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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

Effect of Reformate Components on PEMFC Performance Dilution and Reverse Water Gas Shift Reaction  

E-print Network

Effect of Reformate Components on PEMFC Performance Dilution and Reverse Water Gas Shift Reaction on the performance of proton exchange membrane fuel cells PEMFCs with Pt and Pt/Ru alloy anodes. The performance with N2 /H2 mixtures. The same deviations were observed with CO2 /H2 mixtures for a PEMFC with a Pt

Van Zee, John W.

3

Maximizing H 2 production by combined partial oxidation of CH 4 and water gas shift reaction  

Microsoft Academic Search

A dense ceramic membrane reactor has been constructed to exclusively transport oxygen for the partial oxidation of methane (CH4) to syngas (a mixture of CO and H2) at temperatures of 850–900°C. H2 production is enhanced in a second catalytic reactor through the water gas shift reaction, in which the CO reacts with steam that is injected into the reactor at

P. S. Maiya; T. J. Anderson; R. L. Mieville; J. T. Dusek; J. J. Picciolo; U. Balachandran

2000-01-01

4

The application of zeolites of predetermined permeability to the ''water gas shift reaction''  

Microsoft Academic Search

A flow sheet is presented for the isolation of pure hydrogen from the gas mixture generated by the well known water-gas shift reaction Hâ+CO=Hâ+COâ Separation of the resulting gas mixture is performed on three modified selective zeolite beds. By applying a highly integrated flow pattern with extended recycling of regeneration process streams to the reactor, the only gaseous waste stream

H. Dworschak; P. DeVievre; G. Peeters; G. Pierini; E. F. Vansant

1985-01-01

5

Reaction steps for the water-gas shift reaction and NOx storage\\/reduction catalysts studied by FTIR methods  

Microsoft Academic Search

Proton exchange membrane (PEM) fuel cells are an environmentally friendly source of energy since they are roughly twice as fuel efficient as internal combustion engines. The source of H2 is generally from hydrocarbons through the catalytic reforming and water-gas shift (WGS) reactions. The challenge on the WGS reaction is to find a catalyst that is more stable but has the

Joshua Lynn Ratts

2008-01-01

6

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

7

Carbon capture by sorption-enhanced water-gas shift reaction process using hydrotalcite-based material  

Microsoft Academic Search

A novel route for precombustion decarbonization is the sorption-enhanced water-gas shift (SEWGS) process. In this process carbon dioxide is removed from a synthesis gas at elevated temperature by adsorption. Simultaneously, carbon monoxide is converted to carbon dioxide by the water-gas shift reaction. The periodic adsorption and desorption of carbon dioxide is induced by a pressure swing cycle, and the cyclic

E. R. van Selow; P. D. Cobden; P. A. Verbraeken; J. R. Hufton; R. W. van den Brink

2009-01-01

8

Iron Oxides from Volcanic Soils as Potential Catalysts in the Water Gas Shift Reaction  

SciTech Connect

This study was focused on changes of the iron oxide mineralogy with temperature of two Chilean soils (Andisol and Ultisol) derived from volcanic materials and their use as iron-based catalysts in the water gas shift reaction (WGSR). Ultisol materials produced about twice as much hydrogen than did those from Andisol upon WGSR, but in both cases hydrogen yielding increased as the heating temperature of the soil materials increased from 124 deg. C to 500 deg. C. The room temperature Moessbauer spectra showed an increase of the relative proportion of the magnetically ordered components as temperature increased. Higher heating temperature produced a negative effect on the catalytic activity, whereas the organic matter destruction led to a positive effect, due to an increasing exposition of the iron oxide surfaces; heating the soil sample at 600 deg. C induced changes on the iron oxide mineralogy with a significant decrease of the catalytic activity.

Pizarro, C.; Escudey, M.; Moya, S.A. [Facultad de Quimica y Biologia, USACH, Av. L. B. O'Higgins 3363, Santiago 7254758 (Chile); Fabris, J.D. [Departamento de Quimica, ICEx-UFMG, Pampulha, 31270-901 Belo Horizonte, MG (Brazil)

2005-04-26

9

Water gas shift reaction: homogeneous catalysis by ruthenium and other metal carbonyls  

SciTech Connect

A number of chemical systems are active for homogeneous, solution phase catalysis of the water gas shift reaction (WGSR). Catalysis of the shift reaction appears to be a quite general property of carbonyl complexes in alkaline solutions. The key mechanistic steps for which some kinetics information is available are the activation of coordinated CO by reaction with hydroxide and the reductive elimination of dihydrogen from a resulting metal hydride. Which of these is rate limiting in a cycle is a function of the specific metal system and the specific reaction conditions. A basic solution is not a necessary condition for WGSR catalysis. Although WGSR catalysis is not as general a phenomenon in acidic media, several such systems have been characterized with activities which compare very favorably to those seen in basic solutions. While logical mechanisms have been proposed for several of the better characterized catalysts, it is clear that a more complete mechanistic understanding of the key steps in potential cycles is greatly needed. Recognition of such needs has led to fundamental studies into the acid/base natures of metal carbonyl hydride clusters, of CO activation on cluster and mononuclear metal carbonyls by bases, and of dihydrogen elimination from and declusterification and clusterification reactions of metal carbonyl hydrides. While none of these processes is in itself catalytic, the sum of several represents possible cycles. With regard to the future of homogeneous WGSR catalysts, it is obvious that under the conditions which these have been tested, the known systems are not commercially viable. Certainly, for a reaction such as the WGSR for which effective heterogeneous catalysts are known, it will take substantial advantages for a new system to be an attractive alternative to established technology.

Ford, P.C.

1981-02-01

10

SIC-BASED HYDROGEN SELECTIVE MEMBRANES FOR WATER-GAS-SHIFT REACTION  

SciTech Connect

In the first two years of this project, we focused on the membrane synthesis, characterization and optimization. In the past year, we have concentrated on the product development for improving the efficiency of hydrogen recovery from coal gasifier off-gas via water-gas-shift (WGS) reaction. A mathematical simulation study has been performed to compare the performance of the membrane reactor (MR) vs conventional packed bed rector for WGS reaction. Our result demonstrates that >99.999% conversion can be accomplished via WGS-MR using the hydrogen selective membrane developed by us. Further, water/CO ratio can be reduced, and >97% hydrogen recovery and <200 ppm CO can be accomplished according to the mathematical simulation. Thus, we believe that the operating economics of WGS can be improved significantly based upon the proposed MR concept. In parallel, gas separations and hydrothermal and long-term-storage stability of the hydrogen selected membrane have been experimentally demonstrated using a pilot-scale tubular membrane under a simulated WGS environment. For the remaining period of this project, we will conduct experimental study using the hydrogen selective membrane to verify the performance projected by the mathematical simulation.

Paul K.T. Liu

2002-10-31

11

Combination of autothermal reforming with water-gas-shift reaction—small-scale testing of different water-gas-shift catalysts  

NASA Astrophysics Data System (ADS)

The amount of carbon monoxide in the reformate of the autothermal reforming (ATR) of liquid hydrocarbons can be significantly reduced by means of the water-gas-shift (WGS) reaction. It is possible to directly feed the reformate from the ATR of liquid hydrocarbons to the WGS reactor without deactivation of the WGS catalyst. In a first step, the dry reformate from the ATR and a separately fed stream of steam were used to conduct the WGS reaction. Special emphasis was given to the chemical composition of the reformate which under convenient reaction conditions did not feature any detrimental higher aliphatic or aromatic hydrocarbons. Applying these premises, no catalyst deactivation could be observed. Strong differences concerning the catalytic activity between the three investigated commercial monolithic catalysts could be observed. The most active one showed a very promising catalytic behaviour. At a gas hourly space velocity (GHSV) of 12,250 h -1, CO conversion amounted to 85% at 280 °C. This result reduces the CO concentration in the reformate from 6.1 to about 0.9 vol.%. In a second step, also the non-converted water from the ATR was fed to the reactor for the WGS reaction together with the additional components of the reformate. In this case, also the amount of total carbon dissolved in the water was analysed, which might — after adsorption — have a deleterious effect on the accessibility of the active sites of the WGS catalyst. No catalyst deactivation was observed within almost 90 h under ATR conditions generating only traces of carbon dissolved in the water.

Pasel, J.; Cremer, P.; Wegner, B.; Peters, R.; Stolten, D.

12

SiC-BASED HYDROGEN SELECTIVE MEMBRANES FOR WATER-GAS-SHIFT REACTION  

SciTech Connect

This technical report summarizes our activities conducted in Yr II. In Yr I we successfully demonstrated the feasibility of preparing the hydrogen selective SiC membrane with a chemical vapor deposition (CVD) technique. In addition, a SiC macroporous membrane was fabricated as a substrate candidate for the proposed SiC membrane. In Yr II we have focused on the development of a microporous SiC membrane as an intermediate layer between the substrate and the final membrane layer prepared from CVD. Powders and supported thin silicon carbide films (membranes) were prepared by a sol-gel technique using silica sol precursors as the source of silicon, and phenolic resin as the source of carbon. The powders and films were prepared by the carbothermal reduction reaction between the silica and the carbon source. The XRD analysis indicates that the powders and films consist of SiC, while the surface area measurement indicates that they contain micropores. SEM and AFM studies of the same films also validate this observation. The powders and membranes were also stable under different corrosive and harsh environments. The effects of these different treatments on the internal surface area, pore size distribution, and transport properties, were studied for both the powders and the membranes using the aforementioned techniques and XPS. Finally the SiC membrane materials are shown to have satisfactory hydrothermal stability for the proposed application. In Yr III, we will focus on the demonstration of the potential benefit using the SiC membrane developed from Yr I and II for the water-gas-shift (WGS) reaction.

Paul K.T. Liu

2001-10-16

13

Kinetic modeling and first principles study of the water-gas shift and methanation reaction on group VIII metal catalysts  

Microsoft Academic Search

In this research kinetic modeling and first principles study of the water-gas shift (WGS) and methanation reactions on group VIII metal catalysts were carried out in an effort to develop fundamental mechanistic understanding. These tools were combined with experimental studies for quantitative modeling of WGS over Pt\\/Al2O3 catalysts. Self-consistent, periodic slab density functional theory DFT-GGA calculations were used to investigate

Abhijit A Phatak

2006-01-01

14

A newly proposed cycle for the water gas shift reaction homogeneously catalyzed by platinum and tin chloride  

SciTech Connect

Data previously reported by Cheng and Eisenberg for catalysis of the water gas shift (WGS) reaction by platinum and tin chlorides have been reviewed. A new catalytic cycle for the WGS catalysis that is consistent with more recent studies and the experimental data for the Pt-Sn system is presented. It appears to be likely that the platinum intermediates have the trichlorotin ligand, but the exact nature of the catalytic intermediates is still unknown. 16 refs., 2 figs.

Kubota, Mitsuru (Harvey Mudd College, Claremont, CA (USA))

1990-02-07

15

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

16

Activity, stability and deactivation behavior of Au\\/CeO 2 catalysts in the water gas shift reaction at increased reaction temperature (300 °C)  

Microsoft Academic Search

The effect of increasing the reaction temperature to 300°C on the activity, stability and deactivation behavior of a 4.5wt.% Au\\/CeO2 catalyst in the water gas shift (WGS) reaction in idealized reformate was studied by kinetic and spectroscopic measurements at 300°C and comparison with previously reported data for reaction at 180°C under similar reaction conditions [A. Karpenko, Y. Denkwitz, V. Plzak,

A. Abd El-Moemen; A. Karpenko; Y. Denkwitz; R. J. Behm

2009-01-01

17

Performance of Au/M(x)O(y)/TiO(2) Catalysts in Water-Gas Shift Reaction  

SciTech Connect

Our group recently developed a series of Au/M{sub x}O{sub y}/TiO{sub 2} catalysts for CO oxidation, and demonstrated that some of these catalysts are still active after high-temperature treatment whereas Au/TiO{sub 2} deactivates significantly due to the sintering of gold nanoparticles at elevated temperatures (Ma Z, Overbury SH, Dai S (2007) J Mol Catal A 273:97). In the current work, the performance of Au/M{sub x}O{sub y}/TiO{sub 2} (M = Al, Ca, Fe, Zn, Ga, Y, Zr, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb) catalysts in water-gas shift (WGS) reaction was evaluated. The influences of different metal oxide (M{sub x}O{sub y}) additives and pretreatment temperatures were investigated, and the catalyst stability as a function of reaction time on stream was tested. Some of these novel gold catalysts, with high activity and stability in water-gas shift, furnish new possibilities for further fundamental research and industrial development.

Ma, Zhen [ORNL; Dai, Sheng [ORNL; Yin, Hongfeng [ORNL

2010-01-01

18

Heat Integration of the Water-Gas Shift Reaction System for Carbon Sequestration Ready IGCC Process with Chemical Looping  

SciTech Connect

Integrated gasification combined cycle (IGCC) technology has been considered as an important alternative for efficient power systems that can reduce fuel consumption and CO2 emissions. One of the technological schemes combines water-gas shift reaction and chemical-looping combustion as post gasification techniques in order to produce sequestration-ready CO2 and potentially reduce the size of the gas turbine. However, these schemes have not been energetically integrated and process synthesis techniques can be applied to obtain an optimal flowsheet. This work studies the heat exchange network synthesis (HENS) for the water-gas shift reaction train employing a set of alternative designs provided by Aspen energy analyzer (AEA) and combined in a process superstructure that was simulated in Aspen Plus (AP). This approach allows a rigorous evaluation of the alternative designs and their combinations avoiding all the AEA simplifications (linearized models of heat exchangers). A CAPE-OPEN compliant capability which makes use of a MINLP algorithm for sequential modular simulators was employed to obtain a heat exchange network that provided a cost of energy that was 27% lower than the base case. Highly influential parameters for the pos gasification technologies (i.e. CO/steam ratio, gasifier temperature and pressure) were calculated to obtain the minimum cost of energy while chemical looping parameters (oxidation and reduction temperature) were ensured to be satisfied.

Juan M. Salazara; Stephen E. Zitney; Urmila M. Diwekara

2010-01-01

19

Carbon capture by sorption-enhanced water-gas shift reaction process using hydrotalcite-based material  

SciTech Connect

A novel route for precombustion decarbonization is the sorption-enhanced water-gas shift (SEWGS) process. In this process carbon dioxide is removed from a synthesis gas at elevated temperature by adsorption. Simultaneously, carbon monoxide is converted to carbon dioxide by the water-gas shift reaction. The periodic adsorption and desorption of carbon dioxide is induced by a pressure swing cycle, and the cyclic capacity can be amplified by purging with steam. From previous studies is it known that for SEWGS applications, hydrotalcite-based materials are particularly attractive as sorbent, and commercial high-temperature shift catalysts can be used for the conversion of carbon monoxide. Tablets of a potassium promoted hydrotalcite-based material are characterized in both breakthrough and cyclic experiments in a 2 m tall fixed-bed reactor. When exposed to a mixture of carbon dioxide, steam, and nitrogen at 400{sup o}C, the material shows a breakthrough capacity of 1.4 mmol/g. In subsequent experiments the material was mixed with tablets of promoted iron-chromium shift catalyst and exposed to a mixture of carbon dioxide, carbon monoxide, steam, hydrogen, and nitrogen. It is demonstrated that carbon monoxide conversion can be enhanced to 100% in the presence of a carbon dioxide sorbent. At breakthrough, carbon monoxide and carbon dioxide simultaneously appear at the end of the bed. During more than 300 cycles of adsorption/reaction and desorption, the capture rate, and carbon monoxide conversion are confirmed to be stable. Two different cycle types are investigated: one cycle with a CO{sub 2} rinse step and one cycle with a steam rinse step. The performance of both SEWGS cycles are discussed.

van Selow, E.R.; Cobden, P.D.; Verbraeken, P.A.; Hufton, J.R.; van den Brink, R.W. [Energy research Center of the Netherlands, Petten (Netherlands)

2009-05-15

20

Maximizing H{sub 2} production by combined partial oxidation of CH{sub 4} and water gas shift reaction.  

SciTech Connect

A dense ceramic membrane reactor has been constructed to exclusively transport oxygen for the partial oxidation of methane (CH{sub 4}) to syngas (a mixture of CO and H{sub 2}) at temperatures of 850-900{sup o}C. H2 production is enhanced in a second catalytic reactor through the water gas shift reaction, in which the CO reacts with steam that is injected into the reactor at a controlled rate to produce CO{sub 2} and H{sub 2}. Experiments and thermodynamic calculations were used to establish the optimal lower temperature (400{sup o}C) and lower steam-to-CO ratio (2) to achieve thermodynamic efficiency while maximizing H{sub 2} production. No unusual synergisms were observed by the combination of the two processes and the experimental results are in good agreement with thermodynamic predictions.

Maiya, P. S.; Anderson, T. J.; Mieville, R. L.; Dusek, J. T.; Picciolo, J. J.; Balachandran, U.; Energy Technology

2000-01-01

21

Quantifying the `reverse water gas shift' reaction inside a PEM fuel cell Tao Gu, W.-K. Lee, J.W. Van Zee*  

E-print Network

membrane fuel cells (PEMFCs), and recent evidence has shown that CO2 can react in situ with H2 (i composition, and temperature affect this reaction in a PEMFC for both Pt and Pt/Ru alloy catalysts (PEMFC); Reformate; Reverse water gas shift (RWGS) reaction; CO stripping; Pressure and temperature

Van Zee, John W.

22

SiC-BASED HYDROGEN SELECTIVE MEMBRANES FOR WATER-GAS-SHIFT REACTION  

SciTech Connect

A hydrogen selective membrane as a membrane reactor (MR) can significantly improve the power generation efficiency with a reduced capital and operating cost for the waster-gas-shift reaction. Existing hydrogen selective ceramic membranes are not suitable for the proposed MR due to their poor hydrothermal stability. In this project we have focused on the development of innovative silicon carbide (SiC) based hydrogen selective membranes, which can potentially overcome this technical barrier. During Year I, we have successfully fabricated SiC macro porous membranes via extrusion of commercially available SiC powder, which were then deposited with thin, micro-porous (6 to 40{angstrom} in pore size) films via sol-gel technique as intermediate layers. Finally, an SiC hydrogen selective thin film was deposited on this substrate via our CVD/I technique. The composite membrane thus prepared demonstrated excellent hydrogen selectivity at high temperature ({approx}600 C). More importantly, this membrane also exhibited a much improved hydrothermal stability at 600 C with 50% steam (atmospheric pressure) for nearly 100 hours. In parallel, we have explored an alternative approach to develop a H{sub 2} selective SiC membrane via pyrolysis of selected pre-ceramic polymers. Building upon the positive progress made in the Year I preliminary study, we will conduct an optimization study in Year II to develop an optimized H{sub 2} selective SiC membrane with sufficient hydrothermal stability suitable for the WGS environment.

Unknown

2000-12-01

23

SIC-BASED HYDROGEN SELECTIVE MEMBRANES FOR WATER-GAS-SHIFT REACTION  

SciTech Connect

A hydrogen selective membrane as a membrane reactor (MR) can significantly improve the power generation efficiency with a reduced capital and operating cost for the waster-gas-shift reaction. Existing hydrogen selective ceramic membranes are not suitable for the proposed MR due to their poor hydrothermal stability. In this project we have focused on the development of innovative silicon carbide (SiC) based hydrogen selective membranes, which can potentially overcome this technical barrier. SiC macro-porous membranes have been successfully fabricated via extrusion of commercially available SiC powder. Also, an SiC hydrogen selective thin film was prepared via our CVD/I technique. This composite membrane demonstrated excellent hydrogen selectivity at high temperature ({approx}600 C). More importantly, this membrane also exhibited a much improved hydrothermal stability at 600 C with 50% steam (atmospheric pressure) for nearly 100 hours. In parallel, we have explored an alternative approach to develop a H{sub 2} selective SiC membrane via pyrolysis of selected pre-ceramic polymers and sol-gel techniques. Building upon the positive progress made in the membrane development study, we conducted an optimization study to develop an H{sub 2} selective SiC membrane with sufficient hydrothermal stability suitable for the WGS environment. In addition, mathematical simulation has been performed to compare the performance of the membrane reactor (MR) vs conventional packed bed reactor for WGS reaction. Our result demonstrates that >99.999% conversion can be accomplished via WGS-MR using the hydrogen selective membrane developed by us. Further, water/CO ratio can be reduced, and >97% hydrogen recovery and <200 ppm CO can be accomplished according to the mathematical simulation. Thus, we believe that the operating economics of WGS can be improved significantly based upon the proposed MR concept. In parallel, gas separations and hydrothermal and long-term-storage stability of the hydrogen selected membrane have been experimentally demonstrated using a pilot-scale tubular membrane under a simulated WGS environment.

Paul K.T. Liu

2003-12-01

24

Studies related to the homogeneous catalysis of the water gas shift reaction. Technical progress report, December 1, 1983November 30, 1984  

Microsoft Academic Search

Proposed are investigations related to the catalytic activation of carbon monoxide. These studies will be concerned with the design of catalysts for the water gas shift reaction and related processes such as the hydroformylation of olefins by homogeneous solution phase systems as well as by selected metal catalysts heterogenized by complexation to functional polymers. Also under investigation will be quantitative

Ford

1984-01-01

25

Studies relevant to the catalytic activation of carbon monoxide: the water gas shift reaction and related processes. Technical progress report, December 1, 1983November 30, 1984  

Microsoft Academic Search

Proposed are investigations related to the catalytic activation of carbon monoxide. These studies will be concerned with the design of catalysts for the water gas shift reaction and related processes such as the hydroformylation of olefins by homogeneous solution phase systems as well as by selected metal catalysts heterogenized by complexation to functionalized polymers. Also under investigation will be quantitative

Ford

1984-01-01

26

H2 Production Through the Water-gas Shift Reaction: An In situ Time-resolved X-ray Diffraction Investigation of Manganese OMS-2 Catalyst  

SciTech Connect

Manganese oxide octahedral molecular sieve (OMS-2) catalyst prepared by the reflux method was investigated for hydrogen generation via the water-gas shift reaction. Catalysts were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), The Brunauer-Emmett-Teller (BET) surface area and determination of average oxidation state (AOS). The OMS-2 catalyst showed very good catalytic activity for the water-gas shift reaction to generate hydrogen under laboratory conditions. An in situ study was conducted to monitor the structural changes in the catalyst during the water-gas shift reaction using synchrotron radiation-based time-resolved X-ray diffraction (TR-XRD). During the water-gas shift reaction, the mixed valent OMS-2 catalyst undergoes a structural transformation to form Mn{sub 2}O{sub 3} and finally to form MnO. The study showed that OMS-2 catalysts can be used as inexpensive catalysts for hydrogen generation.

Hanson, J.C.; Sithambaram, S.; Wen, W.; Njagi, E.; Shen, X.-F.; Suib, S.L.

2010-10-01

27

Steam demand reduction of water–gas shift reaction in IGCC power plants with pre-combustion CO 2 capture  

Microsoft Academic Search

This paper presents the results of system assessments that were conducted to compare conventional and advanced water–gas shift reactor sections. The latter are specifically tailored for Integrated Gasification Combined Cycles (IGCC) power plants with pre-combustion CO2 capture. The advanced shift reactor section comprises four staged reactors with distributed feeds of synthesis gas and quench water in between the reactors. Conventional

M. C. Carbo; J. Boon; D. Jansen; H. A. J. van Dijk; J. W. Dijkstra; R. W. van den Brink; A. H. M. Verkooijen

2009-01-01

28

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

29

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

30

Low-temperature water-gas shift reaction over Cu and Ni-loaded cerium oxide catalysts  

Microsoft Academic Search

In this paper we report on the activity of Cu- and Ni-containing cerium oxide catalysts for low-temperature water-gas shift (WGS). Bulk catalysts were prepared in nanocrystalline form by the urea co-precipitation–gelation method. Lanthanum dopant (10at.%) was used as a structural stabilizer of ceria, while the content of Cu or Ni was in the range of 5–15at.% (2–8wt.%). At low metal

Yue Li; Qi Fu; Maria Flytzani-Stephanopoulos

2000-01-01

31

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

32

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

33

A rationally designed CuFe2O4-mesoporous Al2O3 composite towards stable performance of high temperature water-gas shift reaction.  

PubMed

High temperature water-gas shift reaction was demonstrated for the first time on a CuFe2O4-mesoporous alumina nanocomposite between 350 and 550 °C with 70-80% CO-conversion using simulated waste derived syngas under realistic conditions. Despite high Al-content, the catalyst exhibited stable activity, which was attributed to the nano-architectured robust porous nature of alumina integrated with surrounding CuFe2O4. PMID:23928578

Subramanian, Vijayanand; Gnanakumar, Edwin S; Jeong, Dae-Woon; Han, Won-Bi; Gopinath, Chinnakonda S; Roh, Hyun-Seog

2013-12-14

34

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

35

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

36

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 and the temperature dependence of oxygen deposition from CO2 point to an activated step. Consequences of these results

Pfeifer, Holger

37

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

38

Studies related to the homogeneous catalysis of the water gas shift reaction. Technical progress report, December 1, 1983-November 30, 1984  

SciTech Connect

Proposed are investigations related to the catalytic activation of carbon monoxide. These studies will be concerned with the design of catalysts for the water gas shift reaction and related processes such as the hydroformylation of olefins by homogeneous solution phase systems as well as by selected metal catalysts heterogenized by complexation to functional polymers. Also under investigation will be quantitative mechanistic aspects of reactions considered key to probable catalyst cycles. These are principally concerned with the fundamental chemistry of metal carbonyl and metal carbnyl hydride complexes including acid/base properties, reductive elimination, substitution and cluster fragmentation reactions and the nucleophilic activation of metal coordinated carbonyls toward reaction with water or dihydrogen. Goal of these studies is to provide chemical guidelines for the molecular design of new and more efficient catalysts for the utilization of carbonaceous materials such as coal for the production of fuels and other organic chemicals.

Ford, P.C.

1984-01-01

39

Studies relevant to the catalytic activation of carbon monoxide: the water gas shift reaction and related processes. Technical progress report, December 1, 1983-November 30, 1984  

SciTech Connect

Proposed are investigations related to the catalytic activation of carbon monoxide. These studies will be concerned with the design of catalysts for the water gas shift reaction and related processes such as the hydroformylation of olefins by homogeneous solution phase systems as well as by selected metal catalysts heterogenized by complexation to functionalized polymers. Also under investigation will be quantitative mechanistic aspects of reactions considered key to probable catalyst cycles. These are principally concerned with the fundamental chemistry of metal carbonyl and metal carbonyl hydride complexes including acid/base properties, reductive elimination, substitution and cluster fragmentation reactions and the nucleophilic activation of metal coordinated carbonyls toward reaction with water or dihydrogen. The goal of these studies is to provide chemical guidelines for the molecular design of new and more efficient catalysts for the utilization of carbonaceous materials such as coal for the production of fuels and other organic chemicals. 70 references.

Ford, P.C.

1984-01-01

40

A Common Single-Site Pt(II)-O(OH)x- Species Stabilized by Sodium on "Active" and "Inert" Supports Catalyzes the Water-Gas Shift Reaction.  

PubMed

While it has long been known that different types of support oxides have different capabilities to anchor metals and thus tailor the catalytic behavior, it is not always clear whether the support is a mere carrier of the active metal site, itself not participating directly in the reaction pathway. We report that catalytically similar single-atom-centric Pt sites are formed by binding to sodium ions through -O ligands, the ensemble being equally effective on supports as diverse as TiO2, L-zeolites, and mesoporous silica MCM-41. Loading of 0.5 wt % Pt on all of these supports preserves the Pt in atomic dispersion as Pt(II), and the Pt-O(OH)x- species catalyzes the water-gas shift reaction from ?120 to 400 °C. Since the effect of the support is "indirect," these findings pave the way for the use of a variety of earth-abundant supports as carriers of atomically dispersed platinum for applications in catalytic fuel-gas processing. PMID:25746682

Yang, Ming; Liu, Jilei; Lee, Sungsik; Zugic, Branko; Huang, Jun; Allard, Lawrence F; Flytzani-Stephanopoulos, Maria

2015-03-18

41

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

E-print Network

for the degree of MASTER OF SCIENCE December 1982 Ma)or Subject: Chemical Engineering DESULFURIZATION OF A COAL MODEL COMPOUND BY IN SITU HYDROGEN GENERATION THROUGH WATER-GAS SHIFT REACTION A Thesis by MEYYAPPAN KUMAR Approved as to style and content... by ( Chairman of Committee ) ( Member ) ( Member ) ( Head of Department ) December 1982 AB S TRACT Desulfurization Of A Coal Model Compound By In Situ Hydrogen Generation Through Water-Gas Shift Reaction December 1982 Meyyappan Kumar, B. S. , University...

Kumar, Meyyappan

1982-01-01

42

WATER-GAS SHIFT WITH INTEGRATED HYDROGEN SEPARATION  

SciTech Connect

Optimization of the water-gas shift (WGS) reaction system for hydrogen production for fuel cells is of particular interest to the energy industry. To this end, it is desirable to couple the WGS reaction to hydrogen separation using a semi-permeable membrane, with both processes carried out at high temperature to improve reaction kinetics. Reduced equilibrium conversion of the WGS reaction at high temperatures is overcome by product H{sub 2} removal via the membrane. This project involves fundamental research and development of novel cerium oxide-based catalysts for the water-gas-shift reaction and the integration of these catalysts with Pd-alloy H{sub 2}-separation membranes supplying high purity hydrogen for fuel cell use. Conditions matching the requirements of coal gasifier-exit gas streams will be examined in the project. In the first year of the project, we prepared a series of nanostructured Cu- and Fe-containing ceria catalysts by a special gelation/precipitation technique followed by air calcination at 650 C. Each sample was characterized by ICP for elemental composition analysis, BET-N2 desorption for surface area measurement, and by temperature-programmed reduction in H{sub 2} to evaluate catalyst reducibility. Screening WGS tests with catalyst powders were conducted in a flow microreactor at temperatures in the range of 200-550 C. On the basis of both activity and stability of catalysts in simulated coal gas, and in CO{sub 2}-rich gases, a Cu-CeO{sub 2} catalyst formulation was selected for further study in this project. Details from the catalyst development and testing work are given in this report. Also in this report, we present H{sub 2} permeation data collected with unsupported flat membranes of pure Pd and Pd-alloys over a wide temperature window.

Maria Flytzani-Stephanopoulos; Jerry Meldon; Xiaomei Qi

2001-12-01

43

WATER-GAS SHIFT WITH INTEGRATED HYDROGEN SEPARATION PROCESS  

SciTech Connect

This project involved fundamental research and development of novel cerium oxide-based catalysts for the water-gas-shift reaction and the integration of these catalysts with Pd-alloy H{sub 2} -separation membranes supplying high purity hydrogen for fuel cell use. Conditions matching the requirements of coal gasifier-exit gas streams were examined in the project. Cu-cerium oxide was identified as the most promising high-temperature water-gas shift catalyst for integration with H{sub 2}-selective membranes. Formulations containing iron oxide were found to deactivate in the presence of CO{sub 2}. Cu-containing ceria catalysts, on the other hand, showed high stability in CO{sub 2}-rich gases. This type gas will be present over much of the catalyst, as the membrane removes the hydrogen produced from the shift reaction. The high-temperature shift catalyst composition was optimized by proper selection of dopant type and amount in ceria. The formulation 10at%Cu-Ce(30at%La)O{sub x} showed the best performance, and was selected for further kinetic studies. WGS reaction rates were measured in a simulated coal-gas mixture. The apparent activation energy, measured over aged catalysts, was equal to 70.2 kJ/mol. Reaction orders in CO, H{sub 2}O, CO{sub 2} and H{sub 2} were found to be 0.8, 0.2, -0.3, and -0.3, respectively. This shows that H{sub 2}O has very little effect on the reaction rate, and that both CO{sub 2} and H{sub 2} weakly inhibit the reaction. Good stability of catalyst performance was found in 40-hr long tests. A flat (38 cm{sup 2}) Pd-Cu alloy membrane reactor was used with the catalyst washcoated on oxidized aluminum screens close coupled with the membrane. To achieve higher loadings, catalyst granules were layered on the membrane itself to test the combined HTS activity/ H{sub 2} -separation efficiency of the composite. Simulated coal gas mixtures were used and the effect of membrane on the conversion of CO over the catalyst was evidenced at high space velocities. Equilibrium CO conversion at 400 C was measured at a space velocity of 30,000 h{sup -1} with the 10{micro}m- thick Pd{sub 60}Cu{sub 40} membrane operating under a pressure differential of 100 psi. No carbon deposition took place during operation. The performance of the coupled Cu-ceria catalyst/membrane system at 400 C was stable in {approx} 30 h of continuous operation. The overall conclusion from this project is that Cu-doped ceria catalysts are suitable for use in high-temperature water-gas shift membrane reactors. CO{sub 2}-rich operation does not affect the catalyst activity or stability; neither does it affect hydrogen permeation through the Pd-Cu membrane. Operation in the temperature range of 400-430 C is recommended.

Maria Flytzani-Stephanopoulos; Xiaomei Qi; Scott Kronewitter

2004-02-01

44

WATER-GAS SHIFT WITH INTEGRATED HYDROGEN SEPARATION PROCESS  

SciTech Connect

Optimization of the water-gas shift (WGS) reaction system for hydrogen production for fuel cells is of particular interest to the energy industry. To this end, it is desirable to couple the WGS reaction to hydrogen separation using a semi-permeable membrane, with both processes carried out at high temperatures to improve reaction kinetics and permeation. Reduced equilibrium conversion of the WGS reaction at high temperatures is overcome by product H{sub 2} removal via the membrane. This project involves fundamental research and development of novel cerium oxide-based catalysts for the water-gas-shift reaction and the integration of these catalysts with Pd-alloy H{sub 2}-separation membranes supplying high purity hydrogen for fuel cell use. Conditions matching the requirements of coal gasifier-exit gas streams will be examined in the project. The first-year screening studies of WGS catalysts identified Cu-ceria as the most promising high-temperature shift catalyst for integration with H{sub 2}-selective membranes. Formulations containing iron oxide were found to deactivate in the presence of CO{sub 2}, and were thus eliminated from further consideration. Cu-containing ceria catalysts, on the other hand, showed high stability in CO{sub 2}-rich gases. This type gas will be present over much of the catalyst, as the membrane removes the hydrogen produced from the shift reaction. Several catalyst formulations were prepared, characterized and tested in the first year of study. Details from the catalyst development and testing work were given in our first annual technical report. Hydrogen permeation through Pd and Pd-alloy foils was investigated in a small membrane reactor constructed during the first year of the project. The effect of temperature on the hydrogen flux through pure Pd, Pd{sub 60}Cu{sub 40} and Pd{sub 75}Ag{sub 25} alloy membranes, each 25 {micro}m thick, was evaluated in the temperature range from 250 C to 500 C at upstream pressure of 4.4 atm and permeate hydrogen pressure of 1 atm. Flux decay was observed for the Pd-Cu membrane above 500 C. From 350-450 C, an average hydrogen flux value of 0.2 mol H{sub 2}/m{sup 2}/s was measured over this Pd-alloy membrane. These results are in good agreement with literature data. In this year's report, we discuss reaction rate measurements, optimization of catalyst kinetics by proper choice of dopant oxide (lanthana) in ceria, long-term stability studies, and H{sub 2} permeation data collected with unsupported flat, 10 {micro}m-thick Pd-Cu membranes over a wide temperature window and in various gas mixtures. The high-temperature shift catalyst composition was further improved, by proper selection of dopant type and amount. The formulation 10 at%Cu-Ce(30 at%La)Ox was the best; this was selected for further kinetic studies. WGS reaction rates were measured in a simulated coal-gas mixture. The stability of catalyst performance was examined in 40-hr long tests. A series of hydrogen permeation tests were conducted in a small flat-membrane reactor using the 10 m{micro}-thick Pd-Cu membranes. Small inhibitory effects of CO and CO{sub 2} were found at temperatures above 350 C, while H{sub 2}O vapor had no effect on hydrogen permeation. No carbon deposition took place during many hours of membrane operation. The reaction extent on the blank (catalyst-free) membrane was also negligible. A larger flat-membrane reactor will be used next year with the catalyst wash coated on screens close coupled with the Pd-Cu membrane.

