Kinetics

On the relationship between structure and reaction rate in olefin ring-closing metathesis

by David Nelson

Crystal Structure of ChrR - A Quinone Reductase with the Capacity to Reduce Chromate

by Sebastien Poulain

PLoS ONE, 2012
Eswaramoorthy S and Poulain S (equal contributors), Hienerwadel R, Brémond N, Sylvester MD, Zhang Y-B, Berthomieu C, Van Der Lelie D, Matin A.

The Escherichia coli ChrR enzyme is an obligatory two-electron quinone reductase that has many applications, such as... more The Escherichia coli ChrR enzyme is an obligatory two-electron quinone reductase that has many applications, such as in chromate bioremediation. Its crystal structure, solved at 2.2 Å resolution, shows that it belongs to the flavodoxin superfamily in which flavin mononucleotide (FMN) is firmly anchored to the protein. ChrR crystallized as a tetramer, and size exclusion chromatography showed that this is the oligomeric form that catalyzes chromate reduction. Within the tetramer, the dimers interact by a pair of two hydrogen bond networks, each involving Tyr128 and Glu146 of one dimer and Arg125 and Tyr85 of the other; the latter extends to one of the redox FMN cofactors. Changes in each of these amino acids enhanced chromate reductase activity of the enzyme, showing that this network is centrally involved in chromate reduction.

Kinetics and reactional pathway of Imazapyr photocatalytic degradation Influence of pH and metallic ions

by Marion CARRIER

Non-isothermal kinetic analysis of the devolatilization of corn cobs and sugar cane bagasse in an inert atmosphere

by Marion CARRIER

RBS STUDY OF THE EFFECT OF ARSENIC AND PHOSPHORUS INTERFACIAL SEGREGATION UPON THE SINTERING OF CONTACTS BETWEEN IMPLANTED POLYCRYSTALLINE SILICON AND ALUMINUM -SILICON(1%)

by Nicole Herbots

Nicole HERBOTS *, Maurice LOBET and Femand Van de WIELE
Microekxtronics Lab, Uniwrsite Catholique de Lmamin, 3, place du Levant. B - 1348 Louvain -la - Neuve, Belgium
Nuclear Instruments and Methods in Physics Research B7/8 (1985) 278-286 North-Holland, Amsterdam

The sintering behavior of the interface between Al :Si(l%) alloy and polycrystalline Si (poly-Si) was studied as a... more The sintering behavior of the interface between Al :Si(l%) alloy and polycrystalline Si (poly-Si) was studied as a function of the poly-Si implantation dose by combining RBS, SEM, TEM and X-ray microanalysis. Two different N-dopants were used: arsenic and phosphorus. The dopants were implanted in the poly-Si layer and thermal annealing was used to obtain dopant segregation towards the poly-Si interfacea.
After sir&ring, two main effects were detected: (1) Al-Si eutectic phase precipitates and Si crystallites are formed at the interface. (2) The density of precipitates is a function of the implantation dose. For doses above 1 x lOI5 at./cm2. segregated arsenic and phosphorus are found to completely inhibit this precipitation process, provided that the segregation peak of the dopant profile is preserved before metallization.
Several conclusions can be drawn: for surface concentrations higher than 8~10’~ at./cm3, arsenic and phosphorus inhibit the precipitation of the Al-Si eutectic phase, and thus inhibit interactions between the films at the interface. Moreover, argon gas, usedfor sputtering deposition of aluminum, segregated at the poly-Si/Al: Si(l%) interface and may also inhibit the metal-semiconductor interdiffusion.

Arsenic Dopant Influence upon the Sintering Behavior of the Aluminum‐Polysilicon Interface

by Nicole Herbots

REF: J. Electrochem. Soc., Volume 131, Issue 3, pp. 645-652 (1984)
(Issue Date: March 1984).

