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Sample records for high-angle annular dark

  1. Influence of spatial and temporal coherences on atomic resolution high angle annular dark field imaging.

    Science.gov (United States)

    Beyer, Andreas; Belz, Jürgen; Knaub, Nikolai; Jandieri, Kakhaber; Volz, Kerstin

    2016-10-01

    Aberration-corrected (scanning) transmission electron microscopy ((S)TEM) has become a widely used technique when information on the chemical composition is sought on an atomic scale. To extract the desired information, complementary simulations of the scattering process are inevitable. Often the partial spatial and temporal coherences are neglected in the simulations, although they can have a huge influence on the high resolution images. With the example of binary gallium phosphide (GaP) we elucidate the influence of the source size and shape as well as the chromatic aberration on the high angle annular dark field (HAADF) intensity. We achieve a very good quantitative agreement between the frozen phonon simulation and experiment for different sample thicknesses when a Lorentzian source distribution is assumed and the effect of the chromatic aberration is considered. Additionally the influence of amorphous layers introduced by the preparation of the TEM samples is discussed. Taking into account these parameters, the intensity in the whole unit cell of GaP, i.e. at the positions of the different atomic columns and in the region between them, is described correctly. With the knowledge of the decisive parameters, the determination of the chemical composition of more complex, multinary materials becomes feasible.

  2. Modelling of AlAs/GaAs interfacial structures using high-angle annular dark field (HAADF) image simulations.

    Science.gov (United States)

    Robb, Paul D; Finnie, Michael; Craven, Alan J

    2012-07-01

    High angle annular dark field (HAADF) image simulations were performed on a series of AlAs/GaAs interfacial models using the frozen-phonon multislice method. Three general types of models were considered-perfect, vicinal/sawtooth and diffusion. These were chosen to demonstrate how HAADF image measurements are influenced by different interfacial structures in the technologically important III-V semiconductor system. For each model, interfacial sharpness was calculated as a function of depth and compared to aberration-corrected HAADF experiments of two types of AlAs/GaAs interfaces. The results show that the sharpness measured from HAADF imaging changes in a complicated manner with thickness for complex interfacial structures. For vicinal structures, it was revealed that the type of material that the probe projects through first of all has a significant effect on the measured sharpness. An increase in the vicinal angle was also shown to generate a wider interface in the random step model. The Moison diffusion model produced an increase in the interface width with depth which closely matched the experimental results of the AlAs-on-GaAs interface. In contrast, the interface width decreased as a function of depth in the linear diffusion model. Only in the case of the perfect model was it possible to ascertain the underlying structure directly from HAADF image analysis.

  3. Extraction of structural and chemical information from high angle annular dark-field image by an improved peaks finding method.

    Science.gov (United States)

    Yin, Wenhao; Huang, Rong; Qi, Ruijuan; Duan, Chungang

    2016-09-01

    With the development of spherical aberration (Cs) corrected scanning transmission electron microscopy (STEM), high angle annular dark filed (HAADF) imaging technique has been widely applied in the microstructure characterization of various advanced materials with atomic resolution. However, current qualitative interpretation of the HAADF image is not enough to extract all the useful information. Here a modified peaks finding method was proposed to quantify the HAADF-STEM image to extract structural and chemical information. Firstly, an automatic segmentation technique including numerical filters and watershed algorithm was used to define the sub-areas for each atomic column. Then a 2D Gaussian fitting was carried out to determine the atomic column positions precisely, which provides the geometric information at the unit-cell scale. Furthermore, a self-adaptive integration based on the column position and the covariance of statistical Gaussian distribution were performed. The integrated intensities show very high sensitivity on the mean atomic number with improved signal-to-noise (S/N) ratio. Consequently, the polarization map and strain distributions were rebuilt from a HAADF-STEM image of the rhombohedral and tetragonal BiFeO3 interface and a MnO2 monolayer in LaAlO3 /SrMnO3 /SrTiO3 heterostructure was discerned from its neighbor TiO2 layers. Microsc. Res. Tech. 79:820-826, 2016. © 2016 Wiley Periodicals, Inc.

  4. Boron concentration profiling by high angle annular dark field-scanning transmission electron microscopy in homoepitaxial δ-doped diamond layers

    Energy Technology Data Exchange (ETDEWEB)

    Araújo, D.; Alegre, M. P.; Piñero, J. C. [Dpto Ciencia de los Materiales, Facultad de Ciencias, Universidad de Cádiz, 11510 Puerto Real (Cádiz) (Spain); Fiori, A.; Bustarret, E. [Institut Néel, CNRS-Université Joseph Fourier, 25 av. des Martyrs, 38042 Grenoble (France); Jomard, F. [Groupe d' Etude de la Matière Condensée (GEMaC), UMR 8635 du CNRS, UVSQ, 45 av. des Etats-Unis, 78035 Versailles Cedex (France)

    2013-07-22

    To develop further diamond related devices, the concentration and spatial location of dopants should be controlled down to the nanometer scale. Scanning transmission electron microscopy using the high angle annular dark field mode is shown to be sensitive to boron doping in diamond epilayers. An analytical procedure is described, whereby local boron concentrations above 10{sup 20} cm{sup −3} were quantitatively derived down to nanometer resolution from the signal dependence on thickness and boron content. Experimental boron local doping profiles measured on diamond p{sup −}/p{sup ++}/p{sup −} multilayers are compared to macroscopic profiles obtained by secondary ion mass spectrometry, avoiding reported artefacts.

  5. Estimation of mass thickness response of embedded aggregated silica nanospheres from high angle annular dark-field scanning transmission electron micrographs.

    Science.gov (United States)

    Nordin, M; Abrahamsson, C; Blomqvist, C H; Häbel, H; Röding, M; Olsson, E; Nydén, M; Rudemo, M

    2014-02-01

    In this study, we investigate the functional behaviour of the intensity in high-angle annular dark field scanning transmission electron micrograph images. The model material is a silica particle (20 nm) gel at 5 wt%. By assuming that the intensity response is monotonically increasing with increasing mass thickness of silica, an estimate of the functional form is calculated using a maximum likelihood approach. We conclude that a linear functional form of the intensity provides a fair estimate but that a power function is significantly better for estimating the amount of silica in the z-direction. The work adds to the development of quantifying material properties from electron micrographs, especially in the field of tomography methods and three-dimensional quantitative structural characterization from a scanning transmission electron micrograph. It also provides means for direct three-dimensional quantitative structural characterization from a scanning transmission electron micrograph.

  6. Quantitative composition determination at the atomic level using model-based high-angle annular dark field scanning transmission electron microscopy.

    Science.gov (United States)

    Martinez, G T; Rosenauer, A; De Backer, A; Verbeeck, J; Van Aert, S

    2014-02-01

    High angle annular dark field scanning transmission electron microscopy (HAADF STEM) images provide sample information which is sensitive to the chemical composition. The image intensities indeed scale with the mean atomic number Z. To some extent, chemically different atomic column types can therefore be visually distinguished. However, in order to quantify the atomic column composition with high accuracy and precision, model-based methods are necessary. Therefore, an empirical incoherent parametric imaging model can be used of which the unknown parameters are determined using statistical parameter estimation theory (Van Aert et al., 2009, [1]). In this paper, it will be shown how this method can be combined with frozen lattice multislice simulations in order to evolve from a relative toward an absolute quantification of the composition of single atomic columns with mixed atom types. Furthermore, the validity of the model assumptions are explored and discussed.

  7. Three-dimensional shapes and distribution of FePd nanoparticles observed by electron tomography using high-angle annular dark-field scanning transmission electron microscopy

    Science.gov (United States)

    Sato, Kazuhisa; Aoyagi, Kenta; Konno, Toyohiko J.

    2010-01-01

    We have studied three-dimensional shapes and distribution of FePd nanoparticles, prepared by electron beam deposition and postdeposition annealing, by means of single-axis tilt tomography using atomic number contrasts obtained by high-angle annular dark-field scanning transmission electron microscopy. Particle size, shape, and locations were reconstructed by weighted backprojection (WBP), as well as by simultaneous iterative reconstruction technique (SIRT). We have also estimated the particle size by simple extrapolation of tilt-series original data sets, which proved to be quite powerful. The results of the two algorithms for reconstruction have been compared quantitatively with those obtained by the extrapolation method and those independently reported by electron holography. It was found that the reconstructed intensity map by WBP contains a small amount of dotlike artifacts, which do not exist in the results by SIRT, and that the particle surface obtained by WBP is rougher than that by SIRT. We demonstrate, on the other hand, that WBP yields a better estimation of the particle size in the z direction than SIRT does, most likely due to the presence of a "missing wedge" in the original data set.

  8. Intergrowth structure of α-phase in β-type TmAlB{sub 4} compound studied by high-angle annular detector dark-field scanning transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yubuta, Kunio, E-mail: yubuta@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Mori, Takao [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Tsukuba 305-0044 (Japan); Leithe-Jasper, Andreas; Borrmann, Horst; Grin, Yuri [Max-Plank-Institut für Chemische Physik fester Stöffe, 01187 Dresden (Germany); Okada, Shigeru [Department of Science and Engineering, Kokushikan University, Tokyo 154-8515 (Japan); Shishido, Toetsu [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2014-11-15

    Nanostructure of a ThMoB{sub 4}-type (β-type) TmAlB{sub 4} compound, in which YCrB{sub 4}-type (α-type) domains are locally intergrown, is studied by high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM). Z-contrast images by HAADF-STEM directly represent the arrangements of Tm atoms located at centers of heptagonal atomic columns of B atoms as bright dots, and give us detailed information of intergrowth of type domains in the matrix of the β-type phase, which coherently occurs. Structural and bonding analyses for β-TmAlB{sub 4} point out the closeness in atomic interactions and energy of the α- and β-type structures which support the easy formation of such nanostructure intergrowths. From combination between HAADF-STEM and electronic structure calculation, a detailed local crystal structure with intrinsic building defects is effectively revealed. - Graphical abstract: Nanostructure of a ThMoB{sub 4}-type (β-type) TmAlB{sub 4} compound, in which YCrB{sub 4}-type (α-type) domains are locally intergrown, is studied by high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM). Z-contrast images by HAADF-STEM directly represent arrangements of Tm atoms located at centers of heptagonal atomic columns of B atoms as bright dots, and give us detailed information of the characteristic intergrowth structure of type domains in the matrix of the β-type phase. - Highlights: • HAADF-STEM images directly represent arrangements of Tm atoms as bright dots. • The α-type planar domains coherently intergrown in the β-type matrix. • Bright strips appear at overlapped regions of Tm hexagons along interfaces between α- and β-type domains.

  9. Quantitative annular dark field electron microscopy using single electron signals.

    Science.gov (United States)

    Ishikawa, Ryo; Lupini, Andrew R; Findlay, Scott D; Pennycook, Stephen J

    2014-02-01

    One of the difficulties in analyzing atomic resolution electron microscope images is that the sample thickness is usually unknown or has to be fitted from parameters that are not precisely known. An accurate measure of thickness, ideally on a column-by-column basis, parameter free, and with single atom accuracy, would be of great value for many applications, such as matching to simulations. Here we propose such a quantification method for annular dark field scanning transmission electron microscopy by using the single electron intensity level of the detector. This method has the advantage that we can routinely quantify annular dark field images operating at both low and high beam currents, and under high dynamic range conditions, which is useful for the quantification of ultra-thin or light-element materials. To facilitate atom counting at the atomic scale we use the mean intensity in an annular dark field image averaged over a primitive cell, with no free parameters to be fitted. To illustrate the potential of our method, we demonstrate counting the number of Al (or N) atoms in a wurtzite-type aluminum nitride single crystal at each primitive cell over the range of 3-99 atoms.

  10. Experimental quantification of annular dark-field images in scanning transmission electron microscopy.

    Science.gov (United States)

    Lebeau, James M; Stemmer, Susanne

    2008-11-01

    This paper reports on a method to obtain atomic resolution Z-contrast (high-angle annular dark-field) images with intensities normalized to the incident beam. The procedure bypasses the built-in signal processing hardware of the microscope to obtain the large dynamic range necessary for consecutive measurements of the incident beam and the intensities in the Z-contrast image. The method is also used to characterize the response of the annular dark-field detector output, including conditions that avoid saturation and result in a linear relationship between the electron flux reaching the detector and its output. We also characterize the uniformity of the detector response across its entire area and determine its size and shape, which are needed as input for image simulations. We present normalized intensity images of a SrTiO(3) single crystal as a function of thickness. Averaged, normalized atom column intensities and the background intensity are extracted from these images. The results from the approach developed here can be used for direct, quantitative comparisons with image simulations without any need for scaling.

  11. Direct imaging of light elements by annular dark-field aberration-corrected scanning transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lotnyk, Andriy, E-mail: andriy.lotnyk@iom-leipzig.de; Poppitz, David; Gerlach, Jürgen W.; Rauschenbach, Bernd [Leibniz Institute of Surface Modification, Permoserstr. 15, D-04318 Leipzig (Germany)

    2014-02-17

    In this report, we show that an annular dark-field detector in an aberration-corrected scanning transmission electron microscope allows the direct observation of light element columns in crystalline lattices. At specific imaging conditions, an enhancement of the intensities of light element columns in the presence of heavy element columns is observed. Experimental results are presented for imaging the nitrogen and carbon atomic columns at the GaN-SiC interface and within the GaN and SiC compounds. The crystal polarity of GaN at the interface is identified. The obtained findings are discussed and are well supported by image simulations.

  12. Quantitative annular dark-field imaging of single-layer graphene-II: atomic-resolution image contrast.

    Science.gov (United States)

    Yamashita, Shunsuke; Koshiya, Shogo; Nagai, Takuro; Kikkawa, Jun; Ishizuka, Kazuo; Kimoto, Koji

    2015-12-01

    We have investigated how accurately atomic-resolution annular dark-field (ADF) images match between experiments and simulations to conduct more reliable crystal structure analyses. Quantitative ADF imaging, in which the ADF intensity at each pixel represents the fraction of the incident probe current, allows us to perform direct comparisons with simulations without the use of fitting parameters. Although the conventional comparison suffers from experimental uncertainties such as an amorphous surface layer and specimen thickness, in this study we eliminated such uncertainties by using a single-layer graphene as a specimen. Furthermore, to reduce image distortion and shot noises in experimental images, multiple acquisitions with drift correction were performed, and the atomic ADF contrast was quantitatively acquired. To reproduce the experimental ADF contrast, we used three distribution functions as the effective source distribution in simulations. The optimum distribution function and its full-width at half-maximum were evaluated by measuring the residuals between the experimental and simulated images. It was found that the experimental images could be explained well by a linear combination of a Gaussian function and a Lorentzian function with a longer tail than the Gaussian function.

  13. Dose limited reliability of quantitative annular dark field scanning transmission electron microscopy for nano-particle atom-counting

    Energy Technology Data Exchange (ETDEWEB)

    De Backer, A.; Martinez, G.T. [Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); MacArthur, K.E.; Jones, L. [Department of Materials, University of Oxford, 16 Parks Road, Oxford OX1 3PH (United Kingdom); Béché, A. [Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Nellist, P.D. [Department of Materials, University of Oxford, 16 Parks Road, Oxford OX1 3PH (United Kingdom); Van Aert, S., E-mail: sandra.vanaert@uantwerpen.be [Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium)

    2015-04-15

    Quantitative annular dark field scanning transmission electron microscopy (ADF STEM) has become a powerful technique to characterise nano-particles on an atomic scale. Because of their limited size and beam sensitivity, the atomic structure of such particles may become extremely challenging to determine. Therefore keeping the incoming electron dose to a minimum is important. However, this may reduce the reliability of quantitative ADF STEM which will here be demonstrated for nano-particle atom-counting. Based on experimental ADF STEM images of a real industrial catalyst, we discuss the limits for counting the number of atoms in a projected atomic column with single atom sensitivity. We diagnose these limits by combining a thorough statistical method and detailed image simulations. - Highlights: • Limited size and beam sensitivity of nano-particles challenge their quantification. • Keeping the electron dose to a minimum is therefore important. • Reliability of quantitative ADF STEM for atom-counting is demonstrated. • Limits for single atom sensitivity are discussed. • Limits are diagnosed by combining simulations and a statistical method.

  14. Imaging properties of bright-field and annular-dark-field scanning confocal electron microscopy: II. Point spread function analysis

    Energy Technology Data Exchange (ETDEWEB)

    Mitsuishi, K., E-mail: Mitsuishi.Kazutaka@nims.go.jp [Surface Physics and Structure Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Hashimoto, A.; Takeguchi, M. [Surface Physics and Structure Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Shimojo, M. [Department of Materials Science and Engineering, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548 (Japan); Ishizuka, K. [Surface Physics and Structure Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); HREM Research Inc., 14-48 Matsukazedai, Higashimatsuyama, Saitama 355-0055 (Japan)

    2012-01-15

    The imaging properties of bright field and annular dark field scanning confocal electron microscopy (BF-SCEM and ADF-SCEM) are discussed based on their point spread functions (PSFs) in comparison with multislice simulations. Although the PSFs of BF-SCEM and ADF-SCEM show similar hourglass shapes, their numerical distributions are quite different: BF-SCEM PSF is always positive and shows a center of symmetry whereas the ADF-SCEM PSF is complex and has Hermitian symmetry. These PSF properties explain the large elongation effect in BF-SCEM for laterally extended object and almost no-elongation in ADF-SCEM, illustrating the importance of the numerical analysis of PSFs. The Hermitian symmetry of the ADF-SCEM PSF results in an interesting 'edge enhancement effect' at the interface. Simulation using the PSF and the multislice method verified this effect at GaAs surfaces and InAs interfaces embedded in GaAs. This unique feature of ADF-SCEM can potentially be useful for depth sectioning. It is also pointed out that a PSF imaging model cannot be applicable for BF-SCEM of a phase object, when the system is symmetric and aberration free. -- Highlights: Black-Right-Pointing-Pointer The properties of scanning confocal electron microscopy (SCEM) are discussed by PSF. Black-Right-Pointing-Pointer The PSFs of BF- and ADF-SCEM show similar shapes, but values are quite different. Black-Right-Pointing-Pointer This explains the large elongation effect in BF and no-elongation in ADF. Black-Right-Pointing-Pointer The ADF-SCEM PSF shows 'edge enhancement effect' that is useful for depth sectioning.

  15. What atomic resolution annular dark field imaging can tell us about gold nanoparticles on TiO{sub 2} (1 1 0)

    Energy Technology Data Exchange (ETDEWEB)

    Findlay, S.D., E-mail: scott@sigma.t.u-tokyo.ac.jp [Institute of Engineering Innovation, The University of Tokyo, Tokyo 116-0013 (Japan); Shibata, N. [Institute of Engineering Innovation, The University of Tokyo, Tokyo 116-0013 (Japan); PRESTO, Japan Science and Technology Agency, Saitama 332-0012 (Japan); Ikuhara, Y. [Institute of Engineering Innovation, The University of Tokyo, Tokyo 116-0013 (Japan); Nanostructures Research Laboratory, Japan Fine Ceramic Center, Nagoya 456-8587 (Japan); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2009-11-15

    Annular dark field scanning transmission electron microscopy imaging was recently applied to a catalyst consisting of gold nanoparticles on TiO{sub 2} (1 1 0), showing directly that the gold atoms in small nanoparticles preferentially attach to specific sites on the TiO{sub 2} (1 1 0) surface. Here, through simulation, a parameter exploration of the imaging conditions which maximise the visibility of such nanoparticles is presented. Aberration correction, finite source size and profile imaging are all considered while trying to extracting the maximum amount of information from a given sample. Comment is made on the role of the thermal vibration of the atoms in the nanoparticle, the magnitude of which is generally not known a priori but which affects the visibility of the nanoparticles in this imaging mode.

  16. Direct oxygen imaging within a ceramic interface, with some observations upon the dark contrast at the grain boundary

    Energy Technology Data Exchange (ETDEWEB)

    Findlay, S.D., E-mail: scott@sigma.t.u-tokyo.ac.jp [Institute of Engineering Innovation, The University of Tokyo, Tokyo 116-0013 (Japan); Azuma, S. [Institute of Engineering Innovation, The University of Tokyo, Tokyo 116-0013 (Japan); Shibata, N. [Institute of Engineering Innovation, The University of Tokyo, Tokyo 116-0013 (Japan); PRESTO, Japan Science and Technology Agency, Saitama 332-0012 (Japan); Okunishi, E. [JEOL Ltd., Tokyo 196-8558 (Japan); Ikuhara, Y. [Institute of Engineering Innovation, The University of Tokyo, Tokyo 116-0013 (Japan); Nanostructures Research Laboratory, Japan Fine Ceramic Center, Nagoya 456-8587 (Japan); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2011-03-15

    Annular bright field scanning transmission electron microscopy, which has recently been established to produce directly interpretable images with both light and heavier atomic columns visible simultaneously, is shown to allow directly interpretable imaging of the oxygen columns within the {Sigma}13[12-bar 10](101-bar 4) pyramidal twin grain boundary in {alpha}-Al{sub 2}O{sub 3}. By using information in the high-angle annular dark field image and annular bright field images simultaneously, we estimate the specimen thickness and finite source size, and use them to explore in simulation the issue of dark contrast in the vicinity of the grain boundary in the annular dark field image. -- Research highlights: {yields} Simultaneous HAADF and ABF images of a pristine {Sigma}13 grain boundary in {alpha}-Al{sub 2}O{sub 3}. {yields} Oxygen columns are clearly visible in the grain boundary in the ABF image. {yields} ABF is more robust than HAADF for imaging defect structures. {yields} Thickness and source size are estimated from quantitative analysis of the contrast. {yields} Dark contrast at the grain boundary in HAADF is likely due to strain and vacancies.

  17. Subcutaneous granuloma annulare

    Directory of Open Access Journals (Sweden)

    Dhar Sandipan

    1994-01-01

    Full Text Available Two cases of subcutaneos granuloma annulare are reported. Clinical presentation was in the form of hard subcutaneous nodules; histopathology confirmed the clinical diagnosis. The cases were unique because of onset in adult hood, occurrence over unusual sites and absence of classical lesions of granuloma annulare elsewhere.

  18. Subcutaneous granuloma annulare

    Directory of Open Access Journals (Sweden)

    Dhar Sandipan

    1993-01-01

    Full Text Available Two cases of subcutaneous granuloma annulare are reported. Clinical presentation was in the form of hard subcutaneous nodules, histopathology confirmed the clinical diagnosis. The cases were unique because of onset in adult age, occurrence over unusual sites and absence of classical lesions of granuloma annulare elsewhere.

  19. Eosinophilic annular erythema.

    Science.gov (United States)

    Sempau, Leticia; Larralde, Margarita; Luna, Paula Carolina; Casas, Jose; Staiger, Hernan

    2012-03-15

    Eosinophilic annular erythema is a rare benign recurrent disease, originally described in children, characterized by the recurrent appearance of persistent non-pruritic, urticarial annular lesions. Histologically a perivascular infiltrate composed of lymphocytes and abundant eosinophils in the dermis is exhibited. We report the case of a 15-year-old boy who presented with a 4-year history of recurrent flares of erythematous annular plaques on the trunk and extremities. The lesions resolved spontaneously after 3-5 weeks with no accompanying signs. A biopsy showed a mainly perivascular lymphocytic infiltrate with numerous eosinophils in the dermis.

  20. Annular pancreas (image)

    Science.gov (United States)

    Annular pancreas is an abnormal ring or collar of pancreatic tissue that encircles the duodenum (the part of the ... intestine that connects to stomach). This portion of pancreas can constrict the duodenum and block or impair ...

  1. Generalized granuloma annulare

    Directory of Open Access Journals (Sweden)

    Khatri M

    1995-01-01

    Full Text Available A 35-years-old female patient had generalized pruritic papular lesions, distributed like dermatitis herpetiformis for last 4 years. Histopathologic changes were typical of granuloma annulare with negative results of direct immunofluorescence. The patient did not have association of diabetes mellitus or any other systemic disease. She failed to respond to dapsone therapy and 13-cis-retinoic acid.

  2. Atomistic aspects of crack propagation along high angle grain boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, D. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering

    1997-12-31

    The author presents atomistic simulations of the crack tip configuration near a high angle {Sigma} = 5 [001](210) symmetrical tilt grain boundary in NiAl. The simulations were carried out using molecular statics and embedded atom (EAM) potentials. The cracks are stabilized near a Griffith condition involving the cohesive energy of the grain boundary. The atomistic configurations of the tip region are different in the presence of the high angle grain boundary than in the bulk. Three different configurations of the grain boundary were studied corresponding to different local compositions. It was found that in ordered NiAl, cracks along symmetrical tilt boundaries show a more brittle behavior for Al rich boundaries than for Ni-rich boundaries. Lattice trapping effects in grain boundary fracture were found to be more significant than in the bulk.

  3. Non-linear Flight Dynamics at High Angles of Attack

    DEFF Research Database (Denmark)

    Granasy, P.; Sørensen, C.B.; Mosekilde, Erik

    1998-01-01

    The methods of nonlinear dynamics are applied to the longitudinal motion of a vectored thrust aircraft, in particular the behavior at high angles of attack. Our model contains analytic nonlinear aerodynamical coefficients based on NASA windtunnel experiments on the F-18 high-alpha research vehicle...... (HARV). When the aircraft is forced with small thrust deflections whilst in poststall equilibrium, chaotic motion is observed at certain frequencies. At other frequencies, several limiting states coexist....

  4. High angle of attack aerodynamics subsonic, transonic, and supersonic flows

    CERN Document Server

    Rom, Josef

    1992-01-01

    The aerodynamics of aircraft at high angles of attack is a subject which is being pursued diligently, because the modern agile fighter aircraft and many of the current generation of missiles must perform well at very high incidence, near and beyond stall. However, a comprehensive presentation of the methods and results applicable to the studies of the complex aerodynamics at high angle of attack has not been covered in monographs or textbooks. This book is not the usual textbook in that it goes beyond just presenting the basic theoretical and experimental know-how, since it contains reference material to practical calculation methods and technical and experimental results which can be useful to the practicing aerospace engineers and scientists. It can certainly be used as a text and reference book for graduate courses on subjects related to high angles of attack aerodynamics and for topics related to three-dimensional separation in viscous flow courses. In addition, the book is addressed to the aerodynamicist...

  5. [Disseminated granuloma annulare].

    Science.gov (United States)

    Kansky, A

    1975-09-01

    A case of generalized granuloma annulare in a 55 year old man is reported. The disease appeared five years before the first admission to the hospital. A large number of bluish-red or skin-colour papules were scattered mainly around the earlobes, buttocks and on the extremities. Some of the lesions were lined up in rings or plaques. Small depigmented and brownish scars were present. Two biopsies revealed characteristic foci of complete collagen degeneration accompanied by a palisading infiltrate in the upper dermis. Treatment with tuberculostatics and antimalarics was without improvement. The lesions cleared after a course of prednison, but reappeared when the drug was discontinued.

  6. Annular recuperator design

    Science.gov (United States)

    Kang, Yungmo

    2005-10-04

    An annular heat recuperator is formed with alternating hot and cold cells to separate counter-flowing hot and cold fluid streams. Each cold cell has a fluid inlet formed in the inner diameter of the recuperator near one axial end, and a fluid outlet formed in the outer diameter of the recuperator near the other axial end to evenly distribute fluid mass flow throughout the cell. Cold cells may be joined with the outlet of one cell fluidly connected to the inlet of an adjacent downstream cell to form multi-stage cells.

  7. Portal Annular Pancreas

    Science.gov (United States)

    Harnoss, Jonathan M.; Harnoss, Julian C.; Diener, Markus K.; Contin, Pietro; Ulrich, Alexis B.; Büchler, Markus W.; Schmitz-Winnenthal, Friedrich H.

    2014-01-01

    Abstract Portal annular pancreas (PAP) is an asymptomatic congenital pancreas anomaly, in which portal and/or mesenteric veins are encased by pancreas tissue. The aim of the study was to determine the role of PAP in pancreatic surgery as well as its management and potential complication, specifically, postoperative pancreatic fistula (POPF). On the basis of a case report, the MEDLINE and ISI Web of Science databases were systematically reviewed up to September 2012. All articles describing a case of PAP were considered. In summary, 21 studies with 59 cases were included. The overall prevalence of PAP was 2.4% and the patients' mean (SD) age was 55.9 (16.2) years. The POPF rate in patients with PAP (12 pancreaticoduodenectomies and 3 distal pancreatectomies) was 46.7% (in accordance with the definition of the International Study Group of Pancreatic Surgery). Portal annular pancreas is a quite unattended pancreatic variant with high prevalence and therefore still remains a clinical challenge to avoid postoperative complications. To decrease the risk for POPF, attentive preoperative diagnostics should also focus on PAP. In pancreaticoduodenectomy, a shift of the resection plane to the pancreas tail should be considered; in extensive pancreatectomy, coverage of the pancreatic remnant by the falciform ligament could be a treatment option. PMID:25207658

  8. Multiple annular linear diffractive axicons.

    Science.gov (United States)

    Bialic, Emilie; de la Tocnaye, Jean-Louis de Bougrenet

    2011-04-01

    We propose a chromatic analysis of multiple annular linear diffractive axicons. Large aperture axicons are optical devices providing achromatic nondiffracting beams, with an extended depth of focus, when illuminated by a white light source, due to chromatic foci superimposition. Annular apertures introduce chromatic foci separation, and because chromatic aberrations result in focal segment axial shifts, polychromatic imaging properties are partially lost. We investigate here various design parameters that can be used to achieve color splitting, filtering, and combining using these properties. In order to improve the low-power efficiency of a single annular axicon, we suggest a spatial multiplexing of concentric annular axicons with different sizes and periods we call multiple annular aperture diffractive axicons (MALDAs). These are chosen to maintain focal depths while enabling color imaging with sufficient diffraction efficiency. Illustrations are given for binary phase diffractive axicons, considering technical aspects such as grating design wavelength and phase dependence due to the grating thickness.

  9. Annular Hybrid Rocket Motor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Engineers at SpaceDev have conducted a preliminary design and analysis of a proprietary annular design concept for a hybrid motor. A U.S. Patent application has been...

  10. Annular Elastolytic Giant Cell Granuloma

    Directory of Open Access Journals (Sweden)

    Khandpur Sujay

    2001-01-01

    Full Text Available The clinical and histopathological features of annular elastolytic giant cell granuloma in a 42â€"year-old female patient are described. The condition presented as annular erythematous plaques over sun- exposed skin sparing the face. Histopathology revealed dense granulomatous infiltrate consisting of numerous giant cells and lymphohistiocytes without any palisading arrangement or necrobiosis. The features differentiating it from other similar granulomatous disorders are discussed.

  11. Manufacture of annular cermet articles

    Science.gov (United States)

    Forsberg, Charles W.; Sikka, Vinod K.

    2004-11-02

    A method to produce annular-shaped, metal-clad cermet components directly produces the form and avoids multiple fabrication steps such as rolling and welding. The method includes the steps of: providing an annular hollow form with inner and outer side walls; filling the form with a particulate mixture of ceramic and metal; closing, evacuating, and hermetically sealing the form; heating the form to an appropriate temperature; and applying force to consolidate the particulate mixture into solid cermet.

  12. Annular lipoatrophy of the ankles.

    Science.gov (United States)

    Dimson, Otobia G; Esterly, Nancy B

    2006-02-01

    Lipoatrophic panniculitis likely represents a group of disorders characterized by an inflammatory panniculitis followed by lipoatrophy. It occurs locally in a variety of settings and has been reported in the literature under various terms, including annular atrophic connective tissue panniculitis of the ankles, annular and semicircular lipoatrophy, abdominal lipoatrophy, and connective tissue panniculitis. Herein, a case of annular lipoatrophy of the ankles is described in a 6-year-old girl with autoimmune thyroid disease. Histologically, a mixed lobular panniculitis with lipophages was present. This pattern resembles that seen in lipoatrophic panniculitis. After a single, acute episode of an inflammatory process with subsequent lipoatrophy, her skin lesions have stabilized for 2 years requiring no treatment.

  13. Eosinophilic annular erythema in childhood - Case report*

    Science.gov (United States)

    Abarzúa, Alvaro; Giesen, Laura; Silva, Sergio; González, Sergio

    2016-01-01

    Eosinophilic annular erythema is a rare, benign, recurrent disease, clinically characterized by persistent, annular, erythematous lesions, revealing histopathologically perivascular infiltrates with abundant eosinophils. This report describes an unusual case of eosinophilic annular erythema in a 3-year-old female, requiring sustained doses of hydroxychloroquine to be adequately controlled. PMID:27579748

  14. Benign concentric annular macular dystrophy

    Directory of Open Access Journals (Sweden)

    Luísa Salles de Moura Mendonça

    2015-06-01

    Full Text Available The purpose of the authors is to show clinical findings of a patient with benign concentric annular macular dystrophy, which is an unusual condition, and part of the "bull’s eye" maculopathy differential diagnosis. An ophthalmologic examination with color perception, fluorescein angiography, and ocular electrophysiology was performed.

  15. The Pinning by Particles of Low and High Angle Grain Boundaries during Grain Growth

    DEFF Research Database (Denmark)

    Tweed, C.J.; Ralph, B.; Hansen, Niels

    1984-01-01

    and coworkers. These estimates of local driving pressures have shown that they are similar for both the low and the high angle boundaries encountered in the samples. The pinning effects by particles at high angle boundaries are in general accord with the model due to Zener whilst those at low angle boundaries...

  16. A Reconfigurable Radiation Pattern Annular Slot Antenna

    OpenAIRE

    Aziz, NA; Radhi, A; Nilavalan, R

    2016-01-01

    This paper contemplate a theoretical analysis of a pattern reconfigurable antenna using annular slot antenna operating in low frequency. A shorting pin is inserted to allow the annular slot antenna to have an omnidirectional radiation pattern like a monopole antenna. The reconfigurable antenna consists of numerous metal cylinders arranged around the annular slot antenna. By controlling pin diodes associated with the metal cylinders, the antenna is capable of working up in different dire...

  17. Confocal Annular Josephson Tunnel Junctions

    Science.gov (United States)

    Monaco, Roberto

    2016-09-01

    The physics of Josephson tunnel junctions drastically depends on their geometrical configurations and here we show that also tiny geometrical details play a determinant role. More specifically, we develop the theory of short and long annular Josephson tunnel junctions delimited by two confocal ellipses. The behavior of a circular annular Josephson tunnel junction is then seen to be simply a special case of the above result. For junctions having a normalized perimeter less than one, the threshold curves in the presence of an in-plane magnetic field of arbitrary orientations are derived and computed even in the case with trapped Josephson vortices. For longer junctions, a numerical analysis is carried out after the derivation of the appropriate motion equation for the Josephson phase. We found that the system is modeled by a modified and perturbed sine-Gordon equation with a space-dependent effective Josephson penetration length inversely proportional to the local junction width. Both the fluxon statics and dynamics are deeply affected by the non-uniform annulus width. Static zero-field multiple-fluxon solutions exist even in the presence of a large bias current. The tangential velocity of a traveling fluxon is not determined by the balance between the driving and drag forces due to the dissipative losses. Furthermore, the fluxon motion is characterized by a strong radial inward acceleration which causes electromagnetic radiation concentrated at the ellipse equatorial points.

  18. Soliton bunching in annular Josephson junctions

    DEFF Research Database (Denmark)

    Vernik, I.V; Lazarides, Nickos; Sørensen, Mads Peter

    1996-01-01

    By studying soliton (fluxon) motion in long annular Josephson junctions it is possible to avoid the influence of the boundaries and soliton-soliton collisions present in linear junctions. A new experimental design consisting of a niobium coil placed on top of an annular junction has been used...

  19. Optimum annular focusing by a phase plate

    CERN Document Server

    Arrizón, Victor; Aguirre-Olivas, Dilia; Mellado-Villaseñor, Gabriel

    2015-01-01

    Conventional light focusing, i. e. concentration of an extended optical field within a small area around a point, is a frequently used process in Optics. An important extension to conventional focusing is the generation of the annular focal field of an optical beam. We discuss a simple optical setup that achieves this kind of focusing employing a phase plate as unique optical component. We first establish the class of beams that being transmitted through the phase plate can be focused into an annular field with topological charge of arbitrary integer order q. Then, for each beam in this class we determine the plate transmittance that generates the focal field with the maximum possible peak intensity. In particular, we discuss and implement experimentally the optimum annular focusing of a Gaussian beam. The attributes of optimum annular focal fields, namely the high peak intensity, intensity gradient and narrow annular section, are advantageous for different applications of such structured fields.

  20. [Generalized granuloma annulare or diffuse dermal histiocytosis?].

    Science.gov (United States)

    Kretzschmar, L; Biel, K; Luger, T A; Goerdt, S

    1995-08-01

    Generalized granuloma annulare is a rare variant of granuloma annulare affecting the trunk and extremities with a multitude of lesions. In contrast to localized granuloma annulare, generalized granuloma annulare occurs in older patients, shows a stronger association with diabetes, and is characteristically chronic. Like our 55-year-old patient, most patients present with papules and annular plaques; less often, macular or non-annular lesions may be encountered. Histology often fails to show necrobiotic or necrotic connective tissue changes demarcated by a palisading granuloma. Instead, there are diffuse dermal, band-like or nodular aggregations of histiocytes intermingled with some multinucleated giant cells and a predominantly lymphocytic infiltrate in the periphery. Because of its special characteristics, it has been suggested that generalized granuloma annulare might constitute a separate disease entity and that it should be classed among the primary cutaneous histiocytoses as a diffuse dermal histiocytosis. Using immunohistochemistry to determine the macrophage phenotype of the lesional histiocytes, we have shown that generalized granuloma annulare is not a cutaneous histiocytosis. Neither MS-1 high-molecular-weight protein, a new specific marker for cutaneous non-Langerhans cell histiocytoses, nor CD1a, the well-known marker for Langerhans cells and Langerhans cell histiocytoses, is expressed by the lesional histiocytes of our patient. In contrast, the antigen expression pattern was diagnostic for non-infectious granulomas and was highly similar to that in localized granuloma annulare. In contrast to the successful treatment of localized granuloma annulare reported with intralesional interferon beta-1, systemic treatment with interferon alpha-2b (9 x 10(6) units three times a week) was ineffective.

  1. Lattice Boltzmann Method used for the aircraft characteristics computation at high angle of attack

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Traditional Finite Volume Method(FVM)and Lattice Boltzmann Method(LBM)are both used to compute the high angle attack aerodynamic characteristics of the benchmark aircraft model named CT-1.Even though the software requires flow on the order of Ma<0.4,simulation at Ma=0.5 is run in PowerFLOW after theoretical analysis.The consistency with the wind tunnel testing is satisfied,especially for the LBM which can produce perfect results at high angle attack.PowerFLOW can accurately capture the detail of flows because it is inherently time-dependent and parallel and suits large-scale computation very well.

  2. Bifurcation analysis of polynomial models for longitudinal motion at high angle of attack

    Institute of Scientific and Technical Information of China (English)

    Shi Zhongke; Fan Li

    2013-01-01

    To investigate the longitudinal motion stability of aircraft maneuvers conveniently,a new stability analysis approach is presented in this paper.Based on describing longitudinal aerodynamics at high angle-of-attack (α < 50°) motion by polynomials,a union structure of two-order differential equation is suggested.By means of nonlinear theory and method,analytical and global bifurcation analyses of the polynomial differential systems are provided for the study of the nonlinear phenomena of high angle-of-attack flight.Applying the theories of bifurcations,many kinds of bifurcations,such as equilibrium,Hopf,homoclinic (heteroclinic) orbit and double limit cycle bifurcations are discussed and the existence conditions for these bifurcations as well as formulas for calculating bifurcation curves are derived.The bifurcation curves divide the parameter plane into several regions; moreover,the complete bifurcation diagrams and phase portraits in different regions are obtained.Finally,our conclusions are applied to analyzing the stability and bifurcations of a practical example of a high angle-of-attack flight as well as the effects of elevator deflection on the asymptotic stability regions of equilibrium.The model and analytical methods presented in this paper can be used to study the nonlinear flight dynamic of longitudinal stall at high angle of attack.

  3. Wing-Alone Aerodynamic Characteristics to High Angles of Attack at Subsonic and Transonic Speeds.

    Science.gov (United States)

    1982-11-01

    indicators of symmetry since the wings were unbanked within the limits of tolerances and flow angularity. Longitudinal, spanwise, and vertical... unbanked wings at subsonic and transonic speeds from low to high angles of attack. The wing planforms varied in aspect ratio and taper ratio with

  4. Divergent Field Annular Ion Engine Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed work investigates an approach that would allow an annular ion engine geometry to achieve ion beam currents approaching the Child-Langmuir limit. In this...

  5. A clinical study of annular cyclitis

    Directory of Open Access Journals (Sweden)

    Marilita Michael Moschos

    2009-02-01

    Full Text Available Marilita Michael Moschos1, Yan Guex-Crosier2, Ioannis Margetis1, Leonidas Zografos21Department of Ophthalmology, University of Athens, Greece; 2Jules Gonin Eye Hospital, University of Lausanne, SwitzerlandPurpose: To investigate six cases of annular cyclitis.Methods: All patients with impairment of visual acuity underwent complete ophthalmologic examination, color fundus photography, laboratory tests and fluorescein angiography. Indocyanine green (ICG angiography and B-scan ultrasonography were also performed in three cases in order to diagnose the disease.Results: All patients presented a unilateral or bilateral granulomatous uveitis, associated with inflammatory annular cyclitis. They had a shallow anterior chamber, a mildly elevated intraocular pressure (under 25 mm Hg and an annular serous retinal detachment. A resolution was observed after specific therapy associated with systemic prednisolone therapy and antiglaucomatous drops.Conclusion: This is the first description of an observational study of six patients with inflammatory annular cyclitis.Keywords: cyclitis, uveitis, malignant glaucoma

  6. Dark matter and dark energy

    CERN Multimedia

    Caldwell, Robert

    2009-01-01

    "Observations continue to indicate that the Universe is dominated by invisible components - dark matter and dark energy. Shedding light on this cosmic darkness is a priority for astronomers and physicists" (3 pages)

  7. Adaptive optics scanning ophthalmoscopy with annular pupils.

    Science.gov (United States)

    Sulai, Yusufu N; Dubra, Alfredo

    2012-07-01

    Annular apodization of the illumination and/or imaging pupils of an adaptive optics scanning light ophthalmoscope (AOSLO) for improving transverse resolution was evaluated using three different normalized inner radii (0.26, 0.39 and 0.52). In vivo imaging of the human photoreceptor mosaic at 0.5 and 10° from fixation indicates that the use of an annular illumination pupil and a circular imaging pupil provides the most benefit of all configurations when using a one Airy disk diameter pinhole, in agreement with the paraxial confocal microscopy theory. Annular illumination pupils with 0.26 and 0.39 normalized inner radii performed best in terms of the narrowing of the autocorrelation central lobe (between 7 and 12%), and the increase in manual and automated photoreceptor counts (8 to 20% more cones and 11 to 29% more rods). It was observed that the use of annular pupils with large inner radii can result in multi-modal cone photoreceptor intensity profiles. The effect of the annular masks on the average photoreceptor intensity is consistent with the Stiles-Crawford effect (SCE). This indicates that combinations of images of the same photoreceptors with different apodization configurations and/or annular masks can be used to distinguish cones from rods, even when the former have complex multi-modal intensity profiles. In addition to narrowing the point spread function transversally, the use of annular apodizing masks also elongates it axially, a fact that can be used for extending the depth of focus of techniques such as adaptive optics optical coherence tomography (AOOCT). Finally, the positive results from this work suggest that annular pupil apodization could be used in refractive or catadioptric adaptive optics ophthalmoscopes to mitigate undesired back-reflections.

  8. Annular-Cross-Section CFE Chamber

    Science.gov (United States)

    Sharnez, Rizwan; Sammons, David W.

    1994-01-01

    Proposed continuous-flow-electrophoresis (CFE) chamber of annular cross section offers advantages over conventional CFE chamber, and wedge-cross-section chamber described in "Increasing Sensitivity in Continuous-Flow Electrophoresis" (MFS-26176). In comparison with wedge-shaped chamber, chamber of annular cross section virtually eliminates such wall effects as electro-osmosis and transverse gradients of velocity. Sensitivity enhanced by incorporating gradient maker and radial (collateral) flow.

  9. Economic Recovery of Oil Trapped at Fan Margins Using High Angle Wells and Multiple Hydraulic Fractures

    Energy Technology Data Exchange (ETDEWEB)

    Mike L. Laue

    1997-05-30

    The distal fan margin in the northeast portion of the Yowlumne field contains significant reserves but is not economical to develop using vertical wells. Numerous interbedded shales and deteriorating rock properties limit producibility. In addition, extreme depths (13,000 ft) present a challenging environment for hydraulic fracturing and artificial lift. Lastly, a mature waterflood increases risk because of the uncertainty with size and location of flood fronts. This project attempts to demonstrate the effectiveness of exploiting the distal fan margin of this slope-basin clastic reservoir through the use of a high-angle well completed with multiple hydraulic-fracture treatments. The combination of a high-angle (or horizontal) well and hydraulic fracturing will allow greater pay exposure than can be achieved with conventional vertical wells while maintaining vertical communication between thin interbedded layers and the wellbore. The equivalent production rate and reserves of three vertical wells are anticipated at one-half to two-thirds the cost.

  10. Research on taper zone coupling from single-core fiber to annular-core hollow beam fiber

    Science.gov (United States)

    Tong, Chengguo; Zhang, Tao; Li, Jianqi; Wang, Pengfei; Kang, Chong; Yuan, Libo

    2016-11-01

    We designed and manufactured a novel annular-core hollow beam fiber which could directly yield ring light with a central dark spot inside the beam employing MCVD technique and a custom-made fiber drawing tower. The tapered fiber zone geometric shapes at varied stretching speed between the single-core fiber and the annular-core hollow beam fiber were studied theoretically. According to the beam propagation method, the bi-tapered coupling energy transmission between these two fibers was simulated and analyzed. Moreover, by adopting a fusion splicing and stretching technique at the fiber-linked point, an effective coupling approach had been fulfilled.

  11. Dark Matter

    OpenAIRE

    Einasto, Jaan

    2013-01-01

    I give a review of the development of the concept of dark matter. The dark matter story passed through several stages from a minor observational puzzle to a major challenge for theory of elementary particles. Modern data suggest that dark matter is the dominant matter component in the Universe, and that it consists of some unknown non-baryonic particles. Dark matter is the dominant matter component in the Universe, thus properties of dark matter particles determine the structure of the cosmic...

  12. CFD Simulation of Annular Centrifugal Extractors

    Directory of Open Access Journals (Sweden)

    S. Vedantam

    2012-01-01

    Full Text Available Annular centrifugal extractors (ACE, also called annular centrifugal contactors offer several advantages over the other conventional process equipment such as low hold-up, high process throughput, low residence time, low solvent inventory and high turn down ratio. The equipment provides a very high value of mass transfer coefficient and interfacial area in the annular zone because of the high level of power consumption per unit volume and separation inside the rotor due to the high g of centrifugal field. For the development of rational and reliable design procedures, it is important to understand the flow patterns in the mixer and settler zones. Computational Fluid Dynamics (CFD has played a major role in the constant evolution and improvements of this device. During the past thirty years, a large number of investigators have undertaken CFD simulations. All these publications have been carefully and critically analyzed and a coherent picture of the present status has been presented in this review paper. Initially, review of the single phase studies in the annular region has been presented, followed by the separator region. In continuation, the two-phase CFD simulations involving liquid-liquid and gas-liquid flow in the annular as well as separator regions have been reviewed. Suggestions have been made for the future work for bridging the existing knowledge gaps. In particular, emphasis has been given to the application of CFD simulations for the design of this equipment.

  13. Sediment particle entrainment in an obstructed annular

    Energy Technology Data Exchange (ETDEWEB)

    Loureiro, Bruno Venturini; Siqueira, Renato do Nascimento [Faculdade do Centro Leste (UCL), Serra, ES (Brazil). Lab. de Fenomenos de Transporte], e-mail: brunovl@ucl.br, e-mail: renatons@ucl.br

    2006-07-01

    Flow in an annular region with internal cylinder rotation is a classic problem in fluid mechanics and has been widely studied. Besides its importance as a fundamental problem, flow in annular regions has several practical applications. This project was motivated by an application of this kind of flow to the drilling of oil and gas wells. In this work, an erosion apparatus was constructed in order to study the effect of the internal cylinder rotation on particle entrainment in an obstructed annular space and bed package as well. The study also analyzed the influence of height of the particles bed on the process performance. The experiment was designed so that the internal cylinder rotation could be measured by an encoder. The fluid temperature was measured by a thermocouple and the experiments were carried out at the temperature of 25 deg C. The study revealed that the particle entrainment for the height of the bed that is close to the center of the cylinders is negligible and the internal cylinder rotation provokes the movement and packing of the bed. For lower height of the bed, with same dimension of the annular gap, the particle entrainment process was satisfactory and the bed compaction was smaller than in the previous case, leading to a more efficient cleaning process in the annular space. (author)

  14. Identification of High Angle Structures Controlling the Geothermal System at Rye Patch, Nevada.

    Science.gov (United States)

    Ehni, W. J.

    2001-12-01

    The successful completion of a recent well in the Rye Patch Geothermal field, located in Pershing County, Nevada, supports the geologic and geophysical interpretation that high angle structures control this geothermal system. Although lower angle structures are present, hot water migrates up from deeper sources along high angle faults more efficiently than structures with a shallower dip. Earlier attempts to develop the resource focused on structures that dipped at an angle between 60 and 70 degrees from horizontal. Recently acquired geophysical data indicated that numerous high angle structures were present in the area, with dips between 80 and 90 degrees. Original drilling targets focused on the subsurface projection of a surface structure, mapped as the Rye Patch fault, with an erroneously low angle. These early attempts at drilling were discouraging and might have been more successful if additional geology and geophysics were used to evaluate the geothermal system and map the Rye Patch fault more accurately. The successful completion of the most recent well can be attributed to the incorporation of the geology of previous wells with additional geology and geophysics. Temperature gradient holes were used to confirm that the Rye Patch fault provided the primary plumbing for this geothermal system, and 3D seismic data indicated that most of the structures had dips between 80 and 90 degrees. Geothermometry at Rye Patch indicates that the resource has a relatively high quartz equilibrium temperature and it is speculated that the higher the angle of the structural control, the higher the resource temperature. The dip of Basin and Range normal faults varies considerably and the interpretation of these structures for geothermal, fossil geothermal mineral prospects, and or oil and gas prospects is important. At Rye Patch, the high angle structure feeds geothermal fluids into cavernous limestone beds, dipping to the west usually between 40 and 60 degrees, which is a

  15. Surface pressure model for simple delta wings at high angles of attack

    Indian Academy of Sciences (India)

    A A Pashilkar

    2001-12-01

    A new aerodynamic modelling approach is proposed for the longitudinal static characteristics of a simple delta wing. It captures the static variation of normal force and pitching moment characteristics throughout the angle of attack range. The pressure model is based on parametrizing the surface pressure distribution on a simple delta wing. The model is then extended to a wing/body combination where body-alone data are also available. The model is shown to be simple and consistent with experimental data. The pressure model can be used as a first approximation for the load estimation on the delta wing at high angles of attack.

  16. Prediction of forces and moments on finned bodies at high angle of attack in transonic flow

    Energy Technology Data Exchange (ETDEWEB)

    Oberkampf, W. L.

    1981-04-01

    This report describes a theoretical method for the prediction of fin forces and moments on bodies at high angle of attack in subsonic and transonic flow. The body is assumed to be a circular cylinder with cruciform fins (or wings) of arbitrary planform. The body can have an arbitrary roll (or bank) angle, and each fin can have individual control deflection. The method combines a body vortex flow model and lifting surface theory to predict the normal force distribution over each fin surface. Extensive comparisons are made between theory and experiment for various planform fins. A description of the use of the computer program that implements the method is given.

  17. Magnus effects at high angles of attack and critical Reynolds numbers

    Science.gov (United States)

    Seginer, A.; Ringel, M.

    1983-01-01

    The Magnus force and moment experienced by a yawed, spinning cylinder were studied experimentally in low speed and subsonic flows at high angles of attack and critical Reynolds numbers. Flow-field visualization aided in describing a flow model that divides the Magnus phenomenon into a subcritical region, where reverse Magnus loads are experienced, and a supercritical region where these loads are not encountered. The roles of the spin rate, angle of attack, and crossflow Reynolds number in determining the boundaries of the subcritical region and the variations of the Magnus loads were studied.

  18. Stitching algorithm for annular subaperture interferometry

    Institute of Scientific and Technical Information of China (English)

    Xi Hou; Fan Wu; Li Yang; Shibin Wu; Qiang Chen

    2006-01-01

    @@ Annular subaperture interferometry (ASI) has been developed for low cost and flexible test of rotationally symmetric aspheric surfaces, in which accurately combining the subaperture measurement data corrupted by misalignments and noise into a complete surface figure is the key problem. By introducing the Zernike annular polynomials which are orthogonal over annulus, a method that eliminates the coupling problem in the earlier algorithm based on Zernike circle polynomials is proposed. Vector-matrix notation is used to simplify the description and calculations. The performance of this reduction method is evaluated by numerical simulation. The results prove this method with high precision and good anti-noise capability.

  19. Annular, erythematous skin lesions in a neonate

    Directory of Open Access Journals (Sweden)

    Aparna Palit

    2012-01-01

    Full Text Available A 7-day-old premature female infant presented with rapidly progressive, erythematous, annular skin lesions from the 5 th day of life. She was diagnosed provisionally as a case of neonatal lupus erythematosus and was investigated accordingly. Histopathological examination of the skin biopsy specimen revealed presence of hyphae of dermatophytes in the stratum corneum, and the diagnosis was changed to tinea corporis. Differential diagnosis of the annular erythema of infancy has been discussed and the importance of scraping a scaly lesion for KOH preparation in the diagnostic work-up of such a patient has been highlighted.

  20. Optimal Thrust Vectoring for an Annular Aerospike Nozzle Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Recent success of an annular aerospike flight test by NASA Dryden has prompted keen interest in providing thrust vector capability to the annular aerospike nozzle...

  1. Dark matter

    OpenAIRE

    Einasto, J.

    2011-01-01

    I give a review of the development of the concept of dark matter. The dark matter story passed through several stages from a minor observational puzzle to a major challenge for theory of elementary particles. Modern data suggest that dark matter is the dominant matter component in the Universe, and that it consists of some unknown non-baryonic particles. Properties of dark matter particles determine the structure of the cosmic web.

  2. Study on flow behavior and structure over chined fuselage at high angle of attack

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A study of leeward vortex structure over chined fuselage and the effects of micro tip perturbation on its vortex flow have been carried out in wind tunnel experiments at Reynolds numbers from 1.26×105 to 5.04×105 with PIV and pressure measurement techniques.Firstly,the experiment results have proved that micro tip perturbation has no effects on the vortex flow and its aerodynamic characteristics over chined fuselage at high angle of attack,in which there are not any non-deterministic flow behaviors.Secondly,the evolution of leeward vortex structure over chined fuselage along the axis of model can be divided into four flow regimes:linear conical developed regime,decay regime of leeward vortex intensity,asymmetric leeward vortex break down regime and completely break down regime.And a correlation between leeward vortex structure and sectional aerodynamic force was also revealed in the present paper.Thirdly,the experiment results show the behavior of leeward vortex core trajectories and zonal characteristics of leeward vortex structure with angles of attack.Finally,the experiment results of Reynolds number effect on the leeward vortex flow have further confirmed research conclusions from previous studies:the flows over chined fuselage at high angles of attack are insensitive to variation of Reynolds number,and there is a little effect on the secondary boundary layer separation and the suction peak induced by leeward vortex.

