Chris C. Diem to Mr. Meredith (13 October 1962)

https://egrove.olemiss.edu/mercorr_pro/2156/thumbnail.jp

Wide-angle perfect absorber/thermal emitter in the THz regime

We show that a perfect absorber/thermal emitter exhibiting an absorption peak of 99.9% can be achieved in metallic nanostructures that can be easily fabricated. The very high absorption is maintained for large angles with a minimal shift in the center frequency and can be tuned throughout the visible and near-infrared regime by scaling the nanostructure dimensions. The stability of the spectral features at high temperatures is tested by simulations using a range of material parameters.Comment: Submitted to Phys. Rev. Let

Spearfishing-induced behavioral changes of an unharvested species inside and outside a marine protected area.

By prohibiting fishing, marine protected areas (MPAs) provide a refuge for harvested species. Humans are often perceived as predators by prey and therefore respond fearfully to humans. Thus, fish responses to humans inside and outside of an MPA can provide insights into their perception of humans as a predatory threat. Previous studies have found differences in the distance that harvested species of fish initiate flight (flight initiation distance-FID) from humans inside and outside an MPA, but less is known about unharvested species. We focused on whether the lined bristletooth Ctenochaetus striatus, an unharvested surgeonfish, can discriminate between a snorkeler and a snorkeler with a spear gun inside and outside of a no-take MPA in Mo'orea, French Polynesia. Additionally, we incorporated starting distance (the distance between the person and prey at the start of an experimental approach), a variable that has been found to be important in assessing prey escape decisions in terrestrial species, but that has not been extensively studied in aquatic systems. Lined bristletooth FID was significantly greater in the presence of a spear gun and varied depending on if the spear gun encounter was inside or outside of the MPA. These results imply a degree of sophistication of fish antipredator behavior, generate questions as to how a nontargeted species of fish could acquire fear of humans, and demonstrate that behavioral surveys can provide insights about antipredator behavior

What is the minimal systemic risk in financial exposure networks?

We quantify how much systemic risk can be eliminated in financial contract networks by rearranging their network topology. By using mixed integer linear programming, financial linkages are optimally organized, whereas the overall economic conditions of banks, such as capital buffers, total interbank assets and liabilities, and average risk-weighted exposure remain unchanged. We apply the new optimization procedure to 10 snapshots of the Austrian interbank market where we focus on the largest 70 banks covering 71% of the market volume. The optimization reduces systemic risk (measured in DebtRank) by about 70%, showing the huge potential that changing the network structure has on the mitigation of financial contagion. Existing capital levels would need to be scaled up by a factor of 3.3 to obtain similar levels of DebtRank. These findings underline the importance of macro-prudential rules that focus on the structure of financial networks. The new optimization procedure allows us to benchmark actual networks to networks with minimal systemic risk. We find that simple topological measures, like link density, degree assortativity, or clustering coefficient, fail to explain the large differences in systemic risk between actual and optimal networks. We find that if the most systemically relevant banks are tightly connected, overall systemic risk is higher than if they are unconnected

Who is Afraid of School Choice?

This study uses survey data to investigate attitudes among Swiss voters to different models offering more freedom of choice in the educational system. The findings indicate clear opposition to the use of taxpayer money to fund private schools, while free choice between public schools seems to appeal to a majority. The analyses show that the approval-opposition heterogeneity is mainly based on an explicable, rational calculation of personal utility. Approval rates are much higher among groups or individuals who see a personal advantage in more school choice, such as parents of school-age children, urban/metropolitan area residents and those on a low income. In contrast, residents of small to medium-sized centers of population, high-income groups, and individuals with a teaching qualification oppose more school choice. The analyses also indicate differences between the country’s language regions, attributable to intercultural differences in what people consider the state’s role to be.school choice, survey, private schools, education vouchers