Maria Flytzani-Stephanopoulos, PI; Jerry Meldon, Co-PI; Xiaomei Qi

2002-12-01

45

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

46

Development of Novel Water-Gas-Shift Membrane Reactor  

E-print Network

- Pressure Differential - No Moving Parts #12;Novel Membrane Process for H2 Purification H2 CO2 Air with CO2Development of Novel Water- Gas-Shift Membrane Reactor Addressing Barrier L: H2 Purification ppm CO at High Pressure Used for Reforming - Overcome Barrier L: H2 Purification/CO Clean-up - Achieve

47

In Situ Studies of the Active Sites for the Water Gas Shift Reaction over Cu?CeO 2 Catalysts:  Complex Interaction between Metallic Copper and Oxygen Vacancies of Ceria  

Microsoft Academic Search

New information about the active sites for the water gas shift (WGS) reaction over Cu-CeO2 systems was obtained using in-situ, time-resolved X-ray diffraction (TR-XRD), X-ray absorption spectroscopy (TR-XAS, Cu K and Ce L3 edges), and infrared spectroscopy (DRIFTS). Cu-CeO2 nanoparticles prepared by a novel reversed microemulsion method (doped Ce1-xCuxO2 sample) and an impregnation method (impregnated CuOx\\/ CeO2 sample) were studied.

Xianqin Wang; Jonathan C. Hanson; Daniel Gamarra; Arturo Martinez-Arias; Marcos Fernandez-Garcia

2006-01-01

48

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

49

In Situ Studies of the Active Sites for the Water Gas Shift Reaction over Cu-CeO2 Catalysts: Complex Interaction Between Metallic Copper and Oxygen Vacancies of Ceria  

SciTech Connect

New information about the active sites for the water gas shift (WGS) reaction over Cu-CeO{sub 2} systems was obtained using in-situ, time-resolved X-ray diffraction (TR-XRD), X-ray absorption spectroscopy (TR-XAS, Cu K and Ce L3 edges), and infrared spectroscopy (DRIFTS). Cu-CeO{sub 2} nanoparticles prepared by a novel reversed microemulsion method (doped Ce1-xCuxO2 sample) and an impregnation method (impregnated CuO{sub x}/CeO{sub 2} sample) were studied. The results from all of the samples indicate that both metallic copper and oxygen vacancies in ceria were involved in the generation of active sites for the WGS reaction. Evidence was found for a synergistic Cu-O vacancy interaction. This interaction enhances the chemical activity of Cu, and the presence of Cu facilitates the formation of O vacancies in ceria under reaction conditions. Water dissociation occurred on the O vacancy sites or the Cu-O vacancy interface. No significant amounts of formate were formed on the catalysts during the WGS reaction. The presence of strongly bound carbonates is an important factor for the deactivation of the catalysts at high temperatures. This work identifies for the first time the active sites for the WGS reaction on Cu-CeO{sub 2} catalysts and illustrates the importance of in situ structural studies for heterogeneous catalytic reactions.

Wang,X.; Rodriguez, J.; Hanson, J.; Gamarra, D.; Martinez-Arias, A.; Fernandez-Garcia, M.

2006-01-01

50

In situ studies of the active sites for the water gas shift reaction over Cu-CeO2 catalysts: complex interaction between metallic copper and oxygen vacancies of ceria.  

PubMed

New information about the active sites for the water gas shift (WGS) reaction over Cu-CeO2 systems was obtained using in-situ, time-resolved X-ray diffraction (TR-XRD), X-ray absorption spectroscopy (TR-XAS, Cu K and Ce L3 edges), and infrared spectroscopy (DRIFTS). Cu-CeO2 nanoparticles prepared by a novel reversed microemulsion method (doped Ce1-xCuxO2 sample) and an impregnation method (impregnated CuOx/CeO2 sample) were studied. The results from all of the samples indicate that both metallic copper and oxygen vacancies in ceria were involved in the generation of active sites for the WGS reaction. Evidence was found for a synergistic Cu-Ovacancy interaction. This interaction enhances the chemical activity of Cu, and the presence of Cu facilitates the formation of O vacancies in ceria under reaction conditions. Water dissociation occurred on the Ovacancy sites or the Cu-Ovacancy interface. No significant amounts of formate were formed on the catalysts during the WGS reaction. The presence of strongly bound carbonates is an important factor for the deactivation of the catalysts at high temperatures. This work identifies for the first time the active sites for the WGS reaction on Cu-CeO2 catalysts and illustrates the importance of in situ structural studies for heterogeneous catalytic reactions. PMID:16471552

Wang, Xianqin; Rodriguez, José A; Hanson, Jonathan C; Gamarra, Daniel; Martínez-Arias, Arturo; Fernández-García, Marcos

2006-01-12

51

Cr-free Fe-based metal oxide catalysts for high temperature water gas shift reaction of fuel processor using LPG  

SciTech Connect

The goal of this study was to identify the most suitable chromium-free iron-based catalysts for the HTS (high temperature shift) reaction of a fuel processor using LPG. Hexavalent chromium (Cr6+) in the commercial HTS catalyst has been regarded as hazardous material. We selected Ni and Co as the substitution for chromium in the Fe-based HTS catalyst and investigated the HTS activities of these Crfree catalysts at LPG reformate condition. Cr-free Fe-based catalysts which contain Ni, Zn, or Co instead of Cr were prepared by coprecipitation method and the performance of the catalysts in HTS was evaluated under gas mixture conditions (42% H2, 10% CO, 37% H2O, 8% CO2, and 3% CH4; R (reduction factor): about 1.2) similar to the gases from steam reforming of LPG (100% conversion at steam/carbon ratio = 3), which is higher than R (under 1) of typically studied LNG reformate condition. Among the prepared Cr-free Febased catalysts, the 5 wt%-Co/Fe/20 wt%-Ni and 5 wt%-Zn/Fe/20 wt%-Ni catalysts showed good catalytic activity under this reaction condition simulating LPG reformate gas.

lee, Joon Y.; Lee, Dae-Won; Lee, Kwan Young; Wang, Yong

2009-08-15

52

Selective hydrogenation of 1,3-cyclooctadiene and diphenylacetylene on copper using the water-gas shift reaction as a hydrogen source  

SciTech Connect

Selective catalytic hydrogenation of polyenes and acetylenes to monoolefins of a particular configuration is a matter of great interest in synthetic chemistry. Studies in this field have been principally devoted to the efficiency of catalytic systems and to the mechanism of the dihydrogen activation; many examples of stereo and regioselectivities have been discussed using either homogeneous or heterogeneous catalysts for the reduction of various compounds (substrates) with molecular hydrogen. In the course of studies on selective hydrogenation reactions catalyzed by transition metal derivatives, it has been found that water and carbon monoxide can be employed as reagents in place of the more expensive pure dihydrogen for the partial hydrogenation of 1,3-cyclooctadiene (C/sub 8/H/sub 12/) and of diphenylethyne (C/sub 14/H/sub 10/); these reactions are promoted by copper catalysts under relatively mild conditions. Experimental conditions and results are reported.

Fragale, C.; Gargano, M.; Rossi, M.

1983-04-01

53

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

Microsoft Academic Search

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

Thomas Barton; Tiberiu Popa

2009-01-01

54

Development of Novel Water-Gas Shift Membrane Reactor  

SciTech Connect

This report summarizes the objectives, technical barrier, approach, and accomplishments for the development of a novel water-gas-shift (WGS) membrane reactor for hydrogen enhancement and CO reduction. We have synthesized novel CO{sub 2}-selective membranes with high CO{sub 2} permeabilities and high CO{sub 2}/H{sub 2} and CO{sub 2}/CO selectivities by incorporating amino groups in polymer networks. We have also developed a one-dimensional non-isothermal model for the countercurrent WGS membrane reactor. The modeling results have shown that H{sub 2} enhancement (>99.6% H{sub 2} for the steam reforming of methane and >54% H{sub 2} for the autothermal reforming of gasoline with air on a dry basis) via CO{sub 2} removal and CO reduction to 10 ppm or lower are achievable for synthesis gases. With this model, we have elucidated the effects of system parameters, including CO{sub 2}/H{sub 2} selectivity, CO{sub 2} permeability, sweep/feed flow rate ratio, feed temperature, sweep temperature, feed pressure, catalyst activity, and feed CO concentration, on the membrane reactor performance. Based on the modeling study using the membrane data obtained, we showed the feasibility of achieving H{sub 2} enhancement via CO{sub 2} removal, CO reduction to {le} 10 ppm, and high H{sub 2} recovery. Using the membrane synthesized, we have obtained <10 ppm CO in the H{sub 2} product in WGS membrane reactor experiments. From the experiments, we verified the model developed. In addition, we removed CO{sub 2} from a syngas containing 17% CO{sub 2} to about 30 ppm. The CO{sub 2} removal data agreed well with the model developed. The syngas with about 0.1% CO{sub 2} and 1% CO was processed to convert the carbon oxides to methane via methanation to obtain <5 ppm CO in the H{sub 2} product.

Ho, W. S. Winston

2004-12-29

55

Development of an advanced water-gas shift conversion system. Final report  

SciTech Connect

Pacific Northwest Laboratory has completed initial exploratory research to investigate the chemistry and use of a pressurized aqueous catalyst system for conducting the water-gas shift reaction. The research was done under sponsorship of the USDOE Morgantown Energy Technology Center. A 1.0 liter continuous bench scale reactor system was built and operated to investigate water-gas shift chemistry at high pressure. Details regarding the chemistry of the aqueous, base-catalyzed system in both batch and continuous reactors are presented for a temperature range of 200 to 350/sup 0/C and pressures from 500 to 3000 psig. The catalyst choice is sodium carbonate at a concentration of 6% in water, but any material which can generate hydroxide ions at the process conditions will effectively catalyze the reaction. This report summarizes the results of the bench-scale research on the concept and presents a discussion of optimum operating conditions, pressure effects and limitations, kinetic data, effects of gas flow rates, catalyst type, and preliminary concept evaluation. 16 refs., 29 figs., 8 tabs.

Sealock, L.J. Jr.; Elliott, D.C.; Butner, R.S.

1985-04-01

56

WATER-GAS SHIFT KINETICS OVER IRON OXIDE CATALYSTS AT MEMBRANE REACTOR CONDITIONS  

SciTech Connect

The kinetics of water-gas shift were studied over ferrochrome catalysts under conditions with high carbon dioxide partial pressures, such as would be expected in a membrane reactor. The catalyst activity is inhibited by increasing carbon dioxide partial pressure. A microkinetic model of the reaction kinetics was developed. The model indicated that catalyst performance could be improved by decreasing the strength of surface oxygen bonds. Literature data indicated that adding either ceria or copper to the catalyst as a promoter might impart this desired effect. Ceria-promoted ferrochrome catalysts did not perform any better than unpromoted catalyst at the conditions tested, but copper-promoted ferrochrome catalysts did offer an improvement over the base ferrochrome material. A different class of water-gas shift catalyst, sulfided CoMo/Al{sub 2}O{sub 3} is not affected by carbon dioxide and may be a good alternative to the ferrochrome system, provided other constraints, notably the requisite sulfur level and maximum temperature, are not too limiting. A model was developed for an adiabatic, high-temperature water-gas shift membrane reactor. Simulation results indicate that an excess of steam in the feed (three moles of water per mole of CO) is beneficial even in a membrane reactor as it reduces the rate of adiabatic temperature rise. The simulations also indicate that much greater improvement can be attained by improving the catalyst as opposed to improving the membrane. Further, eliminating the inhibition by carbon dioxide will have a greater impact than will increasing the catalyst activity (assuming inhibition is still operative). Follow-up research into the use of sulfide catalysts with continued kinetic and reactor modeling is suggested.

Carl R.F. Lund

2002-08-02

57

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

SciTech Connect

A Co/MgO/SiO[sub 2] Fischer-Tropsch catalyst was operated simultaneously with a Cu/ZnO/Al[sub 2]O[sub 3] water-gas-shift catalyst in a slurry reactor for over 400 hours. The process conditions were held constant at a temperature of 240[degrees]C, a pressure of 0.79 MPa, and a 1.1 H[sub 2]/CO feed of 0.065 Nl/min-g.cat. The Fischer-Tropsch activity remained constant at the level predicted by the operation of the Co/MgO/SiO[sub 2] catalyst alone. The water-gas-shift reaction was near equilibrium. The hydrocarbon product distribution of the combined catalyst system was stable and matched that of the CO/MgO/SiO[sub 2] operating alone under similar conditions. The combined catalyst system exhibited a high selectivity to n-alkanes. Neither catalysts's operation appeared to have a detrimental effect on that of the other, showing promise for future option.

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

1990-01-01

58

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

59

A new generation of water gas shift catalysts for fuel cell applications  

NASA Astrophysics Data System (ADS)

The generation of high-purity hydrogen from hydrocarbon fuels for fuel cell applications is essential for efficient operation of the solid polymer electrolyte (PEM) fuel cell. In general, most feasible strategies to generate hydrogen from hydrocarbon fuels consist of a reforming step to generate a mixture of H 2, CO, CO 2 and H 2O (steam) followed by water gas shift (WGS) and CO clean-up steps. The WGS reaction is industrially carried out using two particulate catalysts—FeCr and CuZn—at temperatures between 350-500 and 180-250 °C, respectively. Both catalysts are pyrophoric: they spontaneously generate heat to dangerously high temperatures when exposed to air after activation. In addition, CuZn needs to be carefully activated before use. We have developed a base metal non-pyrophoric alternative to commercial CuZn. The catalyst, referred to as Selectra Shift, activates in process gas, has stable activity under a wide variety of process conditions and is safer if accidentally exposed to air. It therefore represents a safer alternative to the commercial CuZn for fuel cell applications. In addition, Engelhard has developed base metal and precious metal monolith WGS catalysts for applications where the catalyst must be optimized for small reactor volumes, lower pressure drop and mechanical integrity. Inhibitors are added to the precious metal catalyst to suppress the undesirable methanation side reaction.

Ruettinger, Wolfgang; Ilinich, Oleg; Farrauto, Robert J.

60

Operation, Modeling and Analysis of the Reverse Water Gas Shift Process  

NASA Technical Reports Server (NTRS)

The Reverse Water Gas Shift process is a candidate technology for water and oxygen production on Mars under the In-Situ Propellant Production project. This report focuses on the operation and analysis of the Reverse Water Gas Shift (RWGS) process, which has been constructed at Kennedy Space Center. A summary of results from the initial operation of the RWGS, process along with an analysis of these results is included in this report. In addition an evaluation of a material balance model developed from the work performed previously under the summer program is included along with recommendations for further experimental work.

Whitlow, Jonathan E.

2001-01-01

61

Single-stage temperature-controllable water gas shift reactor with catalytic nickel plates  

NASA Astrophysics Data System (ADS)

In this study, a microstructured reactor with catalytic nickel plates is newly designed and developed for proper heat management in an exothermic water gas shift WGS reaction. The reactor is designed to increase the reactor capacity simply by numbering-up a set of a catalyst layers and heat exchanger layers. The WGS reactor is built up with two sets of a catalyst layers and heat exchanger layers. The performance of the reactor is verified by WGS testing with the variation of the furnace temperatures, gas hourly space velocity (GHSV) and coolant (N2) flow rate. At a GHSV of 10,000 h-1, CO conversion reaches the equilibrium value with a CH4 selectivity of ?0.5% at the furnace temperature of ?375 °C. At high GHSV (40,000 h-1), CO conversion decreases considerably because of the heat from the exothermic WGS reaction at a large reactants mass. By increasing the coolant flow rate, the heat from the WGS reaction is properly managed, leading an increase of the CO conversion to the equilibrium value at GHSV of 40,000 h-1.

Park, Jin-Woo; Lee, Sung-Wook; Lee, Chun-Boo; Park, Jong-Soo; Lee, Dong-Wook; Kim, Sung-Hyun; Kim, Sung-Soo; Ryi, Shin-Kun

2014-02-01

62

Argonne National Laboratory Chemical Engineering Division Water-gas shift catalysis  

E-print Network

Argonne National Laboratory Chemical Engineering Division Water-gas shift catalysis Sara Yu Choung in decreased deactivation with a bimetallic formulation. · Select additional mixed-oxide systems for study 2002: Began long-term durability and H2S poisoning studies June 2003: Begin testing of catalysts

63

Noble metal water gas shift catalysis: Kinetics study and reactor design  

Microsoft Academic Search

Based on the water gas shift (WGS) catalytic mechanism on precious metal catalyst, a Langmuir–Hinshelwood (LH) kinetics model was derived for the operating conditions of syngas from natural gas reforming at near-ambient pressure. A power law kinetics model was also presented for comparative purpose. These two kinetics models were integrated in a dynamic distributed reactor model for design of full-scale

Jian Sun; Joel DesJardins; John Buglass; Ke Liu

2005-01-01

64

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

65

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

66

Iron-ceria Aerogels Doped with Palladium as Water-gas Shift Catalysts for the Production of Hydrogen  

SciTech Connect

Mixed 4.5% iron oxide-95.5% cerium oxide aerogels doped with 1% and 2% palladium (Pd) by weight have been synthesized, and their activities for the catalysis of water-gas shift (WGS) reaction have been determined. The aerogels were synthesized using propylene oxide as the proton scavenger for the initiation of hydrolysis and polycondensation of a homogeneous alcoholic solution of cerium(III) chloride heptahydrate and iron(III) chloride hexahydrate precursor. Palladium was doped onto some of these materials by gas-phase incorporation (GPI) using ({eta}{sup 3}-allyl)({eta}{sup 5}-cyclopentadienyl)palladium as the volatile Pd precursor. Water-gas shift catalytic activities were evaluated in a six-channel fixed-bed reactor at atmospheric pressure and reaction temperatures ranging from 150 to 350 C. Both 1% and 2% Pd-doped 4.5% iron oxide-95.5% cerium oxide aerogels showed WGS activities that increased significantly from 150 to 350 C. The activities of 1% Pd-doped 4.5% iron oxide-95.5% cerium oxide aerogels were also compared with that of the 1% Pd-doped ceria aerogel without iron. The WGS activity of 1% Pd on 4.5% iron oxide-95.5% cerium oxide aerogels is substantially higher (5 times) than the activity of 1% Pd-doped ceria aerogel without iron. The gas-phase incorporation results in a better Pd dispersion. Ceria aerogel provides a nonrigid structure wherein iron is not significantly incorporated inside the matrix, thereby resulting in better contact between the Fe and Pd and thus enhancing the WGS activity. Further, neither Fe nor Pd is reduced during the ceria-aerogel-catalyzed WGS reaction. This behavior contrasts with that noted for other Fe-based WGS catalysts, in which the original ferric oxide is typically reduced to a nonstoichiometric magnetite form.

Bali, S.; Huggins, F; Ernst, R; Pugmire, R; Huffman, G; Eyring, E

2010-01-01

67

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

SciTech Connect

A cobalt Fischer-Tropsch catalyst (CO/MgO/silica) was reduced and slurried in combination with reduced Cu/ZnO/Al[sub 2]0[sub 3] water-gas-shift catalyst. Combined catalyst system was run at fixed process conditions for more than 400 hours. The system showed stable selectivity. The Cu/ZnO/Al[sub 2]0[sub 3] water-gas-shift catalyst remained reasonably active in the presence of the cobalt catalyst. Hydrocarbon selectivity of the cobalt and Cu/ZnO/Al[sub 2]0[sub 3] catalyst system compared favorably to selectivity of iron-based catalysts. Methane selectivity was slightly higher for the cobalt-based system, but C[sub 5][sup +] selectivity was essentially the same. The hydrocarbon product distribution appeared to exhibit a double-a behavior. a[sub 1] was near 0.80 which is higher than that of iron catalysts, while a[sub 2] was calculated to be 0.86 which is somewhat lower than would be typical for an iron-based catalyst.

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

1988-01-01

68

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

69

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

70

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

Microsoft Academic Search

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

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

2008-01-01

71

Water gas shift membrane reactor for CO 2 control in IGCC systems: techno-economic feasibility study  

Microsoft Academic Search

A novel reactor concept, the water gas shift membrane reactor (WGS-MR) for CO2 removal in IGCC systems has been investigated. In order to establish full insight in the possibilities of the application of such a reactor, a multidisciplinary feasibility study has been carried out comprising system integration studies, catalyst research, membrane research, membrane reactor modelling and bench scale membrane reactor

M Bracht; P. T Alderliesten; R Kloster; R Pruschek; G Haupt; E Xue; J. R. H Ross; M. K Koukou; N Papayannakos

1997-01-01

72

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

73

Lyapunov-Based Sensor Failure Detection And Recovery For The Reverse Water Gas Shift Process  

NASA Technical Reports Server (NTRS)

Livingstone, a model-based AI software system, is planned for use in the autonomous fault diagnosis, reconfiguration, and control of the oxygen-producing reverse water gas shift (RWGS) process test-bed located in the Applied Chemistry Laboratory at KSC. In this report the RWGS process is first briefly described and an overview of Livingstone is given. Next, a Lyapunov-based approach for detecting and recovering from sensor failures, differing significantly from that used by Livingstone, is presented. In this new method, models used are in terms of the defining differential equations of system components, thus differing from the qualitative, static models used by Livingstone. An easily computed scalar inequality constraint, expressed in terms of sensed system variables, is used to determine the existence of sensor failures. In the event of sensor failure, an observer/estimator is used for determining which sensors have failed. The theory underlying the new approach is developed. Finally, a recommendation is made to use the Lyapunov-based approach to complement the capability of Livingstone and to use this combination in the RWGS process.

Haralambous, Michael G.

2001-01-01

74

Design of water gas shift catalysts for hydrogen production in fuel processors  

NASA Astrophysics Data System (ADS)

Low sulfur hydrocarbon fuels can be converted to fuel cell grade H2 using a compact fuel processor architecture. The necessary high volumetric activity water gas shift (WGS) Pt on ceria-zirconia catalysts reacts CO-rich reformate with steam to yield H2 and CO2. Such highly selective, non-pyrophoric noble metal/Ce[1-(x+y)]ZrxDpyO2 catalysts were developed through coordinated atomic modeling, syntheses, structural characterization, kinetic performance tests, and micro-kinetic analyses. Density functional simulations made with the VASP code suggested that the undoped catalyst WGS activity would be limited by the strong binding of CO intermediates, blocking the reoxidation of the reduced oxide by water. These predictions were confirmed by in situ cylindrical internal reflection-Fourier transform infrared spectroscopy and by micro-kinetic analyses of the micro-reactor results. Atomic simulations were used to evaluate the impact transition metal dopants had on the surface chemistry of cubic ceria-zirconia. VASP predicted that acidic transition metal dopants such as Nb, Mo, Ta, and W would increase the oxide surface affinity for water and thus increase the turnover rate of the catalyst. The efficacy of Mo-doped ceria-zirconia compositions was confirmed at lower temperatures in replicated catalyst synthesis-reactor studies.

Opalka, S. M.; Vanderspurt, T. H.; Radhakrishnan, R.; She, Y.; Willigan, R. R.

2008-02-01

75

LYAPUNOV-Based Sensor Failure Detection and Recovery for the Reverse Water Gas Shift Process  

NASA Technical Reports Server (NTRS)

Livingstone, a model-based AI software system, is planned for use in the autonomous fault diagnosis, reconfiguration, and control of the oxygen-producing reverse water gas shift (RWGS) process test-bed located in the Applied Chemistry Laboratory at KSC. In this report the RWGS process is first briefly described and an overview of Livingstone is given. Next, a Lyapunov-based approach for detecting and recovering from sensor failures, differing significantly from that used by Livingstone, is presented. In this new method, models used are in t e m of the defining differential equations of system components, thus differing from the qualitative, static models used by Livingstone. An easily computed scalar inequality constraint, expressed in terms of sensed system variables, is used to determine the existence of sensor failures. In the event of sensor failure, an observer/estimator is used for determining which sensors have failed. The theory underlying the new approach is developed. Finally, a recommendation is made to use the Lyapunov-based approach to complement the capability of Livingstone and to use this combination in the RWGS process.

Haralambous, Michael G.

2002-01-01

76

Kinetics of oxygen-enhanced water gas shift on bimetallic catalysts and the roles of metals and support  

NASA Astrophysics Data System (ADS)

The post-processing of reformate is an important step in producing hydrogen (H2) with low carbon monoxide (CO) for low temperature fuel cells from syn-gas. However, the conventional process consists of three steps, i.e. two steps of water gas shift (WGS) and preferential oxidation (PROX) of CO, and it is not suitable for mobile applications due to the large volume of water gas shift (WGS) catalysts and conditioning and/or regeneration necessary for these catalysts. Aiming at replacing those three steps by a simple one-step process, small amount of oxygen was added to WGS (the reaction called oxygen-enhanced water gas shift or OWGS) to promote the reaction kinetics and low pyrophoric ceria-supported bimetallic catalysts were employed for stable performance in this reaction. Not only CO conversion, but also H2 yield was found to increase by the O2 addition on CeO2-supported catalysts. The characteristics of OWGS, high H2 production rate at 200 to 300°C at short contact time where unreacted O2 exists, evidenced the impact of O2 addition on surface species on the catalyst. Around 1.5 of reaction order in CO for various CeO2-supported metal catalysts for OWGS compared to reaction orders in CO ranging from -0.1 to 0.6 depending on metal species for WGS shows O2 addition decreases CO coverage to free up the active sites for co-reactant (H2O) adsorption and activation. Among the monometallic and bimetallic catalysts, Pt-Cu and Pd-Cu bimetallic catalysts were superior to monometallic catalysts in OWGS. These bimetallic components were found to form alloys where noble metal is surrounded mainly by Cu to have strong interaction between noble metal and copper resulting in high OWGS activity and low pyrophoric property. The metal loadings were optimized for CeO2-supported Pd-Cu bimetallic system and 2 wt% Pd with 5 -- 10 wt% Cu were found to be the optimum for the present OWGS condition. In the kinetic study, Pd in Pd-Cu was shown to increase the active sites for H2O dissociation and/or the subsequent reaction with chemisorbed CO as well as Pd keeps Cu in reduced state. Cu was found to keep Pd dispersed, suppress H2 activation on Pd, and facilitate CO 2 desorption from catalyst surface. While composition and structure of metal have large impacts on OWGS performance, CeO2 was shown to create new sites for H2O activation at metal-ceria interfacial region in concert with metal. These new sites strongly activate H2O to drive OWGS and WGS compared to the pure metallic sites which are present in majority on Al2O3-supported catalyst. The observed two regimes of turnover rate, the one dependent on catalyst surface area and the other independent of surface area, strongly suggested bifunctional reaction pathway where the reaction rate is determined by activation of H2O and by association of chemisorbed CO and H 2O. The associative route was also evidenced by pulse response study where the reaction occurs only when CO and H2O pulses are supplied together, and thus pre-adsorbed species such as formate and carbonate identified by FT-IR are proven to be spectators. No correlation between WGS rate and isotopic exchange rate of molecularly adsorbed D2O with H 2 showed H2O dissociation is necessary for WGS to occur. Long duration tests revealed CeO2-supported Pd-Cu, Pt-Cu and Cu catalysts are stable in OWGS condition compared to Pt, Pd, and Al 2O3-supported Pd-Cu catalysts which exhibited continuous deactivation during about 70 hours of test. The addition of Cu prevents agglomeration of monometallic Pd and carbonate formation on monometallic Pt during the reaction. The better activity and stability of Pd-Cu and Pt-Cu bimetallic catalysts in the realistic OWGS condition were ascribed to the unique active sites consisting of highly dispersed Pd in Cu or Pt in Cu on CeO2, which are good for H2O activation with low reaction inhibition by the product gases. Pt monometallic catalyst showed and highest activity in OWGS in the absence of product gases, but this was found vulnerable in the presence of product gases due to strong adsorption of H2 and CO2 on t

Kugai, Junichiro

77

Pilot Scale Water Gas Shift - Membrane Device for Hydrogen from Coal  

SciTech Connect

The objectives of the project were to build pilot scale hydrogen separation systems for use in a gasification product stream. This device would demonstrate fabrication and manufacturing techniques for producing commercially ready facilities. The design was a 2 lb/day hydrogen device which included composite hydrogen separation membranes, a water gas shift monolith catalyst, and stainless steel structural components. Synkera Technologies was to prepare hydrogen separation membranes with metallic rims, and to adjust the alloy composition in their membranes to a palladium-gold composition which is sulfur resistant. Chart was to confirm their brazing technology for bonding the metallic rims of the composite membranes to their structural components and design and build the 2 lbs/day device incorporating membranes and catalysts. WRI prepared the catalysts and completed the testing of the membranes and devices on coal derived syngas. The reactor incorporated eighteen 2'' by 7'' composite palladium alloy membranes. These membranes were assembled with three stacks of three paired membranes. Initial vacuum testing and visual inspection indicated that some membranes were cracked, either in transportation or in testing. During replacement of the failed membranes, while pulling a vacuum on the back side of the membranes, folds were formed in the flexible composite membranes. In some instances these folds led to cracks, primarily at the interface between the alumina and the aluminum rim. The design of the 2 lb/day device was compromised by the lack of any membrane isolation. A leak in any membrane failed the entire device. A large number of tests were undertaken to bring the full 2 lb per day hydrogen capacity on line, but no single test lasted more than 48 hours. Subsequent tests to replace the mechanical seals with brazing have been promising, but the technology remains promising but not proven.

Barton, Tom

2013-06-30

78

Performance of sorption-enhanced water-gas shift as a pre-combustion CO 2 capture technology  

Microsoft Academic Search

The sorption-enhanced water-gas shift (SEWGS) process is a promising technology for pre-combustion decarbonisation. It is well suited for decarbonising syngas produced from natural-gas and coal based fuels in combined-cycle power production schemes. Higher capture rates could be obtained by SEWGS at lower efficiency penalties and at lower costs than by absorption. In the SEWGS process, multiple reactor vessels are packed

E. R. van Selow; P. D. Cobden; R. W. van den Brink; J. R. Hufton; A. Wright

2009-01-01

79

Slurry phase Fischer-Tropsch synthesis: Cobalt plus a water-gas shift catalyst. [Quarterly] report, July 1, 1990--September 30, 1990  

SciTech Connect

A Co/MgO/SiO{sub 2} Fischer-Tropsch catalyst was operated simultaneously with a Cu/ZnO/Al{sub 2}O{sub 3} water-gas-shift catalyst in a slurry reactor for over 400 hours. The process conditions were held constant at a temperature of 240{degrees}C, a pressure of 0.79 MPa, and a 1.1 H{sub 2}/CO feed of 0.065 Nl/min-g.cat. The Fischer-Tropsch activity remained constant at the level predicted by the operation of the Co/MgO/SiO{sub 2} catalyst alone. The water-gas-shift reaction was near equilibrium. The hydrocarbon product distribution of the combined catalyst system was stable and matched that of the CO/MgO/SiO{sub 2} operating alone under similar conditions. The combined catalyst system exhibited a high selectivity to n-alkanes. Neither catalysts`s operation appeared to have a detrimental effect on that of the other, showing promise for future option.

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

1990-12-31

80

Parametric Gasification of Oak and Pine Feedstocks Using the TCPDU and Slipstream Water-Gas Shift Catalysis  

SciTech Connect

With oak and pine feedstocks, the Gasification of Biomass to Hydrogen project maximizes hydrogen production using the Full Stream Reformer during water-gas shift fixed-bed reactor testing. Results indicate that higher steam-to-biomass ratio and higher thermal cracker temperature yield higher hydrogen concentration. NREL's techno-economic models and analyses indicate hydrogen production from biomass may be viable at an estimated cost of $1.77/kg (current) and $1.47/kg (advanced in 2015). To verify these estimates, NREL used the Thermochemical Process Development Unit (TCPDU), an integrated system of unit operations that investigates biomass thermochemical conversion to gaseous and liquid fuels and chemicals.

Hrdlicka, J.; Feik, C.; Carpenter, D.; Pomeroy, M.

2008-12-01

81

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts. Final technical progress report, September 12, 1991--December 11, 1994  

SciTech Connect

The objective of this research was to investigate sulfur-resistant catalysts for the conversion of synthesis gas having H{sub 2}/CO {le} 1 into C{sub 1}--C{sub 4} alcohols, especially ethanol, by a highly selective and efficient pathway, while also promoting the water gas shift reaction (WGSR). The catalysts chosen are bifunctional, base-hydrogenation, sulfur-tolerant transition metal sulfides with heavy alkali, e.g. Cs{sup +}, promoter dispersed on their surfaces. The modes of activation of H{sub 2} and CO on MoS{sub 2} and alkali-doped MoS{sub 2} were considered, and computational analyses of the thermodynamic stability of transition metal sulfides and of the electronic structure of these sulfide catalysts were carried out. In the preparation of the cesium-promoted MoS{sub 2} catalysts, a variety of preparation methods using CsOOCH were examined. In all cases, doping with CsOOCH led to a lost of surface area. The undoped molybdenum disulfide catalyst only produced hydrocarbons. Cs-doped MoS{sub 2} catalysts all produced linear alcohols, along with smaller amounts of hydrocarbons. With a 20 wt% CsOOCH/MoS{sub 2} catalyst, temperature, pressure, and flow rate dependences of the synthesis reactions were investigated in the presence and absence of H{sub 2}S in the H{sub 2}/CO = 1/1 synthesis gas during short term testing experiments. It was shown that with a carefully prepared 10 wt% CsOOCH/MoS{sub 2} catalyst, reproducible and high alcohol synthesis activity could be obtained. For example, at 295 C with H{sub 2}/CO = 1 synthesis gas at 8.3 MPa and with GHSV = 7,760 l/kg cat/hr, the total alcohol space time yield was ca 300 g/kg cat/hr (accompanied with a hydrocarbon space time yield of ca 60 g/kg cat/hr). Over a testing period of ca 130 hr, no net deactivation of the catalyst was observed. 90 refs., 82 figs., 14 tabs.

