424 research outputs found

    Construction of Parseval wavelets from redundant filter systems

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    We consider wavelets in L^2(R^d) which have generalized multiresolutions. This means that the initial resolution subspace V_0 in L^2(R^d) is not singly generated. As a result, the representation of the integer lattice Z^d restricted to V_0 has a nontrivial multiplicity function. We show how the corresponding analysis and synthesis for these wavelets can be understood in terms of unitary-matrix-valued functions on a torus acting on a certain vector bundle. Specifically, we show how the wavelet functions on R^d can be constructed directly from the generalized wavelet filters.Comment: 34 pages, AMS-LaTeX ("amsproc" document class) v2 changes minor typos in Sections 1 and 4, v3 adds a number of references on GMRA theory and wavelet multiplicity analysis; v4 adds material on pages 2, 3, 5 and 10, and two more reference

    In-Space Propulsion Solar Electric Propulsion Program Overview of 2006

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    The primary source of electric propulsion development throughout NASA is implemented by the In-Space Propulsion Technology Project at the NASA MSFC under the management of the Science Mission Directorate. The Solar Electric Propulsion technology area's objective is to develop near and mid-term SEP technology to enhance or enable mission capture while minimizing risk and cost to the end user. Major activities include developing NASA s Evolutionary Xenon Thruster (NEXT), implementing a Standard Architecture, and developing a long life High Voltage Hall Accelerator (HiVHAC). Lower level investments include advanced feed system development, advanced cathode testing and xenon recovery testing. Progress on current investments and future plans are discussed

    Building Future Capacity of School Psychologists to Address the Demand for Inclusive Evidence-Based Consultation: Moving Beyond K-12 to Include School Readiness Frameworks

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    There is high demand for future school psychologists to address the need for continuous evidence-based consultation that moves beyond K-12 settings, and includes evidence-based consultation to promote school readiness for infants and toddlers with and at risk for developmental disabilities. While there exists a demand for school psychologists in infant and toddler settings, the primary focus of training programs is preparing graduates to work in school-based settings. Currently, a gap exists in graduate training opportunities in evidence-based consultation practices that support school readiness for infants and toddlers with and at risk for disabilities served through Part C services. While school psychologists typically are trained on evidence-based consultation mechanisms that have largely been utilized in K-12 contexts, they rarely receive consultation training with families of infants and toddlers. Therefore, expansion of training is necessary to support infants and toddlers through evidence-based consultation models. To underscore the importance of continuity in application of evidence-based consultation models, the current manuscript compares an evidence-based consultation model validated in K-12 settings and a consultation model for promoting infant and toddler developmental competencies. An illustration of the application of evidence-based consultation frameworks within multi-tiered systems of support and recommendations for graduate training, to better prepare school psychologists for work in birth-to-three settings, is provided

    Low-loss criterion and effective area considerations for photonic crystal fibers

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    We study the class of endlessly single-mode all-silica photonic crystal fibers with a triangular air-hole cladding. We consider the sensibility to longitudinal nonuniformities and the consequences and limitations for realizing low-loss large-mode area photonic crystal fibers. We also discuss the dominating scattering mechanism and experimentally we confirm that both macro and micro-bending can be the limiting factor.Comment: Accepted for Journal of Optics A - Pure and Applied Optic

    Harmonic analysis of iterated function systems with overlap

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    In this paper we extend previous work on IFSs without overlap. Our method involves systems of operators generalizing the more familiar Cuntz relations from operator algebra theory, and from subband filter operators in signal processing.Comment: 37 page

