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1

Gold-based catalysts for the water–gas shift reaction: Active sites and reaction mechanism  

Microsoft Academic Search

The water–gas shift (WGS, CO+H2O?H2+CO2) reaction was studied on a series of gold\\/oxide catalysts. The results of in situ measurements with X-ray absorption spectroscopy indicate that the active phase of Au-ceria and Au-titania catalysts under the reaction conditions of the water–gas shift consists of metallic nanoparticles of gold on a partially reduced oxide support. In spite of the lack of

José A. Rodriguez

2011-01-01

2

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

Microsoft Academic Search

Coal gasification in conjunction with the water-gas shift reaction represents a significant resource for the production of hydrogen, a gas of considerable industrial value. Current industrial water-gas shift reaction (WGSR) processes are operated in two stages: a high temperature shift (HTS) stage operating at about 350°C over sulfur-tolerant catalysts, followed by a low temperature shift (LTS) stage operating at about

R. B. Jr. Wilson; M. F. Asaro; E. J. Crawford; B. J. Wood; R. M. Laine; R. H. Schwaar

1989-01-01

3

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

Microsoft Academic Search

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

Peter C. Ford

1981-01-01

4

Homogeneous catalysis by ruthenium carbonyl in alkaline solution: the water gas shift reaction  

Microsoft Academic Search

The possible catalysis of the water gas shift reaction by metal carbonyl complexes is explored and conditions are described where a homogeneous solution prepared from triruthenium dodecacarbonyl (Ruâ(CO)ââ) is an active catalyst under relatively mild conditions. It is additionally noteworthy that the catalyst is very active toward decomposition of formate to Hâ and COâ under conditions active for the water

Richard M. Laine; Robert G. Rinker; Peter C. Ford

1977-01-01

5

Homogeneous catalysis of the water gas shift reaction by mixed-metal (iron\\/ruthenium) catalysts  

Microsoft Academic Search

For the water gas shift reaction HâO + CO ..-->.. COâ + Hâ, homogeneous catalysts may be prepared from ruthenium carbonyl. Mixed Ru\\/Fe carbonyl catalysts are more active in basic solutions than either one of these carbonyls alone. Activities of those and other carbonyl catalysts are tabulated. The mechanism of the catalytic effect is discussed. (DLC)

Peter C. Ford; Robert G. Rinker; Charles Ungermann; Richard M. Laine; Vincent Landis; Sergio A. Moya

1978-01-01

6

Water gas shift reaction kinetics and reactor modeling for fuel cell grade hydrogen  

Microsoft Academic Search

The kinetics of the water gas shift reaction was studied to evaluate existing reaction mechanisms, test various rate expressions and simulate the performance in a methanol fuel processor for fuel cell applications. The reaction was carried out in a micro reactor testing unit using a commercial Sud-Chemie Cu\\/ZnO\\/Al2O3 catalyst between 120 and 250°C with a range of feed rates and

Yongtaek Choi; Harvey G. Stenger

2003-01-01

7

Desulfurization by in situ hydrogen generation through water gas shift reaction  

Microsoft Academic Search

Sulfur removal from benzothiophene was realized by in situ hydrogen generation through the water gas shift reaction. Benzothiophene dissolved in decalin (2% S by weight) was fed to a trickle-bed reactor concurrent with carbon monoxide and water. A commercial Ni-Mo\\/AlâOâ catalyst was employed after presulfiding. Reaction conditions were 1000 psia and 310-370 °C, which is within the operating range of

Meyyappan Kumar; Aydin Akgerman; Rayford G. Anthony

1984-01-01

8

Studies of the water-gas-shift reaction with ceria-supported precious metals  

Microsoft Academic Search

Ceria-supported precious metals have great potential for use as water-gas-shift (WGS) catalysts in fuel processors for fuel-cell applications. In this paper, we review the mechanisms that have been proposed for these catalysts and discuss the deactivation that has been observed. Since a redox mechanism appears to explain the observations about the reaction best, we briefly review what is known about

R. J. Gorte; S. Zhao

2005-01-01

9

Effect of active sites for a water–gas shift reaction on Cu nanoparticles  

Microsoft Academic Search

The effect on the water–gas shift reaction of active sites on Cu nanoparticles on silica prepared by atomic layer epitaxy was investigated. The Cu nanoparticles are proposed to contain two major active sites on the surface, defect sites on Cu particles (L1 sites) and sites having strong interactions with oxide support on highly dispersed and\\/or isolated Cu particles (L2 sites).

Ching-Shiun Chen; Tzu-Wen Lai; Chen-Chih Chen

2010-01-01

10

Reactant-promoted reaction mechanism for catalytic water-gas shift reaction on MgO  

SciTech Connect

The behavior of reaction intermediates in the catalytic water-gas shift reaction (WGSR) on the MgO surface was studied by means of FT-IR spectroscopy. The hydroxyl groups on top of coordinatively unsaturated Mg atoms reacted with CO to produce three kinds of surface formates of unidentate, bidentate, and bridge types in the order bridge > unidentate > bidentate. Unidentate-type formate was produced at room temperature and decomposed at ca. 450 K. The formation and decomposition of bridge- and bidentate-type formates proceeded at higher temperatures (ca. 400 and 550 K, respectively). In the presence of adsorbed water, unidentate-type formate changed into bridge-type formate and hence most formates are bridge type under reaction conditions. Contrary to previous reports, formate intermediates were never converted to H{sub 2} and CO{sub 2} in the absence of H{sub 2}O. While all the formates decompose to CO and surface OH by themselves, adsorbed water promoted the decomposition of formates to the WGSR products H{sub 2} and CO{sub 2} through electronic interaction between the adsorbed water and the formate. The reaction rate of WGSR at steady state agreed with the decomposition rate of the bridge-type formate intermediate to H{sub 2} and CO{sub 2} in the presence of water.

Shido, Takafumi; Asakura, Kiyotaka; Iwasawa, Yasuhiro (Univ. of Tokyo (Japan))

1990-03-01

11

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

12

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

SciTech Connect

The purpose of this report is to update and reorganize our recent review on homogeneous catalysis of the water-gas shift reaction (WGSR) based on recent literature publications and patents. This updated version will serve as a means of selecting 10 candidate catalyst systems for use in developing effective, sulfur-tolerant, low temperature WGSR catalysts. This report discusses the variations possible in the basic chemistry associated with WGSR catalytic cycles, including basic, acidic, and neutral conditions. Then individual mechanism for specific WGSR catalyst systems are discussed. Finally, on the basis of the literature reports, a list is presented of candidate catalysts and basic systems we have chosen for study in Task 3.

Laine, R.M.

1986-01-20

13

Vehicle exhaust catalysis: I. The relative importance of catalytic oxidation, steam reforming and water-gas shift reactions  

Microsoft Academic Search

The activity of a monolithic three-way catalyst has been compared with the performance of the individual metals (Pt, Pd, Rh) for oxidation, steam reforming and water-gas shift. The presence of ceria was found to accelerate the last two reactions. The orders of activity were found to be: oxidation — presence or absence of ceria, Pt > Pd > three-way >

B. I. Whittington; C. J. Jiang; D. L. Trimm

1995-01-01

14

The gold–ruthenium–iron oxide catalytic system for the low temperature water–gas-shift reaction  

Microsoft Academic Search

The water–gas-shift reaction has been carried out over Au–Ru supported on ?-Fe2O3 catalyst at various reaction temperatures ranging from 373 to 513K at atmospheric pressure. Activity of the bimetallic Au–Ru\\/iron oxide compared with Au\\/iron oxide and Ru\\/iron oxide catalysts has been found to be higher over all the reaction temperatures studied. All the fresh and spent samples were characterised by

Akula Venugopal; James Aluha; Daniel Mogano; Mike S. Scurrell

2003-01-01

15

Desulfurization of dibenzothiophene by in situ hydrogen generation through a water gas shift reaction  

Microsoft Academic Search

Global depletion of sweet crude necessitates greater use of high sulfur content hydrocarbon resources. Because of this and the prohibitive cost of producing pure hydrogen, hydrodesulfurization is becoming a major cost factor in petroleum and coal liquid refining. This study indicates that hydrodesulfurization can be achieved by generating the hydrogen necessary for the reaction in situ with the water gas

Bruce D. Hook; Aydin Akgerman

1986-01-01

16

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

17

Influence of the monoclinic and tetragonal zirconia phases on the water gas shift reaction. A theoretical study.  

PubMed

We present a theoretical study of the water gas shift reaction taking place on zirconia surfaces modeled by monoclinic and tetragonal clusters. In order to understand the charge transfer between the active species, in this work we analyze the influence of the geometry of monoclinic and tetragonal zirconia using reactivity descriptors such as electronic chemical potential (?), charge transfer (?N) and molecular hardness (?). We have found that the most preferred surface is tetragonal zirconia (tZrO2) indicating also that low charge transfer systems will generate less stable intermediates, that will allow to facilitate desorption process. PMID:23377895

Cerón, María Luisa; Herrera, Barbara; Araya, Paulo; Gracia, Francisco; Toro-Labbé, Alejandro

2013-02-02

18

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

SciTech Connect

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

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

1986-04-01

19

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

20

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

21

Atomically dispersed Au-(OH)x species bound on titania catalyze the low-temperature water-gas shift reaction.  

PubMed

We report a new method for stabilizing appreciable loadings (~1 wt %) of isolated gold atoms on titania and show that these catalyze the low-temperature water-gas shift reaction. The method combines a typical gold deposition/precipitation method with UV irradiation of the titania support suspended in ethanol. Dissociation of H2O on the thus-created Au-O-TiO(x) sites is facile. At higher gold loadings, nanoparticles are formed, but they were shown to add no further activity to the atomically bound gold on titania. Removal of this "excess" gold by sodium cyanide leaching leaves the activity intact and the atomically dispersed gold still bound on titania. The new materials may catalyze a number of other reactions that require oxidized active metal sites. PMID:23437858

Yang, Ming; Allard, Lawrence F; Flytzani-Stephanopoulos, Maria

2013-03-01

22

In Situ Time-Resolved Characterization of Ni-MoO2 Catalysts for the Water-Gas Shift Reaction  

SciTech Connect

Active catalysts for the water-gas shift (WGS, CO + H2O ? H2 + CO2) reaction were synthesized from nickel molybdates ({beta}-NiMoO4 and nH2O{center_dot}NiMoO4) as precursors, and their structural transformations were monitored using in situ time-resolved X-ray diffraction and X-ray absorption near-edge spectroscopy. In general, the nickel molybdates were not stable and underwent partial reduction in the presence of CO or CO/H2O mixtures at high temperatures. The interaction of {beta}-NiMoO4 with the WGS reactants at 500 C led to the formation of a mixture of Ni (24 nm particle size) and MoO2 (10 nm particle size). These Ni-MoO2 systems displayed good catalytic activity at 350, 400, and 500 C. At 350 and 400 C, catalytic tests revealed that the Ni-MoO2 system was much more active than isolated Ni (some activity) or isolated MoO2 (negligible activity). Thus, cooperative interactions between the admetal and oxide support were probably responsible for the high WGS activity of Ni-MoO2. In a second synthetic approach, the NiMoO4 hydrate was reduced to a mixture of metallic Ni, NiO, and amorphous molybdenum oxide by direct reaction with H2 gas at 350 C. In the first pass of the water-gas shift reaction, MoO2 appeared gradually at 500 C with a concurrent increase of the catalytic activity. For these catalysts, the particle size of Ni (4 nm) was much smaller than that of the MoO2 (13 nm). These systems were found to be much more active WGS catalysts than Cu-MoO2, which in turn is superior to commercial low-temperature Cu-ZnO catalysts.

Wen,W.; Calderon, J.; Brito, J.; Marinkovic, N.; Hanson, J.; Rodriquez, J.

2008-01-01

23

Low temperature, sulfur tolerant homogeneous catalysts for the water-gas shift reaction. Task 1, Topical report No. 1  

SciTech Connect

The purpose of this report is to update and reorganize our recent review on homogeneous catalysis of the water-gas shift reaction (WGSR) based on recent literature publications and patents. This updated version will serve as a means of selecting 10 candidate catalyst systems for use in developing effective, sulfur-tolerant, low temperature WGSR catalysts. This report discusses the variations possible in the basic chemistry associated with WGSR catalytic cycles, including basic, acidic, and neutral conditions. Then individual mechanism for specific WGSR catalyst systems are discussed. Finally, on the basis of the literature reports, a list is presented of candidate catalysts and basic systems we have chosen for study in Task 3.

Laine, R.M.

1986-01-20

24

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

25

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

26

A comparative evaluation of cobalt chromium oxide, cobalt manganese oxide, cobalt manganese oxide, and copper manganese oxide as catalysts for the water-gas shift reaction  

Microsoft Academic Search

Cobalt chromium oxide, cobalt manganese oxide, and copper manganese oxide have been compared as catalysts for the water-gas shift reaction. Cobalt chromium oxide and cobalt manganese oxide catalysts can give both high activity and long lifetimes for this reaction. Cobalt chromium oxide catalysts display higher activity compared to the other catalyst systems and this is shown that both the cobalt

G. J. Hutchings; R. G. Copperthwaite; F. M. Gottschalk; R. Hunter; J. Mellor; S. W. Orchard; T. Sangiorgio

1992-01-01

27

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

28

Activity and stability of nanostructured gold-cerium oxide catalysts for the water-gas shift reaction  

NASA Astrophysics Data System (ADS)

Advanced low-temperature water-gas shift (LTS) catalysts of high activity and stability are under development to produce essentially CO-free hydrogen to feed PEM fuel cells for power generation. Materials based on nanocrystalline cerium oxide (ceria) are among the most promising LTS catalysts. Understanding the structural properties relationship with the WGS activity is fundamentally important in order to rational design the catalysts. Various gold structures, such as metallic gold nanoparticles, cluster and cations were found in gold-ceria sample containing 4--8 at% gold. To discriminate between the various gold species, leaching of the gold-ceria in sodium cyanide was conducted. The metallic gold and all other gold species not in close association with ceria were removed by leaching. A small amount of gold remained in the leached samples. The exact content of non-leachable gold was a function of the parent catalyst properties. Similar data were collected from Pt-ceria samples. STEM or HRTEM, coupled with EDX showed no gold or platinum particles remaining; only what appeared to be very fine clusters or atomically dispersed gold or platinum. Cationic gold or platinum was identified in these samples by XPS. The unexpected finding was that the catalytic activity of the leached samples was similar or slightly better than that of the parent catalyst after removal of the metallic gold or platinum particles by cyanide leaching. Thus, metallic nanoparticles are not necessary; they are mere spectators in the water-gas shift reaction. Nonmetallic gold or platinum species strongly associated with surface cerium-oxygen groups are responsible for the activity, since the extra gold or platinum present in the parent material does not increase the reaction rate; nor does it change the activation energy of the reaction. The importance of the oxide support properties became clear by this work. The amount of gold or platinum retained in active form depends on the surface properties of ceria. Addition of certain metals and dopants significantly enhances the reducibility of ceria. Temperature-programmed reduction of metal-ceria samples performed with H2 or CO, identified that the surface oxygen of ceria is weakened by the presence of the metal. The reduction of oxygen of gold-ceria by CO begins at ambient temperatures, while the onset of surface reduction of the metal-free Ce(La)Ox is at 200--250°C. The WGS activity and reducibility both depend on the preparation of ceria, the dispersion of the metal additive and ceria particle size. However, no dependence on the metal particle size was found. (Abstract shortened by UMI.)

Fu, Qi

29

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

30

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

31

Hydrogen production through the water-gas shift reaction: thermodynamic equilibrium versus experimental results over supported Ni catalysts  

SciTech Connect

This paper discusses the experimental results of the water-gas shift reaction over supported nickel catalysts in comparison to thermodynamic equilibrium composition at the same reaction conditions. The effects of different supports on the performance of H{sub 2} production over nickel-supported catalysts are also evaluated at both low and high temperatures. Ceria-promoted nickel catalyst supported on powder alumina (Ni/CeO{sub 2}-Al{sub 2}O{sub 3}) demonstrated excellent performance. The catalyst was not stable at low temperature (250{sup o}C) but showed good stability at high temperature (450{sup o}C). At 450{sup o}C, with a catalyst loading of 0.05 g, CO/S (S = steam) ratio of 1:3, and gas hourly space velocity (GHSV) - 200 L h{sup -1} g{sub cat}{sup -1}, the activity of Ni/CeO{sub 2}-Al{sub 2}O{sub 3} was 95% with a H{sub 2} yield of 52% and a H{sub 2} selectivity of 73%.

Agus Haryanto; Sandun D. Fernando; S.D. Filip To; Philip H. Steele; Lester Pordesimo; Sushil Adhikari [Mississippi State University, MS (United States). Agricultural and Biological Engineering Department

2009-05-15

32

Studies related to the homogeneous catalysis of the water gas shift reaction. Final technical report, August 1, 1977November 30, 1984  

Microsoft Academic Search

The research carried out under the sponsorship of this contract was concerned with the development and the fundamental mechanistic evaluation of homogeneous catalysts for the water gas shift reaction (HâO + CO=Hâ + COâ). The scope of these studies included the screening and optimization of new catalysts and quantitative studies of key steps of proposed catalytic cycles. Such investigations provide

Ford

1984-01-01

33

Water-Gas --Shift Reaction on Gold Nanoparticles Supported on Iron Oxide Surfaces: A Scanning Tunneling Microscopy/Spectroscopy Study  

NASA Astrophysics Data System (ADS)

We present a Scanning Tunneling Microscopy (STM)/Scanning Tunneling Spectroscopy (STS) study of the Water-Gas-Shift reaction on a model catalyst system consisting of supported gold nanoparticles on a reduced Fe3O4(111) surface in ultrahigh vacuum. Gold forms two electrically distinct nanoparticles on an iron oxide surface upon annealing multilayer Au/Fe3O4(111) at 500 ^oC for 15 minutes. STS measurements show that large gold nanoparticles (˜ 8 nm) exhibit a metallic electronic structure while single gold adatoms bonded to the oxygen sites of the Fe3O4(111) surface are likely positively charged. This Au/Fe3O4(111) system is dosed with CO and H2O at various temperatures. The site specific adsorption and the interaction of CO with the Au nanoparticles will be presented and discussed along with the observation of the site specific dissociative adsorption of H2O to elucidate the catalytic properties of Au nanoparticles on a reducible iron oxide surface.

Taeg Rim, Kwang; Eom, Daejin; Liu, Li; Raitano, Joan; Chan, Siu-Wai; Flytzani-Stepanopoulous, Maria; Flynn, George

2010-03-01

34

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

35

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

36

Microchannel reactors for fuel processing applications. I. Water gas shift reactor  

Microsoft Academic Search

The water gas shift reactor is one of the critical components of a multi-reactor fuel processing system that supports distributed energy production through the use of a fuel cell. The water gas shift reaction converts carbon monoxide (produced in the primary conversion stage of the fuel processor) and water to carbon dioxide and hydrogen. The water gas shift reaction has

A. Y. Tonkovich; J. L. Zilka; M. J. LaMont; Y. Wang; R. S. Wegeng

1999-01-01

37

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

SciTech Connect

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

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

2011-12-31

38

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

39

Water–gas shift reaction over sulfided molybdenum catalysts supported on TiO 2–ZrO 2 mixed oxides  

Microsoft Academic Search

Supported sulfided molybdenum and nickel–molybdenum catalysts were applied in the water–gas shift (WGS) reaction with sulfided feed. TiO2, ZrO2 and binary systems of TiO2–ZrO2, in which composition was changed in 10wt.% intervals, were used as the supports for sulfided Mo and Ni–Mo catalysts. The concentration of Mo (8wt.%) and Ni (3wt.%) was the same in all studied catalysts. Supports and

M. Laniecki; M. Ignacik

2006-01-01

40

Effect of morphological characteristics of TiO 2-supported noble metal catalysts on their activity for the water–gas shift reaction  

Microsoft Academic Search

The catalytic activity of M\\/TiO2 catalysts (M=Pt, Rh, Ru, Pd) for the water–gas shift (WGS) reaction has been investigated in the temperature range of 150–450°C with respect to the structural and morphological properties of the dispersed metallic phase and the support. It has been found that the turnover frequency (TOF) of CO conversion varies in the order of Pt>Rh>Ru>Pd, with

Paraskevi Panagiotopoulou; Dimitris I Kondarides

2004-01-01

41

Activity of CeOx and TiOx Nanoparticles Grown on Au(111) in the Water-Gas Shift Reaction  

Microsoft Academic Search

The high performance of Au-CeO2 and Au-TiO2 catalysts in the water-gas shift (WGS) reaction (H2O + CO-->H2 + CO2) relies heavily on the direct participation of the oxide in the catalytic process. Although clean Au(111) is not catalytically active for the WGS, gold surfaces that are 20 to 30% covered by ceria or titania nanoparticles have activities comparable to those

J. A. Rodriguez; S. Ma; P. Liu; J. Hrbek; J. Evans; M. Pérez

2007-01-01

42

Studies of the water-gas-shift reaction on ceria-supported Pt, Pd, and Rh: Implications for oxygen-storage properties  

Microsoft Academic Search

Steady-state, water-gas-shift kinetics were measured on model, ceria-supported, Pd, Pt, and Rh catalysts and compared to rates obtained on alumina-supported catalysts. When ceria was calcined at low temperatures prior to addition of the precious metal, the specific rates were found to be identical for each of the metals, with an activation energy of 11 ± 1 kcal\\/mol and reaction orders

T. Bunluesin; R. J. Gorte; G. W. Graham

1998-01-01

43

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

44

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

SciTech Connect

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

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

1999-07-19

45

Simulation of high-temperature water-gas shift reactors  

Microsoft Academic Search

A rate equation for water-gas shift reaction over a high-temperature shift catalyst (FeâOâ-CrâOâ) has been developed. This rate equation accounts for the effects of temperature, pressure, age of the catalyst, and HâS content of the reacting gases on the catalyst behavior. The effect of diffusion of reactants and products inside the catalyst pores has also been considered. Subsequently, this rate

C. P. P. Singh; D. N. Saraf

1977-01-01

46

Wall-catalyzed Water-Gas Shift Reaction in Multi-tubular, Pd and 80wt%Pd-20wt%Cu Membrane Reactors at 1173K  

SciTech Connect

The high-temperature, water-gas shift reaction was conducted in 100 wt%Pd and 80 wt%Pd–20 wt%Cu (Pd80 wt%Cu) shell-and-tube membrane reactors at 1173 K with a 241 kPa (35 psig) trans-membrane pressure differential in the absence of heterogeneous catalyst particles. The tube bundle consisted of four parallel 15.25 cm long, 3.175 mm OD Pd-based tubes with a wall thickness of 125 ?m. The modest catalytic activity of the Pd-based membrane surface for the forward WGSR, the high rate of hydrogen extraction through the Pd-based membranes, and the long residence times (1–5 s) resulted in a dramatic shift in carbon monoxide conversions of 93% at 1173 K and a 1.5:1 steam-to-carbon monoxide feed ratio—a value well above the equilibrium value of 54% associated with a conventional (non-membrane) reactor. Carbon monoxide conversions decreased from 93% to 66% and hydrogen recovery from 90% to 85% at a residence time of 5 s when the Pd was replaced with Pd80 wt%Cu, due to the lower permeance of the Pd80 wt%Cu alloy. SEM-EDS analysis of the membrane tubes suggested that the water-gas shift environment caused pinhole formation in the retentate surfaces of the Pd and Pd80 wt%Cu after approximately 8 days of operation.

Osemwengie, I.; Enick, R.M.; Killmeyer, R.P.

2007-07-20

47

A comparative evaluation of cobalt chromium oxide, cobalt manganese oxide, cobalt manganese oxide, and copper manganese oxide as catalysts for the water-gas shift reaction  

SciTech Connect

Cobalt chromium oxide, cobalt manganese oxide, and copper manganese oxide have been compared as catalysts for the water-gas shift reaction. Cobalt chromium oxide and cobalt manganese oxide catalysts can give both high activity and long lifetimes for this reaction. Cobalt chromium oxide catalysts display higher activity compared to the other catalyst systems and this is shown that both the cobalt chromium oxide and the cobalt manganese oxide catalysts are not sensitive to the presence of up to 240 ppm feedstock sulphur impurities (H{sub 2}S and COS) and high catalyst activity can be maintained either in the presence or in the absence of feedstock sulphur. The copper manganese oxide catalysts are demonstrated to be particularly sensitive to feedstock sulphur, being significantly poisoned at levels as low as 1 ppm H{sub 2}S. An investigation of the mechanism of the water-gas shift mechanism over the three catalyst systems is also described using both kinetic and model reagent studies. Based on these studies, a mechanism is proposed for the cobalt- and copper-containing catalyst systems involving the formation of a surface formate intermediate.

Hutchings, G.J. (Univ. of Liverpool (United Kingdom)); Copperthwaite, R.G.; Gottschalk, F.M.; Hunter, R.; Mellor, J.; Orchard, S.W.; Sangiorgio, T. (Univ. of the Witwatersrand, Johannesburg (South Africa))

1992-10-01

48

Water-gas shift reaction on metal nanoclusters encapsulated in mesoporous ceria studied with ambient-pressure X-ray photoelectron spectroscopy.  

PubMed

Metal nanoclusters (Au, Pt, Pd, Cu) encapsulated in channels of mesoporous ceria (mp-CeO(2)) were synthesized. The activation energies of water-gas shift (WGS) reaction performed at oxide-metal interfaces of metal nanoclusters encapsulated in mp-CeO(2) (M@mp-CeO(2)) are lower than those of metal nanoclusters impregnated on ceria nanorods (M/rod-CeO(2)). In situ studies using ambient-pressure XPS (AP-XPS) suggested that the surface chemistry of the internal concave surface of CeO(2) pores of M@mp-CeO(2) is different from that of external surfaces of CeO(2) of M/rod-CeO(2) under reaction conditions. AP-XPS identified the metallic state of the metal nanoclusters of these WGS catalysts (M@mp-CeO(2) and M/rod-CeO(2)) under a WGS reaction condition. The lower activation energy of M@mp-CeO(2) in contrast to M/rod-CeO(2) is related to the different surface chemistry of the two types of CeO(2) under the same reaction condition. PMID:22978416

Wen, Cun; Zhu, Yuan; Ye, Yingchun; Zhang, Shiran; Cheng, Fang; Liu, Yi; Wang, Paul; Tao, Franklin Feng

2012-09-21

49

Characterization of CeO2-Supported Cu-Pd Bimetallic Catalyst for the Oxygen-Assisted Water-Gas Shift Reaction  

SciTech Connect

This study was focused to investigate the roles of Cu and Pd in CuPd/CeO2 bimetallic catalysts containing 20-30 wt% Cu and 0.5-1 wt% Pd used in the oxygen-assisted water-gas shift (OWGS) reaction employing a combined bulk and surface characterization techniques such as XRD, TPR, CO chemisorption, and in-situ XPS. The catalytic activity for CO conversion and the stability of catalyst during on-stream operation increased by the addition of Cu to Pd/CeO2 or Pd to Cu/CeO2 monometallic catalysts, especially when the OWGS reaction was performed under low temperatures, below 200oC. The bimetallic catalyst after leaching with nitric acid retained about 60% of its original activity. The TPR of monometallic Cu/CeO2 showed reduction of CuO supported on CeO2 in two distinct regions, around 150 and 250oC. The high temperature peak disappeared and reduction occurred in a single step around 150oC upon Pd addition. The Pd dispersion decreased from 38.5% for Pd/CeO2 to below 1% for CuPd/CeO2 bimetallic catalyst. In-situ XPS studies showed a shift in Cu 2p peaks toward lower binding energy (BE) with concommitant shift in the Pd 3d peaks toward higher BE. Addition of Pd decreased the surface Cu concentration while the concentration of Pd remained unaltered. All these observations indicated the formation of Cu-Pd surface alloy. The valence band XP spectra collected below 10 eV corroborated the core level XP spectra and indicated that Cu is mainly involved in the catalytic reaction. The improved catalytic activity and stability of CuPd/CeO2 bimetallic catalyst was attributed to the alloy formation.

Fox, Elise; Velu, Subramani; Engelhard, Mark H.; Chin, Ya-Huei; Miller, Jeffrey T.; Kropf, Jeremy; Song, Chunshan

2008-12-10

50

Low temperature water–gas shift: in situ DRIFTS-reaction study of ceria surface area on the evolution of formates on Pt\\/CeO 2 fuel processing catalysts for fuel cell applications  

Microsoft Academic Search

Steady state infrared (IR) measurements for adsorption of only CO and under water–gas shift (WGS) reaction conditions indicate that formates are present on the surface of reduced ceria, and that their concentrations vary with surface area of partially reduced ceria. Under steady state WGS, the concentrations of surface formates are strongly limited at high CO conversions. However, at low temperatures

Gary Jacobs; Leann Williams; Uschi Graham; Gerald A Thomas; Dennis E Sparks; Burtron H Davis

2003-01-01

51

Novel Au/La2O3 and Au/La2O2SO4 catalysts for the water-gas shift reaction prepared via an anion adsorption method.  

PubMed

An anion-adsorption technique in which [Au(OH)(4)](-) is preferentially adsorbed onto La(2)O(3) and La(2)O(2)SO(4) surfaces is used to prepare two catalysts active for the low-temperature water-gas shift reaction. PMID:22498919

Lessard, Joseph D; Valsamakis, Ioannis; Flytzani-Stephanopoulos, Maria

2012-04-12

52

Microchannel Reactors for Fuel Processing Applications I. Water Gas Shift Reactor  

SciTech Connect

The water gas shift reactor is one of the critical components of a multi-reactor fuel processing system that supports distributed energy production through the use of a fuel cell. The water gas shift reaction converts carbon monoxide (produced in the primary conversion stage of the fuel processor) and water to carbon dioxide and hydrogen. The water gas shift reaction has slow observed kinetics, with multiple-second contact times, which are cited in fixed-bed reactors. The intrinsic reaction kinetics, however, are measured to be fast, with millisecond contact times, which enables miniaturized deployment in a microchannel reactor. Microchannel reactors reduce heat and mass transport limitations for reactions, and thus facilitate exploiting fast intrinsic reaction kinetics, ie. high effectiveness factors. The implications of this work suggest that a water gas shift reactor for fuel processor (and other applications) will approach sizes one to two orders of magnitude smaller than conventional processing hardware.

Tonkovich, Annalee Y. (Battelle Memorial Instituted); Zilka, Jennifer L. (Previous PNNL Employee); Lamont, Micheal J. (BATTELLE COLUMBUS OFFICE); Wang, Yong (BATTELLE (PACIFIC NW LAB)); Wegeng, Robert S. (BATTELLE (PACIFIC NW LAB))

1998-10-17

53

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

SciTech Connect

In this quarter, we have focused on the completion of the loose ends of the experimental study. A series of CO{sub 2}-affinity membranes (carbonaceous base) prepared previously were characterized and evaluated for their suitability for the proposed application The CO{sub 2} permeance and selectivity are 0.5 to >3 m{sup 3}/m{sub 2}/hr/bar and 4 to 10 for CO{sub 2} over nitrogen respectively. Based upon its performance dependence on temperature and pore size, we conclude that this type of CO{sub 2} affinity membrane shows significant surface affinity to CO{sub 2} over nitrogen even at the temperature as high as 220 C, which is within the typical operating condition for LTS-WGS. Future study should focus on mixture separations for CO/CO{sub 2}/H{sub 2} to establish the selectivity of CO{sub 2} over CO and H{sub 2} which are present in the WGS reaction of the coal gasifier off-gas.

Paul K.T. Liu

2005-06-01

54

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

SciTech Connect

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

Paul K. T. Liu

2005-01-31

55

Catalytic links among the water–gas shift, water-assisted formic acid decomposition, and methanol steam reforming reactions over Pt-promoted thoria  

Microsoft Academic Search

Implied in the proposed water–gas shift (WGS) mechanisms for Pt\\/ceria and Pt\\/thoria catalysts is the presumption that reduced defect centers are formed on the surface. This X-ray absorption near-edge spectroscopy study provides direct results indicating that Pt facilitates reduction in the surface shell of thoria. Mechanistic arguments from in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) are provided suggesting

Gary Jacobs; Patricia M. Patterson; Uschi M. Graham; Adam C. Crawford; Alan Dozier; Burtron H. Davis

2005-01-01

56

Flame synthesis of nanosized Cu-Ce-O, Ni-Ce-O, and Fe-Ce-O catalysts for the water-gas shift (WGS) reaction.  

