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1

Water-gas-shift reaction on metal nanoparticles and surfaces  

NASA Astrophysics Data System (ADS)

Density functional theory was employed to investigate the water-gas-shift reaction (WGS, CO +H2O?H2+CO2) on Au29 and Cu29 nanoparticles seen with scanning tunneling microscopy in model Au /CeO2(111) and Cu /CeO2(111) catalysts. Au(100) and Cu(100) surfaces were also included for comparison. According to the calculations of the authors, the WGS on these systems operate via either redox or associative carboxyl mechanism, while the rate-limiting step is the same, water dissociation. The WGS activity decreases in a sequence: Cu29>Cu(100)>Au29>Au(100), which agrees well with the experimental observations. Both nanoparticles are more active than their parent bulk surfaces. The nanoscale promotion on the WGS activity is associated with the low-coordinated corner and the edge sites as well as the fluxionality of the particles, which makes the nanoparticles more active than the flat surfaces for breaking the O-H bond. In addition, the role of the oxide support during the WGS was addressed by comparing the activity seen in the calculations of the authors for the Au29 and Cu29 nanoparticles and activity reported for X /CeO2(111) and X /ZnO(000?¯)(X =Cu or Au) surfaces.

Liu, Ping; Rodriguez, José A.

2007-04-01

2

Mechanisms of the water-gas-shift reaction by iron pentacarbonyl in the gas phase.  

PubMed

We analyzed the mechanisms of the water-gas-shift reaction catalyzed by Fe(CO) 5/OH (-) in the gas phase using DFT methods. The systematic analysis of the accessible reaction mechanisms and the consideration of the Gibbs free energies allows for different reaction routes than previously suggested. In the dominant catalytic cycle, the hydride [FeH(CO) 4]- is the important intermediate. Associative reaction mechanisms are not favorable under moderate and low pressures. At high pressure, a side reaction takes over and prevents the conversion of H 2O and CO to H 2 and CO 2 and leads to the formation of HCOOH. PMID:18754658

Rozanska, Xavier; Vuilleumier, Rodolphe

2008-10-01

3

Theoretical revisit of a Fe(CO)(5)-catalyzed water-gas shift reaction.  

PubMed

We have revisited the water-gas shift reaction catalyzed by iron pentacarbonyl at the DFT-B3LYP level. The reaction mechanism proposed by Rozanska and Vuilleumier (Inorg. Chem. 2008, 47, 8635-8640) has been followed and revised. The results show that transition states TS4/5 and TS5/2_a actually connect other intermediates rather than those suggested by Rozanska and Vuilleumier. Furthermore, the entire reaction has been proven to proceed with processes 1 --> 2 --> 3 --> 4 --> 6 --> 7 --> 2. It is the first time that species 6 and 7 are reported as intermediates for this reaction mechanism. PMID:20199050

Zhang, Fuli; Zhao, Liang; Xu, Chunming; Chen, Yu

2010-04-01

4

Kinetics of reverse water gas shift (RWGS) reaction on metal disulfide catalysts  

Microsoft Academic Search

The hydrogenation of CO2 was studied on disulfides of molybdenum and tungsten by comparison with that on the group VIII metals of Fe, Co, and Ni supported on Al2O3. The hydrogenation activity was lower on the disulfides on a per active site of catalyst basis than on the transition metals, however, the selective reverse water gas shift (RWGS) reaction (CO2

Toshihiko Osaki; Norichika Narita; Tatsuro Horiuchi; Toyohiko Sugiyama; Hiroyuki Masuda; Kenzi Suzuki

1997-01-01

5

Homogeneous catalysis of the water gas shift reaction using iron pentacarbonyl  

Microsoft Academic Search

Measurements have been carried out to determine the rate of hydrogen production by the water gas shift reaction (CO + HâO ..-->.. COâ + Hâ) operating at temperatures less than 200°C with iron pentacarbonyl serving as a catalyst precursor in a basic methanol-water solution. Turnover numbers of 2000 mol Hâ\\/mol Fe(CO)â per day are achieved at 180°C with this system.

Allen D. King; R. B. King; D. B. Yang

1980-01-01

6

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

DOEpatents

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

Siriwardane, Ranjani V; Fisher, II, James C

2013-12-31

7

A mini review on the chemistry and catalysis of the water gas shift reaction  

E-print Network

Water gas shift (WGS) reaction is a chemical reaction in which carbon monoxide reacts with water vapor to form carbon dioxide and hydrogen. It is an important reaction industrially used in conjunction with steam reforming of hydrocarbons for the production of high purity hydrogen. Grenoble et al examined the roles of both active metals and metal oxide support on the kinetics of the WGS reaction. They found out that the turn over numbers of various Al2O3 supported transition metals decreased in the trend of Cu, Re, Co, Ru, Ni, Pt, Os, Au, Fe, Pd, Rh, and Ir, which corresponds nicely to the observed volcano shaped correlation between catalytic activities and respective CO adsorption heat. This is a strong indication that CO gets activated on the metal surface during the reaction and different metals have different activation energies. The authors also observed that the turn over number of Pt/Al2O3 was one order of magnitude higher than that of Pt/SiO2, indicating a strong support effect, which the authors ascri...

Zhao, Zhun

2014-01-01

8

Homogeneous catalysis of the water gas shift reaction using iron pentacarbonyl  

SciTech Connect

Measurements have been carried out to determine the rate of hydrogen production by the water gas shift reaction (CO + H/sub 2/O ..-->.. CO/sub 2/ + H/sub 2/) operating at temperatures less than 200/sup 0/C with iron pentacarbonyl serving as a catalyst precursor in a basic methanol-water solution. Turnover numbers of 2000 mol H/sub 2//mol Fe(CO)/sub 5/ per day are achieved at 180/sup 0/C with this system. The reaction is shown to be zero order with respect to carbon monoxide. The temperature dependence of this reaction corresponds to an activation energy of 22 kcal/mol. It is shown that a threshold pressure of carbon monoxide exists above which the catalytic reduction of water can be sustained. Below this pressure, the Fe(CO)/sub 5/ is destroyed in a stoichiometric reduction of water. The overall kinetics of this reaction as well as this threshold phenomenon can be explained according to previously published mechanisms.

King, A.D. Jr.; King, R.B.; Yang, D.B.

1980-01-30

9

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

SciTech Connect

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

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

2013-12-01

10

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

NASA Astrophysics Data System (ADS)

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

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

11

Orthogonal optimization of Carboxydothermus hydrogenoformans culture medium for hydrogen production from carbon monoxide by biological water-gas shift reaction  

Microsoft Academic Search

The objective of the present study was to investigate the optimal nutritional requirements for hydrogen production from carbon monoxide by biological water-gas shift (WGS) reaction with Carboxydothermus hydrogenoformans using orthogonal layout methods. Cultures of C. hydrogenoformans on the medium as formulated by the strain supplier (Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH) unexpectedly showed a large content in inorganic material.

Ya Zhao; Ruxandra Cimpoia; Zhijun Liu; Serge R. Guiot

2011-01-01

12

Effects of H/sub 2/S on molten carbonate fuel cells. Literature survey of water-gas shift reaction  

SciTech Connect

A vast difference of opinion currently exists with regard to the effect of H/sub 2/S-containing fuel gases on the rate of the water gas shift reaction in state-of-the-art molten carbonate fuel cell anodes. One position is that the water gas shift reaction will ultimately be poisoned by the H/sub 2/S regardless of concentration. Another position is that H/sub 2/S will have very little effect on the rate of the water gas shift reaction at concentrations as high as 10 ppM/v. When using fuel gases with high CO concentrations, the rapid attainment of equilibrium with respect to the water gas shift reaction is essential for high fuel gas conversions and good fuel cell performance. Therefore, resolving this difference of opinion is considered important in defining the requisite gas stream cleanup for coal gasification/molten carbonate fuel cell power plants where the CO may represent up to 50% of the fuel content of the fuel gas. This report summarizes the results of a recent review conducted by the Institute of Gas Technology under contract to the DOE on this subject. Our review indicates that both stated positions have some merit when the details of the experiments are taken into account. We have found that H/sub 2/S decreases the rate of the water gas shift reaction but that the magnitude of the decrease depends to a large extent upon the molten carbonate fuel cell anode composition. Anodes with significant chromium contents (approx. 10 wt %) appear to demonstrate greater activity for promoting this water gas shift reaction in the presence of H/sub 2/S than anodes without. Based on recent experiments conducted at IGT, it was found that a 90% nickel/10% chrome anode maintain about 30% of its initial activity in promoting the water gas shift reaction in the presence of between 5 and 30 ppM/v. On the other hand, under similar conditions, a 100% nickel anode was found to retain less than 3% of its initial activity. 11 references.

Remick, R.J.; Anderson, G.L.

1985-01-01

13

Hydrodechlorination of 1,2-dichloroethane by rhodium catalysts under water gas shift reaction conditions  

Microsoft Academic Search

Homogeneous catalysts prepared from rhodium trichloride in aqueous aromatic amines have been shown to reduce C–Cl bonds under mild water gas shift conditions (T=100°C, PCO=1.0 atm). In a 4-picoline\\/water solvent mixture, 1,2-dichloroethane is reduced to ethylene and ethane in yields compatible with the consumption of the reducing agent CO and with the formation of CO2. Variation of the catalyst solutions

Elizeu Trabuco; Peter C. Ford

1999-01-01

14

Effect of calcination temperature on the catalytic activity of copper supported on ?-alumina for the water-gas-shift reaction  

Microsoft Academic Search

The effect of calcination temperature on the catalytic activity for water-gas-shift (WGS) reaction was investigated for copper\\/alumina catalysts prepared by the impregnation method. The catalyst calcined at 1073K, followed by the treatment in H2 at 523K, showed a high activity for WGS reaction. XRD and H2-TPR measurements revealed that the catalyst calcined at 1073K contained both highly dispersed CuO and

Hidenori Yahiro; Kenta Nakaya; Tetsuya Yamamoto; Kazuhiko Saiki; Hiroyuki Yamaura

2006-01-01

15

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

PubMed

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

Flytzani-Stephanopoulos, Maria

2014-03-18

16

Activity and stability of low-content gold–cerium oxide catalysts for the water–gas shift reaction  

Microsoft Academic Search

We report here on the high activity and stability of low-content gold–cerium oxide catalysts for the water–gas shift reaction (WGS). These catalysts are reversible in cyclic reduction–oxidation treatment up to 400°C, are non-pyrophoric, and are thus potential candidates for application to hydrogen generation for fuel cell power production. Low-content (0.2–0.9at.%) gold–ceria samples were prepared by single-pot synthesis by the urea

Qi Fu; Weiling Deng; Howard Saltsburg; Maria Flytzani-Stephanopoulos

2005-01-01

17

Effects of H/sub 2/S on molten carbonate fuel cell performance. II. The water gas shift reaction  

SciTech Connect

This report summarizes the results of a recent review conducted by the Institute of Gas Technology under contract to the DOE on this subject. Our review indicates that both stated positions have some merit when the details of the experiments are taken into account. We have found that H/sub 2/S decreases the rate of the water gas shift reaction but that the magnitude of the decrease depends to a large extent upon the molten carbonate fuel cell anode composition. Anodes with significant chromium contents (approx.10 wt %) appear to demonstrate greater activity for promoting this water gas shift reaction in the presence of H/sub 2/S than anodes without. Based on recent experiments conducted at IGT, it was found that a 90% nickel/10% chrome anode maintain about 30% of its initial activity in promoting the water gas shift reaction in the presence of between 5 and 30 ppM/v. On the other hand, under similar conditions, a 100% nickel anode was found to retain less than 3% of its initial activity.

Anderson, G.L.

1984-08-01

18

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

E-print Network

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

Frenkel, Anatoly

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

Structure Sensitivity of the Low-temperature Water-gas Shift Reaction on Cu–CeO2 catalysts  

SciTech Connect

We have investigated the structure sensitivity of the water-gas shift (WGS) reaction on Cu-CeO{sub 2} catalysts prepared at the nanoscale by different techniques. On the surface of ceria, different CuO{sub x} structures exist. We show here that only the strongly bound Cu-[O{sub x}]-Ce species, probably associated with the surface oxygen vacancies of ceria, are active for catalyzing the low-temperature WGS reaction. Weakly bound CuO{sub x} clusters and CuO nanoparticles are spectator species in the reaction. Isolated Cu{sup 2+} ions doping the ceria surface are not active themselves, but they are important in that they create oxygen vacancies and can be used as a reservoir of copper to replenish surface Cu removed by leaching or sintering. Accordingly, synthesis techniques such as coprecipitation that allow for extensive solubility of Cu in ceria should be preferred over impregnation, deposition-precipitation, ion exchange or another two-step method whereby the copper precursor is added to already made ceria nanocrystals. For the synthesis of different structures, we have used two methods: a homogeneous coprecipitation (CP), involving hexamethylenetetramine as the precipitating agent and the pH buffer; and a deposition-precipitation (DP) technique. In the latter case, the ceria supports were first synthesized at the nanoscale with different shapes (rods, cubes) to investigate any potential shape effect on the reaction. Cu-CeO{sub 2} catalysts with different copper contents up to ca. 20 at.% were prepared. An indirect shape effect of CeO{sub 2}, manifested by the propensity to form oxygen vacancies and strongly bind copper in the active form, was established; i.e. the water-gas shift reaction is not structure-sensitive. The apparent activation energy of the reaction on all samples was similar, 50 {+-} 10 kJ/mol, in a product-free (2% CO-10% H{sub 2}O) gas mixture.

Si, R.; Zhang, L.; Raitano, J.; Yi, N.; Chan, S.-W.; Flytzani-Stephanopoulos, M.

2012-01-17

21

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

22

Mechanisms of the water-gas shift reaction catalyzed by ruthenium pentacarbonyl: a density functional theory study.  

PubMed

The mechanism of the water-gas shift reaction catalyzed by Ru(CO)5 is analyzed using density functional methods in solution within the conductor-like screening model. Four different mechanistic pathways have been considered. It turned out that the incorporation of solvent effects is very important for a reasonable comparison among the mechanistic alternatives. The explicit inclusion of a water solvent molecule significantly changes the barriers of those steps which involve proton transfer in the transition state. The corresponding barriers are either lowered or increased, depending on the structure of the corresponding cyclic transition states. The results show that protolysis steps become competitive due to solution effects. The formation of formic acid as an intermediate in another, alternative pathway is also found to be competitive. PMID:23600366

Schulz, Hannes; Görling, Andreas; Hieringer, Wolfgang

2013-05-01

23

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

24

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

25

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

26

H2 production Through the Water-gas Shift Reaction: An in Situ Time-resolved X-ray Diffraction Investigation of Manganese OMS-2 Catalyst  

SciTech Connect

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

Sithambaram, S.; Wen, W; Njagi, E; Shen, X; Hanson, J; Suib, S

2010-01-01

27

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

SciTech Connect

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

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

2010-10-01

28

The activation of gold and the water-gas shift reaction: insights from studies with model catalysts.  

PubMed

The activation of gold in catalytic reactions has been the subject of intensive research that has led to the transformation of one of the least chemically reactive elements to a catalyst with excellent activity and selectivity. Scientists have performed numerous systematic experimental and theoretical studies using model systems, which have explained the role of Au in chemical reactions with progressively increasing degrees of structural and chemical complexity. We present an overview of recent studies of model Au(111), CeOx/Au(111), and Au/CeOx/TiO2(110) surfaces that use Au in different structural configurations specifically for the water-gas shift reaction (WGS, CO + H2O ? CO2 + H2), an important industrial process for the purification of CO. We demonstrate the significance of key structural components of the Au-based supported catalysts such as the metal-oxide interface (Au-Ox) toward the WGS catalytic activity, a "structure-activity" relationship. In the WGS reaction, Au(111) or Au nanoparticles have poor catalytic performance due to their inability to activate one of the most important steps of the reaction, the breaking of O-H bonds in the dissociation of water (H2O ? OH + H). The relatively large energetic barrier can be overcome by using O on Au(111) to facilitate the formation of OH at low temperatures, with eventual CO2 and H2 production upon reaction between CO and the adsorbed OH. However, the inability to replace the reacted O prevents a sustainable catalytic process from occurring on Au(111). The addition of a small concentration of CeOx nanoparticles on top of the Au(111) surface facilitates this rate-determining step and easily continues the catalytic cycle in the production of H2. We have discovered that CeOx nanoparticles in contact with Au(111) are rich in Ce(3+). They also have a distinct metal-oxide interface, which sustains excellent activity for the WGS reaction via the formation of a unique carboxylate intermediate, making CeOx/Au(111) more active than Cu/ZnO(0001?), Cu(100), and Cu(111) which are the typical catalysts for this reaction. Taking this knowledge one step further, bringing these components (oxide and metal nanoparticles) together over a second oxide in Au/CeOx/TiO2 produces a system with unique morphological and electronic properties. The result is a superior catalyst for the WGS reaction, both as a model system (Au/CeOx/TiO2(110)) and as powder material (Au/CeOx/TiO2(anatase)) optimized directly in a series of systematic investigations. PMID:24191672

Rodriguez, José A; Senanayake, Sanjaya D; Stacchiola, Dario; Liu, Ping; Hrbek, Jan

2014-03-18

29

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

30

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

31

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

32

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

E-print Network

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

Hardy, AliciA Jillian Jackson, 1978-

2004-01-01

33

Experimental and modeling studies on the low-temperature water-gas shift reaction in a dense Pd–Ag packed-bed membrane reactor  

Microsoft Academic Search

In this work, an experimental and modeling study is described, focusing on the performance of a Pd–Ag membrane reactor recently proposed and suitable for the production of ultra-pure hydrogen. A packed-bed membrane reactor (MR) with a “finger-like” membrane configuration has been used for carrying out the water-gas shift reaction (WGS) in the region of low temperature operation using a simulated

Diogo Mendes; Sandra Sá; Silvano Tosti; José M. Sousa; Luis M. Madeira; Adélio Mendes

2011-01-01

34

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

PubMed

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

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

2013-12-14

35

Water–Gas Shift Reaction Over Aluminum Promoted Cu\\/CeO 2 Nanocatalysts Characterized by XRD, BET, TPR and Cyclic Voltammetry (CV)  

Microsoft Academic Search

A series of aluminum promoted Cu\\/CeO2 nanocatalysts with aluminum content in the range of 0–5wt.% were prepared by co-precipitation method and examined with respect\\u000a to their catalytic performance for the water–gas shift (WGS) reaction. The catalysts were characterized by XRD, BET, H2-TPR and cyclic voltammetry (CV) techniques. The results indicate that catalytic activity increases with the aluminum content\\u000a at first,

Lei Li; Yingying Zhan; Qi Zheng; Yuanhui Zheng; Xingyi Lin; Dalin Li; Junjiang Zhu

2007-01-01

36

Charge Polarization at a Au-TiC Interface and the Generation of Highly Active and Selective Catalysts for the Low-Temperature Water-Gas Shift Reaction.  

PubMed

Au atoms in contact with TiC(001) undergo significant charge polarization. Strong metal-support interactions make Au/TiC(001) an excellent catalyst for the low-temperature water-gas shift (WGS), with turnover frequencies orders of magnitude larger than those observed for conventional metal/oxide catalysts. DFT calculations indicate that the WGS reaction follows an associative mechanism with HOCO as a key intermediate. PMID:25196121

Rodriguez, José A; Ramírez, Pedro J; Asara, Gian Giacomo; Viñes, Francesc; Evans, Jaime; Liu, Ping; Ricart, Josep M; Illas, Francesc

2014-10-13

37

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

NASA Astrophysics Data System (ADS)

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

Lin, Jiann-Horng

38

In Situ Time-Resolved Characterization of Novel Cu-MoO2 Catalysts During the Water-Gas Shift Reaction  

SciTech Connect

A novel and active Cu-MoO{sub 2} catalyst was synthesized by partial reduction of a precursor CuMoO{sub 4} mixed-metal oxide with CO or H{sub 2} at 200-250 C. The phase transformations of Cu-MoO{sub 2} during H{sub 2} reduction and the water-gas shift reaction could be followed by In situ time resolved XRD techniques. During the reduction process the diffraction pattern of the CuMoO{sub 4} collapsed and the copper metal lines were observed on an amorphous material background that was assigned to molybdenum oxides. During the first pass of water-gas shift (WGS) reaction, diffraction lines for Cu{sub 6}Mo{sub 5}O{sub 18} and MoO{sub 2} appeared around 350 C and Cu{sub 6}Mo{sub 5}O{sub 18} was further transformed to Cu/MoO{sub 2} at higher temperature. During subsequent passes, significant WGS catalytic activity was observed with relatively stable plateaus in product formation around 350, 400 and 500 C. The interfacial interactions between Cu clusters and MoO{sub 2} increased the water-gas shift catalytic activities at 350 and 400 C.

Wen ,W.; Liu, J.; White, M.; Marinkovic, N.; Hanson, J.; Rodriguez, J.

2007-01-01

39

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

NASA Astrophysics Data System (ADS)

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

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

1998-03-01

40

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

SciTech Connect

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

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

1999-07-19

41

In Situ Time-Resolved Characterization of Au-CeO2 Catalysts During Water Gas Shift Reactions: presence of Au and O Vacancies in the Active Phase  

SciTech Connect

Synchrotron-based in situ time-resolved x-ray diffraction and x-ray absorption spectroscopies were used to study the behavior of nanostructured {l_brace}Au+AuO{sub x}{r_brace}-CeO{sub 2} catalysts under the water-gas shift (WGS) reaction. At temperatures above 250 C, a complete AuO{sub x}{yields}Au transformation was observed with high catalytic activity. Photoemission results for the oxidation and reduction of Au nanoparticles supported on rough ceria films or a CeO{sub 2}(111) single crystal corroborate that cationic Au{sup {delta}} species cannot be the key sites responsible for the WGS activity at high temperatures. The rate determining steps for the WGS seem to occur at the gold-ceria interface, with the active sites involving small gold clusters (<2 nm) and O vacancies.

Wang,X.; Rodriguez, J.; Hanson, J.; Perez, M.; Evans, J.

2005-01-01

42

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

E-print Network

*, Department of Physics, Yeshiva University, New York, New York 10016, United States Department of Chemical and compositional changes of the partially reduced iron oxide Fe2O3 and 3% chromium oxide-modified iron oxide (3% Cr (1) At industrial plants, the WGS reaction is usually carried out at two different temperature ranges

Frenkel, Anatoly

43

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

E-print Network

reactor is a fixed bed catalytic reactor in which ]ow flow rates of gas and liquid pass concurrently downflow through the bed. The liquid phase "trickles" down the catalyst bed, wetting the packing and saturating the pores while the gas passes through... the voids left by the packing. Trickle bed reactors are particularly suited for HDS reactions since hydrogen in thc gas phase This thesis is presented in the style and format of the industriei Engineering Chemistry Process Design end Development...

Hook, Bruce David

2012-06-07

44

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

SciTech Connect

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

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

2014-01-01

45

Morphological effects of the nanostructured ceria support on the activity and stability of CuO/CeO2 catalysts for the water-gas shift reaction.  

