Autumn Storms Trigger Enhanced Export of Iron, Phosphorus, and Carbon from a Forested Vermont Catchment

Autumn leaf fall may be an important driver of annual stream loading in forested catchments due to the introduction of large amounts of labile organic matter. In light of climate change projections for an intensification of the autumnal hydrological cycle for northern temperate forests, there is an increasing demand to understand this leaf fall period, and the extent to which it may drive water quality. In this study, we examine the export and biogeochemical coupling of dissolved organic carbon (DOC), iron (Fe), aluminum (Al), and phosphorus (P) during autumn and summer storms to understand the effects of seasonality and storm timing and magnitude on stream loading dynamics. We utilize in situ spectrophotometric sensors to measure UV-Vis light absorbance with high temporal resolution in order to quantify rapid changes in stream chemistry during storm events. We also explore the potential to project concentrations of the aforementioned parameters using partial least squares regression (PLSR) and high frequency absorbance data. Post leaf fall autumn storms resulted in the export of 23% of total study DOC in a 2-week period, as well as the largest fluxes of Fe and Al observed over the study period. These results may have important implications for nutrient loading in the receiving water body, Lake Champlain

Exciton effective mass enhancement in coupled quantum wells in electric and magnetic fields

We present a calculation of exciton states in semiconductor coupled quantum wells (CQWs) in the presence of electric and magnetic fields applied perpendicular to the QW plane. The exciton Schr\"odinger equation is solved in real space in three dimensions to obtain the Landau levels of both direct and indirect excitons. Calculation of the exciton energy levels and oscillator strengths enables mapping of the electric and magnetic field dependence of the exciton absorption spectrum. For the ground state of the system, we evaluate the Bohr radius, optical lifetime, binding energy and dipole moment. The exciton mass renormalization due to the magnetic field is calculated using a perturbative approach. We predict a non-monotonous dependence of the exciton ground state effective mass on magnetic field. Such a trend is explained in a classical picture, in terms of the ground state tending from an indirect to a direct exciton with increasing magnetic field.Comment: 20 pages, 7 figure

Benefits of Ambulation in Older Adult Population

Background: Loss of mobility is an outcome of aging. Decreased ambulation leads to a loss of mobility and ultimately a loss of independence. There are additional health risks associated with loss of mobility. There can be challenges to facilitating ambulation and mobility in an aging population. Objective: A literature review of the benefits of ambulation/mobility and the risks of loss of mobility was conducted. The purpose was to promote ambulation/mobility in a community-based setting and educate those caring for the adult population about the importance of ambulation. Methods: A presentation was provided to staff and participants of an adult day care center, and data was gathered on the efficacy of the presentation. A pre-test and post-test method to gather information was used. Results: The education provided was effective as evidenced by improvement in each of the five test questions. Following the educational session with staff, an improvement from the pre-test to the post-test was noted. The installation of signs for participants in determining their walking distance was placed on the community path. Conclusions: An educational session at a senior community center increased participants\u27 knowledge of exercise and its benefits. Staff and participants were encouraged to learn about the advantages of the walking path already in place. This will assist in the use of the walking path and increase daily ambulation at the facility

The Deep SWIRE Field III. WIYN Spectroscopy

We present the results of spectroscopy using HYDRA on the WIYN 3.5m telescope of objects in the deep SWIRE radio field. The goal of the project was to determine spectroscopic redshifts for as many of the brighter objects in the field as possible, especially those detected in the radio and at 24 microns. These redshifts are primarily being used in studies of galaxy evolution and the connection of that evolution to AGN and star-formation. Redshifts measured for 365 individual objects are reported. The redshifts range from 0.03 to 2.5, mostly with z < 0.9. The sources were selected to be within the WIYN HYDRA field of approximately 30' in radius from the center of the SWIRE deep field, 10h46m00s, 59d 01'00" (J2000). Optical sources for spectroscopic observation were selected from a r-band image of the field. A priority list of spectroscopic targets was established in the following order: 20cm detections, 24 micron detections, galaxies with r < 20 and the balance made up of fainter galaxies in the field. We provide a table listing the galaxy positions, measured redshift and error, and note any emission lines that were visible in the spectrum. In practice almost all the galaxies with r < 19 were observed including all of the radio sources and most of the 24 microns sources with r < 20 and a sample of radio sources which had fainter optical counterparts on the r-band image.Comment: 6 pages, 3 tables, 2 figures, full electronic tables at http://www.aoc.nrao.edu/~fowen/papers/SWIRE/WIYNpaper3/, accepted ApJ Suppl Serie