PubMed

A flame synthesis method has been used to prepare nanosized, high-surface-area Cu-Ce-O, Ni-Ce-O, and Fe-Ce-O catalysts from aqueous solutions of metal acetate precursors. The particles were formed by vaporization of the precursors followed by reaction and then gas to particle conversion. The specific surface areas of the synthesized powders ranged from 127 to 163 m(2)/g. High-resolution transmission electron microscope imaging showed that the particle diameters for the ceria materials are in the range of 3-10 nm, and a thin layer of amorphous material was observed on the surface of the particles. The presence and surface enrichment of the transition-metal oxides (CuO, NiO, and Fe(2)O(3)) on the ceria particles were detected using X-ray photoelectron spectroscopy. Electron energy-loss spectroscopic studies suggest the formation of a core-shell structure in the as-prepared particles. Extended X-ray absorption fine structure studies suggest that the dopants in all M-Ce-O systems are almost isostructural with their oxide counterparts, indicating the doping materials form separate oxide phases (CuO, Fe(2)O(3), NiO) within the host matrix (CeO(2)). Etching results confirm that most of the transition-metal oxides are present on the surface of CeO(2), easily dissolved by nitric acid. The performance of the flame-synthesized catalysts was examined toward water-gas shift (WGS) activity for fuel processing applications. The WGS activity of metal ceria catalysts decreases in the order Cu-Ce-O > Ni-Ce-O > Fe-Ce-O > CeO(2) with a feed mixture having a hydrogen to carbon monoxide (H(2)/CO) ratio of 1. There was no methane formation for these catalysts under the tested conditions. PMID:20356136

Pati, Ranjan K; Lee, Ivan C; Hou, Sicong; Akhuemonkhan, Osifo; Gaskell, Karen J; Wang, Qi; Frenkel, Anatoly I; Chu, Deryn; Salamanca-Riba, Lourdes G; Ehrman, Sheryl H

2009-11-01

57

Unusual Physical and Chemical Properties of Ni in Ce1-xNixO2-y Oxides: Structural Characterization and Catalytic Activity for the Water Gas Shift Reaction  

SciTech Connect

The structural and electronic properties of Ce{sub 1-x}Ni{sub x}O{sub 2-y} nanosystems prepared by a reverse microemulsion method were characterized with synchrotron-based X-ray diffraction, X-ray absorption spectroscopy, Raman spectroscopy, and density functional calculations. The Ce{sub 1-x}Ni{sub x}O{sub 2-y} systems adopt a lattice with a fluorite-type structure with an acute local order where Ni displays a strongly distorted (oxygen) nearest-neighbor coordination and the presence of Ni atoms as first cation distances, pointing to the existence of Ni-O-Ni entities embedded into the ceria lattice. A Ni {leftrightarrow} Ce exchange within the CeO{sub 2} leads to a charge redistribution and the appearance of O vacancies. The Ni?O bonds in Ce{sub 1-x}Ni{sub x}O{sub 2-y} are more difficult to reduce than the bonds in pure NiO. The specific structural configuration of Ni inside the mixed-metal oxide leads to a unique catalyst with a high activity for the water gas shift (CO + H{sub 2}O {yields} H{sub 2} + CO{sub 2}) reaction and a simultaneous reduction of the methanation activity of nickel. Characterization results indicate that small particles of metallic Ni at the interface position of a ceria network may be the key for high WGS activity and that the formate?carbonate route is operative for the production of hydrogen.

Rodriguez, J.A.; Barrio, L.; Kubacka, A.; Zhou, G.; Estrella, M.; Mart& #305; nez-Arias, A.; Hanson, J.C.; Fernandez-Garc& #305; a, M.

2010-07-29

58

Unusual Physical and Chemical Properties of Ni in Ce1-xNixO2-y Oxides: Structural Characterization and Catalytic Activity for the Water Gas Shift Reaction  

SciTech Connect

The structural and electronic properties of Ce{sub 1-x}Ni{sub x}O{sub 2-y} nanosystems prepared by a reverse microemulsion method were characterized with synchrotron-based X-ray diffraction, X-ray absorption spectroscopy, Raman spectroscopy, and density functional calculations. The Ce{sub 1-x}Ni{sub x}O{sub 2-y} systems adopt a lattice with a fluorite-type structure with an acute local order where Ni displays a strongly distorted (oxygen) nearest-neighbor coordination and the presence of Ni atoms as first cation distances, pointing to the existence of Ni-O-Ni entities embedded into the ceria lattice. A Ni {leftrightarrow} Ce exchange within the CeO{sub 2} leads to a charge redistribution and the appearance of O vacancies. The Ni-O bonds in Ce{sub 1-x}Ni{sub x}O{sub 2-y} are more difficult to reduce than the bonds in pure NiO. The specific structural configuration of Ni inside the mixed-metal oxide leads to a unique catalyst with a high activity for the water gas shift (CO + H{sub 2}O {yields} H{sub 2} + CO{sub 2}) reaction and a simultaneous reduction of the methanation activity of nickel. Characterization results indicate that small particles of metallic Ni at the interface position of a ceria network may be the key for high WGS activity and that the formate-carbonate route is operative for the production of hydrogen.

Barrio, L.; Kubacka, A; Zhou, G; Estrella, M; Martinez-Arias, A; Hanson, J; Fernandez-Garcia, M; Rodriguez, J

2010-01-01

59

Biological Water-Gas Shift Conversion of Carbon Monoxide to Hydrogen: Milestone Completion Report  

SciTech Connect

This report summarizes the results of research and economic analysis on a biological water-gas shift process for the production of hydrogen. The organism Rubrivivax gelatinosus CBS is a photosynthetic bacteria which can perform the water-gas shift reaction under anaerobic conditions. The report describes some of the technical issues regarding the process, addresses some claimed benefits of the process and presents some results from economic studies of different process configurations.

Amos, W. A.

2004-01-01

60

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

61

Comparison of the Activity of Au/CeO2 and Au/Fe2O3 Catalysts for the CO Oxidation and the Water-gas Shift Reactions  

SciTech Connect

We compare the activity and relevant gold species of nanostructured gold-cerium oxide and gold-iron oxide catalysts for the CO oxidation by dioxygen and water. Well dispersed gold nanoparticles in reduced form provide the active sites for the CO oxidation reaction on both oxide supports. On the other hand, oxidized gold species, strongly bound on the support catalyze the water-gas shift reaction. Gold species weakly bound to ceria (doped with lanthana) or iron oxide can be removed by sodium cyanide at pH {>=}12. Both parent and leached catalysts were investigated. The activity of the leached gold-iron oxide catalyst in CO oxidation is approximately two orders of magnitude lower than that of the parent material. However, after exposure to H{sub 2} up to 400 C gold diffuses out and is in reduced form on the surface, a process accompanied by a dramatic enhancement of the CO oxidation activity. Similar results were found with the gold-ceria catalysts. On the other hand, pre-reduction of the calcined leached catalyst samples did not promote their water-gas shift activity. UV-Vis, XANES and XPS were used to probe the oxidation state of the catalysts after various treatments.

Deng,W.; Carpenter, C.; Yi, N.; Flytzani-Stephanopoulos, M.

2007-01-01

62

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

63

Flame Synthesis of Nanosized Cu-Ce-O, Ni-Ce-O, and Fe-Ce-O Catalysts for the Water-Gas Shift (WGS) Reaction.  

National Technical Information Service (NTIS)

A flame synthesis method has been used to prepare nanosized, high- surface-area Cu-Ce-O, Ni-Ce-O, and Fe-Ce-O catalysts from aqueous solutions of metal acetate precursors. The particles were formed by vaporization of the precursors followed by reaction an...

I. C. Lee K. J. Gaskell O. Akhuemonkhan R. K. Pati S. Hou

2009-01-01

64

Water–gas shift activity of Au and Cu nanoparticles supported on molybdenum oxides  

Microsoft Academic Search

The water–gas shift (WGS, CO+H2O?H2+CO2) reaction was studied on a series of gold\\/molybdena and copper\\/molybdena surfaces. Films of MoO2 were grown by exposing a Mo(110) substrate to NO2 at 1000K. Then, Au and Cu nanoparticles were deposited on the oxide surfaces and their WGS activity was measured in a reaction cell (PCO=20Torr; PH2O=10?Torr; T=575–650K). Although bulk metallic Au is inactive

J. A. Rodríguez; P. Liu; J. Hrbek; M. Pérez; J. Evans

2008-01-01

65

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

66

Unraveling the Active Site in Copper-Ceria Systems for the Water-Gas Shift Reaction: In Situ Characterization of an Inverse Powder CeO2-x/CuO-Cu Catalyst  

SciTech Connect

An inverse powder system composed of CeO{sub 2} nanoparticles dispersed over a CuO-Cu matrix is proposed as a novel catalyst for the water-gas shift reaction. This inverse CeO{sub 2}/CuO-Cu catalyst exhibits a higher activity than standard Cu/CeO{sub 2} catalysts. In situ synchrotron characterization techniques were employed to follow the structural changes of CeO{sub 2}/CuO-Cu under reaction conditions. Time-resolved X-ray diffraction experiments showed the transformation of CuO to metallic Cu via a Cu{sub 2}O intermediate. Short-order structural changes were followed by pair distribution function analysis and corroborated the results obtained by diffraction. Moreover, X-ray absorption spectroscopy also revealed oxidation state changes from Cu{sup 2+} to Cu{sup 0} and the partial reduction of CeO{sub x} nanoparticles. The activity data obtained by mass spectrometry revealed that hydrogen production starts once the copper has been fully reduced. The strong interaction of ceria and copper boosted the catalytic performance of the sample. The inverse catalyst was active at low temperatures, stable to several reaction runs and to redox cycles. These characteristics are highly valuable for mobile fuel cell applications. The active phases of the inverse CeO{sub 2}/CuO-Cu catalyst are partially reduced ceria nanoparticles strongly interacting with metallic copper. The nature and structure of the ceria nanoparticles are of critical importance because they are involved in processes related to water dissociation over the catalyst surface.

Barrio, L.; Estrella, M; Zhou, G; Wen, W; Hanson, J; Hungria, A; Hornes, A; Fernandez-Garcia, M; Martinez-Arias, A; Rodriguez, J

2010-01-01

67

Unraveling the Active Site in Copper-ceria Systems for the Water Gas Shift Reaction: In-situ Characterization of an Inverse Powder CeO2-x/CuO-Cu Catalyst  

SciTech Connect

An inverse powder system composed of CeO{sub 2} nanoparticles dispersed over a CuO-Cu matrix is proposed as a novel catalyst for the water-gas shift reaction. This inverse CeO{sub 2}/CuO-Cu catalyst exhibits a higher activity than standard Cu/CeO{sub 2} catalysts. In situ synchrotron characterization techniques were employed to follow the structural changes of CeO{sub 2}/CuO-Cu under reaction conditions. Time-resolved X-ray diffraction experiments showed the transformation of CuO to metallic Cu via a Cu{sub 2}O intermediate. Short-order structural changes were followed by pair distribution function analysis and corroborated the results obtained by diffraction. Moreover, X-ray absorption spectroscopy also revealed oxidation state changes from Cu{sup 2+} to Cu{sup 0} and the partial reduction of CeOx nanoparticles. The activity data obtained by mass spectrometry revealed that hydrogen production starts once the copper has been fully reduced. The strong interaction of ceria and copper boosted the catalytic performance of the sample. The inverse catalyst was active at low temperatures, stable to several reaction runs and to redox cycles. These characteristics are highly valuable for mobile fuel cell applications. The active phases of the inverse CeO{sub 2}/CuO-Cu catalyst are partially reduced ceria nanoparticles strongly interacting with metallic copper. The nature and structure of the ceria nanoparticles are of critical importance because they are involved in processes related to water dissociation over the catalyst surface.

Rodriguez, J.A.; Barrio, L.; Estrella, M.; Zhou, G.; Wen, W.; Hanson, J.C.; Hungría, A.B.; Hornés, A.; Fernández-García, M.; Arturo Martínez-Arias, A.

2010-03-04

68

Investigation of the characteristics of a compact steam reformer integrated with a water-gas shift reactor  

Microsoft Academic Search

The objective of this study is to investigate numerically a compact steam methane reforming (SMR) system integrated with a water-gas shift (WGS) reactor. Separate numerical models are established for the combustion part, SMR and WGS reaction bed. The concentration of species at the exits of the SMR and WGS bed, and the temperatures in the WGS bed are in good

Yong-Seog Seo; Dong-Joo Seo; Yu-Taek Seo; Wang-Lai Yoon

2006-01-01

69

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

70

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

71

Water-gas shift on gold catalysts: catalyst systems and fundamental studies.  

PubMed

Since the pioneering finding by Haruta et al. that small gold nanoparticles on reducible supports can be highly active for low-temperature CO oxidation, the synthesis, characterization, and application of supported gold catalysts have attracted much attention. The water-gas shift reaction (WGSR: CO + H2O = CO2 + H2) is important for removing CO and upgrading the purity of H2 for fuel cell applications, ammonia synthesis, and selective hydrogenation processes. In recent years, much attention has been paid to exploration the possibility of using supported gold nanocatalysts for WGSR and understanding the fundamental aspects related to catalyst deactivation mechanisms, nature of active sites, and reaction mechanisms. Here we summarize recent advances in the development of supported gold catalysts for this reaction and fundamental insights that can be gained, and furnish our assessment on the status of research progress. PMID:23928722

Tao, Franklin Feng; Ma, Zhen

2013-08-28

72

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% Al{sub 2}O{sub 3}, with 8 wt% Cr{sub 2}O{sub 3}, 4 wt% CuO, and the balance Fe{sub 2}O{sub 3}. All of the catalysts were compared to a reference WGS catalyst (88 wt% FeO{sub x}, 8 wt% Cr{sub 2}O{sub 3}, 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/ft{sup 2} based on a 600 psi syngas inlet pressure and corresponded to membranes costing $191 per square foot. Over 40 hours of 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 in

Thomas Barton; Tiberiu Popa

2009-06-30

73

Metal/ceria water-gas shift catalysts for automotive polymer electrolyte fuel cell system.  

SciTech Connect

Polymer electrolyte fuel cell (PEFC) systems are a leading candidate for replacing the internal combustion engine in light duty vehicles. One method of generating the hydrogen necessary for the PEFC is reforming a liquid fuel, such as methanol or gasoline, via partial oxidation, steam reforming, or autothermal reforming (a combination of partial oxidation and steam reforming). The H{sub 2}-rich reformate can contain as much as 10% carbon monoxide. Carbon monoxide has been shown to poison the platinum-based anode catalyst at concentrations as low as 10 ppm,1 necessitating removal of CO to this level before passing the reformate to the fuel cell stack. The water-gas shift (WGS) reaction, CO + H{sub 2}O {rightleftharpoons} CO{sub 2} + H{sub 2}, is used to convert the bulk of the reformate CO to CO{sub 2}. Industrially, the WGS reaction is conducted over two catalysts, which operate in different temperature regimes. One catalyst is a FeCr mixed oxide, which operates at 350-450 C and is termed the high-temperature shift (HTS) catalyst. The second catalyst is a CuZn mixed oxide, which operates at 200-250 C and is termed the low-temperature shift (LTS) catalyst. Although these two catalysts are used industrially in the production of H{sub 2} for ammonia synthesis, they have major drawbacks that make them unsuitable for transportation applications. Both the LTS and the HTS catalysts must first be ''activated'' before being used. For example, the copper in the copper oxide/zinc oxide LTS catalyst must first be reduced to elemental copper in situ before it becomes active for the WGS reaction. This reduction reaction is exothermic and must be carried out under well- controlled conditions using a dilute hydrogen stream (1 vol% H{sub 2}) to prevent high catalyst temperatures, which can result in sintering (agglomeration) of the copper particles and loss of active surface area for the WGS reaction. Also, once the catalyst has been activated by reduction, it must be protected from exposure to ambient air to prevent re-oxidation of the copper. The activated catalyst must also be protected from the condensation of liquids, for example, during start-up or transient operation. For these reasons, a more thermally rugged catalyst is needed which has sufficient activity to operate at the low temperatures that are thermodynamically necessary to achieve low CO concentrations.

Myers, D. J.; Krebs, J. F.; Carter, J. D.; Kumar, R.; Krumpelt, M.

2002-01-11

74

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

Microsoft Academic Search

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 H2, CO, CO2 and H2O (steam) followed by water gas shift (WGS) and CO

Wolfgang Ruettinger; Oleg Ilinich; Robert J. Farrauto

2003-01-01

75

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

76

Trends in Low Temperature Water Gas Shift Reactivity on Transition Metals  

SciTech Connect

Low-temperature water–gas shift reactivity trends on transition metals were investigated with the use of a microkinetic model based on a redox mechanism. It is established that the adsorption energies for carbon monoxide and oxygen can describe to a large extent changes in the remaining activation and adsorption energies through linear correlations. In comparisons with experimental data it is found that the model predicts well the order of catalytic activities for transition metals, although it fails to quantitatively describe the experimental data. This discrepancy could be due to the assumption that the redox mechanism dominates and to the neglect of adsorbate interactions, which play an important role at high coverages. The model predicts that the activity of copper can be improved by increasing the strengths with which carbon monoxide and oxygen are bonded to the surface, thus suggesting possible directions for improving the catalyst for low-temperature WGSR.

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

2005-01-25

77

Toward water-gas shift enhancement and carbon capture in gasification environments  

SciTech Connect

The United States Department of Energy's National Energy Technology Laboratory (NETL) is aggressively pursuing research and development directed towards mitigating apprehensions over fuel independence, energy availability and reliability and environmental issues, especially as related to global warming. The production of “synthesis gas” (syngas) from indigenous carbonaceous feedstocks has the potential to address some of these energy and environmental concerns. The abundance of coal in the US in conjunction with the flexibility of syngas, which can be converted to electricity, hydrogen and/or liquid fuels, is considered a promising near- to mid-term component in the transition to a renewable energy society. Hydrogen membranes, implemented as a means of separation or integrated as a water-gas shift membrane reactor (WGSMR), have been identified as a promising means of maximizing the production of pure hydrogen while simultaneously yielding a high-pressure, concentrated CO2-containing stream ready for sequestration.

Morreale, B.D.; Howard, B.; Taylor, C.; Osemwengie, I.; Enick, R.M.; Miller, J.B.; Sholl, D.S.; Alfonso, D.R.; Ciocco, M.V.

2007-08-01

78

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

79

In situ/operando studies for the production of hydrogen through the water-gas shift on metal oxide catalysts.  

PubMed

In this perspective article, we show how a series of in situ techniques {X-ray diffraction (XRD), pair-distribution-function analysis (PDF), X-ray absorption fine structure (XAFS), environmental transmission electron microscopy (ETEM), infrared spectroscopy (IR), ambient-pressure X-ray photoelectron spectroscopy (AP-XPS)} can be combined to perform detailed studies of the structural, electronic and chemical properties of metal oxide catalysts used for the production of hydrogen through the water-gas shift reaction (WGS, CO + H2O ? H2 + CO2). Under reaction conditions most WGS catalysts undergo chemical transformations that drastically modify their composition with respect to that obtained during the synthesis process. Experiments of time-resolved in situ XRD, XAFS, and PDF indicate that the active phase of catalysts which combine Cu, Au or Pt with oxides such as ZnO, CeO2, TiO2, CeOx/TiO2 and Fe2O3 essentially involves nanoparticles of the reduced noble metals. The oxide support undergoes partial reduction and is not a simple spectator, facilitating the dissociation of water and in some cases modifying the chemical properties of the supported metal. Therefore, to optimize the performance of these catalysts one must take into consideration the properties of the metal and oxide phases. IR and AP-XPS have been used to study the reaction mechanism for the WGS on metal oxide catalysts. Data of IR spectroscopy indicate that formate species are not necessarily involved in the main reaction path for the water-gas shift on Cu-, Au- and Pt-based catalysts. Thus, a pure redox mechanism or associative mechanisms that involve either carbonate-like (CO3, HCO3) or carboxyl (HOCO) species should be considered. In the last two decades, there have been tremendous advances in our ability to study catalytic materials under reaction conditions and we are moving towards the major goal of fully understanding how the active sites for the production of hydrogen through the WGS actually work. PMID:23660768

Rodriguez, José A; Hanson, Jonathan C; Stacchiola, Dario; Senanayake, Sanjaya D

2013-05-09

80

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

81

Catalytic membranes for facilitating the water-gas shift reaction  

SciTech Connect

This program is directed at furthering the development of a metal- membrane-based process for economically producing pure hydrogen from the raw gasifier stream. A related program is directed at developing a metal-membrane-based process for cleanly and efficiently removing hydrogen sulfide from the hot gas stream. Both of these processes would be accomplished at 500{degree}C to 800{degree}C and are based on a novel hydrogen-permeable composite-metal membrane. Specific program objectives include (1) design, fabrication, and demonstration of pre-prototype membrane modules; (2) improving the membrane composition to increase the hydrogen flux; (3) evaluating membrane lifetime; and (4) conducting engineering and economic analyses of the processes.

Edlund, D.J. [Bend Research, Inc., OR (United States)

1993-08-01

82

Exposed Surfaces on Shape-Controlled Ceria Nanoparticles Revealed through AC-TEM and Water-Gas Shift Reactivity.  

PubMed

Aberration-corrected transmission electron microscopy and high-angle annular dark field imaging was used to investigate the surface structures and internal defects of CeO2 nanoparticles (octahedra, rods, and cubes). Further, their catalytic reactivity in the water-gas shift (WGS) reaction and the exposed surface sites by using FTIR spectroscopy were tested. Rods and octahedra expose stable (111) surfaces whereas cubes have primarily (100) facets. Rods also had internal voids and surface steps. The exposed planes are consistent with observed reactivity patterns, and the normalized WGS reactivity of octahedra and rods were similar, but the cubes were more reactive. In?situ FTIR spectroscopy showed that rods and octahedra exhibit similar spectra for ?OH groups and that carbonates and formates formed upon exposure to CO whereas for cubes clear differences were observed. These results provide definitive information on the nature of the exposed surfaces in these CeO2 nanostructures and their influence on the WGS reactivity. PMID:24108516

Agarwal, Shilpa; Lefferts, Leon; Mojet, Barbara L; Ligthart, D A J Michel; Hensen, Emiel J M; Mitchell, David R G; Erasmus, Willem J; Anderson, Bruce G; Olivier, Ezra J; Neethling, Johannes H; Datye, Abhaya K

2013-09-24

83

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

84

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

85

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

SciTech Connect

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

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

2008-05-31

86

Surface interfaces in low temperature water-gas shift: The metal oxide synergy, the assistance of co-adsorbed water, and alkali doping  

Microsoft Academic Search

With new developments in polymer electrolyte membrane fuel cells, interest is growing in fuel processor technology for converting feedstocks to hydrogen. One critical step in the process to convert CO and purify hydrogen is low temperature water-gas shift (LTS). Control of the LTS rate can be achieved by designing catalysts in a way that produces and rapidly decomposes the surface

Gary Jacobs; Burtron H. Davis

2010-01-01

87

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

88

Deactivation of Pt\\/CeO 2 water-gas shift catalysts due to shutdown\\/startup modes for fuel cell applications  

Microsoft Academic Search

Fuel cells and its fuel processor will be frequently shutdown and re-started depending on the power demand. Deactivation of Pt\\/CeO2 water-gas shift catalysts under conditions simulating shutdown was observed and studied using a combination of techniques such as Fourier-transform infrared (FT-IR) spectroscopy, high-resolution transmission electron microscopy (HRTEM), CO chemisorption and catalytic activity test. Results show that formation of carbonates occurs

Xinsheng Liu; Wolfgang Ruettinger; Xiaoming Xu; Robert Farrauto

2005-01-01

89

Cr-free Fe-based water-gas shift catalysts prepared through propylene oxide-assisted sol–gel technique  

Microsoft Academic Search

Chromium-free Fe-based water-gas shift catalysts were prepared through a gelation agent-assisted sol–gel route utilizing propylene oxide and citric acid as the gelation agents. Catalyst preparation using propylene oxide is a “one-pot” method that is cleaner, more eco-friendly and less time consuming over our previously developed sol–gel method for preparing Fe–Al–Cu and leads to comparable activities. The effect of Cu loading

Preshit Gawade; Burcu Mirkelamoglu; Bing Tan; Umit S. Ozkan

2010-01-01

90

In-situ Characterization of CuFe2O4 and Cu/Fe3O4 Water-Gas Shift Catalysts  

SciTech Connect

Mixtures of copper and iron oxides are used as industrial catalysts for the water-gas shift (WGS, CO + H2O ? H2 + CO2). In-situ time-resolved X-ray diffraction, X-ray absorption fine structure, and atomic pair distribution function analysis were used to study the reduction of CuFe2O4 with CO and the behavior of CuFe2O4 and Cu/Fe2O3 catalysts under WGS reaction conditions. Metal?oxygen?metal interactions enhance the stability of Cu2+ and Fe3+ in the CuFe2O4 lattice, and the mixed-metal oxide is much more difficult to reduce than CuO or Fe2O3. Furthermore, after heating mixtures of CuFe2O4/CuO in the presence of CO or CO/H2O, the cations of CuO migrate into octahedral sites of the CuFe2O4 lattice at temperatures (200-250 oC) in which CuO is not stable. Above 250 oC, copper leaves the oxide, the occupancy of the octahedral sites in CuFe2O4 decreases, and diffraction lines for metallic Cu appear. From 350 to 450 oC, there is a massive reduction of CuFe2O4 with the formation of metallic Cu and Fe3O4. At this point, the sample becomes catalytically active for the production of H2 from the reaction of H2O with CO. Neutral Cu0 (i.e. no Cu+1 or Cu+2 cations) is the active species in the catalysts, but interactions with the oxide support are necessary in order to obtain high catalytic activity. These studies illustrate the importance of in-situ characterization when dealing with mixed-metal oxide WGS catalysts.

Rodriguez,J.A.; Estrella, M.; Barrio, L.; Zhou, G.; Wang, X.; Wang, Q.; Wen, W.; Hanson, J.C.; Frenkel, A.

2009-08-13

91

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts; Technical progress report, June 1992--August 1992  

SciTech Connect

During this quarter, high pressure (up to 100 atm = 10.3 MPa), high temperature (up to 350{degrees}C) catalyst testing was carried out with the 20 Wt% CS/MoS{sub 2} catalyst that was prepared. It was verified that this is an active catalyst for the synthesis of linear C{sub l}-C{sub 4} alcohols and that the yield increases with increasing temperature. However, the product selectivity is shifted toward enhanced hydrocarbon production, principally of methane. Temperature, pressure, and flow rate dependences of the synthesis reactions were also 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. The temperature seemed to produce the largest effect on alcohol yield and on the hydrocarbon selectivity, with both increasing with increasing temperature. The presence of 45.5 ppM H{sub 2}S in the synthesis gas did increase the C{sub 2}{sup +} alcohol/methanol molar ratio at 285{degrees}C, but this effect was not noticeable at higher temperatures under the reaction conditions that were employed. On the other hand, the presence of H{sub 2}S decreased the yield of methane at high temperatures (340--350{degrees}C), but this effect was not noticeable at the lower temperatures that were utilized. At high temperature and pressure (350{degrees}C and 10.3 MPa) with 45.5 ppM H{sub 2}S in the synthesis gas, it was shown that increasing the gas hourly space velocity of the synthesis gas reactant significantly decreased the yield of methane, while affecting the yield of alcohols to a much lesser extent.

Klier, K.; Herman, R.G.; Deemer, M.

1992-09-01

92

Modified zeolite membrane reactor for high temperature water gas shift reaction  

Microsoft Academic Search

A porous ?-alumina tube supported MFI-type zeolite membrane was modified by depositing molecular silica species in the zeolitic channels via in situ catalytic cracking of methyl diethoxysilane at a limited number of active sites. The modified zeolite membrane exhibited a H2\\/CO2 perm-selectivity of 68.3 with H2 permeance of 2.94×10?7mol\\/m2sPa at 550°C. The modified zeolite membrane tube was packed with a

Zhong Tang; Seok-Jhin Kim; Gunugunuri K. Reddy; Junhang Dong; Panagiotis Smirniotis

2010-01-01

93

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

94

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

SciTech Connect

During calcination of the precipitated and dried MoS{sub 3} to form MOS{sub 2}, it was found that small sample sizes were needed to provide thermal control of the highly exothermic decomposition reaction in the 8 mm ID quartz tube used for this purpose. Characterization of MoS{sub 2} and Cs/MoS{sub 2} catalysts have been carried out by X-ray powder diffraction (XRD) after each synthesis step. In addition, the XRD analyses were conducted after prolonged air exposure of the Cs-doped MoS{sub 2} catalyst. It was shown that prolonged exposure to the ambient atmosphere led to segregation and crystallization of the cesium formate dopant. Thus, catalytic testing should be carried out with freshly prepared samples that are protected from the ambient atmosphere. Catalytic testing is underway to determine if there is an inverse correlation of catalytic activity and selectivity with prolonged air exposure of the catalyst.

Klier, K.; Herman, R.; Deemer, M.

1994-03-01

95

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

96

CO(2) Selective Ceramic Membrane for Water-Gas Shift Reaction with Concomitant for the Recovery of CO(2).  

National Technical Information Service (NTIS)

The study in the previous quarterly report suggested the possibility that hydrotalcite crystals in the neighborhood of 0.2 micrometers or greater are immediately formed when the two solutions are combined together. The conventional approach (such as metho...

P. K. T. Liu

2001-01-01

97

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

SciTech Connect

During Year I this project has been focused on these two topic areas: (i) understanding comprehensively the CO{sub 2} affinity vs temperature, reversibility of CO{sub 2} affinity, and the role of water in order to select an optimum hydrotalcite composition for membrane preparation, and (ii) developing a membrane synthesis protocol for depositing the hydrotalcite material into a commercially available ceramic membrane from us. This annual report documents the progress we have made in these areas. In summary, the Year I study has demonstrated the technical feasibility of preparing a hydrotalcite. The proposed membrane synthesis protocol will be refined and optimized in Year II. In addition, surface analysis techniques employing FTIR and DRIFTS have been developed. These techniques have been applied to a hydrotalcite model compound to demonstrate our ability to screen hydrotalcite materials in terms of its composition and % of cation substitution. These techniques will be utilized in Year II to formulate an optimized hydrotalcite candidate for preparing a membrane with maximized CO{sub 2} transport at the proposed process condition.

Paul K.T. Liu

2001-09-30

98

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

SciTech Connect

For the purpose of process simulation and economic analysis of the proposed CO{sub 2} selective membrane process, we began to generate the equilibrium and rate data at the operating condition interested to our applications. In this quarter, we have concentrated on the experiments at 200 C and CO{sub 2} pressure of 0 to 1 bar. In this report we present the equilibrium isotherm and transport rate data and the mathematical treatment using the commonly accepted Langmuir and linear driving force equations. The results from this analysis were then compared with the literature published data. In general, our equilibrium capacity is higher than the literature reported data while the linear driving force model is adequate to describe the rate data obtained from 0 to 1 bar CO{sub 2} pressure. In the next month, we will begin the experimental study at higher temperatures (i.e., 300 and 400 C) to complete our thermodynamic and kinetic database for process simulation.

Paul K.T. Liu

2004-08-01

99

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

SciTech Connect

For the purpose of process simulation and economic analysis of the proposed CO{sub 2} selective membrane process, we began to generate the equilibrium and rate data at the operating condition interested to our applications. In the last quarter we presented the results obtained at 200 C. In this quarter, we have concentrated on the experiments at 250 C and CO{sub 2} pressure of 0 to 1 bar. In this report we present the equilibrium isotherm and the mathematical treatment using the commonly accepted Langmuir equation. The data fit the Langmuir isotherm well and will be used for future adsorber and membrane reactor modeling. In addition, unsupported hydrotalcite membranes have been successfully synthesized on the silicon wafer with micro-channels. The membrane developed in this quarter ranges 2 to 5 {micro}m in thickness. No visible cracks or defects were observed. Performance characterization of these membranes will begin in the next quarter. Since the interference from substrate in the characterization of the supported membrane is no longer existent, it is hoped that the hydrotalcite membrane thus formed can be optimized for its CO{sub 2} selectivity and performance with the aid of the morphological and performance characterization.

Paul K. T. Liu

2004-11-01

100

Noble metal ions incorporated in lattice points of perovskites - water gas shift activity of BaCe1-xPtxO3-d  

NASA Astrophysics Data System (ADS)

Recently precious metals supported on oxides were reported to be very promising catalysts for the lower-temperature WGS reaction. Here we report the synthesis of platinum doped barium cerate and its use as catalysts for WGS reaction. It has been found that maximum CO conversion was obtained at 3500C which enhanced after the first cycle. XPS analysis shows that after the first cycle more ionic Platinum species are present on the surface of the catalyst. Neutron diffraction at room temperature shows that the oxygen vacancies are in the O2 position and increases with increasing Pt substitution.

Jijil, C. P.; Rajarajan, A. K.; Devi, R. Nandini

2012-06-01

101

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

102

Water–gas shift activity of K-promoted (Ni)Mo\\/?-Al 2 O 3 systems in sulfur-containing feed  

Microsoft Academic Search

The effect of potassium additive on the catalytic activity of nickel–molybdenum alumina-supported systems has been studied\\u000a by varying the molybdenum content within 5–18 mass% MoO3, reaction temperature from 180 to 400 (500)°C, and steam to gas ratio of 0.3, 0.7, and 1. It has been established that potassium\\u000a reduces the activity of one-component Mo-containing samples, while, independent of molybdenum loading,

Dimitrinka Nikolova; Rumeana Edreva-Kardjieva; Tatyana Grozeva

2011-01-01

103

CO2 Selective Ceramic Membrane for Water-Gas-Shift Reaction with Concomitant Recovery of CO2. Quarterly Report, July 1, 2004-September 30, 2004.  

