13,644 research outputs found

    Annona muricata (graviola): toxic or therapeutic

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    This paper examines annona muricata (graviola): toxic or therapeutic

    Symmetries of quasiplatonic Riemann surfaces

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    We state and prove a corrected version of a theorem of Singerman, which relates the existence of symmetries (anticonformal involutions) of a quasiplatonic Riemann surface S\mathcal S (one uniformised by a normal subgroup NN of finite index in a cocompact triangle group Δ\Delta) to the properties of the group G=Δ/NG=\Delta/N. We give examples to illustrate the revised necessary and sufficient conditions for the existence of symmetries, and we relate them to properties of the associated dessins d'enfants, or hypermaps

    Evaluation of a Multizone Impedance Eduction Method

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    A computational study is used to evaluate the PyCHE impedance eduction method developed at the NASA Langley Research Center. This method combines an aeroacoustic duct propagation code based on numerical solution to the convected Helmholtz equation with a global optimizer that uses the Differential Evolution algorithm. The efficacy of this method is evaluated with acoustic pressure data simulated to represent that measured with one-zone, two-zone, and three-zone liners mounted in the NASA Langley Grazing Flow Impedance Tube. The PyCHE method has a normalized impedance error of approximately 0.2 for (uniform) one-zone liners with a length of at least 5, and produces quite reasonable results for liners as short as 2. Whereas the impedance of the liner has an effect on eduction accuracy, the amount of attenuation is shown to be the dominant parameter. Similar results are observed for two-zone liners, for which the impedance of each zone is unique. The two-zone results also indicate it is more difficult to accurately educe resistance than reactance, and a zone length of at least 6 (slightly longer than for uniform liners) is needed to limit the normalized error to 0.2. The PyCHE method is also demonstrated to successfully educe the impedances for each zone of a three-zone liner. These results are sufficiently encouraging to warrant the continued usage of the PyCHE impedance eduction method for single and multizone liners

    Second Data Release of the 6dF Galaxy Survey

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    The 6dF Galaxy Survey is measuring around 150000 redshifts and 15000 peculiar velocities from galaxies over the southern sky at |b|>10 degrees. When complete, it will be the largest survey of its kind by more than an order of magnitude. Here we describe the characteristics of the Second Incremental Data Release (DR2) and provide an update of the survey. This follows earlier data made public in December 2002 and March 2004. A total of 83014 sources now have their spectra, redshifts, near-infrared and optical photometry available online and searchable through an SQL database at http://www-wfau.roe.ac.uk/6dFGS/.Comment: 11 pages, 7 figures. Submitted to PASA. High resolution versions of the figures can be obtained from http://www.aao.gov.au/local/www/6df/Publication

    Status of HPV vaccine introduction and barriers to country uptake.

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    During the last 12 years, over 80 countries have introduced national HPV vaccination programs. The majority of these countries are high or upper-middle income countries. The barriers to HPV vaccine introduction remain greatest in those countries with the highest burden of cervical cancer and the most need for vaccination. Innovation and global leadership is required to increase and sustain introductions in low income and lower-middle income countries

    Optimization of Acoustic Pressure Measurements for Impedance Eduction

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    As noise constraints become increasingly stringent, there is continued emphasis on the development of improved acoustic liner concepts to reduce the amount of fan noise radiated to communities surrounding airports. As a result, multiple analytical prediction tools and experimental rigs have been developed by industry and academia to support liner evaluation. NASA Langley has also placed considerable effort in this area over the last three decades. More recently, a finite element code (Q3D) based on a quasi-3D implementation of the convected Helmholtz equation has been combined with measured data acquired in the Langley Grazing Incidence Tube (GIT) to reduce liner impedance in the presence of grazing flow. A new Curved Duct Test Rig (CDTR) has also been developed to allow evaluation of liners in the presence of grazing flow and controlled, higher-order modes, with straight and curved waveguides. Upgraded versions of each of these two test rigs are expected to begin operation by early 2008. The Grazing Flow Impedance Tube (GFIT) will replace the GIT, and additional capabilities will be incorporated into the CDTR. The current investigation uses the Q3D finite element code to evaluate some of the key capabilities of these two test rigs. First, the Q3D code is used to evaluate the microphone distribution designed for the GFIT. Liners ranging in length from 51 to 610 mm are investigated to determine whether acceptable impedance eduction can be achieved with microphones placed on the wall opposite the liner. This analysis indicates the best results are achieved for liner lengths of at least 203 mm. Next, the effects of moving this GFIT microphone array to the wall adjacent to the liner are evaluated, and acceptable results are achieved if the microphones are placed off the centerline. Finally, the code is used to investigate potential microphone placements in the CDTR rigid wall adjacent to the wall containing an acoustic liner, to determine if sufficient fidelity can be achieved with 32 microphones available for this purpose. Initial results indicate 32 microphones can provide acceptable measurements to support impedance eduction with this test rig