Terahertz emitters based on microcavity dipolaritons

We propose the use of dipolaritons -- quantum well excitons with large dipole moment, coupled to a planar microcavity -- for generating terahertz (THz) radiation. This is achieved by exciting the system with two THz detuned lasers that leads to dipole moment oscillations of the exciton polariton at the detuning frequency, thus generating a THz emission. We have optimized the structural parameters of a system with microcavity embedded AlGaAs double quantum wells and shown that the THz emission intensity is maximized if the laser frequencies both match different dipolariton states. The influence of the electronic tunnel coupling between the wells on the frequency and intensity of the THz radiation is also investigated, demonstrating a trade-off between the polariton dipole moment and the Rabi splitting.Comment: 4 pages, 4 figures. This article has been submitted to Applied Physics Letter

Drift-diffusion model of the fragmentation of the external ring structure in the photoluminescence pattern of indirect excitons in coupled quantum wells

Under optical excitation, coupled quantum wells are known to reveal fascinating features in the photoluminescence pattern originating from dipole orientated indirect excitons. The appearance of an external ring has been attributed to macroscopic charge separation in the quantum well plane. We present a classical model of non-linear diffusion to account for the observed fragmentation of the external ring into a periodic array of islands. The model incorporates the Coulomb interactions between electrons, holes and indirect excitons. At low temperatures, these interactions lead to pattern formation similar to the experimentally observed ring fragmentation. The fragmentation is found to persist to temperatures above the quantum degeneracy temperature of indirect excitons.Comment: 5 pages, 3 figure

Preliminary evaluation of a micro-based repeated measures testing system

A need exists for an automated performance test system to study the effects of various treatments which are of interest to the aerospace medical community, i.e., the effects of drugs and environmental stress. The ethics and pragmatics of such assessment demand that repeated measures in small groups of subjects be the customary research paradigm. Test stability, reliability-efficiency and factor structure take on extreme significance; in a program of study by the U.S. Navy, 80 percent of 150 tests failed to meet minimum metric requirements. The best is being programmed on a portable microprocessor and administered along with tests in their original formats in order to examine their metric properties in the computerized mode. Twenty subjects have been tested over four replications on a 6.0 minute computerized battery (six tests) and which compared with five paper and pencil marker tests. All tests achieved stability within the four test sessions, reliability-efficiencies were high (r greater than .707 for three minutes testing), and the computerized tests were largely comparable to the paper and pencil version from which they were derived. This computerized performance test system is portable, inexpensive and rugged

Crime Statistics We Would Like to See

Every day government agencies, especially those involved in law enforcement, deluge us with crime statistics intended to impress upon us the view that we are undergoing a crime wave and that more police, prosecutors, and prisons, as well as new and tougher laws, are needed

SWATstika Policing

At 9:35 p.m. on Tuesday, Jan. 24, 2006, in Fairfax county, Virginia, a police SWAT team, armed to the teeth, decked out in battle fatigues, helmets, flak vests, and other military accouterments, arrived at the townhouse of Dr. Salvatore J. Culosi, Jr., a 37-year old optometrist. Culosi was a suspected bookie who had been making illegal sports bets from his home, and Fairfax police had obtained a warrant for his arrest and a search warrant to search his residence for gambling paraphernalia. Culosi had no history of violent behavior and his alleged crimes were nondangerous, but the practice in Fairfax county is for the local SWAT team to serve almost all search warrants. The unarmed, unresisting Culosi was in front of his residence when they arrived, weapons drawn in accordance with police protocol. As they began encircling Culosi, one of the officers, apparently accidentally, fired his large .45 cal. Heckler & Koch handgun, striking Culosi in the chest and killing him instantly. Predictably, the fearsome, fascistic trend towards militarizing American police by, among other things, transforming the serving of warrants into paramilitary commando operations, had resulted once again in lethal police violence and the unjustified death of an American citizen