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Sample records for anisotropy probe wmap

  1. Wilkinson Microwave Anisotropy Probe (WMAP) Attitude Estimation Filter Comparison

    Science.gov (United States)

    Harman, Richard R.

    2005-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) spacecraft was launched in June of 2001. The sensor complement of WMAP consists of two Autonomous Star Trackers (ASTs), two Fine Sun Sensors (FSSs), and a gyro package which contains redundancy about one of the WMAP body axes. The onboard attitude estimation filter consists of an extended Kalman filter (EKF) solving for attitude and gyro bias errors which are then resolved into a spacecraft attitude quaternion and gyro bias. A pseudo-linear Kalman filter has been developed which directly estimates the spacecraft attitude quaternion, rate, and gyro bias. In this paper, the performance of the two filters is compared for the two major control modes of WMAP: inertial mode and observation mode.

  2. Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Likelihoods and Parameters from the WMAP Data

    Science.gov (United States)

    Dunkey, J.; Komatsu, E.; Nolta, M.R.; Spergel, D.N.; Larson, D.; Hinshaw, G.; Page, L.; Bennett, C.L.; Gold, B.; Jarosik, N.; Weiland, J.L.; Halpern, M.; Hill, R.S.; Kogut, A.; Limon, M.; Meyer, S.S.; Tucker, G.S.; Wollack, E.; Wright, E.L.

    2008-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP), launched in 2001, has mapped out the Cosmic Microwave Background with unprecedented accuracy over the whole sky. Its observations have led to the establishment of a simple concordance cosmological model for the contents and evolution of the universe, consistent with virtually all other astronomical measurements. The WMAP first-year and three-year data have allowed us to place strong constraints on the parameters describing the ACDM model. a flat universe filled with baryons, cold dark matter, neutrinos. and a cosmological constant. with initial fluctuations described by nearly scale-invariant power law fluctuations, as well as placing limits on extensions to this simple model (Spergel et al. 2003. 2007). With all-sky measurements of the polarization anisotropy (Kogut et al. 2003; Page et al. 2007), two orders of magnitude smaller than the intensity fluctuations. WMAP has not only given us an additional picture of the universe as it transitioned from ionized to neutral at redshift z approx.1100. but also an observation of the later reionization of the universe by the first stars. In this paper we present cosmological constraints from WMAP alone. for both the ACDM model and a set of possible extensions. We also consider tlle consistency of WMAP constraints with other recent astronomical observations. This is one of seven five-year WMAP papers. Hinshaw et al. (2008) describe the data processing and basic results. Hill et al. (2008) present new beam models arid window functions, Gold et al. (2008) describe the emission from Galactic foregrounds, and Wright et al. (2008) the emission from extra-Galactic point sources. The angular power spectra are described in Nolta et al. (2008), and Komatsu et al. (2008) present and interpret cosmological constraints based on combining WMAP with other data. WMAP observations are used to produce full-sky maps of the CMB in five frequency bands centered at 23, 33, 41, 61, and 94 GHz

  3. Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Likelihoods and Parameters from the WMAP data

    CERN Document Server

    Dunkley, J; Nolta, M R; Spergel, D N; Larson, D; Hinshaw, G; Page, L; Bennett, C L; Gold, B; Jarosik, N; Weiland, J L; Halpern, M; Hill, R S; Kogut, A; Limon, M; Meyer, S S; Tucker, G S; Wollack, E; Wright, E L

    2008-01-01

    This paper focuses on cosmological constraints derived from analysis of WMAP data alone. A simple LCDM cosmological model fits the five-year WMAP temperature and polarization data. The basic parameters of the model are consistent with the three-year data and now better constrained: Omega_b h^2 = 0.02273+-0.00062, Omega_c h^2 = 0.1099+-0.0062, Omega_L = 0.742+-0.030, n_s = 0.963+0.014- 0.015, tau = 0.087+-0.017, sigma_8 = 0.796+-0.036. With five years of polarization data, we have measured the optical depth to reionization, tau>0, at 5 sigma significance. The redshift of an instantaneous reionization is constrained to be z_reion = 11.0+-1.4 with 68% confidence. This excludes a sudden reionization of the universe at z=6 at more than 3.5 sigma significance, suggesting that reionization was an extended process. Using two different methods for polarized foreground cleaning, and foreground marginalization, we get consistent estimates for the optical depth. This cosmological model also fits small-scale CMB data, and...

  4. Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results

    Science.gov (United States)

    Hinshaw, G.; Larson, D.; Komatsu, E.; Spergel, D. N.; Bennett, C. L.; Dunkley, J.; Nolta, M. R.; Halpern, M.; Hill, R. S.; Odegard, N.; Page, L.; Smith, K. L.; Weiland, J. L.; Gold, B.; Jarosik, N.; Kogut, A.; Limon, M.; Meyer, S. S.; Tucker, G. S.; Wollack, E.; Wright, E. L.

    2013-01-01

    We present cosmological parameter constraints based on the final nine-year Wilkinson Microwave Anisotropy Probe (WMAP) data, in conjunction with a number of additional cosmological data sets. The WMAP data alone, and in combination, continue to be remarkably well fit by a six-parameter Lambda-CDM model. When WMAP data are combined with measurements of the high-l cosmic microwave background anisotropy, the baryon acoustic oscillation scale, and the Hubble constant, the matter and energy densities Omega(sub b)h(exp 2), Omega(sub c)h(exp 2)and Omega(sub Lambda), are each determined to a precision of approx. 1.5%. The amplitude of the primordial spectrum is measured to within 3%, and there is now evidence for a tilt in the primordial spectrum at the 5 sigma level, confirming the first detection of tilt based on the five-year WMAP data. At the end of the WMAP mission, the nine-year data decrease the allowable volume of the six-dimensional Lambda-CDM parameter space by a factor of 68,000 relative to pre-WMAP measurements. We investigate a number of data combinations and show that their Lambda-CDM parameter fits are consistent. New limits on deviations from the six-parameter model are presented, for example: the fractional contribution of tensor modes is limited to r sub kappa) = (0.0027 (sub +0.0039) (sup -0.0038;) the summed mass of neutrinos is limited to Sigma M(sub nu) sub eff) = 3.84 +/- 0+/-40, when the full data are analyzed. The joint constraint on N(sub eff) and the primordial helium abundance, Y(sub He), agrees with the prediction of standard big bang nucleosynthesis. We compare recent Planck measurements of the Sunyaev-Zel'dovich effect with our seven-year measurements, and show their mutual agreement. Our analysis of the polarization pattern around temperature extrema is updated. This confirms a fundamental prediction of the standard cosmological model and provides a striking illustration of acoustic oscillations and adiabatic initial conditions in the early

  5. NINE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP) OBSERVATIONS: FINAL MAPS AND RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, C. L.; Larson, D.; Weiland, J. L. [Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218-2686 (United States); Jarosik, N.; Page, L. [Department of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544-0708 (United States); Hinshaw, G.; Halpern, M. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada); Odegard, N.; Hill, R. S. [ADNET Systems, Inc., 7515 Mission Drive, Suite A100, Lanham, MD 20706 (United States); Smith, K. M. [Perimeter Institute for Theoretical Physics, Waterloo, ON N2L 2Y5 (Canada); Gold, B. [School of Physics and Astronomy, University of Minnesota, 116 Church Street S.E., Minneapolis, MN 55455 (United States); Komatsu, E. [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild Str. 1, D-85741 Garching (Germany); Nolta, M. R. [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, University of Toronto, Toronto, ON M5S 3H8 (Canada); Spergel, D. N. [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544-1001 (United States); Wollack, E.; Kogut, A. [Code 665, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Dunkley, J. [Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Limon, M. [Columbia Astrophysics Laboratory, 550 West 120th Street, Mail Code 5247, New York, NY 10027-6902 (United States); Meyer, S. S. [Departments of Astrophysics and Physics, KICP and EFI, University of Chicago, Chicago, IL 60637 (United States); Tucker, G. S., E-mail: cbennett@jhu.edu [Department of Physics, Brown University, 182 Hope Street, Providence, RI 02912-1843 (United States); and others

    2013-10-01

    We present the final nine-year maps and basic results from the Wilkinson Microwave Anisotropy Probe (WMAP) mission. The full nine-year analysis of the time-ordered data provides updated characterizations and calibrations of the experiment. We also provide new nine-year full sky temperature maps that were processed to reduce the asymmetry of the effective beams. Temperature and polarization sky maps are examined to separate cosmic microwave background (CMB) anisotropy from foreground emission, and both types of signals are analyzed in detail. We provide new point source catalogs as well as new diffuse and point source foreground masks. An updated template-removal process is used for cosmological analysis; new foreground fits are performed, and new foreground-reduced CMB maps are presented. We now implement an optimal C {sup –1} weighting to compute the temperature angular power spectrum. The WMAP mission has resulted in a highly constrained ΛCDM cosmological model with precise and accurate parameters in agreement with a host of other cosmological measurements. When WMAP data are combined with finer scale CMB, baryon acoustic oscillation, and Hubble constant measurements, we find that big bang nucleosynthesis is well supported and there is no compelling evidence for a non-standard number of neutrino species (N {sub eff} = 3.84 ± 0.40). The model fit also implies that the age of the universe is t {sub 0} = 13.772 ± 0.059 Gyr, and the fit Hubble constant is H {sub 0} = 69.32 ± 0.80 km s{sup –1} Mpc{sup –1}. Inflation is also supported: the fluctuations are adiabatic, with Gaussian random phases; the detection of a deviation of the scalar spectral index from unity, reported earlier by the WMAP team, now has high statistical significance (n{sub s} = 0.9608 ± 0.0080); and the universe is close to flat/Euclidean (Ω{sub k} = -0.0027{sup +0.0039}{sub -0.0038}). Overall, the WMAP mission has resulted in a reduction of the cosmological parameter volume by a factor

  6. NINE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP) OBSERVATIONS: COSMOLOGICAL PARAMETER RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Hinshaw, G.; Halpern, M. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada); Larson, D.; Bennett, C. L.; Weiland, J. L. [Department of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218-2686 (United States); Komatsu, E. [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild Str. 1, D-85741 Garching (Germany); Spergel, D. N. [Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), Todai Institutes for Advanced Study, University of Tokyo, Kashiwa 277-8583 (Japan); Dunkley, J. [Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH (United Kingdom); Nolta, M. R. [Canadian Institute for Theoretical Astrophysics, 60 St. George St., University of Toronto, Toronto, ON M5S 3H8 (Canada); Hill, R. S.; Odegard, N. [ADNET Systems, Inc., 7515 Mission Dr., Suite A100 Lanham, MD 20706 (United States); Page, L.; Jarosik, N. [Department of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544-0708 (United States); Smith, K. M. [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544-1001 (United States); Gold, B. [University of Minnesota, School of Physics and Astronomy, 116 Church Street S.E., Minneapolis, MN 55455 (United States); Kogut, A.; Wollack, E. [Code 665, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Limon, M. [Columbia Astrophysics Laboratory, 550 W. 120th St., Mail Code 5247, New York, NY 10027-6902 (United States); Meyer, S. S. [Departments of Astrophysics and Physics, KICP and EFI, University of Chicago, Chicago, IL 60637 (United States); Tucker, G. S., E-mail: hinshaw@physics.ubc.ca [Department of Physics, Brown University, 182 Hope St., Providence, RI 02912-1843 (United States); and others

    2013-10-01

    We present cosmological parameter constraints based on the final nine-year Wilkinson Microwave Anisotropy Probe (WMAP) data, in conjunction with a number of additional cosmological data sets. The WMAP data alone, and in combination, continue to be remarkably well fit by a six-parameter ΛCDM model. When WMAP data are combined with measurements of the high-l cosmic microwave background anisotropy, the baryon acoustic oscillation scale, and the Hubble constant, the matter and energy densities, Ω {sub b} h {sup 2}, Ω {sub c} h {sup 2}, and Ω{sub Λ}, are each determined to a precision of ∼1.5%. The amplitude of the primordial spectrum is measured to within 3%, and there is now evidence for a tilt in the primordial spectrum at the 5σ level, confirming the first detection of tilt based on the five-year WMAP data. At the end of the WMAP mission, the nine-year data decrease the allowable volume of the six-dimensional ΛCDM parameter space by a factor of 68,000 relative to pre-WMAP measurements. We investigate a number of data combinations and show that their ΛCDM parameter fits are consistent. New limits on deviations from the six-parameter model are presented, for example: the fractional contribution of tensor modes is limited to r < 0.13 (95% CL); the spatial curvature parameter is limited to Ω{sub k} = -0.0027{sup +0.0039}{sub -0.0038}; the summed mass of neutrinos is limited to Σm {sub ν} < 0.44 eV (95% CL); and the number of relativistic species is found to lie within N {sub eff} = 3.84 ± 0.40, when the full data are analyzed. The joint constraint on N {sub eff} and the primordial helium abundance, Y {sub He}, agrees with the prediction of standard big bang nucleosynthesis. We compare recent Planck measurements of the Sunyaev-Zel'dovich effect with our seven-year measurements, and show their mutual agreement. Our analysis of the polarization pattern around temperature extrema is updated. This confirms a fundamental prediction of the standard

  7. Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results

    Science.gov (United States)

    Bennett, C. L.; Larson, D.; Weiland, J. L.; Jaorsik, N.; Hinshaw, G.; Odegard, N.; Smith, K. M.; Hill, R. S.; Gold, B.; Halpern, M; Komatsu, E.; Nolta, M. R.; Page, L.; Spergel, D. N.; Wollack, E.; Dunkley, J.; Kogut, A.; Limon,, M.; Meyer, S. S.; Tucker, G. S.; Wright, E. L.

    2013-01-01

    We present the final nine-year maps and basic results from the Wilkinson Microwave Anisotropy Probe (WMAP) mission. The full nine-year analysis of the time-ordered data provides updated characterizations and calibrations of the experiment. We also provide new nine-year full sky temperature maps that were processed to reduce the asymmetry of the effective beams. Temperature and polarization sky maps are examined to separate cosmic microwave background (CMB) anisotropy from foreground emission, and both types of signals are analyzed in detail.We provide new point source catalogs as well as new diffuse and point source foreground masks. An updated template-removal process is used for cosmological analysis; new foreground fits are performed, and new foreground reduced are presented.We nowimplement an optimal C(exp -1)1 weighting to compute the temperature angular power spectrum. The WMAP mission has resulted in a highly constrained Lambda-CDM cosmological model with precise and accurate parameters in agreement with a host of other cosmological measurements. When WMAP data are combined with finer scale CMB, baryon acoustic oscillation, and Hubble constant measurements, we find that big bang nucleosynthesis is well supported and there is no compelling evidence for a non-standard number of neutrino species (N(sub eff) = 3.84 +/- 0.40). The model fit also implies that the age of the universe is (sub 0) = 13.772 +/- 0.059 Gyr, and the fit Hubble constant is H(sub 0) = 69.32 +/- 0.80 km/s/ Mpc. Inflation is also supported: the fluctuations are adiabatic, with Gaussian random phases; the detection of a deviation of the scalar spectral index from unity, reported earlier by the WMAP team, now has high statistical significance (n(sub s) = 0.9608+/-0.0080); and the universe is close to flat/Euclidean (Omega = -0.0027+0.0039/-0.0038). Overall, the WMAP mission has resulted in a reduction of the cosmological parameter volume by a factor of 68,000 for the standard six

  8. Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Data Processing, Sky Maps, and Basic Results

    Science.gov (United States)

    Weiland, J.L.; Hill, R.S.; Odegard, 3.; Larson, D.; Bennett, C.L.; Dunkley, J.; Jarosik, N.; Page, L.; Spergel, D.N.; Halpern, M.; Meyer, S.S.; Tucker, G.S.; Wright, E.L.

    2008-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) is a Medium-Class Explorer (MIDEX) satellite aimed at elucidating cosmology through full-sky observations of the cosmic microwave background (CMB). The WMAP full-sky maps of the temperature and polarization anisotropy in five frequency bands provide our most accurate view to date of conditions in the early universe. The multi-frequency data facilitate the separation of the CMB signal from foreground emission arising both from our Galaxy and from extragalactic sources. The CMB angular power spectrum derived from these maps exhibits a highly coherent acoustic peak structure which makes it possible to extract a wealth of information about the composition and history of the universe. as well as the processes that seeded the fluctuations. WMAP data have played a key role in establishing ACDM as the new standard model of cosmology (Bennett et al. 2003: Spergel et al. 2003; Hinshaw et al. 2007: Spergel et al. 2007): a flat universe dominated by dark energy, supplemented by dark matter and atoms with density fluctuations seeded by a Gaussian, adiabatic, nearly scale invariant process. The basic properties of this universe are determined by five numbers: the density of matter, the density of atoms. the age of the universe (or equivalently, the Hubble constant today), the amplitude of the initial fluctuations, and their scale dependence. By accurately measuring the first few peaks in the angular power spectrum, WMAP data have enabled the following accomplishments: Showing the dark matter must be non-baryonic and interact only weakly with atoms and radiation. The WMAP measurement of the dark matter density puts important constraints on supersymmetric dark matter models and on the properties of other dark matter candidates. With five years of data and a better determination of our beam response, this measurement has been significantly improved. Precise determination of the density of atoms in the universe. The agreement between

  9. Seven-year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Are There Cosmic Microwave Background Anomalies?

    Science.gov (United States)

    Bennett, C. L.; Hill, R. S.; Hinshaw, G.; Larson, D.; Smith, K. M.; Dunkley, J.; Gold, B.; Halpern, M.; Jarosik, N.; Kogut, A.; Komatsu, E.; Limon, M.; Meyer, S. S.; Nolta, M. R.; Odegard, N.; Page, L.; Spergel, D. N.; Tucker, G. S.; Weiland, J. L.; Wollack, E.; Wright, E. L.