Klier, K.; Herman, R.G.; Deemer, M.; Richards-Babb, M.; Carr, T.

1995-07-01

82

Transition metal carbides, nitrides and borides, and their oxygen containing analogs useful as water gas shift catalysts  

DOEpatents

Mono- and bimetallic transition metal carbides, nitrides and borides, and their oxygen containing analogs (e.g. oxycarbides) for use as water gas shift catalysts are described. In a preferred embodiment, the catalysts have the general formula of M1.sub.A M2.sub.B Z.sub.C O.sub.D, wherein M1 is selected from the group consisting of Mo, W, and combinations thereof; M2 is selected from the group consisting of Fe, Ni, Cu, Co, and combinations thereof; Z is selected from the group consisting of carbon, nitrogen, boron, and combinations thereof; A is an integer; B is 0 or an integer greater than 0; C is an integer; O is oxygen; and D is 0 or an integer greater than 0. The catalysts exhibit good reactivity, stability, and sulfur tolerance, as compared to conventional water shift gas catalysts. These catalysts hold promise for use in conjunction with proton exchange membrane fuel cell powered systems.

Thompson, Levi T.; Patt, Jeremy; Moon, Dong Ju; Phillips, Cory

2003-09-23

83

Do Ni/Cu and Cu/Ni alloys have different catalytic performances towards water-gas shift? A density functional theory investigation.  

PubMed

Density functional calculations were preformed to investigate whether adding Ni into a Cu surface (denoted as Cu/Ni) or adding Cu into a Ni surface (Ni/Cu) is more efficient for catalyzing the water-gas shift (WGS)? The reactions of water dissociation and monoxide dissociation were selected to assess the activity and selectivity towards WGS, respectively. Our results show that Ni-atom modification of surfaces is thermodynamically favorable for both reactions. Kinetically, compared with pure Cu, water dissociation is greatly facilitated on Ni-modified surfaces, and the activity is insensitive to the Ni concentration; however, monoxide dissociation is not well-promoted on one Ni-atom-modified surfaces, but two Ni-atom modification can notably decrease the dissociation barriers. Overall, on the basis of these results, we conclude that 1) the catalytic performance of bimetallic metals is superior to monometallic ones; 2) at the same Ni concentration on the surface, Cu/Ni and Ni/Cu alloys have almost the same performance towards WGS; and 3) to acquire high WGS performance, the surface Ni atoms should either be low in concentration or highly dispersed. PMID:25044560

Huang, Yu Cheng; Zhou, Tao; Liu, Hai; Ling, ChongYi; Wang, SuFan; Du, Jin Yan

2014-08-25

84

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

85

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

86

In situ cell for combined XRD and on-line catalysis tests: Studies of Cu-based water gas shift and methanol catalysts  

Microsoft Academic Search

A newly developed in situ X-ray diffraction (XRD) cell has been used to obtain information on the structure of binary Cu-Zn and ternary Cu-Zn-Al catalysts during reduction and water gas shift and methanol synthesis. A major advantage of the cell is that it also serves as an ideal plug flow catalytic reactor such that realistic catalytic and structural information can

B. S. Clausen; G. Steffensen; B. Fabius; J. Villadsen; H. Topsoe; R. Feidenhansl

1991-01-01

87

Slurry phase Fischer-Tropsch synthesis: Cobalt plus a water-gas shift catalyst. [Quarterly] report, October 1, 1988--December 31, 1988  

SciTech Connect

A cobalt Fischer-Tropsch catalyst (CO/MgO/silica) was reduced and slurried in combination with reduced Cu/ZnO/Al{sub 2}0{sub 3} water-gas-shift catalyst. Combined catalyst system was run at fixed process conditions for more than 400 hours. The system showed stable selectivity. The Cu/ZnO/Al{sub 2}0{sub 3} water-gas-shift catalyst remained reasonably active in the presence of the cobalt catalyst. Hydrocarbon selectivity of the cobalt and Cu/ZnO/Al{sub 2}0{sub 3} catalyst system compared favorably to selectivity of iron-based catalysts. Methane selectivity was slightly higher for the cobalt-based system, but C{sub 5}{sup +} selectivity was essentially the same. The hydrocarbon product distribution appeared to exhibit a double-a behavior. a{sub 1} was near 0.80 which is higher than that of iron catalysts, while a{sub 2} was calculated to be 0.86 which is somewhat lower than would be typical for an iron-based catalyst.

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

1988-12-31

88

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

89

Determination of the Effect of Coal/Biomass-Derived Syngas Contaminants on the Performance of Fischer-Tropsch and Water-Gas-Shift Catalysts  

SciTech Connect

Today, nearly all liquid fuels and commodity chemicals are produced from non-renewable resources such as crude oil and natural gas. Because of increasing scrutiny of carbon dioxide (CO{sub 2}) emissions produced using traditional fossil-fuel resources, the utilization of alternative feedstocks for the production of power, hydrogen, value-added chemicals, and high-quality hydrocarbon fuels such as diesel and substitute natural gas (SNG) is critical to meeting the rapidly growing energy needs of modern society. Coal and biomass are particularly attractive as alternative feedstocks because of the abundant reserves of these resources worldwide. The strategy of co-gasification of coal/biomass (CB) mixtures to produce syngas for synthesis of Fischer-Tropsch (FT) fuels offers distinct advantages over gasification of either coal or biomass alone. Co-feeding coal with biomass offers the opportunity to exploit economies of scale that are difficult to achieve in biomass gasification, while the addition of biomass to the coal gasifier feed leverages proven coal gasification technology and allows CO{sub 2} credit benefits. Syngas generated from CB mixtures will have a unique contaminant composition because coal and biomass possess different concentrations and types of contaminants, and the final syngas composition is also strongly influenced by the gasification technology used. Syngas cleanup for gasification of CB mixtures will need to address this unique contaminant composition to support downstream processing and equipment. To investigate the impact of CB gasification on the production of transportation fuels by FT synthesis, RTI International conducted thermodynamic studies to identify trace contaminants that will react with water-gas-shift and FT catalysts and built several automated microreactor systems to investigate the effect of single components and the synergistic effects of multiple contaminants on water-gas-shift and FT catalyst performance. The contaminants investigated were sodium chloride (NaCl), potassium chloride (KCl), hydrogen sulfide (H{sub 2}S), carbonyl sulfide (COS), ammonia (NH{sub 3}), and combinations thereof. This report details the thermodynamic studies and the individual and multi-contaminant results from this testing program.

Trembly, Jason; Cooper, Matthew; Farmer, Justin; Turk, Brian; Gupta, Raghubir

2010-12-31

90

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

91

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

92

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

93

Nuclear field shift effect in chemical exchange reactions  

NASA Astrophysics Data System (ADS)

The classic theory of stable isotope fractionation in chemical exchange reactions has been established by Bigeleisen, Mayer, and Urey in 1947. The theory was based on the difference of molecular vibrational energies of isotopomers that are proportional to the respective masses, and hence, results in mass-dependent isotope effect only. In 1996, this conventional mass-dependent theory has been expanded by Bigeleisen to include a mass-independent term named the nuclear field shift effect. The nuclear field shift is an isotope shift in orbital electrons, which results from the isotopic difference in nuclear size and shape. The new equation defined by Bigeleisen (at a constant temperature) can be simply expressed as, ln ? = ? A + (? m/mm') B, where ? is the isotope separation factor, ? isotopic difference in mean-square nuclear charge radius, ?m difference between isotopic masses m and m'. A and B are scaling factors of the nuclear field shift effect and the conventional mass effect, respectively. Since this new theory was presented, the mass-independent isotope fractionation of various elements, e.g, Ti, Cr, Ni, Zn, Sr, Zr, Mo, Ru, Cd, Te, Ba, Nd, Sm, Gd, Yb, and U, found in chemical exchange systems has been successfully explained as the nuclear field shift effect. In our most recent studies, the nuclear field shift effect of Cr, Mo, Ru, Cd, and Te isotopes has been found in laboratory scale experiments. The isotopes of these elements were fractionated by using a liquid-liquid extraction system (a ligand exchange system) at room temperature. The isotopic analysis was performed by the multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) with a typical precision of <100 ppm (at ENS Lyon or UC Davis). Isotope enrichment factors did not show mass-dependent trend, but possessed a similar variation of their nuclear charge radii. For Cr, we tested a different chemical exchange system (a redox system): at high temperature (723-1023 K), an eutectic melt was contacted with a liquid metal. In this system, the nuclear field shift effect of Cr was also found. All these experimental results suggest that the nuclear field shift effect may occur in every chemical exchange reaction at various temperatures to various degrees. Therefore, isotopic anomalies found in a natural system might be partly or largely affected by the nuclear field shift effect via chemical reactions occurred in the nature. In order to clarify the degree and significance of its contribution, we may need to pay more attention to the nuclear field shift effect created chemically.

Fujii, T.; Moynier, F.; Yin, Q.; Albarède, F.

2007-12-01

94

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

E-print Network

Pretreatment on HDS Activity Cobalt-molybdenum catalysts have been the workhorse of HDS processes for years. De Beer et el. (1976) have shown that nickel (Ni) or cobalt (Co) promoted molybdena-alumina (Mo-Al) catalysts are more active than tungsten sulfide... Engineering, Inc. A Flame ionization detector was used to detect the compounds as they left the column. Samples for injection were prepared by diluting 50 ul of liquid product in 0. 5 ml of carbon disulfide in a small viaL Of this solution. 0. 1 al 19...

Hook, Bruce David

1984-01-01

95

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

SciTech Connect

To become a viable CO{sub 2} transport membrane, a reversible interaction between CO{sub 2} and the membrane material at the operating condition is a must. In the past quarter, we have conducted a comprehensive reversibility study using TGA and MS at {approx}200 C for both adsorption and desorption. This quarterly report summarizes the results. Evidently, CO{sub 2} can be reversible adsorbed and desorbed on the hydrotalcite surface via a pressure swing operation (i.e., between 1 bar and vacuum). About 2wt% working capacity was obtained. Even in the presence of water, the reversibility still holds. In the next quarter, we will focus on the reversibility under other operating conditions and the kinetic aspect of the reversibility study.

Paul K.T. Liu

2002-03-01

96

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

SciTech Connect

Hydrotalcite material properties, specifically its CO{sub 2} reversibility, are critical to the performance of the proposed hydrotalcite-based membrane. In this report, we summarize the fundamental study we have performed using TGA, TGA/MS, and DRIFTS to quantify the degree of CO{sub 2} reversibility for the temperature range from 200 to 300 C. Results from these three separate studies consistently exhibit the CO{sub 2} reversibility. In addition, water effect appears negligible. Finally a high-pressure experimental study was performed to determine the reversibility under the actual operating condition. The results from this high-pressure (CO{sub 2}) study also demonstrate the CO{sub 2} reversibility. In the next quarter, we will continue the high-pressure experiment in the presence of high-pressure steam to quantify its effect under the actual WGS environment. The quantitative information obtained from this study will then be incorporated in a mathematical model describing the CO{sub 2} permeance as a function of the membrane layer thickness.

Paul K.T. Liu

2003-05-20

97

Investigation of the Reverse Water Gas Shift Reaction for Production of Oxygen From Mars Atmospheric Carbon Dioxide  

NASA Technical Reports Server (NTRS)

The first phase of the research includes a comprehensive analytical study examining the potential applications for engineering subsystems and mission strategies made possible by such RWGS based subsystems, and will include an actual experimental demonstration and performance characterization of a full-scale brassboard RWGS working unit. By the time of this presentation the laboratory demonstration unit will not yet be operational but we will present the results of our analytical studies to date and plans for the ongoing work.

Meyer, Tom; Zubrin, Robert

1997-01-01

98

Carburetting water gas  

Microsoft Academic Search

This patent describes a carburetted water-gas set consisting of a generator and a substantially vertical carburetor having a refractory lining and baffles each extending more than half-way across the interior to divide the interior into superposed zones connected in a series by large openings at alternately opposite sides of the carburetor. These said zones are of a horizontal cross sectional

R. P. Jones; R. L. Ellis

1940-01-01

99

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

100

The effect of platinum in Cu-Ce-Zr and Cu-Zn-Al mixed oxide catalysts for water–gas shift  

Microsoft Academic Search

Cu-Ce-Zr and Cu-Zn-Al mixed oxide catalysts were prepared by homogeneous co-precipitation with urea. Pt was wet-impregnated on the mixed oxide catalysts. The WGS activity of Cu-Ce-Zr and Cu-Zn-Al mixed oxide catalysts can be related to the Cu reducibility in these catalysts. Low-temperature reducibility correlates with low-temperature activity. Pre-reduction is not absolutely necessary when performing the WGS reaction above the Cu

Florian Huber; John Walmsley; Hilde Venvik; Anders Holmen

2008-01-01

101

Continuous process of making carburetted water gas  

Microsoft Academic Search

This patent describes a continuous process for making carburetted water gas in a retort by feeding fragmentary solid refractory material which does not enter actively into the gas-making reactions to the upper part of a retort. The process involves externally and continuously heating said retort and the refractory material; progressively feeding oil to the heated refractory material in the retort

R. M. Chatterton; P. F. Paffen

1943-01-01

102

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

103

Water-Gas Shift Membrane Reactor Studies  

E-print Network

Reactor Fuels and Chemicals Generator Steam Turbine Combustion Turbine Heat Recovery Steam Generator Combustor Air Generator Stack Electric Power Electric Power Electric Power Hydrogen H2 Separation Fuel Cells

104

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

105

Modeling Xylene Reactions over ZSM-5 Zeolite in a Riser Simulator: 1,3 versus 1,2-Methyl Shift  

E-print Network

Modeling Xylene Reactions over ZSM-5 Zeolite in a Riser Simulator: 1,3 versus 1,2-Methyl Shift S shift), and a second scheme that assumes the reactions to proceed via 1,2-methyl shift only (o-xylene m ZSM-5 zeolite catalyst, and the 1,3-methyl shift reaction path is a better representation

Al-Khattaf, Sulaiman

106

Carburetted water-gas generator  

Microsoft Academic Search

This patent describes a carburetted water-gas set having an enclosing wall having partition extending thereacross, a generator, a superheater, and a carburetor, all arranged in the order named. The apparatus has a means of connecting the top of said generator and the top of said carburetor. The partition between the carburetor and superheater have an opening in its bottom with

Tenney

1934-01-01

107

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

108

Selective hydrogenation of 1,3-cyclooctadiene and diphenylacetylene on copper using the water-gas shift reaction as a hydrogen source  

Microsoft Academic Search

Selective catalytic hydrogenation of polyenes and acetylenes to monoolefins of a particular configuration is a matter of great interest in synthetic chemistry. Studies in this field have been principally devoted to the efficiency of catalytic systems and to the mechanism of the dihydrogen activation; many examples of stereo and regioselectivities have been discussed using either homogeneous or heterogeneous catalysts for

C. Fragale; M. Gargano; M. Rossi

1983-01-01

109

Synthesis of Na-Stabilized Nonporous tZrO2 Supports and Pt/t-ZrO2 Catalysts and Application to Water-Gas-Shift Reaction  

E-print Network

Synthesis of Na-Stabilized Nonporous tZrO2 Supports and Pt/t-ZrO2 Catalysts and Application, Indiana 47907, United States ABSTRACT: t-ZrO2, synthesized under hydrothermal treatment conditions at 150 °C for 20 h using NaOH as the mineralizer, was phase stable up to 600 °C in air. The t-ZrO2 calcined

Poeppelmeier, Kenneth R.

110

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

111

Gold supported on well-ordered ceria films: nucleation, growth and morphology in CO oxidation reaction  

E-print Network

are found to be stable in O2 ambient up to 10 mbar, meanwhile gold sintering emerges at CO pressures above oxidation reaction. KEY WORDS: gold; ceria; CO oxidation; thin films; scanning tunneling microscopy. 1 oxidation, selective oxidation of propene to propene oxide, water gas shift reaction, NO reduction

Gao, Hongjun

112

Shift in the speed of reaction-diffusion equation with a cut-off: Pushed and bistable fronts  

NASA Astrophysics Data System (ADS)

We study the change in the speed of pushed and bistable fronts of the reaction-diffusion equation in the presence of a small cut-off. We give explicit formulas for the shift in the speed for arbitrary reaction terms f(u). The dependence of the speed shift on the cut-off parameter is a function of the front speed and profile in the absence of the cut-off. In order to determine the speed shift we solve the leading order approximation to the front profile u(z) in the neighborhood of the leading edge and use a variational principle for the speed. We apply the general formula to the Nagumo equation and recover the results which have been obtained recently by geometric analysis. The formulas given are of general validity and we also apply them to a class of reaction terms which have not been considered elsewhere.

Benguria, R. D.; Depassier, M. C.

2014-07-01

113

Process of manufacturing carburetted water gas  

Microsoft Academic Search

This patent describes a process of manufacturing carburetted water gas by upwardly blasting the fuel bed in the generator with air admitted at the bottom of the generator and burning the blast gases in the carburetting apparatus with air admitted to the latter and passed therethrough. The process involves effecting a steam run upwardly through the fuel bed, admitted at

Steinwedell

1940-01-01

114

Process of manufacturing carburetted water gas  

Microsoft Academic Search

This patent involves a processes for manufacturing carburetted water gas, in which a known cycle of operations consists in first upwardly blasting the fuel bed in the generator with air admitted at the bottom of the generator and burning the blow gases in the carbureting apparatus with air admitted. It will then effect steam run upwardly through the fuel bed

Stookey

1951-01-01

115

Process of making carburetted water gas  

Microsoft Academic Search

This patent describes a process of manufacturing water gas by alternately introducing an air blast and a steam run into the fuel bed of a gas generator. Then admitting heavy oil into the top of the generator simultaneously with the steam run to enrich the resulting gas. The said air blast is introduced in a reverse direction into the generator

G. J. Nordmeyer; T. W. Stone

1934-01-01

116

Process of manufacturing carburetted water gas  

Microsoft Academic Search

This patent describes a process of manufacturing carburetted water gas by the use of heavy oil as the carburetting medium in a gas-making set including a generator and conduits connecting the top of the generator and the bottom of the generator. The carburetting apparatus and flow-direction control valves provide a process consisting of upwardly blasting the fuel bed in the

Steinwedell

1940-01-01

117

Low-gravity carburetted water gas  

Microsoft Academic Search

This paper discusses a process of manufacturing carburetted water gas in a set comprising a generator, carburetor, and superheater. The process involves the following steps: air blasting the fuel bed and simultaneously burning the blast gases so produced with secondary air introduced adjacent the upper marginal edge of the fuel bed; making an uprun with steam through the generator; making

J. A. Perry; E. L. Hall

1935-01-01

118

Process for manufacturing carburetted water gas  

Microsoft Academic Search

This patent describes a process of manufacturing water gas in an apparatus including a generator having a bed of solid fuel and a superposed carburetting chamber. The process consists in separately and successively passing air blasts and steam in opposite directions through fuel bed, admitting heavy oil into the carburetting chamber of said generator coincidentally with the steam runs to

Nordmeyer

1934-01-01

119

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

120

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

E-print Network

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's spin degrees of freedom to its decohering vibrational reservoir leads to a shift of the radical-pair's 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.

K. M. Vitalis; I. K. Kominis

2014-09-28

121

Ultrafast photoinduced charge-shift reactions in electron donor-acceptor 9-arylacridinium ions  

NASA Astrophysics Data System (ADS)

Charge-shift species arising from intramolecular electron transfer have been identified for 9-aryl derivatives of the 10-methylacridinium ion through observation of red-shifted fluorescence emission bands and the appearance of radical(ion) transients (CH3CN and CH2Cl2 solvents) using laser flash photolysis. Rates of forward and return charge-shift processes have been determined, the former occurring in the 1 ps time domain with small effects associated with changes in solvent and the electron donor substituent. Rates for return electron transfer were a strong function of the donor oxidation potential and showed acceleration with decreased driving force (inverted behavior). The lifetimes for charge-shift intermediates could be 'tuned' over three orders of magnitude as the result of changes in acridinium structure and solvent.

Jones, Guilford, II; Farahat, Mohammad S.; Greenfield, Scott R.; Gosztola, David J.; Wasielewski, Michael R.

1994-10-01

122

Temperature-Shift Speed Dependence of Nonspecific Amplification of Polymerase Chain Reaction Examined by 1480 nm Photothermal Transition Speed Controllable High-Speed Polymerase Chain Reaction System  

NASA Astrophysics Data System (ADS)

We have examined the contribution of temperature shift speed from denaturation to extension for the reduction of nonspecific amplification caused by the mismatched primer-target attachment. We have newly developed the photothermal quantitative polymerase chain reaction (qPCR) system, in which the direct absorption of a 1480 nm infrared laser beam was controlled by a rotating gradient neutral density (ND) filter to acquire the precise control of the desired speed of temperature shift between 60 and 95 °C up to 1 s. The results showed that a quick shift of the temperature during the qPCR procedure reduced nonspecific amplicons with a significant reduction of qPCR time when we have chosen proper primer sets, whereas the non-proper primer set amplified nonspecific amplicons in the fast qPCR. The results indicate that the potential of quick qPCR using proper primers can reduce nonspecific amplification and the required time for qPCR measurement, and the necessity of more precise check of the matching of the primer template adequate for the fast temperature shift and for quick qPCR analysis.

Terazono, Hideyuki; Hattori, Akihiro; Kim, Hyonchol; Takei, Hiroyuki; Nomura, Fumimasa; Kaneko, Tomoyuki; Yasuda, Kenji

2013-06-01

123

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

124

A spiking neural model of strategy shifting in a simple reaction time task Trevor Bekolay1  

E-print Network

synaptic weight changes. Simple reaction-time task House lights extinguished Foreperiod 1.0 s Lever press Lever release Premature trial Foreperiod 1.0 s Response window 0.6 s Lever press Trigger stimulus Lever release Correct trial Reward delivery Foreperiod 1.0 s Response window 0.6 s Lever press Trigger stimulus

Anderson, Charles H.

125

Multicomponent reaction engineering model for Fe-catalyzed Fischer–Tropsch synthesis in commercial scale slurry bubble column reactors  

Microsoft Academic Search

A multicomponent mathematical model is presented for a large-scale slurry bubble column reactor operating in the heterogeneous or churn-turbulent flow regime. The model accounts for both the Fischer–Tropsch reaction as well as the water gas shift reaction and the individual paraffin and olefin formation rates. It provides all the data necessary for reliable scale up, process optimization and prediction of

Gerard P. van der Laan; Antonie A. C. M. Beenackers; Rajamani Krishna

1999-01-01

126

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

127

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

128

Process of making blue and carburetted water gas  

Microsoft Academic Search

This patent describes an improvement in the method of manufacturing water gas by progressively air blasting a generator fuel bed to incandescence at vertically spaced levels in successive zones with the lowermost airblast level in the bottom zone of said fuel bed. The process continues by admitting steam to the fuel bed above the lowermost air-blast level, introducing fluxing material

1934-01-01

129

Evidence of nonelectrochemical shift reaction on a CO-tolerant high-entropy state Pt-Ru anode catalyst for reliable and efficient residential fuel cell systems.  

PubMed

A randomly mixed monodispersed nanosized Pt-Ru catalyst, an ultimate catalyst for CO oxidation reaction, was prepared by the rapid quenching method. The mechanism of CO oxidation reaction on the Pt-Ru anode catalyst was elucidated by investigating the relation between the rate of CO oxidation reaction and the current density. The rate of CO oxidation reaction increased with an increase in unoccupied sites kinetically formed by hydrogen oxidation reaction, and the rate was independent of anode potential. Results of extended X-ray absorption fine structure spectroscopy showed the combination of N(Pt-Ru)/(N(Pt-Ru) + N(Pt-Pt)) ? M(Ru)/(M(Pt) + M(Ru)) and N(Ru-Pt)/(N(Ru-Pt) + N(Ru-Ru)) ? M(Pt)/(M(Ru) + M(Pt)), where N(Pt-Ru)(N(Ru-Pt)), N(Pt-Pt)(N(Ru-Ru)), M(Pt), and M(Ru) are the coordination numbers from Pt(Ru) to Ru(Pt) and Pt (Ru) to Pt (Ru) and the molar ratios of Pt and Ru, respectively. This indicates that Pt and Ru were mixed with a completely random distribution. A high-entropy state of dispersion of Pt and Ru could be maintained by rapid quenching from a high temperature. It is concluded that a nonelectrochemical shift reaction on a randomly mixed Pt-Ru catalyst is important to enhance the efficiency of residential fuel cell systems under operation conditions. PMID:22876851

Takeguchi, Tatsuya; Yamanaka, Toshiro; Asakura, Kiyotaka; Muhamad, Ernee Noryana; Uosaki, Kohei; Ueda, Wataru

2012-09-01

130

Method of jointly manufacturing carburetted water gas and volatile hydrocarbon motor fuels  

Microsoft Academic Search

This patent describes a method method of jointly manufacturing carburetted water gas and volatile hydrocarbon motor fuel by air blasting a bed of carbonaceous fuel to incandescence. It involves passing the heated blast gases as produced over heat-absorbent material to heat the same, steam blasting the incandescent bed to produce water gas, passing the heated water gas over the said

1926-01-01

131

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

132

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

133

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

134

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. PMID:25550721

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

135

Thermal cyclization of phenylallenes that contain ortho-1,3-dioxolan-2-yl groups: new cascade reactions initiated by 1,5-hydride shifts of acetalic H atoms.  

PubMed

A series of 2-(1,3-dioxolan-2-yl)phenylallenes that contained a range of substituents (alkyl, aryl, phosphinyl, alkoxycarbonyl, sulfonyl) at the cumulenic C3 position were prepared by using a diverse range of synthetic strategies and converted into their respective 1-(2-hydroxy)-ethoxy-2-substituted naphthalenes by smooth thermal activation in toluene solution. Electron-withdrawing groups at the C3 position accelerated these tandem processes, which consisted of 1) an initial hydride-like [1,5]-H shift of the acetalic H atom onto the central cumulene carbon atom; 2) a subsequent 6?-electrocyclic ring-closure of the resulting reactive ortho-xylylenes; and 3) a final aromatization step with concomitant ring-opening of the 1,3-dioxolane fragment. If the 1,3-dioxolane ring of the starting allenes was replaced by a dimethoxymethyl group, the reactions led to mixtures of two disubstituted naphthalenes, which were formed by the migration of either the acetalic H atom or the methoxy group, with the latter migration occurring to a lesser extent. Two of the final 1,2-disubstituted naphthalenes were converted into their corresponding naphtho-fused dioxaphosphepine or dioxepinone through an intramolecular transesterification reaction. A DFT computational study accounted for the beneficial influence of the 1,3-dioxolane fragment on the carbon atom from which the H-shift took place and also of the electron-withdrawing substituents on the allene terminus. Remarkably, in the processes that contained a sulfonyl substituent, the conrotatory 6?-electrocyclization step was of lower activation energy than the alternative disrotatory mode. PMID:24123192

Alajarin, Mateo; Bonillo, Baltasar; Marin-Luna, Marta; Sanchez-Andrada, Pilar; Vidal, Angel

2013-11-18

136

reactions  

Microsoft Academic Search

Gene regulatory, signal transduction and metabolic networks are major areas of interest in the newly emerging field of systems biology. In living cells, stochastic dynamics play an important role; however, the kinetic parameters of biochemical reactions necessary for modelling these processes are often not accessible directly through experiments. The problem of estimating stochastic reaction constants from molecule count data measured,

S. Reinker; R. M. Altman; J. Timmer

137

On Factors Controlling AirWater Gas Exchange in a Large Tidal River  

E-print Network

On Factors Controlling Air­Water Gas Exchange in a Large Tidal River David T. Ho & Peter Schlosser and Estuarine Research Federation 2011 Abstract Air­water gas exchange is an important process in aquatic for determining gas exchange over a range of temporal and spatial scales in the ocean and these measurements have

Ho, David

138

AIR-WATER GAS EXCHANGE: MECHANISMS GOVERNING THE COMBINED EFFECTS OF WIND AND RAIN ON THE GAS TRANSFER  

E-print Network

AIR-WATER GAS EXCHANGE: MECHANISMS GOVERNING THE COMBINED EFFECTS OF WIND AND RAIN ON THE GAS, rain and iv #12;their effects on air-water gas and momentum exchanges. Funding for the Everglades, and for their continued support for the past two and a half decades. v #12;ABSTRACT Air-water gas exchange is an important

Luther, Douglas S.

139

Separation of intron 22 inversion type 1 and 2 of hemophilia A by modified inverse-shifting polymerase chain reaction and capillary gel electrophoresis.  

PubMed

An inverse-shifting polymerase chain reaction (IS-PCR) combined with short-end capillary gel electrophoresis (CGE) was developed for genotyping of intron 22 inversion Type 1 (Inv22-1) and Type 2 (Inv22-2) of hemophilia A (HA). Severe HA cases are affected by intron 22 inversion around 45-50%. Inv22-1 has higher frequency than Inv22-2. The aim of this study is to distinguish them by genotyping. In order to improve Inv22 genotyping efficiency, five primers were designed and applied to differentiate the wild type, Inv22-1, Inv22-2 and carrier. Three amplicons of 405, 457 and 512 bp were recognized for wild type; 333, 457 and 584 bp for Inv22-1; 385, 405 and 584 bp for Inv22-2. The Inv22-1 carrier has 5 amplicons including 333, 405, 457, 512, 584 bp and Inv22-2 carrier is differentiated by 385, 405, 457, 512 and 584 bp. The amplicons between Inv22-1 and Inv22-2 carriers are only different in 333 bp for Inv22-1 carrier and 385 bp for Inv22-2 carrier. Capillary gel electrophoresis (CGE) was used for separation within 5 min. The separation voltage was set at 8 kV (cathode at detector), and the temperature was kept at 25°C. The sieving matrix was 89 mM Tris, 89 mM boric acid, 2mM EDTA containing 0.4% (w/v) HPMC and 1 ?M of YO-PRO(®)-1 Iodide. Total of 50 HA patients (including 35 non-Inv22, 14 Inv22-1, and one Inv22-2 patients) and 7 HA carriers were diagnosed in the application. Seven random samples (5 patients and 2 carriers) were subjected to comparison and gave identical results of DNA sequencing and this modified IS-PCR. PMID:25159417

Pan, Tzu-Yu; Chiou, Shyh-Shin; Wang, Chun-Chi; Wu, Shou-Mei

2014-12-01

140

KINETIC UNDERSTANDING OF THE SYNGAS-TO-DME REACTION SYSTEM AND ITS IMPLICATIONS TO PROCESS AND ECONOMICS  

SciTech Connect

In a single-step synthesis gas-to-dimethyl ether process, synthesis gas (or syngas, a mixture of H{sub 2} and CO) is converted into dimethyl ether (DME) in a single reactor. The three reactions involved in this process, methanol synthesis, methanol dehydration and water gas shift, form an interesting reaction network. The interplay among these three reactions results in excellent syngas conversion or reactor productivity. A fundamental understanding of this interplay helps to explain many experimental and simulation observations, to identify optimal reaction conditions, and to provide guidelines for process development. The higher syngas conversion or reactor productivity in the syngas-to-DME reaction system, compared to that in the syngas-to-methanol reaction system, is referred to as chemical synergy. This synergy exhibits a strong dependence on the composition of the reactor feed. To demonstrate the extent of this dependence, simulations with adjusted activity for each reaction were performed to reveal the relative rate of each reaction. The results show that the water gas shift reaction is the most rapid, being practically controlled by the equilibrium. Both methanol synthesis and methanol dehydration reactions are kinetically controlled. The kinetics of the dehydration reactions is greater than that of the methanol synthesis reaction in the CO-rich regime. However, the rates of these two reactions come closer as the H{sub 2} concentration in the reactor feed increases. The role of the dehydration reaction is to remove the equilibrium barrier for the methanol synthesis reaction. The role of the water gas shift reaction is more complex; it helps the kinetics of methanol dehydration by keeping the water concentration low, which in turn enhances methanol synthesis. It also readjusts the H{sub 2}:CO ratio in the reactor as the reactions proceed. In the CO-rich regime, the water gas shift reaction supplements the limiting reactant, H{sub 2}, by reacting water with CO. This enhances both the kinetics and thermodynamic driving force of the methanol synthesis reaction. In the H{sub 2}-rich regime, water gas shift consumes the limiting reactant, CO, which harms both the kinetics and thermodynamics of methanol synthesis. An understanding of these complex roles of the methanol dehydration and water gas shift reactions and of their dependence on the syngas composition explains why the synergy is high in the CO-rich regime, but decreases with increasing H{sub 2} or CO{sub 2} content in the reactor feed. The methanol equivalent productivity of the syngas-to-DME reactor is also a strong function of the reactor feed. A mathematical approach was developed to understand this dependence. The approach divides a power law type of rate equation into two terms, the kinetic term (the rate of the forward reaction) and the thermodynamics or driving force term (1- approach to equilibrium). The equations for the best feed composition for each term were derived. The approach was developed for the single reaction system, and then extended to the syngas-to-DME reaction system. The equations provide insights into why and how the methanol synthesis in the syngasto-DME system depends on the other two reactions. They can also be used to calculate the best feed composition for a given conversion. The analysis shows that for typical commercial syngas conversion, the optimal H{sub 2}:CO ratio for the LPDME{trademark} reactor is around 1-to-1, in good agreement with the results from the simulation. While the 1-to-1 feed provides a good foundation for some process configurations, it does not match the composition of natural gas-derived syngas, which typically has a H{sub 2}:CO ratio of 2:1 or greater. The process would also produce one CO{sub 2} molecule for every DME product, both a materials utilization and an environmental problem. However, recycling CO{sub 2} to the syngas generation unit can solve all of these problems. Integration schemes with different syngas generation technologies (dry reforming, steam methane reforming and partial oxidation) were

Xiang-Dong Peng

2002-12-01

141

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

142

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

143

Scaling up a water-gas flow model with mass exchange A. Bourgeat1 M. Jurak2  

E-print Network

Scaling up a water-gas flow model with mass exchange A. Bourgeat1 M. Jurak2 1ICJ, UMR 5208-phase compressible flow with mass exchange Upscaling A. Bourgeat, M. Jurak () Water-gas flow CE-MoMaS, Calais Oct Oct 2006 A. Bourgeat, M. Jurak () Water-gas flow CE-MoMaS, Calais Oct 2006 1 / 31 #12;Outline Two

Rogina, Mladen

144

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

145

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

146

Environmental turbulent mixing controls on air-water gas exchange in marine and aquatic systems  

E-print Network

Environmental turbulent mixing controls on air-water gas exchange in marine and aquatic systems is not well known. Widely used models of gas exchange rates are based on empirical relationships linked turbulence that predicts gas exchange for a range of aquatic and marine processes. Findings indicate

Ho, David

147

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

148

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts. Technical progress report, March 1993--May 1993  

SciTech Connect

Study of preparation of MoS{sub 3}, decomposition to form MoS{sub 2}, and the Cs-containing reagents and techniques to achieve surface doping of the MoS{sub 2} with Cs was begun. Goal is to achieve a high surface area catalyst containing lower quantities of the Cs promoter in a highly dispersed state. Using high resolution electron spectroscopy for chemical analysis and solid state Extended Hueckel (EH) theory investigation and interpretation of electronic structure of MoS{sub 2} (hexagonal 2H form, 2 MoS{sub 2} molecules/unit cell) was carried out. The theoretical valence band of MoS{sub 2} was obtained by modification of density of states. Qualitative agreement theoretical and experimental MoS{sub 2} valence bands was obtained after parameterization of EH input ionization potentials H{sub ii} and Slater-type orbital (STO) double zeta coefficients c{sub i}. Theoretical energy dispersion curves 2-D and 3-D MoS{sub 2} also compared well with experimental energy dispersion curves. Highest occupied band of valence band is shown to consist of contributions not only from Mo 4d{sub z2} orbitals but also from Mo 4d{sub xy} and Mo 4d{sub x2-y2} orbitals. The theoretical systems 2-D MoS{sub 2} and 3-D MoS{sub 2}, containing zero for the former and an infinite number of Van der Waals gaps for the latter, exhibit direct and indirect gaps, respectively. Nature of 2H-MoS{sub 2} indirect gap is found to be directly linked to the interaction of crystal orbitals across Van der Waals gap between adjacent layers of MoS{sub 2} in the realistic 3-D model. Thus, the electronic properties and ability of adsorbing and activating hydrogen of very small and thin particles of MoS{sub 2} might be expected to be different from large bulk particles of MoS{sub 2}.

