An approach to the use of macrophytes for monitoring standing waters

Under the EC Water Framework Directive (WFD), each Member State is required to devise a comprehensive national monitoring programme for surface waters, incorporating hydromorphological, physico-chemical and biological elements. This paper describes one aspect of the biota - the macrophyte flora - to classify standing waters and to monitor their water quality. The evolution of this method is described and suggestions for its future development are made

Heteroskedasticity-Robust Inference in Finite Samples

Since the advent of heteroskedasticity-robust standard errors, several papers have proposed adjustments to the original White formulation. We replicate earlier findings that each of these adjusted estimators performs quite poorly in finite samples. We propose a class of alternative heteroskedasticity-robust tests of linear hypotheses based on an Edgeworth expansions of the test statistic distribution. Our preferred test outperforms existing methods in both size and power for low, moderate, and severe levels of heteroskedasticity.

A General Expression for Symmetry Factors of Feynman Diagrams

The calculation of the symmetry factor corresponding to a given Feynman diagram is well known to be a tedious problem. We have derived a simple formula for these symmetry factors. Our formula works for any diagram in scalar theory ($\phi^3$ and $\phi^4$ interactions), spinor QED, scalar QED, or QCD.Comment: RevTex 11 pages with 10 figure

Muon Collider Overview: Progress and Future Plans

Besides continued work on the parameters of a 3-4 and 0.5 TeV CoM collider, many studies are now concentrating on a machine near 100 GeV that could be a factory for the s-channel production of Higgs particles. We mention the research on the various components in such muon colliders, starting from the proton accelerator needed to generate pions from a heavy-Z target and proceeding through the phase rotation and decay channel, muon cooling, acceleration, storage in a ring and the collider detector. We also mention theoretical and experimental R&D plans for the next several years that should lead to a better understanding of the design and feasibility issues for all of the components. This note is a summary of a report updating the progress on the R&D since the Feasibility Study of Muon Colliders presented at the Workshop Snowmass'96.Comment: 3 pages, 2 figures, LaTex EPAC format; to be published Proceedings of the EPAC98 Conference, Stockholm, Sweden, June 1998. Additional information and articles at http://www.cap.bnl.gov/mumu

An Estimation of the Efficient Size of Sugarcane Enterprises for Farmers in Trinidad

This research paper provides an estimation of the efficient size of operation for sugarcane farmers in Trinidad. The estimates were based on a sample of two hundred and twenty-seven farmers selected from a cost of sugarcane production survey. To identify the efficient size of operation the ordinary least square estimation technique was used. The identification of the efficient size of operation allowed a test of the hypothesis that the minimum point on the long run average cost curve was significantly greater than the average enterprise size of six acres. The long run total cost curve was estimated and the cubic functional form provided the best fit based on both the adjusted R2 and the result from the Wald test. The results of the estimation process indicated that the optimal size was 32 acres of sugarcane and that 98% of the farmers operated at less than this size.Cost function, cost elasticity, efficient size, sugar-cane, Trinidad, Agribusiness, Farm Management, Research Methods/ Statistical Methods,

Study of radiatively sustained cesium plasmas for solar energy conversion

The results of a study aimed at developing a high temperature solar electric converter are reported. The converter concept is based on the use of an alkali plasma to serve as both an efficient high temperature collector of solar radiation as well as the working fluid for a high temperature working cycle. The working cycle is a simple magnetohydrodynamic (MHD) Rankine cycle employing a solid electrode Faraday MHD channel. Research milestones include the construction of a theoretical model for coupling sunlight in a cesium plasma and the experimental demonstration of cesium plasma heating with a solar simulator in excellent agreement with the theory. Analysis of a solar MHD working cycle in which excimer laser power rather than electric power is extracted is also presented. The analysis predicts a positive gain coefficient on the cesium-xenon excimer laser transition

Strengths and Silences: The Experiences of Lesbian, Gay, Bisexual and Transgender Students in Rural and Small Town Schools