AUTHORS Nicole Herbots, Fernand Van de Wiele, and Maurice Lobet
Laboratoire de Microelectronique, Universite Catholique de Louvain, Louvain-la-Neuve, Belgium

Robert G. Elliman
Department of Communication and Electronic Engineering, Royal Melbourne Institute of Technology, Melbourne, Australia

Interdiffusion between thin films of aluminum (Al) and polycrystalline silicon (poly-Si) has been studied with the... more Interdiffusion between thin films of aluminum (Al) and polycrystalline silicon (poly-Si) has been studied with the purposeof obtaining a stable interface upon sintering for IC metallization. The solid-phase crystal regrowth of Si due to this lowtemperature interdiffusion has also been investigated. Dopant segregation towards the interfaces and the grain boundariesof arsenic-implanted poly-Si was used successfully to control the kinetics of Al-poly-Si interactions. The correlation betweenthe arsenic depth profiles, the Si-layer microstructure, and the sintering behavior of the Al-poly-Si interface wasmeasured by RBS, (scanning) AES, SEM, TEM, and grazing incidence x-rays. Quantitative results and discussion of thediffusion mechanisms at work are presented. It is shown that the presence of an arsenic segregation peak on top of thepoly-Si layer stabilizes Al/poly-Si interface. A concentration of 1019 atom/cm3 appears to be a minimum threshold forsintering at 465°C.

ATOMIC TRANSPORT KINETICS ACROSS Al/Si INTERFACES

by Nicole Herbots

Controlled vocabularies and semantics in systems biology

by Anna Zhukova

Courtot M., Juty N., Knüpfer C., Waltemath D., Zhukova A., Dräger A., Dumontier M., Finney A., Golebiewski M., Hastings J., Hoops S., Keating S., Kell D.B., Kerrien S., Lawson J., Lister A., Lu J., Machne R., Mendes P., Pocock M., Rodriguez N., Villeger A., Wilkinson D.J., Wimalaratne S., Laibe C., Hucka M., Le Novère N. (2011) Molecular Systems Biology, 7:543

The use of computational modeling to describe and analyze biological systems is at the heart of systems biology. Model... more The use of computational modeling to describe and analyze biological systems is at the heart of systems biology. Model structures, simulation descriptions and numerical results can be encoded in structured formats, but there is an increasing need to provide an additional semantic layer. Semantic information adds meaning to components of structured descriptions to help identify and interpret them unambiguously. Ontologies are one of the tools frequently used for this purpose. We describe here three ontologies created specifically to address the needs of the systems biology community. The Systems Biology Ontology (SBO) provides semantic information about the model components. The Kinetic Simulation Algorithm Ontology (KiSAO) supplies information about existing algorithms available for the simulation of systems biology models, their characterization and interrelationships. The Terminology for the Description of Dynamics (TEDDY) categorizes dynamical features of the simulation results and general systems behavior. The provision of semantic information extends a model's longevity and facilitates its reuse. It provides useful insight into the biology of modeled processes, and may be used to make informed decisions on subsequent simulation experiments.

Photochromic Ruthenium Sulfoxide Complexes: Evidence for Isomerization Through a Conical Intersection

by Beth Anne McClure

B.A. McClure, N.V. Mockus, D.P. Butcher, D.A. Lutterman, C. Turro, J.L. Petersen, J.J. Rack; Inorganic Chemistry, 2009, 48(17), 8084.

Excited State Distortion in Photochromic Ruthenium Sulfoxide Complexes

by Beth Anne McClure

B. A. McClure, E. R. Abrams, J. J. Rack. J. Am. Chem. Soc. 2010, 132 (15), 5428-5436

http://pubs.acs.org/doi/abs/10.1021%2Fja9099399

Probing 'Spin-Forbidden'Oxygen-Atom Transfer: Gas-Phase Reactions of Chromium− Porphyrin Complexes

by Francesco Lanucara

Purification and kinetic characterization of chicken liver inorganic pyrophosphatase.

