Central station applications planning activities and supporting studies

The application of photovoltaic technology in central station (utility) power generation plants is considered. A program of data collection and analysis designed to provide additional information about the subset of the utility market that was identified as the initial target for photovoltaic penetration, the oil-dependent utilities (especially muncipals) of the U.S. Sunbelt, is described along with a series of interviews designed to ascertain utility industry opinions about the National Photovoltaic Program as it relates to central station applications

Darth Fader: Using wavelets to obtain accurate redshifts of spectra at very low signal-to-noise

We present the DARTH FADER algorithm, a new wavelet-based method for estimating redshifts of galaxy spectra in spectral surveys that is particularly adept in the very low SNR regime. We use a standard cross-correlation method to estimate the redshifts of galaxies, using a template set built using a PCA analysis on a set of simulated, noise-free spectra. Darth Fader employs wavelet filtering to both estimate the continuum & to extract prominent line features in each galaxy spectrum. A simple selection criterion based on the number of features present in the spectrum is then used to clean the catalogue: galaxies with fewer than six total features are removed as we are unlikely to obtain a reliable redshift estimate. Applying our wavelet-based cleaning algorithm to a simulated testing set, we successfully build a clean catalogue including extremely low signal-to-noise data (SNR=2.0), for which we are able to obtain a 5.1% catastrophic failure rate in the redshift estimates (compared with 34.5% prior to cleaning). We also show that for a catalogue with uniformly mixed SNRs between 1.0 & 20.0, with realistic pixel-dependent noise, it is possible to obtain redshifts with a catastrophic failure rate of 3.3% after cleaning (as compared to 22.7% before cleaning). Whilst we do not test this algorithm exhaustively on real data, we present a proof of concept of the applicability of this method to real data, showing that the wavelet filtering techniques perform well when applied to some typical spectra from the SDSS archive. The Darth Fader algorithm provides a robust method for extracting spectral features from very noisy spectra. The resulting clean catalogue gives an extremely low rate of catastrophic failures, even when the spectra have a very low SNR. For very large sky surveys, this technique may offer a significant boost in the number of faint galaxies with accurately determined redshifts.Comment: 22 pages, 15 figures. Accepted for publication in Astronomy & Astrophysic

Statistical multi-moment bifurcations in random delay coupled swarms

We study the effects of discrete, randomly distributed time delays on the dynamics of a coupled system of self-propelling particles. Bifurcation analysis on a mean field approximation of the system reveals that the system possesses patterns with certain universal characteristics that depend on distinguished moments of the time delay distribution. Specifically, we show both theoretically and numerically that although bifurcations of simple patterns, such as translations, change stability only as a function of the first moment of the time delay distribution, more complex patterns arising from Hopf bifurcations depend on all of the moments

The Population Dynamics of the Brittlestar Ophioderma brevispinum in Near- and Farshore Seagrass Habitats of Port Saint Joseph Bay, Florida

The population dynamics of the brittlestar Ophioderma brevispinum were followed monthly from Jan. 1995 to March 1996 in a near- and farshore seagrass bed in Saint Joseph Bay, FL. Abiotic (sea water temperature and salinity) and biotic (seagrass cover and sublethal predation) factors that could influence populations were also measured. Densities of individuals at both sites peaked in winter and spring, then declined dramatically in early summer months, and increased once again in the early fall at the offshore site and in the late fall at the nearshore site. Mean monthly disc diameters of individuals did not reveal any evidence of juvenile recruitment, suggesting seasonal migrations of adults into and out of near- and farshore seagrass beds. Seagrass cover at both sites varied substantially with season, with the highest cover in the summer months when brittlestar densities were lowest. Sublethal predation, as measured indirectly by counting the numbers of arm tips regenerating in individuals, did not differ significantly between sites except for the month of Feb. 1995, when levels of arm tip regeneration were higher among individuals at the nearshore site. The high overall incidence of individuals with regenerating arms at both sites suggests that predators exert persistent sublethal predatory pressure and may contribute to mortality. Individuals may migrate into deeper water during summer months to avoid thermal stress, hypoxia, or high levels of ultraviolet radiation and to avoid predation when predator densities are likely to be highest

Ballistic spin transport in exciton gases

Traditional spintronics relies on spin transport by charge carriers, such as electrons in semiconductor crystals. This brings several complications: the Pauli principle prevents the carriers from moving with the same speed; Coulomb repulsion leads to rapid dephasing of electron flows. Spin-optronics is a valuable alternative to traditional spintronics. In spin-optronic devices the spin currents are carried by electrically neutral bosonic quasi-particles: excitons or exciton-polaritons. They can form highly coherent quantum liquids and carry spins over macroscopic distances. The price to pay is a finite life-time of the bosonic spin carriers. We present the theory of exciton ballistic spin transport which may be applied to a range of systems where bosonic spin transport has been reported, in particular, to indirect excitons in coupled GaAs/AlGaAs quantum wells. We describe the effect of spin-orbit interaction of electrons and holes on the exciton spin, account for the Zeeman effect induced by external magnetic fields, long range and short range exchange splittings of the exciton resonances. We also consider exciton transport in the non-linear regime and discuss the definitions of exciton spin current, polarization current and spin conductivity.Comment: 16 pages, 10 figures to be published in Phys. Rev.

Are there leaks in your product pipeline?

Jump Starting Technologies, Patent Issues, and Translational Medicine Poster SessionSuccessful businesses move new products through the development pipeline swiftly and efficiently. An integral part of this process is the research design and execution. The field of statistics can provide knowledge and guidance that aides a successful flow through the developmental pipeline. The involvement of a professional statistician as a team member can help plug potential leaks and increase your probability of success. It pays to consider all sources of measurement variation in the design of an experiment and to account for them in the data analysis. Randomly assigning subjects to treatments reduces bias and controls for important, but unknown, factors. Various randomization strategies differ in their time and cost. More powerful analyses are possible when subjects are matched so that when different treatments are compared, other sources of variation are controlled. More powerful experiments are more sensitive at the same cost as less powerful experiments. When baseline measurements are incorporated into data analysis, treatment effects beyond baseline can be identified. Sample sizes should be large enough to detect real differences, yet small enough to be manageable and cost effective. New technology allows the measurement of many variables at many time points. The skills of a statistician can be useful in collaboration with the scientist to find the best way to transform large amounts of data into useful information. Finally, the presentation of study results needs to include the relevant statistical methods. Potential investors want to see data and be confident it has been subjected to the appropriate analysis. Meeting the requirements of regulatory agencies (FDA and EPA) will proceed more quickly if the analysis has been conducted by a professional statistician. The University of Missouri System has statisticians on several campuses. There are graduate programs at the University of Missouri, UMKC and Missouri University of Science and Technology. Graduate students are available for internships and/or summer employment. Graduate student support often leads to long term collaborations with statistics faculty

Depression in Right Hemisphere Disorder

Between 25-79% of stroke survivors suffer depression, which can lead to limited recovery, decreased quality of life, and increased mortality. In adults with right hemisphere disorder (RHD), the cause(s) of depression have been unclear. Our results showed that significantly more adults with RHD were depressed than normal controls, and that adults with RHD were significantly more depressed than normal controls. In both groups, depression was significantly related with loneliness. In adults with RHD, depression was also significantly related with social support. No demographic or lesion-related variables were associated with increased depression in our samples. Suggestions for treatment research are offered