Showing papers by "United States Department of Energy published in 1985"

Determining modes and fractal dimension of turbulent flows

Abstract: Research on the abstract properties of the Navier–Stokes equations in three dimensions has cast a new light on the time-asymptotic approximate solutions of those equations. Here heuristic arguments, based on the rigorous results of that research, are used to show the intimate relationship between the sufficient number of degrees of freedom describing fluid flow and the bound on the fractal dimension of the Navier–Stokes attractor. In particular it is demonstrated how the conventional estimate of the number of degrees of freedom, based on purely physical and dimensional arguments, can be obtained from the properties of the Navier–Stokes equation. Also the Reynolds-number dependence of the sufficient number of degrees of freedom and of the dimension of the attractor in function space is elucidated.

Excimer laser phototherapy for the dissolution of abnormal growth

Abstract: Removal of abnormal human tissue with reduced thermal damage is achieved by selecting a laser having a wavelength in the order of 290-400 nm, orienting a laser-transmitting glass member toward the abnormal tissue and directing the laser through the glass member at power densities, pulse rates, and times sufficient to cause multiphoton absorption and bond breaking by Coulomb repulsion rather than thermal destruction. The glass member may include a laser beam concentrator provided by a lens or cone at the tissue-treatment end to increase the beam energy per unit area and reduce the treatment area.

Current status of bioassays in genetic toxicology — The dominant lethal assay: A report of the U.S. environmental protection agency gene-tox program☆

Abstract: The term dominant lethal may be defined as death of the heterozygote arising through multiple chromosomal breaks. The assay is generally conducted by treating male animals, usually mice or rats, acutely (1 dose), subacutely (5 doses), or over the entire period of spermatogenesis. Animals treated acutely or subacutely are mated at weekly intervals to females for a sufficient number of weeks to cover the period of spermatogenesis. Those treated for the entire spermatogenic cycle are mated for 1 or 2 successive weeks at the termination of treatment. Females usually are killed at 14 days of pregnancy and examined for the number of total implantations in the uterus, the number of implantations classified as early deaths, and, in some cases, the number of corpora lutea. The category of early death is the most significant index of dominant lethality. A total of 249 papers were reviewed and 140 chemicals were evaluated. Of the 140 chemicals, 65 were positive by the criteria used by the Work Group in evaluating each publication. The category of "positive" includes those responses of a borderline nature. 99 chemicals were declared negative. There is considerable overlap of chemicals in both categories, which accounts for the incongruity in the total number of chemicals tested and the number considered positive and negative. A total of 44 animal carcinogens have been tested in the dominant lethal assay, 26 of which were positive and 18 negative for a correlation of 59%. The role of the assay should be that of confirming positive results from lower tier chromosomal aberration-detecting systems (confirming in the sense of indicating the ability of the chemical to penetrate gonadal tissue and to produce cytogenetic damage). The dominant lethal assay should not be used as a risk assessment method.

Critical currents of cross-type superconducting-normal-superconducting junctions in perpendicular magnetic fields.

Abstract: The maximum supercurrent that can be carried in an applied perpendicular magnetic field by a superconducting--normal-metal--superconducting (SNS) junction consisting of a square normal-metal layer sandwiched between two crossed perpendicular superconducting strips is investigated theoretically and experimentally. For weak applied fields the critical current is suppressed reversibly, as induced Meissner screening currents flow into the SNS sandwich and generate a spatially varying magnetic field largely parallel to the junction, thereby altering the local phase difference. For stronger applied fields the critical current is changed irreversibly as vortices enter and become pinned in the junction. When the pinned vortices in the two superconductors are misaligned, the local magnetic field, which flows mostly parallel to the junction in carrying magnetic flux ${\ensuremath{\varphi}}_{0}$=hc/2e from one vortex to the other, strongly alters the phase difference across the junction near the two vortices. The theory predicts complex patterns of the supercurrent density, which should be directly observable using laser or electron-beam scanning techniques.

Reactive power compensating system

Abstract: The reactive power of an induction machine is compensated by providing fixed capacitors on each phase line for the minimum compensation required, sensing the current on one line at the time its voltage crosses zero to determine the actual compensation required for each phase, and selecting switched capacitors on each line to provide the balance of the compensation required.

Optical properties of Nd3+ in lead phosphate glasses

Abstract: Measurements of optical absorption and emission spectra of Nd3+ in lead phosphate glasses at 295 K are compared with results reported earlier for various metaphosphate glasses. The Judd-Ofelt intensity parameters for high-lead-content phosphate glasses are the smallest observed thus far for metaphosphate glasses with divalent network modifier cations.