National Technical Information Service (NTIS)

For the purpose of process simulation and economic analysis of the proposed CO(sub 2) selective membrane process, we began to generate the equilibrium and rate data at the operating condition interested to our applications. In the last quarter we presente...

P. K. Liu

2004-01-01

104

Genesis and evolution of surface species during Pt atomic layer deposition on oxide supports characterized by in-situ XAFS analysis and water-gas shift reaction  

Microsoft Academic Search

Platinum atomic layer deposition (ALD) using MeCpPtMe was employed to prepare high loadings of uniform-sized, 1-2 nm Pt nanoparticles on high surface area AlO, TiO, and SrTiO supports. X-ray absorption fine structure was utilized to monitor the changes in the Pt species during each step of the synthesis. The temperature, precursor exposure time, treatment gas, and number of ALD cycles

Worajit Setthapun; W. Damion Williams; Seung Min Kim; Hao Feng; Jeffrey W. Elam; Federico A. Rabuffetti; Kenneth R. Poeppelmeier; Peter C. Stair; Eric A. Stach; Fabio H. Ribeiro; Jeffrey T. Miller; Christopher L. Marshall

2010-01-01

105

On a thermodynamic limitation of the water-gas potentiometry using solid electrolyte cells  

Microsoft Academic Search

Possibilities of the water-gas potentiometry using oxide ion-conducting solid electrolytes may be restricted by side reactions in the gas being analyzed. Changes in electrode potentials caused by simultaneous interfering equilibria in the water gas were investigated over a temperature range 1200 to 400°C for different initial gas compositions. Formation reactions of carbon and methane proved to be the side reactions

Reinhold Hartung; Hans-Heinrich Möbius

1994-01-01

106

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts  

SciTech Connect

During this quarter, the high pressure (up to 100 atm), high temperature (up to 350{degrees}C) catalyst testing system was rebuilt with clean tubing, etc. A new preparation of MoS{sub 2} catalyst was carried out, and this catalyst will be doped with alkali and tested during the next quarter of research.

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

1992-06-01

107

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts  

SciTech Connect

During this quarter, the surface areas of various catalysts were determined. The surface area of the catalyst tested last quarter was determined for the undoped catalyst, the doped catalyst before testing, and the doped catalyst after testing. These surface areas were then compared with ones reported earlier. After testing under high temperature and high pressure conditions for 551 hours, there was a loss of surface area. This might be due possibly to agglomeration of cesium formate on the surface. Higher surface area catalysts were also produced. Two samples of MoS[sub 2] were synthesized with surface areas of 96 m2/g and 91 m2/g. These were obtained by varying the heating rate of MoS[sub 3] and the calcination temperature.

Klier, K.; Herman, R.G.; Deemer, M.

1992-12-01

108

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts  

SciTech Connect

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

Klier, K.; Herman, R.G.

1992-03-01

109

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts  

SciTech Connect

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

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

1991-12-01

110

Utilizing the dynamic stark shift as a probe for dielectric relaxation in photosynthetic reaction centers during charge separation.  

PubMed

In photosynthetic reaction centers, the electric field generated by light-induced charge separation produces electrochromic shifts in the transitions of reaction center pigments. The extent of this Stark shift indirectly reflects the effective field strength at a particular cofactor in the complex. The dynamics of the effective field strength near the two monomeric bacteriochlorophylls (BA and BB) in purple photosynthetic bacterial reaction centers has been explored near physiological temperature by monitoring the time-dependent Stark shift during charge separation (dynamic Stark shift). This dynamic Stark shift was determined through analysis of femtosecond time-resolved absorbance change spectra recorded in wild type reaction centers and in four mutants at position M210. In both wild type and the mutants, the kinetics of the dynamic Stark shift differ from those of electron transfer, though not in the same way. In wild type, the initial electron transfer and the increase in the effective field strength near the active-side monomer bacteriochlorophyll (BA) occur in synchrony, but the two signals diverge on the time scale of electron transfer to the quinone. In contrast, when tyrosine is replaced by aspartic acid at M210, the kinetics of the BA Stark shift and the initial electron transfer differ, but transfer to the quinone coincides with the decay of the Stark shift. This is interpreted in terms of differences in the dynamics of the local dielectric environment between the mutants and the wild type. In wild type, comparison of the Stark shifts associated with BA and BB on the two quasi-symmetric halves of the reaction center structure confirm that the effective dielectric constants near these cofactors are quite different when the reaction center is in the state P(+)QA(-), as previously determined by Steffen et al. at 1.5 K ( Steffen , M. A. ; et al. Science 1994 , 264 , 810 - 816 ). However, it is not possible to determine from static, low-temperature measurments if the difference in the effective dielectric constant between the two sides of the reaction center is manifest on the time scale of initial electron transfer. By comparing directly the Stark shift dynamics of the ground-state spectra of the two monomer bacteriochlorophylls, it is evident that there is, in fact, a large dielectric difference between protein environments of the two quasi-symmetric electron-transfer branches on the time scale of initial electron transfer and that the effective dielectric constant in the region continues to evolve on a time scale of hundreds of picoseconds. PMID:23799254

Guo, Zhi; Lin, Su; Woodbury, Neal W

2013-07-10

111

Features of the reaction of heterocyclic analogs of chalcone with lanthanide shift reagents  

SciTech Connect

The PMR spectra of heterocyclic analogs of 2-hydroxychalcone containing thiazole, benzofuran, triazole, imidazole, benzodioxane, or pyridine rings in the presence of lanthanide shift reagents are studied. It is found that the most effective reagent for modifying the spectra of these compounds is Yb(fod)3. The broadening of the spectra of 2-hydroxy chalcones in the presence of lanthanide shift reagents is explained by the dynamic effects of complex formation. An example is given of the determination of the conformation of molecules of 2-hydroxychalcone by the simultaneous use of lanthanide shift reagents and the homonuclear Overhauser effect. 9 refs., 1 fig., 1 tab.

Turov, A.V.; Khilya, V.P. [Taras Shevchenko Kiev Univ. (Russian Federation)

1994-10-01

112

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

113

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

NASA Astrophysics Data System (ADS)

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

Lazar, James G.; Ross, John

1990-01-01

114

Radial electric field formation by the gyrocenter shifts of the charge exchange reactions at the boundary of fusion device  

SciTech Connect

As an important future energy source nuclear fusion researchers have been trying to solve the problem of radial electric field formation: the key factor of H-mode (high confinement mode) phenomena. Although a profound analysis has been developed on the turbulence suppression by ExB flow (E is the electric field and B is the magnetic field) as a basic mechanism of H-mode transition, the origin of the electric field and its relation with the neutrals are not fully explained. In this paper a novel model of radial electric field formation achieved by gyrocenter shifts during the charge exchange reactions and ion elastic scatterings with the neutrals is analyzed. From this analysis the formula of radial current density by the poloidal momentum sink at the reactions of charge exchange with boundary neutrals is developed with an example calculation for a given plasma condition similar to the experiment. The profile and absolute value of the saturated radial electric field are in agreement with the experimental results. An H-mode transition scenario is discussed by the gyrocenter shift model.

Lee, K.C. [Department of Applied Science, University of California, Davis, California 95616 (United States)

2006-06-15

115

Side feeding patterns and nuclear lifetime determinations by the Doppler shift attenuation method in ({alpha},n{gamma}) reactions  

SciTech Connect

{gamma} rays were measured at several angles in both singles and coincidence mode in the {sup 119}Sn({alpha},n{gamma}){sup 122}Te reaction at 15 MeV on a thick target. Lifetimes of excited states in {sup 122}Te were determined from a Monte Carlo Doppler shift attenuation method (DSAM) analysis of the Doppler broadened lines shapes of {gamma} rays de-exciting the levels. A comparison of several deduced lifetimes with recent results obtained with the (n,n{sup '}) reaction allowed us to validate the choice of a parameter used to calculate the contribution of the side feeding times. The ingredients of the DSAM line-shape analysis (stopping power, description of instrumental line shapes, and side feeding evaluation) are presented in some detail. It is concluded that with proper treatment of side feeding, a DSAM line-shape analysis of peaks in singles or coincidence spectra obtained following the ({alpha},n{gamma}) reaction is able to provide rather accurate values for the lifetimes of levels with low and medium spins.

Mihai, C.; Filipescu, D.; Ivascu, M.; Bucurescu, D.; Cata-Danil, G.; Cata-Danil, I.; Deleanu, D.; Ghita, D.; Glodariu, T.; Marginean, N.; Marginean, R.; Negret, A.; Pascu, S.; Sava, T.; Stroe, L.; Suliman, G.; Zamfir, N. V. [Horia Hulubei National Institute of Physics and Nuclear Engineering, R-76900 Bucharest (Romania); Pasternak, A. A. [Cyclotron Laboratory, A.F. Ioffe Physical Technical Institute, RV-194021 St. Petersburg (Russian Federation); Lobach, Yu. N. [Institute for Nuclear Research UAS, pr. Nauki 47, 252028 Kiev (Ukraine)

2010-03-15

116

Reactions of different food classes during subcritical water gasification for hydrogen gas production  

Microsoft Academic Search

The reactions of different food classes during alkaline subcritical water gasification have been investigated with a view on hydrogen gas production. Experiments were conducted with sub-stoichiometric amounts of H2O2 for partial oxidation. NaOH was added to aid sample decomposition, reduce char\\/tar formation and to promote water-gas shift reaction. In general, hydrogen gas production depended on the class of food wastes

Rattana Muangrat; Jude A. Onwudili; Paul T. Williams

117

Continuous medium theory for nonequilibrium solvation: II. Interaction energy between solute charge and reaction field and single-sphere model for spectral shift.  

PubMed

On the basis of continuous medium theory, a model for evaluation of spectral shifts in solution has been developed in this work. The interaction energy between solute dipole and reaction field and the self-energy of the reaction field have been formulated through derivations. Applying the interaction energy expression together with the point dipole approximation to the case of spherical cavity produces new formulations of spectral shifts. The same expression of electrostatic free energy of the nonequilibrium state is achieved by integrating the change of the electrostatic free energy for a charging process. Moreover, generalized formulations evaluating spectral shifts have been established in the charge-potential notation, and the reduction of them to the point dipole case consistently leads to the same formulations of spectral shifts as those by interaction energy approach. Mutual supports provide convincing evidences for the reliability of the present results. In this work, attentions are particularly paid to the conclusion of zero self-energy of the reaction field, which is different from the previous theory. Reasoning and arguments are given on this point. From the present derivations, it is concluded that the spectral shifts of light absorption and emission were theoretically exaggerated in the past, in particular, by a factor of 2 for the spectral shift sum. PMID:15011255

Li, Xiang-Yuan; Fu, Ke-Xiang; Zhu, Quan; Shan, Min-Hua

2004-04-30

118

A multidimensional approach to the analysis of chemical shift titration experiments in the frame of a multiple reaction scheme.  

PubMed

We present a method for fitting curves acquired by chemical shift titration experiments, in the frame of a three-step complexation mechanism. To that end, we have implemented a fitting procedure, based on a nonlinear least squares fitting method, that determines the best fitting curve using a "coarse grid search" approach and provides distributions for the different parameters of the complexation model that are compatible with the experimental precision. The resulting analysis protocol is first described and validated on a theoretical data set. We show its ability to converge to the true parameter values of the simulated reaction scheme and to evaluate complexation constants together with multidimensional uncertainties. Then, we apply this protocol to the study of the supramolecular interactions, in aqueous solution, between a lanthanide complex and three different model molecules, using NMR titration experiments. We show that within the uncertainty that can be evaluated from the parameter distributions generated during our analysis, the affinities between the lanthanide derivative and each model molecule can be discriminated, and we propose values for the corresponding thermodynamic constants. Copyright © 2013 John Wiley & Sons, Ltd. PMID:23955873

D'Aléo, Anthony; Dumont, Elise; Maury, Olivier; Giraud, Nicolas

2013-08-16

119

Posterior-anterior body weight shift during stance period studied by measuring sole-floor reaction forces during healthy and hemiplegic human walking  

Microsoft Academic Search

Posterior-anterior body weight shift during stance phase of human overground locomotion was investigated by recording sole-floor reaction force from five anatomically discrete points with strain gauge transducers of 14mm diameter attached firmly to the sole of bare foot. At first the subject was asked to walk straight on the laboratory floor at his\\/her preferred velocity. Then the subject was asked

Nobuyoshi Kobayashi; Tateo Warabi; Masamichi Kato; Kiichi Kiriyama; Toshikazu Yoshida; Susumu Chiba

2006-01-01

120

Nonseparable transition state theory for nonzero total angular momentum: Implications for {ital J} shifting and application to the OH+H{sub 2} reaction  

SciTech Connect

We report vibration/rotation energies of the OHH{sub 2} transition state using the code {open_quotes}Multimode,{close_quotes} for total angular momentum J=0, 1, and 4. Rotation is treated in the adiabatic rotation approximation for J=1 and 4, as well as exactly, i.e., including Coriolis coupling, for J=1. State-dependent rotation constants are obtained using the adiabatic rotation energies from the J=0 and 1 calculations and shown to predict accurately the adiabatic rotation rovibrational energies for J=4. These rotation constants are used in new {ital J}-shifting calculations of the thermal rate constant for the reaction OH+H{sub 2}{r_arrow}H{sub 2}O+H using results from a previous accurate calculation of the rate constant for J=0 [U. Manthe, T. Seideman, and W. H. Miller, J. Chem. Phys. {bold 99}, 10078 (1993); {bold 101}, 4759 (1994)]. Comparisons with previous {ital J}-shifting and recent centrifugal sudden calculations of the rate constant [D. H. Zhang, J. C. Light, and S-Y. Lee, J. Chem. Phys. {bold 109}, 79 (1998)] of this reaction are presented. A modification of the previous centrifugal sudden rate constant is made and shown to yield results that are in good agreement with the new {ital J}-shifting calculations. Finally, an assessment of Coriolis coupling is made. {copyright} {ital 1999 American Institute of Physics.}

Bowman, J.M.; Shnider, H.M. [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322 (United States)

1999-03-01

121

A detailed comparison of centrifugal sudden and J-shift estimates of the reactive properties of the N + N2 reaction.  

PubMed

An extended comparison of the reactive properties of the N + N(2) exchange reaction calculated on a non-collinear dominant potential energy surface using both a centrifugal sudden and a J-shift quantum method is reported. The choice of carrying out such an investigation for N + N(2) is motivated by the fact that the best available (and currently used for spacecraft re-entry simulations) computed set of kinetic data has been worked out using the low level J-shift approximation though based on exact quantum zero total angular momentum probabilities. The fact that our investigation is carried out for a heavy system and a potential energy surface free of wells in the strong interaction region minimizes the occurrence of tunnel, resonance and interference effects which would make the rationalization of the result difficult and the centrifugal sudden treatment less accurate. The study has provided evidence of two important limits of the J-shift approximation: the wrong determination of the maximum value of the total angular momentum quantum number J contributing to reactivity and the lack of deformation of the partial reactive probability dependence on energy at fixed J value. Accordingly, it has been found that the J-shift state-specific cross sections underestimate the corresponding CS values when the initial diatomic rotational energy is low while the situation reverses when the initial diatomic rotational energy is high. PMID:20024416

Garcia, Ernesto; Sánchez, Carlos; Saracibar, Amaia; Laganà, Antonio; Skouteris, Dimitris

2009-10-27

122

Doppler shift as a tool for studies of resonant (p,n) reactions with RIBs: Spectroscopy of 7He  

Microsoft Academic Search

We report on a new methods for studies of neutron rich systems through resonant (p,n) reaction with radioactive ion beams. A specific example of the spectroscopy of 7He and future application of the proposed methods are discussed.

P. Boutachkov; G. V. Rogachev; V. Z. Goldberg; A. Aprahamian; F. D. Becchetti; J. P. Bychowski; Y. Chen; G. Chubarian; P. A. Deyoung; J. J. Kolata; L. O. Lamm; G. F. Peaslee; M. Quinn; B. B. Skorodumov; A. Wöhr

2006-01-01

123

Hydrothermal reactions of formaldehyde and formic acid: Free-energy analysis of equilibrium  

NASA Astrophysics Data System (ADS)

The chemical equilibria concerning formaldehyde and formic acid are computationally investigated in water over a wide range of thermodynamic conditions. The free energy is evaluated in the method of energy representation for the solvent effect on the decomposition processes of these two compounds. The solvation is found to suppress the production of nonpolar species from a polar. In the two competitive decomposition reactions of formic acid, the solvent strongly inhibits the decarboxylation (HCOOH-->CO2+H2) and its effect is relatively weak for the decarbonylation (HCOOH-->CO+H2O). The equilibrium weights for the two decomposition pathways of formic acid are determined by the equilibrium constant of the water-gas-shift reaction (CO+H2O-->CO2+H2), which is an essential and useful process in fuel technology. The reaction control by the solvent is then examined for the water-gas-shift reaction. Through the comparison of the equilibrium constants in the absence and presence of solvent, even the favorable side of the reaction is shown to be tuned by the solvent density and temperature. The reaction equilibrium is further treated for aldehyde disproportionation reactions involving formaldehyde and formic acid. The disproportionation reactions are found to be subject to relatively weak solvent effects and to be dominated by the electronic contribution.

Matubayasi, Nobuyuki; Nakahara, Masaru

2005-02-01

124

Model Dependence of Kinetic Shifts in Unimolecular Reactions: The Dissociation of the Cations of Benzene and n-Butylbenzene.  

National Technical Information Service (NTIS)

Statistical adiabatic channel model/classical trajectory (SACM/CT) calculations have been performed for transitional mode dynamics in the simple bond fission reactions of C6H6(+) > C6H5(+) + H and n-C6H5C4H9(+) > C7H7(+) + n-C3H7. Reduced-dimensionality m...

J. Troe V. G. Ushakov A. A. Viggiano

2005-01-01

125

Model Dependence of Kinetic Shifts in Unimolecular Reactions: The Dissociation of the Cations of Benzene and n-Butylbenzene.  

National Technical Information Service (NTIS)

Statistical adiabatic channel model/classical trajectory (SACM/CT) calculations have been performed for transitional mode dynamics in the simple bond fission reactions of C6H6+ --> C6H5+ + H and n-C6H5C4H9+ --> C7H7+ + n-C3H7. Reduced-dimensionality model...

J. Troe V. G. Ushakov A. A. Viggiano

2006-01-01

126

Properties of Hybrid Water\\/Gas DC Arc Plasma Torch  

Microsoft Academic Search

A new type of plasma torch with combined stabilization of electric arc by water vortex and gas flow was investigated. This hybrid water\\/gas stabilization offers the possibility of adjusting plasma jet parameters within a wide range from high-enthalpy low-density plasmas typical for liquid stabilized torches to lower enthalpy higher density plasmas generated in gas stabilized torches. The torch was operated

Milan Hrabovsky; V. Kopeckykopecky; Viktor Sember; Tetyana Kavka; Oleksiy Chumak; Milos Konrad

2006-01-01

127

Metal\\/ceria water-gas shift catalysts for automotive polymer electrolyte fuel cell system  

Microsoft Academic Search

Polymer electrolyte fuel cell (PEFC) systems are a leading candidate for replacing the internal combustion engine in light duty vehicles. One method of generating the hydrogen necessary for the PEFC is reforming a liquid fuel, such as methanol or gasoline, via partial oxidation, steam reforming, or autothermal reforming (a combination of partial oxidation and steam reforming). The Hâ-rich reformate can

D. J. Myers; J. F. Krebs; J. D. Carter; R. Kumar; M. Krumpelt

2002-01-01

128

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

SciTech Connect

The rate of synthesis gas consumption over a cobalt FischerTropsch catalyst was measured in a well-mixed, continuous-flow, slurry reactor at 220 to 240[degrees]C, 0.5 to 1.5 MPa, H[sub 2]/CO feed ratios of 1.5 to 3.5 and conversions of 7 to 68% of hydrogen and 11 to 73% of carbon monoxide. The inhibiting effect of carbon monoxide was determined quantitatively and a Langmuir-Hinshelwood-type equation of the following form was found to best represent the results: -R[sub H[sub 2+Co

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

1989-01-01

129

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

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

The phase-shift method for determining Langmuir and Temkin adsorption isotherms of over-potentially deposited hydrogen for the cathodic H 2 evolution reaction at the poly- Pt \\/ H 2 SO 4 aqueous electrolyte interface  

Microsoft Academic Search

A linear relationship between the behavior (-? vs. E) of the phase shift (0??-??90?) for the optimum intermediate frequency and that (? vs. E) of the fractional surface coverage (1???0) of over-potentially deposited hydrogen (OPD H) for the cathodic H2 evolution reaction (HER), i.e., the phase-shift method, at the poly-Pt\\/0.5M H2SO4 aqueous electrolyte interface has been verified using cyclic voltammetric,

Jang H. Chun; Sang K. Jeon; Nam Y. Kim; Jin Y. Chun

2005-01-01

132

The phase-shift method for determining Langmuir adsorption isotherms of over-potentially deposited hydrogen for the cathodic H 2 evolution reaction at poly-Re\\/aqueous electrolyte interfaces  

Microsoft Academic Search

A linear relationship between the behavior (?? vs. E) of the phase shift (0°????90°) for the optimum intermediate frequency and that (? vs. E) of the fractional surface coverage (1???0) of over-potentially deposited hydrogen (OPD H) for the cathodic H2 evolution reaction (HER), i.e., the phase-shift method, at poly-Re\\/0.5MH2SO4 and 0.1M KOH aqueous electrolyte interfaces has been suggested and verified

Jang H. Chun; Sang K. Jeon; Keuk H. Ra; Jin Y. Chun

2005-01-01

133

[Posttranslational reactions resulting in a long-wavelength shift in the spectra of asFP595 protein from Anemonia sulcata].  

PubMed

In most fluorescent proteins characterized by light absorption and emission in the red and the far-red spectral region (550-650 nm), the chromophore pi system is extended at the expense of the additional oxidation of the GFP-like structure and the formation of an acylimine substituent. As distinct from these proteins, the photoactivateable protein asFP595 contains a chromophore with the keto group substituted for an acylimine substituent. In this work, we studied the reactions that result in a bathochromic shift in the spectrum of asFP595. Maturation kinetics analysis has shown the generation of the immature form containing a protonated chromophore (absorption at 420 nm) at the intermediate step, as in the case of other red fluorescent proteins, which then is isobestically converted into the final mature form (568 nm). Mass spectrometric analysis of the chromopeptide isolated from immature asFP595 has demonstrated that the intermediate form contains a GFP-type chromophore. It has also been found that the oxidation of the GFP chromophore is accompanied by the generation of an equimolar amount of hydro gen peroxide. The intermediate products of oxidation have been analyzed by the mutagenesis of the first chromophore-generating amino acid residue. It has been demonstrated that in the case of all mutants studied, chromophore synthesis does not terminate at the stage of the acylimine derivative, but immediately results in the fragmentation of the main chain of the protein and in the formation of the keto form. PMID:20386585

Pakhomov, A A; Tret'iakova, Iu A; Martynov, V I

134

On the analysis of CO 2 , H 2 - and CO, H 2 -mixtures by water-gas potentiometry with solid electrolyte cells  

Microsoft Academic Search

The potentiometric analysis of CO2, H2 and CO, H2O-mixtures using oxide ion-conducting solid electrolytes requires the adjustment of the water-gas equilibrium without side\\u000a reactions in the high-temperature galvanic cell. Conventional cell designs suitable for the analysis of H2, H2O and CO, CO2-mixtures are not applicable due to the insufficient gas residence times in the cells and the insufficient catalytical activity

Reinhold Hartung

1996-01-01

135

Determination of the Langmuir adsorption isotherms of under- and over-potentially deposited hydrogen for the cathodic H 2 evolution reaction at poly-Ir\\/aqueous electrolyte interfaces using the phase-shift method  

Microsoft Academic Search

The Langmuir adsorption isotherms of under-potentially deposited hydrogen (UPD H) and over-potentially deposited hydrogen (OPD H) for the cathodic H2 evolution reaction (HER) at poly-Ir\\/0.5M H2SO4 and 0.05M KOH aqueous electrolyte interfaces have been studied using cyclic voltammetric, differential pulse voltammetric, and ac impedance techniques. The behavior of the lagged phase shift (0°????90°) for the optimum intermediate frequency can be

Jang H. Chun; Sang K. Jeon; Bok K. Kim; Jin Y. Chun

2005-01-01

136

Shift Registers  

NSDL National Science Digital Library

All About Circuits is a website that âÂÂprovides a series of online textbooks covering electricity and electronics.â Written by Tony R. Kuphaldt, the textbooks available here are wonderful resources for students, teachers, and anyone who is interested in learning more about electronics. This specific section, Shift Registers, is the twelfth chapter in Volume IV âÂÂDigital. A few of the topics covered in this chapter include: Serial-in, serial-out shift register, Parallel-in, parallel-out shift register, and Ring counters. Diagrams and detailed descriptions of concepts are included throughout the chapter to provide users with a comprehensive lesson. Visitors to the site are also encouraged to discuss concepts and topics using the All About Circuits discussion forums (registration with the site is required to post materials).

Kuphaldt, Tony R.

2008-07-18

137

The Shifting \\  

Microsoft Academic Search

In the past decade, numerous ICT-related investigation powers have been introduced or extended. Have these shifted the balance between criminal investigation and privacy? Do governments allow more privacy infringements for the sake of law enforcement than they used to do? As a first step towards answering these questions, this paper presents the results of a case study of communications interception

Bert-Jaap Koops

2003-01-01

138

On the mechanisms and behavior of coal syngas transport and reaction within the anode of a solid oxide fuel cell  

SciTech Connect

It is expected that in future years high temperature fuel cells will be coupled with coal gasification technology to produce electric power, as well as other valuable commercial products. Numerous technical investigations have already shown the feasibility of such systems at the system level as well as in the details of fuel cell operation. This paper focuses on the operation of an anode comprised of conventional solid oxide fuel cell anode materials (Ni/YSZ cermets) when operating on coal syngas. A model is presented for the transport of gases through the anode, as well as gas specie reactions within the anode consisting of methane reforming and water-gas shift. The model is validated by making comparisons to data and other models from the literature. The model is then employed to analyze transport performance within the anode over operating pressures between 1 and 15 atm. Results show the pressure effects on specie profiles, diffusion losses, and cell heating. Specifically, there is a maximum pressure (8 atm) under which hydrogen is produced by the methane-steam reaction; operating at higher pressure will produce methane. In addition, the concentration overpotential decreases as pressure increases from 1 to 5 atm after which it again increases. Finally, the model predicts a significant amount of heating due to the net reforming and water-gas shift reactions that should be considered by developers of these future systems.

Gemmen, R.S.; Trembly, J.P.

2006-10-27

139

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

140

Advanced Water-Gas Shift Membrane Reactor. Final Technical Report, 1 July 2005 to 30 June 2007.  

National Technical Information Service (NTIS)

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...

R. Radhakrishnan R. Willigan S. Opalka S. C. Emerson T. H. Vanderspurt

2007-01-01

141

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

142

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts. Technical progress report, March--May 1992  

SciTech Connect

During this quarter, the high pressure (up to 100 atm), high temperature (up to 350{degrees}C) catalyst testing system was rebuilt with clean tubing, etc. A new preparation of MoS{sub 2} catalyst was carried out, and this catalyst will be doped with alkali and tested during the next quarter of research.

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

1992-06-01

143

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts. Technical progress report, March 1994--May 1994  

SciTech Connect

During this quarter, the cesium formate-doped and the undoped molybdenum disulfide previously prepared were sent out to Galbraith Laboratories for elemental analysis for cesium, molybdenum, and sulfur. A new Na/MoS{sub 2} catalyst was prepared under an inert atmosphere by an intercalation technique using sodium metal dissolved in liquid ammonia. This sample will be fully characterized. An all-glass apparatus was constructed for carrying out systematic intercalation procedures with alkali metals dissolved in liquid ammonia. This apparatus will insure that the dispersed catalysts are prepared in an oxygen/moisture-free environment. The stainless steel continuous flow high pressure/high temperature catalyst testing system was rebuilt and the analytical end of the unit was upgraded.

Klier, K; Herman, R.G.; Deemer, M.

1994-06-01

144

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts. Technical progress report, September 1992--November 1992  

SciTech Connect

During this quarter, the surface areas of various catalysts were determined. The surface area of the catalyst tested last quarter was determined for the undoped catalyst, the doped catalyst before testing, and the doped catalyst after testing. These surface areas were then compared with ones reported earlier. After testing under high temperature and high pressure conditions for 551 hours, there was a loss of surface area. This might be due possibly to agglomeration of cesium formate on the surface. Higher surface area catalysts were also produced. Two samples of MoS{sub 2} were synthesized with surface areas of 96 m2/g and 91 m2/g. These were obtained by varying the heating rate of MoS{sub 3} and the calcination temperature.

Klier, K.; Herman, R.G.; Deemer, M.

1992-12-01

145

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

SciTech Connect

Various preparation methods of synthesizing molybdenum disulfide and various alkali doping procedures were studied to determine if various preparation paramenters affected catalyst activity. Testing was performed on an undoped molybdenum disulfide sample with H{sub 2}/CO = 1 synthesis gas at 8.1 MPa and at temperatures of 245, 255, 265, 275, 280, 300, 320, and 295C, and only hydrocarbons were formed. A methanol injection experiment with undoped catalyst showed that homologation of methanol did not occur over the undoped MOS{sub 2}. Catalytic testing on a cesium formate doped molybdenum disulfide catalyst corresponding to 9 wt% Cs/MoS{sub 2} at 8.1 MPa and temperatures of 245, 255, 265, 275, 285, and 295C, mostly linear alcohols. The CS/MOS{sub 2} sample was protected from air exposure during preparation and testiag. As with the other recently tested alkali-promoted MOS{sub 2} catalysts, this cataylst was not as active as previous CS/MOS{sub 2} catalysts [1], and some deactivation during these systematic studies was observed. X-Ray powder diffraction and BET surface area measurements are being used to characterize the catalysts, and electron microscopy analyses are being carried out.

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

1993-09-01

146

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

SciTech Connect

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

Klier, K.; Herman, R.G.

1992-03-01

147

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts. Technical progress report, September--November 1991  

SciTech Connect

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

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

1991-12-01

148

Low temperature water gas shift: the link between the catalysis of WGS and formic acid decomposition over Pt\\/ceria  

Microsoft Academic Search

Partial reduction of the ceria surface leads to the formation of bridging Type II OH groups, as reported previously. These were found to react with formic acid to yield bidentate formate and water, or with CO directly to form bidentate formate. In both WGS and formic acid decomposition via dehydrogenation whereby a high water\\/CO or water\\/formic acid ratio was utilized,

Gary Jacobs; Patricia M. Patterson; Uschi M. Graham; Adam C. Crawford; Burtron H. Davis

2005-01-01

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

Turbulence and Wave Breaking Effects on Air-Water Gas Exchange  

Microsoft Academic Search

We present an experimental characterization of the effects of turbulence and breaking gravity waves on air-water gas exchange in standing waves. We identify two regimes that govern aeration rates: turbulent transport when no wave breaking occurs and bubble dominated transport when wave breaking occurs. In both regimes, we correlate the qualitative changes in the aeration rate with corresponding changes in

Evelyn J. Boettcher; Jay Fineberg; Daniel P. Lathrop

2000-01-01

151

Study of a three-phase flow metering process for oil-water-gas flows.  

National Technical Information Service (NTIS)

We propose a theoretical and experimental study of a three-phase flow metering process for oil-water-gas flows. The selected process is based on a combination of a mixer, a Venturi and ultrasonic methods. To perform an experimental validation of this proc...

C. Boyer

1996-01-01

152

Reactions at the metal vertex of a ruthenacarborane cluster. Activation of carbon monoxide by closo-3,3,3-(CO)/sub 3/-3,1,2-RuC/sub 2/B/sub 9/H/sub 11/  

SciTech Connect

The /sup 11/B FTNMR analyses and quenching studies of the reaction solutions suggest the inactivity of closo-3,3,3-(CO)/sub 3/-3,1,2-RuC/sub 2/B/sub 9/H/sub 11/ (1) as a water gas shift process catalyst is a consequence of the conflicting pH demands of the individual steps in the proposed mechanism. The alkaline conditions necessary for attack on 1 and decarboxylation to produce the anionic dicarbonyl hydride complex are prohibitive for its reconversion to 1, which requires acidic conditions. 14 references, 1 figure, 1 table.

Behnken, P.E.; Hawthorne, M.F.

1984-10-10

153

Combined Effects of Wind and Rain on Air-Water Gas Exchange  

NASA Astrophysics Data System (ADS)

In constraining local and global carbon cycle budgets, it is important to know the air-water gas transfer velocity (k). Historically, k has been parameterized by wind speed or rain rate separately, and pilot experiments in the laboratory with wind and rain suggested that these parameterizations may be linearly additive (Ho et al., 2007). Here we present results from a series of experiments completed at the University of Delaware’s Air-Sea Interaction Laboratory (ASIL) that aim to study the combined effect of wind and rain on air-water gas exchange. Experimental conditions included 11 wind speeds and 6 rain rates, where gas transfer velocity, turbulent kinetic energy, and bubble size and density were measured. Our results indicate that these effects are not linearly additive, particularly at higher wind speeds (approximately 19 m/s). At these higher wind speeds wind contributes significantly more to the total kinetic energy flux than the rain. These results corroborate findings at the ASIL from 2008 (Harrison et al., in prep). Here, we further examine changes in turbulence due to wind and rain and bubble production due to rain at the air-water interface to elucidate the nonlinear effects of wind and rain on air-water gas exchange. References Harrison, E., et al. (in prep), The combined effect of rain and wind on air-water gas exchange. Ho, D. T., et al. (2007), The combined effect of rain and wind on air-water gas exchange: A feasibility study, Journal of Marine Systems, 66(1-4), 150-160.

