23 research outputs found
High-pressure behaviour of GeO2: a simulation study
In this work we study the high pressure behaviour of liquid and glassy GeO2
by means of molecular dynamics simulations. The interaction potential, which
includes dipole polarization effects, was parameterized from first-principles
calculations. Our simulations reproduce the most recent experimental data to a
high degree of precision. The proportion of the various GeOn polyhedra is
determined as a function of the pressure: a smooth transition from tetrahedral
to octahedral network is observed. Finally, the study of high-pressure, liquid
germania confirms that this material presents an anomalous behaviour of the
diffusivity as observed in analog systems such as silica and water. The
importance of penta-coordinated germanium ions for such behaviour is stressed.Comment: 16 pages, 4 figures, accepted as a Fast Track Communication on
Journal of Physics: Condensed Matte
Comparative classical and ab initio Molecular Dynamics study of molten and glassy germanium dioxide
A Molecular Dynamics (MD) study of static and dynamic properties of molten
and glassy germanium dioxide is presented. The interactions between the atoms
are modelled by the classical pair potential proposed by Oeffner and Elliott
(OE) [Oeffner R D and Elliott S R 1998, Phys. Rev. B, 58, 14791]. We compare
our results to experiments and previous simulations. In addition, an ab initio
method, the so-called Car-Parrinello Molecular Dynamics (CPMD), is applied to
check the accuracy of the structural properties, as obtained by the classical
MD simulations with the OE potential. As in a similar study for SiO2, the
structure predicted by CPMD is only slightly softer than that resulting from
the classical MD. In contrast to earlier simulations, both the static structure
and dynamic properties are in very good agreement with pertinent experimental
data. MD simulations with the OE potential are also used to study the
relaxation dynamics. As previously found for SiO2, for high temperatures the
dynamics of molten GeO2 is compatible with a description in terms of mode
coupling theory.Comment: 27 pages, 16 figure
Analysis of genes encoding two unique type IIa immunoglobulin G-binding proteins expressed by a single group A streptococcal isolate.
An emm-like gene (emmL) and a fcrA gene from group A streptococcal strain 64/14 (emmL64/14 and fcrA64/14) were amplified by PCR and force cloned into the heat-inducible expression vector pJLA 602. The emmL gene encoded a recombinant protein that bound human IgG1, IgG2, and IgG4 in a nonimmune fashion. This is the reactivity profile of a type IIa IgG-binding protein. The emmL64/14 gene product was antigenically similar to the previously identified high-molecular-weight type IIa IgG-binding protein of strain 64/14 and had an N-terminal sequence identical to that of the wild-type protein. The fcrA gene also encoded a recombinant protein with type IIa functional activity. This protein was similar to the lower-molecular-weight type IIa IgG-binding protein previously isolated from strain 64/14 and was antigenically distinct from the higher-molecular-weight type IIa protein encoded by the emmL64/14 gene. The sequences for both genes including the intervening regions are presented. The emmL gene demonstrates significant homology to other class I emm and emmL genes expressed by opacity factor-negative group A streptococcal isolates. The fcrA gene was found to be homologous to other fcrA genes normally present in opacity factor-positive group A isolates. The sequence upstream of the fcrA gene and the intervening sequence between the end of the fcrA gene and the start of the emmL gene were similar to those reported for other fcrA genes
A group A streptococcal Enn protein potentially resulting from intergenomic recombination exhibits atypical immunoglobulin-binding characteristics
Syntheses of heterocycles, CLIX: Syntheses of fused heterocycles from malonic acid derivatives
Simulations of Glassforming Network Fluids: Classical Molecular Dynamics versus Car-Parrinello Molecular Dynamics
Identification des RĂ©gimes Alimentaires de la Larve D'un Insecte EntomophagePhanerotoma Flavitestacea [Hym.: Braconidae]
The psychometric evaluation of a three-dimension elementary science attitude survey
This study describes the development of an instrument to investigate elementary students attitudes toward science. As a result of the instrument development process employed, the finalized instrument consisted of 28-items separated into three dimensions. The instrument was found to exhibit acceptable ranges of internal consistency. Confirmatory Factor Analysis showed three factors that clustered into the three dimensions of attitude identified and concurrent validity was evidenced as correlations were found when comparing attitude measures with the instrument to students’ perceptions of their science classrooms. Based on the analyses completed, the instrument appears to be useful for assessing student attitude toward science
Managing Componentware Development --
We present the characteristics of component-based software engineering and derive the requirements for a corresponding development process