PubMed

Three CuO/CeO2 catalyst with different morphologies of ceria, namely nanospheres, nanorods and nanocubes, were synthesized and used to catalyze the water-gas shift (WGS) reaction. The reactivity tests showed that the Cu supported on the ceria nanospheres exhibited both the highest activity and superior stability when compared with the nanocube and nanorod ceria catalysts. Operando X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) methods were used to characterize these catalysts in their working state. High resolution electron microscopy (HRTEM, STEM) was used to look at the local atomic structure and nano-scale morphology. Our results show that the morphology of the ceria support, which can involve different crystal faces and concentrations of defects and imperfections, has a critical impact on the catalytic properties and influences: (1) the dispersion of CuO in the as-synthesized catalyst; (2) the particle size of metallic Cu upon reduction during the WGS reaction, (3) the stability of the metallic Cu upon variations of temperature, and (4) the dissociation of water on the ceria support. The nanosphere ceria catalyst showed an excellent water dissociation capability, the best dispersion of Cu and a strong Cu-Ce interaction, therefore delivering the best performance among the three WGS catalysts. The metallic Cu, which is the active species during the WGS reaction, was more stabilized on the nanospheres than on the nanorods and nanocubes and thus led to a better stability of the nanosphere catalyst than the other two architectures. Each catalyst exhibited a distinctive line-shape in the 800-1600 cm(-1) region of the DRIFTS spectra, pointing to the existence of different types of carbonate or carboxylate species as surface intermediates for the WGS. PMID:25012908

Yao, S Y; Xu, W Q; Johnston-Peck, A C; Zhao, F Z; Liu, Z Y; Luo, S; Senanayake, S D; Martínez-Arias, A; Liu, W J; Rodriguez, J A

2014-08-28

46

Ceria-based Catalysts for the Production of H2 Through the Water-gas-shift Reaction: Time-Resolved XRD and XAFS Studies  

SciTech Connect

Hydrogen is a potential alternate energy source for satisfying many of our energy needs. In this work, we studied H2 production from the water-gas-shift (WGS) reaction over Ce1-x Cu x O2 catalysts, prepared with a novel microemulsion method, using two synchrotron-based techniques: time-resolved X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS). The results are compared with those reported for conventional CuO x /CeO2 and AuO x /CeO2 catalysts obtained through impregnation of ceria. For the fresh Ce1-x Cu x O2 catalysts, the results of XAFS measurements at the Cu K-edge indicate that Cu is in an oxidation state higher than in CuO. Nevertheless, under WGS reaction conditions the Ce1-x Cu x O2 catalysts undergo reduction and the active phase contains very small particles of metallic Cu and CeO2-x . Time-resolved XRD and XAFS results also indicate that Cud+ and Aud+ species present in fresh CuO x /CeO2 and AuO x /CeO2 catalysts do not survive above 200 C under the WGS conditions. In all these systems, the ceria lattice displayed a significant increase after exposure to CO and a decrease in H2O, indicating that CO reduced ceria while H2O oxidized it. Our data suggest that H2O dissociation occurred on the Ovacancy sites or the Cu-Ovacancy and Au-Ovacancy interfaces. The rate of H2 generation by a Ce0.95Cu0.05O2 catalyst was comparable to that of a 5 wt% CuO x /CeO2 catalyst and much bigger than those of pure ceria or CuO.

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

2008-01-01

47

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

48

WATER-GAS SHIFT WITH INTEGRATED HYDROGEN SEPARATION  

SciTech Connect

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

Maria Flytzani-Stephanopoulos; Jerry Meldon; Xiaomei Qi

2001-12-01

49

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

PubMed

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

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

2013-08-20

50

Water-Gas Shift Membrane Reactor Studies  

E-print Network

Reactor Fuels and Chemicals Generator Steam Turbine Combustion Turbine Heat Recovery Steam Generator Coal, Petroleum coke, Biomass, Waste, etc. Gasifier Particulate Removal Air Separator Oxygen Air Steam Particulates Steam Solid Waste Gas Cleanup Sulfur Byproduct Compressed Air Synthesis Gas Conversion Shift

51

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

E-print Network

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

52

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

Microsoft Academic Search

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

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

2006-01-01

53

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

54

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

Microsoft Academic Search

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

Qi Fu; Howard Saltsburg; Maria Flytzani-Stephanopoulos

2003-01-01

55

Nature of Ptn/TiO2(110) Interface under Water-Gas Shift Reaction Conditions: A Constrained ab Initio Thermodynamics Study  

SciTech Connect

The electronic structure of small Ptn (n = 1-8) clusters supported on the stoichiometric and partially reduced rutile TiO2(110) surface have been investigated using density functional theory. Pt atoms prefer to form a close-packed structure with (111) facet near an oxygen vacancy of the TiO2 support and a less dense structure with (100) facet away from oxygen vacant sites. Themain focus of this study is on identifying a realistic catalyst model for the Pt/TiO2 interface under watergas shift (WGS) reaction conditions. Constrained ab initio thermodynamic simulations on the stability of oxygen vacancies and formation of adsorbed gas phase molecules such as oxygen, CO, and hydrogen at the metal/oxide interface reveal that under WGS reaction conditions the formation of surface oxygen vacancies are thermodynamically favorable, platinum oxide species (PtOx) can easily be reduced and should not be present, CO adsorbs only weakly on interfacial Pt atoms, and CO poisoning of these sites should be less important. While hydrogen generally interacts weakly with interfacial Pt atoms, it forms very stable hydride species on Pt atoms neighboring an oxygen vacancy of the TiO2(110) support, possibly negatively affecting the WGS reaction rate.

Ammal, Salai Cheettu; Heyden, Andreas

2011-10-06

56

Argonne National Laboratory Chemical Engineering Division Water-gas shift catalysis  

E-print Network

of support via dissociation of water Approach #12;Argonne National Laboratory Chemical Engineering DivisionArgonne National Laboratory Chemical Engineering Division Water-gas shift catalysis Sara Yu Choung Objective is to develop water-gas shift catalysts for on- board fuel processing · Meet the DOE technical

57

Development of an advanced water-gas shift conversion system. Quarterly progress report, May-July 1984  

Microsoft Academic Search

The objective of current work is to conduct research and development to investigate the use of an aqueous catalyst system for conducting the water-gas shift reaction. This objective will be accomplished by performing continuous laboratory scale experimentation designed to prove the technical concept. The initial phase of the project will provide the data base required to establish operating parameters as

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

1984-01-01

58

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

SciTech Connect

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

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

1985-04-01

59

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

2013-10-01

60

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

SciTech Connect

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

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

1990-01-01

61

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

Microsoft Academic Search

The objective of this research was to investigate sulfur-resistant catalysts for the conversion of synthesis gas having Hâ\\/CO ⤠1 into Câ--Câ 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

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

1995-01-01

62

Probing the low-temperature water-gas shift activity of alkali-promoted platinum catalysts stabilized on carbon supports.  

PubMed

We report on the direct promotional effect of sodium on the water-gas shift activity of platinum supported on oxygen-free multiwalled carbon nanotubes. Whereas the Na-free Pt catalysts are shown to be completely inactive, the addition of sodium is found to improve the water-gas shift activity to levels comparable to those obtained with highly active Pt catalysts on metal oxide supports. The structure and morphology of the catalyst surface was followed using aberration-corrected HAADF-STEM, which showed that atomically dispersed platinum species are stabilized by the addition of sodium. In situ atmospheric-pressure X-ray photoelectron spectroscopy (AP-XPS) experiments demonstrated that oxidized platinum Pt-OHx contributions in the Pt 4f signal are higher in the presence of sodium, providing evidence for a previously reported active-site structure of the form Pt-Nax-Oy-(OH)z. Pt remained oxidized in all redox experiments, even when a H2-rich gas mixture was used, but the extent of its oxidation followed the oxidation potential of the gas. These findings offer new insights into the nature of the active platinum-based site for the water-gas shift reaction. A strong inhibitory effect of hydrogen was observed on the reaction kinetics, effectively raising the apparent activation energy from 70 ± 5 kJ/mol (in product-free gas) to 105 ± 7 kJ/mol (in full reformate gas). Increased hydrogen uptake was observed on these materials when both Pt and Na were present on the catalyst, suggesting that hydrogen desorption might limit the water-gas shift reaction rate under such conditions. PMID:24502260

Zugic, Branko; Zhang, Shiran; Bell, David C; Tao, Franklin Feng; Flytzani-Stephanopoulos, Maria

2014-02-26

63

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

64

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts  

SciTech Connect

During this quarter, high pressure (8.1 MPa) and high temperature (up to 350[degrees]C) catalytic testing was carried out with a 10 wt% cesium doped molybdenum disulfide for 188.5 hr. The doping of the catalyst was carried out under vacuum, instead of evaporating a methanolic solution of cesium formate. This procedure proved to initially provide an active catalyst, although the catalyst was not as active as previously reported [1] for a similarly prepared catalyst. Upon prolonged testing, deactivation of the catalyst was observed. Surprisingly, the selectivity pattern was reversed from that of the fresh catalyst, i.e. the alcohol synthesis selectivity increased with increasing reaction temperature rather than decreased. The causes of this deactivation and selectivity reversal have not yet been determined, but characterization studies are underway with this catalyst.

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

1993-03-01

65

Au-mixed lanthanum/cerium oxide catalysts for water-gas-shift  

SciTech Connect

We report on the synthesis of highly homogeneous mixed La/Ce-oxides via a microemulsion-templated approach, and their evaluation as active supports for Au in the water gas shift (WGS) reaction. Both structure and reducibility of the oxides could be tailored by adjusting the La content across the entire range of La:Ce-ratios. The reducibility of the Au-free oxides shows an optimum at ?25% La content, which can be traced back to improved oxygen mobility due to formation of oxygen vacancies and to the formation of more strongly bound oxygen upon La addition. Deposition of Au onto these oxides gives rise to an additional, low-temperature reduction peak, presumably due to hydrogen spill-over from the noble metal onto the oxide support. The WGS activity of Au/La{sub x}Ce{sub 1?x}O{sub 2?0.5x} catalysts correlates closely with the reducibility of the oxide supports, and hence with La content, demonstrating that carefully controlled synthesis of nanostructured catalysts with uniform, tailored composition allows for fine control of reactive properties of these materials, and might ultimately open the way towards a more rational design of catalysts.

Wang, Yanan; Liang, Shuang; Cao, Anmin; Thompson, Robert L; Veser, Goetz

2010-08-01

66

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

SciTech Connect

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

Ferraris, John

2013-09-30

67

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

68

An innovative catalyst system for slurry-phase Fischer-Tropsch synthesis: Cobalt plus a water-gas-shift catalyst  

SciTech Connect

The feasibility of using a mechanical mixture of a Co/MgO/SiO{sub 2} Fischer-Tropsch catalyst and a Cu-ZnO/Al{sub 2}O{sub 3} water-gas-shift (WGS) catalyst for hydrocarbon synthesis in a slurry reactor has been established. Such a mixture can combine the superior product distribution from cobalt with the high activity for the WGS reaction characteristic of iron. Weight ratios of Co/MgO/SiO{sub 2} to Cu-ZnO/Al{sub 2}O{sub 3} of 0.27 and 0.51 for the two catalysts were studied at 240{degrees}C, 0.79 MPa, and in situ H{sub 2}/CO ratios between 0.8 and 3.0. Each catalyst mixture showed stable Fischer-Tropsch activity for about 400 hours-on-stream at a level comparable to the cobalt catalyst operating alone. The Cu-ZnO/Al{sub 2}O{sub 3} catalyst exhibited a very slow loss of activity under these conditions, but when operated alone it was stable in a slurry reactor at 200--220{degrees}C, 0.79--1.48 MPa, and H{sub 2}/CO in situ ratios between 1.0 and 2.0. The presence of the water-gas-shift catalyst did not affect the long-term stability of the primary Fischer-Tropsch selectivity, but did increase the extent of secondary reactions, such as l-alkene hydrogenation and isomerization.

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

1991-07-01

69

Activity and durability of water-gas shift catalysts used for the steam reforming of methanol  

NASA Astrophysics Data System (ADS)

Commercially available water-gas shift catalysts were tested for methanol steam reforming in small-scale packed bed reactors at atmospheric pressure. The results showed that while the initial activity of chromia or zinc oxide catalysts was lower than that of copper-based catalysts, the durability of the chromia preparations was far superior to that of the copper-based samples at the temperatures investigated. Kinetic modeling suggested that copper and zinc oxide catalysts have deactivated by sintering of the metal phase; instead, the deactivation of chromia catalysts is consistent with feed poisoning. A zinc oxide/chromia catalyst was among the most active, and it certainly was the most stable, catalyst tested.

Löffler, D. G.; McDermott, S. D.; Renn, C. N.

70

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

71

In-situ Characterization of Water-Gas Shift Catalysts using Time-Resolved X-ray Diffraction  

SciTech Connect

Time-resolved X-ray diffraction (XRD) has emerged as a powerful technique for studying the behavior of heterogeneous catalysts (metal oxides, sulfides, carbides, phosphides, zeolites, etc.) in-situ during reaction conditions. The technique can identify the active phase of a heterogeneous catalyst and how its structure changes after interacting with the reactants and products (80 K < T < 1200 K; P < 50 atm). In this article, we review a series of recent works that use in-situ time-resolved XRD for studying the water-gas shift reaction (WGS, CO + H2O ? H2 + CO2) over several mixed-metal oxides: CuMoO4, NiMoO4, Ce1-xCuxO2-d and CuFe2O4. Under reaction conditions the oxides undergo partial reduction. Neutral Cu0 (i.e. no Cu1+ or Cu2+ cations) and Ni0 are 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 important role played by O vacancies in the mechanism for the WGS. In the case of Ce1-xCuxO2-d, Rietveld refinement shows expansions/contractions in the oxide lattice which track steps within the WGS process: CO(gas) + O(oxi) ? CO2(gas) + O(vac); H2O(gas) + O(vac) ? O(oxi) + H2(gas).

Rodriguez, J.; Hanson, J; Wen, W; Wang, X; Brito, J; Martnez-Arias, A; Fernandez-Garca, M

2009-01-01

72

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

73

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

NASA Technical Reports Server (NTRS)

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

Haralambous, Michael G.

2001-01-01

74

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

NASA Technical Reports Server (NTRS)

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

Haralambous, Michael G.

2002-01-01

75

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

NASA Astrophysics Data System (ADS)

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

Kugai, Junichiro

76

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

2013-10-01

77

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

SciTech Connect

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

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

1990-12-31

78

An innovative catalyst system for slurry-phase Fischer-Tropsch synthesis: Cobalt plus a water-gas-shift catalyst. Final technical report  

SciTech Connect

The feasibility of using a mechanical mixture of a Co/MgO/SiO{sub 2} Fischer-Tropsch catalyst and a Cu-ZnO/Al{sub 2}O{sub 3} water-gas-shift (WGS) catalyst for hydrocarbon synthesis in a slurry reactor has been established. Such a mixture can combine the superior product distribution from cobalt with the high activity for the WGS reaction characteristic of iron. Weight ratios of Co/MgO/SiO{sub 2} to Cu-ZnO/Al{sub 2}O{sub 3} of 0.27 and 0.51 for the two catalysts were studied at 240{degrees}C, 0.79 MPa, and in situ H{sub 2}/CO ratios between 0.8 and 3.0. Each catalyst mixture showed stable Fischer-Tropsch activity for about 400 hours-on-stream at a level comparable to the cobalt catalyst operating alone. The Cu-ZnO/Al{sub 2}O{sub 3} catalyst exhibited a very slow loss of activity under these conditions, but when operated alone it was stable in a slurry reactor at 200--220{degrees}C, 0.79--1.48 MPa, and H{sub 2}/CO in situ ratios between 1.0 and 2.0. The presence of the water-gas-shift catalyst did not affect the long-term stability of the primary Fischer-Tropsch selectivity, but did increase the extent of secondary reactions, such as l-alkene hydrogenation and isomerization.

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

1991-07-01

79

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

80

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

PubMed

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

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

2014-08-25

81

Sorption-Enhanced Synthetic Natural Gas (SNG) Production from Syngas: A Novel Process Combining CO Methanation, Water-Gas Shift, and CO2 Capture  

SciTech Connect

Synthetic natural gas (SNG) production from syngas is under investigation again due to the desire for less dependency from imports and the opportunity for increasing coal utilization and reducing green house gas emission. CO methanation is highly exothermic and substantial heat is liberated which can lead to process thermal imbalance and deactivation of the catalyst. As a result, conversion per pass is limited and substantial syngas recycle is employed in conventional processes. Furthermore, the conversion of syngas to SNG is typically performed at moderate temperatures (275 to 325°C) to ensure high CH4 yields since this reaction is thermodynamically limited. In this study, the effectiveness of a novel integrated process for the SNG production from syngas at high temperature (i.e. 600?C) was investigated. This integrated process consists of combining a CO methanation nickel-based catalyst with a high temperature CO2 capture sorbent in a single reactor. Integration with CO2 separation eliminates the reverse-water-gas shift and the requirement for a separate water-gas shift (WGS) unit. Easing of thermodynamic constraint offers the opportunity of enhancing yield to CH4 at higher operating temperature (500-700ºC) which also favors methanation kinetics and improves the overall process efficiency due to exploitation of reaction heat at higher temperatures. Furthermore, simultaneous CO2 capture eliminates green house gas emission. In this work, sorption-enhanced CO methanation was demonstrated using a mixture of a 68% CaO/32% MgAl2O4 sorbent and a CO methanation catalyst (Ni/Al2O3, Ni/MgAl2O4, or Ni/SiC) utilizing a syngas ratio (H2/CO) of 1, gas-hour-space velocity (GHSV) of 22 000 hr-1, pressure of 1 bar and a temperature of 600oC. These conditions resulted in ~90% yield to methane, which was maintained until the sorbent became saturated with CO2. By contrast, without the use of sorbent, equilibrium yield to methane is only 22%. Cyclic stability of the methanation catalyst and durability of the sorbent were also studied in the multiple carbonation-decarbonation cycle studies proving the potential of this integrated process in a practical application.

Lebarbier, Vanessa MC; Dagle, Robert A.; Kovarik, Libor; Albrecht, Karl O.; Li, Xiaohong S.; Li, Liyu; Taylor, Charles E.; Bao, Xinhe; Wang, Yong

2014-01-01

82

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

83

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

Microsoft Academic Search

The production of clean fuel faces the challenges of high production cost and complying with stricter environmental regulations. In this research, the ability of using a novel technology of upgrading heavy oil to treat Light Gas Oil (LGO) will be investigated. The target of this project is to produce cleaner transportation fuel with much lower cost of production. Recently, a

Abdulaziz Alghamdi

2009-01-01

84

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

SciTech Connect

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

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

1988-12-31

85

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

86

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts. Technical progress report, December 1992--February 1993  

SciTech Connect

During this quarter, high pressure (8.1 MPa) and high temperature (up to 350{degrees}C) catalytic testing was carried out with a 10 wt% cesium doped molybdenum disulfide for 188.5 hr. The doping of the catalyst was carried out under vacuum, instead of evaporating a methanolic solution of cesium formate. This procedure proved to initially provide an active catalyst, although the catalyst was not as active as previously reported [1] for a similarly prepared catalyst. Upon prolonged testing, deactivation of the catalyst was observed. Surprisingly, the selectivity pattern was reversed from that of the fresh catalyst, i.e. the alcohol synthesis selectivity increased with increasing reaction temperature rather than decreased. The causes of this deactivation and selectivity reversal have not yet been determined, but characterization studies are underway with this catalyst.

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

1993-03-01

87

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

88

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

89

Red Shift from Gravitational Back Reaction  

E-print Network

Deviations from geodesic motion caused by gravitational radiation have been discussed in the last decades to describe the motion of particles or photons in strong fields around collapsed objects. On cosmological scale this effect, which in the first order is caused by the finite speed of gravitational interaction, is important also in the weak field limit. In this paper the energy loss by transfer to the gravitational potential is determined in a quasi-Newtonian approximation for the examples of a static Einstein universe and for an expanding universe with flat metric. In both cases the resulting red shift is a considerable fraction of the total red shift and requires an adjustment of the age and the matter composition in our models of the universe.

Ernst Fischer

2007-03-30

90

Hydrogen production from a combination of the water-gas shift and redox cycle process of methane partial oxidation via lattice oxygen over LaFeO3 perovskite catalyst.  

PubMed

A redox cycle process, in which CH4 and air are periodically brought into contact with a solid oxide packed in a fixed-bed reactor, combined with the water-gas shift (WGS) reaction, is proposed for hydrogen production. The sole oxidant for partial oxidation of methane (POM) is found to be lattice oxygen instead of gaseous oxygen. A perovskite-type LaFeO3 oxide was prepared by a sol-gel method and employed as an oxygen storage material in this process. The results indicate that, under appropriate reaction conditions, methane can be oxidized to CO and H2 by the lattice oxygen of LaFeO3 perovskite oxide with a selectivity higher than 95% and the consumed lattice oxygen can be replenished in a reoxidation procedure by a redox operation. It is suggested that the POM to H2/CO by using the lattice oxygen of the oxygen storage materials instead of gaseous oxygen should be possibly applicable. The LaFeO3 perovskite oxide maintained relatively high catalytic activity and structural stability, while the carbonaceous deposits, which come from the dissociation of CH4 in the pulse reaction, occurred due to the low migration rate of lattice oxygen from the bulk toward the surface. A new dissociation-oxidation mechanism for this POM without gaseous oxygen is proposed based on the transient responses of the products checked at different surface states via both pulse reaction and switch reaction over the LaFeO3 catalyst. In the absence of gaseous-phase oxygen, the rate-determining step of methane conversion is the migration rate of lattice oxygen, but the process can be carried out in optimized cycles. The product distribution for POM over LaFeO3 catalyst in the absence of gaseous oxygen was determined by the concentration of surface oxygen, which is relevant with the migration rate of lattice oxygen from the bulk toward the surface. This process of hydrogen production via selective oxidation of methane by lattice oxygen is better in avoiding the deep oxidation (to CO2) and enhancing the selectivity. Therefore, this new route is superior to general POM in stability (resistance to carbonaceous deposition), safety (effectively avoiding accidental explosion), ease of operation and optimization, and low cost (making use of air not oxygen). PMID:17181232

Dai, Xiao Ping; Wu, Qiong; Li, Ran Jia; Yu, Chang Chun; Hao, Zheng Ping

2006-12-28

91

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

92

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

SciTech Connect

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

Paul K.T. Liu

2003-05-20

93

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

SciTech Connect

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

Paul K.T. Liu

2002-03-01

94

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

SciTech Connect

In this quarter, we have made progress in the three approaches selected for preparing CO{sub 2}-affinity membrane. A defect free nanoporous membrane was prepared via slip casting. This membrane will then be used for post treatment to seal the micropores to become a non-porous membrane with CO{sub 2} affinity. This post treatment study will be our focus in the next several quarters. Polymeric gel as a precursor was successfully prepared, which will be used for subsequent thin film deposition. Preparation of a defect-free thin film from this precursor will be our future focus using the sol-gel approach. Finally, the third approach, in-situ impregnation approach, was modified. Although we were able to deposit the precursor within the porous of the membrane, we have not been able to enhance the pH in-situ. Designing an unconventional approach to alternate the pH in-situ will be our focus of the next quarter.

Paul K. T. Liu

2003-03-14

95

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

SciTech Connect

As part of our optimization effort, we have conducted a comprehensive study to investigate the morphology and crystal growth kinetics of hydrotalcite powder formation. Based upon the information obtained from this study, we resumed the membrane optimization activities. Although the selectivity of the membrane remains in the Knudsen regime, the permeance decreases along with the number of impregnation. Thus, the permeance could be reduced to a minimum through repeated impregnation. Then, the membrane can be sealed with chemical vapor deposition technique. More characterization results on the membranes prepared will be available in the next quarterly report.

