Topographical scattering of waves: a spectral approach

The topographical scattering of gravity waves is investigated using a spectral energy balance equation that accounts for first order wave-bottom Bragg scattering. This model represents the bottom topography and surface waves with spectra, and evaluates a Bragg scattering source term that is theoretically valid for small bottom and surface slopes and slowly varying spectral properties. The robustness of the model is tested for a variety of topographies uniform along one horizontal dimension including nearly sinusoidal, linear ramp and step profiles. Results are compared with reflections computed using an accurate method that applies integral matching along vertical boundaries of a series of steps. For small bottom amplitudes, the source term representation yields accurate reflection estimates even for a localized scatterer. This result is proved for small bottom amplitudes $h$ relative to the mean water depth $H$. Wave reflection by small amplitude bottom topography thus depends primarily on the bottom elevation variance at the Bragg resonance scales, and is insensitive to the detailed shape of the bottom profile. Relative errors in the energy reflection coefficient are found to be typically $2h/H$.Comment: Second revision for Journal of Waterways Ports and Coastal Engineerin

Representation of Africa online: sourcing practice and frames of reference

The dominant perspective on the representation of Africa in the western media claims that western media coverage is bias and crisis orientated and the liberal perspective claims that the coverage of Africa is not as negative as is often assumed. However, there is a paucity of literature on the representation of Africa online. This research enquiry is relevant because literature claims that the Internet has the potential to resolve the journalistic predicament of representing other culture through political participation and deliberation. But this requires a re-orientation of the sourcing practice of news organization to embrace sensitivity to and knowledge of African cultures. Moreover, the journalistic predicament can be resolved or not depending on the news gathering approach adopted by the news organization. Literature has identified two approaches, that is, ‘gatekeeping’ used mainly by dominant traditional media and ‘gatewatching’ used by alternative media in their quest to counter mainstream ideology. This study examines the impacts of the ‘gatewatching’ approach adopted by Africa Have Your Say (AHYS) website on its representation and frames of reference of Africa. It uses on-site observation, in-depth interviews and textual analysis to gather data. The study found that although the sourcing practice at the AHYS is elaborate and complex, the ‘gatewatching’ approach makes its susceptible to second level agenda setting. Hence, its frame repeats the attributes and tone used by the mainstream traditional media. However, a minority of users did not use repeat this frame in their comments

Morphology Effectively Controls Singlet-Triplet Exciton Relaxation and Charge Transport in Organic Semiconductors

We present a comparative study of ultrafast photo-conversion dynamics in tetracene (Tc) and pentacene (Pc) single crystals and Pc films using optical pump-probe spectroscopy. Photo-induced absorption in Tc and Pc crystals is activated and temperature-independent respectively, demonstrating dominant singlet-triplet exciton fission. In Pc films (as well as C$_{60}$-doped films) this decay channel is suppressed by electron trapping. These results demonstrate the central role of crystallinity and purity in photogeneration processes and will constrain the design of future photovoltaic devices.Comment:

Infrastructure Hardening: A Competitive Co-evolutionary Methodology Inspired by Neo-Darwinian Arms Races

The world is increasingly dependent on critical infrastructures such as the electric power grid, water, gas, and oil transport systems, which are susceptible to cascading failures that can result from a few faults. Due to the combinatorial complexity in the search spaces involved, most traditional search techniques are inappropriate for identifying these faults and potential protections against them. This paper provides a computational methodology employing competitive coevolution to simultaneously identify low-effort, high-impact faults and corresponding means of hardening infrastructures against them. A power system case study provides empirical evidence that our proposed methodology is capable of identifying cost effective modifications to substantially improve the fault tolerance of critical infrastructures

Menominee Tribe Health Care Program Planning

Federal legislation authorized the Menominee Indian Tribe of Wisconsin to obtain benefits and services from the Health Services Administration. IHS has developed a health care program for the Tribe that is based on an analysis of their health needs. This study was undertaken to research and evaluate Tribal health services, design a health care plan, and implement an adequate health care delivery program.Information was collected on tribal health problems through existing service records and other supporting data. An analysis of health problems and services was done in three areas: 1) health and socioeconomic problems; 2) health service resources; and 3) a comparison of problems and services. This was followed by the development of alternatives. The final health care plan included provisions for services. facilities, staffing, financial considerations. and implementation.Primary outpatient care is available to serve the Tribe in four counties. The utilization and availability of primary care facilities is not adequate. Barriers to the services include lack of transportation, and a lack of educational programs to teach the procedures for obtaining health care. A general prejudice against treatment at the health care facilities exists. Secondary in-patient care is available to any tribal member within thirty minutes travel time. Long-term care is also available, however, services are fragmented. The major health care problems for the Menominee Tribe are perinatal mortality, infant mortality, congenital abnormalities, otitis media, respiratory diseases, dental diseases, infectious and communicable diseases, accidents, diabetes, alcoholism, vision problems, obesity, and drug abuse. Health problems are directly related to thesocioeconomic status of the Tribe including poverty, lack of work, lack of health insurance, low educational attainment, lack of telephones, lack of central heating, lack of plumbing, lack of transportation, illegitimacy, overcrowded housing, outmigration, and multi-parity.Facilities should be consolidated and centralized. Specifications for the facilities, staffing requirements and square footage necessary are listed. Financial recommendations were proposed with the major one being an incorporated, nonprofit health care organization, enabling the Menominees to own and operate the outpatient facility. Alternatives to service delivery in three basic areas--program alternatives, facility-related alternatives, and financial alternative--were discussed in detail