Solving the Coulomb scattering problem using the complex scaling method

Based on the work of Nuttall and Cohen [Phys. Rev. {\bf 188} (1969) 1542] and Resigno et al{} [Phys. Rev. A {\bf 55} (1997) 4253] we present a rigorous formalism for solving the scattering problem for long-range interactions without using exact asymptotic boundary conditions. The long-range interaction may contain both Coulomb and short-range potentials. The exterior complex scaling method, applied to a specially constructed inhomogeneous Schr\"odinger equation, transforms the scattering problem into a boundary problem with zero boundary conditions. The local and integral representations for the scattering amplitudes have been derived. The formalism is illustrated with numerical examples.Comment: 3 pages, 3 figure

Dissociative electron attachment to the H2O molecule. I. Complex-valued potential-energy surfaces for the 2B1, 2A1, and 2B2 metastable states of the water anion

We present the results of calculations defining global, three-dimensional representations of the complex-valued potential-energy surfaces of the doublet B1, doublet A1, and doublet B2 metastable states of the water anion that underlie the physical process of dissociative electron attachment to water. The real part of the resonance energies is obtained from configuration-interaction calculations performed in a restricted Hilbert space, while the imaginary part of the energies (the widths) is derived from complex Kohn scattering calculations. A diabatization is performed on the 2A1 and 2B2 surfaces, due to the presence of a conical intersection between them. We discuss the implications that the shapes of the constructed potential-energy surfaces will have upon the nuclear dynamics of dissociative electron attachment to H2O. This work originally appeared as Phys Rev A 75, 012710 (2007). Typesetting errors in the published version have been corrected here.Comment: Corrected version of PRA 75, 012710 (2007

Dissociative electron attachment to the H2O molecule. II. Nuclear dynamics on coupled electronic surfaces within the local complex potential model

We report the results of a first-principles study of dissociative electron attachment to H2O. The cross sections are obtained from nuclear dynamics calculations carried out in full dimensionality within the local complex potential model by using the multi-configuration time-dependent Hartree method. The calculations employ our previously obtained global, complex-valued, potential-energy surfaces for the three (doublet B1, doublet A1, and doublet B2) electronic Feshbach resonances involved in this process. These three metastable states of H2O- undergo several degeneracies, and we incorporate both the Renner-Teller coupling between the B1 and A1 states as well as the conical intersection between the A1 and B2 states into our treatment. The nuclear dynamics are inherently multidimensional and involve branching between different final product arrangements as well as extensive excitation of the diatomic fragment. Our results successfully mirror the qualitative features of the major fragment channels observed, but are less successful in reproducing the available results for some of the minor channels. We comment on the applicability of the local complex potential model to such a complicated resonant system.Comment: Corrected version of Phys Rev A 75, 012711 (2007

Pitfalls of Transparency: Lessons Learned from the Milford Flats Fire

The Community Environmental Monitoring Program (CEMP) consists of a network of 29 radiation and weather monitoring stations located over a 160,000-km2 area of southern Nevada, southwestern Utah, and southeastern California. The program provides stakeholders with a hands-on role in the monitoring for airborne radioactivity that could result from ongoing or past activities on the Nevada Test Site (NTS). The CEMP’s mission includes provisions for the transparency of the monitoring data as well as public accessibility to these data. This is accomplished through direct stakeholder participation, public outreach, and near real-time uploads of monitoring data to a publicly accessible web site located at http://cemp.dri.edu/. In early July 2007, a lightning strike ignited a wildfire just outside the city of Milford in southeastern Utah. This fire, named the Milford Flats Fire, grew rapidly and eventually became the largest wildfire in recorded history in the state, burning approximately 567 square miles. At about the same time, the pressurized ion chamber (PIC) located at the CEMP station in Milford began reporting average exposure rates that ranged from four to seven times normal for the area. Initially, it was believed that elevated readings could be a result of gamma-emitting radon progeny released by the fire and transported in smoke plumes. The U.S. Department of Energy issued a press release offering this as a possible first explanation, and the release received a great amount of attention, particularly in the state of Utah, where concerns were expressed that the fire could be causing re-suspension of radionuclides associated with fallout from past nuclear testing at the NTS. Subsequent analyses of particulate air filter samples obtained from the Milford station, as well as an examination of the data reported by the PIC, the timing of the incident, and diagnostic testing on the PIC, showed that the abnormal gamma readings were a result of instrument malfunction. WM2008 Conference, February 24-28, 2008, Phoenix, AZ This paper will review the data from the PIC and the analytical results of air filter samples collected at Milford, and present lessons learned from the Milford Flats Fire Incident on providing real-time access to monitoring data for the public

Development of Mountain Climate Generator and Snowpack model for Erosion Predictions in the Western United States Using WEPP, Progress Report No. 1