    2011-02-01

    statistical combination of the full-sky anisotropy fluctuations. It may be due, in part, to chance alignments between the primary and secondary anisotropy, but this only shifts the coincidence from within the last scattering surface to between it and the local matter density distribution. While this alignment appears to be remarkable, there was no model that predicted it, nor has there been a model that provides a compelling retrodiction. We examine claims of a hemispherical or dipole power asymmetry across the sky and find that the evidence for these claims is not statistically significant. We confirm the claim of a strong quadrupolar power asymmetry effect, but there is considerable evidence that the effect is not cosmological. The likely explanation is an insufficient handling of beam asymmetries. We conclude that there is no compelling evidence for deviations from the ΛCDM model, which is generally an acceptable statistical fit to WMAP and other cosmological data. WMAP is the result of a partnership between Princeton University and NASA's Goddard Space Flight Center. Scientific guidance is provided by the WMAP Science Team.

  10. First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations Parameter Estimation Methodology

    CERN Document Server

    Verde, L; Spergel, D N; Nolta, M R; Bennett, C L; Halpern, M; Hinshaw, G; Jarosik, N C; Kogut, A J; Limon, M; Meyer, S S; Page, L; Tucker, G S; Wollack, E; Wright, E L

    2003-01-01

    We describe our methodology for comparing the WMAP measurements of the cosmic microwave background (CMB) and other complementary data sets to theoretical models. The unprecedented quality of the WMAP data, and the tight constraints on cosmological parameters that are derived, require a rigorous analysis so that the approximations made in the modeling do not lead to significant biases. We describe our use of the likelihood function to characterize the statistical properties of the microwave background sky. We outline the use of the Monte Carlo Markov Chains to explore the likelihood of the data given a model to determine the best fit cosmological parameters and their uncertainties. We add to the WMAP data the l>~700 CBI and ACBAR measurements of the CMB, the galaxy power spectrum at z~0 obtained from the 2dF galaxy redshift survey (2dFGRS), and the matter power spectrum at z~3 as measured with the Ly alpha forest. These last two data sets complement the CMB measurements by probing the matter power spectrum of ...

  11. Seven-year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation

    OpenAIRE

    Komatsu, E.; Smith, K. M.; Dunkley, J.; Bennett, C. L.; Gold, B.; Hinshaw, G.; Jarosik, N.; D. Larson; Nolta, M. R.; Page, L; Spergel, D. N.; Halpern, M.; Hill, R S; Kogut, A.; Limon, M.

    2011-01-01

    (Abridged) The 7-year WMAP data and improved astrophysical data rigorously test the standard cosmological model and its extensions. By combining WMAP with the latest distance measurements from BAO and H0 measurement, we determine the parameters of the simplest LCDM model. The power-law index of the primordial power spectrum is n_s=0.968+-0.012, a measurement that excludes the scale-invariant spectrum by 99.5%CL. The other parameters are also improved from the 5-year results. Notable examples ...

  12. Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Planets and Celestial Calibration Sources

    CERN Document Server

    Weiland, J L; Hill, R S; Wollack, E; Hinshaw, G; Greason, M R; Jarosik, N; Page, L; Bennett, C L; Dunkley, J; Gold, B; Halpern, M; Kogut, A; Komatsu, E; Larson, D; Limon, M; Meyer, S S; Nolta, M R; Smith, K M; Spergel, D N; Tucker, G S; Wright, E L

    2010-01-01

    We present WMAP seven-year observations of bright sources which are often used as calibrators at microwave frequencies. Ten objects are studied in five frequency bands (23 - 94 GHz): the outer planets (Mars, Jupiter, Saturn, Uranus and Neptune) and five fixed celestial sources (Cas A, Tau A, Cyg A, 3C274 and 3C58). The seven-year analysis of Jupiter provides temperatures which are within 1-sigma of the previously published WMAP five-year values, with slightly tighter constraints on variability with orbital phase, and limits (but no detections) on linear polarization. Scaling factors are provided which, when multiplied by the Wright Mars thermal model predictions at 350 micron, reproduce WMAP seasonally averaged observations of Mars within ~2%. An empirical model is described which fits brightness variations of Saturn due to geometrical effects and can be used to predict the WMAP observations to within 3%. Seven-year mean temperatures for Uranus and Neptune are also tabulated. Uncertainties in Uranus temperatu...

  13. Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Galactic Foreground Emission

    CERN Document Server

    Gold, B; Weiland, J L; Hill, R S; Kogut, A; Bennett, C L; Hinshaw, G; Dunkley, J; Halpern, M; Jarosik, N; Komatsu, E; Larson, D; Limon, M; Meyer, S S; Nolta, M R; Page, L; Smith, K M; Spergel, D N; Tucker, G S; Wollack, E; Wright, E L

    2010-01-01

    [Abridged] We present updated estimates of Galactic foreground emission using seven years of WMAP data. Using the power spectrum of differences between multi-frequency template-cleaned maps, we find no evidence for foreground contamination outside of the updated (KQ85y7) foreground mask. We place a 15 microKelvin upper bound on rms foreground contamination in the cleaned maps used for cosmological analysis. We find no indication in the polarization data of an extra "haze" of hard synchrotron emission from energetic electrons near the Galactic center. We provide an updated map of the cosmic microwave background (CMB) using the internal linear combination (ILC) method, updated foreground masks, and updates to point source catalogs with 62 newly detected sources. Also new are tests of the Markov chain Monte Carlo (MCMC) foreground fitting procedure against systematics in the time-stream data, and tests against the observed beam asymmetry. Within a few degrees of the Galactic plane, WMAP total intensity data show...

  14. Limits on SUSY GUTs and Defects Formation in Hybrid Inflationary Models with Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations

    CERN Document Server

    Fraisse, A A

    2006-01-01

    We confront the predicted effects of hybrid inflationary models on the Cosmic Microwave Background (CMB) with three years of Wilkinson Microwave Anisotropy Probe (WMAP) observations. Using model selection, we compare the ability of a simple flat power-law LCDM model to describe the data to hybrid inflationary models involving global or local cosmic strings, or global textures. We find that it is statistically impossible to distinguish between these models: they all give a similar description of the data, the maximum ratio of the various evidences involved being never higher than e^{0.1 \\pm 0.5}. We then derive the maximum contribution that topological defects can make to the CMB, and place an upper bound on the possible value of cosmic strings tension of G\\mu \\leq 2.1 \\times 10^{-7} (68% CL). Finally, we give the corresponding constraints on the strings and D-strings masses, as well as limits on the D- and F-term coupling constants (\\kappa and \\lambda) and mass scales (M and \\sqrt{\\xi}).

  15. Results from the Wilkinson Microwave Anisotropy Probe

    Science.gov (United States)

    Komatsu, E.; Bennett, Charles L.; Komatsu, Eiichiro

    2015-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) mapped the distribution of temperature and polarization over the entire sky in five microwave frequency bands. These full-sky maps were used to obtain measurements of temperature and polarization anisotropy of the cosmic microwave background with the unprecedented accuracy and precision. The analysis of two-point correlation functions of temperature and polarization data gives determinations of the fundamental cosmological parameters such as the age and composition of the universe, as well as the key parameters describing the physics of inflation, which is further constrained by three-point correlation functions. WMAP observations alone reduced the flat ? cold dark matter (Lambda Cold Dark Matter) cosmological model (six) parameter volume by a factor of > 68, 000 compared with pre-WMAP measurements. The WMAP observations (sometimes in combination with other astrophysical probes) convincingly show the existence of non-baryonic dark matter, the cosmic neutrino background, flatness of spatial geometry of the universe, a deviation from a scale-invariant spectrum of initial scalar fluctuations, and that the current universe is undergoing an accelerated expansion. The WMAP observations provide the strongest ever support for inflation; namely, the structures we see in the universe originate from quantum fluctuations generated during inflation.

  16. Probing dark energy with steerable wavelets through correlation of WMAP and NVSS local morphological measures

    CERN Document Server

    McEwen, J D; Hobson, M P; Vandergheynst, P; Lasenby, A N

    2007-01-01

    Using local morphological measures on the sphere defined through a steerable wavelet analysis, we examine the three-year WMAP and the NVSS data for correlation induced by the integrated Sachs-Wolfe (ISW) effect. The steerable wavelet constructed from the second derivative of a Gaussian allows one to define three local morphological measures, namely the signed-intensity, orientation and elongation of local features. Detections of correlation between the WMAP and NVSS data are made with each of these morphological measures. The most significant detection is obtained in the correlation of the signed-intensity of local features at a significance of 99.9%. By inspecting signed-intensity sky maps, it is possible for the first time to see the correlation between the WMAP and NVSS data by eye. Foreground contamination and instrumental systematics in the WMAP data are ruled out as the source of all significant detections of correlation. Our results provide new insight on the ISW effect by probing the morphological nat...

  17. THE ATACAMA COSMOLOGY TELESCOPE: CALIBRATION WITH THE WILKINSON MICROWAVE ANISOTROPY PROBE USING CROSS-CORRELATIONS

    International Nuclear Information System (INIS)

    We present a new calibration method based on cross-correlations with the Wilkinson Microwave Anisotropy Probe (WMAP) and apply it to data from the Atacama Cosmology Telescope (ACT). ACT's observing strategy and map-making procedure allows an unbiased reconstruction of the modes in the maps over a wide range of multipoles. By directly matching the ACT maps to WMAP observations in the multipole range of 400 < l < 1000, we determine the absolute calibration with an uncertainty of 2% in temperature. The precise measurement of the calibration error directly impacts the uncertainties in the cosmological parameters estimated from the ACT power spectra. We also present a combined map based on ACT and WMAP data that has a high signal-to-noise ratio over a wide range of multipoles.

  18. Probing the Dark Flow signal in WMAP 9 yr and PLANCK cosmic microwave background maps

    CERN Document Server

    Atrio-Barandela, Fernando; Ebeling, Harald; Fixsen, Dale J; Kocevski, Dale

    2014-01-01

    The "dark flow" dipole is a statistically significant dipole found at the position of galaxy clusters in filtered maps of Cosmic Microwave Background (CMB) temperature anisotropies. The dipole measured in {\\it WMAP} 3, 5 and 7 yr data releases was roughly aligned with the all-sky CMB dipole and correlated with cluster X-ray luminosity. We analyzed the final {\\it WMAP} 9 yr and the first {\\it Planck} data releases using a catalog of 980 clusters outside the Kp0 mask to test our earlier findings. The dipoles measured on these new data sets are fully compatible with our earlier estimates, being similar in amplitude and direction to our previous results and in disagreement with the results of an earlier study by the {\\it Planck} Collaboration. Further, in {\\it Planck} data dipoles are independent of frequency, ruling out the Thermal Sunyaev-Zeldovich as the source of the effect. The signal is dominated by the most massive clusters, with a statistical significance better than 99\\%, slightly larger than in {\\it WMA...

  19. Inflation model constraints from the Wilkinson Microwave Anisotropy Probe three-year data

    Energy Technology Data Exchange (ETDEWEB)

    Kinney, William H.; /SUNY, Buffalo; Kolb, Edward W.; /Fermilab /Chicago U., Astron. Astrophys. Ctr.; Melchiorri, Alessandro; /Rome U. /INFN, Rome; Riotto, Antonio; /CERN

    2006-05-01

    We extract parameters relevant for distinguishing among single-field inflation models from the Wilkinson Microwave Anisotropy Probe (WMAP) three-year data set, and also from WMAP in combination with the Sloan Digital Sky Survey (SDSS) galaxy power spectrum. Our analysis leads to the following conclusions: (1) the Harrison-Zel'dovich model is consistent with both data sets at a 95% confidence level; (2) there is no strong evidence for running of the spectral index of scalar perturbations; (3) Potentials of the form V {infinity} {phi}{sup P} are consistent with the data for p = 2, and are marginally consistent with the WMAP data considered alone for p = 4, but ruled out by WMAP combined with SDSS. We perform a ''Monte Carlo reconstruction'' of the inflationary potential, and find that: (1) there is no evidence to support an observational lower bound on the amplitude of gravitational waves produced during inflation; (2) models such as simple hybrid potentials which evolve toward an inflationary late-time attractor in the space of flow parameters are strongly disfavored by the data, (3) models selected with even a weak slow-roll prior strongly cluster in the region favoring a ''red'' power spectrum and no running of the spectral index, consistent with simple single-field inflation models.

  20. Inflation model constraints from the Wilkinson Microwave Anisotropy Probe three-year data

    CERN Document Server

    Kinney, W H; Melchiorri, A; Riotto, Antonio; Kinney, William H.; Kolb, Edward W.; Melchiorri, Alessandro; Riotto, Antonio

    2006-01-01

    We extract parameters relevant for distinguishing among single-field inflation models from the Wilkinson Microwave Anisotropy Probe (WMAP) three-year data set, and also from WMAP in combination with the Sloan Digital Sky Survey (SDSS) galaxy power spectrum. Our analysis leads to the following conclusions: 1) the Harrison--Zel'dovich model is consistent with both data sets at a 95% confidence level; 2) there is no strong evidence for running of the spectral index of scalar perturbations; 3) Potentials of the form V \\propto \\phi^p are consistent with the data for p = 2, and are marginally consistent with the WMAP data considered alone for p = 4, but ruled out by WMAP combined with SDSS. We perform a "Monte Carlo reconstruction" of the inflationary potential, and find that: 1) there is no evidence to support an observational lower bound on the amplitude of gravitational waves produced during inflation; 2) models such as simple hybrid potentials which evolve toward an inflationary late-time attractor in the space...

  1. Pseudo-Dipole Signal Removal from WMAP Data

    OpenAIRE

    Liu, Hao; Li, Ti-Pei

    2010-01-01

    It is discovered in our previous work that different observational systematics, e.g., errors of antenna pointing directions, asynchronous between the attitude and science data, can generate pseudo-dipole signal in full-sky maps of the cosmic microwave background (CMB) anisotropy published by The Wilkinson Microwave Anisotropy Probe (WMAP) team. Now the antenna sidelobe response to the Doppler signal is found to be able to produce similar effect as well. In this work, independent to the source...

  2. Wilkinson Microwave Anisotropy Probe 7-yr constraints on fNL with a fast wavelet estimator

    CERN Document Server

    Casaponsa, B; Curto, A; Martínez-González, E; Vielva, P

    2010-01-01

    A new method to constrain the local non-linear coupling parameter fNL based on a fast wavelet decomposition is presented. Using a multiresolution wavelet adapted to the HEALPix pixelization, we have developed a method that is 10^2 times faster than previous estimators based on isotropic wavelets and 10^3 faster than the KSW bispectrum estimator, at the resolution of the Wilkinson Microwave Anisotropy Probe (WMAP) data. The method has been applied to the WMAP 7-yr V+W combined map, imposing constraints on fNL of -69 < fNL < 65 at the 95 per cent CL. This result has been obtained after correcting for the contribution of the residual point sources which has been estimated to be fNL = 7 +/- 6. In addition, a Gaussianity analysis of the data has been carried out using the third order moments of the wavelet coefficients, finding consistency with Gaussianity. Although the constrainsts imposed on fNL are less stringent than those found with optimal estimators, we believe that a very fast method, as the one prop...

  3. Missing completely of CMB quadrupole in WMAP data

    OpenAIRE

    Liu, Hao; Li, Ti-Pei

    2012-01-01

    In cosmic microwave background (CMB) experiments, foreground-cleaned temperature maps are still contaminated by the residual dipole due to uncertainties of the Doppler dipole direction and microwave radiometer sidelobe. To obtain reliable CMB maps, such contamination has to be carefully removed from observed data. We have previously built a software package for map-making, residual dipole-contamination removal, and power spectrum estimation from the Wilkinson Microwave Anisotropy Probe (WMAP)...

  4. WMAP: A Radiological Analysis

    Directory of Open Access Journals (Sweden)

    Robitaille P.-M.

    2007-01-01

    Full Text Available In this work, results obtained by the WMAP satellite are analyzed by invoking established practices for signal acquisition and processing in nuclear magnetic resonance (NMR and magnetic resonance imaging (MRI. Dynamic range, image reconstruction, signal to noise, resolution, contrast, and reproducibility are specifically discussed. WMAP images do not meet accepted standards in medical imaging research. WMAP images are obtained by attempting to remove a galactic foreground contamination which is 1,000 times more intense than the desired signal. Unlike water suppression in biological NMR, this is accomplished without the ability to affect the signal at the source and without a priori knowledge. Resulting WMAP images have an exceedingly low signal to noise (maximum 1–2 and are heavily governed by data processing. Final WMAP internal linear combination (ILC images are made from 12 section images. Each of these, in turn, is processed using a separate linear combination of data. The WMAP team extracts cosmological implications from their data, while ignoring that the ILC coefficients do not remain constant from year to year. In contrast to standard practices in medicine, difference images utilized to test reproducibility are presented at substantially reduced resolution. ILC images are not presented for year two and three. Rather, year-1 data is signal averaged in a combined 3-year data set. Proper tests of reproducibility require viewing separate yearly ILC images. Fluctuations in the WMAP images arise from the inability to remove the galactic foreground, and in the significant yearly variations in the foreground itself. Variations in the map outside the galactic plane are significant, preventing any cosmological analysis due to yearly changes. This occurs despite the masking of more than 300 image locations. It will be advanced that any “signal” observed by WMAP is the result of foreground effects, not only from our galaxy, but indeed yearly

  5. Correlation Analysis between Tibet AS-$\\gamma$ TeV Cosmic Ray and WMAP Nine-year Data

    CERN Document Server

    Yin, Qian-Qing

    2015-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) team subtracted template-based foreground models to produce foreground-reduced maps, and masked point sources and uncertain sky regions directly; however, whether foreground residuals exist in the WMAP foreground-reduced maps is still an open question. Here, we use Pearson correlation coefficient (PCC) analysis with AS-$\\gamma$ TeV cosmic ray (CR) data to probe possible foreground residuals in the WMAP nine-year data. The correlation results between the CR and foreground-contained maps (WMAP foreground-unreduced maps, WMAP template-based and MEM foreground models) suggest that: (1) CRs can trace foregrounds in the WMAP data; (2) at least some TeV CRs originate from the Milky Way; (3) foregrounds may be related to the existence of CR anisotropy (loss-cone and tail-in structures); (4) there exist differences among different types of foregrounds in the declination range of $< 15^{\\circ}$. Then, we generate 10,000 mock CMB sky maps to describe the cosmic variance...

