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Articles 1 - 11 of 11
Full-Text Articles in Physics
Microscopic Theory Of Network Glasses, Randall Hall, Peter Wolynes
Microscopic Theory Of Network Glasses, Randall Hall, Peter Wolynes
Randall W. Hall
A theory of the glass transition of network liquids is developed using self-consistent phonon and liquid state approaches. The dynamical transition and entropy crisis characteristic of random first-order transitions are mapped as a function of the degree of bonding and density. Using a scaling relation for a soft-core model to crudely translate the densities into temperatures, theory predicts that the ratio of the dynamical transition temperature to the laboratory transition temperature rises as the degree of bonding increases, while the Kauzmann temperature falls explaining why highly coordinated liquids are “strong” while van der Waals liquids without coordination are “fragile.”
Transitions Of Tethered Chain Molecules Under Tension, Jutta Luettmer-Strathmann, Kurt Binder
Transitions Of Tethered Chain Molecules Under Tension, Jutta Luettmer-Strathmann, Kurt Binder
Jutta Luettmer-Strathmann
An applied tension force changes the equilibrium conformations of a polymer chain tethered to a planar substrate and thus affects the adsorption transition as well as the coil-globule and crystallization transitions. Conversely, solvent quality and surface attraction are reflected in equilibrium force-extension curves that can be measured in experiments. To investigate these effects theoretically, we study tethered chains under tension with Wang-Landau simulations of a bond-fluctuation lattice model. Applying our model to pulling experiments on biological molecules we obtain a good description of experimental data in the intermediate force range, where universal features dominate and finite size effects are small. …
Ab Initio Study Of Formazan And 3-Nitroformazan, G. Buemi, F. Zuccarello, P. Venuvanalingam, M. Ramalingam, Salai Ammal
Ab Initio Study Of Formazan And 3-Nitroformazan, G. Buemi, F. Zuccarello, P. Venuvanalingam, M. Ramalingam, Salai Ammal
Salai C. Ammal
Formazan and 3-nitroformazan have been investigated at abinitio level (MP2/6-31G** and B3LYP/6-31G**) in all their possible conformations, for studying the various possibilities of intramolecular hydrogen bonding formation. The trans-syn-s-cis (TSSC), known also asyellowform, has been found to be the most stable conformer (at least in the gas phase) in both compounds. This particular structure is strongly stabilized by a N–H···N hydrogen bridge, which gives rise to a hexatomic chelate ring, with the possibility of a proton transfer process.This closely resembles that of malondialdehyde, previously studied, in the evolution of the potential energy shape but with a greater barrier height. Various …
Obtaining Mixed Ionic/Electronic Conductivity In Perovskite Oxides In A Reducing Environment: A Computational Prediction For Doped Srtio3, S. Suthirakun, Salai Ammal, G. Xiao, Fanglin Chen, Kevin Huang, Hans-Conrad Zur Loye, Andreas Heyden
Obtaining Mixed Ionic/Electronic Conductivity In Perovskite Oxides In A Reducing Environment: A Computational Prediction For Doped Srtio3, S. Suthirakun, Salai Ammal, G. Xiao, Fanglin Chen, Kevin Huang, Hans-Conrad Zur Loye, Andreas Heyden
Salai C. Ammal
No abstract provided.
Computer-Aided Design Of Novel Heterogeneous Catalysts—A Combinatorial Computational Chemistry Approach, K. Yajima, Y. Ueda, H. Tsuruya, T. Kanougi, Y. Oumi, Salai Ammal, S. Takami, M. Kubo, A. Miyamoto
Computer-Aided Design Of Novel Heterogeneous Catalysts—A Combinatorial Computational Chemistry Approach, K. Yajima, Y. Ueda, H. Tsuruya, T. Kanougi, Y. Oumi, Salai Ammal, S. Takami, M. Kubo, A. Miyamoto
Salai C. Ammal
No abstract provided.