  3. COMPUTATION OF FIELD STRUCTURE AND AERODYNAMIC CHARACTERISTICS OF DELTA WINGS AT HIGH ANGLES OF ATTACK

    Institute of Scientific and Technical Information of China (English)

    YANG Li-zhi; GAO Zheng-hong

    2005-01-01

    A numerical investigation of the structure of the vortical flowfield over delta wings at high angles of attack in longitudinal and with small sideslip angle is presented.Three-dimensional Navier-Stokes numerical simulations were carried out to predict the complex leeward-side flowfield characteristics that are dominated by the effect of the breakdown of the leading-edge vortices. The methods that analyze the flowfield structure quantitatively were given by using flowfield data from the computational results. In the region before the vortex breakdown, the vortex axes are approximated as being straight line. As the angle of attack increases, the vortex axes are closer to the root chord, and farther away from the wing surface. Along the vortex axes, as the adverse pressure gradients occur, the axial velocity decreases, that is, λ is negative, so the vortex is unstable, and it is possible to breakdown. The occurrence of the breakdown results in the instability of lateral motion for a delta wing, and the lateral moment diverges after a small perturbation occurs at high angles of attack. However,after a critical angle of attack is reached, the vortices breakdown completely at the wing apex, and the instability resulting from the vortex breakdown disappears.

  4. Annular beam with segmented phase gradients

    Directory of Open Access Journals (Sweden)

    Shubo Cheng

    2016-08-01

    Full Text Available An annular beam with a single uniform-intensity ring and multiple segments of phase gradients is proposed in this paper. Different from the conventional superposed vortices, such as the modulated optical vortices and the collinear superposition of multiple orbital angular momentum modes, the designed annular beam has a doughnut intensity distribution whose radius is independent of the phase distribution of the beam in the imaging plane. The phase distribution along the circumference of the doughnut beam can be segmented with different phase gradients. Similar to a vortex beam, the annular beam can also exert torques and rotate a trapped particle owing to the orbital angular momentum of the beam. As the beam possesses different phase gradients, the rotation velocity of the trapped particle can be varied along the circumference. The simulation and experimental results show that an annular beam with three segments of different phase gradients can rotate particles with controlled velocities. The beam has potential applications in optical trapping and optical information processing.

  5. Fluxon Dynamics in Elliptic Annular Josephson Junctions

    DEFF Research Database (Denmark)

    Monaco, Roberto; Mygind, Jesper

    2016-01-01

    We analyze the dynamics of a magnetic flux quantum (current vortex) trapped in a current-biased long planar elliptic annular Josephson tunnel junction. The system is modeled by a perturbed sine-Gordon equation that determines the spatial and temporal behavior of the phase difference across the tu...

  6. Annular beam with segmented phase gradients

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Shubo; Wu, Liang [School of Physics and Electronics, Central South University, Changsha, Hunan 410083 (China); Tao, Shaohua, E-mail: eshtao@csu.edu.cn [School of Physics and Electronics, Central South University, Changsha, Hunan 410083 (China); Hunan Key Laboratory for Super-microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha, Hunan 410083 (China)

    2016-08-15

    An annular beam with a single uniform-intensity ring and multiple segments of phase gradients is proposed in this paper. Different from the conventional superposed vortices, such as the modulated optical vortices and the collinear superposition of multiple orbital angular momentum modes, the designed annular beam has a doughnut intensity distribution whose radius is independent of the phase distribution of the beam in the imaging plane. The phase distribution along the circumference of the doughnut beam can be segmented with different phase gradients. Similar to a vortex beam, the annular beam can also exert torques and rotate a trapped particle owing to the orbital angular momentum of the beam. As the beam possesses different phase gradients, the rotation velocity of the trapped particle can be varied along the circumference. The simulation and experimental results show that an annular beam with three segments of different phase gradients can rotate particles with controlled velocities. The beam has potential applications in optical trapping and optical information processing.

  7. Annular lichenoid syphilis: A rare entity.

    Science.gov (United States)

    Khurana, Ananta; Singal, Archana; Gupta, Seema

    2014-01-01

    Syphilis is a disease known for centuries, but still continues to be a diagnostic challenge as the myriad manifestations of secondary syphilis can mimic a lot many dermatological disorders. Lichenoid syphilis is an uncommon entity, reported only occasionally in the penicillin era. We present the case of a 32-year-old woman presenting with localized annular lichenoid lesions on the neck.

  8. A New Annular Shear Piezoelectric Accelerometer

    DEFF Research Database (Denmark)

    Liu, Bin; Kriegbaum, B.

    2000-01-01

    This paper describes the construction and performance of a recently introduced Annular Shear piezoelectric accelerometer, Type 4511. The design has insulated and double-shielded case. The accelerometer housing is made of stainless steel, AISI 316L. Piezoceramic PZ23 is used. The seismic mass...... interface for sensors including mixed-mode communication protocols and transducer electronic data sheet (TEDS)....

  9. Annular Pressure Seals and Hydrostatic Bearings

    Science.gov (United States)

    2006-11-01

    affecting the rotordynamics of liquid turbopumps, in particular those handling large density fluids. Highlights on the bulk-flow analysis of annular seals... rotordynamic stability. Hydrostatic bearings rely on external fluid pressurization to generate load support and large centering stiffnesses, even in...SEALS IN PUMP APPLICATIONS Seal rotordynamic characteristic have a primary influence on the stability response of high-performance turbomachinery [1

  10. ASYMMETRIC VORTICES FLOW OVER SLENDER BODY AND ITS ACTIVE CONTROL AT HIGH ANGLE OF ATTACK

    Institute of Scientific and Technical Information of China (English)

    DENG Xueying; WANG Yankui

    2004-01-01

    The studies of asymmetric vortices flow over slender body and its active control at high angles of attack have significant importance for both academic field and engineering area. This paper attempts to provide an update state of art to the investigations on the fields of forebody asymmetric vortices. This review emphasizes the correlation between micro-perturbation on the model nose and its response and evolution behaviors of the asymmetric vortices. The critical issues are discussed,which include the formation and evolution mechanism of asymmetric multi-vortices; main behaviors of asymmetric vortices flow including its deterministic feature and vortices flow structure; the evolution and development of asymmetric vortices under the perturbation on the model nose; forebody vortex active control especially discussed micro-perturbation active control concept and technique in more detail. However present understanding in this area is still very limited and this paper tries to identify the key unknown problems in the concluding remarks.

  11. Bifurcation analysis and stability design for aircraft longitudinal motion with high angle of attack

    Directory of Open Access Journals (Sweden)

    Xin Qi

    2015-02-01

    Full Text Available Bifurcation analysis and stability design for aircraft longitudinal motion are investigated when the nonlinearity in flight dynamics takes place severely at high angle of attack regime. To predict the special nonlinear flight phenomena, bifurcation theory and continuation method are employed to systematically analyze the nonlinear motions. With the refinement of the flight dynamics for F-8 Crusader longitudinal motion, a framework is derived to identify the stationary bifurcation and dynamic bifurcation for high-dimensional system. Case study shows that the F-8 longitudinal motion undergoes saddle node bifurcation, Hopf bifurcation, Zero-Hopf bifurcation and branch point bifurcation under certain conditions. Moreover, the Hopf bifurcation renders series of multiple frequency pitch oscillation phenomena, which deteriorate the flight control stability severely. To relieve the adverse effects of these phenomena, a stabilization control based on gain scheduling and polynomial fitting for F-8 longitudinal motion is presented to enlarge the flight envelope. Simulation results validate the effectiveness of the proposed scheme.

  12. Towards weighing individual atoms by high-angle scattering of electrons

    CERN Document Server

    Argentero, G; Kotakoski, J; Eder, F R; Meyer, J C

    2015-01-01

    We consider theoretically the energy loss of electrons scattered to high angles when assuming that the primary beam can be limited to a single atom. We discuss the possibility of identifying the isotopes of light elements and of extracting information about phonons in this signal. The energy loss is related to the mass of the much heavier nucleus, and is spread out due to atomic vibrations. Importantly, while the width of the broadening is much larger than the energy separation of isotopes, only the shift in the peak positions must be detected if the beam is limited to a single atom. We conclude that the experimental case will be challenging but is not excluded by the physical principles as far as considered here. Moreover, the initial experiments demonstrate the separation of gold and carbon based on a signal that is related to their mass, rather than their atomic number.

  13. Flight validation of ground-based assessment for control power requirements at high angles of attack

    Science.gov (United States)

    Ogburn, Marilyn E.; Ross, Holly M.; Foster, John V.; Pahle, Joseph W.; Sternberg, Charles A.; Traven, Ricardo; Lackey, James B.; Abbott, Troy D.

    1994-01-01

    A review is presented in viewgraph format of an ongoing NASA/U.S. Navy study to determine control power requirements at high angles of attack for the next generation high-performance aircraft. This paper focuses on recent flight test activities using the NASA High Alpha Research Vehicle (HARV), which are intended to validate results of previous ground-based simulation studies. The purpose of this study is discussed, and the overall program structure, approach, and objectives are described. Results from two areas of investigation are presented: (1) nose-down control power requirements and (2) lateral-directional control power requirements. Selected results which illustrate issues and challenges that are being addressed in the study are discussed including test methodology, comparisons between simulation and flight, and general lessons learned.

  14. Quasi-periodic dynamics of a high angle of attack aircraft

    Science.gov (United States)

    Rohith, G.; Sinha, Nandan K.

    2017-01-01

    High angle of attack maneuvers closer to stall is a commonly accessed flight regime especially in case of fighter aircrafts. Stall and post-stall dynamics are dominated by nonlinearities which make the analysis difficult. Presence of external factors such as wind makes the system even more complex. Rich nonlinearities point to the possibility of existence of chaotic solutions. Past studies in this area confirm the development of such solutions. These studies are mainly concentrated on very high angle of attack regimes, which may not be practically easily accessible. This paper examines the possibility of existence of chaotic solutions in the lower, more accessible areas in the post stall domain. The analysis is composed of the study of effect of external wind as an agent to drive the system towards the possibility of a chaotic solution. Investigations reveal presence of quasi-periodic solutions, which are characterized by two incommensurate frequencies. This solution appears in the time simulation by varying the control parameter viz., wind. The solutions correspond to the values in the lower region of the angle of attack versus elevator bifurcation curve in the post-stall region. A steady wind is considered for the analysis and explores the possibility of chaotic motion by increasing the wind in a step wise manner. It is found that wind adds extra energy to the system which in turn drives the system in to chaos. The analysis is done with the help of phase portrait, Poincare map and amplitude spectrum and a quasi-periodic route to chaos via torus doubling is also presented.

  15. Investigation on high angle of attack characteristics of hypersonic space vehicle

    Institute of Scientific and Technical Information of China (English)

    HUANG Wei; LI ShiBin; LIU Jun; WANG ZhenGuo

    2012-01-01

    The high angle of attack characteristics play an important role in the aerodynamic performances of the hypersonic space vehicle.The three-dimensional Reynolds Averaged Navier-Stokes (RANS) equations and the two-equation RNG k-ε turbulence model have been employed to investigate the influence of the high angle of attack on the lift-to-drag ratio and the flow field characteristics of the hypersonic space vehicle,and the contributions of each component to the aerodynamic forces of the vehicle have been discussed as well.At the same time,in order to validate the numerical method,the predicted results have been compared with the available experimental data of a hypersonic slender vehicle,and the grid independency has been analyzed.The obtained results show that the predicted lift-to-drag ratio and pitching moment coefficient show very good agreement with the experimental data in the open literature,and the grid system makes only a slight difference to the numerical results.There exists an optimal angle of attack for the aerodynamic performance of the hypersonic space vehicle,and its value is 20°.When the angle of attack is 20°,the high pressure does not leak from around the leading edge to the upper surface.With the further increasing of the angle of attack,the high pressure spreads from the wing tips to the central area of the vehicle,and overflows from the leading edge again.Further,the head plays an important role in the drag performance of the vehicle,and the lift percentage of the flaperon is larger than that of the rudderevator.This illustrates that the optimization of the flaperon configuration is a great work for the improvement of the aerodynamic performance of the hypersonic space vehicle,especially for a high lift-to-drag ratio.

  16. Dark GPC

    DEFF Research Database (Denmark)

    Banas, Andrew Rafael; Villangca, Mark Jayson; Palima, Darwin;

    2016-01-01

    in a 3x intensified user defined input mask shape against a dark background. In this work, we emphasize GPC’s capability of optimal destructive interference, normally used to create the dark background surrounding the shaped light. We also study input parameters wherein the locations of light...... and darkness are interchanged with respect to typical GPC output, thus resulting to a well-defined structured darkness. The conditions that give destructive interference for the output are then applied to near-arbitrary shapes. Preliminary experimental results are presented using dynamic spatial light...... modulator to form scaled arbitrary darkness shapes. Supporting demonstrations that reverse the light and dark regions of amplitude-modulated input are also presented as a related case of structuring destructive interference. Our analysis and experimental demonstrations show a simplified approach...

  17. Dynamics of bouncing droplets in annular cavities

    Science.gov (United States)

    Lentz, Zachary Louis; Jalali, Mir Abbas; Alam, Mohammad-Reza

    2014-11-01

    In a cylindrical bath of silicon oil, vertically excited by a frequency of 45 Hz, we trace the motion of bouncing droplets as they fill an annular region. We compute the mean tangential and radial velocity components of the droplets and show that the maximum tangential velocity is larger than the maximum radial velocity by one order of magnitude. Velocity dispersions have almost equal levels in the radial and tangential directions, and their mean values are 1/4 times smaller than the mean tangential velocity. These results show that bouncing droplets undergo random motions within annular cavities determined by the interference patterns of self-induced circumferential waves. We derive analytical relations between the velocity dispersion and the wavelength of surface waves, and calculate the mean tangential velocity of droplets using the random kicks that they experience at the boundaries of the cavity by inward and outward traveling waves.

  18. Non newtonian annular alloy solidification in mould

    Energy Technology Data Exchange (ETDEWEB)

    Moraga, Nelson O.; Garrido, Carlos P. [Universidad de La Serena, Departamento de Ingenieria Mecanica, La Serena (Chile); Castillo, Ernesto F. [Universidad de Santiago de Chile, Departamento de Ingenieria Mecanica, Santiago (Chile)

    2012-08-15

    The annular solidification of an aluminium-silicon alloy in a graphite mould with a geometry consisting of horizontal concentric cylinders is studied numerically. The analysis incorporates the behavior of non-Newtonian, pseudoplastic (n=0.2), Newtonian (n=1), and dilatant (n=1.5) fluids. The fluid mechanics and heat transfer coupled with a transient model of convection diffusion are solved using the finite volume method and the SIMPLE algorithm. Solidification is described in terms of a liquid fraction of a phase change that varies linearly with temperature. The final results make it possible to infer that the fluid dynamics and heat transfer of solidification in an annular geometry are affected by the non-Newtonian nature of the fluid, speeding up the process when the fluid is pseudoplastic. (orig.)

  19. Annular and Total Solar Eclipses of 2003

    Science.gov (United States)

    Espenak, Fred; Anderson, Jay

    2002-01-01

    On Saturday, 2003 May 31, an annular eclipse of the Sun will be visible from a broad corridor that traverses the North Atlantic. The path of the Moon's antumbral shadow begins in northern Scotland, crosses Iceland and central Greenland, and ends at sunrise in Baffin Bay (Canada). A partial eclipse will be seen within the much broader path of the Moon's penumbral shadow, which includes most of Europe, the Middle East, central and northern Asia, and northwestern North America. The trajectory of the Moon's shadow is quite unusual during this event. The shadow axis passes to the far north where it barely grazes Earth's surface. In fact, the northern edge of the antumbra actually misses Earth so that one path limit is defined by the day/night terminator rather than by the shadow's upper edge. As a result, the track of annularity has a peculiar "D" shape that is nearly 1200 kilometers wide. Since the eclipse occurs just three weeks prior to the northern summer solstice, Earth's northern axis is pointed sunwards by 22.8 deg. As seen from the Sun, the antumbral shadow actually passes between the North Pole and the terminator. As a consequence of this extraordinary geometry, the path of annularity runs from east to west rather than the more typical west to east. The event transpires near the Moon's ascending node in Taurus five degrees north of Aldebaran. Since apogee occurs three days earlier (May 28 at 13 UT), the Moon's apparent diameter (29.6 arc-minutes) is still too small to completely cover the Sun (31.6 arc-minutes) resulting in an annular eclipse.

  20. Dark Matter and Dark Radiation

    CERN Document Server

    Ackerman, Lotty; Carroll, Sean M; Kamionkowski, Marc

    2008-01-01

    We explore the feasibility and astrophysical consequences of a new long-range U(1) gauge field ("dark electromagnetism") that couples only to dark matter, not to the Standard Model. The dark matter consists of an equal number of positive and negative charges under the new force, but annihilations are suppressed if the dark matter mass is sufficiently high and the dark fine-structure constant $\\hat\\alpha$ is sufficiently small. The correct relic abundance can be obtained if the dark matter also couples to the conventional weak interactions, and we verify that this is consistent with particle-physics constraints. The primary limit on $\\hat\\alpha$ comes from the demand that the dark matter be effectively collisionless in galactic dynamics, which implies $\\hat\\alpha \\lesssim 10^{-4}$ for TeV-scale dark matter. These values are easily compatible with constraints from structure formation and primordial nucleosynthesis. We raise the prospect of interesting new plasma effects in dark matter dynamics, which remain to ...

  1. Monte Carlo electron-trajectory simulations in bright-field and dark-field STEM: Implications for tomography of thick biological sections

    Energy Technology Data Exchange (ETDEWEB)

    Sousa, A.A.; Hohmann-Marriott, M.F.; Zhang, G. [Laboratory of Bioengineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bldg. 13, Rm. 3N17, 13 South Drive, Bethesda, MD 20892-5766 (United States); Leapman, R.D. [Laboratory of Bioengineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bldg. 13, Rm. 3N17, 13 South Drive, Bethesda, MD 20892-5766 (United States)], E-mail: leapmanr@mail.nih.gov

    2009-02-15

    A Monte Carlo electron-trajectory calculation has been implemented to assess the optimal detector configuration for scanning transmission electron microscopy (STEM) tomography of thick biological sections. By modeling specimens containing 2 and 3 at% osmium in a carbon matrix, it was found that for 1-{mu}m-thick samples the bright-field (BF) and annular dark-field (ADF) signals give similar contrast and signal-to-noise ratio provided the ADF inner angle and BF outer angle are chosen optimally. Spatial resolution in STEM imaging of thick sections is compromised by multiple elastic scattering which results in a spread of scattering angles and thus a spread in lateral distances of the electrons leaving the bottom surface. However, the simulations reveal that a large fraction of these multiply scattered electrons are excluded from the BF detector, which results in higher spatial resolution in BF than in high-angle ADF images for objects situated towards the bottom of the sample. The calculations imply that STEM electron tomography of thick sections should be performed using a BF rather than an ADF detector. This advantage was verified by recording simultaneous BF and high-angle ADF STEM tomographic tilt series from a stained 600-nm-thick section of C. elegans. It was found that loss of spatial resolution occurred markedly at the bottom surface of the specimen in the ADF STEM but significantly less in the BF STEM tomographic reconstruction. Our results indicate that it might be feasible to use BF STEM tomography to determine the 3D structure of whole eukaryotic microorganisms prepared by freeze-substitution, embedding, and sectioning.

  2. Mandibular advancement surgery in high-angle and low-angle class II patients: different long-term skeletal responses.

    Science.gov (United States)

    Mobarak, K A; Espeland, L; Krogstad, O; Lyberg, T

    2001-04-01

    The objective of this cephalometric study was to compare skeletal stability and the time course of postoperative changes in high-angle and low-angle Class II patients after mandibular advancement surgery. The subjects were 61 consecutive mandibular retrognathism patients whose treatment included bilateral sagittal split osteotomy and rigid fixation. The patients were divided according to the preoperative mandibular plane angle; the 20 patients with the lowest mandibular plane angle (20.8 degrees +/- 4.9 degrees ) constituted the low-angle group, while the 20 cases with the highest mandibular plane angle (43.0 degrees +/- 4.0 degrees ) represented the high-angle group. Lateral cephalograms were taken on 6 occasions: immediately before surgery, immediately after surgery, 2 and 6 months after surgery, and 1 and 3 years after surgery. Results demonstrated that the high-angle and low-angle groups had different patterns of surgical and postoperative changes. High-angle patients were associated with both a higher frequency and a greater magnitude of horizontal relapse. While 95% of the total relapse took place during the first 2 months after surgery in the low-angle group, high-angle patients demonstrated a more continuous relapse pattern, with a significant proportion (38%) occurring late in the follow-up period. Possible reasons for the different postsurgical response are discussed.

  3. Towards weighing individual atoms by high-angle scattering of electrons

    Energy Technology Data Exchange (ETDEWEB)

    Argentero, G.; Mangler, C.; Kotakoski, J.; Eder, F.R.; Meyer, J.C., E-mail: Jannik.Meyer@univie.ac.at

    2015-04-15

    We consider theoretically the energy loss of electrons scattered to high angles when assuming that the primary beam can be limited to a single atom. We discuss the possibility of identifying the isotopes of light elements and of extracting information about phonons in this signal. The energy loss is related to the mass of the much heavier nucleus, and is spread out due to atomic vibrations. Importantly, while the width of the broadening is much larger than the energy separation of isotopes, only the shift in the peak positions must be detected if the beam is limited to a single atom. We conclude that the experimental case will be challenging but is not excluded by the physical principles as far as considered here. Moreover, the initial experiments demonstrate that the separation of gold and carbon based on a signal that is related to their mass, rather than their atomic number. - Highlights: • We explore how energy loss spectroscopy could be used to obtain information about the mass, rather than the charge, of atoms. • The dose and precision that would be needed to distinguish between the two isotopes of carbon, C12 and C13, is estimated. • Signal broadening due to phonons is included in the calculation. • Initial experiments show the separation between gold and carbon based on their mass rather than charge.

  4. Dynamic surface measurements on a model helicopter rotor during blade slap at high angles of attack

    Science.gov (United States)

    Hubbard, J. E., Jr.; Harris, W. L.

    1982-01-01

    The modern helicopter offers a unique operational capability to both the public and private sectors. However, the use of the helicopter may become severely limited due to the radiated noise generated by the rotor system. A description is presented of some of the experimental results obtained with a model helicopter rotor in an anechoic wind tunnel with regard to blade stall as a source mechanism of blade slap. Attention is given to dynamic rotor blade surface phenomena and the resulting far field impulsive noise from the model helicopter rotor at high angles of attack and low tip speed. The results of the investigation strongly implicates the boundary layer as playing an important role in blade slap due to blade/vortex interaction (BVI) in a highly loaded rotor. Intermittent stall cannot be ruled out as a possible source mechanism for blade slap. This implies that blade surface characteristics, airfoil shape and local Reynolds number may now be used as tools to reduce the resultant far-field sound pressure levels in helicopters.

  5. Bifurcation analysis and stability design for aircraft longitudinal motion with high angle of attack

    Institute of Scientific and Technical Information of China (English)

    Xin Qi; Shi Zhongke

    2015-01-01

    Bifurcation analysis and stability design for aircraft longitudinal motion are investigated when the nonlinearity in flight dynamics takes place severely at high angle of attack regime. To pre-dict the special nonlinear flight phenomena, bifurcation theory and continuation method are employed to systematically analyze the nonlinear motions. With the refinement of the flight dynam-ics for F-8 Crusader longitudinal motion, a framework is derived to identify the stationary bifurca-tion and dynamic bifurcation for high-dimensional system. Case study shows that the F-8 longitudinal motion undergoes saddle node bifurcation, Hopf bifurcation, Zero-Hopf bifurcation and branch point bifurcation under certain conditions. Moreover, the Hopf bifurcation renders ser-ies of multiple frequency pitch oscillation phenomena, which deteriorate the flight control stability severely. To relieve the adverse effects of these phenomena, a stabilization control based on gain scheduling and polynomial fitting for F-8 longitudinal motion is presented to enlarge the flight envelope. Simulation results validate the effectiveness of the proposed scheme.

  6. High angle of attack: Forebody flow physics and design emphasizing directional stability

    Science.gov (United States)

    Ravi, R.

    A framework for understanding the fundamental physics of flowfields over forebody type shapes at low speed, high angle of attack conditions with special emphasis on sideslip has been established. Computational Fluid Dynamics (CFD) has been used to study flowfieids over experimentally investigated forebodies: the Lamont tangent-ogive forebody, the F-5A forebody and the Erickson chine forebody. A modified version of a current advanced code, CFL3D, was used to solve the Euler and thin-layer Navier-Stokes equations. The Navier-Stokes equations used a form of the Baldwin-Lomax turbulence model modified to account for massive crossflow separation. Using the insight provided by the solutions obtained using CFD, together with comparison with limited available data, the aerodynamics of forebodies with positive directional stability has been revealed. An unconventional way of presenting the results is used to illustrate how a positive contribution to directional stability arises. Based on this new understanding, a parametric study was then conducted to determine which shapes promote a positive contribution to directional stability. The effect of cross-sectional shape on directional stability was found to be very significant. Broad chine-shaped cross-sections were found to promote directional stability. Also, directional stability is improved if the chine is placed closer to the top of the cross-section. Planform shapes also played an important role in determining the forebody directional stability characteristics. This initial parametric study has been used to propose some guidelines for aerodynamic design to promote positive directional stability.

  7. Effect of Annular Slit Geometry on Characteristics of Spiral Jet

    Institute of Scientific and Technical Information of China (English)

    Shigeru Matsuo; Kwon-Hee Lee; Shinsuke Oda; Toshiaki Setoguchi; Heuy-Dong Kim

    2003-01-01

    A spiral flow using an annular slit connected to a conical cylinder does not need special device to generate a tangential velocity component of the flow and differs from swirling flows. Pressurized fluid is supplied to an annular chamber and injected into the convergent nozzle through the annular slit. The annular jet develops into the spiral flow. In the present study, a spiral jet discharged out of nozzle exit was obtained by using a convergent nozzle and an annular slit set in nozzle inlet, and the effect of annular slit geometry on characteristics of the spiral jet was investigated by using a Laser Doppler Velocimeter (LDV) experimentally. Furthermore, velocity distributions of the spiral jet were compared with those of a normal jet.

  8. Limited Diffraction Maps for Pulsed Wave Annular Arrays

    OpenAIRE

    Fox, Paul D.

    2002-01-01

    A procedure is provided for decomposing the linear field of flat pulsed wave annular arrays into an equivalent set of known limited diffraction Bessel beams. Each Bessel beam propagates with known characteristics, enabling good insight into the propagation of annular fields to be obtained. Numerical examples are given in the context of a 10-ring annular array operating at a central frequency of 2.5 MHz in water.

  9. Granuloma annulare localized to the shaft of the penis

    DEFF Research Database (Denmark)

    Trap, R; Wiebe, B

    1993-01-01

    A case of granuloma annulare localized to the shaft of the penis is reported. The differential diagnoses are discussed. Penile granuloma annulare is a rare disorder and it is concluded that biopsies of penile lesions are recommended to verify the correct diagnosis.......A case of granuloma annulare localized to the shaft of the penis is reported. The differential diagnoses are discussed. Penile granuloma annulare is a rare disorder and it is concluded that biopsies of penile lesions are recommended to verify the correct diagnosis....

  10. Arcuate, annular, and polycyclic inflammatory and infectious lesions.

    Science.gov (United States)

    Sharma, Amit; Lambert, Phelps J; Maghari, Amin; Lambert, W Clark

    2011-01-01

    Common shapes encountered in dermatologic diseases include linear, nummular, annular, polycyclic, and arciform. The last three have a relatively restricted differential, which must be entirely explored. It is not uncommon for a single disease to present in annular, arciform or polycyclic configurations; moreover, the lesions may evolve from being arciform to annular and then become polycyclic. Regardless, recognizing the arrangement of the defect will undoubtedly help in making a diagnosis and guiding subsequent management. We explore diseases that often present in annular, arciform, and/or polycyclic forms.

  11. Granuloma annulare localized to the shaft of the penis

    DEFF Research Database (Denmark)

    Trap, R; Wiebe, B

    1993-01-01

    A case of granuloma annulare localized to the shaft of the penis is reported. The differential diagnoses are discussed. Penile granuloma annulare is a rare disorder and it is concluded that biopsies of penile lesions are recommended to verify the correct diagnosis.......A case of granuloma annulare localized to the shaft of the penis is reported. The differential diagnoses are discussed. Penile granuloma annulare is a rare disorder and it is concluded that biopsies of penile lesions are recommended to verify the correct diagnosis....

  12. Dark Matter

    Science.gov (United States)

    Lincoln, Don

    2013-01-01

    It's a dark, dark universe out there, and I don't mean because the night sky is black. After all, once you leave the shadow of the Earth and get out into space, you're surrounded by countless lights glittering everywhere you look. But for all of Sagan's billions and billions of stars and galaxies, it's a jaw-dropping fact that the ordinary kind of…

  13. Dark GPC

    Science.gov (United States)

    Bañas, Andrew R.; Villangca, Mark J.; Palima, Darwin; Glückstad, Jesper

    2016-03-01

    Generalized Phase Contrast (GPC) is an efficient method for efficiently shaping light into speckle-free contiguous optical distributions useful in diverse applications such as static beam shaping, optical manipulation and recently, for excitation in two-photon optogenetics. GPC typically results in a 3x intensified user defined input mask shape against a dark background. In this work, we emphasize GPC's capability of optimal destructive interference, normally used to create the dark background surrounding the shaped light. We also study input parameters wherein the locations of light and darkness are interchanged with respect to typical GPC output, thus resulting to a well-defined structured darkness. The conditions that give destructive interference for the output are then applied to near-arbitrary shapes. Preliminary experimental results are presented using dynamic spatial light modulator to form scaled arbitrary darkness shapes. Supporting demonstrations that reverse the light and dark regions of amplitude-modulated input are also presented as a related case of structuring destructive interference. Our analysis and experimental demonstrations show a simplified approach in the generation of extended regions of destructive interference within coherent beams.

  14. Annular lupus vulgaris mimicking tinea cruris.

    Science.gov (United States)

    Heo, Young Soo; Shin, Won Woong; Kim, Yong Ju; Song, Hae Jun; Oh, Chil Hwan

    2010-05-01

    Cutaneous tuberculosis is an infrequent form of extrapulmonary tuberculosis. It is often clinically and histopathologically confused with various cutaneous disorders. A 36-year-old man attended our clinic with slowly progressive, asymptomatic, annular skin lesions on both the thighs and buttocks for 10 years. He consulted with many physicians and was improperly treated with an oral antifungal agent for several months under the diagnosis of tinea cruris, but no resolution of his condition was observed. A diagnosis of lupus vulgaris was made based on the histopathologic examination and the polymerase chain reaction assay. Anti-tuberculosis therapy was administered and the lesions started to regress.

  15. Wave turbulence in annular wave tank

    Science.gov (United States)

    Onorato, Miguel; Stramignoni, Ettore

    2014-05-01

    We perform experiments in an annular wind wave tank at the Dipartimento di Fisica, Universita' di Torino. The external diameter of the tank is 5 meters while the internal one is 1 meter. The tank is equipped by two air fans which can lead to a wind of maximum 5 m/s. The present set up is capable of studying the generation of waves and the development of wind wave spectra for large duration. We have performed different tests including different wind speeds. For large wind speed we observe the formation of spectra consistent with Kolmogorv-Zakharov predictions.

  16. Annular Lupus Vulgaris Mimicking Tinea Cruris

    Science.gov (United States)

    Heo, Young Soo; Shin, Won Woong; Kim, Yong Ju; Song, Hae Jun

    2010-01-01

    Cutaneous tuberculosis is an infrequent form of extrapulmonary tuberculosis. It is often clinically and histopathologically confused with various cutaneous disorders. A 36-year-old man attended our clinic with slowly progressive, asymptomatic, annular skin lesions on both the thighs and buttocks for 10 years. He consulted with many physicians and was improperly treated with an oral antifungal agent for several months under the diagnosis of tinea cruris, but no resolution of his condition was observed. A diagnosis of lupus vulgaris was made based on the histopathologic examination and the polymerase chain reaction assay. Anti-tuberculosis therapy was administered and the lesions started to regress. PMID:20548922

  17. Tank evaluation system shielded annular tank application

    Energy Technology Data Exchange (ETDEWEB)

    Freier, D.A.

    1988-10-04

    TEST (Tank Evaluation SysTem) is a research project utilizing neutron interrogation techniques to analyze the content of nuclear poisons and moderators in tank shielding. TEST experiments were performed on an experimental SAT (Shielded Annular Tank) at the Rocky Flats Plant. The purpose of these experiments was threefold: (1) to assess TEST application to SATs, (2) to determine if Nuclear Safety inspection criteria could be met, and (3) to perform a preliminary calibration of TEST for SATs. Several experiments were performed, including measurements of 11 tank shielding configurations, source-simulated holdup experiments, analysis of three detector modes, resolution studies, and TEST scanner geometry experiments. 1 ref., 21 figs., 4 tabs.

  18. Finite stretching of an annular plate.

    Science.gov (United States)

    Biricikoglu, V.; Kalnins, A.

    1971-01-01

    The problem of the finite stretching of an annular plate which is bonded to a rigid inclusion at its inner edge is considered. The material is assumed to be isotropic and incompressible with a Mooney-type constitutive law. It is shown that the inclusion of the effect of the transverse normal strain leads to a rapid variation in thickness which is confined to a narrow edge zone. The explicit solutions to the boundary layer equations, which govern the behavior of the plate near the edges, are presented.

  19. Annular and semicircular lipoatrophies. Report of three cases and review of the literature.

    Science.gov (United States)

    Rongioletti, F; Rebora, A

    1989-03-01

    Two cases of semicircular lipoatrophy and one of annular lipoatrophy are presented. The reasons why semicircular lipoatrophy, annular lipoatrophy, and annular atrophy of the ankles seem to be different clinical entities are discussed.

  20. Annular and Total Solar Eclipses of 2010

    Science.gov (United States)

    Espenak, Fred; Anderson, J.

    2008-01-01

    While most NASA eclipse bulletins cover a single eclipse, this publication presents predictions for two solar eclipses during 2010. This has required a different organization of the material into the following sections. Section 1 -- Eclipse Predictions: The section consists of a general discussion about the eclipse path maps, Besselian elements, shadow contacts, eclipse path tables, local circumstances tables, and the lunar limb profile. Section 2 -- Annular Solar Eclipse of 2010 Ja n 15: The section covers predictions and weather prospects for the annular eclipse. Section 3 -- Total Solar Eclipse of 2010 Jul 11: The se ction covers predictions and weather prospects for the total eclipse. Section 4 -- Observing Eclipses: The section provides information on eye safety, solar filters, eclipse photography, and making contact timings from the path limits. Section 5 -- Eclipse Resources: The final section contains a number of resources including information on the IAU Working Group on Eclipses, the Solar Eclipse Mailing List, the NASA eclipse bulletins on the Internet, Web sites for the two 2010 eclipses, and a summary identifying the algorithms, ephemerides, and paramete rs used in the eclipse predictions.

  1. Signatures of an annular Fermi sea

    Science.gov (United States)

    Jo, Insun; Liu, Yang; Pfeiffer, L. N.; West, K. W.; Baldwin, K. W.; Shayegan, M.; Winkler, R.

    2017-01-01

    The concept of a Fermi surface, the constant-energy surface containing all the occupied electron states in momentum, or wave-vector (k ) , space plays a key role in determining electronic properties of conductors. In two-dimensional (2D) carrier systems, the Fermi surface becomes a contour which, in the simplest case, encircles the occupied states. In this case, the area enclosed by the contour, which we refer to as the Fermi sea (FS), is a simple disk. Here we report the observation of an FS with a new topology, namely, an FS in the shape of an annulus. Such an FS is expected in a variety of 2D systems where the energy band dispersion supports a ring of extrema at finite k , but its experimental observation has been elusive. Our study provides (1) theoretical evidence for the presence of an annular FS in 2D hole systems confined to wide GaAs quantum wells and (2) experimental signatures of the onset of its occupation as an abrupt rise in the sample resistance, accompanied by a sudden appearance of Shubnikov-de Haas oscillations at an unexpectedly high frequency whose value does not simply correspond to the (negligible) density of holes contained within the annular FS.

  2. Limited Diffraction Maps for Pulsed Wave Annular Arrays

    DEFF Research Database (Denmark)

    Fox, Paul D.

    2002-01-01

    A procedure is provided for decomposing the linear field of flat pulsed wave annular arrays into an equivalent set of known limited diffraction Bessel beams. Each Bessel beam propagates with known characteristics, enabling good insight into the propagation of annular fields to be obtained...

  3. Effect of annular secondary conductor in a linear electromagnetic stirrer

    Indian Academy of Sciences (India)

    R Madhavan; V Ramanarayanan

    2008-10-01

    This paper presents the variation of average axial force density in the annular secondary conductor of a linear electromagnetic stirrer. Different geometries of secondaries are considered for numerical and experimental validation namely, 1. hollow annular ring, 2. annular ring with a solid cylinder and 3. solid cylinder. Experimental and numerical simulations are performed for a 2-pole in house built 15 kW linear electromagnetic stirrer (EMS). It is observed for a supply current of 200 A at 30 Hz the force densities in the hollow annular ring is 67% higher than the equivalent solid cylinder. The same values are 33% for annular ring with a solid cylinder. Force density variation with supply frequency and current are also reported. Numerical simulations using finite element model are validated with experimental results.

  4. Vortex beam based more stable annular laser guide star

    Science.gov (United States)

    Luo, Ruiyao; Cui, Wenda; Li, Lei; Sun, Quan; He, Yulong; Wang, Hongyan; Ning, Yu; Xu, Xiaojun

    2016-11-01

    We present an annular laser guide star (LGS) concept for large ground-based telescopes in this paper. The more stable annular LGS is generated by turbulence-resisted vortex beam. In the uplink, a vortex beam tends to wander more slightly than a Gaussian beam does in atmospheric turbulence. This may enable an annular LGS to wander more slightly than a traditional Gaussian beam generated LGS does, which would ease the burden of uplink tip-tilt mirror and benefit a dynamical closed-loop adaptive optics system. We conducted numerical simulation to validate the feasibility of this concept. And we have gotten 31% reduced variance of spot wandering of annular LGS. Besides, we set up a spatial light modulator based laser guide star simulator for beam propagation in turbulent atmosphere to experimentally test the annular LGS concept. Preliminary experimental results are given. To the best of our knowledge, it is the first time this concept is formulated.

  5. Dark Energy

    CERN Document Server

    Kesavan, Aruna

    2009-01-01

    Dark energy is one of the mysteries of modern science. It is unlike any known form of matter or energy and has been detected so far only by its gravitational effect of repulsion. Owing to its effects being discernible only at very very large distance scales, dark energy was only detected at the turn of the last century when technology had advanced enough to observe a greater part of the universe in finer detail. The aim of the report is to gain a better understanding of the mysterious dark energy. To this end, both theoretical methods and observational evidence are studied. Three lines of evidence, namely , the redshift data of type Ia supernovae, estimates of the age of the universe by various methods, and the anisotropies in the cosmic background radiation, build the case for existence of dark energy. The supernova data indicate that the expansion of the universe is accelerating. The ages of the oldest star clusters in the universe indicate that the universe is older than previously thought to be. The aniso...

  6. Trauma-related papular granuloma annular.

    Science.gov (United States)

    Hu, Stephanie W; Kaplan, Jennifer; Patel, Rishi R; Kamino, Hideko

    2013-12-16

    Granuloma annulare (GA) is a benign, granulomatous disease with several clinical manifestations, which include localized, generalized, perforating, subcutaneous, patch, papular, and linear forms. We report a case of papular GA of the dorsal aspects of the hands that arose after repeated, direct trauma to the site of subsequent involvement. Although multiple etiologies for GA have been proposed, which include ultraviolet light, arthropod bites, trauma, tuberculin skin tests, viral infections, and PUVA photochemotherapy, the underlying pathogenesis of the disorder remains unclear. However, owing to the key histopathologic findings of focal collagen and elastic fiber degeneration and mucin deosition in GA, it is not surprising that cutaneous trauma may have played a role in connective tissue injury, subsequent degeneration, and the production of a granulomatous response with increased mucin deposition.

  7. Annular nanoantenna on fibre micro-axicon.

    Science.gov (United States)

    Grosjean, T; Fahys, A; Suarez, M; Charraut, D; Salut, R; Courjon, D

    2008-02-01

    In this paper, we propose to extend the concept of loop antenna to the optical domain. The aim is to develop a new generation of optical nanocollectors that are sensitive to specific electric or magnetic vectorial field components. For validating our approach, a preliminary one-micron-diameter gold nanoring is micromachined on the apex of a cone lens obtained from a tapered optical fibre. It is shown that such a nano-object behaves as a nano-antenna able to detect the longitudinal electric field from a Bessel beam in radial polarization and the longitudinal magnetic component from a Bessel beam in azimuthal polarization. In the latter case, the annular nano-antenna exhibits the properties of an optical inductance.

  8. Recurrent Annular Peripheral Choroidal Detachment after Trabeculectomy

    Science.gov (United States)

    Liu, Shaohui; Sun, Lisa L.; Kavanaugh, A. Scott; Langford, Marlyn P.; Liang, Chanping

    2013-01-01

    We report a challenging case of recurrent flat anterior chamber without hypotony after trabeculectomy in a 54-year-old Black male with a remote history of steroid-treated polymyositis, cataract surgery, and uncontrolled open angle glaucoma. The patient presented with a flat chamber on postoperative day 11, but had a normal fundus exam and intraocular pressure (IOP). Flat chamber persisted despite treatment with cycloplegics, steroids, and a Healon injection into the anterior chamber. A transverse B-scan of the peripheral fundus revealed a shallow annular peripheral choroidal detachment. The suprachoroidal fluid was drained. The patient presented 3 days later with a recurrent flat chamber and an annular peripheral choroidal effusion. The fluid was removed and reinforcement of the scleral flap was performed with the resolution of the flat anterior chamber. A large corneal epithelial defect developed after the second drainage. The oral prednisone was tapered quickly and the topical steroid was decreased. One week later, his vision decreased to count fingers with severe corneal stromal edema and Descemet's membrane folds that improved to 20/50 within 24 h of resumption of the oral steroid and frequent topical steroid. The patient's visual acuity improved to 20/20 following a slow withdrawal of the oral and topical steroid. Eight months after surgery, the IOP was 15 mm Hg without glaucoma medication. The detection of a shallow anterior choroidal detachment by transverse B-scan is critical to making the correct diagnosis. Severe cornea edema can occur if the steroid is withdrawn too quickly. Thus, steroids should be tapered cautiously in steroid-dependent patients. PMID:24348402

  9. Recurrent Annular Peripheral Choroidal Detachment after Trabeculectomy

    Directory of Open Access Journals (Sweden)

    Shaohui Liu

    2013-10-01

    Full Text Available We report a challenging case of recurrent flat anterior chamber without hypotony after trabeculectomy in a 54-year-old Black male with a remote history of steroid-treated polymyositis, cataract surgery, and uncontrolled open angle glaucoma. The patient presented with a flat chamber on postoperative day 11, but had a normal fundus exam and intraocular pressure (IOP. Flat chamber persisted despite treatment with cycloplegics, steroids, and a Healon injection into the anterior chamber. A transverse B-scan of the peripheral fundus revealed a shallow annular peripheral choroidal detachment. The suprachoroidal fluid was drained. The patient presented 3 days later with a recurrent flat chamber and an annular peripheral choroidal effusion. The fluid was removed and reinforcement of the scleral flap was performed with the resolution of the flat anterior chamber. A large corneal epithelial defect developed after the second drainage. The oral prednisone was tapered quickly and the topical steroid was decreased. One week later, his vision decreased to count fingers with severe corneal stromal edema and Descemet's membrane folds that improved to 20/50 within 24 h of resumption of the oral steroid and frequent topical steroid. The patient's visual acuity improved to 20/20 following a slow withdrawal of the oral and topical steroid. Eight months after surgery, the IOP was 15 mm Hg without glaucoma medication. The detection of a shallow anterior choroidal detachment by transverse B-scan is critical to making the correct diagnosis. Severe cornea edema can occur if the steroid is withdrawn too quickly. Thus, steroids should be tapered cautiously in steroid-dependent patients.

  10. Annular MHD Physics for Turbojet Energy Bypass

    Science.gov (United States)

    Schneider, Steven J.

    2011-01-01

    The use of annular Hall type MHD generator/accelerator ducts for turbojet energy bypass is evaluated assuming weakly ionized flows obtained from pulsed nanosecond discharges. The equations for a 1-D, axisymmetric MHD generator/accelerator are derived and numerically integrated to determine the generator/accelerator performance characteristics. The concept offers a shockless means of interacting with high speed inlet flows and potentially offers variable inlet geometry performance without the complexity of moving parts simply by varying the generator loading parameter. The cycle analysis conducted iteratively with a spike inlet and turbojet flying at M = 7 at 30 km altitude is estimated to have a positive thrust per unit mass flow of 185 N-s/kg. The turbojet allowable combustor temperature is set at an aggressive 2200 deg K. The annular MHD Hall generator/accelerator is L = 3 m in length with a B(sub r) = 5 Tesla magnetic field and a conductivity of sigma = 5 mho/m for the generator and sigma= 1.0 mho/m for the accelerator. The calculated isentropic efficiency for the generator is eta(sub sg) = 84 percent at an enthalpy extraction ratio, eta(sub Ng) = 0.63. The calculated isentropic efficiency for the accelerator is eta(sub sa) = 81 percent at an enthalpy addition ratio, eta(sub Na) = 0.62. An assessment of the ionization fraction necessary to achieve a conductivity of sigma = 1.0 mho/m is n(sub e)/n = 1.90 X 10(exp -6), and for sigma = 5.0 mho/m is n(sub e)/n = 9.52 X 10(exp -6).

  11. Characteristics of Electromagnetic Pulse Coupling into Annular Apertures

    Directory of Open Access Journals (Sweden)

    Yan-Peng Sun

    2013-11-01

    Full Text Available Electromagnetic pulse (EMP coupling into the annular apertures can disturb or damage much electronic equipment. To enhance electronic system’s  capability of anti-electromagnetic interference, the finite difference time domain method (FDTD was employed to study the characteristics of electromagnetic pulse coupling into the cavity enclosures with annular apertures. The coupling characteristics of annular apertures with different shapes (rectangle, square and circle were discussed. It shows that, in the case of the same aperture area, the coupling energy of electromagnetic pulse into the circular annular aperture is smaller than that into the rectangular and the square ones. To the rectangular annular aperture, while the polarization direction of the incident electromagnetic pulse is perpendicular to the long side of the rectangular annular aperture, the coupling energy is larger when the aspect ratio of the rectangular annular aperture is larger. The coupling effect of incident pulse with short pulse width is obviously better than the one with longer pulse width. The resonance phenomenon of the coupled waveform occurs in the cavity.

  12. AEROX: Computer program for transonic aircraft aerodynamics to high angles of attack. Volume 1: Aerodynamic methods and program users' guide

    Science.gov (United States)

    Axelson, J. A.

    1977-01-01

    The AEROX program estimates lift, induced-drag and pitching moments to high angles (typ. 60 deg) for wings and for wingbody combinations with or without an aft horizontal tail. Minimum drag coefficients are not estimated, but may be input for inclusion in the total aerodynamic parameters which are output in listed and plotted formats. The theory, users' guide, test cases, and program listing are presented.

  13. Radiation and reflection acoustical fields of an annular phased array

    Institute of Scientific and Technical Information of China (English)

    LAI Puxiang; ZHANG Bixing; WANG Chenghao

    2007-01-01

    The characteristics of the radiation and reflection acoustical fields of an annular phased array are investigated. The effects of the element number, element radius, interelement spacing, centre frequency, focus position, and other parameters on the radiation acoustical field of the annular phased array is theoretically studied. In experiment, an annular transducer with 8 equal-area elements is designed and fabricated, and a series of experimental measurements are conducted. The radiation acoustical field and its reflection on a liquid-solid interface are theoretically and experimentally studied. The experimental result is in good agreement with the theoretical one.

  14. Multiple Scattering: Dispersion, Temperature Dependence, and Annular Pistons

    CERN Document Server

    Milton, Kimball A; Parashar, Prachi; Cavero-Pelaez, Ines; Brevik, Iver; Ellingsen, Simen A

    2010-01-01

    We review various applications of the multiple scattering approach to the calculation of Casimir forces between separate bodies, including dispersion, wedge geometries, annular pistons, and temperature dependence. Exact results are obtained in many cases.

  15. Phased annular array transducers for ultrasonic guided wave applications

    Science.gov (United States)

    Yan, Fei; Borigo, Cody; Liang, Yue; Koduru, Jaya P.; Rose, Joseph L.

    2011-04-01

    Mode and frequency control always plays an important role in ultrasonic guided wave applications. In this paper, theoretical understanding of guided wave excitations of axisymmetric sources on plate structures is established. It is shown that a wave number spectrum can be used to investigate the guided wave excitations of an axisymmetric source. The wave number spectrum is calculated from a Hankel transform of the axial source loading profile. On the basis of the theoretical understanding, phased annular array transducers are developed as a powerful tool for guided wave mode and frequency control. By applying appropriate time delays to phase the multiple elements of an annular array transducer, guided wave mode and frequency tuning can be achieved fully electronically. The phased annular array transducers have been successfully used for various applications. Example applications presented in this paper include phased annular arrays for guided wave beamforming and a novel ultrasonic vibration modal analysis technique for damage detection.

  16. Virtual cathode microwave generator having annular anode slit

    Science.gov (United States)

    Kwan, Thomas J. T.; Snell, Charles M.

    1988-01-01

    A microwave generator is provided for generating microwaves substantially from virtual cathode oscillation. Electrons are emitted from a cathode and accelerated to an anode which is spaced apart from the cathode. The anode has an annular slit therethrough effective to form the virtual cathode. The anode is at least one range thickness relative to electrons reflecting from the virtual cathode. A magnet is provided to produce an optimum magnetic field having the field strength effective to form an annular beam from the emitted electrons in substantial alignment with the annular anode slit. The magnetic field, however, does permit the reflected electrons to axially diverge from the annular beam. The reflected electrons are absorbed by the anode in returning to the real cathode, such that substantially no reflexing electrons occur. The resulting microwaves are produced with a single dominant mode and are substantially monochromatic relative to conventional virtual cathode microwave generators.

  17. Polyharmonic functions of infinite order on annular regions

    OpenAIRE

    Kounchev, Ognyan; Render, Hermann

    2013-01-01

    Polyharmonic functions $f$ of infinite order and type $\\tau$ on annular regions are systematically studied. The first main result states that the Fourier-Laplace coefficients $f_{k,l}(r)$ of a polyharmonic function $f$ of infinite order and type $0$ can be extended to analytic functions on the complex plane cut along the negative semiaxis. The second main result gives a constructive procedure via Fourier-Laplace series for the analytic extension of a polyharmonic function on annular ...

  18. Experiments on soliton motion in annular Josephson junctions

    DEFF Research Database (Denmark)

    Davidson, A.; Dueholm, B.; Pedersen, Niels Falsig

    1986-01-01

    We report here the results of an extensive experimental investigation of soliton dynamics in Josephson junctions of different annular geometries. The annular geometry is unique in that it allows for the study of undisturbed soliton motion as well as soliton–antisoliton collisons, since there are ...... for a single trapped soliton, and evidence linking the stability of the soliton to surface damping. Journal of Applied Physics is copyrighted by The American Institute of Physics....

  19. New mitral annular force transducer optimized to distinguish annular segments and multi-plane forces.

    Science.gov (United States)

    Skov, Søren Nielsen; Røpcke, Diana Mathilde; Ilkjær, Christine; Rasmussen, Jonas; Tjørnild, Marcell Juan; Jimenez, Jorge H; Yoganathan, Ajit P; Nygaard, Hans; Nielsen, Sten Lyager; Jensen, Morten Olgaard

    2016-03-21

    Limited knowledge exists about the forces acting on mitral valve annuloplasty repair devices. The aim of this study was to develop a new mitral annular force transducer to measure the forces acting on clinically used mitral valve annuloplasty devices. The design of an X-shaped transducer in the present study was optimized for simultaneous in- and out-of-plane force measurements. Each arm was mounted with strain gauges on four circumferential elements to measure out-of-plane forces, and the central parts of the X-arms were mounted with two strain gauges to measure in-plane forces. A dedicated calibration setup was developed to calibrate isolated forces with tension and compression for in- and out-of-plane measurements. With this setup, it was possible with linear equations to isolate and distinguish measured forces between the two planes and minimize transducer arm crosstalk. An in-vitro test was performed to verify the crosstalk elimination method and the assumptions behind it. The force transducer was implanted and evaluated in an 80kg porcine in-vivo model. Following crosstalk elimination, in-plane systolic force accumulation was found to be in average 4.0±0.1N and the out-of-plane annular segments experienced an average force of 1.4±0.4N. Directions of the systolic out-of-plane forces indicated movements towards a saddle shaped annulus, and the transducer was able to measure independent directional forces in individual annular segments. Further measurements with the new transducer coupled with clinical annuloplasty rings will provide a detailed insight into the biomechanical dynamics of these devices.

  20. Solar cycle modulation of Southern Annular Mode

    Science.gov (United States)

    Kuroda, Yuhji

    2016-04-01

    Climate is known to be affected by various factors, including oceanic changes and volcanic eruptions. 11-year solar cycle change is one of such important factors. Observational analysis shows that the winter-mean North Atlantic Oscillation (NAO) and late-winter/spring Southern Annular Mode (SAM) show structural modulation associated with 11-year solar cycle. In fact, these signals tend to extend from surface to upper stratosphere and persistent longer period only in the High Solar (HS) years. In the present study, we used 35-year record of ERA-Interim reanalysis data and performed wave-energy and momentum analysis on the solar-cycle modulation of the SAM to examine key factors to create such solar-SAM relationship. It is found that enhanced wave-mean flow interaction tends to take place in the middle stratosphere in association with enhanced energy input from diabatic heating on September only in HS years. The result suggests atmospheric and solar conditions on September are keys to create solar-SAM relationship.

  1. Impulsively started, steady and pulsated annular inflows

    Science.gov (United States)

    Abdel-Raouf, Emad; Sharif, Muhammad A. R.; Baker, John

    2017-04-01

    A computational investigation was carried out on low Reynolds number laminar inflow starting annular jets using multiple blocking ratios and atmospheric ambient conditions. The jet exit velocity conditions are imposed as steady, unit pulsed, and sinusoidal pulsed while the jet surroundings and the far-field jet inlet upstream conditions are left atmospheric. The reason is to examine the flow behavior in and around the jet inlet under these conditions. The pulsation mode behavior is analyzed based on the resultant of the momentum and pressure forces at the entry of the annulus, the circulation and vortex formation, and the propulsion efficiency of the inflow jets. The results show that under certain conditions, the net force of inflow jets (sinusoidal pulsed jets in particular) could point opposite to the flow direction due to the adverse pressure drops in the flow. The propulsion efficiency is also found to increase with pulsation frequency and the sinusoidal pulsed inflow jets are more efficient than the unit pulsed inflow jets. In addition, steady inflow jets did not trigger the formation of vortices, while unit and sinusoidal pulsed inflow jets triggered the formation of vortices under a certain range of frequencies.

  2. Sonographic evaluation of digital annular pulley tears

    Energy Technology Data Exchange (ETDEWEB)

    Martinoli, C.; Derchi, L.E. [Istituto di Radiologia, Universita di Genova, Genoa (Italy); Bianchi, S.; Garcia, J.F. [Dept. de Radiologie, Hopital Cantonal Universitaire de Geneve (Switzerland); Nebiolo, M. [Reparto Pronto Soccorso Medico, Pietra Ligure (Italy)

    2000-07-01

    Objective. To evaluate the sonographic (US) appearance of digital annular pulley (DAP) tears in high-level rock climbers. Design and patients. We performed a retrospective analysis of the US examinations of 16 high-level rock climbers with clinical signs of DAP lesions. MRI and surgical evaluation were performed in five and three patients respectively. The normal US and MRI appearances of DAP were evaluated in 40 and three normal fingers respectively. Results. Nine of 16 patients presented a DAP tear. In eight subjects (seven with complete tears involving the fourth finger and one the fifth finger), US diagnosis was based on the indirect sign of volar bowstringing of the flexor tendons. Injured pulleys were not appreciated by US. Tears concerned the A2 and A3 in six patients and the A3 and A4 in two patients. A2 pulley thickening and hypoechogenicity compatible with a partial tear was demonstrated in one patient. MRI and surgical data correlated well with the US findings. Four patients had tenosynovitis of the flexor tendons but no evidence of pulley disruption. US examinations of three patients were normal. In the healthy subjects US demonstrated DAP in 16 of 40 digits. Conclusion. US can diagnose DAP tears and correlates with the MRI and surgical data. Because of its low cost and non-invasiveness we suggest US as the first imaging modality in the evaluation of injuries of the digital pulley. (orig.)