  6. What have we learnt from Wilkinson microwave anisotropy probe?

    Indian Academy of Sciences (India)

    Robert G Crittenden

    2004-10-01

    It has been a little over a year since WMAP produced its dramatic new glimpse of the cosmic microwave background. I review the results of the WMAP mission and the science that has arisen from it, focusing on the qualitatively new features of the data: the temperature-polarization correlation, correlations with large scale structure, the large-scale power deficit and its implications, and the search for non-Gaussianity.

  7. Intermediate inflation in light of the three-year WMAP observations

    CERN Document Server

    Barrow, J D; Pahud, C; Barrow, John D; Liddle, Andrew R

    2006-01-01

    The three-year observations from the Wilkinson Microwave Anisotropy Probe have been hailed as giving the first clear indication of a spectral index n_s0 is given (within the slow-roll approximation) by a version of the intermediate inflation model with expansion rate H(t) \\propto t^{-1/3}. We assess the status of this model in light of the WMAP3 data.

  8. EVOLUTION OF THE COSMIC MICROWAVE BACKGROUND POWER SPECTRUM ACROSS WILKINSON MICROWAVE ANISOTROPY PROBE DATA RELEASES: A NONPARAMETRIC ANALYSIS

    International Nuclear Information System (INIS)

    Using a nonparametric function estimation methodology, we present a comparative analysis of the Wilkinson Microwave Anisotropy Probe (WMAP) 1-, 3-, 5-, and 7-year data releases for the cosmic microwave background (CMB) angular power spectrum with respect to the following key questions. (1) How well is the power spectrum determined by the data alone? (2) How well is the ΛCDM model supported by a model-independent, data-driven analysis? (3) What are the realistic uncertainties on peak/dip locations and heights? Our results show that the height of the power spectrum is well determined by data alone for multipole l approximately less than 546 (1-year), 667 (3-year), 804 (5-year), and 842 (7-year data). We show that parametric fits based on the ΛCDM model are remarkably close to our nonparametric fits in l-regions where data are sufficiently precise. In contrast, the power spectrum for an HΛCDM model is progressively pushed away from our nonparametric fit as data quality improves with successive data realizations, suggesting incompatibility of this particular cosmological model with respect to the WMAP data sets. We present uncertainties on peak/dip locations and heights at the 95% (2σ) level of confidence and show how these uncertainties translate into hyperbolic 'bands' on the acoustic scale (lA ) and peak shift (φm) parameters. Based on the confidence set for the 7-year data, we argue that the low-l upturn in the CMB power spectrum cannot be ruled out at any confidence level in excess of about 10% (≈0.12σ). Additional outcomes of this work are a numerical formulation for minimization of a noise-weighted risk function subject to monotonicity constraints, a prescription for obtaining nonparametric fits that are closer to cosmological expectations on smoothness, and a method for sampling cosmologically meaningful power spectrum variations from the confidence set of a nonparametric fit.

  9. Performance of the Microwave Anisotropy Probe AST-201 Star Trackers

    Science.gov (United States)

    Ward, David K.; vanBezooijen, Roelof; Bauer, Frank H. (Technical Monitor)

    2002-01-01

    The Microwave Anisotropy Probe (MAP) was launched to create a full-sky map of the cosmic microwave background. MAP incorporates two modified Lockheed Martin AST-201 (Autonomous Star Tracker) star trackers. The AST-201 employs an eight element radiation hardened lens assembly which is used to focus an image on a charge coupled device (CCD). The CCD image is then processed by a star identification algorithm which outputs a three-axis attitude. A CCD-shift algorithm called Time Delayed Integration (TDI) was also included in each star tracker. In order to provide some radiation effect filtering during MAP's three to five phasing loop passes through the Van Allen radiation belts, a simple pixel filtering scheme was implemented, rather than using a more complex, but more robust windowing algorithm. The trackers also include a fiber optic data interface. This paper details the ground testing that was accomplished on the MAP trackers.

  10. A high-significance detection of non-Gaussianity in the WMAP 5-year data using directional spherical wavelets

    CERN Document Server

    McEwen, J D; Lasenby, A N; Mortlock, D J

    2008-01-01

    We repeat the directional spherical real Morlet wavelet analysis, used to detect non-Gaussianity in the Wilkinson Microwave Anisotropy Probe (WMAP) 1-year and 3-year data (McEwen et al. 2005, 2006a), on the WMAP 5-year data. The non-Gaussian signal detected previously is present in the 5-year data at a slightly increased statistical significance of approximately 99%. Localised regions that contribute most strongly to the non-Gaussian signal are found to be very similar to those detected in the previous releases of the WMAP data. When the localised regions detected in the 5-year data are excluded from the analysis the non-Gaussian signal is eliminated.

  11. On the Ionization of Luminous WMAP Sources in the Galaxy : Constraints from He Recombination Line Observations with the GBT

    CERN Document Server

    Roshi, D Anish; Rosero, Viviana; Vaddi, Sravani

    2012-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) free-free foreground emission map is used to identify diffuse ionized regions (DIR) in the Galaxy (Rahman & Murray 2010). It has been found that the 18 most luminous WMAP sources produce more than half of the total ionizing luminosity of the Galaxy. We observed radio recombination lines (RRLs) toward the luminous WMAP source G49.75-0.45 with the Green Bank Telescope near 1.4 GHz. Hydrogen RRL is detected toward the source but no helium line is detected, implying that n_He+/n_H+ ~10 times to explain the observations. If selective absorption of He- ionizing photons by dust is causing this additional attenuation, then the ratio of dust absorption cross sections for He- and H- ionizing photons should be > ~6.

  12. Tests of Cosmological Inhomogeneity Using WMAP

    Science.gov (United States)

    Shubert, Richard; Tatineni, Mahidhar

    2016-06-01

    This paper reports on the latest results obtained from studies of the calibrated Time-Ordered Data of the Wilkinson Microwave Anisotropy Probe (9-yr) mission that has in the past been used to determine the anisotropy of the Cosmic Microwave Background Radiation, although with a novel objective. The purpose of this work has been to examine what can be inferred from these data about the local inhomogeneity of the CMBR, which would be in this case an apparent radial variation of the brightness (or effective temperature) at the same point of the celestial sky as seen by the WMAP spacecraft instruments from the center of observation, namely the Sun. The usual studies of anisotropy normally have averaged the observed temperature of any given point on the celestial sky over one full annual orbit of the WMAP spacecraft around the Sun to produce the well-known maps. Inhomogeneity of the kind being sought here, however, would manifest itself as a systematic variation of the apparent temperature at that point as a function of the orbital position of the spacecraft. The detection of such inhomogeneity, if it could be confirmed by subsequent observations, could significantly impact the standard cosmological paradigm. The computational approach used thus far in that search, over the last four years of study by supercomputer facilities at UCSD, has been to examine the differences of temperature seen of the same points on the sky, taken in pairs corresponding to the pointing directions of the A and B radiometer horns of the instrument, from different orbital positions of the spacecraft. From those observed differences of temperature and the corresponding angular separations of the respective orbital positions — here limited to values greater than or equal to 44 degrees out of a maximum available range of 1 – 45 degrees — an apparent radial gradient of temperature could be computed with lowest uncertainties. A small but significant gradient of temperature tentatively has been

  13. Frequentist comparison of CMB local extrema statistics in the five-year WMAP data with two anisotropic cosmological models

    CERN Document Server

    Hou, Zhen; Górski, K M; Groeneboom, N E; Eriksen, H K

    2009-01-01

    We present local extrema studies of two models that introduce a preferred direction into the observed cosmic microwave background (CMB) temperature field. In particular, we make a frequentist comparison of the one- and two-point statistics for the dipole modulation and ACW models with data from the five-year Wilkinson Microwave Anisotropy Probe (WMAP). This analysis is motivated by previously revealed anomalies in the WMAP data, and particularly the difference in the statistical nature of the temperature anisotropies when analysed in hemispherical partitions. The analysis of the one-point statistics indicates that the previously determined hemispherical variance difficulties can be apparently overcome by a dipole modulation field, but new inconsistencies arise if the mean and the l-dependence of the statistics are considered. The two-point correlation functions of the local extrema, the temperature pair product and the point-point spatial pair-count, demonstrate that the impact of such a modulation is to over...

  14. Five-Year Wilkinson Microwave Anisotropy Probe Observations: Data Processing, Sky Maps, and Basic Results

    Science.gov (United States)

    Hinshaw, G.; Weiland, J. L.; Hill, R. S.; Odegard, N.; Larson, D.; Bennett, C. L.; Dunkley, J.; Gold, B.; Greason, M. R.; Jarosik, N.; Komatsu, E.; Nolta, M. R.; Page, L.; Spergel, D. N.; Wollack, E.; Halpern, M.; Kogut, A.; Limon, M.; Meyer, S. S.; Tucker, G. S.; Wright, E. L.

    2010-01-01

    We present new full-sky temperature and polarization maps in five frequency bands from 23 to 94 GHz, based on data from the first five years of the Wilkinson Microwave Anisotropy Probe (WMAP) sky survey. The new maps are consistent with previous maps and are more sensitive. The five-year maps incorporate several improvements in data processing made possible by the additional years of data and by a more complete analysis of the instrument calibration and in-flight beam response. We present several new tests for systematic errors in the polarization data and conclude that W-band polarization data is not yet suitable for cosmological studies, but we suggest directions for further study. We do find that Ka-band data is suitable for use; in conjunction with the additional years of data, the addition of Ka band to the previously used Q- and V-band channels significantly reduces the uncertainty in the optical depth parameter, tau. Further scientific results from the five-year data analysis are presented in six companion papers and are summarized in Section 7 of this paper. With the five-year WMAP data, we detect no convincing deviations from the minimal six-parameter ACDM model: a flat universe dominated by a cosmological constant, with adiabatic and nearly scale-invariant Gaussian fluctuations. Using WMAP data combined with measurements of Type Ia supernovae and Baryon Acoustic Oscillations in the galaxy distribution, we find (68% CL uncertainties): OMEGA(sub b)h(sup 2) = 0.02267(sup +0.00058)(sub -0.00059), OMEGA(sub c)h(sup 2) = 0.1131 plus or minus 0.0034, OMEGA(sub logical and) = 0.726 plus or minus 0.015, ns = .960 plus or minus 0.013, tau = 0.84 plus or minus 0.016, and DELTA(sup 2)(sub R) = (22.445 plus or minus 0.096) x 10(exp -9) at k = 0.002 Mpc(exp -1). From these we derive sigma(sub 8) = 0.812 plus or minus 0.026, H(sub 0) = 70.5 plus or minus 1.3 kilometers per second Mpc(exp -1), OMEGA(sub b) = 0.0456 plus or minus 0.0015, OMEGA(sub c) = .228 plus or minus

  15. Cosmic microwave background snapshots: pre-WMAP and post-WMAP.

    Science.gov (United States)

    Bond, J Richard; Contaldi, Carlo; Pogosyan, Dmitry

    2003-11-15

    We highlight the remarkable evolution in the cosmic microwave background (CMB) power spectrum C(l) as a function of multipole l over the past few years, and in the cosmological parameters for minimal inflation models derived from it: from anisotropy results before 2000; in 2000 and 2001 from Boomerang, Maxima and the Degree Angular Scale Interferometer (DASI), extending l to approximately 1000; and in 2002 from the Cosmic Background Imager (CBI), Very Small Array (VSA), ARCHEOPS and Arcminute Cosmology Bolometer Array Receiver (ACBAR), extending l to approximately 3000, with more from Boomerang and DASI as well. Pre-WMAP (pre-Wilkinson Microwave Anisotropy Probe) optimal band powers are in good agreement with each other and with the exquisite one-year WMAP results, unveiled in February 2003, which now dominate the l less, similar 600 bands. These CMB experiments significantly increased the case for accelerated expansion in the early Universe (the inflationary paradigm) and at the current epoch (dark energy dominance) when they were combined with "prior" probabilities on the parameters. The minimal inflation parameter set, [omega(b), omega(cdm), Omega(tot), Omega(Lambda), n(s), tau(C), sigma(8)], is applied in the same way to the evolving data. C(l) database and Monte Carlo Markov Chain (MCMC) methods are shown to give similar values, which are highly stable over time and for different prior choices, with the increasing precision best characterized by decreasing errors on uncorrelated "parameter eigenmodes". Priors applied range from weak ones to stronger constraints from the expansion rate (HST-h), from cosmic acceleration from supernovae (SN1) and from galaxy clustering, gravitational lensing and local cluster abundance (LSS). After marginalizing over the other cosmic and experimental variables for the weak + LSS prior, the pre-WMAP data of January 2003 compared with the post-WMAP data of March 2003 give Omega(tot) = 1.03(-0.04)(+0.05) compared with 1

  16. Looking for Cosmological Alfven Waves in WMAP Data

    OpenAIRE

    Chen, Gang; Mukherjee, Pia; Kahniashvili, Tina; Ratra, Bharat; Wang, Yun

    2004-01-01

    A primordial cosmological magnetic field induces and supports vorticity or Alfven waves, which in turn generate cosmic microwave background (CMB) anisotropies. A homogeneous primordial magnetic field with fixed direction induces correlations between the $a_{l-1,m}$ and $a_{l+1,m}$ multipole coefficients of the CMB temperature anisotropy field. We discuss the constraints that can be placed on the strength of such a primordial magnetic field using CMB anisotropy data from the WMAP experiment. W...

  17. Kinematic Sunyaev-Zel'dovich Effect with Projected Fields: A Novel Probe of the Baryon Distribution with Planck, WMAP, and WISE Data

    Science.gov (United States)

    Hill, J. Colin; Ferraro, Simone; Battaglia, Nick; Liu, Jia; Spergel, David N.

    2016-07-01

    The kinematic Sunyaev-Zel'dovich (KSZ) effect—the Doppler boosting of cosmic microwave background (CMB) photons due to Compton scattering off free electrons with nonzero bulk velocity—probes the abundance and the distribution of baryons in the Universe. All KSZ measurements to date have explicitly required spectroscopic redshifts. Here, we implement a novel estimator for the KSZ—large-scale structure cross-correlation based on projected fields: it does not require redshift estimates for individual objects, allowing KSZ measurements from large-scale imaging surveys. We apply this estimator to cleaned CMB temperature maps constructed from Planck and WMAP data and a galaxy sample from the Wide-field Infrared Survey Explorer (WISE). We measure the KSZ effect at 3.8 σ - 4.5 σ significance, depending on the use of additional WISE galaxy bias constraints. We verify that our measurements are robust to possible dust emission from the WISE galaxies. Assuming the standard Λ cold dark matter cosmology, we directly constrain (fb/0.158 ) (ffree/1.0 ) =1.48 ±0.19 (statistical error only) at redshift z ≈0.4 , where fb is the fraction of matter in baryonic form and ffree is the free electron fraction. This is the tightest KSZ-derived constraint reported to date on these parameters. Astronomers have long known that baryons do not trace dark matter on ˜ kiloparsec scales and there has been strong evidence that galaxies are baryon poor. The consistency between the fb value found here and the values inferred from analyses of the primordial CMB and big bang nucleosynthesis verifies that baryons approximately trace the dark matter distribution down to ˜ megaparsec scales. While our projected-field estimator is already competitive with other KSZ approaches when applied to current data sets (because we are able to use the full-sky WISE photometric survey), it will yield enormous signal-to-noise ratios when applied to upcoming high-resolution, multifrequency CMB surveys.

  18. Kinematic Sunyaev-Zel'dovich Effect with Projected Fields: A Novel Probe of the Baryon Distribution with Planck, WMAP, and WISE Data.

    Science.gov (United States)

    Hill, J Colin; Ferraro, Simone; Battaglia, Nick; Liu, Jia; Spergel, David N

    2016-07-29

    The kinematic Sunyaev-Zel'dovich (KSZ) effect-the Doppler boosting of cosmic microwave background (CMB) photons due to Compton scattering off free electrons with nonzero bulk velocity-probes the abundance and the distribution of baryons in the Universe. All KSZ measurements to date have explicitly required spectroscopic redshifts. Here, we implement a novel estimator for the KSZ-large-scale structure cross-correlation based on projected fields: it does not require redshift estimates for individual objects, allowing KSZ measurements from large-scale imaging surveys. We apply this estimator to cleaned CMB temperature maps constructed from Planck and WMAP data and a galaxy sample from the Wide-field Infrared Survey Explorer (WISE). We measure the KSZ effect at 3.8σ-4.5σ significance, depending on the use of additional WISE galaxy bias constraints. We verify that our measurements are robust to possible dust emission from the WISE galaxies. Assuming the standard Λ cold dark matter cosmology, we directly constrain (f_{b}/0.158)(f_{free}/1.0)=1.48±0.19 (statistical error only) at redshift z≈0.4, where f_{b} is the fraction of matter in baryonic form and f_{free} is the free electron fraction. This is the tightest KSZ-derived constraint reported to date on these parameters. Astronomers have long known that baryons do not trace dark matter on ∼ kiloparsec scales and there has been strong evidence that galaxies are baryon poor. The consistency between the f_{b} value found here and the values inferred from analyses of the primordial CMB and big bang nucleosynthesis verifies that baryons approximately trace the dark matter distribution down to ∼ megaparsec scales. While our projected-field estimator is already competitive with other KSZ approaches when applied to current data sets (because we are able to use the full-sky WISE photometric survey), it will yield enormous signal-to-noise ratios when applied to upcoming high-resolution, multifrequency CMB surveys.

