431 research outputs found
The Global Competitive Challenge For EMBA Students
This article describes the birth and development of an innovative international business course called the Global Competitive Challenge. The paper highlights the process of developing the course and how the course is being updated to meet the requirements of current participants in an EMBA program
Genetic structure of Tribolium castaneum populations in mills
We investigated the genetic diversity and differentiation among nine populations of Tribolium castaneum using eight polymorphic loci, including microsatellites and other insertion-deletion polymorphisms (=âindelsâ). Samples were collected in food processing/storage facilities located in Kansas, Nebraska, California, Louisiana, Florida and Puerto Rico. Standard population genetic analysis was applied, and an assignment test was used to assign individuals to their genetic population. All loci were polymorphic across populations, with the number of alleles per locus-population combination varying from three to fourteen. Among 72 locus-by-population combinations, 31 deviated significantly from Hardy-Weinberg equilibrium, which was associated with a deficiency in heterozygosity. Tribolium castaneum populations show some level of genetic structuring. Genetic differentiation between populations, using FST estimates, was significant, with FST varying from 0.018 to 0.149. AMOVA indicated that 8.32% of the variation in allele frequency resulted from comparisons among populations. Genetic distance was not significantly correlated with geographic distance. Correct assignment to the genetic population was possible in only 56% of all individuals. Together, these results revealed that geographically distinct populations of T. castaneum had low to moderate levels of genetic differentiation that was not correlated with geographic distance, and the genotypic profile of the individuals did not provide enough information for fingerprinting them with their source population. Keywords: Tribolium castaneum, Population genetics, Genetic structure, FST, Genetic fingerprintin
Metric tensor as the dynamical variable for variable cell-shape molecular dynamics
We propose a new variable cell-shape molecular dynamics algorithm where the
dynamical variables associated with the cell are the six independent dot
products between the vectors defining the cell instead of the nine cartesian
components of those vectors. Our choice of the metric tensor as the dynamical
variable automatically eliminates the cell orientation from the dynamics.
Furthermore, choosing for the cell kinetic energy a simple scalar that is
quadratic in the time derivatives of the metric tensor, makes the dynamics
invariant with respect to the choice of the simulation cell edges. Choosing the
densitary character of that scalar allows us to have a dynamics that obeys the
virial theorem. We derive the equations of motion for the two conditions of
constant external pressure and constant thermodynamic tension. We also show
that using the metric as variable is convenient for structural optimization
under those two conditions. We use simulations for Ar with Lennard-Jones
parameters and for Si with forces and stresses calculated from first-principles
of density functional theory to illustrate the applications of the method.Comment: 10 pages + 6 figures, Latex, to be published in Physical Review
Predicting the response of a submillimeter bolometer to cosmic rays
Bolometers designed to detect. submillimeter radiation also respond to cosmic, gamma, and x rays. Because detectors cannot be fully shielded from such energy sources, it is necessary to understand the effect of a photon or cosmic-ray particle being absorbed. The resulting signal (known as a glitch) can then be removed from raw data. We present measurements using an Americium-241 gamma radiation source to irradiate a prototype bolometer for the High Frequency Instrument in the Planck Surveyor satellite. Our measurements showed no variation in response depending on where the radiation was absorbed, demonstrating that the bolometer absorber and thermistor thermalize quickly. The bolometer has previously been fully characterized both electrically and optically. We find that using optically measured time constants underestimates the time taken for the detector to recover from a radiation absorption event. However, a full thermal model for the bolometer, with parameters taken from electrical and optical measurements, provides accurate time constants. Slight deviations from the model were seen at high energies; these can be accounted for by use of an extended model
Correlation between structure and electrical transport in ion-irradiated graphene grown on Cu foils
Graphene grown by chemical vapor deposition and supported on SiO2 and
sapphire substrates was studied following controlled introduction of defects
induced by 35 keV carbon ion irradiation. Changes in Raman spectra following
fluences ranging from 10^12 cm^-2 to 10^15 cm^-2 indicate that the structure of
graphene evolves from a highly ordered layer, to a patchwork of disordered
domains, to an essentially amorphous film. These structural changes result in a
dramatic decrease in the Hall mobility by orders of magnitude while,
remarkably, the Hall concentration remains almost unchanged, suggesting that
the Fermi level is pinned at a hole concentration near 1x10^13 cm^-2. A model
for scattering by resonant scatterers is in good agreement with mobility
measurements up to an ion fluence of 1x10^14 cm^-2
Heat flow model for pulsed laser melting and rapid solidification of ion implanted GaAs
Some of the authors thank for the support of the Center for Nanoscale Systems (CNS) at Harvard University is acknowledged. Harvard-CNS is a member of the National Nanotechnology Infrastructure Network (NNIN), which is supported by the National Science Foundation under NSF award No. ECS-0335765. K. M. Yu and J. W. Beeman were supported by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.Some of the authors thank for the support of the Center for Nanoscale Systems (CNS) at Harvard University is acknowledged. Harvard-CNS is a member of the National Nanotechnology Infrastructure Network (NNIN), which is supported by the National Science Foundation under NSF award No. ECS-0335765. K. M. Yu and J. W. Beeman were supported by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
Nonequilibrium molecular dynamics simulation of rapid directional solidification
We present the results of non-equilibrium molecular dynamics simulations for
the growth of a solid binary alloy from its liquid phase. The regime of high
pulling velocities, , for which there is a progressive transition from
solute segregation to solute trapping, is considered. In the segregation
regime, we recover the exponential form of the concentration profile within the
liquid phase. Solute trapping is shown to settle in progressively as is
increased and our results are in good agreement with the theoretical
predictions of Aziz [J. Appl. Phys. {\bf 53}, 1158 (1981)]. In addition, the
fluid advection velocity is shown to remain directly proportional to , even
at the highest velocities considered here (ms).Comment: Submitted to Phys. Rev.
Mn L3,2 X-ray Absorption Spectroscopy And Magnetic Circular Dichroism In Ferromagnetic (Ga,Mn)P
We have measured the X-ray absorption (XAS) and X-ray magnetic circular
dichroism (XMCD) at the Mn L3,2 edges in ferromagnetic Ga1-xMnxP films for
0.018<x<0.042. Large XMCD asymmetries at the L3 edge indicate significant
spin-polarization of the density of states at the Fermi energy. The spectral
shapes of the XAS and XMCD are nearly identical with those for Ga1-xMnxAs
indicating that the hybridization of Mn d states and anion p states is similar
in the two materials. Finally, compensation with sulfur donors not only lowers
the ferromagnetic Curie temperature but also reduces the spin polarization of
the hole states.Comment: 2 pages, 1 figure; To appear in the Proceedings of the 28th
International Conference on the Physics of Semiconductors (ICPS-28, Vienna,
Austria, July 24-28, 2006
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