244 research outputs found

    High Performance Lyot and PIAA Coronagraphy for Arbitrarily shaped Telescope Apertures

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    Two high performance coronagraphic approaches compatible with segmented and obstructed telescope pupils are described. Both concepts use entrance pupil amplitude apodization and a combined phase and amplitude focal plane mask to achieve full coronagraphic extinction of an on-axis point source. While the first concept, named Apodized Pupil Complex Mask Lyot Coronagraph (APCMLC), relies on a transmission mask to perform the pupil apodization, the second concept, named Phase-Induced Amplitude Apodization complex mask coronagraph (PIAACMC), uses beam remapping for lossless apodization. Both concepts theoretically offer complete coronagraphic extinction (infinite contrast) of a point source in monochromatic light, with high throughput and sub-lambda/D inner working angle, regardless of aperture shape. The PIAACMC offers nearly 100% throughput and approaches the fundamental coronagraph performance limit imposed by first principles. The steps toward designing the coronagraphs for arbitrary apertures are described for monochromatic light. Designs for the APCMLC and the higher performance PIAACMC are shown for several monolith and segmented apertures, such as the apertures of the Subaru Telescope, Giant Magellan Telescope (GMT), Thirty Meter Telescope (TMT), the European Extremely Large Telescope (E-ELT) and the Large Binocular Telescope (LBT). Performance in broadband light is also quantified, suggesting that the monochromatic designs are suitable for use in up to 20% wide spectral bands for ground-based telescopes.Comment: 19 pages, 12 figures, accepted for publication in Ap

    Impact of Mobile Broadband Data Access on Police Operations: An Exploratory Case Study of One Medium-Sized Municipal Police Department

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    As used in this study, “mobility” refers to “an inherent ability to move about,“ and “mobile computing” is a generic term that refers to the functional capabilities possible for end users as they complete tasks from various physical locations. “Broadband” refers to the relatively wide bandwidth characteristics of the wireless transmission medium and its corresponding ability to support multiple users and/or transport suitable quantities of data. “Mobile broadband” is used as a generic term to collectively refer to both terms in the context of the aggregate capabilities made possible through their use compared to other available mobile solutions and/or data. This study notes the lack of public-safety access to wireless broadband data, given resource limitations and a lack of independent evidence that would justify procurement of such technologies for police work. The current study’s deployment and assessment of this technology involved its use by the Brookline Police Department (BPD). Overall, the semi-structured interviews suggest that the wireless broadband technology was implemented with minimal difficulties and produced a number of perceived benefits for the BPD. The most direct benefit was the ease with which departmental technologies could be managed. Additional benefits were associated with increased access to timely information, increased information flow, and increased quality of reports. Structured interviews indicated that a few weeks of training sessions and ongoing informal bulletin and email disseminations were needed to overcome skepticism about the transition to wireless broadband. Most of the uniform personnel did not oppose the implementation nor did they perceive that the department was opposed to the transition. 39 tables, 3 figures, 93 references, and appended methodological details and supplementary data.National Institute of Justice (NIJ), US Department of Justice, Grant Number: 2010-IJ-CX-K02

    Synthesis, reactivity, and coordination chemistry relevant to the copolymerization of CO2 and epoxides by first row transition metal schiff base complexes

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    Excepting agricultural based products, which themselves require a great deal of energy to produce, our supply of natural resources such as minerals, metal ore, fresh water, coal, oil and natural gas are all limited in supply. The depletion of these substances is imminent and this knowledge weighs heavily on humankind. The utilization of CO2 for the production of polycarbonates is one attempt at exploiting a profoundly abundant and renewable resource. The importance of research in this and similar fields justifies the detailed study of the chemicals and procedures involved with this chemistry. This current work concentrates on the fundamental study of transition metal Schiff base complexes that have shown a great deal of promise in their ability to catalyze the copolymerization of CO2 and epoxide to form aliphatic polycarbonates. A new chromium(III) Schiff base complex has been synthesized and evaluated for its ability to catalyze the formation of polymer. The ligand employed bears an N2O2 coordination sphere identical to the widely utilized chromium(III) and cobalt(III) salen catalysts. This complex was shown to be active towards the copolymerization of CO2 and cyclohexene oxide. Although the activity was less than that seen with chromium(III) salen complex, the study demonstrates that new ligand systems are available beyond salen and deserve further attention. A class of manganese(III) Schiff base complexes was also synthesized and evaluated as catalysts. Although crystallographic data has shown that these complexes are structural analogs to chromium(III) salens, the difference in metal center leads to a nearly complete elimination of catalytic activity. Such a marked difference has been taken advantage of by using this very low activity to study the ring-opening of epoxide in the initial step of the copolymerization both mechanistically and kinetically. It has also been utilized in an evaluation of the coordination chemistry of the polymerization process. This has led to some valuable conclusions about the nature and role of the metal center that previously have not been studied. Manganese(III) salen complexes were also synthesized and evaluated in an effort to compare these important ligands to other Schiff bases and confirm the findings mentioned above