  19. The Kinematic Sunyaev-Zel'dovich Effect with Projected Fields: A Novel Probe of the Baryon Distribution with Planck, WMAP, and WISE Data

    CERN Document Server

    Hill, J Colin; Battaglia, Nick; Liu, Jia; Spergel, David N

    2016-01-01

    The kinematic Sunyaev-Zel'dovich (kSZ) effect - the Doppler boosting of cosmic microwave background (CMB) photons due to Compton-scattering off free electrons with non-zero bulk velocity - is an ideal tool to probe the abundance and distribution of baryons in the Universe. All kSZ measurements to date have explicitly required spectroscopic redshifts. Here, we implement a novel estimator for the kSZ - large-scale structure cross-correlation based on projected fields: it does not require redshift estimates for individual objects, allowing kSZ measurements from large-scale imaging surveys for the first time. We apply this estimator to cleaned CMB temperature maps constructed from Planck and Wilkinson Microwave Anisotropy Probe data and a galaxy sample from the Wide-field Infrared Survey Explorer (WISE). We measure the kSZ effect at 3.8-4.5$\\sigma$ significance, depending on the use of additional WISE galaxy bias constraints. We verify that our measurements are robust to possible dust emission from the WISE galax...

  20. Non-Gaussian Signatures in the Temperature Fluctuation Observed by the WMAP

    CERN Document Server

    Park, C G

    2004-01-01

    We present results from the test of Gaussianity of the whole sky sub-degree scale CMB temperature anisotropy measured by the WMAP. We calculate the genus from the foreground-subtracted WMAP maps and measure the genus shift parameters defined at negative and positive threshold levels (\\Delta\

  1. Large-Scale Cosmic-Ray Anisotropy as a Probe of Interstellar Turbulence

    CERN Document Server

    Giacinti, Gwenael

    2016-01-01

    We calculate the large-scale cosmic-ray (CR) anisotropies predicted for a range of Goldreich-Sridhar (GS) and isotropic models of interstellar turbulence, and compare them with IceTop data. In general, the predicted CR anisotropy is not a pure dipole; the cold spots reported at 400 TeV and 2 PeV are consistent with a GS model that contains a smooth deficit of parallel-propagating waves and a broad resonance function, although some other possibilities cannot, as yet, be ruled out. In particular, isotropic fast magnetosonic wave turbulence can match the observations at high energy, but cannot accommodate an energy-dependence in the shape of the CR anisotropy. Our findings suggest that improved data on the large-scale CR anisotropy could provide a valuable probe of the properties - notably the power-spectrum - of the local interstellar turbulence.

  2. The giant arc statistics in the three year WMAP cosmological model

    CERN Document Server

    Li, G L; Jing, Y P; Mo, H J; Gao, L; Lin, W P

    2006-01-01

    We use high-resolution $N$-body simulations to investigate the optical depth of giant arcs with length-to-width ratio larger than 7.5 and 10 in the `standard' $\\LCDM$ model with $\\sigma_8=0.9$ and $\\Omega_{\\rm m,0}=0.3$ and a model based on three-year Wilkinson Microwave Anisotropy Probe (WMAP) data. We find that, in dark-matter only simulations, the lensing probability in the three-year WMAP model (with $\\sigma_8=0.74$ and $\\Omega_{\\rm m,0}=0.238)$ decreases by a factor of $\\sim 6$ compared with that in the `standard' $\\LCDM$ model. The effects of baryonic cooling, star formation and feedbacks are uncertain, but we argue that baryons will only increase the the lensing cross-section by a moderate factor, $\\sim 2$. We conclude that the low central value of $\\sigma_8$ and $\\Omega_{\\rm m,0}$ preferred by the WMAP three-year data may be too low to be compatible with observations if conventional assumptions of the background source population are correct.

  3. Concordance of Kinematics and Lensing of Elliptical Galaxies with WMAP Cosmology

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    We explore degeneracies in strong lensing model so to make time delay data consistent with the WMAP (Wilkinson Microwave Anisotropy Probe) cosmology. Previous models using a singular isothermal lens often yield a time delay between the observed multiple images too small than the observed value if we "hardwire" the now widely quoted post-WMAP "high" value of the Hubble constant (H0 ~ 71 ± 4 km s-1 Mpc-1). Alternatively, the lens density profile (star plus dark matter) is required to be locally steeper than r-2 (isothermal) profile near the Einstein radius (of the order 3 kpc) to fit the time delays; a naive extrapolation of a very steep profile to large radius would imply a lens halo with a scale length of the order only 3 kpc, too compact to be consistent with CDM. We explore more sophisticated, mathematically smooth, positive lens mass density profiles which are consistent with a large halo and the post-WMAP H0. Thanks to the spherical monopole degeneracy, the "reshuffling" of the mass in a lens model does not affect the quality of the fit to the image positions, amplifications, and image time delays. Even better, unlike the better-known mass sheet degeneracy, the stellar mass-to-light and the H0 value are not affected either. We apply this monopole degeneracy to the quadruple imaged time-delay system PG 1115+080. Finally we discuss the implications of the time delay data on the newly proposed relativistic MOND theory.

  4. The Optical Design and Characterization of the Microwave Anisotropy Probe

    CERN Document Server

    Page, L; Barnes, C; Bennett, C; Halpern, M; Hinshaw, G; Jarosik, N C; Kogut, A J; Limon, M; Meyer, S S; Spergel, D N; Tucker, G S; Wilkinson, D T; Wollack, E; Wright, E L

    2003-01-01

    The primary goal of the MAP satellite, now in orbit, is to make high fidelity polarization sensitive maps of the full sky in five frequency bands between 20 and 100 GHz. From these maps we will characterize the properties of the cosmic microwave background (CMB) anisotropy and Galactic and extragalactic emission on angular scales ranging from the effective beam size, <0.23 degree, to the full sky. MAP is a differential microwave radiometer. Two back-to-back shaped offset Gregorian telescopes feed two mirror symmetric arrays of ten corrugated feeds. We describe the prelaunch design and characterization of the optical system, compare the optical models to the measurements, and consider multiple possible sources of systematic error.

  5. Rotational Doppler Effect: A Probe for Molecular Orbitals Anisotropy.

    Science.gov (United States)

    Miao, Quan; Travnikova, Oksana; Gel'mukhanov, Faris; Kimberg, Victor; Sun, Yu-Ping; Thomas, T Darrah; Nicolas, Christophe; Patanen, Minna; Miron, Catalin

    2015-05-01

    The vibrationally resolved X-ray photoelectron spectra of X2Σg+(3σg−1) and B2Σu+(2σu−1) states of N2+ were recorded for different photon energies and orientations of the polarization vector. Clear dependencies of the spectral line widths on the X-ray polarization as well as on the symmetry of the final electronic states are observed. Contrary to the translational Doppler, the rotational Doppler broadening is sensitive to the photoelectron emission anisotropy. On the basis of theoretical modeling, we suggest that the different rotational Doppler broadenings observed for gerade and ungerade final states result from a Young's double-slit interference phenomenon.

  6. Rotational Doppler Effect: A Probe for Molecular Orbitals Anisotropy.

    Science.gov (United States)

    Miao, Quan; Travnikova, Oksana; Gel'mukhanov, Faris; Kimberg, Victor; Sun, Yu-Ping; Thomas, T Darrah; Nicolas, Christophe; Patanen, Minna; Miron, Catalin

    2015-05-01

    The vibrationally resolved X-ray photoelectron spectra of X2Σg+(3σg−1) and B2Σu+(2σu−1) states of N2+ were recorded for different photon energies and orientations of the polarization vector. Clear dependencies of the spectral line widths on the X-ray polarization as well as on the symmetry of the final electronic states are observed. Contrary to the translational Doppler, the rotational Doppler broadening is sensitive to the photoelectron emission anisotropy. On the basis of theoretical modeling, we suggest that the different rotational Doppler broadenings observed for gerade and ungerade final states result from a Young's double-slit interference phenomenon. PMID:26263315

  7. Probing pre-inflationary anisotropy with directional variations in the gravitational wave background

    CERN Document Server

    Furuya, Yu; Sendouda, Yuuiti

    2016-01-01

    We perform a detailed analysis on a primordial gravitational-wave background amplified during a Kasner-like pre-inflationary phase allowing for general triaxial anisotropies. It is found that the predicted angular distribution map of gravitational-wave intensity on large scales exhibits topologically distinctive patterns according to the degree of the pre-inflationary anisotropy, thereby serving as a potential probe for the pre-inflationary early universe with future all-sky observations of gravitational waves. We also derive an observational limit on the amplitude of such anisotropic gravitational waves from the B-mode polarisation of the cosmic microwave background.

  8. Probing Ricci dark energy model with perturbations by using WMAP seven-year cosmic microwave background measurements, BAO and Type Ia supernovae

    CERN Document Server

    Wang, Yuting; Gui, Yuanxing; 10.1103/PhysRevD.84.063513

    2011-01-01

    In this paper, we investigate the Ricci dark energy model with perturbations through the joint constraints of current cosmological data sets from dynamical and geometrical perspectives. We use the full cosmic microwave background information from WMAP seven-year data, the baryon acoustic oscillations from the Sloan Digital Sky Survey and the Two Degree Galaxy Redshift Survey, and type Ia supernovae from the Union2 compilation of the Supernova Cosmology Project Collaboration. A global constraint is performed by employing the Markov chain Monte Carlo method. With the best-fitting results, we show the differences of cosmic microwave background power spectra and background evolutions for the cosmological constant model and Ricci dark energy model with perturbations.

  9. Brane inflation and the WMAP data: a Bayesian analysis

    CERN Document Server

    Lorenz, Larissa; Ringeval, Christophe

    2007-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) constraints on string inspired ``brane inflation'' are investigated. Here, the inflaton field is interpreted as the distance between two branes placed in a flux-enriched background geometry and has a Dirac-Born-Infeld (DBI) kinetic term. Our method relies on an exact numerical integration of the inflationary power spectra coupled to a Markov-Chain Monte-Carlo exploration of the parameter space. This analysis is valid for any perturbative value of the string coupling constant and of the string length, and includes a phenomenological modelling of the reheating era to describe the post-inflationary evolution. It is found that the data favour a scenario where inflation stops by violation of the slow-roll conditions well before brane annihilation, rather than by tachyonic instability. Concerning the background geometry, it is established that log(v) > -10 at 95% confidence level (CL), where "v" is the dimensionless ratio of the five-dimensional sub-manifold at the ba...

  10. Do We Live in a Vanilla Universe? Theoretical Perspectives on WMAP

    Science.gov (United States)

    Easther, Richard

    2004-02-01

    I discuss the theoretical implications of the WMAP results, stressing WMAP's detection of a correlation between the E-mode polarization and temperature anisotropies, which provides strong support for the overall inflationary paradigm. I point out that almost all inflationary models have a ``vanilla limit,'' where their parameters cannot be distinguished from a genuinely de Sitter inflationary phase. Because its findings are consistent with vanilla inflation, WMAP cannot exclude entire classes of inflationary models. Finally, I summarize hints in the current dataset that the CMB contains relics of new physics, and the possibility that we can use observational data to reconstruct the inflaton potential.

  11. Do We Live in a Vanilla Universe? Theoretical Perspectives on WMAP

    CERN Document Server

    Easther, R

    2003-01-01

    I discuss the theoretical implications of the WMAP results, stressing WMAP's detection of a correlation between the E-mode polarization and temperature anisotropies, which provides strong support for the overall inflationary paradigm. I point out that almost all inflationary models have a ``vanilla limit,'' where their parameters cannot be distinguished from a genuinely de Sitter inflationary phase. Because its findings are consistent with vanilla inflation, WMAP cannot exclude entire classes of inflationary models. Finally, I summarize hints in the current dataset that the CMB contains relics of new physics, and the possibility that we can use observational data to reconstruct the inflaton potential.

  12. Anisotropies of gravitational-wave standard sirens as a new cosmological probe without redshift information

    Science.gov (United States)

    Nishizawa, Atsushi; Namikawa, Toshiya; Taruya, Atsushi

    2016-03-01

    Gravitational waves (GWs) from compact binary stars at cosmological distances are promising and powerful cosmological probes, referred to as the GW standard sirens. With future GW detectors, we will be able to precisely measure source luminosity distances out to a redshift z 5. To extract cosmological information, previous studies using the GW standard sirens rely on source redshift information obtained through an extensive electromagnetic follow-up campaign. However, the redshift identification is typically time-consuming and rather challenging. Here we propose a novel method for cosmology with the GW standard sirens free from the redshift measurements. Utilizing the anisotropies of the number density and luminosity distances of compact binaries originated from the large-scale structure, we show that (i) this anisotropies can be measured even at very high-redshifts (z = 2), (ii) the expected constraints on the primordial non-Gaussianity with Einstein Telescope would be comparable to or even better than the other large-scale structure probes at the same epoch, (iii) the cross-correlation with other cosmological observations is found to have high-statistical significance. A.N. was supported by JSPS Postdoctoral Fellowships for Research Abroad No. 25-180.

  13. Star Formation in Massive Clusters via the Wilkinson Microwave Anisotropy Probe and the Spitzer Glimpse Survey

    CERN Document Server

    Murray, N W

    2009-01-01

    We use the WMAP maximum entropy method foreground emission map combined with previously determined distances to giant HII regions to measure the free-free flux at Earth and the free-free luminosity of the galaxy. We find a total flux f_\

  14. The Maneuver Planning Process for the Microwave Anisotropy Probe (MAP) Mission

    Science.gov (United States)

    Mesarch, Michael A.; Andrews, Stephen F.; Bauer, Frank (Technical Monitor)

    2002-01-01

    The Microwave Anisotropy Probe (MAP) mission utilized a strategy combining highly eccentric phasing loops with a lunar gravity assist to provide a zero-cost insertion into a Lissajous orbit about the Sun-Earth/Moon L2 point. Maneuvers were executed at the phasing loop perigees to correct for launch vehicle errors and to target the lunar gravity assist so that a suitable orbit at L2 was achieved. This paper will discuss the maneuver planning process for designing, verifying, and executing MAP's maneuvers. This paper will also describe how commercial off-the-shelf (COTS) tools were used to execute these tasks and produce a command sequence ready for upload to the spacecraft. These COTS tools included Satellite Tool Kit, MATLAB, and Matrix-X.

  15. The Microwave Anisotropy Probe (MAP) Guidance, Navigation, and Control Hardware Suite

    Science.gov (United States)

    Ward, David K.; Davis, Gary T.; O'Donnell, James R., Jr.

    2002-01-01

    The on-orbit success of the Microwave Anisotropy Probe (MAP) Guidance, Navigation, and Control System can partially be attributed to the performance of a hardware suite chosen to meet the complex attitude determination and control requirements of the mission. To meet these requirements, a diverse set of components was used. The set included two Lockheed Martin AST-201 star trackers, two Kearfott Two-Axis Rate Assemblies mounted to provide X, Y and redundant Z-axis rates, two Adcole Digital Sun Sensor heads sharing one set of electronics, twelve Adcole Coarse Sun Sensor eyes, three Ithaco E-sized Reaction Wheel Assemblies, a Propulsion Subsystem that employed eight Primex Rocket Engine Modules, and a pair of Goddard-designed Attitude Control Electronics which connect all of the components to the spacecraft processor. The performance of this hardware is documented, as are some of the spacecraft accommodations and lessons learned that came from working with this particular set of hardware.

  16. Anisotropy and probe-medium interactions in the microrheology of nematic fluids.

    Energy Technology Data Exchange (ETDEWEB)

    Cordoba, Andres; Stieger, Tillmann; Mazza, Marco G.; Schoen, Martin; de Pablo, Juan J.

    2016-01-01

    A theoretical formalism is presented to analyze and interpret microrheology experiments in anisotropic fluids with nematic order. The predictions of that approach are examined in the context of a simple coarse-grained molecular model which is simulated using nonequilibrium molecular dynamics calculations. The proposed formalism is used to study the effect of confinement, the type of anchoring at the probe-particle surface, and the strength of the nematic field on the rheological response functions obtained from probe-particle active microrheology. As expected, a stronger nematic field leads to increased anisotropy in the rheological response of the material. It is also found that the defect structures that arise around the probe particle, which are determined by the type of anchoring and the particle size, have a significant effect on the rheological response observed in microrheology simulations. Independent estimates of the bulk dynamic modulus of the model nematic fluid considered here are obtained from small-amplitude oscillatory shear simulations with Lees Edwards boundary conditions. The results of simulations indicate that the dynamic modulus extracted from particle-probe microrheology is different from that obtained in the absence of the particle, but that the differences decrease as the size of the defect also decreases. Importantly, the results of the nematic microrheology theory proposed here are in much closer agreement with simulations than those from earlier formalisms conceived for isotropic fluids. As such, it is anticipated that the theoretical framework advanced in this study could provide a useful tool for interpretation of microrheology experiments in systems such as liquid crystals and confined macromolecular solutions or gels.

