Showing papers by "United States Department of Energy published in 2000"

6% magnetic-field-induced strain by twin-boundary motion in ferromagnetic Ni–Mn–Ga

Abstract: Field-induced strains of 6% are reported in ferromagnetic Ni–Mn–Ga martensites at room temperature. The strains are the result of twin boundary motion driven largely by the Zeeman energy difference across the twin boundary. The strain measured parallel to the applied magnetic field is negative in the sample/field geometry used here. The strain saturates in fields of order 400 kA/m and is blocked by a compressive stress of order 2 MPa applied orthogonal to the magnetic field. The strain versus field curves exhibit appreciable hysteresis associated with the motion of the twin boundaries. A simple model accounts quantitatively for the dependence of strain on magnetic field and external stress using as input parameters only measured quantities.

Excited Doublet States of Electrochemically Generated Aromatic Imide and Diimide Radical Anions

Abstract: The radical anions of aromatic diimides have been implicated recently in a wide variety of photochemical electron transfer reactions. Photoexcitation of these radical anions produces powerfully reducing species. Yet, the properties of the π* excited doublet states of these organic radical anions remain obscure. The radical anions of three aromatic imides with increasingly larger π systems, N-(2,5-di-tert-butylphenyl)phthalimide, 1, N-(2,5-di-tert-butylphenyl)-1,8-naphthalimide, 2, and N-(2,5-di-tert-butylphenyl)perylene-3,4-dicarboximide, 3, as well as the three corresponding aromatic diimides, N,N‘-bis(2,5-di-tert-butylphenyl)pyromellitimide, 4a, N,N‘-bis(2,5-di-tert-butylphenyl)-naphthalene-1,8:4,5-tetracarboxydiimide, 5a, and N,N‘-bis(2,5-di-tert-butylphenyl)perylene-3,4:9,10-tetracarboxydiimide, 6, were produced by electrochemical reduction of the neutral molecules in an optically transparent thin layer electrochemical cell. The radical anions of these imides and diimides all exhibit intense visible a...

Novel Sorbents For Mercury Removal From Flue Gas

Abstract: A laboratory-scale packed-bed reactor system is used to screen sorbents for their capability to remove elemental mercury from various carrier gases When the carrier gas is argon, an on-line atomic fluorescence spectrophotometer (AFS), used in a continuous mode, monitors the elemental mercury concentration in the inlet and outlet streams of the packed-bed reactor The mercury concentration in the reactor inlet gas and the reactor temperature are held constant during a test For more complex carrier gases, the capacity is determined off-line by analyzing the spent sorbent with either a cold vapor atomic absorption spectrophotometer (CVAAS) or an inductively coupled argon plasma atomic emission spectrophotometer (ICP-AES) The capacities and breakthrough times of several commercially available activated carbons as well as novel sorbents were determined as a function of various parameters The mechanisms of mercury removal by the sorbents are suggested by combining the results of the packed-bed testing with

Predicting Financial Crashes Using Discrete Scale Invariance

Abstract: We present a synthesis of all the available empirical evidence in the light of recent theoretical developments for the existence of characteristic log-periodic signatures of growing bubbles in a variety of markets including 8 unrelated crashes from 1929 to 1998 on stock markets as diverse as the US, Hong-Kong or the Russian market and on currencies. To our knowledge, no major financial crash preceded by an extended bubble has occurred in the past 2 decades without exhibiting such log-periodic signatures.

A New Set of Arabidopsis Expressed Sequence Tags from Developing Seeds. The Metabolic Pathway from Carbohydrates to Seed Oil

Abstract: Large-scale single-pass sequencing of cDNAs from different plants has provided an extensive reservoir for the cloning of genes, the evaluation of tissue-specific gene expression, markers for map-based cloning, and the annotation of genomic sequences. Although as of January 2000 GenBank contained over 220,000 entries of expressed sequence tags (ESTs) from plants, most publicly available plant ESTs are derived from vegetative tissues and relatively few ESTs are specifically derived from developing seeds. However, important morphogenetic processes are exclusively associated with seed and embryo development and the metabolism of seeds is tailored toward the accumulation of economically valuable storage compounds such as oil. Here we describe a new set of ESTs from Arabidopsis, which has been derived from 5- to 13-d-old immature seeds. Close to 28,000 cDNAs have been screened by DNA/DNA hybridization and approximately 10,500 new Arabidopsis ESTs have been generated and analyzed using different bioinformatics tools. Approximately 40% of the ESTs currently have no match in dbEST, suggesting many represent mRNAs derived from genes that are specifically expressed in seeds. Although these data can be mined with many different biological questions in mind, this study emphasizes the import of photosynthate into developing embryos, its conversion into seed oil, and the regulation of this pathway.