  3. Vibration of an eccentrically clamped annular plate

    Science.gov (United States)

    Tseng, J.-G.; Wickert, J. A.

    1994-04-01

    Small amplitude vibration of an eccentric annular plate, which is free along its outer edge and clamped along the interior, is investigated through experimental and analytical methods. A disk with this geometry, or a stacked array in which the clamping and symmetry axes of each disk are nominally coincident, is common in data storage and brake systems applications. In the present case, the geometric imperfections on the boundary can have important implications for the disk's dynamic response. Changes that occur in the natural frequency spectrum, the mode shapes, and the free response under eccentric mounting are studied through laboratory measurements and an approximate discrete model of the plate. The natural frequencies and modes are found through global discretization of the Kamke quotient for a classical thin plate. For the axisymmetric geometry, the natural frequencies of the sine and cosine vibration modes for a specified number of nodal diameters are repeated. With increasing eccentricity, on the other hand, each pair of repeated frequencies splits at a rate that depends on the number of nodal diameters. Over a range of clamping and eccentricity ratios, the model's predictions are compared to the measured results.

  4. Dark Tourism

    OpenAIRE

    Bali-Hudáková, Lenka

    2008-01-01

    This thesis is focused on the variability of the demand and the development of new trends in the fields of the tourism industry. Special attention is devoted to a new arising trend of the Dark Tourism. This trend has appeared in the end of the 20th century and it has gained the attraction of media, tourists, tourism specialists and other stakeholders. First part of the thesis is concerned with the variety of the tourism industry and the ethic question of the tourism development. The other par...

  5. Dark Tourism

    OpenAIRE

    Bali-Hudáková, Lenka

    2008-01-01

    This thesis is focused on the variability of the demand and the development of new trends in the fields of the tourism industry. Special attention is devoted to a new arising trend of the Dark Tourism. This trend has appeared in the end of the 20th century and it has gained the attraction of media, tourists, tourism specialists and other stakeholders. First part of the thesis is concerned with the variety of the tourism industry and the ethic question of the tourism development. The other par...

  6. Dark Web

    CERN Document Server

    Chen, Hsinchun

    2012-01-01

    The University of Arizona Artificial Intelligence Lab (AI Lab) Dark Web project is a long-term scientific research program that aims to study and understand the international terrorism (Jihadist) phenomena via a computational, data-centric approach. We aim to collect "ALL" web content generated by international terrorist groups, including web sites, forums, chat rooms, blogs, social networking sites, videos, virtual world, etc. We have developed various multilingual data mining, text mining, and web mining techniques to perform link analysis, content analysis, web metrics (technical

  7. X-ray diffraction from bone employing annular and semi-annular beams.

    Science.gov (United States)

    Dicken, A J; Evans, J P O; Rogers, K D; Stone, N; Greenwood, C; Godber, S X; Prokopiou, D; Clement, J G; Lyburn, I D; Martin, R M; Zioupos, P

    2015-08-07

    There is a compelling need for accurate, low cost diagnostics to identify osteo-tissues that are associated with a high risk of fracture within an individual. To satisfy this requirement the quantification of bone characteristics such as 'bone quality' need to exceed that provided currently by densitometry. Bone mineral chemistry and microstructure can be determined from coherent x-ray scatter signatures of bone specimens. Therefore, if these signatures can be measured, in vivo, to an appropriate accuracy it should be possible by extending terms within a fracture risk model to improve fracture risk prediction.In this preliminary study we present an examination of a new x-ray diffraction technique that employs hollow annular and semi-annular beams to measure aspects of 'bone quality'. We present diffractograms obtained with our approach from ex vivo bone specimens at Mo Kα and W Kα energies. Primary data is parameterized to provide estimates of bone characteristics and to indicate the precision with which these can be determined.

  8. On the mixing enhancement in annular flows

    Science.gov (United States)

    Moradi, H. V.; Floryan, J. M.

    2017-02-01

    The potential for mixing enhancement associated with the use of axisymmetric ribs in annular flows has been analyzed. The enhancement relies on the use of streamwise vortices produced by the centrifugal instability. Conditions leading to the formation of such vortices have been established for a wide range of geometric parameters of interest using linear stability theory. It has been demonstrated that vortices can be formed only in the presence of ribs with O(1) wavelengths. Slopes of the bounding walls in the case of the long wavelength ribs are too small to create centrifugal forces sufficient for flow destabilization. In the case of short wavelength ribs, the slopes become excessively large, resulting in the stream moving away from the wall and becoming rectilinear and, thus, reducing the magnitude of the centrifugal force field. It has been shown that decreasing the annulus' radius reduces the critical Reynolds number when ribs are placed at the inner cylinder but increases when the ribs are placed at the outer cylinder. The onset of the shear-driven instability has been investigated as the resulting travelling waves may interfere with the formation of vortices. It has been shown that the axisymmetric waves play the critical role for annuli with large radii while the spiral waves play the critical role for annuli with small radii. The ribs always reduce the critical Reynolds number for the travelling waves when compared with the onset conditions for smooth annuli. The conduit geometries giving preference to the formation of vortices while avoiding creation of the travelling waves have been identified. It is demonstrated that predictions of flow characteristics determined through the analysis of sinusoidal ribs provide a good approximation of the flow response to ribs of arbitrary shape.

  9. Far-field Diffraction Properties of Annular Walsh Filters

    Directory of Open Access Journals (Sweden)

    Pubali Mukherjee

    2013-01-01

    Full Text Available Annular Walsh filters are derived from the rotationally symmetric annular Walsh functions which form a complete set of orthogonal functions that take on values either +1 or −1 over the domain specified by the inner and outer radii of the annulus. The value of any annular Walsh function is taken as zero from the centre of the circular aperture to the inner radius of the annulus. The three values 0, +1, and −1 in an annular Walsh function can be realized in a corresponding annular Walsh filter by using transmission values of zero amplitude (i.e., an obscuration, unity amplitude and zero phase, and unity amplitude and phase, respectively. Not only the order of the Walsh filter but also the size of the inner radius of the annulus provides an additional degree of freedom in tailoring of point spread function by using these filters for pupil plane filtering in imaging systems. In this report, we present the far-field amplitude characteristics of some of these filters to underscore their potential for effective use in several demanding applications like high-resolution microscopy, optical data storage, microlithography, optical encryption, and optical micromanipulation.

  10. Stratospheric Annular Modes Induced By Stationary Wave Forcing

    Science.gov (United States)

    Körnich, H.; Schmitz, G.

    The variability of the winter stratosphere shows distinguishable features in the north- ern and southern hemisphere. Since these differences are based on the different plan- etary waves of the underlying atmosphere, we explore the mechanism how stationary wave forcing in the troposphere can induce a stratospheric Annular Mode using a simple GCM. The model KMCM (Kühlungsborn Mechanistic Circulation Model) extends from the ground up to 60 km height and produces a reasonable winter climate. It takes into account the different large-scale wave forcings in the troposphere as prescribed pro- cesses. This allows us to examine the stratospheric Annular-Mode generation depend- ing on different wave forcings under perpetual January conditions. Principal com- ponent analysis is applied to identify the variability patterns of the geopotential and of the zonally averaged zonal wind. By this way, it is shown that the amplitude and composition of the orographic and thermal eddy forcing determines the stratospheric Annular Mode and the related downward propagation in the temperature field. Further model simplifications are introduced in order to understand the mechanism of the stratospheric AM-generation. Using a linear model version we illuminate the influence of the different wave forcing processes on the Annular Modes. Addition- ally, a constant-troposphere model is used to clarify the importance of transient and stationary waves. Finally, the Annular Mode is interpreted in terms of the dynamical coupling of the troposphere and stratosphere.

  11. Interacting Agegraphic Dark Energy

    OpenAIRE

    Wei, Hao; Cai, Rong-Gen

    2007-01-01

    A new dark energy model, named "agegraphic dark energy", has been proposed recently, based on the so-called K\\'{a}rolyh\\'{a}zy uncertainty relation, which arises from quantum mechanics together with general relativity. In this note, we extend the original agegraphic dark energy model by including the interaction between agegraphic dark energy and pressureless (dark) matter. In the interacting agegraphic dark energy model, there are many interesting features different from the original agegrap...

  12. Compositional Control of the Mixed Anion Alloys in Gallium-Free InAs/InAsSb Superlattice Materials for Infrared Sensing (Postprint)

    Science.gov (United States)

    2015-08-28

    lack ical and radients change eded to t of this produce lish this s/35 Å elength e mixed ptimize Ls were scillator e linear ery fine...transmission electron microscopy image of a Ga-free SL structure grown for the present study. The image was obtained using the high-angle annular dark-field...release (PA): distribution unlimited. Figure 4. A High-angle annular dark field transmission electron

  13. Dark energy without dark energy

    CERN Document Server

    Wiltshire, David L

    2007-01-01

    An overview is presented of a recently proposed "radically conservative" solution to the problem of dark energy in cosmology. The proposal yields a model universe which appears to be quantitatively viable, in terms of its fit to supernovae luminosity distances, the angular scale of the sound horizon in the cosmic microwave background (CMB) anisotropy spectrum, and the baryon acoustic oscillation scale. It may simultaneously resolve key anomalies relating to primordial lithium abundances, CMB ellipticity, the expansion age of the universe and the Hubble bubble feature. The model uses only general relativity, and matter obeying the strong energy condition, but revisits operational issues in interpreting average measurements in our presently inhomogeneous universe, from first principles. The present overview examines both the foundational issues concerning the definition of gravitational energy in a dynamically expanding space, the quantitative predictions of the new model and its best-fit cosmological parameter...

  14. Multifold Laser Resonator for Annular Gain Media.

    Science.gov (United States)

    Duncan, Arlene

    Available from UMI in association with The British Library. A pair of spherical mirrors enclosing an off-axis beam in a hyperboloidal ray trajectory describes a Herriott Cell. Placed inside a linear Fabry Perot resonator, a multifold laser resonator is formed. By considering this resonator when coupled to a coaxial, annular geometry, RF discharge excited CO_2 gain media in a sealed-off configuration, this thesis aims to formulate the scaling laws and characterise the main features of these devices. To help establish a design baseline and to allow the determination of practical results, the scaling laws are developed with an (arbitrary) limit on the physical size of the laser module of 100 x 10 x 10cm. Within this size, design algorithms demonstrate the limitation on scaling power to about 460W. Output beam characteristics are investigated for a range of multifold lasers to determine the effects the choice of design parameters has and the predicted TEM _{00} output expected. All incongruities are found to be primarily dependent on whether or not the beam traverses the complete Herriott Cell, but more directly on the radial gain and refractive index variations present in the gain medium. In terms of polarization, image rotation and astigmatism, the Cell has been analysed to determine the non-planar influence. Theoretical and experimental results tie in with the conclusions from the previous observations. The use of tolerance equations and a study of deviations in beam spot positions on the mirrors under misalignments illustrates; dependence on electrode dimensions; greatest sensitivity to Cell mirror tilts; and a shift in the ray envelope cross-section from circular to elliptical on all resonator adjustments. At all stages results are compared with existing multifold lasers and other lasers with similar output powers. As a whole the thesis demonstrates the potential of these lasers in the medium power range as sealed-off devices with excellent mode quality. Increased

  15. Development of microprocessor-based laser velocimeter and its application to measurement of jet exhausts and flows over missiles at high angles of attack

    Science.gov (United States)

    Harwell, K. E.; Farmer, W. M.; Hornkohl, J. O.; Stallings, E.

    1981-03-01

    During the past three years, personnel have developed a unique three-component laser velocimeter for the in situ measurement of particle and/or gas velocities in flow fields produced behind bodies at high angles of attack and in jet exhaust plumes. This report describes the development of the laser velocimeter and its subsequent application of the measurement of the velocity distribution and vortex structure in free jets and in flows over missiles at high angles of attack.

  16. Vibration Analysis of Annular Sector Plates under Different Boundary Conditions

    Directory of Open Access Journals (Sweden)

    Dongyan Shi

    2014-01-01

    Full Text Available An analytical framework is developed for the vibration analysis of annular sector plates with general elastic restraints along each edge of plates. Regardless of boundary conditions, the displacement solution is invariably expressed as a new form of trigonometric expansion with accelerated convergence. The expansion coefficients are treated as the generalized coordinates and determined using the Rayleigh-Ritz technique. This work allows a capability of modeling annular sector plates under a variety of boundary conditions and changing the boundary conditions as easily as modifying the material properties or dimensions of the plates. Of equal importance, the proposed approach is universally applicable to annular sector plates of any inclusion angles up to 2π. The reliability and accuracy of the current method are adequately validated through numerical examples.

  17. Inverted annular flow heat transfer in a natural circulation loop

    Energy Technology Data Exchange (ETDEWEB)

    Ozawa, M.; Umekawa, H.; Shiba, Y.; Yano, T. [Kansai Univ., Osaka (Japan)

    1998-07-01

    Gravity-feed reflooding experiment was conducted in a natural circulation loop of liquid nitrogen. The cooling curve of high temperature tube wall had a characteristic feature, i.e. initial rapid cooling with steam binding, relatively long-time plateau, gradual decrease with or without flow oscillation, and final drastic decrease during quenching process. Such phenomena had close relationship to the heated wall dynamics and heating power transient. To provide fundamental understanding on the present phenomena, the heat transfer data in inverted annular and dispersed flows were obtained under steady or oscillatory flow condition. The experimental data suggested that the heat transfer coefficient in the inverted annular or dispersed flow regimes is a slightly increasing function of heat flux but significantly depended on the tube diameter. The flow oscillation deteriorated heat transfer slightly in the inverted annular and dispersed flow regimes but significantly in the quenching process.

  18. Portal Annular Pancreas: A Rare and Overlooked Anomaly

    Science.gov (United States)

    Mittal, Puneet; Gupta, Ranjana; Mittal, Amit; Ahmed, Arshad

    2017-01-01

    Summary Background Portal annular pancreas is a rare pancreatic developmental anomaly which is often overlooked at imaging, and often diagnosed retrospectively when it is detected incidentally at the time of surgery. Although the anomaly itself is asymptomatic, it becomes important in cases where pancreatic resection/anastomosis is planned, because of varying ductal anatomy, risk of ductal injury and increased risk of postoperative pancreatic fistula formation. Case Report We present imaging findings in a case of portal annular pancreas in a 45-year-old male patient. Conclusions Portal annular pancreas is a rare and often neglected pancreatic anomaly due to a lack of awareness of this entity. With the advent of MDCT and MRI, accurate preoperative diagnosis of this condition is possible.

  19. Annular lupus vulgaris: an unusual case undiagnosed for five years.

    Science.gov (United States)

    Gönül, Müzeyyen; Kiliç, Arzu; Külcü Cakmak, Seray; Gül, Ulker; Koçak, Oğuzhan; Demiriz, Murat

    2007-01-01

    Tuberculosis is still a serious problem in both developing and developed countries. It is often confused with various cutaneous disorders both clinically and histopathologically.A 46-year-old woman attended our clinic with progressive, asymptomatic, annular skin lesions on her right upper extremity for 5 years. She had received many different therapies for these lesions at other institutions previously but these medications were not effective and the lesions deteriorated. On dermatological examination, well-demarcated, irregular bordered, violaceous colored, elevated and crusted annular lesions on her right hand dorsum and forearm were observed. She was diagnosed as having lupus vulgaris clinically and histopathologically. Antituberculosis therapy was administered and regression of the lesions started in the second week of medication.We report a case of long-standing, undiagnosed and uncommon, annular form of lupus vulgaris. We want to stress that clinical and histopathological findings are still important for the diagnosis of cutaneous tuberculosis.

  20. High-angle triple-axis specimen holder for three-dimensional diffraction contrast imaging in transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hata, S., E-mail: hata.satoshi.207@m.kyushu-u.ac.jp [Department of Electrical and Materials Science, Kyushu University, Kasuga, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Miyazaki, H. [Mel-Build, Nishi-ku, Fukuoka 819-0052 (Japan); Miyazaki, S. [FEI Company Japan Ltd., Minato-ku, Tokyo 108-0075 (Japan); Mitsuhara, M. [Department of Electrical and Materials Science, Kyushu University, Kasuga, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Tanaka, M.; Kaneko, K.; Higashida, K. [Department of Materials Science and Engineering, Kyushu University, Nishi-ku, Fukuoka 819-0395 (Japan); Ikeda, K.; Nakashima, H. [Department of Electrical and Materials Science, Kyushu University, Kasuga, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Matsumura, S. [Department of Applied Physics and Nuclear Engineering, Kyushu University, Nishi-ku, Fukuoka 819-0395 (Japan); Barnard, J.S. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Sharp, J.H. [Department of Materials Science and Engineering, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD (United Kingdom); Midgley, P.A. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)

    2011-07-15

    Electron tomography requires a wide angular range of specimen-tilt for a reliable three-dimensional (3D) reconstruction. Although specimen holders are commercially available for tomography, they have several limitations, including tilting capability in only one or two axes at most, e.g. tilt-rotate. For amorphous specimens, the image contrast depends on mass and thickness only and the single-tilt holder is adequate for most tomographic image acquisitions. On the other hand, for crystalline materials where image contrast is strongly dependent on diffraction conditions, current commercially available tomography holders are inadequate, because they lack tilt capability in all three orthogonal axes needed to maintain a constant diffraction condition over the whole tilt range. We have developed a high-angle triple-axis (HATA) tomography specimen holder capable of high-angle tilting for the primary horizontal axis with tilting capability in the other (orthogonal) horizontal and vertical axes. This allows the user to trim the specimen tilt to obtain the desired diffraction condition over the whole tilt range of the tomography series. To demonstrate its capabilities, we have used this triple-axis tomography holder with a dual-axis tilt series (the specimen was rotated by 90{sup o} ex-situ between series) to obtain tomographic reconstructions of dislocation arrangements in plastically deformed austenitic steel foils. -- Highlights: {yields} A double tilt-rotate specimen holder for diffraction contrast imaging in electron tomography. {yields} Precise alignment of a diffraction condition for tilt-series acquisition of TEM/STEM images. {yields} Complete visualization of 3D dislocation arrangements by dual-axis STEM tomography.

  1. Light Dark Matter and Dark Radiation

    CERN Document Server

    Heo, Jae Ho

    2015-01-01

    The light dark matter particles freeze out after neutrino decoupling. If the dark matter particle couples to neutrino or electromagnetic plasma, the late time entropy production by dark matter annihilations can change the neutrino-to-photon temperature ratio, and equally effective number of neutrinos. We study the effect of dark matter annihilations in the thermal equilibrium approximation and non-equilibrium method (freeze-out mechanism), and constrain both results with Planck observations. We demonstrate that the bound of dark matter mass and the possibility of the existence of extra radiation particles are more tightly constrained in the non-equilibrium method.

  2. Enhanced spontaneous emission rate in annular plasmonic nanocavities

    Science.gov (United States)

    Kroekenstoel, E. J. A.; Verhagen, E.; Walters, R. J.; Kuipers, L.; Polman, A.

    2009-12-01

    The spontaneous emission rate of erbium ions is enhanced by coupling to localized plasmonic resonances in subwavelength annular apertures in a Au film. The Er3+ ions, embedded in SiO2, are selectively located inside the apertures. The annular apertures act as nanocavities, enhancing the local density of optical states at the Er emission wavelength of 1.54 μm when the cavities are tuned to that wavelength. We show that this leads to an eightfold increase of the photoluminescence intensity, in conjunction with a 2.4-fold enhancement of the spontaneous emission rate.

  3. Annular elastolytic giant cell granuloma in association with Hashimoto's thyroiditis

    Directory of Open Access Journals (Sweden)

    Rishi Hassan

    2016-01-01

    Full Text Available Annular elastolytic giant cell granuloma (AEGCG is a rare granulomatous skin disease characterized clinically by annular plaques with elevated borders and atrophic centers found mainly on sun-exposed skin and histologically by diffuse granulomatous infiltrates composed of multinucleated giant cells, histiocytes and lymphocytes in the dermis along with phagocytosis of elastic fibers by multinucleated giant cells. We report a case of AEGCG in a 50-year-old woman and is highlighted for the classical clinical and histological findings of the disease and its rare co-existence with Hashimoto's thyroiditis.

  4. Polarization-independent waveguiding with annular photonic crystals.

    Science.gov (United States)

    Cicek, Ahmet; Ulug, Bulent

    2009-09-28

    A linear waveguide in an annular photonic crystal composed of a square array of annular dielectric rods in air is demonstrated to guide transverse electric and transverse magnetic modes simultaneously. Overlapping of the guided bands in the full band gap of the photonic crystal is shown to be achieved through an appropriate set of geometric parameters. Results of Finite-Difference Time-Domain simulations to demonstrate polarization-independent waveguiding with low loss and wavelength-order confinement are presented. Transmission through a 90 degrees bend is also demonstrated.

  5. Mathematical Model of Combustion in Blunt Annular Ceramic Burner

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The computer simulation of the combustion process in blast furnace (BF) stove has been studied by using the k-ε-g turbulent diffusion flame model. The combustion process in blunt annular ceramic burner was calculated by using the software. The profiles of gas and air velocity, temperature of the combustion products, concentration of the components, and the shape and length of the flame during combustion have been researched . Compared with the original annular ceramic burner, the new design of the blunt one improves the mixing of the gas and the air significantly, and shortened the length of the flame.

  6. Mitral-aortic annular enlargement: modification of Manouguian's technique

    Directory of Open Access Journals (Sweden)

    Costa Mario Gesteira

    2002-01-01

    Full Text Available We hereby present a technical modification for mitral-aortic annular enlargement. The mitral valve is replaced through the retro-septal approach, avoiding patches for left atrial roof closure. We report a mitral-aortic valve replacement in a patient whose original annuli would preclude adequate prostheses. The simultaneous annular enlargement may be necessary for avoiding patient-prosthesis mismatch and for reconstructing destroyed mitral and aortic annuli. The technique may minimize the risk of bleeding and of paravalvular leakage, using an approach well known to cardiac surgeons.

  7. Multi-functional annular fairing for coupling launch abort motor to space vehicle

    Science.gov (United States)

    Camarda, Charles J. (Inventor); Scotti, Stephen J. (Inventor); Buning, Pieter G. (Inventor); Bauer, Steven X. S. (Inventor); Engelund, Walter C. (Inventor); Schuster, David M. (Inventor)

    2011-01-01

    An annular fairing having aerodynamic, thermal, structural and acoustic attributes couples a launch abort motor to a space vehicle having a payload of concern mounted on top of a rocket propulsion system. A first end of the annular fairing is fixedly attached to the launch abort motor while a second end of the annular fairing is attached in a releasable fashion to an aft region of the payload. The annular fairing increases in diameter between its first and second ends.

  8. Phosphorus detection in vitrified bacteria by cryo-STEM annular dark-field analysis.

    Science.gov (United States)

    Wolf, Sharon Grayer; Rez, Peter; Elbaum, Michael

    2015-11-01

    Bacterial cells often contain dense granules. Among these, polyphosphate bodies (PPBs) store inorganic phosphate for a variety of essential functions. Identification of PPBs has until now been accomplished by analytical methods that required drying or chemically fixing the cells. These methods entail large electron doses that are incompatible with low-dose imaging of cryogenic specimens. We show here that Scanning Transmission Electron Microscopy (STEM) of fully hydrated, intact, vitrified bacteria provides a simple means for mapping of phosphorus-containing dense granules based on quantitative sensitivity of the electron scattering to atomic number. A coarse resolution of the scattering angles distinguishes phosphorus from the abundant lighter atoms: carbon, nitrogen and oxygen. The theoretical basis is similar to Z contrast of materials science. EDX provides a positive identification of phosphorus, but importantly, the method need not involve a more severe electron dose than that required for imaging. The approach should prove useful in general for mapping of heavy elements in cryopreserved specimens when the element identity is known from the biological context. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

  9. 75 FR 23582 - Annular Casing Pressure Management for Offshore Wells

    Science.gov (United States)

    2010-05-04

    ... casing pressure. This rule will promote human safety and environmental protection, and require Outer... Minerals Management Service 30 CFR Part 250 RIN 1010-AD47 Annular Casing Pressure Management for Offshore... will establish regulations to address sustained casing pressure in oil and gas wells completed in the...

  10. Design curves for circular and annular duct silencers

    Science.gov (United States)

    Watson, Willie R.; Ramakrishnan, R.

    1989-01-01

    Conventional models of sound propagation between porous walls (Scott, 1946) are adapted in order to calculate design curves for the lined circular and annular-duct silencers used in HVAC systems. The derivation of the governing equations is outlined, and results for two typical cases are presented graphically. Good agreement with published experimental data is demonstrated.

  11. Modeling and control of water disinfection process in annular photoreactors

    NARCIS (Netherlands)

    Keesman, K.J.; Vries, D.; Mourik, van S.; Zwart, H.

    2007-01-01

    Abstract¿ As an alternative or addition to complex physical modeling, in this paper transfer function models of the disinfection process in annular photoreactors under different flow conditions are derived. These transfer function models allow an analytical evaluation of the system dynamics and the

  12. Modelling of water disinfection process in annular photoreactors

    NARCIS (Netherlands)

    Keesman, K.J.; Parasoglou, M.; Vries, D.

    2006-01-01

    As an alternative or addition to complex physical modelling, in this paper transfer function models of the disinfection process in annular photoreactors under different flow conditions are derived. These transfer function models allow an analytical evaluation of the system dynamics and the control s

  13. Modeling and control of water disinfection process in annular photoreactors

    NARCIS (Netherlands)

    Keesman, K.J.; Vries, D.; Mourik, van S.; Zwart, H.J.; Tzafestas, S.

    2007-01-01

    As an alternative or addition to complex physical modeling, in this paper transfer function models of the disinfection process in annular photoreactors under different flow conditions are derived. These transfer function models allow an analytical evaluation of the system dynamics and the control st

  14. Fluxon dynamics in long annular Josephson tunnel junctions

    DEFF Research Database (Denmark)

    Martucciello, N.; Mygind, Jesper; Koshelets, V.P.

    1998-01-01

    Single-fluxon dynamics has been experimentally investigated in high-quality Nb/Al-AlOx/Nb annular Josephson tunnel junctions having a radius much larger than the Josephson penetration depth. Strong evidence of self-field effects is observed. An external magnetic field in the barrier plane acts...

  15. Annular-cladding erbium doped multicore fiber for SDM amplification.

    Science.gov (United States)

    Jin, Cang; Ung, Bora; Messaddeq, Younès; LaRochelle, Sophie

    2015-11-16

    We propose and numerically investigate annular-cladding erbium doped multicore fibers (AC-EDMCF) with either solid or air hole inner cladding to enhance the pump power efficiency in optical amplifiers for spatial division multiplexing (SDM) transmission links. We first propose an all-glass fiber in which a central inner cladding region with a depressed refractive index is introduced to confine the pump inside a ring-shaped region overlapping the multiple signal cores. Through numerical simulations, we determine signal core and annular pump cladding parameters respecting fabrication constraints. We also propose and examine a multi-spot injection scheme for launching the pump in the annular cladding. With this all-glass fiber with annular cladding, our results predict 10 dB increase in gain and 21% pump power savings compared to the standard double cladding design. We also investigate a fiber with an air hole inner cladding to further enhance the pump power confinement and minimize power leaking into the inner cladding. The results are compared to the all-glass AC-EDMCF.

  16. Conformal Gravity: Dark Matter and Dark Energy

    Directory of Open Access Journals (Sweden)

    Robert K. Nesbet

    2013-01-01

    Full Text Available This short review examines recent progress in understanding dark matter, dark energy, and galactic halos using theory that departs minimally from standard particle physics and cosmology. Strict conformal symmetry (local Weyl scaling covariance, postulated for all elementary massless fields, retains standard fermion and gauge boson theory but modifies Einstein–Hilbert general relativity and the Higgs scalar field model, with no new physical fields. Subgalactic phenomenology is retained. Without invoking dark matter, conformal gravity and a conformal Higgs model fit empirical data on galactic rotational velocities, galactic halos, and Hubble expansion including dark energy.

  17. The potential link between high angle grain boundary morphology and grain boundary deformation in a nickel-based superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Carter, Jennifer L.W., E-mail: jennifer.w.carter@case.edu [Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 44321 (United States); Sosa, John M. [Center for Accelerated Maturation of Materials, The Ohio State University, Columbus, OH 44321 (United States); Shade, Paul A. [Air Force Research Laboratory, Materials & Manufacturing Directorate, AFRL/RXCM, Wright-Patterson AFB, Dayton, OH 45433 (United States); Fraser, Hamish L. [Center for Accelerated Maturation of Materials, The Ohio State University, Columbus, OH 44321 (United States); Uchic, Michael D. [Air Force Research Laboratory, Materials & Manufacturing Directorate, AFRL/RXCM, Wright-Patterson AFB, Dayton, OH 45433 (United States); Mills, Michael J. [Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 44321 (United States)

    2015-07-29

    Focused ion beam (FIB) based serial sectioning was utilized to characterize the morphology of two high angle grain boundaries (HAGB) in a nickel based superalloy, one that experienced grain boundary sliding (GBS) and the other experienced strain accumulation, during elevated temperature constant stress loading conditions. A custom script was utilized to serial section and collect ion-induced secondary electron images from the FIB-SEM system. The MATLAB based MIPAR{sup TM} software was utilized to align, segment and reconstruct 3D volumes from the sectioned images. Analysis of the 3D data indicates that the HAGB that exhibited GBS had microscale curvature that was planar in nature, and local serrations on the order of ±150 nm. In contrast, the HAGB that exhibited strain accumulation was not planar and had local serrations an order of magnitude greater than the other grain boundary. It is hypothesized that the serrations and the local grain boundary network are key factors in determining which grain boundaries experience GBS during creep deformation.

  18. Dark Axion Portal

    OpenAIRE

    Kaneta, Kunio; Lee, Hye-Sung(Theory Division, CERN, CH-1211, Geneva 23, Switzerland); Yun, Seokhoon

    2016-01-01

    The dark photon and the axion (or axion-like particle) are among the popular light particles of the hidden sector. Each of them has been actively searched for through the couplings called the vector portal and the axion portal. We introduce a new portal connecting the dark photon and the axion (axion-photon-dark photon, axion-dark photon-dark photon), which emerges in the presence of the two particles. This dark axion portal is genuinely new couplings, not just from a product of the vector po...

  19. Dark Matter Constituents

    CERN Document Server

    Bergström, L

    2005-01-01

    As cosmology has entered a phase of precision experiments, the content of the universe has been established to contain interesting and not yet fully understood components, namely dark energy and dark matter. While the cause and exact nature of the dark energy remains mysterious, there is greater hope to connect the dark matter to current models of particle physics. Supersymmetric models provide several excellent candidates for dark matter, with the lightest neutralino the prime example. This and other dark matter candidates are discussed, and prospects for their detection summarized. Some methods of detection are explained, and indications of signals in present data are critically examined.

  20. Ultrafast laser parallel microdrilling using multiple annular beams generated by a spatial light modulator

    Science.gov (United States)

    Kuang, Zheng; Perrie, Walter; Edwardson, Stuart P.; Fearon, Eamonn; Dearden, Geoff

    2014-03-01

    Ultrafast laser parallel microdrilling using diffractive multiple annular beam patterns is demonstrated in this paper. The annular beam was generated by diffractive axicon computer generated holograms (CGHs) using a spatial light modulator. The diameter of the annular beam can be easily adjusted by varying the radius of the smallest ring in the axicon. Multiple annular beams with arbitrary arrangement and multiple annular beam arrays were generated by superimposing an axicon CGH onto a grating and lenses algorithm calculated multi-beam CGH and a binary Dammann grating CGH, respectively. Microholes were drilled through a 0.03 mm thick stainless steel foil using the multiple annular beams. By avoiding huge laser output attenuation and mechanical annular scanning, the processing is ˜200 times faster than the normal single beam processing.

  1. DarkSide search for dark matter

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, T.; Alton, D.; Arisaka, K.; Back, H. O.; Beltrame, P.; Benziger, J.; Bonfini, G.; Brigatti, A.; Brodsky, J.; Bussino, S.; Cadonati, L.; Calaprice, F.; Candela, A.; Cao, H.; Cavalcante, P.; Chepurnov, A.; Chidzik, S.; Cocco, A. G.; Condon, C.; D' Angelo, D.; Davini, S.; Vincenzi, M. De; Haas, E. De; Derbin, A.; Pietro, G. Di; Dratchnev, I.; Durben, D.; Empl, A.; Etenko, A.; Fan, A.; Fiorillo, G.; Franco, D.; Fomenko, K.; Forster, G.; Gabriele, F.; Galbiati, C.; Gazzana, S.; Ghiano, C.; Goretti, A.; Grandi, L.; Gromov, M.; Guan, M.; Guo, C.; Guray, G.; Hungerford, E. V.; Ianni, Al; Ianni, An; Joliet, C.; Kayunov, A.; Keeter, K.; Kendziora, C.; Kidner, S.; Klemmer, R.; Kobychev, V.; Koh, G.; Komor, M.; Korablev, D.; Korga, G.; Li, P.; Loer, B.; Lombardi, P.; Love, C.; Ludhova, L.; Luitz, S.; Lukyanchenko, L.; Lund, A.; Lung, K.; Ma, Y.; Machulin, I.; Mari, S.; Maricic, J.; Martoff, C. J.; Meregaglia, A.; Meroni, E.; Meyers, P.; Mohayai, T.; Montanari, D.; Montuschi, M.; Monzani, M. E.; Mosteiro, P.; Mount, B.; Muratova, V.; Nelson, A.; Nemtzow, A.; Nurakhov, N.; Orsini, M.; Ortica, F.; Pallavicini, M.; Pantic, E.; Parmeggiano, S.; Parsells, R.; Pelliccia, N.; Perasso, L.; Perasso, S.; Perfetto, F.; Pinsky, L.; Pocar, A.; Pordes, S.; Randle, K.; Ranucci, G.; Razeto, A.; Romani, A.; Rossi, B.; Rossi, N.; Rountree, S. D.; Saggese, P.; Saldanha, R.; Salvo, C.; Sands, W.; Seigar, M.; Semenov, D.; Shields, E.; Skorokhvatov, M.; Smirnov, O.; Sotnikov, A.; Sukhotin, S.; Suvarov, Y.; Tartaglia, R.; Tatarowicz, J.; Testera, G.; Thompson, J.; Tonazzo, A.; Unzhakov, E.; Vogelaar, R. B.; Wang, H.; Westerdale, S.; Wojcik, M.; Wright, A.; Xu, J.; Yang, C.; Zavatarelli, S.; Zehfus, M.; Zhong, W.; Zuzel, G.

    2013-11-22

    The DarkSide staged program utilizes a two-phase time projection chamber (TPC) with liquid argon as the target material for the scattering of dark matter particles. Efficient background reduction is achieved using low radioactivity underground argon as well as several experimental handles such as pulse shape, ratio of ionization over scintillation signal, 3D event reconstruction, and active neutron and muon vetos. The DarkSide-10 prototype detector has proven high scintillation light yield, which is a particularly important parameter as it sets the energy threshold for the pulse shape discrimination technique. The DarkSide-50 detector system, currently in commissioning phase at the Gran Sasso Underground Laboratory, will reach a sensitivity to dark matter spin-independent scattering cross section of 10-45 cm2 within 3 years of operation.

  2. Codecaying Dark Matter.

    Science.gov (United States)

    Dror, Jeff Asaf; Kuflik, Eric; Ng, Wee Hao

    2016-11-18

    We propose a new mechanism for thermal dark matter freeze-out, called codecaying dark matter. Multicomponent dark sectors with degenerate particles and out-of-equilibrium decays can codecay to obtain the observed relic density. The dark matter density is exponentially depleted through the decay of nearly degenerate particles rather than from Boltzmann suppression. The relic abundance is set by the dark matter annihilation cross section, which is predicted to be boosted, and the decay rate of the dark sector particles. The mechanism is viable in a broad range of dark matter parameter space, with a robust prediction of an enhanced indirect detection signal. Finally, we present a simple model that realizes codecaying dark matter.

  3. The dark side of cosmology: dark matter and dark energy.

    Science.gov (United States)

    Spergel, David N

    2015-03-06

    A simple model with only six parameters (the age of the universe, the density of atoms, the density of matter, the amplitude of the initial fluctuations, the scale dependence of this amplitude, and the epoch of first star formation) fits all of our cosmological data . Although simple, this standard model is strange. The model implies that most of the matter in our Galaxy is in the form of "dark matter," a new type of particle not yet detected in the laboratory, and most of the energy in the universe is in the form of "dark energy," energy associated with empty space. Both dark matter and dark energy require extensions to our current understanding of particle physics or point toward a breakdown of general relativity on cosmological scales.

  4. An experimental study of an airfoil with a bio-inspired leading edge device at high angles of attack

    Science.gov (United States)

    Mandadzhiev, Boris A.; Lynch, Michael K.; Chamorro, Leonardo P.; Wissa, Aimy A.

    2017-09-01

    Robust and predictable aerodynamic performance of unmanned aerial vehicles at the limits of their design envelope is critical for safety and mission adaptability. Deployable aerodynamic surfaces from the wing leading or trailing edges are often used to extend the aerodynamic envelope (e.g. slats and flaps). Birds have also evolved feathers at the leading edge (LE) of their wings, known as the alula, which enables them to perform high angles of attack maneuvers. In this study, a series of wind tunnel experiments are performed to quantify the effect of various deployment parameters of an alula-like LE device on the aerodynamic performance of a cambered airfoil (S1223) at stall and post stall conditions. The alula relative angle of attack, measured from the mean chord of the airfoil, is varied to modulate tip-vortex strength, while the alula deflection angle is varied to modulate the distance between the tip vortex and the wing surface. Integrated lift force measurements were collected at various alula-inspired device configurations. The effect of the alula-inspired device on the boundary layer velocity profile and turbulence intensity were investigated through hot-wire anemometer measurements. Results show that as alula deflection angle increases, the lift coefficient also increase especially at lower alula relative angles of attack. Moreover, at post stall wing angles of attack, the wake velocity deficit is reduced in the presence of alula device, confirming the mitigation of the wing adverse pressure gradient. The results are in strong agreement with measurements taken on bird wings showing delayed flow reversal and extended range of operational angles of attack. An engineered alula-inspired device has the potential to improve mission adaptability in small unmanned air vehicles during low Reynolds number flight.

  5. Dark Energy Scaling from Dark Matter to Acceleration

    OpenAIRE

    Bielefeld, Jannis; Caldwell, Robert R.; Linder, Eric V.

    2014-01-01

    The dark sector of the Universe need not be completely separable into distinct dark matter and dark energy components. We consider a model of early dark energy in which the dark energy mimics a dark matter component in both evolution and perturbations at early times. Barotropic aether dark energy scales as a fixed fraction, possibly greater than one, of the dark matter density and has vanishing sound speed at early times before undergoing a transition. This gives signatures not only in cosmic...

  6. Cannibal Dark Matter

    CERN Document Server

    Pappadopulo, Duccio; Trevisan, Gabriele

    2016-01-01

    A thermally decoupled hidden sector of particles, with a mass gap, generically enters a phase of cannibalism in the early Universe. The Standard Model sector becomes exponentially colder than the hidden sector. We propose the Cannibal Dark Matter framework, where dark matter resides in a cannibalizing sector with a relic density set by 2-to-2 annihilations. Observable signals of Cannibal Dark Matter include a boosted rate for indirect detection, new relativistic degrees of freedom, and warm dark matter.

  7. Dark Matter Effective Theory

    DEFF Research Database (Denmark)

    Del Nobile, Eugenio; Sannino, Francesco

    2012-01-01

    We organize the effective (self)interaction terms for complex scalar dark matter candidates which are either an isosinglet, isodoublet or an isotriplet with respect to the weak interactions. The classification has been performed ordering the operators in inverse powers of the dark matter cutoff...... scale. We assume Lorentz invariance, color and charge neutrality. We also introduce potentially interesting dark matter induced flavor-changing operators. Our general framework allows for model independent investigations of dark matter properties....

  8. Dark stars: a review.

    Science.gov (United States)

    Freese, Katherine; Rindler-Daller, Tanja; Spolyar, Douglas; Valluri, Monica

    2016-06-01

    Dark stars are stellar objects made (almost entirely) of hydrogen and helium, but powered by the heat from dark matter annihilation, rather than by fusion. They are in hydrostatic and thermal equilibrium, but with an unusual power source. Weakly interacting massive particles (WIMPs), among the best candidates for dark matter, can be their own antimatter and can annihilate inside the star, thereby providing a heat source. Although dark matter constitutes only [Formula: see text]0.1% of the stellar mass, this amount is sufficient to power the star for millions to billions of years. Thus, the first phase of stellar evolution in the history of the Universe may have been dark stars. We review how dark stars come into existence, how they grow as long as dark matter fuel persists, and their stellar structure and evolution. The studies were done in two different ways, first assuming polytropic interiors and more recently using the MESA stellar evolution code; the basic results are the same. Dark stars are giant, puffy (∼10 AU) and cool (surface temperatures  ∼10 000 K) objects. We follow the evolution of dark stars from their inception at  ∼[Formula: see text] as they accrete mass from their surroundings to become supermassive stars, some even reaching masses  >[Formula: see text] and luminosities  >[Formula: see text], making them detectable with the upcoming James Webb Space Telescope. Once the dark matter runs out and the dark star dies, it may collapse to a black hole; thus dark stars may provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation may exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The current review briefly discusses dark stars existing today, but focuses on the early generation of dark stars.

  9. Mimicking Dark Matter

    OpenAIRE

    Bel, Lluís

    2017-01-01

    I show that a very simple model in the context of Newtonian physics promoted to a first approximation of general relativity can mimic Dark matter and explain most of its intriguing properties. Namely: i) Dark matter is a halo associated to ordinary matter; ii) Dark matter does not interact with ordinary matter nor with itself; iii) Its influence grows with the size of the aggregate of ordinary matter that is considered, and iv) Dark matter influences the propagation of light.

  10. Impeded Dark Matter

    OpenAIRE

    Kopp, Joachim; Liu, Jia; Slatyer, Tracy R.; Wang, Xiao-Ping; Xue, Wei

    2016-01-01

    We consider a new class of thermal dark matter models, dubbed "Impeded Dark Matter", in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. We demonstrate that either case can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonst...

  11. Dark stars: a review

    Science.gov (United States)

    Freese, Katherine; Rindler-Daller, Tanja; Spolyar, Douglas; Valluri, Monica

    2016-06-01

    Dark stars are stellar objects made (almost entirely) of hydrogen and helium, but powered by the heat from dark matter annihilation, rather than by fusion. They are in hydrostatic and thermal equilibrium, but with an unusual power source. Weakly interacting massive particles (WIMPs), among the best candidates for dark matter, can be their own antimatter and can annihilate inside the star, thereby providing a heat source. Although dark matter constitutes only ≲ 0.1% of the stellar mass, this amount is sufficient to power the star for millions to billions of years. Thus, the first phase of stellar evolution in the history of the Universe may have been dark stars. We review how dark stars come into existence, how they grow as long as dark matter fuel persists, and their stellar structure and evolution. The studies were done in two different ways, first assuming polytropic interiors and more recently using the MESA stellar evolution code; the basic results are the same. Dark stars are giant, puffy (˜10 AU) and cool (surface temperatures  ˜10 000 K) objects. We follow the evolution of dark stars from their inception at  ˜1{{M}⊙} as they accrete mass from their surroundings to become supermassive stars, some even reaching masses  >{{10}6}{{M}⊙} and luminosities  >{{10}10}{{L}⊙} , making them detectable with the upcoming James Webb Space Telescope. Once the dark matter runs out and the dark star dies, it may collapse to a black hole; thus dark stars may provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation may exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The current review briefly discusses dark stars existing today, but focuses on the early generation of dark stars.

  12. Light Chiral Dark Sector

    CERN Document Server

    Harigaya, Keisuke

    2016-01-01

    An interesting possibility for dark matter is a scalar particle of mass of order 10 MeV-1 GeV, interacting with a U(1) gauge boson (dark photon) which mixes with the photon. We present a simple and natural model realizing this possibility. The dark matter arises as a composite pseudo Nambu-Goldstone boson (dark pion) in a non-Abelian gauge sector, which also gives a mass to the dark photon. For a fixed non-Abelian gauge group, SU(N), and a U(1) charge of the constituent dark quarks, the model has only three free parameters: the dynamical scale of the non-Abelian gauge theory, the gauge coupling of the dark photon, and the mixing parameter between the dark and standard model photons. In particular, the gauge symmetry of the model does not allow any mass term for the dark quarks, and stability of the dark pion is understood as a result of an accidental global symmetry. The model has a significant parameter space in which thermal relic dark pions comprise all of the dark matter, consistently with all experimenta...

  13. Energy and Exergy Analysis of an Annular Thermoelectric Heat Pump

    Science.gov (United States)

    Kaushik, S. C.; Manikandan, S.; Hans, Ranjana

    2016-07-01

    In this paper, the concept of an annular thermoelectric heat pump (ATEHP) has been introduced. An exoreversible thermodynamic model of the ATEHP considering the Thomson effect in conjunction with Peltier, Joule and Fourier heat conduction has been investigated using exergy analysis. New expressions for dimensionless heating power, optimum current at the maximum energy, exergy efficiency conditions and dimensionless irreversibilities in the ATEHP are derived. The results show that the heating power, energy and exergy efficiency of the ATEHP are lower than the flat-plate thermoelectric heat pump. The effects of annular shape parameter ( S r = r 2 /r 1), dimensionless temperature ratio ( θ = T h /T c) and the electrical contact resistances on the heating power, energy/exergy efficiency of an ATEHP have been studied. This study will help in the designing of actual ATEHP systems.

  14. Wind generated rogue waves in an annular wave flume

    CERN Document Server

    Toffoli, A; Salman, H; Monbaliu, J; Frascoli, F; Dafilis, M; Stramignoni, E; Forza, R; Manfrin, M; Onorato, M

    2016-01-01

    We investigate experimentally the statistical properties of a wind-generated wave field and the spontaneous formation of rogue waves in an annular flume. Unlike many experiments on rogue waves, where waves are mechanically generated, here the wave field is forced naturally by wind as it is in the ocean. What is unique about the present experiment is that the annular geometry of the tank makes waves propagating circularly in an {\\it unlimited-fetch} condition. Within this peculiar framework, we discuss the temporal evolution of the statistical properties of the surface elevation. We show that rogue waves and heavy-tail statistics may develop naturally during the growth of the waves just before the wave height reaches a stationary condition. Our results shed new light on the formation of rogue waves in a natural environment.

  15. Wind Generated Rogue Waves in an Annular Wave Flume.

    Science.gov (United States)

    Toffoli, A; Proment, D; Salman, H; Monbaliu, J; Frascoli, F; Dafilis, M; Stramignoni, E; Forza, R; Manfrin, M; Onorato, M

    2017-04-07

    We investigate experimentally the statistical properties of a wind-generated wave field and the spontaneous formation of rogue waves in an annular flume. Unlike many experiments on rogue waves where waves are mechanically generated, here the wave field is forced naturally by wind as it is in the ocean. What is unique about the present experiment is that the annular geometry of the tank makes waves propagating circularly in an unlimited-fetch condition. Within this peculiar framework, we discuss the temporal evolution of the statistical properties of the surface elevation. We show that rogue waves and heavy-tail statistics may develop naturally during the growth of the waves just before the wave height reaches a stationary condition. Our results shed new light on the formation of rogue waves in a natural environment.

  16. High Thrust-to-Power Annular Engine Technology

    Science.gov (United States)

    Patterson, Michael J.; Thomas, Robert E.; Crofton, Mark W.; Young, Jason A.; Foster, John E.

    2015-01-01

    Gridded ion engines have the highest efficiency and total impulse of any mature electric propulsion technology, and have been successfully implemented for primary propulsion in both geocentric and heliocentric environments with excellent ground/in-space correlation of performance. However, they have not been optimized to maximize thrust-to-power, an important parameter for Earth orbit transfer applications. This publication discusses technology development work intended to maximize this parameter. These activities include investigating the capabilities of a non-conventional design approach, the annular engine, which has the potential of exceeding the thrust-to-power of other EP technologies. This publication discusses the status of this work, including the fabrication and initial tests of a large-area annular engine. This work is being conducted in collaboration among NASA Glenn Research Center, The Aerospace Corporation, and the University of Michigan.

  17. Production of annular flat-topped vortex beams

    Institute of Scientific and Technical Information of China (English)

    Jiannong Chen; Yongjiang Yu; Feifei Wang

    2011-01-01

    @@ A model of an annular flat-topped vortex beam based on multi-Gaussian superimposition is proposed. We experimentally produce this beam with a computer-generated hologram (CGH) displayed on a spatial light modulator (SLM). The power of the beam is concentrated on a single-ring structure and has an extremely strong radial intensity gradient. This beam facilitates various applications ranging from Sisyphus atom cooling to micro-particle trapping.%A model of an annular fiat-topped vortex beam based on multi-Gaussian superimposition is proposed. We experimentally produce this beam with a computer-generated hologram (CGH) displayed on a spatial light modulator (SLM). The power of the beam is concentrated on a single-ring structure and has an extremely strong radial intensity gradient. This beam facilitates various applications ranging from Sisyphus atom cooling to micro-particle trapping.

  18. Axisymmetric buckling of laminated thick annular spherical cap

    Science.gov (United States)

    Dumir, P. C.; Dube, G. P.; Mallick, A.

    2005-03-01

    Axisymmetric buckling analysis is presented for moderately thick laminated shallow annular spherical cap under transverse load. Buckling under central ring load and uniformly distributed transverse load, applied statically or as a step function load is considered. The central circular opening is either free or plugged by a rigid central mass or reinforced by a rigid ring. Annular spherical caps have been analysed for clamped and simple supports with movable and immovable inplane edge conditions. The governing equations of the Marguerre-type, first order shear deformation shallow shell theory (FSDT), formulated in terms of transverse deflection w, the rotation ψ of the normal to the midsurface and the stress function Φ, are solved by the orthogonal point collocation method. Typical numerical results for static and dynamic buckling loads for FSDT are compared with the classical lamination theory and the dependence of the effect of the shear deformation on the thickness parameter for various boundary conditions is investigated.

  19. Dark Mass Creation During EWPT Via Dark Energy Interaction

    OpenAIRE

    Leonard S. Kisslinger; Casper, Steven

    2013-01-01

    We add Dark Matter Dark Energy terms with a quintessence field interacting with a Dark Matter field to a MSSM EW Lagrangian previously used to calculate the magnetic field created during the EWPT. From the expectation value of the quintessence field we estimate the Dark Matter mass for parameters used in previous work on Dark Matter-Dark Energy interactions.

  20. Hydraulic forces caused by annular pressure seals in centrifugal pumps

    Science.gov (United States)

    Iino, T.; Kaneko, H.

    1980-01-01

    The hydraulic forces caused by annular pressure seals were investigated. The measured inlet and exit loss coefficients of the flow through the seals were much smaller than the conventional values. The results indicate that the damping coefficient and the inertia coefficient of the fluid film in the seal are not affected much by the rotational speed or the eccentricity of the rotor, though the stiffness coefficient seemed to be influenced by the eccentricity.

  1. Southern annular mode: tropical-extratropical interactions and impacts

    CSIR Research Space (South Africa)

    Fauchereau, N

    2009-09-01

    Full Text Available ?Dept.,?University?of?Cape?Town,?South?Africa 1.?Introduction The?Southern?Annular?Mode?(SAM,?also?called?Antarctic? Oscillation)?is?the?dominant?mode?of?extratropical?(south? of ? 20S) ? low?frequency ? atmospheric ? variability ? ? in ? the? Southern?Hemisphere.?It ?basically...?with?a?seasonally?adjusted?principal?component? index,?17th?Climate?diagnostics?workshop,?Norman,?OK,? 52?57. ...

  2. Flow of viscoplastic fluids in eccentric annular geometries

    DEFF Research Database (Denmark)

    Szabo, Peter; Hassager, Ole

    1992-01-01

    A classification of flowfields for the flow of a Bingham fluid in general eccentric annular geometries is presented. Simple arguments show that a singularity can exist in the stress gradient on boundaries between zones with yielded and un-yielded fluid respectively. A Finite Element code is used...... to verify this property of the Bingham fluid. An analytical solution for the flowfield in case of small eccentricities is derived....

  3. Pattern dynamics in an annular CO2 laser

    OpenAIRE

    Ramon, M.L. (M. L.); R. Meucci; Allaria, E.; Boccaletti, S.

    2000-01-01

    Competition among modes in an annular CO2 laser has been experimentally and numerically analyzed. During the coexistence of di erent patterns, each of them resulting from the interaction of two transverse modes with opposite angular momentum, chaos has been experimentally detected. A numerical model, derived from the Maxwell-Bloch equations and including symmetry breaking terms, enables the interpretation of the main experimental features.

  4. Standing wave acoustic levitation on an annular plate

    Science.gov (United States)

    Kandemir, Mehmet Hakan; Çalışkan, Mehmet

    2016-11-01

    In standing wave acoustic levitation technique, a standing wave is formed between a source and a reflector. Particles can be attracted towards pressure nodes in standing waves owing to a spring action through which particles can be suspended in air. This operation can be performed on continuous structures as well as in several numbers of axes. In this study an annular acoustic levitation arrangement is introduced. Design features of the arrangement are discussed in detail. Bending modes of the annular plate, known as the most efficient sound generation mechanism in such structures, are focused on. Several types of bending modes of the plate are simulated and evaluated by computer simulations. Waveguides are designed to amplify waves coming from sources of excitation, that are, transducers. With the right positioning of the reflector plate, standing waves are formed in the space between the annular vibrating plate and the reflector plate. Radiation forces are also predicted. It is demonstrated that small particles can be suspended in air at pressure nodes of the standing wave corresponding to a particular bending mode.

  5. Annular lesions of cutaneous sarcoidosis with granulomatous vasculitis.

    Science.gov (United States)

    Mizuno, Kana; Nguyen, Chuyen Thi Hong; Ueda-Hayakawa, Ikuko; Okamoto, Hiroyuki

    2017-05-01

    Sarcoidosis is known to be involved in diseases with vasculitis as sarcoid vasculitis. However, vasculitis in cutaneous sarcoidal lesions is extremely rare. Here we describe a case of sarcoidosis with multiple annular skin lesions with granulomatous vasculitis. A 62-year-old female was diagnosed with sarcoidosis by chest-abdominal computed tomographic examination and laboratory tests. The skin lesions had appeared on her lower limbs 2 years before. Physical examination showed multiple infiltrated annular eruptions on the lower extremities. A skin biopsy of an area of erythema showed multiple non-caseating epithelioid cell granulomas in the dermis and subcutaneous fat and granulomatous vasculitis with fibrinoid degeneration in the subcutaneous fat. There are two types of vasculitis in sarcoidosis: leukocytoclastic and granulomatous vasculitis. Ulcers and livedo were more common in granulomatous vasculitis than in leukocytoclastic vasculitis. The present case had unique annular skin lesions of sarcoidosis with granulomatous vasculitis. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  6. Allopurinol induced granuloma annulare in a patient of lepromatous leprosy

    Directory of Open Access Journals (Sweden)

    Satyendra Kumar Singh

    2013-01-01

    Full Text Available Granuloma annulare (GA is a benign, inflammatory dermatosis involving dermis or subcutis with unknown etiology and poorly understood pathology. GA has characteristic histological features of necrobiosis, granuloma formation and abundant mucin deposition. Various predisposing factors, systemic diseases and drugs have been implicated in the etiology. We hereby describe a case of 70 year old male who was a known case of lepromatous leprosy, taking multidrug therapy for 6 months presented with multiple discrete, annular, firm, non tender, smooth surfaced skin colored papular lesions ranging in size from 0.5-1 cm over back for 1 month. There was past history of intake of allopurinol for hyperuricemia which was started 1 year back. There was history of similar lesions 6 months back which healed within 1 month of stopping allopurinol and he started taking the drug for the past 4 months on his own without any medical advice. Histopathological examination showed superficial and deep perivascular lymphocytic infiltrate with numerous histiocytes scattered in the intersititum of reticular dermis and abundant mucin in between the histiocytes. Allopurinol was implicated as an etiological agent and dramatic improvement was seen after stopping the drug for a period of 4 weeks. Naranjo′s algorithm showed a probable association with a score of 6. Thus the final diagnosis of allopurinol induced generalised interstitial granuolma annulare was made. Patient was advised to continue antileprotic drugs, low purine diet and avoid allopurinol intake.