Eggleston, S.; Harrison, E.; Ho, D. T.; Veron, F.

2010-12-01

154

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

155

The combined effect of rain and wind on air–water gas exchange: A feasibility study  

Microsoft Academic Search

A series of experiments were conducted at University of Delaware's Air–Sea Interaction Laboratory to examine the combined effects of rain and wind on air–water gas exchange. During this study, ASIL WRX I, a combination of 3 rain rates and 4 wind speeds were used, for a total of 12 different environmental conditions. The SF6 evasion method was used to determine

David T. Ho; Fabrice Veron; Emily Harrison; Larry F. Bliven; Nicholas Scott; Wade R. McGillis

2007-01-01

156

Corrosion of API 5L B and X52 in crude oil\\/water\\/gas mixtures  

Microsoft Academic Search

Laboratory and field tests were conducted to evaluate the corrosion behavior of API 5L grade B and X52 steels using Furrial's crude oil in the presence of water and gas containing carbon dioxide (COâ) and hydrogen sulfide (HâS). The results suggest that the corrosiveness of this crude oil\\/water\\/gas mixture is not detrimental to either steel. However, pitting corrosion was observed.

J. J. Perdomo; J. J. Gonzalez; A. Viloria; H. De Veer; Y. De Abreu

2000-01-01

157

A Second-Order Godunov Method for Wave Problems in Coupled Solid-Water-Gas Systems  

NASA Astrophysics Data System (ADS)

We present a second-order Godunov method for computing unsteady, one-dimensional wave problems with fracture and cavitation in coupled solid-water-gas systems. The method employs a hydro-elasto-plastic body, the Tait equation, and the ideal gas law for solid, water, and gaseous phases, respectively, and models both fractures and cavities as vacuum zones with distinct borders. The numerical approach utilizes a Lagrangian formulation in conjunction with local solid-water-gas-vacuum Riemann problems, which have unique solutions and can be solved efficiently. The various phases are treated in a unified manner and no supplementary interface conditions are necessary for tracking material boundaries. Calculations are carried out for Riemann problems, wave propagation and reflection in a water-rock-air system, and spallation and cavitation in an explosion-steel-water-gas system. It is shown that the Godunov method has high resolution for shocks and phase interfaces, clearly resolves elastic and plastic waves, and successfully describes onset and propagation of fracture and cavitation zones.

Tang, H. S.; Sotiropoulos, F.

1999-05-01

158

Nonlinear interaction between rain- and wind-induced air-water gas exchange  

NASA Astrophysics Data System (ADS)

The combined effects of rain and wind on air-water gas exchange were investigated with a series of experiments conducted at University of Delaware's Air-Sea Interaction Laboratory (ASIL). During this study, the third ASIL Wind and Rain Experiment (WRX 3), a combination of three rain rates and eight wind speeds were executed using aqueous mass balances of SF6 to determine gas transfer velocities, k(600). In addition, measurements of wave properties, currents, and turbulence were obtained. Study results show that rain and wind effects combine nonlinearly to enhance air-water gas exchange. Also, rainfall appears to contribute significantly to the total air-water gas flux at low wind speeds, while at higher speeds rain effects appear to be negligible. We find that the range of conditions over which the rain effects are important is well defined by the ratio of rain kinetic energy flux to that of the wind. A nonlinear parameterization of k(600) for the combined effects of rain and wind is proposed. We extend this parameterization to field conditions and obtain the approximate rain rate and wind speed conditions where rain is expected to have a significant effect on air-sea gas exchange. Low wind speed-high rain rate regions such as the tropics are regions where rain is expected to play a significant role.

Harrison, E. L.; Veron, F.; Ho, D. T.; Reid, M. C.; Orton, P.; McGillis, W. R.

2012-03-01

159

Gear shift control mechanism  

Microsoft Academic Search

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

Janson

1987-01-01

160

Two-Step Hydride Shift to Aryl Carbonium Ions.  

National Technical Information Service (NTIS)

A typical reaction of carbonium ions is the hydride shift from hydrocarbons. Mechanisms have been suggested where the shift is regarded as a one-step process. The authors report that perchlorodiphenylcarbonium hexa-chloroantimonate reacts with cycloheptat...

A. Rodriguez-Siurana J. Castaner J. Riera-Figueras M. Ballester

1971-01-01

161

Corrosion of API 5L B and X52 in crude oil/water/gas mixtures  

SciTech Connect

Laboratory and field tests were conducted to evaluate the corrosion behavior of API 5L grade B and X52 steels using Furrial's crude oil in the presence of water and gas containing carbon dioxide (CO{sub 2}) and hydrogen sulfide (H{sub 2}S). The results suggest that the corrosiveness of this crude oil/water/gas mixture is not detrimental to either steel. However, pitting corrosion was observed. The low general corrosion rates measured were attributed to the natural inhibiting properties of the crude oil.

Perdomo, J.J.; Gonzalez, J.J.; Viloria, A.; De Veer, H.; De Abreu, Y.

2000-02-01

162

Metallocarboranes Structurally Engineered for the Reduction of Carbon Monoxide.  

National Technical Information Service (NTIS)

The research performed under the auspices of the above Department of Energy grant has been primarily concerned with the preparation of rhoda- and ruthenacarborane complexes as possible catalysts for the water gas shift reaction. Water gas shift activity h...

M. F. Hawthorne

1982-01-01

163

Air-water gas exchange of organochlorine pesticides in Taihu Lake, China.  

PubMed

Previous research in the Taihu Lake Region (TLR) of China found high levels of atmospheric organochlorine pesticides (OCPs). To understand the sources and the environmental behaviors of these OCPs in the TLR, research on air-water gas exchange was performed in 2004. Hexachlorocyclohexanes (HCHs), DDT related compounds (DDTs), cis-chlordane (CC), trans-chlordane (TC), heptachlor (HEPT), and alpha-endosulfan in both air and water samples were analyzed, and air-water gas exchange fluxes of these compounds were calculated. The net volatilization flux of alpha-HCH was 58 ng m(-2) day(-1), suggesting that the residue of technical HCH in the lake sediment might have been an important source of alpha-HCH to the air of this region after the ban of technical HCH two decades ago. The main components of technical chlordane, TC, CC, and HEPT, each had net volatilization fluxes >230 ng m(-2) day(-1), suggesting that waste discharge from manufacturing plants in the upper region was the main source of chlordane to the lake. Unlike alpha-HCH and chlordane, o,p'-DDT and alpha-endosulfan had net deposition fluxes, suggesting that these compounds were transported through the atmosphere from land sources and then deposited into the lake. The correlation between air concentrations and ambient air temperature indicated that the current sources of o,p'-DDT and alpha-endosulfan were from land; alpha-HCH and chlordane were mainly from the lake. PMID:18409615

Qiu, Xinghua; Zhu, Tong; Wang, Feng; Hu, Jianxin

2008-03-15

164

Improving nursing shift-to-shift report.  

PubMed

In 2002, the Winnipeg Regional Health Authority commissioned an external review for improvements to patient care. From this review arose the Achieving Benchmarks through Collaboration Project, which was composed of 32 projects and a number of subprojects. One such subproject dealt with the reconfiguration of the nursing shift-to-shift report. Its mandate was to improve report, thus making it more efficient, effective, and consistent. This article is a review of this reconfiguration. PMID:17149090

Benson, Ember; Rippin-Sisler, Catherine; Jabusch, Kimberly; Keast, Shelley

165

Tandem pseudopericyclic reactions: [1,5]-X sigmatropic shift/6pi-electrocyclic ring closure converting N-(2-X-carbonyl)phenyl ketenimines into 2-X-quinolin-4(3H)-ones.  

PubMed

N-(2-X-Carbonyl)phenyl ketenimines undergo, under mild thermal conditions, [1,5]-migration of the X group from the carbonyl carbon to the electron-deficient central carbon atom of the ketenimine fragment, followed by a 6pi-electrocyclic ring closure of the resulting ketene to provide 2-X-substituted quinolin-4(3H)-ones in a sequential one-pot manner. The X groups tested are electron-donor groups, such as alkylthio, arylthio, arylseleno, aryloxy, and amino. When involving alkylthio, arylthio, and arylseleno groups, the complete transformation takes place in refluxing toluene, whereas for aryloxy and amino groups the starting ketenimines must be heated at 230 degrees C in a sealed tube in the absence of solvent. The mechanism for the conversion of these ketenimines into quinolin-4(3H)-ones has been studied by ab initio and DFT calculations, using as model compounds N-(2-X-carbonyl)vinyl ketenimines bearing different X groups (X = F, Cl, OH, SH, NH(2), and PH(2)) converting into 4(3H)-pyridones. This computational study afforded two general reaction pathways for the first step of the sequence, the [1,5]-X shift, depending on the nature of X. When X is F, Cl, OH, or SH, the migration occurs in a concerted mode, whereas when X is NH(2) or PH(2), it involves a two-step sequence. The order of migratory aptitudes of the X substituents at the acyl group is predicted to be PH(2) > Cl > SH > NH(2) > F> OH. The second step of the full transformation, the 6pi-electrocyclic ring closure, is calculated to be concerted and with low energy barriers in all the cases. We have included in the calculations an alternative mode of cyclization of the N-(2-X-carbonyl)vinyl ketenimines, the 6pi-electrocyclic ring closure leading to 1,3-oxazines that involves its 1-oxo-5-aza-1,3,5-hexatrienic system. Additionally, the pseudopericyclic topology of the transition states for some of the [1,5]-X migrations (X = F, Cl, OH, SH), for the 6pi-electrocyclization of the ketene intermediates to the 4(3H)-pyridones, and for the 6pi-electrocyclization of the starting ketenimines into 1,3-oxazines could be established on the basis of their geometries, natural bond orbital analyses, and magnetic properties. The calculations predict that the 4(3H)-pyridones are the thermodynamically controlled products and that the 1,3-oxazines should be the kinetically controlled ones. PMID:17025302

Alajarín, Mateo; Ortín, María-Mar; Sanchez-Andrada, Pilar; Vidal, Angel

2006-10-13

166

Water-gas exchange of organochlorine pesticides at Lake Chaohu, a large Chinese lake.  

PubMed

Organochlorine pesticides (OCPs), a potential threat to ecosystems and human health, are still widely residual in the environment. The residual levels of OCPs in the water and gas phase were monitored in Lake Chaohu, a large Chinese lake, from March 2010 to February 2011. Nineteen types of OCPs were detected in the water with a total concentration of 7.27 ± 3.32 ng/l. Aldrin, DDTs and HCHs were the major OCPs in the water, accounting for 38.3%, 28.9% and 23.6% of the total, respectively. The highest mean concentration (12.32 ng/l) in the water was found in September, while the lowest (1.74 ng/l) was found in November. Twenty types of gaseous OCPs were detected in the atmosphere with a total concentration of 542.0 ± 636.5 pg/m(3). Endosulfan, DDTs and chlordane were the major gaseous OCPs in the atmosphere, accounting for 48.9%, 22.5% and 14.4% of the total, respectively. The mean concentration of gaseous OCPs was significantly higher in summer than in winter. o,p'-DDE was the main metabolite of DDT in both the water and gas phase. Of the HCHs, 52.3% existed as ?-HCH in the water, while ?-HCH (37.9%) and ?-HCH (30.9%) were dominant isomers in the gas phase. The average fluxes were -21.11, -3.30, -152.41, -35.50 and -1314.15 ng/(m(2) day) for ?-HCH, ?-HCH, HCB, DDT and DDE, respectively. The water-gas exchanges of the five types of OCPs indicate that water was the main potential source of gaseous OCPs in the atmosphere. A sensitivity analysis indicated that the water-gas flux of ?-HCH, ?-HCH and DDT is more vulnerable than that of HCB and DDE to the variation of the parameters. The possible source of the HCHs in the water was from the historical usage of lindane; however, that in the air was mainly from the recent usage of lindane. The technical DDT and dicofol might be the source of DDTs in the water and air. PMID:23238597

Ouyang, Hui-Ling; He, Wei; Qin, Ning; Kong, Xiang-Zhen; Liu, Wen-Xiu; He, Qi-Shuang; Yang, Chen; Jiang, Yu-Jiao; Wang, Qing-Mei; Yang, Bin; Xu, Fu-Liu

2012-12-13

167

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

168

Style Shift in Translation  

ERIC Educational Resources Information Center

|The phenomenon of style shift in translated texts is ascribed mainly to textual incompatibility in terms of rhetorical asymmetry and divergence at the formality level. Mandatory shifts result from a systematic dissimilarity between the source language and the target language in terms of the underlying system of syntax, semantics and rhetorical…

Al-Qinai, Jamal

2009-01-01

169

SPECTRAL SHIFT CONTROL REACTOR  

Microsoft Academic Search

The Spectral Shift Control Reactor is a variation of the pressurized-; water reactor. Reactivity control is accomplished by varying the concentration ; of a heavy water-water mixture in the primary loop of the reactor. The addition ; of heavy water changes the relative number of neutrons at any particular energy ; (that is, shifts the neutron spectrum), resulting in more

R. W. Deuster; Z. Levine

1961-01-01

170

Josephson shift registers  

NASA Astrophysics Data System (ADS)

A review of Josephson shift-register circuits that have been designed, fabricated, or tested is presented with emphasis on work in the 1980s. Operating speed is most important, since it often limits system performance. Older designs used square-wave clocks, but most modern designs use offset sine waves, with either two or three phases. Operating margins and gate bias uniformity are key concerns. The fastest measured Josephson shift register operated at 2.3 GHz, which compares well with a GaAs shift register that consumes 250 times more power. The difficulties of high-speed testing have prevented many Josephson shift registers from being operated at their highest speeds. Computer simulations suggest that 30-GHz operaton is possible with current Nb/Al2O3/Nb technology. Junctions with critical current densities near 10 kA/sq cm would make 100-GHz shift registers feasible.

Przybysz, John X.

1989-08-01

171

Reaction products from the subcritical water gasification of food wastes and glucose with NaOH and H2O2.  

PubMed

The gasification of some selected components of food wastes using H(2)O(2) as the oxidant and in the presence of NaOH has been investigated under subcritical water conditions. Hydrogen production was enhanced when both NaOH and H(2)O(2) were used compared to when either NaOH or H(2)O(2) alone was used or in their absence. Results indicated that the H(2)O(2) acted to partially oxidize the samples while NaOH significantly increased hydrogen gas yields by promoting the water-gas shift reaction with subsequent CO(2) capture. In the presence of NaOH, the main components were Na(2)CO(3), CH(3)COONa and CH(3)COONa.3H(2)O. Char and tar production were suppressed in the presence of NaOH. PMID:20427179

Muangrat, Rattana; Onwudili, Jude A; Williams, Paul T

2010-04-27

172

Auditory Attention Shifting.  

National Technical Information Service (NTIS)

This research effort measured the spectral and temporal dynamics of human auditory attentional control, concentrating on the requirements for efficient shifting of auditory attention within the frequency spectrum of normal human hearing.

A. Reeves B. Scharf

2008-01-01

173

Shifting human color memory  

Microsoft Academic Search

Persons who witnessed an automobile accident involving a green car were exposed to information that the car was blue. On a\\u000a subsequent color recognition test, most subjects shifted their color selection in the direction of the misleading information\\u000a and away from the actual perceived color. Shifting was greater for subjects who did not initially commit themselves to a color\\u000a selection.

Elizabeth F. Loftus

1977-01-01

174

Slurry phase Fischer-Tropsch synthesis: Cobalt plus a water-gas shift catalyst. [Quarterly] report, October 1, 1989--December 31, 1989  

SciTech Connect

The rate of synthesis gas consumption over a cobalt FischerTropsch catalyst was measured in a well-mixed, continuous-flow, slurry reactor at 220 to 240{degrees}C, 0.5 to 1.5 MPa, H{sub 2}/CO feed ratios of 1.5 to 3.5 and conversions of 7 to 68% of hydrogen and 11 to 73% of carbon monoxide. The inhibiting effect of carbon monoxide was determined quantitatively and a Langmuir-Hinshelwood-type equation of the following form was found to best represent the results: -R{sub H{sub 2+Co}} = (a P{sub CO}P{sub H{sub 2}})/(1 + b P{sub CO}){sup 2}. The apparent activation energy was 93 to 95 kJ/mol. Data from previous studies on cobalt-based Fischer-Tropsch catalysts are also well correlated with this rate expression.

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

1989-12-31

175

Proton Chemical Shifts  

NSDL National Science Digital Library

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

Reich, Hans J.

2007-11-16

176

Style shifting in commercials  

Microsoft Academic Search

This paper presents a quantitative analysis of style shifting in a corpus of Flemish radio and television commercials. Previous research draws attention to styling processes in advertising language, as discursive actions indexing social meanings. It will be shown that the exploitation of different stylistic varieties in our corpus can be analyzed along the same lines. The analysis presented here focuses

Sofie Van Gijsel; Dirk Speelman; Dirk Geeraerts

2008-01-01

177

The shift in windpower  

Microsoft Academic Search

Despite new production records, the near-term market for new windpower projects in the US remains bleak. Congressional incentives and project proposals in the mid-1990s offer promise, but for now most development has shifted to Europe. During 1992 and 1993 the largest wind projects developed by US companies will not be in the US, but in the United Kingdom and Spain.

Gipe

1992-01-01

178

Regime Shift in Antitrust  

Microsoft Academic Search

This paper empirically models the longer-run deep-seated shift in intellectual thinking that followed the Chicago School’s criticism of the older antitrust doctrine, the shorter-run driving forces related to switches of the political party in power, merger waves, changes in economic activity and the level of funding and quantifies their impact on enforcement by the Antitrust Division of the U.S. Department

Vivek Ghosal

2007-01-01

179

The shifting beverage landscape.  

PubMed

STOREY, M.L. The shifting beverage landscape. PHYSIOL BEHAV, 2010. - Simultaneous lifestyle changes have occurred in the last few decades, creating an imbalance in energy intake and energy expenditure that has led to overweight and obesity. Trends in the food supply show that total daily calories available per capita increased 28% since 1970. Total energy intake among men and women has also increased dramatically since that time. Some have suggested that intake of beverages has had a disproportional impact on obesity. Data collected by the Beverage Marketing Corporation between 1988-2008 demonstrate that, in reality, fewer calories per ounce are being produced by the beverage industry. Moreover, data from the National Cancer Institute show that soft drink intake represents 5.5% of daily calories. Data from NHANES 1999-2003 vs. 2003-06 may demonstrate a shift in beverage consumption for age/gender groups, ages 6 to>60years. The beverages provided in schools have significantly changed since 2006 when the beverage industry implemented School Beverage Guidelines. This voluntary action has removed full-calorie soft drinks from participating schools across the country. This shift to lower-calorie and smaller-portion beverages in school has led to a significant decrease in total beverage calories in schools. These data support the concept that to prevent and treat obesity, public health efforts should focus on energy balance and that a narrow focus on sweetened beverages is unlikely to have any meaningful impact on this complex problem. PMID:20188750

Storey, Maureen

2010-02-25

180

Doppler broadening induced spectral shift effects on reactor safety  

Microsoft Academic Search

It is commonly accepted that the resonance reaction rate of any material increases when the temperature is raised. However, in a nuclear reactor the increase in resonance reaction rates with temperature at relatively high energy shifts the neutron spectrum in such a way that a net decrease in the neutron flux results at lower energies. This finding suggested that the

Alapour

1980-01-01

181

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

182

Shift Work: Improving Daytime Sleep  

MedlinePLUS

... be reprinted for personal, noncommercial use only. Shift work: Improving daytime sleep By Mayo Clinic staff Original ... multitasking and learn how to focus Healthy at work (4) Shift work: Improving daytime sleep Sitting risks: ...

183

Sentiment Classification and Polarity Shifting  

Microsoft Academic Search

Polarity shifting marked by various linguistic structures has been a challenge to automatic sentiment classification. In this paper, we propose a machine learning approach to incorporate polarity shifting information into a document-level sentiment classification system. First, a feature selection method is adopted to automatically generate the training data for a binary classifier on polarity shifting detection of sentences. Then, by

Shoushan Li; Sophia Yat Mei Lee; Ying Chen; Chu-Ren Huang; Guodong Zhou

2010-01-01

184

Mean shift-based clustering  

Microsoft Academic Search

In this paper, a mean shift-based clustering algorithm is proposed. The mean shift is a kernel-type weighted mean procedure. Herein, we first discuss three classes of Gaussian, Cauchy and generalized Epanechnikov kernels with their shadows. The robust properties of the mean shift based on these three kernels are then investigated. According to the mountain function concepts, we propose a graphical

Kuo-lung Wu; Miin-shen Yang

2007-01-01

185

THE MOB SHIFT SIMULATION FRAMEWORK  

Microsoft Academic Search

MOB SHIFT is a domain specific simulation framework enabling the timely and cost-effective analysis, design and evaluation of competing Mobile Offshore Base concepts. It was developed in SHIFT, a specification language for describing dynamic networks of hybrid automata. The expressive power of SHIFT provides a compact notation for modeling spatial and logical relationships in a dynamic environment and for modeling

J. Borges de Sous; A. Girard; N. Kourjanskaia

1999-01-01

186

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

187

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

ERIC Educational Resources Information Center

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

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

2013-01-01

188

Hydraulically actuated well shifting tool  

SciTech Connect

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

Roth, B.A.

1992-10-20

189

Nuclear field shift in natural environments  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

190

Lamb shift for static atoms outside a Schwarzschild black hole  

SciTech Connect

We study, by separately calculating the contributions of vacuum fluctuations and radiation reaction to the atomic energy level shift, the Lamb shift of a static two-level atom interacting with real massless scalar fields in the Boulware, Unruh, and Hartle-Hawking vacuums outside a Schwarzschild black hole. We find that in the Boulware vacuum, the Lamb shift gets a correction arising as a result of the backscattering of vacuum field modes off the space-time curvature, which is reminiscent of the correction to the Lamb shift induced by the presence of cavities. However, when the Unruh and Hartle-Hawking vacua are concerned, our results show that the Lamb shift behaves as if the atom were irradiated by a thermal radiation or immersed in a thermal bath at the Hawking temperature, depending on whether the scalar field is in the Unruh or the Hartle-Hawking vacuum. Remarkably, the thermal radiation is always backscattered by the space-time geometry.

Zhou Wenting [Department of Physics and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Yu Hongwei [Department of Physics and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Center for Nonlinear Science and Department of Physics, Ningbo University, Ningbo, Zhejiang 315211 (China)

2010-11-15

191

Shift work, safety, and aging.  

PubMed

It has long been recognized that older shift workers may have shorter and more disturbed day sleeps between successive night shifts than their younger colleagues. This has given rise to considerable concern over the safety of aging shift workers because of the increasing age of the work force and increases in retirement age. Because there have been no direct studies of the combined effects of shift work and age on safety, the present paper begins by reviewing the literature relating safety to features of shift systems. It then considers the general effect of age on occupational injury rates before examining existing evidence of the combined effects of shift work and age on performance capabilities. The results of the literature review indicate that when the a priori risk is constant, there is reasonably clear evidence that injury rates are higher at night, and that they increase over successive night shifts more rapidly than over successive day shifts. Further, although occupational injuries are less frequent in older workers, those that do occur tend to be more serious. Finally, there is some suggestive evidence from studies of objectively measured performance capabilities that older workers may be less able to both maintain their performance over the course of a night shift and cope with longer spans of successive night shifts. It is concluded that it seems possible, even though unproven as yet, that older workers may be at greater risk both to injury and accident on the night shift. There is a strong need for future epidemiological studies of the combined effects of shift work and age on injuries and accidents, and that these should attempt to separate the effects of age per se from those of generation. PMID:18484360

Folkard, Simon

2008-04-01

192

Shift work and pathological conditions  

PubMed Central

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

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

2006-01-01

193

Thermochromic shifts in supercritical fluids  

SciTech Connect

Thermochromic shifts of organic solute molecules in supercritical CO{sub 2} under conditions of both constant pressure and density are compared to previous studies of solvatochromic shifts at isothermal conditions. Similar solvatochromic and thermochromic shifts are seen as a function of density for supercritical CO{sub 2}. At constant density a small thermochromic shift ({approx}400 cm{sup {minus}1}) for supercritical CO{sub 2} was seen for both 2-nitroanisole and 4-ethylnitrobenzene. The excited-state dipole moments for 2-nitroanisole, as calculated from the thermochromic and solvatochromic data, were in agreement.

Yonker, C.R.; Smith, R.D. (Pacific Northwest Lab., Richland, WA (USA))

1989-02-23

194

Portable shift register  

SciTech Connect

An electronics package for a small, battery-operated, self-contained, neutron coincidence counter based on a portable shift-register (PSR) has been developed. The counter was developed for applications not adequately addressed by commercial packages, including in-plant measurements to demonstrate compliance with regulations (domestic and international), in-plant process control, and in-field measurements (environmental monitoring or safeguards). Our package's features, which address these applications, include the following: Small size for portability and ease of installation;battery or mains operation; a built-in battery to power the unit and a typical detector such as a small sample counter, for over 6 h if power lines are bad or noisy, if there is a temporary absence of power, or if portability is desired; complete support, including bias, for standard neutron detectors; a powerful communications package to easily facilitate robust external control over a serial port; and a C-library to simplify creating external control programs in computers or other controllers. Whereas the PSR specifically addresses the applications mentioned above, it also performs all the measurements made by previous electronics packages for neutron coincidence counters developed at Los Alamos and commercialized. The PSR electronics package, exclusive of carrying handle, is 8 by 10 by 20 cm; it contains the circuit boards, battery, and bias supply and weighs less than 2 kg. This instrument package is the second in an emerging family of portable measurement instruments being developed; the first was the Miniature and Modular Multichannel Analyzer (M[sup 3]CA). The PSR makes extensive use of hardware and software developed for the M[sup 3]CA; like the M[sup 3]CA, it is intended primarily for use with an external controller interfaced over a serial channel.

Halbig, J.K.; Bourret, S.C.; Hansen, W.J.; Hicks, D.V.; Klosterbuer, S.F.; Krick, M.S.

1994-01-01

195

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

NASA Astrophysics Data System (ADS)

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

Poindexter, C.; Variano, E. A.

2010-12-01

196

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

197

Health Effects of Shift Work  

PubMed Central

More than 13.5 million American workers, close to 20 percent of the work force, are assigned to evening or night shifts. In some industries such as automobile, petrochemical and textile manufacturing the proportion of shift workers is greater than 50 percent. As the popularity of shift work and other “alternative work schedules” grows, concern is increasing over the disturbance created in the lives of workers and their families by these economically and socially useful innovations. Twenty percent of workers are unable to tolerate shift work. Daily physiologic variations termed circadian rhythms are interactive and require a high degree of phase relationship to produce subjective feelings of wellbeing. Disturbance of these activities, circadian desynchronization, whether from passage over time zones or from shift rotation, results in health effects such as disturbance of the quantity and quality of sleep, disturbance of gastrointestinal and other organ system activities, and aggravation of diseases such as diabetes mellitus, epilepsy and thyrotoxicosis. Worker selection can reduce the number of health problems resulting from shift work. The periodic examination of shift workers is recommended.

LaDou, Joseph

1982-01-01

198

Interpretations of cosmological spectral shifts  

NASA Astrophysics Data System (ADS)

It is shown that for Robertson-Walker models with flat or closed space sections, all of the cosmological spectral shift can be attributed to the non-flat connection (and thus indirectly to space-time curvature). For Robertson-Walker models with hyperbolic space sections, it is shown that cosmological spectral shifts uniquely split up into "kinematic" and "gravitational" parts provided that distances are small. For large distances no such unique split-up exists in general. A number of common, but incorrect assertions found in the literature regarding interpretations of cosmological spectral shifts, is pointed out.

Østvang, Dag

2013-03-01

199

Perihelium Shifts in Central Potentials.  

National Technical Information Service (NTIS)

Motivated by the rigorous results on level ordering for arbitrary central potentials recently derived in the literature a classical treatment of the perihelium shifts is presented, based on the consideration of those orbits which lie in the vicinity of a ...

A. E. A. Amorim P. L. Ferreira

1987-01-01

200

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

201

Mean Shift Analysis and Applications  

Microsoft Academic Search

A nonparametric estimator of density gradient, themean shift, is employed in the joint, spatial-range(value) domain of gray level and color images for discontinuitypreserving filtering and image segmentation.Properties of the mean shift are reviewed and its convergenceon lattices is proven. The proposed filteringmethod associates with each pixel in the image the closestlocal mode in the density distribution of the jointdomain. Segmentation

Dorin Comaniciu; Peter Meer

1999-01-01

202

Art of the paradigm shift.  

PubMed

How long has it been since you've had a good paradigm shift? No, it's nothing you can plan. Nothing you can simply tick off that perennial list of To Do's tucked away in your pocket or some unoccupied sulcus of your brain. Paradigm shifts simply happen when you are on a journey of discovery. Once they happen, they change forever the way you look at the world. PMID:9197637

Masson, V

203

Reactions & Rates  

NSDL National Science Digital Library

Explore what makes a reaction happen by colliding atoms and molecules. Design experiments with different reactions, concentrations, and temperatures. When are reactions reversible? What affects the rate of a reaction?

Simulations, Phet I.; Koch, Linda; Lemaster, Ron; Loeblein, Trish; Perkins, Kathy; Gratny, Mindy

2006-12-01

204

Drug Reactions  

MedlinePLUS

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

205

Enhanced Hydrogen Production Integrated with CO2 Separation in a Single-Stage Reactor. Final Technical Report, October 1, 2003-September 30, 2008.  

National Technical Information Service (NTIS)

High purity hydrogen is commercially produced from syngas by the Water Gas Shift Reaction (WGSR) in high and low temperature shift reactors using iron oxide and copper catalysts respectively. However, the WGSR is thermodynamically limited at high temperat...

B. Sakadjian D. Wong H. Gupta L. Fan M. Iyer S. Ramkumar

2008-01-01

206

The study of ternary shift register sequence  

Microsoft Academic Search

The possibility of realizing a ternary shift register is pointed out. A ternary shift register sequence is discussed and analyzed in detail. Some conclusions about linear and nonlinear ternary shift register sequences are drawn

Zheng Qi-Lun; Chen Yong-Qiang

1989-01-01

207

[Health consequences of shift work].  

PubMed

In humans many biochemical, physiological and behavioral processes occur in a rhythmic manner. Accumulating experimental and epidemiological evidence indicate that disturbances in biological rhythms could lead to unfavorable alterations in body function, thus exerting negative health impact. In industrialized countries, it is estimated that between 15 and 30% of the working population is involved in some kind of permanent night work and rotating shift work. Today, shift work is regarded as a significant occupational stressor which has marked negative effects on both health and well-being. This review surveys data on association between shift work and health problems, including sleep disorders, cardiovascular disease, peptic ulcer, metabolic syndrome, breast cancer and undesirable pregnancy outcome. PMID:22010477

Andrzejczak, Dariusz; Kapa?a-Kempa, Magdalena; Zawilska, Jolanta B

2011-01-01

208

Estimation of Doppler Shift and Differential Doppler Shift.  

National Technical Information Service (NTIS)

This report is concerned with the measurement of frequency (Doppler shift) by a collection of sensors which may be grouped into two or more clusters (subarrays). The signal may be a sinusoid, or it may be a narrowband gaussian process whose center frequen...

P. M. Schultheiss

1977-01-01

209

Spectral shifts with polarization control  

NASA Astrophysics Data System (ADS)

The spectral behavior of a limited bandwidth light with different polarization states reflected from an air-water interface near the absorption band of water is theoretically investigated. The results indicate that, at oblique incidence, the reflected wave’s spectral change is blue- or red-shifted for different polarizations and the shift is most obvious when the angle is close to the Brewster angle. This phenomenon can be used as a polarization spectrum selector, and a data transmission scheme utilizing this effect is also proposed.

Han, Pin

2013-10-01

210

Decrease in carbonyl sulfide in the feed to Claus converters by shift catalysts  

SciTech Connect

The principal reaction in the burner in a Claus plant is the combustion of part of the hydrogen sulfide to form sulfur dioxide, which can react with more hydrogen sulfide to form sulfur. Alumina or commercial shift catalysts were used downstream of a Claus burner to shift carbon monoxide to carbon dioxide before it could react to form carbonyl sulfide. The shift catalysts were effective in preventing formation of carbonyl sulfide, thereby decreasing sulfur losses.