Paul K.T. Liu

2002-08-01

96

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

97

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

SciTech Connect

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

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

2010-09-30

98

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

SciTech Connect

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

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

2006-06-01

99

Electronic shift register memory based on molecular electron-transfer reactions  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

100

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

PubMed

Commercial chemiluminescent reagents emit across a broad portion of the electromagnetic spectrum (400-500?nm). A challenge to the use of chemiluminescence to monitor biological processes is the presence of interfering substances in the biological optical window. In the present study, longer wavelength emitting fluorophores (the organic dyes Alexa 568 and Alexa 647), and a semiconductor nanoparticle (QDOT800) were used to red-shift the emission from commercially available 1,2-dioxetane-based chemiluminescent substrate reactions. By adding non-conjugated fluorescent emitters into chemiluminescent reaction mixtures, an emission peak occurred at the predicted wavelength of the fluorescent emitter. The excitation and emission from QDOT800 was preserved in the presence of a 100?µm-thick glass barrier separating it from the chemiluminescent reaction components. The maximum tissue phantom penetration by QDOT800 emission was 8.5?mm; in comparison, the native chemiluminescent emission at 500?nm was unable to penetrate the thinnest tissue phantom of 2.5?mm. The described method for red-shifted emissions from chemiluminescent reactions does not require direct interaction between the chemiluminescent reaction and the fluorescent emitters. This suggests that the mechanism of chemiluminescent excitation of fluorophores and QDOT800 is not exclusive to chemiluminescence resonance energy transfer or sensitized chemiluminescence, but rather by broad energization from the native chemiluminescent emission. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24760607

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

2014-09-01

101

Comparative studies of low-temperature watergas shift reaction over Pt=CeO2, Au=CeO2,  

E-print Network

Comparative studies of low-temperature water­gas shift reaction over Pt=CeO2, Au=CeO2, and Au=Fe2O3; accepted 13 March 2003 Abstract We studied catalytic low-temperature water­gas shift (WGS) reaction over is a high temperature shift catalyst, which consists of oxides of iron and chromium and is used at 400

Gulari, Erdogan

102

ALTERNATIVE GENERATION OF H2, CO AND H2, CO2 MIXTURES FROM STEAM-CARBON DIOXIDE REFORMING OF METHANE AND THE WATER GAS SHIFT WITH PERMEABLE (MEMBRANE) REACTORS  

Microsoft Academic Search

A new process is proposed which converts CO2 and CH4 containing gas streams to synthesis gas, a mixture of CO and H2via the catalytic reaction scheme of steam-carbon dioxide reforming of methane or the respective one of only carbon dioxide reforming of methane, in permeable (membrane) reactors. The membrane reformer (permreactor) can be made by reactive or inert materials such

SAVVAS VASILEIADIS; ZOE ZIAKA

1999-01-01

103

Nonclassical aryl radicals: Intermediates or transition states for the hydrogen shift reactions?  

SciTech Connect

Electronic properties of aryl radicals obtained by removing single hydrogen atoms from the sterically congested regions of benzo[c]phenanthrene, biphenyl, triphenylene, phenanthrene, and perylene are studied at the UBLYP/6-311G** level of theory. Two structures are considered by each radical, the classical one involving a C-H{hor_ellipsis}C arrangement of atoms and the nonclassical one possessing a three-center C-H-C linkage. The five nonclassical radicals under study are found to be transition states for degenerate 1,4- and 1,5-hydrogen shift reactions that interconvert the classical species. However, the results of the present calculations indicate that the nonclassical structures with the C-H distances in the C-H-C linkages shorter than 1.34 {angstrom} should be energy minima representing potentially observable chemical systems. The predicted energy barrier to the 1,5-hydrogen shift in the 1-benzo[c]phenanthrenyl radical is only 9.3 kcal/mol with the zero-point energies included, making the hydrogen migration in this system facile at relatively low temperatures. Rigorous analysis of the computed electronic wave functions provides a clear-cut picture of bonding in both the classical and nonclassical aryl radicals. 2 figs., 4 tabs.

Cioslowski, J.; Liu, G.; Moncrieff, D. [Florida State Univ., Tallahassee, FL (United States)] [Florida State Univ., Tallahassee, FL (United States)

1996-06-14

104

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

2013-09-26

105

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

E-print Network

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

Gao, Hongjun

106

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

107

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

108

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts  

Microsoft Academic Search

During this quarter, high pressure (8.1 MPa) and high temperature (up to 350[degrees]C) catalytic testing was carried out with a 10 wt% cesium doped molybdenum disulfide for 188.5 hr. The doping of the catalyst was carried out under vacuum, instead of evaporating a methanolic solution of cesium formate. This procedure proved to initially provide an active catalyst, although the catalyst

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

1993-01-01

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

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

111

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

112

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

113

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

E-print Network

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

Myagmarjav Odsuren; Kiyoshi Kato; Masayuki Aikawa; Takayuki Myo

2014-03-21

114

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

E-print Network

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

Odsuren, Myagmarjav; Aikawa, Masayuki; Myo, Takayuki

2014-01-01

115

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

NASA Astrophysics Data System (ADS)

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

Odsuren, Myagmarjav; Kat?, Kiyoshi; Aikawa, Masayuki; Myo, Takayuki

2014-03-01

116

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

117

Kinetic analysis of the phenyl-shift reaction in $\\beta$-O-4 lignin model compounds: A computational study.  

SciTech Connect

The phenyl-shift reaction in $\\beta$-phenethyl phenyl ether ($\\beta - \\rm PhCH_2CH_2OPh$, $\\beta$-PPE) is an integral step in the pyrolysis of PPE, which is a model compound for the $\\beta$-O-4 linkage in lignin. We investigated the influence of natural occurring substituents (hydroxy, methoxy) on the reaction rate by calculating relative rate constant using density functional theory in combination with transition state theory, including anharmonic correction for low-frequency modes. The phenyl-shift reaction proceeds through an intermediate and the overall rate constants were computed invoking the steady-state approximation (its validity was confirmed). Substituents on the phenethyl group have only little influence on the rate constants. If a methoxy substituent is located in para position of the phenyl ring adjacent to the ether oxygen, the energies of the intermediate and second transition state are lowered, but the overall rate constant is not significantly altered. This is a consequence of the dominating first transition from pre-complex to intermediate in the overall rate constant. {\\it O}- and di-{\\it o}-methoxy substituents accelerate the phenyl-migration rate compared to $\\beta$-PPE.

Beste, Ariana [ORNL; Buchanan III, A C [ORNL

2011-01-01

118

Deuterium studies reveal a new mechanism for the formose reaction involving hydride shifts.  

PubMed

In the formose reaction, formaldehyde is converted to glycolaldehyde, its dimer, under credible prebiotic conditions. Breslow proposed a mechanism for the process in 1959, but recent studies by Benner showed that it was wrong in detail. Our present studies clarify the mechanism, which involves the original Breslow intermediates but some different connecting steps. PMID:24575857

Appayee, Chandrakumar; Breslow, Ronald

2014-03-12

119

Water Gas and Ice in Protostellar Envelopes  

NASA Astrophysics Data System (ADS)

Infrared-bright protostars form a unique class of sources for which both water gas and ice can be observed. We introduce a Simplified Water Network (SWaN) to model the data and test it against full gas-grain models as well as Herschel-HIFI spectra of a Class 0 protostar. The combined Herschel-HIFI and Spitzer/VLT data on nine sources are then compared and analysed using SWaN, giving typical ice/gas ratios of 1e3 at the core edge and up to 1e7 deeper into the core. A quantification of the oxygen budget reveals that a large fraction of the oxygen is still unidentified.

Schmalzl, Markus; van Dishoeck, Ewine; Mottram, Joseph; Visser, Ruud; Kristensen, Lars; Albertsson, Tobias; Walsh, Catherine

2013-07-01

120

WGS reaction in a membrane reactor using a porous stainless steel supported silica membrane  

Microsoft Academic Search

Water gas shift reaction for hydrogen production was studied in a catalytic membrane reactor using a supported silica membrane at 220–290°C temperature and 2–6bar pressure ranges. A CO conversion higher than the thermodynamic equilibrium of a traditional reactor was obtained. The best result, 95% CO conversion, was achieved at 4bar and 280°C.The membrane was also characterized in terms of permeance

A. Brunetti; G. Barbieri; E. Drioli; K.-H. Lee; B. Sea; D.-W. Lee

2007-01-01

121

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)] [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322 (United States)

1999-03-01

122

Nonseparable transition state theory for nonzero total angular momentum: Implications for J shifting and application to the OH+H2 reaction  

NASA Astrophysics Data System (ADS)

We report vibration/rotation energies of the OHH2 transition state using the code ``Multimode,'' 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 J-shifting calculations of the thermal rate constant for the reaction OH+H2-->H2O+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. 99, 10078 (1993); 101, 4759 (1994)]. Comparisons with previous J-shifting and recent centrifugal sudden calculations of the rate constant [D. H. Zhang, J. C. Light, and S-Y. Lee, J. Chem. Phys. 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 J-shifting calculations. Finally, an assessment of Coriolis coupling is made.

Bowman, Joel M.; Shnider, Heather M.

1999-03-01

123

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

E-print Network

on triangular reaction path which assumes a direct interconversion between o- and p-xylene isomers (1,3-methyl-xylene p-xylene). The rate constants and activation energies are obtained from simplified kinetic models. The results provide ample evidence to suggest that direct interconversion between o- and p-xylene isomers (a 1

Al-Khattaf, Sulaiman

124

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

E-print Network

of the kinetic group for their constant support. Vii TABLE OF CONTENTS CHAPTER PAGE I INTRODUCTION II LITERATURE REVIEW III EXPERIMENTAL APPARATUS Feea System Fixea Bed Reactor Sample Collection System Isothermal Bath and Temperature Control 30 30 32... I ill I. -'I c, p C a~ . vnv v av ~J molybdate catalyst containing 2. 4 '4 Co and 6. 7 0 No Conversion data were obtained with a steaoy state flow reactor packed with particles of a commercial cobalt molybdate catalyst. Givens and Venuto (1970...

Kumar, Meyyappan

2012-06-07

125

CERIA-BASED WATER-GAS-SHIFT CATALYSTS S. Swartz, A-M. Azad, M. Seabaugh  

E-print Network

catalysts based on ceria-supported precious metals. Our work has demonstrated that Pt/ceria catalysts offer on the WGS performance of ceria-supported precious metal catalysts, with widely varying results [1 of mechanisms: over-reduction of ceria, build-up of carbonaceous species on the catalyst, and loss of precious

Azad, Abdul-Majeed

126

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

PubMed

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

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

2014-10-01

127

Effect of time pressure on attentional shift and anticipatory postural control during unilateral shoulder abduction reactions in an oddball-like paradigm  

PubMed Central

Background The effect of time pressure on attentional shift and anticipatory postural control was investigated during unilateral shoulder abduction reactions in an oddball-like paradigm. Methods A cue signal (S1) - imperative signal (S2) sequence was repeated with various S2-S1 intervals (1.0, 1.5, and 2.0 s). S2 comprised target and non-target stimuli presented at the position (9° to the left or the right) indicated by S1. Right shoulder abduction was performed only in response to target stimuli, which were presented with a 30% probability. The P1, N1, N2, and P3 components of event-related potentials were analyzed, and onset times of postural muscles (electromyographic activity of erector spinae and gluteus medius) were quantified with respect to middle deltoid activation. Results There was no significant effect of S2-S1 interval on the latency or amplitude of P1, N1, or N2. The percentage of subjects with bimodal P3 peaks was significantly smaller and the slope of the P3 waveform in the 100 ms after the first peak was significantly steeper with a 1.0-s S2-S1 interval than with a 1.5- or 2.0-s S2-S1 interval. The onset of postural muscle activity was significantly later in the shorter interval conditions. Conclusions These results suggest that with a shorter S2-S1 interval, that is, higher time pressure, attention was allocated to hasten the latter part of cognitive processing that may relate to attentional shift from S2 to next S1, which led to insufficient postural preparation associated with arm movement and anticipatory attention directed to S2. PMID:24968935

2014-01-01

128

Investigation of dispersed iron alloy catalysts in the carbon monoxide-hydrogen synthesis reaction. Progress report, August 1, 1980-July 31, 1981  

SciTech Connect

The past year has seen completion of two major tasks in the research program: (1) a detailed study of the characterization of particle size in supported ..cap alpha..-Fe/sub 2/O/sub 3/ and related characterizations of the reduced metal with silica gel support; (2) a reaction study of a series of silica supported Fe-Ni, Fe-Co, Fe-Cu, Fe-K and the corresponding pure metals. Synthesis activity and selectivity were particular objectives of this work, and a particular correlation of the conversion dependence of selectivity and water-gas shift activity was observed. We feel this to be an important finding: the catalysts which are good water-gas shift catalysts are the ones which are inhibited during the synthesis. A mechanism of product inhibition by water formation has been proposed to explain the conversion dependence of selectivity.

Butt, J.B.; Schwartz, L.H.

1981-04-01

129

Carburization of steels in a circulatory system using water-gas atmospheres  

Microsoft Academic Search

In order to economize on raw materials for producing controlled atmospheres and to avoid the air pollution caused by exhausted\\u000a atmospheres, the feasibility of carburizing steel by using recirculated water-gas atmospheres was investigated. Water-gas\\u000a was generated in a closed system and an open system respectively, and steel samples were heated under the water-gas atmospheres.\\u000a Based on the heating results of

Y. C. Chen; G. S. Lu

1992-01-01

130

Numerical Simulation of Water--Gas Flow and Transport Processes in Coastal Aquifers  

E-print Network

Numerical Simulation of Water--Gas Flow and Transport Processes in Coastal Aquifers Reinhard processes as supposed before. If methane occurs as a gas phase, it has a significant influence on the results. KEY WORDS: water--gas flow, methane migration, multiphase / multicomponent model 1. INTRODUCTION

Cirpka, Olaf Arie

131

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

PubMed

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

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

2014-12-01

132

Stick shift  

E-print Network

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

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

2004-01-01

133

Sulfur tolerant metal doped Fe\\/Ce catalysts for high temperature WGS reaction at low steam to CO ratios – XPS and Mössbauer spectroscopic study  

Microsoft Academic Search

High temperature water gas shift reaction (WGS) at low steam to CO ratios has been investigated over Fe2.4Ce0.3M0.3O4 (M=Cr, Co, Zr, Hf, and Mo) type of spinels in the temperature region of 400–550°C and in the presence of sulfur. Remarkably, both Cr- and Co-doped Fe\\/Ce catalysts show excellent activity at steam to CO ratio as low as 1.5. Other dopants

Gunugunuri K. Reddy; P. Boolchand; Panagiotis G. Smirniotis

2011-01-01

134

Fluid Shifts  

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

135

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

136

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

137

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

138

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

139

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

140

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts. Technical progress report, December 1992February 1993  

Microsoft Academic Search

During this quarter, high pressure (8.1 MPa) and high temperature (up to 350°C) catalytic testing was carried out with a 10 wt% cesium doped molybdenum disulfide for 188.5 hr. The doping of the catalyst was carried out under vacuum, instead of evaporating a methanolic solution of cesium formate. This procedure proved to initially provide an active catalyst, although the catalyst

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

1993-01-01

141

Ethanol synthesis and water gas shift over bifunctional sulfide catalysts. Technical progress report, December 1993--February 1994  

SciTech Connect

During this quarter, a 10 wt % CsOOCH/MoS{sub 2} catalyst was prepared for catalytic testing using slight modifications of previous attempted preparations. The MoS{sub 2} was prepared from MoS{sub 3} via thermal decomposition. The resultant product was then doped using an aqueous solution of cesium formate under vacuum. The doped catalyst was then loaded into a single pass fixed-bed tubular flow reactor under nitrogen to minimize exposure to air. The catalyst was pretreated with 2 vol % H{sub 2}/98 vol % N{sub 2} at 400C and then tested at 8.3 MPa at 245, 256, 265, 175, and 295C for a total of 168 hours. The catalyst displayed the activity and selectivity similar to that of previous workers. The surface areas of the doped and undoped catalysts were also determined.

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

1994-04-01

142

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

Microsoft Academic Search

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 Hâ\\/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

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

1993-01-01

143

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

Microsoft Academic Search

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\\/MoSâ 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

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

1994-01-01

144

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

145

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

146

CHLORIDE POISONING OF WATER GAS SHIFT ACTIVITY ON NICKEL CATALYSTS DURING STEAM REFORMING. (R822721C633)  

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

147

CHLORIDE POISONING OF WATER GAS SHIFT ACTIVITY ON NICKEL CATALYSTS DURING STEAM REFORMING. (R826694C633)  

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

148

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

DOEpatents

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

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

1980-01-01

149

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

PubMed

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

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

2014-02-01

150

Laboratory support for in situ gasification: reaction kinetics. Annual report October 1977-September 1978  

SciTech Connect

This work is directed toward support studies for the national program for the development and demonstration of in situ coal gasification processes. The objective of this work is to determine the reaction-controlling variables and reaction kinetics for the gasification of chars obtained by pyrolyzing coal in simulated underground gasification conditions. The reactions being studied and to be studied include steam-char, CO/sub 2/-char, H/sub 2/-char, the water-gas shift reaction, and the methanation reaction. In this report are presented data regarding the kinetics of the reaction of steam with chars prepared from Pittsburgh seam high-volatile bituminous coal. In addition, a reaction model is described correlating the steam-char reaction rates measured earlier for Hanna subbituminous coal with operating conditions including temperature, partial pressures of steam and hydrogen, and extent of carbon gasification. Partial results are presented and discussed for an investigation of structural parameters of Hanna char as a function of pyrolysis conditions and extent of carbon gasified.

Young, J.E.; Wong, S.H.; Johnson, J.E.; Sikand, N.; Jonke, A.A.

1980-02-01

151

THE EFFECT OF WATER-GAS TAR ON OYSTERS By Philip H. Mitchell  

E-print Network

of Fisheries at Woods Hole could not then be carried further. The tar was obtained from the separator taken under comparable conditions from the same separator at another time showed, according in these experiments, and weighing 83.2 grams, was put into a battery jar with 40 c. c. of water-gas tar and 2,500 c. c

152

On Factors Controlling AirWater Gas Exchange in a Large Tidal River  

E-print Network

and estuaries. Here, we present gas transfer velocities measured in the tidal Hudson River with a method widely that wind is the dominant driver of gas exchange in the tidal Hudson River, with negligible contribution variables and gas exchange in tidal inland waters. Keywords Air­water gas exchange . 3 He/SF6 . Hudson River

Ho, David

153

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

E-print Network

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

Jaehne, Bernd

154

Observation of a short, strong hydrogen bond in the active site of hydroxynitrile lyase from Hevea brasiliensis explains a large pKa shift of the catalytic base induced by the reaction intermediate.  

PubMed

The hydroxynitrile lyase from Hevea brasiliensis (HbHNL) uses a catalytic triad consisting of Ser(80)-His(235)-Asp(207) to enhance the basicity of Ser(80)-O gamma for abstracting a proton from the OH group of the substrate cyanohydrin. Following the observation of a relatively short distance between a carboxyl oxygen of Asp(207) and the N delta(1)(His(235)) in a 1.1 A crystal structure of HbHNL, we here show by (1)H and (15)N-NMR spectroscopy that a short, strong hydrogen bond (SSHB) is formed between the two residues upon binding of the competitive inhibitor thiocyanate to HbHNL: the proton resonance of H-N delta 1(His(235)) moves from 15.41 ppm in the free enzyme to 19.35 ppm in the complex, the largest downfield shift observed so far upon inhibitor binding. Simultaneously, the D/H fractionation factor decreases from 0.98 to 0.35. In the observable pH range, i.e. between pH 4 and 10, no significant changes in chemical shifts (and therefore hydrogen bond strength) were observed for free HbHNL. For the complex with thiocyanate, the 19.35 ppm signal returned to 15.41 ppm at approximately pH 8, which indicates a pK(a) near this value for the H-N epsilon(2)(His(235)). These NMR results were analyzed on the basis of finite difference Poisson-Boltzmann calculations, which yielded the relative free energies of four protonation states of the His(235)-Asp(207) pair in solution as well as in the protein environment with and without bound inhibitor. The calculations explain all the NMR features, i.e. they suggest why a short, strong hydrogen bond is formed upon inhibitor binding and why this short, strong hydrogen bond reverts back to a normal one at approximately pH 8. Importantly, the computations also yield a shift of the free energy of the anionic state relative to the zwitterionic reference state by about 10.6 kcal/mol, equivalent to a shift in the apparent pK(a) of His(235) from 2.5 to 10. This huge inhibitor-induced increase in basicity is a prerequisite for His(235) to act as general base in the HbHNL-catalyzed cyanohydrin reaction. PMID:14597632

Stranzl, Gudrun R; Gruber, Karl; Steinkellner, Georg; Zangger, Klaus; Schwab, Helmut; Kratky, Christoph

2004-01-30

155

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

E-print Network

AIR-WATER GAS EXCHANGE: MECHANISMS GOVERNING THE COMBINED EFFECTS OF WIND AND RAIN ON THE GAS at the Florida International University for water sample analysis during the Everglades experiment presented here, rain and iv #12;their effects on air-water gas and momentum exchanges. Funding for the Everglades

Luther, Douglas S.

156

First Principles (DFT) Characterization of Rh(I) /dppp-Catalyzed C?H Activation by Tandem 1,2-Addition/1,4-Rh Shift Reactions of Norbornene to Phenylboronic Acid.  

PubMed

The C?H activation in the tandem, "merry-go-round", [(dppp)Rh]-catalyzed (dppp=1,3-bis(diphenylphosphino)propane), four-fold addition of norborene to PhB(OH)2 has been postulated to occur by a C(alkyl)?H oxidative addition to square-pyramidal Rh(III) ?H species, which in turn undergoes a C(aryl)?H reductive elimination. Our DFT calculations confirm the Rh(I) /Rh(III) mechanism. At the IEFPCM(toluene, 373.15?K)/PBE0/DGDZVP level of theory, the oxidative addition barrier was calculated to be 12.9?kcal?mol(-1) , and that of reductive elimination was 5.0?kcal?mol(-1) . The observed selectivity of the reaction correlates well with the relative energy barriers of the cycle steps. The higher barrier (20.9?kcal?mol(-1) ) for norbornyl-Rh protonation ensures that the reaction is steered towards the 1,4-shift (total barrier of 16.3?kcal?mol(-1) ), acting as an equilibration shuttle. The carborhodation (13.2?kcal?mol(-1) ) proceeds through a lower barrier than the protonation (16.7?kcal?mol(-1) ) of the rearranged aryl-Rh species in the absence of o- or m-substituents, ensuring multiple carborhodations take place. However, for 2,5-dimethylphenyl, which was used as a model substrate, the barrier for carborhodation is increased to 19.4?kcal?mol(-1) , explaining the observed termination of the reaction at 1,2,3,4-tetra(exo-norborn-2-yl)benzene. Finally, calculations with (Z)-2-butene gave a carborhodation barrier of 20.2?kcal?mol(-1) , suggesting that carborhodation of non-strained, open-chain substrates would be disfavored relative to protonation. PMID:25264169

Kantchev, Eric Assen B; Pangestu, Surya R; Zhou, Feng; Sullivan, Michael B; Su, Hai-Bin

2014-11-17

157

Double Shift Evaluation: Student Questionnaire.  

ERIC Educational Resources Information Center

This 15-item student questionnaire is part of a study conducted in the Springfield, Illinois high schools to evaluate the double shift scheduling program instituted there. Students' reactions and opinions concerning the new scheduling technique are elicited by the forced-choice and open-ended items. See also TM 000 881-882, 884 for information on…

Springfield School District 186, IL.

158

Double Shift Evaluation: Parent Questionnaire.  

ERIC Educational Resources Information Center

This 13-item parent questionnaire is part of a study conducted in the Springfield, Illinois high schools to evaluate the double shift scheduling program instituted there. Parents' reactions and opinions concerning the new scheduling technique are determined by a combination of forced-choice and open-ended questions. See also TM 000 881, 883-884…

Springfield School District 186, IL.

159

Double Shift Evaluation: Faculty Questionnaire.  

ERIC Educational Resources Information Center

This 32-item faculty questionnaire is part of a study conducted in the Springfield, Illinois high schools to evaluate the double shift scheduling program instituted there. Teachers' reactions and opinions on the new scheduling technique are determined by the forced-choice and open-ended items. See also TM 000 881-883 for information on the study,…

Springfield School District 186, IL.

