14,306 research outputs found
Short research report : a comparison of emotional intelligence levels between students in experiential and didactic college programs
Short Research Report: A Comparison of Emotional Intelligence Levels between Students in Experiential and Didactic College Programspeer-reviewe
NASA Lidar system support and MOPA technology demonstration
A series of lidar design and technology demonstration tasks in support of a CO2 lidar program is discussed. The first of these tasks is discussed in Section VI of this report under the heading of NASA Optical Lidar Design and it consists of detailed recommendations for the layout of a CO2 Doppler lidar incorporating then existing NASA optical components and mounts. The second phase of this work consisted of the design, development, and delivery to NASA of a novel acousto-optic laser frequency stabilization system for use with the existing NASA ring laser transmitter. The second major task in this program encompasses the design and experimental demonstration of a master oscillator-power amplifier (MOPA) laser transmitter utilizing a commercially available laser as the amplifier. The MOPA design including the low chirp master oscillator is discussed in detail. Experimental results are given for one, two and three pass amplification. The report includes operating procedures for the MOPA system
Higher Order Modulation Equations for a Boussinesq Equation
In order to investigate corrections to the common KdV approximation to long
waves, we derive modulation equations for the evolution of long wavelength
initial data for a Boussinesq equation. The equations governing the corrections
to the KdV approximation are explicitly solvable and we prove estimates showing
that they do indeed give a significantly better approximation than the KdV
equation alone. We also present the results of numerical experiments which show
that the error estimates we derive are essentially optimal
Intersection tests for single marker QTL analysis can be more powerful than two marker QTL analysis
BACKGROUND: It has been reported in the quantitative trait locus (QTL) literature that when testing for QTL location and effect, the statistical power supporting methodologies based on two markers and their estimated genetic map is higher than for the genetic map independent methodologies known as single marker analyses. Close examination of these reports reveals that the two marker approaches are more powerful than single marker analyses only in certain cases. Simulation studies are a commonly used tool to determine the behavior of test statistics under known conditions. We conducted a simulation study to assess the general behavior of an intersection test and a two marker test under a variety of conditions. The study was designed to reveal whether two marker tests are always more powerful than intersection tests, or whether there are cases when an intersection test may outperform the two marker approach. We present a reanalysis of a data set from a QTL study of ovariole number in Drosophila melanogaster. RESULTS: Our simulation study results show that there are situations where the single marker intersection test equals or outperforms the two marker test. The intersection test and the two marker test identify overlapping regions in the reanalysis of the Drosophila melanogaster data. The region identified is consistent with a regression based interval mapping analysis. CONCLUSION: We find that the intersection test is appropriate for analysis of QTL data. This approach has the advantage of simplicity and for certain situations supplies equivalent or more powerful results than a comparable two marker test
Effect of Photometric Redshift Uncertainties on Weak Lensing Tomography
We perform a systematic analysis of the effects of photometric redshift
uncertainties on weak lensing tomography. We describe the photo-z distribution
with a bias and Gaussian scatter that are allowed to vary arbitrarily between
intervals of dz = 0.1 in redshift.While the mere presence of bias and scatter
does not substantially degrade dark energy information, uncertainties in both
parameters do. For a fiducial next-generation survey each would need to be
known to better than about 0.003-0.01 in redshift for each interval in order to
lead to less than a factor of 1.5 increase in the dark energy parameter errors.
The more stringent requirement corresponds to a larger dark energy parameter
space, when redshift variation in the equation of state of dark energy is
allowed.Of order 10^4-10^5 galaxies with spectroscopic redshifts fairly sampled
from the source galaxy distribution will be needed to achieve this level of
calibration. If the sample is composed of multiple galaxy types, a fair sample
would be required for each. These requirements increase in stringency for more
ambitious surveys; we quantify such scalings with a convenient fitting formula.