  7. Guided Wave Annular Array Sensor Design for Improved Tomographic Imaging

    Science.gov (United States)

    Koduru, Jaya Prakash; Rose, Joseph L.

    2009-03-01

    Guided wave tomography for structural health monitoring is fast emerging as a reliable tool for the detection and monitoring of hotspots in a structure, for any defects arising from corrosion, crack growth etc. To date guided wave tomography has been successfully tested on aircraft wings, pipes, pipe elbows, and weld joints. Structures practically deployed are subjected to harsh environments like exposure to rain, changes in temperature and humidity. A reliable tomography system should take into account these environmental factors to avoid false alarms. The lack of mode control with piezoceramic disk sensors makes it very sensitive to traces of water leading to false alarms. In this study we explore the design of annular array sensors to provide mode control for improved structural tomography, in particular, addressing the false alarm potential of water loading. Clearly defined actuation lines in the phase velocity dispersion curve space are calculated. A dominant in-plane displacement point is found to provide a solution to the water loading problem. The improvement in the tomographic images with the annular array sensors in the presence of water traces is clearly illustrated with a series of experiments. An annular array design philosophy for other problems in NDE/SHM is also discussed.

  8. A New Atom Trap The Annular Shell Atom Trap (ASAT)

    CERN Document Server

    Pilloff, H S; Pilloff, Herschel S.; Horbatsch, Marko

    2002-01-01

    In the course of exploring some aspects of atom guiding in a hollow, optical fiber, a small negative potential energy well was found just in front of the repulsive or guiding barrier. This results from the optical dipole and the van der Waals potentials. The ground state for atoms bound in this negative potential well was determined by numerically solving the Schrodinger eq. and it was found that this negative well could serve as an atom trap. This trap is referred to as the Annular Shell Atom Trap or ASAT because of the geometry of the trapped atoms which are located in the locus of points defining a very thin annular shell just in front of the guiding barrier. A unique feature of the ASAT is the compression of the atoms from the entire volume to the volume of the annular shell resulting in a very high density of atoms in this trap. This trap may have applications to very low temperatures using evaporative cooling and possibly the formation of BEC. Finally, a scheme is discussed for taking advantage of the d...

  9. Droplet sizes, dynamics and deposition in vertical annular flow

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, J C.B.; Dukler, A E

    1985-10-01

    The role of droplets in vertical upwards annular flow is investigated, focusing on the droplet size distributions, dynamics, and deposition phenomena. An experimental program was performed based on a new laser optical technique developed in these laboratories and implemented here for annular flow. This permitted the simultaneous measurement of droplet size, axial and radial velocity. The dependence of droplet size distributions on flow conditions is analyzed. The Upper-Log Normal function proves to be a good model for the size distribution. The mechanism controlling the maximum stable drop size was found to result from the interaction of the pressure fluctuations of the turbulent flow of the gas core with the droplet. The average axial droplet velocity showed a weak dependence on gas rates. This can be explained once the droplet size distribution and droplet size-velocity relationship are analyzed simultaneously. The surprising result from the droplet conditional analysis is that larger droplet travel faster than smaller ones. This dependence cannot be explained if the drag curves used do not take into account the high levels of turbulence present in the gas core in annular flow. If these are considered, then interesting new situations of multiplicity and stability of droplet terminal velocities are encountered. Also, the observed size-velocity relationship can be explained. A droplet deposition is formulated based on the particle inertia control. This permitted the calculation of rates of drop deposition directly from the droplet size and velocities data.

  10. Interactions between dark energy and dark matter

    Energy Technology Data Exchange (ETDEWEB)

    Baldi, Marco

    2009-03-20

    We have investigated interacting dark energy cosmologies both concerning their impact on the background evolution of the Universe and their effects on cosmological structure growth. For the former aspect, we have developed a cosmological model featuring a matter species consisting of particles with a mass that increases with time. In such model the appearance of a Growing Matter component, which is negligible in early cosmology, dramatically slows down the evolution of the dark energy scalar field at a redshift around six, and triggers the onset of the accelerated expansion of the Universe, therefore addressing the Coincidence Problem. We propose to identify this Growing Matter component with cosmic neutrinos, in which case the present dark energy density can be related to the measured average mass of neutrinos. For the latter aspect, we have implemented the new physical features of interacting dark energy models into the cosmological N-body code GADGET-2, and we present the results of a series of high-resolution simulations for a simple realization of dark energy interaction. As a consequence of the new physics, cold dark matter and baryon distributions evolve differently both in the linear and in the non-linear regime of structure formation. Already on large scales, a linear bias develops between these two components, which is further enhanced by the non-linear evolution. We also find, in contrast with previous work, that the density profiles of cold dark matter halos are less concentrated in coupled dark energy cosmologies compared with {lambda}{sub CDM}. Also, the baryon fraction in halos in the coupled models is significantly reduced below the universal baryon fraction. These features alleviate tensions between observations and the {lambda}{sub CDM} model on small scales. Our methodology is ideally suited to explore the predictions of coupled dark energy models in the fully non-linear regime, which can provide powerful constraints for the viable parameter

  11. Dark microglia: Why are they dark?

    Science.gov (United States)

    Bisht, Kanchan; Sharma, Kaushik; Lacoste, Baptiste; Tremblay, Marie-Ève

    2016-01-01

    Using transmission electron microscopy (TEM) we recently characterized a microglial phenotype that is induced by chronic stress, fractalkine receptor deficiency, aging, or Alzheimer disease pathology. These 'dark' microglia appear overly active compared with the normal microglia, reaching for synaptic clefts, and extensively engulfing pre-synaptic axon terminals and post-synaptic dendritic spines. From these findings we hypothesized that dark microglia could be specifically implicated in the pathological remodeling of neuronal circuits, which impairs learning, memory, and other essential cognitive functions. In the present addendum we further discuss about the possible causes of their dark appearance under TEM.

  12. Natural Dark Energy

    CERN Document Server

    Scott, Douglas

    2007-01-01

    It is now well accepted that both Dark Matter and Dark Energy are required in any successful cosmological model. Although there is ample evidence that both Dark components are necessary, the conventional theories make no prediction for the contributions from each of them. Moreover, there is usually no intrinsic relationship between the two components, and no understanding of the nature of the mysteries of the Dark Sector. Here we suggest that if the Dark Side is so seductive then we should not be restricted to just 2 components. We further suggest that the most natural model has 5 distinct forms of Dark Energy in addition to the usual Dark Matter, each contributing precisely equally to the cosmic energy density budget.

  13. Impeded Dark Matter

    CERN Document Server

    Kopp, Joachim; Slatyer, Tracy R; Wang, Xiao-Ping; Xue, Wei

    2016-01-01

    We consider a new class of thermal dark matter models, dubbed "Impeded Dark Matter", in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. We demonstrate that either case can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonstrate that the annihilation cross-section for Impeded Dark Matter depends linearly on the dark matter velocity or may even be kinematically forbidden, making this scenario almost insensitive to constraints from the cosmic microwave background and from observations of dwarf galaxies. Accordingly, it may be possible for Impeded Dark Matter to yield observable signals in clusters or the Galactic center, with no corresponding signal in dwarfs. For positive mass splitting, we show that the annihilation cross-section is suppress...

  14. Dark Axion Portal

    CERN Document Server

    Kaneta, Kunio; Yun, Seokhoon

    2016-01-01

    The dark photon and the axion (or axion-like particle) are among the popular light particles of the hidden sector. Each of them has been actively searched for through the couplings called the vector portal and the axion portal. We introduce a new portal connecting the dark photon and the axion (axion--photon--dark photon, axion--dark photon--dark photon), which emerges in the presence of the two particles. This dark axion portal is genuinely new couplings, not just from a product of the vector portal and the axion portal, because of the internal structure of these couplings. We present a simple model that realizes the dark axion portal and discuss why it warrants rich phenomenology.

  15. Development of high frequency annular array ultrasound transducers

    Science.gov (United States)

    Gottlieb, Emanuel John

    The advantage of ultrasonic annular arrays over conventional single element transducers has been in the ability to transmit focus at multiple points throughout the depth of field, as well as receive dynamic focus. Today, annular, linear and multidimensional array imaging systems are not commercially available at frequencies greater than 20 MHz. The fabrication technology used to develop a high frequency (>50 MHz) annular array transducer is presented. A 9 mum P(VDF-TrFE) film was bonded to gold annuli electrodes on the top layer of a two sided polyimide flexible circuit. Each annulus was separated by a 30 mum kerf and had several electroplated micro vias that connected to electrode traces on the bottom side of the polyimide flexible circuit. The array's performance was evaluated by measuring the electrical impedance, pulse echo response and crosstalk measurement for each element in the array. In order to improve device sensitivity each element was electrically matched to an impedance magnitude of 50 O and 0° phase at resonance. The average round trip insertion loss measured for the array and compensated for diffraction effects was -33.5 dB. The measured average center frequency and bandwidth of an element was 55 MHz and 47 respectively. The measured crosstalk between adjacent elements remained below -29 dB at the center frequency in water. A vertical wire phantom was imaged using a single focus transmit beamformer and dynamic focusing receive beamformer. This image showed a significant improvement in lateral resolution over a range of 9 mm after the dynamic focusing receive algorithm was applied. These results correlated well with predictions from a Field II simulation. After beamforming the minimum lateral resolution (-6 dB) was 108 mum at the focus. Preliminary ultrasound B-mode images of the rabbit eye using this transducer were shown in conjunction with a multi-channel digital beamformer. A feasibility study of designing and fabricating tunable copolymer

  16. Holographic dark energy interacting with dark matter

    CERN Document Server

    Forte, Mónica I

    2012-01-01

    We investigate a spatially flat Friedmann-Robertson-Walker (FRW) cosmological model with cold dark matter coupled to a dark energy which is given by the modified holographic Ricci cutoff. The interaction used is linear in both dark energy densities, the total energy density and its derivative. Using the statistical method of $\\chi^2$-function for the Hubble data, we obtain $H_0=73.6km/sMpc$, $\\omega_s=\\gamma_s -1=-0.842$ for the asymptotic equation of state and $ z_{acc}= 0.89 $. The estimated values of $\\Omega_{c0}$ which fulfill the current observational bounds corresponds to a dark energy density varying in the range $0.25R < \\ro_x < 0.27R$.

  17. Dark Forces and Light Dark Matter

    Energy Technology Data Exchange (ETDEWEB)

    Hooper, Dan [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Weiner, Neal [New York Univ., NY (United States); Xue, Wei [Rue University (Canada)

    2012-09-01

    We consider a simple class of models in which the dark matter, X, is coupled to a new gauge boson, phi, with a relatively low mass (m_phi \\sim 100 MeV-3 GeV). Neither the dark matter nor the new gauge boson have tree-level couplings to the Standard Model. The dark matter in this model annihilates to phi pairs, and for a coupling of g_X \\sim 0.06 (m_X/10 GeV)^1/2 yields a thermal relic abundance consistent with the cosmological density of dark matter. The phi's produced in such annihilations decay through a small degree of kinetic mixing with the photon to combinations of Standard Model leptons and mesons. For dark matter with a mass of \\sim10 GeV, the shape of the resulting gamma-ray spectrum provides a good fit to that observed from the Galactic Center, and can also provide the very hard electron spectrum required to account for the observed synchrotron emission from the Milky Way's radio filaments. For kinetic mixing near the level naively expected from loop-suppressed operators (epsilon \\sim 10^{-4}), the dark matter is predicted to scatter elastically with protons with a cross section consistent with that required to accommodate the signals reported by DAMA/LIBRA, CoGeNT and CRESST-II.

  18. Dark nebulae, dark lanes, and dust belts

    CERN Document Server

    Cooke, Antony

    2012-01-01

    As probably the only book of its type, this work is aimed at the observer who wants to spend time with something less conventional than the usual fare. Because we usually see objects in space by means of illumination of one kind or another, it has become routine to see them only in these terms. However, part of almost everything that we see is the defining dimension of dark shading, or even the complete obscuration of entire regions in space. Thus this book is focused on everything dark in space: those dark voids in the stellar fabric that mystified astronomers of old; the dark lanes reported in many star clusters; the magical dust belts or dusty regions that have given so many galaxies their identities; the great swirling 'folds' that we associate with bright nebulae; the small dark feature detectable even in some planetary nebulae; and more. Many observers pay scant attention to dark objects and details. Perhaps they are insufficiently aware of them or of the viewing potential they hold, but also it may be...

  19. Annular Pulse Shaping Technique for Large-Diameter Kolsky Bar Experiments on Concrete

    Science.gov (United States)

    2014-10-01

    lt ag e (V ) Time (microsecond) Fig. 5 Linear incident wave generated using an annular copper pulse shaper (O.D. = 25.4 mm, I.D. = 14.4 mm). Note that...AFRL-RW-EG-TP-2014-005 Annular Pulse Shaping Technique for Large- Diameter Kolsky Bar Experiments on Concrete...NUMBER (Include area code) 13-6-2014 Technical Publication October 2012 - February 2014 ANNULAR PULSE SHAPING TECHNIQUE FOR LARGE-DIAMETER KOLSKY BAR

  20. Elastic Properties of the Annular Ligament of the Human Stapes—AFM Measurement

    OpenAIRE

    Kwacz, Monika; Rymuza, Zygmunt; Michałowski, Marcin; Wysocki, Jarosław

    2015-01-01

    Elastic properties of the human stapes annular ligament were determined in the physiological range of the ligament deflection using atomic force microscopy and temporal bone specimens. The annular ligament stiffness was determined based on the experimental load-deflection curves. The elastic modulus (Young’s modulus) for a simplified geometry was calculated using the Kirchhoff–Love theory for thin plates. The results obtained in this study showed that the annular ligament is a linear elastic ...

  1. Chiral Dark Sector

    CERN Document Server

    Co, Raymond T; Nomura, Yasunori

    2016-01-01

    We present a simple and natural dark sector model in which dark matter particles arise as composite states of hidden strong dynamics and their stability is ensured by accidental symmetries. The model has only a few free parameters. In particular, the gauge symmetry of the model forbids the masses of dark quarks, and the confinement scale of the dynamics provides the unique mass scale of the model. The gauge group contains an Abelian symmetry $U(1)_D$, which couples the dark and standard model sectors through kinetic mixing. This model, despite its simple structure, has rich and distinctive phenomenology. In the case where the dark pion becomes massive due to $U(1)_D$ quantum corrections, direct and indirect detection experiments can probe thermal relic dark matter which is generically a mixture of the dark pion and the dark baryon, and the Large Hadron Collider can discover the $U(1)_D$ gauge boson. Alternatively, if the dark pion stays light due to a specific $U(1)_D$ charge assignment of the dark quarks, th...

  2. An Annular Gap Acceleration Model for γ-ray Emission of Pulsars

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    If the binding energy of the pulsar's surface is not so high (the case of a neutron star), both negative and positive charges will flow out freely from the surface of the star. An annular free flow model for γ-ray emission of pulsars is suggested. It is emphasized that:(1) Two kinds of acceleration regions (annular and core) need to be taken into account. The annular acceleration region is defined by the magnetic field lines that cross the null charge surface within the light cylinder. (2) If the potential drop in the annular region of a pulsar is high enough (normally the case for young pulsars), charges in both the annular and the core regions could be accelerated and produce primary gamma-rays. Secondary pairs are generated in both regions and stream outwards to power the broadband radiations. (3) The potential drop grows more rapidly in the annular region than in the core region. The annular acceleration process is a key process for producing the observed wide emission beams. (4)The advantages of both the polar cap and outer gap models are retained in this model. The geometric properties of the γ-ray emission from the annular flow are analogous to that presented in a previous work by Qiao et al., which match the observations well. (5) Since charges with different signs leave the pulsar through the annular and the core regions respectively, the current closure problem can be partially solved.

  3. Pancreaticoduodenectomy for pancreas carcinoma occurring in the annular pancreas: report of a case.

    Science.gov (United States)

    Kawaida, Hiromichi; Kono, Hiroshi; Watanabe, Mitsuaki; Maki, Akira; Amemiya, Hidetake; Matsuda, Masanori; Fujii, Hideki; Fukasawa, Mitsuharu; Takahashi, Ei; Sano, Katsuhiro; Inoue, Tomohiro

    2015-08-01

    The annular pancreas is a rare congenital anomaly in which a ring of the pancreas parenchyma surrounds the second part of the duodenum. Malignant tumors are extremely rare in patients with an annular pancreas. A 64-year-old man presented with appetite loss and vomiting. Abdominal contrast-enhanced computed tomography (CT) indicated pancreas parenchyma surrounding the second part of the duodenum, and a hypovascular area occupying lesion in the annular pancreas. Subtotal stomach-preserving pancreaticoduodenectomy was performed. Histopathology showed pancreatic carcinoma occurring in the complete annular pancreas.

  4. Links between granuloma annulare, necrobiosis lipoidica diabeticorum and childhood diabetes: a matter of time?

    Science.gov (United States)

    Davison, James E; Davies, Alison; Moss, Celia; Kirk, Jeremy M W; Taibjee, Saleem M; Agwu, J Chizo

    2010-01-01

    Diabetes mellitus is associated with a range of dermatologic presentations, including granuloma annulare and necrobiosis lipoidica diabeticorum. Granuloma annulare occurs earlier than necrobiosis lipoidica diabeticorum and the association with diabetes mellitus is much weaker. We describe two children with diabetes who both developed granuloma annulare and later, necrobiosis lipoidica diabeticorum. We postulate that the early onset and transient nature of granuloma annulare, compared with the later onset and persistence of necrobiosis lipoidica diabeticorum, might account for the different apparent rates of association with diabetes mellitus.

  5. Electron beam diagnostic system using computed tomography and an annular sensor

    Science.gov (United States)

    Elmer, John W.; Teruya, Alan T.

    2014-07-29

    A system for analyzing an electron beam including a circular electron beam diagnostic sensor adapted to receive the electron beam, the circular electron beam diagnostic sensor having a central axis; an annular sensor structure operatively connected to the circular electron beam diagnostic sensor, wherein the sensor structure receives the electron beam; a system for sweeping the electron beam radially outward from the central axis of the circular electron beam diagnostic sensor to the annular sensor structure wherein the electron beam is intercepted by the annular sensor structure; and a device for measuring the electron beam that is intercepted by the annular sensor structure.

  6. Neutrinos and dark matter

    Energy Technology Data Exchange (ETDEWEB)

    Ibarra, Alejandro [Physik-Department T30d, Technische Universität München, James-Franck-Straße, 85748 Garching (Germany)

    2015-07-15

    Neutrinos could be key particles to unravel the nature of the dark matter of the Universe. On the one hand, sterile neutrinos in minimal extensions of the Standard Model are excellent dark matter candidates, producing potentially observable signals in the form of a line in the X-ray sky. On the other hand, the annihilation or the decay of dark matter particles produces, in many plausible dark matter scenarios, a neutrino flux that could be detected at neutrino telescopes, thus providing non-gravitational evidence for dark matter. More conservatively, the non-observation of a significant excess in the neutrino fluxes with respect to the expected astrophysical backgrounds can be used to constrain dark matter properties, such as the self-annihilation cross section, the scattering cross section with nucleons and the lifetime.

  7. Dark energy and extended dark matter halos

    Science.gov (United States)

    Chernin, A. D.; Teerikorpi, P.; Valtonen, M. J.; Dolgachev, V. P.; Domozhilova, L. M.; Byrd, G. G.

    2012-03-01

    The cosmological mean matter (dark and baryonic) density measured in the units of the critical density is Ωm = 0.27. Independently, the local mean density is estimated to be Ωloc = 0.08-0.23 from recent data on galaxy groups at redshifts up to z = 0.01-0.03 (as published by Crook et al. 2007, ApJ, 655, 790 and Makarov & Karachentsev 2011, MNRAS, 412, 2498). If the lower values of Ωloc are reliable, as Makarov & Karachentsev and some other observers prefer, does this mean that the Local Universe of 100-300 Mpc across is an underdensity in the cosmic matter distribution? Or could it nevertheless be representative of the mean cosmic density or even be an overdensity due to the Local Supercluster therein. We focus on dark matter halos of groups of galaxies and check how much dark mass the invisible outer layers of the halos are able to host. The outer layers are usually devoid of bright galaxies and cannot be seen at large distances. The key factor which bounds the size of an isolated halo is the local antigravity produced by the omnipresent background of dark energy. A gravitationally bound halo does not extend beyond the zero-gravity surface where the gravity of matter and the antigravity of dark energy balance, thus defining a natural upper size of a system. We use our theory of local dynamical effects of dark energy to estimate the maximal sizes and masses of the extended dark halos. Using data from three recent catalogs of galaxy groups, we show that the calculated mass bounds conform with the assumption that a significant amount of dark matter is located in the invisible outer parts of the extended halos, sufficient to fill the gap between the observed and expected local matter density. Nearby groups of galaxies and the Virgo cluster have dark halos which seem to extend up to their zero-gravity surfaces. If the extended halo is a common feature of gravitationally bound systems on scales of galaxy groups and clusters, the Local Universe could be typical or even

  8. Geometry optimization of linear and annular plasma synthetic jet actuators

    Science.gov (United States)

    Neretti, G.; Seri, P.; Taglioli, M.; Shaw, A.; Iza, F.; Borghi, C. A.

    2017-01-01

    The electrohydrodynamic (EHD) interaction induced in atmospheric air pressure by a surface dielectric barrier discharge (DBD) actuator has been experimentally investigated. Plasma synthetic jet actuators (PSJAs) are DBD actuators able to induce an air stream perpendicular to the actuator surface. These devices can be used in the field of aerodynamics to prevent or induce flow separation, modify the laminar to turbulent transition inside the boundary layer, and stabilize or mix air flows. They can also be used to enhance indirect plasma treatment effects, increasing the reactive species delivery rate onto surfaces and liquids. This can play a major role in plasma processing and chemical kinetics modelling, where often only diffusive mechanisms are considered. This paper reports on the importance that different electrode geometries can have on the performance of different PSJAs. A series of DBD aerodynamic actuators designed to produce perpendicular jets has been fabricated on two-layer printed circuit boards (PCBs). Both linear and annular geometries were considered, testing different upper electrode distances in the linear case and different diameters in the annular one. An AC voltage supplied at a peak of 11.5 kV and a frequency of 5 kHz was used. Lower electrodes were connected to the ground and buried in epoxy resin to avoid undesired plasma generation on the lower actuator surface. Voltage and current measurements were carried out to evaluate the active power delivered to the discharges. Schlieren imaging allowed the induced jets to be visualized and gave an estimate of their evolution and geometry. Pitot tube measurements were performed to obtain the velocity profiles of the PSJAs and to estimate the mechanical power delivered to the fluid. The optimal values of the inter-electrode distance and diameter were found in order to maximize jet velocity, mechanical power or efficiency. Annular geometries were found to achieve the best performance.

  9. Dark matter and cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Schramm, D.N.

    1992-03-01

    The cosmological dark matter problem is reviewed. The Big Bang Nucleosynthesis constraints on the baryon density are compared with the densities implied by visible matter, dark halos, dynamics of clusters, gravitational lenses, large-scale velocity flows, and the {Omega} = 1 flatness/inflation argument. It is shown that (1) the majority of baryons are dark; and (2) non-baryonic dark matter is probably required on large scales. It is also noted that halo dark matter could be either baryonic or non-baryonic. Descrimination between ``cold`` and ``hot`` non-baryonic candidates is shown to depend on the assumed ``seeds`` that stimulate structure formation. Gaussian density fluctuations, such as those induced by quantum fluctuations, favor cold dark matter, whereas topological defects such as strings, textures or domain walls may work equally or better with hot dark matter. A possible connection between cold dark matter, globular cluster ages and the Hubble constant is mentioned. Recent large-scale structure measurements, coupled with microwave anisotropy limits, are shown to raise some questions for the previously favored density fluctuation picture. Accelerator and underground limits on dark matter candidates are also reviewed.

  10. Dark matter and cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Schramm, D.N.

    1992-03-01

    The cosmological dark matter problem is reviewed. The Big Bang Nucleosynthesis constraints on the baryon density are compared with the densities implied by visible matter, dark halos, dynamics of clusters, gravitational lenses, large-scale velocity flows, and the {Omega} = 1 flatness/inflation argument. It is shown that (1) the majority of baryons are dark; and (2) non-baryonic dark matter is probably required on large scales. It is also noted that halo dark matter could be either baryonic or non-baryonic. Descrimination between cold'' and hot'' non-baryonic candidates is shown to depend on the assumed seeds'' that stimulate structure formation. Gaussian density fluctuations, such as those induced by quantum fluctuations, favor cold dark matter, whereas topological defects such as strings, textures or domain walls may work equally or better with hot dark matter. A possible connection between cold dark matter, globular cluster ages and the Hubble constant is mentioned. Recent large-scale structure measurements, coupled with microwave anisotropy limits, are shown to raise some questions for the previously favored density fluctuation picture. Accelerator and underground limits on dark matter candidates are also reviewed.

  11. Metastable dark energy

    CERN Document Server

    Landim, Ricardo G

    2016-01-01

    We build a model of metastable dark energy, in which the observed vacuum energy is the value of the scalar potential at the false vacuum. The scalar potential is given by a sum of even self-interactions up to order six. The deviation from the Minkowski vacuum is due to a term suppressed by the Planck scale. The decay time of the metastable vacuum can easily accommodate a mean life time compatible with the age of the universe. The metastable dark energy is also embedded into a model with $SU(2)_R$ symmetry. The dark energy doublet and the dark matter doublet naturally interact with each other. A three-body decay of the dark energy particle into (cold and warm) dark matter can be as long as large fraction of the age of the universe, if the mediator is massive enough, the lower bound being at intermediate energy level some orders below the grand unification scale. Such a decay shows a different form of interaction between dark matter and dark energy, and the model opens a new window to investigate the dark secto...

  12. Metastable dark energy

    Directory of Open Access Journals (Sweden)

    Ricardo G. Landim

    2017-01-01

    Full Text Available We build a model of metastable dark energy, in which the observed vacuum energy is the value of the scalar potential at the false vacuum. The scalar potential is given by a sum of even self-interactions up to order six. The deviation from the Minkowski vacuum is due to a term suppressed by the Planck scale. The decay time of the metastable vacuum can easily accommodate a mean life time compatible with the age of the universe. The metastable dark energy is also embedded into a model with SU(2R symmetry. The dark energy doublet and the dark matter doublet naturally interact with each other. A three-body decay of the dark energy particle into (cold and warm dark matter can be as long as large fraction of the age of the universe, if the mediator is massive enough, the lower bound being at intermediate energy level some orders below the grand unification scale. Such a decay shows a different form of interaction between dark matter and dark energy, and the model opens a new window to investigate the dark sector from the point-of-view of particle physics.

  13. Dipolar Dark Matter

    CERN Document Server

    Blanchet, Luc

    2015-01-01

    Massive gravity theories have been developed as viable IR modifications of gravity motivated by dark energy and the problem of the cosmological constant. On the other hand, modified gravity and modified dark matter theories were developed with the aim of solving the problems of standard cold dark matter at galactic scales. Here we propose to adapt the framework of ghost-free massive bigravity theories to reformulate the problem of dark matter at galactic scales. We investigate a promising alternative to dark matter called dipolar dark matter (DDM) in which two different species of dark matter are separately coupled to the two metrics of bigravity and are linked together by an internal vector field. We show that this model successfully reproduces the phenomenology of dark matter at galactic scales (i.e. MOND) as a result of a mechanism of gravitational polarisation. The model is safe in the gravitational sector, but because the two types of dark matter interact through the vector field, a ghostly degree of fre...

  14. Working the Dark Side

    DEFF Research Database (Denmark)

    Bjering, Jens Christian Borrebye

    half—dark side—documents the making and nature of the dark side by analyzing a series of legal memos from the Department of Justice's Office of Legal Council and from the White House and concludes by relating its findings to traditional ideas about emergency action, national security, and torture....... By analyzing official reports and testimonies from soldiers partaking in the War On Terror, the dissertation's second part—dark arts—focuses on the transformation of the dark side into a productive space in which “information” and the hunt for said information overshadowed all legal, ethical, or political...

  15. Axisymmetric Natural Frequencies of Statically Loaded Annular Plates

    Directory of Open Access Journals (Sweden)

    Eihab M. Abdel-Rahman

    2003-01-01

    Full Text Available We present a numerical procedure to solve the axisymmetric vibration problem of statically loaded annular plates. We use the von Kármán nonlinear plate model to account for large deformations and study the effect of static deflections on the natural frequencies and mode shapes for six combinations of boundary conditions. The shooting method is used to solve the resulting eigenvalue problem. Our results show that static deformations have a significant effect on the natural frequencies and small effect on the mode shapes of the plate. Further, the results show that the presence of in-plane stresses has a significant effect on the natural frequencies.

  16. Understanding Wave-mean Flow Feedbacks and Tropospheric Annular Variability

    Science.gov (United States)

    Lorenz, D. J.

    2016-12-01

    The structure of internal tropospheric variability is important for determining the impact of the stratosphere on the troposphere. This study aims to better understand the fundamental dynamical mechanisms that control the feedbacks between the eddies and the mean flow, which in turn select the tropospheric annular mode. Recent work using Rossby Wave Chromatography suggests that "barotropic processes", which directly impact the meridional propagation of wave activity (specifically the reflectivity of the poleward flank of the mid-latitude jet), are more important for the positive feedback between the annular mode and the eddies than "baroclinic processes", which involve changes in the generation of wave activity by baroclinic instability. In this study, experiments with a fully nonlinear quasi-geostrophic model are discussed which provide independent confirmation of the importance of barotropic versus baroclinic processes. The experiments take advantage of the steady-state balance at upper-levels between the meridional gradient in diabatic heating and the second derivative of the upper-level EP flux divergence. Simulations with standard Newtonian heating are compared to simulations with constant-in-time heating taken from the climatology of the standard run and it is found that the forced annular mode response to changes in surface friction is very similar. Moreover, as expected from the annular mode response, the eddy momentum fluxes are also very similar. This is despite the fact that the upper-level EP flux divergence is very different between the two simulations (upper-level EP flux divergence must remain constant in the constant heating simulation while in the standard simulation there is no such constraint). The upper-level balances are maintained by a large change in the baroclinic wave source (i.e. vertical EP flux), which is accompanied by little momentum flux change. Therefore the eddy momentum fluxes appear to be relatively insensitive to the wave

  17. Comparison of superresolution effects with annular phase and amplitude filters.

    Science.gov (United States)

    Luo, Hongxin; Zhou, Changhe

    2004-12-01

    The characteristics of annular amplitude and phase filters are compared. The behavior of two-zone phase and amplitude filters as the inner zone is increased is studied in detail. Numerical simulations show that a phase filter can achieve a superresolution effect, a circular Dammann effect, and flat-topped intensity for different applications, whereas a two-zone amplitude filter can generate only a superresolution effect. The experimental results show that both amplitude and phase filters can achieve superresolution. Generally, a phase superresolution filter is recommended for its higher efficiency and its special diffraction patterns that are impossible to achieve with an amplitude filter.

  18. Analysis of Cold Flowfield of Multi—Annular Opposed Jets

    Institute of Scientific and Technical Information of China (English)

    H.F.Zhao; G.C.Benelli

    1992-01-01

    The technique of the use of multi-annular opposed jets as different from using swirl and bluff body creates an excellent recirculation zone with desired size in a large space.The size of ecirculation,the magnitude of reverse velocity and turbulence intensity are much greater than those formed by bluff body.Factors affecting the flowfield include the velocity ration of the opposed jets to the primary air J.the diameter and construction of the opposed jet ring,secondary air velocity and configuration,and confined or unconfined flow condition and so on.This method is a promising way for flame stabilization in combustion technology.

  19. Histiocytoid Sweet's syndrome presenting with annular erythematous plaques*

    Science.gov (United States)

    Marcarini, Renata; de Araujo, Raquel Nardelli; Nóbrega, Monisa Martins; Medeiros, Karina Bittencourt; Gripp, Alexandre Carlos; Maceira, Juan Manuel Piñeiro

    2016-01-01

    Histiocytoid Sweet's Syndrome is a rare inflammatory disease described in 2005 as a variant of the classical Sweet's Syndrome (SS). Histopathologically, the dermal inflammatory infiltrate is composed mainly of mononuclear cells that have a histiocytic appearance and represent immature myeloid cells. We describe a case of Histiocytoid Sweet's Syndrome in an 18-year-old man. Although this patient had clinical manifestations compatible with SS, the cutaneous lesions consisted of erythematous annular plaques, which are not typical for this entity and have not been described in histiocytic form so far. The histiocytic subtype was confirmed by histopathological analysis that showed positivity for myeloperoxidase in multiple cells with histiocytic appearance.

  20. Final Technical Report for the MIT Annular Fuel Research Project

    Energy Technology Data Exchange (ETDEWEB)

    Mujid S. Kazimi; Pavel Hejzlar

    2008-01-31

    MIT-NFC-PR-082 (January 2006) Abstract This summary provides an overview of the results of the U.S. DOE funded NERI (Nuclear Research ENergy Initiative) program on development of the internally and externally cooled annular fuel for high power density PWRs. This new fuel was proposed by MIT to allow a substantial increase in poer density (on the order of 30% or higher) while maintaining or improving safety margins. A comprehensive study was performed by a team consisting of MIT (lead organization), Westinghuse Electric Corporation, Gamma Engineering Corporation, Framatome ANP(formerly Duke Engineering) and Atomic Energy of Canada Limited.

  1. Unusual Presentation of Acute Annular Urticaria: A Case Report

    Directory of Open Access Journals (Sweden)

    Gilles Guerrier

    2011-01-01

    Full Text Available Acute urticarial lesions may display central clearing with ecchymotic or haemorrhagic hue, often misdiagnosed as erythema multiforme, serum-sickness-like reactions, or urticarial vasculitis. We report a case of acute annular urticaria with unusual presentation occurring in a 20-month-old child to emphasize the distinctive morphologic manifestations in a single disease. Clinicians who care for children should be able to differentiate acute urticaria from its clinical mimics. A directed history and physical examination can reliably orientate necessary diagnostic testing and allow for appropriate treatment.

  2. Analysis of the pressure response of high angle multiple (HAM) fractures intersecting a welbore; Kokeisha multi fracture (HAM) kosei ni okeru atsuryoku oto kaiseki ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Ujo, S.; Osato, K. [Geothermal Energy Research and Development Co. Ltd., Tokyo (Japan); Arihara, N. [Waseda University, Tokyo (Japan); Schroeder, R.

    1996-05-01

    This paper reports pressure response analysis on wells piercing a high angle multi (HAM) fracture model. In this model which is defined on a three-dimensional space, a plurality of slanted fractures intersect with wells at high angles (however, intersection of fractures with each other is not considered). With respect to the pressure response analysis method using this model, the paper presents a basic differential equation on pressure drawdown and boundary conditions in the wells taking flows in the fractures pseudo-linear, as well as external boundary conditions in calculation regions (a reservoir spreads to an infinite distance, and its top and bottom are closed by non-water permeating beds). The paper also indicates that results of calculating a single vertical fracture model and a slanted fracture model by using a numerical computation program (MULFRAC) based on the above equations agree well respectively with the existing calculation results (calculations performed by Erlougher and Cinco et al). 5 refs., 6 figs.

  3. Quantum Field Theory of Interacting Dark Matter/Dark Energy: Dark Monodromies

    OpenAIRE

    D'Amico, Guido; Hamill, Teresa; Kaloper, Nemanja

    2016-01-01

    We discuss how to formulate a quantum field theory of dark energy interacting with dark matter. We show that the proposals based on the assumption that dark matter is made up of heavy particles with masses which are very sensitive to the value of dark energy are strongly constrained. Quintessence-generated long range forces and radiative stability of the quintessence potential require that such dark matter and dark energy are completely decoupled. However, if dark energy and a fraction of dar...

  4. Geometry and evolution of low-angle normal faults (LANF) within a Cenozoic high-angle rift system, Thailand: Implications for sedimentology and the mechanisms of LANF development

    Science.gov (United States)

    Morley, Chris K.

    2009-10-01

    At least eight examples of large (5-35 km heave), low-angle normal faults (LANFs, 20°-30° dip) occur in the Cenozoic rift basins of Thailand and laterally pass into high-angle extensional fault systems. Three large-displacement LANFs are found in late Oligocene-Miocene onshore rift basins (Suphan Buri, Phitsanulok, and Chiang Mai basins), they have (1) developed contemporaneous with, or after the onset of, high-angle extension, (2) acted as paths for magma and associated fluids, and (3) impacted sedimentation patterns. Displacement on low-angle faults appears to be episodic, marked by onset of lacustrine conditions followed by axial progradation of deltaic systems that infilled the lakes during periods of low or no displacement. The Chiang Mai LANF is a low-angle (15°-25°), high-displacement (15-35 km heave), ESE dipping LANF immediately east of the late early Miocene Doi Inthanon and Doi Suthep metamorphic core complexes. Early Cenozoic transpressional crustal thickening followed by the northward motion of India coupled with Burma relative to east Burma and Thailand (˜40-30 Ma) caused migmatization and gneiss dome uplift in the late Oligocene of the core complex region, followed by LANF activity. LANF displacement lasted 4-6 Ma during the early Miocene and possibly transported a late Oligocene-early Miocene high-angle rift system 35 km east. Other LANFs in Thailand have lower displacements and no associated metamorphic core complexes. The three LANFs were initiated as low-angle faults, not by isostatic rotation of high-angle faults. The low-angle dips appear to follow preexisting low-angle fabrics (thrusts, shear zones, and other low-angle ductile foliations) predominantly developed during Late Paleozoic and early Paleogene episodes of thrusting and folding.

  5. 大斜度测井中井径缩径问题分析%Analysis of Well diameter reducing problem in high angle deviated well

    Institute of Scientific and Technical Information of China (English)

    周奇; 霍海鑫

    2015-01-01

    本文通过总结从事测井解释与验收工作的工作经验,论述大斜度井的井径缩径问题产生的原因及对策.%this paper summarizes the work experience of working in the field of well logging interpretation and acceptance,discusses the causes and the countermeasures of problems on high Angle deviated Wells caliper reducing.

  6. Dark Matter Detection in Space

    OpenAIRE

    Feng, Jonathan L.

    2004-01-01

    I review prospects for detecting dark matter in space-based experiments, with an emphasis on recent developments. I propose the ``Martha Stewart criterion'' for identifying dark matter candidates that are particularly worth investigation and focus on three that satisfy it: neutralino dark matter, Kaluza-Klein dark matter, and superWIMP gravitino dark matter.

  7. Simulator study of the effectiveness of an automatic control system designed to improve the high-angle-of-attack characteristics of a fighter airplane

    Science.gov (United States)

    Gilbert, W. P.; Nguyen, L. T.; Vangunst, R. W.

    1976-01-01

    A piloted, fixed-base simulation was conducted to study the effectiveness of some automatic control system features designed to improve the stability and control characteristics of fighter airplanes at high angles of attack. These features include an angle-of-attack limiter, a normal-acceleration limiter, an aileron-rudder interconnect, and a stability-axis yaw damper. The study was based on a current lightweight fighter prototype. The aerodynamic data used in the simulation were measured on a 0.15-scale model at low Reynolds number and low subsonic Mach number. The simulation was conducted on the Langley differential maneuvering simulator, and the evaluation involved representative combat maneuvering. Results of the investigation show the fully augmented airplane to be quite stable and maneuverable throughout the operational angle-of-attack range. The angle-of-attack/normal-acceleration limiting feature of the pitch control system is found to be a necessity to avoid angle-of-attack excursions at high angles of attack. The aileron-rudder interconnect system is shown to be very effective in making the airplane departure resistant while the stability-axis yaw damper provided improved high-angle-of-attack roll performance with a minimum of sideslip excursions.

  8. Dark Energy vs. Dark Matter: Towards a Unifying Scalar Field?

    OpenAIRE

    Arbey, A.

    2008-01-01

    The standard model of cosmology suggests the existence of two components, "dark matter" and "dark energy", which determine the fate of the Universe. Their nature is still under investigation, and no direct proof of their existences has emerged yet. There exist alternative models which reinterpret the cosmological observations, for example by replacing the dark energy/dark matter hypothesis by the existence of a unique dark component, the dark fluid, which is able to mimic the behaviour of bot...

  9. Asymptotically Safe Dark Matter

    DEFF Research Database (Denmark)

    Sannino, Francesco; Shoemaker, Ian M.

    2015-01-01

    We introduce a new paradigm for dark matter (DM) interactions in which the interaction strength is asymptotically safe. In models of this type, the coupling strength is small at low energies but increases at higher energies, and asymptotically approaches a finite constant value. The resulting...... searches are the primary ways to constrain or discover asymptotically safe dark matter....

  10. The Dark Matter Problem

    NARCIS (Netherlands)

    Sanders, Robert H.

    2014-01-01

    1. Introduction; 2. Early history of the dark matter hypothesis; 3. The stability of disk galaxies: the dark halo solutions; 4. Direct evidence: extended rotation curves of spiral galaxies; 5. The maximum disk: light traces mass; 6. Cosmology and the birth of astroparticle physics; 7. Clusters revis

  11. Asymptotically Safe Dark Matter

    DEFF Research Database (Denmark)

    Sannino, Francesco; Shoemaker, Ian M.

    2015-01-01

    We introduce a new paradigm for dark matter (DM) interactions in which the interaction strength is asymptotically safe. In models of this type, the coupling strength is small at low energies but increases at higher energies, and asymptotically approaches a finite constant value. The resulting...... searches are the primary ways to constrain or discover asymptotically safe dark matter....

  12. The Dark Matter Problem

    NARCIS (Netherlands)

    Sanders, Robert H.

    1. Introduction; 2. Early history of the dark matter hypothesis; 3. The stability of disk galaxies: the dark halo solutions; 4. Direct evidence: extended rotation curves of spiral galaxies; 5. The maximum disk: light traces mass; 6. Cosmology and the birth of astroparticle physics; 7. Clusters

  13. Working the Dark Edges

    Science.gov (United States)

    Weston, Anthony

    2014-01-01

    Environmentalism's wider and wilder possibilities today appear as regions of seeming darkness that bracket or frame acceptable environmental thinking. One of these barely-mentionable darknesses is outer space--the cosmos. Another is the inner and chthonic powers of the land and natural beings generally. This essay aims to bring these two kinds of…

  14. Annular bullous lesions with atypical erythema multiforme in leprosy.

    Science.gov (United States)

    Shah, Aishani; Mahajan, Rashmi; Ninama, Kishan; Bilimoria, Freny

    2014-09-01

    Erythema nodosum leprosum (ENL) is an immune complex-mediated reaction that may complicate the course of multibacillary leprosy. Bullous lesions in Type II reaction, though reported, are exceedingly rare. We report the case of a 32 year old female patient who presented initially at our OPD with erythema nodosum. Cutaneous examination revealed impaired sensation over dorsum of right foot and thickened right lateral popliteal nerve. Slit skin smear (SSS) from ear lobes revealed AFB with a bacteriological index of 2+. She was started on MDT, tablet ofloxacin 200 mg twice a day, and 30 mg oral prednisolone. Two months later, she presented with generalised pruritus, large target lesions over the back, and hemorrhagic bullae over lower extremities and annular pattern of bullae, over both arms. A SSS was repeated which was positive for AFB. Histopathology from bullous lesions was consistent with ENL. Direct Immunofluorescence (DIF) study was negative. Our patient improved rapidly after she was started on thalidomide 100 mg twice daily, with withdrawal of ofloxacin. Erythema Multiforme (EMF) and annular bullous lesions have been reported in patients on treatment with ofloxacin. This case is being presented due to the unusual and varied manifestation of Type II lepra reaction in a 34 year old female patient.

  15. Linear and nonlinear stability of periodic orbits in annular billiards.

    Science.gov (United States)

    Dettmann, Carl P; Fain, Vitaly

    2017-04-01

    An annular billiard is a dynamical system in which a particle moves freely in a disk except for elastic collisions with the boundary and also a circular scatterer in the interior of the disk. We investigate the stability properties of some periodic orbits in annular billiards in which the scatterer is touching or close to the boundary. We analytically show that there exist linearly stable periodic orbits of an arbitrary period for scatterers with decreasing radii that are located near the boundary of the disk. As the position of the scatterer moves away from a symmetry line of a periodic orbit, the stability of periodic orbits changes from elliptic to hyperbolic, corresponding to a saddle-center bifurcation. When the scatterer is tangent to the boundary, the periodic orbit is parabolic. We prove that slightly changing the reflection angle of the orbit in the tangential situation leads to the existence of Kolmogorov-Arnold-Moser islands. Thus, we show that there exists a decreasing to zero sequence of open intervals of scatterer radii, along which the billiard table is not ergodic.

  16. Droplet entrainment rate in gas-liquid annular flow

    Energy Technology Data Exchange (ETDEWEB)

    Sawant, P. [Energy Research Inc., Rockville, Maryland (United States); Liu, Y.; Ishii, M. [Purdue Univ., West Lafayette, Indiana (United States); Mori, M. [Tokyo Electric Power Co., Inc., Yokohama (Japan); Chen, S. [Purdue Univ., West Lafayette, Indiana (United States)

    2011-07-01

    Droplet entrainment and deposition are the two most important physical phenomena in the gas-liquid annular two-phase flow. Modeling of these phenomena is essential for the estimation of dryout margins in the Light Water Reactors (LWRs) and the boilers. In this study, gas-liquid annular two-phase flow experiments are performed in a vertical round tube test section under adiabatic conditions. Air-water and organic fluid Freon-113 are used as the test fluids. The experiments covered a wide range of pressure and flow conditions. Liquid film extraction technique was used for the measurement of droplet entrainment and deposition rates. Additionally, the thickness of liquid film was measured in the air-water experiments using the ring type conductance probes. In this paper, the experimental data on entrainment rate is used to analyze the currently available correlations in the literature. The analysis showed that the existing correlations failed to predict the data at high gas velocity conditions. At high gas velocity, the experimental entrainment rate approaches a maximum limiting value; however, the correlations predicted continuously increasing entrainment rate as the gas velocity increases. (author)

  17. Portal annular pancreas: a systematic review of a clinical challenge.

    Science.gov (United States)

    Harnoss, Jonathan M; Harnoss, Julian C; Diener, Markus K; Contin, Pietro; Ulrich, Alexis B; Büchler, Markus W; Schmitz-Winnenthal, Friedrich H

    2014-10-01

    Portal annular pancreas (PAP) is an asymptomatic congenital pancreas anomaly, in which portal and/or mesenteric veins are encased by pancreas tissue. The aim of the study was to determine the role of PAP in pancreatic surgery as well as its management and potential complication, specifically, postoperative pancreatic fistula (POPF).On the basis of a case report, the MEDLINE and ISI Web of Science databases were systematically reviewed up to September 2012. All articles describing a case of PAP were considered.In summary, 21 studies with 59 cases were included. The overall prevalence of PAP was 2.4% and the patients' mean (SD) age was 55.9 (16.2) years. The POPF rate in patients with PAP (12 pancreaticoduodenectomies and 3 distal pancreatectomies) was 46.7% (in accordance with the definition of the International Study Group of Pancreatic Surgery).Portal annular pancreas is a quite unattended pancreatic variant with high prevalence and therefore still remains a clinical challenge to avoid postoperative complications. To decrease the risk for POPF, attentive preoperative diagnostics should also focus on PAP. In pancreaticoduodenectomy, a shift of the resection plane to the pancreas tail should be considered; in extensive pancreatectomy, coverage of the pancreatic remnant by the falciform ligament could be a treatment option.

  18. Electroactive liquid lens driven by an annular membrane.

    Science.gov (United States)

    Wei, Kang; Domicone, Nicholas Wade; Zhao, Yi

    2014-03-01

    Unlike traditional focalization that recruits multiple moving lens elements to adjust focus, liquid lenses deliver adaptive focusing by simply tuning the surface profile of liquid or the elastomer that encloses liquid. Its simple and compact configuration, low cost, and actuation efficiency promise wide industrial, medical, and consumer applications. Dielectric elastomers (DEs), one type of commercially available soft active material, have been a good fit for creating adaptive optics. In this Letter, we present an adaptive, membrane-sealed liquid lens hydrostatically coupled to a concentric annular DE actuator. Electric actuation deforms the annular DE, which induces fluid transmission between the lens part and the actuation part for lens actuation. The maximum measured focal range was from 25.4 to 105.2 mm within 1.0 kV, which significantly outperforms the existing DE-actuated liquid lenses and eliminates the need for prestraining. The lens also enables varied focal ranges by simply adjusting its initial surface sagitta, providing flexibility for practical imaging applications.

  19. Flow properties of particles in a model annular shear cell

    Science.gov (United States)

    Wang, X.; Zhu, H. P.; Yu, A. B.

    2012-05-01

    In order to quantitatively investigate the mechanical and rheological properties of solid flow in a shear cell under conditions relevant to those in an annular cell, we performed a series of discrete particle simulations of slightly polydispersed spheres from quasi-static to intermediate flow regimes. It is shown that the average values of stress tensor components are uniformly distributed in the cell space away from the stationary walls; however, some degree of inhomogeneity in their spatial distributions does exist. A linear relationship between the (internal/external) shear and normal stresses prevails in the shear cell and the internal and external friction coefficients can compare well with each other. It is confirmed that annular shear cells are reasonably effective as a method of measuring particle flow properties. The so-called I-rheology proposed by Jop et al. [Nature (London) 441, 727 (2006)] is rigorously tested in this cell system. The results unambiguously display that the I-rheology can effectively describe the intermediate flow regime with a high correlation coefficient. However, significant deviations take place when it is applied to the quasi-static regime, which corresponds to very small values of inertial number.

  20. Non-null annular subaperture stitching interferometry for aspheric test

    Science.gov (United States)

    Zhang, Lei; Liu, Dong; Shi, Tu; Yang, Yongying; Chong, Shiyao; Miao, Liang; Huang, Wei; Shen, Yibing; Bai, Jian

    2015-10-01

    A non-null annular subaperture stitching interferometry (NASSI), combining the subaperture stitching idea and non-null test method, is proposed for steep aspheric testing. Compared with standard annular subaperture stitching interferometry (ASSI), a partial null lens (PNL) is employed as an alternative to the transmission sphere, to generate different aspherical wavefronts as the references. The coverage subaperture number would thus be reduced greatly for the better performance of aspherical wavefronts in matching the local slope of aspheric surfaces. Instead of various mathematical stitching algorithms, a simultaneous reverse optimizing reconstruction (SROR) method based on system modeling and ray tracing is proposed for full aperture figure error reconstruction. All the subaperture measurements are simulated simultaneously with a multi-configuration model in a ray-tracing program, including the interferometric system modeling and subaperture misalignments modeling. With the multi-configuration model, full aperture figure error would be extracted in form of Zernike polynomials from subapertures wavefront data by the SROR method. This method concurrently accomplishes subaperture retrace error and misalignment correction, requiring neither complex mathematical algorithms nor subaperture overlaps. A numerical simulation exhibits the comparison of the performance of the NASSI and standard ASSI, which demonstrates the high accuracy of the NASSI in testing steep aspheric. Experimental results of NASSI are shown to be in good agreement with that of Zygo® VerifireTM Asphere interferometer.

  1. Flow measurements in a curved-wall annular contraction

    Energy Technology Data Exchange (ETDEWEB)

    Agrawal, A.K.; Tinneti, A.; Gollahalli, S.R. [Univ. of Oklahoma, Norman, OK (United States). Gas Turbine Systems Lab.

    1999-07-01

    Flow development in an annular contraction is of fundamental and practical importance in various applications including the gas turbine systems. This paper describes an experimental study of flow characteristics in a curved wall annular contraction. The results are presented in terms of the velocity vectors, surface pressure coefficients, static and stagnation pressure distributions, and profiles of mean velocities, turbulence intensity, and Reynolds shear stress. The flow conditions at the entrance were varied to evaluate how they affected the flow development in the passage. Results show that the contraction produced uniform static pressure and axial velocity profiles at the exit plane. Higher inlet turbulence affected the Reynolds shear stress in the contraction although the change in the static and total pressure fields was insignificant. The overall stagnation pressure loss was only 2 to 3 percent of the dynamic head at the contraction exit plane. Results showing only typical data are included in this paper. More extensive data sets to validate computer codes are available from the authors.

  2. Characterization of interfacial waves in horizontal core-annular flow

    Science.gov (United States)

    Tripathi, Sumit; Bhattacharya, Amitabh; Singh, Ramesh; Tabor, Rico F.

    2016-11-01

    In this work, we characterize interfacial waves in horizontal core annular flow (CAF) of fuel-oil and water. Experimental studies on CAF were performed in an acrylic pipe of 15.5mm internal diameter, and the time evolution of the oil-water interface shape was recorded with a high speed camera for a range of different flow-rates of oil (Qo) and water (Qw). The power spectrum of the interface shape shows a range of notable features. First, there is negligible energy in wavenumbers larger than 2 π / a , where a is the thickness of the annulus. Second, for high Qo /Qw , there is no single dominant wavelength, as the flow in the confined annulus does not allow formation of a preferred mode. Third, for lower Qo /Qw , a dominant mode arises at a wavenumber of 2 π / a . We also observe that the power spectrum of the interface shape depends weakly on Qw, and strongly on Qo, perhaps because the net shear rate in the annulus appears to depend weakly on Qw as well. We also attempt to build a general empirical model for CAF by relating the interfacial stress (calculated via the mean pressure gradient) to the flow rate in the annulus, the annular thickness and the core velocity. Authors are thankful to Orica Mining Services (Australia) for the financial support.

  3. Design Attributes and Scale Up Testing of Annular Centrifugal Contactors

    Energy Technology Data Exchange (ETDEWEB)

    David H. Meikrantz; Jack D. Law

    2005-04-01

    Annular centrifugal contactors are being used for rapid yet efficient liquid- liquid processing in numerous industrial and government applications. Commercialization of this technology began eleven years ago and now units with throughputs ranging from 0.25 to 700 liters per minute are readily available. Separation, washing, and extraction processes all benefit from the use of this relatively new commercial tool. Processing advantages of this technology include: low in-process volume per stage, rapid mixing and separation in a single unit, connection-in-series for multi-stage use, and a wide operating range of input flow rates and phase ratios without adjustment. Recent design enhancements have been added to simplify maintenance, improve inspection ability, and provide increased reliability. Cartridge-style bearing and mechanical rotary seal assemblies that can include liquid-leak sensors are employed to enhance remote operations, minimize maintenance downtime, prevent equipment damage, and extend service life. Clean-in-place capability eliminates the need for disassembly, facilitates the use of contactors for feed clarification, and can be automated for continuous operation. In nuclear fuel cycle studies, aqueous based separations are being developed that efficiently partition uranium, actinides, and fission products via liquid-liquid solvent extraction. Thus, annular centrifugal contactors are destined to play a significant role in the design of such new processes. Laboratory scale studies using mini-contactors have demonstrated feasibility for many such separation processes but validation at an engineering scale is needed to support actual process design.

  4. A compact annular ring microstrip antenna for WSN applications.

    Science.gov (United States)

    Wang, Daihua; Song, Linli; Zhou, Hanchang; Zhang, Zhijie

    2012-01-01

    A compact annular ring microstrip antenna was proposed for a wireless sensor network (WSN) application in the 2.4 GHz band. In this paper the major considerations of the conformal antenna design were the compact size and the impact on antenna's performance of a steel installation base. By using a chip resistor of large resistance (120 Ω) the antenna size was reduced to 38% of that a conventional annular ring patch antenna. With the addition of the steel installation base the resonant frequency of the antenna increases about 4.2% and the bandwidth reduces from 17.5% to 11.7% by adjusting the load resistance simultaneously. Several key parameters were discussed and optimized, and the antenna was fabricated and its performance measured. The antenna is well matched at 2.4 GHz with 34.2 dB return loss and -2.5 dBi peak gain. Meanwhile, it exhibits excellent radiation patterns with very low cross-polarization levels.