Klier, K.; Herman, R.G.; Richards-Babb, M.

1993-06-01

149

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

150

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

151

Stabilization of water\\/gas oil emulsions by desulfurizing cells of Gordonia alkanivorans RIPI90A  

Microsoft Academic Search

a biphasic system. The main goal of the current work was to study the behaviour of resting-cells of this strain in biphasic organic media. Resting-cells showed strong affinity for sulfurous organic substrates and were able to stabilize water\\/gas oil emulsions by attaching to the interface without decreasing the surface tension of their environment. This was consistent with the behaviour of

Ghasemali Mohebali; Andrew Ball; Ashk Kaytash; Behnam Rasekh

2007-01-01

152

Reaction pathways and catalyst requirements in the synthesis of isobutanol from CO and H{sub 2}  

SciTech Connect

The synthesis of isobutanol and methanol from CO/H{sub 2} on K-Cu-Mg-CeO{sub x} catalysts is inhibited by CO{sub 2}, one of the reaction products. Alcohol coupling reactions show that CO{sub 2} decreases the rates of both alcohol dehydrogenation and base-catalyzed chain growth condensation reactions. Basic site density and reactivity were determined using a {sup 12}CO{sub 2}/{sup 13}CO{sub 2} isotopic transient technique. Addition of K to Cu-Mg-CeO{sub x} increases both basic site density and strength, but influences weakly the rate of base-catalyzed alcohol coupling reactions. Cu enhances the rates of alcohol dehydrogenation, and Ce increases Cu dispersion and stabilizes high surface area MgO. The cross-coupling reactions of acetaldehyde and {sup 13}C-labeled methanol produce singly-labeled propionaldehyde, suggesting that it forms by the condensation of acetaldehyde and a reactive intermediate derived from methanol. Isobutyraldehyde, a precursor to isobutanol, forms via the condensation of propionaldehyde and reactive C{sub 1} species resulting from methanol. Temperature-programmed surface reaction studies of preadsorbed ethanol have shown that CO decreases the rate of base-catalyzed self-condensation reactions of ethanol to acetone, possibly due to the poisoning of basic and metal sites by the CO{sub 2} formed from CO by water-gas shift or Boudouard reactions.

Xu, M.; Stephens, B.L.; Gines, M.J.L.; Iglesia, E. [Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering

1996-12-31

153

The reaction of European lobster larvae (Homarus gammarus) to different quality food: effects of ontogenetic shifts and pre-feeding history.  

PubMed

Young larval stages of many organisms represent bottlenecks in the life-history of many species. The high mortality commonly observed in, for example, decapod larvae has often been linked to poor nutrition, with most studies focussing on food quantity. Here, we focus instead on the effects of quality and have investigated its effects on the nutritional condition of lobster larvae. We established a tri-trophic food chain consisting of the cryptophyte Rhodomonas salina, the calanoid copepod Acartia tonsa and larvae of the European lobster Homarus gammarus. In a set of experiments, we manipulated the C:N:P stoichiometry of the primary producers, and accordingly those of the primary consumer. In a first experiment, R. salina was grown under N- and P-limitation and the nutrient content of the algae was manipulated by addition of the limiting nutrient to create a food quality gradient. In a second experiment, the effect on lobster larvae of long- and short-term exposure to food of varying quality during ontogenetic development was investigated. The condition of the lobster larvae was negatively affected even by subtle N- and P-nutrient limitations of the algae. Furthermore, younger lobster larvae were more vulnerable to nutrient limitation than older ones, suggesting an ontogenetic shift in the capacity of lobster larvae to cope with low quality food. The results presented here might have substantial consequences for the survival of lobster larvae in the field, as, in the light of future climate change and re-oligotrophication of the North Sea, lobster larvae might face marked changes in temperature and nutrient conditions, thus significantly altering their condition and growth. PMID:24072442

Schoo, Katherina L; Aberle, Nicole; Malzahn, Arne M; Schmalenbach, Isabel; Boersma, Maarten

2014-02-01

154

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

Microsoft Academic Search

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 gamma-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

Donghui Li; Yingxiang Wu; Keren Wang; Xingfu Zhong

2007-01-01

155

Shifting sugars and shifting paradigms.  

PubMed

No organism lives in a constant environment. Based on classical studies in molecular biology, many have viewed microbes as following strict rules for shifting their metabolic activities when prevailing conditions change. For example, students learn that the bacterium Escherichia coli makes proteins for digesting lactose only when lactose is available and glucose, a better sugar, is not. However, recent studies, including three PLOS Biology papers examining sugar utilization in the budding yeast Saccharomyces cerevisiae, show that considerable heterogeneity in response to complex environments exists within and between populations. These results join similar recent results in other organisms that suggest that microbial populations anticipate predictable environmental changes and hedge their bets against unpredictable ones. The classical view therefore represents but one special case in a range of evolutionary adaptations to environmental changes that all organisms face. PMID:25688600

Siegal, Mark L

2015-02-01

156

Shifting Sugars and Shifting Paradigms  

PubMed Central

No organism lives in a constant environment. Based on classical studies in molecular biology, many have viewed microbes as following strict rules for shifting their metabolic activities when prevailing conditions change. For example, students learn that the bacterium Escherichia coli makes proteins for digesting lactose only when lactose is available and glucose, a better sugar, is not. However, recent studies, including three PLOS Biology papers examining sugar utilization in the budding yeast Saccharomyces cerevisiae, show that considerable heterogeneity in response to complex environments exists within and between populations. These results join similar recent results in other organisms that suggest that microbial populations anticipate predictable environmental changes and hedge their bets against unpredictable ones. The classical view therefore represents but one special case in a range of evolutionary adaptations to environmental changes that all organisms face. PMID:25688600

Siegal, Mark L.

2015-01-01

157

Isotope Shifts  

NASA Astrophysics Data System (ADS)

A three parameter formula (3P) for isotope shifts r^2(n)= n C +n)n-1)/2A+[n/2]B is related to he staggering parameter G= 2 [r^2(n+1)-r^2(n)]/[r^(n+2)-r^2(n)] If A+B=0 then G=1 (no staggering). If A=0 there is no n dependence to the staggering.One can get G to almost be plus or minus infinity for certain n,but this does not necessarily mean that there are major changes in the nuclear structure. We consider Potassium and Argon isotopes. We also consider quadrupole and monopole core polarization with a delta interaction. We vary the oscillator length parameter of the valence particle but keep the core values fixed. We find for both modes the amount of core polarization decreases as we increase the radius of the valence particle relative to that of the core (for small deviations from the case where the core and valence length parameters are the same).

Zamick, Larry

2010-11-01

158

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

159

Integrated reformer and shift reactor  

DOEpatents

A hydrocarbon fuel reformer for producing diatomic hydrogen gas is disclosed. The reformer includes a first reaction vessel, a shift reactor vessel annularly disposed about the first reaction vessel, including a first shift reactor zone, and a first helical tube disposed within the first shift reactor zone having an inlet end communicating with a water supply source. The water supply source is preferably adapted to supply liquid-phase water to the first helical tube at flow conditions sufficient to ensure discharge of liquid-phase and steam-phase water from an outlet end of the first helical tube. The reformer may further include a first catalyst bed disposed in the first shift reactor zone, having a low-temperature shift catalyst in contact with the first helical tube. The catalyst bed includes a plurality of coil sections disposed in coaxial relation to other coil sections and to the central longitudinal axis of the reformer, each coil section extending between the first and second ends, and each coil section being in direct fluid communication with at least one other coil section.

Bentley, Jeffrey M.; Clawson, Lawrence G.; Mitchell, William L.; Dorson, Matthew H.

2006-06-27

160

Arithmetic shift operators  

Microsoft Academic Search

\\u000a Verilog-1995 provides two simple shift operators: The >> token represents a bitwise shift-right operation. The << token represents\\u000a a bitwise shift-left operation. Both shift operators will shift the bits in the first operand the number of times indicated\\u000a by the value in the second operand. The bits which are vacated by the shift are always zero filled.

Stuart Sutherland

161

The primary donor cation P + rad in photosynthetic reaction centers of site-directed mutants of Rhodobacter sphaeroides: g-tensor shifts revealed by high-field EPR at 360 GHz/12.8 T  

NASA Astrophysics Data System (ADS)

The frozen solution electron paramagnetic resonance spectrum of the primary donor cation P + rad in reaction centers of site-directed mutants of Rhodobacter ( Rb.) sphaeroides has been obtained at a microwave frequency ?=360 GHz and a magnetic field B0=12.8 T. Due to the high Zeeman resolution of the powder pattern, all three principal components of the rhombic g-tensors at T=160 K could be determined with high accuracy. We compare spectra of the site-directed mutants, in which the axial ligand histidine M202 of the primary donor is replaced by glutamic acid (HE(M202)) or leucine (HL(M202)), with those of the strain R26, whose primary donor is similar to that of the wild type and only lacks the carotenoid. For HE(M202), this is the first determination of its g-tensor with the principal components gxx=2.00335(3), gyy=2.00236(2) and gzz=2.00191(2). While in R26 the primary donor is a bacteriochlorophyll a dimer, the HL(M202) and HE(M202) mutants have previously been shown to be bacteriochlorophyll:bacteriopheophytin heterodimers. Their g-tensor anisotropy ? g= gxx- gzz shows significant variations in opposite directions when compared with R26, with an increased anisotropy for HE(M202) and a decreased one for HL(M202). Calculations employing Density Functional Theory suggest that the observed shifts originate in different torsional angles of the acetyl group attached to the spin-carrying bacteriochlorophyll half L of the dimer.

Fuchs, Martin R.; Schnegg, Alexander; Plato, Martin; Schulz, Claudia; Müh, Frank; Lubitz, Wolfgang; Möbius, Klaus

2003-11-01

162

Air-water gas exchange of organochlorine compounds in Lake Baikal, Russia  

SciTech Connect

Air and surface water samples were collected at Lake Baikal, Russia, during June 1991 to determine concentrations of organochlorine pesticides and polychlorinated biphenyl (PCB) congeners. These data were combined with Henry`s law constants to estimate the gas flux rate across the air-water interface of each compound class. Air samples were collected at Lake Baikal and from nearby Irkutsk. Water samples were collected from three mid-lake stations and at the mouth of two major tributaries. Average air concentrations of chlorinated bornanes (14 pg m{sup -3}), chlordanes (4.9 pg m{sup -3}), and hexachlorobenzene (HCB) (194 pg m{sup -3}) were similar to global backgound of Arctic levels. However, air concentrations of hexachlorocyclohexanes (HCHs), DDTs, and PCBs were closer to those observed in the Great Lakes region. Significantly higher levels of these three compound classes in air over Irkutsk suggests that regional atmospheric transport and deposition may be an important source of these persistent compounds to Lake Baikal. Air-water gas exchange calculations resulted in net depositional flux values for {alpha}-HCH, {gamma}-HCH, DDTs, and chlorinated bornanes at 112, 23, 3.6, and 2.4 ng m{sup -2} d{sup -1}, respectively. The total net flux of 22 PCB congeners, chlordanes, and HCB was from water to air (volatilization) at 47, 1.8, and 32 ng m{sup -2} d{sup -1}, respectively. 50 refs., 7 figs., 5 tabs.

McConnell, L.L. [USDA, Beltsville, MD (United States)] [USDA, Beltsville, MD (United States); Kucklick, J.R. [National Marine Fisheries Service, Charleston, SC (United States)] [National Marine Fisheries Service, Charleston, SC (United States); Bidleman, T.F. [Univ. of South Carolina, Columbia, SC (United States)] [Univ. of South Carolina, Columbia, SC (United States); Ivanov, G.P. [Limnological Inst., Irkutsk (Russian Federation)] [Limnological Inst., Irkutsk (Russian Federation); Chernyak, S.M. [Inst. of Fisheries, Moscow (Russian Federation)] [Inst. of Fisheries, Moscow (Russian Federation)

1996-10-01

163

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

164

Gear shift control mechanism  

SciTech Connect

A gear shift control mechanism is described comprising: multiple shift rods directed substantially parallel to one another, each rod carrying a shift fork for axial movement; a shift lever supported for pivotal movement about a first axis directed parallel to the axes of the shift rods and for pivotal movement about a second axis directed substantially perpendicular to the axes of the shift rods. The lever is moveable about the first axis and the second axis into engagement with a selected shift fork; interlock means located on each lateral side of the shift lever and mounted for pivotal movement about the first axis for blocking engagement with the shift forks; detent means for holding the shift lever in multiple predetermined angular positions about the second axis; and spring means located on a lateral side of the shift lever and mounted for pivotal movement about the first axis into interference contact with the shift forks for producing a force tending to resiliently bias the shift lever out of engagement with the selected shift fork.

Janson, D.A.

1987-03-10

165

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

166

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

167

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

168

Improved calculation of relativistic shift and isotope shift in Mg I  

E-print Network

We present an ab initio method of calculation of isotope shift and relativistic shift in atoms with a few valence electrons. It is based on an energy calculation involving combination of the configuration interaction method and many-body perturbation theory. This work is motivated by analyses of quasar absorption spectra that suggest that the fine structure constant, alpha, was smaller at an early epoch. Relativistic shifts are needed to measure this variation of alpha, while isotope shifts are needed to resolve systematic effects in this study. The isotope shifts can also be used to measure isotopic abundances in gas clouds in the early universe, which are needed to study nuclear reactions in stars and supernovae and test models of chemical evolution. This paper shows that isotope shift in magnesium can be calculated to very high precision using our new method.

Berengut, J C; Kozlov, M G

2005-01-01

169

Improved calculation of relativistic shift and isotope shift in Mg I  

E-print Network

We present an ab initio method of calculation of isotope shift and relativistic shift in atoms with a few valence electrons. It is based on an energy calculation involving combination of the configuration interaction method and many-body perturbation theory. This work is motivated by analyses of quasar absorption spectra that suggest that the fine structure constant, alpha, was smaller at an early epoch. Relativistic shifts are needed to measure this variation of alpha, while isotope shifts are needed to resolve systematic effects in this study. The isotope shifts can also be used to measure isotopic abundances in gas clouds in the early universe, which are needed to study nuclear reactions in stars and supernovae and test models of chemical evolution. This paper shows that isotope shift in magnesium can be calculated to very high precision using our new method.

J. C. Berengut; V. V. Flambaum; M. G. Kozlov

2005-07-08

170

Hot compressed water—a suitable and sustainable solvent and reaction medium?  

NASA Astrophysics Data System (ADS)

Hot compressed water in the sub- and supercritical state exhibits exciting physical and chemical properties, which can be varied continuously from gas-like to liquid-like behaviour. Correspondingly, the solvent properties can change from non-polar behaviour as present, for example, in organic solvents to highly ionic characteristics like in salt melts. This opens up several promising opportunities for separation processes and chemical reactions. Under supercritical conditions, substantial amounts of gases and organic substances can homogeneously be mixed with water, which then can be separated by adjusting the subcritical conditions by forming additional phases. This can beneficially be combined with chemical reactions occurring in the homogeneous state leading to integrated processes, which are more effective and competitive. Three approaches to the technical application of hot compressed water are presented to show and discuss the technology, potential, technical hurdles and future research demand in this area of research and development. In supercritical water oxidation (SCWO) water is used as a medium in which organic pollutants are completely degraded under the addition of oxygen, which is completely miscible with water under the process conditions of up to 650 °C and pressures around 25 MPa. Thus, high space-time yields in compact reactor designs can be realized. Hydrogen is produced from biomass by hydrothermal gasification. Here, in an excess of water, the reaction at temperatures up to 700 °C and pressures around 30 MPa directly leads to valuable hydrogen instead of synthetic gas, as in conventional gasification processes, or methane at subcritical conditions in water. After reaction, pressurized hydrogen is obtained and can easily be enriched due to the different partition coefficients of hydrogen and carbon dioxide between the aqueous and gas phase. Even homogeneous catalysis is possible in supercritical water. This has been demonstrated with the cobalt-catalysed cyclotrimerization of acetylenes to form benzene derivatives or hydroformylation to produce aldehydes from olefins. There, only the addition of CO is necessary, the H2 required being formed by the equilibrium of the water-gas-shift reaction. After a homogeneous reaction in the supercritical state, the reaction mixture can be separated at subcritical conditions. In support of the chemical and technical developments and to principally understand the experimental findings fundamental aspects have to be investigated as well. Intensive studies have been devoted to chemical kinetics including the modelling with elementary reaction steps, e.g. to separate ionic and radical reaction pathways. Depending on the reaction conditions, ionic or radical reaction pathways can be favoured or suppressed, allowing for control selectivity. Furthermore, corrosion of relevant reactor materials has been investigated.

Dinjus, E.; Kruse, A.

2004-04-01

171

Making Shifts toward Proficiency  

ERIC Educational Resources Information Center

The Leading for Mathematical Proficiency (LMP) Framework (Bay-Williams et al.) has three components: (1) The Standards for Mathematical Practice; (2) Shifts in classroom practice; and (3) Teaching skills. This article briefly describes each component of the LMP framework and then focuses more in depth on the second component, the shifts in…

McGatha, Maggie B.; Bay-Williams, Jennifer M.

2013-01-01

172

Shift work, cancer and \\  

Microsoft Academic Search

This commentary intends to instigate discussions about upcoming epidemiologic research, and its interpretation, into putative links between shift work, involving circadian disruption or chronodisruption [CD], and the development of internal cancers. In 2007, the International Agency for Research on Cancer (IARC) convened an expert group to examine the carcinogenicity of shift work, inter alia characterized by light exposures at unusual

Thomas C Erren

2010-01-01

173

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

174

Technology Development for Iron and Cobalt Fischer-Tropsch Catalysts Quarterly Report  

E-print Network

shifts of the edge energy from 7123 eV (Fe ) to 7112 eV (Fe ) along3+ 0 with changes in the near FTS and water-gas shift reaction rates, decreased the selectivity to methane and increased that the addition of CO inhibited2 2 the formation of CO via water-gas shift reactions but did not affect the FTS

Kentucky, University of

175

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

176

Differences between left- and right-hand reaction time rhythms: indications of shifts in strategies of human brain activity 1 This work is part of the Ph.D. thesis of Mr. Y. Shub. 1  

Microsoft Academic Search

Reaction time (RT) measurements serve as quantitative indices for pilots' cognitive processes of the brain. To examine if laterality exists in the brain hemispheres we measured, by the use of a Pilot Evaluation System (PES), right- and left-hand performance rhythms as indicative of RT to audible and visual stimuli. The tests included sets of simple tasks and complex ones to

Yosi Shub; Israel E Ashkenazi; Alain Reinberg

1997-01-01

177

Gasification of biomass in water\\/gas-stabilized plasma for syngas production  

Microsoft Academic Search

The experimental reactor PLASGAS for plasma pyrolysis and vitrification equipped with the hybrid gas-water stabilized torch\\u000a was used in the experiments. The plasma torch is characterized by low density, high temperature plasma with very low mass\\u000a flow rates and high enthalpy. High plasma enthalpy is advantageous for adjustment of higher reaction temperatures with high\\u000a energy efficiency. Gasification of biomass was

M. Hrabovsky; M. Konrad; V. Kopecky; M. Hlina; T. Kavka; G. van Oost; E. Beeckman; B. Defoort

2006-01-01

178

Evaluating reaction pathways of hydrothermal abiotic organic synthesis at elevated temperatures and pressures using carbon isotopes  

NASA Astrophysics Data System (ADS)

Experiments were performed to better understand the role of environmental factors on reaction pathways and corresponding carbon isotope fractionations during abiotic hydrothermal synthesis of organic compounds using piston cylinder apparatus at 750 °C and 5.5 kbars. Chemical compositions of experimental products and corresponding carbon isotopic values were obtained by a Pyrolysis-GC-MS-IRMS system. Alkanes (methane and ethane), straight-chain saturated alcohols (ethanol and n-butanol) and monocarboxylic acids (formic and acetic acids) were generated with ethanol being the only organic compound with higher ?13C than CO2. CO was not detected in experimental products owing to the favorable water-gas shift reaction under high water pressure conditions. The pattern of ?13C values of CO2, carboxylic acids and alkanes are consistent with their equilibrium isotope relationships: CO2 > carboxylic acids > alkanes, but the magnitude of the fractionation among them is higher than predicted isotope equilibrium values. In particular, the isotopic fractionation between CO2 and CH4 remained constant at ?31‰, indicating a kinetic effect during CO2 reduction processes. No "isotope reversal" of ?13C values for alkanes or carboxylic acids was observed, which indicates a different reaction pathway than what is typically observed during Fischer-Tropsch synthesis under gas phase conditions. Under constraints imposed in experiments, the anomalous 13C isotope enrichment in ethanol suggests that hydroxymethylene is the organic intermediate, and that the generation of other organic compounds enriched in 12C were facilitated by subsequent Rayleigh fractionation of hydroxymethylene reacting with H2 and/or H2O. Carbon isotope fractionation data obtained in this study are instrumental in assessing the controlling factors on abiotic formation of organic compounds in hydrothermal systems. Knowledge on how environmental conditions affect reaction pathways of abiotic synthesis of organic compounds is critical for understanding deep subsurface ecosystems and the origin of organic compounds on Mars and other planets.

Fu, Qi; Socki, Richard A.; Niles, Paul B.

2015-04-01

179

Calculating Expectation Shift  

E-print Network

This paper concerns the problem of calculating expectation shift due to variability which tends to occur whenever the function of a random variable is nonlinear and especially tends to occur in the neighborhood of a local ...

Frey, Daniel

2011-01-01

180

Isotope Shift in Magnesium  

Microsoft Academic Search

The previous investigations concerning the isotope shift of magnesium have been repeated and extended by means of an improved atomic beam source and a Perot-Fabry interferometer. The values of Meissner have been checked to within experimental error in most cases. In addition, several new lines have been resolved, and their isotope shifts determined. The 31P-m1D series has been resolved from

L. G. Mundie; K. W. Meissner

1944-01-01

181

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

182

Eluding catastrophic shifts.  

PubMed

Transitions between regimes with radically different properties are ubiquitous in nature. Such transitions can occur either smoothly or in an abrupt and catastrophic fashion. Important examples of the latter can be found in ecology, climate sciences, and economics, to name a few, where regime shifts have catastrophic consequences that are mostly irreversible (e.g., desertification, coral reef collapses, and market crashes). Predicting and preventing these abrupt transitions remains a challenging and important task. Usually, simple deterministic equations are used to model and rationalize these complex situations. However, stochastic effects might have a profound effect. Here we use 1D and 2D spatially explicit models to show that intrinsic (demographic) stochasticity can alter deterministic predictions dramatically, especially in the presence of other realistic features such as limited mobility or spatial heterogeneity. In particular, these ingredients can alter the possibility of catastrophic shifts by giving rise to much smoother and easily reversible continuous ones. The ideas presented here can help further understand catastrophic shifts and contribute to the discussion about the possibility of preventing such shifts to minimize their disruptive ecological, economic, and societal consequences. PMID:25825772

Villa Martín, Paula; Bonachela, Juan A; Levin, Simon A; Muñoz, Miguel A

2015-04-14

183

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.

184

Recovery from work shifts: how long does it take?  

PubMed

Although regulations on work hours usually include a minimum weekly rest period, there is little empirical evidence concerning recovery from work. Shift-working nurses (N = 61) used a handheld computer for 28 days to complete self-ratings, cognitive-performance tasks, and a sleep diary. Many measures were worse on rest days that followed a night shift rather than a day shift and tended to be worse on first rest days compared with subsequent rest days. Alertness was lowest on the 1st rest day following a night shift. Social satisfaction was better on workdays that were preceded by 2 rather than 1 rest day. Reaction time decreased over consecutive night shifts and tended to increase over rest days following night shifts. The results are interpreted as being consistent with the combined adaptive costs of fatigue and adjustment to and from a nocturnal routine. The practical implications for scheduling rest days are considered. PMID:7706194

Totterdell, P; Spelten, E; Smith, L; Barton, J; Folkard, S

1995-02-01

185

Shifts that divide population  

NASA Astrophysics Data System (ADS)

How does a population of organisms in an ecosystem or of people in a society respond to rapid shifts in the environment? Answers to this question are critical to our ability to anticipate and cope with a changing ecohydrological system. We have developed a generic model of adaptation mechanisms, based on replicator dynamics, in which we derive a simple and insightful threshold condition that separates two important types of responses: 'cohesive transition' in which the whole population changes gradually together, and 'population-dividing transition' in which the population splits into two groups with one eventually dominating the other. The threshold depends on the magnitude of the shift and the shape of the fitness landscape. Division in populations can fundamentally alter the functioning of and induce subsequent feedbacks within the system; knowing the condition that gives rise to such division is thus fundamentally important.

Muneepeerakul, Rachata; Qubbaj, Murad; Aggarwal, Rimjhim; Anderies, John M.; Janssen, Marco

2014-05-01

186

VOLUME 85, NUMBER 9 P H Y S I C A L R E V I E W L E T T E R S 28 AUGUST 2000 Turbulence and Wave Breaking Effects on Air-Water Gas Exchange  

E-print Network

-made systems. For instance, in waste water treatment where bioremediation is used in large man-made water Breaking Effects on Air-Water Gas Exchange Evelyn J. Boettcher,1 Jay Fineberg,1,2 and Daniel P. Lathrop1 1 gravity waves on air-water gas exchange in standing waves. We identify two regimes that govern aeration

Fineberg, Jay

187

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

188

Strong shift equivalence theory and the shift equivalence problem  

Microsoft Academic Search

This paper discusses strong shift equivalence and counterexamples to the long standing Shift Equivalence Problem in symbolic dynamics. We also discuss how strong shift equivalence theory is closely related to areas of mathematics outside dynamics such as algebraic K-theory, cyclic homology, and topological quantum eld theory.

J. B. WAGONER

1999-01-01

189

Simplified power shift transmission  

SciTech Connect

A multi-speed transmission is described for transferring power between a first shaft and a second shaft, the transmission comprising: a compound planetary assembly including a sun gear, a ring gear concentric with the sun gear, a reaction gear concentric with the ring gear, a planetary gear carrier rotatably supporting first and second sets of planet gears, the first planet gear set intermeshing with the ring gear. The sun gear and the second planet gear set intermesh with the first planet gear set and the reaction gear, means for selectively coupling the first shaft with the sun gear and the reaction gear, and means for selectively preventing rotation of the ring gear, and reaction gear and the planetary carrier; a simple planetary assembly comprising a sun gear component concentric with the sun gear of the compound planetary assembly, a ring gear component concentric with both of the sun gears, and a planetary gear carrier component rotatably supporting a set of planet gears, the planet gear set meshing with the sun gear and the ring gear of the simple planetary.

Michael, R.A.

1987-04-21

190

Shifting Times Tables  

NSDL National Science Digital Library

This activity provides students with an opportunity to recognize arithmetic sequences and at the same time reinforces identifying multiples. The interactivity displays five numbers and the student must discover the times table pattern and the numerical shift. On Levels 1 and 2, the first five numbers in the sequence are given and on Levels 3 and 4, the numbers given could be any five numbers in the sequence. The Teachers' Notes page offers rationale, suggestions for implementation, discussion questions, ideas for extension and support.

191

Isotope Shift in Magnesium  

Microsoft Academic Search

A theoretical investigation is made to see whether nuclear motion alone can account for observed fine structure in magnesium, especially for the lines 31S0-31P1, 31S0-33P1, 31P1-31D2, 33P-33D, and the limit of the series 31P1-n1D2. Both by calculation with explicit radial functions and by the choice of theoretical parameters to fit observed shifts, it is shown that the values of the

John P. Vinti

1939-01-01

192

[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

193

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

194

Transmission shift control assembly  

SciTech Connect

This patent describes a transmission shift control assembly mounted on a steering column having a longitudinal axis comprising: bracket means secured to the steering column; transmission shift cable means having a portion secured to the bracket means and a portion linearly movable relative to the secured portion; mounting means on the bracket cable drive arm means having an axis and being rotatably mounted on the rotary axis on the mounting means oblique to the longitudinal axis and including a cable connecting portion secured to the movable portion of the cable means and lever mounting means adjacent the mounting means; operator control means including lever means, pin means for pivotally mounting the lever means on the lever mounting means on an axis substantially perpendicular to the rotary axis and positioning arm means formed on the lever means and extending from the pin means; and detent gate means disposed on the bracket means in position to abut the positioning arm means for limiting the extent of pivotal movement of the lever means.

Dzioba, D.L.

1989-04-18

195

Transitioning to 12-hour shifts  

Microsoft Academic Search

In 1989, Yankee Rowe nuclear power station successfully implemented a 12-hour shift schedule for all shiftworkers (control room personnel, auxiliary operators, and radiation protection shift technicians) with many positive effects on morale, motivation, and performance. The transition from an 8-hour to a 12-hour shift schedule was initiated, organized, and promoted by the shiftworkers themselves after they had identified numerous inadequacies

P. S. Suter; S. M. Cervassi

1993-01-01

196

Calculation of relativistic and isotope shifts in Mg I  

SciTech Connect

We present an ab initio method of calculation of the isotope and relativistic shifts in atoms with a few valence electrons. It is based on an energy calculation involving the combination of the configuration-interaction method and many-body perturbation theory. This work is motivated by analyses of quasar absorption spectra that suggest that the fine-structure constant {alpha} was smaller at an early epoch. Relativistic shifts are needed to measure this variation of {alpha}, while isotope shifts are needed to resolve systematic effects in this study. The isotope shifts can also be used to measure isotopic abundances in gas clouds in the early universe, which are needed to study nuclear reactions in stars and supernovae and test models of chemical evolution. This paper shows that the isotope shift in magnesium can be calculated to very high precision using our method.

Berengut, J.C.; Flambaum, V.V.; Kozlov, M.G. [School of Physics, University of New South Wales, Sydney 2052 (Australia); Petersburg Nuclear Physics Institute, Gatchina, 188300 (Russian Federation)

2005-10-15

197

Energy shifted level densities in the rare earth region  

E-print Network

The density of accessible levels at low spin in the (3-He,alpha gamma) reaction has been extracted for the 161,162-Dy and 171,172-Yb nuclei. The energy shift between the level densities of the even-odd and even-even isotopes is measured as a function of excitation energy. The results are compared with predictions from various semi-empirical models. The energy shift procedure works well for excitation energies between 3.5 and 7 MeV in the even-even nucleus, provided that a proper level density function is used. The experimental energy shift is close to the pairing gap parameter Delta.

M. Guttormsen; M. Hjorth-Jensen; E. Melby; J. Rekstad; A. Schiller; S. Siem

2000-01-27

198

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

199

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

200

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

201

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

202

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

203

Perceived shift. South Africa.  

PubMed

This speech challenges the global community to commit to reducing HIV/AIDS in Durban, South Africa, where 1 in 4 adults is infected with the virus. A commitment of resources and energy would show good faith in fairness, generate unstoppable momentum in the prevention and control of HIV/AIDS, provide a genuine renewal in the war against this disease, and set an example for other low income, resource poor, and HIV-epidemic countries. In 2000, the 13th Annual International AIDS Conference will be suitably located in Durban in a region with the highest rates of HIV/AIDS. The 1998 UNAIDS report states that 70% of those infected with HIV (21 million) are in Africa. A shift in program effort and political will would mark a turning point in the war against AIDS. There are four "P's" behind prevention and control of the HIV/AIDS epidemic: politicians, people, private sector, and programs. It is suggested that next year's conference should include political will that will become unshakable. Budgets need to be realistic. People should have unquestionable tolerance, acceptance, and generosity. Community organizations should be strengthened. Discrimination should be stopped. Science needs to be advanced. The private sector's involvement should be meaningful and supportive. Programs should be appropriate, affordable, and accessible. Many gaps need to be bridged and many people need to enlist their aid. The author urges that conference participants remember the afflicted poor and plan for a rebirth and renewal of hope. PMID:12294629

Coovadia, H

1998-01-01

204

General rules for nuclear reactions Nuclear reactions | the transformations between di erent atomic nuclei | need to  

E-print Network

is longer than the life time of the Universe! The inverse decay will result in a shift of the nuclear chargeGeneral rules for nuclear reactions Nuclear reactions | the transformations between di erent atomic of a certain kind need to be the same on both side of the equation". However, in nuclear reactions

Boettcher, Markus

205

Technology Development for Iron and Cobalt Fischer-Tropsch Catalysts Quarterly Report  

E-print Network

water gas shift reaction rates and CO2 2 #12;3 selectivity during Fischer-Tropsch synthesis on Fe Government or any agency thereof. #12;2 Abstract CAER The effects of copper on Fischer-Tropsch activity, selectivity and water-gas shift activity were studied over a wide range of syngas conversion. Three catalyst

Kentucky, University of

206

Astronomy Ranking Task: Doppler Shift  

E-print Network

Astronomy Ranking Task: Doppler Shift Exercise #4 Description: An important line in the absorption D 657 nm E 646 nm A. Ranking instructions: Rank the size of the Doppler shift (from largest to smallest) observed tonight for the light from each star (A ­ E). Ranking Order: Largest 1 ____ 2 ____ 3

Farritor, Shane

207

Astronomy Ranking Task: Doppler Shift  

E-print Network

, the Doppler shift of the light from the stars would all be the same. _____ (indicate with a check markAstronomy Ranking Task: Doppler Shift Exercise #3 Description: The first spectrum shown below (blue light) and that the right end of each spectrum corresponds with longer wavelengths (red light

Farritor, Shane

208

Allergic reactions  

MedlinePLUS

... more often in people who have a family history of allergies . Substances that don't bother most people ( ... reaction is getting worse. The person has a history of severe allergic reactions (check for a medical ID ...