Gens, T.A. (BOC Group Technical Center, Murray Hill, NJ (United States))

1994-07-01

211

Raman shift of rare earth cobalt oxides  

NASA Astrophysics Data System (ADS)

RCoO3(R=La, Ce, Pr, Nd, Sm, Eu, Gd and Dy) perovskites prepared using the solid-state reaction method were examined by Raman spectroscopy. The Raman active Phonons in the RCoO3 perovskites crystallized in cubic symmetry for RCoO3 (R=La, Ce, Pr and Nd) and orthorhombic symmetry for RCoO3 (R=Sm, Eu, Gd, and Dy) were reported. The Raman spectra of RCoO3 perovskites were strongly dependent on the ionic radius of the rare earth elements, and the frequency shift of the most intense modes of the orthorhombic samples were correlated with some structural parameters such as Co-O bond distances, ionic radius of the rare earth elements and John-Teller distortion. It is clear that Raman spectroscopy has the advantage of being very sensitive to structure distortion and oxygen motion.

Wang, Weiran; Zhao, Yan; Han, Xueying

2010-05-01

212

Cyclotron frequency shifts arising from polarization forces  

NASA Astrophysics Data System (ADS)

The cyclotron frequency of a charged particle in a uniform magnetic field B is related to its mass m and charge q by the relationship ?c = qB/m. This simple relationship forms the basis for sensitive mass comparisons using ion cyclotron resonance mass spectroscopy, with applications ranging from the identification of biomolecules and the study of chemical reaction rates to determinations of the fine structure constant of atomic spectra. Here we report the observation of a deviation from the cyclotron frequency relationship for polarizable particles: in high-accuracy measurements of a single CO+ ion, a dipole induced in the orbiting ion shifts the measured cyclotron frequency. We use this cyclotron frequency shift to measure non-destructively the quantum state of the CO+ ion. The effect also provides a means to determine to a few per cent the body-frame dipole moment of CO+, thus establishing a method for measuring dipole moments of molecular ions for which few comparably accurate measurements exist. The general perturbation that we describe here affects the most precise mass comparisons attainable today, with applications including direct tests of Einstein's mass-energy relationship and charge-parity-time reversal symmetry, and possibly the weighing of chemical bonds.

Thompson, James K.; Rainville, Simon; Pritchard, David E.

2004-07-01

213

Shifting Patterns of Deadly Violence.  

ERIC Educational Resources Information Center

While it is true that the total suicide rates has varied little, this composite figure masks a dramatic shift in the risk of suicide by age. In recent years there has been a reduction of suicide at older ages reciprocated by an unprecedented increase of suicide and homicide at younger ages. (Author)

Seiden, Richard H.; Freitas, Raymond P.

1980-01-01

214

Technology Counts 2012: Virtual Shift  

ERIC Educational Resources Information Center

|Virtual education is moving into that intersection where rising popularity meets calls for greater accountability. How the virtual education movement responds to those calls will have a significant impact on how it evolves in K-12 over the next five to 10 years. This report tackles this shift in the virtual education landscape. It examines the…

Education Week, 2012

2012-01-01

215

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

216

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

217

Doppler Shift in a Plasma.  

National Technical Information Service (NTIS)

It is first shown that the ideal electron plasma (presence of protons neglected) is unique among all dispersive media in that it does not distinguish any inertial frame of reference in terms of utility. The theory of the Doppler shift in an ideal plasma i...

B. Manz

1968-01-01

218

Technology Counts 2012: Virtual Shift  

ERIC Educational Resources Information Center

Virtual education is moving into that intersection where rising popularity meets calls for greater accountability. How the virtual education movement responds to those calls will have a significant impact on how it evolves in K-12 over the next five to 10 years. This report tackles this shift in the virtual education landscape. It examines the…

Education Week, 2012

2012-01-01

219

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

220

Polarity Shifting: Corpus Construction and Analysis  

Microsoft Academic Search

Polarity shifting has been a challenge to automatic sentiment classification. In this paper, we create a corpus which consists of polarity-shifted sentences in various kinds of product reviews. In the corpus, both the sentimental words and shifting trigger words are annotated. Furthermore, we analyze all the polarity shifted sentences and categorize them into five categories: opinion-itself, holder, target, time and

Xiaoqian Zhang; Shoushan Li; Guodong Zhou; Hongxia Zhao

2011-01-01

221

Mean Shift Is a Bound Optimization  

Microsoft Academic Search

ABSTRACT We build on the current understanding of mean shift as an optimization procedure We demonstrate that in the case of piecewise constant kernels mean shift is equivalent to Newton's method Further, we prove that for all kernels the mean shift procedure is a quadratic bound maximization INDEX TERMS Mean shift, bound optimization, Newton's method, adaptive gradient descent, mode seeking

Mark Fashing; Carlo Tomasi

2005-01-01

222

Cognitive shifts related to interactive information retrieval  

Microsoft Academic Search

Purpose – Interactive information retrieval (IR) involves many human cognitive shifts at different information behaviour levels. Cognitive science defines a cognitive shift or shift in cognitive focus as triggered by the brain's response and change due to some external force. This paper aims to provide an explication of the concept of “cognitive shift” and then report results from a study

Amanda Spink; Cheryl Dee

2007-01-01

223

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

224

CLASS Shifts in Modeling Instruction  

NSDL National Science Digital Library

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

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

2008-09-15

225

Forward shift from reverse replay  

Microsoft Academic Search

In a recent experimental paper Lee et al. (Neuron 51:639–650, 2006) showed that the firing patterns of CA1 complex-spike neurons gradually shifted forward across trials toward prospective\\u000a goal locations within a recording session over multiple trials. Here we propose a simple model of this result based on the\\u000a phenomenon of awake sequence reverse replay (Foster and Wilson, Nature 440(7084):615–617, 2006) which

Adam Ponzi

2009-01-01

226

In situ Characterization of Pt Catalysts Supported on Ceria Modified TiO(2) for the WGS reaction: Influence of Ceria Loading  

SciTech Connect

This work analyzes the influence of cerium content (6-15 wt%) on a TiO{sub 2} support over the structure and water gas shift (WGS) activity of Pt catalysts. The structural properties of these Pt/Ce-TiO{sub 2} catalysts were characterized by XRD, TEM and XANES. Physicochemical characterization of the catalysts showed differences in the structure and dispersion of Ce entities on the support with Ce loading. For the samples with low ceria content (6 wt%), cerium is deposited on the support in the form of CeO{sub x} clusters in a highly dispersed state in close interaction with the Ti atoms. The formation of CeO{sub x} clusters at low Ce-loading on the support facilitates the dispersion of small particles of Pt and improves the reducibility of ceria component at low temperatures. The changes in platinum dispersion and support reducibility with Ce-loading on the TiO{sub 2} support lead to significant differences in the WGS activity. Pt supported on the sample with lower Ce content (6 wt%) shows better activity than those corresponding to catalysts with higher Ce content (15 wt%). Activity measurements coupled with catalysts characterization suggest that the improvement in the reducibility of the support with lower Ce content was associated with the presence of CeO{sub x} clusters of high reducibility that improve the chemical activity of the oxide-metal interfaces at which the WGS reaction takes place.

Rodriguez J. A.; Barrio, L.; Zhou, G.; Gonzalez, I.D.; Estrella, M.; Hanson, J.; Navarro, R.M.; Fierro, J.L.G.

2012-01-01

227

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

228

A Doppler Shift Speed Gun  

NASA Astrophysics Data System (ADS)

This is a fun and educational lab for any audience at the middle school level and above to learn about the Doppler shift and waves in general. The participants should review the basic properties of waves and, with some Socratic questioning, form their own hypothesis of what will happen to a sound wave when it is emitted by a moving object. Participants then construct their own instrument and test their hypothesis in both a qualitative and quantitative manner. The main part of this lab involves using a computer program and simple math to correctly measure the speed of an object, using only the waves emitted from it.

Sherman, Reid

229

Incoherent and coherent tune shifts  

SciTech Connect

The longitudinal and transverse microwave instabilities are the two important limiting factors for the performance of an accelerator. Comparing with the fairly unified approach for the longitudinal microwave instabilities, different approaches have been used to define the transverse microwave instabilities. One reason of this is related to the role played by the space charge incoherent and coherent tune shifts. In this article, the transverse microwave instabilities will be discussed by defining separately the roles of the space charge incoherent and coherent tunes, which are represented by the space charge transverse impedances. Preliminary results for the AGS as proton driver are presented by using this approach.

Zhang, S.Y. [Brookhaven National Lab., Upton, NY (United States). AGS Dept.

1995-12-31

230

Holistic Debriefing: A Paradigm Shift in Leadership.  

National Technical Information Service (NTIS)

From time to time, paradigm shifts occur in leadership in the sense that fundamental assumptions about the mechanisms in human performance change. We are currently undergoing a paradigm shift in society that might highlight Servant leadership as highly ef...

R. Folland

2009-01-01

231

Rewards and Challenges of Shift Work  

MedlinePLUS

... out sleep-depriving distractions. Purchase a “white noise” machine. Studies show that shift workers and non-shift ... peaceful sounds, such as ocean waves. White noise machines block out extraneous, not-so-peaceful sounds. You’ ...

232

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

233

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

Robertson, William C.

2010-03-01

234

Theory of Low Energy Nuclear Reactions  

Microsoft Academic Search

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

Erich Vogt

1962-01-01

235

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

236

Accuracy improvement of phase shift interferometry  

Microsoft Academic Search

An approach to improve the accuracy of phase-shift interferometry is presented. In this paper, an algorithm for estimating phase shift step errors is demonstrated. The algorithm is based on the fact that the sinusoidal intensity data from the same pixels of two interferograms with different phase shifts form an elliptic Lissajous curve. The elliptic Lissajous curve can be fitted by

Kee S. Moon; Yiding Wang

2003-01-01

237

Light shift compensated quantum memories  

NASA Astrophysics Data System (ADS)

Quantum telecommunication could provide secure long-distance data transfer. Direct transmission losses in optical fiber scale exponentially with distance. The quantum repeater protocol allows one to reach polynomial scaling of the communication rate with distance. The quantum repeater relies on long-lived quantum memory elements. Here we report on our recent progress in extending the lifetime of quantum memory based on an ensemble of cold rubidium atoms confined in an optical lattice. Previously observed coherence times (˜ 7 ms) were limited by ac Stark broadening of the ground state hyperfine transition. Two different light shift compensation schemes based on two photon transitions and magnetically-dressed optical potentials are reported. We reach ˜1/3 second lifetimes for stored classical light pulses and similar values for single quanta.

Dudin, Yaroslav O.; Zhao, Ran; Jenkins, Stewart D.; Kennedy, Brian; Kuzmich, Alex

2010-03-01

238

The effect of potassium addition on the state of the components in the oxide precursor of the (Ni)(Mo)\\/?-Al 2O 3 water-gas shift catalysts: FT-IR, diffuse reflectance and Raman spectroscopic studies  

Microsoft Academic Search

One-component samples containing K, Ni, and various concentrations of Mo were prepared by incipient wetness impregnation technique. Bi- and tri- component samples have been prepared from the calcined one- and bi-component samples following the same procedure. The samples were characterized by SSA, FT-IR, DRS and Raman measurements.The decrease of the ratio Ni2+(Td)\\/Ni2+(Oh) with the increase of Mo loading and the

D. Nikolova; R. Edreva-Kardjieva; M. Giurginca; A. Meghea; J. Vakros; G. A. Voyiatzis; Ch. Kordulis

2007-01-01

239

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  

Microsoft Academic Search

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

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

2010-01-01

240

Production of Synthetic Fuels by Co-Electrolysis of Steam and Carbon Dioxide  

Microsoft Academic Search

Co-electrolysis of H2O and CO2 was studied in solid oxide cells (SOCs) supported by nickel-\\/yittria-stabilized zirconia (Ni\\/YSZ) electrode. Polarization characterization indicates that electrochemical reduction of both CO2 and H2O occurs during co-electrolysis. In parallel with the electrochemical reactions, the equilibrium of the water–gas shift reaction is reached, and moreover, CO is produced via the water–gas shift reaction. The degradation observed

Sune Dalgaard Ebbesen; Christopher Graves; Mogens Mogensen

2009-01-01

241

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

242

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

243

Shifting boundaries in professional care.  

PubMed Central

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

Hopkins, A; Solomon, J; Abelson, J

1996-01-01

244

Azoxy rearrangement reactions  

NASA Astrophysics Data System (ADS)

The mechanisms of several types of azoxy compound (XN(O)NY) rearrangement reactions have been studied using density functional theory (DFT) with the B3LYP exchange-correlation potential. The substituents X and Y are taken from the set H, CH , F, C H , Cl and CN. The 6-311 + G(d,p) basis set was used to optimize up to ten equilibrium and transition state structures for a given pair of X and Y substituents; except for azoxybenzene where a 6- 311(+)G(d) basis set was used. All geometric structures were characterized by a frequency calculation. The reaction path for converting XN (O)N Y to XN N (O)Y via a concerted intramolecular shift of the oxygen atom from N to N involves three equilibrium and two saddle-point structures. The relatively high (about 70-80 kcalmol1) calculated barrier height to reaction and its independence of the nature of the X and Y substituents is attributed to characteristic orbital, atomic charge and structural factors along the reaction path. Cis trans isomerization across N-- N in the NH(O)NH azoxy compound and across N-N in the ring XNONY oxadiaziridine intermediate is found to have a barrier height of at least - 1 about 30 kcalmol . Single-point CCSD(T)/DFT energy differences are found to be somewhat smaller than the DFT calculated values. 3 6 5

Basch, Harold; Hoz, Tova

245

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.

246

Host shifts and evolutionary radiations of butterflies  

PubMed Central

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

Fordyce, James A.

2010-01-01

247

Kinetics and mechanism of the CO shift on Cu\\/ZnO. II. Kinetics of the decomposition of formic acid  

Microsoft Academic Search

The decomposition of formic acid over the Cu\\/ZnO catalyst used in earlier work on CO shift kinetics has been examined. The reaction proceeds through a formate-type surface intermediate, the decomposition of which is rate determining. Surface coverage is rather high. The rate of formic acid decomposition is similar to that of the forward shift reaction and shows about the same

T. Van Herwijnen; R. T. Guczalski; W. A. De Jong

1980-01-01

248

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

249

Isomer-shift analogue in neutron resonances  

Microsoft Academic Search

For the first time, the recently predicted chemical shift of neutron resonances, to be regarded as an analogue to the Mössbauer isomer shift, has been experimentally observed studying the 6.67 eV resonance of 238U. The experimental shifts were determined by a chi-square fitting technique from the time-of-flight transmission spectra of metallic uranium and four uranium compounds measured at the Dubna

A. Meister; D. Pabst; L. B. Pikelner; K. Seidel

1981-01-01

250

In vivo sodium chemical shift imaging.  

PubMed

The shift reagents thulium(III) 1,4,7,10-tetraazacyclododecane N,N',N",N"'tetramethylenephosphonate (TmDOTP5-), and dysprosium(III)triethylenetetramine-hexaacetate (DyTTHA3-) are compared in this work for their uses in sodium chemical shift imaging (NaCSI). In a series of experiments using phantoms we evaluated the relative contributions of bulk magnetic susceptibility (BMS) effects and hyperfine shifts to the induced 23Na chemical shift for these two shift reagents. The ratios of BMS effects to hyperfine shifts suggest that TmDOTP5- should be a more effective shift reagent than DyTTHA3- for 23Na NMR spectroscopy as well as NaCSI. The dependence on pH and free Ca2+ concentration of the 23Na NMR frequency shift induced by TmDOTP5- was evaluated. It was found that TmDOTP5- produces good spectral resolution under physiologic conditions. Examples presented from in vivo NaCSI experiments using TmDOTP5- to study diffusion in the posterior chamber of the rabbit eye and to monitor the rate of clearance of aqueous fluid from the anterior chamber demonstrate the effectiveness of this new shift reagent and of the NaCSI technique for in vivo studies. PMID:1310341

Kohler, S J; Kolodny, N H; Celi, A C; Burr, T A; Weinberg, D; D'Amico, D J; Gragoudas, E S

1992-01-01

251

Enzymatic synthesis in biphasic aqueous-organic systems. II. Shift of ionic equilibria.  

PubMed

Ionic equilibria in "water-water-immiscible organic solvent" systems have been studied. It has been shown that in such systems shift of the apparent pK value of acids and bases takes place (compared to aqueous solutions), the value of the shift being rather high, up to 5 and more pH units (with 2,4-dinitrophenyltryptophan as an acid and neutral red as a base). The pK shift of ionogenic reagents observed in biphasic systems can be used in preparative organic synthesis for increasing the yield of end products in enzyme-catalyzed reactions. In connection with this, the physico-chemical reasons for the equilibrium shift in a chemical reaction that involves one or two ionogenic reagents are theoretically analyzed. The above approach has been tested with two alpha-chymotrypsin-catalyzed reactions, i.e., synthesis of N-benzoyl-L-phenylalanine ethyl ester (from NBz-LPhe-OH and ethanol) and synthesis of N-acetyl-L-tryptophanyl-L-leucine amide (from NAc-LTrp-OH and LLeu-NH2). In water the equilibria in these reactions are shifted almost entirely towards the starting reagents with the yield of end product being negligibly low. In biphasic systems consisting of chloroform +5% (v/v) water or ethyl acetate +2% (v/v) water, the yield of both the ester and the dipeptide reaches 100%. PMID:7213763

Martinek, K; Semenov, A N

1981-03-13

252

Can sunlight shift the Earth onto a different orbit?  

NASA Astrophysics Data System (ADS)

This article comes from a question asked by a student of mine: if the Sun radiates energy in the form of electromagnetic waves, could they shift the Earth from its current orbit on a suitable timescale? The answer to such a question is apparently obvious and trivial. Nevertheless, it requires an instructive reasoning and interesting estimates of orders of magnitude. Given the particularly positive reaction of my students to the solution given to the question, I think it is useful to report it here for the possible benefit of other students.

Esposito, S.

2011-09-01

253

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.

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

2009-01-01

254

Exercise, energy balance and the shift worker.  

PubMed

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 in shift workers have not been confirmed. 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 randomized 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 randomized controlled trials of physical activity or dietary interventions have 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

2008-01-01

255

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

PubMed

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

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

2012-05-03

256

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 ...

257

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.

School, Maryland V.

258

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

259

Shifted normal forms of polynomial matrices  

Microsoft Academic Search

In this paper we study the problem of transforming, via invertiblecolumn operations, a matrix polynomial into a varietyof shifted forms. Examples of forms covered in our frameworkinclude a column reduced form, a triangular form, aHermite normal form or a Popov normal form along withtheir shifted counterparts.

Bernhard Beckermann; George Labahn; Gilles Villard

1999-01-01

260

Color Shifts Following Rapid Eye Movements.  

National Technical Information Service (NTIS)

Changes in hue, somewhat analogous to the Bezold-Brucke shift, are seen when test flashes are presented immediately following a saccade. These color shifts are mostly toward the 'yellower' wavelengths and appear to be due to an increase in neural activity...

W. Richards

1969-01-01

261

NMR Landscapes for Chemical Shift Prediction.  

PubMed

The ability to reliably predict NMR chemical shifts plays an important role in elucidating the structure of organic molecules. Additionally, an intriguing question is how the multitude of variable factors (structural, electronic, and environmental) correlate with the actual electromagnetic shielding effect that determines the chemical shift value. This work presents NMRscape as a new tool for understanding these correlations by constructing the landscape that describes the relationship between the chemical shift value and the moieties bonded to a molecular scaffold. The scaffold may be as small as a single atom probed by NMR or a larger molecular framework containing the probed atom. NMRscape operates with only a list of the chemical moieties bonded to the scaffold, without utilizing any potentially biasing chemometric descriptors. The corresponding chemical shift landscape is constructed based on fundamental physical principles, which makes NMRscape a credible chemical shift prediction and analysis tool. As an illustration, we demonstrate that NMRscape can predict (13)C chemical shifts with an accuracy exceeding the substituent chemical shift (SCS) increment, hierarchical organization of spherical environments (HOSE), and neural networks (NN), methods for three distinct families of molecules sharing a common scaffold structure with moieties placed at two variable sites. The constructed NMR landscapes confirmed known empirical rules relating chemical shift values to the variation of chemical moieties on a scaffold, as well as uncovered hitherto hidden relationships. The practical importance of NMRscape is discussed. PMID:22900681

Moore, Katharine W; Li, Richard; Pelczer, Istvan; Rabitz, Herschel

2012-08-29

262

The wavenumber shift in SAR interferometry  

Microsoft Academic Search

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

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

1994-01-01

263

Language Shift in a Singapore Family.  

ERIC Educational Resources Information Center

Discusses the major language shift in Singapore from the familial use of varieties of Chinese other than Mandarin towards the languages of education, English and Mandarin. An ethnographic study is presented of a Singaporean Chinese family that has moved from Cantonese to English, and the underlying pressures leading to this shift are examined. (19…

Gupta, Anthea Fraser; Yeok, Siew Pui

1995-01-01

264

Entropy functionals associated to shifts dynamical systems  

NASA Astrophysics Data System (ADS)

We construct entropy functionals which discriminate the measures which converge to equilibrium in the case of shifts dynamical systems. In particular for K-shifts it is proved that some functionals associated to them decrease monotonically to zero. On leave of absence from Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile.

Martinez, S.; Tirapegui, E.

1983-12-01

265

Nonphotic Phase Shifting in Hamster Clock Mutants  

Microsoft Academic Search

Golden hamsters with the tau mutation were kept in the dark and induced to become active through confinement to a novel running wheel for 3 hr. The response of the mutants to this nonphotic phase-shifting stimulus differed from that of wild-type hamsters. The mutants showed larger phase shifts, and their phase response curves differed in shape, with an advance portion

N. Mrosovsky; Peggy A. Salmon; Michael Menaker; Martin R. Ralph

1992-01-01

266

Measurement of the differential Doppler shift  

Microsoft Academic Search

Doppler shifts between narrow-band signals observed at one or more pairs of receivers and originated from a remote source of radiation are useful for estimating source location and track. This paper deals with an instrumentationally attractive approach of estimating differential Doppler shifts by making center frequency measurements at each receiver output and subtracting them in a pairwise fashion. For low

EHUD WEINSTEIN

1982-01-01

267

Isotope shift and interacting boson model  

NASA Astrophysics Data System (ADS)

The Interacting Boson Model (IBM) description, for the isotope shift is reviewed. A schematic explanation of the basic properties is given first. The calculations for Xe-Ba-Ce and Sm isotopes are reported. For the former, the IBM-2 calculation is repeated and the isotope shift is analyzed with new parameters. For Sm isotopes, the sdg IBM-2 is used for the first time. Both, calculations present good agreement to experiment, with a rather global value of the parameter for the deformed isotope shift. In addition, two other topics are discussed; one is a microscopic calculation of the spherical isotope shift, and the other is a striking correlation between the deformed isotope shift and the M1 excitation strength to the scissors mode.

Otsuka, Takaharu

1992-10-01

268

Vibrational line shifts in supercritical fluids  

SciTech Connect

A microscopic statistical mechanical theory of solvent-induced vibrational line shifts of dilute solutes in supercritical fluids is presented. The theory is based on a simple model of a spherical solute present at infinite dilution in a fluid of spherical solvent particles. A microscopic expression for the vibrational line shift is given, which involves the solute-solvent radial distribution function and interaction potentials. The distribution function is obtained from integral equations and from Monte Carlo simulations. The theory is applied to study the experimentally observed anomalous density dependence of line shifts in supercritical fluids in the vicinity of the critical point. Model calculations of spectral shifts are performed for a range of solvent densities and temperatures and model potential parameters. In addition, a quantitative comparison of the theory with experimental data on vibrational spectral shifts is performed, and the agreement is satisfactory.

Egorov, S.A.; Skinner, J.L.

2000-01-27

269

Accuracy improvement of phase shift interferometry  

NASA Astrophysics Data System (ADS)

An approach to improve the accuracy of phase-shift interferometry is presented. In this paper, an algorithm for estimating phase shift step errors is demonstrated. The algorithm is based on the fact that the sinusoidal intensity data from the same pixels of two interferograms with different phase shifts form an elliptic Lissajous curve. The elliptic Lissajous curve can be fitted by the least squares method from which the phase shift steps can be accurately estimated. The estimated phase shift step errors are then compensated to measure 3D topography of specimen. In addition, the approach provides a simple technique of measuring 3D topography without sophisticated actuation mechanism. Simulations and experiments also demonstrate that the intensity noise in interferograms provides very small effect on the accuracy of the algorithm.

Moon, Kee S.; Wang, Yiding

2003-10-01

270

Chlorine poisoning of Rh??Al 2 O 3 catalysts in the toluene steam dealkylation  

Microsoft Academic Search

Chlorinating a rhodium alumina catalyst in the toluene steam dealkylation results in a weak reversible poisoning which affects mainly the CO conversion reactions (methanation and water gas shift). Selectivity to benzene is practically not influenced by chlorine.

D. Duprez; P. Pereira; A. Miloudi; J. Barbier; R. Maurel

1980-01-01

271

5 CFR 532.505 - Night shift differentials.  

Code of Federal Regulations, 2010 CFR

...is temporarily assigned to a day shift or to a night shift having a lower night...schedule involving work on both day and night shifts shall be paid a night...not regularly assigned to a day shift or a night shift but whose shift is...

2009-01-01

272

5 CFR 532.505 - Night shift differentials.  

Code of Federal Regulations, 2010 CFR

...is temporarily assigned to a day shift or to a night shift having a lower night...schedule involving work on both day and night shifts shall be paid a night...not regularly assigned to a day shift or a night shift but whose shift is...

2010-01-01

273

Effects of working permanent night shifts and two shifts on cognitive and psychomotor performance  

Microsoft Academic Search

Objectives: The study aimed to clarify whether cognitive and psychomotor performance, which are important for occupational and traffic safety, are impaired by working permanent night shifts (NSs) compared with early–late two shifts (TSs) and whether age and chronobiological type influences the relationship between shift and performance. Methods: The study included 44 male automobile workers, 20 working TSs and 24 working

Raluca Petru; Marc Wittmann; Dennis Nowak; Bodo Birkholz; Peter Angerer

2005-01-01

274

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).

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

2013-01-01

275

New types of 'combined' pericyclic reactions  

NASA Astrophysics Data System (ADS)

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

Magdesieva, Tatyana V.

2013-03-01

276

Limits to superweak amplification of beam shifts  

NASA Astrophysics Data System (ADS)

The magnitudes of beam shifts (Goos-H\\"anchen and Imbert-Fedorov, spatial and angular) are greatly enhanced when a reflected light beam is postselected by an analyzer, by analogy with superweak measurements in quantum theory. Particularly strong enhancements can be expected close to angles at which no light is transmitted for a fixed initial and final polarizations. We derive a formula for the angular and spatial shifts at such angles (which includes the Brewster angle), and we show that their maximum size is limited by higher-order terms from the reflection coefficients occurring in the Artmann shift formula.

Götte, Jörg B.; Dennis, Mark R.

2013-07-01

277

Visual sensitivities tuned by heterochronic shifts in opsin gene expression  

PubMed Central

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

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

2008-01-01

278

Peripherality of breakup reactions  

SciTech Connect

The sensitivity of elastic breakup to the interior of the projectile wave function is analyzed. Breakup calculations of loosely bound nuclei ({sup 8}B and {sup 11}Be) are performed with two different descriptions of the projectile. The descriptions differ strongly in the interior of the wave function, but exhibit identical asymptotic properties, namely the same asymptotic normalisation coefficient, and phase shifts. Breakup calculations are performed at intermediate energies (40-70 MeV/nucleon) on lead and carbon targets as well as at low energy (26 MeV) on a nickel target. No dependence on the projectile description is observed. This result confirms that breakup reactions are peripheral in the sense that they probe only the external part of the wave function. These measurements are thus not directly sensitive to the total normalization of the wave function, i.e., spectroscopic factor.

Capel, P. [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T2A3 (Canada); Nunes, F. M. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824 (United States)

2007-05-15

279

Adaptation to shift work: physiologically based modeling of the effects of lighting and shifts' start time.  

PubMed

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

2013-01-04

280

Reaction Time  

NSDL National Science Digital Library

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

Horton, Michael

2009-05-30

281

Language Maintenance, Language Shift, and Occupational Achievement in the United States.  

National Technical Information Service (NTIS)

This report reviews the literature on discriminatory reactions to accents. It tests to see if having a non-English mother-tongue has a negative effect on occupational achievement. It also tests to see if shift to English, switching to English as most ofte...

J. Angle

1977-01-01

282

Effects of Napping on Night Shift Performance.  

National Technical Information Service (NTIS)

This study represents a collaborative effort between the Federal Aviation Administration's Civil Aeromedical Institute and the US Army Aeromedical Research Laboratory to investigate the effects of napping on the midnight shift as a potential countermeasur...

P. S. Della Rocco C. Comperatore L. Caldwell C. Cruz

2000-01-01

283

Zero-quantum filtered pure shift TOCSY.  

PubMed

The high spectral resolution provided by the pure shift TOCSY experiment can be significantly improved by zero-quantum filtering which eliminates dispersive anti-phase contributions from the spectrum. PMID:23164750

Koivisto, Jari J

2012-11-19

284

Doppler Shift Methods for Plasma Diagnostics,  

National Technical Information Service (NTIS)

Work to develop novel advanced laser spectroscopy plasma diagnostic methods is described. The methods are based on observing the doppler shift in the absorption liners of ionic species. Two methods under study are Velocity Modulated Laser Spectroscopy and...

M. Sassi J. W. Daily

1987-01-01

285

A shifting seasonality of schizophrenic births.  

PubMed

In view of recent findings in Japan, and in England and Wales, data on schizophrenic births in the United States were reexamined to see if seasonal shifts had occurred. In Missouri a progressive shift from February to April and May was noted between 1921 and 1930 and between 1941 and 1950. In five New England states there was no shift over the same period. Data were then obtained to compare the Missouri shift with two hypotheses previously put forward to explain schizophrenic birth seasonality: (1) that it is related to the seasonality of general births, and (2) that it is related to seasonal temperature variation. Neither hypothesis was supported by the data. PMID:427335

Torrey, E F; Torrey, B B

1979-02-01

286

Shift work, risk factors and cardiovascular disease.  

PubMed

The literature on shift work, morbidity and mortality from cardiovascular disease, and changes in traditional risk factors is reviewed. Seventeen studies have dealt with shift work and cardiovascular disease risk. On balance, shift workers were found to have a 40% increase in risk. Causal mechanisms of this risk via known cardiovascular risk factors, in relation to circadian rhythms, disturbed sociotemporal patterns, social support, stress, behavior (smoking, diet, alcohol, exercise), and biochemical changes (cholesterol, triglycerides, etc) are discussed. The risk is probably multifactorial, but the literature has focused on the behavior of shift workers and has neglected other possible causal connections. In most studies methodological problems are present; these problems are related to selection bias, exposure classification, outcome classification, and the appropriateness of comparison groups. Suggestions for the direction of future research on this topic are proposed. PMID:10360463

Bøggild, H; Knutsson, A

1999-04-01

287

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

288

Shifted set families, degree sequences, and plethysm  

Microsoft Academic Search

We study, in three parts, degree sequences of k-families (or k-uniform hypergraphs) and shifted k-families. The first part collects for the first time in one place, various implications such as: Threshold implies Uniquely Realizable implies Degree-Maximal implies Shifted, which are equivalent concepts for 2-families (=simple graphs), but strict implications for k-families with k > 2. The implication that uniquely realizable

Caroline Klivans; Victor Reiner

2006-01-01

289

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

290

Centralizing physician office functions. A paradigm shift.  

PubMed

Recent trends show that organizations that once thought business office centralization was beneficial are re-thinking their strategies and decentralizing business office functions. This article focuses on the paradigm shift from business office centralization to decentralization and the political factors effecting this shift. It provides actual case summaries to demonstrate what has transpired, and presents an alternative strategy to establishing successful business office functions, a hybrid business office. PMID:10662475

Croopnick, J G

291

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

2012-10-03

292

Isomer-shift analogue in neutron resonances  

NASA Astrophysics Data System (ADS)

For the first time, the recently predicted chemical shift of neutron resonances, to be regarded as an analogue to the Mössbauer isomer shift, has been experimentally observed studying the 6.67 eV resonance of 238U. The experimental shifts were determined by a chi-square fitting technique from the time-of-flight transmission spectra of metallic uranium and four uranium compounds measured at the Dubna IBR-30 pulsed reactor. A computational method has been applied to estimate, and compensate for, the influence of the crystal-lattice vibrations on the experimental values thus obtained. The electron density differences at the nucleus have been calculated for the various sample pairs using available data on chemical X-ray shifts in uranium compounds, on Mössbauer isomer shifts in isovalent neptunium compounds and on free-ion electron densities. The resonance shift results lead to the conclusion that the mean-square charge radius of 238U diminishes by 1.7-0.8+1.2 fm2 upon capturing the resonance neutron.

Meister, A.; Pabst, D.; Pikelner, L. B.; Seidel, K.

