Spatially filtered wave-front sensor for high-order adaptive optics

Adaptive optics (AO) systems take sampled measurements of the wave-front phase. Because in the general case the spatial-frequency content of the phase aberration is not band limited, aliasing will occur. This aliasing will cause increased residual error and increased scattered light in the point-spread function (PSF). The spatially filtered wave-front sensor (SFWFS) mitigates this phenomenon by using a field stop at a focal plane before the wave-front sensor. This stop acts as a low-pass filter on the phase, significantly reducing the high-spatial-frequency content phase seen by the wave-front sensor at moderate to high Strehl ratios. We study the properties and performance of the SFWFS for open- and closed-loop correction of atmospheric turbulence, segmented-primary-mirror errors, and sensing with broadband light. In closed loop the filter reduces high-spatial-frequency phase power by a factor of 10(3) to 10(8). In a full AO-system simulation, this translates to a reduction by up to 625 times in the residual error power due to aliasing over a specific spatial frequency range. The final PSF (generated with apodization of the pupil) has up to a 100 times reduction in intensity out to lambda/2d.     

Graphitic carbon nanofiber (GCNF)/polymer materials. I. GCNF/epoxy monoliths using hexanediamine linker molecules

Processing methods have been optimized for the formation of graphitic carbon nanofiber (GCNF)/epoxy nanocomposites containing GCNFs highly dispersed throughout a thermoset epoxy matrix. GCNFs having a herringbone atomic structure are surface-derivatized with bifunctional hexanediamine linker molecules (GCNF-HDA) capable of covalent binding to an epoxy matrix during thermal curing and are cut to smaller dimension using high-power ultrasonication. GCNF-HDA nanofibers are dispersed in epoxy resin at 0.3 wt.% loading using variable levels of ultrasonication processing prior to thermal curing. Effects of sonication power on the quality of the GCNF-HDA/epoxy material obtained after curing have been determined from flexural property measurements, thermomechanical analysis and SEM/TEM imaging. GCNF-HDA/epoxy material of the highest quality is obtained using low-power sonication, although high-power sonication for short periods gives improved flexural properties without lowering the glass transition temperature. Good dispersion and polymer wetting of the GCNF component is evident on the nanoscale.     

Snowmelt sources of methylmercury to high arctic ecosystems

Mercury in humans and other top predators living in the Arctic is present at elevated levels. Since only methylmercury (MeHg) bioaccumulates in food chains, sources of MeHg need to be identified. Recently, wetlands in the High Arctic were found to produce MeHg, and this was confirmed in laboratory soil incubations. In the present study both wetlands and snowmelt water were evaluated as sources of MeHg to Arctic ecosystems in Nunavut. Three substudies took place on Cornwallis Island, and one took place on Ellesmere Island. First, the effect of wetland presence in lake watersheds was evaluated by comparing four lakes with wetlands present to four lakes without wetlands present. Next, two individual wetlands were spatially and temporally investigated. Finally, three basin tributaries were evaluated for snowmelt MeHg sources. Catchments on Cornwallis Island with wetlands did not have an observable effect on MeHg levels in downstream lake water, but the wetland on Ellesmere Island contributed significant MeHg. In contrast, calculated yields of MeHg in tributaries draining snowmelt on Cornwallis Island were higher (ca. 1.5 mg km(-2) day(-1)) than those measured in temperate catchments characterized by wetlands. Methylmercury and total Hg concentrations in lakes, wetlands, and basin tributaries showed a strong temporal trend that corresponded to inputs from snowmelt water in late spring. This study revealed that wetland export of MeHg to downstream Arctic lakes is site dependent, and snowmelt water was the most significant source of MeHg to Arctic ecosystems located on Cornwallis Island.     

Quantatitive assessment of enzyme immobilization capacity in porous silicon

Immobilized enzyme systems are important in a broad range of applications, from biological sensing to the industrial-scale biocatalytic synthesis of chiral products. We demonstrate the ability to systematically vary and quantitatively assess the immobilization capacity of porous silicon thin films for the enzyme glutathione-S-transferase in a manner predicted by a simple geometric model of the porous silicon matrix. We find that the immobilization capacity quantatitively correlates with systematic changes in the device thickness. These results are significant since, despite the wide range over which porous silicon morphology and surface area can be varied, few attempts have been made to systematically characterize surface binding capacity. Our findings suggest that porous silicon can be an ideal matrix, where immobilization of a predictable quantity of biological material is desired.     

The Emotional Wardrobe

Since the industrial revolution, fashion and technology have been linked through the textile and manufacturing industries, a relationship that has propelled technical innovation and aesthetic and social change. Today, a new alliance is emerging through the integration of electronic technology and smart materials on the body. This study addresses the integration of technology with clothing from a fashion perspective, and examines its expressive and interactive potential. It proposes the concept of The Emotional Wardrobe: clothing that represents and stimulates emotional response through the interface of technology. It asks if fashion can offer a more personal and provocative definition of self, which actively involves the wearer in a mutable aesthetic identity. A multi-disciplinary framework combines fashion, material science and the real-time, affective computing platform, called AffectiveWare. By merging technology and fashion, The Emotional Wardrobe becomes a poetic interface, shifting emphasis from human–computer interaction to computer-aided, human–human communication.     