    The 6dF Galaxy Survey: Dependence of halo occupation on stellar mass

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    In this paper we study the stellar-mass dependence of galaxy clustering in the 6dF Galaxy Survey. The near-infrared selection of 6dFGS allows more reliable stellar mass estimates compared to optical bands used in other galaxy surveys. Using the Halo Occupation Distribution (HOD) model, we investigate the trend of dark matter halo mass and satellite fraction with stellar mass by measuring the projected correlation function, wp(rp)w_p(r_p). We find that the typical halo mass (M1M_1) as well as the satellite power law index (α\alpha) increase with stellar mass. This indicates, (1) that galaxies with higher stellar mass sit in more massive dark matter halos and (2) that these more massive dark matter halos accumulate satellites faster with growing mass compared to halos occupied by low stellar mass galaxies. Furthermore we find a relation between M1M_1 and the minimum dark matter halo mass (MminM_{\rm min}) of M1≈22 MminM_1 \approx 22\,M_{\rm min}, in agreement with similar findings for SDSS galaxies. The satellite fraction of 6dFGS galaxies declines with increasing stellar mass from 21% at Mstellar=2.6×1010h−2 M⊙M_{\rm stellar} = 2.6\times10^{10}h^{-2}\,M_{\odot} to 12% at Mstellar=5.4×1010h−2 M⊙M_{\rm stellar} = 5.4\times10^{10}h^{-2}\,M_{\odot} indicating that high stellar mass galaxies are more likely to be central galaxies. We compare our results to two different semi-analytic models derived from the Millennium Simulation, finding some disagreement. Our results can be used for placing new constraints on semi-analytic models in the future, particularly the behaviour of luminous red satellites. Finally we compare our results to studies of halo occupation using galaxy-galaxy weak lensing. We find good overall agreement, representing a valuable crosscheck for these two different tools of studying the matter distribution in the Universe.Comment: 17 pages, 11 figures. arXiv admin note: text overlap with arXiv:1104.2447 by other author

    Improving community readiness for change through coalition capacity building: Evidence from a multisite intervention

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    Often, community coalitions are facilitators of community-level changes when addressing underage drinking. Although studies have shown that enhancing coalition capacity is related to improved internal functioning, the relationship between enhanced capacity and community readiness for change is not well established. The present study used a pretest–posttest design to examine whether enhancing coalition capacity through training and technical assistance was associated with improved community readiness and coalition-facilitated community-level changes. Seven Kansas communities engaged in an intensive capacity building intervention through implementation of the Strategic Prevention Framework. The results indicated strong correlations between increased coalition capacity, changes in community readiness stages, and the number of community changes facilitated. The results suggest that strengthening coalition capacity through training and technical assistance may improve community readiness for change and enable the implementation of community-wide program and environmental changes

    An Investigation of Two Acoustic Propagation Codes for Three-Dimensional Geometries

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    The ability to predict fan noise within complex three-dimensional aircraft engine nacelle geometries is a valuable tool in studying low-noise designs. Recent years have seen the development of aeroacoustic propagation codes using various levels of approximation to obtain such a capability. In light of this, it is beneficial to pursue a design paradigm that incorporates the strengths of the various tools. The development of a quasi-3D methodology (Q3D-FEM) at NASA Langley has brought these ideas to mind in relation to the framework of the CDUCT-LaRC acoustic propagation and radiation tool. As more extensive three dimensional codes become available, it would seem appropriate to incorporate these tools into a framework similar to CDUCT-LaRC and use them in a complementary manner. This work focuses on such an approach in beginning the steps toward a systematic assessment of the errors, and hence the trade-offs, involved in the use of these codes. To illustrate this point, CDUCT-LaRC was used to study benchmark hardwall duct problems to quantify errors caused by wave propagation in directions far removed from that defined by the parabolic approximation. Configurations incorporating acoustic treatment were also studied with CDUCT-LaRC and Q3D-FEM. The cases presented show that acoustic treatment diminishes the effects of CDUCT-LaRC phase error as the solutions are attenuated. The results of the Q3D-FEM were very promising and matched the analytic solution very well. Overall, these tests were meant to serve as a step toward the systematic study of errors inherent in the propagation module of CDUCT-LaRC, as well as an initial test of the higher fidelity Q3D-FEM code
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