209

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.

Minerva Deland School

2011-10-03

210

Special Reactions  

NSDL National Science Digital Library

The basics of chemical reactions were covered in the first chemistry book, including how to write and balance chemical equations that represent those reactions. There is also a quick review of chemical reactions in Chapter 1 of this book. We're going to d

William C. Robertson, Ph.D.

2010-03-01

211

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

212

Nonlocality in deuteron stripping reactions.  

PubMed

We propose a new method for the analysis of deuteron stripping reactions, A(d,p)B, in which the nonlocality of nucleon-nucleus interactions and three-body degrees of freedom are accounted for in a consistent way. The model deals with equivalent local nucleon potentials taken at an energy shifted by ?40??MeV from the "E(d)/2" value frequently used in the analysis of experimental data, where E(d) is the incident deuteron energy. The "E(d)/2" rule lies at the heart of all three-body analyses of (d, p) reactions performed so far with the aim of obtaining nuclear structure properties such as spectroscopic factors and asymptotic normalization coefficients that are crucial for our understanding of nuclear shell evolution in neutron- and proton-rich regions of the nuclear periodic table and for predicting the cross sections of stellar reactions. The large predicted shift arises from the large relative kinetic energy of the neutron and proton in the incident deuteron in those components of the n+p+A wave function that dominate the (d, p) reaction amplitude. The large shift reduces the effective d-A potentials and leads to a change in predicted (d, p) cross sections, thus affecting the interpretation of these reactions in terms of nuclear structure. PMID:25166525

Timofeyuk, N K; Johnson, R C

2013-03-15

213

Rate constant for OH,,2 ... reaction  

E-print Network

Rate constant for OH,,2 ...+O,,3 P...\\H,,2 S...+O2,,3 g - ... reaction on an improved ab initio and the rate constant for the title reaction was obtained using a J-shifting method. The calculated rate lower rate at temperature range below 30 K, offering a possible explanation for the "interstellar oxygen

Honvault, Pascal

214

Marine biological shifts and climate.  

PubMed

Phenological, biogeographic and community shifts are among the reported responses of marine ecosystems and their species to climate change. However, despite both the profound consequences for ecosystem functioning and services, our understanding of the root causes underlying these biological changes remains rudimentary. Here, we show that a significant proportion of the responses of species and communities to climate change are deterministic at some emergent spatio-temporal scales, enabling testable predictions and more accurate projections of future changes. We propose a theory based on the concept of the ecological niche to connect phenological, biogeographic and long-term community shifts. The theory explains approximately 70% of the phenological and biogeographic shifts of a key zooplankton Calanus finmarchicus in the North Atlantic and approximately 56% of the long-term shifts in copepods observed in the North Sea during the period 1958-2009. PMID:24718760

Beaugrand, Grégory; Goberville, Eric; Luczak, Christophe; Kirby, Richard R

2014-05-22

215

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

216

Visual motion shifts saccade targets.  

PubMed

Saccades are made thousands of times a day and are the principal means of localizing objects in our environment. However, the saccade system faces the challenge of accurately localizing objects as they are constantly moving relative to the eye and head. Any delays in processing could cause errors in saccadic localization. To compensate for these delays, the saccade system might use one or more sources of information to predict future target locations, including changes in position of the object over time, or its motion. Another possibility is that motion influences the represented position of the object for saccadic targeting, without requiring an actual change in target position. We tested whether the saccade system can use motion-induced position shifts to update the represented spatial location of a saccade target, by using static drifting Gabor patches with either a soft or a hard aperture as saccade targets. In both conditions, the aperture always remained at a fixed retinal location. The soft aperture Gabor patch resulted in an illusory position shift, whereas the hard aperture stimulus maintained the motion signals but resulted in a smaller illusory position shift. Thus, motion energy and target location were equated, but a position shift was generated in only one condition. We measured saccadic localization of these targets and found that saccades were indeed shifted, but only with a soft-aperture Gabor patch. Our results suggest that motion shifts the programmed locations of saccade targets, and this remapped location guides saccadic localization. PMID:24888754

Kosovicheva, Anna A; Wolfe, Benjamin A; Whitney, David

2014-08-01

217

Enzyme catalysed tandem reactions.  

PubMed

To transfer to the laboratory, the excellent efficiency shown by enzymes in Nature, biocatalysis, had to mimic several synthetic strategies used by the living organisms. Biosynthetic pathways are examples of tandem catalysis and may be assimilated in the biocatalysis field for the use of isolated multi-enzyme systems in the homogeneous phase. The concurrent action of several enzymes that work sequentially presents extraordinary advantages from the synthetic point of view, since it permits a reversible process to become irreversible, to shift the equilibrium reaction in such a way that enantiopure compounds can be obtained from prochiral or racemic substrates, reduce or eliminate problems due to product inhibition or prevent the shortage of substrates by dilution or degradation in the bulk media, etc. In this review we want to illustrate the developments of recent studies involving in vitro multi-enzyme reactions for the synthesis of different classes of organic compounds. PMID:23490810

Oroz-Guinea, Isabel; García-Junceda, Eduardo

2013-04-01

218

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.

2012-06-26

219

Named Reactions  

NSDL National Science Digital Library

This Web site lists 95 of the most important named reactions in organic chemistry. Each is linked to a Web page that gives the primary reference and equations for one or more recent literature examples that illustrate the use of the reaction.

220

Chemical Reactions  

NSDL National Science Digital Library

We are going go over a general view of reactions to prepare us for our unit on Chemical Reactions! Have fun learning! WARNING: If you are caught looking at ANY other site, without permission, you will be sent to the ALC, and you will not participate in any other computer activities for the rest of the year. Get your worksheet and begin! Overview Take this quiz and have me come over and sign off on your worksheet when you have completed the quiz! Overview Quiz Next let's take a look at what effect the rate of a chemical reaction. Rates of Reactions Another quiz, another check off by me! Rates of Reactions Quiz Now how do we measure how fast a ...

Mrs. Hicken

2009-05-04

221

Stereospecific synthesis of alkylidenecyclopropanes via sequential cyclopropene carbomagnesation/1,3-carbon shift  

PubMed Central

Alkylidenecyclopropanes can be synthesized from enantiomerically enriched cyclopropene derivatives with >99% stereotransfer and good to excellent yield. The protocol comprises the stereoselective reaction of Grignard reagents with 1-alkoxymethyl-3-hydroxymethyl cyclopropenes and a stereospecific [1,3] carbon shift reaction. PMID:20462206

Xie, Xiaocong; Yang, Zhe; Fox, Joseph M.

2010-01-01

222

Integrated Microreactors for Reaction Automation: New Approaches to Reaction Development  

NASA Astrophysics Data System (ADS)

Applications of microsystems (microreactors) in continuous-flow chemistry have expanded rapidly over the past two decades, with numerous reports of higher conversions and yields compared to conventional batch benchtop equipment. Synthesis applications are enhanced by chemical information gained from integrating microreactor components with sensors, actuators, and automated fluid handling. Moreover, miniaturized systems allow experiments on well-defined samples at conditions not easily accessed by conventional means, such as reactions at high pressure and temperatures. The wealth of synthesis information that could potentially be acquired through use of microreactors integrated with physical sensors and analytical chemistry techniques for online reaction monitoring has not yet been well explored. The increased efficiency resulting from use of continuous-flow microreactor platforms to automate reaction screening and optimization encourages a shift from current batchwise chemical reaction development to this new approach. We review advances in this new area and provide application examples of online monitoring and automation.

McMullen, Jonathan P.; Jensen, Klavs F.

2010-07-01

223

Shift control mechanism for a manual transmission  

SciTech Connect

This patent describes a shift control mechanism for a manual transmission having a transmission gear housing and a manual shift selecting lever. It comprises a shift selecting shaft mounted within the transmission gear housing for rotation and axial translation in response to selective manipulation of the shift selecting lever; a shift sleeve supported from the transmission gear housing; an actuating member secured to the shift selecting shaft for rotation and axial translation with the shift selecting shaft; synchronizer assemblies; the actuating member individually operating the synchronizer assemblies in response to selected manipulation of the shift selecting lever; alignment guide means interactive between the shift selecting shaft and the transmission gear housing to permit axial translation of the shift selecting shaft only when the shift selecting shaft has been rotated to align a locator means with a locating means.

Gugin, D.G.

1991-08-06

224

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

225

Illinois Shifting Gears Policy Evaluation  

ERIC Educational Resources Information Center

Illinois Shifting Gears is a multilevel initiative that has simultaneously created bridge programs in the field and altered state policy to facilitate the creation of more programs in the future. These efforts have informed each other, giving policymakers the opportunity to interact with practitioners, troubleshoot bridge programs, and make…

Weitzel, Peter C.

2009-01-01

226

Leadership Shifts in Changing Field  

ERIC Educational Resources Information Center

As groups representing local and state education players struggle to remain relevant in a policy conversation often dominated by foundations, think tanks, new advocacy groups, and political and business figures, a shift in leadership has been under way at major associations. Most of the changes have come as part of the natural churn; former…

Zubrzycki, Jaclyn

2013-01-01

227

Organizational change as shifting conversations  

Microsoft Academic Search

This article explores producing and managing change within conversationally constructed realities. Conversations are proposed as both the medium and product of reality construction within which change is a process of shifting conversations in the network of conversations that constitute organizations. In this context, change entails bringing new conversations into a sustained existence and the job of change managers is to

Jeffrey D. Ford

1999-01-01

228

Motivating change: shifting the paradigm  

Microsoft Academic Search

The broader framing of the decision-making processes of stakeholders within the sustainability debate is explored in the context of a paradigm shift that acknowledges the world as a complex, dynamic system. There is merit in adopting a paradigm informed by, and therefore suitable for dealing with, living systems, particularly as the paradigm is founded on holistic and flexible strategies. To

Chrisna du Plessis; Raymond J. Cole

2011-01-01

229

Flexible shift scheduling of physicians.  

PubMed

This research addresses a shift scheduling problem in which physicians at a German university hospital are assigned to demand periods over a planning horizon that can extend up to several weeks. When performing the scheduling it is necessary to take into account a variety of legal and institutional constraints that are imposed by a national labor agreement, which governs all physicians in German university hospitals. Currently, most medical departments develop their staff schedules manually at great cost and time. To solve the problem, a new modeling approach is developed that requires shifts to be generated implicitly. Rather than beginning with a predetermined number of shift types and start times, shifts are allowed to start at every pre-defined period in the planning horizon and extend up to 13 h with an hour-long break included. The objective is to find an assignment such that the total hours that have to be paid out as overtime are minimal under the restrictions given by the labor agreement. The problem is formulated as a mixed-integer program and solved with CPLEX. During the solution process individual lines-of-work are constructed for each physician. Using data from an anesthesia department, computational results indicate that high quality schedules can be obtained much more quickly than by current practice. PMID:19739361

Brunner, Jens O; Bard, Jonathan F; Kolisch, Rainer

2009-09-01

230

Imbert-Fedorov shift at metamaterial interfaces  

Microsoft Academic Search

We analyze the transverse shift (Imbert-Fedorov shift) of a focused beam upon reflection at stratified (doubly dispersive) metamaterials. In deriving analytical expressions for the reflection of a focused beam at such an interface this shift can be quantitatively forecast. Solely based on symmetry considerations of the vectorial reflection coefficient we analyze potential geometries where such a shift occurs. Contrary to

C. Menzel; C. Rockstuhl; T. Paul; S. Fahr; F. Lederer

2008-01-01

231

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 ...

232

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

233

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

234

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

235

Periodic-Finite-Type Shift Spaces  

Microsoft Academic Search

We study the class of periodic-finite-type (PFT) shift spaces, which can be used to model time-varying constrained codes used in digital magnetic recording systems. A PFT shift is deter- mined by a finite list of periodically forbidden words. We show that the class of PFT shifts properly contains all finite-type (FT) shifts, and the class of almost finite-type (AFT) shifts

Marie-Pierre Beal; Maxime Crochemore; Bruce E. Moision; Paul H. Siegel

2011-01-01

236

Frequency shifts in gravitational resonance spectroscopy  

NASA Astrophysics Data System (ADS)

Quantum states of ultracold neutrons in a gravitational field are characterized through gravitational resonance spectroscopy. This paper discusses systematic effects that appear in the spectroscopic measurements. The discussed frequency shifts—which we call the 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.; Nesvizhevsky, V. V.; Pignol, G.; Protasov, K. V.; Rebreyend, D.; Kupriyanova, E. A.; Voronin, A. Yu.

2015-02-01

237

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

238

Shift Gray Codes Aaron Michael Williams  

E-print Network

the permutation (j j -1 i) to the indices of s. Right-shifts include prefix-shifts (i = 1) and adjacent to the balanced parentheses (()()). Given a string s = s1s2 sn, the right-shift operation shift(s,i,j) replaces the substring sisi+1 sj by si+1 sjsi. In other words, si is right-shifted into position j by applying

Williams, Aaron

239

CLASS Shifts in Modeling Instruction  

NASA Astrophysics Data System (ADS)

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 University's 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; O'Brien, George

2008-10-01

240

A hidden shift quantum algorithm  

NASA Astrophysics Data System (ADS)

We examine the application of quantum algorithms to the non-Abelian hidden subgroup problem and focus on the dihedral hidden subgroup problem (DHSP). Ettinger and Høyer have recently discovered an algorithm which, although efficient in the number of operations of the quantum computation, requires classical post-processing which grows exponentially with the size of the input. We first show that the DHSP can be reduced to another problem: how to efficiently estimate an unknown shift k, in a one-to-one map f:??f(x), and x?f(x?k), with k and f unknown. We devise an algorithm which uses amplitude amplification to obtain an estimate for the unknown shift k in a number O((M)1/2) oracle calls.

Twamley, J.

2000-12-01

241

Isotope Shift in Mg I  

Microsoft Academic Search

The lines of the Mg I spectrum, lying in the visible and in the photographic infrared regions, have been examined and some of them found to show structure. It is pointed out that the structure should be attributed to isotope shift, which, in the case of the 3s3p1P-3s3d1D series, owes its origin to the fact that the smd1D terms, perturbed

R. F. Bacher; R. A. Sawyer

1935-01-01

242

Hadronic shift in pionic hydrogen  

NASA Astrophysics Data System (ADS)

The hadronic shift in pionic hydrogen has been redetermined to be ? 1 s = 7.086 ± 0.007(stat) ± 0.006(sys) eV by X-ray spectroscopy of ground-state transitions applying various energy calibration schemes. The experiment was performed at the high-intensity low-energy pion beam of the Paul Scherrer Institut by using the cyclotron trap and an ultimate-resolution Bragg spectrometer with bent crystals.

Hennebach, M.; Anagnostopoulos, D. F.; Dax, A.; Fuhrmann, H.; Gotta, D.; Gruber, A.; Hirtl, A.; Indelicato, P.; Liu, Y.-W.; Manil, B.; Markushin, V. E.; Rusi el Hassani, A. J.; Simons, L. M.; Trassinelli, M.; Zmeskal, J.

2014-12-01

243

A 14-h night-shift in the control room of a fire brigade.  

PubMed

All 29 operators in the control room of a fire brigade performed test sessions during work and leisure time at 2-h intervals on a day with a 14-h night-shift, a day off and a day with a 10-h morning shift. The test sessions consisted of a visual search choice reaction time test and two Sternberg memory search tests (1 or 5 letters had to be memorized). Furthermore, the operators recorded their oral temperature and their subjective alertness before each test session. The subject also kept a diary of work and sleep times for 14 days. The circadian rhythm of body temperature was hardly changed by a single night-shift. Parallel to the body temperature, the subjective alertness fell significantly during the night-shift reaching a minimum value at 06:00 h. The mean reaction times increased non-significantly at the end of the night-shift and the results of the two Sternberg memory search tests showed no significant trends. The sleep of the operators after the night-shift was on average reduced to 5 hs 34 min. The results of subjective rating of alertness and reaction time test are interpreted as effects of the combined influences of circadian rhythmicity, sleep loss and time on professional task. Most results support the conclusion that a 14-h night-shift without extensive breaks is not acceptable. PMID:11539390

Knauth, P; Keller, J; Schindele, G; Totterdell, P

1995-01-01

244

Shift Work and Endocrine Disorders  

PubMed Central

The objective of this review was to investigate the impact of shift and night work on metabolic processes and the role of alterations in the sleep-wake cycle and feeding times and environmental changes in the occurrence of metabolic disorders. The literature review was performed by searching three electronic databases for relevant studies published in the last 10 years. The methodological quality of each study was assessed, and best-evidence synthesis was applied to draw conclusions. The literature has shown changes in concentrations of melatonin, cortisol, ghrelin, and leptin among shift workers. Melatonin has been implicated for its role in the synthesis and action of insulin. The action of this hormone also regulates the expression of transporter glucose type 4 or triggers phosphorylation of the insulin receptor. Therefore, a reduction in melatonin can be associated with an increase in insulin resistance and a propensity for the development of diabetes. Moreover, shift work can negatively affect sleep and contribute to sedentarism, unhealthy eating habits, and stress. Recent studies on metabolic processes have increasingly revealed their complexity. Physiological changes induced in workers who invert their activity-rest cycle to fulfill work hours include disruptions in metabolic processes. PMID:25892993

Ulhôa, M. A.; Marqueze, E. C.; Burgos, L. G. A.; Moreno, C. R. C.

2015-01-01

245

Frequency shift discrimination: Can homing pigeons locate infrasounds by Doppler shifts?  

Microsoft Academic Search

Summary Homing pigeons can detect small shifts in sound frequency at 1, 2, 5, 10, and 20 Hz. Their thresholds range from a 1% shift at 20 Hz to a 7% shift at 1 Hz. The frequency shifts used were designed to simulate the natural Doppler shifts resulting from changes in flight path. Their ability was sufficiently sensitive to make

Douglas B. Quine; Melvin L. Kreithen

1981-01-01

246

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

247

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

Michael Horton

2009-05-30

248

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.

WGBH Boston

2003-01-01

249

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

PubMed Central

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 effect” relative to the TD children occurred for the children with autism in conditions involving the reaction time when shifting from sound to light but not from light to sound. No exaggerated MSE was found for the adults with autism; rather, their responses were characterized by a generalized slowness relative to the adults with TD. These results suggest a lag in maturational development in autism in basic information processing mechanisms. PMID:22865151

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

2012-01-01

250

The shifting center of human genome mapping  

SciTech Connect

This succinct article describes the shifting hub of genetic mapping efforts from Paris, France to Cambridge, Massachusetts. Many reasons for this shift are discussed, including breakthrough technologies, funding, and coordinated research efforts.

Johnson, E.; Hodgson, J.

1996-02-01

251

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

252

Cortisol shifts financial risk preferences  

PubMed Central

Risk taking is central to human activity. Consequently, it lies at the focal point of behavioral sciences such as neuroscience, economics, and finance. Many influential models from these sciences assume that financial risk preferences form a stable trait. Is this assumption justified and, if not, what causes the appetite for risk to fluctuate? We have previously found that traders experience a sustained increase in the stress hormone cortisol when the amount of uncertainty, in the form of market volatility, increases. Here we ask whether these elevated cortisol levels shift risk preferences. Using a double-blind, placebo-controlled, cross-over protocol we raised cortisol levels in volunteers over 8 d to the same extent previously observed in traders. We then tested for the utility and probability weighting functions underlying their risk taking and found that participants became more risk-averse. We also observed that the weighting of probabilities became more distorted among men relative to women. These results suggest that risk preferences are highly dynamic. Specifically, the stress response calibrates risk taking to our circumstances, reducing it in times of prolonged uncertainty, such as a financial crisis. Physiology-induced shifts in risk preferences may thus be an underappreciated cause of market instability. PMID:24550472

Kandasamy, Narayanan; Hardy, Ben; Page, Lionel; Schaffner, Markus; Graggaber, Johann; Powlson, Andrew S.; Fletcher, Paul C.; Gurnell, Mark; Coates, John

2014-01-01

253

Cortisol shifts financial risk preferences.  

PubMed

Risk taking is central to human activity. Consequently, it lies at the focal point of behavioral sciences such as neuroscience, economics, and finance. Many influential models from these sciences assume that financial risk preferences form a stable trait. Is this assumption justified and, if not, what causes the appetite for risk to fluctuate? We have previously found that traders experience a sustained increase in the stress hormone cortisol when the amount of uncertainty, in the form of market volatility, increases. Here we ask whether these elevated cortisol levels shift risk preferences. Using a double-blind, placebo-controlled, cross-over protocol we raised cortisol levels in volunteers over 8 d to the same extent previously observed in traders. We then tested for the utility and probability weighting functions underlying their risk taking and found that participants became more risk-averse. We also observed that the weighting of probabilities became more distorted among men relative to women. These results suggest that risk preferences are highly dynamic. Specifically, the stress response calibrates risk taking to our circumstances, reducing it in times of prolonged uncertainty, such as a financial crisis. Physiology-induced shifts in risk preferences may thus be an underappreciated cause of market instability. PMID:24550472

Kandasamy, Narayanan; Hardy, Ben; Page, Lionel; Schaffner, Markus; Graggaber, Johann; Powlson, Andrew S; Fletcher, Paul C; Gurnell, Mark; Coates, John

2014-03-01

254

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

255

Mean Shift, Mode Seeking, and Clustering  

Microsoft Academic Search

Abstract-Mean shift, a simple iterative procedure that shifts each data point to the average of data points in its neighborhood, is generalized and analyzed in this paper. This generalization makes some k-means like clustering algorithms its special cases. It is shown that mean shift is a mode-seeking process on a surface constructed with a \\

Yizong Cheng

1995-01-01

256

Interpreting lateral dynamic weight shifts using a simple inverted pendulum model.  

PubMed

Seventy-five young, healthy adults completed a lateral weight-shifting activity in which each shifted his/her center of pressure (CoP) to visually displayed target locations with the aid of visual CoP feedback. Each subject's CoP data were modeled using a single-link inverted pendulum system with a spring-damper at the joint. This extends the simple inverted pendulum model of static balance in the sagittal plane to lateral weight-shifting balance. The model controlled pendulum angle using PD control and a ramp setpoint trajectory, and weight-shifting was characterized by both shift speed and a non-minimum phase (NMP) behavior metric. This NMP behavior metric examines the force magnitude at shift initiation and provides weight-shifting balance performance information that parallels the examination of peak ground reaction forces in gait analysis. Control parameters were optimized on a subject-by-subject basis to match balance metrics for modeled results to metric values calculated from experimental data. Overall, the model matches experimental data well (average percent error of 0.35% for shifting speed and 0.05% for NMP behavior). These results suggest that the single-link inverted pendulum model can be used effectively to capture lateral weight-shifting balance, as it has been shown to model static balance. PMID:24708905

Kennedy, Michael W; Bretl, Timothy; Schmiedeler, James P

2014-05-01

257

[Effects of shift work on health].  

PubMed

20% of employees in industrialized countries are concerned by shift work. Nevertheless, there is very little information in general medical journals about the effects of shift work on health. Shift work can have several major effects on health such as cardiovascular and digestive disorders among others, as demonstrated by several studies in recent decades. Shift work has attracted considerable attention recently when it was declared probable carcinogen by the International Agency for research on cancer. We review the health disorders that may be generated or aggravated by shift work and illustrate the problem by two case studies of occupational medicine and discuss the appropriate attitude to take. PMID:19066146

Ntawuruhunga, Emmanuel; Chouanière, Dominique; Danuser, Brigitta; Praz-Christinaz, Sophie-Maria

2008-11-26

258

Gear-shift mechanism for manual transmission  

SciTech Connect

This patent describes a gear-shift mechanism for a manual transmission comprising a housing for the transmission; a movable shaft mounted in place within the housing for both axial and rotary movements and being operatively connected to a manual shift lever to be axially shifted from its neutral position to a forward or reverse position in selecting operation of the manual shift lever and to be rotated at its shifted position in shifting operation of the manual shift lever; a shift-and-select lever fixed to an intermediate portion of the movable shaft; an interlock member rotatably mounted in place on the movable shaft and having a pair of interlock arms located at the opposite sides of the shift-and-select lever; means for restricting rotary movement of the interlock member and permitting axial movement of the same; a pair of resilient means for centering the movable shaft to retain the shift-and-select lever and the interlock member in their neutral positions; and first, second and third shift heads arranged in sequence within the housing.

Fukuchi, H.

1986-07-22

259

Human Eye-Head Gaze Shifts in a Distractor Task. I. Truncated Gaze Shifts  

E-print Network

, coordinated movements of both the eyes (eye-re-head) and head (head-re-space) that serve to reorientHuman Eye-Head Gaze Shifts in a Distractor Task. I. Truncated Gaze Shifts BRIAN D. CORNEIL,1, and Douglas P. Munoz. Human eye-head gaze shifts in a distractor task. I. Truncated gaze shifts. J

Munoz, Douglas Perry

260

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.

Oregon Museum of Science and Industry

1997-01-01

261

Thermonuclear reaction rates. II  

Microsoft Academic Search

A revision and updating of charged particle reactions involving nuclei ; with A less than or approximately equal to 30, except for the $sup ; 2$H(d,$gamma$)⁴He reaction whose reaction rate is very uncertain, is ; presented. Reactions involving neutrons are treated as neutron-producing ; reactions but factors for calculating the reverse reaction rate are provided for ; all reactions. The

W. A. Fowler; G. R. Caughlan; B. A. Zimmerman

1975-01-01

262

Air-Water Gas Exchange  

Microsoft Academic Search

The exchange of inert and sparingly soluble gases -- including carbon dioxide, methane, and oxygen -- between the atmosphere and oceans is controlled by a thin 20- to 200-µm-thick boundary layer at the top of the ocean. The hydrodynamics in this layer are significantly different from boundary layers at rigid walls, since the orbital motion of the waves is of

B. Jähne; H. Haußecker

1998-01-01

263

Shifting Baselines, Science, and Society  

NASA Astrophysics Data System (ADS)

All of us have a deeply personal concept of nature based upon our childhood perceptions of the world around us, and of the subsequent degradation of nature by the experiences of our lifetimes. Yet even the most rudimentary knowledge of history clearly demonstrates that the modern rise of human population and consumption have wreaked havoc on global ecosystems to the extent that nowhere is close to natural or pristine and that most places have been increasingly degraded over many centuries. This disconnect between direct personal experience and abstract historical perspective is the problem of "shifting baselines" that is the fundamental impediment to basic scientific understanding and environmental policy, and affects scientists as much as the general public, business, and government. Scientists in particular suffer from the inability to directly observe and experimentally verify causes and effects of previous changes in ecosystems that now bear so little resemblance to their natural state. Under the circumstances, it is essential for scientists to draw scientific conclusions based on imperfect data and to publicly explain, defend, and discuss their conclusions as the best possible science given present information. The failure to do so makes science virtually irrelevant to social and environmental policy and government.

Jackson, J. B.

2006-12-01

264

Red Shifts and Existing Speculations  

NASA Astrophysics Data System (ADS)

There are many current flaws, mysteries, and errors in the standard model of the universe - all based upon speculative interpretation of many excellent and verified observations. The most serious cause of some errors is the speculation about the meaning of the redshifts observed in the 1930s by Hubble. He ascribed the redshifts as due to ``an apparent Doppler effect''. This led to speculation that the remote stars were receding, and the universe was expanding -- although without observational proof of the actual receding velocity of the stars. The age of the universe, based upon the Hubble constant is pure speculation because of lack of velocity demonstration. The belief in expansion, the big bang, and of inflation should be reexamined. Also, the redshift cannot always be used as a distance measure, particularly for photons from quasars containing massive black holes that can reduce photon energy through gravitational attraction. If the linear Hubble constant is extrapolated to the most remote super novae and beyond, it would eventually require that the corresponding photon energy go to zero or become negative -- according to Hubble linear relationship. This should require a reexamination of the meaning of the red shift and the speculative consequences and give a model with fewer mysteries.

Aisenberg, Sol

2009-03-01

265

Shift mechanism for engine starting apparatus  

SciTech Connect

This patent describes a shift lever mechanism for translating axial movement of the plunger of a starter solenoid into axial movement of a pinion of an engine starting apparatus. This apparatus consists of, a starter solenoid having an axially shiftable plunger and a coil winding, a spring opposing pull-in movement of the plunger and a solenoid switch operated to a closed condition when the plunger is completely pulled-in, a shift lever actuator carried by the plunger for axial movement therewith. The actuator has a pair of spaced surfaces, a pivotally mounted shift lever one end of which is adapted to be coupled to the pinion. The opposite end of the shift lever has a pair of opposed shift lever surfaces that respectively engage the surfaces on the actuator. The actuator surfaces and the shift lever surfaces are substantially engaged when the shift lever is in an at rest postion. The surfaces on the shift lever are at different radial distances from the pivot point of the shift lever and are arranged relative to the surfaces on the actuator such that when the solenoid plunger pulls-in the surface on the shift lever that is at the greater radial distance from the pivot point is moved by a surface of the actuator and the other surface on the shift lever becomes separated by a predetermined amount from its cooperating surface on the actuator. The amount of separation is sufficient to allow the solenoid switch to be actuated to an open condition when the solenoid coil winding is deenergized and the spring shifts and plunger to reengage the separated surfaces.

Colvin, J.A.; Colvill, R.G.; Smock, A.L.

1986-04-01

266

Total Antioxidant Capacity and Malondialdehyde in Depressive Rotational Shift Workers  

PubMed Central

Shift work is associated with sleep deprivation, occupational stress, and increased risk of depression. Depressed patients show increased oxidative stress. During excessive oxidative stress, Malondialdehyde (MDA) increases and total antioxidant capacity (TAC) decreases in body. This cross-sectional study was conducted to determine the serum level of TAC and MDA among depressed rotational shift workers in Shahid Tondooyan Tehran Oil Refinery. 21-item Beck Depression Inventory was used to measure depression level. The level of TAC and MDA was measured by 8 mL fasting blood sample. MDA was determined by thiobarbituric acid reaction. Serum total antioxidants were measured using the ABTS. Results of this study showed that TAC mean and standard deviation concentration was 2.451 (±0.536)?mg/dL and MDA was 3.725 (±1.098)?mic·mol/L, and mean and standard deviation of depression score and BMI were 14.07 (±3.84) and 24.92 (±3.65)?kg/m2, respectively. Depression score had a positive correlation with rotational shift work experience and work experience (r = 0.218 and r = 0.212), respectively, (P < 0.05). PMID:23690799

Khajehnasiri, Farahnaz; Mortazavi, Seyed Bagher; Allameh, Abdolamir; Akhondzadeh, Shahin; Hashemi, Hassan

2013-01-01

267

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

268

Temperature effects on enzyme-catalyzed reactions within a cell: Monte Carlo simulations for coupled reaction and diffusion  

NASA Astrophysics Data System (ADS)

We report Monte Carlo simulations of temperature effects on single-step enzymatic reactions with varied rate constants and diffusion coefficients. For typical systems, where the intrinsic reaction rate is more sensitive to temperature than diffusion, the overall reaction is rate-limited at low temperatures and diffusion-limited at high temperatures. The effective activation energy shifts to a much lower value as temperature is increased. Our results show that the temperature dependence of enzyme-catalyzed reactions within a cell may be only loosely related to a potential energy barrier height. The effective activation energy may be strongly affected by coupling of reaction and diffusion.

Nangia, Shivangi; Anderson, James B.

2013-01-01

269

Contributors to shift work tolerance in South Korean nurses working rotating shift.  

PubMed

Shift workers have rapidly increased in South Korea; however, there is no published research exploring shift work tolerance among South Korean workers. This study aimed to investigate factors related to shift work tolerance in South Korean nurses. The sample comprised of 660 nurses who worked shifts in a large hospital in South Korea. A structured questionnaire included following comprehensive variables: demographic (age and number of children), individual (morningness and self-esteem), psychosocial (social support and job stress), lifestyle (alcohol consumption, physical activity, and BMI), and working condition factors (number of night shifts and working hours). Shift work tolerance was measured in terms of insomnia, fatigue, and depression. The results of hierarchical regressions indicate that all variables, except for three, number of children, BMI, and working hours, were related to at least one of the symptoms associated with shift work tolerance. Based on these results, we offer some practical implications to help improve shift work tolerance of workers. PMID:25448057

Jung, Hye-Sun; Lee, Bokim

2014-10-01

270

Computer-aided design of shift schedules  

Microsoft Academic Search

The complexities encountered in the design of shift schedules for continuous work, especially if such a design is to perform optimally against the criteria of organizational demands and ergonomics protocols simultaneously, inevitably demand computer support. This paper reports on the concept and development of a PC-based computer program for the design of shift schedules for continuous work with regular or

FRIEDHELM NACHREINER; LING QIN; HILTRAUD GRZECH-SUKALO; INA HEDDEN

1993-01-01

271

Gravitational Bending of Light with Frequency Shifts  

E-print Network

Non-static gravitational fields generally introduce frequency shifts when bending light. In this paper, I discuss the frequency shifts induced in the bending of light by moving masses. As examples, I treat the recently discovered high-velocity pulsar PSR 2224+65 and a typical Einstein ring.

P. D. Morley

1993-11-15

272

BIODIVERSITY Accounting for tree line shift, glacier  

E-print Network

BIODIVERSITY RESEARCH Accounting for tree line shift, glacier retreat and primary succession land cover (tree line shift, glacier retreat and primary succession) into species distribution model. Methods We fit linear mixed effects (LME) models to historical changes in forest and glacier cover

Zimmermann, Niklaus E.

273

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

274

Lamb Shift in Nonrelativistic Quantum Electrodynamics.  

ERIC Educational Resources Information Center

The bound electron self-energy or Lamb shift is calculated in nonrelativistic quantum electrodynamics. Retardation is retained and also an interaction previously dropped in other nonrelativistic approaches is kept. Results are finite without introducing a cutoff and lead to a Lamb shift in hydrogen of 1030.9 MHz. (Author/JN)

Grotch, Howard

1981-01-01

275

Apparatus for controlling transmission gear shift selection  

SciTech Connect

In an automotive engine having an electrical power source and an automatic or semi-automatic transmission including a manually operated transmission gear shift lever having at least two forward drive positions, an apparatus is described which consists of: (a) a speed sensing means for sensing the rotation speed of the engine and generating an output signal when the engine reaches a preselected rotational speed; and (b) a gear shifting means for changing the shift positions of the gear shift lever from a first drive position to a second drive position automatically in response to the output signal from the speed sensing means, the gear shifting means including (i) a latch actuable between open and closed positions, (ii) a normally de-energized solenoid having a plunger connected to the latch and operable to move the latch to the open position when the solenoid is energized by the electrical power source, (iii) a relay means for allowing the energizing of the solenoid by the power source in response to the output signal from the speed sensing means, and (iv) an actuating means, including a spring biased linkage mechanism operably connected to the gear shift lever and the latch, for actuating the movement of the gear shift lever from the first drive position to the second drive position in response to movement of the latch from the closed to the open position, thereby causing gear shifting to occur when the engine reaches the preselected rotational speed.

