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1

Effects of water-gas shift reaction on simulated performance of a molten carbonate fuel cell  

Microsoft Academic Search

A molten carbonate fuel cell (MCFC) is simulated. In order to determine the effects of the water-gas shift reaction, the calculated results such as temperature distribution, voltage distribution, conversion and performance, are compared with those calculated excluding the shift reaction. Uniformity in the temperature profile is deteriorated due to the shift reaction. At the entrance, hydrogen is consumed rapidly in

Mi-Hyun Kim; Hong-Kyu Park; Gui-Yung Chung; Hee-Chun Lim; Suk-Woo Nam; Tae-Hoon Lim; Seong-Ahn Hong

2002-01-01

2

Water-Gas Shift Membrane Reactor Studies  

E-print Network

Water-Gas Shift Membrane Reactor Studies Richard Killmeyer, Kurt Rothenberger, and Bret Howard US" unfavorable equilibrium to produce more H2 #12;Equilibrium Conversion for the Water Gas Shift Reaction [CO]0 the Consideration of Reaction Kinetics and Mass Transport Phenomena - Forward Water-Gas Shift Kinetics - Reverse

3

Water Gas Shift Catalysis  

Microsoft Academic Search

Developments in water gas shift (WGS) catalysis, especially during the last decade, are reviewed. Recent developments include the development of 1 chromium?free catalysts that can operate at lower steam to gas ratios and 2 more active catalysts that can operate at gas hourly space velocities above 40,000 h. A current challenge is to develop catalysts for use in fuel cell applications.

Chandra Ratnasamy; Jon P. Wagner

2009-01-01

4

Minimization of steam requirements and enhancement of water-gas shift reaction with warm gas temperature CO2 removal  

DOEpatents

The disclosure utilizes a hydroxide sorbent for humidification and CO.sub.2 removal from a gaseous stream comprised of CO and CO.sub.2 prior to entry into a water-gas-shift reactor, in order to decrease CO.sub.2 concentration and increase H.sub.2O concentration and shift the water-gas shift reaction toward the forward reaction products CO.sub.2 and H.sub.2. The hydroxide sorbent may be utilized for absorbtion of CO.sub.2 exiting the water-gas shift reactor, producing an enriched H.sub.2 stream. The disclosure further provides for regeneration of the hydroxide sorbent at temperature approximating water-gas shift conditions, and for utilizing H.sub.2O product liberated as a result of the CO.sub.2 absorption.

Siriwardane, Ranjani V; Fisher, II, James C

2013-12-31

5

Low temperature, sulfur tolerant homogeneous catalysts for the water-gas shift reaction  

SciTech Connect

The objective of this project is to identify, prepare, test, characterize, and evaluate a practical, homogeneous catalyst for a water-gas shift process. The project effort is divided into the following five tasks: (1) Update SRI's recent review of the literature on the catalysis of the water-gas shift reaction (WGSR) to include references after 1982 and those in the patent literature. Based on this review, SRI will choose ten candidate systems to be evaluated as to their abilities to catalyze the WGSR using syngas derived from gasified coal. (2) Develop a test plan designed to effectively evaluate both the catalysts and, to some extent, reactor configuration for WGSR catalysis. (3) Perform a series of experiments to identify the most effective and economical of the ten candidate catalysts and then further evaluate the reaction kinetics of at least one selected catalyst system to develop sufficient data to provide the basis for the work in Task 4. (4) Develop a mathematical model of the final candidate system that uses rate expressions to describe the catalytic process. (5) Perform a techno-economical evaluation of the catalyst in terms of a proposed plant design based on the reaction model, current costs, and standard chemical engineering practice and compare the proposed design with a conventional hydrogen plant.

Laine, R.M.; Wood, B.J.; Krishnan, G.N.

1986-04-01

6

Hydrodesulphurization of Light Gas Oil using hydrogen from the Water Gas Shift Reaction  

NASA Astrophysics Data System (ADS)

The production of clean fuel faces the challenges of high production cost and complying with stricter environmental regulations. In this research, the ability of using a novel technology of upgrading heavy oil to treat Light Gas Oil (LGO) will be investigated. The target of this project is to produce cleaner transportation fuel with much lower cost of production. Recently, a novel process for upgrading of heavy oil has been developed at University of Waterloo. It is combining the two essential processes in bitumen upgrading; emulsion breaking and hydroprocessing into one process. The water in the emulsion is used to generate in situ hydrogen from the Water Gas Shift Reaction (WGSR). This hydrogen can be used for the hydrogenation and hydrotreating reaction which includes sulfur removal instead of the expensive molecular hydrogen. This process can be carried out for the upgrading of the bitumen emulsion which would improve its quality. In this study, the hydrodesulphurization (HDS) of LGO was conducted using in situ hydrogen produced via the Water Gas Shift Reaction (WGSR). The main objective of this experimental study is to evaluate the possibility of producing clean LGO over dispersed molybdenum sulphide catalyst and to evaluate the effect of different promoters and syn-gas on the activity of the dispersed Mo catalyst. Experiments were carried out in a 300 ml Autoclave batch reactor under 600 psi (initially) at 391°C for 1 to 3 hours and different amounts of water. After the hydrotreating reaction, the gas samples were collected and the conversion of carbon monoxide to hydrogen via WGSR was determined using a refinery gas analyzer. The sulphur content in liquid sample was analyzed via X-Ray Fluorescence. Experimental results showed that using more water will enhance WGSR but at the same time inhibits the HDS reaction. It was also shown that the amount of sulfur removed depends on the reaction time. The plan is to investigate the effect of synthesis gas (syngas) molar ratio by varying CO to H2 ratio. It is also planned to use different catalysts promoters and compare them with the un-promoted Mo based catalysts to achieve the optimum reaction conditions for treating LGO. The results of this study showed that Ni and Co have a promoting effect over unpromoted Mo catalysts for both HDS and WGSR. Ni was found to be the best promoter for both reactions. Fe showed no significant effect for both WGSR and HDS. V and K have a good promoting effect in WGSR but they inhibited the HDS reaction. Potassium was found to be the strongest inhibitor for the HDS reaction since no sulfur was removed during the reaction. Keywords. LGO, HDS, in situ H2, WGSR, oil upgrading, syn-gas.

Alghamdi, Abdulaziz

2009-12-01

7

Mechanism of the Water Gas Shift Reaction on Pt: First Principles, Experiments, and Microkinetic Modeling  

SciTech Connect

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. We present a microkinetic model as well as experimental data for the low-temperature water gas shift (WGS) reaction catalyzed by Pt at temperatures from 523 to 573 K and for various gas compositions at a pressure of 1 atm. Thermodynamic and kinetic parameters for the model are derived from periodic, self-consistent density functional theory (DFT-GGA) calculations on Pt(111). The destabilizing effect of high CO surface coverage on the binding energies of surface species is quantified through DFT calculations and accounted for in the microkinetic model. Deviations of specific fitted model parameters from DFT calculated parameters on Pt(111) point to the possible role of steps/defects in this reaction. Our model predicts reaction rates and reaction orders in good agreement with our experiments. The calculated and experimental apparent activation energies are 67.8 kJ/mol and 71.4 kJ/mol, respectively. The model shows that the most significant reaction channel proceeds via a carboxyl (COOH) intermediate. Formate (HCOO), which has been experimentally observed and thought to be the key WGS intermediate in the literature, is shown to act only as a spectator species.

Grabow, Lars C.; Gokhale, Amit A.; Evans, Steven T.; Dumesic, James A.; Mavrikakis, Manos

2008-03-27

8

Role of homogeneous formate complexes in the water gas shift reaction catalyzed by the group 6 metal carbonyls  

Microsoft Academic Search

The mechanism of the homogeneous water gas shift reaction catalyzed by the group 6 metal carbonyls involves the intermediacy of a formate complex. Catalytic pressure reactions as well as stoichiometric photolysis and pyrolysis experiments provide support for this mechanism. 10 references, 1 table.

William A. R. Slegeir; Richard S. Sapienza; Richard Rayford; Lillian Lam

1982-01-01

9

Density Functional Theory and Reaction Kinetics Studies of the Water–Gas Shift Reaction on Pt–Re Catalysts  

SciTech Connect

Periodic, self-consistent density functional theory calculations (DFT-GGA-PW91) on Pt(111) and Pt3Re(111) surfaces, reaction kinetics measurements, and microkinetic modeling are employed to study the mechanism of the water–gas shift (WGS) reaction over Pt and Pt–Re catalysts. The values of the reaction rates and reaction orders predicted by the model are in agreement with the ones experimentally determined; the calculated apparent activation energies are matched to within 6% of the experimental values. The primary reaction pathway is predicted to take place through adsorbed carboxyl (COOH) species, whereas formate (HCOO) is predicted to be a spectator species. We conclude that the clean Pt(111) is a good representation of the active site for the WGS reaction on Pt catalysts, whereas the active sites on the Pt–Re alloy catalyst likely contain partially oxidized metal ensembles.

Carrasquillo-Flores, Ronald; Gallo, Jean Marcel R.; Hahn, Konstanze; Dumesic, James A.; Mavrikakis, Manos

2013-12-01

10

Gold atoms stabilized on various supports catalyze the water-gas shift reaction.  

PubMed

For important chemical reactions that are catalyzed by single-site metal centers, such as the water-gas shift (WGS) reaction that converts carbon monoxide and water to hydrogen and carbon dioxide, atomically dispersed supported metal catalysts offer maximum atom efficiency. Researchers have found that for platinum metal supported on ceria and doped ceria in the automobile exhaust catalyst, atomic Pt-Ox-Ce species are the active WGS reaction sites. More recently, preparations of gold at the nanoscale have shown that this relatively "new material" is an active and often more selective catalyst than platinum for a variety of reactions, including the WGS reaction. The activity of gold is typically attributed to a size effect, while the interface of gold with the support has also been reported as important for oxidation reactions, but exactly how this comes about has not been probed satisfactorily. Typical supported metal catalysts prepared by traditional techniques have a heterogeneous population of particles, nanoclusters, subnanometer species, and isolated atoms/ions on the support surfaces, making the identification of the active sites difficult. Both we and other researchers have clearly shown that gold nanoparticles are spectator species in the WGS reaction. Evidence has now amassed that the gold active site for the WGS reaction is atomic, that is, Au-Ox species catalyze the reaction, similar to Pt-Ox. In this Account, we review the relevant literature to conclude that the intrinsic activity of the Au-Ox(OH)-S site, where S is a support, is the same for any S. The support effect is indirect, through its carrying (or binding) capacity for the active sites. Destabilization of the gold under reducing conditions through the formation of clusters and nanoparticles is accompanied by a measurable activity loss. Therefore, it is necessary to investigate the destabilizing effect of different reaction gas mixtures on the gold atom sites and to consider regeneration methods that effectively redisperse the gold clusters into atoms. For gold catalysts, we can remove weakly bound clusters and nanoparticles from certain supports by leaching techniques. Because of this, we can prepare a uniform dispersion of gold atoms/ions strongly bound to the support surface by this two-step (loading followed by leaching) approach. Presently, one-step preparation methods to maximize the number of the single atom sites on various supports need to be developed, specific to the type of the selected support. Often, it will be beneficial to alter the surface properties of the support to enhance metal ion anchoring, for example, by shape and size control of the support or by the use of light-assisted deposition and anchoring of the metal on photoresponsive supports. Because of their importance for practical catalyst development, synthesis methods are discussed at some length in this Account. PMID:24266870

Flytzani-Stephanopoulos, Maria

2014-03-18

11

Reaction-Relevant Gold Structures in the Low Temperature Water-Gas Shift Reaction on Weiling Deng, Anatoly I. Frenkel, Rui Si, and Maria Flytzani-Stephanopoulos*,  

E-print Network

Reaction-Relevant Gold Structures in the Low Temperature Water-Gas Shift Reaction on Au-CeO2 structure (EXAFS) studies have been conducted to follow gold structural changes of low-content (gold in oxygen gas at 150 °C. Gold in the fresh (400 °C-calcined) material was atomically dispersed in cerium

Frenkel, Anatoly

12

Low temperature, sulfur tolerant homogeneous catalysts for the water-gas shift reaction. Task 2, Test plan  

SciTech Connect

The objective of this project is to identify, prepare, test, characterize, and evaluate a practical, homogeneous catalyst for a water-gas shift process. The project effort is divided into the following five tasks: (1) Update SRI`s recent review of the literature on the catalysis of the water-gas shift reaction (WGSR) to include references after 1982 and those in the patent literature. Based on this review, SRI will choose ten candidate systems to be evaluated as to their abilities to catalyze the WGSR using syngas derived from gasified coal. (2) Develop a test plan designed to effectively evaluate both the catalysts and, to some extent, reactor configuration for WGSR catalysis. (3) Perform a series of experiments to identify the most effective and economical of the ten candidate catalysts and then further evaluate the reaction kinetics of at least one selected catalyst system to develop sufficient data to provide the basis for the work in Task 4. (4) Develop a mathematical model of the final candidate system that uses rate expressions to describe the catalytic process. (5) Perform a techno-economical evaluation of the catalyst in terms of a proposed plant design based on the reaction model, current costs, and standard chemical engineering practice and compare the proposed design with a conventional hydrogen plant.

Laine, R.M.; Wood, B.J.; Krishnan, G.N.

1986-04-01

13

Water-gas shift reaction on oxide/Cu(111): Rational catalyst screening from density functional theory  

NASA Astrophysics Data System (ADS)

Developing improved catalysts based on a fundamental understanding of reaction mechanism has become one of the grand challenges in catalysis. A theoretical understanding and screening the metal-oxide composite catalysts for the water-gas shift (WGS) reaction is presented here. Density functional theory was employed to identify the key step for the WGS reaction on the Au, Cu-oxide catalysts, where the calculated reaction energy for water dissociation correlates well with the experimental measured WGS activity. Accordingly, the calculated reaction energy for water dissociation was used as the scaling descriptor to screen the inverse model catalysts, oxide/Cu(111), for the better WGS activity. Our calculations predict that the WGS activity increases in a sequence: Cu(111), ZnO/Cu(111) < TiO2/Cu(111), ZrO2/Cu(111) < MoO3/Cu(111). Our results imply that the high performances of Au, Cu-oxide nanocatalysts in the WGS reaction rely heavily on the direct participation of both oxide and metal sites. The degree that the oxide is reduced by Cu plays an important role in determining the WGS activity of oxide/Cu catalysts. The reducible oxide can be transformed from the fully oxidized form to the reduced form due to the interaction with Cu and, therefore, the transfer of electron density from Cu, which helps in releasing the bottleneck water dissociation and, therefore, facilitating the WGS reaction on copper.

Liu, Ping

2010-11-01

14

CO2 SELECTIVE CERAMIC MEMBRANE FOR WATER-GAS SHIFT REACTION WITH CONCOMITANT RECOVERY OF CO2  

SciTech Connect

Two process schemes have been investigated by us for the use of hydrotalcites we prepared as CO{sub 2} adsorbents to enhance water gas shift (WGS) reaction: Case I involves the adsorption enhanced WGS packed bed reactor and Case II involves the adsorption enhanced WGS membrane reactor. Both cases will achieve the same objective as the hydrotalcite membrane reactor: i.e., improving the WGS reactor efficiency via the concomitant removal of CO{sub 2} for sequestration. In this report a detailed investigation of the design characteristics and performance of Case II, termed the Hybrid Adsorbent-Membrane Reactor (HAMR), is presented. The HAMR system includes a packed-bed catalytic membrane reactor (hydrogen selective) coupling the WGS reaction (in a porous hydrogen selective membrane) with CO{sub 2} removal with an adsorbent in the permeate side. The reactor characteristics have been investigated for a range of permeance and selectivity relevant to the aforementioned application. The HAMR system shows enhanced CO conversion, hydrogen yield, and product purity, and provides good promise for reducing the hostile operating conditions of conventional WGS reactors, and for meeting the CO{sub 2} sequestration objective. In the next quarterly report we will present the simulation result for Case I as well as the progress on hydrotalcite membrane synthesis.

Paul K. T. Liu

2004-02-19

15

Untangling the water gas shift from Fischer-Tropsch: a Gordian knot. [185 references  

SciTech Connect

The water gas shift reaction is an integral part of the Fischer-Tropsch synthesis. Although it may appear convenient to consider the water gas shift a separate reaction, in some cases, a detailed examination of the mechanism indicates theat the water gas shift and other synthesis gas reactions share several elementary reactions. Experimental support for the relevant elementary reactions for the water gas shift on metals, metal oxides, and in homogeneous solution is examined, from both surface and complex chemistry. Multiple paths leading to a net water gas shift reaction may be available; oxygen transfer and reaction through C-H-O intermediates may take place. 185 references, 6 tables.

Rofer-Depoorter, C.K.

1983-01-01

16

On the mechanism of the reverse water gas shift reaction: Dynamic TAP reactor studies of the oxidizing capability of CO2 on a Au/CeO2 catalyst  

E-print Network

On the mechanism of the reverse water gas shift reaction: Dynamic TAP reactor studies The mechanism of the Reverse Water Gas Shift (RWGS) reaction on a Au/CeO2 supported catalyst, in particular the role of the redox mechanism, was investigated by exploring the activity of CO2 for Au assisted CeO2

Pfeifer, Holger

17

Analysis of a duo-selecting membrane reactor for the water-gas shift  

E-print Network

The water-gas shift reaction is an exothermic and reversible catalytic process that converts carbon monoxide and water (steam) to hydrogen and carbon dioxide. In regard to energy-related issues, the water-gas shift is part ...

Hardy, AliciA Jillian Jackson, 1978-

2004-01-01

18

Water-Gas Shift and CO Methanation Reactions over Ni-CeO2(111) Catalysts  

SciTech Connect

X-ray and ultraviolet photoelectron spectroscopies were used to study the interaction of Ni atoms with CeO2(111) surfaces. Upon adsorption on CeO2(111) at 300 K, nickel remains in a metallic state. Heating to elevated temperatures (500 800 K) leads to partial reduction of the ceria substrate with the formation of Ni2? species that exists as NiO and/or Ce1-xNixO2-y. Interactions of nickel with the oxide substrate significantly reduce the density of occupied Ni 3d states near the Fermi level. The results of core-level photoemission and near-edge X-ray absorption fine structure point to weakly bound CO species on CeO2(111) which are clearly distinguishable from the formation of chemisorbed carbonates. In the presence of Ni, a stronger interaction is observed with chemisorption of CO on the admetal. When the Ni is in contact with Ce?3 cations, CO dissociates on the surface at 300 K forming NiCx compounds that may be involved in the formation of CH4 at higher temperatures. At medium and large Ni coverages ([0.3 ML), the Ni/CeO2(111) surfaces are able to catalyze the production of methane from CO and H2, with an activity slightly higher than that of Ni(100) or Ni(111). On the other hand, at small coverages of Ni (\\0.3 ML), the Ni/CeO2(111) surfaces exhibit a very low activity for CO methanation but are very good catalysts for the water gas shift reaction.

Senanayake, Sanjaya D [ORNL; Evans, Jaime [Universidad Central de Venezuela; Agnoli, Stefano [Brookhaven National Laboratory (BNL); Barrio, Laura [Brookhaven National Laboratory (BNL); Chen, Tsung-Liang [ORNL; Hrbek, Jan [Brookhaven National Laboratory (BNL); Radriguez, Jose [Brookhaven National Laboratory (BNL)

2011-01-01

19

Water-Gas Shift and CO Methanation Reactions over Ni-CeO2(111) Catalysts  

SciTech Connect

X-ray and ultraviolet photoelectron spectroscopies were used to study the interaction of Ni atoms with CeO{sub 2}(111) surfaces. Upon adsorption on CeO{sub 2}(111) at 300 K, nickel remains in a metallic state. Heating to elevated temperatures (500-800 K) leads to partial reduction of the ceria substrate with the formation of Ni{sup 2+} species that exists as NiO and/or Ce{sub 1-x}Ni{sub x}O{sub 2-y}. Interactions of nickel with the oxide substrate significantly reduce the density of occupied Ni 3d states near the Fermi level. The results of core-level photoemission and near-edge X-ray absorption fine structure point to weakly bound CO species on CeO{sub 2}(111) which are clearly distinguishable from the formation of chemisorbed carbonates. In the presence of Ni, a stronger interaction is observed with chemisorption of CO on the admetal. When the Ni is in contact with Ce{sup +3} cations, CO dissociates on the surface at 300 K forming NiC{sub x} compounds that may be involved in the formation of CH{sub 4} at higher temperatures. At medium and large Ni coverages (>0.3 ML), the Ni/CeO{sub 2}(111) surfaces are able to catalyze the production of methane from CO and H{sub 2}, with an activity slightly higher than that of Ni(100) or Ni(111). On the other hand, at small coverages of Ni (<0.3 ML), the Ni/CeO{sub 2}(111) surfaces exhibit a very low activity for CO methanation but are very good catalysts for the water-gas shift reaction.

S Senanayake; J Evans; S Agnoli; L Barrio; T Chen; J Hrbek; J Rodriguez

2011-12-31

20

CO2 SELECTIVE CERAMIC MEMBRANE FOR WATER-GAS-SHIFT REACTION WITH CONCOMITANT RECOVERY OF CO2  

SciTech Connect

A high temperature membrane reactor (MR) has been developed to enhance the water-gas-shift (WGS) reaction efficiency with concomitant CO{sub 2} removal for sequestration. This improved WGS-MR with CO{sub 2} recovery capability is ideally suitable for integration into the Integrated Gasification Combined-Cycle (IGCC) power generation system. Two different CO{sub 2}-affinity materials were selected in this study. The Mg-Al-CO{sub 3}-layered double hydroxide (LDH) was investigated as an adsorbent or a membrane for CO{sub 2} separation. The adsorption isotherm and intraparticle diffusivity for the LDH-based adsorbent were experimentally determined, and suitable for low temperature shift (LTS) of WGS. The LDH-based membranes were synthesized using our commercial ceramic membranes as substrate. These experimental membranes were characterized comprehensively in terms of their morphology, and CO{sub 2} permeance and selectivity to demonstrate the technical feasibility. In parallel, an alternative material-base membrane, carbonaceous membrane developed by us, was characterized, which also demonstrated enhanced CO{sub 2} selectivity at the LTS-WGS condition. With optimization on membrane defect reduction, these two types of membrane could be used commercially as CO{sub 2}-affinity membranes for the proposed application. Based upon the unique CO{sub 2} affinity of the LDHs at the LTS/WGS environment, we developed an innovative membrane reactor, Hybrid Adsorption and Membrane Reactor (HAMR), to achieve {approx}100% CO conversion, produce a high purity hydrogen product and deliver a concentrated CO{sub 2} stream for disposal. A mathematical model was developed to simulate this unique one -step process. Finally a benchtop reactor was employed to generate experimental data, which were consistent with the prediction from the HAMR mathematical model. In summary, the project objective, enhancing WGS efficiency for hydrogen production with concomitant CO{sub 2} removal for sequestration, has been theoretically and experimentally demonstrated via the developed one-step reactor, HAMR. Future development on reactor scale up and field testing is recommended.

Paul K.T. Liu

2005-07-15

21

Supported Copper, Nickel and Copper-Nickel Nanoparticle Catalysts for Low Temperature Water-Gas-Shift Reaction  

NASA Astrophysics Data System (ADS)

Hydrogen is being considered worldwide as a future replacement for gasoline, diesel fuel, natural gas in both the transportation and non-transportation sectors. Hydrogen is a versatile energy carrier that can be produced from a variety of widely available primary energy sources, including coal, natural gas, biomass, solar, wind, and nuclear power. Coal, the most abundant fossil fuel on the planet, is being looked at as the possible future major source of H2, due to the development of the integrated gasification combined cycle (IGCC) and integrated gasification fuel cell technologies (IGFC). The gasification of coal produces syngas consisting of predominately carbon monoxide and hydrogen with some remaining hydrocarbons, carbon dioxide and water. Then, the water-gas shift reaction is used to convert CO to CO2 and additional hydrogen. The present work describes the synthesis of model Cu, Ni and Cu-Ni catalysts prepared from metal colloids, and compares their behavior in the WGS reaction to that of traditional impregnation catalysts. Initially, we systematically explored the performance of traditional Cu, Ni and Cu-Ni WGS catalysts made by impregnation methods. Various bimetallic Cu-Ni catalysts were prepared by supported impregnation and compared to monometallic Cu and Ni catalysts. The presence of Cu in bimetallic catalysts suppressed undesirable methanation side reaction, while the Ni component was important for high WGS activity. Colloidal Cu, Ni and Cu-Ni alloy nanoparticles obtained by chemical reduction were deposited onto alumina to prepare supported catalysts. The resulting Cu and Ni nanoparticle catalysts were found to be 2.5 times more active in the WGS reaction per unit mass of active metal as compared to catalysts prepared by the conventional impregnation technique. The powder XRD and HAADF-STEM provided evidence supporting the formation of Cu-Ni particles containing the Cu core and Cu-Ni alloy shell. The XPS data indicated surface segregation of Cu in the bimetallic Cu-Ni catalysts after reduction. The colloidal Cu5Ni5 alloy catalyst exhibited the WGS reaction rate that was higher than that observed over colloidal Cu and Ni catalysts indicating for the very first time a favorable bimetallic effect for the Cu-Ni system. The presence of Cu in these bimetallic catalysts induced favorable structural and electronic effects not only for enhancing the WGS activity, but also for suppressing methane yield. Bimetallic Cu-Ni catalysts possessing a core-shell structure were synthesized that provided important insights into their structure-activity relationships in the WGS reaction. We employed a successive reduction route to synthesize Cu Ni and Ni Cu core-shell nanoparticles and deposited them onto alumina support to obtain supported bimetallic catalysts. The powder XRD patterns, CO chemisorption data, and UV-vis spectra indicated the formation of core-shell structures in the bimetallic Cu-Ni nanoparticles. Cu Ni catalysts showed similar WGS activities to supported Ni catalysts but lower methanation activity. Suppressed methanation activity observed for Cu Ni nanoparticles may be due to Cu segregation to the surface. Supported Ni Cu catalysts displayed WGS activity comparable to supported Cu catalysts. Therefore, these findings strongly suggested that supported Cu, Ni and Cu-Ni alloy nanoparticle catalysts prepared from metal colloids are very promising as highly active WGS catalysts.

Lin, Jiann-Horng

22

The synthesis of methanol and the reverse water-gas shift reaction over Zn-deposited Cu(100) and Cu(110) surfaces: comparison with Zn/Cu(111)  

NASA Astrophysics Data System (ADS)

The catalytic activity of Zn vapor-deposited Cu(100) and Cu(110) surfaces for methanol synthesis by the hydrogenation of CO 2 and the reverse water-gas shift reaction were studied using an XPS apparatus combined with a high-pressure flow reactor (18 atm). At a reaction temperature of 523 K, no promotional effect of Zn was observed for the methanol synthesis on both Zn/Cu(100) and Zn/Cu(110). The results were quite different from those for Zn/Cu(111), on which a significant promotion of methanol synthesis activity appeared to be due to the deposition of Zn, indicating that the promotional effect of Zn was sensitive to the surface structure of Cu. However, hysteresis was observed in the catalytic activity for methanol synthesis over the Zn/Cu(110) surface upon heating above 543 K in the reaction mixture. The activity became twice that measured before heating, which was close to the methanol synthesis activity of Zn/Cu(111) at the same Zn coverage. On the other hand, no such hysteresis was observed for the reverse water-gas shift reaction on Zn/Cu(110), indicating that the active site for methanol synthesis was not identical to that for the reverse water-gas shift reaction. In the post-reaction surface analysis, formate species was detected on both Zn/Cu(100) and Zn/Cu(110), whose coverage increased with increasing Zn coverage at 0< ?Zn<0.2. No correlation between the formate coverage and the methanol synthesis activity was obtained, which was in contrast to the results for Zn/Cu(111). Thus, the structure sensitivity observed in the catalytic activity of methanol synthesis over Zn-deposited Cu surfaces is ascribed to the significant difference in the reactivity of the formate intermediate.

Nakamura, I.; Fujitani, T.; Uchijima, T.; Nakamura, J.

1998-03-01

23

Theoretical study of gas-phase reactions of Fe(CO){sub 5} with OH{sup {minus}} and their relevance for the water gas shift reaction  

SciTech Connect

Revision of the homogeneously Fe(CO){sub 5}-catalyzed water gas shift reaction in the gas phase has been performed by means of quantum chemical calculations using gradient-corrected density functional theory (B3LYP) and ab initio methods at the CCSD(T) level. The classically assumed reaction path has been scrutinized step by step, and enlarged with novel mechanistic proposals. The calculations lend additional credit to some of the previously accepted steps in the catalytic cycle, such as the initial attack of OH{sup {minus}} to Fe(CO){sub 5} and also to the recently accepted decarboxylation of (CO){sub 4}FeCOOH{sup {minus}} (via a concerted mechanism involving a four-centered transition state), as well as to the acidification of the metal hydride (CO){sub 4}Fe{sub 4}H{sub {minus}} with water to yield the dihydride (CO){sub 4}FeH{sub 2}. The present investigation also examines in terms of energies and activation barriers the existence/participation of new intermediates (in particular, a metalloformate species, a water-hydride adduct, and a dihydrogen complex), not mentioned in prior studies. Finally, a transition-metal-containing S{sub N}2-type reaction is explored for the last stages of this chemical process as a mechanistic alternative to regenerate the starting catalyst.

Torrent, M.; Sola, M. [Univ. de Girona (Spain). Institut de Quimica Computacional] [Univ. de Girona (Spain). Institut de Quimica Computacional; Frenking, G. [Philipps-Universitaet Marburg (Germany)] [Philipps-Universitaet Marburg (Germany)

1999-07-19

24

Advanced Water-Gas Shift Membrane Reactor  

SciTech Connect

The overall objectives for this project were: (1) to identify a suitable PdCu tri-metallic alloy membrane with high stability and commercially relevant hydrogen permeation in the presence of trace amounts of carbon monoxide and sulfur; and (2) to identify and synthesize a water gas shift catalyst with a high operating life that is sulfur and chlorine tolerant at low concentrations of these impurities. This work successfully achieved the first project objective to identify a suitable PdCu tri-metallic alloy membrane composition, Pd{sub 0.47}Cu{sub 0.52}G5{sub 0.01}, that was selected based on atomistic and thermodynamic modeling alone. The second objective was partially successful in that catalysts were identified and evaluated that can withstand sulfur in high concentrations and at high pressures, but a long operating life was not achieved at the end of the project. From the limited durability testing it appears that the best catalyst, Pt-Re/Ce{sub 0.333}Zr{sub 0.333}E4{sub 0.333}O{sub 2}, is unable to maintain a long operating life at space velocities of 200,000 h{sup -1}. The reasons for the low durability do not appear to be related to the high concentrations of H{sub 2}S, but rather due to the high operating pressure and the influence the pressure has on the WGS reaction at this space velocity.

Sean Emerson; Thomas Vanderspurt; Susanne Opalka; Rakesh Radhakrishnan; Rhonda Willigan

2009-01-07

25

Ceria modified three-dimensionally ordered macro-porous Pt\\/TiO 2 catalysts for water-gas shift reaction  

Microsoft Academic Search

Three-dimensionally ordered macro-porous (3DOM) TiO2 and ceria-modified 3DOM TiO2 supported platinum catalysts were prepared with template and impregnation methods, and the resultant samples were characterized by scanning electron microscopy(SEM), X-ray diffractometer(XRD), high-resolution transmission electron microscopy(HRTEM) and temperature programmed reduction(TPR) techniques. The catalytic performances over the platinum-based catalysts were investigated for water-gas shift (WGS) reaction in a wide temperature range (180–360

Hao LIANG; Yuan ZHANG; Yuan LIU

2009-01-01

26

Gold catalysts supported on ceria doped by rare earth metals for water gas shift reaction: Influence of the preparation method  

Microsoft Academic Search

Gold catalysts based on ceria, doped by various RE metals (La, Sm, Gd, Yb, Y) were studied. The influence of the preparation methods on structure, properties and catalytic activity in the WGS reaction was investigated. The catalysts’ supports were prepared using two different methods: co-precipitation (CP) and mechanochemical activation (MA). The catalysts were tested in a wide temperature interval without

D. Andreeva; I. Ivanov; L. Ilieva; M. V. Abrashev; R. Zanella; J. W. Sobczak; W. Lisowski; M. Kantcheva; G. Avdeev; K. Petrov

2009-01-01

27

Hydordesulfurization of dibenzothiophene using hydrogen generated in situ by the water-gas shift reaction in a trickle bed reactor  

E-print Network

of the sulfur containing compounds found in oil to desulfurize. A trickle bed reactor was used for the hydrodesulfurization reaction. A data analysis program was developed which accounts for the volatility of the liquid phase in the trickle bed reactor. Zero... chromatograph from Varian Vista 44 for a sample of product liquid. 37 10 Product distribution for hydrodesulfurization of dibenzothiophene with hydrogen generated in situ. 38 INTRODUCTION The increasing use of higher sulfur content petroleum crude oils...

Hook, Bruce David

1984-01-01

28

CO{sub 2} SELECTIVE CERAMIC MEMBRANE FOR WATER-GAS-SHIFT REACTION WITH CONCOMITANT RECOVERY OF CO{sub 2}  

SciTech Connect

Our CO{sub 2}-affinity material synthesis activities thus far have offered two base materials suitable for hydrogen production via low temperature water gas shift reaction (LTS-WGS) with concomitant removal of CO{sub 2} for sequestration. They include (i) a nanoporous CO{sub 2}-affinity membrane and (ii) a hydrotalcite based CO-affinity adsorbent. These two materials offer a commercially viable opportunity for implementing an innovative process concept termed the hybrid adsorbent-membrane reactor (HAMR) for LTS-WGS, proposed by us in a previous quarterly report. A complete mathematical model has been developed in this quarter to describe the HAMR system, which offers process flexibility to incorporate both catalysts and adsorbents in the reactor as well as permeate sides. In comparison with the preliminary mathematical model we reported previously, this improved model incorporates ''time'' as an independent variable to realistically simulate the unsteady state nature of the adsorptive portion of the process. In the next quarterly report, we will complete the simulation to demonstrate the potential benefit of the proposed process based upon the performance parameters experimentally obtained from the CO{sub 2}-affinity adsorbent and membrane developed from this project.

Paul K. T. Liu

2005-01-31

29

On the Importance of Metal–Oxide Interface Sites for the Water–Gas Shift Reaction Over Pt/CeO2 Catalysts  

SciTech Connect

The mechanism of water–gas shift reaction at the three-phase boundary of Pt/CeO2 catalysts has been investigated using density functional theory and microkinetic modeling to better understand the importance of metal–oxide interface sites in heterogeneous catalysis. Analysis of a microkinetic model based on parameters obtained from first principles suggests that both the “Redox pathway” and the “Associative carboxyl pathway with redox regeneration” could operate on Pt/CeO2 catalysts. Although (1) only few interfacial Pt atoms are found to be catalytically active at low temperatures due to strong adsorption of CO and (2) interfacial O–H bond breakage is difficult due to the high reducibility of ceria, interface sites are 2–3 orders of magnitude more active than Pt (1 1 1) and stepped Pt surface sites and therefore effectively determine the overall activity of Pt/CeO2. The high activity of Pt/CeO2 interface sites originates from a significantly enhanced water activation and dissociation at interfacial oxygen vacancies.

Aranifard, Sara; Ammal, Salai Cheettu; Heyden, Andreas

2014-01-01

30

Development of Novel Water-Gas-Shift Membrane Reactor  

E-print Network

· Low Temperature CO2-Selective Membrane · High Temperature CO2-Selective Membrane Reformer Water Gas 8000 10000 90 110 130 150 170 190 Temperature (o C) CO2Permeability(Barrers) Membrane D, 2.1 atm FeedDevelopment of Novel Water- Gas-Shift Membrane Reactor Addressing Barrier L: H2 Purification

31

Activity, durability and microstructural characterization of ex-nitrate and ex-chloride Pt\\/Ce 0.56Zr 0.44O 2 catalysts for low temperature water gas shift reaction  

Microsoft Academic Search

Ex-nitrate and ex-chloride Pt over Ce0.56Zr0.44O2 have been prepared by a single-step solution combustion synthesis (SCS) and are compared with the corresponding catalyst prepared by incipient wetness impregnation (IWI) of platinum over the bare support for the water gas shift reaction under a simulated reformate gas composition. All the catalysts have similar surface areas (23–27m2g?1). Structural and microscopic characterization shows

Arup Gayen; Marta Boaro; Carla de Leitenburg; Jordi Llorca; Alessandro Trovarelli

2010-01-01

32

Unique properties of ceria nanoparticles supported on metals: novel inverse ceria/copper catalysts for CO oxidation and the water-gas shift reaction.  

PubMed

Oxides play a central role in important industrial processes, including applications such as the production of renewable energy, remediation of environmental pollutants, and the synthesis of fine chemicals. They were originally used as catalyst supports and were thought to be chemically inert, but now they are used to build catalysts tailored toward improved selectivity and activity in chemical reactions. Many studies have compared the morphological, electronic, and chemical properties of oxide materials with those of unoxidized metals. Researchers know much less about the properties of oxides at the nanoscale, which display distinct behavior from their bulk counterparts. More is known about metal nanoparticles. Inverse-model catalysts, composed of oxide nanoparticles supported on metal or oxide substrates instead of the reverse (oxides supporting metal nanoparticles), are excellent tools for systematically testing the properties of novel catalytic oxide materials. Inverse models are prepared in situ and can be studied with a variety of surface science tools (e.g. scanning tunneling microscopy, X-ray photoemission spectroscopy, ultraviolet photoemission spectroscopy, low-energy electron microscopy) and theoretical tools (e.g. density functional theory). Meanwhile, their catalytic activity can be tested simultaneously in a reactor. This approach makes it possible to identify specific functions or structures that affect catalyst performance or reaction selectivity. Insights gained from these tests help to tailor powder systems, with the primary objective of rational design (experimental and theoretical) of catalysts for specific chemical reactions. This Account describes the properties of inverse catalysts composed of CeOx nanoparticles supported on Cu(111) or CuOx/Cu(111) as determined through the methods described above. Ceria is an important material for redox chemistry because of its interchangeable oxidation states (Ce?? and Ce³?). Cu(111), meanwhile, is a standard catalyst for reactions such as CO oxidation and the water-gas shift (WGS). This metal serves as an ideal replacement for other noble metals that are neither abundant nor cost effective. To prepare the inverse system we deposited nanoparticles (2-20 nm) of cerium oxide onto the Cu(111) surface. During this process, the Cu(111) surface grows an oxide layer that is characteristic of Cu?O (Cu¹?). This oxide can influence the growth of ceria nanoparticles. Evidence suggests triangular-shaped CeO?(111) grows on Cu?O(111) surfaces while rectangular CeO?(100) grows on Cu?O?(111) surfaces. We used the CeOx/Cu?O/Cu(111) inverse system to study two catalytic processes: the WGS (CO + H?O ? CO? + H?) and CO oxidation (2CO + O? ? 2CO?). We discovered that the addition of small amounts of ceria nanoparticles can activate the Cu(111) surface and achieve remarkable enhancement of catalytic activity in the investigated reactions. In the case of the WGS, the CeOx nanoparticle facilitated this process by acting at the interface with Cu to dissociate water. In the CO oxidation case, an enhancement in the dissociation of O? by the nanoparticles was a key factor. The strong interaction between CeOx nanoparticles and Cu(111) when preoxidized and reduced in CO resulted in a massive surface reconstruction of the copper substrate with the introduction of microterraces that covered 25-35% of the surface. This constitutes a new mechanism for surface reconstruction not observed before. These microterraces helped to facilitate a further enhancement of activity towards the WGS by opening an additional channel for the dissociation of water. In summary, inverse catalysts of CeOx/Cu(111) and CeO?/Cu?O/Cu(111) demonstrate the versatility of a model system to obtain insightful knowledge of catalytic processes. These systems will continue to offer a unique opportunity to probe key catalytic components and elucidate the relationship between structure and reactivity of novel materials and reactions in the future. PMID:23286528

Senanayake, Sanjaya D; Stacchiola, Dario; Rodriguez, Jose A

2013-08-20

33

Biological Water Gas Shift DOE Hydrogen, Fuel Cell, and Infrastructure  

E-print Network

­ Physiology and Molecular Biology: · Understand the microbe's genetic system for genetic engineering for water-gas shift ­ Integrated Engineering and Operation: · Increase reactor productivity · Operate ­ Integrated Engineering and Operation: · Understand high-pressure bioreactor dynamics #12;Project Timeline

34

Active Nonmetallic Au and Pt Species on Ceria-Based Water-Gas Shift Catalysts  

Microsoft Academic Search

Traditional analysis of reactions catalyzed by supported metals involves the structure of the metallic particles. However, we report here that for the class of nanostructured gold- or platinum-cerium oxide catalysts, which are active for the water-gas shift reaction, metal nanoparticles do not participate in the reaction. Nonmetallic gold or platinum species strongly associated with surface cerium-oxygen groups are responsible for

Qi Fu; Howard Saltsburg; Maria Flytzani-Stephanopoulos

2003-01-01

35

Statistical optimization by response surface methodology for water-gas shift reaction in a H 2-rich stream over Cu–Zn–Fe composite-oxide catalysts  

Microsoft Academic Search

The catalytic performance of Cu–Zn–Fe composite-oxide catalysts prepared by the urea–nitrate combustion (UNC) method for the WGS reaction was investigated in this study. The catalysts were characterized by means of X-ray diffraction (XRD), X-ray fluorescence (XRF), and the Brunauer–Emmet–Teller (BET) method. In order to reduce the total number of experiments to achieve the optimal condition of CO conversion in the

Nutthavich Thouchprasitchai; Apanee Luengnaruemitchai; Sangobtip Pongstabodee

2011-01-01

36

The Integration of a Structural Water Gas Shift Catalyst with a Vanadium Alloy Hydrogen Transport Device  

SciTech Connect

This project is in response to a requirement for a system that combines water gas shift technology with separation technology for coal derived synthesis gas. The justification of such a system would be improved efficiency for the overall hydrogen production. By removing hydrogen from the synthesis gas stream, the water gas shift equilibrium would force more carbon monoxide to carbon dioxide and maximize the total hydrogen produced. Additional benefit would derive from the reduction in capital cost of plant by the removal of one step in the process by integrating water gas shift with the membrane separation device. The answer turns out to be that the integration of hydrogen separation and water gas shift catalysis is possible and desirable. There are no significant roadblocks to that combination of technologies. The problem becomes one of design and selection of materials to optimize, or at least maximize performance of the two integrated steps. A goal of the project was to investigate the effects of alloying elements on the performance of vanadium membranes with respect to hydrogen flux and fabricability. Vanadium was chosen as a compromise between performance and cost. It is clear that the vanadium alloys for this application can be produced, but the approach is not simple and the results inconsistent. For any future contracts, large single batches of alloy would be obtained and rolled with larger facilities to produce the most consistent thin foils possible. Brazing was identified as a very likely choice for sealing the membranes to structural components. As alloying was beneficial to hydrogen transport, it became important to identify where those alloying elements might be detrimental to brazing. Cataloging positive and negative alloying effects was a significant portion of the initial project work on vanadium alloying. A water gas shift catalyst with ceramic like structural characteristics was the second large goal of the project. Alumina was added as a component of conventional high temperature water gas shift iron oxide based catalysts. The catalysts contained Fe-Al-Cr-Cu-O and were synthesized by co-precipitation. A series of catalysts were prepared with 5 to 50 wt% Al2O3, with 8 wt% Cr2O3, 4 wt% CuO, and the balance Fe2O3. All of the catalysts were compared to a reference WGS catalyst (88 wt% FeOx, 8 wt% Cr2O3, and 4 wt% CuO) with no alumina. Alumina addition to conventional high temperature water gas shift catalysts at concentrations of approximately 15 wt% increased CO conversion rates and increase thermal stability. A series of high temperature water gas shift catalysts containing iron, chromia, and copper oxides were prepared with small amounts of added ceria in the system Fe-Cr-Cu-Ce-O. The catalysts were also tested kinetically under WGS conditions. 2-4 wt% ceria addition (at the expense of the iron oxide content) resulted in increased reaction rates (from 22-32% higher) compared to the reference catalyst. The project goal of a 10,000 liter per day WGS-membrane reactor was achieved by a device operating on coal derived syngas containing significant amounts of carbon monoxide and hydrogen sulfide. The membrane flux was equivalent to 52 scfh/ft2 based on a 600 psi syngas inlet pressure and corresponded to membranes costing $191 per square foot. Over 40 hours of iv exposure time to syngas has been achieved for a double membrane reactor. Two modules of the Chart reactor were tested under coal syngas for over 75 hours with a single module tested for 50 hours. The permeance values for the Chart membranes were similar to the REB reactor though total flux was reduced due to significantly thicker membranes. Overall testing of membrane reactors on coal derived syngas was over 115 hours for all reactors tested. Testing of the REB double membrane device exceeded 40 hours. Performance of the double membrane reactor has been similar to the results for the single reactor with good maintenance of flux even after these long exposures to hydrogen sulfide. Of special interest is that the flux is highest at the start of each e

Barton, Thomas; Argyle, Morris; Popa, Tiberiu

2009-06-30

37

Trends in low-temperature water–gas shift reactivity on transition metals  

Microsoft Academic Search

Low-temperature water–gas shift reactivity trends on transition metals were investigated with the use of a microkinetic model based on a redox mechanism. It is established that the adsorption energies for carbon monoxide and oxygen can describe to a large extent changes in the remaining activation and adsorption energies through linear correlations. In comparisons with experimental data it is found that

N. Schumacher; A. Boisen; S. Dahl; Amit A. Gokhale; Shampa Kandoi; Lars C. Grabow; James A. Dumesic; Manos Mavrikakis; I. Chorkendorff

2005-01-01

38

Atomistic Thermodynamic Approach for Determining Cu Catalyst Morphologies Under Reactive Water-Gas-Shift Conditions  

NASA Astrophysics Data System (ADS)

The water gas shift reactions (WGS) are widely used in several industrial processes and are catalyzed by Cu catalysts. In coal derived syngas, there are sulfur (S) impurities which can adsorb on the Cu surfaces and block the active sites of the catalyst and can result in catalyst deactivation. The sulfur adsorption will compete with other possible adsorbates such as CO, O, H and CO2 making a quantitative estimate of the impact of sulfur on reactivity difficult. To determine the interactions between these possible adsorbates with Cu, the adsorption properties of these different adsorbates on low Miller index facets of Cu surfaces were studied in the limit where these surfaces are in thermodynamic equilibrium with the reactive environment. The effect of S adsorption on the surface electronic structure was significant and coverage dependent. In addition to a site-blocking deactivation mechanism, we found that sulfur modifies the surface electronic structure in a way that makes the Cu less reactive. Our results show that the adsorbates play a key role in defining the catalyst morphologies. We conclude that the presence of sulfur and other reactive adsorbates can impact the reactivity of the catalysts through several mechanisms including site-blocking, surface electronic structure modification and changes in the distribution and types of reactive sites through catalyst morphology changes.

Inoglu, Nilay; Kitchin, John

2009-03-01

39

Microkinetics of water-gas shift over sulfided Mo/Al{sub 2}O{sub 3} catalysts  

SciTech Connect

A microkinetic model was developed to explain the catalysis of the water-gas shift reaction by sulfided, alumina-supported molybdenum. IN this model, the reaction takes place through a regenerative (reduction-oxidation) scheme wherein the catalyst surface is alternately oxidized by water and then reduced by carbon monoxide. The surface of the catalyst is equilibrated with gas-phase H{sub 2}S under all reaction conditions studied. Coverages predicted by the model are consistent with the adsorption behavior of molybdenum sulfide catalysts. Simulations indicate that the effects of steam and H{sub 2}S levels are closely related. A maximum in CO conversion with increasing steam level may only occur at certain H{sub 2}S levels, and the ordering of CO conversion with increasing H{sub 2}S levels may invert as the steam level is changed.

Lund, C.R.F. [SUNY, Buffalo, NY (United States). Chemical Engineering Dept.] [SUNY, Buffalo, NY (United States). Chemical Engineering Dept.

1996-08-01

40

Integrated Water Gas Shift Membrane Reactors Utilizing Novel, Non Precious Metal Mixed Matrix Membrane  

SciTech Connect

Nanoparticles of zeolitic imidazolate frameworks and other related hybrid materials were prepared by modifying published synthesis procedures by introducing bases, changing stoichiometric ratios, or adjusting reaction conditions. These materials were stable at temperatures >300 °C and were compatible with the polymer matrices used to prepare mixed- matrix membranes (MMMs). MMMs tested at 300 °C exhibited a >30 fold increase in permeability, compared to those measured at 35 °C, while maintaining H{sub 2}/CO{sub 2} selectivity. Measurements at high pressure (up to 30 atm) and high temperature (up to 300 °C) resulted in an increase in gas flux across the membrane with retention of selectivity. No variations in permeability were observed at high pressures at either 35 or 300 °C. CO{sub 2}-induced plasticization was not observed for Matrimid®, VTEC, and PBI polymers or their MMMs at 30 atm and 300 °C. Membrane surface modification by cross-linking with ethanol diamine resulted in an increase in H{sub 2}/CO{sub 2} selectivity at 35 °C. Spectrometric analysis showed that the cross-linking was effective to temperatures <150 °C. At higher temperatures, the cross-linked membranes exhibit a H{sub 2}/CO{sub 2} selectivity similar to the uncross-linked polymer. Performance of the polybenzimidazole (PBI) hollow fibers prepared at Santa Fe Science and Technology (SFST, Inc.) showed increased flux o to a flat PBI membrane. A water-gas shift reactor has been built and currently being optimized for testing under DOE conditions.