Structures and dynamical properties of C n , Si n , Ge n , and Sn n clusters with n up to 13

Abstract: Car-Parrinello molecular dynamics simulated annealings were carried out for clusters ${\mathrm{Si}}_{n},$ ${\mathrm{Ge}}_{n},$ and ${\mathrm{Sn}}_{n}$ $(nl~13).$ We investigate the temperature regions in which these clusters transform from a ``liquidlike'' phase to a ``solidlike'' phase, and then from the ``solidlike'' phase to the ground-state structures. Additional simulated annealing was also performed for the cluster ${\mathrm{C}}_{13}$ which is selected as a prototype of small carbon clusters. In addition to the discovery of structures for Sn and Ge clusters, our simulation results also provide insights into the dynamics of cluster formation.

Impact of Flue Gas Conditions on Mercury Uptake by Sulfur-Impregnated Activated Carbon

Abstract: Novel sulfur-impregnated activated carbons (SIACs) have shown excellent mercury uptake capacity when pure nitrogen was used as a carrier gas. This study investigated the impact of various gas const...

Mode of action of liver tumor induction by trichloroethylene and its metabolites, trichloroacetate and dichloroacetate.

Abstract: Trichloroethylene (TCE) induces liver cancer in mice but not in rats Three metabolites of TCE may contribute--chloral hydrate (CH), dichloroacetate (DCA), and trichloroacetate (TCA) CH and TCA appear capable of only inducing liver tumors in mice, but DCA is active in rats as well The concentrations of TCA in blood required to induce liver cancer approach the mM range Concentrations of DCA in blood associated with carcinogenesis are in the sub-microM range The carcinogenic activity of CH is largely dependent on its conversion to TCA and/or DCA TCA is a peroxisome proliferator in the same dose range that induces liver cancer Mice with targeted disruptions of the peroxisome proliferator-activated receptor alpha (PPAR-alpha) are insensitive to the liver cancer-inducing properties of other peroxisome proliferators Human cells do not display the responses associated with PPAR-alpha that are observed in rodents This may be attributed to lower levels of expressed PPAR-alpha in human liver DCA treatment produces liver tumors with a different phenotype than TCA Its tumorigenic effects are closely associated with differential effects on cell replication rates in tumors, normal hepatocytes, and suppression of apoptosis Growth of DCA-induced tumors has been shown to arrest after cessation of treatment The DCA and TCA adequately account for the hepatocarcinogenic responses to TCE Low-level exposure to TCE is not likely to induce liver cancer in humans Higher exposures to TCE could affect sensitive populations Sensitivity could be based on different metabolic capacities for TCE or its metabolites or result from certain chronic diseases that have a genetic basis

The Red-Absorbing Chlorophyll a Antenna States of Photosystem I: A Hole-Burning Study of Synechocystis sp. PCC 6803 and Its Mutants

Abstract: Low temperature (4.2 K) absorption and hole-burned spectra are presented for the trimeric (wild-type, WT) photosystem I complex of the cyanobacterium Synechocystis sp. PCC 6803, its monomeric form, and mutants deficient in the PsaF, K, L, and M protein subunits. High-pressure- and Stark-hole-burning data for the WT trimer are presented as well as its temperature-dependent Qy-absorption and -fluorescence spectra. Taken as a whole, the data lead to assignment of a new and lowest energy antenna Qy-state located at 714 nm at low temperatures. It is this state that is responsible for the fluorescence in the low-temperature limit and not the previously identified antenna Qy-state near 708 nm. The data indicate that the 714 nm state is associated with strongly coupled chlorophyll a molecules (perhaps a dimer) and possesses significant charge transfer character. The red chlorophylls absorbing at 708 and 714 nm do not appear to be directly bound to any of the above protein subunits. The results are consistent with...