by D Syiem

The kinetics of ferrocene volatilisation from an ionic liquid

by Leigh Aldous

C. Fu, L. Aldous, E. J. F. Dickinson, N. S. A. Manan, and R. G. Compton, ChemPhysChem, 2011, 12(9), 1708–1713.

http://dx.doi.org/DOI:10.1002/cphc.201100204

The volatilisation of ferrocene (Fc), dissolved in the ionic liquid N-butyl-N-methylpyrrolidinium... more The volatilisation of ferrocene (Fc), dissolved in the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [C 4mpyrr][NTf2], to the gas phase has been indirectly monitored by cyclic voltammetry and chronoamperometry. Simulation of the observed trends in concentration with time using a simple model allowed quantification of the process. Volatilisation of dissolved Fc under flowing wet and dry dinitrogen gas (N2) was found to be kinetically limited with a rate constant in the region of 2× 10-7 cm s-1. The activation energy of diffusion for Fc was found to be 28.2±0.7 kJ mol-1, while the activation energy of volatilisation of Fc from [C4mpyrr][NTf2] to dry N2 was found to be 85±2 kJ mol-1.

http://dx.doi.org/DOI:10.1002/cphc.201100204

The Group I Alkali metals in ionic liquids: Electrodeposition and determination of their kinetic and thermodynamic properties

by Leigh Aldous

Rahmat Wibowo, Leigh Aldous, Sarah E. Ward-Jones and Richard G. Compton, Electrochemical Society - 218th ECS Meeting Abstracts 2010, MA 2010-02 3, pp. 2171

http://link.aip.org/link/?MAECES/1002/2171/1

Work relating to the electrodeposition of the Group I Alkali metals (Li, Na, K, Rb and Cs) from a range of ILs will be... more Work relating to the electrodeposition of the Group I Alkali metals (Li, Na, K, Rb and Cs) from a range of ILs will be described, an extensive range of fundamental parameters briefly presented, and the electrochemical analysis and simulation methods utilised in their quantification discussed.

Initially a suitable IL had to be determined. Work relating to the electrodeposition of Na and Li from 12 ILs will be briefly discussed.1,2 Extension of the electrochemical window, alloy formation and underpotential deposition will also be noted.2,3 After demonstrating the applicability of [C4mPyrr][NTf2], the cyclic voltammetry for all five metals will be presented.4

The formal potential, Ef0, is the most fundamental thermodynamic parameter. This value, combined with kinetic parameters such as the electrochemical rate constant, k0, and the transfer coefficient, α, can be used to determine if a metal can be electrodeposited from an electrolyte of choice.

By combining cyclic voltammetry and simulation, the values of Ef0 (vs. Fc/Fc+), k0 and α for the M/M+ redox couples have been quantified for all five metals in the IL [C4mPyrr][NTf2] for the first time. The experimental conditions and simulation used to quantify these values will be discussed, as well as compared with the known values in more conventional solvents. Briefly, the simulation5 assumes the deposition and stripping processes follow Butler-Volmer kinetics and diffusion follows Fick’s Second Law, allowing the concentration gradients to be solved using a series of partial differential equations, and the current as a function of time can then be calculated. After metal deposition and prior to metal stripping the system is that of a defined M/M+ system, and the potential-current transient in this region is sufficiently sensitive to Ef0, α and k0 for their determination.

Detailed studies on Li and Na as a function of temperature provided a further range of fundamental thermodynamic parameters, namely the change in entropy (ΔS0), activation energy (Ea) and diffusional activation energy (Ea,D). The effect of temperature on the formal potential (dEf0/dT) and diffusion coefficient (D) were also quantified. Finally, the ΔGosolv (vs. Fc/Fc+) has been estimated for the five M+ ions.

Comparison of Ef0 (vs. Fc/Fc+) throughout the Group demonstrates that the trend in [C4mPyrr][NTf2] most closely resembles propylene carbonate in terms of increasing reactivity down the group, in comparison to solvents such as H2O, DMSO and DMF.