1981-06-01

293

Comparison of multiframe phase-shifting algorithms with unknown value of phase shift  

NASA Astrophysics Data System (ADS)

Our work analyzes several multiframe phase-shifting algorithms with unknown values of phase shifts. The presented paper offers new algorithms for evaluation of phase values in interferometric measurements. Nonlinear multi-frame phase-shifting algorithms, which use five, six and seven intensity frames to determine phase values in interferometric measurements, are described theoretically. The proposed algorithms compensate for linear phase-shift errors, i.e. miscalibration of phase-shift, which are very common in practice of interferometric measurements. The phase-shift value is assumed unknown but constant in these algorithms, so that at least four phase shifted intensity frames have to be recorded. An advantage of the described algorithms is a possibility of pointwise phase-shift calculation. An analysis of proposed algorithms with respect to possible influences on the process of interferometric measurements is also carried out. Several important potential error sources were chosen and the sensitivity and accuracy of phase evaluation algorithms was compared. The algorithms derived in this work can be used in any phase-shifting measurement technique and they offer the advantage of insensitivity to the linear phase-shift errors.

Novak, Jiri; Miks, Antonin

2003-05-01

294

Air-water gas exchange of chlorinated pesticides in four lakes spanning a 1,205 meter elevation range in the Canadian Rocky Mountains.  

PubMed

Concentrations of selected persistent organic pollutants (POPs) in air and water were measured from four lakes that transect the Canadian Rocky Mountains. These data were used in combination with wind velocity and temperature-adjusted Henry's law constants to estimate the direction and magnitude of chemical exchange across the air-water interface of these lakes. Bow Lake (1,975 m above sea level [masl]) was studied during the summers of 1998 through 2000; Donald (770 masl) was studied during the summer of 1999; Dixon Dam Lake (946 masl) and Kananaskis Lake (1,667 masl) were studied during the summer of 2000. Hexachlorobenzene (HCB) and dieldrin volatilized from Bow Lake in spring and summer of 1998 to 2000 at a rate of 0.92 +/-1.1 and 0.55+/-0.37 ng m(-2) d(-1), respectively. The alpha-endosulfan deposited to Bow Lake at a rate of 3.4+/-2.2 ng m(-2) d(-1). Direction of gas exchange for gamma-hexachlorocyclohexane (gamma-HCH) changed from net deposition in 1998 to net volatilization in 1999, partly because of a surge in y-HCH concentrations in the water at Bow Lake in 1999. Average gamma-HCH concentrations in air declined steadily over the three-year period, from 0.021 ng m(-3) in 1998, to 0.0023 ng m(-3) in 2000, and to volatilization in 1999 and 2000. Neither the concentrations of organochlorine compounds (OCs) in air and water, nor the direction and rate of air-water gas exchange correlate with temperature or elevation. In general, losses of pesticides by outflow were greater than the amount exchanged across the air-water interface in these lakes. PMID:15683168

Wilkinson, Andrew C; Kimpe, Lynda E; Blais, Jules M

2005-01-01

295

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

296

Ecohydrological monitoring blindness to Arctic ecosystem regime shifts  

Microsoft Academic Search

We have investigated, mapped the reported evidence for, and systematized the feedback mechanisms of three different types of climate-driven inland ecosystem regime shifts in the Arctic: (i) shift from tundra to shrubland or forest, (ii) shift from terrestrial ecosystems to thermokarst lakes and wetlands, and (iii) shift from thermokarst lakes and wetlands to terrestrial ecosystems. These shifts have reportedly occurred

J. Mård Karlsson; A. Bring; G. Destouni

2010-01-01

297

[Comparison of shift work and night shifts: impacts on health and wellbeing among sanitary workers].  

PubMed

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 quality of the shift and looks at the implications for individual health and wellbeing, during the wellbeing, during the shift. Three groups of sanitary workers, one working in the morning, one working two shifts, and the other working three, took part. All completed a version of the standard shiftwork index (SSI), a set of self reported questionnaires related to health and wellbeing. The three groups differed on many outcome measures, although the differences that did exist didn't suggested advantages for one shift system over the others. PMID:23393869

Della Betta, F; Martinellit, R; Del Re, C; Tarquini, M; Fantasia, D; Paoletti, A

298

Complex energy shift and background phase shift for simulated electron-molecular shape resonances  

NASA Astrophysics Data System (ADS)

Feshbach-Fano resonance theory (FFRT) is used to determine the energy dependence of the complex energy shift function, consisting of the real energy shift and the resonance width, and the background phase shift for several simulated molecular shape resonances. Attention is paid to the way the choice of the quasibound state (QBS) function required in the FFRT affects these energy dependencies. An overlap criterion for choosing an optimal QBS function is proposed. Using our treatment on t -butylchloride, carbon tetrachloride, ethylene, and benzene, we give numerical results for specific cases of l=1 through 4. We find that the real energy shift function does not vary greatly over the width of the resonance, although the magnitude of the shift can be fairly large. We also find that the behavior of the background phase shift due to orthogonality scattering is sensitive to the presence of long-range potentials.

Gallup, G. A.

2005-02-01

299

Complex energy shift and background phase shift for simulated electron-molecular shape resonances  

SciTech Connect

Feshbach-Fano resonance theory (FFRT) is used to determine the energy dependence of the complex energy shift function, consisting of the real energy shift and the resonance width, and the background phase shift for several simulated molecular shape resonances. Attention is paid to the way the choice of the quasibound state (QBS) function required in the FFRT affects these energy dependencies. An overlap criterion for choosing an optimal QBS function is proposed. Using our treatment on t-butylchloride, carbon tetrachloride, ethylene, and benzene, we give numerical results for specific cases of l=1 through 4. We find that the real energy shift function does not vary greatly over the width of the resonance, although the magnitude of the shift can be fairly large. We also find that the behavior of the background phase shift due to orthogonality scattering is sensitive to the presence of long-range potentials.

Gallup, G.A. [Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0111 (United States)

2005-02-01

300

Reactions of Singlet Oxygen with Enol Esters.  

National Technical Information Service (NTIS)

Singlet oxygenation of (l-adamantylidene)ethyl acetate (4) and 6,6-dimethylcyclohex-l-enyl acetate (7) produces only ene reaction products. Photooxygenation of Delta 1,6-2-oxabicyclo(4.4.0)decen-3-one (9), in contrast, yields ene, acyl-shifted, and (2+2)c...

S. L. Wilson G. B. Schuster

1985-01-01

301

The thermodynamics of human reaction times  

Microsoft Academic Search

I present a new approach for the interpretation of reaction time (RT) data from behavioral experi- ments. From a physical perspective, the entropy of the RT distribution provides a model-free estimate of the amount of processing performed by the cognitive system. In this way, the focus is shifted from the conventional interpretation of individual RTs being either long or short,

DEL PRADO MART

302

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.

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

2013-01-01

303

Isomer Shifts in Solid State Chemistry  

NASA Astrophysics Data System (ADS)

The isomer shift of the Mössbauer resonance is a rather unique quantity that cannot be obtained by any of the other techniques used for measuring hyperfine interactions in solids, such as NMR or perturbed angular correlations (TDPAC). It shifts the resonance pattern as a whole without affecting the magnetic dipole and electric quadrupole hyperfine splittings. Methods that measure only these hyperfine splittings are insensitive to the isomer shift. The magnitude of the observed shift is proportional to the product of a nuclear parameter, the change ??r 2? of the nuclear radius that goes along with the Mössbauer transition, and to an electronic property of the material, the electron density ?(0) at the Mössbauer nucleus or, more precisely, to the difference ??(0) of the electron densities at the Mössbauer nuclei in the materials of which the source and the absorber are made. The electron density at the nucleus is due to s-electrons and, to a lesser extent and mainly in heavy nuclei, to relativistic p1 / 2-electrons. All the other electrons have a vanishing density inside the nucleus and do not contribute. Thus, to a very good accuracy, the Mössbauer isomer shift enables one to obtain information on the s-electron density at the Mössbauer nuclei in solids.

Wagner, F. E.; Stievano, L.

304

Object-based attention: shifting or uncertainty?  

PubMed

The contribution of object-based attentional guidance to visual processing is widely accepted, and recent models of attentional selection now include both space- and object-based representations. Nevertheless, although the mechanism of space-based attentional selection has been well characterized, the mechanism underlying object-based attentional selection remains poorly understood. Recent attempts at identifying the mechanism giving rise to object-based attentional selection have put forth two conflicting alternatives. The first suggests that object-based effects are driven by attentional uncertainty (i.e., the attentional prioritization hypothesis), whereas the second suggests that objects guide attentional selection only when an attentional shift is necessitated (i.e., the attentional-shifting hypothesis). Here, we directly investigated which of the two suggested accounts drives object-based effects, by pitting attentional certainty against attentional shifting. In a series of four experiments, we manipulated the certainty of target location, shifting of attention, and the stimulus onset asynchrony. It was observed that object-based effects depended solely on certainty of the forthcoming target location. These results suggest that attentional prioritization, and not a mere shift of attention, gives rise to object-based guidance of attentional selection. In addition, these results lend further support to the attentional prioritization account of object-based attention and provide further constraints on the mechanisms of object-based selection. PMID:20952774

Drummond, Leslie; Shomstein, Sarah

2010-10-01

305

Social reasoning about 'second-shift' parenting.  

PubMed

The present study investigated children's and adolescents' social reasoning about parenting roles in the home, specifically 'second-shift parenting' by a mother or father. Surveys were administered to children (age 10) and adolescents (age 13), nearly evenly divided by gender (N= 200) in which two hypothetical scenarios were evaluated. Participants were asked to evaluate and justify second-shift parenting arrangements for the family overall, for the parent in the role, and for the child in the family. Results showed that participants expected mothers rather than fathers to take on the second-shift role, and second-shift parenting was evaluated as more unfair for fathers than for mothers. Personal choice reasoning was used for justifying arrangements for the second-shift parent and moral reasoning was used for justifying arrangements for the child. Social reasoning about the context of parental caretaking roles was multifaceted and varied by age and gender of participant more so than by self-reported personal family arrangements. PMID:21592152

Sinno, Stefanie M; Killen, Melanie

2011-01-12

306

Catalytic reforming of methane with carbon dioxide over nickel catalysts II. Reaction kinetics  

Microsoft Academic Search

The reforming of methane with carbon dioxide was studied over nickel supported on SiO2, TiO2, MgO and activated carbon. Specific activities on a turnover frequency basis were in the order: Ni\\/TiO2 > Ni\\/C > Ni\\/SiO2 > Ni\\/MgO. Interestingly, a 2-fold increase in activation energy for this reaction was observed over Ni\\/TiO2 after several hours time on stream. The reverse water-gas

Michael C. J. Bradford; M. Alber Vannice

1996-01-01

307

Classical and Quantum Radiation Reaction  

NASA Astrophysics Data System (ADS)

This thesis reports on work undertaken in comparing the effects of the phenomenon of radiation reaction in classical and quantum theories of electrodynamics. Specifically, it is concerned with the prediction of the change in position of a particle due to the inclusion of the self-force in the theory. We calculate this position shift for the classical theory, treating radiation reaction as a perturbation in line with the reduction of order procedure. We calculate the contributions to the position shift in the hbar-> 0 limit of quantum field theory to order e(2) in the coupling, the order of the classical self-force. These calculations contain the emission and forward scattering one loop processes of quantum electrodynamics. The quantum calculations are completed for the case of a particle represented by a scalar field wave packet and then for a particle represented by the Dirac spinor field. We additionally give an alternative derivation of the scalar results using the interpretation of radiation reaction via a Green's function decomposition, in order to explain and contrast the results achieved.

Martin, Giles D. R.

2008-05-01

308

Automatic phase shift determination using corrlation method  

NASA Astrophysics Data System (ADS)

An automatic method for the determination of phase shift in phase stepping digital speckle pattern interferometry (DSPI) is proposed by using a digital correlation procedure. The process first detects the fringe interval from an auto-correlation of an image row in a reference fringe pattern and then calculates the shifts between that and three other phase shifted fringe patterns. In order to facilitate the correlation, a special reference surface is used for which the fringe spacing is uniform. Phase calculation algorithm and data analysis approach are presented. The results of computer simulation to validate the technique and DSPI experiments are shown, error estimations are given and limitations and effectiveness of the technique are discussed.

Wang, L. S.; Dobbins, B. N.; Jambunathan, K.; He, S. P.; Button, B. L.

309

12 hour shifts the Nambour Hospital experience.  

PubMed

Union members have a lengthy history of campaigning for fair working hours and conditions. The success of such campaigns has led to the implementation of the eight hour working day and the 40 hour and then 38 hour week as industrial standards. More recently though, calls for greater flexibility in their shift arrangements by nurses at Nambour Hospital have led to a voluntary 12 hour shift being implemented in their Intensive Care Unit. While union members are protective of their hard won gains in achieving reduced working hours through the 8 hour day--ICU nurses at Nambour Hospital say the voluntary 12 hour shift initiative goes a way in addressing their work/life balance issues. PMID:17879604

2007-08-01

310

Differential Stark shifts in the hydrogen maser  

SciTech Connect

The theory of the Stark shift of hydrogen ground-state hyperfine levels has been tested at the 2.4% level of accuracy in a hydrogen maser. The quadratic-Stark-shift coefficient for the hyperfine-transition frequency was experimentally found to be delta..nu.. x 10/sup -14/ Hz (V/m)/sup -2/, where the electric field was perpendicular to the axis of quantization. The quoted uncertainty corresponds to one standard deviation. The uncertainty has contributions from the statistics of the data and from systematic effects. A number of possible sources of systematic error or unwanted frequency shifts has been tested. The theoretically predicted coefficient delta..nu.. x 10/sup -14/ Hz (V/m)/sup -2/ is in reasonable agreement with the present experimental result.

Stuart, J.G.; Larson, D.J.; Ramsey, N.F.

1980-11-01

311

Cardiac autonomic imbalance in female nurses with shift work  

Microsoft Academic Search

The pathophysiology underlying the shift work-related cardiovascular disease is still poorly understood. The chronic effects of shift work on cardiac autonomic functions were assessed in 47 hospital nurses working under a rotating three-shift system (shift nurses) and 36 public health nurses without shift work (non-shift nurses). The heart rate variability, %LF and %HF (i.e., proportions of sympathetic and vagal activities,

Noriko Ishii; Miwako Dakeishi; Makiko Sasaki; Toyoto Iwata; Katsuyuki Murata

2005-01-01

312

Optical current sensor using phase shift algorithms  

NASA Astrophysics Data System (ADS)

A new fiber-optic current sensor (FOCS) is described which employs phase shifting algorithms to process the optical signal. In this approach the sensing element consists of a coil low birefringence fiber placed between one polarizer and four analyzers. In the polarimeter layout, the output light from the current sensing element is divided into four beams through three nonpolarizing beamsplitters, and in each beam path is placed an analyzer and a detector. This paper discusses the characteristics of the optical current sensors, specifically for relaying applications were measurement of fault current is required. The design of the sensor, results and shift algorithms for electrical current characterization will be presented.

Flores, Jorge L.; García-Torales, Guillermo; Ortiz, Víctor H.

2007-10-01

313

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 .

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

2013-01-01

314

Lamb shift in the muonic helium ion  

SciTech Connect

The Lamb shift (2P{sub 1/2}-2S{sub 1/2}) in the muonic helium ion ({mu}-{sub 2}{sup 4}He){sup +} is calculated with the account of contributions of orders {alpha}{sup 3}, {alpha}{sup 4}, {alpha}{sup 5}, and {alpha}{sup 6}. Special attention is given to corrections of the electron vacuum polarization, the nuclear structure, and recoil effects. The obtained numerical value of the Lamb shift 1381.72 meV can be considered as a reliable estimate for the comparison with experimental data.

Martynenko, A. P. [Samara State University, 443011, Pavlov Street 1, Samara (Russian Federation)

2007-07-15

315

Lamb shift in the muonic deuterium atom  

SciTech Connect

We present an investigation of the Lamb shift (2P{sub 1/2}-2S{sub 1/2}) in the muonic deuterium ({mu}D) atom using the three-dimensional quasipotential method in quantum electrodynamics. The vacuum polarization, nuclear-structure, and recoil effects are calculated with the account of contributions of orders {alpha}{sup 3}, {alpha}{sup 4}, {alpha}{sup 5}, and {alpha}{sup 6}. The results are compared with earlier performed calculations. The obtained numerical value of the Lamb shift at 202.4139 meV can be considered a reliable estimate for comparison with forthcoming experimental data.

Krutov, A. A.; Martynenko, A. P. [Samara State University, Pavlov street 1, 443011, Samara (Russian Federation); Samara State University, Pavlov Street 1, 443011, Samara, Russia and Samara State Aerospace University named after academician S.P. Korolyov, Moskovskoye Shosse 34, 443086, Samara (Russian Federation)

2011-11-15

316

Frequency shift in the moving periodic structure  

SciTech Connect

The interaction between the electromagnetic wave and the moving periodic structure is analyzed. The main physical effect revealed by theoretical analysis is that the frequency shift of the scattered or transmitted mode is proportional to the speed and the mode order m over the period a. The frequency shift is independent of the incidence direction and the carrier frequency. The physical effect is verified by an experiment. The analysis released here is fundamental in speed measurement and may have certain significance in interdisciplinary fields.

Dong Tianlin; Xia Dan [Department of Electronics and Information, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

2008-09-15

317

Doppler frequency shift of sound apparatus  

NASA Astrophysics Data System (ADS)

A large 1-m diameter rotary table with a semicircular waveguide along its periphery is the basis of the Doppler frequency shift of sound apparatus. A ``button'' speaker is attached to the outer edge of the rotary table and a microphone pickup is positioned on the wall of the waveguide at its midpoint. At approximate speeds of 25 mph (11 m/s), the velocity measured from the frequency shift between the approaching and receding speaker compared to the velocity measured from the repeat sound pattern agree to within 1%. The microphone output is fed successively to our 10 computer stations.

Schier, Walter

2011-04-01

318

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.  

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

1998-01-01

319

Solvent Stark Effects and Spectral Shifts. II.  

National Technical Information Service (NTIS)

Solvent shifts of the energies of the lowest exp 1 L/sub a/ bands of the electronic absorption spectra of anthracene, chrysene, phenanthrene, and tetracene and of the lowest exp 1 L/sub b/ bands of the electronic absorption spectra of naphthalene, phenant...

M. Nicol J. Swain Y. Y. Shum R. Merin R. H. H. Chen

1981-01-01

320

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.

321

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

322

DIURNAL BODY TEMPERATURE CURVES IN SHIFT WORKERS  

Microsoft Academic Search

Observations on body temperature at rest of three workers inexperienced in shift work presented, when working in dayshift, the normal well-known diurnal curve, and when working in nightshift a pattern significantly different from the normal one. The throe subjects showed a striking congruence of curves. During a nightshift, period of several weeks in succession every week appeared to involve a

J. H. van LOON

1963-01-01

323

Paradigm shifts in the video game industry  

Microsoft Academic Search

Purpose – The purpose of this paper is to identify, characterize, and discuss paradigm shifts that have occurred in the video game industry with some emphasis on competition and competitiveness. Design\\/methodology\\/approach – Basically, the paper depends upon a review of the literature associated with video game development. Past history is taken from texts and academic papers dealing with the subject.

Peter Zackariasson; Timothy L. Wilson

2010-01-01

324

The shift in the therapeutic paradigm: Osseointegration  

Microsoft Academic Search

The loss of teeth is an extremely traumatic and upsetting experience. The accompanying feelings of grief and loss are compounded by the inherent inadequacies of complete dentures. It is hardly surprising that many edentulous people and their dentists have searched long and hard for a viable alternative. This article places in perspective the shift that has occurred in the therapeutic

David M. Davis

1998-01-01

325

Correlation Shifts and Real Estate Portfolio Management  

Microsoft Academic Search

Executive Summary. The success of any diversification strategy depends on the quality of the estimated corre- lation between assets. It is well known, however, that there is a tendency for the average correlation among assets to increase when the market falls and vice-versa. This suggests that correlation shifts can be modeled as a function of the market return. This is

Stephen L. Lee

326

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

327

Meal composition and shift work performance.  

PubMed

Research indicates that the ability to perform a task can be affected by the composition of the meal preceding the task. This study investigated the effect of shift workers' consumption of a medium-fat, medium-carbohydrate meal on alertness scores. Six subjects (four men, two women) aged 19 to 44 recorded food intake, sleep, and quality of sleep for two weeks, and measured their body temperature and performed cognitive tests during two night shifts at baseline and in test periods. The Stanford Sleepiness Scale (SSS) was used to quantify sleepiness, and a Paced Auditory Serial Addition Test (PASAT) was used to measure cognitive performance. In comparison with the score at baseline, when subjects had a low-fat, high-carbohydrate dietary intake (1,335 kcal/5,588 kJ, 56% carbohydrate, 28% fat), the 1.6-second PASAT score improved significantly (p=0.042) during night shifts when subjects consumed a test meal (987 kcal/4,131 kJ, 46% carbohydrate, 42% fat). No statistically significant difference in SSS was found between baseline and test periods. The reduced body temperature between 2400 hours and 0530 hours was similar for both baseline and test periods. Meal composition and size during night shifts may affect cognitive performance. PMID:15780155

Love, Heather L; Watters, Corilee A; Chang, Wei-Ching

2005-01-01

328

Helping Administrators Identify Shifts in Enrollment Patterns.  

ERIC Educational Resources Information Center

The spiraling cost of higher education has led to questions of accountability and cost effectiveness and called more attention to budgetary and financial structures. This shift in decision-making responsibilities is closely tied to recent changes in enrollment growth that has reached a static or declining stage. In view of this trend,…

Salley, Charles D.

329

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.

330

Mean shift for accurate license plate localization  

Microsoft Academic Search

This paper presents a region-based algorithm for accurate license plate localization, where mean shift is utilized to filter and segment color vehicle images into candidate regions. Three features are extracted in order to decide whether a candidate region represents a real license plate, namely, rectangularity, aspect ratio, and edge density. Then, the Mahalanobis classifier is used with respect to above

Wenjing Jia; Huaifeng Zhang; Xiangjian He; M. Piccardi

2005-01-01

331

Betatron tune shifts and Laslett image coefficients  

SciTech Connect

The complicated expressions of betatron tune shifts in terms of Laslett image coefficients are explained. The expressions of image coefficients for a centered or off-centered beam inside an elliptical or rectangular vacuum chamber are gathered. Typos in earlier literature are corrected.

K. Y. Ng

2001-07-20

332

A Tectonic Shift in Global Higher Education  

ERIC Educational Resources Information Center

|Europeans lament that their universities are lagging behind those in the United States, while Americans worry that their academic leadership is threatened by complacency. Both groups, however, are missing the tectonic shift that will transform the map of higher education worldwide--the growth of universities in the developing world. Spreading…

Daniel, John; Kanwar, Asha; Uvalic-Trumbic, Stamenka

2006-01-01

333

Majors' Shift to Natural Gas, The  

EIA Publications

The Majors' Shift to Natural Gas investigates the factors that have guided the United States' major energy producers' growth in U.S. natural gas production relative to oil production. The analysis draws heavily on financial and operating data from the Energy Information Administration's Financial Reporting System (FRS)

Bruce Bawks

2001-09-01

334

State Immunity, China and Its Shifting Position  

Microsoft Academic Search

This paper argues that China may well consider a probable shift of its position on the principle of State immunity from the absolute doctrine to the restrictive doctrine for the purpose of better accommodating the rapid growth of the private sector in China's economic structure and significantly enhancing the judicial protection of the interest of Chinese private entities actively involved

Dahai QI

2008-01-01

335

Shift mechanism for engine starting apparatus  

Microsoft Academic Search

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

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

1986-01-01

336

Josephson shift register design and layout  

NASA Astrophysics Data System (ADS)

Integrated circuit chips were designed and fabricated, based on a Josephson shift register circuit that simulated operation at 25 GHz using the SPICE program. The 6.25-sq mm chip featured a twelve-gate, four-stage shift register fabricated with Nb/AlOx/Nb Josephson junctions with a design value of 2000 A/sq cm critical current density. SUPERCOMPACT, a general program for the design of monolithic microwave integrated circuits, was used to model the effects of layout geometry on the uniformity and phase coherence of logic gate bias currents. A layout geometry for the superconductive transmission lines and thin-film bias resistors was developed. The original SPICE-designed circuit was modified as a result of these calculations. Modeling indicated that bias current variations could be limited to 3 percent for all possible logic states of the shift register, and phase coherence of the gates could be maintained to within 2 deg at 10 GHz. The fundamental soundness of the circuit design was demonstrated by the proper operation of fabricated shift registers.

Przybysz, John X.; Blaugher, R. D.; Buttyan, J.

1989-03-01

337

Shifting cultivation systems practised in Bhutan  

Microsoft Academic Search

In the highlands of Bhutan shifting cultivation remains an important land use practice, covering an area of approximately 200,000 ha. Two systems, bush fallow and grass fallow, are described and discussed. The traditional methods used in the two systems are well adapted to available resources. The systems differ in fallow vegetation, altitude range, major crops, fallow period, farming tools, clearing

W. Roder; O. Calvert; Y. Dorji

1992-01-01

338

A Phase-Shift Ultrasonic Flowmeter  

Microsoft Academic Search

An ultrasonic flowmeter using phase-shift techniques has been developed to measure phasic blood flow in animals. Lead zirconate titanate transducers are located diagonally opposed over the vessel so that 1-Mc ultrasound may be transmitted alternately upstream and downstream. The upstream and downstream transit times are measured by heterodyning the 1-Mc receiver crystal output to 10 kc, and then feeding this

W. C. Zarnstorff; C. A. Castillo; C. W. Crumpton

1962-01-01

339

Six necessary mind shifts for implementing strategy  

Microsoft Academic Search

Purpose – In the last few years the field of strategy implementation has been growing. Much of the current literature explains the “why”. This paper aims to shift the thinking from the “why” to the “how”. Leaders are now beginning to state that they understand that it is important to implement as well as design the strategy and are asking

Robin Speculand

2009-01-01

340

Rotative quadrature phase-shift keying  

NASA Astrophysics Data System (ADS)

A rotative quadrature phase-shift keying (RQPSK) modulation scheme is proposed. By rotating the QPSK signal constellation by pi/2, either clockwise or anticlockwise, during a symbol duration, the conventional QPSK scheme can be modified to transmit 3 bits per symbol to achieve both power and bandwidth efficiency.

Liu, J.; Kim, J.; Kwatra, S. C.; Stevens, G. H.

1992-06-01

341

Deindustrialization and the Shift to Services.  

ERIC Educational Resources Information Center

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

Kutscher, Ronald E.; Personick, Valerie A.

1986-01-01

342

Deindustrialization and the Shift to Services.  

ERIC Educational Resources Information Center

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

Kutscher, Ronald E.; Personick, Valerie A.

1986-01-01

343

Editorial: Counseling implications of boundary shifting, II  

Microsoft Academic Search

In writing my editorial for the first Internanonal Journal for the Advancement of Counselhng special issue devoted to counseling implications of boundary shifting during the summer of 1990, I stated that I felt as if I were viewing the world situation through a kaleidoscope and that \\

Bea Wehrly

1992-01-01

344

The shifting values of authenticity and fakes  

Microsoft Academic Search

The present article discusses the shifting values of authenticity and fakes. Using a biographical approach and the notion of things' social life it examines an Egyptianised relief which according to the author is probably the work of the 'Master of Berlin', Oxan Aslanian, and investigates the wider context in which the object was conceived. The period under consideration is from

S.-A. Naguib

345

Cultural shifts: humanities to science to computation  

Microsoft Academic Search

It is argued here that the essential phenomenon of import which C.P. Snow de- scribed in 1959 as that of two distinct non-communicating cultures { one of 'literary intellectuals' one of 'scientic intellectuals' { is better described as a shift in emphasis within the university culture from a humanities dominated one to a science dominated one. Society in general and

R. W. Oldford

346

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

347

Benchmark Bonds Interactions under Regime Shifts  

Microsoft Academic Search

AbstractIn the present paper we examine the interactions among five benchmark ten year government bonds, namely those of the USA, Germany, France, Italy and the Netherlands. Our aim is to illustrate empirically a net of interactions existing among the major bond markets of Europe and the US market taking into account shifts in the underlying stochastic processes. For this purpose,

Dimitris A. Georgoutsos; Petros M. Migiakis

2012-01-01

348

Cost Shifting: A Public Policy Debate.  

National Technical Information Service (NTIS)

Cost shifting refers to the practice of hospitals charging one group of patients more because another group of patients does not pay an appropriate share of the costs incurred to provide care. It is alleged that payment under Medicare, Medicaid, and even ...

B. W. Greenman

1984-01-01

349

Wavelength shifting and bandwidth broadening in DCG  

Microsoft Academic Search

Experimental results are described concerning the influence of processing parameters on the spectral selectivity of reflection holograms recorded in dichromated gelatin. The aim of this investigation was to produce holographic gratings with well-defined filter properties and to shift the central wavelength toward the red spectral region and to broaden their bandwidth.

Dorina Corlatan; Martin Schaefer; Gerhard Anders

1991-01-01

350

Early dynamics of the semantic priming shift  

PubMed Central

Semantic processing of sequences of words requires the cognitive system to keep several word meanings simultaneously activated in working memory with limited capacity. The real- time updating of the sequence of word meanings relies on dynamic changes in the associates to the words that are activated. Protocols involving two sequential primes report a semantic priming shift from larger priming of associates to the first prime to larger priming of associates to the second prime, in a range of long SOAs (stimulus-onset asynchronies) between the second prime and the target. However, the possibility for an early semantic priming shift is still to be tested, and its dynamics as a function of association strength remain unknown. Three multiple priming experiments are proposed that cross-manipulate association strength between each of two successive primes and a target, for different values of short SOAs and prime durations. Results show an early priming shift ranging from priming of associates to the first prime only to priming of strong associates to the first prime and all of the associates to the second prime. We investigated the neural basis of the early priming shift by using a network model of spike frequency adaptive cortical neurons (e.g., Deco & Rolls, 2005), able to code different association strengths between the primes and the target. The cortical network model provides a description of the early dynamics of the priming shift in terms of pro-active and retro-active interferences within populations of excitatory neurons regulated by fast and unselective inhibitory feedback.

Lavigne, Frederic; Chanquoy, Lucile; Dumercy, Laurent; Vitu, Francoise

2013-01-01

351

Sleep Loss and Fatigue in Shift Work and Shift Work Disorder  

PubMed Central

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

Akerstedt, Torbjorn; Wright, Kenneth P.

2010-01-01

352

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

PubMed

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

Rose, Katrin; Cottenier, Stefaan

2012-07-11

353

Two-stage coal liquefaction without gas-phase hydrogen  

DOEpatents

A process is provided for the production of a hydrogen-donor solvent useful in the liquefaction of coal, wherein the water-gas shift reaction is used to produce hydrogen while simultaneously hydrogenating a donor solvent. A process for the liquefaction of coal using said solvent is also provided. The process enables avoiding the use of a separate water-gas shift reactor as well as high pressure equipment for liquefaction. 3 tabs.

Stephens, H.P.

1986-06-05

354

Neural origin of cognitive shifting in young children  

Microsoft Academic Search

Cognitive shifting is the ability to adapt to changes in the environment. Extensive research has revealed that the prefrontal cortex plays an important role in cognitive shifting. Adult neuroimaging studies have shown that the inferior prefrontal cortex is activated during cognitive shifting tasks. Developmental studies have shown that cognitive shifting changes significantly during preschool years. It is known that 3-year-old

Yusuke Moriguchi; Kazuo Hiraki

2009-01-01

355

Of vowel shifts great, small, long and short  

Microsoft Academic Search

This paper argues that the development of Early Modern English short vowels can be accounted for in terms of a chain shift which essentially lowered and centralised them. The shift, which we propose to call Short Vowel Shift, is as coherent and systematic as the comparably well established Great Vowel Shift. At the same time it is argued that both

Herbert Schendl; Nikolaus Ritt

2002-01-01

356

Synthetic routes to fluorescent dyes exhibiting large Stokes shifts.  

PubMed

Derivatives of isomeric 2-(hydroxytolyl)-4,6-dimethylamino-1,3,5-triazines have been synthesized in high yields in a controlled manner using a multistep reaction sequence. Iodination of either 2-(1'-hydroxy-6'-methylphen-2'-yl)- or 2-(1'-hydroxy-4'-methylphen-2'-yl)-4,6-dimethylamino-1,3,5-triazine with ICl provides species differing in the positioning of the iodo group relative to the hydroxyl which readily undergo Suzuki, Sonogashira, and Heck reactions under Pd(0) catalysis. Thus, thienyl, bisthienyl, and 3,4-ethylenedioxythienyl groups have been directly grafted, while unsubstituted polycyclic aromatics such as pyrene and perylene have been linked via alkyne bridges, as have ethynyldifluoroborondipyrromethane (BODIPY) dyes prepared in situ. The presence of a hydrogen bond in the ground state involving the hydroxyl substituent has been established by proton NMR and several X-ray structure determinations. All of the new dyes with a simple substituent (phenyl, thienyl) exhibited a pronounced green fluorescence resulting from an intramolecular proton transfer in the excited state (ESIPT) which produces a large Stokes shift (>10,000 cm(-1)). With other dyes, the fluorescence of the keto form responsible for the ESIPT process could be used as the input energy in efficient intramolecular energy transfer processes. Replacing perylene with pyrene allowed reversal of the direction of energy transfer from the polyaromatic module to the keto form. PMID:22834858

Rihn, Sandra; Retailleau, Pascal; De Nicola, Antoinette; Ulrich, Gilles; Ziessel, Raymond

2012-07-30

357

Phase-shifting Zernike interferometer wavefront sensor  

NASA Astrophysics Data System (ADS)

The canonical Zernike phase-contrast technique transforms a phase object in one plane into an intensity object in the conjugate plane. This is done by applying a static ?/2 phase shift to the central core (~ ?/D) of the PSF which is intermediate between the input and output planes. Here we present a new architecture for this sensor. First, the optical system is simple and all reflective. Second, the phase shift in the central core of the PSF is dynamic and or arbitrary size. This common-path, all-reflective design makes it minimally sensitive to vibration, polarization and wavelength. We review the theory of operation, describe the optical system, summarize numerical simulations and sensitivities and review results from a laboratory demonstration of this novel instrument.

