On the cotangent cohomology of rational surface singularities with almost reduced fundamental cycle

We prove dimension formulas for the cotangent spaces $T^{1}$ and $T^{2}$ for a class of rational surface singularities by calculating a correction term in the general dimension formulas. We get that it is zero if the dual graph of the rational surface singularity $X$ does not contain a particular type of configurations, and this generalizes a result of Theo de Jong stating that the correction term $c(X)$ is zero for rational determinantal surface singularities. In particular our result implies that $c(X)$ is zero for Riemenschneiders quasi-determinantal rational surface singularities, and this also generalise results for qoutient singularities.Comment: 11 pages, one figur

Scale-Dependent Habitat Selection of Nesting Great Egrets and Snowy Egrets

Foraging habitat selection of nesting Great Egrets ( Ardea alba ) and Snowy Egrets ( Egretta thula ) was investigated within an estuary with extensive impounded salt marsh habitat. Using a geographic information system, available habitat was partitioned into concentric bands at five, ten, and 15 km radius from nesting colonies to assess the relative effects of habitat composition and distance on habitat selection. Snowy Egrets were more likely than Great Egrets to depart colonies and travel to foraging sites in groups, but both species usually arrived at sites that were occupied by other wading birds. Mean flight distances were 6.2 km (SE = 0.4, N = 28, range 1.8-10.7 km) for Great Egrets and 4.7 km (SE = 0.48, N = 31, range 0.7-12.5 km) for Snowy Egrets. At the broadest spatial scale both species used impounded (mostly salt marsh) and estuarine edge habitat more than expected based on availability while avoiding unimpounded (mostly fresh water wetland) habitat. At more local scales habitat use matched availability. Interpretation of habitat preference differed with the types of habitat that were included and the maximum distance that habitat was considered available. These results illustrate that caution is needed when interpreting the results of habitat preference studies when individuals are constrained in their choice of habitats, such as for central place foragers

Vegetation Effects on Fish Distribution in Impounded Salt Marshes

We compared the density and biomass of resident fish in vegetated and unvegetated flooded habitats of impounded salt marshes in the northern Indian River Lagoon (IRL) Estuary of east-central Florida. A 1-m2 throw trap was used to sample fish in randomly located, paired sample plots (n = 198 pairs) over 5 seasons in 7 impoundments. We collected a total of 15 fish taxa, and 88% of the fishes we identified from the samples belonged to three species: Cyprinodon variegatus (Sheepshead Minnow), Gambusia holbrooki (Eastern Mosquitofish), and Poecilia latipinna (Sailfin Molly). Vegetated habitat usually had higher density and biomass of fish. Mean fish density (and 95% confidence interval) for vegetated and unvegetated sites were 8.2 (6.7–9.9) and 2.0 (1.6–2.4) individuals m-2, respectively; mean biomass (and 95% confidence interval) for vegetated and unvegetated sites were 3.0 (2.5–3.7) and 1.1 (0.9–1.4) g m-2, respectively. We confirmed previous findings that impounded salt marshes of the northern IRL Estuary produce a high standing stock of resident fishes. Seasonal patterns of abundance were consistent with fish moving between vegetated and unvegetated habitat as water levels changed in the estuary. Differences in density, mean size, and species composition of resident fishes between vegetated and unvegetated habitats have important implications for movement of biomass and nutrients out of salt marsh by piscivores (e.g., wading birds and fishes) via a trophic relay

Phase-locking in Multi-Frequency Brillouin Oscillator via Four Wave Mixing

Stimulated Brillouin scattering (SBS) and Kerr-nonlinear four wave-mixing (FWM) are among the most important and widely studied nonlinear effects in optical fibres. At high powers SBS can be cascaded producing multiple Stokes waves spaced by the Brillouin frequency shift. Here, we investigate the complex nonlinear interaction of the cascade of Stokes waves, generated in a Fabry-Perot chalcogenide fibre resonator through the combined action of SBS and FWM. We demonstrate the existence of parameter regimes, in which pump and Stokes waves attain a phase-locked steady state. Real-time measurements of 40ps pulses with 8GHz repetition rate are presented, confirming short-and long-term stability. Numerical simulations qualitatively agree with experiments and show the significance of FWM in phase-locking of pump and Stokes waves. Our findings can be applied for the design of novel picosecond pulse sources with GHz repetition rate for optical communication systems

Understanding How Students with Learning Disabilities from an Urban Environment Experience Nature-based Informal Learning

Research has shown that there is an achievement gap with students of color in the urban environment and their White non-urban peers (Norman, Ault, Bentz, & Meskimen, 2001; National Research Council, 2012) additionally an achievement gaps exists between students with disabilities and their non-disabled peers (National Center for Learning Disabilities, 2011). The demand for Science, Technology, Engineering, and Mathematics (STEM) preparation is growing and more students need to be prepared in school for STEM careers (Carlson, 1997). The didactic traditional style of teacher led text book reading has proven unsuccessful for large groups of urban youths and students with disabilities (Kahle, Meece, & Scantlebury, 2000; Haberman, 1991; National Research Council, 2012). Using a hands-on, experiential informal learning environments in science has proven successful in engaging students to the science curriculum (National Research Council, 2012). Nature has also proven to engage students into the curriculum. This study combines these topics and addresses the gap in the literature where these topics overlap. This qualitative case study sought to understand how students with learning disabilities from an urban environment experienced nature-based informal learning. The participants for this exploratory case study informed by ethnographic methods of observation involved seven eighth grade students with learning disabilities from an inclusive science program at a public urban school. The students participated in four nature related informal learning experiences that were aligned to the science curriculum. These students’ experiences were collected from observations, and conducting both one-on-one interviews and focus groups. The data was then triangulated, analyzed thematically, and interpreted. The students’ experiences were shared thematically. The three themes which emerged from the data were: -Hands-on learning is an engaging and a more enjoyable way of learning for students with learning disabilities. -There is not enough science being taught. -Students are not habitually accessing natural areas

National Apology to the Stolen Generations

The University of Notre Dame Australia, Broome Campus will hold a stall in support of the Kimberley Stolen Generation, please come and show your support

Birefringence and polarisation mode-dispersion in spun single-mode fibres

A theoretical and experimental analysis of the polarization properties of twisted single-mode fibers is presented. It is shown that whereas a conventionally twisted fiber possesses considerable optical rotation, a fiber which has a permanent twist imparted by spinning the preform during fiber drawing exhibits almost no polarization anisotropy. It is thus possible to virtually eliminate the commonly observed fiber linear birefringence. As a consequence, fibers made in this way are ideally suited for use in the Faraday-effect current transducer. It is further shown that a permanent twist of a few turns/meter effectively eliminates polarization mode-dispersion. The technique therefore appears attractive for enhancing the bandwidth of very long unrepeatered telecommunication links

Uncertainty, Grades and Student Evaluations

Dr. Stolen is an Associate Professor of Decision Science at the University of Nebraska at Omaha