Executive Summary: This report summarizes work conducted during the initial funding period (November 1, 1989 through June 30, 1990) of a Cooperative Agreement between the United States Forest Service (USFS) and the Utah Water Research Laboratory (UWRL), Utah State University. The purpose of the agreement is to develop a procedure for incorporating western mountain climate into the existing Climate Generator (CLIGEN), which is part of the Water Erosion Prediction Project (WEPP) procedure. In the Western U.S., few meteorological observations exist in high elevation areas where Forest Service properties are located. Therefore, a procedure for estimating climatological variables in mountainous areas is needed to apply WEPP in these regions. A physically-based approach, an expanded and improved orographic precipitation model, is proposed in this report. It will use radiosonde data and also lightning data to simulate convective storms. Climatological sequences thus estimated at ungaged locations will be represented using stochastic models, similar to the approach used in the existing CLIGEN, and their parameters will be available to users through maps. By using these stochastic models, WEPP users can synthesize climate sequences for input to WEPP. Several alternative approaches to developing the Mountain Climate Generator (MCLIGEN) have been formulated and evaluated. These options vary in their spatial resolution. Some will provide synthetic climate inputs whereas others will provide synthetic sequences of water delivery to the ground surface or overland flow delivery. The latter will reduce the user\u27s responsibility for judging adequate snowpack or hydrological simulations, but will enormously increase the effort required for parameterization during the developmental phase. Based on our evaluation, we recommend that Option 2 for generating fine scale climate sequences be adopted. This option appears to satisfy the WEPP spatial resolution requirements of the USFS and requires a reasonable level of developmental effort. We also recommend that Option 3 be available to the users. We recomment that under this option snowpack initial conditions at a specified date be available based on a return period or exceedance probability. Under this option discontinuous simulation periods could be considered. The data, models, and parameters needed to implement the recommended approach can be divided into three parts: 1) climatological process models, 2) a snowpack imulation model, and 3) stochastic models of climatological variables and parameter regionalization. A chapter of the report is devoted to each of these three parts. Each chapter includes a literature review and a description of the proposed methodology and work plan for its development. We further recommend that a comprehensive plan for data collection for validation of the entire WEPP methodology applied to the mountainous Western U.S. be developed. Also, we propose that UWRL take the lead in settin gup a user group for orographic precipitation modelers

Development of Mountain Climate Generator and Snowpack model for Erosion Predictions in the Western United States using WEPP, Reserach Completion Report for Phase II

Executive Summary: This report summarizes work conducted during the funding period (July 1 through September 30, 1990) of a Cooperative Agreement between the United States Forest Service (USFS) and the Utah Water Research Laboratory (UWRL), Utah State University. The purpose of the agreement is to develop a Western Mountain Climate Generator (MCLIGEN) similar in function to the existing Climate Generator (CLIGEN), which is part of the Water Erosion Prediction Project (WEPP) procedure. Also, we are developing a Western U.S. snowpack simulation model for inclusion in WEPP. In the Western U.S., few meteorological observations exist in high elecation areas where Forest Service properties are located. Therefore, a procedure for estimating climatological variables in mountainous areas is needed to apply WEPP in these regions. A physically-based approach, using an expanded and improved orographic precipitation model, is being utilized. It will use radiosonde data and also lighning data to simualte convective storms. Climatological sequences thus estimated at ungaged locatiosn will be represented using stochastic models, similar to the approach used in the existing CLIGEN, and their parameters will be available to users through maps. By using these stochastic models, WEPP usters can synthsize climate sequences for input to WEPP. During the reporting period we have implemented the the Rhea orographic precipitation model and begun preliminary model testing in two regions. Also, we have begun formulation of model modifications for handling convective events. Various snowplack and meteorological data sets have been acquired and others have been ordered. Some of these have been applied in ititial applications of several snowpack models which have been recorded in a modeular form. Work has commenced on the statistical analysis of western climate sequences, including the preliminary assessment of the alternative stochastic model structures. Additional review of literature has been commenced for establishing desing storms and design hydrographs for events of various return periods in mountainous regions. Accomplishments are summarized in three parts: 1) climatological process models, 2) snowpack simulation models, and 3) stochastic models of climatological variablse and parameter regionalization. A chapter of the report is devoted to each of these three parts

Developing and Implementing a Sustainable, Integrated Weed Management Program for herbicide-resistant Poa annua in turfgrass

The ability of Poa annua L. to adapt to most turfgrass environments extends to its ability to develop resistance to commonly used herbicides. Herbicide resistant P. annua is of almost epidemic proportions. The loss of once viable chemical-based treatments pushes practitioners towards more expensive, and often less effective, control strategies. This management guide focuses on integrated weed management (IWM) practices for P. annua control and herbicide resistance—what it is and how to overcome it. Also discussed are resistance mechanisms and documentation of common occurrences of field-level resistance within much of the United States. Finally, a summary of some of the social and economic constraints that practitioners face in the implementation of IWM strategies for P. annua is discussed

Examining increased flexibility in assessment formats

There have been calls in the literature for changes to assessment practices in higher education, to increase flexibility and give learners more control over the assessment process (Boud and Falchikov 2006; Nicol and MacFarlane-Dick 2006; Taras 2002). This article explores the possibilities of allowing student choice in the format used to present their work, as a starting point for changing assessment, based on recent studies and current examples of flexible assessment practice in Higher Education. The benefits of this flexible assessment format approach are highlighted, along with a discussion of classic assessment considerations such as validity, reliability and marking concerns. The role of technology in facilitating assessment method choice is considered, in terms of new opportunities for providing student choice in the way they evidence their learning and present their work. Considerations for implementing flexible assessment choices into the curriculum are presented, along with a call that further research into such practice is needed to develop a comprehensive set of practical recommendations and best practice for implementation of flexible assessment choice into the curriculum. The article should be of interest to curriculum developers and academics considering implementing changes to the assessment process to increase student ownership and control