160

Development of a zero-emissions sulfur-recovery process: 1. Thermochemistry and reaction kinetics of mixtures of H[sub 2]S and CO[sub 2] at high temperature  

SciTech Connect

When hydrogen sulfide is heated above 600 C in the presence of carbon dioxide, the conversion of H[sub 2]S to elemental sulfur is greater than when hydrogen sulfide is heated alone. Formation of elemental sulfur is favored by high temperature, low pressure, and low water content in the gas. The rate-limiting step is the thermal dissociation of H[sub 2]S. The hydrogen then equilibrates rapidly with CO[sub 2], forming CO and H[sub 2]O via the water-gas-shift reaction. The equilibrium of H[sub 2]S dissociation is therefore shifted to favor the formation of elemental sulfur. The main byproduct is COS, which is formed by a reaction between CO[sub 2] and H[sub 2]S that is analogous to the water-gas-shift reaction. A quench rate of 1,000 C/s or greater is sufficient to prevent loss of elemental sulfur by back-reaction or reaction to COS during cooling. Formation of small amounts Of SO[sub 2] and CS[sub 2] is thermodynamically feasible but has not been observed. Molybdenum disulfide is the best catalyst for H[sub 2]S dissociation of those discussed in the literature. A process based on this chemistry has significant advantages over the Claus process in that it need not produce any tail gas, it allows recovery of the chemical (or fuel) value of the hydrogen from the H[sub 2]S, and it requires much less stringent process control.

Towler, G.P.; Lynn, S. (Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering)

1993-11-01

161

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

NASA Astrophysics Data System (ADS)

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

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

2003-11-01

162

Molecular implementation of molecular shift register memories  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

163

Chemical shifts in biomolecules  

PubMed Central

Summary NMR chemical shifts are sensitive probes of stucture and dynamics in proteins. Empirical models, based on a large database of measured shifts, take an input structure and provide increasingly accurate estimates of the corresponding shifts. Quantum chemical calculations can provide the same information, with greater generality but (currently) with less accuracy. These methods are now providing new ways to approach NMR structure determination, and new insights into the conformational dynamics of proteins. PMID:23422068

Case, David A.

2013-01-01

164

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

165

B.Jhne and E. Monahan (eds.), Air-Water GasTransfer, 1995 by AEON Verlag I Physical and Chemical Mechanisms  

E-print Network

Modelling of Interfacial Gas-Liquid Mass Transfer C. R. Chu G. H. Jirka Reaeration in Combined Wind/Stream and Bubbles The Influence of Bubbles on Air-Water Gas Exchange: Results from Gas Transfer Experi- ments duringB.Jähne and E. Monahan (eds.), Air-Water GasTransfer, © 1995 by AEON Verlag I Physical and Chemical

Jaehne, Bernd

166

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

SciTech Connect

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

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

1996-10-01

167

In-water gas combustion in linear and annular gas bubbles  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

168

An ENSO shift revisited  

NASA Astrophysics Data System (ADS)

An influential 1996 paper presented a statistical analysis showing that the prolonged ENSO warm event of the early 1990's was inconsistent with the historical pattern of ENSO variability and therefore concluded that there had been a shift in ENSO behavior possibly connected to global warming. A fundamental problem with this earlier analysis is that the data used to test for a shift in ENSO behavior were not independent of the data used to identify the hypothetical shift. A new analysis is presented that avoids this problem by using more recent data. The results raise a question about the earlier finding.

Solow, Andrew R.

2006-11-01

169

Our World: Fluid Shift  

NASA Video Gallery

Learn about the circulatory system and how gravity aids blood flow in our bodies here on Earth. Find out how NASA flight surgeons help the astronauts deal with the fluid shift that happens during s...

170

Protein Chemical Shift Prediction  

E-print Network

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

Larsen, Anders S

2014-01-01

171

Thermochromic Shifts in Supercritical Fluids.  

National Technical Information Service (NTIS)

Thermochromic shifts of organic solute molecules in supercritical Co2 under conditions of both constant pressure and density are compared to previous studies of solvatochromic shifts at isothermal conditions. Similar solvatochromic and thermochromic shift...

C. R. Yonker, R. D. Smith

1989-01-01

172

Transition to 12-hour shifts - The process and the product  

Microsoft Academic Search

This paper examines Yankee Atomic Electric Company's (YAEC's) transition to a 12-h shift schedule for the operations department staff. It presents the approach to implementation, reactions of both shift workers and management to the new schedule (including perceived benefits and shortcomings), and provides recommendations to others considering this change. Experience demonstrates the ease of any transition when the desire for

Suter

1992-01-01

173

Shifts that divide populations  

NASA Astrophysics Data System (ADS)

If fitness landscape is non-concave, And the shift is wide, Then there is a good chance That population would divide. How does a population of organisms in an ecosystem respond to shifts in the environment? Answers to this question are critical to our understanding of the ecosystem and thus ability to manage it toward more desirable outcomes. We have developed a model of adaptation, based on replicator dynamics, in which we derive a simple but insightful threshold condition that separates two important types of responses: 'cohesive transition' in which the whole population changes gradually together, and 'population-dividing transition' in which the population splits into two groups with one eventually dominating the other. The threshold depends on the magnitude of the shift and the shape of the fitness landscape. Division in populations can fundamentally alter the functioning of the system; knowing the condition that gives rise to such division is thus fundamentally important.

Muneepeerakul, R.; Qubbaj, M. R.; Aggarwal, R.; Anderies, J. M.; Janssen, M. A.

2013-12-01

174

Bedside shift-to-shift nursing report: implementation and outcomes.  

PubMed

One unit's staff developed and evaluated an intervention to relocate shift-to-shift nursing report to the patient's bedside. Despite challenges related to privacy, distractions, and integration of nursing technicians to the change, bedside shift report reduced shift report times and improved nursing satisfaction. PMID:23243785

Evans, Deby; Grunawalt, Julie; McClish, Donna; Wood, Winnie; Friese, Christopher R

2012-01-01

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

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

177

Shifts that divide population  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

178

Ambiguous Red Shifts  

E-print Network

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

Carl E. Wulfman

2010-10-11

179

Shifted reference holographic interferometry.  

PubMed

Conventional holographic interferometry of vibrating objects yields reconstructed images in which the radiance of each point is proportional to the square of the zero-order Bessel function of an argument proportional to the vibration amplitude. Therefore, the vibration pattern appears as a dark outline on the bright background of the nonvibrating points. By appropriately shifting the frequency of the reference radiation used in the recording of the hologram, the radiance of each image point can be made proportional to the square of the first-order Bessel function of the above argument. Nonvibrating points are therefore black and vibrating points appear bright on a black background. A quantitative analysis of the technique is reviewed and extended and shows the shifted-reference method to be almost one order of magnitude more sensitive than the conventional method. Experimental verification of the theory is presented and some possible future applications are indicated. PMID:20125577

Zambuto, M H; Fischer, W K

1973-07-01

180

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

2010-04-26

181

The amazing shift.  

PubMed

Some learn by hearing. Some learn by seeing. We all learn by doing. In an effort to creatively integrate skills evaluation and critical thinking in our new nurses, we developed an educational offering entitled "The Amazing Shift." In this activity, small teams of graduate nurses in our medical-surgical residency are tasked with managing simulated patient scenarios within specific time constraints, similar to managing a multipatient assignment on their unit. This "low-tech" approach has consistently been selected as one of the most meaningful classroom-based activities by the participants. PMID:25237923

Elledge, Carole M

2014-01-01

182

STEM Colorado: Doppler Shift  

NSDL National Science Digital Library

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

Mccray, Richard; Koelemay, Andrew

2008-08-30

183

Transitioning to 12-hour shifts  

Microsoft Academic Search

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

P. S. Suter; S. M. Cervassi

1993-01-01

184

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

185

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

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.

Sommargren, Gary E. (Santa Cruz, CA)

1996-01-01

187

Phase shifting interferometer  

DOEpatents

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

Sommargren, Gary E. (Santa Cruz, CA)

1999-01-01

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

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

190

Seasonal microbial community shift in a saline sewage treatment plant  

Microsoft Academic Search

Activated sludge was monthly sampled from a saline sewage treatment plant of Hong Kong (China) during June 2007 to May 2008\\u000a to analyze the microbial community shift along with environmental variations using denaturing gradient gel electrophoresis\\u000a of polymerase chain reaction amplified 16S rDNA fragments. Environmental changes resulted into a seasonal microbial community\\u000a shift characterized by alterations in species number and

Qingmei Yan; Xuxiang Zhang; Tong Zhang; Herbert H. P. Fang

2011-01-01

191

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

PubMed

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

Li, Shuirong; Gong, Jinlong

2014-11-01

192

[Characteristics of water-gas two-phase CO2 transport in unsaturated zone].  

PubMed

The migration of CO2 in soil was simulated through use of soil column, especially the transformation of CO2 between water and gas phases at wetting front was studied. The soil column in the test was 1 m long and the concentration of CO2 solution was 748 mg/L. Through analysis, it was shown that CO2 migration in water phase was governed by advection, dispersion, reaction and mass transfer between water and gas phases, that in gas phase by advection, dispersion, mass transfer between two phases. Sampling method under dynamic condition of two phase flow in soil column was approached and mass transfer coefficient from water phase to gas phase was determined as 0.00061. This showed that there was certain mass transformation of CO2 from water phase to gas phase and yet it was not so significant. This study can provide the quantitative scientific bases for safety assessment of geological disposal of low and intermediate level radioactive waste and environmental impact assessment of solid waste disposal by landfilling. PMID:14551970

Yu, Yanxin; Chen, Jiajun; Wang, Jinsheng; Yun, Ying; Li, Shushen; Wang, Zhiming

2003-07-01

193

Chemical shift imaging: a review.  

PubMed

Chemical shift is the phenomenon that is seen when an isotope possessing a nuclear magnetic dipole moment resonates at a spectrum of resonance frequencies in a given magnetic field. These resonance frequencies, or chemical shifts, depend on the chemical environments of particular nuclei. Mapping the spatial distribution of nuclei associated with a particular chemical shift (e.g., hydrogen nuclei associated with water molecules or with lipid groups) is called chemical shift imaging. Several techniques of proton chemical shift imaging that have been applied in vivo are presented, and their clinical findings are reported and summarized. Acquiring high-resolution spectra for large numbers of volume elements in two or three dimensions may be prohibitive because of time constraints, but other methods of imaging lipid of water distributions (i.e., selective excitation, selective saturation, or variations in conventional magnetic resonance imaging pulse sequences) can provide chemical shift information. These techniques require less time, but they lack spectral information. Since fat deposition seen by chemical shift imaging may not be demonstrated by conventional magnetic resonance imaging, certain applications of chemical shift imaging, such as in the determination of fatty liver disease, have greater diagnostic utility than conventional magnetic resonance imaging. Furthermore, edge artifacts caused by chemical shift effects can be eliminated by certain selective methods of data acquisition employed in chemical shift imaging. PMID:3008543

Brateman, L

1986-05-01

194

Theoretical investigation of Stokes shifts and reaction pathways  

E-print Network

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

Top, Laken M. (Laken Michelle)

2012-01-01

195

Reactions involving shifting of the double bond in cyclic ethers  

SciTech Connect

4-Methylenetetrahydropyran undergoes isomerization to 4-methyl-5,6-dihydropyran in the presence of sodium on aluminum oxide. Both pyrans are converted to a vinyl ether, viz., 4-methyl-2,3-dihydropyran, under the influence of iron pentacarbonyl.

Ibatullin, U.G.; Petrushina, T.F.; Akhmadeeva, A.A.; Safarov, M.G.

1985-09-01

196

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

197

Rate constant for OH,,2 ... reaction  

E-print Network

. The title reaction is exothermic by 16.7 kcal/mol and its rate constant is decidedly nonRate constant for OH,,2 ...+O,,3 P...\\H,,2 S...+O2,,3 g - ... reaction on an improved ab initio and the rate constant for the title reaction was obtained using a J-shifting method. The calculated rate

Honvault, Pascal

198

Shift scheduling for tank trucks  

Microsoft Academic Search

In this paper we deal with shift scheduling of tank trucks for a small oil company. Given are a set of tank trucks with different characteristics and a set of drivers with different skills. The objective is to assign a feasible driver to every shift of the tank trucks such that legal and safety restrictions are satisfied, the total working

Sigrid Knust; Elisabeth Schumacher

2011-01-01

199

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

SciTech Connect

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

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

2013-01-01

200

Can small shifts in circadian phase affect performance?  

PubMed Central

Small shifts in circadian timing occur frequently as a result of daylight saving time or later weekend sleep. These subtle shifts in circadian phase have been shown to influence subjective sleepiness, but it remains unclear if they can significantly affect performance. In a retrospective analysis we examined performance on the Psychomotor Vigilance Test before bedtime and after wake time in 11 healthy adults on fixed sleep schedules based on their habitual sleep times. The dim light melatonin onset, a marker of circadian timing, was measured on two occasions. An average 1.1 hour shift away from a proposed optimal circadian phase angle (6 hours between melatonin onset and midpoint of sleep) significantly slowed mean, median and fastest 10% reaction times before bedtime and after wake time (p<0.05). These results add to previous reports that suggest that humans may be sensitive to commonly occurring small shifts in circadian timing. PMID:22695081

Burgess, Helen J.; Legasto, Carlo S.; Fogg, Louis F.; Smith, Mark R.

2012-01-01

201

Marine biological shifts and climate.  

PubMed

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

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

2014-05-22

202

Unbiased shifts of Brownian motion  

E-print Network

Let $B=(B_t)_{t\\in\\R}$ be a two-sided standard Brownian motion. An \\emph{unbiased shift} of $B$ is a random time $T$, which is a measurable function of $B$, such that $(B_{T+t}-B_T)_{t\\in\\R}$ is a Brownian motion independent of $B_T$. We characterise unbiased shifts in terms of allocation rules balancing additive functionals of $B$. For any probability distribution $\

Last, Günter; Thorisson, Hermann

2011-01-01

203

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

204

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

E-print Network

the geothermal reservoir rocks. Initial simulation resultssimulation program for non- isothermal multiphase reactive geochemical transport in variably saturated geologic media: Applications to geothermalsimulations of the interactions between injectate water and the mineral, gas, and steam phases present in the geothermal

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

2006-01-01

205

Calculation of isotope shifts and relativistic shifts in C I, C II, C III, and C IV  

SciTech Connect

We present an accurate ab initio method of calculating isotope shifts and relativistic shifts in atomic spectra. We test the method on neutral carbon and three carbon ions. The relativistic shift of carbon lines may allow them to be included in analyses of quasar absorption spectra that seek to measure possible variations in the fine structure constant {alpha} over the lifetime of the Universe. Carbon isotope shifts can be used to measure isotope abundances in gas clouds: isotope abundances are potentially an important source of systematic error in the {alpha}-variation studies. These abundances are also needed to study nuclear reactions in stars and supernovae, and test models of chemical evolution of the Universe.

Berengut, J. C.; Flambaum, V. V.; Kozlov, M. G. [School of Physics, University of New South Wales, Sydney 2052 (Australia); School of Physics, University of New South Wales, Sydney 2052 (Australia) and Physics Division, Argonne National Laboratory, Argonne, Illinois 60439-4843 (United States); Petersburg Nuclear Physics Institute, Gatchina, 188300 (Russian Federation)

2006-01-15

206

Cultural shifts: humanities to science to computation R.W. Oldford  

E-print Network

actively participated in this shift. The natural reaction of the student body is to pursue perceived youthful strength and insecurity, wants recognition from the established `intellectuals'. To me, this seems

Oldford, R.W.

207

Metabolic impact of shift work.  

PubMed

In developing countries, shift work represents a considerable contingent workforce. Recently, studies have shown that overweight and obesity are more prevalent in shift workers than day workers. In addition, shift work has been associated with a higher propensity for the development of many metabolic disorders, such as insulin resistance, diabetes, dislipidemias and metabolic syndrome. Recent data have pointed that decrease of the sleep time, desynchronization of circadian rhythm and alteration of environmental aspects are the main factors related to such problems. Shortened or disturbed sleep is among the most common health-related effects of shift work. The plausible physiological and biological mechanisms are related to the activation of the autonomic nervous system, inflammation, changes in lipid and glucose metabolism, and related changes in the risk for atherosclerosis, metabolic syndrome, and type II diabetes. The present review will discuss the impact of shift work on obesity and metabolic disorders and how disruption of sleep and circadian misalignment may contribute to these metabolic dysfunctions. PMID:22317392

Zimberg, Ioná Zalcman; Fernandes Junior, Silvio A; Crispim, Cibele Aparecida; Tufik, Sergio; de Mello, Marco Tulio

2012-01-01

208

Color shifts following rapid eye movements  

Microsoft Academic Search

Measured the color shifts induced by saccades for spectral lights ranging from 450-650 normal modulation. Results from 2 Os show changes in hue somewhat analogous to the Bezold-Brucke shift. These color shifts are mostly toward the \\

Whitman Richards

1970-01-01

209

The 12-Hour Work Day: Differing Employee Reactions.  

ERIC Educational Resources Information Center

Examined the reactions of employees (N=671) to utilizing a compressed work schedule (i.e., 12-hour shifts) for staffing a continuous process plant. Results showed those who had worked the 12-hour schedule and employees working the 12 PM to 12 AM shift reacted more positively to the 12-hour shift. (JAC)

Breaugh, James A.

1983-01-01

210

A molecular shift register based on electron transfer  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

211

Schedule shifts, cancer and longevity  

PubMed Central

Prompted by a recent report of the possible carcinogenic effect of shiftwork focusing on the disruption of circadian rhythms, we review studies involving shifts in schedule implemented at varying intervals in unicells, insects and mammals, including humans. Results indicate the desirability to account for a broader-than-circadian view. They also suggest the possibility of optimizing schedule shifts by selecting intervals between consecutive shifts associated with potential side-effects such as an increase in cancer risk. Toward this goal, marker rhythmometry is most desirable. The monitoring of blood pressure and heart rate present the added benefit of assessing cardiovascular disease risks resulting not only from an elevated blood pressure but also from abnormal variability in blood pressure and/or heart rate of normotensive as well as hypertensive subjects. PMID:19227006

Cornelissen, Germaine; Halberg, Julia; Halberg, Franz; de la Pena, Salvador Sanchez; Nelson, Walter; Schwartzkopff, Othild; Stoynev, Alexander; Haus, Erhard

2008-01-01

212

Enzyme Reactions  

NSDL National Science Digital Library

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

School, Minerva D.

2011-10-03

213

Reversible Reactions  

NSDL National Science Digital Library

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

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

2005-09-01

214

Nuclear Reactions  

Microsoft Academic Search

Nuclear reactions generate energy in nuclear reactors, in stars, and are responsible for the existence of all elements heavier than hydrogen in the universe. Nuclear reactions denote reactions between nuclei, and between nuclei and other fundamental particles, such as electrons and photons. A short description of the conservation laws and the definition of basic physical quantities is presented, followed by

C. A. Bertulani

2009-01-01

215

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

216

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

217

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

218

Irreversible Investment with Regime Shifts  

Microsoft Academic Search

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

Xin Guo; Jianjun Miao; Erwan Morellecc

2002-01-01

219

Illinois Shifting Gears Policy Evaluation  

ERIC Educational Resources Information Center

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

Weitzel, Peter C.

2009-01-01

220

Foundation Shifts Tack on Studies  

ERIC Educational Resources Information Center

Five years into an eight-year study of its high school improvement efforts, the Bill & Melinda Gates Foundation is shifting its strategy for evaluating the $1.3 billion grant program. The foundation's initiative, which is underwriting change efforts in more than 1,800 schools, is the nation's largest privately funded attempt to improve high…

Viadero, Debra

2006-01-01

221

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

222

Nonlocality in deuteron stripping reactions.  

PubMed

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

Timofeyuk, N K; Johnson, R C

2013-03-15

223

Considerations Based on Reaction Rate on Char Gasification Behavior in Two-stage Gasifier for Biomass  

NASA Astrophysics Data System (ADS)

In order to develop a small-scale gasifier in which biomass can be converted to energy with high efficiency, we planned a gasification process that consists of two parts: pyrolysis part (rotary kiln) and gasification part (downdraft gasifier). We performed fundamental experiments on gasification part and discussed the appropriate conditions such as air supply location, air ratio, air temperature and hearth load. We considered the results by calculating reaction rates of representative reactions on char gasification part and found that water gas reaction is dominant in the reduction area and its behavior gives important information to decide the adequate length of the char layer.

Taniguchi, Miki; Nishiyama, Akio; Sasauchi, Kenichi; Ito, Yusuke; Akamatsu, Fumiteru

224

Doppler phase shifting using dual, switched phase shifting devices  

NASA Technical Reports Server (NTRS)

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

Gutierrez, Roman C. (Inventor)

2002-01-01

225

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

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

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

SciTech Connect

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

Streeter, R.C.

1981-02-01

228

Nuclear Reactions  

Microsoft Academic Search

Nuclear reactions generate energy in nuclear reactors, in stars, and are\\u000aresponsible for the existence of all elements heavier than hydrogen in the\\u000auniverse. Nuclear reactions denote reactions between nuclei, and between nuclei\\u000aand other fundamental particles, such as electrons and photons. A short\\u000adescription of the conservation laws and the definition of basic physical\\u000aquantities is presented, followed by

C. A. Bertulani; B. Kinematics

2009-01-01

229

Accurate phase-shifting digital interferometry  

NASA Astrophysics Data System (ADS)

In phase-shifting interferometry experiments, the accuracy of the phase shift is a major issue. Many experimental and data analyses are done to cancel phase-shift errors inherent to the modulation techniques used. We propose to remove most of the phase-shift error by recourse to a frequency-shifting method. This approach can be applied to both holography and interferometry. We validate the idea with a holographic experiment.

Atlan, M.; Gross, M.; Absil, E.

2007-06-01

230

Possible surface reactions on Mars - Implications for Viking biology results  

NASA Technical Reports Server (NTRS)

The results of two of the three biology experiments carried out on the Viking Mars landers have been simulated. The mixture of organic compounds labeled with carbon-14 used on Mars released carbon dioxide containing carbon-14 when reacted with a simulated Martian surface and atmosphere exposed to ultraviolet light (labeled release experiment). Oxygen was released when metal peroxides or superoxides were treated with water (gas exchange experiment). The simulations suggest that the results of these two Viking experiments can be explained on the basis of reactions of the Martian surface and atmosphere.

Ponnamperuma, C.; Shimoyama, A.; Yamada, M.; Hobo, T.; Pal, R.

1977-01-01

231

KVI Lamb-shift polarimeter  

SciTech Connect

The design and operation of a Lamb-shift polarimeter is discussed. This polarimeter is used to measure the polarization of proton and deuteron beams extracted from the KVI polarized-ion source. The major components of the Lamb-shift polarimeter (LSP) are described in some detail. These include the deceleration lens system, cesium neutralization oven, spin filter, metastable-atom detection system, and the solenoid. Typical operating parameters of the LSP will be given together with some representative spin-polarization measurements. The design criterion of measuring the polarization of a H{sup +} or D{sup +} beam within 60 s and with a statistical uncertainty smaller than 2% has been met.

Beijers, J.P.M.; Kremers, H.R.; Kalantar-Nayestanaki, N. [Kernfysisch Versneller Instituut, Zernikelaan 25, 9747 AA Groningen (Netherlands)

2006-03-15

232

Anthropometric changes and fluid shifts  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

233

Lamb shift in muonic deuterium  

SciTech Connect

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

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

2013-11-07

234

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

235

Boosting Shift-Invariant Features  

NASA Astrophysics Data System (ADS)

This work presents a novel method for training shift-invariant features using a Boosting framework. Features performing local convolutions followed by subsampling are used to achieve shift-invariance. Other systems using this type of features, e.g. Convolutional Neural Networks, use complex feed-forward networks with multiple layers. In contrast, the proposed system adds features one at a time using smoothing spline base classifiers. Feature training optimizes base classifier costs. Boosting sample-reweighting ensures features to be both descriptive and independent. Our system has a lower number of design parameters as comparable systems, so adapting the system to new problems is simple. Also, the stage-wise training makes it very scalable. Experimental results show the competitiveness of our approach.