  17. Mechanical anisotropy and adaptation of metastatic cells probed by magnetic microbeads

    Science.gov (United States)

    Zhang, Zhipeng; Shi, Yanhui; Jhiang, Sissy M.; Menq, Chia-Hsiang

    2010-02-01

    Metastatic cells have the ability to break through the basal lamina, enter the blood vessels, circulate through the vasculature, exit at distant sites, and form secondary tumors. This multi-step process, therefore, clearly indicates the inherent ability of metastatic cells to sense, process, and adapt to the mechanical forces in different surrounding environments. We describe a magnetic probing device that is useful in characterizing the mechanical properties of cells along arbitrary two-dimensional directions. Magnetic force, with the advantages of biocompatibility and specificity, was produced by magnetic poles placed in an octupole configuration and applied to fibronectin-coated magnetic microbeads attached on cell membrane. Cell deformation in response to the applied force was then recorded through the displacement of the microbeads. The motion of the beads was measured by computer processing the video images acquired by a high-speed CMOS camera. Rotating force vectors with constant magnitude while pointing to directions of all 360 degrees were applied to study the mechanical anisotropy of metastatic breast cancer cells MDA-MB-231. The temporal changes in magnitude and directionality of the cellular responses were then analyzed to investigate the cellular adaptation to force stimulation. This probing technology thus has the potential to provide us a better understanding of the mechano-signatures of cells.

  18. On the origin of the cosmic microwave background anisotropies

    OpenAIRE

    Follop, Ria; Rassat, Anais; Cooray, Asantha; Abdalla, Filipe B.

    2007-01-01

    Suggestions have been made that the microwave background observed by COBE and WMAP and dubbed Cosmic Microwave Background (CMB) may have an origin within our own Galaxy or Earth. To consider the signal that may be correlated with Earth, a correlate-by-eye exercise was attempted by overlaying the CMB map from Wilkinson Microwave Anisotropy Probe on a topographical map of Earth. Remarkably, several hot spots in the CMB map are found to be well aligned with either large cities on Earth or region...

  19. The Microwave Anisotropy Probe (MAP): Guidance, Navigation, and Control Hardware Suite

    Science.gov (United States)

    Ward, David K.; Davis, Gary T.; Bauer, Frank H. (Technical Monitor)

    2002-01-01

    The Microwave Anisotropy Probe (MAP) was launched June 30, 2001 to create an all-sky map of the Cosmic Microwave Background. The mission's hardware suite included two Lockheed Martin AST-201 star trackers, two Kearfott Two-Axis Rate Assemblies (TARAs) mounted to provide X, Y and redundant Z-axis rates, two Adcole Digital Sun Sensor (DSS) heads sharing one set of electronics, twelve Adcole Coarse Sun Sensor (CSS) eyes, three Ithaco E-sized Reaction Wheel Assemblies (RWAs), and a Propulsion Subsystem that employed eight PRIMEX Rocket Engine Modules (REMs). This hardware has allowed MAP to meet its various Orbit and Attitude Control Requirements, including performing a complex zero-momentum scan, meeting its attitude determination requirements, and maintaining a trajectory that places MAP in a lissajous orbit around the second Sun-Earth Lagrange point (L2) via phasing loops and a lunar gravity assist. Details of MAP's attitude determination, attitude control, and trajectory design are presented separately. This paper will focus on the performance of the hardware components mentioned above, as well as the significant lessons learned through the use of these components. An emphasis will be placed on spacecraft design modifications that were needed to accommodate existing hardware designs into the MAP Observatory design.

  20. Constraints on single-field inflation with WMAP, SPT and ACT data — a last-minute stand before Planck

    International Nuclear Information System (INIS)

    We constrain models of single field inflation with the pre-Planck CMB data. The data used here is the 9-year Wilkinson Microwave Anisotropy Probe (WMAP) data, South Pole Telescope (SPT) data and Atacama Cosmology Telescope (ACT) data. By adding in running of spectral index parameter, we find that the χ2 is improved by a factor of Δχ2 = 8.44, which strongly indicates the preference of this parameter from current data. In addition, we find that the running of spectral index αs does not change very much even if we switch to different pivot scales, which suggests that the power law expansion of power spectrum is accurate enough till the 1st order term. Furthermore, we find that the joint constraints on r−ns give very tight constraints on single-field inflation models, and the models with power law potential φp can only survive if 0.9∼NL data to constrain the non-trivial sound speed cs. We find that the current constraint is dominated by the power spectrum constraints which have some inconsistency with the constraints from fNL. This poses important questions of consistency between power spectrum and bispectrum of WMAP data

  1. Stacking catalog sources in WMAP data

    CERN Document Server

    Schultz, Kasey W

    2011-01-01

    We stack WMAP 7-year temperature data around extragalactic point sources, showing that the profiles are consistent with WMAP's beam models, in disagreement with the findings of Sawangwit & Shanks (2010). These results require that the source sample's selection is not biased by CMB fluctuations. We compare profiles from sources in the standard WMAP catalog, the WMAP catalog selected from a CMB-free combination of data, and the NVSS catalog, and quantify the agreement with fits to simple parametric beam models. We estimate the biases in source profiles due to alignments with positive CMB fluctuations, finding them roughly consistent with those biases found with the WMAP standard catalog. Addressing those biases, we find source spectral indices significantly steeper than those used by WMAP, with strong evidence for spectral steepening above 61 GHz. Such changes modify the power spectrum correction required for unresolved point sources, and tend to weaken somewhat the evidence for deviation from a Harrison-Ze...

  2. Characterization of Residual Stresses in Ferrous Components by Magnetic Anisotropy Measurements Using a Hall Effect Sensor Array Probe

    Science.gov (United States)

    Lo, C. C. H.

    2011-06-01

    A new surface sensor probe comprising an angular array of Hall effect sensors has been developed for characterization of residual stresses in ferrous materials by means of stress-induced magnetic anisotropy measurements. The sensor probe applies a radially spreading ac magnetic field to a test sample, and detects stray fields in different directions simultaneously to determine the principal stress axes. In situ measurements were conducted on a annealed steel plate under four-point bending stresses to evaluate the probe performance. The ratio of stray field signals measured along and perpendicular to the stress axis varies linearly with the surface stress, indicating the possibility of characterizing residual stresses in ferrous components using the sensor array probe.

  3. Absence of significant cross-correlation between WMAP and SDSS

    CERN Document Server

    Lopez-Corredoira, M; Betancort-Rijo, J

    2010-01-01

    AIMS. Recently, several authors have claimed to detect a significant cross-correlation between microwave WMAP anisotropies and the SDSS galaxy distribution. We repeat these analyses determining different cross-correlation errors: re-sampling errors, and field-to-field fluctuations. The first type of errors make use of overlapping sky regions, while the second type use non-overlapping sky regions. METHODS. For the re-sampling errors we use bootstrap and jack-knife techniques. For the field-to-field fluctuations we use three methods: 1) evaluating the dispersion of the cross-correlation when correlating separated regions of WMAP with the original region of SDSS; 2) using mock Monte Carlo WMAP maps; 3) a new method (developed herein) which gives the error as an integral of the product of the self-correlations of each map. RESULTS. The average cross-correlation for b>30 deg. is significantly larger than the re-sampling errors--both jack-knife and bootstrap give similar results--but it is of the order of the field...

  4. Alignment Measurements of the Microwave Anisotropy Probe (MAP) Instrument in a Thermal/Vacuum Chamber Using Photogrammetry

    Science.gov (United States)

    Hill, Michael D.; Herrera, Acey A.; Crane, J. Allen; Packard, Edward A.; Aviado, Carlos; Sampler, Henry P.; Obenschain, Arthur (Technical Monitor)

    2000-01-01

    The Microwave Anisotropy Probe (MAP) Observatory, scheduled for a late 2000 launch, is designed to measure temperature fluctuations (anisotropy) and produce a high sensitivity and high spatial resolution (photogrammetry (PG) system was chosen to perform the measurements since it is a non-contact measurement system, the measurements can be made relatively quickly and accurately, and the photogrammetric camera can be operated remotely. The hardware and methods developed to perform the MAP alignment measurements using PG proved to be highly successful. The PG measurements met the desired requirements, enabling the desired deformations to be measured and even resolved to an order of magnitude smaller than the imposed requirements. Viable data were provided to the MAP Project for a full analysis of the on-orbit performance of the Instrument's microwave system.

  5. Transport anisotropy as a probe of the interstitial vortex state in superconductors with artificial pinning arrays

    Energy Technology Data Exchange (ETDEWEB)

    Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, Cynthia [Los Alamos National Laboratory

    2008-01-01

    We show using simulations that when interstitial vortices are present in superconductors with periodic pinning arrays, the transport in two perpendicular directions can be anisotropic. The degree of the anisotropy varies as a function of field due to the fact that the interstitial vortex lattice has distinct orderings at different matching fields. The anisotropy is most pronounced at the matching fields but persists at incommensurate fields, and it is most prominent for triangular, honeycomb, and kagome pinning arrays. Square pinning arrays can also show anisotropic transport at certain fields in spite of the fact that the perpendicular directions of the square pinning array are identical. We show that the anisotropy results from distinct vortex dynamical states and that although the critical depinning force may be lower in one direction, the vortex velocity above depinning may also be lower in the same direction for ranges of external drives where both directions are depinned. For honeycomb and kagome pinning arrays, the anisotropy can show multiple reversals as a function of field. We argue that when the pinning sites can be multiply occupied such that no interstitial vortices are present, the anisotropy is strongly reduced or absent.

  6. Direct probe of anisotropy in atom-molecule collisions via quantum scattering resonances

    CERN Document Server

    Klein, Ayelet; Skomorowski, Wojciech; Żuchowski, Piotr S; Pawlak, Mariusz; Janssen, Liesbeth M C; Moiseyev, Nimrod; van de Meerakker, Sebastiaan Y T; van der Avoird, Ad; Koch, Christiane P; Narevicius, Edvardas

    2016-01-01

    Anisotropy is a fundamental property of particle interactions. It occupies a central role in cold and ultra-cold molecular processes, where long range forces have been found to significantly depend on orientation in ultra-cold polar molecule collisions. Recent experiments have demonstrated the emergence of quantum phenomena such as scattering resonances in the cold collisions regime due to quantization of the intermolecular degrees of freedom. Although these states have been shown to be sensitive to interaction details, the effect of anisotropy on quantum resonances has eluded experimental observation so far. Here, we directly measure the anisotropy in atom-molecule interactions via quantum resonances by changing the quantum state of the internal molecular rotor. We observe that a quantum scattering resonance at a collision energy of $k_B$ x 270 mK appears in the Penning ionization of molecular hydrogen with metastable helium only if the molecule is rotationally excited. We use state of the art ab initio and ...

  7. Inflation after WMAP3: Confronting the Slow-Roll and Exact Power Spectra to CMB Data

    CERN Document Server

    Martín, J; Martin, Jerome; Ringeval, Christophe

    2006-01-01

    The implications of the WMAP (Wilkinson Microwave Anisotropy Probe) third year data for inflation are investigated using both the slow-roll approximation and an exact numerical integration of the inflationary power spectra including a phenomenological modelling of the reheating era. At slow-roll leading order, the constraints epsilon1 0 is observed. With regards to the exact numerical integration, large field models, V(phi) \\propto phi^p, with p > 3.1 are now excluded at 95% CL. Small field models, V(phi) \\propto 1-(phi/mu)^p, are still compatible with the data for all values of p. However, if mu/Mpl 1MeV at 95% CL and T_reh > 1TeV at 68% CL. Hybrid models are disfavoured by the data, the best fit model having \\Delta chi^2 = +5 with two extra parameters in comparison with large field models. Running mass models remain compatible, but no prior independent constraints can be obtained. Finally, superimposed oscillations of trans-Planckian origin are studied. The vanilla slow-roll model is still the most probab...

  8. Detection of Anomalous Microwave Emission in the Pleiades Reflection Nebula with WMAP and the COSMOSOMAS Experiment

    CERN Document Server

    Genova-Santos, R; Rubino-Martin, J A; Lopez-Caraballo, C H; Hildebrandt, S R

    2011-01-01

    We present evidence for anomalous microwave emission (AME) in the Pleiades reflection nebula, using data from the seven-year release of the Wilkinson Microwave Anisotropy Probe (WMAP) and from the COSMOSOMAS experiment. The flux integrated in a 1-degree radius around R.A.=56.24^{\\circ}, Dec.=23.78^{\\circ} (J2000) is 2.15 +/- 0.12 Jy at 22.8 GHz, where AME is dominant. COSMOSOMAS data show no significant emission, but allow to set upper limits of 0.94 and 1.58 Jy (99.7% C.L.) respectively at 10.9 and 14.7 GHz, which are crucial to pin down the AME spectrum at these frequencies, and to discard any other emission mechanisms which could have an important contribution to the signal detected at 22.8 GHz. We estimate the expected level of free-free emission from an extinction-corrected H-alpha template, while the thermal dust emission is characterized from infrared DIRBE data and extrapolated to microwave frequencies. When we deduct the contribution from these two components at 22.8 GHz the residual flux, associated...

  9. Baryons do trace dark matter 380,000 years after the big bang: Search for compensated isocurvature perturbations with WMAP 9-year data

    CERN Document Server

    Grin, Daniel; Holder, Gilbert; Doré, Olivier; Kamionkowski, Marc

    2014-01-01

    Primordial isocurvature fluctuations between photons and either neutrinos or non-relativistic species such as baryons or dark matter are known to be sub-dominant to adiabatic fluctuations. Perturbations in the relative densities of baryons and dark matter (known as compensated isocurvature perturbations, or CIPs), however, are surprisingly poorly constrained. CIPs leave no imprint in the cosmic microwave background (CMB) on observable scales, at least at linear order in their amplitude and zeroth order in the amplitude of adiabatic perturbations. It is thus not yet empirically known if baryons trace dark matter at the surface of last scattering. If CIPs exist, they would spatially modulate the Silk damping scale and acoustic horizon, causing distinct fluctuations in the CMB temperature/polarization power spectra across the sky: this effect is first order in both the CIP and adiabatic mode amplitudes. Here, temperature data from the Wilkinson Microwave Anisotropy Probe (WMAP) are used to conduct the first CMB-...

  10. Thermal Reflector System Design and Testing for the Microwave Anisotropy Probe

    OpenAIRE

    Neubert, Hans; Chen, Wayne

    2000-01-01

    Scheduled for a June 2001 launch, the Microwave Anisotropy Probe’s (MAP) mission is to study in detail the cosmic microwave background radiation temperature fluctuations of the universe. The cosmic microwave background is the remnant afterglow of the Big Bang, and the tiny temperature differences from place to place on the sky provides a wealth of information about the basic nature of our universe. The observatory consists of dual back-to-back Gregorian optics and dual differential pseudo-cor...

  11. Direct probe of anisotropy in atom-molecule collisions via quantum scattering resonances

    OpenAIRE

    Klein, Ayelet; Shagam, Yuval; Skomorowski, Wojciech; Żuchowski, Piotr. S.; Pawlak, Mariusz; Janssen, Liesbeth M. C.; Moiseyev, Nimrod; van de Meerakker, Sebastiaan Y. T.; van der Avoird, Ad; Koch, Christiane P.; Narevicius, Edvardas

    2016-01-01

    Anisotropy is a fundamental property of particle interactions. It occupies a central role in cold and ultra-cold molecular processes, where long range forces have been found to significantly depend on orientation in ultra-cold polar molecule collisions. Recent experiments have demonstrated the emergence of quantum phenomena such as scattering resonances in the cold collisions regime due to quantization of the intermolecular degrees of freedom. Although these states have been shown to be sensi...

  12. Probing the Light Speed Anisotropy with respect to the Cosmic Microwave Background Radiation Dipole

    CERN Document Server

    Gurzadyan, V G; Kashin, A L; Margarian, A T; Bartalini, O; Bellini, V; Castoldi, M; D'Angelo, A; Didelez, J P; Salvo, R D; Fantini, A; Gervino, G; Ghio, F; Girolami, B; Giusa, A; Hourany, E; Knyazyan, S; Kuznetsov, V E; Lapik, A; Levi-Sandri, P; Llères, A; Mehrabyan, S S; Moricciani, D; Nedorezov, V; Perrin, C; Rebreyend, D; Russo, G; Rudnev, N; Schärf, C; Sperduto, M L; Sutera, M C; Turinge, A

    2005-01-01

    We have studied the angular fluctuations in the speed of light with respect to the apex of the dipole of Cosmic Microwave Background (CMB) radiation using the experimental data obtained with GRAAL facility, located at the European Synchrotron Radiation Facility (ESRF) in Grenoble. The measurements were based on the stability of the Compton edge of laser photons scattered on the 6 GeV monochromatic electron beam. The results enable to obtain a conservative constraint on the anisotropy in the light speed variations \\Delta c(\\theta)/c < 3 10^{-12}, i.e. with higher precision than from previous experiments.

  13. Probing the epoch of pre-reionization by cross-correlating cosmic microwave and infrared background anisotropies

    CERN Document Server

    Atrio-Barandela, Fernando

    2014-01-01

    The epoch of first star formation and the state of the intergalactic medium (IGM) at that time are not directly observable with current telescopes. The radiation from those early sources is now part of the Cosmic Infrared Background (CIB) and, as these sources ionize the gas around them, the IGM plasma would produce faint temperature anisotropies in the Cosmic Microwave Background (CMB) via the thermal Sunyaev-Zeldovich (TSZ) effect. While these TSZ anisotropies are too faint to be detected, we show that the cross-correlation of maps of source-subtracted CIB fluctuations from {\\it Euclid}, with suitably constructed microwave maps at different frequencies can probe the physical state of the gas during reionization and test/constrain models of the early CIB sources. We identify the frequency-combined CMB-subtracted microwave maps from space and ground-based instruments to show that they can be cross-correlated with the forthcoming all-sky {\\it Euclid} CIB maps to detect the cross-power at scales $\\sim 5'-60'$ w...