Counselor hypothesis-testing strategies.

Conducted 2 experiments relevant to the questioning strategies counselors use in testing their hypotheses about clients. In Exp I, 60 undergraduates were asked to select 12 questions from a list of 38 that would be most helpful in getting to know someone. Ss were asked to test a hypothesis that the other person was an extravert or introvert. The questions were categorized by the experimenters as extraverted, introverted, unbiased, or irrelevant. Most Ss selected a strategy that favored unbiased questions over biased ones. In Exp II, 40 Ss played the roles of clients, and 40 advanced doctoral students in counseling or clinical psychology played the roles of counselors. Counselors were advised that they would soon meet with their client to test a hypothesis that the client possessed or lacked self-control. Counselors were instructed to compose 10 questions to ask the client. The actual interviews were then recorded. The frequency with which counselors developed questions that were confirmatory, disconfirmatory, irrelevant, or unbiased in regard to the hypothesis was not influenced by the specific hypothesis. Results of both experiments do not confirm the hypothesis that counselors preferentially seek information to confirm hypotheses about clients. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Racial and attitudinal factors affecting the perceptions of counselors by Black adolescents.

Presented to 247 Black male and female high school students racial and attitudinal information about a hypothetical male or female counselor and asked them to express their perceptions of the counselor. Attitudinal information about a counselor had a stronger effect than racial information on Ss' perception of the counselor: Counselors portrayed as attitudinally similar were rated significantly higher in attractiveness, trustworthiness, expertness, and social attraction than those portrayed as attitudinally dissimilar. Racial information also influenced perceived attractiveness: White counselors were rated higher than Black ones in attractiveness, although there was no difference in ratings of trustworthiness or expertise. White female counselors were perceived as more expert than their Black female counterparts, whereas the ratings of male counselors were not influenced by the racial variable. Implications for counselor–client relationships and the development of mental health services for minority populations are discussed. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Escherichia coli and enterococci at beaches in the Grand Traverse Bay,Lake Michigan: sources,characteristics, and environmental pathways

This study quantified Escherichia coli (EC) and enterococci (ENT) in beach waters and dominant source materials, correlated these with ambient conditions, and determined selected EC genotypes and ENT phenotypes. Bathing-water ENT criteria were exceeded more frequently than EC criteria, providing conflicting interpretations of water quality. Dominant sources of EC and ENT were bird feces (10(8)/d/bird), storm drains (10(7)/d), and river water (10(11)/d); beach sands, shallow groundwater and detritus were additional sources. Beach-water EC genotypes and ENT phenotypes formed clusters with those from all source types, reflecting diffuse inputs. Some ENT isolates had phenotypes similar to those of human pathogens and/or exhibited high-level resistance to human-use antibiotics. EC and ENT concentrations were influenced by collection time and wind direction. There was a 48-72-h lag between rainfall and elevated EC concentrations at three southern shoreline beaches, but no such lag at western and eastern shoreline beaches, reflecting the influence of beach orientation with respect to cyclic (3-5 d) summer weather patterns. In addition to local contamination sources and processes, conceptual or predictive models of Great Lakes beach water quality should consider regional weather patterns, lake hydrodynamics, and the influence of monitoring method variables (time of day, frequency).     

Detection of staphylococcal enterotoxin B in spiked food samples

Contamination of food with infectious agents, intentional or not, is a global concern with far-reaching economic and social impact. Staphylococcal enterotoxins are a major cause of food poisoning, but most methods for the identification of these agents in food require extensive pretreatment or concentration of the sample prior to analysis. The array biosensor was developed as a portable device for the simultaneous analysis of multiple complex samples for multiple targets with minimal sample preparation. In this study, we use an array biosensor to expand and improve on a staphylococcal enterotoxin B (SEB) assay with the ultimate intent of incorporating testing for SEB into a battery of sensitive and convenient assays for food safety validation. In addition to buffer studies, six different types of food samples, including beverages, homogenates of fruit and meat, and carcass washings, were spiked with SEB, incubated for at least 2 h to permit antigen sequestration, and assayed. For all samples, there were differences in fluorescence intensity, but 0.5 ng of SEB per ml could be detected in <20 min with little if any pretreatment and no sample preconcentration.     

Specificity is complex and time consuming: mutual exclusivity in tyrosine kinase-mediated signaling

Most fundamental cellular processes are transduced through tyrosine kinase (TK)-mediated pathways. For transduction without corruption, the protein-protein interactions involved have to be mutually exclusive. Many of these proteins bind via homologous domains whose binding characteristics suggest that their innate specificity is not sufficiently high to account for the integrity of signal transduction. Stimulation of TK-mediated signals is often accompanied by recruitment of a precise, multimolecular protein complex that is itself capable of imposing specificity. Furthermore, this complex provides protection against phosphatase activity, controlling the longevity of the active signaling complex, and thus influencing outcomes in subsequent downstream events.