Hörnlein, Thomas; Jähne, Bernd

236

Shifting the Parallel Programming Paradigm  

Microsoft Academic Search

Multicore computer architectures are now the standard for desktop computers, high-end servers and personal laptops. Due to the multicore shift in computer architecture, soft- ware engineers must write multithreaded programs to har- ness the resources of these parallel machines. Unfortunately, today's parallel programming techniques are difficult to rea- son about, highly error-prone and challenging to maintain for large-scale software. This

Justin E. Gottschlich; Dwight Y. Winkler; Mark W. Holmes; Jeremy G. Siek; Raytheon Compan

237

Magnetic particles with shifted dipoles  

NASA Astrophysics Data System (ADS)

We present simulations and analytical calculations for a system of magnetic nano-particles that possess a dipole moment that is shifted out of the center of mass, towards the surface, leading to a further asymmetry of the dipolar interaction. In our contribution, we discuss the peculiarities of ground state small clusters, both, with and without an external magnetic field. Small clusters help us to get an insight into the inter-particle interactions and form a building block for studies of larger systems. Without external magnetic field, the ground state structure changes from chains and rings with parallel alignment of moments, usually observed in dipolar particles (Prokopieva et al., 2009 [1]), to pairs and triangles with close to anti-parallel orientation of moments, when the shift of the dipole is increased. We also present magnetization properties of larger systems at finite temperature and observe the influence of the shift in particular on the initial slope of the magnetization curve, namely, the initial susceptibility.

Kantorovich, Sofia; Weeber, Rudolf; Cerdà, Joan J.; Holm, Christian

2011-05-01

238

Reaction Time  

NSDL National Science Digital Library

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

Science, New Y.

1999-01-01

239

Chemical Reactions  

NSDL National Science Digital Library

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

Hicken, Mrs.

2009-05-04

240

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

241

Exact and approximate time-shift operators  

NASA Astrophysics Data System (ADS)

A novel fractional time-shift operator is presented in this paper. It is based on performing a phase shift in the frequency domain, which, of course, corresponds to the desired time shift in the time domain. The operations of transforming to the frequency domain, multiplying by the phase shift, and transforming back to the time domain can be accomplished efficiently using one matrix. This matrix is Toeplitz with terms away from the shift number near zero. By approximating the near zero terms as zero, a banded or truncated Toeplitz matrix results. This reduces the computational load and allows an FIR filter realization for the fractional time shift.

Piper, John E.

2009-05-01

242

Shifting patterns of deadly violence.  

PubMed

To the casual observer, it would seem that the United States' suicide rate has been remarkably steady in recent years. However, this stability may be more apparent than real. While it is true that the total suicide rate 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. The extent of this change during the ten-year period 1966-75 is explored along with possible explanations for the increase of aggressive violet death among young people. PMID:7466891

Seiden, R H; Freitas, R P

1980-01-01

243

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 ...

244

Allergic Reactions  

MedlinePLUS

... For instance, if you have an allergy to pollen, your immune system identifies pollen as an invader or allergen . Your immune system ... it can affect a child's speech and language development. Diagnosing and Treating Allergic Reactions An allergist / immunologist, ...

245

Sleep, sleepiness, fatigue, and performance of 12-hour-shift nurses.  

PubMed

Nurses working 12-h shifts complain of fatigue and insufficient/poor-quality sleep. Objectively measured sleep times have not been often reported. This study describes sleep, sleepiness, fatigue, and neurobehavioral performance over three consecutive 12-h (day and night) shifts for hospital registered nurses. Sleep (actigraphy), sleepiness (Karolinska Sleepiness Scale [KSS]), and vigilance (Performance Vigilance Task [PVT]), were measured serially in 80 registered nurses (RNs). Occupational fatigue (Occupational Fatigue Exhaustion Recovery Scale [OFER]) was assessed at baseline. Sleep was short (mean 5.5?h) between shifts, with little difference between day shift (5.7?h) and night shift (5.4?h). Sleepiness scores were low overall (3 on a 1-9 scale, with higher score indicating greater sleepiness), with 45% of nurses having high level of sleepiness (score ?>?7) on at least one shift. Nurses were progressively sleepier each shift, and night nurses were sleepier toward the end of the shift compared to the beginning. There was extensive caffeine use, presumably to preserve or improve alertness. Fatigue was high in one-third of nurses, with intershift fatigue (not feeling recovered from previous shift at the start of the next shift) being most prominent. There were no statistically significant differences in mean reaction time between day/night shift, consecutive work shift, and time into shift. Lapsing was traitlike, with rare (39% of sample), moderate (53%), and frequent (8%) lapsers. Nurses accrue a considerable sleep debt while working successive 12-h shifts with accompanying fatigue and sleepiness. Certain nurses appear more vulnerable to sleep loss than others, as measured by attention lapses. PMID:22324559

Geiger-Brown, Jeanne; Rogers, Valerie E; Trinkoff, Alison M; Kane, Robert L; Bausell, R Barker; Scharf, Steven M

2012-03-01

246

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.

247

Nanoplasmonic probes of catalytic reactions.  

PubMed

Optical probes of heterogeneous catalytic reactions can be valuable tools for optimization and process control because they can operate under realistic conditions, but often probes lack sensitivity. We have developed a plasmonic sensing method for such reactions based on arrays of nanofabricated gold disks, covered by a thin (approximately 10 nanometer) coating (catalyst support) on which the catalyst nanoparticles are deposited. The sensing particles monitor changes in surface coverage of reactants during catalytic reaction through peak shifts in the optical extinction spectrum. Sensitivities to below 10(-3) monolayers are estimated. The capacity of the method is demonstrated for three catalytic reactions, CO and H2 oxidation on Pt, and NO(x) conversion to N2 on Pt/BaO. PMID:19933104

Larsson, Elin M; Langhammer, Christoph; Zori?, Igor; Kasemo, Bengt

2009-11-20

248

Differential phase shift keyed signal resolver  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

249

Shift conversion catalysts comparison. Final report  

Microsoft Academic Search

Some coal gasification processes require a catalytic shift conversion step prior to methanation. The shift step adjusts the Hâ\\/CO molal ratio in the raw gas so that the methanated gas will meet product quality specifications. This study compares various shift conversion catalysts with regard to economics and commercial plant experience. Two sets of catalyst comparisons are presented. For the first

1977-01-01

250

Chapter Number Amplitude Phase Shift Keying Constellation  

E-print Network

Chapter Number Amplitude Phase Shift Keying Constellation Design and its Applications to Satellite demand to replace or complement conventional modulation schemes, such as Quaternary Phase Shift Keying exceeding 1 Gbps. In this regard, Amplitude Phase Shift Keying (APSK) represents an attractive modulation

Guillén i Fàbregas, Albert

251

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

252

Wittig Reaction 33 Reaction: Synthesis of Alkenes  

E-print Network

elimination reactions (E1 or E2 reactions from alcohols or alkyl halides, for example), in eliminationWittig Reaction 33 The Wittig Reaction: Synthesis of Alkenes Intro The "Wittig Reaction" is one reactions the carbon skeleton is already pre-assembled. In the Wittig reaction, however, two smaller carbon

Jasperse, Craig P.

253

Taxol reactions.  

PubMed

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

Price, Kursteen S; Castells, Mariana C

2002-01-01

254

Prismatic lenses shift time perception.  

PubMed

Previous studies have demonstrated the involvement of spatial codes in the representation of time and numbers. We took advantage of a well-known spatial modulation (prismatic adaptation) to test the hypothesis that the representation of time is spatially oriented from left to right, with smaller time intervals being represented to the left of larger time intervals. Healthy subjects performed a time-reproduction task and a time-bisection task, before and after leftward and rightward prismatic adaptation. Results showed that prismatic adaptation inducing a rightward orientation of spatial attention produced an overestimation of time intervals, whereas prismatic adaptation inducing a leftward shift of spatial attention produced an underestimation of time intervals. These findings not only confirm that temporal intervals are represented as horizontally arranged in space, but also reveal that spatial modulation of time processing most likely occurs via cuing of spatial attention, and that spatial attention can influence the spatial coding of quantity in different dimensions. PMID:19549081

Frassinetti, Francesca; Magnani, Barbara; Oliveri, Massimiliano

2009-08-01

255

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

PubMed Central

This study used the modality shift experiment, a relatively simple reaction time measure to visual and auditory stimuli, to examine attentional shifting within and across modalities in 33 children and 42 adults with high-functioning autism as compared to matched numbers of age- and ability-matched typical controls. An exaggerated “modality shift effect” relative to the TD children occurred for the children with autism in conditions involving the reaction time when shifting from sound to light but not from light to sound. No exaggerated MSE was found for the adults with autism; rather, their responses were characterized by a generalized slowness relative to the adults with TD. These results suggest a lag in maturational development in autism in basic information processing mechanisms. PMID:22865151

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

2012-01-01

256

Reverse shift mechanism for automotive manual transmission  

SciTech Connect

A reverse shift mechanism is described for an automotive manual transmission of a type having a reverse idler gear which is movable to selectively complete a reverse gear train, the reverse shift mechanism comprising: a reverse shift arm having a portion disposed adjacent the reverse idler gear and pivotally carried with respect to a transmission casing so that the portion rocks along a direction of axis of the reverse idler gear in response to shifting operation. The portion of the reverse shift arm is provided with a blind hole which is open at a first end toward the reverse idler gear and is closed at a second end away from the reverse idler gear; and a shift arm shoe carried by the portion of the reverse shift arm adjacent the reverse idler gear for pushing the reverse idler gear. The shift arm shoe has an end adapted to engage with a circumferential groove formed in the reverse idler gear and an opposing end shaped to fit in the blind hole of the reverse shift arm; whereby the shift arm shoe is prevented from coming off during assembly by virtue of a vacuum effect created by air confined in the blind hole by fitting engagement between the opposing end and the blind hole, and is held in place after assembly by being clamped between the groove of the reverse idler gear and the blind hole of the reverse shift arm.

Inui, M.; Ogawa, S.

1987-03-03

257

Amplitude dependent shift of betatron oscillation center  

NASA Astrophysics Data System (ADS)

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

Shoji, Yoshihiko; Takao, Masaru; Nakamura, Takeshi

2014-06-01

258

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

259

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

PubMed

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

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

2014-05-01

260

Paradigm shift in lead design.  

PubMed

During the past 30 years there has been a tremendous development in electrode technology from bulky (90 mm2) to pin-sized (1.0 mm2) electrodes. Simultaneously, impedance has increased from 110 Ohms to >1 kOhms, which has been termed a "paradigm shift" in lead design. If current is responsible for stimulation, why is its impedance a key factor in saving energy? Further, what mechanism is behind this development based on experimental findings and what conclusion can be drawn from it to optimize electrode size? If it is assumed that there is always a layer of nonexcitable tissue between the electrode surface and excitable myocardium and that the electric field (potential gradient) produced by the electrode at this boundary is reaching threshold level, then a formula can be derived for the voltage threshold that completely describes the electrophysiology and electrophysics of a hemispherical electrode. Assuming that the mean chronic threshold for porous steroid-eluting electrodes is 0.6 V with 0.5-ms pulse duration, thickness of nonexcitable tissue can be estimated to be 1.5 mm. Taking into account this measure and the relationship between chronaxie and electrode area, voltage threshold, impedance, and energy as a function of surface area can be calculated. The lowest voltage for 0.5-ms pulse duration is reached with r(o) = 0.5 d, yielding a surface area of 4 mm2 and a voltage threshold of 0.62 V, an impedance of 1 kOhms, and an energy level of 197 nJ. It can be deduced from our findings that a further reduction of surface areas below 1.6 mm2 will not diminish energy threshold substantially, if pulse duration remains at 0.5 ms. Lowest energy is reached with t = chronaxie, yielding an energy level <100 nJ with surface areas < or =1.5 mm2. It is striking to see how well the theoretically derived results correspond to the experimental findings. It is also surprising that the hemispheric model so accurately approximates experimental results with differently shaped electrodes that it can be concluded that electrode shape seems to play a minor role in electrode efficiency. Further energy reduction can only be achieved by reducing the pulse duration to chronaxie. A real paradigm shift will occur only if the fundamentals of electrostimulation in combination with electrophysics are accepted by the pacing community. PMID:10527013

Irnich, W

1999-09-01

261

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

SciTech Connect

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

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

1996-12-01

262

Host shifts and evolutionary radiations of butterflies  

PubMed Central

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

Fordyce, James A.

2010-01-01

263

Plasmonic nanobiosensor with chain reaction amplification mechanism.  

PubMed

Herein we demonstrate a plasmonic nanobiosensor that explores chain reaction amplification mechanisms to transduce chemical signals released in biocatalytic reactions, turning optical signals into a visual spectral range. The sensor has a very simple design: gold nanoparticles resting in the surface of a grafted P2VP film. Changes in the gold nanoparticles' position causes changes in the plasmon coupling mode. This is detected by means of a maximum absorbance shift. PMID:24458909

Recco, Lucas C; Tokarev, Ihor; Minko, Sergiy; Pedrosa, Valber A

2014-01-27

264

The second-order gravitational red shift  

NASA Technical Reports Server (NTRS)

The direct measurement of the nonlinear term of the gravitational field equations by using very stable clocks is discussed along with measuring the perhelion advance of a planet or satellite. These are considered measurements of the second-order gravitational red shift. The exact expression for the frequency shift of light in a gravitational field is derived. Other topics discussed include: The Doppler-cancelling technique; the second-order red shift in a spherically symmetric gravitational field; finite signal transit time; and the reality and interpretation of coordinates in the second-order red shift experiment.

Jaffe, J.

1973-01-01

265

Shift work and diabetes - A systematic review.  

PubMed

Diabetes mellitus is a chronic disease, which has an increasing trend all over the world. Type 2 diabetes constitutes 90% of all diabetes. It is associated with weight gain and insulin resistance. Research during recent years has suggested that shift work could be a risk factor of type 2 diabetes. Since shift work is becoming more common, it could contribute to the increasing trend of diabetes. In this systematic review, we have studied the potential association between shift work and type 2 diabetes. We have also reviewed studies on control of diabetes in relation to shift work. PMID:25290038

Knutsson, Anders; Kempe, Anders

2014-12-01

266

Wave-plate phase shifting method  

NASA Astrophysics Data System (ADS)

This paper proposes a new phase shifting method: wave-plate phase shifting method. By different combinations of a quarter-wave-plate, a half-wave-plate, and an analyzer, phase delays are introduced in the interference light path in order to achieve the phase shifting digital holography. Theoretical analysis, numerical simulation, and experiments are conducted to verify the validity of this method. The numerical simulation shows that the result of the wave-plate phase shifting method is consistent with that of the traditional four-step phase shifting method. The experimental results successfully reconstruct the object light intensity in the image plane. Based on the wave-plate phase shifting method, a pixelated wave-plate array structure is designed to achieve real-time phase shifting digital holography. The wave-plate array phase shifting method not only can reconstruct object image of high quality, but also can be used in dynamic phase measurement. Therefore, pixelated wave-plate array structure and wave-plate array phase shifting method could be widely used in practical applications.

Zhang, Zhigang; Zhang, Qingchuan; Cheng, Teng; Gao, Jie; Wu, Xiaoping

2013-10-01

267

Exercise, Energy Balance and the Shift Worker  

PubMed Central

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

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

2009-01-01

268

In-line phase shift tomosynthesis  

SciTech Connect

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

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

2013-08-15

269

Shift work, sleep, and sleepiness - differences between shift schedules and systems.  

PubMed

In this narrative review, we examined what level of research evidence is available that shift workers' sleep-wake disturbances can be minimized through ergonomic shift scheduling. We classified the pertinent studies conducted on real shift workers in field conditions by the type of shift system and study design (ie, whether the shift systems were modified or not - "treatment" versus "no treatment"). The results of the observational studies in which no changes to the shift system were made (ie, no treatment) showed that, irrespective of the shift system, night and early-morning shifts and quick returns are associated with short sleep and increases in sleepiness. The same is true for very long shifts (>16 hours) and extremely long weekly working hours (>55 hours). For all categories of shift systems, there was a lack of controlled intervention studies, limiting the possibility to provide solution-focused recommendations for shift scheduling. Most of the controlled intervention studies had been conducted on workers under regular 3-shift systems. These studies suggested that a change from slowly backward-rotating shifts to rapidly forward-rotating shifts is advantageous for alertness and, to some degree, sleep. We also found that a change from an 8- to 12-hour shift system does not necessarily result in impairments in the sleep-wake pattern. The level of research evidence was affected by many of the studies' frequent methodological limitations in measuring sleep and sleepiness. In all, to have reliable and solution-focused recommendations for shift scheduling, methodologically sound controlled intervention studies are required in different categories of shift systems. PMID:20119631

Sallinen, Mikael; Kecklund, Göran

2010-03-01

270

Formamidine Reactions  

E-print Network

.36$, 8.44$ Calculated for C ^ O ^ B r , nitrogen = 3.16$. METHYL IS0XAZ0L0N DERIVATIVES. The amido methylene derivatives of methyl lsoxazolon should be obtainable by the same methods as those of phenyl lsoxazolon. There are however, two practical... hydrochloid is neutralized. If it is neutralized with pyirldene the following reaction takes place. CH3 0 -==-C 'COHHR H«C - 0 * COINHR ' 1 II /I 0 CH v " " 1 - = N-O-O-OH, + H,0 f-R UH- H * flTO 3 HO- JT/Ha I t This gives the aMde of 5-methyl...

Griffin, E. L.

1913-05-15

271

The Concept Shifting Test: Adult Normative Data  

ERIC Educational Resources Information Center

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

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

2006-01-01

272

Ternary phase shift keying and its performance  

Microsoft Academic Search

An important class of digital modulation is phase shift keying (PSK). Ternary phase shift keying (TPSK) has not been focused upon until now because it is not suitable for transmitting binary information signals. However, it has theoretically excellent features for mobile communication systems, that is, it has splendid error rate characteristics and minimum amplitude fluctuation among all of the PSK

Makoto Nakamura; Hideyuki Torii

2002-01-01

273

The Risky Shift in Group Betting.  

National Technical Information Service (NTIS)

Two experiments were performed, involving a similar method. Experiment 1 showed for the first time that group discussion can produce a shift toward greater risk in choices among bets. A risky shift was found in two dimensions of risk taking: probability p...

D. G. Pruitt, A. I. Teger

1968-01-01

274

Obesity and shift work: chronobiological aspects.  

PubMed

The present review has the objective of summarising chronobiological aspects of shift work and obesity. There was a systematic search in PubMed databases, using the following descriptors: shift work; obesity; biological clock. Shift work is extremely frequent in several services and industries, in order to systematise the needs for flexibility of the workforce, necessary to optimise productivity and business competitiveness. In developing countries, this population represents a considerable contingent workforce. Recently, studies showed that overweight and obesity are more prevalent in shift workers than day workers. In addition, the literature shows that shift workers seem to gain weight more often than those workers submitted to a usual work day. In conclusion, there is considerable epidemiological evidence that shift work is associated with increased risk for obesity, diabetes and CVD, perhaps as a result of physiological maladaptation to chronically sleeping and eating at abnormal circadian times. The impact of shift work on metabolism supports a possible pathway to the development of obesity and its co-morbities. The present review demonstrated the adverse cardiometabolic implications of circadian misalignment, as occurs chronically with shift workers. PMID:20122305

Antunes, L C; Levandovski, R; Dantas, G; Caumo, W; Hidalgo, M P

2010-06-01

275

STRONG SHIFT EQUIVALENCE OF C-CORRESPONDENCES  

E-print Network

STRONG SHIFT EQUIVALENCE OF C-CORRESPONDENCES PAUL S. MUHLY, DAVID PASK, AND MARK TOMFORDE Abstract papers, [23] by R. Williams and [4] by J. Cuntz and W. Krieger. To understand why, suppose A and B] Williams proved that the shift dynamical systems Date: March 20, 2007. 2000 Mathematics Subject

Pask, David

276

Gravitational Bending of Light with Frequency Shifts  

E-print Network

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

P. D. Morley

1993-11-15

277

Shaping the light/dark pattern for circadian adaptation to night shift work.  

PubMed

This is the second in a series of simulated night shift studies designed to achieve and subsequently maintain a compromise circadian phase position between complete entrainment to the daytime sleep period and no phase shift at all. We predict that this compromise will yield improved night shift alertness and daytime sleep, while still permitting adequate late night sleep and daytime wakefulness on days off. Our goal is to delay the dim light melatonin onset (DLMO) from its baseline phase of approximately 21:00 to our target of approximately 3:00. Healthy young subjects (n=31) underwent three night shifts followed by two days off. Two experimental groups received intermittent bright light pulses during night shifts (total durations of 75 and 120 min per night shift), wore dark sunglasses when outside, slept in dark bedrooms at scheduled times after night shifts and on days off, and received outdoor light exposure upon awakening from sleep. A control group remained in dim room light during night shifts, wore lighter sunglasses, and had unrestricted sleep and outdoor light exposure. After the days off, the DLMO of the experimental groups was approximately 00:00-1:00, not quite at the target of 3:00, but in a good position to reach the target after subsequent night shifts with bright light. The DLMO of the control group changed little from baseline. Experimental subjects performed better than control subjects during night shifts on a reaction time task. Subsequent studies will reveal whether the target phase is achieved and maintained through more alternations of night shifts and days off. PMID:18675836

Smith, Mark R; Cullnan, Erin E; Eastman, Charmane I

2008-10-20

278

Total Antioxidant Capacity and Malondialdehyde in Depressive Rotational Shift Workers  

PubMed Central

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

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

2013-01-01

279

Utilizing bedside shift report to improve the effectiveness of shift handoff.  

PubMed

Handoff of patient information during shift report between nurses is a time of risk and liability. A quality improvement project was conducted on a 23-bed inpatient unit to measure the value of a bedside change-of-shift report in improving the effectiveness of shift report. Indicators including end-of-shift overtime, call light usage, nurse perceptions, and patient satisfaction were impacted by the change in process. PMID:23425914

Cairns, Leslie L; Dudjak, Linda A; Hoffmann, Rosemary L; Lorenz, Holly L

2013-03-01

280

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

PubMed Central

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

2013-01-01

281

Process Optimization of FT-Diesel Production from Lignocellulosic Switchgrass  

E-print Network

/ H2 considering a bypass, a PSA system and water gas shift reaction. Next, the removal of CO2 and H2S, geothermic, wind, only biomass provides a raw material capable of entering the market in the short term

Grossmann, Ignacio E.

282

Published: October 25, 2011 r 2011 American Chemical Society 20384 dx.doi.org/10.1021/ja207551f |J. Am. Chem. Soc. 2011, 133, 2038420398  

E-print Network

for the formation of new CÃ?C and CÃ?O bonds via condensation and esterification reactions. Water-gas shift (WGS)4-type condensation and esterification routes without detectable involvement of the oxide supports. Propanal

Iglesia, Enrique

283

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

Microsoft Academic Search

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

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

1998-01-01

284

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

285

Shifting Mindsets: The Changing Work Roles of Vocational Education and Training Practitioners  

ERIC Educational Resources Information Center

Reforms to Australia's vocational education and training (VET) sector have had a significant impact on practitioners' work in public and private providers. This study analyses practitioners' perceptions of, and reactions to, the changes. The scope of these changes has been substantial and has required shifts to practitioners' habits, norms, skills…

Harris, Roger; Simons, Michele; Clayton, Berwyn

2005-01-01

286

Identifying minimal shift counters: A search technique  

NASA Astrophysics Data System (ADS)

A minimal modulo-m n-stage shift counter is defined as a shift counter with a feedback function of the form Y(sub 1) = y(sub n) direct sum P(sub 1)(y(sub 1), y(sub 2), ..., y(sub n - 1))direct sum ...direct sum P(sub k)(y(sub 1), y(sub 2), ..., y(sub n - 1)), where y(sub n) is either y(sub n) or y''(sub n) and P(sub i)(y(sub 1), y(sub 2), ..., y(sub n - 1)) is a product of literals of state variables. The feedback function is selected from the set of 2(exp 2n - 1) functions that can be represented in this form so as to minimize the number of product terms, the number of literals of a product term, and the total number of literals, in this order. Due to the shift register properties introduced in this brief contribution, it is possible to identify minimal shift counters using a search technique. Minimal shift counters with up to 14 stages have been identified. Except for very small moduli (m less than 2n), minimal shift counters can be operated at higher frequencies and require a smaller area than shift counters designed using other methods.