References

1 R. Wibowo, S. E.W. Jones and R. G. Compton, J. Chem. Eng. Data, 55 (3), 1374–1376, (2010).
2 R. Wibowo, L Aldous, E.I. Rogers, S.E.W. Jones, R.G. Compton, J. Phys. Chem. C, 114, 3618-3626, (2010).
3 R. Wibowo, S.E.W. Jones, R.G. Compton, J. Phys. Chem. B, 113, 12293-12298, (2009).
4 R. Wibowo, L Aldous, S.E.W. Jones, R.G. Compton, Chem. Phys. Lett., accepted, (2010).
5 S.E.W. Jones, F.G. Chevallier, C.A. Paddon, R.G. Compton, Anal. Chem., 79, 4110-19, (2007).

http://link.aip.org/link/?MAECES/1002/2171/1

Volatilisation of ferrocene from ionic liquids: kinetics and mechanism

by Leigh Aldous

Chaopeng Fu, Leigh Aldous, Edmund J. F. Dickinson, Ninie S. A. Manan and Richard G. Compton, Chem. Commun., 2011, 47, 7083-7085.

http://dx.doi.org/DOI:10.1039/C1CC12336J

The evaporation of dissolved ferrocene from non-volatile ionic liquids under a flow of nitrogen gas has been monitored... more The evaporation of dissolved ferrocene from non-volatile ionic liquids under a flow of nitrogen gas has been monitored voltammetrically and modelled mathematically. The rate of volatilisation was found to depend on the surface tension of the ionic liquid, and a model is presented.

http://dx.doi.org/DOI:10.1039/C1CC12336J

The determination of labile Fe in ferrihydrite by ascorbic acid extraction: Methodology, dissolution kinetics and loss of solubility with age and de-watering Chemical Geology, 278:70-79 doi:10.1016/j.chemgeo.2010.09.002 Rob Raiswell, Hong Phuc Vu, Loredana Brinza and Liane G. Benning (2010)

by Liane G. Benning

Lois E. Davidson, Samuel Shaw, and Liane G. Benning (2008) The kinetics and mechanisms of schwertmannite transformation to goethite and hematite under alkaline conditions American Mineralogist 93, 1326–1337 doi:10.2138/am.2008.276

by Liane G. Benning

Dissociation Rates of Urea in the Presence of NiOOH Catalyst: A DFT Analysis

by Damilola Daramola

Journal of Physical Chemistry A 2010, 114, pp11513 - 11521

Single molecule reactions have been studied between nickel oxyhydroxide, urea, and the hydroxide ion to understand the... more Single molecule reactions have been studied between nickel oxyhydroxide, urea, and the hydroxide ion to understand the process of urea dissociation into ammonia, isocyanic acid, cyanate ion, carbon dioxide, and nitrogen. In the absence of hydroxide ions, nickel oxyhydroxide will catalyze urea to form ammonia and isocyanic acid with the rate-limiting step being the formation of ammonia with a rate constant of 1.5 × 10−6 s−1. In the presence of hydroxide, the evolution of ammonia was also the rate-limiting step with a rate constant of 1.4 × 10−26 s−1. In addition, desorption of the cyanate ion presented an energy barrier of 6190 kJ mol−1 suggesting that the cyanate ion cannot be separated from NiOOH unless further reactions occurred. Finally, elementary dissociation reactions with hydroxide ions deprotonating urea to produce nitrogen and carbon dioxide were analyzed. These elementary reactions were investigated along three paths differing in the order that protons were removed and the nitrogen atoms were rotated. The rate-limiting step was found to be the removal of carbon dioxide with a rate constant of 4.3 × 10−65 s−1. Therefore, the catalyst could be deactivated by the surface blockage caused by carbon dioxide adsorption.

Kinetics of Xylanase Fermentation by Recombinant Escherichia coli DH5α in Shake Flask Culture

by Mohd Shamzi Mohamed

Kinetic parameter estimation in hydrocracking using hybrid particle swarm optimization

by Vinod Kumar

This paper provides a continuous lumping model for hydrocracking using molecular weight and true boiling point as the... more This paper provides a continuous lumping model for hydrocracking using molecular weight and true boiling point as the basis. Isomerization and cracking are the two typical global reactions which occur on acid sites of a bifunctional acid-metal hydrocracking catalyst. The latter reaction is considered to model the hydrocracking process. It is assumed that the rate coefficient of the cracking reactions depend on the size of the feed hydrocarbons. The kinetic parameters involved in the continuous lumping model are estimated by using a hybrid particle swarm optimization method. The proposed kinetic methodology is validated with the experimental data cited in the literature.