Ferraris, John

2013-09-30

41

Argonne National Laboratory Chemical Engineering Division Water-gas shift catalysis  

E-print Network

redox activity under WGS reaction conditions. * + CO *-COad * = metal surface site, adsorbs CO 2MO2 Laboratory Chemical Engineering Division Use of modeling helps define our goals · The shift reaction is under

42

An Investigation of the Reverse Water Gas Shift Process and Operating Alternatives  

NASA Technical Reports Server (NTRS)

The Reverse Water Gas Shift (RWGS) process can produce water and ultimately oxygen through electrolysis. This technology is being investigated for possible use in the exploration of Mars as well as a potential process to aid in the regeneration of oxygen from carbon dioxide. The initial part of this report summarizes the results obtained from operation of the RWGS process at Kennedy Space Center during May and June of this year. It has been demonstrated that close to complete conversion can be achieved with the RWGS process under certain operating conditions. The report also presents results obtained through simulation for an alternative staged configuration for RWGS which eliminates the recycle compressor. This configuration looks promising and hence seems worthy of experimental investigation.

Whitlow, Jonathan E.

2002-01-01

43

Slurry phase Fischer-Tropsch synthesis: Cobalt plus a water-gas shift catalyst  

SciTech Connect

This report details experiments performed on three different copper-based catalysts: Cu/Cr[sub 2]O[sub 3], Cu/MnO/Cr[sub 2]O[sub 3] and Cu/ZnO/Al[sub 2]O[sub 3]. Of these three catalysts, the Cu/ZnO/Al[sub 2]O[sub 3] exhibits the greatest stability when slurried in octacosane. More than 1000 hours-on-stream indicate that the catalyst activity is not detrimentally affected by high pressure, high H[sub 2]/CO ratio, or the presence of alkenes. All of these are necessary stability characteristics for the water-gas shift catalyst, if it is to be used in combination with a cobalt Fischer-Tropsch catalyst. A review of documented reduction procedures for cobalt-based Fischer-Tropsch catalysts is presented.

Yates, I.C.; Satterfield, C.N.

1988-01-01

44

X-ray structure and reactivity of (Ru(bpy)/sub 2/(CO)H)PF/sub 6/ x 1/2 C/sub 3/H/sub 6/O (bpy = 2,2'-bipyridyl), a possible intermediate in the water-gas shift reaction catalyzed by ruthenium polypyridyl complexes  

SciTech Connect

The structure of (Ru(C/sub 10/H/sub 8/N/sub 2/)/sub 2/(CO)H)PF/sub 6/ x 1/2 C/sub 3/H/sub 6/O is reported. The compound crystallizes in the monoclinic C2/c space group with unit cell parameters a = 26.680 (4) A, b = 7.005 (3) A, c = 25.936 (2) A, and ..beta.. = 93.96 (2)/sup 0/ (V = 4836.04 A/sup 3/, Z = 8). The cationic species has a cis geometry for CO and H. The ruthenium-hydride and ruthenium-carbon distances are 1.68 (4) and 1.804 (6) A, respectively. The average ruthenium-nitrogen distance is 2.109 A. In acidic solution the title compound acts as a hydride donor to produce dihydrogen gas in a pseudo-first-order reaction; the second-order rate constant for this reaction is 0.105 -/+ 0.01 dm/sup 3/ mol/sup -1/ s/sup -1/ at 303 K with an activation energy 56 -/+ 2 kJ mol/sup -1/. A value of -100 -/+ 8 J mol/sup -1/ deg/sup -1/ has been obtained for the entropy of activation. The consequences of these results for the possible reaction mechanism of the homogeneous water-gas shift reaction catalyzed by (Ru(bpy)/sub 2/(CO)Cl)/sup +/ are discussed. 15 references, 4 figures, 6 tables.

Haasnoot, J.G.; Hinrichs, W.; Weir, O.; Vos, J.G.

1986-11-05

45

A Survey on Various Carbon Sources for Biological Hydrogen Production via the Water-Gas Reaction Using a Photosynthetic Bacterium (Rhodospirillum rubrum)  

Microsoft Academic Search

Growth model of anaerobic photosynthetic bacteria on various carbon sources for fermentative hydrogen production growth from synthesis gas was investigated. It was found that the rate of utilization of carbon monoxide (CO) by Rhodospirillum rubrum on acetate was growth related. A biologically based water-gas shift reaction was catalyzed by the specific bacterium at ambient temperature to convert the gaseous substrate,

Ghasem Najafpour; Habibollah Younesi; Abdul Rahman Mohamed

2006-01-01

46

A Comparative Study of the Water Gas Shift Reaction Over Platinum Catalysts Supported on CeO2, TiO2 and Ce-Modified TiO2  

SciTech Connect

WGS reaction has been investigated on catalysts based on platinum supported over CeO{sub 2}, TiO{sub 2} and Ce-modified TiO{sub 2}. XPS and XANES analyses performed on calcined catalysts revealed a close contact between Pt precursors and cerium species on CeO{sub 2} and Ce-modified TiO{sub 2} supports. TPR results corroborate the intimate contact between Pt and cerium entities in the Pt/Ce-TiO{sub 2} catalyst that facilitates the reducibility of the support at low temperatures while the Ce-O-Ti surface interactions established in the Ce-modified TiO{sub 2} support decreases the reduction of TiO{sub 2} at high temperature. The changes in the support reducibility leads to significant differences in the WGS activity of the studied catalysts. Pt supported on Ce-modified TiO{sub 2} support exhibits better activity than those corresponding to individual CeO{sub 2} and TiO{sub 2}-supported catalysts. Additionally, the Ce-TiO{sub 2}-supported catalyst displays better stability at reaction temperatures higher than 573 K that observed on pure TiO{sub 2}-supported counterpart. Activity measurements, when coupled with the physicochemical characterization of catalysts suggest that the modifications in the surface reducibility of the support play an essential role in the enhancement of activity and stability observed when Pt is supported on the Ce-modified TiO{sub 2} substrate.

Gonzalez, I.; Navarro, R; Wen, W; Marinkovic, N; Rodriguez, J; Rosa, F; Fierro, J

2010-01-01

47

Atomic level study of water-gas shift catalysts via transmission electron microscopy and x-ray spectroscopy  

NASA Astrophysics Data System (ADS)

Water-gas shift (WGS), CO + H2O ? CO2 + H2 (DeltaH° = -41 kJ mol -1), is an industrially important reaction for the production of high purity hydrogen. Commercial Cu/ZnO/Al2O3 catalysts are employed to accelerate this reaction, yet these catalysts suffer from certain drawbacks, including costly regeneration processes and sulfur poisoning. Extensive research is focused on developing new catalysts to replace the current technology. Supported noble metals stand out as promising candidates, yet comprise intricate nanostructures complicating the understanding of their working mechanism. In this study, the structure of the supported Pt catalysts is explored by transmission electron microscopy and X-ray spectroscopy. The effect of the supporting phase and the use of secondary metals on the reaction kinetics is investigated. Structural heterogeneities are quantified and correlated with the kinetic descriptors of the catalysts to develop a fundamental understanding of the catalytic mechanism. The effect of the reaction environment on catalyst structure is examined by in-situ techniques. This study benefitted greatly from the use of model catalysts that provide a convenient medium for the atomic level characterization of nanostructures. Based on these studies, Pt supported on iron oxide nano islands deposited on inert spherical alumina exhibited 48 times higher WGS turnover rate (normalized by the total Pt surface area) than Pt supported on bulk iron oxide. The rate of aqueous phase glycerol reforming reaction of Pt supported on multiwall carbon nanotubes (MWCNT) is promoted by co-impregnating with cobalt. The synthesis resulted in a variety of nanostructures among which Pt-Co bimetallic nanoparticles are found to be responsible for the observed promotion. The unprecedented WGS rate of Pt supported on Mo2C is explored by forming Mo 2C patches on top of MWCNTs and the rate promotion is found to be caused by the Pt-Mo bimetallic entities.

Akatay, Mehmed Cem

48

Robust Low-Cost Water-Gas Shift Membrane Reactor for High-Purity Hydrogen Production form Coal-Derived Syngas  

SciTech Connect

This report details work performed in an effort to develop a low-cost, robust water gas shift membrane reactor to convert coal-derived syngas into high purity hydrogen. A sulfur- and halide-tolerant water gas shift catalyst and a sulfur-tolerant dense metallic hydrogen-permeable membrane were developed. The materials were integrated into a water gas shift membrane reactor in order to demonstrate the production of >99.97% pure hydrogen from a simulated coal-derived syngas stream containing 2000 ppm hydrogen sulfide. The objectives of the program were to (1) develop a contaminant-tolerant water gas shift catalyst that is able to achieve equilibrium carbon monoxide conversion at high space velocity and low steam to carbon monoxide ratio, (2) develop a contaminant-tolerant hydrogen-permeable membrane with a higher permeability than palladium, (3) demonstrate 1 L/h purified hydrogen production from coal-derived syngas in an integrated catalytic membrane reactor, and (4) conduct a cost analysis of the developed technology.

James Torkelson; Neng Ye; Zhijiang Li; Decio Coutinho; Mark Fokema

2008-05-31

49

Kinetic and spectroscopic study of catalysts for water-gas shift and nitrogen oxide removal  

NASA Astrophysics Data System (ADS)

Nitrogen oxides (NOx) are formed in high temperature combustion processes such as in power generation and motor vehicles. Increasingly stringent regulation of these harmful emissions continues to drive interest in developing, understanding and studying new catalytic formulations for exhaust aftertreatment. For mobile sources, predominantly heavy duty diesel engines, selective catalytic reduction (SCR) with NH3 has become the principal means of NO x abatement. An alternative technology developed, but now surpassed by SCR, is NOx Storage Reduction (NSR) catalysis. Both technologies have been studied in our laboratory and are the basis for this dissertation. We studied seven different lean NOx trap (LNT) monolith formulations for NSR ranging from 0.6 to 6.2 wt.% Pt and 4 to 20 wt.% Ba loadings on ?-Al 2O3. The noble metal component of a LNT oxidizes NO to NO 2 aiding in the storage of NO2 on the alkaline earth component. Before the storage component saturates, a reductant such as H2 is introduced into the vehicular exhaust and the stored NOx is released and reduced to N2. Once the storage component is free of NOx, reductant flow is ceased and storage is begun anew. Our research focused on understanding the effects that CO2 and H2O have on the storage capacity of the LNT over short as well as extended periods of time. We found that for high Ba loadings, CO 2 had a consistently detrimental effect on the fast NOx storage capacity (NSC), defined as the amount of NOx the catalyst can store before 1% of the inlet NOx is measured in the reactor outlet. Over long NOx storage periods, CO2 continued to inhibit storage compared to the same catalyst in CO2 free conditions. On low loadings of Ba, however, the inhibition of CO2 was significantly reduced. We found that the loading dependent characteristics of the Ba phase affected the way in which CO2 adsorbed on the storage component, which greatly affected the stability of the species on lower Ba loadings. The less stable adsorbed CO2 proved less competitive for NOx sorption sites, explaining the weak reduction of NSC by CO2 on low Ba loadings. Contrary to CO2, H2O exhibited both beneficial and inhibitory effects on the NSC. Over long periods of time, and at high Ba loadings, the addition of H2O in the feed increased the NSC, attributed to enhanced O2 spillover on the hydroxylated Ba surface allowing greater access to available NOx storage sites. When the Ba loading was reduced, the interaction sphere of Pt particles with the Ba storage component required for O2 to spillover to assist in NOx storage was reduced. Thus, despite the enhanced spillover capacity of oxygen on the hydroxylated storage component other NSC decreasing effects of H2O addition, such as Ba agglomeration, became more dominant and reduced the NSC. Recent developments in selective catalytic reduction have shown Cu and Fe/chabazite (CHA) based zeolites to be particularly well suited to sustaining high catalytic rates without degradation in the harsh environment of diesel engine exhaust. Little has been published about these catalysts as the academic community has just recently learned about the materials and their commercial implementation. Using operando X-ray absorption spectroscopy, combined with first-principles thermodynamics simulations and kinetic analysis, we have studied the nature of the Cu active site on Cu/SSZ-13, Cu/SAPO-34 and Cu/ZSM-5. Examining the catalysts under operando standard SCR conditions (300 ppm NO, 300 ppm NH3, 5% O2, 5% H2O and 5% CO2) showed the catalyst to be in a mixed Cu(I)-Cu(II) oxidation state. Neither the amount of Cu(I) nor Cu(II) individually correlated with the different rates measured on the various zeolite catalysts, and so we proposed that the SCR reaction progresses via a redox mechanism requiring both Cu(I) and Cu(II). First principles thermodynamic calculations found that the redox couple of Cu(I)H2O and Cu(II)(OH)2 were the most thermodynamically stable species of any of the OxHy variants modeled on Cu. The redox nature of the Cu active site was further investigated in a fo

Kispersky, Vincent Frederick

50

Redox cycle stability of mixed oxides used for hydrogen generation in the cyclic water gas shift process  

SciTech Connect

Graphical abstract: - Highlights: • Fe{sub 2}O{sub 3} modified with CaO, SiO{sub 2} and Al{sub 2}O{sub 3} was studied in cyclic water gas shift reactor. • For the first time stability of such oxides were tested for 100 redox cycles. • Optimally added oxides significantly improved the activity and the stability of Fe{sub 2}O{sub 3}. • Increased stability was attributed to the impediment of neck formation. - Abstract: Repeated cycles of the reduction of Fe{sub 3}O{sub 4} with reductive gas, e.g. hydrogen and subsequent oxidation of the reduced iron material with water vapor can be harnessed as a process for the production of pure hydrogen. The redox behavior of iron oxide modified with various amounts of SiO{sub 2}, CaO and Al{sub 2}O{sub 3} was investigated in the present study. The total amount of the additional metal oxides was always below 15 wt%. The samples were prepared by co-precipitation using urea hydrolysis method. The influence of various metal oxides on the hydrogen production capacity and the material stability was studied in detail in terms of temperature-programmed reduction (TPR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET analysis. Furthermore, the activity and the stability of the samples were tested in repeated reduction with diluted H{sub 2} and re-oxidation cycles with H{sub 2}O. The results indicate that combination of several oxides as promoter increases the stability of the iron oxide material by mitigating the sintering process. The positive influence of the oxides in stabilizing the iron oxide material is attributed to the impediment of neck formation responsible for sintering.

Datta, Pradyot, E-mail: pradyot.datta@gmail.com

2013-10-15

51

Size and support effects for the water-gas shift catalysis over gold nanoparticles supported on model Al2O3 and TiO2.  

PubMed

The water-gas shift (WGS) reaction rate per total mole of Au under 7% CO, 8.5% CO(2), 22% H(2)O, and 37% H(2) at 1 atm for Au/Al(2)O(3) catalysts at 180 °C and Au/TiO(2) catalysts at 120 °C varies with the number average Au particle size (d) as d(-2.2±0.2) and d(-2.7±0.1), respectively. The use of nonporous and crystalline, model Al(2)O(3) and TiO(2) supports allowed the imaging of the active catalyst and enabled a precise determination of the Au particle size distribution and particle shape using transmission electron microscopy (TEM). Further, the apparent reaction orders and the stretching frequency of CO adsorbed on Au(0) (near 2100 cm(-1)) determined by diffuse reflectance infrared spectroscopy (DRIFTS) depend on d. Because of the changes in reaction rates, kinetics, and the CO stretching frequency with number average Au particle size, it is determined that the dominant active sites are the low coordinated corner Au sites, which are 3 and 7 times more active than the perimeter Au sites for Au/Al(2)O(3) and Au/TiO(2) catalysts, respectively, and 10 times more active for Au on TiO(2) versus Al(2)O(3). From operando Fourier transform infrared spectroscopy (FTIR) experiments, it is determined that the active Au sites are metallic in nature. In addition, Au/Al(2)O(3) catalysts have a higher apparent H(2)O order (0.63) and lower apparent activation energy (9 kJ mol(-1)) than Au/TiO(2) catalysts with apparent H(2)O order of -0.42 to -0.21 and activation energy of 45-60 kJ mol(-1) at near 120 °C. From these data, we conclude that the support directly participates by activating H(2)O molecules. PMID:22316316

Shekhar, Mayank; Wang, Jun; Lee, Wen-Sheng; Williams, W Damion; Kim, Seung Min; Stach, Eric A; Miller, Jeffrey T; Delgass, W Nicholas; Ribeiro, Fabio H

2012-03-14

52

Slurry phase Fischer-Tropsch synthesis: Cobalt plus a water-gas shift catalyst. [Quarterly] report, June 30, 1988--September 30, 1988  

SciTech Connect

This report details experiments performed on three different copper-based catalysts: Cu/Cr{sub 2}O{sub 3}, Cu/MnO/Cr{sub 2}O{sub 3} and Cu/ZnO/Al{sub 2}O{sub 3}. Of these three catalysts, the Cu/ZnO/Al{sub 2}O{sub 3} exhibits the greatest stability when slurried in octacosane. More than 1000 hours-on-stream indicate that the catalyst activity is not detrimentally affected by high pressure, high H{sub 2}/CO ratio, or the presence of alkenes. All of these are necessary stability characteristics for the water-gas shift catalyst, if it is to be used in combination with a cobalt Fischer-Tropsch catalyst. A review of documented reduction procedures for cobalt-based Fischer-Tropsch catalysts is presented.

Yates, I.C.; Satterfield, C.N.

1988-12-31

53

Effect of adding Co to MoS{sub 2}/Al{sub 2}O{sub 3} upon the kinetics of the water-gas shift  

SciTech Connect

A microkinetic model for the kinetics of the water-gas shift over sulfided CoMo/Al{sub 2}O{sub 3} catalysts was developed starting from a similar model for unpromoted sulfided Mo/Al{sub 2}O{sub 3} catalysts. Co was found to promote the catalyst`s activity only at low CO/H{sub 2}O ratios; at high ratios the Mo catalyst was marginally more active than the CoMo catalyst. The most important different between the two models was the strength of interactions between the surface and hydroxyl groups. The addition of Co increased the stability of hydroxyl groups relative to sulfhydryl groups, and at higher H{sub 2}O concentrations this allowed oxidized surface sites to more readily participate in both steam adsorption and hydrogen desorption steps. The results are most easily reconciled in terms of a promotional model where the Co and Mo are in close proximity and the active sites are similar to sites on unpromoted Mo catalysts.

Lund, C.R.F. [State Univ. of New York, Buffalo, NY (United States). Dept. of Chemical Engineering] [State Univ. of New York, Buffalo, NY (United States). Dept. of Chemical Engineering

1996-09-01

54

Impact of Contaminants Present in Coal-Biomass Derived Synthesis Gas on Water-gas Shift and Fischer-Tropsch Synthesis Catalysts  

SciTech Connect

Co-gasification of biomass and coal in large-scale, Integrated Gasification Combined Cycle (IGCC) plants increases the efficiency and reduces the environmental impact of making synthesis gas ("syngas") that can be used in Coal-Biomass-to-Liquids (CBTL) processes for producing transportation fuels. However, the water-gas shift (WGS) and Fischer-Tropsch synthesis (FTS) catalysts used in these processes may be poisoned by multiple contaminants found in coal-biomass derived syngas; sulfur species, trace toxic metals, halides, nitrogen species, the vapors of alkali metals and their salts (e.g., KCl and NaCl), ammonia, and phosphorous. Thus, it is essential to develop a fundamental understanding of poisoning/inhibition mechanisms before investing in the development of any costly mitigation technologies. We therefore investigated the impact of potential contaminants (H{sub 2}S, NH{sub 3}, HCN, AsH{sub 3}, PH{sub 3}, HCl, NaCl, KCl, AS{sub 3}, NH{sub 4}NO{sub 3}, NH{sub 4}OH, KNO{sub 3}, HBr, HF, and HNO{sub 3}) on the performance and lifetime of commercially available and generic (prepared in-house) WGS and FT catalysts; ferrochrome-based high-temperature WGS catalyst (HT-WGS, Shiftmax 120�, Süd-Chemie), low-temperature Cu/ZnO-based WGS catalyst (LT-WGS, Shiftmax 230�, Süd-Chemie), and iron- and cobalt-based Fischer-Trospch synthesis catalysts (Fe-FT & Co-FT, UK-CAER). In this project, TDA Research, Inc. collaborated with a team at the University of Kentucky Center for Applied Energy Research (UK-CAER) led by Dr. Burt Davis. We first conducted a detailed thermodynamic analysis. The three primary mechanisms whereby the contaminants may deactivate the catalyst are condensation, deposition, and reaction. AsH{sub 3}, PH{sub 3}, H{sub 2}S, HCl, NH{sub 3} and HCN were found to have a major impact on the Fe-FT catalyst by producing reaction products, while NaCl, KCl and PH{sub 3} produce trace amounts of deposition products. The impact of the contaminants on the activity, selectivity, and deactivation rates (lifetime) of the catalysts was determined in bench-scale tests. Most of the contaminants appeared to adsorb onto (or react with) the HT- and LT-WGS catalysts were they were co-fed with the syngas: � 4.5 ppmv AsH{sub 3} or 1 ppmv PH{sub 3} in the syngas impacted the selectivity and CO conversion of both catalysts; � H{sub 2}S slowly degraded both WGS catalysts; - A binary mixture of H{sub 2}S (60 ppmv) and NH{sub 3} (38 ppmv) impacted the activity of the LT-WGS catalyst, but not the HT-WGS catalyst � Moderate levels of NH{sub 3} (100 ppmv) or HCN (10 ppmv) had no impact � NaCl or KCl had essentially no effect on the HT-WGS catalyst, but the activity of the LT-WGS catalyst decreased very slowly Long-term experiments on the Co-FT catalyst at 260 and 270 °C showed that all of the contaminants impacted it to some extent with the exception of NaCl and HF. Irrespective of its source (e.g., NH{sub 3}, KNO{sub 3}, or HNO{sub 3}), ammonia suppressed the activity of the Co-FT catalyst to a moderate degree. There was essentially no impact the Fe-FT catalyst when up to 100 ppmw halide compounds (NaCl and KCl), or up to 40 ppmw alkali bicarbonates (NaHCO{sub 3} and KHCO{sub 3}). After testing, BET analysis showed that the surface areas, and pore volumes and diameters of both WGS catalysts decreased during both single and binary H2S and NH3 tests, which was attributed to sintering and pore filling by the impurities. The HT-WGS catalyst was evaluated with XRD after testing in syngas that contained 1 ppmv PH{sub 3}, or 2 ppmv H{sub 2}S, or both H{sub 2}S (60 ppmv) and NH{sub 3} (38 ppmv). The peaks became sharper during testing, which was indicative of crystal growth and sintering, but no new phases were detected. After LT-WGS tests (3-33 ppmv NH{sub 3} and/or 0-88 ppmv H{sub 2}S) there were a few new phases that appeared, including sulfides. The fresh Fe-FT catalyst was nanocrystalline and amorphous. ICP-AA spectroscopy and other methods (e.g., chromatography) were used to analyze for

Gokhan Alptekin

2012-09-30

55

Water gas furnace  

SciTech Connect

A water gas furnace comprising an outer container to provide a housing in which coke is placed into its lower part. A water container is placed within the housing. The coke is ignited and heats the water in the container converting it into steam. The steam is ejected into the coke, which together with air, produces water gas. Preferably, pumice stones are placed above the coke. The water gas is accepted into the pores of the pumice stones, where the heated pumice stones ignite the water gas, producing heat. The heat is extracted by a heat exchanger provided about the housing.

Gallaro, C.

1985-12-03

56

Application of Operando XAS, XRD, and Raman Spectroscopy for Phase Speciation in Water Gas Shift Reaction Catalysts  

E-print Network

and compositional changes of the partially reduced iron oxide Fe2O3 and 3% chromium oxide-modified iron oxide (3% Cr this approach, we chose an inherently complex catalytic system, a chromium oxide-modified iron oxide for high to avoid overreduction of the Fe3O4 active materials to lower oxides, carbides of metallic iron species

Frenkel, Anatoly

57

Water-gas process  

Microsoft Academic Search

This presents a method of producing gas from culm. The steps consist in igniting a body of the fuel, effecting partial combustion thereof, arresting such combustion before a substantial amount of the ash content has fused, passing steam through the partially consumed fuel to produce water gas, withdrawing most of the partially consumed fuel, and adding fresh fuel to replace

Dechant

1934-01-01

58

Sensitivity of Fischer-Tropsch Synthesis and Water-Gas Shift Catalysts to Poisons from High-Temperature High-Pressure Entrained-Flow (EF) Oxygen-Blown Gasifier Gasification of Coal/Biomass Mixtures  

SciTech Connect

There has been a recent shift in interest in converting not only natural gas and coal derived syngas to Fischer-Tropsch synthesis products, but also converting biomass-derived syngas, as well as syngas derived from coal and biomass mixtures. As such, conventional catalysts based on iron and cobalt may not be suitable without proper development. This is because, while ash, sulfur compounds, traces of metals, halide compounds, and nitrogen-containing chemicals will likely be lower in concentration in syngas derived from mixtures of coal and biomass (i.e., using entrained-flow oxygen-blown gasifier gasification gasification) than solely from coal, other compounds may actually be increased. Of particular concern are compounds containing alkali chemicals like the chlorides of sodium and potassium. In the first year, University of Kentucky Center for Applied Energy Research (UK-CAER) researchers completed a number of tasks aimed at evaluating the sensitivity of cobalt and iron-based Fischer-Tropsch synthesis (FT) catalysts and a commercial iron-chromia high temperature water-gas shift catalyst (WGS) to alkali halides. This included the preparation of large batches of 0.5%Pt-25%Co/Al{sub 2}O{sub 3} and 100Fe: 5.1Si: 3.0K: 2.0Cu (high alpha) catalysts that were split up among the four different entities participating in the overall project; the testing of the catalysts under clean FT and WGS conditions; the testing of the Fe-Cr WGS catalyst under conditions of co-feeding NaCl and KCl; and the construction and start-up of the continuously stirred tank reactors (CSTRs) for poisoning investigations. In the second and third years, researchers from the University of Kentucky Center for Applied Energy Research (UK-CAER) continued the project by evaluating the sensitivity of a commercial iron-chromia high temperature water-gas shift catalyst (WGS) to a number of different compounds, including KHCO{sub 3}, NaHCO{sub 3}, HCl, HBr, HF, H{sub 2}S, NH{sub 3}, and a combination of H{sub 2}S and NH{sub 3}. Cobalt and iron-based Fischer-Tropsch synthesis (FT) catalysts were also subjected to a number of the same compounds in order to evaluate their sensitivities at different concentration levels of added contaminant.

Burton Davis; Gary Jacobs; Wenping Ma; Dennis Sparks; Khalid Azzam; Janet Chakkamadathil Mohandas; Wilson Shafer; Venkat Ramana Rao Pendyala

2011-09-30

59

Sensitivity of Fischer-Tropsch Synthesis and Water-Gas Shift Catalystes to Poisons form High-Temperature High-Pressure Entrained-Flow (EF) Oxygen-Blown Gasifier Gasification of Coal/Biomass Mixtures  

SciTech Connect

There has been a recent shift in interest in converting not only natural gas and coal derived syngas to Fischer-Tropsch synthesis products, but also converting biomass-derived syngas, as well as syngas derived from coal and biomass mixtures. As such, conventional catalysts based on iron and cobalt may not be suitable without proper development. This is because, while ash, sulfur compounds, traces of metals, halide compounds, and nitrogen-containing chemicals will likely be lower in concentration in syngas derived from mixtures of coal and biomass (i.e., using entrained-flow oxygen-blown gasifier gasification gasification) than solely from coal, other compounds may actually be increased. Of particular concern are compounds containing alkali chemicals like the chlorides of sodium and potassium. In the first year, University of Kentucky Center for Applied Energy Research (UK-CAER) researchers completed a number of tasks aimed at evaluating the sensitivity of cobalt and iron-based Fischer-Tropsch synthesis (FT) catalysts and a commercial iron-chromia high temperature water-gas shift catalyst (WGS) to alkali halides. This included the preparation of large batches of 0.5%Pt-25%Co/Al{sub 2}O{sub 3} and 100Fe: 5.1Si: 3.0K: 2.0Cu (high alpha) catalysts that were split up among the four different entities participating in the overall project; the testing of the catalysts under clean FT and WGS conditions; the testing of the Fe-Cr WGS catalyst under conditions of co-feeding NaCl and KCl; and the construction and start-up of the continuously stirred tank reactors (CSTRs) for poisoning investigations.

Burton Davis; Gary Jacobs; Wenping Ma; Khalid Azzam; Janet ChakkamadathilMohandas; Wilson Shafer

2009-09-30

60

Sensitivity of Fischer-Tropsch Synthesis and Water-Gas Shift Catalysts to Poisons from High-Temperature High-Pressure Entrained-Flow (EF) Oxygen-Blown Gasifier Gasification of Coal/Biomass Mixtures  

SciTech Connect

The successful adaptation of conventional cobalt and iron-based Fischer-Tropsch synthesis catalysts for use in converting biomass-derived syngas hinges in part on understanding their susceptibility to byproducts produced during the biomass gasification process. With the possibility that oil production will peak in the near future, and due to concerns in maintaining energy security, the conversion of biomass-derived syngas and syngas derived from coal/biomass blends to Fischer-Tropsch synthesis products to liquid fuels may provide a sustainable path forward, especially considering if carbon sequestration can be successfully demonstrated. However, one current drawback is that it is unknown whether conventional catalysts based on iron and cobalt will be suitable without proper development because, while ash, sulfur compounds, traces of metals, halide compounds, and nitrogen-containing chemicals will likely be lower in concentration in syngas derived from mixtures of coal and biomass (i.e., using an entrained-flow oxygen-blown gasifier) than solely from coal, other byproducts may be present in higher concentrations. The current project examines the impact of a number of potential byproducts of concern from the gasification of biomass process, including compounds containing alkali chemicals like the chlorides of sodium and potassium. In the second year, researchers from the University of Kentucky Center for Applied Energy Research (UK-CAER) continued the project by evaluating the sensitivity of a commercial iron-chromia high temperature water-gas shift catalyst (WGS) to a number of different compounds, including KHCO{sub 3}, NaHCO{sub 3}, HCl, HBr, HF, H{sub 2}S, NH{sub 3}, and a combination of H{sub 2}S and NH{sub 3}. Cobalt and iron-based Fischer-Tropsch synthesis (FT) catalysts were also subjected to a number of the same compounds in order to evaluate their sensitivities.

Burtron Davis; Gary Jacobs; Wenping Ma; Khalid Azzam; Dennis Sparks; Wilson Shafer

2010-09-30

61

Phase shifts in alpha-frequency rhythm detected in electroencephalograms influence reaction time.  

PubMed

Although the phase shifts in ongoing oscillations seen in electroencephalograms (EEGs) and magnetoencephalograms are an important factor in discussions of phase dynamics, such as synchrony and reset, few studies have focused specifically on the phase shift. Here we investigate the relationship between phase shifts in alpha-frequency rhythms and reaction times during a visual simple reaction task by applying our previously described method (Naruse et al., 2013), which enables detection of phase shifts from a single EEG trial. In the left, parietal, and occipital areas, the reaction times in the trials in which phase shifts were detected before the button press were significantly longer than in those in which phase shifts were not so detected. These results indicate that phase shifts in the alpha and mu rhythms relate to variability in reaction times. PMID:25150125

Naruse, Yasushi; Takiyama, Ken; Okada, Masato; Umehara, Hiroaki; Sakaguchi, Yutaka

2015-02-01

62

Acceptance on the move: public reaction to shifting vaccination realities.  

PubMed

This review examines four events related to vaccination that have occurred in recent years: (a) the ongoing recovery from the MMR/Autism scare in the UK, (b) the upgrading of the Varicella vaccine to a universal childhood vaccine, (c) the major effort of authorities to provide a vaccine for A/H1N1 influenza and its rejection by the public, and, d) the current attempts to change the HPV vaccine target from girls only to boys and girls. All of these changes have been met with shifts in the public acceptance of the relevant vaccine. These shifts are characterized not only by the number of people willing to be vaccinated, but also by the attitudes and the motives related to acceptance. Examination of the interrelationship between changes in vaccination realities, and changes in acceptance patterns suggests that today, the public has a better understanding of vaccination, is acting in a more reflexive way, and is capable of changing attitudes and behavior. All together, changes in vaccination enhance debates and dialogues about vaccines, and lead to higher awareness and more conscious acceptance. PMID:22108039

Velan, Baruch

2011-12-01

63

Evaluation of C-14 as a natural tracer for injected fluids at theAidlin sector of The Geysers geothermal system through modeling ofmineral-water-gas Reactions  

SciTech Connect

A reactive-transport model for 14C was developed to test its applicability to the Aidlin geothermal system. Using TOUGHREACT, we developed a 1-D grid to evaluate the effects of water injection and subsequent water-rock-gas interaction on the compositions of the produced fluids. A dual-permeability model of the fracture-matrix system was used to describe reaction-transport processes in which the permeability of the fractures is many orders of magnitude higher than that of the rock matrix. The geochemical system included the principal minerals (K-feldspar, plagioclase, calcite, silica polymorphs) of the metagraywackes that comprise the geothermal reservoir rocks. Initial simulation results predict that the gas-phase CO2 in the reservoir will become more enriched in 14C as air-equilibrated injectate water (with a modern carbon signature) is incorporated into the system, and that these changes will precede accompanying decreases in reservoir temperature. The effects of injection on 14C in the rock matrix will be lessened somewhat because of the dissolution of matrix calcite with ''dead'' carbon.

Dobson, Patrick; Sonnenthal, Eric; Lewicki, Jennifer; Kennedy, Mack

2006-06-01

64

Electronic shift register memory based on molecular electron-transfer reactions  

NASA Technical Reports Server (NTRS)

The design of a shift register memory at the molecular level is described in detail. The memory elements are based on a chain of electron-transfer molecules incorporated on a very large scale integrated (VLSI) substrate, and the information is shifted by photoinduced electron-transfer reactions. The design requirements for such a system are discussed, and several realistic strategies for synthesizing these systems are presented. The immediate advantage of such a hybrid molecular/VLSI device would arise from the possible information storage density. The prospect of considerable savings of energy per bit processed also exists. This molecular shift register memory element design solves the conceptual problems associated with integrating molecular size components with larger (micron) size features on a chip.

Hopfield, J. J.; Onuchic, Jose Nelson; Beratan, David N.

1989-01-01

65

Red-shifted emission from 1,2-dioxetane-based chemiluminescent reactions.  

PubMed

Commercial chemiluminescent reagents emit across a broad portion of the electromagnetic spectrum (400-500?nm). A challenge to the use of chemiluminescence to monitor biological processes is the presence of interfering substances in the biological optical window. In the present study, longer wavelength emitting fluorophores (the organic dyes Alexa 568 and Alexa 647), and a semiconductor nanoparticle (QDOT800) were used to red-shift the emission from commercially available 1,2-dioxetane-based chemiluminescent substrate reactions. By adding non-conjugated fluorescent emitters into chemiluminescent reaction mixtures, an emission peak occurred at the predicted wavelength of the fluorescent emitter. The excitation and emission from QDOT800 was preserved in the presence of a 100?µm-thick glass barrier separating it from the chemiluminescent reaction components. The maximum tissue phantom penetration by QDOT800 emission was 8.5?mm; in comparison, the native chemiluminescent emission at 500?nm was unable to penetrate the thinnest tissue phantom of 2.5?mm. The described method for red-shifted emissions from chemiluminescent reactions does not require direct interaction between the chemiluminescent reaction and the fluorescent emitters. This suggests that the mechanism of chemiluminescent excitation of fluorophores and QDOT800 is not exclusive to chemiluminescence resonance energy transfer or sensitized chemiluminescence, but rather by broad energization from the native chemiluminescent emission. PMID:24760607

Park, Jason Y; Gunpat, Joshua; Liu, Li; Edwards, Brooks; Christie, Alana; Xie, Xian-Jin; Kricka, Larry J; Mason, Ralph P

2014-09-01

66

High-throughput electrophoretic mobility shift assays for quantitative analysis of molecular binding reactions.  

PubMed

We describe a platform for high-throughput electrophoretic mobility shift assays (EMSAs) for identification and characterization of molecular binding reactions. A photopatterned free-standing polyacrylamide gel array comprised of 8 mm-scale polyacrylamide gel strips acts as a chassis for 96 concurrent EMSAs. The high-throughput EMSAs was employed to assess binding of the Vc2 cyclic-di-GMP riboswitch to its ligand. In optimizing the riboswitch EMSAs on the free-standing polyacrylamide gel array, three design considerations were made: minimizing sample injection dispersion, mitigating evaporation from the open free-standing polyacrylamide gel structures during electrophoresis, and controlling unit-to-unit variation across the large-format free-standing polyacrylamide gel array. Optimized electrophoretic mobility shift conditions allowed for 10% difference in mobility shift baseline resolution within 3 min. The powerful 96-plex EMSAs increased the throughput to ?10 data/min, notably more efficient than either conventional slab EMSAs (?0.01 data/min) or even microchannel based microfluidic EMSAs (?0.3 data/min). The free-standing polyacrylamide gel EMSAs yielded reliable quantification of molecular binding and associated mobility shifts for a riboswitch-ligand interaction, thus demonstrating a screening assay platform suitable for riboswitches and potentially a wide range of RNA and other macromolecular targets. PMID:25233437

Pan, Yuchen; Duncombe, Todd A; Kellenberger, Colleen A; Hammond, Ming C; Herr, Amy E

2014-10-21

67

Glow Discharge Enhanced Chemical Reaction: Application in Ammonia Synthesis and Hydrocarbon Gas Cleanup  

E-print Network

reforming ........................................................................................ 12 2.1.5 Water gas shift reaction .............................................................................. 13 2.2 Plasma physics... and thus lower the required reaction temperatures and avoid unwanted by-product formation.[9] 2.2 Plasma physics Plasma is described as the fourth state of matter. Unlike solid, liquid and gas, plasma usually character with high energy, chemical...

Ming, Pingjia

2014-06-05

68

Water-Shift Reaction in the Intertubular Space of a Reactor for Steam Reforming of Natural Gas  

Microsoft Academic Search

An analysis is undertaken to study the experimentally established fact that, in the intertubular space of a reactor for steam reforming of methane, there is a water-shift reaction. A physical model is proposed to explain the possibility of the catalytic reaction in the absence of a specially prepared catalytic surface. It is assumed that there are two catalytic layers, one

M. Kh. Sosna; N. S. Evenchik; A. V. Sirotin

2003-01-01

69

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts  

SciTech Connect

The objective of the proposed research is to investigate and develop a novel catalytic process for the conversion of coal-derived synthesis gas into high octane C{sub 1}-C{sub 4} alcohols, especially ethanol, by a highly selective and efficient pathway. (VC)

Klier, K.; Herman, R.G.

1992-03-01

70

Lamb shift in radical-ion pairs produces a singlet-triplet energy splitting in photosynthetic reaction centers  

NASA Astrophysics Data System (ADS)

Radical-ion pairs, fundamental for understanding photosynthesis and the avian magnetic compass, were recently shown to be biological open quantum systems. We here show that the coupling of the radical-pair spin degrees of freedom to its decohering vibrational reservoir leads to a shift of the radical-pair magnetic energy levels. The Lamb shift Hamiltonian is diagonal in the singlet-triplet basis, and results in a singlet-triplet energy splitting physically indistinguishable from an exchange interaction. This could have significant implications for understanding the energy level structure and the dynamics of photosynthetic reaction centers.

Vitalis, K. M.; Kominis, I. K.

2014-09-01

71

A surface-plasmon resonance phase modulation bio-reaction detection system with (5,1) phase-shifting algorithm  

NASA Astrophysics Data System (ADS)

Surface plasmon resonance (SPR) is a very important metrology in biology detection. Phase modulation is one of the SPR detection technologies and the sample changes can be recognized from the phase variation. It is able to detect very tiny bio sample variation due to its high sensitivity. In this study, the optical system design based on a paraboloidal lens-based surface plasmon resonance instrument will be used to control the SPR critical angle. The charge coupled device camera (CCD camera) will be used to record the images of the bio-reaction and (5,1) phase-shifting algorithm will be adopted to retrieve the phase fringes of the whole spot from the intensity maps. The combination of the angle control SPR system and the (5,1) phase-shifting algorithm will expand the whole spot detection ability from the intensity to phase modulation because the intensity maps are going to be recorded for the (5,1) phase-shifting algorithm calculation. The difference between (5,1) phase-shifting algorithm and Five-Step Algorithm1 is that (5,1) phase-shifting algorithm only needs one image map at one time during the bio reaction and Five-Step Algorithm requires five image maps. Therefore, (5,1) phase-shifting algorithm will reduce the process of experiment and the requirement of the memory. The different concentration alcohols were measured by the optical system to verify the (5,1) phase-shifting algorithm applied in SPR phase modulation measurement and to prove the idea is workable and successful.

Chen, Yi-Hung; Lee, Shu-Sheng; Hsu, I.-Hung; Tseng, Eddie; Lee, Chih-Kung

2007-12-01

72

Decomposition of scattering phase shifts and reaction cross sections using the complex scaling method  

E-print Network

We apply the complex scaling method to the calculation of scattering phase shifts and extract the contributions of resonances in a phase shift and a cross section. The decomposition of the phase shift is shown to be useful to understand the roles of resonant and non-resonant continuum states. As examples, we apply this method to several two-body systems: (i) a schematic model with the Gyarmati potential which produces many resonances, (ii) the alpha-alpha system which has a Coulomb barrier potential in addition to an attractive nuclear interaction, and (iii) the alpha-n system which has no barrier potential. Using different kinds of potentials, we discuss the reliability of this method to investigate the resonance structure in the phase shifts and cross sections.

Myagmarjav Odsuren; Kiyoshi Kato; Masayuki Aikawa; Takayuki Myo

2014-03-21

73

Determination of shift in electrodic reaction rates due to the presence of stress  

NASA Astrophysics Data System (ADS)

An extension of Butler-Volmer formulation is proposed to determine the stress-induced changes in electrodic reaction rates. Gibbs-Duhem equation is used to determine the stress-dependent chemical potential and the corresponding change in the reaction rate. The scope of possible amplification or reduction in the reaction rates due to tensile and compressive stress fields is explored numerically. Though quantitative experimental validation remains to be pursued, behavioral agreement of the extended Butler-Volmer model with some observations made in the field of corrosive dissolution is established. Our numerical results also indicate that in addition to altering the speed of a reaction, a stress field can modify the shape of an anodic dissolution front. The effect of stress-generated surface patterns is also considered. It is well-established that a stress field can create surface patterns due to surface wrinkling or surface diffusion. We determine the possible significance of such patterns on the reaction rate, and identify the factors that may enhance their contribution to electrodic reaction rates.

Sarkar, Swarnavo; Aquino, Wilkins

2013-03-01

74

Behavioral reaction times are correlated with frequency shift in optical imaging signals  

NASA Astrophysics Data System (ADS)

Previous research has examined the relationships between physiological parameters and frequency oscillations in hemodynamic activity of brain. The current study used functional near infrared spectroscopy (fNIRS) to examine the relationship between oscillatory hemodynamics and performance measures during a standard cognitive task. fNIR data (n=7) were collected from 16 optodes distributed over dorsolateral prefrontal and inferior frontal cortex during a standard visual "oddball" task while behavioral reaction times to each stimulus were recorded. A frequency analysis of the fNIRS data revealed that the ratio of the power at 0-30 mHz to the power at 30-150 mHz was correlated with the number of mistakes a subject made as, well as their reaction times. Relatively greater low-frequency oscillations were associated with more mistakes and increased behavioral reaction times.

Akin, Ata; Bunce, Scott

2005-04-01

75

Changes in Mean Concentration, Phase Shifts, and Dissipation in a Forced Oscillatory Reaction  

NASA Astrophysics Data System (ADS)

Experiments are presented that confirm earlier predictions that the mode of supply of reactants to a nonlinear (bio)chemical reaction determines or controls concentrations at steady states far from equilibrium. The oxidation of nicotinamide adenine dinucleotide (NADH) catalyzed by the enzyme horseradish peroxidase with continuous input of oxygen was studied; NAD^+ is continuously recycled to NADH through a glucose-6-phosphate dehydrogenase system. A comparison of steady-state concentrations is made with an oscillatory oxygen input and a constant input at the same average oxygen input for both modes. By varying the frequency and amplitude of the perturbation (O_2 influx), the following may be changed: the average concentration of NADH; the Gibbs free energy difference ? G of the reactants and products at steady state; the average rate of the reaction; the phase relation between the oscillatory rate and ? G; and the dissipation. These results confirm the possibility of an "alternating current chemistry," of control and optimization of thermodynamic efficiency and dissipation by means of external variation of constraints in classes of nonlinear reactions and biological pumps, and of improvements of the yield in such reactions (heterogeneous catalysis, for example).

Lazar, James G.; Ross, John

1990-01-01

76

Producing hydrogen from coals by using a method of reaction integrated novel gasification (HyPr-RING)  

Microsoft Academic Search

A new hydrogen production process, named HyPr-RING, has been proposed. Basic concept of this process is integration of water carbon reaction, water-gas shift reaction and CO absorption in a single reactor. At first thermodynamic analysis was done to judge the possibility of this process. By thermodynamic analysis, high pressure and temperature condition, such as 20 MPa and 1000K, is required

S. Lin; Y. Suzuki; H. Hatano; M. Harada

1999-01-01

77

Enhancement of Equilibrium Shift in Dehydrogenation Reactions Using A Novel Membrane Reactor  

SciTech Connect

Electroless deposition of palladium thin-films on a surface of microporous ceramic substrate has been used to develop a new class of perm-selective inorganic membrane. In our previous two reports, we presented mathematical models to describe transport of hydrogen the palladium-ceramic composite membrane in single-stage permeation cell in cocurrent and countercurrent flow configurations. Analysis shows that the model equations have a singular point. In this report, a method is described how to avoid the singular point in order to solve the model equations numerically. To show the usefulness of the new method, a single-stage gas permeation for a three component system, without chemical reaction under cocurrent flow configuration has been used as an example.

Franklin G. King; Shamsuddin Ilias

1998-05-27

78

Overt and covert visual search in primates: reaction times and gaze shift strategies.  

PubMed

In order to investigate the search performance and strategies of nonhuman primates, two macaque monkeys were trained to search for a target template among differently oriented distractors in both free-gaze and fixed-gaze viewing conditions (overt and covert search). In free-gaze search, reaction times (RT) and eye movements revealed the theoretically predicted characteristics of exhaustive and self-terminating serial search, with certain exceptions that are also observed in humans. RT was linearly related to the number of fixations but not necessarily to the number of items on display. Animals scanned the scenes in a nonrandom manner spending notably more time on targets and items inspected last (just before reaction). The characteristics of free-gaze search were then compared with search performance under fixed gaze (covert search) and with the performance of four human subjects tested in similar experiments. By and large the performance characteristics of both groups were similar; monkeys were slightly faster, and humans more accurate. Both species produced shorter RT in fixed-gaze than in free-gaze search. But while RT slopes of the human subjects still showed the theoretically predicted difference between hits and rejections, slopes of the two monkeys appeared to collapse. Despite considerable priming and short-term learning when similar tests were continuously repeated, no substantial long-term training effects were seen when test conditions and set sizes were frequently varied. Altogether, the data reveal many similarities between human and monkey search behavior but indicate that search is not necessarily restricted to exclusively serial processes. PMID:19618485

Nothdurft, Hans-Christoph; Pigarev, Ivan N; Kastner, Sabine

2009-06-01

79

CO2 mitigation in coal gasification cogeneration systems with integration of the shift reaction, CO2 absorption and methanol production  

NASA Astrophysics Data System (ADS)

Cogeneration of electricity and liquid fuel can achieve higher efficiencies than electricity generation alone in Integrated Gasification Combined Cycle (IGCC), and cogeneration systems are also expected to mitigate CO2 emissions. A proposed methanol-electricity cogeneration system was analyzed in this paper using exergy method to evaluate the specified system. A simple cogeneration scheme and a complicated scheme including the shift reaction and CO2 removal were compared. The results show that the complicated scheme consumes more energy, but has a higher methanol synthesis ratio with partial capture of CO2. In those methanol and electricity cogeneration systems, the CO2 mitigation is not merely an additional process that consumes energy and reduces the overall efficiency, but is integrated into the methanol production.

Duan, Yuanyuan; Zhang, Jin

2004-08-01

80

Lewis acid-catalyzed redox-neutral amination of 2-(3-pyrroline-1-yl)benzaldehydes via intramolecular [1,5]-hydride shift/isomerization reaction  

PubMed Central

Summary Lewis acid-catalyzed redox-neutral amination of 2-(3-pyrroline-1-yl)benzaldehydes via intramolcular [1,5]-hydride shift/isomerization reaction has been realized, using the inherent reducing power of 3-pyrrolines. A series of N-arylpyrrole containing amines are obtained in high yields. PMID:25550755

Jiang, Chun-Huan; Lei, Xiantao; Zhen, Le; Du, Hong-Jin; Wen, Xiaoan

2014-01-01

81

Experimental distinction between phase shifts and time delays: Implications for femtosecond spectroscopy and coherent control of chemical reactions  

NASA Astrophysics Data System (ADS)

Two different definitions of phase shifts and time delays are contrasted and shown to match different experimental methods of generating delayed pulses. Phase shifts and time delays are usually defined in terms of a carrier wave in magnetic resonance, but definitions based on the envelope of a single pulse are useful in optics. It is demonstrated experimentally that a frequency domain measurement using spectral interferometry can simultaneously measure phase shifts with an accuracy of 0.1 rad (2?) and time delays with a precision of 40 attoseconds (2?) for 25 femtosecond optical pulses. Envelope time delays are generated by pathlength differences in an interferometer. Constant spectral phase shifts are demonstrated by diffracting pulses from a variable phase volume diffraction grating. Experimental requirements for phase-resolved spectroscopy are outlined. The theory of phase-locked pulse pair techniques is reexamined, and it is concluded that linear experiments with phase-locked pulse pairs are completely equivalent to Fourier transform absorption spectroscopy and do not measure the refractive index or real part of the susceptibility. It is shown that Fourier sine and cosine transformations of truncated time domain signals which do not match the symmetry of the complete signal can produce a false dispersive susceptibility because they are equivalent to Kramers-Kronig inversion of finite bandwidth absorption data. A procedure for shifting ?/2 phase-locked transients by a quarter cycle of delay to generate a transient with a ?/2 spectral phase shift is given. Equations used to calculate femtosecond nonlinear optical signals have assumed carrier wave delays. Modifications to these equations are required when envelope delays are generated by interferometer pathlength differences and modified equations are given. The modified equations yield significantly different results for phase-resolved or interferometric experiments. In particular, the modified equations are needed to calculate indirectly (interferometrically) detected frequencies and the real and imaginary parts of two-dimensional Fourier transform spectra. The role of the refractive index and real part of the frequency domain susceptibility in nonlinear experiments with phase-locked pulse pairs is explored. It is concluded that experiments such as the heterodyne detected stimulated photon echo are insensitive to nonlinear refractive index changes under some circumstances. Finally, modifications of some equations used in the theory of coherent control are needed to match theory with experimental practice.