  5. A Compact Annular Ring Microstrip Antenna for WSN Applications

    Directory of Open Access Journals (Sweden)

    Daihua Wang

    2012-06-01

    Full Text Available A compact annular ring microstrip antenna was proposed for a wireless sensor network (WSN application in the 2.4 GHz band. In this paper the major considerations of the conformal antenna design were the compact size and the impact on antenna’s performance of a steel installation base. By using a chip resistor of large resistance (120 Ω the antenna size was reduced to 38% of that a conventional annular ring patch antenna. With the addition of the steel installation base the resonant frequency of the antenna increases about 4.2% and the bandwidth reduces from 17.5% to 11.7% by adjusting the load resistance simultaneously. Several key parameters were discussed and optimized, and the antenna was fabricated and its performance measured. The antenna is well matched at 2.4 GHz with 34.2 dB return loss and –2.5 dBi peak gain. Meanwhile, it exhibits excellent radiation patterns with very low cross-polarization levels.

  6. Electrostatic Analysis of Annular Holes Penetrated by Shorted-Cable

    Energy Technology Data Exchange (ETDEWEB)

    Choo, Jae Yul; Kim, Hyung Tae; Park, Hyun Shin; Cho, Young Sik [KINS, Daejeon (Korea, Republic of)

    2016-05-15

    The cabinet has an important role to protect the contained cables and digital modules for the safety function from the external electromagnetic (EM) source. Thus the immunity of an open cabinet against electromagnetic interference (EMI) numerically has been investigated using mode-matching method in. Another path for the external EM source to impinge on inner cables and digital modules is the bottom hole of the cabinet that is penetrated by various cables. Especially the EMI can detrimentally influence on the digital modules through annular space caused by sealing the bottom hole of the cabinet incompletely. Thus it is recently required that the electromagnetic interpretation in the annular hole is performed to remedy electromagnetic problems. Based on the mode-matching method, we solved the electrostatic boundary-value problem for holes penetrating shorted-cable at the bottom of a digital I and C cabinet. The Weber transform and the Hankel transform were applied to formulate the electrostatic potential. The capacitance and potential distribution generated near the penetrating shorted-cable were computed and compared with the result from the previous study.

  7. Design and characterization of the annular cathode high current pulsed electron beam source for circular components

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Wei; Wang, Langping, E-mail: aplpwang@hit.edu.cn; Wang, Xiaofeng

    2016-08-01

    Highlights: • An annular cathode for HCPEB irradiation of circular components was designed. • The processing window for the annular cathode is obtained. • Irradiation thickness uniformity along the circumferential direction exceeds 90%. - Abstract: In order to irradiate circular components with high current pulsed electron beam (HCPEB), an annular cathode based on carbon fiber bunches was designed and fabricated. Using an acceleration voltage of 25 kV, the maximum pulsed irradiation current and energy of this annular cathode can reach 7.9 kA and 300 J, respectively. The irradiation current density distribution of the annular cathode HCPEB source measured along the circumferential direction shows that the annular cathode has good emission uniformity. In addition, four 9310 steel substrates fixed uniformly along the circumferential direction of a metal ring substrate were irradiated by this annular cathode HCPEB source. The surface and cross-section morphologies of the irradiated samples were characterized by scanning electron microscopy (SEM). SEM images of the surface reveal that crater and surface undulation have been formed, which hints that the irradiation energy of the HCPEB process is large enough for surface modification of 9310 steel. Meanwhile, SEM cross-section images exhibit that remelted layers with a thickness of about 5.4 μm have been obtained in all samples, which proves that a good practical irradiation uniformity can be achieved by this annular cathode HCPEB source.

  8. Simultaneous occurrence of ulcerated necrobiosis lipoidica and granuloma annulare in a patient: case report.

    Science.gov (United States)

    Souza, Fernanda Homem de Mello de; Ribeiro, Camila Ferrari; Pereira, Marcela Abou Chami; Mesquita, Lismary; Fabrício, Lincoln

    2011-01-01

    Simultaneous occurrence of granuloma annulare and necrobiosis lipoidica is quite rare. There are seven reported cases in the literature, but only one presenting ulcerated necrobiosis lipoidica. We report a 39-year-old male with histopathologically confirmed granuloma annulare and ulcerated necrobiosis lipoidica, without diabetes mellitus.

  9. Maximizing prosthetic valve size with the Top Hat supra-annular aortic valve

    DEFF Research Database (Denmark)

    Aagaard, Jan; Geha, Alexander S.

    2007-01-01

    BACKGROUND AND AIM OF THE STUDY: The CarboMedics Top Hat supra-annular aortic valve allows a one-size (and often two-size) increase over the standard intra-annular valve. This advantage should minimize the risk of patient-prosthesis mismatch, where the effective prosthetic valve orifice area...

  10. Core-annular flow through a horizontal pipe: Hydrodynamic counterbalancing of buoyancy force on core

    NARCIS (Netherlands)

    Ooms, G.; Vuik, C.; Poesio, P.

    2007-01-01

    A theoretical investigation has been made of core-annular flow: the flow of a high-viscosity liquid core surrounded by a low-viscosity liquid annular layer through a horizontal pipe. Special attention is paid to the question of how the buoyancy force on the core, caused by a density difference betwe

  11. Annular Lichenoid Dermatitis of Youth: A Chronic Case Managed Using Pimecrolimus.

    Science.gov (United States)

    Malachowski, Stephen J; Creasey, Mackenzie; Kinkley, Nancy; Heaphy, Michael R

    2016-11-01

    Annular lichenoid dermatitis of youth, first described in 2003, is a rare and occasionally chronic skin disease. We report a case of annular lichenoid dermatitis of youth relapsing over the course of 5 years successfully treated and maintained with topical pimecrolimus cream.

  12. Core-annular flow through a horizontal pipe: Hydrodynamic counterbalancing of buoyancy force on core

    NARCIS (Netherlands)

    Ooms, G.; Vuik, C.; Poesio, P.

    2007-01-01

    A theoretical investigation has been made of core-annular flow: the flow of a high-viscosity liquid core surrounded by a low-viscosity liquid annular layer through a horizontal pipe. Special attention is paid to the question of how the buoyancy force on the core, caused by a density difference

  13. Erythema annulare centrifugum as presenting sign of activation of breast cancer*

    Science.gov (United States)

    Topal, Ilteris Oguz; Topal, Yunus; Sargan, Aytul; Duman, Hatice; Gungor, Sule; Goncu, Ozgur Emek Kocaturk; Ozekinci, Selver

    2015-01-01

    Erythema annulare centrifugum is a figurate erythema of unknown etiology. It has been associated with many different entities, including infections, food allergy, drug reactions and malignant neoplasms. Herein, we report a case of erythema annulare centrifugum as presenting sign of activation of breastcancer. PMID:26734884

  14. Erythema annulare centrifugum as presenting sign of activation of breast cancer.

    Science.gov (United States)

    Topal, Ilteris Oguz; Topal, Yunus; Sargan, Aytul; Duman, Hatice; Gungor, Sule; Goncu, Ozgur Emek Kocaturk; Ozekinci, Selver

    2015-01-01

    Erythema annulare centrifugum is a figurate erythema of unknown etiology. It has been associated with many different entities, including infections, food allergy, drug reactions and malignant neoplasms. Herein, we report a case of erythema annulare centrifugum as presenting sign of activation of breastcancer.

  15. Resonant SIMP dark matter

    Directory of Open Access Journals (Sweden)

    Soo-Min Choi

    2016-07-01

    Full Text Available We consider a resonant SIMP dark matter in models with two singlet complex scalar fields charged under a local dark U(1D. After the U(1D is broken down to a Z5 discrete subgroup, the lighter scalar field becomes a SIMP dark matter which has the enhanced 3→2 annihilation cross section near the resonance of the heavier scalar field. Bounds on the SIMP self-scattering cross section and the relic density can be fulfilled at the same time for perturbative couplings of SIMP. A small gauge kinetic mixing between the SM hypercharge and dark gauge bosons can be used to make SIMP dark matter in kinetic equilibrium with the SM during freeze-out.

  16. Dark Matter: Introduction

    CERN Document Server

    Rees, Martin J

    2003-01-01

    This short review was prepared as an introduction to the Royal Society's 'Dark Matter' conference. It addresses the embarrassing fact that 95% of the universe is unaccounted for. Favoured dark matter candidates are axions or weakly-interacting particles that have survived from the very early universe, but more exotic options cannot be excluded. Experimental searches are being made for the 'dark' particles but we have indirect clues to their nature too. Comparisons of data (from, eg, gravitational lensing) with numerical simulations of galaxy formation can constrain (eg) the particle velocities and collision cross sections. The mean cosmic density of dark matter (plus baryons) is now pinned down to be only about 30% of the critical density However, other recent evidence -- microwave background anisotropies, complemented by data on distant supernovae -- reveals that our universe actually is 'flat', and that its dominant ingredient (about 70% of the total mass-energy) is something quite unexpected -- 'dark energ...

  17. Is Dark Energy Falsifiable?

    CERN Document Server

    Gibson, Carl H

    2011-01-01

    Is the accelerating expansion of the Universe true, inferred through observations of distant supernovae, and is the implied existence of an enormous amount of anti-gravitational dark energy material driving the accelerating expansion of the universe also true? To be physically useful these propositions must be falsifiable; that is, subject to observational tests that could render them false, and both fail when viscous, diffusive, astro-biological and turbulence effects are included in the interpretation of observations. A more plausible explanation of negative stresses producing the big bang is turbulence at Planck temperatures. Inflation results from gluon viscous stresses at the strong force transition. Anti-gravitational (dark energy) turbulence stresses are powerful but only temporary. No permanent dark energy is needed. At the plasma-gas transition, viscous stresses cause fragmentation of plasma proto-galaxies into dark matter clumps of primordial gas planets, each of which falsifies dark-energy cold-dar...

  18. The Dark Energy Survey

    CERN Document Server

    Abbott, T; Annis, J; Barlow, M; Bebek, C; Bigelow, B; Beldica, C; Bernstein, R; Bridle, S; Brunner, R; Carlstrom, J; Campbell, M; Castander, F; Cunha, C; Diehl, H T; Dodelson, S; Doel, P; Efstathiou, G P; Estrada, J; Evrard, A; Fernndez, E; Flaugher, B; Fosalba, P; Frieman, J A; Gaztaaga, E; Gerdes, D; Gladders, M; Hu, W; Huterer, D; Jain, B; Karliner, I; Kent, S; Lahav, O; Levi, M; Lima, M; Lin, H; Limon, P; Martínez, M; McKay, T; McMahon, R; Merritt, W K; Miller, C; Miralda-Escudé, J; Mohr, J; Nichol, R; Oyaizu, H; Peacock, J; Peoples, John; Perlmutter, S; Plante, R; Ricker, P; Roe, N; Scarpine, V; Schubnell, M; Selen, M; Sheldon, E S; Smith, C; Stebbins, A; Stoughton, C; Suntzeff, N; Sutherland, W; Takada, M; Tarle, G; Tecchio, M; Thaler, J; Tucker, D; Viti, S; Walker, A; Wechsler, R; Weller, J; Wester, W

    2006-01-01

    We describe the Dark Energy Survey (DES), a proposed optical-near infrared survey of 5000 sq. deg of the South Galactic Cap to ~24th magnitude in SDSS griz, that would use a new 3 sq. deg CCD camera to be mounted on the Blanco 4-m telescope at Cerro Telolo Inter-American Observatory (CTIO). The survey data will allow us to measure the dark energy and dark matter densities and the dark energy equation of state through four independent methods: galaxy clusters, weak gravitational lensing tomography, galaxy angular clustering, and supernova distances. These methods are doubly complementary: they constrain different combinations of cosmological model parameters and are subject to different systematic errors. By deriving the four sets of measurements from the same data set with a common analysis framework, we will obtain important cross checks of the systematic errors and thereby make a substantial and robust advance in the precision of dark energy measurements.

  19. Fingerprinting Dark Energy

    CERN Document Server

    Sapone, Domenico

    2009-01-01

    Dark energy perturbations are normally either neglected or else included in a purely numerical way, obscuring their dependence on underlying parameters like the equation of state or the sound speed. However, while many different explanations for the dark energy can have the same equation of state, they usually differ in their perturbations so that these provide a fingerprint for distinguishing between different models with the same equation of state. In this paper we derive simple yet accurate approximations that are able to characterize a specific class of models (encompassing most scalar field models) which is often generically called "dark energy". We then use the approximate solutions to look at the impact of the dark energy perturbations on the dark matter power spectrum and on the integrated Sachs-Wolfe effect in the cosmic microwave background radiation.

  20. Dark Matter and Dark Energy The Critical Questions

    CERN Document Server

    Turner, M S

    2002-01-01

    Stars account for only about 0.5% of the content of the Universe; the bulk of the Universe is optically dark. The dark side of the Universe is comprised of: at least 0.1% light neutrinos; 3.5% +/- 1% baryons; 29% +/- 4% cold dark matter; and 66% +/- 6% dark energy. Now that we have characterized the dark side of the Universe, the challenge is to understand it. The critical questions are: (1) What form do the dark baryons take? (2) What is (are) the constituent(s) of the cold dark matter? (3) What is the nature of the mysterious dark energy that is causing the Universe to speed up.

  1. Dynamical Mutation of Dark Energy

    CERN Document Server

    Abramo, L R; Liberato, L; Rosenfeld, R

    2007-01-01

    We discuss the intriguing possibility that dark energy may change its equation of state in situations where large dark energy fluctuations are present. We show indications of this dynamical mutation in some generic models of dark energy.

  2. Annular core liquid-salt cooled reactor with multiple fuel and blanket zones

    Science.gov (United States)

    Peterson, Per F.

    2013-05-14

    A liquid fluoride salt cooled, high temperature reactor having a reactor vessel with a pebble-bed reactor core. The reactor core comprises a pebble injection inlet located at a bottom end of the reactor core and a pebble defueling outlet located at a top end of the reactor core, an inner reflector, outer reflector, and an annular pebble-bed region disposed in between the inner reflector and outer reflector. The annular pebble-bed region comprises an annular channel configured for receiving pebble fuel at the pebble injection inlet, the pebble fuel comprising a combination of seed and blanket pebbles having a density lower than the coolant such that the pebbles have positive buoyancy and migrate upward in said annular pebble-bed region toward the defueling outlet. The annular pebble-bed region comprises alternating radial layers of seed pebbles and blanket pebbles.

  3. Entrance and exit region friction factor models for annular seal analysis. Ph.D. Thesis

    Science.gov (United States)

    Elrod, David Alan

    1988-01-01

    The Mach number definition and boundary conditions in Nelson's nominally-centered, annular gas seal analysis are revised. A method is described for determining the wall shear stress characteristics of an annular gas seal experimentally. Two friction factor models are developed for annular seal analysis; one model is based on flat-plate flow theory; the other uses empirical entrance and exit region friction factors. The friction factor predictions of the models are compared to experimental results. Each friction model is used in an annular gas seal analysis. The seal characteristics predicted by the two seal analyses are compared to experimental results and to the predictions of Nelson's analysis. The comparisons are for smooth-rotor seals with smooth and honeycomb stators. The comparisons show that the analysis which uses empirical entrance and exit region shear stress models predicts the static and stability characteristics of annular gas seals better than the other analyses. The analyses predict direct stiffness poorly.

  4. Baryons as dark matter

    Energy Technology Data Exchange (ETDEWEB)

    Carr, B.J. [Queen Mary and Westfield Coll., London (United Kingdom). Astronomy Unit]|[Fermi National Accelerator Lab., Batavia, IL (United States). NASA/Fermilab Astrophysics Center

    1997-03-01

    Dark matter may reside in galactic disks, galactic halos, clusters of galaxies and the background Universe. Cosmological nucleosynthesis arguments suggest that only some fraction of the baryons in the Universe are in visible form, so at least some of the dark matter problems could be baryonic. The dark matter in galactic disks (if real) is almost certainly baryonic and, in this case, it is either in white dwarfs or brown dwarfs. The dark matter in galactic halos could be at least partly baryonic and, in this case, it is likely to be contained in the remnants of a first generation of pregalactic or protogalatic stars. The various constrains on the nature of such remnants suggest that brown dwarfs are the most plausible candidates, although (rather perplexingly) microlensing searches currently favor white dwarfs. The dark matter in clusters or intergalactic space could be baryonic only if one gives up the standard cosmological nucleosynthesis scenario or assumes that the dark objects are primordial black holes which formed before nucleosynthesis. If it is non-baryonic and in the form of cold WIMPs (Weakly Interacting Massive Particles), then such particles should also provide some of the halo dark matter. 89 refs., 1 fig., 2 tabs.

  5. Supernovae and Dark Energy

    Science.gov (United States)

    Domínguez, I.; Bravo, E.; Piersanti, L.; Straniero, O.; Tornambé, A.

    2009-08-01

    A decade ago the observations of thermonuclear supernovae at high-redhifts showed that the expansion rate of the Universe is accelerating and since then, the evidence for cosmic acceleration has gotten stronger. This acceleration requires that the Universe is dominated by dark energy, an exotic component characterized by its negative pressure. Nowadays all the available astronomical data (i.e. thermonuclear supernovae, cosmic microwave background, barionic acoustic oscillations, large scale structure, etc.) agree that our Universe is made of about 70% of dark energy, 25% of cold dark matter and only 5% of known, familiar matter. This Universe is geometrically flat, older than previously thought, its destiny is no longer linked to its geometry but to dark energy, and we ignore about 95% of its components. To understand the nature of dark energy is probably the most fundamental problem in physics today. Current astronomical observations are compatible with dark energy being the vacuum energy. Supernovae have played a fundamental role in modern Cosmology and it is expected that they will contribute to unveil the dark energy. In order to do that it is mandatory to understand the limits of supernovae as cosmological distance indicators, improving their precision by a factor 10.

  6. Dark Matter is Baryons

    CERN Document Server

    Soberman, R K; Soberman, Robert K.; Dubin, Maurice

    2001-01-01

    A comet-like, but magnitudes smaller, extremely low albedo interstellar meteoroid population of fragile aggregates with solar type composition, measured in space and terrestrially, is most probably the universal dark matter. Although non-baryonic particles cannot be excluded, only "Big Bang" cosmology predicts an appreciable fraction of such alternate forms. As more counter-physics hypotheses are added to fit observation to the expanding universe assumption, a classical physics alternative proffers dark matter interactive red shifts normally correlated with distance. The cosmic microwave background results from size-independent thermal plateau radiation that emanates from dark matter gravitationally drawn into the Galaxy.

  7. Dark Matter 2014

    Directory of Open Access Journals (Sweden)

    Schumann Marc

    2015-01-01

    Full Text Available This article gives an overview on the status of experimental searches for dark matter at the end of 2014. The main focus is on direct searches for weakly interacting massive particles (WIMPs using underground-based low-background detectors, especially on the new results published in 2014. WIMPs are excellent dark matter candidates, predicted by many theories beyond the standard model of particle physics, and are expected to interact with the target nuclei either via spin-independent (scalar or spin-dependent (axial-vector couplings. Non-WIMP dark matter candidates, especially axions and axion-like particles are also briefly discussed.

  8. Working the Dark Side

    DEFF Research Database (Denmark)

    Bjering, Jens Christian Borrebye

    A few days after the terror attacks of 9/11, then Vice President Dick Cheney appeared on television with a call for “working the dark side.” While still unclear what this expression entailed at the time, Cheney's comment appears in retrospect to almost have been prophetic for the years to come....... By analyzing official reports and testimonies from soldiers partaking in the War On Terror, the dissertation's second part—dark arts—focuses on the transformation of the dark side into a productive space in which “information” and the hunt for said information overshadowed all legal, ethical, or political...

  9. Dark energy crisis

    Energy Technology Data Exchange (ETDEWEB)

    Gu, J.-A. [Leung Center for Cosmology and Particle Astrophysics (LeCosPA), National Taiwan University (NTU), Taipei 10617, Taiwan (China)

    2010-11-01

    In cosmology we are facing the dark energy crisis: How can we survive huge vacuum energy, meanwhile living with tiny dark energy? For the solution to this crisis, we raise several clues and hints, in particular, supersymmetry and the double hierarchy, M{sub p}-M{sub SM}-M{sub DE} (Planck-Standard Model-dark energy scales). These two clues naturally lead to a solution with a supersymmetry-breaking brane-world. The train of thought from the clues to the solution is elucidated.

  10. SBC Dark Current Measurement

    Science.gov (United States)

    Ogaz, Sara

    2013-10-01

    This takes a series of SBC dark measurements over a continuous period of about 6 hours {4 orbits}. The aim is to collect dark images during an extended SBC on-time. Earlier measurements indicate that the dark current increases with SBC on-time and may also be increasing with overall SBC use. The 6-hour time matches the longest time used by any observer. As with all SBC observations this needs continuous SAA free time.This program is executed once per cycle. The last exposures were taken in Mar 2013 under Program 13161.

  11. Auschwitz dark tourism -kohteena

    OpenAIRE

    Kuusimäki, Karita

    2015-01-01

    Dark tourism eli synkkä matkailu on matkustamista kohteisiin, jotka liittyvät jollain tavalla kuolemaan, kauhuun, kärsimykseen tai katastrofeihin. Dark tourism on ilmiönä suhteellisen tuore, mutta sen historia juontaa juurensa jo antiikin ajan gladiaattoritaisteluihin. Ilmiötä on tutkittu jonkin verran ja siitä on tehty muutamia opinnäytetöitä. Yksi tunnetuimmista ja eniten vierailluista dark tourism -kohteista on Auschwitzin keskitysleiri. Auschwitz aloitti toimintansa vuonna 1940 ja le...

  12. Dark matter in voids

    Science.gov (United States)

    Fong, Richard; Doroshkevich, Andrei G.; Turchaninov, Victor I.

    1995-07-01

    The theory of the formation of large-scale structure in the universe through the action of gravitational instability imply the existence of substantial amounts of baryonic dark matter, of the order of 50% of the total baryon content in the universe, in the ``voids'' or under-dense regions seen in the large-scale distribution of galaxies. We discuss also the large-scale structure of dark matter expected in voids and the present and future possibilities for the observation of this baryonic dark matter in ``voids.''

  13. Dark matter in voids

    Energy Technology Data Exchange (ETDEWEB)

    Fong, R. [Department of Physics, University of Durham, Durham, DH1 3LE (United Kingdom); Doroshkevich, A.G. [Keldysh Institute of Applied Mathematics, 125047 Moscow (Russian Federation)]|[Teoretical Astrophysics Centrum, Blegsdamsvej 17, Copenhagen DK 2100 (Denmark); Turchaninov, V.I. [Keldysh Institute of Applied Mathematics, 125047 Moscow (Russian Federation)

    1995-07-01

    The theory of the formation of large-scale structure in the universe through the action of gravitational instability imply the existence of substantial amounts of baryonic dark matter, of the order of 50% of the total baryon content in the universe, in the ``voids`` or under-dense regions seen in the large-scale distribution of galaxies. We discuss also the large-scale structure of dark matter expected in voids and the present and future possibilities for the observation of this baryonic dark matter in ``voids.`` {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  14. Review on Dark Photon

    Directory of Open Access Journals (Sweden)

    Curciarello Francesca

    2016-01-01

    Full Text Available e+e− collider experiments at the intensity frontier are naturally suited to probe the existence of a force beyond the Standard Model between WIMPs, the most viable dark matter candidates. The mediator of this new force, known as dark photon, should be a new vector gauge boson very weakly coupled to the Standard Model photon. No significant signal has been observed so far. I will report on current limits set on the coupling factor ε2 between the photon and the dark photon by e+e− collider experiments.

  15. Dark Matter in ATLAS

    CERN Document Server

    Resconi, Silvia; The ATLAS collaboration

    2016-01-01

    Results of Dark Matter searches in mono-X analysis with the ATLAS experiment at the Large Hadron Collider are reported. The data were collected in proton–proton collisions at a centre-of-mass energy of 13 TeV and correspond to an integrated luminosity of 3.2 fb-1. A description of the main characteristics of each analysis and how the main backgrounds are estimated is shown. The observed data are in agreement with the expected Standard Model backgrounds for all analysis described. Exclusion limits are presented for Dark Matter models including pair production of dark matter candidates.

  16. Enabling Forbidden Dark Matter

    OpenAIRE

    Cline, James; Liu, Hongwan; Slatyer, Tracy; Xue, Wei

    2017-01-01

    The thermal relic density of dark matter is conventionally set by two-body annihilations. We point out that in many simple models, $3 \\to 2$ annihilations can play an important role in determining the relic density over a broad range of model parameters. This occurs when the two-body annihilation is kinematically forbidden, but the $3\\to 2$ process is allowed; we call this scenario "Not-Forbidden Dark Matter". We illustrate this mechanism for a vector portal dark matter model, showing that fo...

  17. The Dark Universe Riddle

    CERN Document Server

    Capistrano, A J S

    2008-01-01

    In this work we review some of the theoretical efforts and experimental evidences related to Dark matter and Dark energy problems in the universe. These dilemmas show us how incomplete our knowledge of gravity is, and how our concepts about the universe must at least be revised. Mainly, on the Wilkinson Microwave Anisotropy Probe (WMAP) fifth year, the data indicates that more than 90% of the total energy density of the universe is dark. Here we discuss the impact of these phenomena imprint on gravitational and quantum field theory's standard history. Moreover, we point out some recent and upcoming projects on Cosmology in a quest to understand theses issues thoroughly.

  18. Dark Matter 2014

    CERN Document Server

    Schumann, Marc

    2015-01-01

    This article gives an overview on the status of experimental searches for dark matter at the end of 2014. The main focus is on direct searches for weakly interacting massive particles (WIMPs) using underground-based low-background detectors, especially on the new results published in 2014. WIMPs are excellent dark matter candidates, predicted by many theories beyond the standard model of particle physics, and are expected to interact with the target nuclei either via spin-independent (scalar) or spin-dependent (axial-vector) couplings. Non-WIMP dark matter candidates, especially axions and axion-like particles are also briefly discussed.

  19. Searches for dark matter

    CERN Document Server

    Feinstein, Fabrice

    2000-01-01

    The fact that the mass of the visible stars could not account for the gravitational cohesion of the galaxies was the first sign of non-visible (i.e. dark) matter in the Universe. Since then, many observational evidences tell us that most of the matter is indeed dark. The nature of this dark matter is still unknown. There are good reasons to think that most of it is not composed of normal matter. These lectures will review the experimental methods, which have been developed to unravel this mystery and will compare their results with theoretical predictions.

  20. Casimir Effect for a Semitransparent Wedge and an Annular Piston

    CERN Document Server

    Milton, Kimball A; Kirsten, Klaus

    2009-01-01

    We consider the Casimir energy due to a massless scalar field in a geometry of an infinite wedge closed by a Dirichlet circular cylinder, where the wedge is formed by $\\delta$-function potentials, so-called semitransparent boundaries. A finite expression for the Casimir energy corresponding to the arc and the presence of both semitransparent potentials is obtained, from which the torque on the sidewalls can be derived. The most interesting part of the calculation is the nontrivial nature of the angular mode functions. Numerical results are obtained which are closely analogous to those recently found for a magnetodielectric wedge, with the same speed of light on both sides of the wedge boundaries. Alternative methods are developed for annular regions with radial semitransparent potentials, based on reduced Green's functions for the angular dependence, which allows calculations using the multiple-scattering formalism. Numerical results corresponding to the torque on the radial plates are likewise computed, whic...

  1. An in-house developed annular bright field detection system

    Science.gov (United States)

    Lari, Leonardo; Wright, Ian; Pingstone, Daniel; Steward, Jonathan; Gilks, Daniel; Lazarov, Vlado K.

    2014-06-01

    Annular bright field (ABF) detectors have been developed in the last few years allowing the direct imaging of low-Z atoms from oxygen down to hydrogen. These types of detectors are now available as standard attachments for the latest generation of top-end electron microscopes. However these systems cannot always be installed in previous generation microscopes. In this paper we report the preliminary results of an in-house implementation of a ABF detection system on a CEOS aberration corrected JEOL 2200FS STEM. This has been obtained by exploiting the standard BF detector coupled with a high vacuum compatible, X-ray tight and retractable shadowing mechanism. This results in the acquisition of near zero-angle scattered electrons with inner collection semi-angle from 2.0 mrad to 23 mrad and outer semi-angle in the range from 3.0 mrad to 35 mrad. The characteristics and performances of this ABF detection system are discussed.

  2. Geometry-Driven Folding of a Floating Annular Sheet.

    Science.gov (United States)

    Paulsen, Joseph D; Démery, Vincent; Toga, K Buğra; Qiu, Zhanlong; Russell, Thomas P; Davidovitch, Benny; Menon, Narayanan

    2017-01-27

    Predicting the large-amplitude deformations of thin elastic sheets is difficult due to the complications of self contact, geometric nonlinearities, and a multitude of low-lying energy states. We study a simple two-dimensional setting where an annular polymer sheet floating on an air-water interface is subjected to different tensions on the inner and outer rims. The sheet folds and wrinkles into many distinct morphologies that break axisymmetry. These states can be understood within a recent geometric approach for determining the gross shape of extremely bendable yet inextensible sheets by extremizing an appropriate area functional. Our analysis explains the remarkable feature that the observed buckling transitions between wrinkled and folded shapes are insensitive to the bending rigidity of the sheet.

  3. Development of annular targets for {sup 99}MO production.

    Energy Technology Data Exchange (ETDEWEB)

    Conner, C.; Lewandowski, E. F.; Snelgrove, J. L.; Liberatore, M. W.; Walker, D. E.; Wiencek, T. C.; McGann, D. J.; Hofman, G. L.; Vandegrift, G. F.

    1999-09-30

    The new annular target performed well during irradiation. The target is inexpensive and provides good heat transfer during irradiation. Based on these and previous tests, we conclude that targets with zirconium tubes and either nickel-plated or zinc-plated foils work well. We proved that we could use aluminum target tubes, which are much cheaper and easier to work with than the zirconium tubes. In aluminum target tubes nickel-plated fission-recoil barriers work well and prevent bonding of the foil to the new target tubes during irradiation. Also, zinc-plated and aluminum-foil barriers appear promising in anodized aluminum tubes. Additional tests are anticipated to address such issues as fission-recoil barrier thickness and uranium foil composition. Overall, however, the target was successful and will provide an inexpensive, efficient way to irradiate LEU metal foil for the production of {sup 99}Mo.

  4. Design of an Annular Disc Subject to Thermomechanical Loading

    Directory of Open Access Journals (Sweden)

    Sergei Alexandrov

    2012-01-01

    Full Text Available Two solutions to design a thin annular disc of variable thickness subject to thermomechanical loading are proposed. It is assumed that the thickness of the disc is everywhere sufficiently small for the stresses to be averaged through the thickness. The state of stress is plane. The initiation of plastic yielding is controlled by Mises yield criterion. The design criterion for one of the solutions proposed requires that the distribution of stresses is uniform over the entire disc. In this case there is a relation between optimal values of the loading parameters at the final stage. The specific shape of the disc corresponds to each pair of such parameters. The other solution is obtained under the additional requirement that the distribution of strains is uniform. This solution exists for the disc of constant thickness at specific values of the loading parameters.

  5. Intermittent Flow of Granular Matter in an Annular Geometry

    Science.gov (United States)

    Brzinski, Ted; Daniels, Karen E.

    Granular solids can be subjected to a finite stress below which the response is elastic. Above this yield stress, however, the material fails catastrophically, undergoing a rapid plastic deformation. In the case of a monotonically increasing stress the material exhibits a characteristic stick-slip response. We investigate the statistics of this intermittent failure in an annular shear geometry, driven with a linear-ramp torque in order to generate the stick-slip behavior. The apparatus is designed to allow visual access to particle trajectories and inter-particle forces (through the use of photoelastic materials). Additionally, twelve piezoelectric sensors at the outer wall measure acoustic emissions due to the plastic deformation of the material. We vary volume fraction, and use both fixed and deformable boundaries. We measure how the distribution of slip size and duration are related to the bulk properties of the packing, and compare to systems with similar governing statistics.

  6. Dynamic Response of Three-Layered Annular Plate with Imperfections

    Directory of Open Access Journals (Sweden)

    Pawlus Dorota

    2015-02-01

    Full Text Available This paper presents the imperfection sensitivity of annular plate with three-layered structure. The plate composed of thin elastic facings and a thicker elastic core is loaded in facing plane. The classical issue of a three-layered plate was solved for dynamic deflection problem using the approximation methods: orthogonalization and finite difference. The solution includes the axisymmetric and asymmetric plate modes of the dynamic stability loss. The evaluation of the rate of plate sensitivity to imperfection of plate preliminary geometry has been enriched by the analysis of plate models built of finite elements. The ABAQUS program has been used. The numerous calculation results in the form of deflection characteristics, buckling modes, values of critical parameters create the view of response of dynamic plate structure with different rate of imperfection and linear in time loading growth, too.

  7. Fluxons in long and annular intrinsic Josephson junction stacks

    Science.gov (United States)

    Clauss, T.; Oehmichen, V.; Mößle, M.; Müller, A.; Weber, A.; Koelle, D.; Kleiner, R.

    2002-12-01

    A promising approach towards a THz oscillator based on intrinsic Josephson junctions in high-temperature superconductors is based on the collective motion of Josephson fluxons, which are predicted to form various configurations ranging from a triangular to a quadratic lattice. Not only for this reason, but certainly also for the sake of basic physics, several experimental and theoretical investigations have been done on the subject of collective fluxon dynamics in stacked intrinsic Josephson junctions. In this paper we will present some experimental results on the fluxon dynamics of long intrinsic Josephson junction stacks made of Bi2Sr2CaCu2O8. The stacks were formed either in an open or in an annular geometry, and clear resonant fluxon modes were observed. Experiments discussed include measurements of current-voltage characteristics in external magnetic fields and in external microwave fields.

  8. Two-phase flow instabilities in a vertical annular channel

    Energy Technology Data Exchange (ETDEWEB)

    Babelli, I.; Nair, S.; Ishii, M. [Purdue Univ., West Lafayette, IN (United States)

    1995-09-01

    An experimental test facility was built to study two-phase flow instabilities in vertical annular channel with emphasis on downward flow under low pressure and low flow conditions. The specific geometry of the test section is similar to the fuel-target sub-channel of the Savannah River Site (SRS) Mark 22 fuel assembly. Critical Heat Flux (CHF) was observed following flow excursion and flow reversal in the test section. Density wave instability was not recorded in this series of experimental runs. The results of this experimental study show that flow excursion is the dominant instability mode under low flow, low pressure, and down flow conditions. The onset of instability data are plotted on the subcooling-Zuber (phase change) numbers stability plane.

  9. A Novel Design of Magnetorheological Damper with Annular Radial Channel

    Directory of Open Access Journals (Sweden)

    Shisha Zhu

    2016-01-01

    Full Text Available With the development of automotive vibration technology, the semiactive suspension system with adjustable damping force and high reliability is taken seriously. The magnetorheological damper (MRD that applies intelligent material (magnetorheological fluid is the key element of this system. It can achieve a continuous and adjustable damping and then reaches the purpose of comfort. In order to improve the damping effect of MRD, this paper presents a MRD, which has magnetorheological (MR effect along annular radial channel. The paper completely designs the structure and magnetic circuit of MRD. Based on the theory of electromagnetism and MR fluid dynamics, the paper analyzes and tests the external characteristics of the MRD by the MATLAB/Simulink and the vibration experiment. The results compared with ordinary MRD reveal that the damping force obviously increases and has wide adjustable range, thus verifying the reasonableness of the damper design.

  10. Fast High Capacity Annular Gas Puff Valve Design Concept

    Science.gov (United States)

    Ruden, Edward

    2000-10-01

    A fast opening gas valve design concept is presented that can theoretically inject a few grams of D2 gas radially outward into a coaxial annular vacuum region with a radius of about 10 cm in less that 100 μ s. The concept employs a single turn 20-30 T pulsed magnetic field coil that axially accelerates an Mg alloy ring, which seals a gas plenum, to high velocity, releasing the gas. Both coil and ring are profiled to minimize stress in the ring. Such a device could be used to supply the initial gas load for a proposed 5 MJ Dense Plasma Focus driven by AFRL's Shiva Star Capacitor bank. The intent here is keep the vacuum current feed insulator under high vacuum during the discharge to avoid surface breakdown. Alternatively, a high energy rep ratable plasma flow opening switch could be supplied with such a valve. This work is funded by the USAF.

  11. Control Rod Reactivity Curves for the Annular Core Research Reactor

    Science.gov (United States)

    Depriest, K. Russell; Kajder, Karen C.; Frye, Jason N.; Denman, Matthew R.

    2009-08-01

    Experiments were conducted at the Annular Core Research Reactor (ACRR) to increase the fidelity of the control rod integral reactivity worth curve. This experiment series was designed to refine the integral reactivity curve used for pulse yield prediction and eliminate the need for operator compensation in the pulse setup. The experiment series consisted of delayed critical and positive period measurements with various ACRR cavity configurations. An improved integral reactivity worth curve for the ACRR control rods has been constructed using the positive period measurements, the delayed critical measurements, and radiation transport modeling of the reactor. A series of prompt period measurements is used to validate that the new control rod curve more accurately predicts the energy yield of the pulse operations. The new reactivity worth curve is compared with the current curve that was developed using traditional approaches.

  12. Stability of Three-Layered Annular Plate with Composite Facings

    Science.gov (United States)

    Pawlus, D.

    2017-02-01

    Paper presents the behaviour of three-layered annular plates subjected to loads acting in plate plane. Plates are composed of laminated fibre-reinforced composite facings and foam core. The static and dynamic parameters of plate critical state were evaluated. The sensitivity of composite structure of plate to the acting of quickly increasing in time loads is shown. The problem has been solved numerically using the finite element method. Results have been compared with ones obtained for plate models with isotropic layers. These plate models have also been calculated solving formulated task analytically and numerically by means of the finite difference method. Solutions to the problem concern the axisymmetrical and asymmetrical plate buckling modes. Numerous presented tables and figures create the image of the stability behaviour of examined composite plates.

  13. Fluxons in long and annular intrinsic Josephson junction stacks

    Energy Technology Data Exchange (ETDEWEB)

    Clauss, T; Oehmichen, V; Moessle, M; Mueller, A; Weber, A; Koelle, D; Kleiner, R [Physikalisches Institut-Experimentalphysik II, Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

    2002-12-01

    A promising approach towards a THz oscillator based on intrinsic Josephson junctions in high-temperature superconductors is based on the collective motion of Josephson fluxons, which are predicted to form various configurations ranging from a triangular to a quadratic lattice. Not only for this reason, but certainly also for the sake of basic physics, several experimental and theoretical investigations have been done on the subject of collective fluxon dynamics in stacked intrinsic Josephson junctions. In this paper we will present some experimental results on the fluxon dynamics of long intrinsic Josephson junction stacks made of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}. The stacks were formed either in an open or in an annular geometry, and clear resonant fluxon modes were observed. Experiments discussed include measurements of current-voltage characteristics in external magnetic fields and in external microwave fields.

  14. Fluxons in long and annular intrinsic Josephson junction stacks

    CERN Document Server

    Clauss, T; Moessle, M; Müller, A; Weber, A; Kölle, D; Kleiner, R

    2002-01-01

    A promising approach towards a THz oscillator based on intrinsic Josephson junctions in high-temperature superconductors is based on the collective motion of Josephson fluxons, which are predicted to form various configurations ranging from a triangular to a quadratic lattice. Not only for this reason, but certainly also for the sake of basic physics, several experimental and theoretical investigations have been done on the subject of collective fluxon dynamics in stacked intrinsic Josephson junctions. In this paper we will present some experimental results on the fluxon dynamics of long intrinsic Josephson junction stacks made of Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8. The stacks were formed either in an open or in an annular geometry, and clear resonant fluxon modes were observed. Experiments discussed include measurements of current-voltage characteristics in external magnetic fields and in external microwave fields.

  15. Performance of annular flow sterilizer irradiated by a germicidal lamp

    Energy Technology Data Exchange (ETDEWEB)

    Sugawara, T.; Yoneya, M.; Ohashi, H. (Akita Univ. (Japan))

    1981-10-01

    Theoretical and experimental studies were conducted on the UV-inactivation characteristics of Bacillus subtilis spores in an annular-flow sterilizer irradiated by a germicidal lamp located at the center of the inner tube. Experimental results for sterilizer performance in laminar spore-suspension flow were well simulated dynamically and statically by theoretical considerations which incorporated multi-targets with single-hit model for the UV-inactivation kinetic and the diffuse light model for the angle characteristic of lamp, along with due attention to the parabolic velocity distribution and the negligible diffusion of spores. Scale on the outside wall of the inner tube was checked by the use of a cylindrical chemical actinometer. Calculated examples elucidate the reason why careful inspection is needed of UV-inactivation kinetics, angle characteristics of lamp, and fluid mixing to evaluate performance of actual flow UV sterilizers at high extent of inactivation up to the order of 99.999%.

  16. Annular elastolytic giant cell granuloma of conjunctiva: A case report

    Directory of Open Access Journals (Sweden)

    Karabi Konar

    2014-01-01

    Full Text Available Annular elastolytic giant cell granuloma is a condition characterized histologically by damaged elastic fibers associated with preponderance of giant cells along with absence of necrobiosis, lipid, mucin, and pallisading granuloma. It usually occurs on sun-damaged skin and hence the previous name actinic granuloma. A similar process occurs on the conjunctiva. Over the past three decades only four cases of conjunctival actinic granuloma have been documented. All the previous patients were females with lesions in nasal or temporal bulbar conjunctiva varying 2-3 mm in size. We report a male patient aged 70 years presenting with a 14 mm × 7 mm fleshy mass on right lower bulbar conjunctiva. Clinical differential diagnoses were lymphoma, squamous cell carcinoma in situ and amyloidosis. Surgical excision followed by histopathology confirmed it to be a case of actinic granuloma. This is the first case of isolated conjunctival actinic granuloma of such a large size reported from India.

  17. Quantum Haplodynamics, Dark Matter, and Dark Energy

    Directory of Open Access Journals (Sweden)

    Harald Fritzsch

    2014-01-01

    of the associated gauge group SU(2h is of the order of Λh≃0.3 TeV. One scalar state has zero haplon number and is the resonance observed at the LHC. In addition, there exist new bound states of haplons with no counterpart in the SM, having a mass of the order of 0.5 TeV up to a few TeV. In particular, a neutral scalar state with haplon number 4 is stable and can provide the dark matter in the universe. The QHD, QCD, and QED couplings can unify at the Planck scale. If this scale changes slowly with cosmic time, all of the fundamental couplings, the masses of the nucleons and of the DM particles, including the cosmological term (or vacuum energy density, will evolve with time. This could explain the dark energy of the universe.

  18. Scalar Field Dark Matter

    CERN Document Server

    Matos, T; Urena-Lopez, L A; Núñez, D

    2001-01-01

    This work is a review of the last results of research on the Scalar Field Dark Matter model of the Universe at cosmological and at galactic level. We present the complete solution to the scalar field cosmological scenario in which the dark matter is modeled by a scalar field $\\Phi$ with the scalar potential $V(\\Phi)=V_{0}(cosh {(\\lambda \\sqrt{\\kappa_{0}}\\Phi)}-1)$ and the dark energy is modeled by a scalar field $\\Psi$, endowed with the scalar potential $\\tilde{V}(\\Psi)= \\tilde{V_{0}}(\\sinh{(\\alpha \\sqrt{\\kappa_{0}}\\Psi)})^{\\beta}$, which together compose the 95% of the total matter energy in the Universe. The model presents successfully deals with the up to date cosmological observations, and is a good candidate to treat the dark matter problem at the galactic level.

  19. Dark matter searches

    CERN Document Server

    Baudis, Laura

    2015-01-01

    One of the major challenges of modern physics is to decipher the nature of dark matter. Astrophysical observations provide ample evidence for the existence of an invisible and dominant mass component in the observable universe, from the scales of galaxies up to the largest cosmological scales. The dark matter could be made of new, yet undiscovered elementary particles, with allowed masses and interaction strengths with normal matter spanning an enormous range. Axions, produced non-thermally in the early universe, and weakly interacting massive particles (WIMPs), which froze out of thermal equilibrium with a relic density matching the observations, represent two well-motivated, generic classes of dark matter candidates. Dark matter axions could be detected by exploiting their predicted coupling to two photons, where the highest sensitivity is reached by experiments using a microwave cavity permeated by a strong magnetic field. WIMPs could be directly observed via scatters off atomic nuclei in underground, ultr...

  20. Cleaning up dark matter

    CERN Multimedia

    Bignami, Giovanni Fabrizio

    2006-01-01

    "An experiment in Italy has found tantalizing but puzzling evidence for axions, one if the leading candidates for dark matter. The authors explain how a pair of spinning neutron stars should settle the issue once and for all." (3 pages)

  1. Holographic Dark Energy

    CERN Document Server

    Wang, Shuang; Li, Miao

    2016-01-01

    We review the paradigm of holographic dark energy (HDE), which arises from a theoretical attempt of applying the holographic principle (HP) to the dark energy (DE) problem. Making use of the HP and the dimensional analysis, we derive the general formula of the energy density of HDE. Then, we describe the properties of HDE model, in which the future event horizon is chosen as the characteristic length scale. We also introduce the theoretical explorations and the observational constraints for this model. Next, in the framework of HDE, we discuss various topics, such as spatial curvature, neutrino, instability of perturbation, time-varying gravitational constant, inflation, black hole and big rip singularity. In addition, from both the theoretical and the observational aspects, we introduce the interacting holographic dark energy scenario, where the interaction between dark matter and HDE is taken into account. Furthermore, we discuss the HDE scenario in various modified gravity (MG) theories, such as Brans-Dick...

  2. Dark Matter Candidates

    Energy Technology Data Exchange (ETDEWEB)

    Baltz, E.

    2004-12-03

    It is now widely accepted that most of mass-energy in the universe is unobserved except by its gravitational effects. Baryons make only about 4% of the total, with ''dark matter'' making up about 23% and the ''dark energy'' responsible for the accelerated expansion of the universe making up the remainder. We focus on the dark matter, which is the primary constituent of galaxies. We outline the observed properties of this material, enumerating some candidates covering 90 orders of magnitude in mass. Finally, we argue that the weak scale (100 GeV) is relevant to new physics, including the dark matter problem.

  3. Temporal dark polariton solitons

    CERN Document Server

    Kartashov, Yaroslav V

    2016-01-01

    We predict that strong coupling between waveguide photons and excitons of quantum well embedded into waveguide results in the formation of hybrid dark and anti-dark light-matter solitons. Such temporal solitons exist due to interplay between repulsive excitonic nonlinearity and giant group velocity dispersion arising in the vicinity of excitonic resonance. Such fully conservative states do not require external pumping to counteract losses and form continuous families parameterized by the power-dependent phase shift and velocity of their motion. Dark solitons are stable in the considerable part of their existence domain, while anti-dark solitons are always unstable. Both families exist outside forbidden frequency gap of the linear system.

  4. Inflatable Dark Matter.

    Science.gov (United States)

    Davoudiasl, Hooman; Hooper, Dan; McDermott, Samuel D

    2016-01-22

    We describe a general scenario, dubbed "inflatable dark matter," in which the density of dark matter particles can be reduced through a short period of late-time inflation in the early Universe. The overproduction of dark matter that is predicted within many, otherwise, well-motivated models of new physics can be elegantly remedied within this context. Thermal relics that would, otherwise, be disfavored can easily be accommodated within this class of scenarios, including dark matter candidates that are very heavy or very light. Furthermore, the nonthermal abundance of grand unified theory or Planck scale axions can be brought to acceptable levels without invoking anthropic tuning of initial conditions. A period of late-time inflation could have occurred over a wide range of scales from ∼MeV to the weak scale or above, and could have been triggered by physics within a hidden sector, with small but not necessarily negligible couplings to the standard model.

  5. Dark matter warms up

    CERN Multimedia

    Peplow, Mark

    2006-01-01

    "Unseen mass looks to be more "tepid" than thought. Astronomers have measured the temperature of dark matter for the first time. The discovery should help particle hunters to identify exactly what this mysterious substance is made of" (1 page)

  6. Distinct annular oligomers captured along the assembly and disassembly pathways of transthyretin amyloid protofibrils.

    Directory of Open Access Journals (Sweden)

    Ricardo H Pires

    Full Text Available BACKGROUND: Defects in protein folding may lead to severe degenerative diseases characterized by the appearance of amyloid fibril deposits. Cytotoxicity in amyloidoses has been linked to poration of the cell membrane that may involve interactions with amyloid intermediates of annular shape. Although annular oligomers have been detected in many amyloidogenic systems, their universality, function and molecular mechanisms of appearance are debated. METHODOLOGY/PRINCIPAL FINDINGS: We investigated with high-resolution in situ atomic force microscopy the assembly and disassembly of transthyretin (TTR amyloid protofibrils formed of the native protein by pH shift. Annular oligomers were the first morphologically distinct intermediates observed in the TTR aggregation pathway. Morphological analysis suggests that they can assemble into a double-stack of octameric rings with a 16 ± 2 nm diameter, and displaying the tendency to form linear structures. According to light scattering data coupled to AFM imaging, annular oligomers appeared to undergo a collapse type of structural transition into spheroid oligomers containing 8-16 monomers. Disassembly of TTR amyloid protofibrils also resulted in the rapid appearance of annular oligomers but with a morphology quite distinct from that observed in the assembly pathway. CONCLUSIONS/SIGNIFICANCE: Our observations indicate that annular oligomers are key dynamic intermediates not only in the assembly but also in the disassembly of TTR protofibrils. The balance between annular and more compact forms of aggregation could be relevant for cytotoxicity in amyloidogenic disorders.

  7. Dark matter universe.

    Science.gov (United States)

    Bahcall, Neta A

    2015-10-06

    Most of the mass in the universe is in the form of dark matter--a new type of nonbaryonic particle not yet detected in the laboratory or in other detection experiments. The evidence for the existence of dark matter through its gravitational impact is clear in astronomical observations--from the early observations of the large motions of galaxies in clusters and the motions of stars and gas in galaxies, to observations of the large-scale structure in the universe, gravitational lensing, and the cosmic microwave background. The extensive data consistently show the dominance of dark matter and quantify its amount and distribution, assuming general relativity is valid. The data inform us that the dark matter is nonbaryonic, is "cold" (i.e., moves nonrelativistically in the early universe), and interacts only weakly with matter other than by gravity. The current Lambda cold dark matter cosmology--a simple (but strange) flat cold dark matter model dominated by a cosmological constant Lambda, with only six basic parameters (including the density of matter and of baryons, the initial mass fluctuations amplitude and its scale dependence, and the age of the universe and of the first stars)--fits remarkably well all the accumulated data. However, what is the dark matter? This is one of the most fundamental open questions in cosmology and particle physics. Its existence requires an extension of our current understanding of particle physics or otherwise point to a modification of gravity on cosmological scales. The exploration and ultimate detection of dark matter are led by experiments for direct and indirect detection of this yet mysterious particle.

  8. Elastically Decoupling Dark Matter

    CERN Document Server

    Kuflik, Eric; Lorier, Nicolas Rey-Le; Tsai, Yu-Dai

    2015-01-01

    We present a novel dark matter candidate, an Elastically Decoupling Relic (ELDER), which is a cold thermal relic whose present abundance is determined by the cross-section of its elastic scattering on Standard Model particles. The dark matter candidate is predicted to have a mass ranging from a few to a few hundred MeV, and an elastic scattering cross-section with electrons, photons and/or neutrinos in the $10^{-3}-1$ fb range.

  9. Elastically Decoupling Dark Matter.

    Science.gov (United States)

    Kuflik, Eric; Perelstein, Maxim; Lorier, Nicolas Rey-Le; Tsai, Yu-Dai

    2016-06-03

    We present a novel dark matter candidate, an elastically decoupling relic, which is a cold thermal relic whose present abundance is determined by the cross section of its elastic scattering on standard model particles. The dark matter candidate is predicted to have a mass ranging from a few to a few hundred MeV, and an elastic scattering cross section with electrons, photons and/or neutrinos in the 10^{-3}-1  fb range.

  10. Antibaryonic dark matter

    CERN Document Server

    Gorbunov, D

    2013-01-01

    Assuming existence of (very) heavy fourth generation of quarks and antiquarks we argue that antibaryon composed of the three heavy antiquarks can be light, stable and invisible, hence a good candidate for the Dark matter particle. Such opportunity allows to keep the baryon number conservation for the generation of the visible baryon asymmetry. The dark matter particles traveling through the ordinary matter will annihilate with nucleons inducing proton(neutron)-decay-like events with ~5GeV energy release in outcoming particles.

  11. Dark radiation from a unified dark fluid model

    CERN Document Server

    Geng, Chao-Qiang; Zhang, Xin

    2014-01-01

    We present a unified dark fluid model to describe the possible evolutionary behavior of $\\Delta N_\\mathrm{eff}$ in dark radiation. This model can be viewed as an interacting model for the dark sectors, in which dark matter interacts with dark radiation. We show that the evolution of $\\Delta N_\\mathrm{eff}$ can be nicely explained without some drawbacks, such as the blowup of $\\Delta N_\\mathrm{eff}$ at the late time and the interaction term at the early time.

  12. Dark Stars: A Review

    CERN Document Server

    Freese, Katherine; Spolyar, Douglas; Valluri, Monica

    2015-01-01

    Dark Stars (DS) are stellar objects made (almost entirely) of ordinary atomic material but powered by the heat from Dark Matter (DM) annihilation (rather than by fusion). Weakly Interacting Massive Particles (WIMPs), among the best candidates for DM, can be their own antimatter and can accumulate inside the star, with their annihilation products thermalizing with and heating the DS. The resulting DSs are in hydrostatic and thermal equilibrium. The first phase of stellar evolution in the history of the Universe may have been dark stars. Though DM constituted only $10^6 M_\\odot$), very bright ($>10^9 L_\\odot$), and potentially detectable with the James Webb Space Telescope (JWST). Once the DM runs out and the dark star dies, it may collapse to a black hole; thus DSs can provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The curre...

  13. Tight focus of a radially polarized and amplitudemodulated annular multi-Gaussian beam

    Institute of Scientific and Technical Information of China (English)

    Chen Jian-Nong; Xu Qin-Feng; Wang Gang

    2011-01-01

    The focusing of a radially polarized beam without annular apodization ora phase filter at the entrance pupil of the objective results in a wide focus and low purity of the longitudinally polarized component.However,the presence of a physical annular apodization or phase filter makes some applications more difficult or even impossible.We propose a radially polarized and amplitude-modulated annular multi-Gaussian beam mode.Numerical simulation shows that it can be focused into a sharper focal spot of 0.125λ2 without additional apodizations or filters.The beam quality describing the purity of longitudinally polarized component is up to 86%.

  14. An analytical model for annular flow boiling heat transfer in microchannel heat sinks

    Energy Technology Data Exchange (ETDEWEB)

    Megahed, A.; Hassan, I. [Concordia University, Montreal, QC (Canada). Dept. of Mechanical and Industrial Engineering

    2009-07-01

    An analytical model has been developed to predict flow boiling heat transfer coefficient in microchannel heat sinks. The new analytical model is proposed to predict the two-phase heat transfer coefficient during annular flow regime based on the separated model. Opposing to the majority of annular flow heat transfer models, the model is based on fundamental conservation principles. The model considers the characteristics of microchannel heat sink during annular flow and eliminates using any empirical closure relations. Comparison with limited experimental data was found to validate the usefulness of this analytical model. The model predicts the experimental data with a mean absolute error 8%. (author)

  15. On the Motion of an Annular Film in Microgravity Gas-Liquid Flow

    Science.gov (United States)

    McQuillen, John B.

    2002-01-01

    Three flow regimes have been identified for gas-liquid flow in a microgravity environment: Bubble, Slug, and Annular. For the slug and annular flow regimes, the behavior observed in vertical upflow in normal gravity is similar to microgravity flow with a thin, symmetrical annular film wetting the tube wall. However, the motion and behavior of this film is significantly different between the normal and low gravity cases. Specifically, the liquid film will slow and come to a stop during low frequency wave motion or slugging. In normal gravity vertical upflow, the film has been observed to slow, stop, and actually reverse direction until it meets the next slug or wave.

  16. Characterization of annular two-phase gas-liquid flows in microgravity

    Science.gov (United States)

    Bousman, W. Scott; Mcquillen, John B.