No single aspect of a photometrically binned selection of galaxies such as
their mean or median suffices, indicating that dark energy parameter
determinations are sensitive to the shape and nature of outliers in the photo-z
redshift distribution.Comment: 10 pages, 12 figures, accepted by Ap
Quantum simulation of multiple-exciton generation in a nanocrystal by a single photon
We have shown theoretically that efficient multiple exciton generation (MEG)
by a single photon can be observed in small nanocrystals (NCs). Our quantum
simulations that include hundreds of thousands of exciton and multi-exciton
states demonstrate that the complex time-dependent dynamics of these states in
a closed electronic system yields a saturated MEG effect on a picosecond
timescale. Including phonon relaxation confirms that efficient MEG requires the
exciton--biexciton coupling time to be faster than exciton relaxation time
Second Order Corrections to Weak Lensing by Large-Scale Structure
We calculate corrections to the power spectrum predictions of weak lensing by
large scale structure due to higher order effects in the gravitational
potential. Using a perturbative approach to third order in transverse
displacements, we calculate a second order correction to the angular power
spectra of E and B mode shear and convergence resulting from dropping the
so-called Born approximation, where one integrates along the unperturbed photon
path. We also consider a correction to the power spectra from the coupling
between lenses at different redshifts. Both effects generate B-mode shear and
the latter also causes a net rotation of the background galaxy images. We show
all these corrections are at least two orders of magnitude below the
convergence or E-mode power and hence relevant only to future ultra high
precision measurements. These analytical calculations are consistent with
previous numerical estimates and validate the use of current large scale
structure weak lensing predictions for cosmological studies and future use of
B-modes as a monitor of systematic effects.Comment: 4 pages, 1 figure, submitted to ApJ
Viral Isolates Derived from Simian Varicella Epizootics Are Genetically Related but Are Distinct from Other Primate Herpesviruses
AbstractEpizootics of a natural varicella-like disease occur in populations of nonhuman primates. Several primate herpesviruses have been isolated from these epizootics, but the relatedness of these isolates to each other is not well-defined. In this study, we demonstrated that the restriction endonuclease (REn) profiles of four epidemiologically distinct isolates were similar, although not identical, indicating that simian varicella epizootics are caused by various strains of simian varicella virus (SVV). The genetic variation among the isolates did not map to a specific region of the SVV genome and REn differences were detected within the SVV DNA long component and the inverted repeat region. Southern blot hybridization demonstrated that SVV is more closely related to varicella-zoster virus than to other primate herpesviruses. The study indicates that the current herpesvirus classification scheme should be changed to include SVV as a single taxonomic group within theVaricellovirusgenus of alphaherpesviruses. In addition, REn profiles of SVV isolates, derived from primary and secondary episodes of simian varicella in the same monkey, were identical, providing evidence for SVV reactivation in a latently infected monkey
Redshift space 21 cm power spectra from reionization
We construct a simple but self-consistent analytic ionization model for rapid
exploration of 21cm power spectrum observables in redshift space. It is fully
described by the average ionization fraction and HII patch size
and has the flexibility to accommodate various reionization scenarios. The
model associates ionization regions with dark matter halos of the number
density required to recover and treats redshift space distortions
self-consistently with the virial velocity of such halos. Based on this model,
we study the line-of-sight structures in the brightness fluctuations since they
are the most immune to foreground contamination. We explore the degeneracy
between the HII patch size and nonlinear redshift space distortion in the one
dimensional power spectrum. We also discuss the limitations experimental
frequency and angular resolutions place on their distinguishability. Angular
resolution dilutes even the radial signal and will be a serious limitation for
resolving small bubbles before the end of reionization. Nonlinear redshift
space distortions suggest that a resolution of order 1 -- 10\arcsec and a
frequency resolution of 10kHz will ultimately be desirable to extract the full
information in the radial field at . First generation instruments
such as LOFAR and MWA can potentially measure radial HII patches of a few
comoving Mpc and larger at the end of reionization and are unlikely to be
affected by nonlinear redshift space distortions.Comment: 13 pages, 10 figures. Revised version. Includes minor changes. Adds
appendix on accomodating a distribution of radii for the HII regions.
Accepted for publication in Ap
- …