Albrecht, Allison W.; Hybl, John D.; Gallagher Faeder, Sarah M.; Jonas, David M.

1999-12-01

82

Lifetime measurements by the Doppler-shift attenuation method in the {sup 115}Sn({alpha},n{gamma}){sup 118}Te reaction  

SciTech Connect

{gamma} rays were measured at several angles in both singles and coincidence modes in the {sup 115}Sn({alpha},n{gamma}){sup 118}Te reaction at 15 MeV on a thick target. Multipolarities and mixing ratios were determined from the {gamma}-ray angular distribution analysis. Lifetimes of 11 low- and medium-spin excited states in {sup 118}Te were determined from a Monte Carlo Doppler-shift attenuation method analysis of the Doppler broadened line shapes of {gamma} rays deexciting the levels. The results are discussed in comparison with the predictions of the interacting boson model.

Mihai, C. [Horia Hulubei National Institute of Physics and Nuclear Engineering, RO-077125 Bucharest (Romania); Faculty of Physics, University of Bucharest, Bucharest (Romania); Pasternak, A. A. [Cyclotron Laboratory, A.F. Ioffe Physical Technical Institute, 194021 St. Petersburg (Russian Federation); Pascu, S.; Filipescu, D.; Ivascu, M.; Bucurescu, D.; Cata-Danil, I.; Deleanu, D.; Ghita, D. G.; Glodariu, T.; Marginean, N.; Marginean, R.; Negret, A.; Sava, T.; Stroe, L.; Suliman, G.; Zamfir, N. V. [Horia Hulubei National Institute of Physics and Nuclear Engineering, RO-077125 Bucharest (Romania); Cata-Danil, G. [Horia Hulubei National Institute of Physics and Nuclear Engineering, RO-077125 Bucharest (Romania); Physics Department, University 'Politehnica' of Bucharest, Bucharest (Romania)

2011-05-15

83

Desulfurization of a coal model compound by in situ hydrogen generation through water-gas shift  

E-print Network

I ill I. -'I c, p C a~ . vnv v av ~J molybdate catalyst containing 2. 4 '4 Co and 6. 7 0 No Conversion data were obtained with a steaoy state flow reactor packed with particles of a commercial cobalt molybdate catalyst. Givens and Venuto (1970... o Benzofhzophene st bv Caly (:mnz Dal;, . J. Carat. i978) Considerable work has been done in order to explain the catalytic nature of the CoO-NoO -Al 0 during hydrode- 3 2 3 sulfurization. Desikan and Amberg (1963) proposed two site theory...

Kumar, Meyyappan

2012-06-07

84

Computational Chemistry-Based Identification of Ultra-Low Temperature Water-Gas-Shift Catalysts  

SciTech Connect

The current work seeks to identify novel, catalytically-active, stable, poison-resistant LWGS catalysts that retain the superior activity typical of conventional Cu catalysts but can be operated at similar or lower temperatures. A database for the Binding Energies (BEs) of the LWGS relevant species, namely CO, O and OH on the most-stable, close-packed facets of a set of 17 catalytically relevant transition metals was established. This BE data and a database of previously established segregation energies was utilized to predict the stability of bimetallic NSAs that could be synthesized by combinations of the 17 parent transition metals. NSAs that were potentially stable both in vacuo and under the influence of strong-binding WGS intermediates were then selected for adsorption studies. A set of 40 NSAs were identified that satisfied all three screener criteria and the binding energies of CO, O and OH were calculated on a set of 66, 43 and 79 NSA candidates respectively. Several NSAs were found that bound intermediates weaker than the monometallic catalysts and were thus potentially poison-resistant. Finally, kinetic studies were performed and resulted in the discovery of a specific NSA-based bimetallic catalyst Cu/Pt that is potentially a promising LWGS catalyst. This stable Cu/Pt subsurface alloy is expected to provide facile H{sub 2}O activation and remain relatively resistant from the poisoning by CO, S and formate intermediates.

Manos Mavrikakis

2008-08-31

85

SurfKin: an ab initio kinetic code for modeling surface reactions.  

PubMed

In this article, we describe a C/C++ program called SurfKin (Surface Kinetics) to construct microkinetic mechanisms for modeling gas-surface reactions. Thermodynamic properties of reaction species are estimated based on density functional theory calculations and statistical mechanics. Rate constants for elementary steps (including adsorption, desorption, and chemical reactions on surfaces) are calculated using the classical collision theory and transition state theory. Methane decomposition and water-gas shift reaction on Ni(111) surface were chosen as test cases to validate the code implementations. The good agreement with literature data suggests this is a powerful tool to facilitate the analysis of complex reactions on surfaces, and thus it helps to effectively construct detailed microkinetic mechanisms for such surface reactions. SurfKin also opens a possibility for designing nanoscale model catalysts. PMID:25111729

Le, Thong Nguyen-Minh; Liu, Bin; Huynh, Lam K

2014-10-01

86

Preparation of neuroprotective condensed 1,4-benzoxazepines by regio- and diastereoselective domino Knoevenagel–[1,5]-hydride shift cyclization reaction  

PubMed Central

Summary Condensed O,N-heterocycles containing tetrahydro-1,4-benzoxazepine and tetrahydroquinoline moieties were prepared by a regio- and diastereoselective domino Knoevenagel–[1,5]-hydride shift cyclization reaction of a 4-aryl-2-phenyl-1,4-benzoxazepine derivative obtained from flavanone. The relative configuration of products were determined by the correlation of 3 J H,H coupling data with the geometry of major conformers accessed by DFT conformational analysis. Separated enantiomers of the products were characterized by HPLC-ECD data, which allowed their configurational assignment on the basis of TDDFT-ECD calculation of the solution conformers. Two compounds showed neuroprotective activities against hydrogen peroxide (H2O2) or ?-amyloid25–35 (A?25–35)-induced cellular injuries in human neuroblastoma SH-SY5Y cells in the range of those of positive controls.

Tóth, László; Fu, Yan; Zhang, Hai Yan; Mándi, Attila; Kövér, Katalin E; Illyés, Tünde-Zita; Kiss-Szikszai, Attila; Balogh, Balázs; Kurtán, Tibor

2014-01-01

87

The Effect of Rain on Air-Water Gas Exchange  

NASA Technical Reports Server (NTRS)

The relationship between gas transfer velocity and rain rate was investigated at NASA's Rain-Sea Interaction Facility (RSIF) using several SF, evasion experiments. During each experiment, a water tank below the rain simulator was supersaturated with SF6, a synthetic gas, and the gas transfer velocities were calculated from the measured decrease in SF6 concentration with time. The results from experiments with IS different rain rates (7 to 10 mm/h) and 1 of 2 drop sizes (2.8 or 4.2 mm diameter) confirm a significant and systematic enhancement of air-water gas exchange by rainfall. The gas transfer velocities derived from our experiment were related to the kinetic energy flux calculated from the rain rate and drop size. The relationship obtained for mono-dropsize rain at the RSIF was extrapolated to natural rain using the kinetic energy flux of natural rain calculated from the Marshall-Palmer raindrop size distribution. Results of laboratory experiments at RSIF were compared to field observations made during a tropical rainstorm in Miami, Florida and show good agreement between laboratory and field data.

Ho, David T.; Bliven, Larry F.; Wanninkhof, Rik; Schlosser, Peter

1997-01-01

88

DFT study of the mechanisms of in water Au(I)-catalyzed tandem [3,3]-rearrangement/Nazarov reaction/[1,2]-hydrogen shift of enynyl acetates: a proton-transport catalysis strategy in the water-catalyzed [1,2]-hydrogen shift.  

PubMed

A computational study with the Becke3LYP density functional was carried out to elucidate the mechanisms of Au(I)-catalyzed reactions of enynyl acetates involving tandem [3,3]-rearrangement, Nazarov reaction, and [1,2]-hydrogen shift. Calculations indicate that the [3,3]-rearrangement is a two-step process with activation free energies below 10 kcal/mol for both steps. The following Nazarov-type 4pi electrocyclic ring-closure reaction of a Au-containing dienyl cation is also easy with an activation free energy of 3.2 kcal/mol in CH2Cl2. The final step in the catalytic cycle is a [1,2]-hydride shift, and this step is the rate-limiting step (with a computed activation free energy of 20.2 kcal/mol) when dry CH2Cl2 is used as the solvent. When this tandem reaction was conducted in wet CH2Cl2, the [1,2]-hydride shift step in dry solution turned to a very efficient water-catalyzed [1,2]-hydrogen shift mechanism with an activation free energy of 16.4 kcal/mol. Because of this, the tandem reaction of enynyl acetates was found to be faster in wet CH2Cl2 as compared to the reaction in dry CH2Cl2. Calculations show that a water-catalyzed [1,2]-hydrogen shift adopts a proton-transport catalysis strategy, in which the acetoxy group in the substrate is critical because it acts as either a proton acceptor when one water molecule is involved in catalysis or a proton-relay stabilizer when a water cluster is involved in catalysis. Water is found to act as a proton shuttle in the proton-transport catalysis strategy. Theoretical discovery of the role of the acetoxy group in the water-catalyzed [1,2]-hydrogen shift process suggests that a transition metal-catalyzed reaction involving a similar hydrogen shift step can be accelerated in water or on water with only a marginal effect, unless a proton-accepting group such as an acetoxy group, which can form a hydrogen bond network with water, is present around this reaction's active site. PMID:18027935

Shi, Fu-Qiang; Li, Xin; Xia, Yuanzhi; Zhang, Liming; Yu, Zhi-Xiang

2007-12-19

89

Shifting Attention  

ERIC Educational Resources Information Center

This article examines the shifts in attention and focus as one teacher introduces and explains an image that represents the processes involved in a numeric problem that his students have been working on. This paper takes a micro-analytic approach to examine how the focus of attention shifts through what the teacher and students do and say in the…

Ingram, Jenni

2014-01-01

90

Stick shift  

E-print Network

Stick Shift is a novel that has undergone several rounds of significant revision. Scott, the book's main character, is a sarcastic American who travels to England to move in with an ex-girlfriend. He experiences all of the ...

Parness, Aaron J. (Aaron Joseph), 1981-

2004-01-01

91

Thermochemical cyclic system for splitting water and/or carbon dioxide by means of cerium compounds and reactions useful therein  

DOEpatents

A thermochemical cyclic process for producing hydrogen from water comprises reacting ceric oxide with monobasic or dibasic alkali metal phosphate to yield a solid reaction product, oxygen and water. The solid reaction product, alkali metal carbonate or bicarbonate, and water, are reacted to yield hydrogen, ceric oxide, carbon dioxide and trialkali metal phosphate. Ceric oxide is recycled. Trialkali metal phosphate, carbon dioxide and water are reacted to yield monobasic or dibasic alkali metal phosphate and alkali metal bicarbonate, which are recycled. The cylic process can be modified for producing carbon monoxide from carbon dioxide by reacting the alkali metal cerous phosphate and alkali metal carbonate or bicarbonate in the absence of water to produce carbon monoxide, ceric oxide, carbon dioxide and trialkali metal phosphate. Carbon monoxide can be converted to hydrogen by the water gas shift reaction.

Bamberger, Carlos E. (Oak Ridge, TN); Robinson, Paul R. (Knoxville, TN)

1980-01-01

92

Fluid Shifts  

NASA Technical Reports Server (NTRS)

INTRODUCTION: Mechanisms responsible for the ocular structural and functional changes that characterize the visual impairment and intracranial pressure (ICP) syndrome (VIIP) are unclear, but hypothesized to be secondary to the cephalad fluid shift experienced in spaceflight. This study will relate the fluid distribution and compartmentalization associated with long-duration spaceflight with VIIP symptoms. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as the VIIP-related effects of those shifts, can be predicted preflight with acute hemodynamic manipulations, and also if lower body negative pressure (LBNP) can reverse the VIIP effects. METHODS: Physiologic variables will be examined pre-, in- and post-flight in 10 International Space Station crewmembers including: fluid compartmentalization (D2O and NaBr dilution); interstitial tissue thickness (ultrasound); vascular dimensions and dynamics (ultrasound and MRI (including cerebrospinal fluid pulsatility)); ocular measures (optical coherence tomography, intraocular pressure, ultrasound); and ICP measures (tympanic membrane displacement, otoacoustic emissions). Pre- and post-flight measures will be assessed while upright, supine and during 15 deg head-down tilt (HDT). In-flight measures will occur early and late during 6 or 12 month missions. LBNP will be evaluated as a countermeasure during HDT and during spaceflight. RESULTS: The first two crewmembers are in the preflight testing phase. Preliminary results characterize the acute fluid shifts experienced from upright, to supine and HDT postures (increased stroke volume, jugular dimensions and measures of ICP) which are reversed with 25 millimeters Hg LBNP. DISCUSSION: Initial results indicate that acute cephalad fluid shifts may be related to VIIP symptoms, but also may be reversible by LBNP. The effect of a chronic fluid shift has yet to be evaluated. Learning Objectives: Current spaceflight VIIP research is described, including novel hardware and countermeasures.

Stenger, M. B.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Laurie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Lui, J.; Macias, B.; Arbeille, P.; Danielson, R.; Chang, D.; Gunga, H.; Johnston, S.; Westby, C.; Ribeiro, L.; Ploutz-Snyder, R.; Smith, S.

2015-01-01

93

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts. Technical progress report, December 1991--February 1992  

SciTech Connect

The objective of the proposed research is to investigate and develop a novel catalytic process for the conversion of coal-derived synthesis gas into high octane C{sub 1}-C{sub 4} alcohols, especially ethanol, by a highly selective and efficient pathway. (VC)

Klier, K.; Herman, R.G.

1992-03-01

94

A Laboratory Study of the Schmidt Number Dependency of Air-Water Gas  

E-print Network

A Laboratory Study of the Schmidt Number Dependency of Air-Water Gas Transfer Kerstin Richter1 measurements in two different wind-wave facilities. Key Words: Schmidt number exponent, transfer velocity. Gas Transfer at Water Surfaces, Kyoto, May 17-21, 2010 copyright Kyoto University Press, 2011 #12

Jaehne, Bernd

95

Bridging silyl groups in sigma-bond metathesis and [1, 2] shifts. An experimental and computational study of the reaction between cerium metallocenes and MeOSiMe3  

SciTech Connect

The reaction of Cp'2CeH (Cp' = 1,2,4-(Me3C)3C5H2 ) with MeOSiMe3 gives Cp'2CeOMe and HSiMe3 and the reaction of the metallacycle, Cp'[(Me3C)2C5H2C(Me) 2CH2]Ce, with MeOSiMe3 yields Cp'2CeOCH2SiMe3, formed from hypothetical Cp'2CeCH2OSiMe3 by a [1, 2] shift also known as a silyl-Wittig rearrangement. Although both cerium products are alkoxides, they are formed by different pathways. DFT calculations on the reaction of the model metallocene, Cp2CeH, and MeOSiMe3 show that the lowest energy pathway is a H for OMe exchange at Ce that occurs by way of a sigma-bond metathesis transition state as SiMe3 exchanges partners. The formation of Cp2CeOCH2SiMe3 occurs by way of a low activation barrier [1, 2]shift of the SiMe3 group in Cp2CeCH2OSiMe3. Calculations on a model metallacycle, Cp[C5H4C(Me)2CH2]Ce, show that the metallacycle favors CH bond activation over sigma-bond metathesis involving the transfer of the SiMe3 group in good agreement with experiment. The sigma-bond metathesis involving the transfer of SiMe3 and the [1, 2]shift of SiMe3 reactions have in common a pentacoordinate silicon at the transition states. A molecular orbital analysis illustrates the connection between these two Si-O bond cleavage reactions and traces the reason why they occur for a silyl but not for an alkyl group to the difference in energy required to form a pentacoordinate silicon or carbon atom in the transition state. This difference clearly distinguishes a silyl from an alkyl group as shown in the study of"Pyrolysis of Tetramethylsilane Yielding Free d-orbitals by Seyferth and Pudvin in ChemTech 1981, 11, 230-233".

Werkema, Evan; Yahia, Ahmed; Maron, Laurent; Eisenstein, Odile; Andersen, Richard

2010-04-21

96

Fluid Shifts  

NASA Technical Reports Server (NTRS)

NASA is focusing on long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but more than 30% of ISS astronauts experience more profound, chronic changes with objective structural and functional findings such as papilledema and choroidal folds. Globe flattening, optic nerve sheath dilation, and optic nerve tortuosity also are apparent. This pattern is referred to as the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with the space flight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration space flight, and to correlate these findings with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during space flight, as well as the VIIP-related effects of those shifts, is predicted by the crewmember's pre-flight condition and responses to acute hemodynamic manipulations (such as head-down tilt). Lastly, we will evaluate the patterns of fluid distribution in ISS astronauts during acute reversal of fluid shifts through application of lower body negative pressure (LBNP) interventions to characterize and explain general and individual responses. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the Figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, calcaneus tissue thickness (by ultrasound); (3) vascular dimensions by ultrasound (jugular veins, cerebral and carotid arteries, vertebral arteries and veins, portal vein); (4) vascular dynamics by MRI (head/neck blood flow, cerebrospinal fluid pulsatility); (5) ocular measures (optical coherence tomography, intraocular pressure, 2-dimensional ultrasound including optic nerve sheath diameter, globe flattening, and retina-choroid thickness, Doppler ultrasound of ophthalmic and retinal arteries, and veins); (6) cardiac variables by ultrasound (inferior vena cava, tricuspid flow and tissue Doppler, pulmonic valve, stroke volume, right heart dimensions and function, four-chamber views); and (7) ICP measures (tympanic membrane displacement, distortion-product otoacoustic emissions, and ICP calculated by MRI). On the ground, acute head-down tilt will induce cephalad fluid shifts, whereas LBNP will oppose these shifts. Controlled Mueller maneuvers will manipulate cardiovascular variables. Through interventions applied before, during, and after flight, we intend to fully evaluate the relationship between fluid shifts and the VIIP syndrome. This study has been selected for flight implementation and is one of the candidate investigations being considered for the one year mission.

Stenger, Michael; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Sargsyan, A.; Martin, D.; Lui, J.; Macias, B.; Arbeille, P.; Platts, S.

2014-01-01

97

A fully coupled model for water-gas-heat reactive transport with methane oxidation in landfill covers.  

PubMed

Methane oxidation in landfill covers is a complex process involving water, gas and heat transfer as well as microbial oxidation. The coupled phenomena of microbial oxidation, water, gas, and heat transfer are not fully understood. In this study, a new model is developed that incorporates water-gas-heat coupled reactive transport in unsaturated soil with methane oxidation. Effects of microbial oxidation-generated water and heat are included. The model is calibrated using published data from a laboratory soil column test. Moreover, a series of parametric studies are carried out to investigate the influence of microbial oxidation-generated water and heat, initial water content on methane oxidation efficiency. Computed and measured results of gas concentration and methane oxidation rate are consistent. It is found that the coupling effects between water-gas-heat transfer and methane oxidation are significant. Ignoring microbial oxidation-generated water and heat can result in a significant difference in methane oxidation efficiency by 100%. PMID:25489976

Ng, C W W; Feng, S; Liu, H W

2015-03-01

98

The adsorption behavior of octafluoropropane at the water/gas interface  

NASA Astrophysics Data System (ADS)

We studied the adsorption behavior of the gas octafluoropropane at the water/gas interface as a function of different pressures. In a custom-made measurement cell, the gas pressure was varied in a range between 1 bar and close to the condensation pressure of octafluoropropane. The electron density profiles of the adsorption layers show that the layer thickness increases with pressure. The evolution of the layer electron density indicates that the bulk electron density is reached if a layer consisting of more than one monolayer of octafluoropropane is adsorbed on the water surface.

Giebel, Friederike; Paulus, Michael; Nase, Julia; Bieder, Steffen; Kiesel, Irena; Tolan, Metin

2014-12-01

99

In-water gas combustion in linear and annular gas bubbles  

NASA Astrophysics Data System (ADS)

A new pulsed-cyclic method of in-water gas combustion was developed with separate feed of fuel gas and oxygen with the focus on development of new technologies for heat generators and submerged propellers. The results of calorimetric and hydrodynamic measurements are presented. In-water combustion of acetylene, hydrogen, and propane was tested with the operation frequency of 2-2.5 Hz and with a linear injector. The combustion dynamics of combustion of stoichiometric mixture with propane (C3H8+5O2) was studied for a bubble near a solid wall; the produced gas bubble continues expansion and oscillations (for the case of linear and annular bubbles). It was demonstrated that gas combustion in annular bubbles produces two same-magnitude pulses of force acting on the wall. The first pulse is produced due to expansion of combustion products, and the second pulse is produced due to axial cumulative processes after bubble collapse. This process shapes an annular vortex which facilitates high-speed convective processes between combustion products and liquid; and this convection produces small-size bubbles.

Teslenko, V. S.; Drozhzhin, A. P.; Medvedev, R. N.; Batraev, I. S.

2014-08-01

100

Reactions of oxygen-containing molecules on transition metal carbides: Surface science insight into potential applications in catalysis and electrocatalysis  

NASA Astrophysics Data System (ADS)

Historically the interest in the catalytic properties of transition metal carbides (TMC) has been inspired by their "Pt-like" properties in the transformation reactions of hydrocarbon molecules. Recent studies, however, have revealed that the reaction pathways of oxygen-containing molecules are significantly different between TMCs and Pt-group metals. Nonetheless, TMCs demonstrate intriguing catalytic properties toward oxygen-containing molecules, either as the catalyst or as the catalytically active substrate to support metal catalysts, in several important catalytic and electrocatalytic applications, including water electrolysis, alcohol electrooxidation, biomass conversion, and water gas shift reactions. In the current review we provide a summary of theoretical and experimental studies of the interaction of TMC surfaces with oxygen-containing molecules, including both inorganic (O2, H2O, CO and CO2) and organic (alcohols, aldehydes, acids and esters) molecules. We will discuss the general trends in the reaction pathways, as well as future research opportunities in surface science studies that would facilitate the utilization of TMCs as catalysts and electrocatalysts.

Stottlemyer, Alan L.; Kelly, Thomas G.; Meng, Qinghe; Chen, Jingguang G.

2012-09-01

101

Reactions of oxygen-containing molecules on transition metal carbides: Surface science insight into potential applications in catalysis and electrocatalysis  

NASA Astrophysics Data System (ADS)

Historically the interest in the catalytic properties of transition metal carbides (TMC) has been inspired by their “Pt-like” properties in the transformation reactions of hydrocarbon molecules. Recent studies, however, have revealed that the reaction pathways of oxygen-containing molecules are significantly different between TMCs and Pt-group metals. Nonetheless, TMCs demonstrate intriguing catalytic properties toward oxygen-containing molecules, either as the catalyst or as the catalytically active substrate to support metal catalysts, in several important catalytic and electrocatalytic applications, including water electrolysis, alcohol electrooxidation, biomass conversion, and water gas shift reactions. In the current review we provide a summary of theoretical and experimental studies of the interaction of TMC surfaces with oxygen-containing molecules, including both inorganic (O2, H2O, CO and CO2) and organic (alcohols, aldehydes, acids and esters) molecules. We will discuss the general trends in the reaction pathways, as well as future research opportunities in surface science studies that would facilitate the utilization of TMCs as catalysts and electrocatalysts.

Stottlemyer, Alan L.; Kelly, Thomas G.; Meng, Qinghe; Chen, Jingguang G.

2012-09-01

102

Volumetric Fraction Dynamic Measurement in Oil-Water-Gas Multiphase Horizontal Pipe Flow with Dual Energy Gamma-Ray  

NASA Astrophysics Data System (ADS)

The problems of how to measuring the volumetric fractions of oil-water-gas multiphase flow are still a problem remaining to be solved in oil industry. With the technological development of nuclear radioactive inspection, dual-energy ?-ray techniques make it possible to investigate the concentration of the different components on the cross-section of oil-water-gas multiphase pipe-flow. The dual-energy Gamma-ray technique is based on the materials attenuation coefficients measurement. It is comprised of two radioactive isotopes of 241Am and 137Cs with emission energies of 59.5keV and 662keV. In order to measuring the material's attenuation dose rate, some nuclear instruments and data acquisition system were designed; a number of static and dynamic tests were carried out in the Multiphase Laboratory, Institute of Mechanics, Chinese Academy of Sciences. The oil-water-gas three phases of medium have been investigated to simulate different media volumetric fraction distributions on the experimental flow loop. The measurement results of attenuation intensities were obtained; the linear attenuation coefficients and the volumetric fractions were studied and measurement error was discussed in this paper as well.

Li, Donghui; Wu, Yingxiang; Wang, Keren; Zhong, Xingfu

2007-06-01

103

Molecular implementation of molecular shift register memories  

NASA Technical Reports Server (NTRS)

An electronic shift register memory (20) at the molecular level is described. The memory elements are based on a chain of electron transfer molecules (22) and the information is shifted by photoinduced (26) electron transfer reactions. Thus, multi-step sequences of charge transfer reactions are used to move charge with high efficiency down a molecular chain. The device integrates compositions of the invention onto a VLSI substrate (36), providing an example of a molecular electronic device which may be fabricated. Three energy level schemes, molecular implementation of these schemes, optical excitation strategies, charge amplification strategies, and error correction strategies are described.

Beratan, David N. (Inventor); Onuchic, Jose N. (Inventor)

1991-01-01

104

Shifting scintillator neutron detector  

DOEpatents

Provided are sensors and methods for detecting thermal neutrons. Provided is an apparatus having a scintillator for absorbing a neutron, the scintillator having a back side for discharging a scintillation light of a first wavelength in response to the absorbed neutron, an array of wavelength-shifting fibers proximate to the back side of the scintillator for shifting the scintillation light of the first wavelength to light of a second wavelength, the wavelength-shifting fibers being disposed in a two-dimensional pattern and defining a plurality of scattering plane pixels where the wavelength-shifting fibers overlap, a plurality of photomultiplier tubes, in coded optical communication with the wavelength-shifting fibers, for converting the light of the second wavelength to an electronic signal, and a processor for processing the electronic signal to identify one of the plurality of scattering plane pixels as indicative of a position within the scintillator where the neutron was absorbed.

Clonts, Lloyd G; Cooper, Ronald G; Crow, Jr., Morris Lowell; Hannah, Bruce W; Hodges, Jason P; Richards, John D; Riedel, Richard A

2014-03-04

105

Design of a Molecular Memory Device: The Electron Transfer Shift Register Memory  

NASA Technical Reports Server (NTRS)

A molecular shift register memory at the molecular level is described. The memory elements consist of molecules can exit in either an oxidized or reduced state and the bits are shifted between the cells with photoinduced electron transfer reactions.

Beratan, D.

1993-01-01

106

Improved feedback shift register  

NASA Technical Reports Server (NTRS)

Design of feedback shift register with three tap feedback decoding scheme is described. Application for obtaining sequence synchronization patterns is examined. Operation of the circuitry is described and drawings of the systems are included.

Perlman, M.

1972-01-01

107

Molecular Electronic Shift Registers  

NASA Technical Reports Server (NTRS)

Molecular-scale shift registers eventually constructed as parts of high-density integrated memory circuits. In principle, variety of organic molecules makes possible large number of different configurations and modes of operation for such shift-register devices. Several classes of devices and implementations in some specific types of molecules proposed. All based on transfer of electrons or holes along chains of repeating molecular units.

Beratan, David N.; Onuchic, Jose N.

1990-01-01

108

Protein Chemical Shift Prediction  

E-print Network

The protein chemical shifts holds a large amount of information about the 3-dimensional structure of the protein. A number of chemical shift predictors based on the relationship between structures resolved with X-ray crystallography and the corresponding experimental chemical shifts have been developed. These empirical predictors are very accurate on X-ray structures but tends to be insensitive to small structural changes. To overcome this limitation it has been suggested to make chemical shift predictors based on quantum mechanical(QM) calculations. In this thesis the development of the QM derived chemical shift predictor Procs14 is presented. Procs14 is based on 2.35 million density functional theory(DFT) calculations on tripeptides and contains corrections for hydrogen bonding, ring current and the effect of the previous and following residue. Procs14 is capable at performing predictions for the 13CA, 13CB, 13CO, 15NH, 1HN and 1HA backbone atoms. In order to benchmark Procs14, a number of QM NMR calculatio...

Larsen, Anders S

2014-01-01

109

Proton Chemical Shifts  

NSDL National Science Digital Library

Created by Hans Reich, professor of organic chemistry at the Uiversity of Wisconsin-Madison, this site contains a compilation of proton chemical shifts and coupling constants. This is an excellent resource for providing students familiarity with Nuclear Magnetic Resonance (NMR) Spectroscopy Data.

Reich, Hans J.

2007-11-16

110

Quantum Shift Register  

E-print Network

We consider a quantum circuit in which shift and rotation operations on qubits are performed by swap gates and controlled swap gates. These operations can be useful for quantum computers performing elementary arithmetic operations such as multiplication and a bit-wise comparison of qubits.

Jae-weon Lee; Eok Kyun Lee; Jaewan Kim; Soonchil Lee

2001-12-19

111

Longitudinal Plasma Resonance Shifts in Gold Nanoparticle Aggregates  

NASA Astrophysics Data System (ADS)

Recent interest in colloidal gold focuses on understanding the tunability of the longitudinal and transverse plasma resonance. It was reported that the reduction of HAuCl4 by Na2S produces gold nanoparticles with an optical absorption in the near infrared. This absorption blue shifts during the course of the reaction. X-ray photoemission spectroscopy (XPS) measurements on this system indicated that there was little sulfur present in the system. A small angle x-ray scattering (SAX) experiment was used to monitor the reaction while simultaneously the UV-VIS spectrum was measured. During the reaction the fractal dimension decreased from 4.154 +/- 0.850 to 0.624 +/- 0.146. The decrease in fractal dimension coincided with the blue shift in the longitudinal plasma resonance from the near IR to the visible. This suggests a change from reaction limited colloid aggregation (RLCA) to diffusion limited colloid aggregation (DLCA), caused the shift in the plasma resonance.

Norman, Thaddeus J., Jr.; Grant, Christian; Magana, Donny; Anderson, Roger W.; Zhang, Jin Z.; Cao, Daliang; Bridges, Frank; Liu, Jun; van Buuren, Tony

2002-11-01

112

Strategies for improving the performance and stability of Ni-based catalysts for reforming reactions.  

PubMed

Owing to the considerable publicity that has been given to petroleum related economic, environmental, and political problems, renewed attention has been focused on the development of highly efficient and stable catalytic materials for the production of chemical/fuel from renewable resources. Supported nickel nanoclusters are widely used for catalytic reforming reactions, which are key processes for generating synthetic gas and/or hydrogen. New challenges were brought out by the extension of feedstock from hydrocarbons to oxygenates derivable from biomass, which could minimize the environmental impact of carbonaceous fuels and allow a smooth transition from fossil fuels to a sustainable energy economy. This tutorial review describes the recent efforts made toward the development of nickel-based catalysts for the production of hydrogen from oxygenated hydrocarbons via steam reforming reactions. In general, three challenges facing the design of Ni catalysts should be addressed. Nickel nanoclusters are apt to sinter under catalytic reforming conditions of high temperatures and in the presence of steam. Severe carbon deposition could also be observed on the catalyst if the surface carbon species adsorbed on metal surface are not removed in time. Additionally, the production of hydrogen rich gas with a low concentration of CO is a challenge using nickel catalysts, which are not so active in the water gas shift reaction. Accordingly, three strategies were presented to address these challenges. First, the methodologies for the preparation of highly dispersed nickel catalysts with strong metal-support interaction were discussed. A second approach-the promotion in the mobility of the surface oxygen-is favored for the yield of desired products while promoting the removal of surface carbon deposition. Finally, the process intensification via the in situ absorption of CO2 could produce a hydrogen rich gas with low CO concentration. These approaches could also guide the design of other types of heterogeneous base-metal catalysts for high temperature processes including methanation, dry reforming, and hydrocarbon combustion. PMID:25182070

Li, Shuirong; Gong, Jinlong

2014-11-01

113

Ambiguous red shifts  

NASA Astrophysics Data System (ADS)

A one-parameter conformal invariance of Maxwell's equations allows the wavelengths of electromagnetic waves to change as they propagate, and do so even in otherwise field-free space. This produces an ambiguity in interpretations of stellar red shifts. Experiments that will determine the value of the group parameter, and thereby remove the ambiguity, are proposed. They are based on an analysis of the anomalous frequency shifts uncovered in the Pioneer 10 and 11 spacecraft studies, and physical interpretation of an isomorphism discovered by E.L. Hill. If the group parameter is found to be non-zero, Hubble's relations will have to be reinterpreted and space-time metrics will have to be altered. The cosmological consequences of the transformations are even more extensive because, though they change frequencies they do not alter the energy and momentum conservation laws of classical and quantum-electrodynamical fields established by Cunningham and by Bia?ynicki-Birula.

Wulfman, Carl E.

2010-12-01

114

The Modality Shift Experiment in Adults and Children with High Functioning Autism  

ERIC Educational Resources Information Center

This study used the modality shift experiment, a relatively simple reaction time measure to visual and auditory stimuli, to examine attentional shifting within and across modalities in 33 children and 42 adults with high-functioning autism as compared to matched numbers of age- and ability-matched typical controls. An exaggerated "modality shift

Williams, Diane L.; Goldstein, Gerald; Minshew, Nancy J.

2013-01-01

115

Wind driven vertical transport in a vegetated, wetland water column with air-water gas exchange  

NASA Astrophysics Data System (ADS)

Flow around arrays of cylinders at low and intermediate Reynolds numbers has been studied numerically, analytically and experimentally. Early results demonstrated that at flow around randomly oriented cylinders exhibits reduced turbulent length scales and reduced diffusivity when compared to similarly forced, unimpeded flows (Nepf 1999). While horizontal dispersion in flows through cylinder arrays has received considerable research attention, the case of vertical dispersion of reactive constituents has not. This case is relevant to the vertical transfer of dissolved gases in wetlands with emergent vegetation. We present results showing that the presence of vegetation can significantly enhance vertical transport, including gas transfer across the air-water interface. Specifically, we study a wind-sheared air-water interface in which randomly arrayed cylinders represent emergent vegetation. Wind is one of several processes that may govern physical dispersion of dissolved gases in wetlands. Wind represents the dominant force for gas transfer across the air-water interface in the ocean. Empirical relationships between wind and the gas transfer coefficient, k, have been used to estimate spatial variability of CO2 exchange across the worlds’ oceans. Because wetlands with emergent vegetation are different from oceans, different model of wind effects is needed. We investigated the vertical transport of dissolved oxygen in a scaled wetland model built inside a laboratory tank equipped with an open-ended wind tunnel. Plastic tubing immersed in water to a depth of approximately 40 cm represented emergent vegetation of cylindrical form such as hard-stem bulrush (Schoenoplectus acutus). After partially removing the oxygen from the tank water via reaction with sodium sulfite, we used an optical probe to measure dissolved oxygen at mid-depth as the tank water re-equilibrated with the air above. We used dissolved oxygen time-series for a range of mean wind speeds to estimate the gas transfer coefficient, k, for both a vegetated condition and a control condition (no cylinders). The presence of cylinders in the tank substantially increased the rate of the gas transfer. For the highest wind speed, the gas transfer coefficient was several times higher when cylinders were present compared to when they were not. The gas transfer coefficient for the vegetated condition also proved sensitive to wind speed, increasing markedly with increasing mean wind speeds. Profiles of dissolved oxygen revealed well-mixed conditions in the bulk water column following prolonged air-flow above the water surface, suggesting application of the thin-film model is appropriate. The enhanced gas exchange observed might be explained by increased turbulent kinetic energy within the water column and the anisotropy of the cylinder array, which constrains horizontal motions more than vertical motions. Improved understanding of gas exchange in vegetated water columns may be of particularly use to investigations of carbon fluxes and soil accretion in wetlands. Reference: Nepf, H. (1999), Drag, turbulence, and diffusion in flow through emergent vegetation, Water Resour. Res., 35(2), 479-489.

Poindexter, C.; Variano, E. A.

2010-12-01

116

Drug Reactions  

MedlinePLUS

... version Drug Reactions Drug Reactions What is an adverse drug reaction? Medicines can treat or prevent illness and ... medicines can cause problems. These problems are called adverse drug reactions. You should know what to do if ...

117

Biological conversion of synthesis gas culture development  

SciTech Connect

Research continues on the conversion of synthesis by shift reactions involving bacteria. Topics discussed here include: biological water gas shift, sulfur gas utilization, experimental screening procedures, water gas shift studies, H{sub 2}S removal studies, COS degradation by selected CO-utilizing bacteria, and indirect COS utilization by Chlorobia. (VC)

Klasson, K.T.; Basu, R.; Johnson, E.R.; Clausen, E.C.; Gaddy, J.L.

1992-03-01

118

STEM Colorado: Doppler Shift  

NSDL National Science Digital Library

This applet demonstrates the Doppler shift. The user can control the frequency of the sound source and the sound speed. The chart recorder at the bottom displays the wave crests as detected by the receiver and their frequency. It also displays the instantaneous wavelength if the ear is at rest. The user can drag the source or the receiver to any location in the display and choose the velocity of each. This is part of a larger collection of applets by STEM Colorado focused mostly on topics in astronomy.

Mccray, Richard; Koelemay, Andrew

2008-08-30

119

[Shifting path of industrial pollution gravity centers and its driving mechanism in Pan-Yangtze River Delta].  

PubMed

Shifting path of industrial pollution gravity centers is the response of environmental special formation during the industry transfer process, in order to prove the responding of industrial pollution gravity centers to industry transfer in economically developed areas, this paper calculates the gravity centers of industrial wastewater, gas and solid patterns and reveals the shifting path and its driving mechanism, using the data of industrial pollution in the Pan-Yangtze River Delta from 2000 to 2010. The results show that the gravity center of the industrial waste in Pan-Yangtze River Delta shifts for sure in the last 10 years, and gravity center of solid waste shifts the maximum distance within the three wastes, which was 180.18 km, and shifting distances for waste gas and waste water were 109.51 km and 85.92 km respectively. Moreover, the gravity center of the industrial waste in Pan-Yangtze River Delta shifts westwards, and gravity centers of waste water, gas and solid shift for 0.40 degrees, 0.17 degrees and 0.03 degrees respectively. The shifting of industrial pollution gravity centers is driven by many factors. The rapid development of the heavy industry in Anhui and Jiangxi provinces results in the westward shifting of the pollutions. The optimization and adjustment of industrial structures in Yangtze River Delta region benefit to alleviating industrial pollution, and high-polluting industries shifted to Anhui and Jiangxi provinces promotes pollution gravity center shifting to west. While the development of massive clean enterprise, strong environmental management efforts and better environmental monitoring system slow the shifting trend of industrial pollution to the east in Yangtze River Delta. The study of industrial pollution gravity shift and its driving mechanism provides a new angle of view to analyze the relationship between economic development and environmental pollution, and also provides academic basis for synthetical management and control of environmental pollution in Pan-Yangtze River Delta, especially in the transition period. PMID:25639121

Zhao, Hai-Xia; Jiang, Xiao-Wei; Cui, Jian-Xin

2014-11-01

120

Formation of C-C and C-O bonds and oxygen removal in reactions of alkanediols, alkanols, and alkanals on copper catalysts.  

PubMed

This study reports evidence for catalytic deoxygenation of alkanols, alkanals, and alkanediols on dispersed Cu clusters with minimal use of external H(2) and with the concurrent formation of new C-C and C-O bonds. These catalysts selectively remove O-atoms from these oxygenates as CO or CO(2) through decarbonylation or decarboxylation routes, respectively, that use C-atoms present within reactants or as H(2)O using H(2) added or formed in situ from CO/H(2)O mixtures via water-gas shift. Cu catalysts fully convert 1,3-propanediol to equilibrated propanol-propanal intermediates that subsequently form larger oxygenates via aldol-type condensation and esterification routes without detectable involvement of the oxide supports. Propanal-propanol-H(2) equilibration is mediated by their chemisorption and interconversion at surfaces via C-H and O-H activation and propoxide intermediates. The kinetic effects of H(2), propanal, and propanol pressures on turnover rates, taken together with measured selectivities and the established chemical events for base-catalyzed condensation and esterification reactions, indicate that both reactions involve kinetically relevant bimolecular steps in which propoxide species, acting as the base, abstract the ?-hydrogen in adsorbed propanal (condensation) or attack the electrophilic C-atom at its carbonyl group (esterification). These weakly held basic alkoxides render Cu surfaces able to mediate C-C and C-O formation reactions typically catalyzed by basic sites inherent in the catalyst, instead of provided by coadsorbed organic moieties. Turnover rates for condensation and esterification reactions decrease with increasing Cu dispersion, because low-coordination corner and edge atoms prevalent on small clusters stabilize adsorbed intermediates and increase the activation barriers for the bimolecular kinetically relevant steps required for both reactions. PMID:22023723

Sad, María E; Neurock, Matthew; Iglesia, Enrique

2011-12-21

121

Nuclear field shift in natural environments  

NASA Astrophysics Data System (ADS)

The nuclear field shift (NFS) is an isotope shift in atomic energy levels caused by a combination of differences in nuclear size and shape and electron densities at the nucleus. The effect of NFS in isotope fractionation was theoretically established by Bigeleisen in 1996 [Bigeleisen J. (1996) J. Am. Chem. Soc. 118:3676-3680] and has been analytically measured in laboratory chemical exchange reactions. More recently, some isotopic variations of heavy elements (Hg, Tl, U) measured in natural systems as well as isotopic anomalies measured for lower-mass elements in meteorites have been attributed to the NFS effect. These isotopic variations open up new and exciting fields of investigations in Earth sciences. In this paper, we review the different natural systems in which NFS has been proposed to be the origin of isotopic variations.

Moynier, Frédéric; Fujii, Toshiyuki; Brennecka, Gregory A.; Nielsen, Sune G.

2013-03-01

122

Referenceless PRF shift thermometry.  

PubMed

The proton resonance frequency (PRF) shift provides a means of measuring temperature changes during minimally invasive thermotherapy. However, conventional PRF thermometry relies on the subtraction of baseline images, which makes it sensitive to tissue motion and frequency drift during the course of treatment. In this study, a new method is presented that eliminates these problems by estimating the background phase from each acquired image phase. In this referenceless method, a polynomial is fit to the background phase outside the heated region in a weighted least-squares fit. Extrapolation of the polynomial to the heated region serves as the background phase estimate, which is then subtracted from the actual phase. The referenceless method is demonstrated on a phantom during laser heating, 0 degrees temperature rise images of in vivo human liver, interstitial laser ablation of porcine liver, and transurethral ultrasound ablation of canine prostate. A good correlation between temperature maps reconstructed with the referenceless and subtraction methods was found. PMID:15170843

Rieke, Viola; Vigen, Karl K; Sommer, Graham; Daniel, Bruce L; Pauly, John M; Butts, Kim

2004-06-01

123

Phase shifting diffraction interferometer  

DOEpatents

An interferometer which has the capability of measuring optical elements and systems with an accuracy of {lambda}/1000 where {lambda} is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about {lambda}/50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms. 8 figs.

Sommargren, G.E.

1996-08-29

124

Phase shifting interferometer  

DOEpatents

An interferometer is disclosed which has the capability of measuring optical elements and systems with an accuracy of {lambda}/1000 where {lambda} is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about {lambda}/50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms. 11 figs.

Sommargren, G.E.

1999-08-03

125

Phase shifting interferometer  

DOEpatents

An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

Sommargren, Gary E. (Santa Cruz, CA)

1999-01-01

126

Phase shifting diffraction interferometer  

DOEpatents

An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

Sommargren, Gary E. (Santa Cruz, CA)

1996-01-01

127

Hydraulically actuated well shifting tool  

SciTech Connect

This patent describes a hydraulically actuated shifting tool for actuating a sliding member in a well tool. It comprises: a housing having a hydraulic fluid bore therein; shifting dog means positioned on the housing for movement away and toward the housing; locking dog means positioned on the housing for movement away and toward the body; shifting dog hydraulic actuating means in fluid communication with the bore for causing engagement of the shifting dogs with the sliding member; locking dog hydraulic actuating means in communication with the bore for causing engagement of the locking dogs with the locking means; and hydraulic shifting means in communication with the bore for causing relative movement between the shifting dog means and the locking dog means for shifting the sliding sleeve.

Roth, B.A.

1992-10-20

128

In-Cylinder Reaction Chemistry and Kinetics During Negative Valve Overlap Fuel Injection Under Low-Oxygen Conditions  

SciTech Connect

Fuel injection into the negative valve overlap (NVO) period is a common method for controlling combustion phasing in homogeneous charge compression ignition (HCCI) as well as other forms of advanced combustion. During this event, at least a portion of the fuel hydrocarbons can be converted to products containing significant levels of H2 and CO, as well as other short chain hydrocarbons by means of thermal cracking, water-gas shift, and partial oxidation reactions, depending on the availability of oxygen and the time-temperature-pressure history. The resulting products alter the autoignition properties of the combined fuel mixture for HCCI. Fuel-rich chemistry in a partial oxidation environment is also relevant to other high efficiency engine concepts (e.g., the dedicated EGR (D-EGR) concept from SWRI). In this study, we used a unique 6-stroke engine cycle to experimentally investigate the chemistry of a range of fuels injected during NVO under low oxygen conditions. Fuels investigated included iso-octane, iso-butanol, ethanol, and methanol. Products from NVO chemistry were highly dependent on fuel type and injection timing, with iso-octane producing less than 1.5% hydrogen and methanol producing more than 8%. We compare the experimental trends with CHEMKIN (single zone, 0-D model) predictions using multiple kinetic mechanisms available in the current literature. Our primary conclusion is that the kinetic mechanisms investigated are unable to accurately predict the magnitude and trends of major species we observed.

Kalaskar, Vickey B [ORNL] [ORNL; Szybist, James P [ORNL] [ORNL; Splitter, Derek A [ORNL] [ORNL; Pihl, Josh A [ORNL] [ORNL; Gao, Zhiming [ORNL] [ORNL; Daw, C Stuart [ORNL] [ORNL

2013-01-01

129

Shift work and pathological conditions  

PubMed Central

Shift work exerts major influences on the physiological functions of the human body. These are primarily mediated by the disruption of circadian rhythms since most body functions are circadian rhythmic. Next to the disturbances caused by changes in the circadian system, shift work has also been suggested to be related to a number of other health disorders. The present study summarizes recently published data on the potential relationship between disorders and shift working. PMID:17156476

van Mark, Anke; Spallek, Michael; Kessel, Richard; Brinkmann, Elke

2006-01-01

130

Theoretical investigation of Stokes shifts and reaction pathways  

E-print Network

Solar thermal fuels and fluorescent solar concentrators provide two ways in which the energy from the sun can be harnessed and stored. While much progress has been made in recent years, there is still much more to learn ...

Top, Laken M. (Laken Michelle)

2012-01-01

131

On Isotope Shifts  

NASA Astrophysics Data System (ADS)

It was noted by Zamick (Ann.Phys66,784(1971) That the same formula used by Talmi and De Shalit for binding energies (Rev.Mod.Phys.34, 704 (1962)) could also be used for nuclear radii i.e. isotope shifts. The argument is simple-both the radius operator and nuclear interaction are scalars under rotation. The formula has the change of square radius relative to a reference as nC+ (n(n-1)/2)A +[n/2]B. There have been many experimental papers which discuss this work as well as associated work by Talmi(NPA 423,189 (1984).The formula was originally used for the Calcium isotopes but most recently for Argon isotopes (K.Blaum et.al. NPA 799,30(2008)).There was also work on the Bismus and Lead Isotopes by M.R. Pearson et.al. (J.Phys G.26,1829(2000)). The formula displays even-odd staggering for both binding energies and nuclear radii.Sheline et.al. discuss ``inverse staggering'' as possibly evidence of Octupole deformation for certain Barium and Cesium isotopes (PRC38,2952(1988)). Other work of note is due to H.D. Wohlfahrt PRC 23,533(1981). It is my feeling that the above and other experimental results are somewhat scattered and it would be useful to collect them all and have a unified discussion of the implications of these very interesting experiments not only with the above formula but with other theoretical formulations. )

Zamick, Larry

2010-02-01

132

Reaction times  

Microsoft Academic Search

Reviews 11 studies dealing with reaction times (1910-1911). Reaction time has been utilized to study a variety of problems. The studies indicate that accurate results can not be obtained without careful attention to the technique of the method of reaction time. The topics covered include effect of intensity of stimulus on reaction time, rapidity of perception of sound and light

Herbert Woodrow

1911-01-01

133

Flexible Schedules and Shift Work.  

ERIC Educational Resources Information Center

Flexible work hours have gained prominence, as more than 25 million workers (27.6% of all full-time workers) can now vary their schedules. However, there has been little change since the mid-1980s in the proportion who work a shift other than a regular daytime shift. (JOW)

Beers, Thomas M.

2000-01-01

134

Particle-coincidences and coplanarity in the Mg binary reaction  

E-print Network

-shift correction, binary reactions, out-of-plane angular correlations, ternary fission Q0-values. PreprintParticle- coincidences and coplanarity in the 32 S + 24 Mg binary reaction C. Wheldon a,b,1 , Tz Cedex 2, France. Abstract The reaction 32S (165.4 MeV) + 24Mg is studied using the binary reaction spec

Paris-Sud XI, Université de

135

Information storage at the molecular level - The design of a molecular shift register memory  

NASA Technical Reports Server (NTRS)

The control of electron transfer rates is discussed and a molecular shift register memory at the molecular level is described. The memory elements are made up of molecules which can exist in either an oxidized or reduced state and the bits can be shifted between the cells with photoinduced electron transfer reactions. The device integrates designed molecules onto a VLSI substrate. A control structure to modify the flow of information along a shift register is indicated schematically.