    1994-01-01

    A series of two-phase gas-liquid flow experiments were developed to study annular flows in microgravity using the NASA Lewis Learjet. A test section was built to measure the liquid film thickness around the perimeter of the tube permitting the three dimensional nature of the gas-liquid interface to be observed. A second test section was used to measure the film thickness, pressure drop and wall shear stress in annular microgravity two-phase flows. Three liquids were studied to determine the effects of liquid viscosity and surface tension. The result of this study provide insight into the wave characteristics, pressure drop and droplet entrainment in microgravity annular flows.

  17. High-power test of annular-ring coupled structures for the J-PARC linac energy upgrade

    Science.gov (United States)

    Tamura, Jun; Ao, Hiroyuki; Nemoto, Yasuo; Asano, Hiroyuki; Suzuki, Takahiro

    2015-02-01

    Annular-ring coupled structures (ACSs) will increase the beam energy of the Japan proton accelerator research complex (J-PARC) linac from 181 to 400 MeV to achieve a beam power of 1 MW for a materials and life science experimental facility. The mass production of the ACS cavities commenced in March 2009. Before the installation, all cavities require power testing. High-power testing is essential not only for confirming the cavity's design performance but also for preventing delays in cavity conditioning schedule. However, the 2011 Tohoku earthquake damaged J-PARC facilities, including the ACS power-test area, and cavity conditioning was interrupted for two years. After the facility's restoration, two ACS cavities (M01 and M11) were conditioned. They performed 15-20% above the designed accelerating field of 4.2 MV/m. As M01 was initially conditioned six years ago, the most recent conditioning time required for M01 was drastically reduced. From this result, we confirmed that long-term stored ACS cavities purged with nitrogen gas do not produce critical cavity performance issues. During high-power operation of M11, which is a unique cavity equipped with a capacitive iris in a waveguide, no significant increases in the temperature and the discharge rate around the capacitive iris were observed. Even considering beam loss due to residual gas scattering, the vacuum pressure was sufficiently low (4 × 10-6 Pa). More stable operation can be expected following a month-long conditioning process before the beam is commissioned. M11's conditioning successfully demonstrated an auto-conditioning program, and we established the conditioning scheme using this auto-conditioning program for all ACS cavities in a limited time and with limited manpower.

  18. Flight-Determined Subsonic Longitudinal Stability and Control Derivatives of the F-18 High Angle of Attack Research Vehicle (HARV) with Thrust Vectoring

    Science.gov (United States)

    Iliff, Kenneth W.; Wang, Kon-Sheng Charles

    1997-01-01

    The subsonic longitudinal stability and control derivatives of the F-18 High Angle of Attack Research Vehicle (HARV) are extracted from dynamic flight data using a maximum likelihood parameter identification technique. The technique uses the linearized aircraft equations of motion in their continuous/discrete form and accounts for state and measurement noise as well as thrust-vectoring effects. State noise is used to model the uncommanded forcing function caused by unsteady aerodynamics over the aircraft, particularly at high angles of attack. Thrust vectoring was implemented using electrohydraulically-actuated nozzle postexit vanes and a specialized research flight control system. During maneuvers, a control system feature provided independent aerodynamic control surface inputs and independent thrust-vectoring vane inputs, thereby eliminating correlations between the aircraft states and controls. Substantial variations in control excitation and dynamic response were exhibited for maneuvers conducted at different angles of attack. Opposing vane interactions caused most thrust-vectoring inputs to experience some exhaust plume interference and thus reduced effectiveness. The estimated stability and control derivatives are plotted, and a discussion relates them to predicted values and maneuver quality.

  19. Cosmological Evolution With Interaction Between Dark Energy And Dark Matter

    CERN Document Server

    Bolotin, Yu L; Lemets, O A; Yerokhin, D A

    2013-01-01

    In this review we consider in detail different theoretical topics associated with interaction in the dark sector. We study linear and nonlinear interactions which depend on the dark matter and dark energy densities. We consider a number of different models (including the holographic dark energy and dark energy in a fractal universe) with interacting dark energy (DE) and dark matter (DM), have done a thorough analysis of these models. The main task of this review was not only to give an idea about the modern set of different models of dark energy, but to show how much can be diverse dynamics of the universe in these models. We find that the dynamics of a Universe that contains interaction in the dark sector can differ significantly from the Standard Cosmological Model (SCM).

  20. Non-Abelian dark matter and dark radiation

    CERN Document Server

    Buen-Abad, Manuel A; Schmaltz, Martin

    2015-01-01

    We propose a new class of dark matter models with unusual phenomenology. What is ordinary about our models is that dark matter particles are WIMPs, they are weakly coupled to the Standard Model and have weak scale masses. What is unusual is that they come in multiplets of a new "dark" non-Abelian gauge group with milli-weak coupling. The massless dark gluons of this dark gauge group contribute to the energy density of the universe as a form of weakly self-interacting dark radiation. In this paper we explore the consequences of having i.) dark matter in multiplets ii.) self-interacting dark radiation and iii.) dark matter which is weakly coupled to dark radiation. We find that i.) dark matter cross sections are modified by multiplicity factors which have significant consequences for collider searches and indirect detection, ii.) dark gluons have thermal abundances which affect the CMB as dark radiation. Unlike additional massless neutrino species the dark gluons are interacting and have vanishing viscosity and...

  1. GUTzilla Dark Matter

    CERN Document Server

    Harigaya, Keisuke; Lou, Hou Keong

    2016-01-01

    Motivated by gauge coupling unification and dark matter, we present an extension to the Standard Model where both are achieved by adding an extra new matter multiplet. Such considerations lead to a Grand Unified Theory with very heavy WIMPzilla dark matter, which has mass greater than ~10^7 GeV and must be produced before reheating ends. Naturally, we refer to this scenario as GUTzilla dark matter. Here we present a minimal GUTzilla model, adding a vector-like quark multiplet to the Standard Model. Proton decay constraints require the new multiplet to be both color and electroweak charged, which prompts us to include a new confining SU(3) gauge group that binds the multiplet into a neutral composite dark matter candidate. Current direct detection constraints are evaded due to the large dark matter mass; meanwhile, next-generation direct detection and proton decay experiments will probe much of the parameter space. The relic abundance is strongly dependent on the dynamics of the hidden confining sector, and we...

  2. Vectorlike sneutrino dark matter

    Science.gov (United States)

    Tang, Yi-Lei; Zhu, Shou-hua

    2016-05-01

    In this paper, we discuss the minimal supersymmetric standard model (MSSM) extended with one vectorlike lepton doublet L -L ¯ and one right-handed neutrino N . The neutral vecotorlike sneutrino can be a candidate of dark matter. To avoid the interaction with the nucleons by exchanging a Z boson, the mass splitting between the real part and the imaginary part of the sneutrino field is needed. Compared with the MSSM sneutrino dark matter, the mass splitting between the vectorlike sneutrino field can be more naturally acquired without large A terms and constraints on the neutralino masses. We have also calculated the relic density and the elastic scattering cross sections with the nucleons in the cases that the dark matter particles coannihilate with or without the MSSM slepton doublets. The elastic scattering cross sections with the nucleons are well below the LUX bounds. In the case that the dark matter coannihilates with all the MSSM slepton doublets, the mass of the dark matter can be as light as 370 GeV.

  3. Levitating dark matter

    Science.gov (United States)

    Kaloper, Nemanja; Padilla, Antonio

    2009-10-01

    A sizable fraction of the total energy density of the universe may be in heavy particles with a net dark U(1)' charge comparable to its mass. When the charges have the same sign the cancellation between their gravitational and gauge forces may lead to a mismatch between different measures of masses in the universe. Measuring galactic masses by orbits of normal matter, such as galaxy rotation curves or lensing, will give the total mass, while the flows of dark matter agglomerates may yield smaller values if the gauge repulsion is not accounted for. If distant galaxies which house light beacons like SNe Ia contain such dark particles, the observations of their cosmic recession may mistake the weaker forces for an extra `antigravity', and infer an effective dark energy equation of state smaller than the real one. In some cases, including that of a cosmological constant, these effects can mimic w < -1. They can also lead to a local variation of galaxy-galaxy forces, yielding a larger `Hubble Flow' in those regions of space that could be taken for a dynamical dark energy, or superhorizon effects.

  4. Coupling q-deformed dark energy to dark matter

    CERN Document Server

    Dil, Emre

    2016-01-01

    We propose a novel coupled dark energy model which is assumed to occur as a q-deformed scalar field and investigate whether it will provide an expanding universe phase. We consider the q-deformed dark energy as coupled to dark matter inhomogeneities. We perform the phase-space analysis of the model by numerical methods and find the late-time accelerated attractor solutions. The attractor solutions imply that the coupled q-deformed dark energy model is consistent with the conventional dark energy models satisfying an acceleration phase of universe. At the end, we compare the cosmological parameters of deformed and standard dark energy models and interpret the implications.

  5. Theoretical and Experimental Investigation of Ultrasonic Focusing with Annular Phased Array

    Institute of Scientific and Technical Information of China (English)

    ZHANG Bi-Xing; WANG Cheng-Hao; LAI Pu-Xiang

    2006-01-01

    @@ The focused acoustic field generated by an annular array transducer and its reflection field on a solid-liquid interface are investigated theoretically and experimentally. Theoretically, the concise analytic expressions about the radiation and reflection acoustic fields of the annular phased array are obtained by the ray approach method (saddle-point method). In experiment, an annular transducer with 8 equal-area elements is designed and fabricated, and a series of experiments about the radiation acoustic field and its reflection on the liquid-solid interface are carried out. The experimental characteristics of the transducer are in good agreement with the numerical ones. It shows the correctness of the theoretical result and the feasibility of dynamic focusing of the experiment system. With the maximum amplitude and its emergence time of the reflection wave, we can acquire the information and the imaging of the reflection interface by the annular phased array dynamic focusing.

  6. Biofilm Community Dynamics in Bench-Scale Annular Reactors Simulating Arrestment of Chloraminated Drinking Water Nitrification

    Science.gov (United States)

    Annular reactors (ARs) were used to study biofilm community succession and provide an ecological insight during nitrification arrestment through simultaneously increasing monochloramine (NH2Cl) and chlorine to nitrogen mass ratios, resulting in four operational periods (I to IV)....

  7. An iterative method for the solution of nonlinear systems using the Faber polynomials for annular sectors

    Energy Technology Data Exchange (ETDEWEB)

    Myers, N.J. [Univ. of Durham (United Kingdom)

    1994-12-31

    The author gives a hybrid method for the iterative solution of linear systems of equations Ax = b, where the matrix (A) is nonsingular, sparse and nonsymmetric. As in a method developed by Starke and Varga the method begins with a number of steps of the Arnoldi method to produce some information on the location of the spectrum of A. This method then switches to an iterative method based on the Faber polynomials for an annular sector placed around these eigenvalue estimates. The Faber polynomials for an annular sector are used because, firstly an annular sector can easily be placed around any eigenvalue estimates bounded away from zero, and secondly the Faber polynomials are known analytically for an annular sector. Finally the author gives three numerical examples, two of which allow comparison with Starke and Varga`s results. The third is an example of a matrix for which many iterative methods would fall, but this method converges.

  8. Annular lichenoid dermatitis of youth--a further case in a 12-year-old girl.

    Science.gov (United States)

    Kleikamp, Stefanie; Kutzner, Heinz; Frosch, Peter J

    2008-08-01

    Annular lichenoid dermatitis of youth was first described by Annessi et al. in 2003. Clinical criteria are persistent erythematous macules and annular lesions with a red-brown edge and a central hypopigmentation usually found on the flanks and groins of children and adolescents. Histologically, the disease is characterized by a lichenoid interface dermatitis with necrotic keratinocytes at the tip of the rete ridges. In our case a 12-year old girl developed annular red-brown macules with papules at the borders in an inframammary location. The histology of the lesion's border showed a lichenoid lymphocytic infiltrate with apoptotic keratinocytes at the tip of rete ridges. The lesions cleared with 0.03% tacrolimus ointment. Annular lichenoid dermatitis of youth is probably a new entity in the group of lichenoid dermatoses.

  9. Design of radial phononic crystal using annular soft material with low-frequency resonant elastic structures

    Science.gov (United States)

    Gao, Nansha; Wu, Jiu Hui; Yu, Lie; Xin, Hang

    2016-10-01

    Using FEM, we theoretically study the vibration properties of radial phononic crystal (RPC) with annular soft material. The band structures, transmission spectra, and displacement fields of eigenmode are given to estimate the starting and cut-off frequency of band gaps. Numerical calculation results show that RPC with annular soft material can yield low-frequency band gaps below 350 Hz. Annular soft material decreases equivalent stiffness of the whole structure effectively, and makes corresponding band gaps move to the lower frequency range. Physical mechanism behind band gaps is the coupling effect between long or traveling wave in plate matrix and the vibrations of corrugations. By changing geometrical dimensions of plate thickness e, the length of silicone rubber h2, and the corrugation width b, we can control the location and width of the first band gap. These research conclusions of RPC structure with annular soft material can potentially be applied to optimize band gaps, generate filters, and design acoustic devices.

  10. THE MAGIC OF DARK TOURISM

    Directory of Open Access Journals (Sweden)

    Erika KULCSÁR

    2015-10-01

    Full Text Available The dark tourism is a form of tourism that is not unanimously accepted by the whole society, but in spite of this fact, the practitioners of dark tourism is a viable segment. Indeed the concept that defines dark tourism is none other than death, and perhaps this is why it will always be a segment that will not be attracted by this form of tourism. Many questions about dark tourism arise. Among them: (1 is dark tourism an area of science attractive for researches? (2 which is the typology of dark tourism? (3 what are the motivating factors that determine practicing dark tourism? This paper provides a detailed analysis of publication behaviour in the field of dark tourism. The article also includes the main results obtained by achieving a quantitative marketing research among students of Sfantu Gheorghe University Extension in order to know their opinion, attitude towards dark tourism.

  11. Instability of Annular Beam with Finite Thickness in Dielectric-Loaded Cylindrical Waveguide

    OpenAIRE

    Tamura, Shusuke; Yamakawa, Mitsuhisa; Takashima, Yusuke; Ogura, Kazuo

    2008-01-01

    The cherenkov and slow cyclotron instabilities driven by an axially injected electron beam in a cylindrical waveguide are studied using a new version of the self-consistent linear theory considering three-dimensional beam perturbations. There are three kinds of models for beam instability analysis, which are based on a cylindrical solid beam, an infinitesimally thin annular beam, and a finitely thick annular beam. Among these models, the beam shape properly representing the often used actual ...

  12. WISPy cold dark matter

    Energy Technology Data Exchange (ETDEWEB)

    Arias, Paola [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Pontificia Univ. Catolica de Chile, Santiago (Chile). Facultad de Fisica; Cadamuro, Davide; Redondo, Javier [Max-Planck-Institut fuer Physik, Muenchen (Germany); Goodsell, Mark [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); European Organization for Nuclear Research (CERN), Geneva (Switzerland); Jaeckel, Joerg [Durham Univ. (United Kingdom). Inst. for Particle Physics Phenomenology; Ringwald, Andreas [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2012-01-15

    Very weakly interacting slim particles (WISPs), such as axion-like particles (ALPs) or hidden photons (HPs), may be non-thermally produced via the misalignment mechanism in the early universe and survive as a cold dark matter population until today. We find that, both for ALPs and HPs whose dominant interactions with the standard model arise from couplings to photons, a huge region in the parameter spaces spanned by photon coupling and ALP or HP mass can give rise to the observed cold dark matter. Remarkably, a large region of this parameter space coincides with that predicted in well motivated models of fundamental physics. A wide range of experimental searches - exploiting haloscopes (direct dark matter searches exploiting microwave cavities), helioscopes (searches for solar ALPs or HPs), or light-shining-through-a-wall techniques - can probe large parts of this parameter space in the foreseeable future. (orig.)

  13. Superheavy dark matter

    CERN Document Server

    Chung, Daniel J.H.; Riotto, Antonio; Chung, Daniel J. H.; Kolb, Edward W.; Riotto, Antonio

    1999-01-01

    We show that, contrary to the standard lore, dark matter may be superheavy (many orders of magnitude larger than the weak scale). We show that massive particles may be produced naturally during the transition from the inflationary phase to either a matter-dominated or radiation-dominated phase as a result of the expansion of the background spacetime acting on vacuum quantum fluctuations of the dark matter field. We find that as long as there are stable particles whose mass is of the order of the inflaton mass (presumably around 10^13 GeV), they will be produced in sufficient abundance to give Omega_0=1 quite independently of any details of the non-gravitational interactions of the dark-matter field.

  14. Dark chocolate exacerbates acne.

    Science.gov (United States)

    Vongraviopap, Saivaree; Asawanonda, Pravit

    2016-05-01

    The effects of chocolate on acne exacerbations have recently been reevaluated. For so many years, it was thought that it had no role in worsening acne. To investigate whether 99% dark chocolate, when consumed in regular daily amounts, would cause acne to worsen in acne-prone male subjects, twenty-five acne prone male subjects were asked to consume 25 g of 99% dark chocolate daily for 4 weeks. Assessments which included Leeds revised acne scores as well as lesion counts took place weekly. Food frequency questionnaire was used, and daily activities were recorded. Statistically significant changes of acne scores and numbers of comedones and inflammatory papules were detected as early as 2 weeks into the study. At 4 weeks, the changes remained statistically significant compared to baseline. Dark chocolate when consumed in normal amounts for 4 weeks can exacerbate acne in male subjects with acne-prone skin. © 2015 The International Society of Dermatology.

  15. Natural minimal dark matter

    CERN Document Server

    Fabbrichesi, Marco

    2015-01-01

    We show how the Higgs boson mass is protected from the potentially large corrections due to the introduction of minimal dark matter if the new physics sector is made supersymmetric. The fermionic dark matter candidate (a 5-plet of $SU(2)_L$) is accompanied by a scalar state. The weak gauge sector is made supersymmetric and the Higgs boson is embedded in a supersymmetric multiplet. The remaining standard model states are non-supersymmetric. Non vanishing corrections to the Higgs boson mass only appear at three-loop level and the model is natural for dark matter masses up to 15 TeV--a value larger than the one required by the cosmological relic density. The construction presented stands as an example of a general approach to naturalness that solves the little hierarchy problem which arises when new physics is added beyond the standard model at an energy scale around 10 TeV.

  16. Nearly Supersymmetric Dark Atoms

    Energy Technology Data Exchange (ETDEWEB)

    Behbahani, Siavosh R.; Jankowiak, Martin; /SLAC /Stanford U., ITP; Rube, Tomas; /Stanford U., ITP; Wacker, Jay G.; /SLAC /Stanford U., ITP

    2011-08-12

    Theories of dark matter that support bound states are an intriguing possibility for the identity of the missing mass of the Universe. This article proposes a class of models of supersymmetric composite dark matter where the interactions with the Standard Model communicate supersymmetry breaking to the dark sector. In these models supersymmetry breaking can be treated as a perturbation on the spectrum of bound states. Using a general formalism, the spectrum with leading supersymmetry effects is computed without specifying the details of the binding dynamics. The interactions of the composite states with the Standard Model are computed and several benchmark models are described. General features of non-relativistic supersymmetric bound states are emphasized.

  17. The Dark Matter Telescope

    CERN Document Server

    Tyson, J A; Angel, J R P; Wittman, David

    2001-01-01

    Weak gravitational lensing enables direct reconstruction of dark matter maps over cosmologically significant volumes. This research is currently telescope-limited. The Dark Matter Telescope (DMT) is a proposed 8.4 m telescope with a 3 degree field of view, with an etendue of 260 $(m. degree)^2$, ten times greater than any other current or planned telescope. With its large etendue and dedicated observational mode, the DMT fills a nearly unexplored region of parameter space and enables projects that would take decades on current facilities. The DMT will be able to reach 10-sigma limiting magnitudes of 27-28 magnitude in the wavelength range .3 - 1 um over a 7 square degree field in 3 nights of dark time. Here we review its unique weak lensing cosmology capabilities and the design that enables those capabilities.

  18. Dark-Skies Awareness

    Science.gov (United States)

    Walker, Constance E.

    2009-05-01

    The arc of the Milky Way seen from a truly dark location is part of our planet's natural heritage. More than one fifth of the world population, two thirds of the United States population and one half of the European Union population have already lost naked eye visibility of the Milky Way. This loss, caused by light pollution, is a serious and growing issue that impacts astronomical research, the economy, ecology, energy conservation, human health, public safety and our shared ability to see the night sky. For this reason, "Dark Skies” is a cornerstone project of the International Year of Astronomy. Its goal is to raise public awareness of the impact of artificial lighting on local environments by getting people worldwide involved in a variety of programs that: 1. Teach about dark skies using new technology (e.g., an activity-based planetarium show on DVD, podcasting, social networking on Facebook and MySpace, a Second Life presence) 2. Provide thematic events on light pollution at star parties and observatory open houses (Dark Skies Discovery Sites, Nights in the (National) Parks, Sidewalk Astronomy) 3. Organize events in the arts (e.g., a photography contest) 4. Involve citizen-scientists in naked-eye and digital-meter star hunting programs (e.g., GLOBE at Night, "How Many Stars?", the Great World Wide Star Count and the radio frequency interference equivalent: "Quiet Skies") and 5. Raise awareness about the link between light pollution and public health, economic issues, ecological consequences, energy conservation, safety and security, and astronomy (e.g., The Starlight Initiative, World Night in Defense of Starlight, International Dark Sky Week, International Dark-Sky Communities, Earth Hour, The Great Switch Out, a traveling exhibit, downloadable posters and brochures). The presentation will provide an update, describe how people can become involved and take a look ahead at the program's sustainability. For more information, visit www.darkskiesawareness.org.

  19. Design and analysis of 19 pin annular fuel rod cluster for pressure tube type boiling water reactor

    Energy Technology Data Exchange (ETDEWEB)

    Deokule, A.P., E-mail: abhijit.deokule1986@gmail.com [Homi Bhabha National Institute, Trombay 400 085, Mumbai (India); Vishnoi, A.K.; Dasgupta, A.; Umasankari, K.; Chandraker, D.K.; Vijayan, P.K. [Bhabha Atomic Research Centre, Trombay 400 085, Mumbai (India)

    2014-09-15

    Highlights: • Development of 19 pin annular fuel rod cluster. • Reactor physics study of designed annular fuel rod cluster. • Thermal hydraulic study of annular fuel rod cluster. - Abstract: An assessment of 33 pin annular fuel rod cluster has been carried out previously for possible use in a pressure tube type boiling water reactor. Despite the benefits such as negative coolant void reactivity and larger heat transfer area, the 33 pin annular fuel rod cluster is having lower discharge burn up as compared to solid fuel rod cluster when all other parameters are kept the same. The power rating of this design cannot be increased beyond 20% of the corresponding solid fuel rod cluster. The limitation on the power is not due to physics parameters rather it comes from the thermal hydraulics side. In order to increase power rating of the annular fuel cluster, keeping same pressure tube diameter, the pin diameter was increased, achieving larger inside flow area. However, this reduces the number of annular fuel rods. In spite of this, the power of the annular fuel cluster can be increased by 30% compared to the solid fuel rod cluster. This makes the nineteen pin annular fuel rod cluster a suitable option to extract more power without any major changes in the existing design of the fuel. In the present study reactor physics and thermal hydraulic analysis carried out with different annular fuel rod cluster geometry is reported in detail.

  20. Triple antibiotic combination therapy may improve but not resolve granuloma annulare.

    Science.gov (United States)

    Simpson, Brenda; Foster, Shannon; Ku, Jennifer H; Simpson, Eric L; Ehst, Benjamin D

    2014-01-01

    Granuloma annulare is a fairly common entity yet lacks reliable treatment options especially when multiple lesions or dissemination exists. A recent case series suggests that a regimen of three oral antibiotics may prove to be an effective treatment. Our objective is to evaluate the efficacy of once monthly triple antibiotic therapy for granuloma annulare. We conducted an open-label prospective study of subjects with at least five lesions of granuloma annulare who received once monthly rifampin, ofloxacin, and minocycline for 6 months. Improvement was measured with a novel objective Granuloma Annulare Severity Index (GASI) scoring system. Twenty-one subjects enrolled. Ten subjects (48%) achieved at least a 50% reduction in their GASI, including three subjects (14%) who reached 75% improvement and one subject (5%) whose skin cleared. Six subjects (29%) had no change or worsening of their granuloma annulare. Median GASI scores decreased significantly by 15 points (p antibiotic use may improve but not clear granuloma annulare over 6 months. Randomized trials may be warranted to further assess this therapy.

  1. Annular structures as intermediates in fibril formation of Alzheimer Abeta17-42.

    Science.gov (United States)

    Zheng, Jie; Jang, Hyunbum; Ma, Buyong; Nussinov, Ruth

    2008-06-05

    We report all-atom molecular dynamics simulations of annular beta-amyloid (17-42) structures, single- and double-layered, in solution. We assess the structural stability and association force of Abeta annular oligomers associated through different interfaces, with a mutated sequence (M35A), and with the oxidation state (M35O). Simulation results show that single-layered annular models display inherent structural instability: one is broken down into linear-like oligomers, and the other collapses. On the other hand, a double-layered annular structure where the two layers interact through their C-termini to form an NC-CN interface (where N and C are the N and C termini, respectively) exhibits high structural stability over the simulation time due to strong hydrophobic interactions and geometrical constraints induced by the closed circular shape. The observed dimensions and molecular weight of the oligomers from atomic force microscopy (AFM) experiments are found to correspond well to our stable double-layered model with the NC-CN interface. Comparison with K3 annular structures derived from the beta 2-microglobulin suggests that the driving force for amyloid formation is sequence specific, strongly dependent on side-chain packing arrangements, structural morphologies, sequence composition, and residue positions. Combined with our previous simulations of linear-like Abeta, K3 peptide, and sup35-derived GNNQQNY peptide, the annular structures provide useful insight into oligomeric structures and driving forces that are critical in amyloid fibril formation.

  2. Depth-targeted transvascular drug delivery by using annular-shaped photomechanical waves

    Science.gov (United States)

    Akiyama, Takuya; Sato, Shunichi; Ashida, Hiroshi; Terakawa, Mitsuhiro

    2011-02-01

    Laser-based drug delivery is attractive for the targeting capability due to high spatial controllability of laser energy. Recently, we found that photomechanical waves (PMWs) can transiently increase the permeability of blood vessels in skin, muscle and brain of rats. In this study, we examined the use of annular-shaped PMWs to increase pressure at target depths due to superposition effect of pressure waves. This can increase the permeability of blood vessels located in the specific depth regions, enabling depth-targeted transvascular drug delivery. Annular PMWs were produced by irradiating a laser-absorbing material with annular-shaped pulsed laser beams that were produced by using an axicon lens. We first examined propagation and pressure characteristics of annular PMWs in tissue phantoms and confirmed an increased pressure at a target depth, which can be controlled by changing laser parameters. We injected Evans blue (EB) into a rat tail vein, and annular PMWs (inner diameter, 3 mm; outer diameter, 5 mm) were applied from the myofascial surface of the anterior tibialis muscle. After perfusion fixation, we observed fluorescence originating from EB in the tissue. We observed intense fluorescence at a target depth region of around 5 mm. These results demonstrate the capability of annular PMWs for depth-targeted transvascular drug delivery.

  3. Fluid-Structure Interaction Analysis on Turbulent Annular Seals of Centrifugal Pumps during Transient Process

    Directory of Open Access Journals (Sweden)

    Qinglei Jiang

    2011-01-01

    Full Text Available The current paper studies the influence of annular seal flow on the transient response of centrifugal pump rotors during the start-up period. A single rotor system and three states of annular seal flow were modeled. These models were solved using numerical integration and finite difference methods. A fluid-structure interaction method was developed. In each time step one of the three annular seal models was chosen to simulate the annular seal flow according to the state of rotor systems. The objective was to obtain a transient response of rotor systems under the influence of fluid-induced forces generated by annular seal flow. This method overcomes some shortcomings of the traditional FSI method by improving the data transfer process between two domains. Calculated results were in good agreement with the experimental results. The annular seal was shown to have a supportive effect on rotor systems. Furthermore, decreasing the seal clearance would enhance this supportive effect. In the transient process, vibration amplitude and critical speed largely changed when the acceleration of the rotor system increased.

  4. Dark Matter and MOOCs

    CERN Document Server

    Salucci, Paolo

    2013-01-01

    To teach the topic of Dark Matter in Galaxies to undergraduate and PhD students is not easy, one reason being that the scientific community has not converged yet to a generally shared knowledge. We argue that the teaching of this topic and its subsequent scientific progress may benefit by Massive Online and Open Courses. The reader of this paper can express his/her opinion on this by means of a confidence vote at: https://moocfellowship.org/submissions/dark-matter-in-galaxies-the-last-mystery

  5. Explaining Holographic Dark Energy

    Directory of Open Access Journals (Sweden)

    Shan Gao

    2013-10-01

    Full Text Available The possible holographic origin of dark energy is investigated. The main existing explanations, namely the UV/IR connection argument of Cohen et al., Thomas’ bulk holography argument, and Ng’s spacetime foam argument, are shown to be not wholly satisfactory. A new explanation is then proposed based on the ideas of Thomas and Ng. It is suggested that dark energy originates from the quantum fluctuations of spacetime limited by the event horizon of the universe. Several potential problems of the explanation are also discussed.

  6. Metastable dark energy

    OpenAIRE

    Landim, Ricardo G.; Elcio Abdalla

    2016-01-01

    We build a model of metastable dark energy, in which the observed vacuum energy is the value of the scalar potential at the false vacuum. The scalar potential is given by a sum of even self-interactions up to order six. The deviation from the Minkowski vacuum is due to a term suppressed by the Planck scale. The decay time of the metastable vacuum can easily accommodate a mean life time compatible with the age of the universe. The metastable dark energy is also embedded into a model with $SU(2...

  7. A Dark Horse

    Institute of Scientific and Technical Information of China (English)

    康成

    2012-01-01

    What s the meamng of a "dark horse "? It's soineone who wins while no one expects it. Han Xiaopeng became an Olympic "dark horse" by winning the gold medal in men's freest~ie aerial skiing ( 自由式滑雪空中技巧) in Turin, Italy. He made two almost perfect jumps for the highest score: Han had never won a world gold medal before, let alone (更不用说) in the Olympics!

  8. Dark Side of the Universe

    CERN Document Server

    2016-01-01

    The Dark Side of the Universe (DSU) workshops bring together a wide range of theorists and experimentalists to discuss current ideas on models of the dark side, and relate them to current and future experiments. This year's DSU will take place in the colorful Norwegian city of Bergen. Topics include dark matter, dark energy, cosmology, and physics beyond the standard model. One of the goals of the workshop is to expose in particular students and young researchers to the fascinating topics of dark matter and dark energy, and to provide them with the opportunity to meet some of the best researchers in these areas .

  9. Sterile neutrino portal to Dark Matter II: exact dark symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Escudero, Miguel; Rius, Nuria [Universidad de Valencia-CSIC, Departamento de Fisica Teorica and IFIC, C/Catedratico Jose Beltran, 2, 46980, Paterna (Spain); Sanz, Veronica [University of Sussex, Department of Physics and Astronomy, Brighton (United Kingdom)

    2017-06-15

    We analyze a simple extension of the standard model (SM) with a dark sector composed of a scalar and a fermion, both singlets under the SM gauge group but charged under a dark sector symmetry group. Sterile neutrinos, which are singlets under both groups, mediate the interactions between the dark sector and the SM particles, and generate masses for the active neutrinos via the seesaw mechanism. We explore the parameter space region where the observed Dark Matter relic abundance is determined by the annihilation into sterile neutrinos, both for fermion and scalar Dark Matter particles. The scalar Dark Matter case provides an interesting alternative to the usual Higgs portal scenario. We also study the constraints from direct Dark Matter searches and the prospects for indirect detection via sterile neutrino decays to leptons, which may be able to rule out Dark Matter masses below and around 100 GeV. (orig.)

  10. New interactions in the dark sector mediated by dark energy

    CERN Document Server

    Brookfield, A W; Hall, L M H

    2007-01-01

    Cosmological observations have revealed the existence of a dark matter sector, which is commonly assumed to be made up of one particle species only. However, this sector might be more complicated than we currently believe: there might be more than one dark matter species (for example two components of cold dark matter or a mixture of hot and cold dark matter) and there may be new interactions between these particles. In this paper we study the possibility of multiple dark matter species and interactions mediated by a dark energy field. We study both the background and the perturbation evolution in these scenarios. We find that the background evolution of a system of multiple dark matter particles (with constant couplings) mimics a single fluid with a time-varying coupling parameter. However, this is no longer true on the perturbative level. We study the case of attractive and repulsive forces as well as a mixture of cold and hot dark matter particles.

  11. Sterile Neutrino portal to Dark Matter II: Exact Dark symmetry

    CERN Document Server

    Escudero, Miguel; Sanz, Verónica

    2016-01-01

    We analyze a simple extension of the Standard Model (SM) with a dark sector composed of a scalar and a fermion, both singlets under the SM gauge group but charged under a dark sector symmetry group. Sterile neutrinos, which are singlets under both groups, mediate the interactions between the dark sector and the SM particles, and generate masses for the active neutrinos via the seesaw mechanism. We explore the parameter space region where the observed Dark Matter relic abundance is determined by the annihilation into sterile neutrinos, both for fermion and scalar Dark Matter particles. The scalar Dark Matter case provides an interesting alternative to the usual Higgs portal scenario. We also study the constraints from direct Dark Matter searches and the prospects for indirect detection via sterile neutrino decays to leptons, which may be able to rule out Dark Matter masses below and around 100 GeV.

  12. A source term model of perturbation in a numerical study on flows around a slender body of revolution at a high angle of attack

    Institute of Scientific and Technical Information of China (English)

    Yang Liu; Dongjun Ma; Dejun Sun; Xieyuan Yin

    2009-01-01

    A numerical study on flows around a slender body of revolution at a high angle of attack is conducted to investigate the influence of strength and circumferential angle of perturbation on flow asymmetry.A source term model is applied to simulate a real geometrical perturbation near the tip of the slender body.It can greatly facilitate the adjustment of perturbation strength.The results show that the bistable phenomenon does not appear any more at a small perturbation strength.For different perturbation strengths,the energy of the asymmetric perturbation flow experiences a similar spatial exponential growth regime with the same growth rate.The appearance of the bistable phenomenon is closely related to nonlinear saturation of the perturbation flow as perturbation strength increases.

  13. Camouflage of a high-angle skeletal Class II open-bite malocclusion in an adult after mini-implant failure during treatment.

    Science.gov (United States)

    Franzotti Sant'Anna, Eduardo; Carneiro da Cunha, Amanda; Paludo Brunetto, Daniel; Franzotti Sant'Anna, Claudia

    2017-03-01

    The treatment of skeletal anterior open-bite malocclusion requires complex orthodontic planning that considers its multifactorial etiology, treatment limitations, and high relapse rates. This case report illustrates a successful treatment approach for a skeletal high-angle Class II malocclusion in an adult with a severe open bite. The treatment consisted of a high-pull headgear therapy after mini-implants failure during fixed orthodontic therapy. Adequate esthetics and function were achieved. Despite its low probability, the unexpected event of mini-implant loosening during complex treatments should be considered. Therefore, classic orthodontic mechanics should be established, especially when treating patients for whom invasive procedures such as miniplates or orthognathic surgery are not available options.

  14. Numerical Study of Transition of an Annular Lift Fan Aircraft

    Directory of Open Access Journals (Sweden)

    Yun Jiang

    2016-09-01

    Full Text Available The present study aimed at studying the transition of annular lift fan aircraft through computational fluid dynamics (CFD simulations. The oscillations of lift and drag, the optimization for the figure of merit, and the characteristics of drag, yawing, rolling and pitching moments in transition are studied. The results show that a two-stage upper and lower fan lift system can generate oscillations of lift and drag in transition, while a single-stage inner and outer fan lift system can eliminate the oscillations. The characteristics of momentum drag of the single-stage fans in transition are similar to that of the two-stage fans, but with the peak of drag lowered from 0.63 to 0.4 of the aircraft weight. The strategy to start transition from a negative angle of attack −21° further reduces the peak of drag to 0.29 of the weight. The strategy also reduces the peak of pitching torque, which needs upward extra thrusts of 0.39 of the weight to eliminate. The peak of rolling moment in transition needs differential upward thrusts of 0.04 of the weight to eliminate. The requirements for extra thrusts in transition lead to a total thrust–weight ratio of 0.7, which makes the aircraft more efficient for high speed cruise flight (higher than 0.7 Ma.

  15. An Unusual Presentation of Annular Pancreas: A Case Report

    Directory of Open Access Journals (Sweden)

    Saleheh Ala

    2015-01-01

    Full Text Available Abstract Annular pancreas (AP is a rare congenital malformation resulting from failure of pancreas ventral anlage rotation with the duodenum. This leads to a ring of pancreatic tissue that envelops the duodenum. Clinical manifestations of AP most commonly develop in infancy or early childhood but can present at any age. The diagnosis of AP, usually suggested by an upper GI series or abdominal CT scan, but surgery is considered the gold standard diagnostic method. Surgical bypass of the annulus in all patients with symptomatic AP is recommended. We report a one year old girl who presented with intermittent, non projectile, non bilious vomiting that occurred 1h to 2h after feeding since neonatal period. Upper GI contrast study demonstrates, a dilated duodenal bulb associated with narrowing of post bulbar area. The patient underwent surgical correction of the obstruction. A bypass of the ectopic pancreas tissue was performed by duodenoduodenostomy. Considering the rarity of this congenital abnormality, presenting with chronic partial duodenal obstruction, and its successful correction by surgical means have prompted us to report the case.

  16. Friction factor of annular Poiseuille flow in a transitional regime

    Directory of Open Access Journals (Sweden)

    Takahiro Ishida

    2016-12-01

    Full Text Available Annular Poiseuille flows in a transitional regime were investigated by direct numerical simulations with an emphasis on turbulent statistics including the friction factor that are affected by the presence of large-scale transitional structures. Five different radius ratios in the range of 0.1–0.8 and several friction Reynolds numbers in the range of 48–150 were analyzed to consider various flow states accompanied by characteristic transitional structures. Three characteristic structures, namely, turbulent–laminar coexistence referred to as “(straight puff,”“helical puff,” and “helical turbulence” were observed. The selection of the structures depends on both the radius ratio and the Reynolds number. The findings indicated that despite the transitional state with a turbulent–laminar coexistence, the helical turbulence resulted in a friction factor that was as high as the fully turbulent value. In contrast, with respect to the occurrence of streamwise-finite transitional structures, such as straight/helical puffs, the friction factor decreased in a stepwise manner toward a laminar level. The turbulent statistics revealed asymmetric distributions with respect to the wall-normal direction wherein the profiles and magnitudes were significantly influenced by the occurrence of transitional structures.

  17. Association between Australian rainfall and the Southern Annular Mode

    Science.gov (United States)

    Meneghini, Belinda; Simmonds, Ian; Smith, Ian N.

    2007-01-01

    In this study, we explore the relationships between seasonal Australian rainfall and the Southern Annular Mode (SAM). We produce two seasonal indices of the SAM: the Antarctic Oscillation Index (AOI), and an Australian regional version (AOIR) using ERA-40 mean sea-level pressure (MSLP) reanalysis data. The seasonal rainfall data are based on gridded monthly rainfall provided by the Australian Bureau of Meteorology.For the period 1958-2002 a significant inverse relationship is found between the SAM and rainfall in southern Australia, while a significant in-phase relationship is found between the SAM and rainfall in northern Australia. Furthermore, widespread significant inverse relationships in southern Australia are only observed in winter, and only with the AOIR. The AOIR accounts for more of the winter rainfall variability in southwest Western Australia, southern South Australia, western and southern Victoria, and western Tasmania than the Southern Oscillation Index. Overall, our results suggest that changes in the SAM may be partly responsible for the current decline in winter rainfall in southern South Australia, Victoria, and Tasmania, but not the long-term decline in southwest Western Australian winter rainfall.

  18. Characterization of Novel Calorimeters in the Annular Core Research Reactor *

    Directory of Open Access Journals (Sweden)

    Hehr Brian D.

    2016-01-01

    Full Text Available A series of pulsed irradiation experiments have been performed in the central cavity of Sandia National Laboratories' Annular Core Research Reactor (ACRR to characterize the responses of a set of elemental calorimeter materials including Si, Zr, Sn, Ta, W, and Bi. Of particular interest was the perturbing effect of the calorimeter itself on the ambient radiation field – a potential concern in dosimetry applications. By placing the calorimeter package into a neutron-thermalizing lead/polyethylene (LP bucket and irradiating both with and without a cadmium wrapper, it was demonstrated that prompt capture gammas generated inside the calorimeters can be a significant contributor to the measured dose in the active disc region. An MCNP model of the experimental setup was shown to replicate measured dose responses to within 10%. The internal (n,γ contribution was found to constitute as much as 50% of the response inside the LP bucket and up to 20% inside the nominal (unmodified cavity environment, with Ta and W exhibiting the largest enhancement due to their sizable (n,γ cross sections. Capture reactions in non-disc components of the calorimeter were estimated to be responsible for up to a few percent of the measured response.

  19. Stability of three-layered core-annular flow

    Science.gov (United States)

    Pillai, Dipin; Pushpavanam, Subramaniam; Sundararajan, T.

    2016-11-01

    Stability of a three-layered core-annular flow is analyzed using the method of modal linear stability analysis. A temporal analysis shows that the flow becomes unstable to two modes of instability when inertial effects are negligible. An energy budget analysis reveals that these two modes correspond to capillary instability associated with each fluid-fluid interface. With an increase in Reynolds number, the system exhibits additional Reynolds stress modes of instabilities. These modes correspond to the Tollmien-Schlichting type of waves associated with high Reynolds number shear flows, and are considered precursor to transition to turbulence. An investigation of the parameter space reveals that the system may simultaneously show up to 5 distinct modes of instability, viz., the two capillary modes at each interface and three Reynolds stress modes in the bulk of each phase. In addition, a spatio-temporal analysis shows that the Reynolds stress modes are always convectively unstable whereas the capillary modes may undergo a transition from convective to absolute instability with decrease in Weber number. To obtain encapsulated droplets in experiments, the operating parameters must be chosen such that the system lies in the regime of convective instability. MHRD-Govt of India, NSF 0968313.

  20. Linear Unsteady Aerodynamic Forces on Vibrating Annular Cascade Blades

    Institute of Scientific and Technical Information of China (English)

    Taketo Nagasaki; Nobuhiko Yamasaki

    2003-01-01

    The paper presents the formulation to compute numerically the unsteady aerodynamic forces on the vibrating annular cascade blades. The formulation is based on the finite volume method. By applying the TVD scheme to the linear unsteady calculations, the precise calculation of the peak of unsteady aerodynamic forces at the shock wave location like the delta function singularity becomes possible without empirical constants. As a further feature of the present paper, results of the present numerical calculation are compared with those of the double lineaxization theory (DLT), which assumes small unsteady and steady disturbances but the unsteady disturbances are much smaller than the steady disturbances. Since DLT requires fax less computational resources than the present numerical calculation, the validation of DLT is quite important from the engineering point of view. Under the conditions of small steady disturbances, a good agreement between these two results is observed, so that the two codes axe cross-validated.The comparison also reveals the limitation on the applicability of DLT.

  1. Influences of phase shift on superresolution performances of annular filters

    Institute of Scientific and Technical Information of China (English)

    Liu Xi-Min; Liu Li-Ren; Bai Li-Hua

    2006-01-01

    This paper investigates the influences of phase shift on superresolution performances of annular filters.Firstly,it investigates the influence of phase shift on axial superresolution.It proves theoretically that axial superresolution can not be obtained by two-zone phase filter with phase shift π.and it gets the phase shift with which axial superresolution can be brought by two-zone phase filter.Secondly,it studies the influence of phase shift on transverse superresolution.It finds that the three-zone phase filter with arbitrary phase shift has an almost equal optimal transverse gain to that of commonly used three-zone phase filter,but can produce a much higher axial superresolution gain.Thirdly,it investigates the influence of phase shift on three-dimensional superresolution.Three-dimensional superresolution capability and design margin of three-zone complex filter with arbitrary phase shift are obtained,which presents the theoretical basis for three-dimensional superresolution design. Finally,it investigates the influence of phase shift on focal shift.To obtain desired focal shifts,it designs a series of three-zone phase filters with different phase shifts.A spatial light modulator (SLM) is used to implement the designed filters.By regulating the voltage imposed on the SLM,an accurate focal shift control iS obtained.

  2. Adipophilin expression in necrobiosis lipoidica, granuloma annulare, and sarcoidosis.

    Science.gov (United States)

    Schulman, Joshua M; LeBoit, Philip E

    2015-03-01

    Necrobiosis lipoidica (NL), granuloma annulare (GA), and sarcoidosis usually are distinguished by clinical presentation and routine microscopy, but their distinction can sometimes be challenging. Historically, a clue to diagnosing NL or GA has been the identification of lipid droplets in the areas of altered collagen, but such studies have required fresh frozen tissue, making them impractical. Here, we present the first report of immunohistochemical staining to detect adipophilin, a membrane protein in lipid droplets, in NL (n = 12), GA (n = 19), sarcoidosis (n = 12), and, as a control for nonspecific tissue damage, nongranulomatous cutaneous necrosis (n = 13). Four patterns of labeling were identified: (1) extracellular, within zones of altered collagen; (2) both intracellular and extracellular, after the distribution of palisaded or scattered histiocytes; (3) intracellular, within clustered histiocytes; and (4) periadnexal. All cases of NL demonstrated pattern 1; nearly all cases of GA (18/19) demonstrated pattern 2; most sarcoidosis (10/12) demonstrated pattern 3; and nongranulomatous necrosis demonstrated either pattern 4 (6/13) or did not stain (6/13), confirming that the antibody to adipophilin did not adhere nonspecifically to the damaged tissue. An additional set of 3 biopsies with overlapping or partially sampled features of NL, GA, and/or sarcoidosis subsequently confirmed the potential utility of adipophilin staining in diagnostically challenging cases. We conclude that the pattern of adipophilin expression is a useful adjunct in the evaluation of granulomatous dermatitis.

  3. Cultivation of Spirulina maxima in an annular photochemical reactor

    Energy Technology Data Exchange (ETDEWEB)

    Leduy, A.; Therien, N.

    1979-08-01

    An 8-L annular photochemical reactor has been designed and built for the cultivation of micro- or semi-microalgae at the laboratory scale. It may be operated in batch or continuous mode and is controlled for pH, temperature, gas mixture ratio (CO/sub 2/ and air), flow rate, light intensity and also illumination type (daylight or plant growth light) and mode (continuous or intermittent). It behaves as a perfect mixed reactor for all concentrations of algal cells. The reactor was used for the cultivation of the blue-green alga Spirulina maxima in a synthetic medium in both batch and continuous operations. At the dilution rate of 0.24 day/sup -1/, the optimal productivity was 0.91 g/L-day for biomass or 0.55 g/L-day for protein. This is equivalent to 14.5 g/m/sup 2/-day for biomass or 8.7 g/m/sup 2/-day for protein. The optimal productivity as well as the chemical composition of the algal biomass were comparable to results obtained from pilot plant studies and reported in the current literature.

  4. Flow Pressure Loss through Straight Annular Corrugated Pipes

    Science.gov (United States)

    Sargent, Joseph R.; Kirk, Daniel R.; Marsell, Brandon; Roth, Jacob; Schallhorn, Paul A.; Pitchford, Brian; Weber, Chris; Bulk, Timothy

    2016-01-01

    Pressure loss through annular corrugated pipes, using fully developed gaseous nitrogen representing purge pipes in spacecraft fairings, was studied to gain insight into a friction factor coefficient for these pipes. Twelve pipes were tested: four Annuflex, four Masterflex and two Titeflex with ¼”, 3/8”, ½” and ¾” inner diameters. Experimental set-up was validated using smooth-pipe and showed good agreement to the Moody diagram. Nitrogen flow rates between 0-200 standard cubic feet per hour were used, producing approximate Reynolds numbers from 300-23,000. Corrugation depth varied from 0.248 = E/D = 0.349 and relative corrugation pitch of 0.192 = P/D = 0.483. Differential pressure per unit length was measured and calculated using 8-9 equidistant pressure taps. A detailed experimental uncertainty analysis, including correlated bias error terms, is presented. Results show larger differential pressure losses than smooth-pipes with similar inner diameters resulting in larger friction factor coefficients.

  5. HAMLET forms annular oligomers when deposited with phospholipid monolayers.

    Science.gov (United States)

    Baumann, Anne; Gjerde, Anja Underhaug; Ying, Ming; Svanborg, Catharina; Holmsen, Holm; Glomm, Wilhelm R; Martinez, Aurora; Halskau, Oyvind

    2012-04-20

    Recently, the anticancer activity of human α-lactalbumin made lethal to tumor cells (HAMLET) has been linked to its increased membrane affinity in vitro, at neutral pH, and ability to cause leakage relative to the inactive native bovine α-lactalbumin (BLA) protein. In this study, atomic force microscopy resolved membrane distortions and annular oligomers (AOs) produced by HAMLET when deposited at neutral pH on mica together with a negatively charged lipid monolayer. BLA, BAMLET (HAMLET's bovine counterpart) and membrane-binding Peptide C, corresponding to BLA residues 75-100, also form AO-like structures under these conditions but at higher subphase concentrations than HAMLET. The N-terminal Peptide A, which binds to membranes at acidic but not at neutral pH, did not form AOs. This suggests a correlation between the capacity of the proteins/peptides to integrate into the membrane at neutral pH-as observed by liposome content leakage and circular dichroism experiments-and the formation of AOs, albeit at higher concentrations. Formation of AOs, which might be important to HAMLET's tumor toxic action, appears related to the increased tendency of the protein to populate intermediately folded states compared to the native protein, the formation of which is promoted by, but not uniquely dependent on, the oleic acid molecules associated with HAMLET. Copyright © 2012 Elsevier Ltd. All rights reserved.

  6. Annular beam shaping system for advanced 3D laser brazing

    Science.gov (United States)

    Pütsch, Oliver; Stollenwerk, Jochen; Kogel-Hollacher, Markus; Traub, Martin

    2012-10-01

    As laser brazing benefits from advantages such as smooth joints and small heat-affected zones, it has become established as a joining technology that is widely used in the automotive industry. With the processing of complex-shaped geometries, recent developed brazing heads suffer, however, from the need for continuous reorientation of the optical system and/or limited accessibility due to lateral wire feeding. This motivates the development of a laser brazing head with coaxial wire feeding and enhanced functionality. An optical system is designed that allows to generate an annular intensity distribution in the working zone. The utilization of complex optical components avoids obscuration of the optical path by the wire feeding. The new design overcomes the disadvantages of the state-of-the-art brazing heads with lateral wire feeding and benefits from the independence of direction while processing complex geometries. To increase the robustness of the brazing process, the beam path also includes a seam tracking system, leading to a more challenging design of the whole optical train. This paper mainly discusses the concept and the optical design of the coaxial brazing head, and also presents the results obtained with a prototype and selected application results.

  7. Current Density Measurements of an Annular-Geometry Ion Engine

    Science.gov (United States)

    Shastry, Rohit; Patterson, Michael J.; Herman, Daniel A.; Foster, John E.

    2012-01-01

    The concept of the annular-geometry ion engine, or AGI-Engine, has been shown to have many potential benefits when scaling electric propulsion technologies to higher power. However, the necessary asymmetric location of the discharge cathode away from thruster centerline could potentially lead to non-uniformities in the discharge not present in conventional geometry ion thrusters. In an effort to characterize the degree of this potential nonuniformity, a number of current density measurements were taken on a breadboard AGI-Engine. Fourteen button probes were used to measure the ion current density of the discharge along a perforated electrode that replaced the ion optics during conditions of simulated beam extraction. Three Faraday probes spaced apart in the vertical direction were also used in a separate test to interrogate the plume of the AGI-Engine during true beam extraction. It was determined that both the discharge and the plume of the AGI-Engine are highly uniform, with variations under most conditions limited to 10% of the average current density in the discharge and 5% of the average current density in the plume. Beam flatness parameter measured 30 mm from the ion optics ranged from 0.85 0.95, and overall uniformity was shown to generally increase with increasing discharge and beam currents. These measurements indicate that the plasma is highly uniform despite the asymmetric location of the discharge cathode.

  8. Measurement of large aspheric surfaces by annular subaperture stitching interferometry

    Institute of Scientific and Technical Information of China (English)

    Xiaokun Wang; Lihui Wang; Longhai Yin; Binzhi Zhang; Di Fan; Xuejun Zhang

    2007-01-01

    A new method for testing aspheric surfaces by annular subaperture stitching interferometry is introduced.It can test large-aperture and large-relative-aperture aspheric surfaces at high resolution, low cost, and high efficiency without auxiliary null optics. The basic principle of the method is described, the synthetical optimization stitching model and effective algorithm are established based on simultaneous least-square fitting. A hyperboloid with an aperture of 350 mm is tested by this method. The obtained peak-to-valley (PV) and root-mean-square (RMS) values of the surface error after stitching are 0.433λ and 0.052λ (λis 632.8 nm), respectively. The reconstructed surface map is coincide with the entire surface map from null test, and the difference of PV and RMS errors between them are 0.031λ and 0.005λ, respectively.This stitching model provides another quantitive method for testing large aspheric surfaces besides null compensation.

  9. Modeling and analysis of thermoacoustic instabilities in an annular combustor

    Science.gov (United States)

    Murthy, Sandeep; Sayadi, Taraneh; Le Chenadec, Vincent; Schmid, Peter

    2015-11-01

    A simplified model is introduced to study thermo-acoustic instabilities in axisymmetric combustion chambers. Such instabilities can be triggered when correlations between heat-release and pressure oscillations exist, leading to undesirable effects. Gas turbine designs typically consist of a periodic assembly of N identical units; as evidenced by documented studies, the coupling across sectors may give rise to unstable modes, which are the highlight of this study. In the proposed model, the governing equations are linearized in the acoustic limit, with each burner modeled as a one-dimensional system, featuring acoustic damping and a compact heat source. The coupling between the burners is accounted for by solving the two-dimensional wave equation over an annular region, perpendicular to the burners, representing the chamber's geometry. The discretization of these equations results in a set of coupled delay-differential equations, that depends on a finite set of parameters. The system's periodicity is leveraged using a recently developed root-of-unity formalism (Schmid et al., 2015). This results in a linear system, which is then subjected to modal and non-modal analysis to explore the influence of the coupled behavior of the burners on the system's stability and receptivity.

  10. Imbalanced superfluid state in an annular disk.

    Science.gov (United States)

    Ye, Fei; Chen, Yan; Wang, Z D; Zhang, F C

    2009-09-02

    The imbalanced superfluid state of spin- 1/2 fermions with s-wave pairing is numerically studied by solving the Bogoliubov-de Gennes equation at zero temperature in an annular disk geometry with narrow radial width. Two distinct types of systems are considered. The first case may be relevant to heavy fermion superconductors, where magnetic field causes spin imbalance via Zeeman interaction and the system is studied in a grand canonical ensemble. As the magnetic field increases, the system is transformed from the uniform superfluid state to the Fulde-Ferrell-Larkin-Ovchinnikov state, and finally to the spin polarized normal state. The second case may be relevant to cold fermionic systems, where the number of fermions of each species is fixed as in a canonical ensemble. In this case, the ground state depends on the pairing strength. For weak pairing, the order parameter exhibits a periodic domain wall lattice pattern with a localized spin distribution at low spin imbalance, and a sinusoidally modulated pattern with extended spin distribution at high spin imbalance. For strong pairing, the phase separation between the superfluid state and polarized normal state is found to be preferable, while the increase of spin imbalance simply changes the ratio between them.

  11. Visual Measurements of Droplet Size in Gas Liquid Annular Flow

    Energy Technology Data Exchange (ETDEWEB)

    Fore, L.B.; Ibrahim, B.B.; Beus, S.G.

