2,033 research outputs found
Examining Collegiality and Social Justice in Academia and the Private Sector: an Exploratory SYMLOG Analysis
This research compares the perceptions of the private sector, high-technology employees to the perceptions of university faculty members regarding organizational culture, social justice and collegiality concepts. The SYMLOG assessment technique was used to record the perceptions of respondents to four different concepts of organizational culture, two different aspects of social justice and two measures of collegiality. Comparative findings of gender differences across the eight concepts raise key organizational culture, legal, measurement, governance, and social policy issues for academia and high tech organizations. The development of a conceptual framework to guide future research and a blueprint to discuss desired organizational change are highlighted
Large-scale atomistic density functional theory calculations of phosphorus-doped silicon quantum bits
We present density functional theory calculations of phosphorus dopants in
bulk silicon and of several properties relating to their use as spin qubits for
quantum computation. Rather than a mixed pseudopotential or a Heitler-London
approach, we have used an explicit treatment for the phosphorus donor and
examined the detailed electronic structure of the system as a function of the
isotropic doping fraction, including lattice relaxation due to the presence of
the impurity. Doping electron densities and spin densities are examined in
order to study the properties of the dopant electron as a function of the
isotropic doping fraction. Doping potentials are also calculated for use in
calculations of the scattering cross-sections of the phosphorus dopants, which
are important in the understanding of electrically detected magnetic resonance
experiments. We find that the electron density around the dopant leads to
non-spherical features in the doping potentials, such as trigonal lobes in the
(001) plane at energy scales of +12 eV near the nucleus and of -700 meV
extending away from the dopants. These features are generally neglected in
effective mass theory and will affect the coupling between the donor electron
and the phosphorus nucleus. Our density functional calculations reveal detail
in the densities and potentials of the dopants which are not evident in
calculations that do not include explicit treatment of the phosphorus donor
atom and relaxation of the crystal lattice. These details can also be used to
parameterize tight-binding models for simulation of large-scale devices.Comment: 22 pages, 8 figure
Structure and energetics of helium adsorption on nanosurfaces
The ground and excited state properties of small helium clusters, 4He_N,
containing nanoscale (~3-10 Angstroms) planar aromatic molecules have been
studied with quantum Monte Carlo methods. Ground state structures and energies
are obtained from importance-sampled, rigid-body diffusion Monte Carlo. Excited
state energies due to helium vibrational motion are evaluated using the
projection operator, imaginary time spectral evolution technique. We examine
the adsorption of N helium atoms (N less than or equal to 24) on a series of
planar aromatic molecules (benzene, naphthalene, anthracene, tetracene,
phthalocyanine). The first layer of helium atoms is well-localized on the
molecule surface, and we find well-defined localized excitations due to
in-plane vibrational motion of helium on the molecule surface. We discuss the
implications of these confined excitations for the molecule spectroscopy.Comment: 6 pages, 2 figures, QFS 2003 Symposium, submitted to J. Low Temp.
Phy
Structure and spectroscopy of doped helium clusters using quantum Monte Carlo techniques
We present a comparative study of the rotational characteristics of various
molecule-doped 4He clusters using quantum Monte Carlo techniques. The
theoretical conclusions obtained from both zero and finite temperature Monte
Carlo studies confirm the presence of two different dynamical regimes that
correlate with the magnitude of the rotational constant of the molecule, i.e.,
fast or slow rotors. For a slow rotor, the effective rotational constant for
the molecule inside the helium droplet can be determined by a microscopic
two-fluid model in which helium densities computed by path integral Monte Carlo
are used as input, as well as by direct computation of excited energy levels.
For a faster rotor, the conditions for application of the two-fluid model for
dynamical analysis are usually not fulfilled and the direct determination of
excitation energies is then mandatory. Quantitative studies for three molecules
are summarized, showing in each case excellent agreement with experimental
results
The relationship between prepuberal hormone levels and sertoli cell number of spermatid production in the beef bull
Producers of beef cattle must become more efficient and the bull is often the component in beef cattle production that either limits or enhances efficiency. Testicular size is positively correlated with sperm producing ability in the bull. Factors affecting testicular size are, consequently, potential indicators of sperm producing capacity. To determine whether prepuberal hormonal levels and Sertoli cell numbers were related to postpuberal testicular size, groups of crossbred bulls were injected with 10 ug of GnRH ethyamide when either 60 (n=8), 90 (n=14), 120 (n=18), or 180 (n=14) days of age. Jugular blood was collected at 0, 1, 2, and 4 hours after GnRH injection and plasma was assayed for gonadotrophins, testosterone and estradiol. Animals were then unilaterally castrated. The testis was weighed and measured. Sections (5 urn) were evaluated for the number of Sertoli cells per testis. A second challenge was administered when the bulls were approximately 14 months of age; blood was collected and assayed as before. The second testis was removed, weighed and measured. Sections (5 um) were evaluated for percentage of tubular areas occupied by spermatids. Prepuberal FSH, testosterone and estradiol did not vary significantly with age (p \u3e0.1) nor were they correlated with Sertoli cell number (p \u3e0.1). Basal LH levels differed significantly with age (p \u3e0.01). Basal LH levels were correlated (r = -.57) with Sertoli cell number. Basal prepuberal levels of LH were negatively correlated (r = -.31) and basal testosterone levels were positively correlated (r = .51) with the number of cross sections containing spermatids. Basal prepuberal LH levels were not significantly different between high and low testicular weight (p \u3e0.1). Sertoli cell number was higher in animals with greater testicular weight (p \u3c0.1). Sertoli cell number was not correlated with spermatid production. These results were probably due to the fact that approximately one-half of the animals in the study were still in the prepuberal state at 14 months, as determined by histological examination. The response of hormonal levels to GnRH stimulation was not a useful predictor of spermatid production of testicular weight, as stimulated levels were correlated with neither. It is concluded that prepuberal LH and testosterone Were correlated with degree of testicular development but not with testicular weight, another criterion of testicular development. Studies of bulls of more advanced age are required to determine if prepuberal LH and testosterone levels are potentially useful as indicators of full testicular function
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