2,422 research outputs found

    Radiative transfer in highly scattering materials - numerical solution and evaluation of approximate analytic solutions

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    Numerical solutions for radiative transport in a class of anisotropically scattering materials are presented. Conditions for convergence and divergence of the iterative method are given and supported by computed results. The relation of two flux theories to the equation of radiative transfer for isotropic scattering is discussed. The adequacy of the two flux approach for the reflectance, radiative flux and radiative flux divergence of highly scattering media is evaluated with respect to solutions of the radiative transfer equation

    Comparison of Magnetic Flux Distribution between a Coronal Hole and a Quiet Region

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    Employing Big Bear Solar Observatory (BBSO) deep magnetograms and Hα{\alpha} images in a quiet region and a coronal hole, observed on September 14 and 16, 2004, respectively, we have explored the magnetic flux emergence, disappearance and distribution in the two regions. The following results are obtained: (1) The evolution of magnetic flux in the quiet region is much faster than that in the coronal hole, as the flux appeared in the form of ephemeral regions in the quiet region is 4.3 times as large as that in the coronal hole, and the flux disappeared in the form of flux cancellation, 2.9 times as fast as in the coronal hole. (2) More magnetic elements with opposite polarities in the quiet region are connected by arch filaments, estimating from magnetograms and Hα{\alpha} images. (3) We measured the magnetic flux of about 1000 magnetic elements in each observing region. The flux distribution of network and intranetwork (IN) elements is similar in both polarities in the quiet region. For network fields in the coronal hole, the number of negative elements is much more than that of positive elements. However for the IN fields, the number of positive elements is much more than that of negative elements. (4) In the coronal hole, the fraction of negative flux change obviously with different threshold flux density. 73% of the magnetic fields with flux density larger than 2 Gauss is negative polarity, and 95% of the magnetic fields is negative, if we only measure the fields with their flux density larger than 20 Gauss. Our results display that in a coronal hole, stronger fields is occupied by one predominant polarity; however the majority of weaker fields, occupied by the other polarity

    Testing the Special Relativity Theory with Neutrino interactions

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    A recent measurement of neutrino velocity by the OPERA experiment and prediction of energy loss of superluminal neutrino via the pair creation process ννe+e\nu\to \nu e^+e^- stimulated a search of isolated e+ee^+e^- pairs in detectors with good tracking capability traversed by a large flux of high energy neutrino like NOMAD. NOMAD has already searched for similar topologies. These results can be reinterpreted to provide stringent limits on special relativity violating parameters separately for each ν\nu species.Comment: 3 pages, 3 figures, 1 table Accepted by EPL (Europhysics Letters

    Dispelling the myths of online education: learning via the information superhighway

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    There continues to be a perception that online education is inferior to traditional education. In the U.S. online learning is more developed than in the U.K. This paper provides insights into a U.S. provision and takes a close look at what are perceived as weaknesses of on line learning and argues that these are not necessarily inherent weaknesses of this form of educational delivery. Then, results of two major studies, undertaken in the U.S. are provided comparing the effectiveness of online education to traditional education as perceived by current MBA students and past graduates. Results of these studies suggest that students of MBA modules and MBA graduates perceive the quality and effectiveness of online education to be similar to, if not higher than, the quality and effectiveness of traditional modules and programmes

    Hybrid stars with the color dielectric and the MIT bag models

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    We study the hadron-quark phase transition in the interior of neutron stars (NS). For the hadronic sector, we use a microscopic equation of state (EOS) involving nucleons and hyperons derived within the Brueckner-Bethe-Goldstone many-body theory, with realistic two-body and three-body forces. For the description of quark matter, we employ both the MIT bag model with a density dependent bag constant, and the color dielectric model. We calculate the structure of NS interiors with the EOS comprising both phases, and we find that the NS maximum masses are never larger than 1.7 solar masses, no matter the model chosen for describing the pure quark phase.Comment: 11 pages, 5 figures, submitted to Phys. Rev.

    Effect of Finish Line Design and Metal Alloy on The Marginal and Internal Gaps of Selective Laser Melting Printed Copings

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    Statement of problem Selective laser melting (SLM) technology has been introduced for printing metal dental restorations from Co-Cr base alloys or Au-Pt high noble alloys. However, information regarding the fit of restorations fabricated by using this technique is limited. Purpose The purpose of this in vitro study was to determine the effect of 3 different finish line designs on the marginal and internal gaps of metal copings made from a base (Co-Cr), high noble (Au-Pd-Ag), and noble alloy (Co-Pd) by using the SLM technology. Material and methods Three Ivorine right maxillary central incisors were prepared with a chamfer, deep chamfer, or shoulder finish line. The preparations were scanned by using a TRIOS scanner, and a total of 90 dies were printed using DPR 10 Resin (30×3 finish line designs). Ten SLM copings were fabricated for each margin design and metal alloy combination for a total of 90 copings (10×3 finish line designs×3 alloys). Copings were cemented onto dies using an autopolymerizing composite-resin luting material. All coping-die assemblies were sectioned buccolingually by using a low-speed diamond saw, and images were obtained by using an inverted bright field metallurgical microscope at ×100 magnification. Marginal and internal gaps were measured at 5 locations: buccal margin, midfacial, incisal, midlingual, and lingual margin. After gap measurements, representative specimens were embedded in autopolymerizing resin and prepared for metallographic examination. A 2-way multivariate analysis of variance (MANOVA) was conducted to determine the overall significance, followed by ANOVA for each dependent variable (α=.05). Results The results indicated that alloy type and finish line had a significant influence on marginal gap of copings (PPP=.337). No statistically significant interactions occurred. Base alloys were printed with almost no observable porosity, whereas noble and high noble alloys exhibited hot tears and porosity. Conclusions The finish line type did not influence the internal gap between copings and dies, whereas the alloy type influenced the marginal gap between copings and dies. SLM-fabricated Co-Cr copings on teeth prepared with a deep chamfer finish line demonstrated the lowest marginal gap

    Dyslipidemia and Adherence to the Mediterranean Diet in Croatian HIV-Infected Patients during the First Year of Highly Active Antiretroviral Therapy

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    We investigated the association of adherence to the Mediterranean diet and other risk factors for dyslipidemia in HIV-infected Croatian patients during the first year of highly active antiretroviral therapy (HAART). Adherence to the Mediterranean diet was determined by a 150-item questionnaire; a 0 to 9-point diet scale was created that stratified respondents as having low adherence (<4 points) and moderate to high adherence (ł 4 points). We interviewed 117 participants between May 2004 and June 2005 and abstracted their serum lipid measurements taken during the first year of HAART. The values of total cholesterol, HDL-cholesterol, LDL-cholesterol and triglycerides increased most prominently in the first 3 to 6 months after initiation of HAART (average increase at 3 months: 25% for total cholesterol, 22% for LDL-cholesterol, 18% for HDL-cholesterol and 43% for triglycerides). A Mediterranean diet and physical activity had no effect on serum lipids. The mean total cholesterol was higher in participants receiving a combination of a non-nucleoside reverse transcriptase inhibitor and a protease inhibitor compared to participants receiving a combination of nucleoside analogs with a non-nucleoside analog or a combination of nucleoside analogs and a protease inhibitor. Among individual drug treatments, indinavir/ritonavir had the most unfavorable lipid profile. We conclude that adherence to a Mediterranean diet does not influence serum lipid profiles during the first year of HAART
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