Wallace, J. Kent; Rao, Shanti; Jensen-Clem, Rebecca M.; Serabyn, Gene

2011-09-01

358

Protein structure determination from NMR chemical shifts  

PubMed Central

NMR spectroscopy plays a major role in the determination of the structures and dynamics of proteins and other biological macromolecules. Chemical shifts are the most readily and accurately measurable NMR parameters, and they reflect with great specificity the conformations of native and nonnative states of proteins. We show, using 11 examples of proteins representative of the major structural classes and containing up to 123 residues, that it is possible to use chemical shifts as structural restraints in combination with a conventional molecular mechanics force field to determine the conformations of proteins at a resolution of 2 ? or better. This strategy should be widely applicable and, subject to further development, will enable quantitative structural analysis to be carried out to address a range of complex biological problems not accessible to current structural techniques.

Cavalli, Andrea; Salvatella, Xavier; Dobson, Christopher M.; Vendruscolo, Michele

2007-01-01

359

Evolutionary shift dynamics on a cycle  

PubMed Central

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.

Allen, Benjamin; Nowak, Martin A.

2012-01-01

360

On the chemical shifts of agostic protons.  

PubMed

Agostic hydrogen atoms in planar d(8) transition metal complexes display a remarkable wide range of chemical shifts from +5 to -10 ppm in the proton NMR spectra. It is therefore surprising that a simple recipe can be elaborated to predict the influence of the local electronic structure of the metal atom on the shielding of the coordinating protons: In cases where the agostic hydrogen atom is pointing to a local Lewis acidic center at the metal the (1)H NMR signal is shifted upfield relative to the scenario where the proton is opposing a local charge concentration at the metal. To trace the physical origin of this empirical relationship, a systematic study has been performed to understand how the (i) topology of the electron density and (ii) orientation of the magnetic field vector, B0, control the paratropic or diatropic characteristics of the induced current density at the metal atom and thus the shielding or deshielding of the agostic protons. PMID:23600565

Barquera-Lozada, José Enrique; Obenhuber, Andreas; Hauf, Christoph; Scherer, Wolfgang

2013-04-19

361

Magnetic susceptibility shift selected imaging: MESSI.  

PubMed

Paramagnetic compounds are often used to enhance contrast in MRI by virtue of their increase in the kinetics of the relaxation of water 1H magnetization. Here, we demonstrate a method for contrast enhancement which is based on the resonance frequency shifts caused by the bulk magnetic susceptibility (BMS) effects of such compounds. This involves the frequency selective excitation in the absence of field gradients, during the imaging sequence, of a portion of the water 1H resonance which is rendered inhomogeneous by BMS shifts only. The image which results is of that portion of the sample which gives rise to the portion of the spectrum excited. A phantom sample which simulates some aspects of tissue, particularly blood vessels with different orientations in the magnetic field, was prepared. The contrast enhancement exhibited here avoids some of the distortions attendant to the use of paramagnetic reagents. This new approach can, in principle, utilize the natural BMS differences found in all tissue. PMID:2255239

Xu, Y; Balschi, J A; Springer, C S

1990-10-01

362

Set shifting deficit in anorexia nervosa.  

PubMed

Anorexia nervosa (AN) is a severe mental illness characterized in part by rigid thinking and ritualized behaviors involving eating and weight. Cognitive rigidity may play a role in the perpetuation of symptoms, and may provide information as to important brain-based abnormalities. Neuropsychological studies of patients with AN have shown cognitive dysfunction, but few have focused on cognitive flexibility. This study assessed set shifting in patients with AN, as a measure of cognitive flexibility. In this study, 15 patients with AN were compared with 11 healthy controls using a neuropsychological battery including the Wisconsin Card Sort Test (WCST). While patients with AN did not differ from controls on 5 measures of neuropsychological function, they made significantly more perseverative errors on the WCST, indicating a problem in set shifting. This finding suggests that patients with AN have a specific neurocognitive abnormality that may play a role in the development and persistence of this disorder. PMID:16903136

Steinglass, Joanna E; Walsh, B Timothy; Stern, Yaakov

2006-05-01

363

The shifting sands of a professional identity.  

PubMed

I decided while an undergraduate that I wanted to be a psychologist. Beyond that, I'm still not sure what I'll do when I grow up. This brief autobiography maps the shifting sands of my professional identity: from psychotherapist to developmental psychopathologist and then to primary concerns with education and training, from psychologist to academic administrator and then back again, to forensic psychologist and on to whatever may come next. Through all of these shifts in focus, however, there has been one recurring theme--the appeal of being an assessment psychologist. The events that kept bringing me back to assessment, whatever else my focus at the time, are recorded in the story that follows. PMID:16171409

Weiner, Irving B

2005-10-01

364

Confocal simultaneous phase-shifting interferometry  

SciTech Connect

In order to implement the ultraprecise measurement with large range and long working distance in confocal microscopy, confocal simultaneous phase-shifting interferometry (C-SPSI) has been presented. Four channel interference signals, with {pi}/2 phase shift between each other, are detected simultaneously in C-SPSI. The actual surface height is then calculated by combining the optical sectioning with the phase unwrapping in the main cycle of the interference phase response, and the main cycle is determined using the bipolar property of differential confocal microscopy. Experimental results showed that 1 nm of axial depth resolution was achieved for either low- or high-NA objective lenses. The reflectivity disturbance resistibility of C-SPSI was demonstrated by imaging a typical microcircuit specimen. C-SPSI breaks through the restriction of low NA on the axial depth resolution of confocal microscopy effectively.

Zhao Chenguang; Tan Jiubin; Tang Jianbo; Liu Tao; Liu Jian

2011-02-10

365

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

366

CHARGE COUPLED 8BIT SHIFT REGISTER  

Microsoft Academic Search

An 8-bit shift register has been developed based on the charge-coupled device concept. The device configuration is essentially that of a linear array of 26 closely spaced MOS capacitors with a p-n junction at either end. A packet of charge is inserted into the first capacitor from one of the p-n junctions and then transferred down the array in a

M. F. Tompsett; G. F. Amelio; G. E. Smith

1970-01-01

367

Proton chemical shifts and ?-electron densities  

Microsoft Academic Search

Theoretical calculations were carried out for the proton chemical shifts and 7r-electron densities in methyl benzoate and dimethyl terephthalate. The parameters of the electronic structure were determined by the LCAO MO approximation. It was found that the magnitude of the proton chemicalshift was greatly influenced by the ~r:electron density at the neighboring carbon atom. Conclusinns were drawn about the conformations

R. M. Aminova; I. D. Morozova

1968-01-01

368

Recognition of freehand sketches using mean shift  

Microsoft Academic Search

Freehand sketching is a natural and powerful means of interpersonal communication. But to date, it still cannot be supported effectively by human-computer interface. In this paper, we propose a robust method for sketch recognition. It uses mean shift, a nonparametric technique which can delineate arbitrarily shaped clusters, as a pre-process to analyze the direction-curvature joint space and suppress the severe

Bo Yu

2003-01-01

369

DNA structures from phosphate chemical shifts  

Microsoft Academic Search

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

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

2010-01-01

370

A High Resolution Phase Shifting Interferometer  

Microsoft Academic Search

Configuration, operation, and performance details of a high resolution phase shifting Twyman-Green interferometer are presented. The instrument was used for density relaxation experiments of very compressible liquid-vapor critical fluids.(A companion talk in the Nonequilibrium Phenomena session under Complex Fluids presents density equilibration work.) A sample assembly contained the cell, beam splitter, phase shifter, and mirrors inside a 6 cm diameter

Michael Bayda; Christoph Bartscher; Allen Wilkinson

1997-01-01

371

Polynomial Shift States of a Chaotic Map  

NASA Astrophysics Data System (ADS)

We present a piecewise- linear map of the unit interval in which the resolvent of the Frobenius- Perron operator, considered in a polynomial basis, has an essen-tial singularity at the origin. Associated with the essential singularity are polynomial shift states, which are obtained from creation and annihilation operators in non- self- dual function spaces. Correlation functions of general polynomial observables have decay components that vanish in a finite time.

Driebe, Dean J.; Ordóñez, Gonzalo E.

1997-12-01

372

??????????:2004???? Olympic Key Visuals and Power Shifts  

Microsoft Academic Search

During the classic Olympic games, no wars were allowed - and god-like heroes replaced the otherwise powerful figures and figurations. In pre-mass mediated societies, this power presentation shift was locally limited. In the era of global media events, it can reach national and trans-cultural scopes. These scopes do not only refer to instant real time communication, but also to communication

Peter LUDES

373

Lamb-shift measurement in hydrogenic phosphorus  

SciTech Connect

The final result of a 2[ital s] [sup 2][ital S][sub 1/2--]2[ital p] [sup 2][ital P][sub 1/2] Lamb-shift measurement by the laser resonance method in hydrogenic phosphorus is reported. Metastable 2[ital s] [sup 2][ital S][sub 1/2] ions were prepared using a [beta][approx]0.08 velocity beam of [sup 31]P[sup 14+] ions obtained from the MP tandem accelerator at the Centre de Recherches Nucleaires in Strasbourg. From the metastable state the transition to the 2[ital p] [sup 2][ital P][sub 3/2] state was induced with a high-power dye laser leading to a measured transition energy of [Delta][ital E]=2.231 33(12) eV. Subtracting the well-known fine-structure splitting [Delta][ital E][sub FS]=2.314 82(2) eV, the Lamb shift is deduced to be [ital E][sub expt]([ital LS])=20 188(29) GHz. This result is compared with the theoretical value [ital E][sub theor]([ital LS])=20 254(10) GHz and with other experimental results for the Lamb shift in the region [ital Z][le]18. Finally, the utility of the Lamb-shift measurements in testing the [ital G]([ital Z][alpha]) function of the self-energy, which includes only terms in ([ital Z][alpha])[sup [ital n

Pross, H. (Bank Verlag GmbH, 5000 Koeln (Germany)); Budelsky, D.; Kremer, L.; Platte, D.; von Brentano, P. (Institut fuer Kernphysik, Universitaet zu Koeln, 5000 Koeln 41 (Germany)); Gassen, J. (Crone GmbH, 4100 Duisburg (Germany)); Mueller, D. (Gesellschaft fuer Schwerionenforschung mbH, 6100 Darmstadt (Germany)); Scheuer, F. (Target Systemelectronic GmbH, 5650 Solingen (Germany)); Pape, A.; Sens, J.C. (Centre de Recherches Nucleaires and Universite Louis Pasteur, 67037 Strasbourg Cedex (France))

1993-09-01

374

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

375

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

376

Continuous chemical reaction chromatography  

SciTech Connect

The past three years have been devoted to investigating simulated countercurrent chomatographic moving bed separators (SCMCS) and simulated countercurrent moving bed reactors (SCMCR). These are novel separators and reactors used for separation, or for carrying out a chemical reaction and separation continuously and simultaneously in fixed bed. In the SCMCR and the SCMCS the process aspects of a countercurrent moving bed, in which a stream of solids flows countercurrent to an inert fluid and past stationary reactant inlet, is simulated by successively switching feed and product take-off streams through a series of inlets located at fixed intervals along a fixed bed or between a series of packed columns. The flow of solids past a fixed feed point, characteristic of countercurrent moving beds, is replaced by motion of the feed past a fixed packed bed. Feed enters a particular column for a fixed length of time, and then is switched to the next column. Product streams are also advanced simultaneously. When the feed point has progressed to the end it is returned to the starting position and the process repeated. The shifting of the feed and the product positions in the direction of fluid flow thus simulates the movement of solids in the opposite direction. The requisite motion between the feed and the bed, which is continuous for true countercurrency, is replaced by periodic, discrete steps in simulated countercurrency. The continuous, steady state operation characteristic of true countercurrency is replaced by periodic transients at each switch of the feed.

Aris, R.; Carr, R.W.

1992-01-01

377

Leaf morphology shift linked to climate change  

PubMed Central

Climate change is driving adaptive shifts within species, but research on plants has been focused on phenology. Leaf morphology has demonstrated links with climate and varies within species along climate gradients. We predicted that, given within-species variation along a climate gradient, a morphological shift should have occurred over time due to climate change. We tested this prediction, taking advantage of latitudinal and altitudinal variations within the Adelaide Geosyncline region, South Australia, historical herbarium specimens (n = 255) and field sampling (n = 274). Leaf width in the study taxon, Dodonaea viscosa subsp. angustissima, was negatively correlated with latitude regionally, and leaf area was negatively correlated with altitude locally. Analysis of herbarium specimens revealed a 2 mm decrease in leaf width (total range 1–9 mm) over 127 years across the region. The results are consistent with a morphological response to contemporary climate change. We conclude that leaf width is linked to maximum temperature regionally (latitude gradient) and leaf area to minimum temperature locally (altitude gradient). These data indicate a morphological shift consistent with a direct response to climate change and could inform provenance selection for restoration with further investigation of the genetic basis and adaptive significance of observed variation.

Guerin, Greg R.; Wen, Haixia; Lowe, Andrew J.

2012-01-01

378

Experience with the shift technical advisor position  

SciTech Connect

The provision of engineering expertise on shift at commercial nuclear power plants has mainly taken the form of the Shift Technical Advisor (STA). This person, acting in a capacity that is part engineer and part operator, is expected to advise the operations crew in the event of an emergency and review plant operating experience during normal circumstances. The position was mandated by the Nuclear Regulatory Commission following the incident at Three Mile Island. This report expands on a growing body of knowledge regarding the effectiveness of the STA. The new data presented here come from interviews with plant personnel and utility officials from nine sites. Researchers from the Pacific Northwest Laboratory (PNL) interviewed plant personnel, including the STA and immediate management, the shift supervisor and management, the training department, and ancillary staff, all of whom affect the intended performance of the STA. The conclusions of the report are that the design of the STA position results in limited contribution during emergencies; more comprehensive ways should be sought to provide the variety and specificity of engineering expertise needed during such times.

Melber, B.D.; Olson, J.; Schreiber, R.E.; Winges, L.

1984-03-01

379

The shifting demographic landscape of influenza.  

PubMed

Background: As Pandemic (H1N1) 2009 influenza spreads around the globe, it strikes school-age children more often than adults. Although there is some evidence of pre-existing immunity among older adults, this alone may not explain the significant gap in age-specific infection rates. Methods & Findings: Based on a retrospective analysis of pandemic strains of influenza from the last century, we show that school-age children typically experience the highest attack rates in primarily naive populations, with the burden shifting to adults during the subsequent season. Using a parsimonious network-based mathematical model which incorporates the changing distribution of contacts in the susceptible population, we demonstrate that new pandemic strains of influenza are expected to shift the epidemiological landscape in exactly this way. Conclusions: Our results provide a simple demographic explanation for the age bias observed for H1N1/09 attack rates, and a prediction that this bias will shift in coming months. These results also have significant implications for the allocation of public health resources including vaccine distribution policies. PMID:20029616

Bansal, Shweta; Pourbohloul, Babak; Hupert, Nathaniel; Grenfell, Bryan; Meyers, Lauren Ancel

2009-10-01

380

Vibration errors in phase-shifting interferometer  

NASA Astrophysics Data System (ADS)

Unexpected mechanical vibrations can significantly degrade the otherwise high accuracy of phase-shifting interferometer (PSI). Because the data acquisition takes place over time, sensitivity to vibration is as a function of the frequency, the phase, the amplitude of vibrations, the smoothness of test surface and the slope coefficient of reference plane. A complete, nonlinear, continuing mathematical model of PSI with well defined longitudinal and transverse vibrations is presented. The approach to quantifying vibration is using the discrete sum formula instead of the continuing integral model. Computer simulations are performed over a range of vibration frequencies and amplitudes for 4,7,11 and 15 frames phase-shift algorithms. Numerical simulation results demonstrate the methods to increase the accuracy of PSI is to choose more phase steps and higher speed CCD camera and PSI with small slope coefficient of reference surface and good smooth test surface has low sensitivity to transverse vibration. Finally programs basing on the phase-shifting interference theory are given to imitate the process of obtaining interferogram with vibrations. After intensity signal is processed through PSI algorithm and phase unwrapping algorithm, the sensitivity of PSI to vibration is achieved and described by the difference of the computer phase and test phase. The results of numerical simulation are supported by several examples on dummy experimental platform.

Wei, Hao-Ming; Xing, Ting-Wen

2009-11-01

381

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.

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

2009-01-01

382

Visual sensitivity shifts with perceived eye position.  

PubMed

Spatial attention can be defined as the selection of a location for privileged stimulus processing. Most oculomotor structures, such as the superior colliculus or the FEFs, play an additional role in visuospatial attention. Indeed, electrical stimulation of these structures can cause changes in visual sensitivity that are location specific. We have proposed that the recently discovered ocular proprioceptive area in the human postcentral gyrus (S1(EYE)) may have a similar function. This suggestion was based on the observation that a reduction of excitability in this area with TMS causes not only a shift in perceived eye position but also lateralized changes in visual sensitivity. Here we investigated whether these shifts in perceived gaze position and visual sensitivity are spatially congruent. After continuous theta burst stimulation over S1(EYE), participants underestimated own eye rotation, so that saccades from a lateral eye rotation undershoot a central sound (Experiment 1). They discriminated letters faster if they were presented nearer the orbit midline (Experiment 2) and spent less time looking at locations nearer the orbit midline when searching for a nonexistent target in a letter array (Experiment 3). This suggests that visual sensitivity increased nearer the orbit midline, in the same direction as the shift in perceived eye position. This spatial congruence argues for a functional coupling between the cortical eye position signal in the somatosensory cortex and visuospatial attention. PMID:23469887

Odoj, Bartholomäus; Balslev, Daniela

2013-03-07

383

New color-shifting security devices  

NASA Astrophysics Data System (ADS)

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

Moia, Franco

2004-06-01

384

Age differences in strategy shift: Retrieval avoidance or general shift reluctance?  

PubMed

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 attending to only that part of the stimulus. We adapted the AVT to include conditions that 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. (PsycINFO Database Record (c) 2013 APA, all rights reserved). PMID:23088195

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

2012-10-22

385

Calculation of 13C Chemical Shifts in RNA Nucleosides: Structure-13C Chemical Shift Relationships  

NASA Astrophysics Data System (ADS)

Isotropic 13C chemical shifts of the ribose sugar in model RNA nucleosides are calculated using SCF and DFT-GIAO ab initio methods for different combinations of ribose sugar pucker, exocyclic torsion angle, and glycosidic torsion angle. Idealized conformations were obtained using structures that were fully optimized by ab initio DFT methods starting with averaged parameters from a collection of crystallographic data. Solid-state coordinates of accurate crystal or neutron diffraction structures were also examined directly without optimization. The resulting 13C chemical shifts for the two sets of calculations are then compared. The GIAO-DFT method overestimates the shifts by an average of 5 ppm while the GIAO-SCF underestimates the shifts by the same amount. However, in the majority of cases the errors appear to be systematic, as the slope of a plot of calculated vs experimental shifts is very close to unity, with minimal scatter. The values of the 13C NMR shifts of the ribose sugar are therefore sufficiently precise to allow for statistical separation of sugar puckering modes and exocyclic torsion angle conformers, based on the canonical equation model formulated in a previous paper.

Rossi, Paolo; Harbison, Gerard S.

2001-07-01

386

Solvent Effects on Oxygen-17 Chemical Shifts in Methyl Formate: Linear Solvation Shift Relationships  

NASA Astrophysics Data System (ADS)

A multiple linear regression analysis has been carried out using the Kamlet-Abboud-Taft solvatochromic parameters in order to quantify the solvent effects on the 17O chemical shifts of methyl formate (MF). The influence of the solvents upon the carbonyl oxygen chemical shifts is smaller for MF than for N-methylformamide (NMF). The influence (in parts per million) of the solvent polarity-polarizability reduces from -21.9?* in amides to -9.6?* in MF. The influence of the solvent hydrogen-bond-donor acidities reduces from -42.0? in formamides to -16.9? in MF. The solvent effects upon the dicoordinated oxygen chemical shifts of MF are smaller in magnitude and opposite in direction, i.e., 4.8?* and 2.6?, than those for the carbonyl oxygen. 17O hydration shifts have been calculated for the NMF + (H2O)6 and MF + (H2O)5 complexes by the ab initio GIAO method at the 6-311 + G** level. The hydration shifts calculated for the carbonyl oxygens of NMF and MF and for the dicoordinated oxygen of MF, -102.4, -64.7, and 17.6 ppm, respectively, show the same trend as the corresponding empirical hydration shifts, -101.7, -42.0, and 14.2 ppm.

de Kowalewski, Dora G.; Kowalewski, Valdemar J.; Contreras, Ruben H.; Díez, Ernesto; Casanueva, Jorge; San Fabián, Jesús; Esteban, Angel L.; Galache, Maria P.

2001-01-01

387

No indication of f{sub 0}(1370) in {pi}{pi} phase shift analyses  

SciTech Connect

The scalar meson f{sub 0}(1370) - indicated in particular in the low energy pp-bar{yields}3 body reactions - is a crucial element in certain schemes of the scalar meson spectroscopy including glueballs. The most definitive results can be obtained from elastic and inelastic {pi}{pi} phase shift analyses using the constraints from unitarity where the discrete ambiguities can be identified and resolved. We reconsider the phase shift analyses for {pi}{sup +{pi}-{yields}{pi}+{pi}-}, {pi}{sup 0{pi}0}, KK-bar, {eta}{eta}. While a clear resonance signal for f{sub 0}(1500) in the resp. Argand diagrams is seen in all channels above a large 'background' from f{sub 0}(600) there is no clear signal of a second resonance 'f{sub 0}(1370)' in this mass range in any reaction, at the level of {approx}10% branching ratio into {pi}{pi}.

Ochs, Wolfgang [Max-Planck-Institut fuer Physik, D-80805 Munich, Foehringer Ring 6 (Germany)

2010-08-05

388

Hydricity-promoted [1,5]-H shifts in acetalic ketenimines and carbodiimides.  

PubMed

2-monosubstituted 1,3-dioxolanes and dithiolanes act as hydride-releasing fragments, transferring intramolecularly their acetalic H atom to the central carbon of ketenimine functions. The presumed products of these migrations, o-quinomethanimines, undergo in situ 6pi-electrocyclization. A computational study supports this mechanism and the hydride-shift character of the first step. Carbodiimides were also suitable substrates, although less reactive. [reaction: see text]. PMID:17107093

Alajarín, Mateo; Bonillo, Baltasar; Ortín, María-Mar; Sánchez-Andrada, Pilar; Vidal, Angel

2006-11-23

389

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

390

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.

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

2011-01-01

391

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

392

Space sickness and fluid shifts: a hypothesis.  

PubMed

In a sample of 64 first-time Space Shuttle crew members, 9 preflight variables related to fluid, electrolyte, and cardiovascular status were previously found to be significantly related to space sickness. The nine variables are serum uric acid, red cell count, environmental temperature at the launch site, serum phosphate, urine osmolality, serum thyroxine, sitting systolic blood pressure, calculated blood volume, and serum chloride. Using discriminant analysis, these preflight variables were used to correctly classify the 64 astronauts according to their space sickness incidence (NOTSICK or SICK) with 80% success, using two methods of pseudo-crossvalidation. Symptoms of motion sickness may be induced on Earth, either with a sufficiently high level of vestibular stimulation or with less vestibular stimulation after reducing the threshold for motion sickness induction. Some of the nine predictor variables support a fluid shift hypothesis of space sickness etiology by which central volume expansion in weightlessness may lower the threshold required for novel vestibular stimulation to cause space sickness. According to this hypothesis, some astronauts suffer a greater central volume expansion than do others, causing them to have greater physiologic responses to fluid shifts, which, in turn, proportionally reduces their threshold for induction of space sickness. The hypothesis is supported by preflight and postflight echocardiographic comparisons of heart volumes in 19 shuttle astronauts. The postflight left ventricular diastolic volume index was decreased by 34 +/- 3% in the astronauts with MODERATE or SEVERE space sickness, but only 9 +/- 5% (P < .05) in the NONE or MILD group, indicating that an exaggerated physiologic adaptation to fluid shifts is associated with space sickness. PMID:8083397

Simanonok, K E; Charles, J B

1994-06-01

393

Responsibility for retirement planning shifts to employees.  

PubMed

In recent years, organizations have shifted away from offering their employees defined benefit plans that promise specified income streams to employees when they retire. Instead, they are offering employees defined contribution plans, which rely on investment performance, as directed by plan participants, to generate sufficient retirement income. Healthcare financial managers who work in organizations that offer retirement plans for their employees find themselves increasingly prevailed upon to play the role of instructor to plan participants. While some financial managers may not relish the role, the more successful financial managers are at helping plan participants achieve their retirement income goals, the better the chance of healthcare organizations avoiding future liability problems. PMID:10146045

Van Gelder, N

1994-08-01

394

Approaching a state shift in Earth's biosphere.  

PubMed

Localized ecological systems are known to shift abruptly and irreversibly from one state to another when they are forced across critical thresholds. Here we review evidence that the global ecosystem as a whole can react in the same way and is approaching a planetary-scale critical transition as a result of human influence. The plausibility of a planetary-scale 'tipping point' highlights the need to improve biological forecasting by detecting early warning signs of critical transitions on global as well as local scales, and by detecting feedbacks that promote such transitions. It is also necessary to address root causes of how humans are forcing biological changes. PMID:22678279

Barnosky, Anthony D; Hadly, Elizabeth A; Bascompte, Jordi; Berlow, Eric L; Brown, James H; Fortelius, Mikael; Getz, Wayne M; Harte, John; Hastings, Alan; Marquet, Pablo A; Martinez, Neo D; Mooers, Arne; Roopnarine, Peter; Vermeij, Geerat; Williams, John W; Gillespie, Rosemary; Kitzes, Justin; Marshall, Charles; Matzke, Nicholas; Mindell, David P; Revilla, Eloy; Smith, Adam B

2012-06-06

395

Higher-order phase shift reconstruction approach  

SciTech Connect

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.

Cong Wenxiang; Wang Ge [Biomedical Imaging Division, School of Biomedical Engineering and Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 (United States)

2010-10-15

396

Oxyhemoglobin saturation measurements by green spectral shift  

NASA Astrophysics Data System (ADS)

From an analysis of new hemoglobin solution transmission spectra at various oxygen saturations (SO2), path lengths, and pH, we find the determination of SO2 by using the classical oximetry technique to be poorly calibrated. We used this data set to develop a proposed method for SO2 determination based on the spectral shift of the hemoglobin transmission minimum between 475 and 510 nm. The method does not require accurate knowledge of hemoglobin extinction coefficients and is linear in relation to SO2 despite changes in path length, pH, or hemoglobin concentration.

Denninghoff, Kurt R.; Chipman, Russell A.; Hillman, Lloyd W.

2006-04-01

397

Space charge effects: tune shifts and resonances  

SciTech Connect

The effects of space charge and beam-beam interactions on single particle motion in the transverse degree of freedom are considered. The space charge force and the resulting incoherent tune shift are described, and examples are given from the AGS and CERN's PSB. Equations of motion are given for resonances in the presence of the space charge force, and particle behavior is examined under resonance and space charge conditions. Resonance phase space structure is described with and without space charge. Uniform and bunched beams are compared. Beam-beam forces and resonances and beam-beam detuning are described. 18 refs., 15 figs. (LEW)

Weng, W.T.

1986-08-01

398

Neutrino Oscillation Phase Shift from Quantum Gravity  

NASA Astrophysics Data System (ADS)

The phase shift of neutrino oscillation could be discussed in the frame work of quantum gravity. Quantum gravity (Planck scale effects) leads to an effective SU(2) L × U(1) invariant dimension-5 Lagrangian involving, neutrino and Higgs fields. On symmetry breaking, this operator gives rise to correction to the neutrino masses and mixing. We compute the neutrino oscillation phase due to Planck scale effects. The gravitational interaction ( M X = M pl ) demands that the element of this perturbation matrix should be independent of flavor indices. In this paper, we study the quantum gravity effects on neutrino oscillation phases, namely modified dispersion relation for neutrino oscillation phases.

Koranga, Bipin Singh

2012-12-01

399

Spatially Shifted Beam Approach to Subwavelength Focusing  

NASA Astrophysics Data System (ADS)

Although negative-refractive-index metamaterials have successfully achieved subwavelength focusing, image resolution is limited by the presence of losses. In this Letter, a metal transmission screen with subwavelength spaced slots is proposed that focuses the near-field beyond the diffraction limit and, furthermore, is easily scaled from microwave frequencies to the optical regime. An analytical model based on the superposition of shifted-beam patterns is developed that agrees very well with full-wave simulations and is corroborated by experimental results at microwave frequencies.

Markley, Loïc; Wong, Alex M. H.; Wang, Yan; Eleftheriades, George V.

2008-09-01

400

A limit theorem for shifted Schur measures  

Microsoft Academic Search

To each partition $\\\\lambda=(\\\\lambda_1,\\\\lambda_2,\\\\ldots)$ with\\u000adistinct parts we assign the probability $Q_\\\\lambda(x)\\u000aP_\\\\lambda(y)\\/Z$, where $Q_\\\\lambda$ and $P_\\\\lambda$ are the Schur\\u000a$Q$-functions and $Z$ is a normalization constant. This measure,\\u000awhich we call the shifted Schur measure, is analogous to the\\u000amuch-studied Schur measure. For the specialization of the first\\u000a$m$ coordinates of $x$ and the first $n$ coordinates of $y$

Craig A. Tracy; Harold Widom

401

Reducing gain shifts in photomultiplier tubes  

DOEpatents

A means is provided for reducing gain shifts in multiplier tubes due to varying event count rates. It includes means for limiting the number of cascaded, active dynodes of the multiplier tube to a predetermined number with the last of predetermined number of dynodes being the output terminal of the tube. This output is applied to an amplifier to make up for the gain sacrificed by not totally utilizing all available active stages of the tube. Further reduction is obtained by illuminating the predetermined number of dynodes with a light source of such intensity that noise appearing at the output dynode associated with the illumination is negligible.

Cohn, Charles E. (Clarendon Hills, IL)

1976-01-01

402

Dual payoff band control of reaction time  

Microsoft Academic Search

The location of a S’s simple reaction time (RT) distribution can be controlled by differential reinforcement of RTs that fall\\u000a within specified temporal limits called a payoff band. Both humans and monkeys can gradually shift the location of a single\\u000a RT distribution over hundreds of milliseconds in accord with changing payoff band requirements. This study establishes that\\u000a trained human Ss

Carol A. Saslow

1974-01-01

403

Why are bird migration dates shifting? A review of weather and climate effects on avian migratory phenology  

Microsoft Academic Search

Many studies have reported statistically significant associations between bird migratory phenology and climatic variables, and, consequently, it is mostly accepted that recent shifts in migra- tion dates are a reaction to present climate change. Impacts of weather and climate on departure date, progression and stopover frequency and duration have been reviewed in order to explain the current knowledge of climatic

Oscar Gordo

2007-01-01

404

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

405

SHIFT: Server for hidden stops analysis in frame-shifted translation  

PubMed Central

Background Frameshift is one of the three classes of recoding. Frame-shifts lead to waste of energy, resources and activity of the biosynthetic machinery. In addition, some peptides synthesized after frame-shifts are probably cytotoxic which serve as plausible cause for innumerable number of diseases and disorders such as muscular dystrophies, lysosomal storage disorders, and cancer. Hidden stop codons occur naturally in coding sequences among all organisms. These codons are associated with the early termination of translation for incorrect reading frame selection and help to reduce the metabolic cost related to the frameshift events. Researchers have identified several consequences of hidden stop codons and their association with myriad disorders. However the wealth of information available is speckled and not effortlessly acquiescent to data-mining. To reduce this gap, this work describes an algorithmic web based tool to study hidden stops in frameshifted translation for all the lineages through respective genetic code systems. Findings This paper describes SHIFT, an algorithmic web application tool that provides a user-friendly interface for identifying and analyzing hidden stops in frameshifted translation of genomic sequences for all available genetic code systems. We have calculated the correlation between codon usage frequencies and the plausible contribution of codons towards hidden stops in an off-frame context. Markovian chains of various order have been used to model hidden stops in frameshifted peptides and their evolutionary association with naturally occurring hidden stops. In order to obtain reliable and persuasive estimates for the naturally occurring and predicted hidden stops statistical measures have been implemented. Conclusions This paper presented SHIFT, an algorithmic tool that allows user-friendly exploration, analysis, and visualization of hidden stop codons in frameshifted translations. It is expected that this web based tool would serve as a useful complement for analyzing hidden stop codons in all available genetic code systems. SHIFT is freely available for academic and research purpose at http://www.nuccore.org/shift/.