Planarization of metal films for multilevel interconnects

Abstract: In the fabrication of multilevel integrated circuits, each metal layer is anarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

Recirculating electric air filter

Abstract: An electric air filter cartridge has a cylindrical inner high voltage eleode, a layer of filter material, and an outer ground electrode formed of a plurality of segments moveably connected together. The outer electrode can be easily opened to remove or insert filter material. Air flows through the two electrodes and the filter material and is exhausted from the center of the inner electrode.

Method for preparing configured silicon carbide whisker-reinforced alumina ceramic articles

Abstract: A ceramic article of alumina reinforced with silicon carbide whiskers suitable for the fabrication into articles of complex geometry are provided by pressureless sintering and hot isostatic pressing steps. In accordance with the method of the invention a mixture of 5 to 10 vol. % silicon carbide whiskers 0.5 to 5 wt. % of a sintering aid such as yttria and the balance alumina powders is ball-milled and pressureless sintered in the desired configuration in the desired configuration an inert atmosphere at a temperature of about 1800° C. to provide a self-supporting configured composite of a density of at least about 94% theoretical density. The composite is then hot isostatically pressed at a temperature and pressure adequate to provide configured articles of at least about 98% of theoretical density which is sufficient to provide the article with sufficient strength and fracture toughness for use in most structural applications such as gas turbine blades, cylinders, and other components of advanced heat engines.

Copper-silver-titanium-tin filler metal for direct brazing of structural ceramics

Abstract: A method of joining ceramics and metals to themselves and to one another at about 800° C. is described using a brazing filler metal consisting essentially of 35 to 50 at. % copper, 40 to 50 at. % silver, 1 to 15 at. % titanium, and 2 to 8 at. % tin. This method produces strong joints that can withstand high service temperatures and oxidizing environments.

The relationship of a coal fired power plant to the levels of polycyclic aromatic hydrocarbons (PAH) in the sediment of Cayuga Lake

Abstract: The influence of Milliken Station, a coal-fired power plant, on the distribution of PAH in the sediment of Cayuga Lake was investigated. Except for a small, confined area near the stacks, the Milliken power plant was found to have no discernible effect on PAH levels in Cayuga Lake. It is believed that stack emissions are either masked by other sources or are atmospherically transported and deposited elsewhere. The highest PAH levels measured were found in marinas or areas of the lake receiving urban runoff. Concentrations found in these areas were, in several cases, an order of magnitude greater than those fround elsewhere on the lake. PAH concentrations for most of the Cayuga Lake sediment were typical of levels reported for other rural northeastern lakes including some in remote areas. Region wide atmospheric deposition appears to be the prime source of PAH entering Cayuga Lake. The PAH carcinogens, 3-methyl-cholantrene and 7,12 dimethylbenzanthracene were not detected in any sediments nor where any nitrogen heterocyclic PAIL PAH inputs from local sources were found to decline in concentration very rapidly with distance from their sources.

Progressing batch hydrolysis process

Abstract: A progressive batch hydrolysis process for producing sugar from a lignocellulosic feedstock, comprising passing a stream of dilute acid serially through a plurality of percolation hydrolysis reactors charged with said feedstock, at a flow rate, temperature and pressure sufficient to substantially convert all the cellulose component of the feedstock to glucose; cooling said dilute acid stream containing glucose, after exiting the last percolation hydrolysis reactor, then feeding said dilute acid stream serially through a plurality of prehydrolysis percolation reactors, charged with said feedstock, at a flow rate, temperature and pressure sufficient to substantially convert all the hemicellulose component of said feedstock to glucose; and cooling the dilute acid stream containing glucose after it exits the last prehydrolysis reactor.

Polysilane positive photoresist materials and methods for their use

Abstract: New polysilane copolymers comprise recurring units of --Si(X)(Y)-- and Si(A)(B)--, Si(X)(Y) being different from Si(A)(B), wherein X and Y together have 1-13 carbon atoms, and X and Y each independently is hydrogen, alkyl, cycloalkyl, phenyl, alkylphenyl, or phenylalkyl, with the proviso that only one of X and Y contains a phenyl moiety, or together X and Y are an alkylene group forming a ring with the adjoining Si atom, and wherein A and B together have 3-13 carbon atoms, and A and B each independently is alkyl or cycloalkyl, with the proviso (a) that when one of A and B is ethyl, the other is not methyl or ethyl, and (b) that when one of A and B is n-propyl and the other is methyl, X and Y are not both methyl. Corresponding homopolysilanes are also provided. Upon ultraviolet irradiation, they photodepolymerize to form volatile products. As a result, they represent a new class of photoresists which enable direct formation of a positive image eliminating the heretofore required development step.