    2000-07-01

    Drop size distributions have been measured for nitrogen-water annular flow in a 9.67 mm hydraulic diameter duct, at system pressures of 3.4 and 17 atm and a temperature of 38 C. These new data extend the range of conditions represented by existing data in the open literature, primarily through an increase in system pressure. Since most existing correlations were developed from data obtained at lower pressures, it should be expected that the higher-pressure data presented in this paper would not necessarily follow those correlations. The correlation of Tatterson, et al. (1977) does not predict the new data very well, while the correlation of Kataoka, et al. (1983) only predicts those data taken at the lower pressure of 3.4 atm. However, the maximum drop size correlation of Kocamustafaogullari, et al. (1994) does predict the current data to a reasonable approximation. Similarly, their correlation for the Sauter mean diameter can predict the new data, provided the coefficient in the equation is adjusted.

  12. Reactor pulse repeatability studies at the annular core research reactor

    Energy Technology Data Exchange (ETDEWEB)

    DePriest, K.R. [Applied Nuclear Technologies, Sandia National Laboratories, Mail Stop 1146, Post Office Box 5800, Albuquerque, NM 87185-1146 (United States); Trinh, T.Q. [Nuclear Facility Operations, Sandia National Laboratories, Mail Stop 0614, Post Office Box 5800, Albuquerque, NM 87185-1146 (United States); Luker, S. M. [Applied Nuclear Technologies, Sandia National Laboratories, Mail Stop 1146, Post Office Box 5800, Albuquerque, NM 87185-1146 (United States)

    2011-07-01

    The Annular Core Research Reactor (ACRR) at Sandia National Laboratories is a water-moderated pool-type reactor designed for testing many types of objects in the pulse and steady-state mode of operations. Personnel at Sandia began working to improve the repeatability of pulse operations for experimenters in the facility. The ACRR has a unique UO{sub 2}-BeO fuel that makes the task of producing repeatable pulses difficult with the current operating procedure. The ACRR produces a significant quantity of photoneutrons through the {sup 9}Be({gamma}, n){sup 8}Be reaction in the fuel elements. The photoneutrons are the result of the gammas produced during fission and in fission product decay, so their production is very much dependent on the reactor power history and changes throughout the day/week of experiments in the facility. Because the photoneutrons interfere with the delayed-critical measurements required for accurate pulse reactivity prediction, a new operating procedure was created. The photoneutron effects at delayed critical are minimized when using the modified procedure. In addition, the pulse element removal time is standardized for all pulse operations with the modified procedure, and this produces less variation in reactivity removal times. (authors)

  13. Domain-adaptive finite difference methods for collapsing annular liquid jets

    Science.gov (United States)

    Ramos, J. I.

    1993-01-01

    A domain-adaptive technique which maps a time-dependent, curvilinear geometry into a unit square is used to determine the steady state mass absorption rate and the collapse of annular liquid jets. A method of lines is used to solve the one-dimensional fluid dynamics equations written in weak conservation-law form, and upwind differences are employed to evaluate the axial convective fluxes. The unknown, time-dependent, axial location of the downstream boundary is determined from the solution of an ordinary differential equation which is nonlinearly coupled to the fluid dynamics and gas concentration equations. The equation for the gas concentration in the annular liquid jet is written in strong conservation-law form and solved by means of a method of lines at high Peclet numbers and a line Gauss-Seidel method at low Peclet numbers. The effects of the number of grid points along and across the annular jet, time step, and discretization of the radial convective fluxes on both the steady state mass absorption rate and the jet's collapse rate have been analyzed on staggered and non-staggered grids. The steady state mass absorption rate and the collapse of annular liquid jets are determined as a function of the Froude, Peclet and Weber numbers, annular jet's thickness-to-radius ratio at the nozzle exit, initial pressure difference across the annular jet, nozzle exit angle, temperature of the gas enclosed by the annular jet, pressure of the gas surrounding the jet, solubilities at the inner and outer interfaces of the annular jet, and gas concentration at the nozzle exit. It is shown that the steady state mass absorption rate is proportional to the inverse square root of the Peclet number except for low values of this parameter, and that the possible mathematical incompatibilities in the concentration field at the nozzle exit exert a great influence on the steady state mass absorption rate and on the jet collapse. It is also shown that the steady state mass absorption

  14. Fabrication of two-color annular hybrid wave plate for three-dimensional super-resolution microscopy

    Science.gov (United States)

    Kumagai, Hiroshi; Iketaki, Yoshinori; Jahn, Kornel; Bokor, Nador

    2016-03-01

    In super-resolution microscopy, we use fluorescence depletion, where an erase beam quenches a molecule in the S1 state generated by a pump beam, and then prevents fluorescence from the S1 state. When a tight doughnut shaped erase beam with is focused on the dyed sample together with a Gaussian pump beam, the remaining fluorescence spot in the focal plane becomes smaller than the diffraction-limited size. Applying destructive interference to the erase beam, erase beam has a minute three-dimensional dark spot surrounded by the light near the focal region. Since this spot introduces fluorescence depletion along the optical axis as in the focal plane, we can achieve three-dimensional super-resolution microscopy. However, to overcome the diffraction limit, an extremely precise optical alignment is required for projecting the focused pump beam into the dark spot of the erase beam. To resolve this technical issue, we fabricated a two-color annular hybrid wave plate (TAHWP) by combining two multi-order wave quartz plates. Although the pump and erase beams co-axially pass through the plate; the pump beam retains its original Gaussian shape, while the erase beam undergoes destructive interference. Inserting the TAHWP into a commercial scanning laser microscope, a three-dimensional spherical fluorescence spot with a volume of (~100 nm)3 can be created. Beside eliminating alignment problems and yielding a compact setup, the TAHWP makes our proposed method very suitable for commercial microscope systems. In this study, we report about detailed fabrication procedure and three-dimensional image properties given by the TAHWP.

  15. Dark energy and dark matter from primordial QGP

    Energy Technology Data Exchange (ETDEWEB)

    Vaidya, Vaishali, E-mail: vaidvavaishali24@gmail.com; Upadhyaya, G. K., E-mail: gopalujiain@yahoo.co.in [School of Studies in Physics, Vikram University Ujjain (India)

    2015-07-31

    Coloured relics servived after hadronization might have given birth to dark matter and dark energy. Theoretical ideas to solve mystery of cosmic acceleration, its origin and its status with reference to recent past are of much interest and are being proposed by many workers. In the present paper, we present a critical review of work done to understand the earliest appearance of dark matter and dark energy in the scenario of primordial quark gluon plasma (QGP) phase after Big Bang.

  16. Dark Matter and Dark Energy: Summary and Future Directions

    OpenAIRE

    Ellis, John

    2003-01-01

    This paper reviews the progress reported at this Royal Society Discussion Meeting and advertizes some possible future directions in our drive to understand dark matter and dark energy. Additionally, a first attempt is made to place in context the exciting new results from the WMAP satellite, which were published shortly after this Meeting. In the first part of this review, pieces of observational evidence shown here that bear on the amounts of dark matter and dark energy are reviewed. Subsequ...

  17. Residual Non-Abelian Dark Matter and Dark Radiation

    OpenAIRE

    Ko, P.; Tang, Yong

    2016-01-01

    We propose a novel particle physics model in which vector dark matter (VDM) and dark radiation (DR) originate from the same non-Abelian dark sector. We show an illustrating example where dark $SU(3)$ is spontaneously broken into $SU(2)$ subgroup by the nonzero vacuum expectation value of a complex scalar in fundamental representation of $SU(3)$. The massless gauge bosons associated with the residual unbroken $SU(2)$ constitute DR and help to relieve the tension in Hubble constant measurements...

  18. Unified Description of Dark Energy and Dark Matter

    OpenAIRE

    Petry, Walter

    2008-01-01

    Dark energy in the universe is assumed to be vacuum energy. The energy-momentum of vacuum is described by a scale-dependent cosmological constant. The equations of motion imply for the density of matter (dust) the sum of the usual matter density (luminous matter) and an additional matter density (dark matter) similar to the dark energy. The scale-dependent cosmological constant is given up to an exponent which is approximated by the experimentally decided density parameters of dark matter and...

  19. Interactive Unified Dark Energy and Dark Matter from Scalar Fields

    OpenAIRE

    Benisty, David; Guendelman, E. I.

    2017-01-01

    Here we generalize ideas of unified Dark Matter Dark Energy in the context of Two Measure Theories and of Dynamical space time Theories. In Two Measure Theories one uses metric independent volume elements and this allows to construct unified Dark Matter Dark Energy, where the cosmological constant appears as an integration constant associated to the eq. of motion of the measure fields. The Dynamical space time Theories generalize the Two Measure Theories by introducing a vector field whose eq...

  20. Dark influences: imprints of dark satellites on dwarf galaxies

    NARCIS (Netherlands)

    Starkenburg, T. K.; Helmi, A.

    2015-01-01

    Context. In the context of the current Λ cold dark matter cosmological model small dark matter halos are abundant and satellites of dwarf galaxies are expected to be predominantly dark. Since low mass galaxies have smaller baryon fractions, interactions with these satellites may leave particularly d

  1. Nonthermal production of dark radiation and dark matter

    Science.gov (United States)

    Reece, Matthew; Roxlo, Thomas

    2016-09-01

    Dark matter may be coupled to dark radiation: light degrees of freedom that mediate forces between dark sector particles. Cosmological constraints favor dark radiation that is colder than Standard Model radiation. In models with fixed couplings between dark matter and the Standard Model, these constraints can be difficult to satisfy if thermal equilibrium is assumed in the early universe. We construct a model of asymmetric reheating of the visible and dark sectors from late decays of a long-lived particle (for instance, a modulus). We show, as a proof of principle, that such a model can populate a sufficiently cold dark sector while also generating baryon and dark matter asymmetries through the out-of-equilibrium decay. We frame much of our discussion in terms of the scenario of dissipative dark matter, as in the Double-Disk Dark Matter scenario. However, our results may also be of interest for other scenarios like the Twin Higgs model that are in danger of overproducing dark radiation due to nonnegligible dark-visible couplings.

  2. High Angle of Attack Aerodynamics

    Science.gov (United States)

    1979-01-01

    autour du bond d’attaque au voisinage du fuselage rosto attachd, le bord d’attaquo 6tant At Ia fois arrondi ot cambr6. En quittant le fuselage le rayon ...ont Wt obtenus par d~u~l~ration on pallor aux diff~rents contrages . Pour offectuer une comparaison avec Ia soufflerle i1 oat n~cessaire do corriger les...Lo Longueur de l’ogive CL to de moment de roulis r Rayon de 1’Omoussement Cm de moment de tangage S Surface de r~f~rence :maltre - couple Cn de

  3. A Dark Matter Superfluid

    CERN Document Server

    Khoury, Justin

    2015-01-01

    In this talk we present a novel framework that unifies the stunning success of MOND on galactic scales with the triumph of the LambdaCDM model on cosmological scales. This is achieved through the rich and well-studied physics of superfluidity. The dark matter and MOND components have a common origin, representing different phases of a single underlying substance. In galaxies, dark matter thermalizes and condenses to form a superfluid phase. The superfluid phonons couple to baryonic matter particles and mediate a MOND-like force. Our framework naturally distinguishes between galaxies (where MOND is successful) and galaxy clusters (where MOND is not): dark matter has a higher temperature in clusters, and hence is in a mixture of superfluid and normal phase. The rich and well-studied physics of superfluidity leads to a number of striking observational signatures, which we briefly discuss. Remarkably the critical temperature and equation of state of the dark matter superfluid are similar to those of known cold at...

  4. Dark Blue II

    OpenAIRE

    2013-01-01

    Dark Blue II, high fired porcelain, decorated with cobalt chloride, woodfired with salt. 10,5 x 10,5 x 19 cm. Ferdigstilt: 2012. Innkjøpt til Collection of The American Museum of Ceramic Art, Pomona, California, USA.

  5. Dichromatic Dark Matter

    CERN Document Server

    Bai, Yang; Zhao, Yue

    2012-01-01

    Both the robust INTEGRAL 511 keV gamma-ray line and the recent tentative hint of the 135 GeV gamma-ray line from Fermi-LAT have similar signal morphologies, and may be produced from the same dark matter annihilation. Motivated by this observation, we construct a dark matter model to explain both signals and to accommodate the two required annihilation cross sections that are different by more than six orders of magnitude. In our model, to generate the low-energy positrons for INTEGRAL, dark matter particles annihilate into a complex scalar that couples to photon via a charge-radius operator. The complex scalar contains an excited state decaying into the ground state plus an off-shell photon to generate a pair of positron and electron. Two charged particles with non-degenerate masses are necessary for generating this charge-radius operator. One charged particle is predicted to be long-lived and have a mass around 3.8 TeV to explain the dark matter thermal relic abundance from its late decay. The other charged ...

  6. Dichromatic dark matter

    Science.gov (United States)

    Bai, Yang; Su, Meng; Zhao, Yue

    2013-02-01

    Both the robust INTEGRAL 511 keV gamma-ray line and the recent tentative hint of the 135 GeV gamma-ray line from Fermi-LAT have similar signal morphologies, and may be produced from the same dark matter annihilation. Motivated by this observation, we construct a dark matter model to explain both signals and to accommodate the two required annihilation cross sections that are different by more than six orders of magnitude. In our model, to generate the low-energy positrons for INTEGRAL, dark matter particles annihilate into a complex scalar that couples to photon via a charge-radius operator. The complex scalar contains an excited state decaying into the ground state plus an off-shell photon to generate a pair of positron and electron. Two charged particles with non-degenerate masses are necessary for generating this charge-radius operator. One charged particle is predicted to be long-lived and have a mass around 3.8 TeV to explain the dark matter thermal relic abundance from its late decay. The other charged particle is predicted to have a mass below 1 TeV given the ratio of the two signal cross sections. The 14 TeV LHC will concretely test the main parameter space of this lighter charged particle.

  7. The Universal Dark Matter

    CERN Document Server

    Soberman, R K; Soberman, Robert K.; Dubin, Maurice

    2006-01-01

    Fragile volatile aggregates with extremely low albedo, gravitationally drawn into the solar system are likely from the dark matter dominating the universal mass. Characteristics of this meteoric population permitted avoiding detection through a half-century's search. Measurements from space probes and in the upper atmosphere prove their existence and confirm their elusive properties.

  8. Template Composite Dark Matter

    DEFF Research Database (Denmark)

    Drach, Vincent; Hietanen, Ari; Pica, Claudio

    2015-01-01

    We present a non perturbative study of SU(2) gauge theory with two fundamental Dirac flavours. We discuss how the model can be used as a template for composite Dark Matter (DM). We estimate one particular interaction of the DM candidate with the Standard Model : the interaction through photon...

  9. Template Composite Dark Matter

    DEFF Research Database (Denmark)

    Drach, Vincent; Hietanen, Ari; Pica, Claudio

    2015-01-01

    We present a non perturbative study of SU(2) gauge theory with two fundamental Dirac flavours. We discuss how the model can be used as a template for composite Dark Matter (DM). We estimate one particular interaction of the DM candidate with the Standard Model : the interaction through photon...

  10. Exceptional composite dark matter

    Science.gov (United States)

    Ballesteros, Guillermo; Carmona, Adrián; Chala, Mikael

    2017-07-01

    We study the dark matter phenomenology of non-minimal composite Higgs models with SO(7) broken to the exceptional group G_2. In addition to the Higgs, three pseudo-Nambu-Goldstone bosons arise, one of which is electrically neutral. A parity symmetry is enough to ensure this resonance is stable. In fact, if the breaking of the Goldstone symmetry is driven by the fermion sector, this Z_2 symmetry is automatically unbroken in the electroweak phase. In this case, the relic density, as well as the expected indirect, direct and collider signals are then uniquely determined by the value of the compositeness scale, f. Current experimental bounds allow one to account for a large fraction of the dark matter of the Universe if the dark matter particle is part of an electroweak triplet. The totality of the relic abundance can be accommodated if instead this particle is a composite singlet. In both cases, the scale f and the dark matter mass are of the order of a few TeV.

  11. Dark Matter Superfluidity

    CERN Document Server

    Khoury, Justin

    2016-01-01

    In this talk I summarize a novel framework that unifies the stunning success of MOND on galactic scales with the triumph of the $\\Lambda$CDM model on cosmological scales. This is achieved through the rich and well-studied physics of superfluidity. The dark matter and MOND components have a common origin, representing different phases of a single underlying substance. In galaxies, dark matter thermalizes and condenses to form a superfluid phase. The superfluid phonons couple to baryonic matter particles and mediate a MOND-like force. This framework naturally distinguishes between galaxies (where MOND is successful) and galaxy clusters (where MOND is not): dark matter has a higher temperature in clusters, and hence is in a mixture of superfluid and normal phase. The rich and well-studied physics of superfluidity leads to a number of striking observational signatures, which we briefly discuss. Remarkably the critical temperature and equation of state of the dark matter superfluid are similar to those of known co...

  12. Levitating Dark Matter

    CERN Document Server

    Kaloper, Nemanja

    2009-01-01

    A sizable fraction of the total energy density of the universe may be in heavy particles with a net dark $U(1)'$ charge equal to its mass, such as the BPS states in string theory. When the charges have the same sign the cancellation between their gravitational and gauge forces may lead to a mismatch between different measures of masses in the universe. Measuring galactic masses by orbits of normal matter, such as galaxy rotation curves or lensing, will give the total mass, while the flows of dark matter agglomerates may yield smaller values if the gauge repulsion is not accounted for. If distant galaxies which house light beacons like SNe Ia contain such dark particles, the observations of their cosmic recession may mistake the weaker forces for an extra `antigravity', and infer an effective dark energy equation of state smaller than the real one. In some cases, including that of a cosmological constant, these effects can mimic $w<-1$. They can also lead to a {\\it local} variation of galaxy-galaxy forces, ...

  13. Inflatable Dark Matter

    CERN Document Server

    Davoudiasl, Hooman; McDermott, Samuel D

    2016-01-01

    We describe a general scenario, dubbed "Inflatable Dark Matter", in which the density of dark matter particles can be reduced through a short period of late-time inflation in the early universe. The overproduction of dark matter that is predicted within many otherwise well-motivated models of new physics can be elegantly remedied within this context, without the need to tune underlying parameters or to appeal to anthropic considerations. Thermal relics that would otherwise be disfavored can easily be accommodated within this class of scenarios, including dark matter candidates that are very heavy or very light. Furthermore, the non-thermal abundance of GUT or Planck scale axions can be brought to acceptable levels, without invoking anthropic tuning of initial conditions. A period of late-time inflation could have occurred over a wide range of scales from ~ MeV to the weak scale or above, and could have been triggered by physics within a hidden sector, with small but not necessarily negligible couplings to the...

  14. Asymmetric condensed dark matter

    Science.gov (United States)

    Aguirre, Anthony; Diez-Tejedor, Alberto

    2016-04-01

    We explore the viability of a boson dark matter candidate with an asymmetry between the number densities of particles and antiparticles. A simple thermal field theory analysis confirms that, under certain general conditions, this component would develop a Bose-Einstein condensate in the early universe that, for appropriate model parameters, could survive the ensuing cosmological evolution until now. The condensation of a dark matter component in equilibrium with the thermal plasma is a relativistic process, hence the amount of matter dictated by the charge asymmetry is complemented by a hot relic density frozen out at the time of decoupling. Contrary to the case of ordinary WIMPs, dark matter particles in a condensate must be lighter than a few tens of eV so that the density from thermal relics is not too large. Big-Bang nucleosynthesis constrains the temperature of decoupling to the scale of the QCD phase transition or above. This requires large dark matter-to-photon ratios and very weak interactions with standard model particles.

  15. Neutrinos and dark energy

    Energy Technology Data Exchange (ETDEWEB)

    Schrempp, L.

    2008-02-15

    From the observed late-time acceleration of cosmic expansion arises the quest for the nature of Dark Energy. As has been widely discussed, the cosmic neutrino background naturally qualifies for a connection with the Dark Energy sector and as a result could play a key role for the origin of cosmic acceleration. In this thesis we explore various theoretical aspects and phenomenological consequences arising from non-standard neutrino interactions, which dynamically link the cosmic neutrino background and a slowly-evolving scalar field of the dark sector. In the considered scenario, known as Neutrino Dark Energy, the complex interplay between the neutrinos and the scalar field not only allows to explain cosmic acceleration, but intriguingly, as a distinct signature, also gives rise to dynamical, time-dependent neutrino masses. In a first analysis, we thoroughly investigate an astrophysical high energy neutrino process which is sensitive to neutrino masses. We work out, both semi-analytically and numerically, the generic clear-cut signatures arising from a possible time variation of neutrino masses which we compare to the corresponding results for constant neutrino masses. Finally, we demonstrate that even for the lowest possible neutrino mass scale, it is feasible for the radio telescope LOFAR to reveal a variation of neutrino masses and therefore to probe the nature of Dark Energy within the next decade. A second independent analysis deals with the recently challenged stability of Neutrino Dark Energy against the strong growth of hydrodynamic perturbations, driven by the new scalar force felt between neutrinos. Within the framework of linear cosmological perturbation theory, we derive the equation of motion of the neutrino perturbations in a model-independent way. This equation allows to deduce an analytical stability condition which translates into a comfortable upper bound on the scalar-neutrino coupling which is determined by the ratio of the densities in cold dark

  16. An elusive vector dark matter

    Directory of Open Access Journals (Sweden)

    Chuan-Ren Chen

    2015-02-01

    Full Text Available Even though the sensitivity of direct dark matter search experiments reaches the level of about 10−45 cm2, no confident signal of dark matter has been observed. We point out that, if dark matter is a vector boson, the null result in direct dark matter search experiments may be due to the destructive effects in dark-matter–nucleon elastic scattering. We illustrate the scenario using a modified Higgs portal model that includes exotic quarks. The significant cancellation can occur for a certain mass gap between new heavy quark and dark matter. As a result, the spin-independent dark-matter–nucleon elastic scattering is so suppressed that the future direct search experiments will hardly observe the signal of dark matter.

  17. Dynamics of Teleparallel Dark Energy

    CERN Document Server

    Wei, Hao

    2011-01-01

    Recently, motivated by the similar one in the framework of General Relativity (GR), Geng et al.} proposed to allow a non-minimal coupling between quintessence and gravity in the framework of teleparallel gravity. They found that this non-minimally coupled quintessence in the framework of teleparallel gravity has a richer structure, and named it "teleparallel dark energy". In the present work, we note that there might be a deep and unknown connection between teleparallel dark energy and Elko spinor dark energy. Motivated by this observation and the previous results of Elko spinor dark energy, we try to study the dynamics of teleparallel dark energy. We find that there exist only some dark-energy-dominated de Sitter attractors. No scaling attractor has been found unfortunately. So, similar to Elko spinor dark energy, teleparallel dark energy is also plagued with the cosmological coincidence problem, although it has an extra free model parameter $\\xi$.

  18. Dark matter detection

    Science.gov (United States)

    Baudis, Laura

    2016-08-01

    More than 80 years after its first postulation in modern form, the existence and distribution of dark matter in our Universe is well established. Dark matter is the gravitational glue that holds together galaxies, galaxy clusters and structures on the largest cosmological scales, and an essential component to explain the observed fluctuations in the cosmic microwave background. Yet its existence is inferred indirectly, through its gravitational influence on luminous matter, and its nature is not known. A viable hypothesis is that dark matter is made of new, elementary particles, with allowed masses and interaction strengths spanning a wide range. Two well-motivated classes of candidates are axions and weakly interacting massive particles (WIMPs), and experimental efforts have now reached sensitivities that allow them to test this hypothesis. Axions, produced non-thermally in the early Universe, can be detected by exploiting their predicted couplings to photons and electrons. WIMPs can be detected directly by looking for their collisions with atomic nuclei ultra-low background detectors, or indirectly, through the observation of their annihilation products such as neutrinos, gamma rays, positrons and antiprotons over the astrophysical background. A complementary method is the production of dark matter particles at colliders such as the Large Hadron Collider, where they could be observed indirectly via missing transverse energy, or via associated particle production. I will review the main experimental efforts to search for dark matter particles, and the existing constraints on the interaction cross sections. I will also discuss future experiments, their complementarity and their ability to measure the properties of these particles.

  19. Welcome to the dark side

    CERN Multimedia

    Hogan, Jenny

    2007-01-01

    "Physicists says that 96% of the Universe is unseen, and appeal tot he ideas of "dark matter" and "dark energy" to make up the difference. In the first of two articles, jeanny hogan reports that attempts to identify the mysterious dark matter are on the verge of success. In the second, Geoff Brumfiel asks why dark energy, hailed as a breakthrough when discovered a decade ago, is proving more frustrating than ever tot he scientists who study it." (4,5 pages)

  20. A Stab in the Dark?

    OpenAIRE

    Tompson, Lisa; Bowers, Kate

    2013-01-01

    Objectives: Test the influence of darkness in the street robbery crime event alongside temperature. Methods: Negative binomial regression models tested darkness and temperature as predictors of street robbery. Units of analysis were four 6-hr time intervals in two U.K. study areas that have different levels of darkness and variations of temperature throughout the year. Results: Darkness is a key factor related to robbery events in both study areas. Traversing from full daylight to full darkne...

  1. A Supersymmetric Dark Disk Universe

    CERN Document Server

    Fischler, Willy; Tangarife, Walter

    2014-01-01

    We present a model of partially interacting dark matter (PIDM) within the framework of supersymmetry with gauge mediated symmetry breaking. Dark sector atoms are produced through Affleck-Dine baryogenesis in the dark sector while avoiding the production of Q-ball relics. We discuss the astrophysical constraints relevant for this model and the possibility of dark galactic disk formation. In addition, jet emission from rotating black holes is discussed in the context of this class of models.

  2. Three-dimensional imaging of individual point defects using selective detection angles in annular dark field scanning transmission electron microscopy.

    Science.gov (United States)

    Johnson, Jared M; Im, Soohyun; Windl, Wolfgang; Hwang, Jinwoo

    2017-01-01

    We propose a new scanning transmission electron microscopy (STEM) technique that can realize the three-dimensional (3D) characterization of vacancies, lighter and heavier dopants with high precision. Using multislice STEM imaging and diffraction simulations of β-Ga2O3 and SrTiO3, we show that selecting a small range of low scattering angles can make the contrast of the defect-containing atomic columns substantially more depth-dependent. The origin of the depth-dependence is the de-channeling of electrons due to the existence of a point defect in the atomic column, which creates extra "ripples" at low scattering angles. The highest contrast of the point defect can be achieved when the de-channeling signal is captured using the 20-40mrad detection angle range. The effect of sample thickness, crystal orientation, local strain, probe convergence angle, and experimental uncertainty to the depth-dependent contrast of the point defect will also be discussed. The proposed technique therefore opens new possibilities for highly precise 3D structural characterization of individual point defects in functional materials.

  3. A Physical Source of Dark Energy and Dark Matter

    CERN Document Server

    Gontijo, I

    2012-01-01

    A physical mechanism that produces three energy components is proposed as the common origin of dark energy and dark matter. The first two have equations of state W ~ 0 and act like dark matter, while the last has W ~ -1 at low redshifts making it a candidate for dark energy. These are used to model the supernovae Union2 data resulting in a curve fitting identical to the LAMBDACDM model. This model opens new avenues for Cosmology research and implies a re-interpretation of the dark components as a scalar field stored in the metric of spacetime.

  4. Dynamics of dark energy with a coupling to dark matter

    CERN Document Server

    Boehmer, Christian G; Lazkoz, Ruth; Maartens, Roy

    2008-01-01

    Dark energy and dark matter are the dominant sources in the evolution of the late universe. They are currently only indirectly detected via their gravitational effects, and there could be a coupling between them without violating observational constraints. We investigate the background dynamics when dark energy is modelled as exponential quintessence, and is coupled to dark matter via simple models of energy exchange. We introduce a new form of dark sector coupling, which leads to a more complicated dynamical phase space and has a better physical motivation than previous mathematically similar couplings.

  5. Coupling q-deformed dark energy to dark matter

    OpenAIRE

    Emre Dil

    2016-01-01

    We propose a novel coupled dark energy model which is assumed to occur as a q-deformed scalar field and investigate whether it will provide an expanding universe phase. We consider the q-deformed dark energy as coupled to dark matter inhomogeneities. We perform the phase-space analysis of the model by numerical methods and find the late-time accelerated attractor solutions. The attractor solutions imply that the coupled q-deformed dark energy model is consistent with the conventional dark ene...

  6. How dark chocolate is processed

    Science.gov (United States)

    This month’s column will continue the theme of “How Is It Processed?” The column will focus on dark chocolate. The botanical name for the cacao tree is Theobroma cacao, which literally means “food of the Gods.” Dark chocolate is both delicious and nutritious. Production of dark chocolate will be des...

  7. Dark Matter Searches at LHC

    CERN Document Server

    Terashi, Koji; The ATLAS collaboration

    2017-01-01

    This talk will present dark matter searches at the LHC in the PIC2017 conference. The main emphasis is placed on the direct dark matter searches while the interpretation of searches for SUSY and invisible Higgs signals for the dark matter is also presented.

  8. Dark matter on the lattice

    OpenAIRE

    Lewis, Randy

    2014-01-01

    Several collaborations have recently performed lattice calculations aimed specifically at dark matter, including work with SU(2), SU(3), SU(4) and SO(4) gauge theories to represent the dark sector. Highlights of these studies are presented here, after a reminder of how lattice calculations in QCD itself are helping with the hunt for dark matter.

  9. Dark matter in the Galaxy

    OpenAIRE

    Bilic, Neven; Tupper, Gary B.; Viollier, Raoul D.

    2002-01-01

    After a brief introduction to standard cosmology and the dark matter problem in the the Universe, we consider a self-gravitating noninteracting fermion gas at nonzero temperature as a model for the dark matter halo of the Galaxy. This fermion gas model is then shown to imply the existence of a supermassive compact dark object at the Galactic center.

  10. The DarkSide Program

    Directory of Open Access Journals (Sweden)

    Rossi B.

    2016-01-01

    Full Text Available DarkSide-50 at Gran Sasso underground laboratory (LNGS, Italy, is a direct dark matter search experiment based on a liquid argon TPC. DS-50 has completed its first dark matter run using atmospheric argon as target. The detector performances and the results of the first physics run are presented in this proceeding.

  11. Dark Matter in the Universe

    Indian Academy of Sciences (India)

    2017-02-01

    Vera Rubin gave an evening lecture during the 19th General Assembly of the International Astronomical Union, in 1985 at New Delhi, on dark matter. It was a lucid introduction to the issues regarding dark matter, as well as a comprehensive review of the evidences for dark matter. This extraordinary lecture, aimed towards non-specialists, is reprinted below.

  12. Quantum field theory of interacting dark matter and dark energy: Dark monodromies

    Science.gov (United States)

    D'Amico, Guido; Hamill, Teresa; Kaloper, Nemanja

    2016-11-01

    We discuss how to formulate a quantum field theory of dark energy interacting with dark matter. We show that the proposals based on the assumption that dark matter is made up of heavy particles with masses which are very sensitive to the value of dark energy are strongly constrained. Quintessence-generated long-range forces and radiative stability of the quintessence potential require that such dark matter and dark energy are completely decoupled. However, if dark energy and a fraction of dark matter are very light axions, they can have significant mixings which are radiatively stable and perfectly consistent with quantum field theory. Such models can naturally occur in multi-axion realizations of monodromies. The mixings yield interesting signatures which are observable and are within current cosmological limits but could be constrained further by future observations.

  13. Quantum Field Theory of Interacting Dark Matter/Dark Energy: Dark Monodromies

    CERN Document Server

    D'Amico, Guido; Kaloper, Nemanja

    2016-01-01

    We discuss how to formulate a quantum field theory of dark energy interacting with dark matter. We show that the proposals based on the assumption that dark matter is made up of heavy particles with masses which are very sensitive to the value of dark energy are strongly constrained. Quintessence-generated long range forces and radiative stability of the quintessence potential require that such dark matter and dark energy are completely decoupled. However, if dark energy and a fraction of dark matter are very light axions, they can have significant mixings which are radiatively stable and perfectly consistent with quantum field theory. Such models can naturally occur in multi-axion realizations of monodromies. The mixings yield interesting signatures which are observable and are within current cosmological limits but could be constrained further by future observations.

  14. Dark Energy Coupled with Dark Matter in the Accelerating Universe

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yang

    2004-01-01

    @@ To model the observed Universe containing both dark energy and dark matter, we study the effective Yang-Mills condensate model of dark energy and add a non-relativistic matter component as the dark matter, which is generated out of the decaying dark energy at a constant rate Г, a parameter of our model. For the Universe driven by these two components, the dynamic evolution still has asymptotic behaviour: the expansion of the Universe is accelerating with an asymptotically constant rate H, and the densities of both components approach to finite constant values. Moreover, ΩA≈ 0.7 for dark energy and Ωm ≈ 0.3 for dark matter are achieved if the decay rate Г is chosen such that Г/H~ 1.

  15. Classification of annular bed flow patterns and investigation on their influence on the bottom spray fluid bed coating process.

    Science.gov (United States)

    Wang, Li Kun; Heng, Paul Wan Sia; Liew, Celine Valeria

    2010-05-01

    This study aims to classify annular bed flow patterns in the bottom spray fluid bed coating process, study their influence on coat uniformity and investigate the feasibility of developing real-time annular bed flow pattern detection as a PAT tool. High-speed imaging and particle image velocimetry were used to visualize annular bed flow. Color coating and subsequent tristimulus colorimetry were employed to determine influence of annular bed flow pattern on coat uniformity. Feasibility of monitoring annular bed flow pattern through an observation window was tested using miniaturized particle velocity field and time series particle velocity orientation information. Three types of annular bed flow patterns were identified. Plug flow gave the best coat uniformity followed by global and localized fluidization. Plug flow may be advantageous for high spray-rate conditions, large-scale coating and prevention of particle segregation. Plug flow could be differentiated from the other flow patterns through a simulated observation window. Annular bed flow patterns were classified and found to influence particle coat uniformity noticeably. Availability of annular bed flow information for large-scale coaters would enable adjustments for process optimization. This study highlights the potential of monitoring annular bed flow pattern as a PAT tool.

  16. Dilaton-assisted dark matter.

    Science.gov (United States)

    Bai, Yang; Carena, Marcela; Lykken, Joseph

    2009-12-31

    A dilaton could be the dominant messenger between standard model fields and dark matter. The measured dark matter relic abundance relates the dark matter mass and spin to the conformal breaking scale. The dark matter-nucleon spin-independent cross section is predicted in terms of the dilaton mass. We compute the current constraints on the dilaton from LEP and Tevatron experiments, and the gamma-ray signal from dark matter annihilation to dilatons that could be observed by Fermi Large Area Telescope.

  17. THE MAGIC OF DARK TOURISM

    OpenAIRE

    Erika KULCSÁR; Rozalina Zsófia SIMON

    2015-01-01

    The dark tourism is a form of tourism that is not unanimously accepted by the whole society, but in spite of this fact, the practitioners of dark tourism is a viable segment. Indeed the concept that defines dark tourism is none other than death, and perhaps this is why it will always be a segment that will not be attracted by this form of tourism. Many questions about dark tourism arise. Among them: (1) is dark tourism an area of science attractive for researches? (2) which is the typology of...

  18. Effects of dark atom excitations

    CERN Document Server

    Cudell, Jean-René; Wallemacq, Quentin

    2014-01-01

    New stable quarks and charged leptons may exist and be hidden from detection, as they are bound by Coulomb interaction in neutral dark atoms of composite dark matter. This possibility leads to fundamentally new types of indirect effects related to the excitation of such dark atoms followed by their electromagnetic de-excitation. Stable -2 charged particles, bound to primordial helium in O-helium (OHe) atoms, represent the simplest model of dark atoms. Here we consider the structure of OHe atomic levels which is a necessary input for the indirect tests of such composite dark matter scenarios, and we give the spectrum of electromagnetic transitions from the levels excited in OHe collisions.

  19. Dark matter search in CMS

    CERN Document Server

    Vartak, Adish

    2017-01-01

    The dark matter search program at the LHC covers a wide range of final states and targets a variety of possible interactions between dark matter and standard model particles. A summary of the dark matter searches performed at the CMS experiment, using proton-proton collision data collected at a center of energy of 13 TeV, is presented.Searches performed in various final states are described, and results interpreted in terms of several dark matter models are presented. These results are also compared to the results from direct and indirect dark matter searches.

  20. Chaining Mimes in the Dark: Dark Energy Scaling from Dark Matter to Acceleration

    CERN Document Server

    Bielefeld, Jannis; Linder, Eric V

    2014-01-01

    The dark sector of the Universe need not be completely separable into distinct dark matter and dark energy components. We consider a model of early dark energy in which the dark energy mimics a dark matter component in both evolution and perturbations at early times. Barotropic aether dark energy scales as a fixed fraction, possibly greater than one, of the dark matter density and has vanishing sound speed at early times before undergoing a transition. This gives signatures not only in cosmic expansion but in sound speed and inhomogeneities, and in number of effective neutrino species. Model parameters describe the timing, sharpness of the transition, and the relative abundance at early times. Upon comparison with current data, we find viable regimes in which the dark energy behaves like dark matter at early times: for transitions well before recombination the dark energy to dark matter fraction can equal or exceed unity, while for transitions near recombination the ratio can only be a few percent. After the ...

  1. Dark Radiative Inverse Seesaw

    CERN Document Server

    Ahriche, Amine; Nasri, Salah

    2016-01-01

    We present a minimal model that simultaneously accounts for neutrino masses and the origin of dark matter (DM) and where the electroweak phase transition is strong enough to allow for electroweak baryogenesis. The Standard Model is enlarged with a Majorana fermion, three generations of chiral fermion pairs, and a single complex scalar that plays a central role in DM production and phenomenology, neutrino masses, and the strength of the phase transition. All the new fields are singlets under the SM gauge group. Neutrino masses are generated via a new variant of radiative inverse seesaw where the required small mass term is generated via loops involving DM and no large hierarchy is assumed among the mass scales. The model offers all the advantage of low-scale neutrino mass models as well as a viable dark matter candidate that is testable with direct detection experiments.

  2. Dark matter from unification

    DEFF Research Database (Denmark)

    Kainulainen, Kimmo; Tuominen, Kimmo; Virkajärvi, Jussi Tuomas

    2013-01-01

    We consider a minimal extension of the Standard Model (SM), which leads to unification of the SM coupling constants, breaks electroweak symmetry dynamically by a new strongly coupled sector and leads to novel dark matter candidates. In this model, the coupling constant unification requires...... eigenstates of this sector and determine the resulting relic density. The results are constrained by available data from colliders and direct and indirect dark matter experiments. We find the model viable and outline briefly future research directions....... the existence of electroweak triplet and doublet fermions singlet under QCD and new strong dynamics underlying the Higgs sector. Among these new matter fields and a new right handed neutrino, we consider the mass and mixing patterns of the neutral states. We argue for a symmetry stabilizing the lightest mass...

  3. Radiative light dark matter

    Science.gov (United States)

    Dedes, A.; Karamitros, D.; Pilaftsis, A.

    2017-06-01

    We present a Peccei-Quinn (PQ)-symmetric two-Higgs doublet model that naturally predicts a fermionic singlet dark matter in the mass range 10 keV-1 GeV. The origin of the smallness of the mass of this light singlet fermion arises predominantly at the one-loop level, upon soft or spontaneous breakdown of the PQ symmetry via a complex scalar field in a fashion similar to the so-called Dine-Fischler-Sredniki-Zhitnitsky axion model. The mass generation of this fermionic radiative light dark matter (RLDM) requires the existence of two heavy vectorlike SU(2) isodoublets, which are not charged under the PQ symmetry. We show how the RLDM can be produced via the freeze-in mechanism, thus accounting for the missing matter in the Universe. Finally, we briefly discuss possible theoretical and phenomenological implications of the RLDM model for the strong C P problem and the CERN Large Hadron Collider (LHC).

  4. Dark Skies Rangers

    Science.gov (United States)

    Doran, Rosa

    2015-08-01

    Creating awareness about the importance of the protection of our dark skies is the main goal of the Dark Skies Rangers project, a joint effort from the NOAO and the Galileo Teacher Training Program. Hundreds of schools and thousands of students have been reached by this program. We will focus in particular on the experience being developed in Portugal where several municipalities have now received street light auditing produced by students with suggestions on how to enhance the energy efficiency of illumination of specific urban areas. In the International Year of Light we are investing our efforts in exporting the successful Portuguese experience to other countries. The recipe is simple: train teachers, engage students, foster the participation of local community and involve local authorities in the process. In this symposium we hope to draft the cookbook for the near future.

  5. A dark energy multiverse

    Energy Technology Data Exchange (ETDEWEB)

    Robles-Perez, Salvador; Martin-Moruno, Prado; Rozas-Fernandez, Alberto; Gonzalez-Diaz, Pedro F [Colina de los Chopos, Instituto de Matematicas y Fisica Fundamental, Consejo Superior de Investigaciones CientIficas, Serrano 121, 28006 Madrid (Spain)

    2007-05-21

    We present cosmic solutions corresponding to universes filled with dark and phantom energy, all having a negative cosmological constant. All such solutions contain infinite singularities, successively and equally distributed along time, which can be either big bang/crunches or big rips singularities. Classically these solutions can be regarded as associated with multiverse scenarios, being those corresponding to phantom energy that may describe the current accelerating universe. (fast track communication)

  6. Alternatives to Dark Matter (?)

    OpenAIRE

    Aguirre, Anthony

    2003-01-01

    It has long been known that Newtonian dynamics applied to the visible matter in galaxies and clusters does not correctly describe the dynamics of those systems. While this is generally taken as evidence for dark matter it is in principle possible that instead Newtonian dynamics (and with it General Relativity) breaks down in these systems. Indeed there have been a number of proposals as to how standard gravitational dynamics might be modified so as to correctly explain galactic dynamics witho...

  7. R^2 Dark Matter

    CERN Document Server

    Cembranos, Jose A R

    2010-01-01

    There is a non-trivial four-derivative extension of the gravitational spectrum that is free of ghosts and phenomenologically viable. It is the so called $R^2$-gravity since it is defined by the only addition of a term proportional to the square of the scalar curvature. Just the presence of this term does not improve the ultraviolet behaviour of Einstein gravity but introduces one additional scalar degree of freedom that can account for the dark matter of our Universe.

  8. Signals of Supersymmetric Dark Matter

    CERN Document Server

    Abbas, A

    2000-01-01

    The Lightest Supersymmetric Particle predicted in most of the supersymmetric scenarios is an ideal candidate for the dark matter of cosmology. Their detection is of extreme significance today. Recently there have been intriguing signals of a 59 Gev neutralino dark matter at DAMA in Gran Sasso. We look at other possible signatures of dark matter in astrophysical and geological frameworks. The passage of the earth through dense clumps of dark matter would produce large quantities of heat in the interior of this planet through the capture and subsequent annihilation of dark matter particles. This heat would lead to large-scale volcanism which could in turn have caused mass extinctions. The periodicity of such volcanic outbursts agrees with the frequency of palaeontological mass extinctions as well as the observed periodicity in the occurrence of the largest flood basalt provinces on the globe. Binary character of these extinctions is another unique aspect of this signature of dark matter. In addition dark matter...

  9. End of a Dark Age?

    CERN Document Server

    Stuckey, W M; Sten, A K; Silberstein, Michael

    2016-01-01

    We argue that dark matter and dark energy phenomena associated with galactic rotation curves, X-ray cluster mass profiles, and type Ia supernova data can be accounted for via small corrections to idealized general relativistic spacetime geometries due to disordered locality. Accordingly, we fit THINGS rotation curve data rivaling modified Newtonian dynamics, ROSAT/ASCA X-ray cluster mass profile data rivaling metric-skew-tensor gravity, and SCP Union2.1 SN Ia data rivaling $\\Lambda$CDM without non-baryonic dark matter or a cosmological constant. In the case of dark matter, we geometrically modify proper mass interior to the Schwarzschild solution. In the case of dark energy, we modify proper distance in Einstein-deSitter cosmology. Therefore, the phenomena of dark matter and dark energy may be chimeras created by an errant belief that spacetime is a differentiable manifold rather than a disordered graph.

  10. Plasma dark matter direct detection

    CERN Document Server

    Clarke, Jackson D

    2015-01-01

    Dark matter in spiral galaxies like the Milky Way may take the form of a dark plasma. Hidden sector dark matter charged under an unbroken $U(1)'$ gauge interaction provides a simple and well defined particle physics model realising this possibility. The assumed $U(1)'$ neutrality of the Universe then implies (at least) two oppositely charged dark matter components with self-interactions mediated via a massless "dark photon" (the $U(1)'$ gauge boson). In addition to nuclear recoils such dark matter can give rise to keV electron recoils in direct detection experiments. In this context, the detailed physical properties of the dark matter plasma interacting with the Earth is required. This is a complex system, which is here modelled as a fluid governed by the magnetohydrodynamic equations. These equations are numerically solved for some illustrative examples, and implications for direct detection experiments discussed. In particular, the analysis presented here leaves open the intriguing possibility that the DAMA...

  11. Hydraulic study of drilling fluid flow in circular and annular tubes

    Energy Technology Data Exchange (ETDEWEB)

    Scheid, C.M.; Calcada, L.A.; Braga, E.R.; Paraiso, E.C.H. [Universidade Federal Rural do Rio de Janeiro (PPGEQ/UFRRJ), Seropedica, RJ (Brazil). Programa de Pos-Graduacao em Engenharia Quimica. Dept. de Engenharia Qumica], E-mail: calcada@ufrrj.br; Martins, A. L. [Petroleo Brasileiro S.A. (CENPES/PETROBRAS), Rio de Janeiro, RJ (Brazil). Centro de Pesquisas

    2011-10-15

    This study investigates the drilling fluid flow behavior of two water-based drilling fluids in circular and annular tubes. The study has four main objectives: 1) to evaluate correlations between the Power Law and the Casson rheological models, 2) to characterize the flow behavior, 3) to evaluate five hydraulic-diameter equations, and 4) to evaluate the correlations of five turbulent flow-friction factors. The experimental fluid flow loop consisted of one positive displacement pump of 25 HP connected to a 500-liter tank agitated by a 3-HP mixer. The fluids passed through six meters long tubes, arranged in three horizontal rows with independent inlets and outlets. The circular tubes had a 1 inch diameter and were configured as two concentric annular tubes. Annular Tube I had an outer diameter of 1 1/4 inch and an inner diameter of 1/2 inch. Annular Tube II had an outer diameter of 2 inches and an inner diameter of 3/4 inch. The results show that, for the fluids in exam, correlations proposed in the literature were inaccurate as far as predicting hydraulic diameter, estimating pressure drop, and defining the flow regime. In general, the performance of those correlations depended on the fluid properties and on the system's geometry. Finally, literature parameters for some of the correlations were estimated for the two drilling fluids studied. These estimations improved the predictive capacity of calculating the friction factor for real drilling fluids applications for both circular and annular tubes. (author)

  12. Propagation characteristics of annular laser beams passing through the reflection Bragg grating with deformation

    Science.gov (United States)

    Yin, Suqin; Zhang, Bin; Dan, Youquan

    2011-06-01

    When high-power annular laser beams produced by the unstable resonator pass through the volume Bragg grating (VBG), absorption of light in the VBG will induce a temperature increment, resulting in changes in surface distortion. Considering that the surface distortion of the grating induces index and period differences, the scalar wave equations for the annular laser beams propagating in the VBG have been solved numerically and iteratively using finite-difference and sparse matrix methods. The variation in intensity distributions, the total power reflection coefficient, and the power in the bucket (PIB) for the annular laser beams passing through the reflection VBG with deformation have been analyzed quantitatively. It can be shown that the surface distortion of the VBG and the beam orders of the annular beams affect evidently the intensity distributions, the power reflection coefficient, and the PIB of the output beam. The peak intensity decreases as the deformation of the VBG increases. The total power reflection efficiency decreases significantly with the increase in deformations of the VBG. The PIB of the output beam decreases as the obscuration ratio β and the deformation of the VBG increase. For the given obscuration ratio β, the influence of deformation of reflection VBG on the PIB of the annular beams is more sensitive with increase in distortion of the VBG and decrease in beam order.

  13. Time delay controlled annular array transducers for omnidirectional guided wave mode control in plate like structures

    Science.gov (United States)

    Koduru, Jaya P.; Rose, Joseph L.

    2014-10-01

    Guided waves in plate like structures offer several modes with unique characteristics that can be taken advantage for nondestructive inspection applications. Conditions relating to the structure under inspection like the surrounding media, liquid loading, coatings etc require the use of special modes for successful inspection. Therefore, transducers that can excite mode controlled guided waves are essential for defect detection and discrimination in structures. Array transducers with annular elements can generate omnidirectional guided waves in plate like structures. However, the wave modes excited are limited to a particular wavelength governed by the element spacing. This limitation on the annular array transducers can be overcome by controlling the phase at each element relative to one another. In this work, annular array transducer construction techniques are theoretically examined and the optimum phase delays between the annular elements to excite a desired guided wave mode are calculated. A five element comb type annular array transducer is fabricated utilizing 1-3 type piezocomposite material. The mode control capability of the transducer is experimentally verified by selectively exciting the A0 and S0 guided wave modes in an aluminum plate like structure.

  14. Repeated mitral valve replacement in a patient with extensive annular calcification

    Directory of Open Access Journals (Sweden)

    Kitamura Tadashi

    2011-11-01

    Full Text Available Abstract Background Mitral valve replacement in the presence of severe annular calcification is a technical challenge. Case report A 47-year-old lady who had undergone mitral and aortic valve replacement for rheumatic disease 27 years before presented with dyspnea. At reoperation, extensive mitral annular calcification was hindering the disc motion of the Starr-Edwards mitral prosthesis. The old prosthesis was removed and a St Jude Medical mechanical valve was implanted after thorough annular debridement. Postoperatively the patient developed paravalvular leak and hemolytic anemia, subsequently undergoing reoperation three days later. The mitral valve was replaced with an Edwards MIRA valve, with a bulkier sewing cuff, after more aggressive annular debridement. Although initially there was no paravalvular leak, it recurred five days later. The patient also developed a small cerebral hemorrhage. As the paravalvular leak and hemolytic anemia gradually worsened, the patient underwent reoperation 14 days later. A Carpentier-Edwards bioprosthetic valve with equine pericardial patches, one to cover the debrided calcified annulus, another as a collar around the prosthesis, was used to eliminate paravalvular leak. At 7 years postoperatively the patient is doing well without any evidence of paravalvular leak or structural valve deterioration. Conclusion Mitral valve replacement using a bioprosthesis with equine pericardial patches was useful to overcome recurrent paravalvular leak due to severe mitral annular calcification.

  15. Tunguska Dark Matter Ball

    CERN Document Server

    Froggatt, C D

    2014-01-01

    It is suggested that the Tunguska event in June 1908 cm-large was due to a cm-large ball of a condensate of bound states of 6 top and 6 anti-top quarks containing highly compressed ordinary matter. Such balls are supposed to make up the dark matter as we earlier proposed. The expected rate of impact of this kind of dark matter ball with the earth seems to crudely match a time scale of 200 years between the impacts. The main explosion of the Tunguska event is explained in our picture as material coming out from deep within the earth, where it has been heated and compressed by the ball penetrating to a depth of several thousand km. Thus the effect has some similarity with volcanic activity as suggested by Kundt. We discuss the possible identification of kimberlite pipes with earlier Tunguska-like events. A discussion of how the dark matter balls may have formed in the early universe is also given.

  16. The Dark Molecular Gas

    CERN Document Server

    Wolfire, Mark G; McKee, Christopher F

    2010-01-01

    The mass of molecular gas in an interstellar cloud is often measured using line emission from low rotational levels of CO, which are sensitive to the CO mass, and then scaling to the assumed molecular hydrogen H_2 mass. However, a significant H_2 mass may lie outside the CO region, in the outer regions of the molecular cloud where the gas phase carbon resides in C or C+. Here, H_2 self-shields or is shielded by dust from UV photodissociation, where as CO is photodissociated. This H_2 gas is "dark" in molecular transitions because of the absence of CO and other trace molecules, and because H_2 emits so weakly at temperatures 10 K < T < 100 K typical of this molecular component. This component has been indirectly observed through other tracers of mass such as gamma rays produced in cosmic ray collisions with the gas and far-infrared/submillimeter wavelength dust continuum radiation. In this paper we theoretically model this dark mass and find that the fraction of the molecular mass in this dark component ...

  17. Asymmetric condensed dark matter

    CERN Document Server

    Aguirre, Anthony

    2015-01-01

    We explore the viability of a boson dark matter candidate with an asymmetry between the number densities of particles and antiparticles. A simple thermal field theory analysis confirms that, under certain general conditions, this component would develop a Bose-Einstein condensate in the early universe that, for appropriate model parameters, could survive the ensuing cosmological evolution until now. The condensation of a dark matter component in equilibrium with the thermal plasma is a relativistic process, hence the amount of matter dictated by the charge asymmetry is complemented by a hot relic density frozen out at the time of decoupling. Contrary to the case of ordinary WIMPs, dark matter particles in a condensate can be very light, $10^{-22}\\,{\\rm eV} \\lesssim m \\lesssim 10^2\\,{\\rm eV}$; the lower limit arises from constraints on small-scale structure formation, while the upper bound ensures that the density from thermal relics is not too large. Big-Bang nucleosynthesis constrains the temperature of deco...

  18. Lee Wick Dark Energy

    CERN Document Server

    Lee, Seokcheon

    2008-01-01

    We consider the cosmological application of Lee-Wick theory where a field has a higher derivative kinetic operators. The higher derivative term can be eliminated by introducing a set of auxiliary fields. We investigate the cosmological evolutions of these fields as a candidate of dark energy. This model has the same structure as so called ``quintom' model except the form of potentials and the sign of the slope of the potentials. This model can give the stable late time phantom dominated scaling solution ($\\omega_{\\DE} < -1$) or tracking attractors ($\\omega_{\\DE} = 0$) depending on the choice of the slopes of the potential. In order to be a viable dark energy candidate, the present energy density contrast of dark energy ($\\Omega_{\\DE}^{(0)}$) should be close to an observed value (0.73) at the same time. However, a simple toy model of the theory can not satisfy both $\\omega_{\\DE}^{(0)} \\simeq -1$ and $\\Omega_{\\DE}^{(0)} = 0.73$. This is also true for any quintom model in literatures unless we suffer from the...

  19. Overview of magnetic bearing control and linearization approaches for annular magnetically suspended devices

    Science.gov (United States)

    Groom, N. J.

    1984-01-01

    An overview of magnetic bearing control and linearization approaches which have been considered for annular magnetically suspended devices is presented. These devices include the Annular Momentum Control Device and the Annular Suspension and Pointing System. Two approaches were investigated for controlling the magnetic actuator. One approach involves controlling the upper and lower electromagnets differentially about a bias flux. The bias flux can either be supplied by permanent magnets in the magnetic circuit or by bias currents. In the other approach, either the upper electromagnet or the lower electromagnet is controlled depending on the direction of force required. One advantage of the bias flux is that for small gap perturbations about a fixed operating point, the force-current characteristic is linear. Linearization approaches investigated for individual element control include an analog solution of the nonlinear electromagnet force equation and a microprocessor-based table lookup method.

  20. Elastic Properties of the Annular Ligament of the Human Stapes--AFM Measurement.

    Science.gov (United States)

    Kwacz, Monika; Rymuza, Zygmunt; Michałowski, Marcin; Wysocki, Jarosław

    2015-08-01

    Elastic properties of the human stapes annular ligament were determined in the physiological range of the ligament deflection using atomic force microscopy and temporal bone specimens. The annular ligament stiffness was determined based on the experimental load-deflection curves. The elastic modulus (Young's modulus) for a simplified geometry was calculated using the Kirchhoff-Love theory for thin plates. The results obtained in this study showed that the annular ligament is a linear elastic material up to deflections of about 100 nm, with a stiffness of about 120 N/m and a calculated elastic modulus of about 1.1 MPa. These parameters can be used in numerical and physical models of the middle and/or inner ear.

  1. Dark Atoms and Puzzles of Dark Matter Searches

    CERN Document Server

    Khlopov, M Yu

    2014-01-01

    The nonbaryonic dark matter of the Universe is assumed to consist of new stable forms of matter. Their stability reflects symmetry of micro world and particle candidates for cosmological dark matter are the lightest particles that bear new conserved quantum numbers. Dark matter candidates can appear in the new families of quarks and leptons and the existence of new stable charged leptons and quarks is possible, if they are hidden in elusive "dark atoms". Such possibility, strongly restricted by the constraints on anomalous isotopes of light elements, is not excluded in scenarios that predict stable double charged particles. The excessive -2 charged particles are bound in these scenarios with primordial helium in O-helium "atoms", maintaining specific nuclear-interacting form of the dark matter, which may provide an interesting solution for the puzzles of the direct dark matter searches.