Electrochemical quartz crystal microbalance investigation of the reductive desorption of self-assembled monolayers of alkanethiols and mercaptoalkanoic acids on Au

Abstract: The reductive desorption of self-assembled monolayers (SAMs) of alkanethiols and mercaptoalkanoic acids from gold has been examined in various alkaline solutions and supporting electrolytes using an electrochemical quartz crystal microbalance (EQCM). The desorption exhibits two voltammetric waves: a large dominant wave and another smaller wave at more negative potentials. The appearance of two waves is due to the heterogeneity in the substrate crystallinity and/or in the packing state of the thiol molecules. The desorption charge is calculated after consideration of the charge required to establish the double layer of the uncoated electrode. The mass change per mole of electrons (mpe) for desorption is determined by comparing the frequency change with the total charge passed upon desorption. The mpe increases linearly with the chain length and has a slope close to the mass of CH2, as is expected for a one-electron process. In the case of alkanethiol desorption, however, the mpe is much smaller than the m...

Overview of aircraft radiation exposure and recent ER-2 measurements.

Abstract: The intensity of the different particles making up atmospheric cosmic radiation, their energy distribution, and their potential biological effect on aircraft occupants vary with altitude, geomagnetic latitude, and time in the sun's magnetic activity cycle. Dose rates from cosmic radiation at commercial aviation altitudes are such that crews working on present-day jet aircraft are an occupationally exposed group with a relatively high average effective dose. Crews of future high speed commercial aircraft flying at higher altitudes would be even more exposed. Present calculations of such exposures are uncertain because knowledge of important components of the radiation field comes primarily from theoretical predictions. To help reduce these uncertainties for high-altitude flight, the National Aeronautics and Space Administration (NASA) and the Department of Energy (DOE) started the Atmospheric Ionizing Radiation (AIR) project. The measurement part of the AIR project is an international collaboration of 12 laboratories placing 14 instruments on multiple flights of a NASA ER-2 aircraft. This paper describes the basic features of cosmic radiation in the atmosphere as they relate to exposure of aircraft occupants and then describes the AIR ER-2 measurements and presents some preliminary results from a series of flights in June 1997.

A method for determination of damping for edgewise blade vibrations

Abstract: Violent edgewise blade vibrations have in recent years been a large problem for some stall-regulated wind turbines. Owing to the complexity of the phenomenon, it has been difficult to predict the risk of these vibrations with aeroelastic load prediction tools. One problem is the choice of parameters in the aeroelastic model, e.g. structural damping and aerodynamic aerofoil characteristics. In many cases a high degree of uncertainty in the predicted response exists and the need for experimental verification methods is obvious. In this work a new method to identify the effective damping for the edgewise blade mode shape for wind turbines has been developed. The method consists of an exciter mechanism which makes it possible to excite the edgewise blade mode shapes from the wind turbine nacelle. Furthermore, the method consists of an analysis method which enables a straightforward determination of the damping. The analysis method is based on a local blade whirl description of the edgewise blade vibrations. The method is verified on a Bonus wind turbine, and for this specific turbine the effective damping for edgewise blade vibrations has been determined. The results support the further development of aeroelastic models and show potential for fine-tuning of parameters of importance for the edgewise blade vibration problem. Furthermore, the method can be used for experimental investigation of the risk of edgewise blade vibrations for a specific turbine. Copyright © 2000 John Wiley & Sons, Ltd.

Sol-Gel and Ultrafine Particle Formation via Dielectric Tuning of Inorganic Salt-Alcohol-Water Solutions.

Abstract: Under some conditions, inorganic salts can be as good precursors for sol–gel-type processing as those obtained from expensive metalloorganic precursors such as alkoxides. In this work, the formation of monodispersed hydrous zirconia microsphere particles (particularly nanosized) and gels was achieved in solutions of zirconyl chloride dissolved in alcohol–water mixed solvents. The dielectric property of the mixed alcohol–water solvent directly affects the nucleation and growth of zirconia clusters/particles in homogeneous solutions. A lower dielectric constant of mixed solvent corresponds to a lower solubility of inorganic solute and, thus, a shorter induction period for nucleation as well as higher solid particle growth kinetics. Dynamic light scattering (DLS) was used to monitor the homogeneous nucleation and growth processes, while final particles and gels were studied by scanning electron microscopy (SEM) and high-temperature X-ray diffraction (HTXRD). The sol–gel processes in the mixed solvent system can be adjusted using the processing parameters, including the initial inorganic salt concentration ( C ), alcohol/aqueous medium volume ratio of the mixed solution (RH), incubation temperature ( T ), incubation time ( t ), concentration of hydroxypropyl cellulose (HPC), and ammonia neutralization. Monodispersed submicron and nanoscale ( −3 g/cm 3 ) and ammonia neutralization. Initial salt concentration affects the particle size significantly. Gel materials were obtained under conditions of low RH (1.0). Microstructure and transparency of gels changed significantly from low (0.05 M) to high (0.2 M) concentration of the metal salt. We have also demonstrated that monodispersed particle production can be achieved not only at low temperatures (