Liquid droplet radiator program at the NASA Lewis Research Center

The NASA Lewis Research Center and the Air Force Rocket Propulsion Laboratory (AFRPL) are jointly engaged in a program for technical assessment of the Liquid Droplet Radiator (LDR) concept as an advanced high performance heat ejection component for future space missions. NASA Lewis has responsibility for the technology needed for the droplet generator, for working fluid qualification, and for investigating the physics of droplets in space; NASA Lewis is also conducting systems/mission analyses for potential LDR applications with candidate space power systems. For the droplet generator technology task, both micro-orifice fabrication techniques and droplet stream formation processes have been experimentally investigated. High quality micro-orifices (to 50 micron diameter) are routinely fabricated with automated equipment. Droplet formation studies have established operating boundaries for the generation of controlled and uniform droplet streams. A test rig is currently being installed for the experimental verification, under simulated space conditions, of droplet radiation heat transfer performance analyses and the determination of the effect radiative emissivity of multiple droplet streams. Initial testing has begun in the NASA Lewis Zero-Gravity Facility for investigating droplet stream behavior in microgravity conditions. This includes the effect of orifice wetting on jet dynamics and droplet formation. Results for both Brayton and Stirling power cycles have identified favorable mass and size comparisons of the LDR with conventional radiator concepts

The Learning Styles and Language Learning Strategies of the EFL Students at Tertiary Level

The purpose of this study are to discover the learning styles, and the language learning strategies most preferred, correlation among the variables exists, and the degree of influence each independent variable exerts on the dependent variables. For data collection, the Barsch Learning Styles Inventory and the Strategy Inventory of Language Learning were distributed to 156 students of English at the University of Sriwijaya, Palembang. The results showed that: (1) visual is the most preferred learning style, whereas metacognitive ang effective are the most preferred language learning strategies; (2) certain independent variables have a significant correlation with certain dependent variables, for example, visual with memory, auditory with cognitive, tactile with affective, and semester with compensation; (3) females use a greater variety of language learning strategies than males; and (4) semester has a significant correlation with compensation but not with other strategie

A geometric view of cryptographic equation solving

This paper considers the geometric properties of the Relinearisation algorithm and of the XL algorithm used in cryptology for equation solving. We give a formal description of each algorithm in terms of projective geometry, making particular use of the Veronese variety. We establish the fundamental geometrical connection between the two algorithms and show how both algorithms can be viewed as being equivalent to the problem of finding a matrix of low rank in the linear span of a collection of matrices, a problem sometimes known as the MinRank problem. Furthermore, we generalise the XL algorithm to a geometrically invariant algorithm, which we term the GeometricXL algorithm. The GeometricXL algorithm is a technique which can solve certain equation systems that are not easily soluble by the XL algorithm or by Groebner basis methods

Greenhouse gas emissions (CO2, CH4, and N2O) from several perialpine and alpine hydropower reservoirs by diffusion and loss in turbines

We investigated greenhouse gas emissions (CO2, CH4, and N2O) from reservoirs located across an altitude gradient in Switzerland. These are the first results of greenhouse gas emissions from reservoirs at high elevations in the Alps. Depth profiles were taken in 11 reservoirs located at different altitudes between the years 2003 and 2006. Diffusive trace gas emissions were calculated using surface gas concentrations, wind speeds and transfer velocities. Additionally, methane entering with the inflowing water and methane loss at the turbine was assessed for a subset of the reservoirs. All reservoirs were emitters of carbon dioxide and methane with an average of 970±340mgm−2day−1 (results only from four lowland and one subalpine reservoir) and 0.20±0.15mgm−2day−1, respectively. One reservoir (Lake Wohlen) emitted methane at a much higher rate (1.8±0.9mgm−2day−1) than the other investigated reservoirs. There was no significant difference in methane emissions across the altitude gradient, but average dissolved methane concentrations decreased with increasing elevation. Only lowland reservoirs were sources for N2O (72±22μgm−2day−1), while the subalpine and alpine reservoirs were in equilibrium with atmospheric concentrations. These results indicate reservoirs from subalpine/alpine regions to be only minor contributors of greenhouse gases to the atmosphere compared to other reservoir