Tokarnia, Alice M.

1994-05-01

287

Water in Low-Mass Star-Forming Regions with Herschel: The Link Between Water Gas and Ice in Protostellar Envelopes  

E-print Network

Aims: Our aim is to determine the critical parameters in water chemistry and the contribution of water to the oxygen budget by observing and modelling water gas and ice for a sample of eleven low-mass protostars, for which both forms of water have been observed. Methods: A simplified chemistry network, which is benchmarked against more sophisticated chemical networks, is developed that includes the necessary ingredients to determine the water vapour and ice abundance profiles in the cold, outer envelope in which the temperature increases towards the protostar. Comparing the results from this chemical network to observations of water emission lines and previously published water ice column densities, allows us to probe the influence of various agents (e.g., FUV field, initial abundances, timescales, and kinematics). Results: The observed water ice abundances with respect to hydrogen nuclei in our sample are 30-80ppm, and therefore contain only 10-30% of the volatile oxygen budget of 320ppm. The keys to reprodu...

Schmalzl, M; Walsh, C; Albertsson, T; van Dishoeck, E F; Kristensen, L E; Mottram, J C

2014-01-01

288

U.S. Geological Survey Georgia Water Science Center and Albany Water, Gas, and Light Commission Cooperative Water Program-Summary of Activities, July 2005 through June 2006  

USGS Publications Warehouse

The U.S. Geological Survey (USGS) has been working with the Albany Water, Gas, and Light Commission to monitor ground-water quality and availability since 1977. This report presents the findings for July 2005 through June 2006 and summarizes the ground-water and surface-water conditions for 2005. Water levels in 14 wells were continuously monitored in Dougherty County, Georgia. Water levels in 12 of those wells were above normal, one was normal, and one was below normal. Ground-water samples collected from the Upper Floridan aquifer indicate that nitrate levels have increased in 13 wells and decreased in two wells from a year earlier. A sample also was collected from the Flint River. A trilinear diagram showing the percent composition of selected major cations and anions indicates that the ground-water quality of the Upper Floridan aquifer at the Albany wellfield is distinctly different from the water quality of the Flint River. To improve the understanding of the ground-water flow system and nitrate movement in the Upper Floridan aquifer, the USGS is developing a ground-water flow model in the southwest Albany area, Georgia.

Gordon, Debbie Warner

2006-01-01

289

Giant Compton Shifts in Hyperbolic Metamaterial  

E-print Network

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

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

2014-01-01

290

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

NASA Astrophysics Data System (ADS)

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

Adachi, Masaaki; Sunada, Satoshi

2014-09-01

291

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

PubMed Central

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

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

2013-01-01

292

Tracking a phase-shift-keyed signal  

NASA Technical Reports Server (NTRS)

In detector, phase shifter is used to generate negative phase shift opposing detected phase angle. This produces converted series sideband and component carrier, with residual carrier signal and converted series sideband and component carrier added together to produce tracking signal.

Villarreal, S.; Lenett, S. D.; Kobayashi, H. S.; Pawlowski, J. F.

1977-01-01

293

Nonlinear effects in phase shift keyed transmission  

Microsoft Academic Search

Phase-shift-keyed modulation formats have recently shown superior performance in some nonlinear transmissions. This paper will review the understanding of their tolerance to various fiber nonlinearities in different transmission regimes in terms of data rate and spectral efficiency.

X. Liu

2004-01-01

294

Novel Solution of Mercury Perihelion Shift  

E-print Network

We present a novel solution of the Mercury perihelion advance shift in the new gravity model. It is found that the non-relativistic reduction of the Dirac equation with the gravitational potential produces the new gravitational potential of $\\displaystyle{V(r)=-{GMm\\over r}+{G^2M^2m^2\\over 2mc^2r^2}}$. This potential can explain the Mercury perihelion advance shift without any free parameters. Also, it can give rise to the $\\omega-$shift of the GPS satellite where the advance shift amounts to $({\\Delta \\omega\\over \\omega})_{th} \\simeq 3.4\\times 10^{-10}$ which should be compared to the recent observed value of $({\\Delta \\omega\\over \\omega})_{exp} \\simeq 4.5\\times 10^{-10}$.

Takehisa Fujita; Naohiro Kanda

2009-11-11

295

Working Night Shift Slows Metabolism, Study Suggests  

MedlinePLUS

... page, please enable JavaScript. Working Night Shift Slows Metabolism, Study Suggests Finding means fewer calories burned, and ... sleeping by day may slow down the body's metabolism, a small study suggests. Researchers found that when ...

296

Prolonged Instability Prior to a Regime Shift  

PubMed Central

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

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

2014-01-01

297

Red Shifts with Obliquely Approaching Light Sources.  

ERIC Educational Resources Information Center

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

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

1988-01-01

298

Prolonged instability prior to a regime shift.  

PubMed

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

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

2014-01-01

299

ENVIRONMENTAL TAX SHIFT: A Discussion Paper for  

E-print Network

........................................................................................................................... 1 2. BACKGROUND: WHAT ARE ENVIRONMENTAL TAXES AND WHAT IS AN ENVIRONMENTAL TAX SHIFT? ....................................................................................................................................... 3 2.1 WHAT ARE TAXES .............................................................................................................. 43 8.2 SELECTIVE TAXATION OF WATER USE, SOLID WASTE DISPOSAL AND CARBON DIOXIDE EMISSIONS USING

300

[Sleep disorders among physicians on shift work].  

PubMed

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

Schlafer, O; Wenzel, V; Högl, B

2014-11-01

301

A Phylogenetic analysis of the Southern Shift  

E-print Network

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

Thomas, Erik Robert

2012-06-07

302

Quadrature-quadrature phase-shift keying  

Microsoft Academic Search

Quadrature-quadrature phase-shift keying (Q2PSK) is a spectrally efficient modulation scheme which utilizes available signal space dimensions in a more efficient way than two-dimensional schemes such as QPSK and MSK (minimum-shift keying). It uses two date shaping pulses and two carriers, which are pairwise quadrature in phase, to create a four-dimensional signal space and increases the transmission rate by a factor

D. Saha; T. G. Birdsall

1989-01-01

303

Illuminating geographical patterns in species' range shifts.  

PubMed

Species' range shifts in response to ongoing climate change have been widely documented, but although complex spatial patterns in species' responses are expected to be common, comprehensive comparisons of species' ranges over time have undergone little investigation. Here, we outline a modeling framework based on historical and current species distribution records for disentangling different drivers (i.e. climatic vs. nonclimatic) and assessing distinct facets (i.e. colonization, extirpation, persistence, and lags) of species' range shifts. We used extensive monitoring data for stream fish assemblages throughout France to assess range shifts for 32 fish species between an initial period (1980-1992) and a contemporary one (2003-2009). Our results provide strong evidence that the responses of individual species varied considerably and exhibited complex mosaics of spatial rearrangements. By dissociating range shifts in climatically suitable and unsuitable habitats, we demonstrated that patterns in climate-driven colonization and extirpation were less marked than those attributed to nonclimatic drivers, although this situation could rapidly shift in the near future. We also found evidence that range shifts could be related to some species' traits and that the traits involved varied depending on the facet of range shift considered. The persistence of populations in climatically unsuitable areas was greater for short-lived species, whereas the extent of the lag behind climate change was greater for long-lived, restricted-range, and low-elevation species. We further demonstrated that nonclimatic extirpations were primarily related to the size of the species' range, whereas climate-driven extirpations were better explained by thermal tolerance. Thus, the proposed framework demonstrated its potential for markedly improving our understanding of the key processes involved in range shifting and also offers a template for informing management decisions. Conservation strategies would greatly benefit from identifying both the geographical patterns and the species' traits associated with complex modifications of species' distributions in response to global changes. PMID:24616088

Grenouillet, Gaël; Comte, Lise

2014-10-01

304

Predicting shifts in generalization gradients with perceptrons.  

PubMed

Perceptron models have been used extensively to model perceptual learning and the effects of discrimination training on generalization, as well as to explore natural classification mechanisms. Here, we assess the ability of existing models to account for the time course of generalization shifts that occur when individuals learn to distinguish sounds. A set of simulations demonstrates that commonly used single-layer and multilayer perceptron networks do not predict transitory shifts in generalization over the course of training but that such dynamics can be accounted for when the output functions of these networks are modified to mimic the properties of cortical tuning curves. The simulations further suggest that prudent selection of stimuli and training criteria can allow for more precise predictions of learning-related shifts in generalization gradients in behavioral experiments. In particular, the simulations predict that individuals will show maximal peak shift after different numbers of trials, that easier contrasts will lead to slower development of shifted peaks, and that whether generalization shifts persist or dissipate will depend on which stimulus dimensions individuals use to distinguish stimuli and how those dimensions are neurally encoded. PMID:21983938

Wisniewski, Matthew G; Radell, Milen L; Guillette, Lauren M; Sturdy, Christopher B; Mercado, Eduardo

2012-06-01

305

Shifts in global vegetation activity dynamics?  

NASA Astrophysics Data System (ADS)

Vegetation belongs to the components of the Earth surface, which are most extensively studied using historic and present satellite records. Recently, these records exceeded a 30-year time span composed of pre-processed fortnightly observations (1981-2011). The existence of monotonic changes and trend shifts present in such records has previously been demonstrated. However, information on timing and type of such trend shifts was lacking at global scale. We detected major shifts in vegetation activity trends and their associated type (either interruptions or reversals) and timing. It appeared that the trend shifts have, over time, increased in frequency, confirming recent findings of increased turnover rates in vegetated areas. Signs of greening-to-browning reversals around the millennium transition were found in many regions (Patagonia, the Sahel, northern Kazakhstan, among others), as well as negative interruptions--'setbacks'--in greening trends (southern Africa, India, Asia Minor, among others). A minority (26%) of all significant trends appeared monotonic, illustrating the importance of shift detection and characterisation. Examples for specific locations of major shifts detected in NDVI3g time series are discussed.

Verbesselt, J.; de Jong, R.; Herold, M.

2013-12-01

306

Backward position shift in apparent motion.  

PubMed

We investigated the perceived position of visual targets in apparent motion. A disc moved horizontally through three positions from -10° to +10° in the far periphery (20° above fixation), generating a compelling impression of apparent motion. In the first experiment, observers compared the position of the middle of the three discs to a subsequently presented reference. Unexpectedly, observers judged its position to be shifted backward, in the direction opposite that of the motion. We then tested the middle disc in sequences of 3, 5, and 7 discs, each covering the same spatial and temporal extents (similar speeds). The backwards shift was only found for the three-disc sequence. With the extra discs approaching more continuous motion, the perceived shift was in the same direction as the apparent motion. Finally, using a localization task with constant static references, we measured the position shifts of all the disc locations for two-disc, three-disc and four-disc apparent motion sequences. The backward shift was found for the second location of all sequences. We suggest that the backward shift of the second element along an apparent motion path is due to an attraction effect induced by the initial point of the motion. PMID:24449638

Li, Hsin-Hung; Shim, Won Mok; Cavanagh, Patrick

2014-01-01

307

Self-organization effects in reactions of macromolecules  

NASA Astrophysics Data System (ADS)

The ability of biomacromolecules to coordinate fast reaction events in their active centers with slow rearrangements of their structure is focused upon. Under real conditions of many sequential reaction turnovers of the macromolecule, the structural shifts caused by single turnovers can be of cumulative character. This, in turn, leads to drastic threshold-like changes of the reaction cycle. In this way, the creative role of dynamical substrate-conformation interactions in the formation of functional regimes of the macromolecule is consistently uncovered.

Christophorov, L. N.

308

Modeling of shift hydraulic system for automatic transmission  

Microsoft Academic Search

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

Gang Tao; Tao Zhang; Huiyan Chen

2011-01-01

309

Phase-shift algorithm for white-light interferometry insensitive to linear errors in phase shift  

Microsoft Academic Search

White-light interference has changes in fringe contrast. When phase-shift techniques are applied to white-light interference,\\u000a the phase-shift algorithm which can extract the phase accurately under the contrast changes is required. There is often another\\u000a requirement that the phase shift between frames should not be restricted to ?\\/2. Computer simulations show that the well-known algorithms have non-negligible errors under both requirements.

Masaaki Adachi

2008-01-01

310

HASH: a program to accurately predict protein H? shifts from neighboring backbone shifts.  

PubMed

Chemical shifts provide not only peak identities for analyzing nuclear magnetic resonance (NMR) data, but also an important source of conformational information for studying protein structures. Current structural studies requiring H(?) chemical shifts suffer from the following limitations. (1) For large proteins, the H(?) chemical shifts can be difficult to assign using conventional NMR triple-resonance experiments, mainly due to the fast transverse relaxation rate of C(?) that restricts the signal sensitivity. (2) Previous chemical shift prediction approaches either require homologous models with high sequence similarity or rely heavily on accurate backbone and side-chain structural coordinates. When neither sequence homologues nor structural coordinates are available, we must resort to other information to predict H(?) chemical shifts. Predicting accurate H(?) chemical shifts using other obtainable information, such as the chemical shifts of nearby backbone atoms (i.e., adjacent atoms in the sequence), can remedy the above dilemmas, and hence advance NMR-based structural studies of proteins. By specifically exploiting the dependencies on chemical shifts of nearby backbone atoms, we propose a novel machine learning algorithm, called HASH, to predict H(?) chemical shifts. HASH combines a new fragment-based chemical shift search approach with a non-parametric regression model, called the generalized additive model, to effectively solve the prediction problem. We demonstrate that the chemical shifts of nearby backbone atoms provide a reliable source of information for predicting accurate H(?) chemical shifts. Our testing results on different possible combinations of input data indicate that HASH has a wide rage of potential NMR applications in structural and biological studies of proteins. PMID:23242797

Zeng, Jianyang; Zhou, Pei; Donald, Bruce Randall

2013-01-01

311

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

Microsoft Academic Search

Objectives—Shiftwork is now a major fea- ture of working life across a broad range of industries. The features of the shift sys- tems operated can impact on the wellbe- ing, performance, and sleep of shiftworkers. This paper reviews the cur- rent state of knowledge on one major characteristic of shift rotas—namely, shift duration.Evidence comparing the relative eVects of eight hour

Lawrence Smith; Simon Folkard; Phil Tucker; Ian Macdonald

312

Hash: a Program to Accurately Predict Protein H? Shifts from Neighboring Backbone Shifts3  

PubMed Central

Chemical shifts provide not only peak identities for analyzing NMR data, but also an important source of conformational information for studying protein structures. Current structural studies requiring H? chemical shifts suffer from the following limitations. (1) For large proteins, the H? chemical shifts can be difficult to assign using conventional NMR triple-resonance experiments, mainly due to the fast transverse relaxation rate of C? that restricts the signal sensitivity. (2) Previous chemical shift prediction approaches either require homologous models with high sequence similarity or rely heavily on accurate backbone and side-chain structural coordinates. When neither sequence homologues nor structural coordinates are available, we must resort to other information to predict H? chemical shifts. Predicting accurate H? chemical shifts using other obtainable information, such as the chemical shifts of nearby backbone atoms (i.e., adjacent atoms in the sequence), can remedy the above dilemmas, and hence advance NMR-based structural studies of proteins. By specifically exploiting the dependencies on chemical shifts of nearby backbone atoms, we propose a novel machine learning algorithm, called Hash, to predict H? chemical shifts. Hash combines a new fragment-based chemical shift search approach with a non-parametric regression model, called the generalized additive model, to effectively solve the prediction problem. We demonstrate that the chemical shifts of nearby backbone atoms provide a reliable source of information for predicting accurate H? chemical shifts. Our testing results on different possible combinations of input data indicate that Hash has a wide rage of potential NMR applications in structural and biological studies of proteins. PMID:23242797

Zeng, Jianyang; Zhou, Pei; Donald, Bruce Randall

2012-01-01

313

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

PubMed

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

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

2011-07-01

314

Nozzle Aerodynamic Stability During a Throat Shift  

NASA Technical Reports Server (NTRS)

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

Kawecki, Edwin J.; Ribeiro, Gregg L.

2005-01-01

315

Chemical Shift Prediction for Denatured Proteins  

PubMed Central

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

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

2013-01-01

316

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

E-print Network

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

Kozlov, Mikhail G

317

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

318

Ne II Stark Width and Shift Regularities  

NASA Astrophysics Data System (ADS)

Stark widths of 48 and Stark shifts of 36 Ne II spectral lines have been measured in a low-pressure pulsed arc plasma. Of these, 21 widths and 25 shifts have not been previously reported. This has allowed us to analyze Stark width and shift regularities in some multiplets and transition arrays of this species. The electron density and temperature in this experiment were in the range 1.12-1.97×1023 m-3 and 25,000-45,000 K, respectively. The results have been compared to data from previous experimental work, as well as to theoretical models. Stark parameter regularities experimentally determined in this work provide a basis for estimating the Stark parameters for Ne II lines that have not yet been observed.

Peláez, R. J.; Djurovic, S.; Cirisan, M.; Rodríguez, F.; Aparicio, J. A.; Mar, S.

2008-11-01

319

Shift work in a security environment  

SciTech Connect

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

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

1993-12-31

320

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

321

What are 12-hour shifts good for?  

PubMed

In the UK many hospitals use 12-hour shifts, believing it to be a cost-efficient means of providing 24-hour nursing care on wards. While healthcare organisations need to find ways to deliver nursing care around the clock and efficiency is a key consideration, nurse leaders have raised concerns about ' whether nurses can function effectively and safely when working long hours (Calkin, 2012; Rogers et al, 2004). In this Policy Plus, we focus specifically on what is known about the impact of shift length on patient safety, employee health and quality of care. PMID:23696995

322

Proton Mass Shift in Muonic Hydrogen Atom  

E-print Network

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

Aiichi Iwazaki

2014-08-11

323

Prostate precancer detection by Stokes Shift Spectroscopy  

NASA Astrophysics Data System (ADS)

Stokes Shift Spectroscopy (SSS) has emerged as a promising modality in the discrimination of normal from different pathological prostate tissues. Stokes shift (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 prostate tissues were observed. The SS spectra of normal, hyperplasia and malignant tissues shows the distinct peaks around 300, 345, 440 and 510 nm is attributed to tryptophan, collagen, NADH and flavin respectively. To quantify the spectral differences between normal and different pathological prostate tissues are verified by statistical analysis.

Jeyasingh, Ebenezar; Pu, Y.; Wang, W. B.; Liu, C. H.; Alfano, R. R.

2011-03-01

324

Phase Shift with LapH Propagators  

E-print Network

The pion-pion scattering phase shift is computed using LapH propagators. The LapH method for computing quark propagators is used to form two-particle correlation functions with a number of different operators. Excited state energies of two-particle states on 2+1 dynamical, anisotropic lattices (Mpi=390 MeV) are computed to determine the phase shift in the isospin-2 channel. The signal for t-to-t diagrams for the isospin-0 channel are also presented to demonstrate the efficacy of the stochastic LapH method which combines LapH with diluted Z4 noise sources.

John Bulava; Justin Foley; Keisuke J. Juge; Colin J. Morningstar; Michael J. Peardon; Chik-Him Wong

2010-11-24

325

Phase Shift with LapH Propagators  

E-print Network

The pion-pion scattering phase shift is computed using LapH propagators. The LapH method for computing quark propagators is used to form two-particle correlation functions with a number of different operators. Excited state energies of two-particle states on 2+1 dynamical, anisotropic lattices (Mpi=390 MeV) are computed to determine the phase shift in the isospin-2 channel. The signal for t-to-t diagrams for the isospin-0 channel are also presented to demonstrate the efficacy of the stochastic LapH method which combines LapH with diluted Z4 noise sources.

Bulava, John; Juge, Keisuke J; Morningstar, Colin J; Peardon, Michael J; Wong, Chik-Him

2010-01-01

326

Parallel phase-shifting digital holographic microscopy  

PubMed Central

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

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

2010-01-01

327

Lamb shift in muonic helium ion  

E-print Network

The Lamb shift (2P_{1/2}-2S_{1/2}) in the muonic helium ion (mu ^4_2He)^+ is calculated with the account of contributions of orders alpha^3, alpha^4, alpha^5 and alpha^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 1379.028 meV can be considered as a reliable estimate for the comparison with experimental data.

A. P. Martynenko

2006-12-22

328

Phase Transitions in Paradigm Shift Models  

PubMed Central

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

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

2013-01-01

329

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

Microsoft Academic Search

OBJECTIVES: The generally agreed view is that there is no ideal shift system, and that most systems will have both advantages and disadvantages. As such, attention has been placed on trying to identify good and bad features of shift systems, with a view to minimising the possible ill health as a consequence of shiftwork. The present study focuses on the

P Tucker; J Barton; S Folkard

1996-01-01

330

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

PubMed

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

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

2009-10-01

331

Water in low-mass star-forming regions with Herschel. The link between water gas and ice in protostellar envelopes  

NASA Astrophysics Data System (ADS)

Aims: Our aim is to determine the critical parameters in water chemistry and the contribution of water to the oxygen budget by observing and modelling water gas and ice for a sample of eleven low-mass protostars, for which both forms of water have been observed. Methods: A simplified chemistry network, which is benchmarked against more sophisticated chemical networks, is developed that includes the necessary ingredients to determine the water vapour and ice abundance profiles in the cold, outer envelope in which the temperature increases towards the protostar. Comparing the results from this chemical network to observations of water emission lines and previously published water ice column densities, allows us to probe the influence of various agents (e.g., far-ultraviolet (FUV) field, initial abundances, timescales, and kinematics). Results: The observed water ice abundances with respect to hydrogen nuclei in our sample are 30-80 ppm, and therefore contain only 10-30% of the volatile oxygen budget of 320 ppm. The keys to reproduce this result are a low initial water ice abundance after the pre-collapse phase together with the fact that atomic oxygen cannot freeze-out and form water ice in regions with Tdust ? 15 K. This requires short prestellar core lifetimes ?0.1 Myr. The water vapour profile is shaped through the interplay of FUV photodesorption, photodissociation, and freeze-out. The water vapour line profiles are an invaluable tracer for the FUV photon flux and envelope kinematics. Conclusions: The finding that only a fraction of the oxygen budget is locked in water ice can be explained either by a short pre-collapse time of ?0.1 Myr at densities of nH ~ 104 cm-3, or by some other process that resets the initial water ice abundance for the post-collapse phase. A key for the understanding of the water ice abundance is the binding energy of atomic oxygen on ice. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Schmalzl, M.; Visser, R.; Walsh, C.; Albertsson, T.; van Dishoeck, E. F.; Kristensen, L. E.; Mottram, J. C.

2014-12-01

332

Shape selective catalysis and reaction mechanisms  

SciTech Connect

A study was made into the problem of selection of catalysts for desired reactions of hydrocarbons. For this catalyst selection, the reaction mechanism must be known. The isomerization of xylene by means of methyl shift on acid zeolites was investigated. Also, the disproportionation of xylene into toluene and trimethylbenzene was studied. Transformations of alkanes on pure zeolites and mechanical mixtures of platinum and alumina and zeolites were also discussed. Diffusional limitations and steric constraints in the neighborhood of the active centers were also covered.