Dynamic Path Bifurcation For The Beckmann Reaction: Observation And Implication, H. Yamataka, M. Sato, H. Hasegawa, Salai Ammal
Dynamic Path Bifurcation For The Beckmann Reaction: Observation And Implication, H. Yamataka, M. Sato, H. Hasegawa, Salai Ammal
Salai C. Ammal
The reaction of oximes to amides, known as the Beckmann rearrangement, may undergo fragmentation to form carbocations + nitriles instead of amides when the cations have reasonable stability. The reactions of oxime derivatives of 1-substituted-phenyl-2-propanones and 3-substituted-phenyl-2-butanones in aqueous solvents gave both rearrangement and fragmentation products, the ratio of which was dependent on substituents. Transition state (TS) optimizations and intrinsic reaction coordinate (IRC) calculations for the reaction of 1-phenyl-2-propanone oximes showed that there is a single TS for each substituted compound. The IRC path from the TS either led to a rearrangement product or a fragmentation product depending on the …
Ab Initio And Dft Investigations Of Lithium/Hydrogen Bonded Complexes Of Trimethylamine, Dimethyl Ether And Dimethyl Sulfide, Salai Ammal, P. Venuvanalingam
Ab Initio And Dft Investigations Of Lithium/Hydrogen Bonded Complexes Of Trimethylamine, Dimethyl Ether And Dimethyl Sulfide, Salai Ammal, P. Venuvanalingam
Salai C. Ammal
Ab initio and DFT computations have been carried out on LiF and HF complexes of a set of n-donors viz. trimethylamine, dimethyl ether and dimethyl sulfide with a 6-31++G(d,p) basis set. The effect of correlation has been included with MP2, MP4 and DFT calculations. NBO analyses of the wavefunctions have been performed to examine the intermolecular interaction at the orbital level. Calculations reveal that these donors form strong n→σ* complexes and computed binding energies of the (CH3)2O···HF complex agree very well with the experimental binding energies from IR spectroscopy. LiF forms stronger complexes than HF, …
Combinatorial Computational Chemistry Approach To The Design Of Metal Oxide Electronics Materials, B. Rodion, Salai Ammal, Y. Inaba, Y. Oumi, S. Takami, M. Kubo, A. Miyamoto, M. Kawasaki, M. Yoshimoto, H. Koinuma
Combinatorial Computational Chemistry Approach To The Design Of Metal Oxide Electronics Materials, B. Rodion, Salai Ammal, Y. Inaba, Y. Oumi, S. Takami, M. Kubo, A. Miyamoto, M. Kawasaki, M. Yoshimoto, H. Koinuma
Salai C. Ammal
Combinatorial chemistry has been developed as an experimental method where it is possible to synthesize hundreds of samples all at once and examine their properties. Recently, we introduced the concept of combinatorial approach to computational chemistry for material design and proposed a new method called `a combinatorial computational chemistry'. In this approach, the effects of large number of dopants, substrates, and buffer layers on the structures, electronic states, and properties of metal oxide electronics material is estimated systematically using computer simulations techniques, in order to predict the best dopant, substrate, and buffer layer for each metal oxide electronics materials.
Chemical Interaction Of Nf3 With Si (Part Ii): Density Functional Calculation Studies, A. Endou, T. Little, A. Yamada, K. Teraishi, M. Kubo, Salai Ammal, A. Miyamoto, M. Kitajima, F. Ohuchi
Chemical Interaction Of Nf3 With Si (Part Ii): Density Functional Calculation Studies, A. Endou, T. Little, A. Yamada, K. Teraishi, M. Kubo, Salai Ammal, A. Miyamoto, M. Kitajima, F. Ohuchi
Salai C. Ammal
No abstract provided.
Characterization Of The Catalytically Active Mn(Ii)-Loaded Arge-Encoded N-Acetyl-L-Ornithine Deacetylase From Escherichia Coli, Wade Mcgregor, Sabina Swierczek, Brian Bennett, Richard Holz
Characterization Of The Catalytically Active Mn(Ii)-Loaded Arge-Encoded N-Acetyl-L-Ornithine Deacetylase From Escherichia Coli, Wade Mcgregor, Sabina Swierczek, Brian Bennett, Richard Holz
Richard C. Holz
The catalytically competent Mn(II)-loaded form of the argE-encoded N-acetyl-l-ornithine deacetylase from Escherichia coli (ArgE) was characterized by kinetic, thermodynamic, and spectroscopic methods. Maximum N-acetyl-l-ornithine (NAO) hydrolytic activity was observed in the presence of one Mn(II) ion with k cat and K m values of 550 s−1 and 0.8 mM, respectively, providing a catalytic efficiency (k cat/K m) of 6.9 × 105 M−1 s−1. The ArgE dissociation constant (K d) for Mn(II) was determined to be 0.18 μM, correlating well with a value obtained by isothermal titration …
Kinetic And Spectroscopic Characterization Of The E134a- And E134d-Altered Dape-Encoded N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase From Haemophilus Influenzae, Ryan Davis, David Bienvenue, Sabina Swierczek, Danuta Gilner, Lakshman Rajagopal, Brian Bennett, Richard Holz
Kinetic And Spectroscopic Characterization Of The E134a- And E134d-Altered Dape-Encoded N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase From Haemophilus Influenzae, Ryan Davis, David Bienvenue, Sabina Swierczek, Danuta Gilner, Lakshman Rajagopal, Brian Bennett, Richard Holz
Richard C. Holz
Glutamate-134 (E134) is proposed to act as the general acid/base during the hydrolysis reaction catalyzed by the dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE) from Haemophilus influenzae. To date, no direct evidence has been reported for the role of E134 during catalytic turnover by DapE. In order to elucidate the catalytic role of E134, altered DapE enzymes were prepared in which E134 was substituted with an alanine and an aspartate residue. The Michaelis constant (K m) does not change upon substitution with aspartate but the rate of the reaction changes drastically in the following order: glutamate (100% activity), aspartate (0.09%), and alanine …