    A Case Study of Mississippi State Penitentiary’s Managed Access Technology

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    Managed access technology allows the completion of authorized calls placed from approved phone numbers (numbers that have been vetted and entered into a database) while blocking calls to or from devices or numbers that have not been pre-approved. This process is often referred to as “white-listing.“ The overall conclusion of this study is that managed access technology does capture a large quantity of cellular transmissions, but it is impossible to determine the rate with which attempted calls or texts successfully elude detection by the system. Even if a hypothetical rate of successful transmission detection was only 40 percent, however, that 40 percent would provide a substantial value-added effect to combating contraband cell phones. Thus, the decision about whether or not to use managed access technology is whether its possibly limited impact (blocking less than 100 percent of contraband calls) is sufficient to warrant the cost of installing and maintaining the managed access system. A series of interviews and teleconferences, in addition to the secondary analysis of managed-access system data, were used to produce a fundamental understanding of managed access technology operations, identify challenges and lessons learned, and develop a baseline of contraband cell phone activity. This report acknowledges that the study did not attempt to quantify potential vulnerabilities or manipulations of managed access systems. Although such an evaluation would be beneficial, it was beyond the scope of this study. 18 figures, 13 tables, 40 references, and appended examples of contraband cell phone activity, MSP managed access system infrastructure, and evaluation protocolsNational Institute of Justice (NIJ), U.S. Department of Justic

    Promotion of healthy nutrition in clinical practice: a cross-sectional survey of practices and barriers among physiotherapists in southeast Nigeria

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    AbstractBackgroundHealthy diet counselling is an important concept in health promotion. Physiotherapists are well positioned to initiate or support healthy nutrition in addition to physical activity counselling, in routine patient consultation.ObjectiveTo determine the practices about and barriers to diet counselling practices among physiotherapists in Southeast Nigeria.MethodsIn this cross-sectional survey, a total of 140 questionnaires were distributed among physiotherapists.ResultsOverall, 103 physiotherapists responded. Physiotherapists are confident and consider the incorporation of dietary counselling very important and of high priority in their daily clinical work. They, however, assessed and counselled on dietary status opportunistically in patients. Notwithstanding, physiotherapists believed that the diet counselling they give could be effective in helping patients change their unhealthy dieting practices. Patients were also amenable to physiotherapists advocating on diet issues as part of their consultation. Several barriers to incorporating diet counselling into physiotherapy practice were identified, including lack of access to a dietician/health promotion staff/counsellors, lack of proper patient education materials, lack of expertise in relation to dietary risk factors' assessment and management, and uncertainty about what dietary services to provide.ConclusionAlthough physiotherapists consider it important to incorporate diet counselling in their daily clinical practice, development and implementation of strategies to improve physiotherapists' diet counselling knowledge, competence, skills, and practice are warranted

    Size distribution of fine particles in stack emissions of a 600-MWe coal-fired power plant

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    International audienceMonitoring emissions of particles with a diameter smaller than 10 ”m (PM10) has become of growing interest. However, measuring such particles is rather difficult. It appears as a result necessary to develop and assess measurement methods for the monitoring of PM10 from stack and fugitive emissions. The aim of the GAEC program [Granulométrie des Aérosols dans les Emissions Canalisées: Aerosol size distribution from stack emissions] is double: to develop monitoring methods and improve knowledge on fine particulate stack emissions. Three institutes were involved in the program: Séchaud Environnement (formerly LECES), INERIS and CERTAM. This paper presents the mains results of the evaluation of a cascade impactor (Johnas), aerosol size distribution measurement techniques (ELPI Dekati, FPS, SMPS TSI) applied on size characterization of fine particulate matter in stack emissions of a 600-MWe coal-fired power plant

    Fulminant meningococcal supraglottitis: An emerging infectious syndrome?

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    We report a case of fulminant supraglottitis with dramatic external cervical swelling due to associated cellulitis. Blood cultures were positive for Neisseria meningitidis. The patient recovered completely after emergency fiberoptic intubation and appropriate antibiotic therapy. We summarize five other cases of meningococcal supraglottitis, all reported since 1995, and discuss possible pathophysiologic mechanisms
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