Guisnet, M.; Perot, G.

1983-01-01

333

Socioeconomic Development and Shifts in Mate Preferences  

Microsoft Academic Search

Mate preferences shift according to contexts such as temporal duration of mateship sought and ecological prevalence of parasites. One important cross-cultural context that has not been explored is a country's socioeconomic development. Because individuals in less developed countries are generally less healthy and possess fewer resources than those in more developed countries, displays of health and resources in a prospective

Emily A. Stone; Todd K. Shackelford; David M. Buss

334

Critical Review--Outsourcing: A Paradigm Shift.  

ERIC Educational Resources Information Center

Discusses trends in outsourcing, provision of goods and services to an organization that were previously delivered in house. Addresses outsourcing in the public sector, advantages and disadvantages, implications for human resource development, and the shift to the new "psychological contract" between employers and employees. (Contains 227…

Kakabadse, Nada; Kakabadse, Andrew

2000-01-01

335

Shifting the management development paradigm for women  

Microsoft Academic Search

Proposes that women will not make significant advances in American businesses unless the focus shifts from a preoccupation on gender awareness to one of multicultural awareness. Discusses the whitewash dilemma and dominant assumptions about women in management to help explain the current management development paradigm that fails to recognize diversity among women. Makes a case for increasing organizational education about

Bonita L. Betters-Reed; Lynda L. Moore

1995-01-01

336

Robert Collins More on Mean-shift  

E-print Network

CSE598G Robert Collins More on Mean-shift R.Collins, CSE, PSU CSE598G Spring 2006 #12;CSE598G is function only of distance from center #12;CSE598G Robert Collins Kernel-Shadow Pairs h'(r) = - c k (r Robert Collins Recall: Kernel Density Estimation Given a set of data samples xi; i=1...n Convolve

Collins, Robert T.

337

A Paradigm Shift to Improve Academic Performance  

ERIC Educational Resources Information Center

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

Rulloda, Rudolfo B.

2009-01-01

338

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

339

Effectiveness of the Twelve-Hour Shift.  

ERIC Educational Resources Information Center

Although labor unions traditionally have fought for shorter working hours, there have been recent reversals in this trend. The Pulp and Paperboard Division of Temple-Eastex Incorporated converted to a 12-hour shift and found that safety improved, productivity increased, and overtime decreased. (JOW)

Brinton, Robert D.

1983-01-01

340

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

341

SECTORAL SHIFT, WEALTH DISTRIBUTION, AND DEVELOPMENT  

Microsoft Academic Search

There are two phenomena widely observed when an economy departs from an underdeveloped state and starts rapid economic growth. One is the shift of production, employment, and consumption from the traditional sector to the modern sector, and the other is a large increase in educational levels of its population. The question is why some economies have succeeded in such structural

Kazuhiro Yuki

2008-01-01

342

Implications of Shifting Technology in Education  

ERIC Educational Resources Information Center

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

Holland, Janet; Holland, John

2014-01-01

343

Differential phase shift keyed communication system  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

344

Rotative quadrature phase-shift keying  

NASA Technical Reports Server (NTRS)

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.

1992-01-01

345

Shifting Standards and Stereotype-Based Judgments  

Microsoft Academic Search

Four studies tested a model of stereotype-based shifts in judgment standards developed by M. Biernat, M. Manis, and T. E. Nelson (1991). The model suggests that subjective judgments of target persons from different social groups may fail to reveal the stereotyped expectations of judges, because they invite the use of different evaluative standards; more \\

Monica Biernat; Melvin Manis

1994-01-01

346

Performance analysis of the impulse shift CVT  

Microsoft Academic Search

Due to rotating inertias within the engine and trans- mission, the response of a vehicle during large engine speed shifts may appear reluctant or even counteractive. To overcome this behaviour, a CVT drivetrain was augmented with a powersplitting planetary gear stage and steel flywheel in the so-called Zero Inertia (ZI) powertrain (1). This transmission concept managed to combine two contradictive

Druten van RM; BG Vroemen; AFA Serrarens; MFM Pesgens

2004-01-01

347

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.

348

Blackbody radiation shifts in optical atomic clocks.  

PubMed

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

Safronova, Marianna; Kozlov, Mikhail; Clark, Charles

2012-03-01

349

Shifts of mathematical thinking in adolescence  

Microsoft Academic Search

This theoretical paper relates key features of the mathematics adolescents are expected to learn in school to other aspects of adolescent development. Difficulties in mathematical learning at that age include changes in perspective and in the actions that are mathematically productive. Commonly-recommended methods of trying to engage adolescents in mathematics do not necessarily enable students to shift to new perceptions

Anne Watson

2010-01-01

350

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.

351

Shift of Meaning and Students' Alternative Concepts  

ERIC Educational Resources Information Center

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

Schmidt, Hans-Jurgen; Volke, Dagmar

2003-01-01

352

II REGIME SHIFTS IN LAKES Introduction  

E-print Network

phytoplankton biomass, turbid water, and high return rates of phosphorus from sediments. Eutrophication. Eutrophication also occurs in flowing waters and oceans (Smith 1998). The oceanic phosphorus cycle appears will focus on three types of regime shifts that have been observed repeatedly in lakes: eutrophication, large

353

Tilting and shifting modes in a spheromak  

SciTech Connect

In the absence of a conducting wall, typical spheromak plasmas are unstable to tilting and/or shifting modes. The effects of the cross-sectional shape, aspect ratio, and the location of a conducting wall on the stability of these modes are investigated.

Jardin, S.C.; Chance, M.S.; Dewar, R.L.; Grimm, R.C.; Monticello, D.A.

1981-04-01

354

Shifting Human Performance Technology to Management.  

ERIC Educational Resources Information Center

Describes the benefits and potential drawbacks of transferring HPT (human performance technology) skills from outside consultants to managers within organizations. Discusses HPT competence and control over work environment, the role of traditional HPT experts after the shift, and three approaches to implementing the change. (PEN)

King, Stephen B.

1998-01-01

355

Gouy phase shift in nondiffracting Bessel beams.  

PubMed

The results of a theoretical and experimental investigation of the Gouy effect in Bessel beams are presented. We point out that the peculiar feature of the Bessel beams of being nondiffracting is related to the accumulation of an extra axial phase shift (i.e., the Gouy phase shift) linearly dependent on the propagation distance. The constant spatial rate of variation of the Gouy phase shift is independent of the order of the Bessel beam, while it is a growing function of the transverse component of the angular spectrum wave-vectors, originated by the transverse confinement of the beam. A free-space Mach-Zehnder interferometer has been set-up for measuring the transverse intensity distribution of the interference between holographically-produced finite-aperture Bessel beams of order from zero up to three and a reference Gaussian beam, at a wavelength of 633 nm. The interference patterns have been registered for different propagation distances and show a spatial periodicity, in agreement with the expected period due to the linear increase of the Gouy phase shift of the realized Bessel beams. PMID:20389732

Martelli, Paolo; Tacca, Matteo; Gatto, Alberto; Moneta, Giorgio; Martinelli, Mario

2010-03-29

356

Hispanics Find Jobs that Shift Migration  

ERIC Educational Resources Information Center

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

Gilroy, Marilyn

2007-01-01

357

Sorting by Placement and Shift Sergi Elizalde  

E-print Network

on billiard balls in a trough, as in Figure 1 below, where the shift is a natural result of moving a ball History Despite its simplicity, homing seems not to have been considered before in the literature procedure, especially as he was able to show it did always terminate, and designed a game around it

Winkler, Peter

358

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

359

Paradigmatic Shift or Tinkering at the Edges?  

ERIC Educational Resources Information Center

In their target paper, "Towards a systemic theory of gifted education," A. Ziegler and S. N. Phillipson present a long awaited call for a paradigmatic shift in thinking within the field of gifted education. The paper considers how educators and researchers within the field could bring about such a change. They challenge the prevailing…

Sutherland, Margaret

2012-01-01

360

Current-induced spin wave Doppler shift  

NASA Astrophysics Data System (ADS)

In metal ferromagnets -namely Fe, Co and Ni and their alloys- magnetism and electrical transport are strongly entangled (itinerant magnetism). This results in a number of properties such as the tunnel and giant magnetoresistance (i.e. the dependence of the electrical resistance on the magnetic state) and the more recently addressed spin transfer (i.e. the ability to manipulate the magnetic state with the help of an electrical current). The spin waves, being the low-energy elementary excitations of any ferromagnet, also exist in itinerant magnets, but they are expected to exhibit some peculiar properties due the itinerant character of the carriers. Accessing these specific properties experimentally could shed a new light on the microscopic mechanism governing itinerant magnetism, which -in turn- could help in optimizing material properties for spintronics applications. As a simple example of these specific properties, it was predicted theoretically that forcing a DC current through a ferromagnetic metal should induce a shift of the frequency of the spin waves [1,2]. This shift can be identified to a Doppler shift undergone by the electron system when it is put in motion by the electrical current. We will show how detailed spin wave measurements allow one to access this current-induced Doppler shift [3]. From an experimental point of view, we will discuss the peculiarities of propagating spin wave spectroscopy experiments carried out at a sub-micrometer length-scale and with MHz frequency resolution. Then, we will discuss the measured value of the Doppler shift in the context of both the old two-current model of spin-polarized transport and the more recent model of adiabatic spin transfer torque. [4pt] [1] P.Lederer and D.L. Mills, Phys.Rev. 148, 542 (1966).[0pt] [2] J. Fernandez-Rossier et al., Phys. Rev. B 69, 174412 (2004)[0pt] [3] V. Vlaminck and M. Bailleul, Science 322, 410 (2008).

Bailleul, Matthieu

2010-03-01

361

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

2012-10-19

362

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

363

Sleep Loss and Fatigue in Shift Work and Shift Work Disorder  

PubMed Central

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

Akerstedt, Torbjorn; Wright, Kenneth P.

2010-01-01

364

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

PubMed

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

Rose, Katrin; Cottenier, Stefaan

2012-08-28

365

Proposal and evaluation of 8-ary elliptical phase shift keying  

Microsoft Academic Search

Some modulation schemes with the general name of elliptical modulation schemes, have been proposed and generally evaluated through computer simulations in our previous works, namely eccentricity shift keying (ESK), inclination angle shift keying (IASK) and elliptical phase shift keying (EPSK). This paper aims to propose and evaluate 8-ary elliptical phase shift keying (8-EPSK), a new modulation scheme with 3-bit information

Chunyi Song; S. Shimarnoto

2005-01-01

366

A CLASS OF NONSOFIC MULTIDIMENSIONAL SHIFT SPACES RONNIE PAVLOV  

E-print Network

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

Pavlov, Ronnie

367

Robust phase-shift estimation method for statistical generalized phase-shifting digital holography.  

PubMed

We propose a robust phase-shift estimation method for statistical generalized phase-shifting digital holography using a slightly off-axis optical configuration. The phase randomness condition in the Fresnel diffraction field of an object can be sufficiently established by the linear phase factor of the oblique incident reference wave. Signed phase-shift values can be estimated with a statistical approach regardless of the statistical properties of the Fresnel diffraction field of the object. We present computer simulations and optical experiments to verify the proposed method. PMID:24977514

Yoshikawa, Nobukazu; Shiratori, Takaaki; Kajihara, Kazuki

2014-06-16

368

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

NASA Technical Reports Server (NTRS)

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

Remington, R.; Pierce, L.

1984-01-01

369

C-13 NMR chemical shifts and visible absorption spectra of unsymmetrical fluoran dye by MO calculations  

Microsoft Academic Search

An unsymmetrical fluoran dye, 3-diethylamino-6-methyl-7-chlorofluoran (DEAMCF) is one of the leuco dyes which shows the coloring-to-decoloring reversible reaction with acidity. We calculated the 13C chemical shieldings of the DEAMCF with the frame model compounds using ab initio gauge invariant atomic orbital methods, and compared it with the experimental shifts. The calculated values of the frame compounds are in good agreement

T. Hoshiba; T Ida; M Mizuno; T Otsuka; K Takaoka; K Endo

2002-01-01

370

Anomalous frequency shifts in the solar system  

E-print Network

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

Jacques Moret-Bailly

2005-07-19

371

Differential phase shift quantum private comparison  

NASA Astrophysics Data System (ADS)

A novel quantum private comparison protocol based on a differential phase shift scheme is presented in this paper. In our protocol, two distrustful participants can compare the equality of information with the help of a semi-honest third party. Taking advantages of differential phase shift scheme, this protocol employs weak coherent pulses instead of single photons and can be implemented without expensive and impractical quantum devices, such as entangled photon source and quantum memory. Therefore, it is simpler and more flexible than previous protocols. Moreover, in principle, nearly 100 % qubit efficiency can be achieved because all photon counts obtained by TP contribute to the comparison. The correctness and security of the protocol are also discussed.

Liu, Xing-tong; Zhang, Bo; Wang, Jian; Tang, Chao-jing; Zhao, Jing-jing

2014-01-01

372

Geometric phase shifts in biological oscillators.  

PubMed

Many intracellular processes continue to oscillate during the cell cycle. Although it is not well-understood how they are affected by discontinuities in the cellular environment, the general assumption is that oscillations remain robust provided the period of cell divisions is much larger than the period of the oscillator. Here, I will show that under these conditions a cell will in fact have to correct for an additional quantity added to the phase of oscillation upon every repetition of the cell cycle. The resulting phase shift is an analogue of the geometric phase, a curious entity first discovered in quantum mechanics. In this letter, I will discuss the theory of the geometric phase shift and demonstrate its relevance to biological oscillations. PMID:24769251

Tourigny, David S

2014-08-21

373

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. PMID:22814475

Allen, Benjamin; Nowak, Martin A.

2012-01-01

374

IC ................................... ... Reaction Product Imaging  

E-print Network

offers two modes of operation. One mode involves imaging of the atomic fragment or reaction productIC ................................... ... Reaction Product Imaging: The H + D2 Reaction Theofanis reaction product imaging. In this experiment, a photolytically produced beam of hydrogen (H) atoms crossed

Zare, Richard N.

375

Iodine Clock Reaction  

NSDL National Science Digital Library

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

376

Robert Collins More on Mean-shift  

E-print Network

1 CSE598G Robert Collins More on Mean-shift R.Collins, CSE, PSU CSE598G Spring 2006 CSE598G Robert only of distance from center CSE598G Robert Collins Kernel-Shadow Pairs h'(r) = - c k (r) Given Gaussian Epanichnikov Gaussian Flat self-replicating! CSE598G Robert Collins Kernel-Shadow Pairs h'(r

Collins, Robert T.

377

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

378

Real Time 3D Brain Shift Compensation  

Microsoft Academic Search

Surgical navigation systems are used intraoperatively to provide the surgeon with a display of preoperative and intraoperative\\u000a data in the same coordinate system and help her or him guide the surgery. However, these systems are subject to inaccuracy\\u000a caused by intraoperative brain movement (brain shift) since commercial systems in use today typically assume that the intracranial\\u000a structures are rigid. Experiments

Oskar M. Skrinjar; James S. Duncan

1999-01-01

379

Raman shifted lasers for medical applications  

Microsoft Academic Search

We propose to operate a Nd:YAG laser at the secondary emission line of 1319 nm and Raman shift in H2 to the first Stokes at 2918 nm near the maximum of water absorption. The quantum efficiency is 45 % and energy conversion of 25 % is achievable in practice. A 300 mJ Nd:YAG laser at 1.32 ?m will produce 75

V. B. Krapchev

1994-01-01

380

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

381

Real-time phase shift interference microscopy.  

PubMed

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

Safrani, Avner; Abdulhalim, Ibrahim

2014-09-01

382

Association Between Positive Affect and Attentional Shifting  

Microsoft Academic Search

This investigation tested the hypothesis that individuals low in positive affect are slower to shift attention from one focus to another. Ninety-six participants completed a self-report mood questionnaire and a standard attentional orienting task. Results indicated a significant correlation between cue validity effects and self-reported positive affect, such that individuals low in positive affect were relatively faster to respond to

Rebecca J. Compton; Derrick Wirtz; Golnaz Pajoumand; Eric Claus; Wendy Heller

2004-01-01

383

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

384

Set Shifting Training with Categorization Tasks  

PubMed Central

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

Soveri, Anna; Waris, Otto; Laine, Matti

2013-01-01

385

Spontaneous microsaccades reflect shifts in covert attention.  

PubMed

Microsaccade rate during fixation is modulated by the presentation of a visual stimulus. When the stimulus is an endogenous attention cue, the ensuing microsaccades tend to be directed toward the cue. This finding has been taken as evidence that microsaccades index the locus of spatial attention. But the vast majority of microsaccades that subjects make are not triggered by visual stimuli. Under natural viewing conditions, spontaneous microsaccades occur frequently (2-3 Hz), even in the absence of a stimulus or a task. While spontaneous microsaccades may depend on low-level visual demands, such as retinal fatigue, image fading, or fixation shifts, it is unknown whether their occurrence corresponds to changes in the attentional state. We developed a protocol to measure whether spontaneous microsaccades reflect shifts in spatial attention. Human subjects fixated a cross while microsaccades were detected from streaming eye-position data. Detection of a microsaccade triggered the appearance of a peripheral ring of grating patches, which were followed by an arrow (a postcue) indicating one of them as the target. The target was either congruent or incongruent (opposite) with respect to the direction of the microsaccade (which preceded the stimulus). Subjects reported the tilt of the target (clockwise or counterclockwise relative to vertical). We found that accuracy was higher for congruent than for incongruent trials. We conclude that the direction of spontaneous microsaccades is inherently linked to shifts in spatial attention. PMID:25297096

Yuval-Greenberg, Shlomit; Merriam, Elisha P; Heeger, David J

2014-10-01

386

A paradigm shift in academic medicine?  

PubMed

The author states that one definition of "paradigm shift" is "the process whereby a governing conceptual framework becomes destabilized and is eventually replaced, more or less wholesale, by a new conceptual consensus." He asks whether recent fundamental changes in academic medicine amount to a paradigm shift, and then briefly describes and comments on 25 changes under way in academic medicine (e.g., the growing importance of cost considerations; focus on episodic care of the acutely ill individual moving instead toward clinical and fiscal responsibility for the health of a population; relative autonomy of the physician evolving to increasing interdependence, both clinical and financial). The author maintains that the basic conceptual framework of academic medicine's core mission--patient care, teaching, and research--remains the same, and that this mission's capacity for good has greatly grown in recent decades. Over the same interval the core business of academic medicine (i.e., its financing) and how that relates to the core mission have indeed become destabilized. These also comprise a "conceptual framework" by which academic medicine has functioned, and that framework is being replaced, compellingly, by what amounts to a new conceptual consensus--in short, a paradigm shift. He urges his colleagues in academic medicine to be clear-eyed, responsive, and innovative, and never to give up as they work to forge a new and sustainable system that maintains and strengthens scholarship and service. PMID:9484184

Rabkin, M T

1998-02-01

387

Control of kinetics and thermodynamics of [1,5]-shifts by aromaticity: a view through the prism of Marcus theory.  

PubMed

The effects of aromatic stabilization on the rates of [1,5]-hydrogen shifts in a series of carbo- and heterocyclic dihydroaromatic compounds were estimated by B3LYP/6-31G computations. The aromatic stabilization energy of the product is directly translated into increased exothermicity of these reactions. Relative trends for a significant range of endothermic and exothermic [1,5]-shifts with different intrinsic activation energies are reliably described by Marcus theory. The effects of aromaticity or antiaromaticity are very large and can lead to dramatic acceleration or deceleration of [1,5]-hydrogen shifts and even to complete disappearance of the reaction barrier. Not only the activation energy but the shape and position of the reaction barrier can be efficiently controlled by changes in the aromaticity of the products, making these systems interesting models for studying hydrogen tunneling. Marcus theory can also be applied successfully to other pericyclic shifts such as [1,5]-shifts which involve chlorine and methyl transfer. PMID:12889962

Alabugin, Igor V; Manoharan, Mariappan; Breiner, Boris; Lewis, Frederick D

2003-08-01

388

Pterandra pyroidea: a case of pollination shift within Neotropical Malpighiaceae  

PubMed Central

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

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

2011-01-01

389

Nuclear field shift effect in the isotope exchange reaction of cadmium using a crown ether  

Microsoft Academic Search

Cadmium isotopes were fractionated by the liquid–liquid extraction technique with a crown ether, dicyclohexano-18-crown-6. The isotopic ratios of mCd\\/111Cd (m: 110, 112, 113, 114, and 116) were measured precisely by the multi-collector inductively coupled plasma spectrometry (MC-ICP-MS). When the isotope enrichment factors were calculated, the odd atomic mass isotopes (111Cd and 113Cd) showed excesses of enrichment comparing to the even

Toshiyuki Fujii; Frédéric Moynier; Philippe Telouk; Francis Albarède

2009-01-01

390

Shape resonances in ion-molecule reaction  

NASA Astrophysics Data System (ADS)

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

Sakimoto, Kazuhiro

2014-01-01

391

Light-shift-induced photonic nonlinearities  

E-print Network

We propose a new method to produce self- and cross-Kerr photonic nonlinearities, using light-induced Stark shifts due to the interaction of a cavity mode with atoms. The proposed experimental set-up is considerably simpler than in previous approaches, while the strength of the nonlinearity obtained with a single atom is the same as in the setting based on electromagnetically induced transparency. Furthermore our scheme can be applied to engineer effective photonic nonlinear interactions whose strength increases with the number of atoms coupled to the cavity mode, leading to photon-photon interactions several orders of magnitude larger than previously considered possible.

Fernando G. S. L. Brandao; Michael J. Hartmann; Martin B. Plenio

2007-05-16

392

Pendulum Shifts, Context, Error, and Personal Accountability  

SciTech Connect

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

Harold Blackman; Oren Hester

2011-09-01

393

A partial differential equation for pseudocontact shift.  

PubMed

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

Charnock, G T P; Kuprov, Ilya

2014-10-01

394

Quasicrystals - a paradigm shift in crystallography?  

PubMed

The discovery of quasicrystals had important consequences for our understanding of long-range order in thermodynamic equilibrium, the definition of the term 'crystal' as well as diffraction theory. Quasicrystals have been observed not only at the atomic scale in binary and ternary intermetallic systems, but also at the mesoscale in self-assembled colloids and block-copolymers, and even at the macroscale in packings of hard polyhedra. How important was the discovery of quasicrystals for crystallography? Did it usher in a scientific revolution and a paradigm shift? These questions are discussed following a short overview of the status of quasicrystal research. PMID:24801696

Steurer, Walter

2014-01-01

395

Spectral shifts in metal-enhanced fluorescence  

NASA Astrophysics Data System (ADS)

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

Karolin, Jan; Geddes, Chris

2014-08-01

396

Estimate of coherent tune shifts for PEP  

SciTech Connect

Transverse and longitudinal instabilities for a bunched PEP beam with a Gaussian distribution are treated using the standard technique in which instability problems are solved by looking for eigenvalues of the linearized Vlasov equation. The eigen solutions are conveniently expanded in terms of the Laquerre polynomials, and the eigenvalues are given by a symmetric matrix whose elements can be expressed in infinite series. The well-known formalism is used to obtain the matrix formula, and then applied numerically to the PEP ring to estimate the transverse coherent tune shifts. The impedance used is that estimated for the PEP RF cavities. The agreement with experimental data seems reasonable.

Yao, C.Y.; Chao, A.W.

1981-02-01

397

Polarization phase shifting dispersed fringe sensor.  