Beratan, David N.; Onuchic, Jose Nelson; Hopfield, J. J.

1989-01-01

136

Refining the shifted topological vertex  

SciTech Connect

We study aspects of the refining and shifting properties of the 3d MacMahon function C{sub 3}(q) used in topological string theory and BKP hierarchy. We derive the explicit expressions of the shifted topological vertex S{sub {lambda}}{sub {mu}}{sub {nu}}(q) and its refined version T{sub {lambda}}{sub {mu}}{sub {nu}}(q,t). These vertices complete results in literature.

Drissi, L. B.; Jehjouh, H.; Saidi, E. H. [Faculte des Sciences, Laboratory/UFR-Physique des Hautes Energies, Rabat, 1014 (Morocco); Groupement National de Physique des Hautes Energies (GNPHE), Siege focal:FS, Rabat, 1014 (Morocco)

2009-01-15

137

Reversible Reactions  

NSDL National Science Digital Library

Watch a reaction proceed over time. How does total energy affect a reaction rate? Vary temperature, barrier height, and potential energies. Record concentrations and time in order to extract rate coefficients. Do temperature dependent studies to extract Arrhenius parameters. This simulation is best used with teacher guidance because it presents an analogy of chemical reactions.

Simulations, Phet I.; Barbera, Jack; Koch, Linda; Lemaster, Ron; Adams, Wendy

2005-09-01

138

Enzyme Reactions  

NSDL National Science Digital Library

This video shows an enzyme reaction lab. The teacher demonstrates how the enzyme, catalase, reacts with hydrogen peroxide (a substrate found in cells). The teacher first demonstrates a normal enzyme reaction. He or she then goes on to show how manipulating temperature and pH will affect the reaction of an enzyme.

School, Minerva D.

2011-10-03

139

Chemical Reactions  

NSDL National Science Digital Library

We don't often stop to think about it, but underlying many of our everyday activities are chemical reactions. From the cooking of an egg to the growth of a child, chemical reactions make things happen. Although many of the reactions that support our lives

National Science Teachers Association (NSTA)

2009-05-01

140

Theory of Low Energy Nuclear Reactions  

Microsoft Academic Search

The principal features of the theory of resonance reactions are ; described in terms of simple examples. A straightforward derivation is given of ; the particular result for the collision matrix found recently to be most useful ; for the description of low energy nuclear reactions. This result is expressed in ; terms of the potential scattering phase shifts and

Erich Vogt

1962-01-01

141

A molecular shift register based on electron transfer  

NASA Technical Reports Server (NTRS)

An electronic shift-register memory at the molecular level is described. The memory elements are based on a chain of electron-transfer molecules and the information is shifted by photoinduced electron-transfer reactions. This device integrates designed electronic molecules onto a very large scale integrated (silicon microelectronic) substrate, providing an example of a 'molecular electronic device' that could actually be made. The design requirements for such a device and possible synthetic strategies are discussed. Devices along these lines should have lower energy usage and enhanced storage density.

Hopfield, J. J.; Onuchic, Josenelson; Beratan, David N.

1988-01-01

142

Combined shift and methanation in a fluidized-bed reactor. Final report, 25 September 1979-31 December 1980  

SciTech Connect

The objective of this program was to demonstrate the feasibility of employing a gas-phase, catalytic, fluidized-bed reactor to carry out the water-gas shift and methanation reactions simultaneously, without product gas recycle. The major portion of the experimental work involved PEDU-scale tests in a 6-inch ID reactor, operating at 1000 psig and temperatures in the range of 900 to 1000/sup 0/F, with a nominal catalyst charge of one cubic foot. These tests included operation for extended time periods (35 to 40 hours) with feed H/sub 2/:CO ratios of 2:1 in the absence of steam, and 1:1 using steam:gas ratios of 0.1:1 to 0.2:1. Five different catalysts were evaluated. Bench-scale tests, each of approximately 10 days' duration, were also conducted. At H/sub 2/:CO = 2:1 (without steam), no significant carbon deposition occurred at temperatures of 800 and 950/sup 0/F. At 1100/sup 0/F, however, considerable carbon formation did occur, possibly due to the onset of CH/sub 4/ pyrolysis. At H/sub 2/:CO = 1:1 and 950/sup 0/F, carbon deposition took place readily in the absence of steam. Small amounts of steam in the feed (e.g., steam:gas ratio = 0.1:1) were effective in inhibiting carbon formation, although larger amounts (steam:gas ratio = 0.5:1) resulted in deactivation and loss of metal surface area through sintering. Results of auxiliary studies at Brigham Young University (BYU) on rates of carbon formation and removal are also presented. As to the relative tendencies of the various catalysts to undergo carbon deposition, results of the BYU studies generally confirmed observations made during PEDU testing at BCR. Catalyst regeneration tests at BYU with 10 percent O/sub 2/ in N/sub 2/ showed that 80 to 96 percent of the original metal surface could be restored at temperatures of 572 to 662/sup 0/F.

Streeter, R.C.

1981-02-01

143

Optimal control of gaze shifts.  

PubMed

To explore the visible world, human beings and other primates often rely on gaze shifts. These are coordinated movements of the eyes and head characterized by stereotypical metrics and kinematics. It is possible to determine the rules that the effectors must obey to execute them rapidly and accurately and the neural commands needed to implement these rules with the help of optimal control theory. In this study, we demonstrate that head-fixed saccades and head-free gaze shifts obey a simple physical principle, "the minimum effort rule." By direct comparison with existing models of the neural control of gaze shifts, we conclude that the neural circuitry that implements the minimum effort rule is one that uses inhibitory cross talk between independent eye and head controllers. PMID:19535584

Kardamakis, Andreas A; Moschovakis, Adonis K

2009-06-17

144

1,5-Rhodium shift in rearrangement of N-arenesulfonylazetidin-3-ols into benzosultams.  

PubMed

Benzosultams are synthesized in an enantiopure form starting from ?-amino acids through a rhodium-catalyzed rearrangement reaction of N-arenesulfonylazetidin-3-ols. Mechanistically, this reaction involves C-C bond cleavage by ?-carbon elimination and C-H bond cleavage by a 1,5-rhodium shift. PMID:24328041

Ishida, Naoki; Shimamoto, Yasuhiro; Yano, Takaaki; Murakami, Masahiro

2013-12-26

145

Shifting of the Earth's Axis  

Microsoft Academic Search

HAVING quoted the Greenwich observations so often, and with all respect, during the last twenty years, in my several Great-Pyramid publications, as showing that there is a slow shifting of the earth's axis going on, with the effect of altering the latitude of places minutely from age to age (see more especially p. 81 of fourth edition of ``Our Inheritance

C. Piazzi-Smyth

1884-01-01

146

The Shift Needed for Sustainability  

ERIC Educational Resources Information Center

Purpose: The purpose of this action research is to begin to assess to what extent organizations have in practice begun to make the shift towards triple bottom line (TBL) sustainability. Design/methodology/approach: A definition of TBL sustainability is provided, and key elements of TBL sustainability considered necessary to success are identified…

Smith, Peter A. C.; Sharicz, Carol

2011-01-01

147

Irreversible Investment with Regime Shifts  

Microsoft Academic Search

Under the real options approach to investment under uncertainty, agents formulate optimal policies under the assumption that firms’ growth prospects do not vary over time. This paper proposes and solves a model of investment decisions in which the growth rate and volatility of the decision variable shift between different states at random times. A value-maximizing investment policy is derived such

Xin Guo; Jianjun Miao; Erwan Morellecc

2002-01-01

148

Reaction Time  

NSDL National Science Digital Library

In this activity, learners explore reaction time and challenge themselves to improve their coordination. Do you want to move faster? Catch that ball that you never seem to see in time? Use a simple test to help you improve your reaction (or response) time.

Science, New Y.

1999-01-01

149

Doppler phase shifting using dual, switched phase shifting devices  

NASA Technical Reports Server (NTRS)

A system of inducing a phase shift using moving reflector elements. The moving reflectors can be moving mirrors or an acousto-optical filter. The moving reflectors oscillate i.e. the move first in a first direction and then in a second direction. Two different reflectors are used so that the light can be switched between the reflectors. During a first portion of the cycle the light is coupled to the first modulator which moves the reflector in the first direction. The second modulator is out of phase with the first modulator, and the light is switched to that second modulator during a second portion of the cycle. The second modulator is also moving in the first direction when the light is applied thereto. In this way, the light obtains a constant direction Doppler shift.

Gutierrez, Roman C. (Inventor)

2002-01-01

150

Frequency shifts in gravitational resonance spectroscopy  

E-print Network

Quantum states of ultracold neutrons in the gravitational field are to be characterized through gravitational resonance spectroscopy. This paper discusses systematic effects that appear in the spectroscopic measurements. The discussed frequency shifts, which we call Stern-Gerlach shift, interference shift, and spectator state shift, appear in conceivable measurement schemes and have general importance. These shifts have to be taken into account in precision experiments.

S. Baeßler; V. V. Nesvizhevsky; G. Pignol; K. V. Protasov; D. Rebreyend; E. A. Kupriyanova; A. Yu. Voronin

2015-01-13

151

Frequency shifts in gravitational resonance spectroscopy  

E-print Network

Quantum states of ultracold neutrons in the gravitational field are to be characterized through gravitational resonance spectroscopy. This paper discusses systematic effects that appear in the spectroscopic measurements. The discussed frequency shifts, which we call Stern-Gerlach shift, interference shift, and spectator state shift, appear in conceivable measurement schemes and have general importance. These shifts have to be taken into account in precision experiments.

Baeßler, S; Pignol, G; Protasov, K V; Rebreyend, D; Kupriyanova, E A; Voronin, A Yu

2015-01-01

152

CLASS Shifts in Modeling Instruction  

NSDL National Science Digital Library

Among the most surprising findings in Physics Education Research is the lack of positive results on attitudinal measures, such as Colorado Learning Attitudes about Science Survey (CLASS) and Maryland Physics Expectations Survey (MPEX). The uniformity with which physics teaching manages to negatively shift attitudes toward physics learning is striking. Strategies which have been shown to improve learning, such as interactive engagement and studio format classes, provide more authentic science experiences for students, yet do not produce positive attitudinal results. Florida International Universityâs Physics Education Research Group has implemented Modeling Instruction in University Physics classes. Using the CLASS as a pre/post measure has shown attitudinal improvements through both semesters of the introductory physics sequence. In this paper, we report positive shifts on the CLASS in two sections of Modeling Physics, one in Mechanics (N=30) and one in Electricity and Magnetism, (N=31) and examine how these results reflect on Modeling Instruction.

Brewe, Eric; Kramer, Laird H.; O'Brien, George

2008-09-15

153

Anthropometric changes and fluid shifts  

NASA Technical Reports Server (NTRS)

In an effort to obtain the most comprehensive and coherent picture of changes under weightlessness, a set of measurements on Skylab 2 was initiated and at every opportunity, additional studies were added. All pertinent information from ancillary sources were gleaned and collated. On Skylab 2, the initial anthropometric studies were scheduled in conjunction with muscle study. A single set of facial photographs was made in-flight. Additional measurements were made on Skylab 3, with photographs and truncal and limb girth measurements in-flight. Prior to Skylab 4, it was felt there was considerable evidence for large and rapid fluid shifts, so a series of in-flight volume and center of mass measurements and infrared photographs were scheduled to be conducted in the Skylab 4 mission. A number of changes were properly documented for the first time, most important of which were the fluid shifts. The following description of Skylab anthropometrics address work done on Skylab 4 primarily.

Thornton, W. E.; Hoffler, G. W.; Rummel, J. A.

1977-01-01

154

Lamb shift in muonic deuterium  

SciTech Connect

We consider the two-photon exchange contribution to the 2P-2S Lamb shift in muonic deuterium in the framework of forward dispersion relations. The dispersion integrals are evaluated with minimal model dependence using experimental data on elastic deuteron form factors and inelastic electron-deuteron scattering, both in the quasielastic and hadronic range. The subtraction constant that is required to ensure convergence of the dispersion relation for the forward Compton amplitude T{sub 1} (?,Q{sup 2}) is related to the deuteron magnetic polarizability ?(Q{sup 2}) and represents the main source of uncertainty in our analysis. We obtain for the Lamb shift ?E{sub 2P-2S} = 1.620±0.190 meV and discuss ways to further reduce this uncertainty.

Gorchtein, Mikhail; Vanderhaeghen, Marc [Institut für Kernphysik, Universität Mainz, 55128 Mainz (Germany); Carlson, Carl E. [Department of Physics, College of William and Mary, Williamsburg, Virginia 23187 (United States)

2013-11-07

155

Multicolor Holography With Phase Shifting  

NASA Technical Reports Server (NTRS)

Prototype apparatus constructed to test feasibility of two-color holographic interferometric scheme in which data for reconstructing holographic wavefront obtained with help of phase-shifting technique. Provides two sets of data needed to solve equations for effects of temperature and concentration. Concept extended to holography at three or more wavelengths to measure three or more phenomena associated with significant variations in index of refraction

Vikram, Chandra S.

1996-01-01

156

Drug Reactions  

MedlinePLUS

Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions. One problem is ...

157

Enzyme Reactions  

NSDL National Science Digital Library

The enzyme reaction rate activity allows students to simulate the effects of variables such as temperature and pH on the reaction rate of the enzyme catalase. This computer simulation is best used after the students have done a wet lab experiment. The value of the simulation is that it requires the students to interpret and analyze the graphical representation of data and it enables the running of mutiple experiments in a short amount of time.

Maryland Virtual High School

158

Methane reforming reaction with carbon dioxide over Ni/SiO{sub 2} catalyst. II. A mechanistic study  

SciTech Connect

The mechanism of the carbon dioxide reforming of methane was investigated over a nickel-on-silica catalyst. Non-steady-state and steady-state isotopic transient experiments combined with in situ DRIFT spectroscopy investigations were used to quantify the amount of the various adspecies present on the working catalyst surface. It was found that as soon as the catalyst is contacted with the reacting mixture, dehydrogenated carbon adspecies originating from the initial adsorption of methane and carbon dioxide are deposited on the nickel particles. Under steady-state reaction conditions, a permanent pool of adspecies equivalent to one monolayer of carbide-like species is continuously fed by the dissociative activation of gaseous methane. This initial activation step of methane is shown to be reversible, since it allows a fast CH{sub 4}/CD{sub 4} exchange characterised by a marked isotopic effect. This pool of adspecies constitutes a reservoir of active carbon able to be oxidised into CO by oxygen atoms arising from the simultaneous carbon dioxide dissociation. This oxidation step which does not involve any C-H bond activation is assumed to be rate limiting since no kinetic isotopic effect is found for the formation of CO under the stoichiometric reforming conditions. Gaseous CO is also directly produced from the latter CO{sub 2} dissociation. Adsorption/desorption equilibria ensure a fast interconversion between gaseous CO{sub 2} and CO, as attested by their isotopic scrambling. A similar adsorption/desorption equilibrium is proposed for H{sub 2}O which, combined with the reversible activation of CO{sub 2} and CO, leads to the achieved water-gas-shift equilibrium. A particular configuration of active sites is proposed on the basis of the main mechanistic statements. 22 refs., 8 figs., 6 tabs.

Kroll, V.C.H.; Swaan, H.M.; Lacombe, S.; Mirodatos, C. [Institut de Recherches sur la Catalyse, Villeurbanne (France)] [Institut de Recherches sur la Catalyse, Villeurbanne (France)

1996-12-01

159

New types of 'combined' pericyclic reactions  

NASA Astrophysics Data System (ADS)

The review is concerned with 'combined' pericyclic reactions, i.e., multistep one-pot reactions involving a cascade of pericyclic steps, as well as concerted processes whose transition states represent superpositions of transition states of two pericyclic reactions. Some typical examples of cascade pericyclic reactions are presented, demonstrating their significance for synthetic practice. The review mainly concerns reactions with a 'combined' pericyclic transition state, e.g., dyotropic shift, bispericyclic reactions and hiscotropic rearrangements. The attention is focussed on detailed analysis of various types of coarctate reactions due to their importance for synthetic chemistry and to thorough elaboration of their theoretical basis, which is in essence a continuation and further development of the Woodward-Hoffmann theory for spirocyclic conjugated systems. The bibliography includes 115 references.

Magdesieva, Tatyana V.

2013-03-01

160

Taxol reactions.  

PubMed

Paclitaxel (Taxol) a taxane antineoplastic agent causing irreversible microtubule aggregation with activity against breast, ovarian, lung, head and neck, bladder, testicular, esophageal, endometrial and other less common tumors was derived from the bark of the Pacific yew (Taxus brevifolia). Phase I trials conducted in the late 1980s were almost halted because of the high frequency of hypersensitivity-like reactions. Respiratory distress (dyspnea and/or bronchospasm), hypotension, and angioedema were the major manifestations, but flushing, urticaria, chest, abdomen, and extremity pains were described also. Reactions occurred on first exposure in the majority of cases raising etiologic questions. The vehicle for paclitaxel Cremophor EL (polyoxyethylated castor oil in 50% ethanol) was strongly suspect as a direct (non-immunoglobulin E dependent) histamine releaser. Premedication regimens and longer infusion times lowered the incidence of reactivity allowing phase II and III trials to progress through the early 1990s. The mechanism(s) underlying paclitaxel hypersensitivity-like reactions is still unknown, and clinical data on probable complement and mast cell activation are lacking. The original clinical trial protocols for paclitaxel required discontinuation of therapy for patients who experienced hypersensitivity-like reactions. Here, we review the current etiologic knowledge of these reactions and describe our clinical approach to allow completion of chemotherapy with this powerful plant-derived agent. PMID:12125509

Price, Kursteen S; Castells, Mariana C

2002-01-01

161

A Phylogenetic analysis of the Southern Shift  

E-print Network

/ and /w/) in the Southern Shift. As with the vowel systems of New York and Philadelphia (Labov, forthcoming), which also occupy intermediate geogzaphical positions, 1t involves a mixture of Southern and Northern features. Although the various shift1ng...

Thomas, Erik Robert

2012-06-07

162

Differential phase shift keyed signal resolver  

NASA Technical Reports Server (NTRS)

A differential phase shift keyed signal resolver resolves the differential phase shift in the incoming signal to determine the data content thereof overcoming phase uncertainty without requiring a transmitted reference signal.

Hopkins, P. M.; Wallingford, W. M. (inventors)

1974-01-01

163

Shift register generators and applications to coding  

NASA Technical Reports Server (NTRS)

The most important properties of shift register generated sequences are exposed. The application of shift registers as multiplication and division circuits leads to the generation of some error correcting and detecting codes.

Morakis, J. C.

1968-01-01

164

Feasibility Analysis of Steam Reforming of Biodiesel by-product Glycerol to Make Hydrogen  

E-print Network

68% of waste glycerol is converted into gaseous mixture. The excess glycerol is recycled back as a feedstock. Water gas shift (WGS) reaction, further convert carbon monoxide into hydrogen and carbon dioxide which is further subjected to separation...

Joshi, Manoj

2009-06-09

165

A Short History of Three Chemical Shifts  

NASA Astrophysics Data System (ADS)

The distinctive term "chemical shift" to designate the position of a spectral signal is used in three forms of spectroscopy: nuclear magnetic resonance (NMR), electron spectroscopy for chemical analysis (ESCA), and Mössbauer spectroscopy. Regrettably, chemical shift has a poor reputation as a technical term. However, the "chemical" environment around an atom of interest influences the electronic environment and hence, leads to spectral shifts. Therefore, using the prefix "chemical" for the shifts observed in the three forms of spectroscopy is appropriate.

Nagaoka, Shin-Ichi

2007-05-01

166

Light-shift modulated photon-echo  

E-print Network

We show that the AC-Stark shift (light-shift) is a powerful and versatile tool to control the emission of a photon-echo in the context of optical storage. As a proof-of-principle, we demonstrate that the photon-echo efficiency can be fully modulated by applying light-shift control pulses in an erbium doped solid. The control of the echo emission is attributed to the spatial gradient induced by the light-shift beam.

Chanelière, Thierry

2015-01-01

167

Continuous-data FIFO bubble shift register  

NASA Technical Reports Server (NTRS)

Simple loop first-in-first-out (FIFO) bubble memory shift register has continuous storage capability. Bubble shift register simplifies chip-control electronics by enabling all control functions to be alined at same bit. FIFO shift register is constructed from passive replicator and annihilator combinations.

Chen, T. T.

1977-01-01

168

Tilt shift determinations with spatial-carrier phase-shift method in temporal phase-shift interferometry  

NASA Astrophysics Data System (ADS)

An algorithm is proposed to deal with tilt-shift errors in temporal phase-shift interferometry (PSI). In the algorithm, the tilt shifts are detected with the spatial-carrier phase-shift (SCPS) method and then the tilt shifts are applied as priori information to the least-squares fittings of phase retrieval. The algorithm combines the best features of the SCPS and the temporal PSI. The algorithm could be applied to interferograms of arbitrary aperture without data extrapolation for the Fourier transform is not involved. Simulations and experiments demonstrate the effectiveness of the algorithm. The statistics of simulation results show a satisfied accuracy in detecting tilt-shift errors. Comparisons of the measurements with and without environmental vibration show that the proposed algorithm could compensate tilt-shift errors and retrieve wavefront phase accurately. The algorithm provides an approach to retrieve wavefront phase for the temporal PSI in vibrating environment.

Liu, Qian; Wang, Yang; He, Jianguo; Ji, Fang; Wang, Baorui

2014-07-01

169

Reaction Time  

NSDL National Science Digital Library

In this activity, learners conduct an experiment to test how fast they can react. Learners try to catch a piece of paper with a ruler printed on it (or a ruler) as quickly as they can. Learners collect data and compare the reaction times of friends and family.

Boston, Wgbh

2003-01-01

170

Reaction Time  

NSDL National Science Digital Library

This lab is not an inquiry activity. There are some students whose reaction times will not allow them to catch a 12 inch ruler. They may use a dowel, stick, strip of cardboard, etc. Although the students are led to believe that the point of the lab is to

Horton, Michael

2009-05-30

171

Amplitude dependent shift of betatron oscillation center  

NASA Astrophysics Data System (ADS)

We have analytically calculated and measured the amplitude-dependent shift of the betatron oscillation center at the electron storage ring, NewSUBARU. The shift is due to nonzero average horizontal deflections at the normal sextupole magnets. The shifted center forms a displaced closed orbit and is measured by a closed orbit distortion measurement system, although no single electron runs on this orbit. The measured shifts by betatron oscillations agreed with the theoretical calculation except the variation of data points, which did not obey the ring symmetry. Additional measurements, whose results included the effect of the circumference shift, experimentally proved the amplitude dependent circumference shift for the first time. We also discuss some applications of the shift, which has never been previously analyzed.

Shoji, Yoshihiko; Takao, Masaru; Nakamura, Takeshi

2014-06-01

172

VERIFICATION OF THE SHIFT MONTE CARLO CODE  

SciTech Connect

Shift is a new hybrid Monte Carlo/deterministic radiation transport code being developed at Oak Ridge National Laboratory. At its current stage of development, Shift includes a fully-functional parallel Monte Carlo capability for simulating eigenvalue and fixed-source multigroup transport problems. This paper focuses on recent efforts to verify Shift s Monte Carlo component using the two-dimensional and three-dimensional C5G7 NEA benchmark problems. Comparisons were made between the benchmark eigenvalues and those output by the Shift code. In addition, mesh-based scalar flux tally results generated by Shift were compared to those obtained using MCNP5 on an identical model and tally grid. The Shift-generated eigenvalues were within three standard deviations of the benchmark and MCNP5 values in all cases. The flux tallies generated by Shift were found to be in very good agreement with those from MCNP

Sly, Nicholas [University of Tennessee, Knoxville (UTK)] [University of Tennessee, Knoxville (UTK); Mervin, Mervin Brenden [University of Tennessee, Knoxville (UTK)] [University of Tennessee, Knoxville (UTK); Mosher, Scott W [ORNL] [ORNL; Evans, Thomas M [ORNL] [ORNL; Wagner, John C [ORNL] [ORNL; Maldonado, G. Ivan [University of Tennessee, Knoxville (UTK)] [University of Tennessee, Knoxville (UTK)

2012-01-01

173

Dynamics and computation in functional shifts  

NASA Astrophysics Data System (ADS)

We introduce a new type of shift dynamics as an extended model of symbolic dynamics, and investigate the characteristics of shift spaces from the viewpoints of both dynamics and computation. This shift dynamics is called a functional shift, which is defined by a set of bi-infinite sequences of some functions on a set of symbols. To analyse the complexity of functional shifts, we measure them in terms of topological entropy, and locate their languages in the Chomsky hierarchy. Through this study, we argue that considering functional shifts from the viewpoints of both dynamics and computation gives us opposite results about the complexity of systems. We also describe a new class of shift spaces whose languages are not recursively enumerable.

Namikawa, Jun; Hashimoto, Takashi

2004-07-01

174

Host shifts and evolutionary radiations of butterflies  

PubMed Central

Ehrlich and Raven proposed a model of coevolution where major host plant shifts of butterflies facilitate a burst of diversification driven by their arrival to a new adaptive zone. One prediction of this model is that reconstructions of historical diversification of butterflies should indicate an increase in diversification rate following major host shifts. Using reconstructed histories of 15 butterfly groups, I tested this prediction and found general agreement with Ehrlich and Raven's model. Butterfly lineages with an inferred major historical host shift showed evidence of diversification rate variation, with a significant acceleration following the host shift. Lineages without an inferred major host shift generally agreed with a constant-rate model of diversification. These results are consistent with the view that host plant associations have played a profound role in the evolutionary history of butterflies, and show that major shifts to chemically distinct plant groups leave a historical footprint that remains detectable today. PMID:20610430

Fordyce, James A.

2010-01-01

175

Shifting boundaries in professional care.  

PubMed Central

The nature of the work undertaken by different health professionals and inter-professional boundaries are constantly shifting. The greater knowledge of users of health care, and the increasing technical and organizational complexity of modern medicine, have partly eroded the control of health professionals over the substance of their work. The definition of a field of work as lying within the province of any one profession is culturally rather than scientifically determined. It is evident that care of good quality should be delivered at the lowest possible cost. This might include delivery of care by a less trained person than heretofore, or by someone with limited but focused training. Sharing of skills is a more sensible subject for discussion than transfer of tasks. We review a number of studies which show the effectiveness of inter-professional substitution in various care settings, and also the effectiveness of substitution by those other than health professionals. The views of users of health services on inter-professional substitution need to be considered. Health professionals and others need to work together to devise innovative ways of delivering effective health care. The legal issues need clarification. PMID:8774532

Hopkins, A; Solomon, J; Abelson, J

1996-01-01

176

Control of Kinetics and Thermodynamics of [1,5]-Shifts by Aromaticity: A View through the Prism of Marcus Theory  

E-print Network

of these reactions. Relative trends for a significant range of endothermic and exothermic [1,5]-shifts with different. The aromatic stabilization energy of the product is directly translated into increased exothermicity and even to complete disappearance of the reaction barrier. Not only the activation energy but the shape

Alabugin, Igor

177

Metal Reactions  

NSDL National Science Digital Library

This is written as a static display, but can easily be adapted to a hands-on experiment for learners to conduct. Sodium phosphate, a clear colorless solution, is combined with six different metal ion solutions. Each metal (copper, nickel, iron, silver, cobalt, and barium) forms a different color and texture precipitate. Learners discover that a chemical reaction can be identified by a color change, and formation of a precipitate. They also learn that metals can be identified by their precipitates. For safety reasons, this activity should be conducted as a demonstration for younger audiences.

2011-11-01

178

Goos-Haenchen shift in complex crystals  

SciTech Connect

The Goos-Haenchen (GH) effect for wave scattering from complex PT-symmetric periodic potentials (complex crystals) is theoretically investigated, with specific reference to optical GH shift in photonic crystal slabs with a sinusoidal periodic modulation of both real and imaginary parts of the dielectric constant. The analysis highlights some distinct and rather unique features as compared to the GH shift found in ordinary crystals. In particular, as opposed to GH shift in ordinary crystals, which is large at the band gap edges, in complex crystals the GH shift can be large inside the reflection (amplification) band and becomes extremely large as the PT symmetry-breaking threshold is approached.

Longhi, Stefano; Della Valle, Giuseppe; Staliunas, Kestutis [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy); Departament de Fisica i Enginyeria Nuclear, Instituci Catalana de Recerca i Estudis Avanats (ICREA), Universitat Politcnica de Catalunya, Colom 11, E-08222 Terrassa, Barcelona (Spain)

2011-10-15

179

Exercise, Energy Balance and the Shift Worker  

PubMed Central

Shift work is now common in society and is not restricted to heavy industry or emergency services, but is increasingly found amongst ‘white collar’ occupations and the growing number of service industries. Participation in shift work is associated with increased body mass index, prevalence of obesity and other health problems. We review the behavioural and biological disturbances that occur during shift work and discuss their impact on leisure-time physical activity and energy balance. Shift work generally decreases opportunities for physical activity and participation in sports. For those shift workers who are able to exercise, subjective and biological responses can be altered if the exercise is taken at unusual times of day and/or if the shift worker is sleep-deprived. These altered responses may in turn impact on the longer-term adherence to an exercise programme. The favourable effects of exercise on body mass control and sleep quality have not been confirmed in shift workers. Similarly, recent reports of relationships between sleep duration and obesity have not been examined in a shift work context. There is no evidence that exercise can mediate certain circadian rhythm characteristics (e.g. amplitude or timing) for improved tolerance to shift work. Total energy intake and meal composition do not seem to be affected by participation in shift work. Meal frequency is generally reduced but snacking is increased on the night shift. Unavailability of preferred foods in the workplace, a lack of time, and a reduced desire to eat at night explain these findings. ‘Normal’ eating habits with the family are also disrupted. The metabolic responses to food are also altered by shift work-mediated disruptions to sleep and circadian rhythms. Whether any interactions on human metabolism exist between timing or content of food intake and physical activity during shift work is not known at present. There are very few randomised controlled studies on the efficacy of physical activity or dietary interventions during shift work. Some favourable effects of such interventions on fatigue levels at work have been reported, but biological and behavioural outcomes relevant to long-term health and energy balance have not been studied adequately. In addition, recruitment and retention of research participants for randomised controlled trials of physical activity or dietary interventions has been very difficult. We present a model of the various behavioural and biological factors relevant to exercise and energy balance during shift work as a framework for future research. PMID:18620467

Atkinson, Greg; Fullick, Sarah; Grindey, Charlotte; Maclaren, Don; Waterhouse, Jim

2009-01-01

180

In-line phase shift tomosynthesis  

SciTech Connect

Purpose: The purpose of this work is to (1) demonstrate laboratory measurements of phase shift images derived from in-line phase-contrast radiographs using the attenuation-partition based algorithm (APBA) of Yan et al.[Opt. Express 18(15), 16074–16089 (2010)], (2) verify that the APBA reconstructed images obey the linearity principle, and (3) reconstruct tomosynthesis phase shift images from a collection of angularly sampled planar phase shift images.Methods: An unmodified, commercially available cabinet x-ray system (Faxitron LX-60) was used in this experiment. This system contains a tungsten anode x-ray tube with a nominal focal spot size of 10 ?m. The digital detector uses CsI/CMOS with a pixel size of 50 × 50 ?m. The phantoms used consisted of one acrylic plate, two polystyrene plates, and a habanero pepper. Tomosynthesis images were reconstructed from 51 images acquired over a ±25° arc. All phase shift images were reconstructed using the APBA.Results: Image contrast derived from the planar phase shift image of an acrylic plate of uniform thickness exceeded the contrast of the traditional attenuation image by an approximate factor of two. Comparison of the planar phase shift images from a single, uniform thickness polystyrene plate with two polystyrene plates demonstrated an approximate linearity of the estimated phase shift with plate thickness (?1600 rad vs ?2970 rad). Tomographic phase shift images of the habanero pepper exhibited acceptable spatial resolution and contrast comparable to the corresponding attenuation image.Conclusions: This work demonstrated the feasibility of laboratory-based phase shift tomosynthesis and suggests that phase shift imaging could potentially provide a new imaging biomarker. Further investigation will be needed to determine if phase shift contrast will be able to provide new tissue contrast information or improved clinical performance.

Hammonds, Jeffrey C.; Price, Ronald R.; Pickens, David R.; Donnelly, Edwin F. [Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee 37232 (United States)] [Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee 37232 (United States)

2013-08-15

181

Shift work and the assessment and management of shift work disorder (SWD).  

PubMed

Nearly 20% of the labor force worldwide, work shifts that include work hours outside 07:00 h to 18:00 h. Shift work is common in many occupations that directly affect the health and safety of others (e.g., protective services, transportation, healthcare), whereas quality of life, health, and safety during shift work and the commute home can affect workers in any field. Increasing evidence indicates that shift-work schedules negatively influence worker physiology, health, and safety. Shift work disrupts circadian sleep and alerting cycles, resulting in disturbed daytime sleep and excessive sleepiness during the work shift. Moreover, shift workers are at risk for shift work disorder (SWD). This review focuses on shift work and the assessment and management of sleepiness and sleep disruption associated with shift work schedules and SWD. Management strategies include approaches to promote sleep, wakefulness, and adaptation of the circadian clock to the imposed work schedule. Additional studies are needed to further our understanding of the mechanisms underlying the health risks of shift work, understanding which shift workers are at most risk of SWD, to investigate treatment options that address the health and safety burdens associated with shift work and SWD, and to further develop and assess the comparative effectiveness of countermeasures and treatment options. PMID:22560640

Wright, Kenneth P; Bogan, Richard K; Wyatt, James K

2013-02-01

182

Four-phase differential phase shift resolver  

NASA Technical Reports Server (NTRS)

Two systems have been developed to resolve phase uncertainty without transmitting reference signals. In both methods signal is impressed on carrier as differential, rather than absolute, phase shift. At the receiver four-phase demodulation and logic process unambiguously resolves differential phase shift of input carrier.

Hopkins, P. M.; Wallingford, W. M.

1973-01-01

183

The wavenumber shift in SAR interferometry  

Microsoft Academic Search

SAR surveys from separate passes show relative shifts of the ground wavenumber spectra that depend on the local slope and the off-nadir angle. The authors discuss the exploitation of this spectral shift for different applications: 1) generation of “low noise” interferograms benefiting phase unwrapping, 2) generation of quick-look interferograms, 3) decorrelation reduction by means of tunable SAR systems (TINSAR), 4)

Fabio Gatelli; Andrea Monti Guamieri; Francesco Parizzi; Paolo Pasquali; Claudio Prati; Fabio Rocca

1994-01-01

184

A simplified, compact static shift register  

NASA Technical Reports Server (NTRS)

Shift register was developed which uses only one D type flip-flop and improves packaging density by approximately 25% over the usual arrangement. Circuit is compromise between full master-slave arrangement and dynamic shift register, with limitation only of length of time that clock can be held high during new data entry.

Pryor, R. L.; Smith, A. M.

1972-01-01

185

Demonstrations: sound source for Doppler shift  

E-print Network

of the Universe Doppler effect The technique for measuring the velocities of very remote galaxies is based uponDemonstrations: ·sound source for Doppler shift ·big balloon and labels Text: Mod. Phys. 8.A, 8.B, 8.C Problems: 1, 3, 6, 7 from Ch. 8 What's important: ·Doppler shift ·Hubble's law ·age

Boal, David

186

A Short History of Three Chemical Shifts  

ERIC Educational Resources Information Center

A short history of chemical shifts in nuclear magnetic resonance (NMR), electron spectroscopy for chemical analysis (ESCA) and Mossbauer spectroscopy, which are useful for chemical studies, is described. The term chemical shift is shown to have originated in the mistaken assumption that nuclei of a given element would all undergo resonance at the…

Nagaoka, Shin-ichi

2007-01-01

187

Comparison of eight and 12 hour shifts: impacts on health, wellbeing, and alertness during the shift.  

PubMed Central

OBJECTIVES: The generally agreed view is that there is no ideal shift system, and that most systems will have both advantages and disadvantages. As such, attention has been placed on trying to identify good and bad features of shift systems, with a view to minimising the possible ill health as a consequence of shiftwork. The present study focuses on the duration of the shift and looks at the implications for individual health, wellbeing, and alertness during the shift of extending the shift from the traditional eight hours to 12. METHODS: Two groups of chemical workers, one working 12 hour shifts and the other working eight hour shifts, took part. All completed a modified version of the standard shiftwork index (SSI), a set of self reported questionnaires related to health and wellbeing. RESULTS: The two groups did not differ on most outcome measures, although the differences that did exist suggested advantages for the 12 hour shift workers over the eight hour shift workers; with the notable exception of rated alertness at certain times of day. CONCLUSIONS: The results are explained in terms of the design of the 12 hour shift system and the specific sequencing of shifts that seem to minimise the potential for the build up of fatigue. Although the current data moderately favour 12 hour shifts, a cautionary note is sounded with regard to the implications of the alertness ratings for performance and safety. PMID:9038802

Tucker, P; Barton, J; Folkard, S

1996-01-01

188

NightShift: NMR shift inference by general hybrid model training - a framework for NMR chemical shift prediction  

PubMed Central

Background NMR chemical shift prediction plays an important role in various applications in computational biology. Among others, structure determination, structure optimization, and the scoring of docking results can profit from efficient and accurate chemical shift estimation from a three-dimensional model. A variety of NMR chemical shift prediction approaches have been presented in the past, but nearly all of these rely on laborious manual data set preparation and the training itself is not automatized, making retraining the model, e.g., if new data is made available, or testing new models a time-consuming manual chore. Results In this work, we present the framework NightShift (NMR Shift Inference by General Hybrid Model Training), which enables automated data set generation as well as model training and evaluation of protein NMR chemical shift prediction. In addition to this main result – the NightShift framework itself – we describe the resulting, automatically generated, data set and, as a proof-of-concept, a random forest model called Spinster that was built using the pipeline. Conclusion By demonstrating that the performance of the automatically generated predictors is at least en par with the state of the art, we conclude that automated data set and predictor generation is well-suited for the design of NMR chemical shift estimators. The framework can be downloaded from https://bitbucket.org/akdehof/nightshift. It requires the open source Biochemical Algorithms Library (BALL), and is available under the conditions of the GNU Lesser General Public License (LGPL). We additionally offer a browser-based user interface to our NightShift instance employing the Galaxy framework via https://ballaxy.bioinf.uni-sb.de/. PMID:23496927

2013-01-01

189

Visual sensitivities tuned by heterochronic shifts in opsin gene expression  

PubMed Central

Background Cichlid fishes have radiated into hundreds of species in the Great Lakes of Africa. Brightly colored males display on leks and vie to be chosen by females as mates. Strong discrimination by females causes differential male mating success, rapid evolution of male color patterns and, possibly, speciation. In addition to differences in color pattern, Lake Malawi cichlids also show some of the largest known shifts in visual sensitivity among closely related species. These shifts result from modulated expression of seven cone opsin genes. However, the mechanisms for this modulated expression are unknown. Results In this work, we ask whether these differences might result from changes in developmental patterning of cone opsin genes. To test this, we compared the developmental pattern of cone opsin gene expression of the Nile tilapia, Oreochromis niloticus, with that of several cichlid species from Lake Malawi. In tilapia, quantitative polymerase chain reaction showed that opsin gene expression changes dynamically from a larval gene set through a juvenile set to a final adult set. In contrast, Lake Malawi species showed one of two developmental patterns. In some species, the expressed gene set changes slowly, either retaining the larval pattern or progressing only from larval to juvenile gene sets (neoteny). In the other species, the same genes are expressed in both larvae and adults but correspond to the tilapia adult genes (direct development). Conclusion Differences in visual sensitivities among species of Lake Malawi cichlids arise through heterochronic shifts relative to the ontogenetic pattern of the tilapia outgroup. Heterochrony has previously been shown to be a powerful mechanism for change in morphological evolution. We found that altering developmental expression patterns is also an important mechanism for altering sensory systems. These resulting sensory shifts will have major impacts on visual communication and could help drive cichlid speciation. PMID:18500997

Carleton, Karen L; Spady, Tyrone C; Streelman, J Todd; Kidd, Michael R; McFarland, William N; Loew, Ellis R

2008-01-01

190

Peak shift in honey bee olfactory learning.  

PubMed

If animals are trained with two similar stimuli such that one is rewarding (S+) and one punishing (S-), then following training animals show a greatest preference not for the S+, but for a novel stimulus that is slightly more different from the S- than the S+ is. This peak shift phenomenon has been widely reported for vertebrates and has recently been demonstrated for bumblebees and honey bees. To explore the nature of peak shift in invertebrates further, here we examined the properties of peak shift in honey bees trained in a free-flight olfactory learning assay. Hexanal and heptanol were mixed in different ratios to create a continuum of odour stimuli. Bees were trained to artificial flowers such that one odour mixture was rewarded with 2 molar sucrose (S+), and one punished with distasteful quinine (S-). After training, bees were given a non-rewarded preference test with five different mixtures of hexanal and heptanol. Following training bees' maximal preference was for an odour mixture slightly more distinct from the S- than the trained S+. This effect was not seen if bees were initially trained with two distinct odours, replicating the classic features of peak shift reported for vertebrates. We propose a conceptual model of how peak shift might occur in honey bees. We argue that peak shift does not require any higher level of processing than the known olfactory learning circuitry of the bee brain and suggest that peak shift is a very general feature of discrimination learning. PMID:24748464

Andrew, Samuel C; Perry, Clint J; Barron, Andrew B; Berthon, Katherine; Peralta, Veronica; Cheng, Ken

2014-09-01

191

Scalar Field Theories with Polynomial Shift Symmetries  

E-print Network

We continue our study of naturalness in nonrelativistic QFTs of the Lifshitz type, focusing on scalar fields that can play the role of Nambu-Goldstone (NG) modes associated with spontaneous symmetry breaking. Such systems allow for an extension of the constant shift symmetry to a shift by a polynomial of degree $P$ in spatial coordinates. These "polynomial shift symmetries" in turn protect the technical naturalness of modes with a higher-order dispersion relation, and lead to a refinement of the proposed classification of infrared Gaussian fixed points available to describe NG modes in nonrelativistic theories. Generic interactions in such theories break the polynomial shift symmetry explicitly to the constant shift. It is thus natural to ask: Given a Gaussian fixed point with polynomial shift symmetry of degree $P$, what are the lowest-dimension operators that preserve this symmetry, and deform the theory into a self-interacting scalar field theory with the shift symmetry of degree $P$? To answer this (essen...

Griffin, Tom; Horava, Petr; Yan, Ziqi

2014-01-01

192

Phase-shift extraction from twice-normalized light intensity changes recorded with random phase shifts  

NASA Astrophysics Data System (ADS)

A simple phase-shift extraction algorithm is proposed for interferograms recorded with random phase shifts that vary over at least 2 ?. The phase-shift-dependent changes in the intensity at two pixels having different phases, selected from one frame, are taken out and normalized. The sum and difference of the two normalized changes are calculated, and both the changes are normalized again along the phase shifts. The normalized sum and difference become the cosine and sine of a term including the random phase shift, respectively. Thereby, the phase shifts are extracted from both twice-normalized intensity changes. An experiment using an interference microscope equipped with a piezoelectric-transducer positioner of an objective lens is conducted to estimate the validity of the algorithm. The algorithm is verified to have satisfactory results when the multiple interferograms used have a sample size of more than 15 frames recorded with random phase shifts.

Adachi, Masaaki; Sunada, Satoshi

2014-09-01

193

Metabolic Shifts in Immunity and Inflammation  

PubMed Central

Sites of ongoing inflammation and triggered immune responses are characterized by significant changes in metabolic activity. Recent studies have indicated that such shifts in tissue metabolism result from a combination of profound recruitment of inflammatory cells (neutrophils and monocytes) and high proliferation rates among lymphocyte populations. The resultant shifts in energy supply and demand can result in metabolic acidosis and diminished delivery and/or availability of oxygen, leading to hypoxia extensive enough to trigger transcriptional and translation changes in tissue phenotype. Such phenotypic shifts can imprint fundamental changes to tissue metabolism. Here, we review recent work addressing metabolic changes and metabolic control of inflammation and immunity. PMID:20368286

Kominsky, Douglas J.; Campbell, Eric L.; Colgan, Sean P.

2014-01-01

194

Deterministic convergence in iterative phase shifting  

SciTech Connect

Previous implementations of the iterative phase shifting method, in which the phase of a test object is computed from measurements using a phase shifting interferometer with unknown positions of the reference, do not provide an accurate way of knowing when convergence has been attained. We present a new approach to this method that allows us to deterministically identify convergence. The method is tested with a home-built Fizeau interferometer that measures optical surfaces polished to {lambda}/100 using the Hydra tool. The intrinsic quality of the measurements is better than 0.5 nm. Other possible applications for this technique include fringe projection or any problem where phase shifting is involved.

Luna, Esteban; Salas, Luis; Sohn, Erika; Ruiz, Elfego; Nunez, Juan M.; Herrera, Joel

2009-03-10

195

Giant Compton Shifts in Hyperbolic Metamaterial  

E-print Network

We study the Compton scattering of light by free electrons inside a hyperbolic medium. We demonstrate that the unconventional dispersion and local density of states of the electromagnetic modes in such media can lead to a giant Compton shift and dramatic enhancement of the scattering cross section. We develop an universal approach for the study of coupled multi-photon processes in nanostructured media and derive the spectral intensity function of the scattered radiation for realistic metamaterial structures. We predict the Compton shift of the order of a few meVs for the infrared spectrum that is at least one order of magnitude larger than the Compton shift in any other system.

Iorsh, Ivan; Ginzburg, Pavel; Belov, Pavel; Kivshar, Yuri

2014-01-01

196

Shifting media induced super-solution imaging  

NASA Astrophysics Data System (ADS)

In this paper, we propose a novel method to achieve super-resolution imaging by utilizing shifting media based on the transformation optics theory. According to the effective medium theory, the homogenous but anisotropic shifting media can be simply replaced by only two kinds of homogenous and isotropic materials in an alternating layered structure. In addition, another scheme of the symmetrical trapezoidal shifting media shells with layered isotropic materials is proposed to realize the super-resolution imaging. Finite element simulations have been performed to prove these ideas.

Du, Yong; Zang, XiaoFei; Shi, Cheng; Ji, XueBin; Zhu, YiMing

2015-02-01

197

First-Principles Study on the Origin of the Different Selectivities for Methanol Steam Reforming on Cu(111) and Pd(111)  

E-print Network

), and partial oxidation of methanol (eq 3). Methanol decomposition is a strongly endothermic reaction producing the water gas shift reaction.7-13 Partial oxidation of methanol is an exothermic process with a rapid start and methanol steam reforming (MSR). The MSR reaction is a less endothermic reaction providing the highest yield

Li, Weixue

198

Adaptation to Shift Work: Physiologically Based Modeling of the Effects of Lighting and Shifts’ Start Time  

PubMed Central

Shift work has become an integral part of our life with almost 20% of the population being involved in different shift schedules in developed countries. However, the atypical work times, especially the night shifts, are associated with reduced quality and quantity of sleep that leads to increase of sleepiness often culminating in accidents. It has been demonstrated that shift workers’ sleepiness can be improved by a proper scheduling of light exposure and optimizing shifts timing. Here, an integrated physiologically-based model of sleep-wake cycles is used to predict adaptation to shift work in different light conditions and for different shift start times for a schedule of four consecutive days of work. The integrated model combines a model of the ascending arousal system in the brain that controls the sleep-wake switch and a human circadian pacemaker model. To validate the application of the integrated model and demonstrate its utility, its dynamics are adjusted to achieve a fit to published experimental results showing adaptation of night shift workers (n?=?8) in conditions of either bright or regular lighting. Further, the model is used to predict the shift workers’ adaptation to the same shift schedule, but for conditions not considered in the experiment. The model demonstrates that the intensity of shift light can be reduced fourfold from that used in the experiment and still produce good adaptation to night work. The model predicts that sleepiness of the workers during night shifts on a protocol with either bright or regular lighting can be significantly improved by starting the shift earlier in the night, e.g.; at 21?00 instead of 00?00. Finally, the study predicts that people of the same chronotype, i.e. with identical sleep times in normal conditions, can have drastically different responses to shift work depending on their intrinsic circadian and homeostatic parameters. PMID:23308206

Postnova, Svetlana; Robinson, Peter A.; Postnov, Dmitry D.

2013-01-01

199

Amplitude dependence of the tune shift  

SciTech Connect

Recent studies in the Tevatron have measured the tune shift as a function of the displacement from a closed orbit. The measured values of tune shift were found to be much smaller than one would expect from the measured distribution of the normal octupole moments in the Tevatron. Tracking studies performed to see if, and under what conditions, the observed results could be obtained are reported. The effect of linear coupling is taken into consideration, and is found to significantly reduce the coefficient of the tune shift. The dependence of the tune shift on the initial coordinate of a particle in the presence of a distribution of octupole moments is calculated. The ''smear'' is calculated as a function of linear coupling. (LEW)

Gelfand, N.M.

1986-03-01

200

Does accounting quality mitigate risk shifting?  

E-print Network

This study examines the effect of financial reporting quality on risk shifting, an investment distortion that is caused by shareholders' incentives to engage in high-risk projects that are detrimental to debt holders. I ...

Loktionov, Yuri V

2009-01-01

201

Red Shifts with Obliquely Approaching Light Sources.  

ERIC Educational Resources Information Center

Refutes the Doppler effect as the explanation of large red shifts in the spectra of distant galaxies and explains the relativistic effects in which the light sources approach the observer obliquely. Provides several diagrams and graphs. (YP)

Head, C. E.; Moore-Head, M. E.

1988-01-01

202

[Sleep disorders among physicians on shift work].  