  2. Unified dark energy-dark matter model with inverse quintessence

    Energy Technology Data Exchange (ETDEWEB)

    Ansoldi, Stefano [ICRA — International Center for Relativistic Astrophysics, INFN — Istituto Nazionale di Fisica Nucleare, and Dipartimento di Matematica e Informatica, Università degli Studi di Udine, via delle Scienze 206, I-33100 Udine (UD) (Italy); Guendelman, Eduardo I., E-mail: ansoldi@fulbrightmail.org, E-mail: guendel@bgu.ac.il [Department of Physics, Ben-Gurion University of the Negeev, Beer-Sheva 84105 (Israel)

    2013-05-01

    We consider a model where both dark energy and dark matter originate from the coupling of a scalar field with a non-canonical kinetic term to, both, a metric measure and a non-metric measure. An interacting dark energy/dark matter scenario can be obtained by introducing an additional scalar that can produce non constant vacuum energy and associated variations in dark matter. The phenomenology is most interesting when the kinetic term of the additional scalar field is ghost-type, since in this case the dark energy vanishes in the early universe and then grows with time. This constitutes an ''inverse quintessence scenario'', where the universe starts from a zero vacuum energy density state, instead of approaching it in the future.

  3. Superheavy Dark Matter in Light of Dark Radiation

    CERN Document Server

    Park, Jong-Chul

    2014-01-01

    Superheavy dark matter can satisfy the observed dark matter abundance if the stability condition is fulfilled. Here, we propose a new Abelian gauge symmetry ${\\rm U(1)}_H$ for the stability of superheavy dark matter as the electromagnetic gauge symmetry to the electron. The new gauge boson associated with ${\\rm U(1)}_H$ contributes to the effective number of relativistic degrees of freedom in the universe as dark radiation, which has been recently measured by several experiments, e.g., PLANCK. We calculate the contribution to dark radiation from the decay of a scalar particle via the superheavy dark matter in the loop. Interestingly enough, this scenario will be probed by a future LHC run in the invisible decay signatures of the Higgs boson.

  4. Coupling q-Deformed Dark Energy to Dark Matter

    Directory of Open Access Journals (Sweden)

    Emre Dil

    2016-01-01

    Full Text Available We propose a novel coupled dark energy model which is assumed to occur as a q-deformed scalar field and investigate whether it will provide an expanding universe phase. We consider the q-deformed dark energy as coupled to dark matter inhomogeneities. We perform the phase-space analysis of the model by numerical methods and find the late-time accelerated attractor solutions. The attractor solutions imply that the coupled q-deformed dark energy model is consistent with the conventional dark energy models satisfying an acceleration phase of universe. At the end, we compare the cosmological parameters of deformed and standard dark energy models and interpret the implications.

  5. Sourcing Dark Matter and Dark Energy from $\\alpha$-attractors

    OpenAIRE

    Mishra, Swagat S.; Sahni, Varun; Shtanov, Yuri(Department of Physics, Taras Shevchenko National University, Kiev, Ukraine)

    2017-01-01

    Recently, Kallosh and Linde have drawn attention to a new family of superconformal inflationary potentials, subsequently called $\\alpha$-attractors. The $\\alpha$-attractor family can interpolate between a large class of inflationary models. It also has an important theoretical underpinning within the framework of supergravity. We demonstrate that the $\\alpha$-attractors have an even wider appeal since they may describe dark matter and perhaps even dark energy. The dark matter associated with ...

  6. Optimization of gap sizes for the high performance of annular nuclear fuels

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Young Doo; Kwon, Soon Bum; Cho, Hui Jeong; Kim, Seong Su [Kyungpook National University, Daegu (Korea, Republic of)

    2015-04-15

    Solid-type nuclear fuels have been used for nuclear reactors for a long time. Many countries are currently developing annular fuels to improve the efficiency of nuclear fuels. The thermoelastic-plastic-creep analyses of solid- and annular-type rods were conducted under the same conditions. The temperature and stress of the solid- and annular-type rods were compared on the basis of gap size. In this study, we examined the advantages and disadvantages of annular-type fuel regarding the temperature and stress of the pellet and cladding. The inner and outer gaps between the pellet and cladding play important roles in the temperature and stress distributions of fuel systems. Therefore, the optimization of gaps in fuel systems was conducted for a low temperature under certain stress conditions. hermoelasticplastic-creep analyses were conducted by using an in-house thermoelastic-plastic-creep finite element analysis program in Visual FORTRAN with the effective stress function algorithm. Nonlinear iterative stress analyses were conducted by nonlinear iterative temperature analyses; that is, a quasi-fully coupled algorithm was applied to this procedure. In this study, the thermoelastic-plastic-creep analysis of pressurized water reactor annular fuels was conducted to determine the contacting tendency of the inner-outer gaps between the annular fuel pellets and cladding, as well as to optimize the gap sizes by using the commercial package PIAnO for efficient heat transfer at certain stress levels. Most analyses were conducted until the gaps disappeared. However, certain analyses lasted for 1582 days, after which the fuels were replaced.

  7. Lorentz symmetry violation, dark matter and dark energy

    CERN Document Server

    Gonzalez-Mestres, Luis

    2009-01-01

    Taking into account the experimental results of the HiRes and AUGER collaborations, the present status of bounds on Lorentz symmetry violation (LSV) patterns is discussed. Although significant constraints will emerge, a wide range of models and values of parameters will still be left open. Cosmological implications of allowed LSV patterns are discussed focusing on the origin of our Universe, the cosmological constant, dark matter and dark energy. Superbradyons (superluminal preons) may be the actual constituents of vacuum and of standard particles, and form equally a cosmological sea leading to new forms of dark matter and dark energy.

  8. Top-Flavoured Dark Matter in Dark Minimal Flavour Violation

    OpenAIRE

    Blanke, Monika; Kast, Simon

    2017-01-01

    We study a simplified model of top-flavoured dark matter in the framework of Dark Minimal Flavour Violation. In this setup the coupling of the dark matter flavour triplet to up-type quarks constitutes the only new source of flavour and CP violation. The parameter space of the model is restricted by LHC searches with missing energy final states, by neutral $D$ meson mixing data, by the observed dark matter relic abundance, and by the absence of signal in direct detection experiments. We consid...

  9. Control of the polychromatic response of an optical system through the use of annular color filters.

    Science.gov (United States)

    Escalera, J C; Yzuel, M J; Campos, J

    1995-04-01

    The use of annular color filters as a tool to modify the polychromatic response of an optical system is investigated. The introduction of filters with transmission that depends on the wavelength produces a significant modification of the chromaticity response. In contrast, the position in the pupil of the annuli in which the color filters are placed modifies mainly the illuminance response. The influence of different types of annular color filter on the transverse and axial responses of the aberration-free system is studied.

  10. Liquid–Liquid Mixing Studies in Annular Centrifugal Contactors Comparing Stationary Mixing Vane Options

    Energy Technology Data Exchange (ETDEWEB)

    Wardle, Kent E.

    2015-11-10

    Comparative studies of multiphase operation of annular centrifugal contactors showing the impact of housing stationary mixing vane configuration. A number of experimental results for several different mixing vane options are reported with selected measurements in a lab-scale 5 cm contactor and 12.5 cm engineering-scale unit. Fewer straight vanes give greater mixingzone hold-up compared to curved vanes. Quantitative comparison of droplet size distribution also showed a significant decrease in mean diameter for four straight vanes versus eight curved vanes. This set of measurements gives a compelling case for careful consideration of mixing vane geometry when evaluating hydraulic operation and extraction process efficiency of annular centrifugal contactors.

  11. Quasi-static transient thermal stresses in a thick annular disc

    Indian Academy of Sciences (India)

    V S Kulkarni; K C Deshmukh

    2007-10-01

    The present paper deals with the determination of transient thermal stresses in a thick annular disc. A thick annular disc is considered having zero initial temperature and subjected to arbitrary heat flux on the upper and lower surfaces where as the fixed circular edges are at zero temperature.The governing heat conduction equation have been solved by using integral transform technique. The results are obtained in series form in terms of Bessel’s functions. The results for displacement and stresses have been computed numerically and are illustrated graphically

  12. DETERMINATION OF TEMPERATURE DISTRIBUTION FOR ANNULAR FINS WITH TEMPERATURE DEPENDENT THERMAL CONDUCTIVITY BY HPM

    Directory of Open Access Journals (Sweden)

    Davood Domairry Ganji

    2011-01-01

    Full Text Available In this paper, homotopy perturbation method has been used to evaluate the temperature distribution of annular fin with temperature-dependent thermal conductivity and to determine the temperature distribution within the fin. This method is useful and practical for solving the nonlinear heat transfer equation, which is associated with variable thermal conductivity condition. The homotopy perturbation method provides an approximate analytical solution in the form of an infinite power series. The annular fin heat transfer rate with temperature-dependent thermal conductivity has been obtained as a function of thermo-geometric fin parameter and the thermal conductivity parameter describing the variation of the thermal conductivity.

  13. Histological study of the annular ligament in the rabbitfish eye (Siganus sp.

    Directory of Open Access Journals (Sweden)

    Marziye Asli

    2012-12-01

    Full Text Available Rabbitfish is economically valuable teleost species which lives in shallow coastalwaters. Two species of rabbit fish have been recognized in southern sea of Iran (Persiangulf as namely Siganus sutor and Siganus javus. In the current study, in order toinvestigate the histology of the annular ligament of the S. javus’ eye, the prepared sectionsof the eyes of twelve healthy specimens were studied under light microscope. The resultsrevealed that annular ligament is a crescent shape structure which is situated between thescleral stroma anteriorly and the iris posteriorly. It contains a vascularized, amorphousand granular matrix with fibers of dense connective tissue; high glycogen content andmelanin pigments.

  14. Near-limit propagation of gaseous detonations in narrow annular channels

    Science.gov (United States)

    Gao, Y.; Ng, H. D.; Lee, J. H. S.

    2017-03-01

    New results on the near-limit behaviors of gaseous detonations in narrow annular channels are reported in this paper. Annular channels of widths 3.2 and 5.9 mm were made using circular inserts in a 50.8 mm-diameter external tube. The length of each annular channel was 1.8 m. Detonations were initiated in a steel driver tube where a small volume of a sensitive C2H2+ 2.5O2 mixture was injected to facilitate detonation initiation. A 2 m length of circular tube with a 50.8 mm diameter preceded the annular channel so that a steady Chapman-Jouguet (CJ) detonation was established prior to entering the annular channel. Four detonable mixtures of C2H2 {+} 2.5O2 {+} 85 % Ar, C2H2 {+} 2.5O2 {+} 70 % Ar, C3H8 {+} 5O2, and CH4 {+} 2O2 were used in the present study. Photodiodes spaced 10 cm throughout the length of both the annular channel and circular tube were used to measure the detonation velocity. In addition, smoked foils were inserted into the annular channel to monitor the cellular structure of the detonation wave. The results show that, well within the detonability limits, the detonation wave propagates along the channel with a small local velocity fluctuation and an average global velocity can be deduced. The average detonation velocity has a small deficit of 5-15 % far from the limits and the velocity rapidly decreases to 0.7V_{CJ}-0.8V_{CJ} when the detonation propagates near the limit. Subsequently, the fluctuation of local velocity also increases as the decreasing initial pressure approaches the limit. In the two annular channels used in this work, no galloping detonations were observed for both the stable and unstable mixtures tested. The present study also confirms that single-headed spinning detonation occurs at the limit, as in a circular tube, rather than the up and down "zig zag" mode in a two-dimensional, rectangular channel.

  15. Radially polarized annular beam generated through a second-harmonic-generation process.

    Science.gov (United States)

    Sato, Shunichi; Kozawa, Yuichi

    2009-10-15

    A radially polarized beam with an annular intensity pattern was generated through a second-harmonic-generation process by focusing an azimuthally polarized Ti:sapphire pulsed laser beam to a c-cut beta-barium borate (BBO) crystal. The annular intensity pattern of the second-harmonic wave had a nearly sixfold symmetry as a result of the nonlinear susceptibility tensor of the BBO crystal. The width of the annulus was as narrow as less than 1/40th of its radius.

  16. Frequency Equations for the In-Plane Vibration of Circular Annular Disks

    OpenAIRE

    S. Bashmal; Bhat, R; S. Rakheja

    2010-01-01

    This paper deals with the in-plane vibration of circular annular disks under combinations of different boundary conditions at the inner and outer edges. The in-plane free vibration of an elastic and isotropic disk is studied on the basis of the two-dimensional linear plane stress theory of elasticity. The exact solution of the in-plane equation of equilibrium of annular disk is attainable, in terms of Bessel functions, for uniform boundary conditions. The frequency equations for different mod...

  17. Elliptic annular Josephson tunnel junctions in an external magnetic field: the statics

    DEFF Research Database (Denmark)

    Monaco, Roberto; Granata, Carmine; Vettoliere, Antonio

    2015-01-01

    symmetric electrodes a transverse magnetic field is equivalent to an in-plane field applied in the direction of the current flow. Varying the ellipse eccentricity we reproduce all known results for linear and ring-shaped JTJs. Experimental data on high-quality Nb/Al-AlOx/Nb elliptic annular junctions...... or in the perpendicular direction. We report a detailed study of both short and long elliptic annular junctions having different eccentricities. For junctions having a normalized perimeter less than one the threshold curves are derived and computed even in the case with one trapped Josephson vortex. For longer junctions...

  18. Heat transfer of bubbly flow on inner wall of annular channel

    Directory of Open Access Journals (Sweden)

    Lobanov Pavel

    2017-01-01

    Full Text Available Experimental investigations of heat transfer from the heated wall to the two-phase bubbly flow were performed in vertical annular channel using air-water system. The IR-thermography and miniature temperature sensors were used to measure heat transfer coefficients. The influence of bubbles on heat transfer is shown in comparison with the case of single phase flow. The presence of bubbles in the flow leads to heat transfer intensification in the annular channel even for low void fractions.

  19. Dynamics of annular bright field imaging in scanning transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Findlay, S.D., E-mail: scott@sigma.t.u-tokyo.ac.jp [Institute of Engineering Innovation, The University of Tokyo, Tokyo 116-0013 (Japan); Shibata, N. [Institute of Engineering Innovation, The University of Tokyo, Tokyo 116-0013 (Japan); PRESTO, Japan Science and Technology Agency, Saitama 332-0012 (Japan); Sawada, H.; Okunishi, E.; Kondo, Y. [JEOL Ltd., Tokyo 196-8558 (Japan); Ikuhara, Y. [Institute of Engineering Innovation, The University of Tokyo, Tokyo 116-0013 (Japan); Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587 (Japan); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2010-06-15

    We explore the dynamics of image formation in the so-called annular bright field mode in scanning transmission electron microscopy, whereby an annular detector is used with detector collection range lying within the cone of illumination, i.e. the bright field region. We show that this imaging mode allows us to reliably image both light and heavy columns over a range of thickness and defocus values, and we explain the contrast mechanisms involved. The role of probe and detector aperture sizes is considered, as is the sensitivity of the method to intercolumn spacing and local disorder.

  20. Experimental Study on Convective Boiling Heat Transfer in Vertical Narrow Gap Annular Tube

    Institute of Scientific and Technical Information of China (English)

    Li Bin; He Anding; Wang Yueshe; Zhou Fangde

    2001-01-01

    Experiments are conducted to investigate the characteristics of single-phase forced-flow convection and boiling heat transfer of R113 flowing through annular tube with gap of 1, 1.5 and 2.5 mm, and also the visualization test are carried out to get two-phase flow regime. The data show that the Nusselt numbers for the narrow-gap are higher than those predicted by traditional large channel correlation and boiling heat transfer is enhanced. Based on the data obtained in this investigation, correlations for single-phase, forced convection and flow boiling in annular tube of different gap size has been developed.

  1. Histological study of the annular ligament in the rabbitfish eye (Siganus sp.).

    Science.gov (United States)

    Asli, Marziye; Mansoori, Forooghsadat; Sattari, Amir

    2012-01-01

    Rabbitfish is economically valuable teleost species which lives in shallow coastal waters. Two species of rabbit fish have been recognized in southern sea of Iran (Persian gulf) as namely Siganus sutor and Siganus javus. In the current study, in order to investigate the histology of the annular ligament of the S. javus' eye, the prepared sections of the eyes of twelve healthy specimens were studied under light microscope. The results revealed that annular ligament is a crescent shape structure which is situated between the scleral stroma anteriorly and the iris posteriorly. It contains a vascularized, amorphous and granular matrix with fibers of dense connective tissue; high glycogen content and melanin pigments.

  2. Generation of annular, high-charge electron beams at the Argonne wakefield accelerator

    Science.gov (United States)

    Wisniewski, E. E.; Li, C.; Gai, W.; Power, J.

    2013-01-01

    We present and discuss the results from the experimental generation of high-charge annular(ring-shaped)electron beams at the Argonne Wakefield Accelerator (AWA). These beams were produced by using laser masks to project annular laser profiles of various inner and outer diameters onto the photocathode of an RF gun. The ring beam is accelerated to 15 MeV, then it is imaged by means of solenoid lenses. Transverse profiles are compared for different solenoid settings. Discussion includes a comparison with Parmela simulations, some applications of high-charge ring beams,and an outline of a planned extension of this study.

  3. Cross-field transport of electrons at the magnetic throat in an annular plasma reactor

    Science.gov (United States)

    Zhang, Yunchao; Charles, Christine; Boswell, Rod

    2017-01-01

    Cross-field transport of electrons has been studied at the magnetic throat of the annular Chi-Kung reactor. This annular configuration allows the creation of a low pressure argon plasma with two distinct electron heating locations by independently operating a radio-frequency antenna surrounding the outer source tube, or an antenna housed inside the inner source tube. The two antenna cases show opposite variation trends in radial profiles of electron energy probability function, electron density, plasma potential and electron temperature. The momentum and energy transport coefficients are obtained from the electron energy probability functions, and the related electron fluxes follow the path of electron cooling across the magnetic throat.

  4. High quantum efficiency annular backside silicon photodiodes for reflectance pulse oximetry in wearable wireless body sensors

    DEFF Research Database (Denmark)

    Duun, Sune Bro; Haahr, Rasmus Grønbek; Hansen, Ole;

    2010-01-01

    The development of annular photodiodes for use in a reflectance pulse oximetry sensor is presented. Wearable and wireless body sensor systems for long-term monitoring require sensors that minimize power consumption. We have fabricated large area 2D ring-shaped silicon photodiodes optimized....../2) cm(-1) are achieved. The photodiodes are incorporated into a wireless pulse oximetry sensor system embedded in an adhesive patch presented elsewhere as 'The Electronic Patch'. The annular photodiodes are fabricated using two masked diffusions of first boron and subsequently phosphor. The surface...

  5. On the levitation force in horizontal core-annular flow with a large viscosity ratio and small density ratio

    NARCIS (Netherlands)

    Ooms, G.; Pourquie, M.J.B.M.; Beerens, J.C.

    2013-01-01

    A numerical study has been made of horizontal core-annular flow: the flow of a high-viscosity liquid core surrounded by a low-viscosity liquid annular layer through a horizontal pipe. Special attention is paid to the question how the buoyancy force on the core, caused by a density difference between

  6. Dark-Field Scanning Transmission Ion Microscopy via Detection of Forward-Scattered Helium Ions with a Microchannel Plate.

    Science.gov (United States)

    Woehl, Taylor J; White, Ryan M; Keller, Robert R

    2016-06-01

    A microchannel plate was used as an ion sensitive detector in a commercial helium ion microscope (HIM) for dark-field transmission imaging of nanomaterials, i.e. scanning transmission ion microscopy (STIM). In contrast to previous transmission HIM approaches that used secondary electron conversion holders, our new approach detects forward-scattered helium ions on a dedicated annular shaped ion sensitive detector. Minimum collection angles between 125 mrad and 325 mrad were obtained by varying the distance of the sample from the microchannel plate detector during imaging. Monte Carlo simulations were used to predict detector angular ranges at which dark-field images with atomic number contrast could be obtained. We demonstrate atomic number contrast imaging via scanning transmission ion imaging of silica-coated gold nanoparticles and magnetite nanoparticles. Although the resolution of STIM is known to be degraded by beam broadening in the substrate, we imaged magnetite nanoparticles with high contrast on a relatively thick silicon nitride substrate. We expect this new approach to annular dark-field STIM will open avenues for more quantitative ion imaging techniques and advance fundamental understanding of underlying ion scattering mechanisms leading to image formation.

  7. Make Dark Matter Charged Again

    CERN Document Server

    Agrawal, Prateek; Randall, Lisa; Scholtz, Jakub

    2016-01-01

    We revisit constraints on dark matter that is charged under a $U(1)$ gauge group in the dark sector, decoupled from Standard Model forces. We find that the strongest constraints in the literature are subject to a number of mitigating factors. For instance, the naive dark matter thermalization timescale in halos is corrected by saturation effects that slow down isotropization for modest ellipticities. The weakened bounds uncover interesting parameter space, making models with weak-scale charged dark matter viable, even with electromagnetic strength interaction. This also leads to the intriguing possibility that dark matter self-interactions within small dwarf galaxies are extremely large, a relatively unexplored regime in current simulations. Such strong interactions suppress heat transfer over scales larger than the dark matter mean free path, inducing a dynamical cutoff length scale above which the system appears to have only feeble interactions. These effects must be taken into account to assess the viabili...

  8. Enter the DarkSide

    Science.gov (United States)

    Davini, Stefano

    2014-04-01

    A wide range of astrophysical measurements evidence that the stars and gas in all galaxies are immersed in a much larger cloud of non-luminous and non-baryonic dark matter. The nature of the dark matter is still totally unknown, and the resolution of the dark matter puzzle is of fundamental importance to cosmology, astrophysics, and elementary particle physics. One of the major lines of researches directing their efforts at detection of dark matter is direct searches of Weakly Interacting Massive Particles (WIMPs) with detectors operated in deep underground laboratories. The new generation of direct searches of WIMPs promises to probe the most interesting region of parameters for the dark matter candidates. I will review and describe the DarkSide-50 underground Argon detector at Laboratori Nazionali del Gran Sasso.

  9. A Stab in the Dark?

    Science.gov (United States)

    Tompson, Lisa

    2013-01-01

    Objectives: Test the influence of darkness in the street robbery crime event alongside temperature. Methods: Negative binomial regression models tested darkness and temperature as predictors of street robbery. Units of analysis were four 6-hr time intervals in two U.K. study areas that have different levels of darkness and variations of temperature throughout the year. Results: Darkness is a key factor related to robbery events in both study areas. Traversing from full daylight to full darkness increased the predicted volume of robbery by a multiple of 2.6 in London and 1.2 in Glasgow. Temperature was significant only in the London study area. Interaction terms did not enhance the predictive power of the models. Conclusion: Darkness is an important driving factor in seasonal variation of street robbery. A further implication of the research is that time of the day patterns are crucial to understanding seasonal trends in crime data. PMID:25076797

  10. Perturbations of Dark Matter Gravity

    CERN Document Server

    Maia, M D; Müller, D; 10.1142/S0218271809015072

    2009-01-01

    Until recently the study of the gravitational field of dark matter was primarily concerned with its local effects on the motion of stars in galaxies and galaxy clusters. On the other hand, the WMAP experiment has shown that the gravitational field produced by dark matter amplifies the higher acoustic modes of the CMBR power spectrum, more intensely than the gravitational field of baryons. Such a wide range of experimental evidences from cosmology to local gravity suggests the necessity of a comprehensive analysis of the dark matter gravitational field per se, regardless of any other attributes that dark matter may eventually possess. In this paper we introduce and apply Nash's theory of perturbative geometry to the study of the dark matter gravitational field alone, in a higher-dimensional framework. It is shown that the dark matter gravitational perturbations in the early universe can be explained by the extrinsic curvature of the standard cosmology. Together with the estimated presence of massive neutrinos,...

  11. On Oscillating Dark Energy

    CERN Document Server

    Linder, E V

    2006-01-01

    Distance-redshift data can impose strong constraints on dark energy models even when the equation of state is oscillatory. Despite the double integral dependence of the distance on the equation of state, precision measurement of the distance-redshift relation for z=0-2 is more incisive than the linear growth factor, CMB last scattering surface distance, and the age of the universe in distinguishing oscillatory behavior from an average behavior. While oscillating models might help solve the coincidence problem (since acceleration occurs periodically), next generation observations will strongly constrain such possibilities.

  12. Dark Matter Velocity Spectroscopy.

    Science.gov (United States)

    Speckhard, Eric G; Ng, Kenny C Y; Beacom, John F; Laha, Ranjan

    2016-01-22

    Dark matter decays or annihilations that produce linelike spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that velocity spectroscopy-the measurement of energy shifts induced by relative motion of source and observer-can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming experiments will have the precision needed. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications.

  13. Dark Matter Velocity Spectroscopy

    CERN Document Server

    Speckhard, Eric G; Beacom, John F; Laha, Ranjan

    2016-01-01

    Dark matter decays or annihilations that produce line-like spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that velocity spectroscopy-the measurement of energy shifts induced by relative motion of source and observer-can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming and proposed experiments will make significant improvements. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications.

  14. Dark Energy Stars

    Energy Technology Data Exchange (ETDEWEB)

    Chapline, G

    2005-03-08

    Event horizons and closed time-like curves cannot exist in the real world for the simple reason that they are inconsistent with quantum mechanics. Following ideas originated by Robert Laughlin, Pawel Mazur, Emil Mottola, David Santiago, and the speaker it is now possible to describe in some detail what happens physically when one approaches and crosses a region of space-time where classical general relativity predicts there should be an infinite red shift surface. This quantum critical physics provides a new perspective on a variety of enigmatic astrophysical phenomena including supernovae explosions, gamma ray bursts, positron emission, and dark matter.

  15. Dark Sunshine: Detecting Dark Matter through Dark Photons from the Sun

    CERN Document Server

    Feng, Jonathan L; Tanedo, Philip

    2016-01-01

    Dark matter may interact with the Standard Model through the kinetic mixing of dark photons, $A'$, with Standard Model photons. Such dark matter will accumulate in the Sun and annihilate into dark photons. The dark photons may then leave the Sun and decay into pairs of charged Standard Model particles that can be detected by the Alpha Magnetic Spectrometer. The directionality of this "dark sunshine" is distinct from all astrophysical backgrounds, providing an opportunity for unambiguous dark matter discovery by AMS. We perform a complete analysis of this scenario including Sommerfeld enhancements of dark matter annihilation and the effect of the Sun's magnetic field on the signal, and we define a set of cuts to optimize the signal probability. With the three years of data already collected, AMS may discover dark matter with mass 1 TeV $\\lesssim m_X \\lesssim$ 10 TeV, dark photon masses $m_{A'} \\sim \\mathcal O(100)$ MeV, and kinetic mixing parameters $10^{-11} \\lesssim \\varepsilon \\lesssim 10^{-8}$. The propose...

  16. LINEARIZATION OF ANNULAR IMAGE OF PANORAMIC ANNULAR LENS%全景环形透镜环形象的线性化研究

    Institute of Scientific and Technical Information of China (English)

    朱方明; 杨国光; 姚炜勇; 程惠全

    2001-01-01

    全景环形透镜(PAL)独特的成象性能,即环绕光轴360°产生一个环形象且景深为无穷远,使得由PAL组成的观测系统没有活动部件能同时观察透镜周围的景物.但PAL所成的环形象不便于人眼观察和测量,有畸变、失真,为此,本文根据图象坐标变换,实现了一种环形象的线性恢复,即首先将环形象线性化处理,再对其进行插值,实验结果表明线性化效果较好.该图象处理技术可以为发挥PAL的许多潜在应用创造条件.%For the special imaging feature of Panoramic Annular Lens,that forming an annular image circling the axis and having endless depth of field,the observing system made up of PAL can be used to observe object around the lens without moving part.But the annular image formed by PAL is not only unconvenient for observation and measurement,but also has distortion phenominon.According to coordinate convertion of image,a method of linearizing annular image is presented.The results show that the effect of linearization is good.With this method,it can be found basis for potential application of PAL.

  17. Dark matter searches with CMS

    CERN Document Server

    Jeitler, Manfred

    2016-01-01

    The existence of dark matter, indicated by astronomical observations, is one of the main proofs of physics beyond the standard model. Despite its abundance, dark matter has not been directly observed yet. This talk presents several searches for dark matter production in proton-proton collisions at 7, 8, and 13 TeV at the LHC, performed by the CMS collaboration. They are interpreted in terms of simplified models with different structures and mediators, as well as generic effective theory terms.

  18. Reference values of tricuspid annular peak systolic velocity in healthy pediatric patients, calculation of z score, and comparison to tricuspid annular plane systolic excursion.

    Science.gov (United States)

    Koestenberger, Martin; Nagel, Bert; Ravekes, William; Avian, Alexander; Heinzl, Bernd; Cvirn, Gerhard; Fritsch, Peter; Fandl, Andrea; Rehak, Thomas; Gamillscheg, Andreas

    2012-01-01

    The tricuspid annular peak systolic velocity (TAPSV) is an echocardiographic measurement assessing right ventricular systolic function in children and adults. We determined the growth-related changes of the TAPSV to establish the references values for the entire pediatric age group. A prospective study was conducted of a group of 860 healthy pediatric patients (age 1 day to 18 years; body surface area [BSA] 0.14 to 2.30 m(2)). We determined the effects of age, gender, and BSA on the TAPSV values. Stepwise linear multiple regression analysis was used to estimate the TAPSV from the age, BSA, and gender. A correlation of normal TAPSV with normal tricuspid annular plane systolic excursion values was performed. The TAPSV ranged from a mean of 7.2 cm/s (z score ± 2: 4.8 to 9.5 cm/s) in the newborn to 14.3 cm/s (z score ± 2: 10.6 to 18.6 cm/s) in the 18-year-old adolescent. The TAPSV values showed a positive correlation with age and BSA, with a nonlinear course. No significant difference was found in the TAPSV values according to gender. A significant correlation was found between the TAPSV and tricuspid annular plane systolic excursion values in our pediatric population. In conclusion, the z scores of the TAPSV values were calculated, and percentile charts were established to serve as reference data for patients with congenital heart disease.

  19. Analysis of the longitudinal handling qualities and pilot-induced-oscillation tendencies of the High-Angle-of-Attack Research Vehicle (HARV)

    Science.gov (United States)

    Hess, Ronald A.

    1994-01-01

    The NASA High-Angle-of Attack Research Vehicle (HARV), a modified F-18 aircraft, experienced handling qualities problems in recent flight tests at NASA Dryden Research Center. Foremost in these problems was the tendency of the pilot-aircraft system to exhibit a potentially dangerous phenomenon known as a pilot-induced oscillation (PIO). When they occur, PIO's can severely restrict performance, sharply dimish mission capabilities, and can even result in aircraft loss. A pilot/vehicle analysis was undertaken with the goal of reducing these PIO tendencies and improving the overall vehicle handling qualities with as few changes as possible to the existing feedback/feedforward flight control laws. Utilizing a pair of analytical pilot models developed by the author, a pilot/vehicle analysis of the existing longitudinal flight control system was undertaken. The analysis included prediction of overall handling qualities levels and PIO susceptability. The analysis indicated that improvement in the flight control system was warranted and led to the formulation of a simple control stick command shaping filter. Analysis of the pilot/vehicle system with the shaping filter indicated significant improvements in handling qualities and PIO tendencies could be achieved. A non-real time simulation of the modified control system was undertaken with a realistic, nonlinear model of the current HARV. Special emphasis was placed upon those details of the command filter implementation which could effect safety of flight. The modified system is currently awaiting evaluation in the real-time, pilot-in-the-loop, Dual-Maneuvering-Simulator (DMS) facility at Langley.

  20. Invisible QCD as Dark Energy

    CERN Document Server

    Alexander, Stephon; Yang, Zhi

    2016-01-01

    We account for the late time acceleration of the Universe by extending the QCD color to a $SU(3)$ invisible sector (IQCD). If the Invisible Chiral symmetry is broken in the early universe, a condensate of dark pions (dpions) and dark gluons (dgluons) forms. The condensate naturally forms due to strong dynamics similar to the Nambu--Jona-Lasinio mechanism. As the Universe evolves from early times to present times the interaction energy between the dgluon and dpion condensate dominates with a negative pressure equation of state and causes late time acceleration. We conclude with a stability analysis of the coupled perturbations of the dark pions and dark gluons.

  1. Dark matter. A light move

    Energy Technology Data Exchange (ETDEWEB)

    Redondo, Javier [Muenchen Univ. (Germany). Arnold Sommerfeld Center; Max-Planck-Institut fuer Physik, Muenchen (Germany); Doebrich, Babette [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2013-11-15

    This proceedings contribution reports from the workshop Dark Matter - a light move, held at DESY in Hamburg in June 2013. Dark Matter particle candidates span a huge parameter range. In particular, well motivated candidates exist also in the sub-eV mass region, for example the axion. Whilst a plethora of searches for rather heavy Dark Matter particles exists, there are only very few experiments aimed at direct detection of sub-eV Dark Matter to this date. The aim of our workshop was to discuss if and how this could be changed in the near future.

  2. The DarkSide project

    Energy Technology Data Exchange (ETDEWEB)

    Agnes, P.; Agostino, L.; Albuquerque, Ivone Freire Da Mota; Alexander, Thomas R.; Alton, A.; Arisaka, K.; Back, Henning O.; Baldin, B.; Biery, K.; Bonfini, G.; Bossa, M.; Bottino, Bianca; Brigatti, A.; Brodsky, J.; Budano, F.; Bussino, Severino; Cadeddu, Matteo; Cadonati, L.; Cadoni, M.; Calaprice, F.; Canci, N.; Candela, A.; Cao, H.; Cariello, M.; Carlini, Macro; Catalanotti, Sergio; Cavalcante, P.; Chepurnov, A.; Cocco, A. G.; Covone, G.; Crippa, L.; D' Angelo, D.; D' Incecco, M.; Davini, S.; De Cecco, Sandro; De Deo, M.; De Vincenzi, Mario; Derbin, A.; Devoto, A.; Di Eusanio, F.; Di Pietro, Giuseppe; Edkins, E.; Empl, Anton; Fan, A.; Fiorillo, G.; Fomenko, K.; Forster, G.; Franco, D.; Gabriele, F.; Galbiati, C.; Giganti, C.; Goretti, A.; Granato, Francesco; Grandi, L.; Gromov, M.; Guan, M. Y.; Guardincerri, Y.; Hackett, B.; Herner, K.; Hungerford, Edward; Ianni, Al.; Ianni, An.; James, I.; Jollet, C.; Keeter, K.; Kendziora, C.; Kobychev, V.; Koh, G.; Korablev, D.; Korga, G.; Kubankin, Alexander; Li, X.; Lissia, M.; Lombardi, P.; Luitz, S.; Ma, Y. Q.; Machulin, I.; Mandarano, A.; Mari, S. M.; Maricic, J.; Marini, L.; Martoff, J.; Meregaglia, A.; Meyers, P. D.; Miletic, T.; Milincic, R.; Montanari, D.; Monte, Alissa; Montuschi, M.; Monzani, M. E.; Mosteiro, P.; Mount, B.; Muratova, V.; Musico, P.; Napolitano, James; Nelson, A.; Odrowski, S.; Orsini, M.; Ortica, F.; Pagani, L.; Pallavicini, Marco; Pantic, E.; Parmeggiano, S.; Pelczar, K.; Pelliccia, N.; Perasso, S.; Pocar, A.; Pordes, S.; Pugachev, D.; Qian, H.; Randle, K.; Ranucci, Gioacchino; Razeto, A.; Reinhold, B.; Renshaw, Andrew; Romani, A.; Rossi, B.; Rossi, N.; Rountree, S. D.; Sablone, D.; Saggese, P.; Saldanha, R.; Sands, W.; Sangiorgio, Samuele; Savarese, Claudio; Segreto, E.; Semenov, D.; Shields, E.; Singh, Parth; Skorokhvatov, Mikhail; Smirnov, Oleg; Sotnikov, Albert; Stanford, Chris; Suvorov, Yura; Tartaglia, Roberto; Tatarowicz, John; Testera, Gemma; Tonazzo, Alessandra; Trinchese, P.; Unzhakov, Eugenii; Vishneva, Alina; Vogelaar, R. B.; Wada, Masayuki; Walker, Susan E.; Wang, H.; Wang, Y.; Watson, A. W.; Westerdale, S.; Wilhelmi, James; Wojcik, M.; Xiang, Xin; Xu, Jingke; Yang, C. G.; Yoo, J.; Zavatarelli, Sandra; Zec, Adam; Zhong, W. L.; Zhu, Chengliang; Zuzel, G.

    2016-02-01

    DarkSide is a graded experimental project based on radiopure argon, and is now, and will be, used in direct dark matter searches. The present DarkSide-50 detector, operating at the Gran Sasso National Laboratory, is a dual-phase, 50 kg, liquid argon time-projection-chamber surrounded by an active liquid scintillator veto. It is designed to be background free in 3 years of operation. DS-50 performances, when filled with atmospheric argon, are reported. However DS-50 filled with underground argon, shows impressive reduction of the 39Ar isotope. The application of this powerful technology in a future generation of the DarkSide program is discussed.

  3. Abnormally dark or light skin

    Science.gov (United States)

    Hyperpigmentation; Hypopigmentation; Skin - abnormally light or dark ... Normal skin contains cells called melanocytes. These cells produce melanin , the substance that gives skin its color. Skin with ...

  4. Monodromy Dark Matter

    Science.gov (United States)

    Jaeckel, Joerg; Mehta, Viraf M.; Witkowski, Lukas T.

    2017-01-01

    Light pseudo-Nambu-Goldstone bosons (pNGBs) such as, e.g. axion-like particles, that are non-thermally produced via the misalignment mechanism are promising dark matter candidates. An important feature of pNGBs is their periodic potential, whose scale of periodicity controls their couplings. As a consequence of the periodicity the maximal potential energy is limited and, hence, producing the observed dark matter density poses significant constraints on the allowed masses and couplings. In the presence of a monodromy, the field range as well as the range of the potential can be significantly extended. As we argue in this paper this has important phenomenological consequences. The constraints on the masses and couplings are ameliorated and couplings to Standard Model particles could be significantly stronger, thereby opening up considerable experimental opportunities. Yet, monodromy models can also give rise to new and qualitatively different features. As a remnant of the periodicity the potential can feature pronounced ``wiggles''. When the field is passing through them quantum fluctuations are enhanced and particles with non-vanishing momentum are produced. Here, we perform a first analysis of this effect and delineate under which circumstances this becomes important. We briefly discuss some possible cosmological consequences.

  5. Dark Matter remains obscure

    CERN Multimedia

    Fabio Capello

    2011-01-01

    It is one of the hidden secrets that literally surround the Universe. Experiments have shown no result so far because trying to capture particles that do not seem to interact with ordinary matter is no trivial exercise. The OSQAR experiment at CERN is dedicated to the search for axions, one of the candidates for Dark Matter. For its difficult challenge, OSQAR counts on one of the world’s most powerful magnets borrowed from the LHC. In a recent publication, the OSQAR collaboration was able to confirm that no axion signal appears out of the background. In other words: the quest is still on.   The OSQAR experiment installed in the SM18 hall. (Photo by F. Capello) The OSQAR “Light Shining Through a Wall” experiment was officially launched in 2007 with the aim of detecting axions, that is, particles that might be the main components of Dark Matter. OSQAR uses the powerful LHC dipole magnet to intensify the predicted photon-axion conversions in the presence of strong m...

  6. Dark Gamma Ray Bursts

    CERN Document Server

    Brdar, Vedran; Liu, Jia

    2016-01-01

    Many theories of dark matter (DM) predict that DM particles can be captured by stars via scattering on ordinary matter. They subsequently condense into a DM core close to the center of the star and eventually annihilate. In this work, we trace DM capture and annihilation rates throughout the life of a massive star and show that this evolution culminates in an intense annihilation burst coincident with the death of the star in a core collapse supernova. The reason is that, along with the stellar interior, also its DM core heats up and contracts, so that the DM density increases rapidly during the final stages of stellar evolution. We argue that, counterintuitively, the annihilation burst is more intense if DM annihilation is a p-wave process than for s-wave annihilation because in the former case, more DM particles survive until the supernova. If among the DM annihilation products are particles like dark photons that can escape the exploding star and decay to Standard Model particles later, the annihilation bu...

  7. (Mainly) axion dark matter

    Science.gov (United States)

    Baer, Howard

    2016-06-01

    The strong CP problem of QCD is at heart a problem of naturalness: why is the FF ˜ term highly suppressed in the QCD Lagrangian when it seems necessary to explain why there are three and not four light pions? The most elegant solution posits a spontaneously broken Peccei-Quinn (PQ) symmetry which requires the existence of the axion field a. The axion field settles to the minimum of its potential thus removing the offensive term but giving rise to the physical axion whose coherent oscillations can make up the cold dark matter. Only now are experiments such as ADMX beginning to explore QCD axion parameter space. Since a bonafide scalar particle- the Higgs boson- has been discovered, one might expect its mass to reside at the axion scale fa ˜ 1011 GeV. The Higgs mass is elegantly stabilized by supersymmetry: in this case the axion is accompanied by its axino and saxion superpartners. Requiring naturalness also in the electroweak sector implies higgsino-like WIMPs so then we expect mixed axion-WIMP dark matter. Ultimately we would expect detection of both an axion and a WIMP while signals for light higgsinos may show up at LHC and must show up at ILC.

  8. The Dark Energy Camera

    CERN Document Server

    Flaugher, B; Honscheid, K; Abbott, T M C; Alvarez, O; Angstadt, R; Annis, J T; Antonik, M; Ballester, O; Beaufore, L; Bernstein, G M; Bernstein, R A; Bigelow, B; Bonati, M; Boprie, D; Brooks, D; Buckley-Geer, E J; Campa, J; Cardiel-Sas, L; Castander, F J; Castilla, J; Cease, H; Cela-Ruiz, J M; Chappa, S; Chi, E; Cooper, C; da Costa, L N; Dede, E; Derylo, G; DePoy, D L; de Vicente, J; Doel, P; Drlica-Wagner, A; Eiting, J; Elliott, A E; Emes, J; Estrada, J; Neto, A Fausti; Finley, D A; Flores, R; Frieman, J; Gerdes, D; Gladders, M D; Gregory, B; Gutierrez, G R; Hao, J; Holland, S E; Holm, S; Huffman, D; Jackson, C; James, D J; Jonas, M; Karcher, A; Karliner, I; Kent, S; Kessler, R; Kozlovsky, M; Kron, R G; Kubik, D; Kuehn, K; Kuhlmann, S; Kuk, K; Lahav, O; Lathrop, A; Lee, J; Levi, M E; Lewis, P; Li, T S; Mandrichenko, I; Marshall, J L; Martinez, G; Merritt, K W; Miquel, R; Munoz, F; Neilsen, E H; Nichol, R C; Nord, B; Ogando, R; Olsen, J; Palio, N; Patton, K; Peoples, J; Plazas, A A; Rauch, J; Reil, K; Rheault, J -P; Roe, N A; Rogers, H; Roodman, A; Sanchez, E; Scarpine, V; Schindler, R H; Schmidt, R; Schmitt, R; Schubnell, M; Schultz, K; Schurter, P; Scott, L; Serrano, S; Shaw, T M; Smith, R C; Soares-Santos, M; Stefanik, A; Stuermer, W; Suchyta, E; Sypniewski, A; Tarle, G; Thaler, J; Tighe, R; Tran, C; Tucker, D; Walker, A R; Wang, G; Watson, M; Weaverdyck, C; Wester, W; Woods, R; Yanny, B

    2015-01-01

    The Dark Energy Camera is a new imager with a 2.2-degree diameter field of view mounted at the prime focus of the Victor M. Blanco 4-meter telescope on Cerro Tololo near La Serena, Chile. The camera was designed and constructed by the Dark Energy Survey Collaboration, and meets or exceeds the stringent requirements designed for the wide-field and supernova surveys for which the collaboration uses it. The camera consists of a five element optical corrector, seven filters, a shutter with a 60 cm aperture, and a CCD focal plane of 250 micron thick fully-depleted CCDs cooled inside a vacuum Dewar. The 570 Mpixel focal plane comprises 62 2kx4k CCDs for imaging and 12 2kx2k CCDs for guiding and focus. The CCDs have 15 microns x15 microns pixels with a plate scale of 0.263 arc sec per pixel. A hexapod system provides state-of-the-art focus and alignment capability. The camera is read out in 20 seconds with 6-9 electrons readout noise. This paper provides a technical description of the camera's engineering, construct...

  9. Planets and Dark Energy

    CERN Document Server

    Gibson, Carl H

    2008-01-01

    Self gravitational fluid mechanical methods termed hydro-gravitational-dynamics (HGD) predict plasma fragmentation 0.03 Myr after the turbulent big bang to form protosuperclustervoids, turbulent protosuperclusters, and protogalaxies at the 0.3 Myr transition from plasma to gas. Linear protogalaxyclusters fragment at 0.003 Mpc viscous-inertial scales along turbulent vortex lines or in spirals, as observed. The plasma protogalaxies fragment on transition into white-hot planet-mass gas clouds (PFPs) in million-solar-mass clumps (PGCs) that become globular-star-clusters (GCs) from tidal forces or dark matter (PGCs) by freezing and diffusion into 0.3 Mpc halos with 97% of the galaxy mass. The weakly collisional non-baryonic dark matter diffuses to > Mpc scales and fragments to form galaxy cluster halos. Stars and larger planets form by binary mergers of the trillion PFPs per PGC, mostly on 0.03 Mpc galaxy accretion disks. Stars deaths depend on rates of planet accretion and internal star mixing. Moderate accretion...

  10. The Dark Energy Camera

    Energy Technology Data Exchange (ETDEWEB)

    Flaugher, B. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States). et al.

    2015-04-11

    The Dark Energy Camera is a new imager with a 2.2-degree diameter field of view mounted at the prime focus of the Victor M. Blanco 4-meter telescope on Cerro Tololo near La Serena, Chile. The camera was designed and constructed by the Dark Energy Survey Collaboration, and meets or exceeds the stringent requirements designed for the wide-field and supernova surveys for which the collaboration uses it. The camera consists of a five element optical corrector, seven filters, a shutter with a 60 cm aperture, and a CCD focal plane of 250-μm thick fully depleted CCDs cooled inside a vacuum Dewar. The 570 Mpixel focal plane comprises 62 2k x 4k CCDs for imaging and 12 2k x 2k CCDs for guiding and focus. The CCDs have 15μm x 15μm pixels with a plate scale of 0.263" per pixel. A hexapod system provides state-of-the-art focus and alignment capability. The camera is read out in 20 seconds with 6-9 electrons readout noise. This paper provides a technical description of the camera's engineering, construction, installation, and current status.

  11. The Dark Knight Falters

    CERN Document Server

    Mirabal, N

    2012-01-01

    Potential line emission at 111 and 129 GeV from 16 unassociated Fermi-LAT point sources has been reported recently by Su & Finkbeiner (2012c). Together with similar features seen by Fermi in a region near the Galactic Centre, the evidence has been interpreted as the spectral signature of dark matter annihilation or internal bremsstrahlung. Through a combination of supervised machine-learning algorithms and archival multiwavelength observations we find that 14 out of the 16 unassociated sources showing the line emission in the Su & Finkbeiner sample are most likely active galactic nuclei (AGN). Based on this new evidence, one must widen the range of possible solutions for the 100-140 GeV excess to include a very distinct astrophysical explanation. While we cannot rule out a dark matter origin for the line emission in the Galactic Centre, we posit that if the detection in the Su & Finkbeiner sample is indeed real it might be related to accretion, bubble, or jet activity in nearby (z < 0.2) AGN. A...

  12. Properties of multi-partite dark states

    OpenAIRE

    Kok, Pieter; Nemoto, Kae; Munro, William J.

    2002-01-01

    We investigate and define dark and semi-dark states for multiple qudit systems. For two-level systems, semi-dark and dark states are equivalent. We show that the semi-dark states are equivalent to the singlet states of the rotation group. They exist for many multiple qudit systems, whereas dark states are quite rare. We then show that when a dark state is collapsed onto another dark state of fewer parties, the resulting state is again dark. Furthermore, one can use two orthogonal multi-qudit ...

  13. Correlation between Dark Matter and Dark Radiation in String Compactifications

    CERN Document Server

    Allahverdi, Rouzbeh; Dutta, Bhaskar; Sinha, Kuver

    2014-01-01

    Reheating in string compactifications is generically driven by the decay of the lightest modulus which produces Standard Model particles, dark matter and light hidden sector degrees of freedom that behave as dark radiation. This common origin allows us to find an interesting correlation between dark matter and dark radiation. By combining present upper bounds on the effective number of neutrino species N_eff with lower bounds on the reheating temperature as a function of the dark matter mass m_DM from Fermi data, we obtain strong constraints on the (N_eff,m_DM)-plane. Most of the allowed region in this plane corresponds to non-thermal scenarios with Higgsino-like dark matter. Thermal dark matter can be allowed only if N_eff tends to its Standard Model value. We show that the above situation is realised in models with perturbative moduli stabilisation where the production of dark radiation is unavoidable since bulk closed string axions remain light and do not get eaten up by anomalous U(1)s.

  14. Dark Viscous Fluid coupled with Dark Matter and future singularity

    CERN Document Server

    Sebastiani, Lorenzo

    2010-01-01

    We study effects of viscous fluid coupled with dark matter in our universe. We consider bulk viscosity in the cosmic fluid and we suppose the existence of a coupling between fluid and dark matter, in order to reproduce a stable de Sitter universe protected against future-time singularities. More general inhomogeneous fluids are studied related to future singularities.

  15. The Photosynthetic Dark Reactions Do Not Operate in the Dark.

    Science.gov (United States)

    Lonergan, Thomas A.

    2000-01-01

    Discusses the common misconception persistent in high school and college level introductory biology texts that "dark reactions" of the Calvin cycle actually occur in the dark. Explains that they are indirectly dependent on the presence of light for their activity. (ASK)

  16. Residual non-Abelian dark matter and dark radiation

    Directory of Open Access Journals (Sweden)

    P. Ko

    2017-05-01

    Full Text Available We propose a novel particle physics model in which vector dark matter (VDM and dark radiation (DR originate from the same non-Abelian dark sector. We show an illustrating example where dark SU(3 is spontaneously broken into SU(2 subgroup by the nonzero vacuum expectation value (VEV of a complex scalar in fundamental representation of SU(3. The massless gauge bosons associated with the residual unbroken SU(2 constitute DR and help to relieve the tension in Hubble constant measurements between Planck and Hubble Space Telescope. In the meantime, massive dark gauge bosons associated with the broken generators are VDM candidates. Intrinsically, this non-Abelian VDM can interact with non-Abelian DR in the cosmic background, which results in a suppressed matter power spectrum and leads to a smaller σ8 for structure formation.

  17. 10 years of dark atoms of composite dark matter

    CERN Document Server

    Khlopov, M Yu

    2015-01-01

    In 2005 Sheldon Glashow has proposed his sinister model, opening the path to composite-dark-matter scenarios, in which heavy stable electrically charged particles bound in neutral atoms play the role of dark matter candidates. Though the general problem of new stable single charged particles, forming with ordinary electrons anomalous isotopes of hydrogen, turned out to be unresolvable in Glashow's scenario, this scenario stimulated development of composite dark matter models, which can avoid the trouble of anomalous isotope overproduction. In the simplest case composite dark matter may consist of -2 charged particles, bound by ordinary Coulomb interaction with primordial helium in OHe dark matter model. The advantage and open problems of this model are discussed.

  18. Exactly solved models of interacting dark matter and dark energy

    CERN Document Server

    Chimento, Luis P

    2012-01-01

    We introduce an effective one-fluid description of the interacting dark sector in a spatially flat Friedmann-Robertson-Walker space-time and investigate the stability of the power-law solutions. We find the "source equation" for the total energy density and determine the energy density of each dark component. We study linear and nonlinear interactions which depend on the dark matter and dark energy densities, their first derivatives, the total energy density with its derivatives up to second order and the scale factor. We solve the evolution equations of the dark components for both interactions, examine exhaustively several examples and show cases where the problem of the coincidence is alleviated. We show that a generic nonlinear interaction gives rise to the "relaxed Chaplygin gas model" whose effective equation of state includes the variable modified Chaplygin gas model while some others nonlinear interactions yield de Sitter and power-law scenarios.

  19. Neutrino signals from dark matter

    Science.gov (United States)

    Erkoca, Arif Emre

    Large-scale neutrino telescopes will be powerful tools to observe multitude of mysterious phenomena happening in the Universe. The dark matter puzzle is listed as one of them. In this study, indirect detection of dark matter via neutrino signals is presented. The upward muon, the contained muon and the hadronic shower fluxes are calculated, assuming annihilation/decay of the dark matter in the core of the astrophysical objects and in the Galactic center. Direct neutrino production and secondary neutrino production from the decay of Standard Model particles produced in the annihilation/decay of dark matter are studied. The results are contrasted to the ones previously obtained in the literature, illustrating the importance of properly treating muon propagation and energy loss for the upward muon flux. The dependence of the dark matter signals on the density profile, the dark matter mass and the detector threshold are discussed. Different dark matter models (gravitino, Kaluza-Klein and leptophilic) which can account for recent observations of some indirect searches are analyzed regarding their detection in the kilometer size neutrino detectors in the near future. Muon and shower rates and the minimum observation times in order to reach 2sigma detection significance are evaluated, with the result suggesting that the optimum cone half angles chosen about the Galactic center are about 10° (50°) for the muon (shower) events. A detailed analysis shows that for the annihilating dark matter models such as the leptophilic and Kaluza-Klein models, upward and contained muon as well as showers yield promising signals for dark matter detection in just a few years of observation, whereas for decaying dark matter models, the same observation times can only be reached with showers. The analytical results for the final fluxes are also obtained as well as parametric forms for the muon and shower fluxes for the dark matter models considered in this study.

  20. SYSTEMATIC STUDIES IN TURNERA (TURNERACEAE II. SERIES ANNULARES, CAPITATAE, PAPILLIFERAE AND MICROPHYLLAE ESTUDIOS SISTEMÁTICOS EN TURNERA (TURNERACEAE II. SERIES ANNULARES, CAPITATAE, MICROPHYLEAE Y PAPILLIFERAE

    Directory of Open Access Journals (Sweden)

    María Mercedes Arbo

    2010-11-01

    Full Text Available

    Turnera L. includes around 100 American species and two African ones, arranged in nine series. In this paper, the following four series embracing 21 species are revised: Annulares, Capitatae, Microphyllae and Papilliferae. Six new taxa are described: Thatschbachii, Thatschbachii var. miniata, Tmaracasana,and T.princeps of the seriesCapitatae, Tasymmetrica of the series Microphyllae, and Tcaatingana of the series Papilliferae. The species of these four series share the common features of simple and glandular hairs, generally well-developed floral peduncle, absent pedicel, linear or elliptic prophylls, generally warty or granulate fruit, and a floral tube, appendicular in nature, in that it is the product of the fusion of the lower part of the calyx and corolla, with the staminal filaments adnate only at the base. In the series Annulares,
    Microphyllae and Papilliferae the leaves and young stems are fragrant, the scent being produced by the glandular hairs, and the floral peduncle is shortly adnate to the petiole. Three
    series, Annulares, Capitatae and Microphyllae, have leaves with generally well developed stipules and a disjunct geographical distribution. The series Annulares and Capitatae have nectaries and villous or hirsute styles, while Microphyllae and Papilliferae lack nectaries and their styles are glabrous or somewhat pilose. In some species of Microphyllae the staminal filaments are joined at the base, forming an annular structure 0,05-0,50 mm high. The seeds are peculiar in Annulares, being very short, with a central, prominent and slightly concave chalaza. In the series Capitatae, the flowers are gathered in short, capitate inflorescences, the length of the peduncles being variable or sometimes wanting, and the seeds are obovoid, reticulate or striate. The leaves of Microphyllae are small, with the stipules adnate to the foliar
    base; setiform glandular hairs, similar to those of