From wave function to crystal morphology: application to urea and alpha-glycine

In this paper the relation between the molecular electron density distribution and the crystal growth morphology is investigated. Accurate charge densities derived from ab initio quantum chemical calculations were partitioned into multipole moments, to calculate the electrostatic contribution to the intermolecular interaction energy. For urea and alpha-glycine the F-faces or connected nets were determined according to the Hartman-Perdok PBC theory. From attachment energy and critical Ising temperature calculations, theoretical growth forms were constructed using different atom-atom potential models. These were compared to the Donnay-Harker model, equilibrium form and experimental growth forms. In the case of alpha-glycine, the theoretical growth forms are in good agreement with crystals grown from aqueous solution. Crystals obtained by sublimation seem to show some faces which are not F-faces sensu stricto

Basis set effects on the electron density and spectroscopic properties of CO

The effect of basis set incompleteness on the deformation density of CO is studied by comparing various STO basis sets with a fully numerical (basis-free) result. A triple-zeta s, p basis plus one 3d and one 4f function appears to be practically converged. The convergence characteristics of other properties (Re, De, ωe, μ0, μ1, electric field gradient (EFG)) with respect to basis set size and type are also investigated. The convergence behaviour is similar for these properties and the deformation densities

Verification, Validation and Testing of Kinetic Mechanisms of Hydrogen Combustion in Fluid Dynamic Computations

A one-step, a two-step, an abridged, a skeletal and four detailed kinetic schemes of hydrogen oxidation have been tested. A new skeletal kinetic scheme of hydrogen oxidation has been developed. The CFD calculations were carried out using ANSYS CFX software. Ignition delay times and speeds of flames were derived from the computational results. The computational data obtained using ANSYS CFX and CHEMKIN, and experimental data were compared. The precision, reliability, and range of validity of the kinetic schemes in CFD simulations were estimated. The impact of kinetic scheme on the results of computations was discussed. The relationship between grid spacing, timestep, accuracy, and computational cost were analyzed.Comment: The alternate reference of this paper: V.P. Zhukov, "Verification, Validation and Testing of Kinetic Models of Hydrogen Combustion in Fluid Dynamic Computations", Paper ID35 at 4th European Conference for Aerospace Sciences, Saint Petersburg, Russia, 4--8 July, 201

Gating of high-mobility two-dimensional electron gases in GaAs/AlGaAs heterostructures

We investigate high-mobility two-dimensional electron gases in AlGaAs heterostructures by employing Schottky-gate-dependent measurements of the samples' electron density and mobility. Surprisingly, we find that two different sample configurations can be set in situ with mobilities diering by a factor of more than two in a wide range of densities. This observation is discussed in view of charge redistributions between the doping layers and is relevant for the design of future gateable high-mobility electron gases

Meer melkeiwit door juiste eiwitvoeding

Het bleek dat de gehalten aan darmverteerbare aminozuren methionine en lysine in het krachtvoer weinig invloed hadden op de opnames aan droge stof, energie (VEM) en eiwit (DVE). Wel werd in twee proeven een duidelijk positief effect gevonden van het gehalte aan darmverteerbaar methionine in het krachtvoer op de melkeiwitproductie

Opname biologisch ruwvoeder stijgt bij lagere krachtvoergift

De resultaten van de eerste 25 lactatieweken op een proef in Heino (stalperiode) geven aan dat bij lagere krachtvoergiften in het begin van de lactatie de ruwvoeropname toeneemt. De totale ds-opname en de melkproductie liggen in deze periode op een lager niveau dan de hoge krachtvoergiften in het begin van de lactatie

Molecular form factors in X-ray crystallography

The calculation of molecular form factors from ab initio molecular electronic wavefunctions is discussed, and a scheme for application to X-ray diffraction structure analysis is given. The method is used to calculate the form factor of the NH+4 molecular ion from three accurate molecular wavefunctions, as well as for the corresponding isolated-atoms arrangement. The merits of the different form factors obtained are tested on experimental single-crystal X-ray diffraction data for NH4F. It appears that the quality of the form factor is determined by the number of centres in the wavefunction basis rather than by the wavefunction energy

Tarwevoedering melkvee beperkt mogelijk

In rantsoenen met uitsluitend graskuil kan bij hoogproductieve melkkoeien een tekort ontstaan aan snelafbreekbare koolhydraten. Granen kunnen hierop een goede aanvulling zijn