PubMed

Sleep disorders in physicians who perform shift work can result in increased risks of health problems that negatively impact performance and patient safety. Even those who cope well with shift work are likely to suffer from sleep disorders. The aim of this manuscript is to discuss possible causes, contributing factors and consequences of sleep disorders in physicians and to identify measures that can improve adaptation to shift work and treatment strategies for shift work-associated sleep disorders. The risk factors that influence the development of sleep disorders in physicians are numerous and include genetic factors (15 % of the population), age (> 50 years), undiagnosed sleep apnea,, alcohol abuse as well as multiple stress factors inherent in clinical duties (including shift work), research, teaching and family obligations. Several studies have reported an increased risk for medical errors in sleep-deprived physicians. Shift workers have an increased risk for psychiatric and cardiovascular diseases and shift work may also be a contributing factor to cancer. A relationship has been reported not only with sleep deprivation and changes in food intake but also with diabetes mellitus, obesity, hypertension and coronary heart disease. Nicotine and alcohol consumption are more frequent among shift workers. Increased sickness and accident rates among physicians when commuting (especially after night shifts) have a socioeconomic impact. In order to reduce fatigue and to improve performance, short naps during shiftwork or naps plus caffeine, have been proposed as coping strategies; however, napping during adverse circadian phases is less effective, if not impossible when unable to fall asleep. Bright and blue light supports alertness during a night shift. After shiftwork, direct sunlight exposure to the retina can be avoided by using dark sunglasses or glasses with orange lenses for commuting home. The home environment for daytime sleeping after a night shift should be very dark to allow endogenous melatonin secretion, which is a night signal and supports continuous sleep. Sleep disorders can be treated with timed light exposure, as well as behavioral and environmental strategies to compensate for sleep deprivation. Fatigue due to sleep deprivation can only be systematically treated with sleep. PMID:25213642

Schlafer, O; Wenzel, V; Högl, B

2014-11-01

203

Robert Collins Mean-Shift Blob Tracking  

E-print Network

1 CSE598G Robert Collins Mean-Shift Blob Tracking through Scale Space Robert Collins, CVPR'03 CSE598G Robert Collins Abstract · Mean-shift tracking · Choosing scale of kernel is an issue · Scale location and scale CSE598G Robert Collins Nice Property x = a K(a-x) w(a) (a-x) a K(a-x) w(a) [a ]H(a-x) w

Collins, Robert T.

204

Robert Collins Mean-Shift Blob Tracking  

E-print Network

CSE598G Robert Collins Mean-Shift Blob Tracking through Scale Space Robert Collins, CVPR'03 #12;CSE598G Robert Collins Abstract · Mean-shift tracking · Choosing scale of kernel is an issue · Scale location and scale #12;CSE598G Robert Collins Nice Property x = a K(a-x) w(a) (a-x) a K(a-x) w(a) [a ]H

Collins, Robert T.

205

Robert Collins Mean-Shift Blob Tracking  

E-print Network

CSE598G Robert Collins Mean-Shift Blob Tracking through Scale Space Robert Collins, CVPR'03 #12;CSE598G Robert Collins Abstract · Mean-shift tracking · Choosing scale of kernel is an issue · Scale location and scale #12;CSE598G Robert Collins Nice Property x = a K(a-x) w(a) (a-x) a K(a-x) w(a) [a ] H

Collins, Robert T.

206

Beta-Shifts, Their Languages, and Computability  

Microsoft Academic Search

For every real number ?>1, the ?-shift is a dynamical system describing iterations of the map x\\u000a ?\\u000a ?\\u000a x mod 1 and is studied intensively in number theory. Each ?-shift has an associated language of finite strings of characters; properties of this language are studied for the additional\\u000a insight they give into the dynamics of the underlying system.\\u000a \\u000a \\u000a We

Jakob Grue Simonsen

2011-01-01

207

Random phase-shifting interferometry without accurately controlling or calibrating the phase shifts.  

PubMed

A random phase-shifting interferometry insensitive to environmental noises is proposed. The relationship between intensity and phase in each pixel is obtained from a large amount of phase-shifting interferograms. In the phase-solving algorithm, the phase shift step length is not taken as a parameter, but the temporal intensity maximum and minimum in each pixel are needed. For finding the extreme values, random passive phase shifts caused by environmental noises are adopted to make the intensity ergodic. Supplementary active phase shifts, which are not accurately controlled or calibrated, are performed to shorten the measurement cycle. Finally, averaging statistically uncorrelated data over a long enough period of time can effectively reduce most random errors. A minitype Fizeau interferometer applying this random phase-shifting method demonstrated the feasibility of it. PMID:19370146

Hao, Qun; Zhu, Qiudong; Hu, Yao

2009-04-15

208

Computational studies of dielectric permittivity effects on chemical shifts of alanine dipeptide  

NASA Astrophysics Data System (ADS)

Dielectric permittivity effect on chemical shifts of alanine dipeptide is studied using hybrid density functional theory. The dependence is shown to be highly sensitive to conformation, and, a reasonable explanation is outlined based on the solvent reaction field model. The danger of the observed shape of dependence for the chemical shift evaluations at low dielectric constant environment, as in the case of protein interior, is emphasized. The nuclear shielding sensitivity towards the dielectric permittivity is examined over different ?/? combinations. Comparison with the experimental data from protein backbone suggests an effective dielectric constant of ?4-5 for protein interior.

Sahakyan, Aleksandr B.

2012-09-01

209

Rapid calculation of protein chemical shifts using bond polarization theory and its application to protein structure refinement.  

PubMed

Although difficult to analyze, NMR chemical shifts provide detailed information on protein structure. We have adapted the semi-empirical bond polarization theory (BPT) to protein chemical shift calculation and chemical shift driven protein structure refinement. A new parameterization for BPT amide nitrogen chemical shift calculation has been derived from MP2 ab initio calculations and successfully evaluated using crystalline tripeptides. We computed the chemical shifts of the small globular protein ubiquitin, demonstrating that BPT calculations can match the results obtained at the DFT level of theory at very low computational cost. In addition to the calculation of chemical shift tensors, BPT allows the calculation of chemical shift gradients and consequently chemical shift driven geometry optimizations. We applied chemical shift driven protein structure refinement to the conformational analysis of a set of Trypanosoma brucei (the causative agent of African sleeping sickness) tryparedoxin peroxidase Px III structures. We found that the interaction of Px III with its reaction partner Tpx seems to be governed by conformational selection rather than by induced fit. PMID:22868284

Jakovkin, Igor; Klipfel, Marco; Muhle-Goll, Claudia; Ulrich, Anne S; Luy, Burkhard; Sternberg, Ulrich

2012-09-21

210

Scalar Field Theories with Polynomial Shift Symmetries  

E-print Network

We continue our study of naturalness in nonrelativistic QFTs of the Lifshitz type, focusing on scalar fields that can play the role of Nambu-Goldstone (NG) modes associated with spontaneous symmetry breaking. Such systems allow for an extension of the constant shift symmetry to a shift by a polynomial of degree $P$ in spatial coordinates. These "polynomial shift symmetries" in turn protect the technical naturalness of modes with a higher-order dispersion relation, and lead to a refinement of the proposed classification of infrared Gaussian fixed points available to describe NG modes in nonrelativistic theories. Generic interactions in such theories break the polynomial shift symmetry explicitly to the constant shift. It is thus natural to ask: Given a Gaussian fixed point with polynomial shift symmetry of degree $P$, what are the lowest-dimension operators that preserve this symmetry, and deform the theory into a self-interacting scalar field theory with the shift symmetry of degree $P$? To answer this (essentially cohomological) question, we develop a new graph-theoretical technique, and use it to prove several classification theorems. First, in the special case of $P=1$ (essentially equivalent to Galileons), we reproduce the known Galileon $N$-point invariants, and find their novel interpretation in terms of graph theory, as an equal-weight sum over all labeled trees with $N$ vertices. Then we extend the classification to $P>1$ and find a whole host of new invariants, including those that represent the most relevant (or least irrelevant) deformations of the corresponding Gaussian fixed points, and we study their uniqueness.

Tom Griffin; Kevin T. Grosvenor; Petr Horava; Ziqi Yan

2014-12-02

211

Calculation of isotope shifts and relativistic shifts in C I, C II, C III, and C IV J. C. Berengut*  

E-print Network

Calculation of isotope shifts and relativistic shifts in C I, C II, C III, and C IV J. C. Berengut of calculating isotope shifts and relativistic shifts in atomic spectra. We test the method on neutral carbon the lifetime of the Universe. Carbon isotope shifts can be used to measure isotope abundances in gas clouds

Kozlov, Mikhail G

212

Personality factors related to shift work tolerance in two- and three-shift workers.  

PubMed

This study aimed to investigate whether different personality variables were associated with shift work tolerance, and whether these potential associations were moderated by various types of shift work. The sample comprised 1505 nurses who worked either two or three rotating shifts. Personality traits were measured in terms of morningness, flexibility, languidity and hardiness. Morningness reflects the tendency to be alert relatively early in the morning and sleepy relatively early in the evening. Flexibility denotes the ability to both work and sleep at odd times of the day, while languidity concerns the tendency to become tired/sleepy when cutting down on sleep. Hardiness relates to resilience to stressful life events. The dependent variables in this study comprised of measures of insomnia, sleepiness, depression and anxiety. Hierarchical regression analyses, which controlled for demographic variables and work load, revealed that Morningness was significantly and negatively related to insomnia. The Morningness by Shift type interaction was overall significant for depressive symptoms. Morningness was near significantly associated with lower levels of depressive symptoms in three-shift workers, but unrelated to depressive symptoms in two-shift workers. Flexibility was associated with higher levels of depressive symptoms. Flexibility by Shift type interaction was significant for insomnia, indicating that flexibility was negatively associated with insomnia for three-shift workers and unrelated with insomnia for two-shift workers. Languidity was associated with higher levels of sleepiness, depressive and anxiety symptoms. Hardiness was associated with lower levels of all four dependent variables. PMID:21172694

Natvik, Sylvia; Bjorvatn, Bjørn; Moen, Bente Elisabeth; Magerøy, Nils; Sivertsen, Børge; Pallesen, Ståle

2011-07-01

213

Catalysis of Photochemical Reactions.  

ERIC Educational Resources Information Center

Offers a classification system of catalytic effects in photochemical reactions, contrasting characteristic properties of photochemical and thermal reactions. Discusses catalysis and sensitization, examples of catalyzed reactions of excepted states, complexing ground state substrates, and catalysis of primary photoproducts. (JM)

Albini, A.

1986-01-01

214

30 CFR 57.9160 - Train movement during shift changes.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Train movement during shift changes. 57...Dumping Traffic Safety § 57.9160 Train movement during shift changes. During shift changes, the movement of underground trains carrying rock or material shall be...

2013-07-01

215

30 CFR 57.9160 - Train movement during shift changes.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Train movement during shift changes. 57...Dumping Traffic Safety § 57.9160 Train movement during shift changes. During shift changes, the movement of underground trains carrying rock or material shall be...

2012-07-01

216

30 CFR 57.9160 - Train movement during shift changes.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Train movement during shift changes. 57...Dumping Traffic Safety § 57.9160 Train movement during shift changes. During shift changes, the movement of underground trains carrying rock or material shall be...

2011-07-01

217

30 CFR 57.9160 - Train movement during shift changes.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Train movement during shift changes. 57...Dumping Traffic Safety § 57.9160 Train movement during shift changes. During shift changes, the movement of underground trains carrying rock or material shall be...

2010-07-01

218

30 CFR 57.9160 - Train movement during shift changes.  

Code of Federal Regulations, 2014 CFR

...2014-07-01 2014-07-01 false Train movement during shift changes. 57...Dumping Traffic Safety § 57.9160 Train movement during shift changes. During shift changes, the movement of underground trains carrying rock or material shall be...

2014-07-01

219

Measurement of the effective focal shift in an optical trap  

E-print Network

, and Steven M. Block Departments of Biological Sciences and Applied Physics, Stanford University, Stanford focal shift. Measurements of this quantity deviate from electromagnetic calculations of the focal shift

Block, Steven

220

Theoretical isotope shifts in neutral barium  

E-print Network

The present work deals with a set of problems in isotope shifts of neutral barium spectral lines. Some well known transitions ($6s^2~^1S_0-6s6p~^{1,3}P^o_1$ and $6s^2~^1S_0-6p^2~^3P_0$) are first investigated. Values of the changes in the nuclear mean-square charge radius are deduced from the available experimental isotope shifts using our ab initio electronic factors. The three sets $\\{ \\delta\\langle r^2\\rangle^{A,A'}\\} $ obtained from these lines are consistent with each other. The combination of the available nuclear mean-square radii with our electronic factors for the $6s5d~^3D_{1,2} -6s6p~^{1}P^o_1$ transitions produces isotope shift values in conflict with the laser spectroscopy measurements of Dammalapati et al. (Eur. Phys. J. D 53, 1 (2009)).

Nazé, Cédric; Godefroid, Michel

2015-01-01

221

Deterministic convergence in iterative phase shifting.  

PubMed

Previous implementations of the iterative phase shifting method, in which the phase of a test object is computed from measurements using a phase shifting interferometer with unknown positions of the reference, do not provide an accurate way of knowing when convergence has been attained. We present a new approach to this method that allows us to deterministically identify convergence. The method is tested with a home-built Fizeau interferometer that measures optical surfaces polished to lambda/100 using the Hydra tool. The intrinsic quality of the measurements is better than 0.5 nm. Other possible applications for this technique include fringe projection or any problem where phase shifting is involved. PMID:19277081

Luna, Esteban; Salas, Luis; Sohn, Erika; Ruiz, Elfego; Nunez, Juan M; Herrera, Joel

2009-03-10

222

The hydroarylation reaction--scope and limitations.  

PubMed

The synthetic potential of stereoselective, palladium-catalyzed hydro(het)arylation reactions of bi-, tri- and tetracyclic (hetero)alkenes in the presence of phospines and arsines as highly efficient ligands was studied. The mechanism of this reductive Heck reaction becomes more complex in the case of benzonorbornenes. Hydroarylation of diazabicyclo-[2.2.1]heptenes provides a stereoselective access to aryldiaminocyclopentanes. Electron-deficient arylpalladium complexes shift the reaction towards the product of a formal 1,2-hydrazidoarylation reaction of 1,3-cyclopentadiene by a stereoselective C-N cleavage. Due to steric reasons, rigid bicyclo[2.2.2]octenes react slower in hydroarylation reactions than the corresponding bicyclo[2.2.1]heptenes. The more flexible bicyclo[4.2.2]decene system already tends to undergo domino-Heck reactions, even under reductive conditions. When a tetracyclic cis-allylcyclopropane is carbopalladated in the presence of formates, the neighboring cyclopropane ring is attacked in the first reported example of a pi,sigma domino-Heck reaction. PMID:20657489

Namyslo, Jan C; Storsberg, Jörg; Klinge, Jens; Gärtner, Christian; Yao, Min-Liang; Ocal, Nuket; Kaufmann, Dieter Eckhard

2010-05-01

223

Knight Shift in Multivalley Semiconductors. I. Theory of Contact, Orbital, and Dipolar Shift and Relativistic Effects  

Microsoft Academic Search

A theory of the Knight shift in degenerate multivalley semiconductors is presented which takes into account the spin-orbit interaction and the relativistic effects on the hyperfine coupling. This theory treats rigorously the spinor character of the wave function and the nontensorial nature of the g matrix. We give a formula for the shift created by an arbitrary ellipsoidal valley. This

B. Sapoval; J. Y. Leloup

1973-01-01

224

Parallel phase-shifting digital holographic microscopy  

PubMed Central

We propose parallel phase-shifting digital holographic microscopy (PPSDHM) which has the ability of three-dimensional (3-D) motion measurement using space-division multiplexing technique. By the PPSDHM, instantaneous information of both the 3-D structure and the phase distributions of specimens can be simultaneously acquired with a single-shot exposure. We constructed a parallel phase-shifting digital holographic microscope consisting of an optical interferometer and an image sensor on which micro polarizers are attached pixel by pixel. The validity of the PPSDHM was experimentally verified by demonstrating the single-shot 3-D imaging and phase-imaging ability of the constructed microscope. PMID:21258494

Tahara, Tatsuki; Ito, Kenichi; Kakue, Takashi; Fujii, Motofumi; Shimozato, Yuki; Awatsuji, Yasuhiro; Nishio, Kenzo; Ura, Shogo; Kubota, Toshihiro; Matoba, Osamu

2010-01-01

225

Proton Mass Shift in Muonic Hydrogen Atom  

E-print Network

We show that the value of the proton mass depends on each bound state of muonic or electronic hydrogen atom. The charged particle bound to the proton produces magnetic field inside the proton. This makes a change to the amount of chiral condensate inside the proton. The change gives rise to the shift in the value of the proton mass. Numerically, the shift in the $2S$ state of the muonic hydrogen atom can be of the order of $0.1$ meV. The effect may solve the puzzle of the proton radius.

Aiichi Iwazaki

2014-08-11

226

Phase Transitions in Paradigm Shift Models  

PubMed Central

Two general models for paradigm shifts, deterministic propagation model (DM) and stochastic propagation model (SM), are proposed to describe paradigm shifts and the adoption of new technological levels. By defining the order parameter based on the diversity of ideas, , it is studied when and how the phase transition or the disappearance of a dominant paradigm occurs as a cost in DM or an innovation probability in SM increases. In addition, we also investigate how the propagation processes affect the transition nature. From analytical calculations and numerical simulations is shown to satisfy the scaling relation for DM with the number of agents . In contrast, in SM scales as . PMID:23951043

Chae, Huiseung; Yook, Soon-Hyung; Kim, Yup

2013-01-01

227

Communication theory and the shift handover report.  

PubMed

The cooperation that makes human society possible is manifested most visibly within the organization and is almost entirely dependent upon the skill with which we communicate (Tortoriello et al, 1978). By understanding concepts related to communication theory, nurses may be better able to analyse areas of communication in their own practice. This article reviews the concepts of communication in terms of definition, function and purpose. The communication process model is examined and the hindrances to effective communication are explored. The shift handover report is analysed and related to group networking theory. Communication theory is then applied to the shift handover process and recommendations for practice are made. PMID:9015988

Odell, A

228

Phase-shift binary digital holography.  

PubMed

We propose phase-shift digital holography (DH) with a one-bit image sensor. In this method, the propagating complex field from an object is binarized by a one-bit sensor using a phase-shifter. The complex field on the hologram plane is then calculated with the one-bit image data. The object field is recovered via Fresnel back-propagation of the calculated hologram and filtering to suppress some artifacts caused by the binarization. The concept was demonstrated in preliminary experiments by using a synthetically binarized hologram with single-shot and multi-shot phase-shift DH. PMID:25490472

Horisaki, Ryoichi; Tahara, Tatsuki

2014-11-15

229

Progress in speckle-shift strain measurement  

NASA Technical Reports Server (NTRS)

The Instrumentation and Control Technology Division of the Lewis Research Center has been developing an in-house capability to make one dimensional and two dimensional optical strain measurements on high temperature test specimens. The measurements are based on a two-beam speckle-shift technique. The development of composite materials for use in high temperature applications is generating interest in using the speckle-shift technique to measure strains on small diameter fibers and wires of various compositions. The results of preliminary speckle correlation tests on wire and fiber specimens are covered, and the advanced system currently under development is described.

Lant, Christian T.; Barranger, John P.; Oberle, Lawrence G.; Greer, Lawrence C., III

1991-01-01

230

Sideband correlation algorithm to detect phase shift and contrast variation in temporal phase-shifting interferometry  

NASA Astrophysics Data System (ADS)

Phase shift error and contrast variation caused by vibration lead to a large measurement error in temporal phase-shifting interferometry (PSI). To suppress the error, a sideband correlation algorithm is proposed to detect phase shift and contrast variation. The tilt factors and translational values of phase shift are determined by analyzing the correlations of spectral sidebands of interferograms. The contrast variations are determined by detecting the modulus of the baseband and sideband correlation result. A least-squares equation with contrast compensation is established to retrieve the wavefront phase. The algorithm requires a set of temporal phase-shifting interferograms, each one also containing a moderate amount of spatial-carrier; the interferograms may have an arbitrary aperture. Simulations demonstrate the reliability, and the experiments under vibration show the practical effectiveness of the algorithm.

Liu, Qian; Wang, Yang; Zhang, Yunfei; Ji, Fang; He, Jianguo

2014-12-01

231

Isoindolones and Related N-Heterocycles via Palladium Nanoparticle-Catalyzed 3Component Cascade Reactions  

Microsoft Academic Search

Non-phosphine-containing cyclopalladated N-heterocycles possessing either\\u000a \\u0009 sp2 C–Pd(II) or\\u000a \\u0009 sp3 C–Pd(II) bonds and simple Pd(II)\\u000a \\u0009 salts are precursors of Pd(0) nanoparticles whose initial\\u000a \\u0009 morphology is dependent on the nature of the precursor. Addition\\u000a \\u0009 of polyvinylpyrrolidone (pvp) dramatically increases catalyst\\u000a \\u0009 lifetime. Nanoparticle generation can be achieved at ambient\\u000a \\u0009 temperature in the presence of carbon monoxide by a process\\u000a \\u0009 akin to the water–gas shift

R. Grigg; V. Sridharan

232

Quantum-mechanics-derived 13Calpha chemical shift server (CheShift) for protein structure validation.  

PubMed

A server (CheShift) has been developed to predict (13)C(alpha) chemical shifts of protein structures. It is based on the generation of 696,916 conformations as a function of the phi, psi, omega, chi1 and chi2 torsional angles for all 20 naturally occurring amino acids. Their (13)C(alpha) chemical shifts were computed at the DFT level of theory with a small basis set and extrapolated, with an empirically-determined linear regression formula, to reproduce the values obtained with a larger basis set. Analysis of the accuracy and sensitivity of the CheShift predictions, in terms of both the correlation coefficient R and the conformational-averaged rmsd between the observed and predicted (13)C(alpha) chemical shifts, was carried out for 3 sets of conformations: (i) 36 x-ray-derived protein structures solved at 2.3 A or better resolution, for which sets of (13)C(alpha) chemical shifts were available; (ii) 15 pairs of x-ray and NMR-derived sets of protein conformations; and (iii) a set of decoys for 3 proteins showing an rmsd with respect to the x-ray structure from which they were derived of up to 3 A. Comparative analysis carried out with 4 popular servers, namely SHIFTS, SHIFTX, SPARTA, and PROSHIFT, for these 3 sets of conformations demonstrated that CheShift is the most sensitive server with which to detect subtle differences between protein models and, hence, to validate protein structures determined by either x-ray or NMR methods, if the observed (13)C(alpha) chemical shifts are available. CheShift is available as a web server. PMID:19805131

Vila, Jorge A; Arnautova, Yelena A; Martin, Osvaldo A; Scheraga, Harold A

2009-10-01

233

Work shift duration: a review comparing eight hour and 12 hour shift systems  

PubMed Central

OBJECTIVES: Shiftwork is now a major feature of working life across a broad range of industries. The features of the shift systems operated can impact on the wellbeing, performance, and sleep of shiftworkers. This paper reviews the current state of knowledge on one major characteristic of shift rotas-namely, shift duration. Evidence comparing the relative effects of eight hour and 12 hour shifts on fatigue and job performance, safety, sleep, and physical and psychological health are considered. At the organisational level, factors such as the mode of system implementation, attitudes towards shift rotas, sickness absence and turnover, overtime, and moonlighting are discussed. METHODS: Manual and electronic searches of the shiftwork research literature were conducted to obtain information on comparisons between eight hour and 12 hour shifts. RESULTS: The research findings are largely equivocal. The bulk of the evidence suggests few differences between eight and 12 hour shifts in the way they affect people. There may even be advantages to 12 hour shifts in terms of lower stress levels, better physical and psychological wellbeing, improved durations and quality of off duty sleep as well as improvements in family relations. On the negative side, the main concerns are fatigue and safety. It is noted that a 12 hour shift does not equate with being active for only 12 hours. CONCLUSIONS: There can be considerable extension of the person's time awake either side of the shift. However, the effects of longer term exposure to extended work days have been relatively uncharted in any systematic way. Longitudinal comparative research into the chronic impact of the compressed working week is needed.   PMID:9624275

Smith, L.; Folkard, S.; Tucker, P.; Macdonald, I.

1998-01-01

234

Moving attention - Evidence for time-invariant shifts of visual selective attention  

NASA Technical Reports Server (NTRS)

Two experiments measured the time to shift spatial selective attention across the visual field to targets 2 or 10 deg from central fixation. A central arrow cued the most likely target location. The direction of attention was inferred from reaction times to expected, unexpected, and neutral locations. The development of a spatial attentional set with time was examined by presenting target probes at varying times after the cue. There were no effects of distance on the time course of the attentional set. Reaction times for far locations were slower than for near, but the effects of attention were evident by 150 msec in both cases. Spatial attention does not shift with a characteristic, fixed velocity. Rather, velocity is proportional to distance, resulting in a movement time that is invariant over the distances tested.

Remington, R.; Pierce, L.

1984-01-01

235

The Glyoxal Clock Reaction  

ERIC Educational Resources Information Center

Research on the glyoxal clock reaction has led to adaptation of the clock reaction to a general chemistry experiment. This particular reaction is just one of many that used formaldehyde in the past. The kinetics of the glyoxal clock makes the reaction suitable as a general chemistry lab using a Calculator Based Laboratory (CBL) or a LabPro. The…

Ealy, Julie B.; Negron, Alexandra Rodriguez; Stephens, Jessica; Stauffer, Rebecca; Furrow, Stanley D.

2007-01-01

236

The Phase Shift in the Jumping Ring  

ERIC Educational Resources Information Center

The popular physics demonstration experiment known as Thomson's Jumping Ring (JR) has been variously explained as a simple example of Lenz's law, or as the result of a phase shift of the ring current relative to the induced emf. The failure of the first-quadrant Lenz's law explanation is shown by the time the ring takes to jump and by levitation.…

Jeffery, Rondo N.; Amiri, Farhang

2008-01-01

237

Lobster Fishing: Shifting Cycles and Changing Traditions  

E-print Network

Lobster Fishing: Shifting Cycles and Changing Traditions S teve Lawrence is a lobster fisherman in Kittery, Maine. He grew up in the area, and has been lobster fishing his entire life, similar to his Lobster Apprentice Program to earn his commercial lobster license before his 18th birthday. Business Steve

New Hampshire, University of

238

Differential phase shift keyed communication system  

NASA Technical Reports Server (NTRS)

A communication system using differential phase-shift-keying (DPSK) transmits and receives binary data without requiring timing or phase reference signals. The system encodes and modulates the data at the transmitter, and decodes and demodulates the data at the receiver, without ambiguity as to the data content.

Hopkins, P. M.; Wallingford, W. M. (inventors)

1974-01-01

239

Modular arithmetic weight and cyclic shifting.  

NASA Technical Reports Server (NTRS)

This note shows that the modular arithmetic weight of an integer is invariant to the cyclic shifts of its radix-2 form. This result leads to a reduced search for the minimum weight codeword in a cyclic AN-code as well as to a better understanding of previous work.

Hartman, W. F.

1972-01-01

240

Robert Collins More on Mean-shift  

E-print Network

1 CSE598G Robert Collins More on Mean-shift R.Collins, CSE, PSU CSE598G Spring 2006 CSE598G Robert Collins Recall: Kernel Density Estimation Given a set of data samples xi; i=1...n Convolve with a kernel at each data point H CSE598G Robert Collins Recall: Kernel Density Estimation For kernel H with bandwidth

Collins, Robert T.

241

Robert Collins More on Mean-shift  

E-print Network

CSE598G Robert Collins More on Mean-shift R.Collins, CSE, PSU CSE598G Spring 2006 #12;CSE598G Robert Collins Recall: Kernel Density Estimation Given a set of data samples xi; i=1...n Convolve centered at each data point H #12;CSE598G Robert Collins Recall: Kernel Density Estimation For kernel H

Collins, Robert T.

242

Special Section Shifting Foundations and Metrics for  

E-print Network

Special Section Shifting Foundations and Metrics for Golden-Cheeked Warbler Recovery JEFF S University Drive, San Marcos, TX 78666, USA ABSTRACT Using the golden-cheeked warbler (Setophaga chrysoparia, density estimation, endangered species, golden-cheeked warbler, occupancy models, population viability

Aspbury, Andrea S. - Department of Biology, Texas State University

243

Phase shifts in nonresonant coherent excitation  

E-print Network

Far-off-resonant pulsed laser fields produce negligible excitation between two atomic states but may induce considerable phase shifts. The acquired phases are usually calculated by using the adiabatic-elimination approximation. We analyze the accuracy of this approximation and derive the conditions for its applicability to the calculation of the phases. We account for various sources of imperfections, ranging from higher terms in the adiabatic-elimination expansion and irreversible population loss to couplings to additional states. We find that, as far as the phase shifts are concerned, the adiabatic elimination is accurate only for a very large detuning. We show that the adiabatic approximation is a far more accurate method for evaluating the phase shifts, with a vast domain of validity; the accuracy is further enhanced by superadiabatic corrections, which reduce the error well below $10^{-4}$. Moreover, owing to the effect of adiabatic population return, the adiabatic and superadiabatic approximations allow one to calculate the phase shifts even for a moderately large detuning, and even when the peak Rabi frequency is larger than the detuning; in these regimes the adiabatic elimination is completely inapplicable. We also derive several exact expressions for the phases using exactly soluble two-state and three-state analytical models.

Boyan T. Torosov; Nikolay V. Vitanov

2009-11-25

244

RQL Fuel Shifting Sector Rig Test  

NASA Technical Reports Server (NTRS)

The low emissions potential of a Rich-Quench-Lean (RQL) combustor for use in the HIgh Speed Civil transport (HSCT) application was evaluated as part of the NASA Critical Propulsion Components (CPC) Program. Fuel shifting as an approach to combustor control was evaluated in a multiple bank RQL combustor, utilizing reduced scale quench technology implemented in a convoluted linear with quench plate concept.

Holdeman, James D. (Technical Monitor); Haid, Daniel A.; Koopman, Frederick S.; Peschke, William O. T.; Siskind, Kenneth S.

2004-01-01

245

Survey Detects Shifting Priorities of School Boards  

ERIC Educational Resources Information Center

The author reports the results of a nationwide survey of school board members which show a shift in focus toward student achievement and away from district-management issues known as the "killer B's": buses, buildings, books, budgets, and bonds. But today's school board members appear not to be as interested in issues that many policy observers…

Samuels, Christina A.

2011-01-01

246

Shift of Meaning and Students' Alternative Concepts  

ERIC Educational Resources Information Center

The purpose of the study was to establish a relationship between the shift of meaning of the concept oxidation that has taken place during the historical development, and students' alternative concepts. First Examination Board papers were examined. The result enabled us to specify the research question. In the main part of the study,…

Schmidt, Hans-Jurgen; Volke, Dagmar

2003-01-01

247

Heart-rate pulse-shift detector  

NASA Technical Reports Server (NTRS)

Detector circuit accurately separates and counts phase-shift pulses over wide range of basic pulse-rate frequency, and also provides reasonable representation of full repetitive EKG waveform. Single telemeter implanted in small animal monitors not only body temperature but also animal movement and heart rate.

Anderson, M.

1974-01-01

248

Earthquake Information Service shifted to USGS  

Microsoft Academic Search

The National Earthquake Information Service, formerly a component of the National Oceanic and Atmospheric Administration, has now been shifted to the U.S. Geological Survey.The quake information group, located in Boulder, Colorado, receives and analyzes worldwide seismic data, determines earthquake epicenter locations, collects earthquake damage data, and makes the data available through publications. The group also provides assistance to other federal

Anonymous

1973-01-01

249

Hispanics Find Jobs that Shift Migration  

ERIC Educational Resources Information Center

Economic opportunity, the force that has driven population shifts for years, is changing the face of migration as Hispanics move into parts of the nation beyond border states and traditional ports of entry. North Carolina, Tennessee, Georgia, and Indiana are experiencing a steady growth in Hispanic population. In addition, West Virginia, Ohio, and…

Gilroy, Marilyn

2007-01-01

250

Deindustrialization and the Shift to Services.  

ERIC Educational Resources Information Center

Bureau of Labor Statistics data show the industrial sector as a whole in healthy shape, but a few manufacturing industries in deep trouble. These industries include tobacco manufacturers, iron and steel foundries, leather products, and steel manufacturers. Also examines shifts in employment and output, job quality, and outlook for the future. (CT)

Kutscher, Ronald E.; Personick, Valerie A.

1986-01-01

251

Generalized Feedback Shift Register Pseudorandom Number Algorithm  

Microsoft Academic Search

The generalized feedback shift register pseudorandom number algorithm has several advantages over all other pseudorandom number generators. These advantages are: (1) it produces multidimensional pseudorandom numbers; (2) it has an arbitrarily long period independent of the word size of the computer on which it is implemented; (3) it is faster than other pseudorandom number generators; (4) the “same” floating-point pseudorandom

T. G. Lewis; W. H. Payne

1973-01-01

252

4, 271287, 2008 Shifts in early spring  

E-print Network

-friendly Version Interactive Discussion Abstract Changes of the winter-to-spring switch-time of the upper air flow extending until 2007. The long-term variation of the air flow in early spring (March) exhibits multipleCPD 4, 271­287, 2008 Shifts in early spring wind regime in North-East Europe S. Keevallik and T

Paris-Sud XI, Université de

253

Working Night Shift Slows Metabolism, Study Suggests  

MedlinePLUS

... daytime routines on their days off. So their biological clocks wouldn't have the chance to flip to a new norm. And where does this leave shift workers? Wright, the dietitian, said that people can do their best to eat healthy foods and fit time in for exercise when they' ...

254

Systems analysis of electricity production from coal using fuel cells  

NASA Astrophysics Data System (ADS)

Gasifiers, heat transfer, gas stability, quench, water-gas shift reaction, reforming-methanation, other catalytic reactions, compressors and expanders, acid-gas removal, the fuel cell, and catalytic combustors are described. System pressure drops, efficiency of rotating power equipment, heat exchangers, chemical reactions, steam systems, and the fuel cell subsystems are discussed.

Fleming, D. K.

1983-11-01

255

Dynamic TAP reactor studies of the oxidizing capability of CO2 on a Au/CeO2 catalyst A first step towards identifying a redox mechanism in  

E-print Network

towards identifying a redox mechanism in the reverse water gas shift reaction L.C. Wang, M. Tahvildar (RWGS) reaction on a Au/CeO2 supported catalyst, in particular the role of the redox mechanism, we have, is significantly lower than that from O2. Both the low reaction probability and the temperature dependence

Ulm, Universität

256

Systems analysis of electricity production from coal using fuel cells  

NASA Technical Reports Server (NTRS)

Gasifiers, heat transfer, gas stability, quench, water-gas shift reaction, reforming-methanation, other catalytic reactions, compressors and expanders, acid-gas removal, the fuel cell, and catalytic combustors are described. System pressure drops, efficiency of rotating power equipment, heat exchangers, chemical reactions, steam systems, and the fuel cell subsystems are discussed.

Fleming, D. K.

1983-01-01

257

A CLASS OF NONSOFIC MULTIDIMENSIONAL SHIFT SPACES RONNIE PAVLOV  

E-print Network

. In this case, we call XF a Zd shift of finite type, or SFT. A slightly more general class of shift spaces, under the fairly mild assumption of topological mixing, any one-dimensional SFT or sofic shift has dense necessary and sufficient conditions for being a Z SFT or sofic shift. 2010 Mathematics Subject

Pavlov, Ronnie

258

Classical toy models for the monopole shift and the quadrupole shift.  

PubMed

The penetration of s- and p(1/2)-electrons into the atomic nucleus leads to a variety of observable effects. The presence of s-electrons inside the nucleus gives rise to the isotope shift in atomic spectroscopy, and to the isomer shift in Mössbauer spectroscopy. Both well-known phenomena are manifestations of the more general monopole shift. In a recent paper (Koch et al., Phys. Rev. A, 2010, 81, 032507), we discussed the existence of the formally analogous quadrupole shift: a tensor correction to the electric quadrupole interaction due to the penetration of relativistic p(1/2)-electrons into the nucleus. The quadrupole shift is predicted to be observable by high-accuracy molecular spectroscopy on a set of 4 molecules (the quadrupole anomaly). The simple physics behind all these related phenomena is easily obscured by an elaborate mathematical formalism that is required for their derivation: a multipole expansion in combination with perturbation theory, invoking quantum physics and ideally relativity. In the present paper, we take a totally different approach. We consider three classical 'toy models' that can be solved by elementary calculus, and that nevertheless contain all essential physics of the monopole and quadrupole shifts. We hope that this intuitive (yet exact) analysis will increase the understanding about multipole shift phenomena in a broader community. PMID:22782015

Rose, Katrin; Cottenier, Stefaan

2012-08-28

259

Sleep Loss and Fatigue in Shift Work and Shift Work Disorder  

PubMed Central

Shift work is highly prevalent in industrialized societies (>20%) but, when it includes night work, it has pronounced negative effects on sleep, subjective and physiological sleepiness, performance, accident risk, as well as on health outcomes such as cardiovascular disease and certain forms of cancer. The reason is the conflict between the day oriented circadian physiology and the requirement for work and sleep at the “wrong” biological time of day. Other factors that negatively impact work shift sleepiness and accident risk include long duration shifts greater than 12 hours and individual vulnerability for phase intolerance that may lead to a diagnosis of shift work disorder; i.e., those shift workers with the greatest sleepiness and performance impairment during the biological night and insomnia during the biological day. Whereas some countermeasures may be used to ameliorate the negative impact of shift work on nighttime sleepiness and daytime insomnia (combined countermeasures may be the best available), there seems at present to be no way to eliminate most of the negative effects of shift work on human physiology and cognition. PMID:20640236

Åkerstedt, Torbjörn; Wright, Kenneth P.

2010-01-01

260

Iterative phase-shifting algorithm immune to random phase shifts and tilts.  

PubMed

An iterative phase-shifting algorithm based on the least-squares principle is developed to overcome the random piston and tilt wavefront errors generated from the phase shifter. The algorithm iteratively calculates the phase distribution and the phase-shifting map to minimize the sum of squared errors in the interferograms. The performance of the algorithm is evaluated via computer simulations and validated by the Fizeau interferometer measurements. The results show that the proposed algorithm has a fast convergence rate and satisfactory phase-estimation accuracy, improving the measurement precision of the phase-shifting interferometers with significant phase-shifter errors. PMID:23669854

Chen, Yi-Chun; Lin, Po-Chih; Lee, Chung-Min; Liang, Chao-Wen

2013-05-10

261

Nuclear waste vitrification efficiency: cold cap reactions  

SciTech Connect

The cost and schedule of nuclear waste treatment and immobilization are greatly affected by the rate of glass production. Various factors influence the performance of a waste-glass melter. One of the most significant, and also one of the least understood, is the process of batch melting. Studies are being conducted to gain fundamental understanding of the batch reactions, particularly those that influence the rate of melting, and models are being developed to link batch makeup and melter operation to the melting rate. Batch melting takes place within the cold cap, i.e., a batch layer floating on the surface of molten glass. The conversion of batch to glass consists of various chemical reactions, phase transitions, and diffusion-controlled processes. These include water evaporation (slurry feed contains as high as 60% water), gas evolution, the melting of salts, the formation of borate melt, reactions of borate melt with molten salts and with amorphous oxides (Fe2O3 and Al2O3), the formation of intermediate crystalline phases, the formation of a continuous glass-forming melt, the growth and collapse of primary foam, and the dissolution of residual solids. To this list we also need to add the formation of secondary foam that originates from molten glass but accumulates on the bottom of the cold cap. This study presents relevant data obtained for a high-level-waste melter feed and introduces a one-dimensional (1D) mathematical model of the cold cap as a step toward an advanced three-dimensional (3D) version for a complete model of the waste glass melter. The 1D model describes the batch-to-glass conversion within the cold cap as it progresses in a vertical direction. With constitutive equations and key parameters based on measured data, and simplified boundary conditions on the cold-cap interfaces with the glass melt and the plenum space of the melter, the model provides sensitivity analysis of the response of the cold cap to the batch makeup and melter conditions. The model demonstrates that batch foaming has a decisive influence on the rate of melting. Understanding the dynamics of the foam layer at the bottom of the cold cap and the heat transfer through it appears crucial for a reliable prediction of the rate of melting as a function of the melter-feed makeup and melter operation parameters. Although the study is focused on a batch for waste vitrification, the authors expect that the outcome will also be relevant for commercial glass melting.

Hrma, Pavel R.; Kruger, Albert A.; Pokorny, Richard

2012-12-15

262

Regularization Ambiguity Problem for the Chern-Simons Shift  

NASA Astrophysics Data System (ADS)

We consider the Chern-Simons parameter shift with the hybrid regularization consisting of the higher covariant derivative (HCD) and the Pauli-Villars (PV) regulators. We show that the shift is closely related to the parity of the regulators and get the shift and no-shift results by a suitable choice of the PV regulators. A naive treatment of the HCD term leads to incorrect value of the shift.

Nittoh, Koh-Ichi; Ebihara, Toru

263

Light-Induced Frequency Shift in Chemical Spirals Valery Petrov, Qi Ouyang, Ge Li, and Harry L. Swinney*  

E-print Network

Light-Induced Frequency Shift in Chemical Spirals Valery Petrov, Qi Ouyang, Ge Li, and Harry L-Tyson relation for the spirals, D /3k2 , is independent of light intensity (D ) 2.5 Ã? 10-6 cm2 /s). Introduction The light-sensitive Belousov-Zhabotinsky (BZ) reaction with a ruthenium-based catalyst is a convenient

Texas at Austin. University of

264

Concatenated shift registers generating maximally spaced phase shifts of PN-sequences  

NASA Technical Reports Server (NTRS)

A large class of linearly concatenated shift registers is shown to generate approximately maximally spaced phase shifts of pn-sequences, for use in pseudorandom number generation. A constructive method is presented for finding members of this class, for almost all degrees for which primitive trinomials exist. The sequences which result are not normally characterized by trinomial recursions, which is desirable since trinomial sequences can have some undesirable randomness properties.

Hurd, W. J.; Welch, L. R.

1977-01-01

265

Evolutionary shift dynamics on a cycle.  

PubMed

We present a new model of evolutionary dynamics in one-dimensional space. Individuals are arranged on a cycle. When a new offspring is born, another individual dies and the rest shift around the cycle to make room. This rule, which is inspired by spatial evolution in somatic tissue and microbial colonies, has the remarkable property that, in the limit of large population size, evolution acts to maximize the payoff of the whole population. Therefore, social dilemmas, in which some individuals benefit at the expense of others, are resolved. We demonstrate this principle for both discrete and continuous games. We also discuss extensions of our model to other one-dimensional spatial configurations. We conclude that shift dynamics in one dimension is an unusually strong promoter of cooperative behavior. PMID:22814475

Allen, Benjamin; Nowak, Martin A

2012-10-21

266

Phase-shifting color digital holography  

NASA Astrophysics Data System (ADS)

Digital holography with a three-wavelength laser and a color CCD has been demonstrated. With the phase shifting of the reference beam, in-line holograms for three wavelengths are recorded simultaneously for derivation of the complex amplitude at each wavelength, and then the three monochromatic images are reconstructed and combined into full-color images in the computer. Laser power variation for wavelengths can be compensated for in the reconstruction process. We have compared the images reconstructed by two algorithms using a single Fourier transformation and a convolution with each other by both experiments and numerical simulations. Phase-shifting errors arising at two of the three wavelengths have proved not to cause serious deterioration of the reconstructed images.

Yamaguchi, Ichirou; Matsumura, Tatsuki; Kato, Jun-ichi

2002-07-01

267

Is the Lamb shift chemically significant?  

NASA Technical Reports Server (NTRS)

The contribution of the Lamb shift to the atomization energies of some prototype molecules, BF3, AlF3, and GaF3, is estimated by a perturbation procedure. It is found to be in the range of 3-5% of the one-electron scalar relativistic contribution to the atomization energy. The maximum absolute value is 0.2 kcal/mol for GaF3. These sample calculations indicate that the Lamb shift is probably small enough to be neglected for energetics of molecules containing light atoms if the target accuracy is 1 kcal/mol, but for higher accuracy calculations and for molecules containing heavy elements it must be considered.

Dyall, Kenneth G.; Bauschlicher, Charles W., Jr.; Schwenke, David W.; Pyykko, Pekka; Arnold, James (Technical Monitor)

2001-01-01

268

Anomalous frequency shifts in the solar system  

E-print Network

The improvements of the observations of the solar system allowed by the use of probes and big instruments let appear several problems: The frequencies of the radio signals received from the probes sent over 5 UA from the Sun are too high; the explanation by spicules or siphon-flows of the frequency shifts of UV emissions observed on the surface of the sun by SOHO is not satisfactory; the anisotropy of the CMB seems bound to the ecliptic. This problems are solved using a coherent optical effect, deduced from standard spectroscopy and easily observed with lasers. In a gas containing atomic hydrogen in states 2S and (or) 2P, transfers of energy between light beams, allowed by thermodynamics, produce the required frequency shifts or amplifications.

Jacques Moret-Bailly

2005-07-19

269

Real-time phase shift interference microscopy.  

PubMed

A real-time phase shift interference microscopy system is presented using a polarization-based Linnik interferometer operating with three synchronized, phase-masked, parallel detectors. Using this method, several important applications that require high speed and accuracy, such as dynamic focusing control, tilt measurement, submicrometer roughness measurement, and 3D profiling of fine structures, are demonstrated in 50 volumes per second and with 2 nm height repeatability. PMID:25166114

Safrani, Avner; Abdulhalim, Ibrahim

2014-09-01

270

DNA structures from phosphate chemical shifts  

Microsoft Academic Search

For B-DNA, the strong linear correlation observed by nuclear magnetic resonance (NMR) between the 31P chemical shifts (dP) and three recurrent internucleotide distances demonstrates the tight coupling between phosphate motions and helicoidal parameters. It allows to translate dP into distance restraints directly exploitable in structural refine- ment. It even provides a new method for refining DNA oligomers with restraints exclusively

Josephine Abi-Ghanem; Brahim Heddi; Nicolas Foloppe; Brigitte Hartmann

2010-01-01

271

Brain Shift Modeling for Use in Neurosurgery  

Microsoft Academic Search

Surgical navigation systems are used intraoperatively to help the surgeon to ascertain her or his position and to guide tools\\u000a within the patient frame with respect to registered structures of interest in the preoperative images. However, these systems\\u000a are subject to inaccuracy caused by intraoperative brain movement (brain shift) since they assume that the intracranial structures\\u000a are rigid. Experiments show

Oskar M. Skrinjar; Dennis D. Spencer; James S. Duncan

1998-01-01

272

Frontal Sinus Fractures: A Conservative Shift  

PubMed Central

This article reflects on the changing management of frontal sinus fractures. Severity of these injuries has decreased tremendously since the universal adoption of seat belts and air bags. Recently, there has been a shift from aggressive surgical management to more conservative management strategies, some forgoing surgery all together. New technologies, such as bioabsorbable plates and endoscopic sinus surgery, are leading the way in improved surgical management strategies and offer promising alternatives to the more traditional approaches. PMID:24436753

Weathers, William M.; Wolfswinkel, Erik M.; Hatef, Daniel A.; Lee, Edward I.; Brown, Rodger H.; Hollier, Larry H.

2013-01-01

273

Stabilizing windings for tilting and shifting modes  

DOEpatents

This invention relates to passive conducting loops for stabilizing a plasma ring against unstable tilting and/or shifting modes. To this end, for example, plasma ring in a spheromak is stabilized by a set of four figure-8 shaped loops having one pair on one side of the plasma and one pair on the other side with each pair comprising two loops whose axes are transverse to each other.

Jardin, Stephen C. (Princeton, NJ); Christensen, Uffe R. (Princeton, NJ)

1984-01-01

274

Stereoscopic watermarking by horizontal noise mean shifting  

NASA Astrophysics Data System (ADS)

Depth-image-based rendering (DIBR) is a method to represent a stereoscopic content. The DIBR consists of a monoscopic center view and an associated per-pixel depth map. Using these two components and given depth condition from a user, the DIBR renders left and right views. The advantages of DIBR are numerous. The user can choose not only the monoscopic or stereoscopic view selectively, but also the depth condition what he prefers when he watches a stereoscopic content. However, in the view of copyright protection, since not only the center view but also each left or right view can be used as a monoscopic content when they are illegally distributed, the watermark signal which is embedded in the center view must have an ability to protect the respective three views. In this study, we solve this problem by exploiting the horizontal noise mean shifting (HNMS) technique. We exploit the fact that the objects in the view are shifted only to horizontal way when the center view renders to the left and right views. Using this fact, the proposed stereoscopic watermarking scheme moves the mean of horizontal noise histogram which is invariant to horizontal shifting, and we achieve good performance as shown in the experimental results.

Lee, Ji-Won; Kim, Hee-Dong; Choi, Hak-Yeol; Choi, Sung-Hee; Lee, Heung-Kyu

2012-03-01

275

Random-phase-shift Fizeau interferometer.  

PubMed

A new and potentially cost efficient kind of vibration-tolerant surface measurement interferometer based on the Fizeau-principle is demonstrated. The crucial novelty of this approach is the combination of two optoelectronic sensors: an image sensor with high spatial resolution and an arrangement of photodiodes with high temporal resolution. The photodiodes continuously measure the random-phase-shifts caused by environmental vibrations in three noncollinear points of the test surface. The high spatial resolution sensor takes several "frozen" images of the test surface by using short exposure times. Under the assumption of rigid body movement the continuously measured phase shifts of the three surface points enable the calculation of a virtual plane that is representative for the position and orientation of the whole test surface. For this purpose a new random-phase-shift algorithm had to be developed. The whole system was tested on an optical table without vibration isolation under the influence of random vibrations. The analysis of the root-mean-square (RMS) over ten different measurements shows a measurement repeatability of about 0.004 wave (approximately 2.5 nm for 632.8 nm laser wavelength). PMID:22193185

Broistedt, Hagen; Doloca, Nicolae Radu; Strube, Sebastian; Tutsch, Rainer

2011-12-20

276

New color-shifting security devices  

NASA Astrophysics Data System (ADS)

The unbroken global increase of forgery and counterfeiting of valuable documents and products steadily requires improved types of optical security devices. Hence, the "security world" is actively seeking for new features which meet high security standards, look attractively and allow easy recognition. One special smart security device created by ROLIC's technology represents a cholesteric device combined with a phase image. On tilting, such devices reveal strong color shifts which are clearly visible to the naked eye. The additional latent image is invisible under normal lighting conditions but can be revealed to human eyes by means of a simple, commercially available linear sheet polarizer. Based on our earlier work, first published in 1981, we now have developed phase change guest-host devices combined with dye-doped cholesteric material for application in new security features. ROLIC has developed sophisticated material systems of cross-linkable cholesteric liquid crystals and suitable cross-linkable dyes which allow to create outstanding cholesteric color-shifting effects not only on light absorbing dark backgrounds but also on bright or even white backgrounds preserving the circularly polarizing state. The new security devices combine unambiguously 1st and 2nd level inspection features and show brilliant colors on black as well as on white substrates. On tilting, the security devices exhibit remarkable color shifts while the integrated hidden images can be revealed by use of a sheet polarizer. Furthermore, due to its very thin material layers, even demanding applications, such as on banknotes can be considered.

