Stability of optically-active charged excitons in quasi-two dimensional systems

A negatively charged quasi-two dimensional exciton ($X^-$) is solved exactly numerically in the presence of a uniform perpendicular B-field. Various quasi-two dimensional geometries are studied. The charge distribution of the $X^-$ parallel to the B-field is found to be crucial in determining the stability of the optically-active $X^-$ and hence its photoluminescence (PL) signature. The theory provides a quantitative explanation of recent experimental results obtained for a GaAs quantum well. Effects are found which cannot be described within a lowest Landau level approximation. PACS: 78.20.Ls 78.66.-w 73.20.DxComment: Minor revisions, mainly removal of the term trion in favour of the term charged-exciton to comply with Physical Review B. To be published as a Rapid Communication in Physical Review

The trophic dynamics of summer flounder (Paralichthys dentatus) in Chesapeake Bay

Data on the trophic dynamics of fishes are needed for management of ecosystems such as Chesapeake Bay. Summer flounder (Paralichthys dentatus) are an abundant seasonal resident of the bay and have the potential to impact foodweb dynamics. Analyses of diet data for late juvenile and adult summer flounder collected from 2002−2006 in Chesapeake Bay were conducted to characterize the role of this flatfish in this estuary and to contribute to our understanding of summer flounder trophic dynamics throughout its range. Despite the diversity of prey, nearly half of the diet comprised mysid shrimp (Neomysis spp.) and bay anchovy (Anchoa mitchilli). Ontogenetic differences in diet and an increase in diet diversity with increasing fish size were documented. Temporal (inter- and intra-annual) changes were also detected, as well as trends in diet reflecting peaks in abundance and diversity of prey. The preponderance of fishes in the diet of summer flounder indicates that this species is an important piscivorous predator in Chesapeake Bay

Dynamics of soap bubble bursting and its implications to volcano acoustics

In order to assess the physical mechanisms at stake when giant gas bubbles burst at the top of a magma conduit, laboratory experiments have been performed. An overpressurized gas cavity is initially closed by a thin liquid film, which suddenly bursts. The acoustic signal produced by the bursting is investigated. The key result is that the amplitude and energy of the acoustic signal strongly depend on the film rupture time. As the rupture time is uncontrolled in the experiments and in the field, the measurement of the acoustic excess pressure in the atmosphere, alone, cannot provide any information on the overpressure inside the bubble before explosion. This could explain the low energy partitioning between infrasound, seismic and explosive dynamics often observed on volcanoes

Consumer Responses to Recent BSE Events

Recent bovine spongiform encephalopathy (BSE, a.k.a. mad cow disease) discoveries in Canadian and U.S. beef cattle have garnered significant media attention, which may have changed consumers’ meat-purchasing behavior. Consumer response is hypothesized and tested within a meat demand system in which response is measured using single-period dummy variables, longer-term dummy variables, and media indices that count positive and negative meat-industry articles. Parameters are estimated using retail scanner data, and cross-species price elasticities are calculated. Results suggest that the BSE events negatively impacted ground beef and chuck roasts, while positively impacting center-cut pork chop demand. Dummy variables explained the variation in meat-budget shares better than did media indices.Consumer/Household Economics,

Managing Lawns to Protect Water Quality: Watering, Fertilizing, and Applying Pesticides

Maintaining a quality lawn requires that you use intensive lawn care practices like watering, fertilizing, and/or applying pesticides. A number of best management practices (BMPs) provide safe-guards for preventing the contamination of surface water and groundwater supplies with lawn fertilizer and/or pesticides

Essential Programs and Services Report of Findings: System Administration Component

SUMMARY This analysis of the System Administration component of Maine’s Essential Programs and Services school funding model was prepared for the Commissioner of Education as part of the ongoing review of the cost formula, as required by Maine statute. Specific elements for analysis were determined in collaboration with the Maine Department of Education

Preliminary Investigation of Maine Virtual Charter School Costs Relative to the Essential Programs and Services Funding Model