  14. Ultrafast magneto-photocurrents as probe of anisotropy relaxation in GaAs

    CERN Document Server

    Schmidt, Christian B; Pierz, Klaus; Bieler, Mark

    2016-01-01

    We induce ultrafast photocurrents in a GaAs crystal exposed to a magnetic field by optical femtosecond excitation. The magneto-photocurrents are studied by time-resolved detection of the simultaneously emitted THz radiation. We find that their dynamics differ considerably from the dynamics of other photocurrents which are expected to follow the temporal shape of the optical intensity. We attribute this difference to the influence of carrier-anisotropy relaxation on the magneto-photocurrents. Our measurements show that the anisotropy relaxation for carrier densities ranging between $10^{16}$ cm$^{-3}$ and $5 \\times 10^{17}$ cm$^{-3}$ occurs on two different time scales. While the slow time constant is approximately 100 fs long and most likely governed by electron-phonon scattering, the fast time constant is on the order of 10 fs and presumably linked to the valence band. Our studies not only help to better understand the microscopic origins of optically induced currents but - being even more important - show t...

  15. A review of the stochastic background of gravitational waves in f(R) gravity with WMAP constrains

    CERN Document Server

    Corda, Christian

    2009-01-01

    This paper is a review of previous works on the stochastic background of gravitational waves (SBGWs) which has been discussed in various peer-reviewed journals and international conferences. The SBGWs is analyzed with the aid of the Wilkinson Microwave Anisotropy Probe (WMAP) data. We emphasize that, in general, in previous works in the literature about the SBGWs, old Cosmic Background Explorer (COBE) data were used. After this, we want to face the problem of how the SBGWs and f(R) gravity (where f(R) is a function of the Ricci scalar R) can be related, showing, vice versa, that a revealed SBGWs could be a powerful probe for a given theory of gravity. In this way, it will also be shown that the conform treatment of SBGWs can be used to parametrize in a natural way f(R) theories. Some interesting examples which have been recently discussed in the literature will be also analysed. The presence and the potential detection of the SBGWs is quite important in the framework of the debate on high-frequency gravitatio...

  16. Multi-resolution internal template cleaning: An application to the Wilkinson Microwave Anisotropy Probe 7-yr polarization data

    CERN Document Server

    Fernández-Cobos, R; Barreiro, R B; Martínez-González, E

    2012-01-01

    Cosmic microwave background (CMB) radiation data obtained by different experiments contain, besides the desired signal, a superposition of microwave sky contributions. We present a fast and robust method, using a wavelet decomposition on the sphere, to recover the CMB signal from microwave maps. An application to \\textit{WMAP} polarization data is presented, showing its good performance particularly in very polluted regions of the sky. The applied wavelet has the advantages of requiring little computational time in its calculations, being adapted to the \\textit{HEALPix} pixelization scheme, and offering the possibility of multi-resolution analysis. The decomposition is implemented as part of a fully internal template fitting method, minimizing the variance of the resulting map at each scale. In terms of residual levels of foregrounds, we get better results to those obtained by the \\textit{WMAP} team working in real space and with additional external data sets. Regarding the instrumental noise level in the cle...

  17. Size-dependent ligand layer dynamics in semiconductor nanocrystals probed by anisotropy measurements.

    Science.gov (United States)

    Hadar, Ido; Abir, Tsafrir; Halivni, Shira; Faust, Adam; Banin, Uri

    2015-10-12

    Colloidal semiconductor nanocrystals (NC) have reached a high level of synthetic control allowing the tuning of their properties, and their use in various applications. However, the surface of NCs and in particular their size-dependent capping organic ligand behavior, which play an important role in the NC synthesis, dispersibility, and optoelectronic properties, is still not well understood. We study the size-dependent properties of the ligand shell on the surface of NCs, by embedding surface bound dyes as a probe within the ligand shell. The reorientation times for these dyes show a linear dependence on the NC surface curvature indicating size-dependent change in viscosity, which is related to a change in the density of the ligand layer because of the geometry of the surface, a unique feature of NCs. Understanding the properties of the ligand shell will allow rational design of the surface to achieve the desired properties, providing an additional important knob for tuning their functionality.

  18. Local structure and magnetism of L10-type FeNi alloy films with perpendicular magnetic anisotropy studied through 57Fe nuclear probes

    International Nuclear Information System (INIS)

    The local structure and magnetism of FeNi alloy films prepared by alternate deposition of Fe and Ni monatomic layers, where perpendicular magnetic anisotropy has been observed, were investigated through 57Fe nuclear probes using Mössbauer spectroscopy. It was confirmed that the films are composed of L10-type ordered FeNi phase and A1-type disordered FeNi phase. For the films grown at 40–70 °C, which have no perpendicular anisotropy, the A1-disordered phase is dominant, whereas for the films grown at 100–190 °C, which have a stronger perpendicular anisotropy, the relative amount of the L10-ordered phase reaches 40% or more. It was clearly shown that the magnetic anisotropy of these films is strongly correlated with the local environments of Fe in the films. The results imply that if a further increase in the ratio of the L10-ordered phase is successfully achieved, one would obtain films with a stronger magnetic anisotropy applicable to perpendicular magnetic recording. (paper)

  19. Cosmological parameters from SDSS and WMAP

    CERN Document Server

    Tegmark, M; Bahcall, Neta A; Berlind, Andreas A; Blanton, M; Budavari, T; Connolly, A; Dodelson, S; Eisenstein, D J; Finkbeiner, D; Frieman, Joshua A; Gunn, J; Hoyle, F; Hui, L; Jain, B; Johnston, D; Kent, S; Lin, H; Nakajima, R; Nichol, R; Ostriker, J P; Pope, A; Sandvik, H; Schlegel, D J; Scoccimarro, R; Scranton, R; Seljak, U; Sheth, R; Stebbins, A; Strauss, M; Szalay, A S; Szapudi, I; Vogeley, M; Wang, X; Weinberg, D; Xu, Y; Zehavi, I

    2004-01-01

    We measure cosmological parameters using the three-dimensional power spectrum P(k) from over 200,000 galaxies in the Sloan Digital Sky Survey (SDSS) in combination with WMAP and other data. Our results are consistent with a ``vanilla'' flat adiabatic Lambda-CDM model without tilt (n=1), running tilt, tensor modes or massive neutrinos. Adding SDSS information more than halves the WMAP-only error bars on some parameters, tightening 1 sigma constraints on the Hubble parameter from h~0.74+0.18-0.07 to h~0.70+0.04-0.03, on the matter density from Omega_m~0.25+/-0.10 to Omega_m~0.30+/-0.04 (1 sigma) and on neutrino masses from <11 eV to <0.6 eV (95%). SDSS helps even more when dropping prior assumptions about curvature, neutrinos, tensor modes and the equation of state. Our results are in substantial agreement with the joint analysis of WMAP and the 2dF Galaxy Redshift Survey, which is an impressive consistency check with independent redshift survey data and analysis techniques. In this paper, we place partic...

  20. Bayesian analysis of anisotropic cosmologies: Bianchi VII_h and WMAP

    CERN Document Server

    McEwen, J D; Feeney, S M; Peiris, H V; Lasenby, A N

    2013-01-01

    We perform a definitive analysis of Bianchi VII_h cosmologies with WMAP observations of the cosmic microwave background (CMB) temperature anisotropies. Bayesian analysis techniques are developed to study anisotropic cosmologies using full-sky and partial-sky, masked CMB temperature data. We apply these techniques to analyse the full-sky internal linear combination (ILC) map and a partial-sky, masked W-band map of WMAP 9-year observations. In addition to the physically motivated Bianchi VII_h model, we examine phenomenological models considered in previous studies, in which the Bianchi VII_h parameters are decoupled from the standard cosmological parameters. In the two phenomenological models considered, Bayes factors of 1.7 and 1.1 units of log-evidence favouring a Bianchi component are found in full-sky ILC data. The corresponding best-fit Bianchi maps recovered are similar for both phenomenological models and are very close to those found in previous studies using earlier WMAP data releases. However, no evi...

  1. Confronting quasi-exponential inflation with WMAP seven

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Barun Kumar; Pal, Supratik; Basu, B., E-mail: barunp1985@rediffmail.com, E-mail: pal@th.physik.uni-bonn.de, E-mail: banasri@isical.ac.in [Physics and Applied Mathematics Unit, Indian Statistical Institute, 203 B.T. Road, Kolkata 700 108 (India)

    2012-04-01

    We confront quasi-exponential models of inflation with WMAP seven years dataset using Hamilton Jacobi formalism. With a phenomenological Hubble parameter, representing quasi exponential inflation, we develop the formalism and subject the analysis to confrontation with WMAP seven using the publicly available code CAMB. The observable parameters are found to fair extremely well with WMAP seven. We also obtain a ratio of tensor to scalar amplitudes which may be detectable in PLANCK.

  2. Joint Planck and WMAP Assessment of Low CMB Multipoles

    CERN Document Server

    Iqbal, Asif; Souradeep, Tarun; Malik, Manzoor A

    2015-01-01

    The remarkable progress in cosmic microwave background (CMB) studies over past decade has led to the era of precision cosmology in striking agreement with the $\\Lambda$CDM model. However, the lack of power in the CMB temperature anisotropies at large angular scales (low-$\\ell$), as has been confirmed by the recent Planck data also (up to $\\ell=40$), is still an open problem. One can avoid to seek an explanation for this problem by attributing the lack of power to cosmic variance or can look for explanations i.e., different inflationary potentials or initial conditions for inflation to begin with, non-trivial topology, ISW effect etc. Features in the primordial power spectrum (PPS) motivated by the early universe physics has been the most common solution to address this problem. In the present work we also follow this approach and consider a set of PPS which have features and constrain the parameters of those using WMAP 9 year and Planck data employing Markov-Chain Monte Carlo (MCMC) analysis. The prominent fe...

  3. A map of the cosmic microwave background radiation from the Wilkinson Microwave Anisotropy Probe (WMAP), showing the large-scale fluctuations (the quadrupole and octopole) isolated by an analysis done partly by theorists at CERN.

    CERN Multimedia

    2004-01-01

    A recent analysis, in part by theorists working at CERN, suggests a new view of the cosmic microwave background radiation. It seems the solar system, rather than the universe, causes the radiation's large-scale fluctuations, similar to the bass in a song.

  4. Detection of Anomalous Microwave Emission in the Pleiades Reflection Nebula with Wilkinson Microwave Anisotropy Probe and the COSMOSOMAS Experiment

    Science.gov (United States)

    Génova-Santos, R.; Rebolo, R.; Rubiño-Martín, J. A.; López-Caraballo, C. H.; Hildebrandt, S. R.

    2011-12-01

    We present evidence for anomalous microwave emission (AME) in the Pleiades reflection nebula, using data from the seven-year release of the Wilkinson Microwave Anisotropy Probe and from the COSMOSOMAS (Cosmological Structures on Medium Angular Scales) experiment. The flux integrated in a 1° radius around R.A. = 56fdg24, decl. = 23fdg78 (J2000) is 2.15 ± 0.12 Jy at 22.8 GHz, where AME is dominant. COSMOSOMAS data show no significant emission, but allow one to set upper limits of 0.94 and 1.58 Jy (99.7% confidence level), respectively, at 10.9 and 14.7 GHz, which are crucial to pin down the AME spectrum at these frequencies, and to discard any other emission mechanisms which could have an important contribution to the signal detected at 22.8 GHz. We estimate the expected level of free-free emission from an extinction-corrected Hα template, while the thermal dust emission is characterized from infrared DIRBE data and extrapolated to microwave frequencies. When we deduct the contribution from these two components at 22.8 GHz, the residual flux, associated with AME, is 2.12 ± 0.12 Jy (17.7σ). The spectral energy distribution from 10 to 60 GHz can be accurately fitted with a model of electric dipole emission from small spinning dust grains distributed in two separated phases of molecular and atomic gas, respectively. The dust emissivity, calculated by correlating the 22.8 GHz data with 100 μm data, is found to be 4.36 ± 0.17 μK (MJy sr-1)-1, a value considerably lower than in typical AME clouds, which present emissivities of ~20 μK (MJy sr-1)-1, although higher than the 0.2 μK (MJy sr-1)-1 of the translucent cloud LDN 1780, where AME has recently been claimed. The physical properties of the Pleiades nebula, in particular its low extinction A V ~ 0.4, indicate that this is indeed a much less opaque object than those where AME has usually been studied. This fact, together with the broad knowledge of the stellar content of this region, provides an excellent

  5. DETECTION OF ANOMALOUS MICROWAVE EMISSION IN THE PLEIADES REFLECTION NEBULA WITH WILKINSON MICROWAVE ANISOTROPY PROBE AND THE COSMOSOMAS EXPERIMENT

    Energy Technology Data Exchange (ETDEWEB)

    Genova-Santos, R.; Rebolo, R.; Rubino-Martin, J. A.; Lopez-Caraballo, C. H.; Hildebrandt, S. R. [Instituto de Astrofisica de Canarias, C/Via Lactea s/n, E-38200 La Laguna, Tenerife (Spain)

    2011-12-10

    We present evidence for anomalous microwave emission (AME) in the Pleiades reflection nebula, using data from the seven-year release of the Wilkinson Microwave Anisotropy Probe and from the COSMOSOMAS (Cosmological Structures on Medium Angular Scales) experiment. The flux integrated in a 1 Degree-Sign radius around R.A. = 56.{sup 0}24, decl. = 23.{sup 0}78 (J2000) is 2.15 {+-} 0.12 Jy at 22.8 GHz, where AME is dominant. COSMOSOMAS data show no significant emission, but allow one to set upper limits of 0.94 and 1.58 Jy (99.7% confidence level), respectively, at 10.9 and 14.7 GHz, which are crucial to pin down the AME spectrum at these frequencies, and to discard any other emission mechanisms which could have an important contribution to the signal detected at 22.8 GHz. We estimate the expected level of free-free emission from an extinction-corrected H{alpha} template, while the thermal dust emission is characterized from infrared DIRBE data and extrapolated to microwave frequencies. When we deduct the contribution from these two components at 22.8 GHz, the residual flux, associated with AME, is 2.12 {+-} 0.12 Jy (17.7{sigma}). The spectral energy distribution from 10 to 60 GHz can be accurately fitted with a model of electric dipole emission from small spinning dust grains distributed in two separated phases of molecular and atomic gas, respectively. The dust emissivity, calculated by correlating the 22.8 GHz data with 100 {mu}m data, is found to be 4.36 {+-} 0.17 {mu}K (MJy sr{sup -1}){sup -1}, a value considerably lower than in typical AME clouds, which present emissivities of {approx}20 {mu}K (MJy sr{sup -1}){sup -1}, although higher than the 0.2 {mu}K (MJy sr{sup -1}){sup -1} of the translucent cloud LDN 1780, where AME has recently been claimed. The physical properties of the Pleiades nebula, in particular its low extinction A{sub V} {approx} 0.4, indicate that this is indeed a much less opaque object than those where AME has usually been studied. This fact

  6. Light element evolution resulting from WMAP data

    CERN Document Server

    Romano, D; Matteucci, F; Chiappini, C; Romano, Donatella; Tosi, Monica; Matteucci, Francesca; Chiappini, Cristina

    2003-01-01

    The recent determination of the baryon-to-photon ratio from WMAP data by Spergel et al. (2003) allows one to fix with unprecedented precision the primordial abundances of the light elements D, 3He, 4He and 7Li in the framework of the standard model of big bang nucleosynthesis. We adopt these primordial abundances and discuss the implications for Galactic chemical evolution, stellar evolution and nucleosynthesis of the light elements. The model predictions on D, 3He and 4He are in excellent agreement with the available data, while a significant depletion of 7Li in low-metallicity stars is required to reproduce the Spite plateau.

  7. Anisotropy of weakly vibrated granular flows.

    Science.gov (United States)

    Wortel, Geert H; van Hecke, Martin

    2015-10-01

    We experimentally probe the anisotropy of weakly vibrated flowing granular media. Depending on the driving parameters-flow rate and vibration strength-this anisotropy varies significantly. We show how the anisotropy collapses when plotted as a function of the driving stresses, uncovering a direct link between stresses and anisotropy. Moreover, our data suggest that for small anisotropies, the shear stresses vanish. Anisotropy of the fabric of granular media thus plays a crucial role in determining the rheology of granular flows. PMID:26565148

  8. Anisotropy of Weakly Vibrated Granular Flows

    OpenAIRE

    Wortel, Geert; Van Hecke, Martin

    2014-01-01

    We experimentally probe the anisotropy of the fabric of weakly vibrated, flowing granular media. Depending on the driving parameters --- flow rate and vibration strength --- this anisotropy varies significantly. We show how the anisotropy collapses when plotted as function of the driving stresses, uncovering a direct link between stresses and anisotropy. Moreover, our data suggests that for small anisotropies, the shear stresses vanish. Anisotropy of the fabric of granular media thus plays a ...