Moia, Franco

2004-06-01

277

Pterandra pyroidea: a case of pollination shift within Neotropical Malpighiaceae  

PubMed Central

Background and Aims Most Neotropical species of Malpighiaceae produce floral fatty oils in calyx glands to attract pollinating oil-collecting bees, which depend on this resource for reproduction. This specialized type of pollination system tends to be lost in members of the family that occur outside the geographic distribution (e.g. Africa) of Neotropical oil-collecting bees. This study focused on the pollination ecology, chemical ecology and reproductive biology of an oil flower species, Pterandra pyroidea (Malpighiaceae) from the Brazilian Cerrado. Populations of this species consist of plants with oil-secreting (glandular) flowers, plants with non-oil-secreting flowers (eglandular) or a mix of both plant types. This study specifically aims to clarify the role of eglandular morphs in this species. Methods Data on pollinators were recorded by in situ observations. Breeding system experiments were conducted by isolating inflorescences and by enzymatic reactions. Floral resources, pollen and floral oils offered by this species were analysed by staining and a combination of various spectroscopic methods. Key Results Eglandular flowers of P. pyroidea do not act as mimics of their oil-producing conspecifics to attract pollinators. Instead, both oil-producing and oil-free flowers depend on pollen-collecting bees for reproduction, and their main pollinators are bumble-bees. Floral oils produced by glandular flowers are less complex than those described in closely related genera. Conclusions Eglandular flowers represent a shift in the pollination system in which oil is being lost and pollen is becoming the main reward of P. pyroidea flowers. Pollination shifts of this kind have hitherto not been demonstrated empirically within Neotropical Malpighiaceae and this species exhibits an unusual transition from a specialized towards a generalized pollination system in an area considered the hotspot of oil-collecting bee diversity in the Neotropics. Transitions of this type provide an opportunity to study ongoing evolutionary mechanisms that promote the persistence of species previously involved in specialized mutualistic relationships. PMID:21610210

Cappellari, Simone C.; Haleem, Muhammad A.; Marsaioli, Anita J.; Tidon, Rosana; Simpson, Beryl B.

2011-01-01

278

Asymmetric tandem 1,5-hydride shift/ring closure for the synthesis of chiral spirooxindole tetrahydroquinolines.  

PubMed

The direct functionalization of sp(3) C?H bonds through a tandem 1,5-hydride shift/ring closure is described. Various optically active spirooxindole tetrahydroquinoline derivatives bearing contiguous quaternary or tertiary stereogenic carbon centers were readily synthesized. A chiral scandium complex of N,N'-dioxide promoted the reactions in good yields (up to 97?%) with excellent diastereoselectivities (>20:1) and enantioselectivities (up to 94?% ee). Kinetic isotope effect (KIE) experiments and internal redox reactions of chiral substrates were conducted, and the results provided intriguing information that helped clarify the mechanism of the reaction. PMID:25421053

Cao, Weidi; Liu, Xiaohua; Guo, Jing; Lin, Lili; Feng, Xiaoming

2015-01-19

279

Microscale Thermite Reactions.  

ERIC Educational Resources Information Center

Describes the adaptation of thermite (aluminum with metal oxides) reactions from whole-class demonstrations to student-run micro-reactions. Lists detailed directions and possible variations of the experiment. (WRM)

Arnaiz, Francisco J.; Aguado, Rafael; Arnaiz, Susana

1998-01-01

280

Classification of clock reactions.  

PubMed

Autocatalytic systems are sometimes designated as clock reactions or reactions that exhibit clock behavior. To resolve the recent dispute over the term clock reaction, we describe a new approach to classify systems featuring clock behavior into three distinct groups: substrate-depletive clock reactions, autocatalysis-driven clock reactions, and systems that have pseudo clock behavior. Many of the well-known classical and recently discovered reactions can conveniently be put into these categories. We also provide a convincing argument for classifying some autocatalytic processes as clock reactions, but it does not necessarily mean that all autocatalytic processes should be classified as autocatalysis-driven clock reactions. This classification can be conveniently performed if the kinetic nature of the given system has been completely elucidated and understood. PMID:25425415

Horváth, Attila K; Nagypál, István

2015-02-23

281

Chemical Reactions (Netorials)  

NSDL National Science Digital Library

Chemical Reactions: this is a resource in the collection "Netorials". The Netorials cover selected topics in first-year chemistry including: Chemical Reactions, Stoichiometry, Thermodynamics, Intermolecular Forces, Acids & Bases, Biomolecules, and Electrochemistry.

282

Microfluidic chemical reaction circuits  

DOEpatents

New microfluidic devices, useful for carrying out chemical reactions, are provided. The devices are adapted for on-chip solvent exchange, chemical processes requiring multiple chemical reactions, and rapid concentration of reagents.

Lee, Chung-cheng (Irvine, CA); Sui, Guodong (Los Angeles, CA); Elizarov, Arkadij (Valley Village, CA); Kolb, Hartmuth C. (Playa del Rey, CA); Huang, Jiang (San Jose, CA); Heath, James R. (South Pasadena, CA); Phelps, Michael E. (Los Angeles, CA); Quake, Stephen R. (Stanford, CA); Tseng, Hsian-rong (Los Angeles, CA); Wyatt, Paul (Tipperary, IE); Daridon, Antoine (Mont-Sur-Rolle, CH)

2012-06-26

283

Eye gaze triggers reflexive attention shifts: Evidence from lateralised ERPs.  

PubMed

Social cues, such as another individual?s eye gaze, provide valuable information regarding the actions and intentions of others. Previous studies have suggested that seeing another?s gaze automatically orients one?s attention in the gaze direction. In this event-related potential (ERP) study, a spatial cuing paradigm was combined with a visual search task in which targets were defined by feature conjunctions in order to eliminate effects of target/distractor salience. Participants viewed centrally presented faces with neutral expressions in which eyes looked to the left or right. The participants? task was to identify a target object (with or without gap) defined by a combination of shape and orientation, which appeared in either the same (cued) or the opposite (uncued) location as the direction of the eye gaze. There was behavioural evidence of a gaze congruency effect, as reaction times (RTs) were faster when the eyes looked towards the target rather than away from the location of the target. The ERP data indicated the presence of significant gaze-congruent early directing attention negativity (EDAN) and anterior directing attention negativity (ADAN), reflecting attention shifts to the cued location in advance of the target presentation. ERP data did not show evidence of later orienting of attention triggered by gaze cues in the late attention-directing attention positivity (LDAP) at posterior sites. The results disclosed the neural response during reflexive attention shifting triggered by gazes and ascertained the relationship among EDAN, ADAN, LDAP and gaze-elicited attention shifts. After the presentation of the target array without salient stimuli, the presence of the N2-posterior-contralateral (N2pc) in the cued trials and the absence in the uncued trials further supported that attention had been directed to the possible target location prior to the target onset. The ERPs in response to the target array also extend our understanding of the neural response that orients spatial attention by providing valuable information about the temporal dynamics without the influence of salience. PMID:25241361

Feng, Qing; Zhang, Xuemin

2014-11-17

284

Chemical Reactions and Stoichiometry  

NSDL National Science Digital Library

In this activity, students explore reactions in which chemical bonds are formed and broken. Students experiment with changing the temperature and the concentration of the atoms in order to see how these affect reaction rates. They also learn how to communicate what happens during a chemical reaction by writing the ratios of reactants and products, known as stoichiometry.

The Concord Consortium

2011-12-11

285

Reaction coordinates for electron transfer reactions  

SciTech Connect

The polarization fluctuation and energy gap formulations of the reaction coordinate for outer sphere electron transfer are linearly related to the constant energy constraint Lagrangian multiplier m in Marcus' theory of electron transfer. The quadratic dependence of the free energies of the reactant and product intermediates on m and m+1, respectively, leads to similar dependence of the free energies on the reaction coordinates and to the same dependence of the activation energy on the reorganization energy and the standard reaction free energy. Within the approximations of a continuum model of the solvent and linear response of the longitudinal polarization to the electric field in Marcus' theory, both formulations of the reaction coordinate are expected to lead to the same results.

Rasaiah, Jayendran C. [Department of Chemistry, University of Maine, Orono, Maine 04469 (United States); Zhu Jianjun [Department of Chemistry, State University of New York, Stonybrook, New York 11790 (United States) and Department of Chemistry, Henan Normal University, Xinxiang, Henan (China)

2008-12-07

286

Chemical Reactions: Investigating Exothermic and Endothermic Reactions  

NSDL National Science Digital Library

This activity is an inquiry-based investigation where students discover the indicators of chemical reactions (endothermic and exothermic) by collecting data and using that data to develop a testable question for further experimentation.

287

Application of the generalized shift operator to the Hankel transform.  

PubMed

It is well known that the Hankel transform possesses neither a shift-modulation nor a convolution-multiplication rule, both of which have found many uses when used with other integral transforms. In this paper, the generalized shift operator, as defined by Levitan, is applied to the Hankel transform. It is shown that under this generalized definition of shift, both convolution and shift theorems now apply to the Hankel transform. The operation of a generalized shift is compared to that of a simple shift via example. PMID:24877034

Baddour, Natalie

2014-01-01

288

NMR characterization of cellulose acetate: Chemical shift assignments, substituent effects, and chemical shift additivity.  

PubMed

A series of cellulose acetates (CA) with degrees of substitution (DS) ranging from 2.92-0.92 dissolved in dimethylsulfoxide (DMSO)-d6 and cellulose dissolved in tetrabutylammonium fluoride (TBAF)/DMSO-d6 were investigated by two-dimensional NMR spectroscopy. The NMR spectroscopic analysis allowed the determination of the (1)H and (13)C NMR chemical shifts of the eight anhydroglucose units (AGUs) that contain CA: 2,3,6-tri-, 2,3-di-, 2,6-di-, 3,6-di-, 2-mono-, 3-mono-, 6-mono-, and unacetylated AGUs. A comparative analysis of the chemical shift data revealed the substituent effect of acetyl groups at the 2-, 3-, and 6-positions on the (1)H and (13)C nuclei in the same AGU. In addition, chemical shift additivity could be applied to the (1)H and (13)C chemical shifts of CA because the chemical shifts of the diacetylated and triacetylated AGUs could be almost completely explained by the acetyl substituent effects at the 2-, 3-, and 6-positions. PMID:25542112

Kono, Hiroyuki; Hashimoto, Hisaho; Shimizu, Yuuichi

2015-03-15

289

Green binary and phase shifting mask  

NASA Astrophysics Data System (ADS)

SixNy/Ni thin film green mask blanks were developed , and are now going to be used to replace general chromium film used for binary mask as well as to replace molydium silicide embedded material for AttPSM for I-line (365 nm), KrF (248 nm), ArF (193 nm) and Contact/Proximity lithography. A bilayer structure of a 1 nm thick opaque, conductive nickel layer and a SixNy layer is proposed for binary and phase-shifting mask. With the good controlling of plasma CVD of SixNy under silane (50 sccm), ammonia (5 sccm) and nitrogen (100 sccm), the pressure is 250 mTorr. and RF frequency 13.56 MHz and power 50 W. SixNy has enough deposition latitude to meet the requirements as an embedded layer for required phase shift 180 degree, and the T% in 193, 248 and 365 nm can be adjusted between 2% to 20% for binary and phase shifting mask usage. Ni can be deposited by E-gun, its sheet resistance Rs is less than 1.435 k?/square. Jeol e-beam system and I-line stepper are used to evaluate these thin film green mask blanks, feature size less than 200 nm half pitch pattern and 0.558 ?m pitch contact hole can be printed. Transmission spectrums of various thickness of SixNy film are inspected by using UV spectrometer and FTIR. Optical constants of the SixNy film are measured by n & k meter and surface roughness is inspected by using Atomic Force Microscope (AFM).

Shy, S. L.; Hong, Chao-Sin; Wu, Cheng-San; Chen, S. J.; Wu, Hung-Yu; Ting, Yung-Chiang

2009-12-01

290

Pendulum Shifts, Context, Error, and Personal Accountability  

SciTech Connect

This paper describes a series of tools that were developed to achieve a balance in under-standing LOWs and the human component of events (including accountability) as the INL continues its shift to a learning culture where people report, are accountable and interested in making a positive difference - and want to report because information is handled correctly and the result benefits both the reporting individual and the organization. We present our model for understanding these interrelationships; the initiatives that were undertaken to improve overall performance.

Harold Blackman; Oren Hester

2011-09-01

291

Scaling Shift in Multicracked Fiber Bundles  

NASA Astrophysics Data System (ADS)

Bundles of fibers, wires, or filaments are ubiquitous structures in both natural and artificial materials. We investigate the bundle degradation induced by an external damaging action through a theoretical model describing an assembly of parallel fibers, progressively damaged by a random population of cracks. Fibers in our model interact by means of a lateral linear coupling, thus retaining structural integrity even after substantial damage. Monte Carlo simulations of the Young's modulus degradation for increasing crack density demonstrate a remarkable scaling shift between an exponential and a power-law regime. Analytical solutions of the model confirm this behavior, and provide a thorough understanding of the underlying physics.

Manca, Fabio; Giordano, Stefano; Palla, Pier Luca; Cleri, Fabrizio

2014-12-01

292

A tentative explanation of cosmological red shift  

NASA Technical Reports Server (NTRS)

The authors suggest a possible alternative explanation of cosmological red shift. They consider that there exists a background field in the universe, and that light (the photon) has an extremely weak interaction with this background, and as result, experiences an energy loss. By analogy with damped oscillations, the authors introduce a dumping term with the first derivative with respect to time in the wave equation. The solution yields a linearly reduced frequency of the light with travel distance. The purpose of this exercise is to demonstrate how a simple alternative interpretation of the Hubble relation can be generated.

Chang, T.; Torr, D. G.

1990-01-01

293

Using Spectral Edge To Measure Doppler Shift  

NASA Technical Reports Server (NTRS)

New pulsed-laser ranging systems implement spectral-edge technique making high-resolution measurements of Doppler frequency shift in signals backscattered from targets. Pulsed laser emits at ultraviolet, visible, or infrared wavelength suitable for generation of desired target. Optical filter ("edge" filter) has sharp spectral transmission function such that middle frequency of laser emission lies on steep portion of slope ("edge") on one side of peak. Frequency inferred from relative amplitudes of signal with and without filtering. Intended for use in measuring velocities of solid and diffuse moving targets like wind, clouds, aerosols, or rain. Applications include measurements of wind shear from airports and aircraft.

Korb, Lawrence

1992-01-01

294

Solar Doppler shifts - Sources of continuous spectra  

NASA Technical Reports Server (NTRS)

Oscillation observations can be used to study nonoscillatory solar phenomena that exhibit Doppler shifts. The paper discusses several effects of these phenomena and their associated temporal and spatial power spectra: (1) they limit the signal-to-noise ratio and sometimes detectability of oscillation modes; (2) there is the potential for better understanding and/or detection of solar phenomena; (3) large-scale convection may spatially modulate oscillation modes, leading to a continuous background spectrum; and (4) in regions of the spectrum where the resolution to separate modes is lacking one can determine upper limits for the integrated effects of modes.

Duvall, T. L., Jr.; Harvey, J. W.

1986-01-01

295

Scaling shift in multicracked fiber bundles.  

PubMed

Bundles of fibers, wires, or filaments are ubiquitous structures in both natural and artificial materials. We investigate the bundle degradation induced by an external damaging action through a theoretical model describing an assembly of parallel fibers, progressively damaged by a random population of cracks. Fibers in our model interact by means of a lateral linear coupling, thus retaining structural integrity even after substantial damage. Monte Carlo simulations of the Young's modulus degradation for increasing crack density demonstrate a remarkable scaling shift between an exponential and a power-law regime. Analytical solutions of the model confirm this behavior, and provide a thorough understanding of the underlying physics. PMID:25554893

Manca, Fabio; Giordano, Stefano; Palla, Pier Luca; Cleri, Fabrizio

2014-12-19

296

Resonance-shifting luminescent solar concentrators  

DOEpatents

An optical system and method to overcome luminescent solar concentrator inefficiencies by resonance-shifting, in which sharply directed emission from a bi-layer cavity into a glass substrate returns to interact with the cavity off-resonance at each subsequent reflection, significantly reducing reabsorption loss en route to the edges. In one embodiment, the system comprises a luminescent solar concentrator comprising a transparent substrate, a luminescent film having a variable thickness; and a low refractive index layer disposed between the transparent substrate and the luminescent film.

Giebink, Noel Christopher; Wiederrecht, Gary P; Wasielewski, Michael R

2014-09-23

297

A partial differential equation for pseudocontact shift.  

PubMed

It is demonstrated that pseudocontact shift (PCS), viewed as a scalar or a tensor field in three dimensions, obeys an elliptic partial differential equation with a source term that depends on the Hessian of the unpaired electron probability density. The equation enables straightforward PCS prediction and analysis in systems with delocalized unpaired electrons, particularly for the nuclei located in their immediate vicinity. It is also shown that the probability density of the unpaired electron may be extracted, using a regularization procedure, from PCS data. PMID:25139283

Charnock, G T P; Kuprov, Ilya

2014-10-01

298

Night Shift May Boost Black Women's Diabetes Risk, Study Finds  

MedlinePLUS

... Night Shift May Boost Black Women's Diabetes Risk, Study Finds Odds are highest for younger women and ... diabetes in black women, according to a new study. "In view of the high prevalence of shift ...

299

MULTISCALE RECONSTRUCTION FOR PHOTON-LIMITED SHIFTED EXCITATION RAMAN SPECTROSCOPY  

E-print Network

MULTISCALE RECONSTRUCTION FOR PHOTON-LIMITED SHIFTED EXCITATION RAMAN SPECTROSCOPY Rebecca Willett excitation Raman spectroscopy results in multiple ob- servations of the sum of a material's fluorescent frequen- cies. The technique, known as Shifted Excitation Raman Difference Spectroscopy (SERDS

Willett, Rebecca

300

Advantages of shift changeovers with meetings: ergonomic analysis of shift supervisors' activity in aircraft building.  

PubMed

Good shift changeovers contribute to ensuring continuity and reliability in shift work. In situations where production is not maintained 24 h a day, changeovers with meetings (SCM) between the two work teams (written plus oral face-to-face handovers) alternate with changeovers without meetings (SCnM; written handovers only). An ergonomic work analysis on an aircraft assembly line showed that (1) incoming and outgoing operators met during the overlap time allotted by the company, and (2) the content of the exchanges was richer for SCMs than for SCnMs. SCMs enabled the operators to pass on and process more aspects of their work than SCnMs did. SCMs also allowed incoming operators to validate their predictions, and enabled both outgoing and incoming operators to update their mental models and work together on peripheral aspects of the technical process over a greater time span. The findings highlight the importance of allowing overlap time in shift work. PMID:21843879

Le Bris, Valérie; Barthe, Béatrice; Marquié, Jean-Claude; Kerguelen, Alain; Aubert, Sophie; Bernadou, Bernadette

2012-03-01

301

An evaluation method for phase shift extraction algorithms in generalized phase-shifting interferometry  

NASA Astrophysics Data System (ADS)

A method to evaluate quantitatively the performance of the phase shift extraction algorithms in generalized phase-shifting interferometry (GPSI) is proposed. A parameter named as reconstruction signal-to-noise ratio (R-SNR) is used as the evaluation measure. The R-SNR is defined with the reconstructed object image as the signal and the residual of the DC term and conjugate image as noise. The more accurate the extracted phase shift is, the less residual of the DC term and conjugate image there is, and then the higher R-SNR is obtained. To avoid the overlap of the DC term and conjugate image and the object image, the off-axis digital holography configuration is adopted. The correctness and effectiveness of the proposed method have been verified by both computer simulation and optical experiments. The major advantage of the proposed method is that it utilizes the experimental detectable data and not only the computer simulation results.

Li, Jie; Wang, Yurong; Meng, Xiangfeng; Yang, Xiulun; Wang, Qingpu

2013-10-01

302

Predator-induced morphological shift in the pea aphid  

PubMed Central

Aphids exhibit a polymorphism whereby individual aphids are either winged or unwinged. The winged dispersal morph is mainly responsible for the colonization of new plants and, in many species, is produced in response to adverse environmental conditions. Aphids are attacked by a wide range of specialized predators and predation has been shown to strongly influence the growth and persistence of aphid colonies. In two experiments, we reared two clones of pea aphid (Acyrthosiphon pisum) in the presence and absence of predatory ladybirds (Coccinella septempunctata or Adalia bipunctata). In both experiments, the presence of a predator enhanced the proportion of winged morphs among the offspring produced by the aphids. The aphid clones differed in their reaction to the presence of a ladybird, suggesting the presence of genetic variation for this trait. A treatment that simulated disturbance caused by predators did not enhance winged offspring production. The experiments indicate that aphids respond to the presence of a predator by producing the dispersal morph which can escape by flight to colonize other plants. In contrast to previous examples of predator-induced defence this shift in prey morphology does not lead to better protection against predator attack, but enables aphids to leave plants when mortality risks are high.

Weisser, W. W.; Braendle, C.; Minoretti, N.

1999-01-01

303

Language lateralization shifts with learning by adults.  

PubMed

For the majority of the population, language is a left-hemisphere lateralized function. During childhood, a pattern of increasing left lateralization for language has been described in brain imaging studies, suggesting that this trait develops. This development could reflect change due to brain maturation or change due to skill acquisition, given that children acquire and refine language skills as they mature. We test the possibility that skill acquisition, independent of age-associated maturation can result in shifts in language lateralization in classic language cortex. We imaged adults exposed to an unfamiliar language during three successive fMRI scans. Participants were then asked to identify specific words embedded in Norwegian sentences. Exposure to these sentences, relative to complex tones, resulted in consistent activation in the left and right superior temporal gyrus. Activation in this region became increasingly left-lateralized with repeated exposure to the unfamiliar language. These results demonstrate that shifts in lateralization can be produced in the short term within a learning context, independent of maturation. PMID:25285756

Plante, Elena; Almryde, Kyle; Patterson, Dianne K; Vance, Christopher J; Asbjørnsen, Arve E

2015-05-01

304

Robust shift and add approach to superresolution  

NASA Astrophysics Data System (ADS)

In the last two decades, many papers have been published, proposing a variety of methods for multi-frame resolution enhancement. These methods, which have a wide range of complexity, memory and time requirements, are usually very sensitive to their assumed model of data and noise, often limiting their utility. Different implementations of the non-iterative Shift and Add concept have been proposed as very fast and effective super-resolution algorithms. The paper of Elad & Hel-Or 2001 provided an adequate mathematical justification for the Shift and Add method for the simple case of an additive Gaussian noise model. In this paper we prove that additive Gaussian distribution is not a proper model for super-resolution noise. Specifically, we show that Lp norm minimization (1<=p<=2) results in a pixelwise weighted mean algorithm which requires the least possible amount of computation time and memory and produces a maximum likelihood solution. We also justify the use of a robust prior information term based on bilateral filter idea. Finally, for the underdetermined case, where the number of non-redundant low-resolution frames are less than square of the resolution enhancement factor, we propose a method for detection and removal of outlier pixels. Our experiments using commercialdigital cameras show that our proposed super-resolution method provides significant improvements in both accuracy and efficiency.

Farsiu, Sina; Robinson, Dirk; Elad, Michael; Milanfar, Peyman

2003-11-01

305

[Hormonal shifts in chronic hepatic diseases].  

PubMed

The authors offer quantitative evaluation of system cooperation of endocrine functions in healthy individuals, and apply a system approach to diagnostics of chronic liver diseases. The study included analysis of rectilinear and curvilinear correlations between endocrine system parameters in healthy individuals, and shifts in the levels of multilateral associations between the concentrations of various hormones in patients with different degree of the pathologic process in the liver. The study revealed system disintegration which occurs in the organism in cases of liver involvement and found that all liver diseases are associated with pronounced shifts in the condition of the hormonal system. The authors recommend distinguishing certain bands of the functional condition of the organism, which would allow determination of health status, risk groups, presence and prognosis of an illness. Analysis of hormonal status revealed elevation of excessiveness coefficient in liver diseases. The study established parameters that do not only allow quantitative evaluation of system disintegration of the endocrine system functioning, but differentiation of these diseases as well. The results suggest that cooperation of hormonal functions and their intermodal stability underlie the functional condition of both the endocrine system and the entire organism. Integral indices, unlike qualitative characteristics of individual functions, possess high diagnostic and prognostic relevance. PMID:16734336

Dronova, T A; Zav'ialov, A V

2006-01-01

306

Shifting seasons, climate change and ecosystem consequences  

NASA Astrophysics Data System (ADS)

In recent decades, the seasonal timing of many biological events (e.g. flowering, breeding, migration) has shifted. These phenological changes are believed to be one of the most conspicuous biological indicators of climate change. Rates and directions of phenological change have differed markedly among species, potentially threatening the seasonal synchrony of key species interactions and ultimately ecosystem functioning. Differences in phenological change among-species at different trophic levels, and with respect to other broad species traits, are likely to be driven by variations in the climatic sensitivity of phenological events. However, as yet, inconsistencies in analytical methods have hampered broad-scale assessments of variation in climate sensitivity among taxonomic and functional groups of organisms. In this presentation, results will be presented from a current collaborative project (http://www.ceh.ac.uk/sci_programmes/shifting-seasons-uk.html) in which many UK long-term data sets are being integrated in order to assess relationships between temperature/precipitation, and the timing of seasonal events for a wide range of plants and animals. Our aim is to assess which organism groups (in which locations/habitats) are most sensitive to climate. Furthermore, the role of anthropogenic climate change as a driver of phenological change is being assessed.

Thackeray, Stephen; Henrys, Peter; Hemming, Deborah; Huntingford, Chris; Bell, James; Leech, David; Wanless, Sarah

2014-05-01

307

Red and blue shifted hydridic bonds.  

PubMed

By performing MP2/aug-cc-pVTZ ab initio calculations for a large set of dimer systems possessing a R-H hydridic bond involved in diverse types of intermolecular interactions (dihydrogen bonds, hydride halogen bonds, hydride hydrogen bonds, and charge-assisted hydride hydrogen bonds), we show that this is rather an elongation than a shortening that a hydride bond undergoes on interaction. Contrary to what might have been expected on the basis of studies in uniform electric field, this elongation is accompanied by a blue instead of red shift of the R-H stretching vibration frequency. We propose that the "additional" elongation of the R-H hydridic bond results from the significant charge outflow from the sigma bonding orbital of R-H that weakens this bond. The more standard red shift obtained for stronger complexes is explained by means of the Hermansson's formula and the particularly strong electric field produced by the H-acceptor molecule. PMID:25043253

Jab?o?ski, Miros?aw

2014-09-15

308

Microstrip Antennas with Broadband Integrated Phase Shifting  

NASA Technical Reports Server (NTRS)

The goal of this research was to investigate the feasibility of using a spiral microstrip antenna that incorporates a thin ferroelectric layer to achieve both radiation and phase shifting. This material is placed between the conductive spiral antenna structure and the grounded substrate. Application of a DC bias between the two arms of the spiral antenna will change the effective permittivity of the radiating structure and the degree of coupling between contiguous spiral arms, therefore changing the phase of the RF signal transmitted or received by the antenna. This could eliminate the need for a separate phase shifter apart from the antenna structure. The potential benefits of such an antenna element compared to traditional phased array elements include: continuous, broadband phase shifting at the antenna, lower overall system losses, lighter, more efficient, and more compact phased arrays, and simpler control algorithms. Professor Jennifer Bernhard, graduate student Gregory Huff, and undergraduate student Brian Huang participated in this effort from March 1, 2000 to February 28, 2001. No inventions resulted from the research undertaken in this cooperative agreement.

Bernhard, Jennifer T.; Romanofsky, Robert R. (Technical Monitor)

2001-01-01

309

Automated manual transmission shift sequence controller  

DOEpatents

A powertrain system for a hybrid vehicle. The hybrid vehicle includes a heat engine, such as a diesel engine, and an electric machine, which operates as both, an electric motor and an alternator, to power the vehicle. The hybrid vehicle also includes a manual-style transmission configured to operate as an automatic transmission from the perspective of the driver. The engine and the electric machine drive an input shaft which in turn drives an output shaft of the transmission. In addition to driving the transmission, the electric machine regulates the speed of the input shaft in order to synchronize the input shaft during either an upshift or downshift of the transmission by either decreasing or increasing the speed of the input shaft. When decreasing the speed of the input shaft, the electric motor functions as an alternator to produce electrical energy which may be stored by a storage device. Operation of the transmission is controlled by a transmission controller which receives input signals and generates output signals to control shift and clutch motors to effect smooth launch, upshift shifts, and downshifts of the transmission, so that the transmission functions substantially as an automatic transmission from the perspective of the driver, while internally substantially functioning as a manual transmission.

Lawrie, Robert E. (Whitmore Lake, MI); Reed, Richard G. (Royal Oak, MI); Rausen, David J. (Denver, CO)

2000-02-01

310

30 CFR 75.362 - On-shift examination.  

Code of Federal Regulations, 2012 CFR

...Persons conducting the on-shift examination shall determine...air on a longwall or shortwall, including areas where... (f) During each shift that coal is produced...place, or longwall or shortwall face, ventilated by...person conducting the on-shift examination in...

2012-07-01

311

30 CFR 75.362 - On-shift examination.  

Code of Federal Regulations, 2010 CFR

...Persons conducting the on-shift examination shall determine...air on a longwall or shortwall, including areas where... (f) During each shift that coal is produced...place, or longwall or shortwall face, ventilated by...person conducting the on-shift examination in...

2010-07-01

312

30 CFR 75.362 - On-shift examination.  

Code of Federal Regulations, 2011 CFR

...Persons conducting the on-shift examination shall determine...air on a longwall or shortwall, including areas where... (f) During each shift that coal is produced...place, or longwall or shortwall face, ventilated by...person conducting the on-shift examination in...

2011-07-01

313

30 CFR 75.362 - On-shift examination.  

Code of Federal Regulations, 2014 CFR

...Persons conducting the on-shift examination shall determine...air on a longwall or shortwall, including areas where... (f) During each shift that coal is produced...place, or longwall or shortwall face, ventilated by...person conducting the on-shift examination in...

2014-07-01

314

30 CFR 75.362 - On-shift examination.  

Code of Federal Regulations, 2013 CFR

...Persons conducting the on-shift examination shall determine...air on a longwall or shortwall, including areas where... (f) During each shift that coal is produced...place, or longwall or shortwall face, ventilated by...person conducting the on-shift examination in...

2013-07-01

315

Package Shift in Plastic-Packaged Bandgap References  

E-print Network

-Mora, and D. Briggs, "Voltage shift in plastic-packaged bandgap references," IEEE Trans. Circuits Sys. ­ II of package shift with temperature for various samples 1. 1. B. Abesinga, G. A. Rincón-Mora, and D. Briggs. Rincón-Mora, and D. Briggs, "Voltage shift in plastic-packaged bandgap references," IEEE Trans. Circuits

Rincon-Mora, Gabriel A.

316

VIEWLS Final recommendations report Shift Gear to Biofuels  

E-print Network

VIEWLS Final recommendations report 1 Shift Gear to Biofuels Results and recommendations from the VIEWLS project November 2005 #12;Shift Gear to Biofuels Final report of the VIEWLS project 2 #12;Shift Gear to Biofuels Final report of the VIEWLS project 3 Preface Biofuels are fuels made from

317

Frequency Constrained ShiftCP Modeling of Neuroimaging Data  

E-print Network

@drcmr.dk Abstract--The shift invariant multi-linear model based on the CandeComp/PARAFAC (CP) model denoted Shift]. Consequently, modeling repeated trials by CP in theory re- solves the ambiguities encountered when modelingFrequency Constrained ShiftCP Modeling of Neuroimaging Data Morten Mørup and Lars K. Hansen Section

318

Pressure-dependent 13 C chemical shifts in proteins: origins  

E-print Network

ARTICLE Pressure-dependent 13 C chemical shifts in proteins: origins and applications David J Pressure-dependent 13 C chemical shifts have been measured for aliphatic carbons in barnase and Protein G. Up to 200 MPa (2 kbar), most shift changes are linear, demonstrating pressure

Williamson, Mike P.

319

Conversion reactions for sodium-ion batteries.  

PubMed

Research on sodium-ion batteries has recently been rediscovered and is currently mainly focused on finding suitable electrode materials that enable cell reactions of high energy densities combined with low cost. Naturally, an assessment of potential electrode materials requires a rational comparison with the analogue reaction in lithium-ion batteries. In this paper, we systematically discuss the broad range of different conversion reactions for sodium-ion batteries based on their basic thermodynamic properties and compare them with their lithium analogues. Capacities, voltages, energy densities and volume expansions are summarized to sketch out the scope for future studies in this research field. We show that for a given conversion electrode material, replacing lithium by sodium leads to a constant shift in cell potential ?E°(Li-Na) depending on the material class. For chlorides ?E°(Li-Na) equals nearly zero. The theoretical energy densities of conversion reactions of sodium with fluorides or chlorides as positive electrode materials typically reach values between 700 W h kg(-1) and 1000 W h kg(-1). Next to the thermodynamic assessment, results on several conversion reactions between copper compounds (CuS, CuO, CuCl, CuCl2) and sodium are being discussed. Reactions with CuS and CuO were chosen because these compounds are frequently studied for conversion reactions with lithium. Chlorides are interesting because of ?E°(Li-Na)? 0 V. As a result of chloride solubility in the electrolyte, the conversion process proceeds at defined potentials under rather small kinetic limitations. PMID:23936905

Klein, Franziska; Jache, Birte; Bhide, Amrtha; Adelhelm, Philipp

2013-10-14

320

The Reaction of Allyl Isothiocyanate with Hydroxyl\\/Water and b-Cyclodextrin Using Ultraviolet Spectrometry  

Microsoft Academic Search

Summary The reaction of allyl isothiocyanate (AITC) with hydroxyl\\/water and b-cyclodextrin (b-CD) in different acidic-alkaline media has been investigated by ultraviolet spectrometry. The kinetic parameters of the reaction were measured. It was found that after AITC translating into thiourea, the absorption peak shifted from 240 to 226 nm and the molar absorptivity increased about 16 times. The reaction can be

Zi-Tao Jiang; Qing-Feng Zhang; Hui-Lin Tian; Rong Li

321

Mechanisms in Knockout Reactions  

NASA Astrophysics Data System (ADS)

We report the first detailed study of the relative importance of the stripping and diffraction mechanisms involved in nucleon knockout reactions, by the use of a coincidence measurement of the residue and fast proton following one-proton knockout reactions. The measurements used the S800 spectrograph in combination with the HiRA detector array at the NSCL. Results for the reactions Be9(C9,B8+X)Y and Be9(B8,Be7+X)Y are presented and compared with theoretical predictions for the two reaction mechanisms calculated using the eikonal model. The data show a clear distinction between the stripping and diffraction mechanisms and the measured relative proportions are very well reproduced by the reaction theory. This agreement adds support to the results of knockout reaction analyses and their applications to the spectroscopy of rare isotopes.

Bazin, D.; Charity, R. J.; de Souza, R. T.; Famiano, M. A.; Gade, A.; Henzl, V.; Henzlova, D.; Hudan, S.; Lee, J.; Lukyanov, S.; Lynch, W. G.; McDaniel, S.; Mocko, M.; Obertelli, A.; Rogers, A. M.; Sobotka, L. G.; Terry, J. R.; Tostevin, J. A.; Tsang, M. B.; Wallace, M. S.

2009-06-01

322

Weathering Reactions and Soil-Groundwater Reactions  

NSDL National Science Digital Library

This 11-page PDF document is part of an environmental geochemistry course taught by Dr. David Sherman at the University of Bristol. The lecture explores the weathering reactions that convert primary minerals into quartz or phyllosilicate clays and iron oxide hydroxides, and the mineral-water reactions that buffer pH and the dissolved ion concentration of groundwater. Also discussed is the manner in which phyllosilicate clays, iron oxides and hydroxides sorb pollutants via ion exchange and adsorption. Helpful diagrams and illustrations accompany the text.

Sherman, David M.; Bristol, University O.

323

Sleeve reaction chamber system  

DOEpatents

A chemical reaction chamber system that combines devices such as doped polysilicon for heating, bulk silicon for convective cooling, and thermoelectric (TE) coolers to augment the heating and cooling rates of the reaction chamber or chambers. In addition the system includes non-silicon-based reaction chambers such as any high thermal conductivity material used in combination with a thermoelectric cooling mechanism (i.e., Peltier device). The heat contained in the thermally conductive part of the system can be used/reused to heat the device, thereby conserving energy and expediting the heating/cooling rates. The system combines a micromachined silicon reaction chamber, for example, with an additional module/device for augmented heating/cooling using the Peltier effect. This additional module is particularly useful in extreme environments (very hot or extremely cold) where augmented heating/cooling would be useful to speed up the thermal cycling rates. The chemical reaction chamber system has various applications for synthesis or processing of organic, inorganic, or biochemical reactions, including the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction.

Northrup, M. Allen (Berkeley, CA); Beeman, Barton V. (San Mateo, CA); Benett, William J. (Livermore, CA); Hadley, Dean R. (Manteca, CA); Landre, Phoebe (Livermore, CA); Lehew, Stacy L. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA)

2009-08-25

324

Radical reactions of borohydrides.  

PubMed

Borohydrides are an important class of reagents in both organic and inorganic chemistry. Though popular as hydride-transfer reagents for reduction, since earlier work from the 1970s, borohydride reagents have also been known to serve as hydrogen-transfer reagents. In pursuit of greener tin hydride substitutes, recent progress has been made to mediate radical C-C bond forming reactions, including Giese reactions, radical carbonylation and addition to HCHO reactions, with borohydride reagents. This review article focuses on state-of-the-art borohydride based radical reactions, also covering earlier work, kinetics and some DFT calculations with respect to the hydrogen transfer mechanism. PMID:25349957

Kawamoto, Takuji; Ryu, Ilhyong

2014-12-28

325

Lateral shift in one-dimensional quasiperiodic chiral photonic crystal  

NASA Astrophysics Data System (ADS)

We investigate the lateral shift of a one-dimensional quasiperiodic photonic crystal consisting of chiral and conventional dielectric materials. The effect of structural irregularity on lateral shift is evaluated by stationary-phase approach. Our results show that the lateral shift can be modulated by varying the structural irregularity in quasiperiodic structure. Besides, the position of peak in lateral shift spectrum stays sensitive to the chiral factor of chiral materials. In comparison with that of periodic structure, quasiperiodic structure provides an extra degree of freedom to manipulate the lateral shift.

Da, Jian; Mo, Qi; Cheng, Yaokun; Liu, Taixiang

2015-02-01

326

Shifting Media, Shifting Paradigms, and the Growing Utility of Narrative as Metaphor.  

ERIC Educational Resources Information Center

Follows particular parallels between oralist and electronic mediation to explore narrative or storytelling as a rhetorical form that transcends mediation. Reviews how writing-based cognition may bind progress in rhetorical practice and theory. Examines how narrative is media-transcendent. Reflects on the nature of media shifts. (SR)

Haynes, W. Lance

1989-01-01

327

Measuring D(d,p)T fusion reactant energy spectra with Doppler shifted fusion products  

SciTech Connect

Deuterium fusion reactant energy spectra have been measured using a diagnostic that records the Doppler shift imparted to charged particle fusion products of the D(d,p)T reaction by the center-of-mass velocity of the deuterium reactants. This diagnostic, known as the fusion ion Doppler shift diagnostic (FIDO) measures fast deuterium energy spectra in the inertial electrostatic confinement (IEC) experiment at the University of Wisconsin-Madison {l_brace}Santarius et al. [Fusion Sci. Technol. 47, 1238 (2005)]{r_brace}, a device to confine high energy light ions in a spherically symmetric, electrostatic potential well. This article details the first measurements of the fusion reactant energy spectra in an IEC device as well as the design and principles of operation of the FIDO diagnostic. Scaling of reactant energy spectra with a variety of experimental parameters have been explored.

Boris, D. R. [Naval Research Laboratory, 4555 Overlook Avenue, South West, Washington, DC 20375 (United States); Kulcinski, G. L.; Santarius, J. F.; Donovan, D. C. [Fusion Technology Institute, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706 (United States); Piefer, G. R. [Phoenix Nuclear Labs, 8123 Forsythia Street, Suite 140, Middleton, Wisconsin 53562 (United States)

2010-06-15

328

Neutron phase shift in moving matter  

SciTech Connect

The effects of a moving medium on the phase of a massive particle are studied theoretically. The discussion explains a recently published Fizeau-type neutron-interferometer experiment. It is shown explicitly that the physics of this experiment can be described either as a manifestation of a time-dependent potential in the Schroedinger equation or as a verification of the Galilean-transformation properties of Schroedinger waves. An intriguing consequence of these considerations is that for most materials no Fizeau phase shift occurs if the boundaries of the moving medium are at rest. However, we point out that such would not be the case in an experiment involving a medium whose potential is velocity dependent.

Horne, M.A.; Zeilinger, A.; Klein, A.G.; Opat, G.I.

1983-07-01

329

Shifting environmental baselines in the Red Sea.  

PubMed

The Red Sea is among the world's top marine biodiversity hotspots. We re-examined coastal ecosystems at sites surveyed during the 1980s using the same methodology. Coral cover increased significantly towards the north, mirroring the reverse pattern for mangroves and other sedimentary ecosystems. Latitudinal patterns are broadly consistent across both surveys and with results from independent studies. Coral cover showed greatest change, declining significantly from a median score of 4 (1000-9999 m(2)) to 2 (10-99m(2)) per quadrat in 2010/11. This may partly reflect impact from coastal construction, which was evident at 40% of sites and has significantly increased in magnitude over 30 years. Beach oil has significantly declined, but shore debris has increased significantly. Although substantial, levels are lower than at some remote ocean atolls. While earlier reports have suggested that the Red Sea is generally healthy, shifting environmental baselines are evident from the current study. PMID:24246651

Price, A R G; Ghazi, S J; Tkaczynski, P J; Venkatachalam, A J; Santillan, A; Pancho, T; Metcalfe, R; Saunders, J

2014-01-15

330

Resisting insects: shifting strategies in chemical control.  

PubMed

Throughout the 20th century, scientists developed a variety of chemical compounds to kill insects and other menaces of agriculture and public health. Yet, in many cases, the target insects outmaneuvered the scientists by developing resistance to insecticides--in much the same way as some bacteria can tolerate antibiotics. Insecticide resistance research has involved scientists from a range of disciplines and a variety of institutional contexts that have often guided research strategy. For example, entomologists working at agricultural stations and universities concentrated on insect physiology and evolutionary genetics, while industrial chemists continued the development of novel compounds capable of killing resistant pests. Collaboration between the two groups beginning in the 1940s did not provide a solution to the resistance, but did lead to a strategic shift from pest control to pest management that continues to the present. PMID:15036923

Ceccatti, John S

2004-03-01

331

Red-Shifted Voltage Sensitive Fluorescent Proteins  

PubMed Central

Summary Electrical signals generated by nerve cells provide the basis of brain function. While single or small numbers of cells are easily accessible using microelectrode recording techniques, less invasive optogenetic methods with spectral properties optimized for in vivo imaging are required for elucidating the operation mechanisms of neuronal circuits composed of large numbers of neurons originating from heterogeneous populations. To this end, we generated and characterized a new series of genetically-encoded voltage sensitive fluorescent proteins by molecular fusion of the voltage sensing domain of Ci-VSP (Ciona intestinalis voltage sensor-containing phosphatase) to red-shifted fluorescent protein operands. We show how these indicator proteins convert voltage-dependent structural rearrangements into a modulation of fluorescence output and demonstrate their applicability for optical recording of individual or simultaneous electrical signals in cultured hippocampal neurons, at single cell resolution without temporal averaging. PMID:20064437

Perron, Amelie; Mutoh, Hiroki; Launey, Thomas; Knöpfel, Thomas

2009-01-01

332

A late shift in accident and emergency.  

PubMed

The Accident and Emergency (A & E) department at Harrogate District Hospital in North Yorkshire, UK, serves a population of 142,000 in a catchment area that covers Harrogate, Knaresborough, Ripon, Nidderdale, part of Wetherby, and occasionally Ilkley and Otley. In 1994, 29,884 new patients attended the department, and 6760 return visits were made. There are large fluctuations in the workload of the department that are difficult to predict. This account of a late shift demonstrates particular problems that are associated with a split site hospital, the transfer of acutely ill and injured patients to specialised units, and how the nursing workforce is depleted by 25% if one nurse is absent due to sickness. PMID:8520944

Woodhouse, A J

1995-10-01

333

Chemical amplification--cavity attenuated phase shift spectroscopy measurements of atmospheric peroxy radicals.  

PubMed

We describe a new instrument for the quantification of atmospheric peroxy radicals (HO2, CH3O2, C2H5O2, etc.) using the chemical amplification method. Peroxy radicals are mixed with high concentrations of NO and CO, causing a chain reaction that produces a measurable increase in NO2 which is quantified by cavity attenuated phase shift (CAPS) spectroscopy, a highly sensitive spectroscopic detection technique. The instrument utilizes two identical reaction chambers, each with a dedicated CAPS NO2 sensor. Similar to all dual-channel chemical amplifiers, one reaction chamber operates in amplification or "ROx" mode and the other in background or "Ox" mode. The peroxy radical mixing ratio is determined by the difference between the two channels' NO2 readings divided by a laboratory-determined chain length. Each reaction chamber alternates between ROx and Ox mode on an anti-synchronized schedule, eliminating the effect of CAPS baseline offsets on the calculated peroxy radical concentrations. The chain length is determined by a new calibration method: peroxyacetyl and methyl peroxy radicals are produced by the photolysis of acetone and quantified as NO2 following reaction with excess NO. We demonstrate the performance of the instrument with results from ambient sampling in Amherst and several diagnostics of its precision. The detection limit while sampling ambient air at a relative humidity (RH) of 40% is 0.6 ppt (1 min average, signal-to-noise ratio =2), with an estimated accuracy of 25% (2?). PMID:25260158

Wood, Ezra C; Charest, John R

2014-10-21

334

Electrode kinetics: reactions  

Microsoft Academic Search

This is Volume 27 in the Comprehensive Chemical Kinetics series. The contributors are Calvo (Argentina), Hamnett (England), O'Sullivan (United States), and Weaver (United States). The book's chapters cover Redox Reactions at Metal-Solution Interfaces, Semiconductor Electrochemistry, and Reactions at Metal Oxide Electrodes. The references date from the 1960s to the mid-1980s. An index is included.

1987-01-01

335

Reactions to Attitudinal Deviancy.  

ERIC Educational Resources Information Center

This paper presents a critical review of empirical and theoretical treatments of group reaction to attitudinal deviancy. Inspired by Festinger's (1950) ideas on resolution of attitudinal discrepancies in groups, Schachter (1951) conducted an experiment that has greatly influenced subsequent research and theory concerning reaction to attitudinal…

Levine, John M.; Allen, Vernon L.

336

Clock Reaction: Outreach Attraction  

ERIC Educational Resources Information Center

Chemistry students are often introduced to the concept of reaction rates through demonstrations or laboratory activities involving the well-known iodine clock reaction. For example, a laboratory experiment involving thiosulfate as an iodine scavenger is part of the first-year general chemistry laboratory curriculum at Dalhousie University. With…

Carpenter, Yuen-ying; Phillips, Heather A.; Jakubinek, Michael B.

2010-01-01

337

Smell the Maillard Reaction  

NSDL National Science Digital Library

In this activity, learners cook amino acids and sugar to explore the range of aromas released. When amino acids and sugars are heated, learners will observe a phenomenon known as the Maillard reaction, also known as the browning reaction. Caution!: Kids, please don't try this at home without the help of an adult. The corn syrup can get very hot, very quickly.

Exploratorium

2012-10-03

338

Oscillating Chemical Reactions  

ERIC Educational Resources Information Center

Describes several oscillating chemical reactions which can be used in undergraduate chemistry laboratories. In one such reaction, ferroin oscillates from red (reducing solution) to blue (oxidizing solution) for about an hour at a frequency which can readily be shown to depend on such factors as the temperature, type of solvent, and concentration…

Hawkins, M. D.; And Others

1975-01-01

339

Solvent Effects on Oxygen-17 Chemical Shifts in Amides. Quantitative Linear Solvation Shift Relationships  

NASA Astrophysics Data System (ADS)

A multiple-linear-regression analysis (MLRA) has been carried out using the Kamlet-Abboud-Taft (KAT) solvatochromic parameters in order to elucidate and quantify the solvent effects on the 17O chemical shifts of N-methylformamide (NMF), N, N-dimethylformamide (DMF), N-methylacetamide (NMA), and N, N-dimethylacetamide (DMA). The chemical shifts of the four molecules show the same dependence (in ppm) on the solvent polarity-polarizability, i.e., -22?*. The influence of the solvent hydrogen-bond-donor (HBD) acidities is slightly larger for the acetamides NMA and DMA, i.e., -48?, than for the formamides NMF and DMF, i.e., -42?. The influence of the solvent hydrogen-bond-acceptor (HBA) basicities is negligible for the nonprotic molecules DMF and DMA but significant for the protic molecules NMF and NMA, i.e., -9?. The effect of substituting the N-H hydrogen by a methyl group amounts to -5.9 ppm in NMF and 5.4 ppm in NMA. The effect of substituting the O=C-H hydrogen amounts to 5.5 ppm in NMF and 16.8 ppm in DMF. The model of specific hydration sites of amides by I. P. Gerothanassis and C. Vakka [ J. Org. Chem.59,2341 (1994)] is settled in a more quantitative basis and the model by M. I. Burgar, T. E. St. Amour, and D. Fiat [ J. Phys. Chem.85,502 (1981)] is critically evaluated. 17O hydration shifts have been calculated for formamide (FOR) by the ab initio LORG method at the 6-31G* level. For a formamide surrounded by the four in-plane molecules of water in the first hydration shell, the calculated 17O shift change due to the four hydrogen bonds, -83.2 ppm, is smaller than the empirical hydration shift, -100 ppm. The 17O shift change from each out-of-plane water molecule hydrogen-bonded to the amide oxygen is -18.0 ppm. These LORG results support the conclusion that no more than four water molecules are hydrogen-bonded to the amide oxygen in formamide.