In 2015, the Maine State Legislature\u27s Joint Standing Committee on Education and Cultural Affairs commissioned the Maine Education Policy Research Institute (MEPRI) to study the state\u27s Essential Program and Services (EPS) K-12 education funding model in relationship to the funding for Maine\u27s two virtual charter schools. The study was initiated with a review of available literature and reports on virtual school funding in other states. Because the structure of Maine\u27s virtual schools differs from typical models in other states, most notably because core academic subject teachers are required to teach from one central physical location, further cost analysis was conducted using only Maine-­based data. The expenditure data available was from one school (Maine Connections Academy) in its first year of operation in 2014-­15. This limits the generalizability of the findings. Data were analyzed by categorizing the virtual school expenditures as much as was possible into nineteen separate components of Maine\u27s Essential Programs and Services funding model. In each category, the report first provides a qualitative description of how the virtual school carries out that type of work. This provides background to aid the reader in understanding how virtual schools operate, and in interpreting any differences in expenditures. Next the quantitative analysis for that cost category is detailed, followed by a concise summary of whether the expenditures for that category were higher, lower, or similar to the EPS cost model, unless inadequate data were available to make a determination. An appendix provides a summary of virtual school policies in other states

Summary Report: Essential Programs and Services Career and Technical Education Component Review

Background The Career and Technical Education (CTE) funding model was implemented in FY2019 after a lengthy period of development. The component was scheduled for a review in FY2020 and FY2021 as part of the ongoing cycle of analysis of all major components of Maine’s Essential Programs and Services (EPS) education cost model. Due to the breadth and complexity of the CTE funding model, and the fact that this is the first time it has been reviewed to see how it is being implemented in actual practice, the findings have been broken into several sections. Appendix A provides the overall plan of analyses, which were divided into two separate reports. The Part I report issued in summer 2021 included analyses related to student enrollment trends, including the impact of the Covid-19 pandemic on program enrollments, as well as analyses related to facilities and maintenance spending. The Part II report issued in March 2022 described the remainder of the analyses, which are divided into three distinct sections based on the source data used in each task. Section I presented findings that were derived from staffing data. Section 2 described patterns from expenditure data from the most recent pre-pandemic program year. Section 3 summarized results of a questionnaire that was administered to all CTEs to gather data that are not routinely collected. The data from the questionnaire responses were needed to address a series of questions posed by the “Maine CTE Subsidy Workgroup,” which was formed by Maine Administrators of Career & Technical Education (MACTE) and the Maine School Superintendent Association (MSSA). The Maine Department of Education (MDOE) agreed to include the questions in the research plan for the EPS component review contract with MEPRI. The research topics and questions came from the Maine Department of Education, prior reports by MEPRI and MDOE, and the MACTE/MSSA CTE Subsidy Workgroup as mentioned above. Some of the information was needed for decisions to be made by MDOE during the continuing implementation of the EPS CTE model. The adequacy of sub-components was evaluated. And in some cases updated model parameters were computed. Miscellaneous topics 2 and questions presented by the MACTE/MSSA Workgroup were also addressed. Additionally, relevant findings were presented to the LD 313 work group, which was established after the MEPRI research project was well underway. The materials prepared by MEPRI for the LD 313 work group are included as Appendix D. The current summary report is a compilation of the findings of the Part I and Part II reports together with a summary of the main findings and elaboration on data and analysis methods. It begins with an overall summary of our most pertinent findings in order to aid the reader in navigating the various sections of the report. A methods section describes the data and the analysis techniques used in the review. Finally, detailed findings are presented in two parts corresponding to the Part I and Part II reports previously submitted

Code wars: steganography, signals intelligence, and terrorism

This paper describes and discusses the process of secret communication known as steganography. The argument advanced here is that terrorists are unlikely to be employing digital steganography to facilitate secret intra-group communication as has been claimed. This is because terrorist use of digital steganography is both technically and operationally implausible. The position adopted in this paper is that terrorists are likely to employ low-tech steganography such as semagrams and null ciphers instead