  9. Cosmological Constraints Using Planck 2015 and WMAP Data

    Science.gov (United States)

    Bennett, Charles

    We propose to use the newly released 2015 Planck mission data to address the questions: (1) How does Planck CMB lensing impact the optical depth and other parameter constraints? (2) Is the WMAP-derived optical depth too high? (3) Are the WMAP and Planck power spectra consistent? (4) Are the WMAP and Planck LCDM parameter constraints consistent? (5) Can the WMAP and Planck foreground model discrepancies be resolved? While the WMAP and Planck CMB cosmology data sets are broadly consistent with each another, important differences exist. For example, we previously determined that the six LCDM parameters inferred from the 2013 Planck data and the 9-year WMAP data differed by ~6-sigma. The newly-released 2015 Planck power spectrum has shifted from the 2013 spectrum by ~4-sigma, and may have reduced the tension with WMAP. We propose to quantify this reduction and, if possible, combine CMB and other cosmological data to determine the best evidence-based LCDM model parameters. If significant differences persist they may indicate experimental systematic effects or signal new physics. One new area of tension with the 2015 Planck data is the determination of the optical depth to scattering of CMB photons. The optical depth inferred from Planck polarization data is somewhat lower than that inferred from WMAP. When the Planck team uses CMB lensing to constrain the optical depth they obtain an even-lower value, in tension with the optical depth derived from CMB polarization data. We propose to independently assess these results. The foreground emission models inferred by the 2015 Planck and WMAP teams are substantially different. We propose to incorporate new Planck data in the three codes we used to produce foreground models in the 9-year WMAP release. This will allow us to understand if the model differences arise from differences in the data or from differences in the model assumptions made by each team. We will re-run the WMAP likelihood with the Planck lensing band

  10. Bayesian analysis of sparse anisotropic universe models and application to the 5-yr WMAP data

    CERN Document Server

    Groeneboom, Nicolaas E

    2008-01-01

    We extend the previously described CMB Gibbs sampling framework to allow for exact Bayesian analysis of anisotropic universe models, and apply this method to the 5-year WMAP temperature observations. This involves adding support for non-diagonal signal covariance matrices, and implementing a general spectral parameter MCMC sampler. As a worked example we apply these techniques to the model recently introduced by Ackerman et al., describing for instance violations of rotational invariance during the inflationary epoch. After verifying the code with simulated data, we analyze the foreground-reduced 5-year WMAP temperature sky maps. For l < 400 and the W-band data, we find tentative evidence for a preferred direction pointing towards (l,b) = (110 deg, 10 deg) with an anisotropy amplitude of g* = 0.15 +- 0.039, nominally equivalent to a 3.8 sigma detection. Similar results are obtained from the V-band data [g* = 0.11 +- 0.039; (l,b) = (130 deg, 20 deg)]. Further, the preferred direction is stable with respect ...

  11. Doppler broadening of positron annihilation radiation as a probe for the anisotropy of free-volume-holes in polymers

    Energy Technology Data Exchange (ETDEWEB)

    Palacio, C.A. [Ghent Univ. (Belgium). Dept. Subatomic and Radiation Physics; Institute of Physics, University of Antioquia, Medellin (Colombia); Djourelov, N. [Ghent Univ. (Belgium). Dept. Subatomic and Radiation Physics; Institute of Nuclear Research and Nuclear Energy, Sofia (Bulgaria); Kuriplach, J. [Department of Low Temperature Physics, Faculty of Mathematics and Physics, Charles Univ., Prague (Czech Republic); Dauwe, C.; Segers, D. [Ghent Univ. (Belgium). Dept. Subatomic and Radiation Physics; Laforest, N. [LMOPS, Universite de Savoie, Le Bourget du Lac (France)

    2007-07-01

    Doppler broadening of annihilation radiation (DBAR) measurements have been performed in uniaxially hot-drawn poly(methylmethacrylate) (PMMA) samples. The DBAR spectra were deconvoluted into three Gaussians. The full width at half-maximum of the narrow component which is due to para-Positronium (p-Ps) self-annihilation is under discussion. An anisotropy of the free volume holes (FVHs) has been detected by measuring the deformed samples at the stretching and transverse directions. The sample deformed at 280% was also measured as a function of the orientation angle (0 -90 ) with respect to the stretching direction. The momentum distribution of p-Ps, which is considered as a structureless particle confined in FVH of ellipsoidal or cuboid shape, was calculated as a function of the potential well size and depth and compared with experiment. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Probing the Cosmic X-Ray and MeV Gamma-Ray Background Radiation through the Anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, Yoshiyuki [Stanford Univ., CA (United States). Kavli Inst. for Particle Astrophysics and Cosmology; SLAC National Accelerator Lab., Menlo Park, CA (United States); Murase, Kohta [Inst. for Advanced Study, Princeton, NJ (United States). School of Natural Sciences; Madejski, Grzegorz M. [Stanford Univ., CA (United States). Kavli Inst. for Particle Astrophysics and Cosmology; SLAC National Accelerator Lab., Menlo Park, CA (United States); Uchiyama, Yasunobu [Stanford Univ., CA (United States). Kavli Inst. for Particle Astrophysics and Cosmology; SLAC National Accelerator Lab., Menlo Park, CA (United States); Rikkyo Univ., Tokyo (Japan). Dept. of Physics

    2013-09-24

    While the cosmic soft X-ray background is very likely to originate from individual Seyfert galaxies, the origin of the cosmic hard X-ray and MeV gamma-ray background is not fully understood. It is expected that Seyferts including Compton thick population may explain the cosmic hard X-ray background. At MeV energy range, Seyferts having non-thermal electrons in coronae above accretion disks or MeV blazars may explain the background radiation. We propose that future measurements of the angular power spectra of anisotropy of the cosmic X-ray and MeV gamma-ray backgrounds will be key to deciphering these backgrounds and the evolution of active galactic nuclei (AGNs). As AGNs trace the cosmic large-scale structure, spatial clustering of AGNs exists. We show that e-ROSITA will clearly detect the correlation signal of unresolved Seyferts at 0.5-2 keV and 2-10 keV bands and will be able to measure the bias parameter of AGNs at both bands. Once the future hard X-ray all sky satellites achieve the sensitivity better than 10-12 erg/cm2/s-1 at 10-30 keV or 30-50 keV - although this is beyond the sensitivities of current hard X-ray all sky monitors - angular power spectra will allow us to independently investigate the fraction of Compton-thick AGNs in all Seyferts. We also find that the expected angular power spectra of Seyferts and blazars in the MeV range are different by about an order of magnitude, where the Poisson term, so-called shot noise, is dominant. Current and future MeV instruments will clearly disentangle the origin of the MeV gamma-ray background through the angular power spectrum.

  13. On the origin of the cosmic microwave background anisotropies

    CERN Document Server

    Follop, Ria; Cooray, Asantha; Abdalla, Filipe B

    2007-01-01

    Suggestions have been made that the microwave background observed by COBE and WMAP and dubbed Cosmic Microwave Background (CMB) may have an origin within our own Galaxy or Earth. To consider the signal that may be correlated with Earth, a correlate-by-eye exercise was attempted by overlaying the CMB map from Wilkinson Microwave Anisotropy Probe on a topographical map of Earth. Remarkably, several hot spots in the CMB map are found to be well aligned with either large cities on Earth or regions of high altitude. To further study the correlations between Earth and CMB, we performed a complicated cross-correlation analysis in the multipole space. The overall correlations are detected at more than 5 sigma confidence level. These results can be naively interpreted to suggest that large angular scale fluctuations in CMB are generated on Earth by a process that traces the altitude relative to a mean radius. Simply extending our analysis, we suggest that cross-correlations between CMB and any other map of a Solar sys...

  14. CMBfit: Rapid WMAP likelihood calculations with normal parameters

    CERN Document Server

    Sandvik, H B; Wang, X; Zaldarriaga, M; Sandvik, Havard B.; Tegmark, Max; Wang, Xiaomin; Zaldarriaga, Matias

    2004-01-01

    We present a method for ultra-fast confrontation of the WMAP cosmic microwave background observations with theoretical models, implemented as a publicly available software package called CMBfit, useful for anyone wishing to measure cosmological parameters by combining WMAP with other observations. The method takes advantage of the underlying physics by transforming into a set of parameters where the WMAP likelihood surface is accurately fit by the exponential of a quartic or sextic polynomial. Building on previous physics based approximations by Hu et.al., Kosowsky et.al. and Chu et.al., it combines their speed with precision cosmology grade accuracy. A Fortran code for computing the WMAP likelihood for a given set of parameters is provided, pre-calibrated against CMBfast, accurate to Delta lnL ~ 0.05 over the entire 2sigma region of the parameter space for 6 parameter ``vanilla'' Lambda CDM models. We also provide 7-parameter fits including spatial curvature, gravitational waves and a running spectral index.

  15. High-frequency radio polarization measurements of WMAP point sources

    CERN Document Server

    Jackson, N; Battye, R A; Gabuzda, D; Taylor, A C

    2009-01-01

    We present polarization measurements at 8.4, 22, and 43 GHz made with the VLA of a complete sample of extragalactic sources stronger than 1 Jy in the 5-year WMAP catalogue and with declinations north of -34 degrees. The observations were motivated by the need to know the polarization properties of radio sources at frequencies of tens of GHz in order to subtract polarized foregrounds for future sensitive Cosmic Microwave Background (CMB) experiments. The total intensity and polarization measurements are generally consistent with comparable VLA calibration measurements for less-variable sources, and within a similar range to WMAP fluxes for unresolved sources. A further paper will present correlations between measured parameters and derive implications for CMB measurements.

  16. Dark matter halo concentrations in the WMAP5 cosmology

    CERN Document Server

    Duffy, Alan R; Kay, Scott T; Vecchia, Claudio Dalla

    2008-01-01

    We use a combination of three large N-body simulations to investigate the dependence of dark matter halo concentrations on halo mass and redshift in the WMAP year 5 cosmology. The median relation between concentration and mass is adequately described by a power-law for halo masses in the range 10^11 - 10^15 Msol/h and redshifts z < 2, regardless of whether the halo density profiles are fit using NFW or Einasto profiles. Compared with recent analyses of the Millennium Simulation, which uses a value of sigma_8 that is higher than allowed by WMAP5, z = 0 halo concentrations are reduced by factors ranging from 23 per cent at 10^11 Msol/h to 16 per cent at 10^14 Msol/h. The predicted concentrations are much lower than inferred from X-ray observations of groups and clusters.

  17. Dark matter implications of the WMAP-Planck Haze

    CERN Document Server

    Egorov, Andrey E; Pierpaoli, Elena; Pietrobon, Davide

    2015-01-01

    Gamma rays and microwave observations of the Galactic Center and surrounding areas indicate the presence of anomalous emission, whose origin remains ambiguous. The possibility of dark matter (DM) annihilation explaining both signals through prompt emission at gamma-rays and secondary emission at microwave frequencies from interactions of high-energy electrons produced in annihilation with the Galactic magnetic fields has attracted much interest in recent years. We investigate the DM interpretation of the Galactic Center gamma-ray excess by searching for the associated synchrotron in the WMAP-Planck data. Considering various magnetic field and cosmic-ray propagation models, we predict the synchrotron emission due to DM annihilation in our Galaxy, and compare it with the WMAP-Planck data at 23-70GHz. In addition to standard microwave foregrounds, we separately model the microwave counterpart to the Fermi Bubbles and the signal due to DM, and use component separation techniques to extract the signal associated w...

  18. Cross-Correlation Detection of Point Sources in the WMAP First Year Data

    Institute of Scientific and Technical Information of China (English)

    Jian-Yin Nie; Shuang-Nan Zhang

    2007-01-01

    We apply a Cross-Correlation (CC) method developed previously for detecting gamma-ray point sources to the WMAP first year data by using the Point-Spread Function of WMAP and obtain a full sky CC coefficient map. We find that the CC method is a powerful tool to examine the WMAP foreground residuals which can be further cleaned accordingly. Evident foreground signals are found in the WMAP foreground cleaned maps and the Tegmark cleaned map. In this process 101 point sources are detected, and 26 of them are new sources additional to the originally listed WMAP 208 sources. We estimate the flux of these new sources and verify them by another method. As a result, a revised mask file based on the WMAP first year data is produced by including these new sources.

  19. Cosmological Analyses Based On The Combined Planck And WMAP Mission Datasets

    Science.gov (United States)

    Bennett, Charles

    We propose to: (1) make a detailed comparison of WMAP, Planck, and other cosmic microwave background (CMB) data to understand areas of conflict, and if possible, resolve them; (2) combine WMAP and Planck data into a unified cosmological dataset; and (3)extend cosmological analyses with the combined data. Recent cosmological measurements have revolutionized cosmology and the CMB has played a crucial role. The Planck mission team just released cosmological data and papers, this on the heels of the WMAP team's release of final nine-year data and papers. This proposal is to compare and attempt to understand the subtle but important differences between the two recently released WMAP and Planck cosmological results, to combine the data so as to benefit from the full available small and larger scale measurements, and to use this to enhance cosmological solutions. The WMAP and Planck CMB cosmology datasets are broadly consistent with one another. Yet, differences exist beyond the fact that Planck data extend to finer angular scales than WMAP data. We propose to go beyond the "quick look" we have done so far to identify and help resolve discrepancies. We provide two examples of the kinds of discrepancies that should be resolved. Even though the Planck data release relied on the absolute calibration established by WMAP the two sets of analyzed data appear to be off by a factor of 0.975. This small but significant discrepancy is difficult to explain and merits investigation. Also, while cosmological parameters from Planck agree with WMAP parameters within 1.1# of the larger WMAP uncertainty, this large a discrepancy is difficult to explain in detail since the cosmic variance uncertainties that play a large role in the parameter uncertainties are common to Planck and WMAP: both missions view the same sky. These are just two examples; additional careful and detailed comparisons are required. Over the course of the last several years a number of scientists around the world

  20. Temperature dependence of the perpendicular magnetic anisotropy in Ta/Co2FeAl/MgO structures probed by Anomalous Hall Effect

    Science.gov (United States)

    Gabor, M. S.; Petrisor, T.; Pop, O.; Colis, S.; Tiusan, C.

    2015-10-01

    We report a detailed study of the temperature dependence of the magnetic anisotropy in Ta/Co2FeAl/MgO structures by means of Anomalous Hall Effect measurements. The volume magnetic anisotropy, although negligible at room temperature, shows a non-negligible value at low temperatures and favors an in-plane easy magnetization axis. The surface magnetic anisotropy, which promotes the perpendicular magnetic easy axis, shows an increase from 0.76 ± 0.05 erg /cm2 at 300 K, up to 1.08 ± 0.04 erg /cm2 at 5 K, attributed to the evolution of the Co2FeAl layer saturation magnetization with temperature.

  1. Constraining hybrid inflation models with WMAP three-year results

    CERN Document Server

    Cardoso, A

    2006-01-01

    We reconsider the original model of quadratic hybrid inflation in light of the WMAP three-year results and study the possibility of obtaining a spectral index of primordial density perturbations, $n_s$, smaller than one from this model. The original hybrid inflation model naturally predicts $n_s\\geq1$ in the false vacuum dominated regime but it is also possible to have $n_s<1$ when the quadratic term dominates. We therefore investigate whether there is also an intermediate regime compatible with the latest constraints, where the scalar field value during the last 50 e-folds of inflation is less than the Planck scale.

  2. PLANCK and WMAP constraints on generalised Hubble flow inflationary trajectories

    Energy Technology Data Exchange (ETDEWEB)

    Contaldi, Carlo R.; Horner, Jonathan S., E-mail: c.contaldi@imperial.ac.uk, E-mail: j.horner11@imperial.ac.uk [Theoretical Physics Group, Blackett Laboratory, Imperial College London, South Kensington, London, SW7 2BZ (United Kingdom)

    2014-08-01

    We use the Hamilton-Jacobi formalism to constrain the space of possible single field, inflationary Hubble flow trajectories when compared to the WMAP and PLANK satellites Cosmic Microwave Background (CMB) results. This method yields posteriors on the space of Hubble Slow Roll (HSR) parameters that uniquely determine the history of the Hubble parameter during the inflating epoch. The trajectories are used to numerically determine the observable primordial power spectrum and bispectra that can then be compared to observations. Our analysis is used to infer the most likely shape of the inflaton potential V(φ) and also yields a prediction for, B, the dimensionless amplitude of the non-Gaussian bispectrum.