2013-01-01

406

Transmission phase shifts of Kondo impurities  

NASA Astrophysics Data System (ADS)

We study the coherent properties of transmission through Kondo impurities by considering an open Aharonov-Bohm ring with an embedded quantum dot. We develop a many-body scattering theory which enables us to calculate the conductance through the dot Gd, the transmission phase shift ?t, and the normalized visibility ? in terms of the single-particle T matrix. For the single-channel Kondo effect, we find at temperatures much below the Kondo temperature TK that ?t=?/2 without any corrections up to order (T/TK)2. The visibility has the form ?=1-(?T/TK)2. For the non-Fermi-liquid fixed point of the two-channel Kondo, we find that ?t=?/2 despite the fact that a scattering phase shift is not defined. The visibility is ?=1/2(1+4??T) with ?˜1/TK, thus, at zero temperature, exactly half of the conductance is carried by single-particle processes, and coherent transmission may actually increase with temperature. We explain that the spin summation masks the inherent scattering phases of the dot, which can be accessed only via a spin-resolved experiment. In addition, we calculate the effect of magnetic field and channel anisotropy, and generalize to the k-channel Kondo case.

Carmi, Assaf; Oreg, Yuval; Berkooz, Micha; Goldhaber-Gordon, David

2012-09-01

407

Saturated Dispersive Extinction Theory of Red Shift  

NASA Astrophysics Data System (ADS)

The Dispersive Extinction Theory (DET) proposed by WangfootnotetextWang, Ling Jun, Physics Essays, 18, No. 2, (2005). offers an alternative to the Big Bang. According to DET, the cosmic red shift is caused by the dispersive extinction of the star light during the propagation from the stars to the earth, instead of being caused by the Doppler shift due to the expansion of the universe.footnotetextHubble, E., Astrophys. J. 64, 321 (1926).^,footnotetextHubble, E., The Realm of the Nebulae, (Yale University Press, New Haven, 1936). DET allows an infinite, stable, non expanding universe, and is immune of the fundamental problems inherent to the Big Bang such as the horizon problem, the extreme violation of the conservation of mass, energy and charge, and the geocentric nature which violates the principle of relativity.footnotetextWang, Ling Jun, Physics Essays, 20, No. 2, (2007). The scenario dealt with in Reference (1) is a one in which the extinction by the space medium is not saturated. This work deals with a different scenario when the extinction is saturated. The saturated extinction causes limited energy loss, and the star light can travel a much greater distance than in the unsaturated scenario.

Wang, Ling Jun

2012-03-01

408

Calculation of Chemical Shift Anisotropy in Proteins  

PubMed Central

Individual peptide groups in proteins must exhibit some variation in the chemical shift anisotropy (CSA) of their constituent atoms, but not much is known about the extent or origins of this dispersion. Direct spectroscopic measurement of CSA remains technically challenging, and theoretical methods can help to overcome these limitations by estimating shielding tensors for arbitrary structures. Here we use an automated fragmentation quantum mechanics/molecular mechanics (AF-QM/MM) approach to compute 15N, 13C? and 1H chemical shift tensors for human ubiquitin and the GB1 and GB3 fragments of staphylococcal protein G. The average and range of variation of the anisotropies is in good agreement with experimental estimates from solid-state NMR, and the variation among residues is somewhat smaller than that estimated from solution-state measurements. Hydrogen-bond effects account for much of the variation, both between helix and sheet regions, and within elements of secondary structure, but other effects (including variations in torsion angles) may play a role as well.

Tang, Sishi; Case, David A.

2011-01-01

409

Bipolar disorder: the shift to overdiagnosis.  

PubMed

Sometimes dramatically changing vogues in diagnostic practice in psychiatry resemble the volatility of international share markets. One such quickly shifting diagnostic area has been that of bipolar disorder (BD). Historically regarded as a relatively uncommon condition until recent decades, the construct of BD underwent a major expansion in the 1990s and 2000s with promulgation of the concept of the soft bipolar spectrum disorder, from which the recent research focus on subthreshold BD presentations was derived. Related to this has been renewed interest in treatments for BD from the pharmaceutical industry. The increasing rates of diagnosis have largely related to BD II, for which there has been a dramatic broadening of diagnostic criteria. This article critically reviews research data, both for broadening the diagnostic criteria for BD and, conversely, for the growing evidence of overdiagnosis in clinical practice. Why does this debate matter? I would suggest that there are many valid reasons to be concerned about overdiagnosis: first, the potential for overtreatment or inappropriate treatment of such patients with mood stabilizing treatments, including antipsychotics; second, the potential for diagnostic oversimplification, with consequent diagnostic deskilling and loss of credibility for the psychiatric profession; and third, the potential major impact on etiologic research for this condition. Psychiatry should not uncritically accept the shift to overdiagnosis, which has developed a rapid momentum in recent decades, in both clinical and academic circles. We must ensure, as a profession, that any change in diagnostic practice is underpinned by rigorous and critical research inquiry. PMID:23149281

Mitchell, Philip B

2012-11-01

410

Automated manual transmission shift sequence controller  

DOEpatents

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

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

2000-02-01

411

Identifying dramatic selection shifts in phylogenetic trees  

PubMed Central

Background The rate of evolution varies spatially along genomes and temporally in time. The presence of evolutionary rate variation is an informative signal that often marks functional regions of genomes and historical selection events. There exist many tests for temporal rate variation, or heterotachy, that start by partitioning sampled sequences into two or more groups and testing rate homogeneity among the groups. I develop a Bayesian method to infer phylogenetic trees with a divergence point, or dramatic temporal shifts in selection pressure that affect many nucleotide sites simultaneously, located at an unknown position in the tree. Results Simulation demonstrates that the method is most able to detect divergence points when rate variation and the number of affected sites is high, but not beyond biologically relevant values. The method is applied to two viral data sets. A divergence point is identified separating the B and C subtypes, two genetically distinct variants of HIV that have spread into different human populations with the AIDS epidemic. In contrast, no strong signal of temporal rate variation is found in a sample of F and H genotypes, two genetic variants of HBV that have likely evolved with humans during their immigration and expansion into the Americas. Conclusion Temporal shifts in evolutionary rate of sufficient magnitude are detectable in the history of sampled sequences. The ability to detect such divergence points without the need to specify a prior hypothesis about the location or timing of the divergence point should help scientists identify historically important selection events and decipher mechanisms of evolution.

Dorman, Karin S

2007-01-01

412

A superdirective array of phase shift sources.  

PubMed

A superdirective array of audio drivers is described, which is compact compared with the acoustic wavelength over some of its frequency range. In order to minimize the overall sound power output, and hence reduce the excitation of the reverberant field when used in an enclosed space, the individual drivers are made directional by using phase shift enclosures. The motivating application for the array is the enhancement of sound from a television, in a particular region of space, to aid hearing impaired listeners. The design is initially investigated, using free-field simulations, by comparing the performance of 8 monopoles, 8 phase shift loudspeakers, and a double array of 16 monopoles, with a contrast maximization formulation. The construction and testing of an array of 8 drivers is then discussed, together with its measured response in an anechoic environment. The result of using acoustic contrast maximization is then compared with a least squares formulation, which demonstrates that the performance of the least squares solution can be made similar to that given by acoustic contrast maximization in this application, with a suitable choice of the target field. PMID:22894197

Simón Gálvez, Marcos F; Elliott, Stephen J; Cheer, Jordan

2012-08-01

413

Shifts in continental moisture cycling patterns  

NASA Astrophysics Data System (ADS)

As our global fresh water resources are becoming more and more stressed it is important to know the origin and fate of atmospheric moisture over continents. The patterns of moisture feedback between evaporation and precipitation over continents (moisture cycling) may shift due to climate change. This research investigates how moisture cycling changes in the IPCC A1B climate scenario. We perform an a posteriori analysis based on data from the ECHAM5 general circulation model. Hereby we compare the results of the control run and the A1B climate scenario. These results allow us to evaluate possible changes in water availability in the future. Moreover, because we are not only analyzing the state variables (e.g. precipitation), but also the shifts in moisture recycling patterns, we are able to show how different regions are connected through the atmosphere and rely on each other for their water resources. This knowledge can help us adapting our land and water management to contribute in a positive way to the allocation of our water resources.

van der Ent, Ruud; Savenije, Hubert; Kunstmann, Harald; Knoche, Richard

2010-05-01

414

Periodicity in the quasar red shift parameter ln (1+z)  

SciTech Connect

Statistical analysis of quasar red shifts suggests a periodicity that cannot be explained by orthodox cosmology. A hypothesis is proposed whereby the cosmological red shift, at least in part, would be non-Doppler in origin.

Kipper, A.

1979-03-01

415

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

416

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

417

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

418

Simulation and parameter optimization of PCV in shift hydraulic system  

Microsoft Academic Search

com, chen _ h J@263.net Abstract-It is well-known that the shift hydraulic system plays a major role in the operation of the stepped automatic transmission. The main functions of the shift hydraulic system are to generate and maintain desired fluid pressures for transmission operation, as well as to initiate gear shifts and control shift quality. Generally, the widely used hydraulic

Tao Zhang; Gang Tao; Huiyan Chen

2011-01-01

419

Accurate estimation of phase-shifting error in digital holography  

Microsoft Academic Search

Phase shifting error is a major error source in phase-shifting digital holography. It affects the quality of the reconstructed object and causes errors in its phase and amplitude calculation. This paper presents a simple method to accurately retrieve the actual phase-shifting value used in practical hologram recording. It therefore provides the possibility of completely eliminating the phase-shifting error in digital

Shuqun Zhang

2004-01-01

420

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

421

Continuous analysis of move suppressed and shifted DMC  

Microsoft Academic Search

“Shifted DMC” (shifted dynamic matrix control) has been empirically shown to have significant improved closed-loop control characteristics over “move-suppressed DMC” where, in the latter, diagonal terms of the dynamic matrix DMC prediction model are augmented to reduce numerical ill conditioning. An added benefit of shifted DMC was that the so-called “shifting parameter,” replacing the move suppression parameter, was easily found

G. C. Kember; R. Dubay; S. E. Mansour

2005-01-01

422

Free energies for acid attack reactions of lithium cobaltate.  

SciTech Connect

The attack of lithium-ion battery cathodes by stray aqueous HF, with resultant dissolution, protonation, and possibly other unintended reactions, can be a significant source of capacity fade. We explore the calculation of reaction free energies of lithium cobaltate in acid by a 'hybrid' method, in which solid-phase free energies are calculated from first principles at the generalized gradient approximation + intrasite coulomb interaction (GGA+U) level and tabulated values of ionization potentials and hydration energies are employed for the aqueous species. Analysis of the dissolution of the binary oxides Li{sub 2}O and CoO suggests that the atomic energies for Co and Li should be shifted from values calculated by first principles to yield accurate reaction free energies within the hybrid method. With the shifted atomic energies, the hybrid method was applied to analyze proton-promoted dissolution and protonation reactions of LiCoO{sub 2} in aqueous acid. Reaction free energies for the dissolution reaction, the reaction to form Co{sub 3}O{sub 4} spinel, and the proton-for-lithium exchange reaction are obtained and compared to empirical values. An extension of the present treatment to consider partial reactions is proposed, with a view to investigating interfacial and environmental effects on the dissolution reaction.

Benedek, R.; van de Walle, A.; Chemical Sciences and Engineering Division; California Inst. of Tech.

2008-01-01

423

Food Use in Households in Three Work-Shift Categories  

Microsoft Academic Search

This study was designed to determine the effect of work shift on the money value, quantity in pounds, and nutritive value of convenience and nonconven ience foods used at home as well as to describe selected food-related practices of households classified by shift status (day, afternoon, or night). Data from 1,325 housekeeping households for whom shift status could be determined

Joanne M. Pearson; Oral Capps; Julein Axelson

1985-01-01

424

Regime Shifts Found in the Northern Hemisphere SST Field  

Microsoft Academic Search

A 'regime shift' is characterized by an abrupt transition from one quasi-steady climatic state to another, and its transition period is much shorter than the lengths of the individual epochs of each climatic state. In the present study, we investigate when regime shifts occurred and what was the difference in climatic states before and after the shifts, using the wintertime

Sayaka YASUNAKA; Kimio HANAWA

2002-01-01

425

Shifts in ENSO coupling processes under global warming  

Microsoft Academic Search

Global warming may shift the properties and dynamics of El Niño. We study the shifts in ENSO couplings in IPCC-AR4 coupled general circulation climate models. First, we compare period, pattern, amplitude and mean state of the Pacific Ocean between the current climate and a high CO2 climate. Next, shifts in ENSO couplings between sea surface temperature (SST), thermocline depth and

Sjoukje Philip; Geert Jan van Oldenborgh

2006-01-01

426

Shifts, duration of work and accident risk of bus drivers  

Microsoft Academic Search

This paper contains the results of a repetitive and comprehensive analysis of accidents of bus drivers, highlighting different aspects of the aetiology of bus drivers' accidents. The results presented in this paper indicate a strong effect of the type of shift on accident risk. Shifts starting in the morning appeared to have a higher risk than shifts starting in the

M. L. I. POKORNY; D. H. J. BLOM; P. VAN LEEUWEN

1987-01-01

427

Paradigm Shifts in and around Special Education in New Zealand.  

ERIC Educational Resources Information Center

|States that the evolution of special education policy that has taken place in the last decade in New Zealand reflects the coalescence of several paradigm shifts. Notes an international shift away from categorizing students in terms of disabilities. Examines tensions inherent in these paradigm shifts and interactions among them. (BT)|

Mitchell, David

2001-01-01

428

Medicare Payment Policy and the Controversy over Hospital Cost Shifting  

Microsoft Academic Search

This article examines (i) the background and debate over cost shifting; (ii) hospitals as business institutions that often shift the financial responsibility for their costs in the form of differential pricing; and (iii) how the cost-shifting debate affects and is affected by Medicare. The aim is to gain a better understanding of how changes in reimbursement by large government health

Rick Mayes; Jason S. Lee

2004-01-01

429

Image and Video Segmentation by Anisotropic Kernel Mean Shift  

Microsoft Academic Search

Mean shift is a nonparametric estimator of density which has been applied to image and video segmentation. Traditional mean shift based segmentation uses a radially symmetric kernel to estimate local density, which is not optimal in view of the often structured nature of image and more particularly video data. In this paper we present an anisotropic kernel mean shift in

Jue Wang; Bo Thiesson; Ying-qing Xu; Michael F. Cohen

2004-01-01

430

RIS3: A program for relativistic isotope shift calculations  

NASA Astrophysics Data System (ADS)

An atomic spectral line is characteristic of the element producing the spectrum. The line also depends on the isotope. The program RIS3 (Relativistic Isotope Shift) calculates the electron density at the origin and the normal and specific mass shift parameters. Combining these electronic quantities with available nuclear data, isotope-dependent energy level shifts are determined.

Nazé, C.; Gaidamauskas, E.; Gaigalas, G.; Godefroid, M.; Jönsson, P.

2013-09-01

431

Location Shift Algorithms in Open Pit Based on GPS  

Microsoft Academic Search

To solve the problem that location shift and statistics of carriage are not accurate when monitoring truck and statistics of ore carriage in the open pit by using GPS, the paper proposes a method to identify location shift and an algorithm to correct location shift, and it also designs a dynamic route generation algorithm of ore truck's carriage in open

Shunling Ruan; Caiwu Lu

2011-01-01

432

Detecting regime shifts in the ocean: Data considerations  

Microsoft Academic Search

We review observational data sets that have been used to detect regime shifts in the ocean. Through exploration of data time series we develop a definition of a regime shift from a pragmatic perspective, in which a shift is considered as an abrupt change from a quantifiable ecosystem state. We conclude that such changes represent a restructuring of the ecosystem

B. deYoung; R. Harris; J. Alheit; G. Beaugrand; N. Mantua; L. Shannon

2004-01-01

433

Neural Network Modeling of Developmental Effects in Discrimination Shifts.  

ERIC Educational Resources Information Center

Presents a theoretical account of human shift learning with the use of neural network tools. Details how simulations using the cascade-correlation algorithm which show that networks can capture the regularities of the discrimination shift literature better than existing psychological theories. Suggests that human developmental differences in shift…

Sirois, Sylvain; Shultz, Thomas R.

1998-01-01

434

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

435

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

436

Does exposure to UV radiation induce a shift to a Th-2-like immune reaction?  

PubMed

In addition to being the primary cause of skin cancer, UV radiation is immune suppressive and there appears to be a link between the ability of UV to suppress the immune response and induce skin cancer. Cytokines made by UV-irradiated keratinocytes play an essential role in activating immune suppression. In particular, we have found that keratinocyte-derived interleukin (IL)-10 is responsible for the systemic impairment of antigen-presenting cell function and the UV-induced suppression of delayed-type hypersensitivity (DTH). Antigen presentation by splenic adherent cells isolated from UV-irradiated mice to T helper-1 type T (Th1) cells is suppressed, whereas antigen presentation to T helper-2 type T (Th2) cells is enhanced. The enhanced antigen presentation to Th2 cells and the impaired presentation to Th1 cells can be reversed in vivo by injecting the UV-irradiated mice with monoclonal anti-IL-10 antibody. Furthermore, immune suppression can be transferred from UV-irradiated mice to normal recipients by adoptive transfer of T cells. Injecting the recipient mice with anti-IL-4 or anti-IL-10 prevents the transfer of immune suppression, suggesting the suppressor cells are Th2 cells. In addition, injecting UV-irradiated mice with IL-12, a cytokine that has been shown to be the primary inducer of Th1 cells, and one that prevents the differentiation of Th2 cells in vivo, reverses UV-induced immune suppression. These findings support the hypothesis that UV exposure activates IL-10 secretion, which depresses the function of Th1 cells, while enhancing the activity of Th2 cells. PMID:8760564

Ullrich, S E

1996-08-01

437

Nitrate attenuation in agricultural catchments: Shifting balances between transport and reaction  

Microsoft Academic Search

Simultaneous observations, across multiple spatial and temporal scales, are needed to understand the complex interactions between hydrological and biogeochemical processes in catchments and the primary controls on NO3? availability and mobility. This paper addresses these issues by using data collected from a detailed field experiment, carried out on two topographically different hillslopes (one steep and the other flat) located within

Carlos J. Ocampo; Carolyn E. Oldham; Murugesu Sivapalan

2006-01-01

438

Calculation of 13C Chemical Shifts in RNA Nucleosides: Structure 13C Chemical Shift Relationships  

Microsoft Academic Search

Isotropic 13C chemical shifts of the ribose sugar in model RNA nucleosides are calculated using SCF and DFT-GIAO ab initio methods for different combinations of ribose sugar pucker, exocyclic torsion angle, and glycosidic torsion angle. Idealized conformations were obtained using structures that were fully optimized by ab initio DFT methods starting with averaged parameters from a collection of crystallographic data.

Paolo Rossi; Gerard S. Harbison

2001-01-01

439

Instantaneous phase-shift Fizeau interferometer utilizing a synchronous frequency shift mechanism  

NASA Astrophysics Data System (ADS)

An on-axis, vibration insensitive, polarization Fizeau interferometer is realized through the use of a pixelated polarization mask spatial carrier phase shifting technique in conjunction with a high coherence source and a polarization frequency shift device. In this arrangement, differential motion between the test and reference surfaces, in conjunction with the polarization frequency shift device, is used to effectively separate the orthogonally polarized test and reference beam components for interference. With both the test and the reference beams on-axis, the common path cancellation advantages of the Fizeau interferometer are maintained. Additionally, the use of a high coherence source eliminates the need to path match the test and reference arms of the interferometer. Using a 1 mW HeNe source, the optimum camera shutter speed, used when measuring a 4% reflector, was 250 usec, resulting in significantly reduced vibration sensitivity. Experimental results show the performance of this new interferometer to be within the specifications of commercial phase shifting interferometers.

Kimbrough, Brad; Frey, Eric; Millerd, James

2008-08-01

440

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

441

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

442

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

443

Cooperative Lamb shift in an ellipsoid  

SciTech Connect

It has been long known that the global cooperative Lamb shift (CLS) in a large superradiantly emitting sphere has equal magnitude but opposite sign to that of a slab. This result was obtained from QED in 1973 for samples of uniform density. This change of sign holds as well for a Gaussian density distribution. The same result is also obtained for either density in the scalar simplification of QED now in frequent use. Since the CLS must be a continuous function of shape, and the slab resembles a limiting case of oblate ellipsoid, there must be some shape of ellipsoid for which the CLS is zero. We report a calculation of CLS for a Gaussian distribution of general azimuthally symmetric ellipsoidal shape. The CLS is found to vanish when the mean square radius is twice as great transversely as longitudinally.

Friedberg, Richard; Manassah, Jamal T. [Department of Physics, Columbia University, New York, New York 10027 (United States); Department of Electrical Engineering, City College of New York, New York 10031 (United States)

2010-06-15

444

Competitive environments induce shifts in host fidelity.  

PubMed

Recent models support the idea of sympatric speciation as a result of the joint effects of disruptive selection and assortative mating. We present experimental data, testing models of speciation through frequency-dependent selection. We show that under high competition on a mixture of resources/hosts, strains of the Seed beetle, Callosobruchus maculatus, change their host fidelity and evolve a more generalistic behaviour in resource utilization among females. The change in host fidelity did not result in disruptive selection and was not followed by assortative mating. This means that only one of three fundamental prerequisites for sympatric speciation evolved as a result of the frequency-dependent selection. We conclude that for this process to work, a shift to a novel food resource as a result of selection must also lead to a loss of preference for the original resource such that individuals are only able to use either one of the two. PMID:20546091

Rova, E; Björklund, M

2010-06-07

445

Regime shift of snow days in Switzerland  

NASA Astrophysics Data System (ADS)

The number of days with a snow depth above a certain threshold is the key factor for winter tourism in an Alpine country like Switzerland. An investigation of 34 long-term stations between 200 and 1800 m asl (above sea level) going back for at least the last 60 years (1948-2007) shows an unprecedented series of low snow winters in the last 20 years. The signal is uniform despite high regional differences. A shift detection analysis revealed a significant step-like decrease in snow days at the end of the 1980's with no clear trend since then. This abrupt change resulted in a loss of 20% to 60% of the total snow days. The stepwise increase of the mean winter temperature at the end of the 1980's and its close correlation with the snow day anomalies corroborate the sensitivity of the mid-latitude winter to the climate change induced temperature increase.

Marty, Christoph

2008-06-01

446

Cascaded nonlinear phase shifts in quasi-phase-matched structures  

NASA Astrophysics Data System (ADS)

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

2007-07-01

447

Using chemical shift perturbation to characterise ligand binding.  

PubMed

Chemical shift perturbation (CSP, chemical shift mapping or complexation-induced changes in chemical shift, CIS) follows changes in the chemical shifts of a protein when a ligand is added, and uses these to determine the location of the binding site, the affinity of the ligand, and/or possibly the structure of the complex. A key factor in determining the appearance of spectra during a titration is the exchange rate between free and bound, or more specifically the off-rate koff. When koff is greater than the chemical shift difference between free and bound, which typically equates to an affinity Kd weaker than about 3?M, then exchange is fast on the chemical shift timescale. Under these circumstances, the observed shift is the population-weighted average of free and bound, which allows Kd to be determined from measurement of peak positions, provided the measurements are made appropriately. (1)H shifts are influenced to a large extent by through-space interactions, whereas (13)C? and (13)C? shifts are influenced more by through-bond effects. (15)N and (13)C' shifts are influenced both by through-bond and by through-space (hydrogen bonding) interactions. For determining the location of a bound ligand on the basis of shift change, the most appropriate method is therefore usually to measure (15)N HSQC spectra, calculate the geometrical distance moved by the peak, weighting (15)N shifts by a factor of about 0.14 compared to (1)H shifts, and select those residues for which the weighted shift change is larger than the standard deviation of the shift for all residues. Other methods are discussed, in particular the measurement of (13)CH3 signals. Slow to intermediate exchange rates lead to line broadening, and make Kd values very difficult to obtain. There is no good way to distinguish changes in chemical shift due to direct binding of the ligand from changes in chemical shift due to allosteric change. Ligand binding at multiple sites can often be characterised, by simultaneous fitting of many measured shift changes, or more simply by adding substoichiometric amounts of ligand. The chemical shift changes can be used as restraints for docking ligand onto protein. By use of quantitative calculations of ligand-induced chemical shift changes, it is becoming possible to determine not just the position but also the orientation of ligands. PMID:23962882

Williamson, Mike P

2013-03-21

448

Effects of spectral shifting on speech perception in noise.  

PubMed

The present study used eight normal-hearing (NH) subjects, listening to acoustic cochlear implant (CI) simulations, to examine the effects of spectral shifting on speech recognition in noise. Speech recognition was measured using spectrally matched and shifted speech (vowels, consonants, and IEEE sentences), generated by 8-channel, sine-wave vocoder. Measurements were made in quiet and in noise (speech-shaped static noise and speech-babble at 5 dB signal-to-noise ratio). One spectral match condition and four spectral shift conditions were investigated: 2 mm, 3 mm, and 4 mm linear shift, and 3 mm shift with compression, in terms of cochlear distance. Results showed that speech recognition scores dropped because of noise and spectral shifting, and that the interactive effects of spectral shifting and background conditions depended on the degree/type of spectral shift, background conditions, and the speech test materials. There was no significant interaction between spectral shifting and two noise conditions for all speech test materials. However, significant interactions between linear spectral shifts and all background conditions were found in sentence recognition; significant interactions between spectral shift types and all background conditions were found in vowel recognition. Overall, the results suggest that tonotopic mismatch may affect performance of CI users in complex listening environments. PMID:20868733

Li, Tianhao; Fu, Qian-Jie

2010-09-22

449

Effects of Spectral Shifting on Speech Perception in Noise  

PubMed Central

The present study used eight normal-hearing (NH) subjects, listening to acoustic cochlear implant (CI) simulations, to examine the effects of spectral shifting on speech recognition in noise. Speech recognition was measured using spectrally matched and shifted speech (vowels, consonants, and IEEE sentences), generated by 8-channel, sine-wave vocoder. Measurements were made in quiet and in noise (speech-shaped static noise and speech-babble at 5 dB signal-to-noise ratio). One spectral match condition and four spectral shift conditions were investigated: 2 mm, 3 mm, and 4 mm linear shift, and 3 mm shift with compression, in terms of cochlear distance. Results showed that speech recognition scores dropped because of noise and spectral shifting, and that the interactive effects of spectral shifting and background conditions depended on the degree/type of spectral shift, background conditions, and the speech test materials. There was no significant interaction between spectral shifting and two noise conditions for all speech test materials. However, significant interactions between linear spectral shifts and all background conditions were found in sentence recognition; significant interactions between spectral shift types and all background conditions were found in vowel recognition. Overall, the results suggest that tonotopic mismatch may affect performance of CI users in complex listening environments.

Li, Tianhao; Fu, Qian-Jie

2010-01-01

450

Implementing a night-shift clinical nurse specialist.  

PubMed

Night-shift nurses receive fewer educational opportunities and less administrative support than do day-shift staff, tend to be newer, with less experience and fewer resources, and experience greater turnover rates, stress, and procedural errors. In an attempt to bridge the gap between day- and night-shift nursing, a night-shift clinical nurse specialist (CNS) position was created in a midsized, community teaching hospital. The goal was to provide an advanced practice presence to improve patient outcomes, communication, education, and cost-effectiveness. The night-shift CNS participated in nursing education and skill certifications, communicated new procedures and information, and created a communication committee specifically for night-shift nurses. Through regular rounding and on-call notification, the CNS was available to every area of the hospital for consultation and clinical assistance and assisted with rapid responses, codes, and traumas. Providing education during night shift reduced overtime costs and increased morale, positively affecting turnover rates. The night-shift CNS position has improved morale and equalized support for night-shift nurses. More research, most notably in specific night-shift metrics, is necessary, and with the implementation of the role in additional facilities, more can be understood about improving patient care and nursing staff satisfaction during night shift. PMID:23222025

Becker, Dawn Marie

451

Coherent control of the Goos-Haenchen shift  

SciTech Connect

The behavior of the Goos-Haenchen (GH) shifts in the reflected and transmitted light beam which is incident on a cavity containing an intracavity medium of three-level or four-level atoms with electromagnetically induced transparency (EIT) is discussed. We report a coherent control of the GH shift in a fixed configuration or device via superluminal and subluminal wave propagation. For superluminal wave propagation, we observe negative GH shifts in the reflected part of the incident light whereas the shifts are positive in the transmitted light beam. This corresponds to the negative group index of the cavity in the former case and positive group index of the cavity in the latter. For subluminal wave propagation, the behavior of the GH shifts in the reflected light changes and positive shifts appear; however, the GH shifts in the transmitted light remains positive. The corresponding group index of the cavity is positive in both cases.

Ziauddin; Qamar, Sajid [Centre for Quantum Physics, COMSATS Institute of Information Technology, Islamabad (Pakistan); Zubairy, M. Suhail [Centre for Quantum Physics, COMSATS Institute of Information Technology, Islamabad (Pakistan); Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843-4242 (United States)

2010-02-15

452

Biochemical Reactions as Computations  

Microsoft Academic Search

Two main mechanisms behind the functioning of biochemical reactions are facilitation and inhibition; these mechanisms are\\u000a also central for the interaction between biochemical reactions. This observation underlies the theory of reaction systems\\u000a which is a formal framework for the investigation of biochemical reactions, and especially interactions between them.

Andrzej Ehrenfeucht; Grzegorz Rozenberg

2007-01-01

453

Catalytic asymmetric Henry reaction  

Microsoft Academic Search

The classical Henry reaction, the coupling of a nitroalkane with a carbonyl compound in the presence of a base, is an important C–C bond forming reaction in organic chemistry giving ?-nitroalcohols, which are useful synthons in organic synthesis. However, an asymmetric version of the reaction, that has been developed recently, gives a new dimension to the classical Henry reaction whereby

Joshodeep Boruwa; Naminita Gogoi; Partha Pratim Saikia; Nabin C. Barua

2006-01-01

454

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

455

Forward (p, n) reactions and nucleon-nucleon scattering  

NASA Astrophysics Data System (ADS)

Forward (p, n) reaction cross sections are expressed in terms of nucleon-nucleon phase shifts. The ratio of the probabilities for triggering Gamow-Teller or Fermi transitions is found to be in quite good agreement with experiment. New np scattering experiments are also suggested in order to improve the interpretation of (p, n) reactions. Permanent address: Service de Physique Théorique, IPN, Bâtiment 210, Université Claude Bernard, 69622 Villeurbanne Cedex, France.

Guichon, P. A. M.

1983-07-01

456

Effects of Changing Shift Schedules from a Full-day to a Half-day Shift before a Night Shift on Physical Activities and Sleep Patterns of Single Nurses and Married Nurses with Children  

Microsoft Academic Search

To clarify the effects of changing shift schedules from a full-day to a half-day before a night shift, 12 single nurses and 18 married nurses with children that engaged in night shift work in a Japanese hospital were investigated. Subjects worked 2 different shift patterns consisting of a night shift after a half-day shift (HF-N) and a night shift after

Misuzu WATANABE; Yasuhiro AKAMATSU; Hikari FURUI; Teruyuki TOMITA; Takemasa WATANABE; Fumio KOBAYASHI

2004-01-01

457

Neural Activity in the Middle Temporal Area and Lateral Intraparietal Area during Endogenously Cued Shifts of Attention  

PubMed Central

We measured the behavioral time course of endogenously cued attentional shifts while recording from neurons in the middle temporal area (MT) and lateral intraparietal area (LIP) of two macaque monkeys. The monkeys were required to detect a subtle speed change of one of two continuously moving stimuli. The likely location of the speed change was cued throughout each trial but could switch at an unpredictable time. Attention was evident as an improvement in detection ability and reaction time at the cued location, and the focus of attention shifted over a 400 ms period in response to a switch of the cued stimulus. Attention modulated the ongoing neural response in both MT and LIP, and the sign of this modulation also rapidly shifted after a cue switch. Our data provide a framework for understanding the link between the neural and behavioral effects of attention. The responses of single neurons to the test stimulus in MT and LIP were correlated with stimulus detection and reaction time and, at the population level, a spike-rate threshold model was able to account for the effect of attention on detection rate and reaction time. In this view, the time course of the attentional shift can be understood as an interaction between the emerging attentional modulation and the neural response to the test stimulus in LIP. We also present evidence that the threshold model is not wholly explained by sensory (feedforward) information but may also be influenced by cognitive (feedback) processes at the time of stimulus detection.

Herrington, Todd M.; Assad, John A.

2010-01-01

458

Paradigm shift in classical elemental analysis.  

PubMed

An inductively coupled plasma (ICP) spectrometer equipped with pneumatic nebulization sample introduction requires mL volumes of sample. For direct elemental analysis of small amounts of solids, an ICP equipped either with a direct sample insertion (DSI) or with an electro-thermal vaporization (ETV) sample introduction system would typically require mg amounts of sample. In my laboratories, we have been developing and characterizing a new sample introduction system we call in-torch vaporization (ITV). The ITV sample introduction system improved significantly the detection limits of ICP spectrometry (both atomic emission and mass spectrometry), thus enabling determinations for micro- and sub-micro size liquid or solid samples. In some case