Bailey, T.M.

1986-07-29

276

Gear shift controller for automatic transmission  

Microsoft Academic Search

A gear shift controller is described for an automatic transmission having a gear shift, comprising: a hydraulic torque converter; a gear change group, having a plurality of gears, each gear providing a different transmission ratio for the transmission of power from the hydraulic torque converter to the output of the transmission, each of the gears comprising a gear train; a

M. Nishikawa; S. Sakai; T. Sakurai

1987-01-01

277

The Concept Shifting Test: Adult Normative Data  

ERIC Educational Resources Information Center

The Concept Shifting Test (CST) is a newly developed Trail Making Type test that measures concept shifting and executive functioning. The purpose of the present study was to determine whether CST performance was affected by age, gender, educational level, or handedness and to establish the normal range of test performance. The CST was…

Van der Elst, Wim; Van Boxtel, Martin P. J.; Van Breukelen, Gerard J. P.; Jolles, Jelle

2006-01-01

278

[Effect of shift work on blood pressure].  

PubMed

The widespread adoption of 24-hour continuous operations in a number of industries has resulted in an increase in the size of the population engaged in shift work. The health effects of shift work have been studied comprehensively. For ischemic heart disease, the reported relative risk of shift workers has ranged from 1.3 to 2.0. In terms of blood pressure, shift work has been clarified to be a significant risk factor for the onset of hypertension and increased blood pressure. Potential mechanisms of these health effects have been associated with disturbed circadian rhythms, sleep and lifestyle problems, increased stress and biochemical changes. Efficient health screening and support to control unhealthy lifestyle factors would be of considerable benefit for maintaining the health of shift workers. PMID:25167759

Suwazono, Yasushi; Nogawa, Kazuhiro

2014-08-01

279

Quality of life in shift work syndrome.  

PubMed

Air Force radar controllers represent an excellent example of night shift workers, as they are obliged to demonstrate perfect alertness during working hours. We set out: a) to assess the quality of life in these shift workers; b) to identify those with shift work syndrome and c) to evaluate the possible effects of triazolam both on their quality of life and sleep. The results reveal an impairment of the quality of life in shift workers, independently of the presence of a circadian rhythm sleep disorder. Quality of life was more severely impaired in subjects with circadian rhythm sleep disorder. Hypnotic therapy brought about an improvement both in the sleep disorder and in the quality of life of subjects affected by shift work syndrome. Selective alertness tests failed to demonstrate any "sedative carry-over" in the treated patients. PMID:9119269

Puca, F M; Perrucci, S; Prudenzano, M P; Savarese, M; Misceo, S; Perilli, S; Palumbo, M; Libro, G; Genco, S

1996-01-01

280

Shift characteristics analysis and smooth shift for an automatic power transmission  

Microsoft Academic Search

Smooth shift is one of the key issues in automatic power transmission control systems. However, the torque sensors are too\\u000a expensive to be used in shift controllers on production vehicles. In order to provide a basic strategy for smooth shifting\\u000a by using RPM sensors only and in order to accomplish the shift within a designated time, this paper studies detailed

Heon-Sul Jeong; Kyo-Ill Lee

2000-01-01

281

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

282

Personality factors predicting changes in shift work tolerance: A longitudinal study among nurses working rotating shifts  

Microsoft Academic Search

The aim of the present study was to investigate the relationship between personality factors (hardiness, morningness, flexibility, and languidity) and longitudinal changes on different measures of shift work tolerance (fatigue, sleepiness, anxiety and depression) over one year among nurses working rotating shifts. A total of 642 female Norwegian nurses working in a rotating three-shift schedule participated in the study. The

Ingvild Saksvik-Lehouillier; Bjørn Bjorvatn; Hilde Hetland; Gro Mjeldheim Sandal; Bente E. Moen; Nils Magerøy; Allison Harvey; Giovanni Costa; Ståle Pallesen

2012-01-01

283

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

284

H 2 Production and CO 2 Separation  

Microsoft Academic Search

\\u000a A promising technology for H2 production and CO2 separation is based on water gas shift reaction operated in water gas shift membrane reactor (WGSMR). In such a reactor the\\u000a synthetic gas reacts with steam in a catalytic bed to produce additional hydrogen and CO2. A H2 selective membrane allows the simultaneous production of hydrogen at a high purity level and

Antonello Di Donato

285

DOI: 10.1002/cssc.201402474 Monitoring Solid Oxide CO2 Capture Sorbents in Action  

E-print Network

process for H2 production, CO2 sorbents are able to shift the reaction equi- librium to the right, thus et al. has recently studied two promising high tempera- ture chemisorbents for the water­gas-shift under WGS reaction condi- tions. H2O þ CO $ H2 þ CO2 ð2Þ A comparison between the two sorbents indicated

Gilchrist, James F.

286

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

287

A continuous-flow model for phonatory reaction time.  

PubMed

The purpose of this study was to validate a proposed continuous-flow model of phonatory reaction time by investigating the temporal order of selected laryngeal and neurophysiological events involved in a phonatory reaction time task. Ten normal speakers participated in a phonatory reaction time task. Laryngeal positioning movements prior to vocal fold closure (laryngeal shift) and onset of vocal fold vibration (acoustic onset) were recorded with an electroglottograph. P300 brain potentials were collected simultaneously, and they served as an index of a central process underlying reaction time. The obtained temporal ordering of laryngeal shift, P300, and acoustic onset supported a continuous-flow model of phonatory reaction time. Use of this model might yield information that is more accurate in explaining physiological function and more precise in describing temporal patterning than the serial model. PMID:2072675

Ferrand, C; Blood, G W; Gilbert, H R

1991-06-01

288

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

289

Search for Higgs Shifts in White Dwarfs  

NASA Astrophysics Data System (ADS)

We report on a search for differential shifts between electronic and vibronic transitions in carbon-rich white dwarfs BPM 27606 and Procyon B. The absence of differential shifts within the spectral resolution and taking into account systematic effects such as space motion and pressure shifts allows us to set the first upper bound of astrophysical origin on the coupling between the Higgs field and the Kreschmann curvature invariant. Our analysis provides the basis for a more general methodology to derive bounds to the coupling of long-range scalar fields to curvature invariants in an astrophysical setting complementary to the ones available from high-energy physics or table-top experiments.

Onofrio, Roberto; Wegner, Gary A.

2014-08-01

290

Search for Higgs shifts in white dwarfs  

E-print Network

We report on a search for differential shifts between electronic and vibronic transitions in carbon-rich white dwarfs BPM 27606 and Procyon B. The absence of differential shifts within the spectral resolution and taking into account systematic effects such as space motion and pressure shifts allows us to set the first upper bound of astrophysical origin on the coupling between the Higgs field and the Kreschmann curvature invariant. Our analysis provides the basis for a more general methodology to derive bounds to the coupling of long-range scalar fields to curvature invariants in an astrophysical setting complementary to the ones available from high-energy physics or table-top experiments.

Roberto Onofrio; Gary A. Wegner

2014-09-30

291

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

292

Blocking of Na+/K+ transport by the MgPO4 complex analogue Co(NH3)4PO4 leaves the Na+/Na(+)-exchange reaction of the sodium pump unaltered and shifts its high-affinity ATP-binding site to a Na(+)-like form.  

PubMed

Inactivation of Na+/K(+)-ATPase activity by the MgPO4 complex analogue Co(NH3)4PO4 leads, in everted red blood cell vesicles, to the parallel inactivation of 22Na+/K+ flux and 86Rb/Rb+ exchange, but leaves the 22Na+/Na(+)-exchange activity and the uncoupled ATP-supported 22Na+ transport unaffected. Furthermore, inactivation of purified Na+/K(+)-ATPase by Co(NH3)4PO4 leads to a parallel decrease of the capacity of the [3H]ouabain receptor site, when binding was studied by the Mg2+/Pi-supported pathway (ouabain-enzyme complex II) but the capacity of the ouabain receptor site was unaltered, when the Na+/Mg2+/ATP-supported pathway (ouabain-enzyme complex I) was used. No change in the dissociation constants of either ouabain receptor complex was observed following inactivation of Na+/K(+)-ATPase. When eosin was used as a marker for the high-affinity ATP-binding site of the E1 conformation, formation of stable E'2.Co(NH3)4PO4 complex led to a shift in the high-affinity ATP-binding site towards the sodium form. This led to an increase in the dissociation constant of the enzyme complex with K+, from 1.4 mM with the unmodified enzyme to 280 mM with the Co(NH3)4PO4-inactivated enzyme. It was concluded, that the effects of Co(NH3)4PO4 on the partial activities of the sodium pump are difficult to reconcile with an alpha, beta-protomeric enzyme working according the Albers-Post scheme. The data are consistent with an alpha 2, beta 2 diprotomeric enzyme of interacting catalytic subunits working with a modified version of the Albers-Post model. PMID:1699757

Buxbaum, E; Schoner, W

1990-10-24

293

Cognitive Set-Shifting in Anorexia Nervosa  

PubMed Central

Objective Adult anorexia nervosa (AN) is associated with inefficient cognitive flexibility and set-shifting. Whether such inefficiencies also characterize adolescent AN is an important area of research. Method Adolescents with AN and matched controls were administered a computerized task that required initial learning of an explicit rule using corrective feedback and learning of a new rule after a set number of trials. Adult patients with AN and controls were also examined. Results Adolescents with AN did not differ from matched controls with respect to set-shifting cost (decrease in performance after rule change), whereas adults with AN had significantly greater set-shifting cost compared with controls. Discussion This study suggests that set-shifting inefficiencies may not be a vulnerability factor for AN development in adolescents with AN, but might become an important aspect of the disorder at later age, and could point towards developmental neurobiologic brain changes that could affect AN at different ages. PMID:22492553

Shott, Megan E.; Filoteo, J. Vincent; Bhatnagar, Kelly A.C.; Peak, Nicole J.; Hagman, Jennifer O.; Rockwell, Roxanne; Kaye, Walter H.; Frank, Guido K.W.

2013-01-01

294

Prolonged Instability Prior to a Regime Shift  

PubMed Central

Regime shifts are generally defined as the point of ‘abrupt’ change in the state of a system. However, a seemingly abrupt transition can be the product of a system reorganization that has been ongoing much longer than is evident in statistical analysis of a single component of the system. Using both univariate and multivariate statistical methods, we tested a long-term high-resolution paleoecological dataset with a known change in species assemblage for a regime shift. Analysis of this dataset with Fisher Information and multivariate time series modeling showed that there was a?2000 year period of instability prior to the regime shift. This period of instability and the subsequent regime shift coincide with regional climate change, indicating that the system is undergoing extrinsic forcing. Paleoecological records offer a unique opportunity to test tools for the detection of thresholds and stable-states, and thus to examine the long-term stability of ecosystems over periods of multiple millennia. PMID:25280010

Spanbauer, Trisha L.; Allen, Craig R.; Angeler, David G.; Eason, Tarsha; Fritz, Sherilyn C.; Garmestani, Ahjond S.; Nash, Kirsty L.; Stone, Jeffery R.

2014-01-01

295

Stage-shift cancer screening model.  

PubMed

A stage-shift cancer screening model is developed in the context of a randomized controlled trial (RCT) of cancer screening. In the model, detection by screening causes the time of diagnosis of the cancer to be advanced so that either the stage at diagnosis is shifted from one stage to the next lower one or the stage of diagnosis is unchanged but the cancer is diagnosed earlier in the stage. These are called external and internal stage shifts, respectively. At each stage the extent of the external and internal shifts and any associated mortality benefits are estimated. Further, the model allows the interrelationships of these benefits within and between stages to be delineated. This then allows us to better understand the results of the RCT. Data from a completed breast cancer screening RCT are used to illustrate the application of the model and its value in improving our understanding of the trial's results. PMID:2681551

Connor, R J; Chu, K C; Smart, C R

1989-01-01

296

Prolonged instability prior to a regime shift.  

PubMed

Regime shifts are generally defined as the point of 'abrupt' change in the state of a system. However, a seemingly abrupt transition can be the product of a system reorganization that has been ongoing much longer than is evident in statistical analysis of a single component of the system. Using both univariate and multivariate statistical methods, we tested a long-term high-resolution paleoecological dataset with a known change in species assemblage for a regime shift. Analysis of this dataset with Fisher Information and multivariate time series modeling showed that there was a?2000 year period of instability prior to the regime shift. This period of instability and the subsequent regime shift coincide with regional climate change, indicating that the system is undergoing extrinsic forcing. Paleoecological records offer a unique opportunity to test tools for the detection of thresholds and stable-states, and thus to examine the long-term stability of ecosystems over periods of multiple millennia. PMID:25280010

Spanbauer, Trisha L; Allen, Craig R; Angeler, David G; Eason, Tarsha; Fritz, Sherilyn C; Garmestani, Ahjond S; Nash, Kirsty L; Stone, Jeffery R

2014-01-01

297

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

298

Shift manager workload assessment - A case study  

SciTech Connect

In early 2003, Bruce Power restarted two of its previously laid up units in the Bruce A generating station, Units 3 and 4. However, due to challenges relating to the availability of personnel with active Shift Manager licenses, an alternate shift structure was proposed to ensure the safe operation of the station. This alternate structure resulted in a redistribution of responsibility, and a need to assess the resulting changes in workload. Atomic Energy of Canada Limited was contracted to perform a workload assessment based on the new shift structure, and to provide recommendations, if necessary, to ensure Shift Managers had sufficient resources available to perform their required duties. This paper discusses the performance of that assessment, and lessons learned as a result of the work performed during the Restart project. (authors)

Berntson, K.; Kozak, A. [Bruce Power, P O Box 1540 B10, Tiverton, Ont. N0G 2T0 (Canada); Malcolm, J. S. [Atomic Energy of Canada Ltd., 2251 Speakman Drive, Mississauga, Ont. L5K 1B2 (Canada)

2006-07-01

299

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

300

Choice Reaction Time in Workers Exposed to Styrene Vapour  

Microsoft Academic Search

1 Behavioural effects of occupational exposure to vapour from styrene-based resin were investigated in 10 female workers with a portable test of choice reaction time. Testing was carried out both at the beginning and end of the day's shift.2 Uptake and metabolism of styrene were assessed by monitoring post-shift urinary mandelic acid excretion rates. By using these data workers were

C. J. Mackay; G. R. Kelman

1986-01-01

301

Isotope shift in the tantalum atomic spectrum  

Microsoft Academic Search

Optical isotope shifts have been measured in 11 lines of the neutral-tantalum spectrum. The tantalum atoms were introduced into a hollow cathode discharge, whose cathode wall was covered with 4 mg of a Ta2O5 sample containing 180Ta enriched to 4.1%. Using laser excitation with either optogalvanic or laser-induced fluorescence detection, the hyperfine constants of the levels involved and the shifts

G. H. Guthöhrlein; G. Helmrich; L. Windholz

1994-01-01

302

Linear Feedback Shift Registers in Virtex Devices  

Microsoft Academic Search

Summary This application note describes the implementation of Linear Feedback Shift Registers (LFSR) using the SRL macroavailable in the Virtex™ and Virtex-II series of FPGAs. The optimal implementation of a 15-bit LFSR, a 52-bit LFSR, and a 118-bit LFSR are discussed in this application note. Introduction The Virtex series of FPGAs have an SRL (Shift Register LUT) macro. This macro

Maria George; Peter Alfke

303

Quantum algorithms for shifted subset problems  

E-print Network

We consider a recently proposed generalisation of the abelian hidden subgroup problem: the shifted subset problem. The problem is to determine a subset S of some abelian group, given access to quantum states of the form |S+x>, for some unknown shift x. We give quantum algorithms to find Hamming spheres and other subsets of the boolean cube {0,1}^n. The algorithms have time complexity polynomial in n and give rise to exponential separations from classical computation.

Ashley Montanaro

2009-02-06

304

The Knight shift of francium in mercury  

Microsoft Academic Search

For Fr in Hg an extremely small Knight shift has been found as compared to the shift known for an alkali metal host. It indicates\\u000a an almost complete loss of the outer s-electron of the alkali atom Fr when embedded in liquid mercury. This may be understood\\u000a as a consequence of the small ionization energy of the Fr atom in

H. Haas; Ch. Stenzel; H.-E. Mahnke; B. Spellmeyer; W.-D. Zeitz

1990-01-01

305

A Phylogenetic analysis of the Southern Shift  

E-print Network

A PHYLOGENETIC ANALYSIS OF THE SOUTHERN SHIFT A Thesis by ERIK ROBERT THOMAS Submitted to the Office of Graduate Studies of Texas ASM University in partial fulfillment of the requirements for the degree of MASTER OF ARTS December 1989... Major Subject: English A PHYLOGENETIC ANALYSIS OF THE SOUTHERN SHIFT A Thesis by ERIK ROBERT THOMAS Approved as to style and content by: Guy Bailey (Chair of Committee) Barbara Johnstone (Member) Robert H. Benson (Member) J. Lawrence Mitchell...

Thomas, Erik Robert

1989-01-01

306

On Thermonuclear Reaction Rates  

E-print Network

Nuclear reactions govern major aspects of the chemical evolution od galaxies and stars. Analytic study of the reaction rates and reaction probability integrals is attempted here. Exact expressions for the reaction rates and reaction probability integrals for nuclear reactions in the case of nonresonant, modified nonresonant, screened nonresonant and resonant cases are given. These are expressed in terms of H-functions, G-functions and in computable series forms. Computational aspects are also discussed.

H. J. Haubold; A. M. Mathai

1996-12-02

307

Invited commentary: Shift work and cancer.  

PubMed

In this issue of the Journal, Parent et al. (Am J Epidemiol. 2012;176(9):751-759) report significant associations between night-shift work and risk of cancer at several sites among men. These findings not only address the need for shift-work studies that evaluate cancers other than breast and prostate cancer but also support the increasing concern that the negative effects of shift work may be broadly applicable to risk of many cancers via the direct oncostatic properties of melatonin. Studies of shift work have been limited by a lack of detailed data for determining which aspects of this multifaceted exposure may be associated with increased cancer risk. Additionally, the influence of individual-level characteristics, such as preference for daytime activity versus nighttime activity or chronotype, has not been considered. In moving forward, launching new cohort studies of shift work and cancer risk is the most tenable approach, though it will be limited by the years of follow-up required in order to accrue adequate numbers of cancer cases. Studies incorporating biomarkers of effect are useful for providing immediate information that can aid not only in identifying the underlying mechanisms of the shift-work-cancer association but also in interpreting existing epidemiologic data and informing the design of future epidemiologic studies of cancer risk. PMID:23035018

Bhatti, Parveen; Mirick, Dana K; Davis, Scott

2012-11-01

308

Modeling of shift hydraulic system for automatic transmission  

Microsoft Academic Search

The main functions of the shift hydraulic system for stepped automatic transmission are to generate and maintain desired clutch pressures for shifting operation, as well as to initiate gear shifts and control shift quality. It consists of supply line pressure regulation system, solenoid valve, pressure control valve (PCV), and wet clutch. This paper presents a dynamic model of the shift

Gang Tao; Tao Zhang; Huiyan Chen

2011-01-01

309

Proton magnetic resonance studies of the chemical shifts occurring in propionic acid-dioxane solutions  

E-print Network

is added. , the dimers break up to form monomers. There i, s formed alternately a hydrogen bond between the monomer ac1d and the water, forming a complex. If the correlation times of the diner state aud oomplex water state ere sufficiently smallv... by Gutowskyv because now the products of the reaction are oonsMsred as contributing Co the shift ~ Here both the assoc1ated end unassoc1ated states have abort lifetimes. If $1 end f B are the shifts of the monomer and complex respectively, and Pj and p2...

Oldham, William J. Bryan

1958-01-01

310

[Dynamics of the hematological shifts in females during antiorthostatic hypokinesia].  

PubMed

The purpose of the present study was to perform comprehensive hematological investigations of females in a 120-day head-down (-5 degrees) bed rest and in the period of recovery. Morphometric, cytochemical parameters of erythrocytes and lymphocytes, erythropoietic activity and turnover of iron were analyzed in 8 female subjects assigned into two groups of 4. In group A, countermeasures were applied throughout the experiment; in group B, they were used only in the recovery period. Shifts observed in a number of parameters of the turnover of iron and morphometry of the blood cells are most likely adaptive by nature and demonstrate the reaction of blood to the hypokinesia and recovery factors. PMID:9156681

Ivanova, S M; Levina, A A; Novoderzhkina, I K; Sarycheva, T G; Belozerova, I N; Tsybul'skaia, M M; Karashtin, V V; Morukov, B V; Kozinets, G I

1997-01-01

311

Shift Work and Circadian Dysregulation of Reproduction  

PubMed Central

Health impairments, including reproductive issues, are associated with working nights or rotating shifts. For example, shift work has been associated with an increased risk of irregular menstrual cycles, endometriosis, infertility, miscarriage, low birth weight or pre-term delivery, and reduced incidence of breastfeeding. Based on what is known about circadian regulation of endocrine rhythms in rodents (and much less in humans), the circadian clock is an integral regulatory part of the reproductive system. When this 24-h program is disordered by environmental perturbation (such as shift work) or genetic alterations, the endocrine system can be impaired. The purpose of this review is to explore the hypothesis that misalignment of reproductive hormones with the environmental light-dark cycle and/or sleep-wake rhythms can disrupt menstrual cycles, pregnancy, and parturition. We highlight the role of the circadian clock in regulating human reproductive physiology and shift work-induced pathology within each step of the reproductive axis while exploring potential mechanisms from the animal model literature. In addition to documenting the reproductive hazards of shift work, we also point out important gaps in our knowledge as critical areas for future investigation. For example, future studies should examine whether forced desynchronization disrupts gonadotropin secretion rhythms and whether there are sleep/wake schedules that are better or worse for the adaptation of the reproductive system to shift work. These studies are necessary in order to define not only whether or not shift work-induced circadian misalignment impairs reproductive capacity, but also to identify strategies for the future that can minimize this desynchronization. PMID:23966978

Gamble, Karen L.; Resuehr, David; Johnson, Carl Hirschie

2013-01-01

312

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

313

arXiv:physics/0507062v18Jul2005 Improved calculation of relativistic shift and isotope shift in Mg I  

E-print Network

arXiv:physics/0507062v18Jul2005 Improved calculation of relativistic shift and isotope shift in Mg) We present an ab initio method of calculation of isotope shift and relativistic shift in atoms are needed to measure this variation of , while isotope shifts are needed to resolve systematic effects

Kozlov, Mikhail G

314

Iodine Clock Reaction  

NSDL National Science Digital Library

This site allows the user to vary initial solution concentration and temperature for the iodine clock reaction. A simulation of the reaction lets reaction times be measured. The data can then be used to determine the order of reaction for the various components.

315

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

316

Nozzle Aerodynamic Stability During a Throat Shift  

NASA Technical Reports Server (NTRS)

An experimental investigation was conducted on the internal aerodynamic stability of a family of two-dimensional (2-D) High Speed Civil Transport (HSCT) nozzle concepts. These nozzles function during takeoff as mixer-ejectors to meet acoustic requirements, and then convert to conventional high-performance convergent-divergent (CD) nozzles at cruise. The transition between takeoff mode and cruise mode results in the aerodynamic throat and the minimum cross-sectional area that controls the engine backpressure shifting location within the nozzle. The stability and steadiness of the nozzle aerodynamics during this so called throat shift process can directly affect the engine aerodynamic stability, and the mechanical design of the nozzle. The objective of the study was to determine if pressure spikes or other perturbations occurred during the throat shift process and, if so, identify the caused mechanisms for the perturbations. The two nozzle concepts modeled in the test program were the fixed chute (FC) and downstream mixer (DSM). These 2-D nozzles differ principally in that the FC has a large over-area between the forward throat and aft throat locations, while the DSM has an over-area of only about 10 percent. The conclusions were that engine mass flow and backpressure can be held constant simultaneously during nozzle throat shifts on this class of nozzles, and mode shifts can be accomplished at a constant mass flow and engine backpressure without upstream pressure perturbations.

Kawecki, Edwin J.; Ribeiro, Gregg L.

2005-01-01

317

Chemical Shift Prediction for Denatured Proteins  

PubMed Central

While chemical shift prediction has played an important role in aspects of protein NMR that include identification of secondary structure, generation of torsion angle constraints for structure determination, and assignment of resonances in spectra of intrinsically disordered proteins, interest has arisen more recently in using it in alternate assignment strategies for crosspeaks in 1H-15N HSQC spectra of sparsely labeled proteins. One such approach involves correlation of crosspeaks in the spectrum of the native protein with those observed in the spectrum of the denatured protein, followed by assignment of the peaks in the latter spectrum. As in the case of disordered proteins, predicted chemical shifts can aid in these assignments. Some previously developed empirical formulas for chemical shift prediction have depended on basis data sets of 20 pentapeptides. In each case the central residue was varied among the 20 amino common acids, with the flanking residues held constant throughout the given series. However, previous choices of solvent conditions and flanking residues make the parameters in these formulas less than ideal for general application to denatured proteins. Here, we report 1H and 15N shifts for a set of alanine based pentapeptides under the low pH urea denaturing conditions that are more appropriate for sparse label assignments. New parameters have been derived and a Perl script was created to facilitate comparison with other parameter sets. A small, but significant, improvement in shift predictions for denatured ubiquitin is demonstrated. PMID:23297019

Sahu, Sarata C.; Nkari, Wendy K.; Morris, Laura C.; Live, David; Gruta, Christian

2013-01-01

318

High Purity Hydrogen Production with In-Situ Carbon Dioxide and Sulfur Capture in a Single Stage Reactor  

Microsoft Academic Search

Enhancement in the production of high purity hydrogen (Hâ) from fuel gas, obtained from coal gasification, is limited by thermodynamics of the water gas shift (WGS) reaction. However, this constraint can be overcome by conducting the WGS in the presence of a COâ-acceptor. The continuous removal of COâ from the reaction mixture helps to drive the equilibrium-limited WGS reaction forward.

Nihar Phalak; Shwetha Ramkumar; Daniel Connell; Zhenchao Sun; Fu-Chen Yu; Niranjani Deshpande; Robert Statnick; Liang-Shih Fan

2011-01-01

319

Numerical analysis of electrical power generation and internal reforming characteristics in seal-less disk-type solid oxide fuel cells  

Microsoft Academic Search

For seal-less type solid oxide fuel cells, its power generation characteristics and distribution of the gas composition depend on not only the electrochemical reaction, but also complex kinetics and transport phenomena, because the internal reforming reaction and the water-gas shift reaction take place together with reverse diffusion of the ambient gas from the surroundings of the cell. The purpose of

Takanobu Shimada; Akihiko Momma; Kiyonami Takano; Tohru Kato

2009-01-01

320

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

321

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

322

Measurement of isotope shift in Eu II  

E-print Network

The isotope shift between singly-charged ^Eu and ^Eu in the 4f^7(^8S^o)6s^9S_4-4f^7(^8S^o)6p_1/2>(J=4) transition at 4129 A has been measured using fast ion beam-laser technique. This Eu line has attracted interest in connection with efforts of obtaining a cosmochronometer based on observed Th/Eu abundance ratios. Knowledge of the isotope shift is of importance in order to check that contaminations from line blends do not contribute to the line intensity of Eu II. The measured value of the isotope shift -0.1527(2) cm-1 (= -4578 MHz) is consistent with the old spectroscopic value of Krebs and Winkler -0.1503(25) cm-1 using a Fabry Perot interferometer, while the accuracy is improved substantially.

Lars Brostrom; Sven Mannervik; Peder Royen; Anders Wannstrom

1995-02-06

323

Understanding and diagnosing shift work disorder.  

PubMed

A significant proportion of the workforce in industrialized countries (16%) are employed as shift workers. These workers may be susceptible to shift work disorder (SWD), a circadian rhythm sleep disorder, particularly those who work at night or on early-morning shifts. Shift work disorder remains an underdiagnosed and undertreated problem among this population. Patients with SWD have difficulty initiating sleep and waking up. Often, these patients have excessive sleepiness during their work shift. Shift work disorder has been associated with decreased productivity, impaired safety, diminished quality of life, and adverse effects on health. Several tools have been validated to assess excessive daytime sleepiness and are often used to assess excessive nighttime sleepiness, such as that experienced in patients with SWD, including the Epworth Sleepiness Scale and the Multiple Sleep Latency Test. The criteria for diagnosing SWD as established by the American Academy of Sleep Medicine (AASM) and published in the International Classification of Sleep Disorders-Second Edition (ICSD-2) were most recently updated in 2005 and thus do not contain newer agents approved for use in patients with SWD. The symptoms of SWD can be treated using behavioral, prescription, and nonprescription therapies. Current treatment guidelines suggest nonpharmacologic interventions, such as exercise and exposure to light. In addition, medications that contain melatonin or caffeine may have clinical benefits in some patients with SWD. However, modafinil and armodafinil are approved by the US Food and Drug Administration to improve wakefulness in patients with excessive sleepiness associated with SWD, and recent data suggest a clinical benefit. The use of these therapies can significantly improve sleep, performance, and quality of life for patients with SWD. PMID:21904091

Thorpy, Michael

2011-09-01

324

Shift work in a security environment  

SciTech Connect

Human beings are diurnal species, normally active by day and asleep by night. Yet over thirty million Americans struggle with work schedules that include an off-normal work effort. The railroads, law enforcement, health services, Department of Defense, factory workers, chemical plants and public services, communications and utility workers must provide some form of around-the-clock effort. Shift work has been around since the advent of recorded history. There has always been a need for some type of off-normal service and assistance. The impact of shift work is replete with tales and factual evidence of an increased personnel error rate; disorders, both personal and family, and of course, increased accident events. In recent memory, the Three Mile Island Nuclear Plant incident, Union Carbide`s explosion in Bhopal, and the Chernobyl Nuclear Plant catastrophe all occurred during off-normal working hours. Yet management overall has done little to correct the production-driven twelve hour, seven day week shift mentality of the nineteenth century. Most schedules in use today are nothing more than cosmetic variations of the old production schedules. This could be driven by a management consideration of the worker`s response to change coupled with a reluctant buy-in of responsibility for the effects of change. Florida Power Corporation has developed for its nuclear security force, a unique work schedule which attempts to employ the sound principles of circadian rhythms coupled with a comprehensive training program to counter the problems associated with shift work. The results over the last four years have seen a marked reduction in the generic problems of personnel errors, absenteeism, unscheduled overtime and turnover rates. Utilization and understanding of this scheduling process for rotational shift work needs to be assessed to determine if the benefits are site specific or provide an expected response to the problems of shift work.

Longhouser, G.A. Jr. [Florida Power Corp., Crystal River, FL (United States)

1993-12-31

325

Gear shift controller for automatic transmission  

SciTech Connect

A gear shift controller is described for an automatic transmission having a gear shift, comprising: a hydraulic torque converter; a gear change group, having a plurality of gears, each gear providing a different transmission ratio for the transmission of power from the hydraulic torque converter to the output of the transmission, each of the gears comprising a gear train; a one-way clutch interposed in at least one of the gear trains; a plurality of clutch means operatively connected with the gear trains for actuating each of the gear trains selectively; a gear change determination circuit operatively connected with the clutch means to control the operation of each of the clutch means according to a predetermined gear shifting program for engaging a gear train selected by the program; a coasting detection circuit for detecting a car in the coasting state; a gear shift limiting circuit, operatively connected with the gear change determination circuit and with the coasting detection circuit. The circuit is for actuating only the gear train in which the one-way clutch is interposed immediately, regardless of the selected gear train and of the operation of the gear change determination circuit, when the coasting detection circuit has determined the car to be coasting; and an operation transfer control system including a brake operation detecting means and a mode selector switch means for transferring the operation of the gear shift limiting circuit. The operation transfer control system is adapted to stop, upon detection of one of the brake operation and a reset state of the mode selector switch, the operation of the gear shift limiting circuit and to place the plurality of clutch means under the control of the gear change determination circuit.

Nishikawa, M.; Sakai, S.; Sakurai, T.

1987-01-20

326

Team Proposes Paradigm Shift in Robotic Space Exploration Team Proposes Paradigm Shift in Robotic Space Exploration  

E-print Network

Team Proposes Paradigm Shift in Robotic Space Exploration Team Proposes Paradigm Shift in Robotic Space Exploration A team of interdisciplinary scientists has unveiled a proposal to make core changes in the robotic exploration of the solar system. In addition to spaceborne orbiters, the "new paradigm" would

Arizona, University of

327

Shift-and-add for astronomical imaging  

NASA Technical Reports Server (NTRS)

Diffraction-limited astronomical images have been obtained utilizing a variant of the shift-and-add method. It is shown that the matched filter approach for extending the weighted shift-and-add method reduces specklegrams from extended objects and from an object dominated by photon noise. The method is aberration-insensitive and yields very high dynamic range results. The iterative method for arriving at the matched filter does not automatically converge in the case of photon-noisy specklegrams for objects with more than one maximum.

Ribak, Erez; Hege, E. Keith; Strobel, Nicolas V.; Christou, Julian C.

1989-01-01

328

Model-based phase shifting interferometry.  

PubMed

A general method of surface profiling with phase-shifting interferometry techniques uses iterative linear regression to fit the sequence of interferograms to a physical model of the cavity. The physical model incorporates all important cavity influences, including environmentally induced rigid-body motion, phase shifter miscalibrations, multiple interference, geometry-induced spatial phase-shift variations, and their cross-couplings. By incorporating an initial estimate of the surface profile and iteratively solving for space- and time-dependent variables separately, convergence is robust and rapid. The technique has no restriction on surface shape or departure. PMID:25090197

Deck, Leslie L

2014-07-20

329

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

330

Thermometry via Light Shifts in Optical Lattices  

E-print Network

For atoms or molecules in optical lattices, conventional thermometry methods are often unsuitable due to low particle numbers or a lack of cycling transitions. However, a differential spectroscopic light shift can map temperature onto the line shape with a low sensitivity to trap anharmonicity. We study narrow molecular transitions to demonstrate precise frequency-based lattice thermometry, as well as carrier cooling. This approach should be applicable down to nanokelvin temperatures. We also discuss how the thermal light shift can affect the accuracy of optical lattice clocks.