    WFC3 Calibration and Data Processing

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    Wide Field Camera 3 (WFC3), a panchromatic imager being developed for the Hubble Space Telescope (HST), is now fully integrated and over the past year has completed first rounds of extensive ground testing at Goddard Space Flight Center (GSFC), in both ambient and thermal-vacuum test environments. This report summarizes the results of those tests and describes the pipeline processing methods that will be used to calibrate WFC3 data. WFC3 is designed to ensure that the superb imaging performance of HST is maintained through the end of the mission and takes advantage of recent developments in detector technology to provide new and unique capabilities for HST. WFC3 contains ultraviolet/visible (UVIS) and near-infrared (IR) imaging channels, offering high sensitivity and wide field of view over the broadest wavelength range of any HST instrument. It is slated to replace the current Wide Field and Planetary Camera 2 during Servicing Mission 4. The WFC3 UVIS channel is based on elements from the Advanced Camera for Surveys (ACS)Wide Field Camera (WFC), with a 4096x4096 pixel Marconi CCD covering a 160x160 arcsecond field of view. The WFC3 UVIS channel is optimized for maximum sensitivity in the near-UV and contains a complement of 48 spectral filters and a grism. The WFC3 IR channel uses a 1024x1024 pixel HgCdTe Hawaii-1R detector array covering a 135x135 arcsecond field of view. The array sensitivity is optimized in the 0.8-1.7micron spectral range. The IR channel accomodates 15 filters and 2 grisms for slitless spectroscopy

    The ALHAMBRA photometric system

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    This paper presents the characterization of the optical range of the ALHAMBRA photometric system, a 20 contiguous, equal-width, medium-band CCD system with wavelength coverage from 3500A to 9700A. The photometric description of the system is done by presenting the full response curve as a product of the filters, CCD and atmospheric transmission curves, and using some first and second order moments of this response function. We also introduce the set of standard stars that defines the system, formed by 31 classic spectrophotometric standard stars which have been used in the calibration of other known photometric systems, and 288 stars, flux calibrated homogeneously, from the Next Generation Spectral Library (NGSL). Based on the NGSL, we determine the transformation equations between Sloan Digital Sky Survey (SDSS) ugriz photometry and the ALHAMBRA photometric system, in order to establish some relations between both systems. Finally we develop and discuss a strategy to calculate the photometric zero points of the different pointings in the ALHAMBRA project.Comment: Astronomical Journal on the 14th of January 201

    County-level associations between tobacco retailer density and smoking prevalence in the USA, 2012

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    We examine whether county-level tobacco retailer density and adult smoking prevalence are positively associated in the United States and determine whether associations differ in metropolitan vs. nonmetropolitan counties. We merged a list of likely tobacco retailers from the 2012 National Establishment Time-Series with smoking prevalence data from the Behavioral Risk Factor Surveillance System for 2828 US counties, as well as state tobacco policy information and county-level demographic data for the same year. We modeled adult smoking prevalence as a function of tobacco retailer density, accounting for clustering of counties within states. Average density in US counties was 1.25 retailers per 1000 people (range = 0.3–4.5). Smoking prevalence was 0.86 percentage points higher in the most retailer-dense counties, compared to the least. This association, however, was only significant for metropolitan counties. Metropolitan counties in the highest tobacco retailer density quartile had smoking prevalence levels that were 1.9 percentage points higher than metropolitan counties in the lowest density quartile. Research should examine whether policies limiting the quantity, type and location of tobacco retailers could reduce smoking prevalence

    Galaxies with unusually high abundances of molecular hydrogen

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    A sample of 66 galaxies from the catalog of Bettoni et al. (CISM) with anomalously high molecular-to-atomic hydrogen mass ratios (M_{mol}/M_{HI}>2) is considered. The sample galaxies do not differ systematically from other galaxies in the catalog with the same morphological types, in terms of their photometric parameters, rotational velocities, dust contents, or the total mass of gas in comparison with galaxies of similar linear sizes and disk angular momentum. This suggests that the overabundance of H2H_2 is due to transition of HI to H_2. Galaxies with bars and active nuclei are found more frequently among galaxies which have M_{mol} estimates in CISM. In a small fraction of galaxies, high M_{mol}/M_{HI} ratios are caused by the overestimation of M_{mol} due to a low conversion factor for the translation of CO-line intensities into the number of H_2 molecules along the line of sight. It is argued that the "molecularization" of the bulk of the gas mass could be due 1) to the concentration of gas in the inner regions of the galactic disks, resulting to a high gas pressure and 2) to relatively low star-formation rate per unit mass of molecular gas which indeed takes place in galaxies with high M_{mol}/M_{HI} ratios.Comment: 11 pages,7 figures, published in Astronomy Report
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