Attenuation of metal oxide ions in inductively coupled plasma mass spectrometry with hydrogen in a hexapole collision cell

Abstract: Some strongly bound metal oxide ions (MO+) can be attenuated in a hexapole collision cell with a mixture of helium and hydrogen gas. Various metal oxide ions with different dissociation energies, such as ZrO+, CeO+, LaO+, SmO+, HoO+, YbO+ and WO+, have been chosen to study the attenuation effect. By adjusting the collision conditions, especially the composition and flow rate of the collision gas and the hexapole dc bias voltage, the MO+/M+ signal ratio can be suppressed by a factor of up to 60 for CeO+ and LaO+ while maintaining ≈20% of the original signal for atomic analyte ions (M+). For the species studied, collisions with H2 improve the MO+/M+ signal ratio more extensively for oxide ions with higher dissociation energies. The same collision conditions also serve to remove most of the ArO+, ArN+ and Ar2+ from the background spectrum.

Numerical study of tilt stability of prolate field-reversed configurations

Abstract: Global stability of the field-reversed configuration (FRC) has been investigated numerically using both three-dimensional magnetohydrodynamic and hybrid (fluid electron and δf particle ion) simulations. The stabilizing effects of velocity shear and finite ion Larmor radius (FLR) on the n=1 internal tilt mode in the prolate FRCs have been studied. Sheared rotation is found to reduce the growth rate, however a large rotation rate with Mach number of M≳1 is required in order for significant reduction in the instability growth rate to occur. Kinetic effects associated with large thermal ion orbits have been studied for different kinetic equilibria. The simulations show that there is a reduction in the tilt mode growth rate due to FLR effects, but complete linear stability has not been found, even when the thermal ion gyroradius is comparable to the distance between the field null and the separatrix. The instability existing beyond the FLR theory threshold could be due to the resonant interaction of the wave with ions whose Doppler shifted frequency matches the betatron frequency.

Discovery of a Novel, Paternally Expressed Ubiquitin-specific Processing Protease Gene through Comparative Analysis of an Imprinted Region of Mouse Chromosome 7 and Human Chromosome 19q13.4

Abstract: Although the two alleles of most mammalian autosomal genes are functionally equivalent, the maternal and paternal copies of a subset of genes are distinguished by genomic imprinting, a mechanism by which one allele is epigenetically modified and repressed, depending upon parental origin. The epigenetic modification that determines imprinting is yet to be defined, but several lines of evidence strongly suggest that differences in DNA methylation and chromatin structure may be part of the molecular mechanism (Tilghman 1999). About 30 different imprinted genes have been isolated from human and mouse DNA, and more imprinted genes are predicted to be present in mammalian genomes (Barlow 1997; Morrison and Reeve 1998). The imprinted genes that have been described to date are clustered in discrete chromosomal regions, and the clustering of those genes is conserved in mammals (Barlow 1995; Bartolomei and Tilghman 1997). These data have been interpreted to imply that genome imprinting is a long-range mechanism that controls allele-specific transcription of multiple genes within a defined chromosomal region (Nicholls 1994; Dittrich et al. 1996; Tilghman et al. 1998, 1999). Imprinted genes exhibit several unique features in addition to parent-of-origin-specific monoallelic expression and differential methylation. The known imprinted genes generally are expressed at early stages of development, and many encode proteins with functions related to embryonic growth (Tilghman 1999). Recent studies also suggest the involvement of imprinted genes in controlling the parental caring behavior of mammals (Lefebvre et al. 1998; Li et al. 1999). Several imprinted genes such as UBE3A (Rougeulle et al. 1998), IGF2 (Moore et al. 1997), ZNF127 (Jong et al. 1999), and IGF2R (Wutz et al. 1997) display bidirectional transcription, producing both sense and antisense transcripts. A number of imprinted genes including H19 and IPW are expressed without any coding capability; the final products of these genes are RNAs rather than proteins (Bartolomei and Tilghman 1997). Imprinted genes also tend to be comosed of relatively small numbers of exons and to contain smaller introns than nonimprinted genes (Hurst et al. 1996), although there are some notable exceptions (e.g., KvLQT1; Lee et al. 1997). Early mouse genetic studies with translocation mutant mice predicted the presence of nine different imprinted domains distributed onto seven chromosomes (Beechey and Cattanach 1996). The chromosomal locations of most imprinted genes, in fact, are consistent with this initial prediction (Imprinting Map; http://www.mgu.har.mrc.ac.uk/imprinting/imptables.html#impmaps). Mouse chromosome 7 (Mmu7) was predicted in these early studies to contain three different imprinted domains, located in centromeric, central, and distal regions (Searle and Beechey 1990). The central and distal regions of Mmu7 are syntenically homologous to intervals of human chromosome 15q13-11 and 11p15, respectively, that contain genes associated with two imprinting genetic disorders—Prader–Willi/Angelman (Nicholls et al. 1998) and Beckwith–Wiedemann syndromes (Reik and Maher 1997). Each of these domains contains several imprinted genes whose order, sequence, and imprinting status are highly conserved in humans and mice. Until recently, only one imprinted gene, Peg3 (paternally expressed gene 3), had been localized to the centromeric imprinted domain of Mmu7 (Kuroiwa et al. 1996) and the homologous region of human chromosome 19q13.4 (Kim et al. 1997a). We exploited the well-developed physical map surrounding human PEG3 and the known conservation of this interval in humans and mice to identify a second mouse-imprinted gene, Zim1 (imprinted zinc-finger gene 1), located downstream of Peg3 (Kim et al. 1999). More recent studies identified a related and homologously positioned human zinc-finger gene, ZIM2, and showed that the gene shares seven 5′-exons with PEG3, a feature that distinguishes this pair of human genes from their closest murine counterparts (Kim et al. 2000). The significant divergence of Zim1 and ZIM2 gene organization and amino acid sequence suggests that the region surrounding PEG3 has undergone significant changes during the course of mammalian evolution. Through analysis of clone contigs spanning homologous segments of Mmu7 and sequenced regions of human 19q13.4, we have isolated and characterized another novel mouse gene, Usp29 (ubiquitin-specific processing protease 29) and have identified its human counterpart. Our analyses show that Usp29 is also imprinted and is expressed mainly from the paternal allele during embryogenesis and in adult brain. The sequence of a full-length 7.6-kb mouse cDNA clone and human coding sequences indicate that Usp29 encodes a novel ubiquitin-specific processing protease, and together with Ube3a may represent a second imprinted gene involved in the ubiquitination pathway.