PubMed

The dispersed fringe sensor (DFS) has been demonstrated as an effective means of measuring mirror segment piston error for telescopes with primary mirror apertures below 10 meters. With larger proposed telescopes such as The Thirty Meter Telescope (TMT) and The European Large Telescope (ELT) including ever more segments, there is a need for improvement in the co-phasing capability for segmented primary mirrors. In this paper a novel DFS that employs polarization phase shifting technology is introduced. This novel technology provides system designers and engineers with a new tool to extend the dynamic range of a DFS. PMID:22418128

Olczak, Gene

2012-02-13

398

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

2012-06-01

399

NUCLEAR WASTE VITRIFICATION EFFICIENCY COLD CAP REACTIONS  

SciTech Connect

The cost and schedule of nuclear waste treatment and immobilization are greatly affected by the rate of glass production. Various factors influence the performance of a waste-glass melter. One of the most significant, and also one of the least understood, is the process of batch melting. Studies are being conducted to gain fundamental understanding of the batch reactions, particularly those that influence the rate of melting, and models are being developed to link batch makeup and melter operation to the melting rate. Batch melting takes place within the cold cap, i.e., a batch layer floating on the surface of molten glass. The conversion of batch to glass consists of various chemical reactions, phase transitions, and diffusion-controlled processes. These include water evaporation (slurry feed contains as high as 60% water), gas evolution, the melting of salts, the formation of borate melt, reactions of borate melt with molten salts and with amorphous oxides (Fe{sub 2}O{sub 3} and Al{sub 2}O{sub 3}), the formation of intermediate crystalline phases, the formation of a continuous glass-forming melt, the growth and collapse of primary foam, and the dissolution of residual solids. To this list we also need to add the formation of secondary foam that originates from molten glass but accumulates on the bottom of the cold cap. This study presents relevant data obtained for a high-level-waste melter feed and introduces a one-dimensional (1D) mathematical model of the cold cap as a step toward an advanced three-dimensional (3D) version for a complete model of the waste glass melter. The 1D model describes the batch-to-glass conversion within the cold cap as it progresses in a vertical direction. With constitutive equations and key parameters based on measured data, and simplified boundary conditions on the cold-cap interfaces with the glass melt and the plenum space of the melter, the model provides sensitivity analysis of the response of the cold cap to the batch makeup and melter conditions. The model demonstrates that batch foaming has a decisive influence on the rate of melting. Understanding the dynamics of the foam layer at the bottom of the cold cap and the heat transfer through it appears crucial for a reliable prediction of the rate of melting as a function of the melter-feed makeup and melter operation parameters. Although the study is focused on a batch for waste vitrification, the authors expect that the outcome will also be relevant for commercial glass melting.

KRUGER AA; HRMA PR; POKORNY R

2011-07-29

400

Generalized phase-shifting algorithm for inhomogeneous phase shift and spatio-temporal fringe visibility variation.  

PubMed

A cascade least-squares scheme for wrapped phase extraction using two or more phase-shifted fringe-patterns with unknown and inhomogeneous surface phase shift is proposed. This algorithm is based on the parameter estimation approach to process fringe-patterns where, except for the interest phase distribution that is a function of the space only, all other parameters are functions of both space and time. Computer simulations and experimental results show that phase computing is possible even when an inhomogeneous phase shift is induced by nonlinearity of the piezoelectric materials or miscalibrated phase shifters. The algorithm's features and its operating conditions will been discussed. Due to the useful properties of this algorithm such as the robustness, computational efficiency, and user-free execution, this proposal could be used in automatic applications. PMID:24663793

Juarez-Salazar, Rigoberto; Robledo-Sanchez, Carlos; Guerrero-Sanchez, Fermin; Rangel-Huerta, A

2014-02-24

401

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

NASA Technical Reports Server (NTRS)

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

Korb, Larry (inventor)

1991-01-01

402

Microscale Thermite Reactions.  

ERIC Educational Resources Information Center

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

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

1998-01-01

403

Treatment and Managing Reactions  

MedlinePLUS

Treatment & Managing Reactions Currently, the only way to prevent a food-allergic reaction is to avoid the problem food. ... treatment plan includes all of the following: Strict avoidance of problem foods Working with your doctor to ...

404

Passivation of Anodic Reactions.  

National Technical Information Service (NTIS)

Extending the Wagner definition of passivity to anodic reactions of chemical species on inert electrodes, passivation of a Pt electrode for the hydrogen oxidation reaction can be explained as being caused by small amounts (fraction of a monolayer) of adso...

S. Schuldiner

1968-01-01

405

Microfluidic chemical reaction circuits  

DOEpatents

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

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

2012-06-26

406

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

407

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. PMID:21866436

Tang, Sishi; Case, David A.

2011-01-01

408

Practical zero-shift tuning in geonium.  

PubMed Central

Compositeness of the electron may show up in a very small deviation of the measured electron g factor from one calculated for a point electron by quantum electrodynamics. The precision of our g measurements is currently limited by an interaction of the cyclotron motion with standing waves in the trap cavity containing the electron. The important element introduced here is the systematic exploration of the trap cavity modes and the electron's coupling to them by measuring the shifted electron g factor gc = gc(omega e) as a function of the cyclotron frequency omega e. By measuring gc values at five different omega e values and modeling the trap cavity by six lumped LC circuits, the L values for the four most important modes may be determined and finally the unshifted g value may be extracted. Auxiliary experiments are relied upon only for the L values of the two least critical cavity modes. By designing the trap as a high-Q microwave cavity, an electron cyclotron and anomaly resonance linewidth one or even two orders of magnitude narrower than in free space may be approached without introducing appreciable frequency shifts. PMID:11607280

Dehmelt, H; Van Dyck, R; Palmer, F

1992-01-01

409

Advanced Receiver For Phase-Shift-Keyed Signals  

NASA Technical Reports Server (NTRS)

ARX II is second "breadboard" version of advanced receiver, a hybrid digital/analog receiving subsystem, extracting symbols and Doppler shifts from weak phase-shift-keyed signals. Useful in terrestrial digital communication systems.

Hinedi, Sami M.

1992-01-01

410

Parallel Graph Decompositions Using Random Shifts Gary L. Miller  

E-print Network

Parallel Graph Decompositions Using Random Shifts Gary L. Miller CMU glmiller@cs.cmu.edu Richard. Our algorithm builds upon the shifted shortest path approach introduced in [Blelloch,Gupta,Koutis,Miller

Miller, Gary L.

411

Topic Shifts in American and Japanese Business Conversation.  

ERIC Educational Resources Information Center

Compares the different ways in which Americans and Japanese people shift topics in business conversations. It is suggested that the different uses of topic-shifting strategies reflect a more profound difference in cultural expectations. (Author/GLR)

Yamada, Haru

1990-01-01

412

Microscale Thermite Reactions  

NASA Astrophysics Data System (ADS)

The reaction of aluminum with the oxides of a variety of elements (aluminothermy, or the Goldschmidt process) illustrates exothermic reactions that require a high activation energy. It is also an appropriate experiment with regard to the discussion of Ellingham diagrams. Because it is spectacular, this reaction is a favorite for demonstrations. When drama is not the main objective, conducting these reactions at microscale level offers numerous advantages over the usual scale.

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

1998-12-01

413

Nuclear Reactions Some Basics  

E-print Network

Q in a reaction ­ Definition: Q = masses BEFORE the reaction ­ masses AFTER the reaction ­ Example: e + 3He e + p + d: Q = (Me + M3He) - (Me + Mp + Md) ­ Q may be >0 (exothermic) or ?) measurements made in a nuclear physics lab experiment. #12;Formal Definition of Cross Section · Consider a beam

Gilfoyle, Jerry

414

Chemical Reactions at Surfaces  

Microsoft Academic Search

Chemical reactions at surfaces underlie some of the most important processes of today, including catalysis, energy conversion, microelectronics, human health and the environment. Understanding surface chemical reactions at a fundamental level is at the core of the field of surface science. The Gordon Research Conference on Chemical Reactions at Surfaces is one of the premiere meetings in the field. The

Nancy Ryan Gray Michael Henderson

2010-01-01

415

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

416

Design of cyclic shift interleavers for Turbo Codes  

Microsoft Academic Search

In this paper we consider cyclic shift interleavers for turbo coding. The properties of cyclic shift interleavers are discussed\\u000a and compared with S-random interleavers. It is shown that the cyclic shift interleavers are equivalent or better than the\\u000a S-random interleavers in the ability to break low weight input patterns. We estimated the performance of turbo codes with\\u000a cyclic shift interleavers

Jinhong Yuan; Branka Vucetic; Wen Feng; Mark Tan

2001-01-01

417

Kinetics of and intermediates in a photocycle branching reaction of the photoactive yellow protein from Ectothiorhodospira halophila  

E-print Network

/Vis spectroscopy. As compared to the parallel dark recovery reaction of the presumed blue-shifted signaling state pKinetics of and intermediates in a photocycle branching reaction of the photoactive yellow protein Abstract We have studied the kinetics of the blue light-induced branching reaction in the photocycle

van Stokkum, Ivo

418

VIEWLS Final recommendations report Shift Gear to Biofuels  

E-print Network

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

419

Understanding Phase Shifting Equivalent Keys and Exhaustive Search  

E-print Network

Understanding Phase Shifting Equivalent Keys and Exhaustive Search C^ome Berbain1, Aline Gouget2 the concept of phase shift- ing equivalent keys in stream ciphers, and exploit this concept in order to mount attacks on some specific ciphers. The idea behind phase shifting equivalent keys is that, for many ciphers

420

The Capacity of Noncoherent Continuous-Phase Frequency Shift Keying  

E-print Network

The Capacity of Noncoherent Continuous-Phase Frequency Shift Keying Shi Cheng, Rohit Iyer Seshadri frequency shift keying (CPFSK). The modulation may use an arbitrary modulation index h and the number and multiple tones when the bandwidth requirement is tight. I. INTRODUCTION Continuous-phase frequency-shift

Valenti, Matthew C.

421

Understanding Phase Shifting Equivalent Keys and Exhaustive Search  

E-print Network

Understanding Phase Shifting Equivalent Keys and Exhaustive Search Câ??ome Berbain 1 , Aline Gouget 2 the concept of phase shift­ ing equivalent keys in stream ciphers, and exploit this concept in order to mount attacks on some specific ciphers. The idea behind phase shifting equivalent keys is that, for many ciphers

422

The Coming Market Shift: Business Strategy and Climate Change*  

E-print Network

#12;7 The Coming Market Shift: Business Strategy and Climate Change* Andrew J Hoffman, University risky strategy, however, in the face of the coming market shift. The debate is thus strategic (not an impending market shift ­ one that will both alter existing markets and create new ones

Hoffman, Andrew J.

423

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

424

30 CFR 75.362 - On-shift examination.  

Code of Federal Regulations, 2013 CFR

...conducted within 3 hours before the oncoming shift. (c) Persons...the start of each shift at each working place...positioned at least 12 inches from the roof...f) During each shift that coal is produced...intervals not exceeding 4 hours, tests for...

2013-07-01

425

30 CFR 75.362 - On-shift examination.  

...conducted within 3 hours before the oncoming shift. (c) Persons...the start of each shift at each working place...positioned at least 12 inches from the roof...f) During each shift that coal is produced...intervals not exceeding 4 hours, tests for...

2014-07-01

426

30 CFR 75.362 - On-shift examination.  

Code of Federal Regulations, 2011 CFR

...conducted within 3 hours before the oncoming shift. (c) Persons...the start of each shift at each working place...positioned at least 12 inches from the roof...f) During each shift that coal is produced...intervals not exceeding 4 hours, tests for...

2011-07-01

427

30 CFR 75.362 - On-shift examination.  

Code of Federal Regulations, 2012 CFR

...conducted within 3 hours before the oncoming shift. (c) Persons...the start of each shift at each working place...positioned at least 12 inches from the roof...f) During each shift that coal is produced...intervals not exceeding 4 hours, tests for...

2012-07-01

428

CIRCADIAN BIOLOGICAL CHARACTERISTICS AFTER SHIFTING SLEEP AND MEAL TIMES  

Microsoft Academic Search

In order to examine differences among individuals and among variables related to the rate of shift of the circadian system, nine male students were studied for 72 h under controlled physical environmental conditions. During this 3-day test, they were subjected to a 12-hour shift in the times of sleep and meals. Differences in the rate of shift from day 1

429

30 CFR 75.362 - On-shift examination.  

Code of Federal Regulations, 2010 CFR

...conducted within 3 hours before the oncoming shift. (c) Persons...the start of each shift at each working place...positioned at least 12 inches from the roof...f) During each shift that coal is produced...intervals not exceeding 4 hours, tests for...

2010-07-01

430

Real Time Mean Shift Tracking using Optical Flow Distribution  

Microsoft Academic Search

This paper describes about real-time object tracking method based on mean shift tracking algorithm. The mean shift tracking algorithm is an efficient technique for tracking object through an image. The original mean shift tracking is proposed to apply the color image based on the color distribution. A near-infrared camera is used with surveillance system to take in the dark. It

N. Oshima; T. Saitoh; R. Konishi

2006-01-01

431

POLLINATOR SHIFTS AND THE ORIGIN AND LOSS OF PLANT  

E-print Network

POLLINATOR SHIFTS AND THE ORIGIN AND LOSS OF PLANT SPECIES1 Diane R. Campbell2 ABSTRACT Pollinators in integrating foraging energetics of animals into our understanding of how shifts in major pollinators influence of conservation have inspired pollination biologists to consider the implications of pollinator shifts and losses

Campbell, Diane

432

Finite size mass shift formula for stable particles revisited  

E-print Network

Luescher's finite size mass shift formula in a periodic finite volume, involving forward scattering amplitudes in the infinite volume, is revisited for the two stable distinguishable particle system. The generalized mass shift formulae for the boson and fermion are derived in the boson-boson and fermion-boson systems, respectively. The nucleon mass shift is discussed in the nucleon-pion system.

Koma, Y; Koma, Yoshiaki; Koma, Miho

2004-01-01

433

Predator-induced morphological shift in the pea aphid  

PubMed Central

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

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

1999-01-01

434

Climate Change and High Mountain Vegetation Shifts  

Microsoft Academic Search

In the 20th century, the global climate has warmed about 0.6 K. High-mountain areas as well as areas of high latitudes are experiencing even greater increases in temperature especially in the last half century. With changing climatic conditions, the determinants of global, and in particular, altitudinal distribution of plants and plant communities are likely to change and a subsequent reaction

Gian-Reto Walther; Richard Pott

435

Experimental Studies of Shift-Work III: Stabilized 12-hour Shift Systems  

Microsoft Academic Search

Twenty-two subjects took part in an experiment to determine whether the relationship botween efficiency at mental tasks and the circadian rhythm of body temperature observed in two earlier studios was affected by an increase in the length of the duty spoil from S to 12 hours. Subjects wore assignod either to a control ‘ day ‘ shift (0800-2000) or a

W. P. COLQUHOUKT; M. J. F. BLAKE; R. S. EDWARDS

1969-01-01

436

Experimental Studies of Shift-Work II: Stabilized 8-hour Shift Systems  

Microsoft Academic Search

Thirty-one subjects were employed in an experiment to determine whether the relationship between efficiency at mental tasks and the circadian rhythm of body temperature observed in an earlier study was affected by an increase in the length of the duty-spell from 4 to 8 hours. Subjects wore assigned either to a control ‘ day ’ shift (O800–1600), a ‘ night

W. P. COLQUHOUN; M. J. F. BLAKE; B.. S. EDWARDS

1968-01-01

437

Mechanisms in knockout reactions  

E-print Network

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

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

2009-02-16

438

Red Shift in a Laboraory Environment  

E-print Network

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

Yuriy A. Yatsunenko; Julian A. Budagov

2011-03-04

439

DNA structures from phosphate chemical shifts  

PubMed Central

For B-DNA, the strong linear correlation observed by nuclear magnetic resonance (NMR) between the 31P chemical shifts (?P) and three recurrent internucleotide distances demonstrates the tight coupling between phosphate motions and helicoidal parameters. It allows to translate ?P into distance restraints directly exploitable in structural refinement. It even provides a new method for refining DNA oligomers with restraints exclusively inferred from ?P. Combined with molecular dynamics in explicit solvent, these restraints lead to a structural and dynamical view of the DNA as detailed as that obtained with conventional and more extensive restraints. Tests with the Jun-Fos oligomer show that this ?P-based strategy can provide a simple and straightforward method to capture DNA properties in solution, from routine NMR experiments on unlabeled samples. PMID:19942687

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

2010-01-01

440

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. PMID:17288568

Dorman, Karin S

2007-01-01

441

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

Microsoft Academic Search

OBJECTIVES: To investigate of the effects of distribution of rest days in 12 hour shift systems. Although several studies have examined the effects of compressing work schedules by comparing 8 and 12 hour shift systems, there is little published research examining the various forms of 12 hour shift system. METHODS: An abridged version of the standard shiftwork index which included

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

1999-01-01

442

Shift-multiplexed self-referential holographic data storage.  

PubMed

The feasibility and the properties of shift-multiplexed self-referential holographic data storage (SR-HDS) were investigated. Although SR-HDS has attractive features as typified by referenceless holographic recording, its multiplexing properties, which are consummately important for holographic data storage, have not been clarified until now. The results of numerical and experimental evaluations of medium shift dependence in SR-HDS clarified that the shift selectivity is almost the same as in collinear holography. Furthermore, 25 datapages were successfully shift-multiplexed with the shift pitch of 8.3 ?m by the numerical simulation. PMID:25090055

Takabayashi, Masanori; Okamoto, Atsushi; Eto, Taisuke; Okamoto, Takashi

2014-07-10

443

s-Wave Collisional Frequency Shift of a Fermion Clock  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

444

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

2010-12-01

445

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

SciTech Connect

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

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

2010-06-15

446

Weathering Reactions and Soil-Groundwater Reactions  

NSDL National Science Digital Library

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

Sherman, David M.; Bristol, University O.

447

Noncanonical Reactions of Flavoenzymes  

PubMed Central

Enzymes containing flavin cofactors are predominantly involved in redox reactions in numerous cellular processes where the protein environment modulates the chemical reactivity of the flavin to either transfer one or two electrons. Some flavoenzymes catalyze reactions with no net redox change. In these reactions, the protein environment modulates the reactivity of the flavin to perform novel chemistries. Recent mechanistic and structural data supporting novel flavin functionalities in reactions catalyzed by chorismate synthase, type II isopentenyl diphosphate isomerase, UDP-galactopyranose mutase, and alkyl-dihydroxyacetonephosphate synthase are presented in this review. In these enzymes, the flavin plays either a direct role in acid/base reactions or as a nucleophile or electrophile. In addition, the flavin cofactor is proposed to function as a “molecular scaffold” in the formation of UDP-galactofuranose and alkyl-dihydroxyacetonephosphate by forming a covalent adduct with reaction intermediates. PMID:23203060

Sobrado, Pablo

2012-01-01

448

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

449

Fundamental studies of retrograde reactions in direct liquefaction  

SciTech Connect

The overall objective of the program was to improve the understanding of retrograde reactions and their dependencies on coal rank and structure, and/or coal modifications and reaction conditions. Because retrograde reactions are competitive with bond breaking reactions, an understanding of both is required to shift the competition in favor of the latter. Related objectives were to clarify the conflicting observations reported in literature on such major topics as the role of oxygen groups in retrograde reactions and to provide a bridge from very fundamental studies on pure compounds to phenomenological studies on actual coal. This information was integrated into the FG-DVC model, which was improved and extended to the liquefaction context.

Serio, M.A.; Solomon, P.R.; Kroo, E.; Charpenay, S.; Bassilakis, R.

1991-12-17

450

Reaction-diffusion textures  

Microsoft Academic Search

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

Andrew P. Witkin; Michael Kass

1991-01-01

451

A generalization of binary minimum shift keying and staggered quadriphase shift keying modulation  

NASA Technical Reports Server (NTRS)

A generalized modulation scheme, which includes minimum shift keying (MSK) and staggered quadriphase shift keying (SQPSK) as special cases, is analyzed. The general modulator is realized as a one-input, two-output sequence transducer whose outputs select the carrier signal for each band. This form of the modulator has the practical advantage of not requiring any RF filtering since there is no actual mixing of the carriers with the modulating signals. It is shown that the optimum demodulator (whether hard-decision or soft-decision) always can make its decisions from the received waveform over two bands when the interference is additive white Gaussian noise, thus generalizing a well-known result for hard decision demodulation of MSK and SQPSK signals. The power spectra of MSK and SQPSK signals are derived to isolate the role played by coherency between the modulating signals and the carriers.

Massey, J. L.

1979-01-01

452

Shifting self, shifting memory: testing the self-memory system model with hypnotic identity delusions.  

PubMed

According to Conway's self-memory system (SMS) model, autobiographical memories may be facilitated, inhibited, or misremembered to be consistent with current self. In 3 experiments, the authors tested this by hypnotically suggesting an identity delusion and indexing whether this shift in self produced a corresponding shift in autobiographical memory. High hypnotizable participants displayed a compelling identity delusion and elicited specific autobiographical events that they could justify when challenged. These memories were reinterpretations of previous experiences that supported the suggested identity. Importantly, autobiographical memories that were no longer consistent with the hypnotically deluded self were less accessible than other memories. The authors discuss these findings in the context of Conway's SMS model and propose 2 accounts of autobiographical remembering during hypnotic and clinical delusions. PMID:23957262

Cox, Rochelle E; Barnier, Amanda J

2013-01-01

453

All-optical modulation format conversion from frequency-shift-keying to phase-shift-keying  

NASA Astrophysics Data System (ADS)

We have realized a novel optical modulation format conversion using double-sideband suppressed-carrier modulation. An optical wideband frequency-shift-keying (FSK) signal, generated by an external FSK modulator, can be directly converted into an optical phase-shift-keying (PSK) signal, where the FSK signal having two spectral components was fed to an optical intensity modulator followed by an optical bandpass filter. Optical frequency of the FSK signal was mapped into optical phase of the bandpass filter output whose phase deviation depends on a chirp of the FSK signal.We demonstrated modulation format conversion from FSK to PSK at 10 Gbps, by using a high-speed optical FSK modulator and a dual electrode Mach-Zehnder intensity modulator.

Kawanishi, Tetsuya; Sakamoto, Takahide; Izutsu, Masayuki

2005-10-01

454

Classic Organic Reactions  

NSDL National Science Digital Library

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

2007-05-12

455

An isotropic chemical shift-chemical shift anisotropic correlation experiment using discrete magic angle turning.  

PubMed

An isotropic-anisotropic shift 2D correlation spectroscopy is introduced that combines the advantages of both magic angle turning (MAT) and magic angle hopping (MAH) technologies. In this new approach, denoted DMAT for "discrete magic angle turning", the sample rotates clockwise followed by an anticlockwise rotation of exactly the same amount with each rotation less or equal than 360 degrees but greater than 240 degrees , with the rotation speed being constant only for times related to the evolution dimension. This back and forth rotation is repeated and synchronized with a special radio frequency (RF) pulse sequence to produce an isotropic-anisotropic shift 2D correlation spectrum. For any spin-interaction of rank-2 such as chemical shift anisotropy, isotropic magnetic susceptibility interaction, and residual homo-nuclear dipolar interaction in biological fluid samples, the projection along the isotropic dimension is a high resolution spectrum. Since a less than 360 degrees sample rotation is involved, the design potentially allows for in situ control over physical parameters such as pressure, flow conditions, feed compositions, and temperature so that true in situ NMR investigations can be carried out. PMID:19246221

Hu, Jian Zhi; Sears, Jesse A; Kwak, Ja Hun; Hoyt, David W; Wang, Yong; Peden, Charles H F

2009-05-01

456

An isotropic chemical shift-chemical shift anisotropic correlation experiment using discrete magic angle turning  

NASA Astrophysics Data System (ADS)

An isotropic-anisotropic shift 2D correlation spectroscopy is introduced that combines the advantages of both magic angle turning (MAT) and magic angle hopping (MAH) technologies. In this new approach, denoted DMAT for "discrete magic angle turning", the sample rotates clockwise followed by an anticlockwise rotation of exactly the same amount with each rotation less or equal than 360° but greater than 240°, with the rotation speed being constan