing, and stochastic realization theory, this characterization is in terms of a complete parameterization using familiar objects from systems theory and proves a conjecture made by Georgiou (1983, 1987). Our basic result, however, also enables us to analyze the robustness of this parameterization with respect to variations in the problem data. The methodology employed is a combination of complex analysis, geometry, linear systems, and nonlinear dynamics     

Dislocations in vapor phase epitaxial GaP

Dislocations in VPE GaP grown on (100) oriented LEC GaP substrates have been characterized, and their origins and effects on LED performance have been investigated. In non-nitrogen doped epilayers, the dislocations are found to originate in the substrate and propagate through the epilayers in straight lines in [100] and <211> directions. The dislocation density of the epilayer is found to be nearly equal to that of the substrate. Introduction of nitrogen during growth of the epilayer has been observed to bend these so-called “inclined≓ dislocations propagating through the layer into [0−1 1] directions in the (100) plane and thus produces segments of [0 −1 1] dislocations to relieve the lattice parameter mismatch due to N. The mismatch dislocation density is observed to be proportional to the N doping level. At very high N doping levels, > 10¹⁹ cm^-3, a large number of new inclined dislocations are observed, which may be in part due to GaN precipitation. The effects of dislocations on LED properties were investigated by measuring dislocation densities in the individual diodes using the electron beam induced current mode of the SEM and comparing this with the spot brightness and luminous flux. The dislocations were observed to produce dark spots in the EL emission in many cases. For a series of runs where all growth and processing parameters were fixed, a good correlation between B/J and dislocation density was observed with B/J decreasing with increasing dislocation density in the range < 1 × 10⁴ cm⁻² to 1 × 10⁶ cm⁻².     

Chaperone-supervised conversion of prion protein to its protease-resistant form

Transmissible spongiform encephalopathies (TSEs) are lethal, infectious disorders of the mammalian nervous system. A TSE hallmark is the conversion of the cellular protein PrPC to disease-associated PrPSc (named for scrapie, the first known TSE). PrPC is protease-sensitive, monomeric, detergent soluble, and primarily alpha-helical; PrPSc is protease-resistant, polymerized, detergent insoluble, and rich in beta-sheet. The "protein-only" hypothesis posits that PrPSc is the infectious TSE agent that directly converts host-encoded PrPC to fresh PrPSc, harming neurons and creating new agents of infection. To gain insight on the conformational transitions of PrP, we tested the ability of several protein chaperones, which supervise the conformational transitions of proteins in diverse ways, to affect conversion of PrPC to its protease-resistant state. None affected conversion in the absence of pre-existing PrPSc. In its presence, only two, GroEL and Hsp104 (heat shock protein 104), significantly affected conversion. Both promoted it, but the reaction characteristics of conversions with the two chaperones were distinct. In contrast, chemical chaperones inhibited conversion. Our findings provide new mechanistic insights into nature of PrP conversions, and provide a new set of tools for studying the process underlying TSE pathogenesis.     

Failure Analysis of Additively Manufactured Polyester Test Specimens Exposed to Various Liquid Media

Journal of Failure Analysis and Prevention - Additive manufacturing platforms that rely on thermoplastic feedstock materials are now expected to fabricate components intended for deployment in a...     

Atomic layer deposition (ALD): A versatile technique for plasmonics and nanobiotechnology

While atomic layer deposition (ALD) has been used for many years as an industrial manufacturing method for microprocessors and displays, this versatile technique is finding increased use in the emerging fields of plasmonics and nanobiotechnology. In particular, ALD coatings can modify metallic surfaces to tune their optical and plasmonic properties, to protect them against unwanted oxidation and contamination, or to create biocompatible surfaces. Furthermore, ALD is unique among thin-film deposition techniques in its ability to meet the processing demands for engineering nanoplasmonic devices, offering conformal deposition of dense and ultra-thin films on high-aspect-ratio nanostructures at temperatures below 100 °C. In this review, we present key features of ALD and describe how it could benefit future applications in plasmonics, nanosciences, and biotechnology.     

The electrochemical oxidation of aqueous sulfur dioxide: A critical review of work with respect to the hybrid sulfur cycle

Literature regarding the mechanism of the electrochemical oxidation of aqueous sulfur dioxide to sulfuric acid has been critically evaluated to provide a detailed understanding of the reaction under various applied conditions. This reaction is of high relevance to the hybrid sulfur cycle for large scale hydrogen production, as well as other industrial applications such as flue gas desulfurisation. Widespread disagreement in the literature and non-reproducible behaviour of the electrochemical oxidation reaction has been found in this review to often be a result of poorly defined electrode preconditioning procedures. It has also been found that the mechanistic pathway of the oxidation reaction is heavily influenced by the electrode material, solution pH and the applied anodic potential. These factors are thought to influence adsorption and the reductive formation of sulfur species at low potentials.