Molecular charge distribution of CO

The difference electron density of CO is studied by comparison of several calculations. It is shown that the Hartree-Fock-Slater and Hartree-Fock methods yield equally good charge-distributions and that the use of minimal basis sets should be avoided

Crystal structure and charge distribution of pyrazine: effects of extinction, thermal diffuse scattering and series termination

The crystal structure and electronic charge distribution of pyrazine (1,4-diazabenzene) has been determined at 184 K by X-ray methods. The structural results of Wheatley [Acta Cryst. (1957), 10, 182-187] have been confirmed. A clear indication of bonding effects is obtained. Neither positional and thermal parameters nor difference-Fourier maps are affected by extinction. The effect of thermal diffuse scattering (TDS) on positional parameters is also negligible. However, after correction for TDS, thermal parameters increase significantly. The difference-Fourier map is influenced by TDS as well as the inclusion of high-order Fourier terms

Charge distribution in the nitrate ion

The difference electron density in the nitrate ion is studied by comparison of some Hartree-Fock-Slater calculations. It is shown that good qualitative agreement with experiment is obtained

First experiences with the H-maser EFOS 1

The results are given on the performance measurements, on the dependence on external temperature, and on external magnetic field of a hydrogen maser. It is compared with another hydrogen maser. Details of the transportation and installation of the maser are given. The hydrogen maser frequency is compared with cesium oscillators to derive long-term behavior

Charge density study with the Maximum Entropy Method on model data of silicon. A search for non-nuclear attractors

1990 Sakata and Sato applied the maximum entropy method (MEM) to a set of structure factors measured earlier by Saka and Kato with the Pendellösung method. They found the presence of non-nuclear attractors, i.e., maxima in the density between two bonded atoms. We applied the MEM to a limited set of Fourier data calculated from a known electron density distribution (EDD) of silicon. The EDD of silicon was calculated with the program ADF-BAND. This program performs electronic structure calculations, including periodicity, based on the density functional theory of Hohenberg and Kohn. No non-nuclear attractor between two bonded silicon atoms was observed in this density. Structure factors were calculated from this density and the same set of structure factors that was measured by Saka and Kato was used in the MEM analysis. The EDD obtained with the MEM shows the same non-nuclear attractors that were later obtained by Sakata and Sato. This means that the non-nuclear attractors in silicon are really an artefact of the MEM

Solar simulation with a rectangular beam

An existing space simulation test facility was modified by enlarging the solar simulator. Because of the restrictions imposed by existing equipment, the shape of the solar beam was altered from a circular to a rectangular cross section in order to adapt the test facility to test objects of increased size. This modification is described together with the results of preliminary measurements

Magneto-optical Kerr effect in Eu1−xCaxB6Eu_{1-x}Ca_{x}B_{6}

We have measured the magneto-optical Kerr rotation of ferromagnetic $Eu_{1-x}Ca_{x}B_{6}$ with x=0.2 and 0.4, as well as of $YbB_{6}$ serving as the non-magnetic reference material. As previously for $EuB_{6}$, we could identify a feature at 1 $eV$ in the Kerr response which is related with electronic transitions involving the localized 4f electron states. The absence of this feature in the data for $YbB_{6}$ confirms the relevance of the partially occupied 4f states in shaping the magneto-optical features of $Eu$-based hexaborides. Disorder by $Ca$-doping broadens the itinerant charge carrier contribution to the magneto-optical spectra

Who Participates in an Internet-Based Research Program for Mothers of Infants? A Secondary Prevention Research Study Among Low-Income Families

Objective: The objective of this study was to evaluate the participation rates and factors associated with nonparticipation among mothers living in low-income households who were invited to join a parent-education and -support research program delivered via the Internet with professional support. Methods: Four hundred and seventy-seven mothers of infants were contacted via a variety of recruitment methods, including presentations at clinics/classes, direct mailings, print advertisement, and Internet posts. Research staff attempted to contact these mothers by phone, to assess their eligibility, and interest in participation. For those who were eligible but declined participation, we assessed reasons for declining and collected demographic information. Results: Seventy-four percent of those eligible agreed to participate in the program. Statistical tests comparing participants and decliners on demographic variables found no significant differences on mother’s age and marital status. There was a significant difference on baby’s age due to many decliners in the prenatal period. Mothers were an average age of 28 years and most were married (65.6%). Our sample of low-income participants was diverse with a large number of Latina mothers. Approximately half had a high-school diploma or less but 84% reported being moderately or very comfortable using a computer and half had a computer at home