Díez, Ernesto; Fabián, Jesús San; Gerothanassis, Ioannis P.; Esteban, Angel L.; Abboud, José-Luis M.; Contreras, Ruben H.; de Kowalewski, Dora G.

1997-01-01

340

Controlling reactivity of nanoporous catalyst materials by tuning reaction product-pore interior interactions: Statistical mechanical modeling  

SciTech Connect

Statistical mechanical modeling is performed of a catalytic conversion reaction within a functionalized nanoporous material to assess the effect of varying the reaction product-pore interior interaction from attractive to repulsive. A strong enhancement in reactivity is observed not just due to the shift in reaction equilibrium towards completion but also due to enhanced transport within the pore resulting from reduced loading. The latter effect is strongest for highly restricted transport (single-file diffusion), and applies even for irreversible reactions. The analysis is performed utilizing a generalized hydrodynamic formulation of the reaction-diffusion equations which can reliably capture the complex interplay between reaction and restricted transport.

Wang, Jing [Ames Laboratory; Ackerman, David M. [Ames Laboratory; Lin, Victor S.-Y. [Ames Laboratory; Pruski, Marek [Ames Laboratory; Evans, James W. [Ames Laboratory

2013-04-02

341

Proton and light ion induced charge exchange reactions in nuclei This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

Proton and light ion induced charge exchange reactions in nuclei This article has been downloaded Scripta. Vol. 48, 101-104, 1993 Proton and Light Ion Induced Charge Exchange Reactions in Nuclei E. Oset) reaction on the neutron target is different to the one with the proton target and has its strength shifted

Fernández de Córdoba, Pedro

342

Science to Practice: Highly Shifted Proton MR imaging—A Shift toward Better Cell Tracking?  

PubMed Central

Summary A “hot spot” magnetic resonance (MR) imaging cell tracking technique has been developed that allows direct detection of dysprosium- or thulium-1,4,7,10-tetraazacyclododecane-?,??,??,??-tetramethyl-1,4,7,10-tetraacetic acid (DOTMA)–labeled protons inside cells. These highly shifted protons may allow specific detection of multiple cell types because it does not rely on acquiring the proton signal from bulk water. PMID:25153271

Bulte, Jeff W. M.

2015-01-01

343

Mechanisms in knockout reactions  

NASA Astrophysics Data System (ADS)

We report on the first detailed study of the mechanisms involved in knockout reactions, via a coincidence measurement of the residue and fast proton in one-proton knockout reactions, using the S800 spectrograph in combination with the HiRA detector array at the NSCL. Results on the reactions ^9Be(^9C,^8B+X)Y and ^9Be(^8B,^7Be+X)Y are presented. They are compared with theoretical predictions for both the diffraction (elastic breakup) and stripping (inelastic breakup) reaction mechanisms, as calculated in the eikonal model. The data shows a clear distinction between the two reaction mechanisms, and the observed respective proportions are very well reproduced by the reaction theory. This agreement supports the results of knockout reaction analyses and their applications to the spectroscopy of rare isotopes. In particular, this add considerable support to the use of the eikonal model as a quantitative tool, able, for example, to determine single-particle spectroscopic strengths in rare isotopes.

Bazin, D.; Charity, R. J.; de Souza, R. T.; Famiano, M. A.; Gade, A.; Henzl, V.; Henzlova, D.; Hudan, S.; Lee, J.; Lukyanov, S.; Lynch, W. G.; McDaniel, S.; Mocko, M.; Obertelli, A.; Rogers, A. M.; Sobotka, L. G.; Terry, J. R.; Tostevin, J. A.; Tsang, M. B.; Wallace, M. S.

2009-10-01

344

Core-level Auger energy shifts in palladium alloys  

NASA Astrophysics Data System (ADS)

We have measured Pd L 3M 4,5M 4,5 Auger shifts in Pd?Cu and Pd?Ag alloys and compared them with the corresponding M 5VV shifts. The same valence band effects which distort the Pd MVV lineshape are reflected in deviations of the shifts of the corresponding 1G 4 peak from the quasi-atomic limit. These deviations are manifested in comparisons with shifts of Pd L 3M 4,5M 4,5 core level spectra, which are well-defined and are naturally invariant in form. Therefore, in alloy studies true core-level Auger energy shifts should be employed. The relation of these shifts to electronic structure determinations is discussed.

Kleiman, G. G.; Landers, R.; de Castro, S. G. C.; Nascente, P. A. P.

1993-05-01

345

Economic design of control charts considering process shift distributions  

NASA Astrophysics Data System (ADS)

Process shift is an important input parameter in the economic design of control charts. Earlier control chart designs considered constant shifts to occur in the mean of the process for a given assignable cause. This assumption has been criticized by many researchers since it may not be realistic to produce a constant shift whenever an assignable cause occurs. To overcome this difficulty, in the present work, a distribution for the shift parameter has been considered instead of a single value for a given assignable cause. Duncan's economic design model for chart has been extended to incorporate the distribution for the process shift parameter. It is proposed to minimize total expected loss-cost to obtain the control chart parameters. Further, three types of process shifts namely, positively skewed, uniform and negatively skewed distributions are considered and the situations where it is appropriate to use the suggested methodology are recommended.

Vommi, Vijayababu; Kasarapu, Rukmini V.

2014-09-01

346

Wavelength-shift-free Mamyshev regenerator  

NASA Astrophysics Data System (ADS)

Optical regeneration is a key technology for next generation high-speed optical networks. All-optical regeneration can increase the reach of transmission systems without expensive optical-to-electrical signal conversion. Among various regeneration schemes, the Mamyshev regenerator attracted particular attention due to its simplicity and robustness. In this paper, we report an all-optical regeneration of a 40 Gbit/s return-to-zero signals. The regenerator proposed is based on the standard Mamyshev regenerator, which the temporal intensity profile and the average power are recovered. This device allows regenerating the signal without wavelength shift, decreasing the complexity and cost when compared with others 2-R regenerators reported. The input signal is first spectrally broadened, by self-phase modulation, after passing through a highly nonlinear fiber. Afterwards, the signal is amplified by a bidirectional erbium doped fiber amplifier, and offset spectral backscattering sliced by a fiber Bragg grating. In the second stage, the signal is spectral broadening and filtered recovering the input wavelength. The transfer function for the regenerator proposed is measured, and the all-optical regeneration is assessed by means of bit-error-rate measurements as well as real-time observation of the signal.

Fernandes, Gil M.; Tiburcio, Bruno; Muga, Nelson J.; Pinto, Armando N.

2013-11-01

347

Plasmon Energy shift in Porous Silicon  

NASA Astrophysics Data System (ADS)

In order to provide experimental support for quantum confinement models describing electronic effects in porous silicon (p-Si) [1], the Si2s and Si2p plasmon losses have been studied by X-Ray Photoelectron Spectroscopy (XPS). Although plasmon losses in the XPS core lines of p-Si have already been reported [2], the modality according to which we performed the experiment and the conclusions are remarkably different. In particular, the plasmon losses observed in the present experiment are representative of the real material (p-Si) since possible artifacts due to ion sputtering have been avoided. We discuss extensively the influence of the satellite structures relative to the oxidized-Silicon core lines, whose presence is expected since oxygen is an intrinsic component of the p-Si anodization process. The p-Si plasmon energy was found at a value 1.5 eV higher than that of bulk Si (17.4 eV), as measured on the cleaned Si substrate as a reference. The magnitude of this shift suggests possible quantum confinement effects ascribed to the p-Si nanostructures. [1]A. G. Cullis and L. T. Canham, Nature 353, 335 (1991) [2]S. Sato, S. Rath, S. Akiyama, S. Nozaki and H. Morisaki, J. Appl. Phys. 86, 1774 (1999)

Mannella, Norman; Gabetta, Giuseppe; Parmigiani, Fulvio

2001-03-01

348

Queering relationships: toward a paradigmatic shift.  

PubMed

This article exposes, and is critical of, the blatant and insidious ways in which a specific brand of heterosexual relationship has been promoted as the ultimate relational form at the expense of others who neither believe in nor practice such idealized relationships. To uncover this multilayered and deeply imbedded ideology, this piece turns to a description and analysis of how various institutions (e.g., organized religion, medicine, education, law, politics, and the family) perpetuate heteronormative practices in general. Next, specific traits considered to constitute the best and most respectable relationship style are identified. Then, notions of how heteronormativity is marketed and reproduced to create a sexual relationship hierarchy--with a certain form of heterosexuality elevated to the top, as the most revered and cherished relational form--are described and analyzed. Turning to the results of such a well-established and entrenched "marketing campaign," the author offers some notes regarding attitudes about sexual relationships gleaned from teaching a course, "Sex and Relationships," for over a decade. Finally, the author explores the merits and potential drawbacks of a paradigmatic shift toward queering relationships and possible directions for theoretical interventions. PMID:14651174

Elia, John P

2003-01-01

349

Vibration Measurement Using Phase-shifting Stroboscopic Holographic Interferometry  

Microsoft Academic Search

A fringe-evaluation system for a vibration measurement is presented, which is based on the phase-shifting method in real-time holographic interferometry. Phase-shifted real-time holographic interferograms are acquired by a TV camera when stroboscopically illuminating the object of interest. An arctangent calculation with phase-shifted fringe patterns gives a phase distribution proportional to the displacement of the object, including the initial phase of

S. Nakadate; H. Saito; T. Nakajima

1986-01-01

350

Polarization-dependent frequency shifts from Rb3He collisions  

Microsoft Academic Search

We present measurements of the frequency shift of the Rb electron-paramagnetic-resonance (EPR) line in the presence of nuclear-polarized 3He gas for the temperature range of 30 to 85 °C. The frequency shift is due to the Fermi-contact interaction between the Rb valence electron and the polarized 3He nucleus. Expressions for both the frequency shift and the spin-exchange cross section are

N. R. Newbury; A. S. Barton; P. Bogorad; G. D. Cates; M. Gatzke; H. Mabuchi; B. Saam

1993-01-01

351

What you need to know about running a shift.  

PubMed

Many junior emergency department nurses are given no formal training in management before they are asked to take charge of shifts. Nurses learn by observing senior staff, but when they first take charge of a busy shift they can be uncertain about what tasks to prioritise and how to manage team members. This article describes some of the techniques they can learn and the observations they should make to run shifts successfully. PMID:25466752

Frazer, Andrew

2014-12-01

352

Frequency shift of a rotating-imbalance vibration source caused by radiative damping in the surrounding medium  

NASA Astrophysics Data System (ADS)

The motion of vibrating bodies in a surrounding fluid is often used to infer the transport properties of the fluid. A new sensor configuration is presented that consists of a rotating imbalance source radiating into an unbounded fluid medium. Under these circumstances, the reaction of the fluid medium onto the vibration source includes a steady state torque that opposes the applied torque required to sustain the rotating imbalance. This reaction torque causes a shift in frequency of the vibration source. The frequency shift is related to the density of the surrounding fluid medium and vibration source characteristics. A description of measurements taken with a rotating-imbalance source located in unbounded water and air is provided. The total mass, eccentricity, and length of the source were 4.1 kg, 3.28(10-4) kgm, and 0.432 m, respectively. Motive torque to drive the imbalance was provided by a permanent-magnet dc motor. For an applied dc voltage that caused the source to operate at a nominal frequency near 150 Hz, a frequency shift of approximately 11 Hz was observed when the source was moved from air to water. Experimentally measured frequency shifts compared favorably with predictions provided by a nonlinear steady state model of the source and surrounding medium.

Novascone, Stephen R.; Anderson, Michael J.; Weinberg, David M.; Cole, Jack H.

2003-10-01

353

Shift work at a modern offshore drilling rig.  

PubMed

The oil and gas exploration and production offshore units are classified as hazardous installations. Work in these facilities is complex, confined and associated with a wide range of risks. The continuous operation is secured by various shift work patterns. The objective of this study was to evaluate how offshore drilling workers perceived shift work at high seas and its impacts on their life and working conditions. The main features of the studied offshore shift work schedules are: long time on board (14 to 28 days), extended shifts (12 hours or more per day), slow rotation (7 to 14 days in the same shift), long sequence of days on the night shift (7 to 14 days in a row) and the extra-long extended journey (18 hours) on shift change and landing days. Interviews revealed a wide range of stressors caused by the offshore shift work, as well as difficulties to conciliate work with family life. It was observed that changes of the family model, leading to role conflicts and social isolation, work in a hazardous environment, perceiving poor sleep when working at night shifts and the imbalance between the expected and actual rewards are the major stressors for the offshore drilling workers. PMID:14564877

Rodrigues, V F; Fischer, F M; Brito, M J

2001-12-01

354

The potential for regime shifts in high latitude terrestrial ecosystems  

NASA Astrophysics Data System (ADS)

Climate constrains the extent of the two major terrestrial biomes at high latitudes: boreal forests and arctic tundra. Model simulations provide considerable evidence that physical and biogeochemical feedbacks from these regions to the climate system act to maintain a status quo of climate and biome distribution. Ongoing anthropogenically driven changes in climate are particularly pronounced in high latitude regions, and empirical evidence for their influence on tundra and boreal ecosystems is mounting. Global vegetation models project changes to accelerate in coming decades, culminating in profound shifts in high latitude biomes by the end of this century. Regime shifts are surprisingly large changes in a system that occur when a it moves between alternative stable states ('attractors'), without the equivalent large shift of an external driver. In association with climate change, regime shifts in ecosystems could theoretically generate significant modifications to ecosystem-climate feedbacks, in the Arctic for example through the respiration or combustion of large amounts of soil carbon. Here we review evidence for historical regime shifts in terrestrial ecosystems at high latitudes, including shifts in species dominance and distribution. We describe ongoing changes in characteristics of these ecosystems, including vegetation productivity, composition, and the fire regime, and discuss whether they can be indicators of impeding regime shifts. Finally, we discuss the potential of exploiting regime shifts in tundra and boreal systems for climate change mitigation or resource management by forcing ecosystems to shift towards a more desirable stable state.

Beck, P. S.; Goetz, S. J.

2011-12-01

355

Plate motion and the secular shift of the mean pole  

NASA Technical Reports Server (NTRS)

The global plate motion indicates that changes in the products of inertia of the earth due to tectonic plate movement may provide a secular shift of the mean pole. A mathematical procedure for calculating this shift based on the plate theory is presented. Explicit expressions were obtained for the dependence of the secular polar shift on the dimensions and locations of the plate boundaries. Numerical results show that the secular motion of the mean pole is 0.0002 sec/year in the direction of 67 W. Hence, it is deduced that the influence of the plate motion on the secular polar shift may account for 10% of the observed value.

Liu, H.; Carpenter, L.; Agreen, R. W.

1973-01-01

356

Doppler shifts in the coma of Comet P/Halley  

NASA Astrophysics Data System (ADS)

The relative radial velocities across 70-100 arcsecs of the coma of Comet P/Halley were measured on four days in 1985-1986 on coude CCD spectrograms in order to search for detectable Doppler shifts. The measurements show a trend of positive velocity with respect to projected distance from the nucleus. The shifts are most clearly observed at r = 1.1 AU, where the relative velocity at 10000 km amounted to 3-4 km/s. The Doppler shifts represent an integration through the whole coma. It is suggested that a proper model of the comet is needed to convert the shifts into true outflow velocities.

Herbig, G. H.

1990-04-01

357

Competition between the tensor light shift and nonlinear Zeeman effect  

SciTech Connect

Many precision measurements (e.g., in spectroscopy, atomic clocks, quantum-information processing, etc.) suffer from systematic errors introduced by the light shift. In our experimental configuration, however, the tensor light shift plays a positive role enabling the observation of spectral features otherwise masked by the cancellation of the transition amplitudes and creating resonances at a frequency unperturbed either by laser power or beam inhomogeneity. These phenomena occur thanks to the special relation between the nonlinear Zeeman and light shift effects. The interplay between these two perturbations is systematically studied and the cancellation of the nonlinear Zeeman effect by the tensor light shift is demonstrated.

Chalupczak, W.; Wojciechowski, A.; Pustelny, S.; Gawlik, W. [National Physical Laboratory, Hampton Road, Teddington, TW11 0LW (United Kingdom); Centrum Badan Magnetooptycznych, M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, PL-30059 Krakow (Poland)

2010-08-15

358

Protonated alcohols are examples of complete charge-shift bonds.  

PubMed

Accurate gas-phase and solution-phase valence bond calculations reveal that protonation of the hydroxyl group of aliphatic alcohols transforms the C-O bond from a principally covalent bond to a complete charge-shift bond with principally "no-bond" character. All bonding in this charge-shift bond is due to resonance between covalent and ionic structures, which is a different bonding mechanism from that of traditional covalent bonds. Until now, charge-shift bonds have been previously identified in inorganic compounds or in exotic organic compounds. This work showcases that charge-shift bonds can occur in common organic species. PMID:25317657

Anderson, Peter; Petit, Alban; Ho, Junming; Mitoraj, Mariusz Pawel; Coote, Michelle L; Danovich, David; Shaik, Sason; Braïda, Benoît; Ess, Daniel H

2014-11-01

359

Oral Hypersensitivity Reactions  

MedlinePLUS

... Million NIDCR/NIH Grant 2015 AAOM Call for Abstract Submissions Upcoming Events 2015 Annual Conference Registration is Now Open 2016 Annual Meeting in Atlanta - Save the Date! Oral Hypersensitivity Reactions ...

360

Types of Allergic Reactions  

MedlinePLUS

... allergies. Substances that don't bother some people (including certain medications) can trigger allergic reactions in others. ... | Terms and Conditions © 1996-2015 Academy of General Dentistry. All Rights Reserved.

361

Reactor for exothermic reactions  

DOEpatents

A liquid phase process is described for oligomerization of C[sub 4] and C[sub 5] isoolefins or the etherification thereof with C[sub 1] to C[sub 6] alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120 to 300 F. Wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.

Smith, L.A. Jr.; Hearn, D.; Jones, E.M. Jr.

1993-03-02

362

Chemisorption And Precipitation Reactions  

EPA Science Inventory

The transport and bioavailability of chemical components within soils is, in part, controlled by partitioning between solids and solution. General terms used to describe these partitioning reactions include chemisorption and precipitation. Chemisorption is inclusive of the suit...

363

Untoward penicillin reactions  

PubMed Central

The literature on untoward reactions following the administration of penicillin is reviewed. These reactions, including a certain number of deaths which have been reported, are of particular interest to health administrations and to WHO in view of the large-scale programmes for controlling the treponematoses which are now under way—programmes affecting millions of people in many parts of the world. The most serious problems are anaphylactic sensitivity phenomena and superinfection or cross-infection with penicillin-resistant organisms, and the reactions involved range in intensity from the mildest to the fatal; the incidence of the latter is estimated at 0.1-0.3 per million injections. The authors point out that with increasing use of penicillin, more persons are likely to become sensitized and the number of reactions can therefore be expected to rise. The best prevention against such an increase is the restriction of the unnecessary use of penicillin. PMID:13596877

Guthe, T.; Idsöe, O.; Willcox, R. R.

1958-01-01

364

Polymerase Chain Reaction  

NSDL National Science Digital Library

This interactive activity adapted from the University of Nebraska's Library of Crop Technologies depicts steps in the polymerase chain reaction (PCR) technique and explains how it is used to efficiently copy sections of DNA for analysis.

WGBH Educational Foundation

2009-12-07

365

An Illuminating Reaction.  

ERIC Educational Resources Information Center

Describes the use of carbide lights as an excellent mechanism for introducing or reviewing many basic chemistry concepts including elements and compounds, endothermic and exothermic reactions, physical and chemical changes, and balancing chemical equations. (JRH)

Matthews, Catherine E.

1996-01-01

366

Nitropyridines: Synthesis and reactions  

Microsoft Academic Search

Reaction of pyridine and substituted pyridines with N2O5 in an organic solvent gives the N-nitropyridinium ion. When this is reacted with SO2\\/HSO3 - in water, 3-nitropyri- dine is obtained (77 % yield). With substituted pyridines, the method gives good yields for 4-substituted and moderate yields for 3-substituted pyridines. The reaction mechanism is not an electrophilic aromatic substitution, but one in

Jan M. Bakke

2003-01-01

367

Safety of chlorination reactions  

Microsoft Academic Search

Chlorination reactions are part of various processes in the chemical industry, to manufacture heavy chemicals, specialty chemicals, pesticides and pharmaceuticals, in inorganic and organic chemistry. They are a valuable tool in organic synthesis.The hazard of processing chlorine involves:u- Gas phase explosion;- Runaway reaction or thermal explosion in the condensed phase.Gas phase explosion hazard with chlorine as an oxidizer is present

Jean-Louis Gustin; Alexandre Fines

1996-01-01

368

Polymerase Chain Reaction  

NSDL National Science Digital Library

Polymerase chain reaction (PCR) enables researchers to produce millions of copies of a specific DNA sequence in approximately two hours. This automated process bypasses the need to use bacteria for amplifying DNA. This animation from Cold Spring Harbor Laboratory's Dolan DNA Learning Center presents Polymerase Chain Reaction through a series of illustrations of the processes involved. Users may view the animation online (Flash is required) or download it for PC or Mac.

369

Strength of Figure-Ground Activity in Monkey Primary Visual Cortex Predicts Saccadic Reaction Time in a Delayed Detection Task  

Microsoft Academic Search

When and where are decisions made? In the visual system a saccade, which is a fast shift of gaze toward a target in the visual scene, is the behavioral outcome of a decision. Current neurophysiological data and reaction time models show that saccadic reaction times are determined by a build-up of activity in motor-related structures, such as the frontal eye

Hans Super; Victor A. F. Lamme

2006-01-01

370

A probabilistic approach for validating protein NMR chemical shift assignments.  

PubMed

It has been estimated that more than 20% of the proteins in the BMRB are improperly referenced and that about 1% of all chemical shift assignments are mis-assigned. These statistics also reflect the likelihood that any newly assigned protein will have shift assignment or shift referencing errors. The relatively high frequency of these errors continues to be a concern for the biomolecular NMR community. While several programs do exist to detect and/or correct chemical shift mis-referencing or chemical shift mis-assignments, most can only do one, or the other. The one program (SHIFTCOR) that is capable of handling both chemical shift mis-referencing and mis-assignments, requires the 3D structure coordinates of the target protein. Given that chemical shift mis-assignments and chemical shift re-referencing issues should ideally be addressed prior to 3D structure determination, there is a clear need to develop a structure-independent approach. Here, we present a new structure-independent protocol, which is based on using residue-specific and secondary structure-specific chemical shift distributions calculated over small (3-6 residue) fragments to identify mis-assigned resonances. The method is also able to identify and re-reference mis-referenced chemical shift assignments. Comparisons against existing re-referencing or mis-assignment detection programs show that the method is as good or superior to existing approaches. The protocol described here has been implemented into a freely available Java program called "Probabilistic Approach for protein Nmr Assignment Validation (PANAV)" and as a web server ( http://redpoll.pharmacy.ualberta.ca/PANAV ) which can be used to validate and/or correct as well as re-reference assigned protein chemical shifts. PMID:20446018

Wang, Bowei; Wang, Yunjun; Wishart, David S

2010-06-01

371

Insects Overshoot the Expected Upslope Shift Caused by Climate Warming  

PubMed Central

Along elevational gradients, climate warming may lead to an upslope shift of the lower and upper range margin of organisms. A recent meta-analysis concluded that these shifts are species specific and considerably differ among taxonomic lineages. We used the opportunity to compare upper range margins of five lineages (plants, beetles, flies, hymenoptera, and birds) between 1902–1904 and 2006–2007 within one region (Bavarian Forest, Central Europe). Based on the increase in the regional mean annual temperature during this period and the regional lapse rate, the upslope shift is expected to be between 51 and 201 m. Averaged across species within lineages, the range margin of all animal lineages shifted upslope, but that of plants did not. For animals, the observed shifts were probably due to shifts in temperature and not to changes in habitat conditions. The range margin of plants is therefore apparently not constrained by temperature, a result contrasting recent findings. The mean shift of birds (165 m) was within the predicted range and consistent with a recent global meta-analysis. However, the upslope shift of the three insect lineages (>260 m) exceeded the expected shift even after considering several sources of uncertainty, which indicated a non-linear response to temperature. Our analysis demonstrated broad differences among lineages in their response to climate change even within one region. Furthermore, on the considered scale, the response of ectothermic animals was not consistent with expectations based on shifts in the mean annual temperature. Irrespective of the reasons for the overshooting of the response of the insects, these shifts lead to reorganizations in the composition of assemblages with consequences for ecosystem processes. PMID:23762439

Bässler, Claus; Hothorn, Torsten; Brandl, Roland; Müller, Jörg

2013-01-01

372

Solvent-induced infrared frequency shifts in aromatic nitriles are quantitatively described by the vibrational Stark effect  

PubMed Central

The physical properties of solvents strongly affect the spectra of dissolved solutes, and this phenomenon can be exploited to gain insight into the solvent-solute interaction. The large solvatochromic shifts observed for many dye molecules in polar solvents are due to variations in the solvent reaction field, and these shifts are widely used to estimate the change in the dye’s dipole moment upon photoexcitation, which is typically on the order of ~1-10 Debye. In contrast, the change in dipole moment for vibrational transitions is approximately two orders of magnitude smaller. Nonetheless, vibrational chromophores display significant solvatochromism, and the relative contributions of specific chemical interactions and electrostatic interactions are debated, complicating the interpretation of vibrational frequency shifts in complex systems such as proteins. Here we present a series of substituted benzonitriles that display widely varying degrees of vibrational solvatochromism. In most cases, this variation can be quantitatively described by the experimentally determined Stark tuning rate, coupled with a simple Onsager-like model of solvation, reinforcing the view that vibrational frequency shifts are largely caused by electrostatic interactions. In addition, we discuss specific cases where continuum solvation models fail to predict solvatochromic shifts, revealing the necessity for more advanced theoretical models that capture local aspects of solute-solvent interactions. PMID:22448878

Levinson, Nicholas M.; Fried, Stephen D.; Boxer, Steven G.

2012-01-01

373

Measurement of the energy distribution of fast excited atoms by Doppler shift spectroscopy in an inertial-electrostatic confinement fusion device  

Microsoft Academic Search

Energy distributions of energetic neutral atoms resulted from charge-exchange reactions between accelerated ions and background atoms or molecules were measured by the Doppler shift spectroscopy in an inertial-electrostatic confinement fusion (IECF) device composed of a spherical vacuum chamber as an anode and a spherical hollow cathode grid concentrically placed in the chamber. Since ions generated between the cathode and the

Kai Masuda; Toshiyuki Mizutani; Kiyoshi Yoshikawa; Kazunobu Nagasaki; Ken Takiyama; Hisayuki Toku; Hirofumi Hashimoto; Akihiro Nagafuchi

2002-01-01

374

[Cutaneous adverse drug reactions.  

PubMed

Cutaneous adverse drug reactions (CADR) represent a heterogeneous field including various clinical patterns without specific features suggesting drug causality. Exanthematous eruptions, urticaria and vasculitis are the most common forms of CADR. Fixed eruption is uncommon in western countries. Serious reactions (fatal outcome, sequelae) represent 2% of CADR: bullous reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis), DRESS (drug reaction with eosinophilia and systemic symptoms or drug-induced hypersensitivity syndrome) and acute generalized exanthematous pustulosis (AGEP). These forms must be quickly diagnosed to guide their management. The main risk factors are immunosuppression, autoimmunity and some HLA alleles in bullous reactions and DRESS. Most systemic drugs may induce cutaneous adverse reactions, especially antibiotics, anticonvulsivants, antineoplastic drugs, non-steroidal anti-inflammatory drugs, allopurinol and contrast media. Pathogenesis includes immediate or delayed immunologic mechanism, usually not related to dose, and pharmacologic/toxic mechanism, commonly dose-dependent or time-dependent. In case of immunologic mechanism, allergologic exploration is possible to clarify drug causality, with a variable sensitivity according to the drug and to the CADR type. It includes epicutaneous patch testing, prick test and intradermal test. However, no in vivo or in vitro test can confirm the drug causality. To determine the cause of the eruption, a logical approach based on clinical characteristics, chronologic factors and elimination of differential diagnosis is required, completed with a literature search. A reporting to pharmacovigilance network is essential in case of a serious CADR whatever the suspected drug and in any case if the involved drug is a newly marketed one or unusually related to cutaneous reactions. PMID:25458866

Lebrun-Vignes, B; Valeyrie-Allanore, L

2014-11-01

375

Chapter 17 Eye-head Gaze shifts Oxford Handbook on Eye Movements  

E-print Network

1 Chapter 17 Eye-head Gaze shifts Oxford Handbook on Eye Movements "The Neural Basis of Gaze Shifts" 1. Kinematics of eye-head gaze shifts a. Terminology for describing eye-head gaze shifts b. Variability in eye and head motion during gaze shifts c. Gaze shifts in complex environments d. Bottom

Corneil, Brian D.

376

Ab initio NMR Chemical Shift Calculations for Biomolecular Systems  

E-print Network

(i.e. J-coupling, relaxation time and NOE), can provide invaluable information on the three-dimensional4 Ab initio NMR Chemical Shift Calculations for Biomolecular Systems Using Fragment Molecular of fragment molecular orbital (FMO)-based NMR chemical shift calculation methods. They successfully lead

Furui, Sadaoki

377

ON THE STRUCTURE OF A SOFIC SHIFT SPACE  

Microsoft Academic Search

The structure of a soc shift space is investigated, and Krieger's embedding theorem and Boyle's factor theorem are generalized to a large class of soc shifts. In symbolic dynamics there are two celebrated results which give necessary and sucient conditions for an irreducible subshift of nite type (SFT) to embed into or factor onto an irreducible SFT with dierent entropy.

KLAUS THOMSEN

378

Author's personal copy Regime shifts in marine ecosystems  

E-print Network

Author's personal copy Regime shifts in marine ecosystems: detection, prediction and management unknown. Marine ecosystems show relatively sudden and dramatic changes in form and function, called regime shifts is timely as we move toward devel- oping ecosystem-based approaches to managing marine systems

deYoung, Brad

379

Detection and Assessment of Ecosystem Regime Shifts from Fisher Information  

EPA Science Inventory

Ecosystem regime shifts, which are long-term system reorganizations, have profound implications for sustainability. There is a great need for indicators of regime shifts, particularly methods that are applicable to data from real systems. We have developed a form of Fisher info...

380

DIET SHIFTS IN BREEDING AND NONBREEDING SPOTTED OWLS  

Microsoft Academic Search

Shifts in the diets of breeding and nonbreeding Spotted Owls (Strix occidentalis) are compared. Breeding owls prey more on larger rodents, and statistical differences in the percentage of large mammalian prey between breeding and nonbreeding owls are apparent only after feeding of young begins. Whether these diet shifts reflect prey availability or in part prey selection is not conclusively determined.

CAMERON W. BARROWS

381

Role of Overtraining in Reversal and Conceptual Shift Behavior  

ERIC Educational Resources Information Center

Sixty college students formed mixed conceptual categories in original learning (e.g., PEACH, SHIRT, PANTS, and PEAR; and SHOE, ORANGE, DRESS, and APPLE). They were then required to perform either a reversal shift or a conceptual shift. Results are discussed in relation with mediation theory. (Editor/RK)

Richman, Charles L.

1973-01-01

382

On Explaining Language Shift: Sociology or Social Psychology of Language?  

ERIC Educational Resources Information Center

This study investigates the potentials and limits of sociolinguistic research on language shift. Starting from a position that the ultimate goal of the research must be to create a general theory of language shift of predictive power, the author examines the explanatory potential of current mainstream research methodology now regarded as canonical…

Maitz, Peter

2011-01-01

383

Shifts in flowering phenology reshape a subalpine plant community.  

PubMed

Phenology--the timing of biological events--is highly sensitive to climate change. However, our general understanding of how phenology responds to climate change is based almost solely on incomplete assessments of phenology (such as first date of flowering) rather than on entire phenological distributions. Using a uniquely comprehensive 39-y flowering phenology dataset from the Colorado Rocky Mountains that contains more than 2 million flower counts, we reveal a diversity of species-level phenological shifts that bring into question the accuracy of previous estimates of long-term phenological change. For 60 species, we show that first, peak, and last flowering rarely shift uniformly and instead usually shift independently of one another, resulting in a diversity of phenological changes through time. Shifts in the timing of first flowering on average overestimate the magnitude of shifts in the timing of peak flowering, fail to predict shifts in the timing of last flowering, and underrepresent the number of species changing phenology in this plant community. Ultimately, this diversity of species-level phenological shifts contributes to altered coflowering patterns within the community, a redistribution of floral abundance across the season, and an expansion of the flowering season by more than I mo during the course of our study period. These results demonstrate the substantial reshaping of ecological communities that can be attributed to shifts in phenology. PMID:24639544

CaraDonna, Paul J; Iler, Amy M; Inouye, David W

2014-04-01

384

Nurse rescheduling with shift preferences and minimal Published as  

E-print Network

Nurse rescheduling with shift preferences and minimal disruption Published as: Clark A. R., and Walker H., Nurse rescheduling with shift preferences and minimal disruption, Journal of Applied hours a day by a limited number of nurses. With a well documented shortage of nurses in many countries

Clark, Alistair

385

Automatic ore image segmentation using mean shift and watershed transform  

Microsoft Academic Search

In this paper, we present a novel method for segmenting ore images specifically for estimating the size distribution of ore material on conveyer belt. The segmentation system uses the mean shift and watershed algorithm. The mean shift algorithm is used to identify pixel clusters of particular modes of the probability density function of the image data. The pixel clusters are

Anthony Amankwah; Chris Aldrich

2011-01-01

386

THE WEIGHTED HOOK LENGTH FORMULA III: SHIFTED TABLEAUX  

E-print Network

THE WEIGHTED HOOK LENGTH FORMULA III: SHIFTED TABLEAUX MATJAZ KONVALINKA Abstract. Recently, a simple proof of the hook length formula was given via the branch- ing rule. In this paper, we extend the results to shifted tableaux. We give a bijective proof of the branching rule for the hook lengths

Konvalinka, Matjaz

387

Fostering Hooks and Shifts: Tutorial Tactics for Guided Mathematical Discovery  

E-print Network

Fostering Hooks and Shifts: Tutorial Tactics for Guided Mathematical Discovery Dor Abrahamson for enhancing, explaining, or evaluating their interaction strategy. Yet when they engage or ``hook-stepped discovery process as ``hooks and shifts'' (Abrahamson et al. 2011). The study reported in the current paper

Wilensky, Uri

388

THE WEIGHTED HOOK LENGTH FORMULA III: SHIFTED TABLEAUX  

E-print Network

THE WEIGHTED HOOK LENGTH FORMULA III: SHIFTED TABLEAUX MATJA Ÿ Z KONVALINKA # Abstract. Recently, a simple proof of the hook length formula was given via the branch­ ing rule. In this paper, we extend the results to shifted tableaux. We give a bijective proof of the branching rule for the hook lengths

Konvalinka, Matjaz

389

Westward shift of the Yellow Sea warm salty tongue  

Microsoft Academic Search

The accumulated in situ hydrographic survey as well as the satellite observed sea surface temperature (SST) show consistent westward shifting of the Yellow Sea Warm Salty Tongue (YSWST) in winter. A 2-D thermal model is used to show the westward shifting of the YSWST due to cooling and advection. The MITgcm is applied to simulate the circulation in the Yellow

Daji Huang; Xiaopeng Fan; Dongfeng Xu; Yuanzheng Tong; Jilan Su

2005-01-01

390

Perceptual Adaptation of Voice Gender Discrimination with Spectrally Shifted Vowels  

ERIC Educational Resources Information Center

Purpose: To determine whether perceptual adaptation improves voice gender discrimination of spectrally shifted vowels and, if so, which acoustic cues contribute to the improvement. Method: Voice gender discrimination was measured for 10 normal-hearing subjects, during 5 days of adaptation to spectrally shifted vowels, produced by processing the…

Li, Tianhao; Fu, Qian-Jie

2011-01-01

391

Mean Shift: A Robust Approach Toward Feature Space Analysis  

Microsoft Academic Search

A general nonparametric technique is proposed for the analysis of a complex multimodal feature space and to delineate arbitrarily shaped clusters in it. The basic computati onal module of the technique is an old pattern recognition procedure, the mean shift. We prove for dis crete data the convergence of a recursive mean shift procedure to the nearest stationary point of

Dorin Comaniciu; Peter Meer

2002-01-01

392

Generalized harmonic spatial coordinates and hyperbolic shift conditions  

E-print Network

We propose a generalization of the condition for harmonic spatial coordinates analogous to the generalization of the harmonic time slices introduced by Bona et al., and closely related to dynamic shift conditions recently proposed by Lindblom and Scheel, and Bona and Palenzuela. These generalized harmonic spatial coordinates imply a condition for the shift vector that has the form of an evolution equation for the shift components. We find that in order to decouple the slicing condition from the evolution equation for the shift it is necessary to use a rescaled shift vector. The initial form of the generalized harmonic shift condition is not spatially covariant, but we propose a simple way to make it fully covariant so that it can be used in coordinate systems other than Cartesian. We also analyze the effect of the shift condition proposed here on the hyperbolicity of the evolution equations of general relativity in 1+1 dimensions and 3+1 spherical symmetry, and study the possible development of blow-ups. Finally, we perform a series of numerical experiments to illustrate the behavior of this shift condition.

Miguel Alcubierre; Alejandro Corichi; José A. González; Darío Núñez; Bernd Reimann; Marcelo Salgado

2005-10-24

393

Shift happens: online education as a new paradigm in learning  

Microsoft Academic Search

This article addresses that paradigmatic shift. It begins by presenting an overview of the history of online education as a context and framework for understanding the state of the art today, especially the use of network technologies for collaborative learning in post-secondary education. Beginning with the innovations of early pioneers as contributing to the paradigmatic shift, it provides a framework

Linda Harasim

2000-01-01

394

Regime shifts, resilience, and biodiversity in ecosystem management  

Microsoft Academic Search

We review the evidence of regime shifts in terrestrial and aquatic environments in relation to resilience of complex adaptive ecosystems and the functional roles of biological diversity in this context. The evidence reveals that the likelihood of regime shifts may increase when humans reduce resilience by such actions as removing response diversity, removing whole functional groups of species, or removing

Carl Folke; Steve Carpenter; Brian Walker; Marten Scheffer; Thomas Elmqvist; Lance Gunderson; C. S. Holling

2004-01-01

395

Consideration on Multiplexing Code Shift Keying on Optical CDMA System  

NASA Astrophysics Data System (ADS)

There is code shift keying as one of effective modulation and demodulation method of signal on optical code division multiple access. We propose multiplexing code shift keying which is improved data rate on each user, by using two or more codewords in one frame, and evaluate it.

Tanaka, Shuhei; Usami, Shogo

396

Vocal Pitch Shift in Congenital Amusia (Pitch Deafness)  

ERIC Educational Resources Information Center

We tested whether congenital amusics, who exhibit pitch perception deficits, nevertheless adjust the pitch of their voice in response to a sudden pitch shift applied to vocal feedback. Nine amusics and matched controls imitated their own previously-recorded speech or singing, while the online feedback they received was shifted mid-utterance by 25…

Hutchins, Sean; Peretz, Isabelle

2013-01-01

397

AUTOMORPHISMS OF BOWENFRANKS GROUPS OF SHIFTS OF FINITE TYPE  

E-print Network

define a shift of finite type (SFT) called a graph shift oe A through the multi­edge digraph GA defined]). Parry and Sullivan [PS] first discovered the generating matrix moves for flow equivalence of SFT equivalence (FE­invariant) of SFT's. Later, Bowen and Franks [BF] proved that the group BF (A) := Z n =(I

Huang, Danrun

398

Paradigm Shift: Understanding and Implementing Change in Second Language Education.  

ERIC Educational Resources Information Center

Describes eight changes that fit the paradigm shift in second language education toward what is often called communicative language teaching: learner autonomy, cooperative learning, curricular integration, focus on meaning, diversity, thinking skills, alternative assessment, and teachers as co-learners. The paradigm shift is examined as an element…

Jacobs, George M.; Farrell, Thomas

2001-01-01

399

On TCM schemes transparent to constant phase and frequency shifts  

Microsoft Academic Search

The problem of digital transmission over a channel with phase ambiguity generated by a constant phase shift or (Doppler) frequency shift is considered. To remove this phase ambiguity differential encoding\\/decoding techniques are used in systems with combined modulation and coding, provided that the transmitted sequence is transparent to the phase rotations of the signal space. Necessary and sufficient conditions for

Yow-Jong Liu; Ezio Biglieri

1990-01-01

400

Empirical NMR Chemical Shift Correlations for Methyl and Methylene Protons.  

ERIC Educational Resources Information Center

Presents an internally consistent set of 63 substituent constants developed for use with the Schoolery Relationship to predict the chemical shifts of methylene protons of acyclic compounds. Chemical shift data used in deriving the constants were taken mainly from primary sources of HNMR (nuclear magnetic resonance) spectra. (JN)

Friedrich, Edwin C.; Runkle, Katherine Gates

1984-01-01

401

Shifting Themes in OECD Country Reviews of Higher Education  

ERIC Educational Resources Information Center

There have been changes in the political economy since the 1980s, and the Organization for Economic Cooperation and Development (OECD) has changed as well. Scholars have noted shifts in OECD discourse in some policy fields since that time: shifts away from what might be called classic neoliberal perspectives. This paper reflects on the changes in…

Hunter, Carrie P.

2013-01-01

402

Hybrid Coherent and Frequency-Shifted-Reference Ultrawideband Radio  

E-print Network

Hybrid Coherent and Frequency-Shifted-Reference Ultrawideband Radio Huaping Liu, Member, IEEE fading channels. Index Terms-- Pulsed ultrawideband, frequency-shifted refer- ence, coherent rake, hybrid in the frequency domain. A receiver thus only has to implement a mixer, and not a delay line, and is thus much

Liu, Huaping

403

Shift dynamics and control of dual-clutch transmissions  

Microsoft Academic Search

Shifts in a dual-clutch transmission (DCT) are realized by torque transfer from one clutch to another without traction interruption due to the controlled slippage of the clutches. The timing of engagement and disengagement of the two clutches is critical for achieving a smooth shift without engine flare and clutch tie-up. This paper presents an analytical model for the simulation, analysis

Manish Kulkarni; Taehyun Shim; Yi Zhang

2007-01-01

404

Topicality and Complexity in the Acquisition of Norwegian Object Shift  

ERIC Educational Resources Information Center

This article investigates the acquisition of object shift in Norwegian child language. We show that object shift is complex derivationally, distributionally, and referentially, and propose a new analysis in terms of IP-internal topicalization. The results of an elicited production study with 27 monolingual Norwegian-speaking children (ages…

Anderssen, Merete; Bentzen, Kristine; Rodina, Yulia

2012-01-01

405

Language Shift and Language Accommodation across Family Generations in Taiwan  

ERIC Educational Resources Information Center

This study explored language shift and accommodation among bilingual Mandarin and Tai-gi (also called Hokkien, Holo, Tai-gu, Taiwan Min, Taiwanese) families in Taiwan. From the 1940s until the 1980s the Chinese Nationalist Party (KMT) on Taiwan promoted Mandarin Chinese. Recent years have witnessed a shift in policy: since 2001 elementary schools…

Sandel, Todd L.; Chao, Wen-Yu; Liang, Chung-Hui

2006-01-01

406

Image shifting for PIV using birefringent and ferroelectric liquid crystals  

Microsoft Academic Search

This paper discusses a new implementation of electrooptical image shifting, used to resolve directional ambiguity in particle image velocimetry (PIV) measurements. The setup uses a ferroelectric liquid crystal (FLC) as a polarization rotator and a birefringent calcite plate as a shifter. The system can be used with non-polarized light sources and fluorescent particles. The minimum shifting time (pulse separation) is

L. Bertuccioli; S. Gopalan; J. Katz

1996-01-01

407

Control of gear shifts in dual clutch transmission powertrains  

Microsoft Academic Search

To achieve the best possible responses during shifting in dual clutch transmissions it is commonplace to integrate clutch and engine control, while the clutch is used to match speeds between the engine and wheels via reduction gears, poor engine control can lead to extended engagement times and rough\\/harsh shift transients. This paper proposes a method for combined speed and torque

Paul D. Walker; Nong Zhang; Richard Tamba

2011-01-01

408

Health consequences of shift work and implications for structural design.  

PubMed

The objective of the study was to perform a literature review on the health consequences of working rotating shifts and implications for structural design. A literature search was performed in June 2012 and a selection of the most relevant peer-review articles was included in the present review. Shift workers are more likely to suffer from a circadian sleep disorder characterized by sleepiness and insomnia. Shift work is associated with decreased productivity, impaired safety, diminished quality of life and adverse effects on health. Circadian disruption resulting from rotating shift work has also been associated with increased risk for metabolic syndrome, diabetes, cardiovascular disease and cancer. This article summarizes the known health effects of shift work and discusses how light can be used as a countermeasure to minimize circadian disruption at night while maintaining alertness. In the context of the lighted environment, implications for the design of newborn intensive care units are also discussed. PMID:23536025

Figueiro, M G; White, R D

2013-04-01

409

Lattice-induced nonadiabatic frequency shifts in optical lattice clocks  

SciTech Connect

We consider the frequency shift in optical lattice clocks which arises from the coupling of the electronic motion to the atomic motion within the lattice. For the simplest of three-dimensional lattice geometries this coupling is shown to affect only clocks based on blue-detuned lattices. We have estimated the size of this shift for the prospective strontium lattice clock operating at the 390-nm blue-detuned magic wavelength. The resulting fractional frequency shift is found to be on the order of 10{sup -18} and is largely overshadowed by the electric quadrupole shift. For lattice clocks based on more complex geometries or other atomic systems, this shift could potentially be a limiting factor in clock accuracy.

Beloy, K. [Centre for Theoretical Chemistry and Physics, New Zealand Institute for Advanced Study, Massey University Auckland, Private Bag 102904, 0745 Auckland (New Zealand)

2010-09-15

410

Color-shifting features for optically variable devices  

NASA Astrophysics Data System (ADS)

The simultaneous engineering of diffractive structures and amterial systems enables innovative appraoches for realizing iridescent color shifts for Optically Variable Devices (OVDs) for document secrity. In a first exmaple, we dmonstrate the interplay between a color-shifting coating, whichfunctions inreflection,a nd embossed gratings,w ith effects inthe first and hgher diffraction orders. In a second exmpale, we demosntrate novel surface-releif, zero-order gratingw hich show a color shift, e.g. green to red, uponrotation by 90 degrees. In a third example, we explore the use of combination gratings to realize color-shifting and color-contrast features. These color-shifting features are integrated within OVD designs in which an observer can easily check the behavior of the feature and verify the authenticity of the document.

Tompkin, Wayne R.; Schilling, Andreas; Staub, Rene

2004-06-01

411

Isotope shifts in francium isotopes Fr-213206 and 221Fr  

NASA Astrophysics Data System (ADS)

We present the isotope shifts of the 7 s1 /2 to 7 p1 /2 transition for francium isotopes 206 -213Fr with reference to 221Fr collected from two experimental periods. The shifts are measured on a sample of atoms prepared within a magneto-optical trap by a fast sweep of radio-frequency sidebands applied to a carrier laser. King plot analysis, which includes literature values for 7 s1 /2 to 7 p3 /2 isotope shifts, provides a field shift constant ratio of 1.0520(10) and a difference between the specific mass shift constants of 170(100) GHz amu between the D1 and D2 transitions, of sufficient precision to differentiate between ab initio calculations.

Collister, R.; Gwinner, G.; Tandecki, M.; Behr, J. A.; Pearson, M. R.; Zhang, J.; Orozco, L. A.; Aubin, S.; Gomez, E.; FrPNC Collaboration

2014-11-01

412

Selective data segment monitoring system. [using shift registers  

NASA Technical Reports Server (NTRS)

High speed data monitoring apparatus is described for displaying the bit pattern of a selected portion of a block of transmitted data comprising a shift register for receiving the transmitted data and for temporarily containing the consecutive data bits. A programmable sync detector for monitoring the contents of the shift register and for generating a sync signal when the shift register contains a predetermined sync code is included. A counter is described for counting the data bits input to the shift register after the sync signal is generated and for generating a count complete signal when a selected number of data bits have been input to the register. A data storage device is used for storing the contents of the shift register at the time the count complete signal is generated.

Wirth, M. N. (inventor)

1976-01-01

413

Nurses’ Shift Length and Overtime Working in 12 European Countries  

PubMed Central

Background: Despite concerns as to whether nurses can perform reliably and effectively when working longer shifts, a pattern of two 12- to 13-hour shifts per day is becoming common in many hospitals to reduce shift to shift handovers, staffing overlap, and hence costs. Objectives: To describe shift patterns of European nurses and investigate whether shift length and working beyond contracted hours (overtime) is associated with nurse-reported care quality, safety, and care left undone. Methods: Cross-sectional survey of 31,627 registered nurses in general medical/surgical units within 488 hospitals across 12 European countries. Results: A total of 50% of nurses worked shifts of ?8 hours, but 15% worked ?12 hours. Typical shift length varied between countries and within some countries. Nurses working for ?12 hours were more likely to report poor or failing patient safety [odds ratio (OR)=1.41; 95% confidence interval (CI), 1.13–1.76], poor/fair quality of care (OR=1.30; 95% CI, 1.10–1.53), and more care activities left undone (RR=1.13; 95% CI, 1.09–1.16). Working overtime was also associated with reports of poor or failing patient safety (OR=1.67; 95% CI, 1.51–1.86), poor/fair quality of care (OR=1.32; 95% CI, 1.23–1.42), and more care left undone (RR=1.29; 95% CI, 1.27–1.31). Conclusions: European registered nurses working shifts of ?12 hours and those working overtime report lower quality and safety and more care left undone. Policies to adopt a 12-hour nursing shift pattern should proceed with caution. Use of overtime working to mitigate staffing shortages or increase flexibility may also incur additional risk to quality. PMID:25226543

Dall’Ora, Chiara; Simon, Michael; Ball, Jane; Lindqvist, Rikard; Rafferty, Anne-Marie; Schoonhoven, Lisette; Tishelman, Carol; Aiken, Linda H.