Mickey McDonald; Bart H. McGuyer; Geoffrey Z. Iwata; Tanya Zelevinsky

2015-03-02

331

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

332

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

333

Thermometry via Light Shifts in Optical Lattices  

NASA Astrophysics Data System (ADS)

For atoms or molecules in optical lattices, conventional thermometry methods are often unsuitable due to low particle numbers or a lack of cycling transitions. However, a differential spectroscopic light shift can map temperature onto the line shape with a low sensitivity to trap anharmonicity. We study narrow molecular transitions to demonstrate precise frequency-based lattice thermometry, as well as carrier cooling. This approach should be applicable down to nanokelvin temperatures. We also discuss how the thermal light shift can affect the accuracy of optical lattice clocks.

McDonald, M.; McGuyer, B. H.; Iwata, G. Z.; Zelevinsky, T.

2015-01-01

334

Thermometry via light shifts in optical lattices.  

PubMed

For atoms or molecules in optical lattices, conventional thermometry methods are often unsuitable due to low particle numbers or a lack of cycling transitions. However, a differential spectroscopic light shift can map temperature onto the line shape with a low sensitivity to trap anharmonicity. We study narrow molecular transitions to demonstrate precise frequency-based lattice thermometry, as well as carrier cooling. This approach should be applicable down to nanokelvin temperatures. We also discuss how the thermal light shift can affect the accuracy of optical lattice clocks. PMID:25635543

McDonald, M; McGuyer, B H; Iwata, G Z; Zelevinsky, T

2015-01-16

335

Power Assist H? Control of Shift Lever with Spring Connected Link  

NASA Astrophysics Data System (ADS)

We have developed the shift lever with a spring connected link. It can detect the reaction force to the operator by using inexpensive displacement sensors such as potentiometers. For this system, we propose a model-based power assist control method. The proposed control system is composed of a reference generator and a feedback controller. The reference generator is introduced to generate an ideal reaction force to the operator. The feedback controller is designed by H? control theory to achieve disturbance attenuation. The effectiveness of the proposed method is shown by experiments.

Hirata, Mitsuo; Ogiwara, Tsutomu; Okamoto, Hitoshi; Adachi, Shuichi; Osamura, Kensuke; Kobayashi, Shinya

336

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

337

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 (Fe{sub 2}O{sub 3} and Al{sub 2}O{sub 3}), 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.

KRUGER AA; HRMA PR; POKORNY R

2011-07-29

338

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

339

A paradigm shift in the conceptualization of psychological trauma in the 20th century  

Microsoft Academic Search

The inclusion of posttraumatic stress disorder (PTSD) in DSM-III in 1980 represented a paradigm shift in the conceptualisation of post-trauma illness. Hitherto, a normal psychological reaction to a terrifying event was considered short-term and reversible. Long-term effects, characterized as “traumatic neurosis”, were regarded as abnormal. Enduring symptoms were explained in terms of hereditary predisposition, early maladaptive experiences or a pre-existing

Edgar Jones; Simon Wessely

2007-01-01

340

Shape resonances in ion-molecule reaction  

NASA Astrophysics Data System (ADS)

A simple analytical formula for the probability of reaction in low-energy ion-molecule collisions is given by Wentzel-Kramers-Brillouin and uniform approximations. By using this formula, one can deal with any type of shape resonances regardless of whether the collision energy is below or above a potential barrier. The reaction probability is completely determined by three parameters: the high-energy limit (P0) of the reaction probability obtained at a collision energy much above the potential barrier, a universal measure (?) of the difference between the collision energy and the barrier top, and a scattering phase shift (?) due to short-range reactive interaction. It is very useful to draw a topographical map of the reaction probability by assuming that P0 is given as a constant and that (?, ?) are independent variables. The energy dependence of the reaction probability in a collision process is represented by the section view along a route actually allowed on this topographical map. A resonance structure appears when the actual route crosses a prominent mountain ridge. It is shown that the reaction probability can be unity at a resonance energy even if the probabilities at off-resonance energies are very small. No sharp tunnelling resonance would be expected in the collision system having P_{0}>2(\\sqrt{2}-1)=0.828.

Sakimoto, Kazuhiro

2014-01-01

341

Rearrangement Reactions Catalyzed by Cytochrome P450s  

PubMed Central

Cytochrome P450s promote a variety of rearrangement reactions both as a consequence of the nature of the radical and other intermediates generated during catalysis, and of the neighboring structures in the substrate that can interact either with the initial radical intermediates or with further downstream products of the reactions. This article will review several kinds of previously published cytochrome P450-catalyzed rearrangement reactions, including changes in stereochemistry, radical clock reactions, allylic rearrangements, “NIH” and related shifts, ring contractions and expansions, and cyclizations that result from neighboring group interactions. Although most of these reactions can be carried out by many members of the cytochrome P450 superfamily, some have only been observed with select P450s, including some reactions that are catalyzed by specific endoperoxidases and cytochrome P450s found in plants. PMID:20971058

Ortiz de Montellano, Paul R.; Nelson, Sidney D.

2010-01-01

342

Regime shifts in the Humboldt Current ecosystem  

Microsoft Academic Search

Of the four major eastern boundary currents, the Humboldt Current (HC) stands out because it is extremely productive, dominated by anchovy dynamics and subject to frequent direct environmental perturbations of the El Niño Southern Oscillation (ENSO). The long-term dynamics of the HC ecosystem are controlled by shifts between alternating anchovy and sardine regimes that restructure the entire ecosystem from phytoplankton

Jürgen Alheit; Miguel Niquen

2004-01-01

343

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

344

Shift factors in ERCOT congestion pricing  

E-print Network

Shift factors in ERCOT congestion pricing Ross Baldick* March 5, 2003 1. Introduction In this paper. In section 2, I begin with a brief discussion of the role of congestion pricing. In section 3, I first. Objectives of Congestion Pricing The objectives of congestion pricing include (Oren, 2002):1 1. efficient use

Baldick, Ross

345

A Paradigm Shift to Improve Academic Performance  

ERIC Educational Resources Information Center

A shift to computer skills for improving academic performances was investigated. The No Child Left Behind Act of 2001 increased the amount of high school dropouts after the Act was enacted. At-risk students were included in this research study. Several models described using teachers for core subjects and mentors to built citizenship skills, along…

Rulloda, Rudolfo B.

2009-01-01

346

Measurement of the Lamb Shift in Muonium.  

NASA Astrophysics Data System (ADS)

This thesis describes the first measurement of the Lamb shift in n = 2 muonium. The muonium atom is a hydrogen-like bound state of two leptons ((mu)('+)e('-)), both of which are believed to be point-like particles. The point-like nature of the constituent particles simplifies and reduces the uncertainty of the application of quantum electro- dynamics (QED) to the calculation of the Lamb shift in the muonium atom. Measurements of the Lamb shift in hydrogen disagree with the predictions of theory by a few standard deviations; however, theo- retical predictions also disagree with each other, partly because of difficulties associated with the treatment of the proton structure. Thus a measurement in the muonium system of similar precision to those already made in the hydrogen system will be a valuable test of QED. This experiment is an investigation of the methods and tech- niques necessary to surmount the difficulties presented by the nature of muonium. The available number of muonium atoms is about 10('+10). times less than that of hydrogen used by Lamb in his first measure- ment. The value obtained for the n = 2 muonium Lamb shift. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). The uncertainty quoted is statistical at the 68% confidence level. Systematic effects were found to contribute a further 2 MHz uncertainty.

Fry, Charles Alan

347

Digital control for phase shift converter  

Microsoft Academic Search

The development of intelligent microgrids with renewable energy sources increased significantly nowadays. The present paper examines and compares analog and digital control of a bidirectional phase shift converter in order to find out which is best suited to be used in intelligent microgrid applications. New small signal models for the direct and reverse power flow transfer modes of the converter

R. Etz; T. Patarau; D. Petreus; S. Daraban; D. Moga

2012-01-01

348

NMR crystallography: the use of chemical shifts  

NASA Astrophysics Data System (ADS)

Measurements of chemical shifts obtained from magic-angle spinning NMR spectra (together with quantum mechanical computations of shielding) can provide valuable information on crystallography. Examples are given of the determination of crystallographic asymmetric units, of molecular symmetry in the solid-state environment, and of crystallographic space group assignment. Measurements of full tensor components for 199Hg have given additional coordination information. The nature of intermolecular hydrogen bonding in cortisone acetate polymorphs and solvates is obtained from chemical shift information, also involving measurement of the full tensor parameters. The resulting data have been used as restraints, built into the computation algorithm, in the analysis of powder diffraction patterns to give full crystal structures. A combination of quantum mechanical computation of shielding and measurement of proton chemical shifts (obtained by high-speed MAS) leads to the determination of the position of a proton in an intermolecular hydrogen bond. A recently-developed computer program specifically based on crystallographic repetition has been shown to give acceptable results. Moreover, NMR chemical shifts can distinguish between static and dynamic disorder in crystalline materials and can be used to determine modes and rates of molecular exchange motion.

Harris, Robin K.

2004-10-01

349

Implications of Shifting Technology in Education  

ERIC Educational Resources Information Center

This article examines the implications of shifting technology trends by looking at what we've lost or are losing, where we are, and where we need to go for making the needed transitions in knowledge and skills. Areas of growth within new media and the tech industry are good indicators of our growing interests in mobility, improved quality,…

Holland, Janet; Holland, John

2014-01-01

350

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

351

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

352

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

353

Shifting perceptions of age in voice  

Microsoft Academic Search

A series of experiments have been carried out in order to identify the acoustical and perceptual correlates of the aging voice. The initial phase of the program was to identify those voice parameters which signal a person's age; the second phase was to systematically shift these parameters in order to determine if a parallel change in perceived age would occur.

Rahul Shrivastav; Harry Hollien; W. S. Brown; Howard B. Rothman; James D. Harnsberger

2003-01-01

354

Structured Intramurals: Shifting Values and Directions.  

ERIC Educational Resources Information Center

Two concurrent developments have led to widespread shifts in the directions of structured intramural programs in higher education. Several universities place an emphasis on student development through administrative leadership training and participation in the governing process of intramural athletic departments. Student duties may include…

Rokosz, Francis M.

355

The Knight shift of francium in cesium  

Microsoft Academic Search

Using the PAD technique the Knight shift for Fr in Cs at 273 K has been measured with the 15? isomer in212Fr. The result 4.9(3)% may be well understood in terms of the conventional analysis. A dominant correction for relativistic effects is the prime source for the extraordinarily large value.

H. Haas; H.-E. Mahnke; W. G. Shen; Ch. Stenzel

1987-01-01

356

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

357

Blackbody radiation shifts in optical atomic clocks.  

PubMed

A review of recent theoretical calculations of blackbody radiation (BBR) shifts in optical atomic clocks is presented. We summarize previous results for monovalent ions that were obtained by a relativistic all-order single-double method, where all single and double excitations of the Dirac- Fock wave function are included to all orders of perturbation theory. A recently developed method for accurate calculations of BBR shifts in divalent atoms is then presented. This approach combines the relativistic all-order method and the configuration interaction method, which provides for accurate treatment of correlation corrections in atoms with two valence electrons. Calculations of the BBR shifts in B+, Al+, and In+ have enabled us to reduce the present fractional uncertainties in the frequencies of their clock transitions as measured at room temperature: to 4 × 10-19 for Al+ and 10-18 for B+ and In+. These uncertainties approach recent estimates of the limits of precision of currently proposed optical atomic clocks. We discuss directions of future theoretical developments for reducing clock uncertainties resulting from blackbody radiation shifts. PMID:22481777

Safronova, Marianna; Kozlov, Mikhail; Clark, Charles

2012-03-01

358

Collisionally Induced Atomic Clock Shifts and Correlations  

E-print Network

We develop a formalism to incorporate exchange symmetry considerations into the calculation of collisional frequency shifts and blackbody radiation effects for atomic clock transitions using a density matrix formalism. The formalism is developed for both fermionic and bosonic atomic clocks. Results for a finite temperature ${}^{87}$Sr ${}^1S_0$ ($F = 9/2$) atomic clock in a magic wavelength optical lattice are presented.

Y. B. Band; I. Osherov

2011-06-23

359

Exact phase shifts for atom interferometry  

Microsoft Academic Search

In the case of an external Hamiltonian at most quadratic in position and momentum operators, we use the ABCD? formulation of atom optics to establish an exact analytical phase shift expression for atom interferometers with arbitrary spatial or temporal beam splitter configurations. This result is expressed in terms of coordinates and momenta of the wave packet centers at the interaction

Ch. Antoine; Ch. J. Bordé

2003-01-01

360

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

361

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

362

The Value Shift of the Russian Greens  

Microsoft Academic Search

The Green movement in the USSR\\/Russia has existed for more than forty years. During this period, seven groups have been shaped and consolidated within the movement (the conservationists, the alternativists, the traditionalists, the civil initiatives, the ecopoliticians, the ecopatriots, and the ecotechnocrats). The aim of this article is to consider the value shift each group underwent during the decade 1992–2001

Oleg Yanitsky

2005-01-01

363

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

364

Attention-Shifting in Frederick Douglass.  

ERIC Educational Resources Information Center

A study explored rhetorical strategies and dynamics within a single speech delivered by Frederick Douglass on July 5, l852 in Rochester, New York, which was considered by speaker and audience to be an Independence Day speech. An examination of the text suggests that Douglass embarked on a strategy of attention-shifting--turning the attention of…

Leroux, Neil R.

365

Chapter Number Amplitude Phase Shift Keying Constellation  

E-print Network

exceeding 1 Gbps. In this regard, Amplitude Phase Shift Keying (APSK) represents an attractive modulation efficiency combined with its inherent robustness against nonlinear distortion. The concept of circular APSK] but, at that time, it was concluded that APSK performs worse than PSK schemes for single carrier

Guillén i Fàbregas, Albert

366

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

367

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

368

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

369

Continuous detonation reaction engine  

NASA Technical Reports Server (NTRS)

Reaction engine operates on the principles of a controlled condensed detonation rather than on the principles of gas expansion. The detonation results in reaction products that are expelled at a much higher velocity.

Lange, O. H.; Stein, R. J.; Tubbs, H. E.

1968-01-01

370

Pulmonary Transfusion Reactions  

PubMed Central

Summary Background In recent years, pulmonary transfusion reactions have gained increasing importance as serious adverse transfusion events. Methods Review of the literature. Results Pulmonary transfusion reactions are not extremely rare and, according to hemovigilance data, important causes of transfusion-induced major morbidity and death. They can be classified as primary with predominant pulmonary injury and secondary as part of another transfusion reaction. Primary reactions include transfusion-related acute lung injury (TRALI), transfusion-associated circulatory overload (TACO) and transfusion-associated dyspnea (TAD). Secondary pulmonary reactions are often observed in the wake of hemolytic transfusion reactions, hypotensive/anaphylactic reactions, and transfusion-transmitted bacterial infections. Conclusion Knowledge and careful management of cases of pulmonary transfusion reactions are essential for correct reporting to blood services and hemovigilance systems. Careful differentiation between TRALI and TACO is important for taking adequate preventive measures. PMID:21512622

Bux, Jürgen; Sachs, Ulrich J. H.

2008-01-01

371

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

372

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

373

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.

374

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

375

Author's personal copy Properties of human eye-head gaze shifts in an anti-gaze shift task  

E-print Network

(head- in-space). Extensive research into saccadic eye movements has produced a refined understandingAuthor's personal copy Properties of human eye-head gaze shifts in an anti-gaze shift task Brendan investigated the metrics and kinematics of human eye-head gaze shifts using the anti-gaze shift task

Corneil, Brian D.

376

Postweld-shift-induced fiber alignment shifts in laser-welded laser module packages: experiments and simulations  

Microsoft Academic Search

The fiber alignment shifts induced by the postweld shift (PWS) in laser-welded transistor outline (TO)-Can-type laser module packages were studied experimentally and numerically. The PWS-induced fiber alignment shifts were quantitatively determined by four geometrical parameters, namely: 1) the lateral shift (r); 2) the position angle (?); 3) the swing angle (?); and 4) the tilt angle (?). The measured coupling

Yi-Cheng Hsu; Ying-Chien Tsai; Jao-Hwa Kuang; Wood-Hi Cheng

2005-01-01

377

Transitional Bubble in Periodic Flow Phase Shift  

NASA Technical Reports Server (NTRS)

One particular characteristic observed in unsteady shear layers is the phase shift relative to the main flow. In attached boundary layers this will have an effect both on the instantaneous skin friction and heat transfer. In separation bubbles the contribution to the drag is dominated by the pressure distribution. However, the most significant effect appears to be the phase shift on the transition process. Unsteady transition behaviour may determine the bursting of the bubble resulting in an un-recoverable full separation. An early analysis of the phase shift was performed by Stokes for the incompressible boundary layer of an oscillating wall and an oscillating main flow. An amplitude overshoot within the shear layer as well as a phase shift were observed that can be attributed to the relatively slow diffusion of viscous stresses compared to the fast change of pressure. Experiments in a low speed facility with the boundary layer of a flat plate were evaluated in respect to phase shift. A pressure distribution similar to that on the suction surface of a turbomachinery aerofoil was superimposed generating a typical transitional separation bubble. A periodically unsteady main flow in the suction type wind tunnel was introduced via a rotating flap downstream of the test section. The experiments covered a range of the three similarity parameters of momentum-loss-thickness Reynolds-number of 92 to 226 and Strouhal-number (reduced frequency) of 0.0001 to 0.0004 at the separation point, and an amplitude range up to 19 %. The free stream turbulence level was less than 1% .Upstream of the separation point the phase shift in the laminar boundary layer does not appear to be affected significantly bay either of the three parameters. The trend perpendicular to the wall is similar to the Stokes analysis. The problem scales well with the wave velocity introduced by Stokes, however, the lag of the main flow near the wall is less than indicated analytically. The separation point comes closest to the Stokes analysis but the phase is still 20 degrees lower at the wall.

Talan, M.; Hourmouziadis, Jean

2004-01-01

378

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

379

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.

380

Adapting to phase shifts, I. An experimental model for jet lag and shift work  

Microsoft Academic Search

An experimental model was developed to measure various behavioral and physiological parameters in a laboratory paradigm mimicking phase shifts that could occur in time-zone transitions and shift work rotas. Volunteers were exposed to 9-h pulses of bright light (1,200 1x) as follows: day (D)1: 1800-0300 h, D2: 2100-0600 h, and D3, 4, 5: 2400-0900 h, each period followd by 8

Stephen Deacon; Josephine Arendt

1996-01-01

381

Nucleon Polarizability Contribution to the Hydrogen Lamb Shift and Hydrogen -- Deuterium Isotope Shift  

E-print Network

The correction to the hydrogen Lamb shift due to the proton electric and magnetic polarizabilities is expressed analytically through their static values, which are known from experiment. The numerical value of the correction to the hydrogen 1S state is $ - 71 \\pm 11 \\pm 7$ Hz. Correction to the H-D 1S-2S -- isotope shift due to the proton and neutron polarizabilities is estimated as $ 53 \\pm 9 \\pm 11$ Hz.

I. B. Khriplovich; R. A. Sen'kov

1998-09-30

382

Reaction efficiency effects on binary chemical reactions  

NASA Astrophysics Data System (ADS)

We study the effect of the variation of reaction efficiency in binary reactions. We use the well-known A + B ? 0 model, which has been extensively studied in the past. We perform simulations on this model where we vary the efficiency of reaction, i.e., when two particles meet they do not instantly react, as has been assumed in previous studies, but they react with a probability ?, where ? is in the range 0 < ? < 1. Our results show that at small ? values the system is reaction limited, but as ? increases it crosses over to a diffusion limited behavior. At early times, for small ? values, the particle density falls slower than for larger ? values. This fall-off goes over a crossover point, around the value of ? = 0.50 for high initial densities. Under a variety of conditions simulated, we find that the crossover point was dependent on the initial concentration but not on the lattice size. For intermediate and long times simulations, all ? values (in the depleted reciprocal density versus time plot) converge to the same behavior. These theoretical results are useful in models of epidemic reactions and epidemic spreading, where a contagion from one neighbor to the next is not always successful but proceeds with a certain probability, an analogous effect with the reaction probability examined in the current work.

Lazaridis, Filippos; Savara, Aditya; Argyrakis, Panos

2014-09-01

383

A microdroplet-based shift register.  

PubMed

A microfluidic device is presented for the serial formation, storage and retrieval of water microdroplets in oil. The principle of operation is similar to that of an electronic shift register. Droplets, considered as units of information, can be arrayed and serially shifted within the device, allowing the controllable positioning of the emulsions and the creation of interfaces between drops. Using this passive system, by exploiting the balance between hydrodynamic pressure and surface tension across a drop due to the device design, droplet networks can be readily arrayed in a series of elements and cascaded within the microchannels in an automatable and high throughput fashion. The results showed the suitability of the system to be used for the formation of artificial lipid bilayers and for the study of biological dynamic processes based on the diffusion of molecules through interfaces. PMID:20856984

Zagnoni, Michele; Cooper, Jonathan M

2010-11-21

384

Critical point shifts in binary fluid mixtures  

NASA Astrophysics Data System (ADS)

An empirical observation is made of an apparent universal shift in the consolute point (Xc=critical composition, Tc=critical temperature) of binary fluid mixtures when the system identity is perturbed. The shift in a ``pure'' system's critical point (Xco, Tco) when perturbed becomes (Xc,Tc) which seems to obey (Tc-Tco)/Tco= (Xc-Xco)/Xco. This relation has been observed to hold in a wide range of systems including closed-loop coexistence curves (guaiacol-glycerol-water, or tertiary butyl alcohol in secondary butyl alcohol and water), deuterated systems (methanol-cyclohexane, or isobutyric acid-water), impurities added to methanol-cyclohexane, the molecular weight dependence in polystyrene-methylcyclohexane, and the pressure dependence of methanol-cyclohexane.

Jacobs, D. T.

1989-07-01

385

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

386

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

387

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

388

Correlation effects on specific isotope shifts  

Microsoft Academic Search

A practical method of obtaining compact atomic non-relativistic wavefunctions adapted to the 2nd order calculation of expectation values of mono- and bi-electronic operators is described. Specific isotope shifts are thus calculated: as a test for the method, in He I 1s2p for which the exact values are known; in Mg I or the virtual transition 3s3p 1P-3P.

J. J. Labarthe

1973-01-01

389

Measurements of isotope shifts in Mg I  

Microsoft Academic Search

The isotope shift in the Mg I transitions lambdalambda 5167, 5172 and 5183 Å (3s3p3P - 3s4s3S) and lambda 5528 Å (3s3p1P - 3s4d1D) has been measured for the isotopes 24Mg, 25Mg and 26Mg. The measurements were carried out with separated isotopes using a scanning Fabry-Perot interferometer.

L. Hallstadius; J. E. Hansen

1977-01-01

390

Collisionally induced atomic clock shifts and correlations  

SciTech Connect

We develop a formalism to incorporate exchange symmetry considerations into the calculation of collisional frequency shifts for atomic clocks using a density-matrix formalism. The formalism is developed for both fermionic and bosonic atomic clocks. Numerical results for a finite-temperature {sup 87}Sr {sup 1}S{sub 0} (F=9/2) atomic clock in a magic wavelength optical lattice are presented.

Band, Y. B.; Osherov, I. [Departments of Chemistry and Electro-Optics and the Ilse Katz Center for Nano-Science, Ben-Gurion University, Beer-Sheva 84105 (Israel)

2011-07-15

391

The muonic hydrogen Lamb-shift experiment  

Microsoft Academic Search

The charge radius of the proton, the simplest nucleus, is known from electron-scattering experiments only with a surprisingly low precision of about 2%. The poor knowledge of the proton charge radius restricts tests of bound-state quantum electrodynamics (QED) to the precision level of about 6 x 10(-6), although the experimental data themselves (1S Lamb shift in hydrogen) have reached a

A. Antognini; F. D. Amaro; F. Biraben; J. M. R. Cardoso; C. A. N. Conde; A. Dax; S. Dhawan; L. M. P. Fernandes; T. W. Hansch; F. J. Hartmann; V. W. Hughes; O. Huot; P. Indelicato; L. Julien; P. Knowles; F. Kottmann; Y. W. Liu; L. Ludhova; C. M. B. Monteiro; F. Mulhauser; F. Nez; P. Rabinowitz; J. M. F. Dos Santos; L. A. Schaller; C. Schwob; D. Taqqu; Jf. C. A. Veloso

2005-01-01

392

Phase shift cavity ring down absorption spectroscopy  

Microsoft Academic Search

Cavity ring down absorption spectroscopy with a continuous light source is used to measure the transition frequencies and absolute absorption coefficient of the weak b1?g+(v? = 2) ? X 3?g?(v? = 0) transition of 18O2. The absorption spectrum is extracted from a measurement of the magnitude of the phase shift that an intensity modulated continuous light beam experiences upon passing

Richard Engeln; Gert von Helden; Giel Berden; Gerard Meijer

1996-01-01

393

Unbiased shifts of Brownian motion Gunter Last  

E-print Network

= (Bt)tR be a two-sided standard Brownian motion. An unbiased shift of B is a random time T, which is a measurable function of B, such that (BT+t -BT )tR is a Brownian motion independent of BT . We characterise distribution on R we construct a stopping time T 0 with the above properties such that BT has distribution

394

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

395

Age Differences in Strategy Shift: Retrieval Avoidance or General Shift Reluctance?  

PubMed Central

Previous studies of metacognitive age differences in skill acquisition strategies have relied exclusively on tasks with a processing shift from an algorithm to retrieval strategy. Older adults’ demonstrated reluctance to shift strategies in such tasks could reflect either a specific aversion to a memory retrieval strategy or a general, inertial resistance to strategy change. Haider and Frensch’s (1999) alphabet verification task (AVT) affords a non-retrieval-based strategy shift. Participants verify the continuation of alphabet strings such as D E F G [4] L, with the bracketed digit indicating a number of letters to be skipped. When all deviations are restricted to the letter-digit-letter portion, participants can speed their responses by selectively attend only to that part of the stimulus. We adapted the AVT to include conditions which promoted shift to a retrieval strategy, a selective attention strategy, or both strategies. Item-level strategy reports were validated by eye movement data. Older adults shifted more slowly to the retrieval strategy but more quickly to the selective attention strategy than young adults, indicating a retrieval-strategy avoidance. Strategy confidence and perceived strategy difficulty correlated with shift to the two strategies in both age groups. Perceived speed of responses with each strategy specifically correlated with older adults’ strategy choices, suggesting that some older adults avoid retrieval because they do not appreciate its efficiency benefits. PMID:23088195

Frank, David J.; Touron, Dayna R.; Hertzog, Christopher

2013-01-01

396

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

397

Projecting the risk of future climate shifts  

NASA Astrophysics Data System (ADS)

Recent research has shown that decadal-to-multidecadal (D2M) climate variability is associated with environmental changes that have important consequences for human activities, such as public health, water availability, frequency of hurricanes, and so forth. As scientists, how do we convert these relationships into decision support products useful to water managers, insurance actuaries, and others, whose principal interest lies in knowing when future climate regime shifts will likely occur that affect long-horizon decisions? Unfortunately, numerical models are far from being able to make deterministic predictions for future D2M climate shifts. However, the recent development of paleoclimate reconstructions of the Atlantic Multidecadal Oscillation (AMO) (Gray et al., [2004]) and Pacific Decadal Oscillation (PDO); (MacDonald and Case, [2005]) give us a viable alternative: to estimate probability distribution functions from long climate index series that allow us to calculate the probability of future D2M regime shifts. In this paper, we show how probabilistic projections can be developed for a specific climate mode - the AMO as represented by the Gray et al. ([2004]) tree-ring reconstruction. The methods are robust and can be applied to any D2M climate mode for which a sufficiently long index series exists, as well as to the growing body of paleo-proxy reconstructions that have become available. The target index need not be a paleo-proxy calibrated against a climate index; it may profitably be calibrated against a specific resource of interest, such as stream flow or lake levels.

Enfield, David B.; Cid-Serrano, Luis

2006-06-01

398

Set shifting training with categorization tasks.  

PubMed

The very few cognitive training studies targeting an important executive function, set shifting, have reported performance improvements that also generalized to untrained tasks. The present randomized controlled trial extends set shifting training research by comparing previously used cued training with uncued training. A computerized adaptation of the Wisconsin Card Sorting Test was utilized as the training task in a pretest-posttest experimental design involving three groups of university students. One group received uncued training (n?=?14), another received cued training (n?=?14) and the control group (n?=?14) only participated in pre- and posttests. The uncued training group showed posttraining performance increases on their training task, but neither training group showed statistically significant transfer effects. Nevertheless, comparison of effect sizes for transfer effects indicated that our results did not differ significantly from the previous studies. Our results suggest that the cognitive effects of computerized set shifting training are mostly task-specific, and would preclude any robust generalization effects with this training. PMID:24324717

Soveri, Anna; Waris, Otto; Laine, Matti

2013-01-01

399

Is there a shift to “active nanostructures”?  

PubMed Central

It has been suggested that an important transition in the long-run trajectory of nanotechnology development is a shift from passive to active nanostructures. Such a shift could present different or increased societal impacts and require new approaches for risk assessment. An active nanostructure “changes or evolves its state during its operation,” according to the National Science Foundation’s (2006) Active Nanostructures and Nanosystems grant solicitation. Active nanostructure examples include nanoelectromechanical systems (NEMS), nanomachines, self-healing materials, targeted drugs and chemicals, energy storage devices, and sensors. This article considers two questions: (a) Is there a “shift” to active nanostructures? (b) How can we characterize the prototypical areas into which active nanostructures may emerge? We build upon the NSF definition of active nanostructures to develop a research publication search strategy, with a particular intent to distinguish between passive and active nanotechnologies. We perform bibliometric analyses and describe the main publication trends from 1995 to 2008. We then describe the prototypes of research that emerge based on reading the abstracts and review papers encountered in our search. Preliminary results suggest that there is a sharp rise in active nanostructures publications in 2006, and this rise is maintained in 2007 and through to early 2008. We present a typology that can be used to describe the kind of active nanostructures that may be commercialized and regulated in the future. PMID:21170117

Youtie, Jan; Porter, Alan L.; Shapira, Philip

2009-01-01

400

Atomic clocks with suppressed blackbody radiation shift.  

PubMed

We develop a concept of atomic clocks where the blackbody radiation shift and its fluctuations can be suppressed by 1-3 orders of magnitude independent of the environmental temperature. The suppression is based on the fact that in a system with two accessible clock transitions (with frequencies ?1 and ?2) which are exposed to the same thermal environment, there exists a "synthetic" frequency ?(syn) ? (?1 - ?12?2) largely immune to the blackbody radiation shift. For example, in the case of 171Yb+ it is possible to create a synthetic-frequency-based clock in which the fractional blackbody radiation shift can be suppressed to the level of 10(-18) in a broad interval near room temperature (300±15??K). We also propose a realization of our method with the use of an optical frequency comb generator stabilized to both frequencies ?1 and ?2, where the frequency ?(syn) is generated as one of the components of the comb spectrum. PMID:21838344

Yudin, V I; Taichenachev, A V; Okhapkin, M V; Bagayev, S N; Tamm, Chr; Peik, E; Huntemann, N; Mehlstäubler, T E; Riehle, F

2011-07-15

401

Theoretical isotope shifts in neutral barium  

NASA Astrophysics Data System (ADS)

The present work deals with a set of problems in isotope shifts of neutral barium spectral lines. Some well-known transitions (6 s2 1S0-6 s 6 p 1,3P1o and 6 s2 1S0-6 p2 3P0) are 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 {? 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 6 s 5 d 3D1 ,2-6 s 6 p 1P1o transitions produces isotope shift values in conflict with the laser spectroscopy measurements of U. Dammalapati et al. [Eur. Phys. J. D 53, 1 (2009), 10.1140/epjd/e2009-00076-x].

Nazé, C.; Li, J. G.; Godefroid, M.

2015-03-01

402

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

403

A phenomenological view of language shift.  

PubMed

Sociolinguistic studies of language shift have in their majority framed their research object in a horizon of theoretically received variables such as class, ethnicity, locality, attitudes etc. In spite of a limited usefulness of such conceptual variables, and of a recently emerging focus on agency, negotiation, and praxis the best results we obtain have not questioned in a coherent and theoretically sound manner the continuing hegemony of mechanistic-metaphorical models (language death, language suicide). In this paper I propose to examine language shift as a multifaceted phenomenon, joining in this respect work by other linguistic anthropologists researching similar areas. I specifically argue that by replacing vertical concepts such as age and generation, and dichotomous logics such as center and periphery with phenomenologically inspired concepts such as typifications, consociateship, contemporariness, and stream of consciousness we are in a better position to generalize about language shift dynamics. Data for this work is derived primarily from the Albanian speech communities of modern Greece, but also from other communities for comparative purposes. PMID:15156728

Tsitsipis, Lukas D

2004-01-01

404

Mechanisms in knockout reactions  

E-print Network

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 $^9$Be($^9$C,$^8$B+X)Y and $^9$Be($^8$B,$^7$Be+X)Y are presented. They are compared with theoretical predictions for both the diffraction and stripping 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.

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

2009-02-16

405

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

E-print Network

electrolyte concentrations in EA, reaction rates in solutions follow the Arrhenius-type temperature dependence considered is 267­343 K. The temperature dependent spectral peak shifts and reaction driving force - Gr to be in very good agreement with the predicted value based on data in room temperature solvents. While the rate

Biswas, Ranjit

406

A classification of nursing and midwifery shift systems.  

PubMed

A classification of 122 shift systems worked by nurses and midwives in the larger general hospitals (400+ beds) in England and Wales was made. The systems were classified along two main dimensions: the degree of flexibility for shift rostering (either regular, irregular or flexible); and the speed of rotation between night and day work (either a permanent night shift or systems of fast or slow internal rotation). This resulted in nine possible categories of shift systems. The most common shift system was a flexible day shift with a permanent night shift. Other features of the systems are discussed, e.g. the start times and durations of shifts, and the relative influence of flexible rostering on these features. This classification is a prerequisite for a further research project aimed at identifying those features of shift systems which are likely to cause the least detrimental effects for the individual nurses concerned. PMID:8449659

Barton, J; Spelten, E R; Smith, L R; Totterdell, P A; Folkard, S

1993-02-01

407

How orbital angular momentum affects beam shifts in optical reflection  

SciTech Connect

It is well known that reflection of a Gaussian light beam (TEM{sub 00}) by a planar dielectric interface leads to four beam shifts when compared to the geometrical-optics prediction. These are the spatial Goos-Haenchen (GH) shift, the angular GH shift, the spatial Imbert-Fedorov (IF) shift, and the angular IF shift. We report here, theoretically and experimentally, that endowing the beam with orbital angular momentum leads to coupling of these four shifts; this is described by a 4x4 mixing matrix.