Carbon dioxide capture process with regenerable sorbents

Abstract: A process to remove carbon dioxide from a gas stream using a cross-flow, or a moving-bed reactor. In the reactor the gas contacts an active material that is an alkali-metal compound, such as an alkali-metal carbonate, alkali-metal oxide, or alkali-metal hydroxide; or in the alternative, an alkaline-earth metal compound, such as an alkaline-earth metal carbonate, alkaline-earth metal oxide, or alkaline-earth metal hydroxide. The active material can be used by itself or supported on a substrate of carbon, alumina, silica, titania or aluminosilicate. When the active material is an alkali-metal compound, the carbon-dioxide reacts with the metal compound to generate bicarbonate. When the active material is an alkaline-earth metal, the carbon dioxide reacts with the metal compound to generate carbonate. Spent sorbent containing the bicarbonate or carbonate is moved to a second reactor where it is heated or treated with a reducing agent such as, natural gas, methane, carbon monoxide hydrogen, or a synthesis gas comprising of a combination of carbon monoxide and hydrogen. The heat or reducing agent releases carbon dioxide gas and regenerates the active material for use as the sorbent material in the first reactor. New sorbent may be added to the regenerated sorbent prior to subsequent passes in the carbon dioxide removal reactor.

Optimization of high temperature sulfur impregnation on activated carbon for permanent sequestration of elemental mercury vapors

Abstract: Following previous success with the use of activated carbon impregnated with sulfur at elevated temperatures for elemental mercury control, possible improvements in the impregnation procedure were evaluated in this study. Adsorbents prepared by thoroughly mixing sulfur and activated carbon in the furnace at the initial sulfur-to-carbon ratio (SCR) ranging from 4:1 to 1:2 showed similar adsorptive behavior in a fixed-bed system. Maintaining a stagnant inert atmosphere during the impregnation process improves sulfur deposition resulting in the enhanced dynamic capacity of the adsorbent when compared to other sulfur impregnated carbons. The fate of spent adsorbents was assessed using a toxicity characteristics leaching procedure (TCLP). Although mercury concentration in all leachates was below the TCLP limit (0.2 mg/L), virgin activated carbon lost a significant fraction of the adsorbed elemental mercury during storage, while no loss was observed for sulfur-impregnated carbons. This finding suggests that vir...