2014-01-01

414

Absolute surface metrology by differencing spatially shifted maps from a phase-shifting interferometer.  

PubMed

Surface measurements of precision optics are commonly made with commercially available phase-shifting Fizeau interferometers that provide data relative to flat or spherical reference surfaces whose unknown errors are comparable to those of the surface being tested. A number of ingenious techniques provide surface measurements that are "absolute," rather than relative to any reference surface. Generally, these techniques require numerous measurements and the introduction of additional surfaces, but still yield absolute information only along certain lines over the surface of interest. A very simple alternative is presented here, in which no additional optics are required beyond the surface under test and the transmission flat (or sphere) defining the interferometric reference surface. The optic under test is measured in three positions, two of which have small lateral shifts along orthogonal directions, nominally comparable to the transverse spatial resolution of the interferometer. The phase structure in the reference surface then cancels out when these measurements are subtracted in pairs, providing a grid of absolute surface height differences between neighboring resolution elements of the surface under test. The full absolute surface, apart from overall phase and tip/tilt, is then recovered by standard wavefront reconstruction techniques. PMID:20634825

Bloemhof, E E

2010-07-15

415

Phase-shift analysis of low-energy $?^{\\pm}p$ elastic-scattering data  

E-print Network

Using electromagnetic corrections previously calculated by means of a potential model, we have made a phase-shift analysis of the $\\pi^\\pm p$ elastic-scattering data up to a pion laboratory kinetic energy of 100 MeV. The hadronic interaction was assumed to be isospin invariant. We found that it was possible to obtain self-consistent databases by removing very few measurements. A pion-nucleon model was fitted to the elastic-scattering database obtained after the removal of the outliers. The model-parameter values showed an impressive stability when the database was subjected to different criteria for the rejection of experiments. Our result for the pseudovector $\\pi N N$ coupling constant (in the standard form) is $0.0733 \\pm 0.0014$. The six hadronic phase shifts up to 100 MeV are given in tabulated form. We also give the values of the s-wave scattering lengths and the p-wave scattering volumes. Big differences in the s-wave part of the interaction were observed when comparing our hadronic phase shifts with those of the current GWU solution. We demonstrate that the hadronic phase shifts obtained from the analysis of the elastic-scattering data cannot reproduce the measurements of the $\\pi^- p$ charge-exchange reaction, thus corroborating past evidence that the hadronic interaction violates isospin invariance. Assuming the validity of the result obtained within the framework of chiral perturbation theory, that the mass difference between the $u$- and the $d$-quark has only a very small effect on the isospin invariance of the purely hadronic interaction, the isospin-invariance violation revealed by the data must arise from the fact that we are dealing with a hadronic interaction which still contains residual effects of electromagnetic origin.

E. Matsinos; W. S. Woolcock; G. C. Oades; G. Rasche; A. Gashi

2006-07-07

416

Arylethynyl Substituted 9,lO-Anthraquinones: Tunable Stokes Shifts by Substitution and Solvent Polarity  

NASA Technical Reports Server (NTRS)

2-Arylethynyl- and 2,6- and 2,7-diarylethynyl-substituted 9,lO-anthraquinones were synthesized via Sonogashira coupling reactions of 2-bromo-, 2,6-dibromo-, and 2,7-dibromo-9,10- anthraquinone with para-substituted phenylacetylenes. While the redox properties of those compounds are almost insensitive to substitution, their absorption maxima are linearly related to the Hammett constants with different slopes for electron donors and electron acceptors. ABI compounds are photoluminescent both in solution (quantum yields of emission <= 6 %), and as solids. The emission spectra have the characteristics of charge-transfer bands with large Stokes shifts (100-250 nm). The charge-transfer character of the emitting state is supported by large dipole moment differences between the ground and the excited state as concluded on the basis of molecular modeling and Lippert-Mataga correlations of the Stokes shifts with solvent polarity. Maximum Stokes shifts are attained by both electron-donating and -withdrawing groups. This is explained by a destabilization of the HOMO by electron donors and a stabilization of the LUMO by electron acceptors. X-ray crystallographic analysis of, for example, 2,7-bisphenylethynfl- 9,lO-anthraquinone reveals a monoclinic P21In space group and no indication for pi-overlap that would promote quenching, thus explaining emission from the solid state. Representative reduced forms of the title compounds were isolated as stable acetates of the corresponding dihydrs-9,10- anthraquinones. The emission of these compounds is blue-shifted relative to the parent oxidized forms and is attributed to internal transitions in the dihydro-9,lO-anthraquinone core.

Yang, Jinhua; Dass, Amala; Rawashdeh, Abdel-Monem M.; Sotiriou-Leventis, Chariklia; Panzner, Matthew J.; Tyson, Daniel S.; Kinder, James D.; Leventis, Nicholas

2004-01-01

417

arXiv:physics/0509253v130Sep2005 Calculation of isotope shifts and relativistic shifts in CI, CII, CIII  

E-print Network

Physics Institute, Gatchina, 188300, Russia (Dated: September 30, 2005) Abstract We present an accurate ab on neutral carbon and three carbon ions. The relativistic shift of carbon lines may allow them to be included constant over the lifetime of the Universe. Carbon isotope shifts can be used to measure isotope

Kozlov, Mikhail G

418

Auditory attentional shifts in reading-disabled students: quantification of attentional effectiveness by the Attentional Shift Index  

Microsoft Academic Search

A controversy has existed for some years regarding auditory attentional skills in reading-disabled children. Data have suggested highly developed attentional skills in groups of reading-disabled students, but reduced attentional shifts have also been documented in equivalent groups. Attentional shifts in dichotic listening with forced or directed attention are usually inferred from a significant interaction between attentional task and ear. However,

Arve E Asbjørnsen; M. P Bryden

1998-01-01

419

Gas Producing Micro-Reaction  

NSDL National Science Digital Library

In this chemistry activity, learners use common chemicals and metals to examine reactions that produce gaseous substances. Learners will identify the gases produced and write a balanced equation for each reaction. Use this activity to also introduce learners to single displacement and double displacement reactions, two types of chemical reactions.

2014-01-28

420

Proton-transfer reaction dynamics  

Microsoft Academic Search

In this article we discuss the progress made in understanding intermolecular and intermolecular reactions of proton (or hydrogen-atom) transfer. Femtosecond real-time probing, together with spectroscopic studies, in molecular beams are presented with selected examples of reactions. Reaction rates, tunneling dynamics and the nature of the reaction coordinate are examined and related to two-state multidimensional potential energy surfaces.

Abderrazzak Douhal; Françoise Lahmani; Ahmed H. Zewail

1996-01-01

421

Inorganic Reaction Mechanisms. Part I  

ERIC Educational Resources Information Center

Provides a collection of data on the mechanistic aspects of inorganic chemical reactions. Wherever possible includes procedures for classroom demonstration or student project work. The material covered includes gas phase reactions, reactions in solution, mechanisms of electron transfer, the reaction between iron III and iodine, and hydrolysis. (GS)

Cooke, D. O.

1976-01-01

422

Passing the Baton: An Experimental Study of Shift Handover  

NASA Technical Reports Server (NTRS)

Shift handovers occur in many safety-critical environments, including aviation maintenance, medicine, air traffic control, and mission control for space shuttle and space station operations. Shift handovers are associated with increased risk of communication failures and human error. In dynamic industries, errors and accidents occur disproportionately after shift handover. Typical shift handovers involve transferring information from an outgoing shift to an incoming shift via written logs, or in some cases, face-to-face briefings. The current study explores the possibility of improving written communication with the support modalities of audio and video recordings, as well as face-to-face briefings. Fifty participants participated in an experimental task which mimicked some of the critical challenges involved in transferring information between shifts in industrial settings. All three support modalities, face-to-face, video, and audio recordings, reduced task errors significantly over written communication alone. The support modality most preferred by participants was face-to-face communication; the least preferred was written communication alone.

Parke, Bonny; Hobbs, Alan; Kanki, Barbara

2010-01-01

423

The human factors of implementing shift work in logging operations.  

PubMed

A fairly recent development in the forest industry is the use of shift work in logging in the southeastern U.S. Logging company owners are implementing shift work as an opportunity to increase production and potentially reduce the cost of producing each unit of wood, without consideration of the potential impacts on the logging crew. There are many documented physiological and psychological impacts on workers from shift work in a variety of industries, although few address forestry workers in the U.S. Semi-structured interviews were performed to gather information about how logging company owners were implementing shift work in seven southeastern states. Data collected during the interviews included employee turnover, shift hours, shift scheduling, safety considerations, and production impacts. Various work schedules were employed. The majority of the schedules encompassed less than 24 hours per day. Permanent and rotating shift schedules were found. None of the logging company owners used more than two crews in a 24-hour period. Additional safety precautions were implemented as a result of working after dark. No in-woods worker accidents or injuries were reported by any of those interviewed. Results indicate that a variety of work schedules can be successfully implemented in the southeastern logging industry. PMID:19044168

Mitchell, D L; Gallagher, T V; Thomas, R E

2008-10-01

424

Colonization dynamics of ciliate morphotypes modified by shifting sandy sediments.  

PubMed

Sandy stream-bed sediments colonized by a diverse ciliate community are subject to various disturbance regimes. In microcosms, we investigated the effect of sediment shifting on the colonization dynamics of 3 ciliate morphotypes differing in morphology, behavior and feeding strategy. The dynamics of the ciliate morphotypes inhabiting sediment pore water and overlying water were observed at 3 sediment shifting frequencies: (1) stable sediments, (2) periodically shifting sediments such as migrating ripples, and (3) continuously shifting sediments as occurring during scour events of the uppermost sediment. Sediment shifting significantly affected the abundance and growth rate of the ciliate morphotypes. The free-swimming filter feeder Dexiostoma campylum was vulnerable to washout by sediment shifting since significantly higher numbers occurred in the overlying water than in pore water. Abundance of D. campylum only increased in pore water of stable sediments. On the contrary, the vagile grasper feeder Chilodonella uncinata and the sessile filter feeder Vorticella convallaria had positive growth rates and successfully colonized sediments that shifted periodically and continuously. Thus, the spatio-temporal pattern of sediment dynamics acts as an essential factor of impact on the structure, distribution and function of ciliate communities in sand-bed streams. PMID:25129834

Risse-Buhl, Ute; Felsmann, Katja; Mutz, Michael

2014-08-01

425

Isotope shift in the sulfur electron affinity: Observation and theory  

SciTech Connect

The sulfur electron affinities {sup e}A(S) are measured by photodetachment microscopy for the two isotopes {sup 32}S and {sup 34}S (16 752.975 3(41) and 16 752.977 6(85) cm{sup -1}, respectively). The isotope shift in the electron affinity is found to be more probably positive, {sup e}A({sup 34}S)- {sup e}A({sup 32}S) =+0.0023(70) cm{sup -1}, but the uncertainty allows for the possibility that it may be either ''normal''[{sup e}A({sup 34}S) > {sup e}A({sup 32}S)] or ''anomalous''[{sup e}A({sup 34}S) < {sup e}A({sup 32}S)]. The isotope shift is estimated theoretically using elaborate correlation models, monitoring the electron affinity and the mass polarization term expectation value. The theoretical analysis predicts a very large specific mass shift (SMS) that counterbalances the normal mass shift (NMS) and produces an anomalous isotope shift {sup e}A({sup 34}S)- {sup e}A({sup 32}S) =-0.0053(24) cm{sup -1}, field shift corrections included. The total isotope shift can always be written as the sum of the NMS (here +0.0169 cm{sup -1}) and a residual isotope shift (RIS). Since the NMS has nearly no uncertainty, the comparison between experimental and theoretical RIS is more fair. With respective values of -0.0146(70) cm{sup -1} and -0.0222(24) cm{sup -1}, these residual isotope shifts are found to agree within the estimated uncertainties.

Carette, Thomas; Scharf, Oliver; Godefroid, Michel [Chimie Quantique et Photophysique, Universite Libre de Bruxelles - CP160/09, B-1050 Brussels (Belgium); Drag, Cyril; Blondel, Christophe; Delsart, Christian [Laboratoire Aime-Cotton, CNRS, Universite Paris-sud, F-91405 Orsay cedex (France); Froese Fischer, Charlotte [National Institute of Standards and Technology Gaithersburg, Maryland 20899-8420 (United States)

2010-04-15

426

The use of the magnetic field effect for studying a chemiluminescent chemical reaction in aqueous solution. Reaction rate constants and lifetimes of intermediate molecules  

NASA Astrophysics Data System (ADS)

The phase shift magnetic field effect technique is applied for investigation of the chemiluminescent (ChL) reaction of luminol oxidation by potassium ferricyanide in aqueous alkali solution. The external modulated magnetic field changed the rate constant of recombination of luminol radicals. Rate constants of intermediate stages of the reaction are obtained: 10 8 M -1 s -1 for diazaquinone reaction with hydrogen peroxide, 2 X 10 6 M -1 s -1 for diazaquinone hydrolysis and 2 X 10 5 s -1 for the decomposition of hydroperoxide, which is a precursor of the light emitter.

Triebel, Michael M.; Totrov, Maxim M.; Zorinyants, George E.; Frankevich, Eugene L.

1993-11-01

427

Thermal 1,3-trityl migrations in Diels-Alder domino reactions of 1-trityl-4-vinyl-1H-imidazoles.  

PubMed

Under thermal conditions, tritylimidazoles have been shown to undergo sterically driven N-->N trityl migrations, in disagreement with previously published reports. These migrations are a key step in several highly diastereoselective domino reaction sequences (Diels-Alder, [1,3]-H shift, [1,3]-trityl migration and Diels-Alder, [1,3]-H shift, [1,3]-trityl migration, Michael reaction) leading to architecturally complex molecules. PMID:20527990

Cotterill, Lynsey J; Harrington, Ross W; Clegg, William; Hall, Michael J

2010-07-01

428

Polarization in inclusive reactions  

Microsoft Academic Search

A formalism for discussing the spin dependence of inclusive reactions is presented. The role of various constraints following from conservation of parity and angular momentum conservation is discussed. Expressions for specific single and double polarization observables are presented. Predictions of the triple-Regge model for these observables are given.

Gary R. Goldstein; Joseph F. Owens

1976-01-01

429

The aromatic ene reaction  

PubMed Central

The ene reaction is a pericyclic process in which an alkene having an allylic hydrogen atom (the ene donor) reacts with a second unsaturated species (the enophile) to form a new product with a transposed ?-bond. The aromatic ene reaction, in which the alkene component is embedded in an aromatic ring, has only been reported in a few (four) instances and has proceeded in low yield (?6%). Here we show efficient aromatic ene reactions in which a thermally generated aryne engages a pendant m-alkylarene substituent to produce a dearomatized isotoluene, itself another versatile but rare reactive intermediate. Our experiments were guided by computational studies that revealed structural features conducive to the aromatic ene process. We proceeded to identify a cascade comprising three reactions: (i) hexadehydro-Diels-Alder (for aryne generation), (ii) intramolecular aromatic ene, and (iii) bimolecular Alder ene. The power of this cascade is evident from the structural complexity of the final products, the considerable scope, and the overall efficiency of these multi-stage, reagent- and byproduct-free, single-pot transformations. PMID:24345944

Niu, Dawen; Hoye, Thomas R.

2014-01-01

430

Parallelization for reaction  

E-print Network

Parallelization for reaction waves with complex chemistry Context Application Background Numerical with complex chemistry S. Descombes 2 M. Duarte 3 T. Dumont 1 V. Louvet 1 M. Massot 3 1Camille Jordan Institute - France 3EM2C Laboratory - Ecole Centrale Paris - France Workshop on Computational and Applied Mathematics

Louvet, Violaine

431

Chemical Reactions at Surfaces  

SciTech Connect

Chemical reactions at surfaces underlie some of the most important processes of today, including catalysis, energy conversion, microelectronics, human health and the environment. Understanding surface chemical reactions at a fundamental level is at the core of the field of surface science. The Gordon Research Conference on Chemical Reactions at Surfaces is one of the premiere meetings in the field. The program this year will cover a broad range of topics, including heterogeneous catalysis and surface chemistry, surfaces in environmental chemistry and energy conversion, reactions at the liquid-solid and liquid-gas interface, electronic materials growth and surface modification, biological interfaces, and electrons and photons at surfaces. An exciting program is planned, with contributions from outstanding speakers and discussion leaders from the international scientific community. The conference provides a dynamic environment with ample time for discussion and interaction. Attendees are encouraged to present posters; the poster sessions are historically well attended and stimulate additional discussions. The conference provides an excellent opportunity for junior researchers (e.g. graduate students or postdocs) to present their work and interact with established leaders in the field.

Michael Henderson and Nancy Ryan Gray

2010-04-14

432

Reaction Formulation: A Bibliography.  

ERIC Educational Resources Information Center

Reaction formation was studied by Sigmund Freud. This defense mechanism may be related to repression, substitution, reversal, and compensation (or over-compensation). Alfred Adler considered compensation a basic process in his individual psychology. Anna Freud discussed some defense mechanisms, and Bibring, Dwyer, Huntington, and Valenstein…

Pedrini, D. T.; Pedrini, Bonnie C.

433

Reaction Time Sound Explanation  

NSDL National Science Digital Library

This experiment presents auditory stimuli and requires the participant to respond after hearing target stimuli under different conditions. This experiment gives students the opportunity to determine whether their reaction times are reliably different for tasks that require slightly different decisions. This page provides guidance for faculty who wish to incorporate this activity into their classroom.

434

Organic Reactions and Biofuels  

NSDL National Science Digital Library

The Advanced Technology Environmental and Energy Center (ATEEC) provides this classroom activity on organic reactions and biofuels. The goal of the lesson is to react methanol with waste oil to synthesize biodiesel. Users must download this resource for viewing, which requires a free log-in. There is no cost to download the item.

435

The aromatic ene reaction  

NASA Astrophysics Data System (ADS)

The ene reaction is a pericyclic process in which an alkene with an allylic hydrogen atom (the ene donor) reacts with a second unsaturated species (the enophile) to form a new product with a transposed ?-bond. The aromatic ene reaction, in which the alkene component is embedded in an aromatic ring, has only been reported in a few (four) instances and has proceeded in low yield (?6%). Here, we show efficient aromatic ene reactions in which a thermally generated aryne intermediate engages a pendant m-alkylarene substituent to produce a dearomatized isotoluene, itself another versatile but rare reactive intermediate. Our experiments were guided by computational studies that revealed structural features conducive to the aromatic ene process. We proceeded to identify a cascade comprising three reactions: (1) hexadehydro-Diels-Alder (for aryne generation), (2) intramolecular aromatic ene and (3) bimolecular Alder ene. The power of this cascade is evident from the structural complexity of the final products, the considerable scope, and the overall efficiency of these multistage, reagent- and by-product-free, single-pot transformations.

Niu, Dawen; Hoye, Thomas R.

2014-01-01

436

A Principal's Reaction  

ERIC Educational Resources Information Center

This article presents a principal's reaction to Catherine Marshall and Michael Ward's article on research on social justice and training for leadership. The author applauds Marshall and Ward's efforts to address what is undoubtedly among the most fundamentally important issues facing principals today. Marshall and Ward illuminate the importance of…

Zaretsky, Lindy

2004-01-01

437

Reaction product imaging  

SciTech Connect

Over the past few years the author has investigated the photochemistry of small molecules using the photofragment imaging technique. Bond energies, spectroscopy of radicals, dissociation dynamics and branching ratios are examples of information obtained by this technique. Along with extending the technique to the study of bimolecular reactions, efforts to make the technique as quantitative as possible have been the focus of the research effort. To this end, the author has measured the bond energy of the C-H bond in acetylene, branching ratios in the dissociation of HI, the energetics of CH{sub 3}Br, CD{sub 3}Br, C{sub 2}H{sub 5}Br and C{sub 2}H{sub 5}OBr dissociation, and the alignment of the CD{sub 3} fragment from CD{sub 3}I photolysis. In an effort to extend the technique to bimolecular reactions the author has studied the reaction of H with HI and the isotopic exchange reaction between H and D{sub 2}.

Chandler, D.W. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01

438

Detection of a small shift in a broad distribution  

NASA Astrophysics Data System (ADS)

Statistical methods for the extraction of a small shift in broad data distributions are examined by means of Monte Carlo simulations. This work was originally motivated by the CERN neutrino beam to Gran Sasso (CNGS) experiment for which the OPERA detector collaboration reported a time shift in a broad distribution with an accuracy of ±7.8 ns, while the fluctuation of the average time turns with ±23.8 ns out to be much larger. Although the physical result of a big shift has been withdrawn, statistical methods that make an identification in a broad distribution with such a small error possible remain of interest.

Berg, Bernd A.

2014-12-01

439

Spin canting induced nonreciprocal Goos-Hänchen shifts.  

PubMed

Recent studies on surface reflection illustrate how light beams can be laterally shifted from the position predicted by geometrical optics, the so called Goos-Hänchen effect. In antiferromagnets this shifts can be controlled with an external magnetic field. We show that a configuration in which spins cant in response to applied magnetic fields enhance possibilities of field controlled shifts. Moreover, we show that nonreciprocal displacements are possible, for both oblique and normal incidence, due to inherent nonreciprocity of the polariton phase with respect to the propagation direction. In the absence of an external field, reciprocal displacements occur. PMID:25402089

Macêdo, R; Stamps, R L; Dumelow, T

2014-11-17

440

Tooth Contact Shift in Loaded Spiral Bevel Gears  

NASA Technical Reports Server (NTRS)

An analytical method is presented to predict the shifts of the contact ellipses of spiral bevel gear teeth under load. The contact ellipse shift is the motion of the tooth contact position from the ideal pitch point to its location under load. The shifts are due to the elastic motions of the gear and pinion supporting shafts and bearings. The calculations include the elastic deflections of the gear shafts and the deflections of the four shaft bearings. The method assumes that the surface curvature of each tooth is constant near the unloaded pitch point. Results from these calculations will help designers reduce transmission weight without seriously reducing transmission performance.

Savage, M.; Altidis, P. C.; Lewicki, D. G.; Coy, J. J.; Litvin, F. L.

1989-01-01

441

Focal shift in tightly focused Laguerre-Gaussian beams  

NASA Astrophysics Data System (ADS)

We study the nonparaxial propagation behavior of Laguerre-Gaussian (LG) beams under the tight focusing condition by using the Rayleigh-Sommerfeld integrals. We obtain an analytical formula and show the focal shift with respect to the geometric focus of a high numerical-aperture objective. An analytical expression for the focal shift of a tightly focused LG beam increases with the focal length while decreases with the beam waist. This approach can be extended to deal with the tight focusing field and the focal shift of LG vector fields with space-variant polarization distributions or other focusing behaviors such as the 4? focusing and the Fresnel zone plates.

Ren, Zhi-Cheng; Qian, Sheng-Xia; Tu, Chenghou; Li, Yongnan; Wang, Hui-Tian

2015-01-01

442

Integrated phase-shifting digital holography using statistical approach  

NASA Astrophysics Data System (ADS)

We propose integrated phase-shifting digital holography using statistical approach. In the integrated phase-shifting scheme, the phase shifts are generated by a reference mirror moving with a uniform velocity, and sequential phaseshifted holograms are captured. Therefore, there is no wait time for stabilization, which offers some advantages such as short measurement time, high phase stability and high noise tolerance. The proposed method does not require precise control and calibration of the phase shifter and synchronization between the phase shifter and the digital image sensor. Therefore, the practical digital holography system with high accuracy can be implemented at low cost.

Yoshikawa, Nobukazu; Kajihara, Kazuki; Shiratori, Takaaki

2014-11-01

443

Quadrature component analysis of interferograms with random phase shifts  

NASA Astrophysics Data System (ADS)

Quadrature component analysis (QCA) is an effective method for analyzing the interferograms if the phase shifts are uniformly distributed in the [0, 2?] range. However, it is hard to meet this requirement in practical applications, so a parameter named the non-orthogonal degree (NOD) is proposed to indicate the degree when the phase shifts are not well distributed. We analyze the relation between the parameter of NOD and the accuracy of the QCA algorithm by numerical simulation. By using the parameter of NOD, the relation between the distribution of the phase shift and the accuracy of the QCA algorithm is obtained. The relation is discussed and verified by numerical simulations and experiments.

Xu, Jiancheng; Chen, Zhao

2014-08-01

444

Excited state intramolecular charge transfer reaction in nonaqueous electrolyte solutions: Temperature dependence  

Microsoft Academic Search

Temperature dependence of the excited state intramolecular charge transfer reaction of 4-(1-azetidinyl)benzonitrile (P4C) in ethyl acetate (EA), acetonitrile (ACN), and ethanol at several concentrations of lithium perchlorate (LiClO4) has been investigated by using the steady state and time resolved fluorescence spectroscopic techniques. The temperature range considered is 267-343 K. The temperature dependent spectral peak shifts and reaction driving force (-DeltaGr)

Tuhin Pradhan; Harun Al Rasid Gazi; Ranjit Biswas

2009-01-01

445

Shifts in Campylobacter species abundance may reflect general microbial community shifts in periodontitis progression  

PubMed Central

Background Oral Campylobacter species have been found to be associated with periodontitis progression. While the etiological significance of Campylobacter rectus is quite established, the association of C. gracilis, C. concisus, and C. curvus with health or disease remains contradictory. Objectives This study hypothesizes that the proportion of species within the Campylobacter genus rather than the absolute abundance of a single species is a suitable indicator for periodontitis progression. Design Subgingival plaque from 90 periodontitis patients and gingival sulcus fluid of 32 healthy individuals were subjected to a newly developed nested PCR approach, in which all Campylobacter spp. were amplified simultaneously. The resulting mixture of 16S-rRNA-gene-amplicons were separated by single-stranded conformation polymorphism (SSCP) gel electrophoresis, followed by sequencing and identification of excised bands and relative quantification of band intensities. In all samples, the abundance of selected periodontitis marker species was determined based on DNA hybridization on a microarray. Results The highly prevalent Campylobacter community was composed of varying proportions of C. rectus, C. gracilis, C. concisus, and C. curvus. Cluster analysis based on SSCP-banding pattern resulted in distinct groups which in turn coincided with significant differences in abundance of established periodontitis marker species (Tannerella forsythia, Porphyromonas gingivalis, and Fusobacterium nucleatum) and progression. Conclusions The shift in the Campylobacter community composition seems to display the general microbial community shift during clinical progression in a simplified manner. The focus on members of the Campylobacter in this study suggests that this genus can be an indicator of ecological changes in the subgingival oral microflora. PMID:25412608

Henne, Karsten; Fuchs, Felix; Kruth, Sebastian; Horz, Hans-Peter; Conrads, Georg

2014-01-01

446

Photoneutron reactions in astrophysics  

NASA Astrophysics Data System (ADS)

Among key problems in nuclear astrophysics, that of obtaining deeper insight into the mechanism of synthesis of chemical elements is of paramount importance. The majority of heavy elements existing in nature are produced in stars via radiative neutron capture in so-called s- and r processes, which are, respectively, slow and fast, in relation to competing ? --decay processes. At the same time, we know 35 neutron-deficient so-called bypassed p-nuclei that lie between 74Se and 196Hg and which cannot originate from the aforementioned s- and r-processes. Their production is possible in ( ?, n), ( ?, p), or ( ?, ?) photonuclear reactions. In view of this, data on photoneutron reactions play an important role in predicting and describing processes leading to the production of p-nuclei. Interest in determining cross sections for photoneutron reactions in the threshold energy region, which is of particular importance for astrophysics, has grown substantially in recent years. The use of modern sources of quasimonoenergetic photons obtained in processes of inverse Compton laser-radiation scattering on relativistic electronsmakes it possible to reveal rather interesting special features of respective cross sections, manifestations of pygmy E1 and M1 resonances, or the production of nuclei in isomeric states, on one hand, and to revisit the problem of systematic discrepancies between data on reaction cross sections from experiments of different types, on the other hand. Data obtained on the basis of our new experimental-theoretical approach to evaluating cross sections for partial photoneutron reactions are invoked in considering these problems.

Varlamov, V. V.; Ishkhanov, B. S.; Orlin, V. N.; Peskov, N. N.; Stopani, K. A.

2014-12-01

447

Transmutations and Isotopic shifts in LENR Experiments: An Overview  

E-print Network

Abstract-- This overview presents a brief summary of observations of products of transmutation reactions which occur in a variety of LENR configurations wherein the “host metal ” nuclei react with loaded deuterium or hydrogen, resulting in the formation of new stable elements or isotopes not present prior to an experimental run. Index Terms—Transmutation reactions, Isotopic anomalies, multi-deuteron capture reactions.

Mahadeva Srinivasan

448

Real-time monitoring of voltage shift based on enzymatically released pyrophosphate using phenylboronic acid-immobilized gate field-effect transistor  

NASA Astrophysics Data System (ADS)

Pyrophosphate (PPi) is ubiquitous in living cells and is often produced by enzymatic reactions, e.g., DNA synthesis by DNA polymerase. We have developed a novel detection system for the voltage shift associated with the change in PPi concentration resulting from an enzymatic reaction using a phenylboronic acid (PBA)-coated gate field-effect transistor (FET), since PBA coating is effective for detecting ion accumulation associated with PPi production from enzymatic reactions. To detect enzymatic reactions more efficiently, we employed the enzyme-electrode conjugation method using specific peptide sequences, which are spontaneously tethered to a gold substrate. The combination of the enzyme-electrode conjugation method with the charge detection using the PBA-coated FET enables the effective detection of enzymatic reactions.

Nishida, Hirokazu; Takahashi, Kiyofumi; Tabuse, Yuki; Kambara, Hideki; Sakata, Toshiya

2014-01-01

449

Blue-shifted and red-shifted hydrogen bonds: Theoretical study of the CH3CHO· · ·HNO complexes  

NASA Astrophysics Data System (ADS)

The blue-shifted and red-shifted H-bonds have been studied in complexes CH3CHO?HNO. At the MP2/6-31G(d), MP2/6-31+G(d,p) MP2/6-311++G(d,p), B3LYP/6-31G(d), B3LYP/6-31+G(d,p) and B3LYP/6-311++G(d,p) levels, the geometric structures and vibrational frequencies of complexes CH3CHO?HNO are calculated by both standard and CP-corrected methods, respectively. Complex A exhibits simultaneously red-shifted C bond H?O and blue-shifted N bond H?O H-bonds. Complex B possesses simultaneously two blue-shifted H-bonds: C bond H?O and N bond H?O. From NBO analysis, it becomes evident that the red-shifted C bond H?O H-bond can be explained on the basis of the two opposite effects: hyperconjugation and rehybridization. The blue-shifted C bond H?O H-bond is a result of conjunct C bond H bond strengthening effects of the hyperconjugation and the rehybridization due to existence of the significant electron density redistribution effect. For the blue-shifted N bond H?O H-bonds, the hyperconjugation is inhibited due to existence of the electron density redistribution effect. The large blue shift of the N bond H stretching frequency is observed because the rehybridization dominates the hyperconjugation.

Yang, Yong; Zhang, Weijun; Gao, Xiaoming

450

An improved shape shifting method of critical area extraction  

NASA Astrophysics Data System (ADS)

As die size and complexity increase, accurate and efficient extraction of the critical area is essential for yield prediction. Aiming at eliminating the potential integration errors of the traditional shape shifting method, an improved shape shifting method is proposed for Manhattan layouts. By mathematical analyses of the relevance of critical areas to defect sizes, the critical area for all defect sizes is modeled as a piecewise quadratic polynomial function of defect size, which can be obtained by extracting critical area for some certain defect sizes. Because the improved method calculates critical areas for all defect sizes instead of several discrete values with traditional shape shifting method, it eliminates the integration error of the average critical area. Experiments on industrial layouts show that the improved shape shifting method can improve the accuracy of the average critical area calculation by 24.3% or reduce about 59.7% computational expense compared with the traditional method.

Jiaojiao, Zhu; Xiaohua, Luo; Lisheng, Chen; Yi, Ye; Xiaolang, Yan

2014-02-01

451

Interactions of light and a temperature shift on seed germination.  

PubMed

Germination of Rumex obtusifolius L. seeds is potentiated to an observable degree in 2 minutes by a single shift in temperature from 20 to 35 C. Half-maximal potentiation requires less than 32 minutes at the higher temperature. Similar sensitivities to shifts in temperature were observed for seeds of Barbarea vulgaris, R.Br. B. verna (Mill.) Asch., and Lepidium virginicum L. A shift in temperature interacts strongly with change in form of phytochrome induced by light on germination of the four kinds of seeds. The potentiated effects for R. obtusifolius are only moderately affected by 40 mum cycloheximide. Both the temperature shift and light actions are apparently independent of processes of synthesis necessary for growth. PMID:16657910

Taylorson, R B; Hendricks, S B

1972-02-01

452

Set shifting impairments in an outpatient eating disorder sample   

E-print Network

Background: Patients with anorexia nervosa have been consistently reported to show impairments in set shifting ability. Such deficits may be associated with characteristics commonly observed in this patient group, such ...

Swanson, Helen M.

2009-01-01

453

Goos-Hänchen shifts of partially coherent light fields.  

PubMed

The Goos-Hänchen (GH) shift refers to a lateral displacement (from the path expected from geometrical optics) along an interface in totally internal reflection. This phenomenon results from a coherence effect. In order to bring to light the role of coherence, the reflection of partially coherent light fields was investigated within the framework of the theory of coherence. A formal expression for the GH shifts of partially coherent light fields is obtained in terms of Mercer's expansion. It is shown that both the spatial coherence and the beam width have an important effect on the GH shift, especially near the critical angles (such as totally reflection angle). These results are important to observe the GH shifts of the beams with imperfect coherence, like x-ray and matter-wave beams. PMID:24329448

Wang, Li-Gang; Zhu, Shi-Yao; Zubairy, M Suhail

2013-11-27

454

Pace of shifts in climate regions increases with global temperature  

E-print Network

Human-induced climate change causes significant changes in local climates, which in turn lead to changes in regional climate zones. Large shifts in the world distribution of Köppen–Geiger climate classifications by the end ...

Mahlstein, Irina

455

Polarization dependent frequency shift induced BER penalty in DPSK demodulators  

Microsoft Academic Search

We experimentally analyzed the induced penalty due to polarization dependent frequency shift (PDf) for 10 GHz and 40 GHz DPSK demodulators, revealing a strong correlation with the PDf ratio and filtering effect of the delay interferometer.

Dragos Cotruta; Xian Xu; David V. Plant; Odile Liboiron-Ladouceur

2009-01-01

456

Goos-Hänchen Shifts of Partially Coherent Light Fields  

NASA Astrophysics Data System (ADS)

The Goos-Hänchen (GH) shift refers to a lateral displacement (from the path expected from geometrical optics) along an interface in totally internal reflection. This phenomenon results from a coherence effect. In order to bring to light the role of coherence, the reflection of partially coherent light fields was investigated within the framework of the theory of coherence. A formal expression for the GH shifts of partially coherent light fields is obtained in terms of Mercer’s expansion. It is shown that both the spatial coherence and the beam width have an important effect on the GH shift, especially near the critical angles (such as totally reflection angle). These results are important to observe the GH shifts of the beams with imperfect coherence, like x-ray and matter-wave beams.

Wang, Li-Gang; Zhu, Shi-Yao; Zubairy, M. Suhail

2013-11-01

457

Interactions of Light and a Temperature Shift on Seed Germination  

PubMed Central

Germination of Rumex obtusifolius L. seeds is potentiated to an observable degree in 2 minutes by a single shift in temperature from 20 to 35 C. Half-maximal potentiation requires less than 32 minutes at the higher temperature. Similar sensitivities to shifts in temperature were observed for seeds of Barbarea vulgaris, R.Br. B. verna (Mill.) Asch., and Lepidium virginicum L. A shift in temperature interacts strongly with change in form of phytochrome induced by light on germination of the four kinds of seeds. The potentiated effects for R. obtusifolius are only moderately affected by 40 ?m cycloheximide. Both the temperature shift and light actions are apparently independent of processes of synthesis necessary for growth. PMID:16657910

Taylorson, R. B.; Hendricks, S. B.

1972-01-01

458

Tackling the blackbody shift in a strontium optical lattice clock  

E-print Network

A major obstacle for optical clocks is the frequency shift due to black body radiation. We discuss how one can tackle this problem in an optical lattice clock; in our case 87-Sr: firstly, by a measurement of the dc Stark shift of the clock transition and, secondly, by interrogating the atoms in a cryogenic environment. Both approaches rely on transporting ultracold atoms over several cm within a probe cycle. We evaluate this approach of mechanically moving the optical lattice and conclude that it is feasible to transport the atoms over 50 mm within 300 ms. With this transport a dc Stark shift measurement will allow to reduce the contribution of the blackbody radiation to the fractional uncertainty below 2 Ã? 10^â??17 at room temperature by improving the shift coefficient known only from atomic structure calculations up to now. We propose a cryogenic environment at 77 K that will reduce this contribution to few parts in 10^â??18.

Middelmann, Thomas; Falke, Stephan; Winfred, Joseph S R Vellore; Riehle, Fritz; Sterr, Uwe

2010-01-01

459

Tackling the blackbody shift in a strontium optical lattice clock  

E-print Network

A major obstacle for optical clocks is the frequency shift due to black body radiation. We discuss how one can tackle this problem in an optical lattice clock; in our case 87-Sr: firstly, by a measurement of the dc Stark shift of the clock transition and, secondly, by interrogating the atoms in a cryogenic environment. Both approaches rely on transporting ultracold atoms over several cm within a probe cycle. We evaluate this approach of mechanically moving the optical lattice and conclude that it is feasible to transport the atoms over 50 mm within 300 ms. With this transport a dc Stark shift measurement will allow to reduce the contribution of the blackbody radiation to the fractional uncertainty below 2 * 10^-17 at room temperature by improving the shift coefficient known only from atomic structure calculations up to now. We propose a cryogenic environment at 77 K that will reduce this contribution to few parts in 10^-18.

Thomas Middelmann; Christian Lisdat; Stephan Falke; Joseph S. R. Vellore Winfred; Fritz Riehle; Uwe Sterr

2010-09-10

460

Assessing the psychological status of the vowel shift rule.  

PubMed

Several experiments designed to test the psychological validity of Chomsky and Halle's (1968) Vowel Shift Rule are reviewed, and both positive and negative evidence is evaluated. Moskowitz's (1973) claim that speakers' knowledge of vowel alternations is due to their knowledge of spelling rules is introduced, and an experiment designed to differentiate between behavior based on the Vowel Shift Rule and on spelling rules is presented in detail. It is shown that subjects in this experiment, and in previous experiments that claimed to have obtained positive evidence for the Vowel Shift Rule, are behaving in accord with spelling rules and not the Vowel Shift Rule. It is argued that literacy is a possible source of psychologically real linguistic knowledge. PMID:6707977

Jaeger, J J

1984-01-01

461

30 CFR 57.22607 - Blasting on shift (III mines).  

Code of Federal Regulations, 2010 CFR

...NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Explosives... When blasting on shift, tests for methane shall be made in the mine atmosphere...not be done when 1.0 percent or more methane is...

2010-07-01

462

30 CFR 57.22607 - Blasting on shift (III mines).  

Code of Federal Regulations, 2011 CFR

...NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Explosives... When blasting on shift, tests for methane shall be made in the mine atmosphere...not be done when 1.0 percent or more methane is...

2011-07-01

463

Red-shifted fluorescence of sound dental hard tissue  

NASA Astrophysics Data System (ADS)

Autofluorescence spectra were recorded in vitro from dentin, enamel, and whole teeth. The spectra exhibited a broad peak shifted by about 50 to 75 nm from the excitation wavelength and the shape of the spectra remained similar regardless of the excitation wavelength. The maximum of the autofluorescence spectra also exhibited a red-shift that depended upon the laser excitation wavelength. The amplitude of the red-shifted fluorescence spectra produced by 444 and 532 nm excitation lasers were compared to that produced by a 405 nm excitation laser. It was determined that the autofluorescence amplitude was not proportional to the inverse fourth power of the excitation laser wavelength. Therefore, the red-shifted fluorescence is not compatible with the previously proposed mechanism of Raman scattering. Instead, the mechanism giving rise to the laser-induced dental autofluorescence is explained by the red-edge-excitation effect.

Zhang, Liang; Nelson, Leonard Y.; Seibel, Eric J.

2011-07-01

464

Lamb Shift of Energy Levels in Quantum Rings  

E-print Network

We study the vacuum radiative corrections to energy levels of a confined electron in quantum rings. The calculations are provided for the Lamb shift of energy levels in low-momentum region of virtual photons and for both one-dimensional and two-dimensional quantum rings. We show that contrary to the well known case of a hydrogen atom the value of the Lamb shift increases with the magnetic momentum quantum number m. We also investigate the dependence of the Lamb shift on magnetic flux piercing the ring and demonstrate a presence of magnetic-flux-dependent oscillations. For one-dimensional ring the value of the shift strongly depends on the radius of the ring. It is extremely small for semiconductor rings but can attain measurable quantities in natural organic ring-shape molecules, such as benzene, cycloalcanes and porphyrins.

G. Yu. Kryuchkyan; O. Kyriienko; I. A. Shelykh

2015-01-06

465

Medical Errors Drop When Docs Communicate Better At Shift Changes  

MedlinePLUS

... sharing features on this page, please enable JavaScript. Medical Errors Drop When Docs Communicate Better at Shift ... method of communication could reduce the rate of medical errors by almost 25 percent. "We were trying ...

466

Quasiparticle calculations of surface core-level shifts  

NASA Astrophysics Data System (ADS)

We report quasiparticle calculations of chemical shifts of core levels at clean and adsorbate-covered Si surfaces. Core-state excitation energies are given as poles of the electronic one-particle Green's function of the many-electron system. To calculate the Green's function, we employ the GW approximation for evaluating the necessary electronic self-energy operator. The core states whose shifts are addressed in this work are explicitly included in the valence shell. We present results for three different surfaces. For the As:Si(111)-(1×1) and H:Si(111)-(1×1) surfaces, we obtain core-level shifts in good agreement with experimental data. For the clean Si(001) surface a high sensitivity of the chemical shifts on the actual dimer structure of the surface is observed.

Rohlfing, Michael; Krüger, Peter; Pollmann, Johannes

1997-07-01

467

Higgs-induced spectroscopic shifts near strong gravity sources  

SciTech Connect

We explore the consequences of the mass generation due to the Higgs field in strong gravity astrophysical environments. The vacuum expectation value of the Higgs field is predicted to depend on the curvature of spacetime, potentially giving rise to peculiar spectroscopic shifts, named hereafter 'Higgs shifts'. Higgs shifts could be searched through dedicated multiwavelength and multispecies surveys with high spatial and spectral resolution near strong gravity sources such as Sagittarius A* or broad searches for signals due to primordial black holes. The possible absence of Higgs shifts in these surveys should provide limits to the coupling between the Higgs particle and the curvature of spacetime, a topic of interest for a recently proposed Higgs-driven inflationary model. We discuss some conceptual issues regarding the coexistence between the Higgs mechanism and gravity, especially for their different handling of fundamental and composite particles.

Onofrio, Roberto [Dipartimento di Fisica 'Galileo Galilei', Universita di Padova, Via Marzolo 8, Padova 35131 (Italy) and ITAMP, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)

2010-09-15

468

Cooperative Lamb Shift in a Mesoscopic Atomic Array  

NASA Astrophysics Data System (ADS)

According to quantum electrodynamics, the exchange of virtual photons in a system of identical quantum emitters causes a shift of its energy levels. Such shifts, known as cooperative Lamb shifts, have been studied mostly in the near-field regime. However, the resonant electromagnetic interaction persists also at large distances, providing coherent coupling between distant atoms. Here, we report a direct spectroscopic observation of the cooperative Lamb shift of an optical electric-dipole transition in an array of Sr+ ions suspended in a Paul trap at inter-ion separations much larger than the resonance wavelength. By controlling the precise positions of the ions, we studied the far-field resonant coupling in chains of up to eight ions, extending to a length of 40 ? m . This method provides a novel tool for experimental exploration of cooperative emission phenomena in extended mesoscopic atomic arrays.

Meir, Z.; Schwartz, O.; Shahmoon, E.; Oron, D.; Ozeri, R.

2014-11-01

469

Hospital Workers Wash Hands Less At End of Shift  

MedlinePLUS

... this page, please enable JavaScript. Hospital Workers Wash Hands Less at End of Shift, Study Finds New ... HealthDay News) -- Health workers in hospitals wash their hands less often as they near the end of ...

470

Adaptive control of hydraulic shift actuation in an automatic transmission  

E-print Network

A low-order dynamic model of a clutch for hydraulic control in an automatic transmission is developed by separating dynamics of the shift into four regions based on clutch piston position. The first three regions of the ...

Thornton, Sarah Marie

2013-01-01

471

Higgs-induced spectroscopic shifts near strong gravity sources  

E-print Network

We explore the consequences of the mass generation due to the Higgs field in strong gravity astrophysical environments. The vacuum expectation value of the Higgs field is predicted to depend on the curvature of spacetime, potentially giving rise to peculiar spectroscopic shifts, named hereafter "Higgs shifts." Higgs shifts could be searched through dedicated multiwavelength and multispecies surveys with high spatial and spectral resolution near strong gravity sources such as Sagittarius A* or broad searches for signals due to primordial black holes. The possible absence of Higgs shifts in these surveys should provide limits to the coupling between the Higgs particle and the curvature of spacetime, a topic of interest for a recently proposed Higgs-driven inflationary model. We discuss some conceptual issues regarding the coexistence between the Higgs mechanism and gravity, especially for their different handling of fundamental and composite particles.

Roberto Onofrio

2010-11-12

472

30 CFR 57.22607 - Blasting on shift (III mines).  

Code of Federal Regulations, 2014 CFR

...2014-07-01 false Blasting on shift (III mines). 57.22607 Section 57.22607 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2014-07-01

473

30 CFR 57.22607 - Blasting on shift (III mines).  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Blasting on shift (III mines). 57.22607 Section 57.22607 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2012-07-01

474

30 CFR 57.22607 - Blasting on shift (III mines).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Blasting on shift (III mines). 57.22607 Section 57.22607 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2013-07-01

475

Lamb shift of energy levels in quantum rings  

NASA Astrophysics Data System (ADS)

We study the vacuum radiative corrections to energy levels of a confined electron in quantum rings. The calculations are provided for the Lamb shift of energy levels in a low-momentum region of virtual photons and for both one-dimensional and two-dimensional quantum rings. We show that contrary to the well known case of a hydrogen atom the value of the Lamb shift increases with the magnetic momentum quantum number m. We also investigate the dependence of the Lamb shift on magnetic flux piercing the ring and demonstrate a presence of magnetic-flux-dependent oscillations. For a one-dimensional ring the value of the shift strongly depends on the radius of the ring. It is small for semiconductor rings but can attain measurable quantities in natural organic ring-shape molecules, such as benzene, cycloalcanes and porphyrins.

Kryuchkyan, G. Yu; Kyriienko, O.; Shelykh, I. A.

2015-01-01

476

Palestinians Across Borders: Shifting Relations to Locality and Community  

E-print Network

1 Palestinians Across Borders: Shifting Relations to Locality and Community Paper presented projects. Palestinian communities as diasporic social spaces Defining Palestinian communities living in exile as a diaspora can be seen as problematic. Some Palestinians may perceive such a label

Paris-Sud XI, Université de

477

Circadian Adaptation to Night Shift Work Influences Sleep, Performance, Mood and the Autonomic Modulation of the Heart  

PubMed Central

Our aim was to investigate how circadian adaptation to night shift work affects psychomotor performance, sleep, subjective alertness and mood, melatonin levels, and heart rate variability (HRV). Fifteen healthy police officers on patrol working rotating shifts participated to a bright light intervention study with 2 participants studied under two conditions. The participants entered the laboratory for 48 h before and after a series of 7 consecutive night shifts in the field. The nighttime and daytime sleep periods were scheduled during the first and second laboratory visit, respectively. The subjects were considered “adapted” to night shifts if their peak salivary melatonin occurred during their daytime sleep period during the second visit. The sleep duration and quality were comparable between laboratory visits in the adapted group, whereas they were reduced during visit 2 in the non-adapted group. Reaction speed was higher at the end of the waking period during the second laboratory visit in the adapted compared to the non-adapted group. Sleep onset latency (SOL) and subjective mood levels were significantly reduced and the LF?HF ratio during daytime sleep was significantly increased in the non-adapted group compared to the adapted group. Circadian adaptation to night shift work led to better performance, alertness and mood levels, longer daytime sleep, and lower sympathetic dominance during daytime sleep. These results suggest that the degree of circadian adaptation to night shift work is associated to different health indices. Longitudinal studies are required to investigate long-term clinical implications of circadian misalignment to atypical work schedules. PMID:23923024

Boudreau, Philippe; Dumont, Guy A.; Boivin, Diane B.

2013-01-01

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Comment on ''Phase-shift extraction and wave-front reconstruction in phase-shifting interferometry with arbitrary phase steps''  

NASA Astrophysics Data System (ADS)

We comment on the recent Letter by Cai et al. [Opt. Lett. 28, 1808 (2003)] in which an approach to phase-shifting interferometry with arbitrary phase steps was proposed. Cai et al. based their method of phase shifting on the idea that the intensities of the reference and object beams can be measured previously, which actually makes the whole posterior phase-shifting procedure absolutely unnecessary. Their method is also based on the statement that the phase of the Fresnel diffraction pattern of a test object if generally a spatially random distribution, which in most situations is wrong.

Ferrari, José A.; Garbusi, Eugenio

2004-06-01