Merano, M.; Hermosa, N.; Woerdman, J. P.; Aiello, A. [Huygens Laboratory, Leiden University, P.O. Box 9504, NL-2300 RA Leiden (Netherlands); Max Planck Institute for the Science of Light, Guenter-Scharowsky-Strasse 1/Bau 24, D-91058 Erlangen (Germany)

2010-08-15

408

Classes of Chemical Reactions Reactions in aqueous media  

E-print Network

Classes of Chemical Reactions Reactions in aqueous media · Precipitation reactions · Acid-Base+ , and Pb2+ #12;Classes of Chemical Reactions Acid-Base Reactions Acid - a substance that is a donor of H Acid-Base Reactions STRONG ACIDS WEAK ACIDS Hydrochloric acid, HCl Hydrofluoric acid, HF Hydrobromic

Zakarian, Armen

409

Aldehyde Coupling Reactions Enantioselective Organocatalytic  

E-print Network

Aldehyde Coupling Reactions Enantioselective Organocatalytic Direct Aldol Reactions of a upon carbohydrate architecture[2] as an important platform for reaction design and methodological advance- ment.[3] Application of the aldol reaction[4] to the synthesis of carbohydrates is well

MacMillan, David W. C.

410

[Reactions after MMR vaccination].  

PubMed

Four months after introducing routine vaccination against measles, mumps and German measles (MMR-vaccination) in Denmark, a questionnaire study of reactions in vaccinated children was carried out. There were significantly fewer reactions in children who had previously developed immunity to measles, either by having had the disease or by vaccination. The reaction frequency after MMR-vaccination of children immune to measles was no greater than that after other vaccinations. Moreover, for all vaccinations, the frequency of reaction was found to decrease significantly with increasing age. The study suggests that a large proportion of the so-called reactions were not caused by vaccination, but were due to common viral infections occurring at random and concurrently with it. The reactions that arose in connection with MMR-vaccination are considered to be of minor importance when compared with often prolonged and more severe course of these diseases. PMID:2363211

Kaaber, K; Samuelsson, I S; Larsen, S O

1990-06-01

411

Metabolic responses on the early shift.  

PubMed

Shiftwork has been associated with a higher propensity for the development of metabolic disorders and obesity. The aim of the study was to investigate concentrations of glucose, cortisol, and insulin among fixed night workers (n = 9), fixed early morning workers (n = 6), and day workers (n = 7). Food intake was recorded for 7 days using a diary. Blood samples were collected every 4 h over the course of 24 h, yielding six samples. Total carbohydrate intake was lowest (p < .0005), whereas fat (p = .03) and protein (p < .0005) were highest on the early morning shifts. Early morning workers also had overall elevated cortisol levels relative to the other two groups. Cortisol levels appeared to be more influenced by time since waking prior to the shift than by time-of-day. Cortisol was highest for the early morning group than the day group 12 h after waking, and both the early morning and night groups had higher levels than the day group 16 h after waking (p < .05 in all cases). In contrast, the homesostatsis model assessment of insulin resistance (HOMA-IR) appeared to be more influenced by time-of-day than by time since waking prior to the shift. The early morning group had higher levels of HOMA-IR at 08:00 h than the other groups (p < .05). In conclusion, the early morning group had the highest overall concentrations of cortisol and tended to have higher levels of HOMA-IR, indicating that more attention should be given to these workers. Moreover, all three groups showed pronounced cortisol levels on awakening, suggesting that they may have adjusted to their awaking time. (Author: heloguarita@rgnutri.com.br ). PMID:20636217

Padilha, Heloisa Guarita; Crispim, Cibele Aparecida; Zimberg, Ioná Zalcman; Folkard, Simon; Tufik, Sérgio; de Mello, Marco Túlio

2010-07-01

412

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

413

Reaction-diffusion textures  

Microsoft Academic Search

We present a method for texture synthesis based on the simulation of a process of local nonlinear interaction, called reaction-diffusion, which has been proposed as a model of biological pattern formation. We extend traditional reaction-diffusion systems by allowing anisotropic and spatially non-uniform diffusion, as well as multiple competing directions of diffusion. We adapt reaction-diffusion system to the needs of computer

Andrew P. Witkin; Michael Kass

1991-01-01

414

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

415

Higher-order phase shift reconstruction approach  

PubMed Central

Purpose: Biological soft tissues encountered in clinical and preclinical imaging mainly consists of atoms of light elements with low atomic numbers and their elemental composition is nearly uniform with little density variation. Hence, x-ray attenuation contrast is relatively poor and cannot achieve satisfactory sensitivity and specificity. In contrast, x-ray phase-contrast provides a new mechanism for soft tissue imaging. The x-ray phase shift of soft tissues is about a thousand times greater than the x-ray absorption over the diagnostic x-ray energy range, yielding a higher signal-to-noise ratio than the attenuation contrast counterpart. Thus, phase-contrast imaging is a promising technique to reveal detailed structural variation in soft tissues, offering a high contrast resolution between healthy and malignant tissues. Here the authors develop a novel phase retrieval method to reconstruct the phase image on the object plane from the intensity measurements. The reconstructed phase image is a projection of the phase shift induced by an object and serves as input to reconstruct the 3D refractive index distribution inside the object using a tomographic reconstruction algorithm. Such x-ray refractive index images can reveal structural features in soft tissues, with excellent resolution differentiating healthy and malignant tissues. Methods: A novel phase retrieval approach is proposed to reconstruct an x-ray phase image of an object based on the paraxial Fresnel–Kirchhoff diffraction theory. A primary advantage of the authors’ approach is higher-order accuracy over that with the conventional linear approximation models, relaxing the current restriction of slow phase variation. The nonlinear terms in the autocorrelation equation of the Fresnel diffraction pattern are eliminated using intensity images measured at different distances in the Fresnel diffraction region, simplifying the phase reconstruction to a linear inverse problem. Numerical experiments are performed to demonstrate the accuracy and stability of the proposed approach. Results: The proposed reconstruction formula is a generalization of the transport of intensity equation (TIE). It has the second-order accuracy compared to the linear model used in the conventional phase retrieval approach. The numerical experiments demonstrate that the accuracy and stability of the proposed phase reconstruction method outperforms the TIE-based reconstruction method. Conclusions: A novel approach has been proposed to retrieve an x-ray phase shift image induced by an object from intensity images measured at different distances in the Fresnel diffraction region. The authors’ approach has the second-order accuracy and is able to retrieve the phase shift of an object stably, overcoming the restriction of slow phase variation assumed by the conventional phase retrieval techniques. PMID:21089757

Cong, Wenxiang; Wang, Ge

2010-01-01

416

Picosecond laser timing by rf phase shifting  

E-print Network

I),ix 116) synchronously pump two cavity-dumped dye lasers. Both Nd:Y AG lasers are mode-locked by the same rf source and therefore generate well-synchronized pulse trains. Timingjitter between cavity dumped pulses from the two dye lasers was determined...://scitationnew.aip.org/termsconditions. Downloaded to IP: 129.237.46.100 On: Tue, 16 Sep 2014 13:55:29 delays between pump and probe pulses in units of 13 ns." As the time delay is scanned by phase shifting, it is necessary simultaneously to adjust the timing of the cavity-dump trig­ ger pulse...

Johnson, Carey K.; Qian, Jun

1990-01-01

417

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

418

Peak wavelength shifts and opponent color theory  

NASA Astrophysics Data System (ADS)

We adapt the tenets of Hering's opponent color theory to the processing of data obtained from a tristimulus colorimeter to independently determine the intensity and possible peak wavelength shift of a narrowband LED. This information may then be used for example in an optical feedback loop to maintain constant intensity and chromaticity for a light source consisting of two LEDs with different peak wavelengths. This approach is particularly useful for LED backlighting of LCD display panels using red, green, and blue LEDs, wherein a tristimulus colorimeter can be used to maintain primary chromaticities to within broadcast standard limits in real time.

Ashdown, Ian; Salsbury, Marc

2007-09-01

419

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

420

Resonance-shifting luminescent solar concentrators  

SciTech Connect

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

421

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

422

Spectral shifts in metal-enhanced fluorescence  

NASA Astrophysics Data System (ADS)

We report a 2 nm red shift in the fluorescence spectra observed for Rhodamine 800 dissolved in glycerol on copper substrates as compared to glass reference samples, suggesting a wavelength dependence of metal enhanced fluorescence. The full width half maximum of the blue-red spectra is about 1 nm narrower as compared to the reference sample. We speculate that the observation correlates with a specific interaction mechanism between the Rhodamine 800 transition dipole, the enhanced electric field, and subsequent plasmon coupling, an observation not yet reported.

Karolin, Jan; Geddes, Chris

2014-08-01

423

Classic Organic Reactions  

NSDL National Science Digital Library

Despite the fact that the Classic Organic Reactions Page was designed for commercial purposes, to demonstrate the capabilities of ChemPen chemical structure drawing software for Windows, the page offers a useful resource for chemistry students and professionals. The creator of this page, and author and proprietor of ChemPen, Dr. Hilton Evans, has cited the literature for each reaction. The site contains drawings for over 300 alphabetically listed classic organic reactions. The list begins with the Acetoacetic Ester Condensation and ends with the Zinke-Suhl Reaction.

424

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

425

SHIFT RADIX SYSTEMS FOR GAUSSIAN INTEGERS AND PETHO'S LOUDSPEAKER  

E-print Network

SHIFT RADIX SYSTEMS FOR GAUSSIAN INTEGERS AND PETHO'S LOUDSPEAKER HORST BRUNOTTE, PETER. An approximation of Petho's Loudspeaker G (0) 1 . The aim of the present note is to study a variant of shift radix

426

Quantitative Measurement of the Doppler Shift at an Ultrasonic Frequency  

ERIC Educational Resources Information Center

Discussed is a Doppler shift laboratory experiment for an introductory college physics course. Ultrasonic transducers and a digital phase detector circuit "black box" are used to overcome room noise and "standing waves" and to produce an observable frequency shift. (SL)

Nerbun, R. C.; Leskovec, R. A.

1976-01-01

427

Edge technique for measurement of laser frequency shifts including the Doppler shift  

NASA Technical Reports Server (NTRS)

A method is disclosed for determining the frequency shift in a laser system by transmitting an outgoing laser beam. An incoming laser beam having a frequency shift is received. A first signal is acquired by transmitting a portion of the incoming laser beam to an energy monitor detector. A second signal is acquired by transmitting a portion of the incoming laser beam through an edge filter to an edge detector, which derives a first normalized signal which is proportional to the transmission of the edge filter at the frequency of the incoming laser beam. A second normalized signal is acquired which is proportional to the transmission of the edge filter at the frequency of the outgoing laser beam. The frequency shift is determined by processing the first and second normalized signals.

Korb, Larry (inventor)

1991-01-01

428

Oxygen vacancy clusters on ceria: Decisive role of cerium f electrons Changjun Zhang,1 Angelos Michaelides,2 David A. King,1 and Stephen J. Jenkins1,*  

E-print Network

reaction catalyzed by Au/CeO2 .5,6 To elucidate the roles of ceria played in those applications of the electronic change upon the removal of oxygen, namely, the localization of resulting excess electrons on Ce f such as automotive exhaust cataly- sis, water-gas shift WGS reactions, fuel cells, and produc- tion and purification

Alavi, Ali

429

XIV.1-Draft ATTACHMENT XIV  

E-print Network

of the water-gas-shift (WGS) reaction. They indicate that cobalt is much higher in cost, and this is likely oxidation over steam reforming is indicated to be that the reaction is self-sustaining and the only heat/CO is produced, and that it more nearly matches that needed for the FTS. In addition, the CO2 and

Kentucky, University of

430

Shift work and diabetes mellitus among male workers in Japan: does the intensity of shift work matter?  

PubMed

The purpose of this study was to examine the association between shift work and diabetes mellitus by separating shift workers according to the intensity of their shift work (seasonal shift work and continuous shift work). Between May and October 2009, we collected data from annual health checkups and questionnaires at a manufacturing company in Shizuoka, Japan. Questionnaires were returned by 1,601 workers (response rate: 96.2%, men/women = 1,314/287). Diabetes mellitus was defined as hemoglobin A1c ? 6.5% and fasting blood sugar ? 126 mg/dl. After exclusions, which included all the women and clerical workers because they did not work in shifts, we analyzed 475 skilled male workers. After adjusting for age, smoking status, frequency of alcohol consumption, and cohabitation status, odds ratios for diabetes mellitus were 0.98 (95% confidence interval [CI]: 0.28-4.81) and 2.10 (95% CI: 0.77-5.71) among seasonal shift workers and continuous shift workers, respectively, compared with non-shift workers. In an age-stratified analysis (<45 years vs. ?45 years), the association between continuous shift work and diabetes mellitus was more pronounced among older participants. Compared with non-shift workers, the risk of diabetes mellitus was increased among continuous shift workers, whereas its effect is limited among seasonal shift workers. PMID:23439506

Ika, Katsuhiko; Suzuki, Etsuji; Mitsuhashi, Toshiharu; Takao, Soshi; Doi, Hiroyuki

2013-01-01

431

Using rigorous selection criteria to investigate marine range shifts  

NASA Astrophysics Data System (ADS)

We reassess whether range shifts in marine organisms are occurring in a direction predicted by causation due to climate using two different methods: a global meta-analysis and a regional analysis of museum records focussing on marine molluscs. Globally we used rigorous selection criteria to investigate studies describing range shifts in marine organisms, including exclusion of single-species studies and those that inferred range shifts through shifting abundance. For each species meeting these criteria (311 species from 13 studies), the distance in kilometres moved per year was calculated, and life history characteristics such as mobility, habitat, dispersal potential and trophic level were recorded to assess if these were linked to the shifts. We also examined the potential correlation between changing sea surface temperatures and range shifts. Regionally we analysed the intertidal mollusc collection of the Australian Museum and Museum of Victoria and consulted with mollusc experts to determine if museum records could be used to detect range shifts in marine invertebrates. The global meta-analysis showed that individual species shifted on average 8.9 km polewards per year. Range shifts were not significantly related to temperature change or life history characteristics with the exception of intertidal and nearshore subtidal fauna showing poleward shifts (6.8 and 14.3 km per decade, respectively) and shelf fauna showing a slight equatorial shift (2.7 km per decade). Our regional analysis showed that 54 of the 634 mollusc species examined shifted their range into or out of the well-surveyed Sydney region. However, closer examination by mollusc experts revealed that the evidence for these shifts was unreliable, and we conclude that caution is required when using museum records in range shift studies. Overall, our study supports previous research showing a poleward shift in response to climate change, although this is an order of magnitude less than values reported in the only other meta-analysis on marine range shifts, possibly owing to the strict selection criteria applied here.

Przeslawski, Rachel; Falkner, Inke; Ashcroft, Michael B.; Hutchings, Pat

2012-11-01

432

Identifying potential evolutionary consequences of climate-driven phenological shifts  

Microsoft Academic Search

Climate change is shifting the phenology of many species throughout the world. While the interspecific consequences of these\\u000a phenological shifts have been well documented, the intraspecific shifts and their resultant evolutionary consequences remain\\u000a relatively unexplored. Here, we present a conceptual framework and overview of how phenological shifts within species can\\u000a drive evolutionary change. We suggest that because the impacts of

Matthew J. Heard; Shelby H. Riskin; Patrick A. Flight

433

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

434

Wright's shifting balance theory: an experimental study.  

PubMed

Experimental confirmation of Wright's shifting balance theory of evolution, one of the most comprehensive theories of adaptive evolution, is presented. The theory is regarded by many as a cornerstone of modern evolutionary thought, but there has been little direct empirical evidence supporting it. Some of its underlying assumptions are viewed as contradictory, and the existence and efficacy of the theory's fundamental adaptive process, interdemic selection, is the focus of controversy. Interdemic selection was imposed on large arrays of laboratory populations of the flour beetle Tribolium castaneum in the manner described by Wright: the differential dispersion of individuals from demes of high fitness into demes of low fitness. A significant increase in average fitness was observed in the experimental arrays when compared to control populations with equivalent but random migration rates. The response was not proportional to the selection differential: The largest response occurred with interdemic selection every two generations rather than every generation or every three generations. The results indicate that the interdemic phase of Wright's shifting balance theory can increase average fitness and suggest that gene interactions are involved in the observed response. PMID:1887214

Wade, M J; Goodnight, C J

1991-08-30

435

Shifting perceptions of age in voice  

NASA Astrophysics Data System (ADS)

A series of experiments have been carried out in order to identify the acoustical and perceptual correlates of the aging voice. The initial phase of the program was to identify those voice parameters which signal a person's age; the second phase was to systematically shift these parameters in order to determine if a parallel change in perceived age would occur. This second study focused on temporal characteristics related to voice. In this instance, standard speech samples for 16 males aged 70-90 years were contrasted with those of 14 males aged 20-33 years. The features studied included the following: (1) sentence duration, (2) word duration, (3) diphthong duration, (4) consonant-vowel ratios, (5) number of pauses and (6) pause duration. Significant differences were found for all relationships. Subsequently, a preliminary study was carried out where the voices were synthesized and the temporal parameters for the two groups shifted toward each other. The preliminary data suggest that such modifications lead especially to the idea that the voices of older individuals actually were those of younger men.

Shrivastav, Rahul; Hollien, Harry; Brown, W. S.; Rothman, Howard B.; Harnsberger, James D.

2003-10-01

436

?/3 Phase-Shift Quantum Searching  

NASA Astrophysics Data System (ADS)

Quantum searching normally consists of an alternate sequence of selective inversion and diffusion operations. The algorithm has been extensively studied and is well understood. However, there was a surprising result that was discovered last year. According to this, if we change the selective inversions to ?/3 phase shifts and adjust the sign of the phase shift in a prescribed manner, we obtain an algorithm that converges monotonically towards the solution [1]. This is in contrast to the well-known search algorithm that has an oscillatory character. This leads to a number of new and interesting applications. For example, if we consider a situation where the probability of getting a target state for a random item, is 1-? (with ? unknown), then the probability of getting a target state after a single query in the new algorithm, can be increased to 1-3circ, classically this can be increased to only 1-2circ. The performance of the new algorithm has recently been proved to be optimal. Another important application of this technique is in correction of systematic errors [2]. References - (1) L.K. Grover (2005), Fixed-point quantum search, Phys. Rev. Letters, Oct. 3, 2005. (2) B.W. Reichardt and L.K. Grover, Quantum error correction of systematic errors using a quantum search framework, Phys. Rev. A, Oct. 25, 2005

Grover, Lov

2006-03-01

437

[Shift- and Nightwork - a scientometric analysis].  

PubMed

Economic restructuring processes in Germany require changes within all social and health care systems regarding night shiftwork. The aim of this paper was to analyse research results referring to shift- and nightwork using scientometric methods. A total of 3092 items could be detected. A constant increase in the number of publications per year since 1977, especially since 1990' was obvious. One third of the research results, a total of 884 articles could be assigned to the USA. Great Britain could be identified with 365 articles and France with 244 published articles. Sleep, Ergonomics and Chronobiology International are the most prolific journals. The Swedish scientist Torbjörn Akerstedt is to this date the most acclaimed researcher referring to his issue. He has written 105 articles about shift- and nightwork. He is not only a most efficient author, but also has the highest h-index [30]. Self-citations and multiple co-authorships distort parameters like impact factor and h-index enormously and should be regarded from a critical point of view. PMID:21442214

van Mark, Anke; Vitzthum, Karin; Höndorf, Franka; Kloss, Lisa; Quarcoo, David; Groneberg, David A

2011-04-01

438

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

439

Reaction of the C 3 carbon cluster with benzene  

NASA Astrophysics Data System (ADS)

Benzene and C 3 are both known to exist in the interstellar medium (ISM). Their reaction has been studied here in cryogenic matrices using Fourier transform infrared (FT-IR) absorption spectroscopy. The reaction produced a weakly bonded complex for which a C-C asymmetric stretch vibrational frequency in the C 3 unit is shifted to lower energy (vs. uncomplexed C 3) by 4.5 and 1.6 cm -1 in Ar and Kr matrices, respectively. The singlet potential surface of the C 3 + C 6H 6 reaction was partially mapped using density functional theory (DFT) theory (B3LYP with 6-31G** and 6-311 + G**). Although thirteen stable products are predicted, only two agree satisfactorily with the observed small shift and the isotopomer frequencies of 13C-substituted C 3 · C 6H 6 complexes. Products formed by the rearrangement of the complex's components apparently have no (or very low) entrance barriers. Finally, a low energy reaction pathway has been computed for the production of a dehydrogenated PAH (with an indene framework) from the reaction of the complexed C 3 and C 6H 6 moieties. Indene has been observed previously in the discharge reactions of benzene where C 3 has also been produced.

Szczepanski, Jan; Wang, Haiyan; Vala, Martin

2004-08-01

440

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

441

Frequency shifting with a solid-state switching capacitor  

NASA Technical Reports Server (NTRS)

Frequency shifting, commonly used in electronic signal processing, is applied in tuning, automatic frequency control, antenna element switching, phase shifting, etc. Frequency shifting can be accomplished economically and reliably with simple circuit comprising conventional resistor and solid-state switching device which can be equivalent to two capacitors, depending on switching state.

Mattauch, R. J.; Viola, T. J., Jr.

1973-01-01

442

30 CFR 57.19067 - Trips during shift changes.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Trips during shift changes. 57.19067 ...Hoisting Procedures § 57.19067 Trips during shift changes. During shift...authorized person shall be in charge of each trip in which persons are...

2010-07-01

443

30 CFR 56.19067 - Trips during shift changes.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Trips during shift changes. 56.19067 ...Hoisting Procedures § 56.19067 Trips during shift changes. During shift...authorized person shall be in charge of each trip in which persons are...

2010-07-01

444

Optimal control of gear shift operations in automatic transmissions  

Microsoft Academic Search

An optimal control approach for gear shift operations in automatic transmissions is proposed in this paper. Starting from a verified model of a typical power train with an automatic transmission a performance measure for evaluating the gear shift process in terms of passengers comfort and control expenditure is developed. The gear shift operation is stated as a multistage decision process

A. Haj-Fraj; F. Pfeiffer

2001-01-01

445

On the Period of a Periodic-Finite-Type Shift  

E-print Network

Periodic-finite-type shifts (PFT's) form a class of sofic shifts that strictly contains the class of shifts of finite type (SFT's). In this paper, we investigate how the notion of "period" inherent in the definition of a PFT causes it to differ from an SFT, and how the period influences the properties of a PFT.

Manada, Akiko

2008-01-01

446

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.

447

Giant positive and negative Goos-Hanchen shift on dielectric  

E-print Network

Giant positive and negative Goos-H¨anchen shift on dielectric gratings caused by guided mode, University of Illinois at Chicago, Chicago, IL, 60607, USA jili@uic.edu Abstract: Giant positive and negative-H¨anchen shift is related to metamaterials or plasmonic materials with ohmic loss, here the giant shift

Li, Jingjing

448

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.

2012-10-03

449

Nuclear Reaction Data Centers  

SciTech Connect

The cooperating Nuclear Reaction Data Centers are involved in the compilation and exchange of nuclear reaction data for incident neutrons, charged particles and photons. Individual centers may also have services in other areas, e.g., evaluated data, nuclear structure and decay data, reactor physics, nuclear safety; some of this information may also be exchanged between interested centers. 20 refs., 1 tab.

McLane, V.; Nordborg, C.; Lemmel, H.D.; Manokhin, V.N.

1988-01-01

450

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

451

Applications of Reaction Rate  

ERIC Educational Resources Information Center

This article presents an assignment in which students are to research and report on a chemical reaction whose increased or decreased rate is of practical importance. Specifically, students are asked to represent the reaction they have chosen with an acceptable chemical equation, identify a factor that influences its rate and explain how and why it…

Cunningham, Kevin

2007-01-01

452

The guaiol color reaction.  

PubMed

The common and biogenetically important sesquiterpene guaiol yields a deep purple color when treated with electrophilic bromine reagents. This interesting color reaction was observed over fifty years ago, but the chemistry of this process has not been investigated. Herein, we present the chemistry of the guaiol color reaction. PMID:12391567

Waddell, Thomas G; Arp, Nathan W; Bodine, Kyle D; Pagni, Richard M

2002-10-01

453

Oscillating Reactions: Two Analogies  

ERIC Educational Resources Information Center

Oscillating chemical reactions are truly spectacular phenomena, and demonstrations are always appreciated by the class. However, explaining such reactions to high school or first-year university students is problematic, because it may seem that no acceptable explanation is possible unless the students have profound knowledge of both physical…

Petruševski, Vladimir M.; Stojanovska, Marina I.; Šoptrajanov, Bojan T.

2007-01-01

454

Chemical burn or reaction  

MedlinePLUS

Chemicals that touch skin can lead to a reaction on the skin, throughout the body, or both. ... leave the person alone and watch carefully for reactions affecting the entire body. Note: If a chemical gets into the eyes, the eyes should be ...

455

Distribution of rest days in 12 hour shift systems: impacts on health, wellbeing, and on shift alertness  

PubMed Central

OBJECTIVES: To investigate of the effects of distribution of rest days in 12 hour shift systems. Although several studies have examined the effects of compressing work schedules by comparing 8 and 12 hour shift systems, there is little published research examining the various forms of 12 hour shift system. METHODS: An abridged version of the standard shiftwork index which included retrospective alertness ratings was completed by a large sample of industrial shiftworkers. The respondents worked 12 hour shift systems that either did or did not incorporate breaks of > 24 hours between the blocks of day and night shifts. For the purposes of the analysis, each of these two groups were further subdivided into those who started their morning shift at 0600 and those who started at 0700. RESULTS: Systems which incorporated rest days between the day and night shifts were associated with slightly higher levels of on shift alertness, slightly lower levels of chronic fatigue, along with longer sleep durations when working night shifts and between rest days. Early changeovers were associated with shorter night sleeps between successive day shifts, but longer and less disturbed day sleeps between night shifts. These effects of changeover time were broadly in agreement with previous research findings. CONCLUSIONS: The distribution of rest days in 12 hour shift systems had only limited effects on the outcome measures, although the few modest differences that were found favoured systems which incorporated rest days between the day and night shifts. It is conceded that the design of the study may have obscured some subtle differences between the shift systems. Nevertheless, it is concluded that the impact of distribution of rest days seems to be minor relative to previously found effects of other features of shift systems--for example, shift duration.   PMID:10448331

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

1999-01-01

456

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

457

An Efficient Image Registration Algorithm Based on Q-Shift Complex Wavelet Transform (Q-Shift CWT)  

Microsoft Academic Search

Shift invariance and directional selectivity are two important transform properties that crucially affected the performance of image registration process in the transform domain. Due to the lack of the pre-mentioned two properties of the discrete wavelet transform (DWT). This paper introduces an efficient image registration technique in the Q-shift complex wavelet transform (Q- shift CWT). It is chosen for its

Hala S. Own

2005-01-01

458

Cascaded nonlinear phase shifts in quasi-phase-matched structures  

SciTech Connect

Cascaded nonlinear phase shifts via second-harmonic generation are theoretically studied for quasi-phase-matched (QPM) structures. Both the effective phase mismatch and the structure itself contribute to the resultant nonlinear phase shift. Depending on the sign of the effective phase mismatch, structural contribution may enhance or depress the nonlinear phase shift. The fundamental wave will experience a nonlinear phase shift even if the effective phase matching is satisfied. By properly designing the effective phase mismatch, QPM structures with large material-based phase mismatch may provide large nonlinear phase shifts before saturation.

Wang Ke; Qian Liejia; Zhang Dongfang; Yang Hua; Zhu Heyuan [State Key Laboratory for Advanced Materials and Devices, Department of Optical Science and Engineering, Laboratory for Advanced Materials, Fudan University, Shanghai 200433 (China)

2007-07-15

459

Effects of pharmacological agents on subcortical resistance shifts  

NASA Technical Reports Server (NTRS)

Microliter quantities of tetrodotoxin, tetraethylammonium chloride, and picrotoxin injected into the inferior colliculus and superior olive of unanesthetized cats differentially affect the amplitude and waveform of click-evoked potentials and evoked resistance shifts. Tetrodotoxin simultaneously reduces the negative phase of the evoked potential and eliminates the evoked resistance shift. Tetraethylammonium enhances the negative evoked potential component, presumably of postsynaptic origin, without significantly altering evoked resistance shift amplitude. Picrotoxin also enhances the negative evoked potential wave but increases evoked resistance shift amplitude. These findings implicate events associated with postsynaptic membrane depolarization in the production of the evoked resistance shift.

Klivington, K. A.

1975-01-01

460

Shifting tolerance for multilayer collinear holographic data storage  

NASA Astrophysics Data System (ADS)

The shifting tolerance of the collinear holographic data storage system is discussed considering its influences on the quality of the reconstructed data pages and the precision of the holographic disk actuator. The diffractive efficiencies with shifting along the x-axis and the z-axis are calculated respectively based on the bit error rates of the reconstructed data pages. The numerical aperture of the objective lens and the recording wavelength show different impacts on the shifting tolerance and the storage density. The orthogonal reference pattern shift multiplexing method is investigated. It is proved that the method could improve the data storage density by keeping the shifting tolerance.

Liu, Jinqiu; Cao, Liangcai; He, Qingsheng; Jin, Guofan

2014-09-01

461

s-Wave collisional frequency shift of a fermion clock.  

PubMed

We report an s-wave collisional frequency shift of an atomic clock based on fermions. In contrast to bosons, the fermion clock shift is insensitive to the population difference of the clock states, set by the first pulse area in Ramsey spectroscopy, ?(1). The fermion shift instead depends strongly on the second pulse area ?(2). It allows the shift to be canceled, nominally at ?(2)=?/2, but correlations perturb the null to slightly larger ?(2). The frequency shift is relevant for optical lattice clocks and increases with the spatial inhomogeneity of the clock excitation field, naturally larger at optical frequencies. PMID:23679589

Hazlett, Eric L; Zhang, Yi; Stites, Ronald W; Gibble, Kurt; O'Hara, Kenneth M

2013-04-19

462

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

463

Red Shift in a Laboraory Environment  

E-print Network

A hypotheses of energy loss for polarization of e-e+ vacuum by a photon passing interstellar space is considered. An excitation and relaxation of vacuum can't run with speed of light due to very small but finite fraction of e-e+ pair mass that creates a retardment in recuperation of deposited energy back to photon. This "forgotten" by many photons energy is finally splashed out in real space as a Relic Radiation. An assumption that such energy loss is proportional to a photon energy conforms to Hubble low of Red Shift and experimental data treated as accelerated expansion of Universe. A possibility of an observation of this type energy loss is considered at high-energy accelerators where energy deposition may reach up hundreds MeV in second.

Yuriy A. Yatsunenko; Julian A. Budagov

2011-03-04

464

Phase-shifting point diffraction interferometer  

DOEpatents

Disclosed is a point diffraction interferometer for evaluating the quality of a test optic. In operation, the point diffraction interferometer includes a source of radiation, the test optic, a beam divider, a reference wave pinhole located at an image plane downstream from the test optic, and a detector for detecting an interference pattern produced between a reference wave emitted by the pinhole and a test wave emitted from the test optic. The beam divider produces separate reference and test beams which focus at different laterally separated positions on the image plane. The reference wave pinhole is placed at a region of high intensity (e.g., the focal point) for the reference beam. This allows reference wave to be produced at a relatively high intensity. Also, the beam divider may include elements for phase shifting one or both of the reference and test beams.

Medecki, Hector (Berkeley, CA)

1998-01-01

465

Phase-shifting point diffraction interferometer  

DOEpatents

Disclosed is a point diffraction interferometer for evaluating the quality of a test optic. In operation, the point diffraction interferometer includes a source of radiation, the test optic, a beam divider, a reference wave pinhole located at an image plane downstream from the test optic, and a detector for detecting an interference pattern produced between a reference wave emitted by the pinhole and a test wave emitted from the test optic. The beam divider produces separate reference and test beams which focus at different laterally separated positions on the image plane. The reference wave pinhole is placed at a region of high intensity (e.g., the focal point) for the reference beam. This allows reference wave to be produced at a relatively high intensity. Also, the beam divider may include elements for phase shifting one or both of the reference and test beams. 8 figs.

Medecki, H.

1998-11-10

466

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

467

Shifted power method for computing tensor eigenvalues.  

SciTech Connect

Recent work on eigenvalues and eigenvectors for tensors of order m >= 3 has been motivated by applications in blind source separation, magnetic resonance imaging, molecular conformation, and more. In this paper, we consider methods for computing real symmetric-tensor eigenpairs of the form Ax{sup m-1} = lambda x subject to ||x||=1, which is closely related to optimal rank-1 approximation of a symmetric tensor. Our contribution is a shifted symmetric higher-order power method (SS-HOPM), which we show is guaranteed to converge to a tensor eigenpair. SS-HOPM can be viewed as a generalization of the power iteration method for matrices or of the symmetric higher-order power method. Additionally, using fixed point analysis, we can characterize exactly which eigenpairs can and cannot be found by the method. Numerical examples are presented, including examples from an extension of the method to finding complex eigenpairs.

Mayo, Jackson R.; Kolda, Tamara Gibson

2010-07-01

468

Stokes shift spectroscopy for breast cancer diagnosis  

NASA Astrophysics Data System (ADS)

The objective of this study is to assess the diagnostic potential of stokes shift (SS) spectroscopy (SSS) for normal and different pathological breast tissues such as fibroadenoma and infiltrating ductal carcinoma. The SS spectra is measured by simultaneously scanning both the excitation and emission wavelengths while keeping a fixed wavelength interval ??=20 nm between them. Characteristic, highly resolved peaks and significant spectral differences between normal and different pathological breast tissues were observed. The SS spectra of normal and different pathological breast tissues shows the distinct peaks around 300, 350, 450, 500 and 600 nm may be attributed to tryptophan, collagen, NADH, flavin and porphyrin respectively. Using SSS technique one can obtain all the key fluorophores in a single scan and hence they can be targeted as a tumor markers in this study. In order to quantify the altered spectral differences between normal and different pathological breast tissues are verified by different ratio parameters.

Jeyasingh, Ebenezar; Prakashrao, Aruna; Singaravelu, Ganesan

2010-02-01

469

Shifted power method for computing tensor eigenpairs.  

SciTech Connect

Recent work on eigenvalues and eigenvectors for tensors of order m {>=} 3 has been motivated by applications in blind source separation, magnetic resonance imaging, molecular conformation, and more. In this paper, we consider methods for computing real symmetric-tensor eigenpairs of the form Ax{sup m-1} = {lambda}x subject to {parallel}x{parallel} = 1, which is closely related to optimal rank-1 approximation of a symmetric tensor. Our contribution is a novel shifted symmetric higher-order power method (SS-HOPM), which we showis guaranteed to converge to a tensor eigenpair. SS-HOPM can be viewed as a generalization of the power iteration method for matrices or of the symmetric higher-order power method. Additionally, using fixed point analysis, we can characterize exactly which eigenpairs can and cannot be found by the method. Numerical examples are presented, including examples from an extension of the method to fnding complex eigenpairs.

Mayo, Jackson R.;