For more than 20 years, GLSEN has worked to make schools safer for all students; it has sought specifically to reduce the bullying and harassment targeted at students' sexual orientation, gender identity, and gender expression. For lesbian, gay, bisexual, and transgender (LGBT) students across the country, violence and harassment experienced in school affect their ability to learn. Although schools in urban areas are typically regarded as more violent or dangerous than schools in other areas, findings from our National School Climate Surveys consistently show that it is most often rural schools that may pose the greatest threats for LGBT students. It may be that community characteristics, such as religious and cultural traditions, income, and educational levels, influence individual beliefs and attitudes toward LGBT people in these areas. It may also be that a lack of positive LGBT-related school resources negatively affects LGBT students' school engagement and academic performance, particularly if they also experience bullying and harassment. Although research on the educational experiences of LGBT youth has grown considerably over the past 25 years, less is known about rural students specifically. This research report examines the experiences of LGBT students in small town and rural areas on matters related to biased language in schools, school safety, harassment and victimization, educational outcomes, school engagement, and LGBT-related resources and support. It also examines the prevalence and utility of LGBT-related resources in rural schools. Finally, this report concludes by advocating for more intentional policies, measures, and programs that protect LGBT students

The 2011 National School Climate Survey: The Experiences of Lesbian, Gay, Bisexual and Transgender Youth in Our Nation's Schools

In 1999, GLSEN identified the need for national data on the experiences of lesbian, gay, bisexual, and transgender (LGBT) students and launched the first National School Climate Survey (NSCS). At the time, the school experiences of LGBT youth were under-documented and nearly absent from national studies of adolescents. For more than a decade, the biennial NSCS has documented the unique challenges LGBT students face and identified interventions that can improve school climate. The survey explores the prevalence of anti-LGBT language and victimization, the effect that these experiences have on LGBT students' achievement and well-being, and the utility of interventions in lessening the negative effects of a hostile school climate and promoting a positive educational experience. The survey also examines demographic and community-level differences in LGBT students' experiences.The NSCS remains one of the few studies to examine the school experiences of LGBT students nationally, and its results have been vital to GLSEN's understanding of the issues that LGBT students face, thereby informing our ongoing work to ensure safe and affirming schools for all.In our 2011 survey, we examine the experiences of LGBT students with regard to indicators of negative school climate:hearing biased remarks, including homophobic remarks, in school;feeling unsafe in school because of personal characteristics, such as sexual orientation, gender expression, or race/ethnicity;missing classes or days of school because of safety reasons; andexperiencing harassment and assault in school.We also examine:the possible negative effects of a hostile school climate on LGBT students' academic achievement, educational aspirations, and psychological well-being;whether or not students report experiences of victimization to school officials or to family members and how these adults address the problem; andhow the school experiences of LGBT students differ by personal and community characteristics.In addition, we demonstrate the degree to which LGBT students have access to supportive resources in school, and we explore the possible benefits of these resources, including:Gay-Straight Alliances (GSAs) or similar clubs;anti-bullying/harassment school policies and laws;supportive school staff; andcurricula that are inclusive of LGBT-related topics.Given that GLSEN has more than a decade of data, we examine changes over the time on indicators of negative school climate and levels of access to LGBT-related resources in schools

Effect of field of view and monocular viewing on angular size judgements in an outdoor scene

Observers typically overestimate the angular size of distant objects. Significantly, overestimations are greater in outdoor settings than in aircraft visual-scene simulators. The effect of field of view and monocular and binocular viewing conditions on angular size estimation in an outdoor field was examined. Subjects adjusted the size of a variable triangle to match the angular size of a standard triangle set at three greater distances. Goggles were used to vary the field of view from 11.5 deg to 90 deg for both monocular and binocular viewing. In addition, an unrestricted monocular and binocular viewing condition was used. It is concluded that neither restricted fields of view similar to those present in visual simulators nor the restriction of monocular viewing causes a significant loss in depth perception in outdoor settings. Thus, neither factor should significantly affect the depth realism of visual simulators