Search Results - (Author, Cooperation:C. Greeff)

2014-09-16

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Amino Acid Sequence ; Arabidopsis/enzymology/*genetics ; Arabidopsis Proteins/*genetics/metabolism ; Cellular Reprogramming/genetics ; Chromosome Mapping ; DNA Methylation ; *Epigenesis, Genetic ; *Gene Expression Regulation, Plant ; Gene Silencing ; MADS Domain Proteins/*genetics ; Molecular Sequence Data ; Mutation ; Sequence Alignment ; Transcription Factors/genetics/metabolism

1089-7550

AIP Digital Archive

Physics

Equilibrium free energies for the α and ω phases of Ti are constructed. The result is a consistent picture of the ambient pressure, static high pressure, and shock data, as well as first-principles electronic structure calculations. The Hugoniot consists of three segments: a metastable α-phase region, a transition region, and an ω-phase branch. All the Hugoniot data are consistent with a transition occurring at ∼12 GPa. An early identification [R. G. McQueen et al., in High Velocity Impact Phenomena, edited by R. Kinslow (Academic, New York, 1970)] of a phase transition at 17.5 GPa appears to have been an artifact. The shock Hugoniot extends further into the metastable region than static data, indicating the existence of a relaxation process occurring on a time scale intermediate between those of the static and dynamic measurements. © 2001 American Institute of Physics.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

The diffusion Monte Carlo method is applied in conjunction with an ab initio effective core potential to compute energies of some neutral and charged states of Al and Al2. The computed ionization potentials, electron affinities and dissociation energies differ from measured values by at most a few hundredths of eV. The computed dissociation energy of Al2 agrees with the most extensive CI calculations. It appears that our dissociation energy for Al−2 is the most accurate to date. The quality of the results indicates that the use of the pseudopotential is not an important limitation on the accuracy of these calculations. Variational wavefunctions with Boys-Handy correlation functions are found to give more than 70% of the correlation energy with 8 optimized parameters. These optimized trial functions are used together with numerical integration to localize the pseudopotential. © 1996 American Institute of Physics.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Variational and diffusion Monte Carlo calculations are carried out on the molecules SiHn (n=1–4), Si2, Si2H6, and Si3H8. The anion SiH3− is also considered. Core electrons are eliminated through the use of an ab initio effective core potential. The atomization energies and various bond energies are compared with experiment and other calculations. The atomization energies of SiH–SiH4 are in good agreement with experiment and with the best other calculations. The calculated electron affinity of SiH3 is within 0.02 eV of the measured value. The calculated atomization energies of the silanes SiH4, Si2H6, and Si3H8 are more consistent with the original heats of formation of Gunn and Green [J. Phys. Chem. 65, 779 (1961); 68, 946 (1964)], without the subsequent corrections [M. W. Chase, Jr., C. A. Davies, J. R. Downey, Jr., D. J. Frurip, R. A. McDonald, and A. N. Syverud, J. Phys. Chem. Ref. Data 14, Suppl. 1 (1985)] made on the assumption that the final state of Si is amorphous. © 1997 American Institute of Physics.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

We describe the development of an ab initio Hartree–Fock (HF) pseudopotential for C that has neither repulsive r−2 nor attractive Coulomb singularities at the nucleus. This potential is tested in HF calculations on small hydrocarbons and shown to give good accuracy in comparison to all-electron calculations. The new pseudopotential is demonstrated to give superior basis set convergence in HF calculations compared to standard ones with r−2 singularities. Diffusion Monte Carlo (DMC) calculations on C and CH with the new potential show substantial improvements in stability at larger time steps compared with conventional pseudopotentials, with negligible time step dependence of the total energy. The resultant CH bond energy, De=83.3(4) kcal/mol, is in good agreement with experiment and with a similar all-electron DMC calculation. © 1998 American Institute of Physics.

Electronic Resource

1432-0800

Springer Online Journal Archives 1860-2000

Energy, Environment Protection, Nuclear Power Engineering

Medicine

Conclusion The total population density was proved to be a sensitive indicator of fenthion pollution and can be used when no analytical facilities are available. Furthermore sampling for chemical analysis is usually limited in volume and frequency, whereas the Crustacea and aquatic Insecta populations are continually present to monitor pollution. It is also an inexpensive method compared to the use of sophisticated collection samplers or resins. The only prerequisite is, that the total population density before pollution must be known, and this can be established by long-term observations.

Electronic Resource