  3. Probing anisotropies of gravitational-wave backgrounds with a space-based interferometer: Geometric properties of antenna patterns and their angular power

    International Nuclear Information System (INIS)

    We discuss the sensitivity to anisotropies of stochastic gravitational-wave backgrounds (GWBs) observed via space-based interferometer. In addition to the unresolved galactic binaries as the most promising GWB source of the planned Laser Interferometer Space Antenna (LISA), the extragalactic sources for GWBs might be detected in the future space missions. The anisotropies of the GWBs thus play a crucial role to discriminate various components of the GWBs. We study general features of antenna pattern sensitivity to the anisotropies of GWBs beyond the low-frequency approximation. We show that the sensitivity of space-based interferometer to GWBs is severely restricted by the data combinations and the symmetries of the detector configuration. The spherical harmonic analysis of the antenna pattern functions reveals that the angular power of the detector response increases with frequency and the detectable multipole moments with effective sensitivity heff∼10-20 Hz-1/2 may reach l∼8-10 at f∼f*=10 mHz in the case of the single LISA detector. However, the cross correlation of optimal interferometric variables is blind to the monopole (l=0) intensity anisotropy, and also to the dipole (l=1) in some case, irrespective of the frequency band. Besides, all the self-correlated signals are shown to be blind to the odd multipole moments (l=odd), independently of the frequency band

  4. The Classical and Quantum Inflaton: the Precise Inflationary Potential and Quantum Inflaton Decay after WMAP

    International Nuclear Information System (INIS)

    We clarify classical inflaton models by considering them as effective field theories a la Ginzburg-Landau. In this approach, the WMAP statement excluding the pure φ4 potential implies the presence of an inflaton mass term at the scale m∼1013GeV. Chaotic, new and hybrid inflation models are studied in an unified manner. In all cases the inflaton potential takes the form V(φ)=m2MPl2v(φMPl), where all coefficients in the polynomial v(φ) are of order (m/MPl)0. If such potential corresponds to supersymmetry breaking, the corresponding susy breaking scale is mMPl∼1016GeV which turns out to coincide with the grand unification (GUT) scale. The inflaton mass is therefore given by a see-saw formula m∼MGUT2/MPl. For red tilted spectrum, the potential which fits the best the present data (vertical bar1-nsvertical bar-bar 0.1,r-bar 0.1) and which best prepares the way for the forthcoming data is a trinomial polynomial with negative quadratic term (new inflation). For blue tilted spectrum, hybrid inflation turns to be the best choice. In both cases, we find an analytic formula relating the inflaton mass with the ratio r of tensor to scalar perturbations and the spectral index ns of scalar perturbations: 106mMPl=127rvertical bar1-nsvertical bar where the numerical coefficient is fixed by the WMAP amplitude of adiabatic perturbations. Implications for string theory are discussed. We then review quantum phenomena during inflation which contribute to relevant observables in the CMB anisotropies and polarization and we focus on inflaton decay. The deviation from the scale invariant power spectrum measured by a small parameter Δ turns to be crucial, Δ regulates the infrared too. In slow roll inflation, Δ is a simple function of the slow roll parameters. We find that quantum fluctuations can self-decay as a consequence of the inflationary expansion through processes which are forbidden in Minkowski space-time. We compute the self-decay of the inflaton quantum fluctuations

  5. Probing anisotropies of gravitational-wave backgrounds with a space-based interferometer: geometric properties of antenna patterns and their angular power

    CERN Document Server

    Kudoh, H; Kudoh, Hideaki; Taruya, Atsushi

    2005-01-01

    We discuss the sensitivity to anisotropies of stochastic gravitational-wave backgrounds (GWBs) observed via space-based interferometer. In addition to the un-resolved Galactic binaries as the most promising GWB source of the planned Laser Interferometer Space Antenna (LISA), the extra-galactic sources for GWBs might be detected in the future space missions. The anisotropies of the GWBs thus play a crucial role to discriminate various components of the GWBs. We study general features of antenna pattern sensitivity to the anisotropies of GWBs beyond the low-frequency approximation. We show that the sensitivity of space-based interferometer to GWBs is severely restricted by the data combinations and the symmetries of the detector configuration. The spherical harmonic analysis of the antenna pattern functions reveals that the angular power of the detector response increases with frequency and the detectable multipole moments with effective sensitivity h_{eff}\\sim 10^{-20} Hz^{-1/2} may reach $\\ell \\sim $ 8 - 10 a...

  6. Is the Pre-WMAP CMB Data Self-consistent?

    CERN Document Server

    Lineweaver, C H; Griffiths, Louise M.

    2003-01-01

    Although individual observational groups vigorously test their data sets for systematic errors, the pre-WMAP CMB observational data set has not yet been collectively tested. Under the assumption that the concordance model is the correct model, we have explored residuals of the observational data with respect to this model to see if any patterns emerge that can be identified with systematic errors. We found no significant trends associated with frequency, frequency channels, calibration source, pointing uncertainty, instrument type, platform and altitude. We did find some evidence at the ~ 1 to ~ 2 sigma level for trends associated with angular scale (l range) and absolute galactic latitude. The slope of the trend in galactic latitude is consistent with low level galactic contamination. The residuals with respect to l may indicate that the concordance model used here needs slight modification. See Griffiths & Lineweaver (2003) for more detail.

  7. Hybrid Inflation Revisited in Light of WMAP5

    CERN Document Server

    Rehman, Mansoor Ur; Wickman, Joshua R

    2009-01-01

    We study the effects of including one-loop radiative corrections in a non-supersymmetric hybrid inflationary model. These corrections can arise from Yukawa couplings between the inflaton and right-handed neutrinos, and induce a maximum in the potential which admits hilltop-type solutions in addition to the standard hybrid solutions. We obtain a red-tilted spectral index $n_s$, consistent with WMAP5 data, for sub-Planckian values of the field. This is in contrast to the tree level hybrid analysis, in which a red-tilted spectrum is achieved only for trans-Planckian values of the field. Successful reheating is obtained at the end of the inflationary phase via conversion of the inflaton and waterfall fields into right-handed neutrinos, whose subsequent decay can explain the observed baryon asymmetry via leptogenesis.

  8. Amiba Observation of CMB Anisotropies

    Science.gov (United States)

    Ng, Kin-Wang

    2003-03-01

    The Array for Microwave Background Anisotropies (AMiBA), a 13-element dual-channel 85-105 GHz interferometer array with full polarization capabilities, is being built to search for high redshift clusters of galaxies via the Sunyaev-Zel'dovich effect as well as to probe the polarization properties of the cosmic microwave background (CMB). We discuss several important issues in the observation of the CMB anisotropies such as observing strategy, l space resolution and mosaicing, optimal estimation of the power spectra, and ground pickup removal.

  9. Information gains from cosmological probes

    Science.gov (United States)

    Grandis, S.; Seehars, S.; Refregier, A.; Amara, A.; Nicola, A.

    2016-05-01

    In light of the growing number of cosmological observations, it is important to develop versatile tools to quantify the constraining power and consistency of cosmological probes. Originally motivated from information theory, we use the relative entropy to compute the information gained by Bayesian updates in units of bits. This measure quantifies both the improvement in precision and the `surprise', i.e. the tension arising from shifts in central values. Our starting point is a WMAP9 prior which we update with observations of the distance ladder, supernovae (SNe), baryon acoustic oscillations (BAO), and weak lensing as well as the 2015 Planck release. We consider the parameters of the flat ΛCDM concordance model and some of its extensions which include curvature and Dark Energy equation of state parameter w. We find that, relative to WMAP9 and within these model spaces, the probes that have provided the greatest gains are Planck (10 bits), followed by BAO surveys (5.1 bits) and SNe experiments (3.1 bits). The other cosmological probes, including weak lensing (1.7 bits) and {H0} measures (1.7 bits), have contributed information but at a lower level. Furthermore, we do not find any significant surprise when updating the constraints of WMAP9 with any of the other experiments, meaning that they are consistent with WMAP9. However, when we choose Planck15 as the prior, we find that, accounting for the full multi-dimensionality of the parameter space, the weak lensing measurements of CFHTLenS produce a large surprise of 4.4 bits which is statistically significant at the 8 σ level. We discuss how the relative entropy provides a versatile and robust framework to compare cosmological probes in the context of current and future surveys.

  10. Statistical isotropy violation in WMAP CMB maps resulting from non-circular beams

    Science.gov (United States)

    Das, Santanu; Mitra, Sanjit; Rotti, Aditya; Pant, Nidhi; Souradeep, Tarun

    2016-06-01

    Statistical isotropy (SI) of cosmic microwave background (CMB) fluctuations is a key observational test to validate the cosmological principle underlying the standard model of cosmology. While a detection of SI violation would have immense cosmological ramification, it is important to recognise their possible origin in systematic effects of observations. The WMAP seven year (WMAP-7) release claimed significant deviation from SI in the bipolar spherical harmonic (BipoSH) coefficients and . Here we present the first explicit reproduction of the measurements reported in WMAP-7, confirming that beam systematics alone can completely account for the measured SI violation. The possibility of such a systematic origin was alluded to in WMAP-7 paper itself and other authors but not as explicitly so as to account for it accurately. We simulate CMB maps using the actual WMAP non-circular beams and scanning strategy. Our estimated BipoSH spectra from these maps match the WMAP-7 results very well. It is also evident that only a very careful and adequately detailed modelling, as carried out here, can conclusively establish that the entire signal arises from non-circular beam effect. This is important since cosmic SI violation signals are expected to be subtle and dismissing a large SI violation signal as observational artefact based on simplistic plausibility arguments run the serious risk of "throwing the baby out with the bathwater".

  11. Characterization of foreground emission at degree angular scale for CMB B-modes observations. Thermal Dust and Synchrotron signal from Planck and WMAP data

    CERN Document Server

    Krachmalnicoff, N; Aumont, J; Bersanelli, M; Mennella, A

    2015-01-01

    We quantify the contamination from polarized diffuse Galactic synchrotron and thermal dust emissions to the B-modes of the CMB anisotropies on the degree angular scale, using data from the Planck and WMAP satellites. We compute power spectra of foreground polarized emissions in 352 circular sky patches located at Galactic latitude |b|>20{\\deg}, each of which covering a fraction of the sky of about 1.5%. We make use of the spectral properties derived from Planck and WMAP data to extrapolate, in frequency, the amplitude of synchrotron and thermal dust B-modes spectra in the multipole bin centered at $\\ell\\simeq80$. In this way we estimate, for each analyzed region, the amplitude and frequency of the foreground minimum. We detect both dust and synchrotron signal, at degree angular scale and at 3 confidence level, in 28 regions. Here the minimum of the foreground emission is found at frequencies between 60 and 100 GHz with an amplitude,expressed in terms of the equivalent tensor-to-scalar ratio, r_FG, between ~0....

  12. Alignment and signed-intensity anomalies in WMAP data

    CERN Document Server

    Vielva, P; Martínez-González, E; Vandergheynst, P

    2007-01-01

    Significant alignment and signed-intensity anomalies of local features of the cosmic microwave background (CMB) are detected on the three-year WMAP data, through a decomposition of the signal with steerable wavelets on the sphere. Firstly, an alignment analysis identifies two mean preferred planes in the sky, both with normal axes close to the CMB dipole axis. The first plane is defined by the directions toward which local CMB features are anomalously aligned. A mean preferred axis is also identified in this plane, located very close to the ecliptic poles axis. The second plane is defined by the directions anomalously avoided by local CMB features. This alignment anomaly provides further insight on the recent results of Wiaux et al. 2006. Secondly, a signed-intensity analysis identifies three mean preferred directions in the southern galactic hemisphere with anomalously large or low temperature of local CMB features: a cold spot essentially identified with the cold spot originally observed by Vielva et al. 20...

  13. CMB reconstruction from the WMAP and Planck PR2 data

    CERN Document Server

    Bobin, J; Starck, J-L

    2015-01-01

    In this article, we describe a new estimate of the Cosmic Microwave Background (CMB) intensity map reconstructed by a joint analysis of the full Planck 2015 data (PR2) and WMAP nine-years. It provides more than a mere update of the CMB map introduced in (Bobin et al. 2014b) since it benefits from an improvement of the component separation method L-GMCA (Local-Generalized Morphological Component Analysis) that allows the efficient separation of correlated components (Bobin et al. 2015). Based on the most recent CMB data, we further confirm previous results (Bobin et al. 2014b) showing that the proposed CMB map estimate exhibits appealing characteristics for astrophysical and cosmological applications: i) it is a full sky map that did not require any inpainting or interpolation post-processing, ii) foreground contamination is showed to be very low even on the galactic center, iii) it does not exhibit any detectable trace of thermal SZ contamination. We show that its power spectrum is in good agreement with the ...

  14. Tentative Detection of Quasar Feedback from WMAP and SDSS Cross-Correlation

    OpenAIRE

    Chatterjee, Suchetana; Ho, Shirley; Newman, Jeffrey A.; Kosowsky, Arthur

    2009-01-01

    We perform a cross-correlation analysis of microwave data from Wilkinson Microwave Anisotropy Probe and photometric quasars from the Sloan Digital Sky Survey, testing for Sunyaev-Zeldovich (SZ) effect from quasars. A statistically significant (2.5 $\\sigma$) temperature decrement exists in the 41 GHz microwave band. A two-component fit to the cross-correlation spectrum incorporating both dust emission and SZ yields a best-fit $y$ parameter of $(7.0 \\pm 3.4)\\times 10^{-7}$. A similar cross-corr...

  15. Probing solute-solvent interaction in 1-ethyl-3-methylimidazolium-based room temperature ionic liquids: A time-resolved fluorescence anisotropy study.

    Science.gov (United States)

    Das, Sudhir Kumar; Sarkar, Moloy

    2014-03-01

    Rotational diffusion of two organic solutes, coumarin153 (C153) and 4-aminophthalimide (AP) has been investigated in four ionic liquids (ILs), viz. 1-ethyl-3-methylimidazolium trifluoroacetate (EMIMTFA), 1-ethyl-3-methylimidazolium ethylsulfate (EMIMESU), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMTFB) and 1-ethyl-3-methylimidazolium tetracyanoborate (EMIMTCB), as a function of temperature. Between the two probes, AP can act as hydrogen-bond-donor to the solvents having hydrogen bond acceptor ability. The results indicate that the rotational dynamics of C153 is mainly governed by the viscosity of the medium. On the other hand, the rotational motion of AP is found to be significantly hindered in the ILs depending on the nature of anions of the ILs. Rotational coupling constant values for AP in the ILs follow the order TFA > ESU > TCB > TFB. The slower rotational motion of AP in these ILs has been attributed to the specific hydrogen bonding interaction between AP and anions of ILs. PMID:24158315

  16. The Atacama Cosmology Telescope: Calibration with WMAP Using Cross-Correlations

    CERN Document Server

    Hajian, Amir; Ade, Peter A R; Aguirre, Paula; Amiri, Mandana; Appel, John William; Barrientos, L Felipe; Battistelli, Elia S; Bond, J Richard; Brown, Ben; Burger, Bryce; Chervenak, Jay; Das, Sudeep; Devlin, Mark J; Dicker, Simon R; Doriese, W Bertrand; Dunkley, Joanna; Dunner, Rolando; Essinger-Hileman, Thomas; Fisher, Ryan P; Fowler, Joseph W; Halpern, Mark; Hasselfield, Matthew; Hernandez-Monteagudo, Carlos; Hilton, Gene C; Hilton, Matt; Hincks, Adam D; Hlozek, Renee; Huffenberger, Kevin M; Hughes, David H; Hughes, John P; Infante, Leopoldo; Irwin, Kent D; Juin, Jean Baptiste; Kaul, Madhuri; Klein, Jeff; Kosowsky, Arthur; Lau, Judy M; Limon, Michele; Lin, Yen-Ting; Lupton, Robert H; Marriage, Tobias A; Marsden, Danica; Mauskopf, Phil; Menanteau, Felipe; Moodley, Kavilan; Moseley, Harvey; Netterfield, Calvin B; Niemack, Michael D; Nolta, Michael R; Page, Lyman A; Parker, Lucas; Partridge, Bruce; Reid, Beth; Sehgal, Neelima; Sherwin, Blake D; Sievers, Jon; Spergel, David N; Staggs, Suzanne T; Swetz, Daniel S; Switzer, Eric R; Thornton, Robert; Trac, Hy; Tucker, Carole; Warne, Ryan; Wollack, Ed; Zhao, Yue

    2010-01-01

    We present a new calibration method based on cross-correlations with WMAP and apply it to data from the Atacama Cosmology Telescope (ACT). ACT's observing strategy and map making procedure allows an unbiased reconstruction of the modes in the maps over a wide range of multipoles. By directly matching the ACT maps to WMAP observations in the multipole range of 400 < ell < 1000, we determine the absolute calibration with an uncertainty of 2% in temperature. The precise measurement of the calibration error directly impacts the uncertainties in the cosmological parameters estimated from the ACT power spectra. We also present a combined map based on ACT and WMAP data that has high signal-to-noise over a wide range of multipoles.

  17. Bianchi Type VII_h Models and the WMAP 3-year Data

    CERN Document Server

    Jaffe, T R; Eriksen, H K; Górski, K M; Hansen, F K

    2006-01-01

    Context. A specific example of Bianchi Type VIIh models, i.e. those including universal rotation (vorticity) and differential expansion (shear), has been shown in Jaffe et al. (2005) to correlate unexpectedly with the WMAP first-year data. Aims. We re-assess the signature of this model in the WMAP 3-year data. Methods. The cross-correlation methods are described in Jaffe et al. (2006a). We use the WMAP 3-year data release, including maps for individual years, and perform additional comparisons to assess the influence of both noise and residual foregrounds and eliminate potential non-cosmological sources for the correlation. Results. We confirm that the signal is detected in both the combined 3-year data and the individual yearly sky maps at a level consistent with our original analysis. The significance of the correlation is not affected by either noise or foreground residuals. Conclusions. The results of our previous study are unchanged.

  18. Model Independent Foreground Power Spectrum Estimation using WMAP 5-year Data

    CERN Document Server

    Ghosh, Tuhin; Jain, Pankaj; Souradeep, Tarun

    2009-01-01

    In this paper, we propose & implement on WMAP 5-year data, a model independent approach of foreground power spectrum estimation for multifrequency observations of CMB experiments. Recently a model independent approach of CMB power spectrum estimation was proposed by Saha et al. 2006. This methodology demonstrates that CMB power spectrum can be reliably estimated solely from WMAP data without assuming any template models for the foreground components. In the current paper, we extend this work to estimate the galactic foreground power spectrum using the WMAP 5 year maps following a self contained analysis. We apply the model independent method in harmonic basis to estimate the foreground power spectrum and frequency dependence of combined foregrounds. We also study the behaviour of synchrotron spectral index variation over different regions of the sky. We compare our results with those obtained from MEM foreground maps which are formed in pixel space. We find that relative to our model independent estimates...

  19. Correlated adiabatic and isocurvature CMB fluctuations in the wake of WMAP

    CERN Document Server

    Valiviita, J; Valiviita, Jussi; Muhonen, Vesa

    2003-01-01

    In the general correlated models, in addition to the usual adiabatic component with a spectral index n_ad1 there is another adiabatic component with a spectral index n_ad2 generated by the entropy perturbation during inflation. We extend the analysis of a correlated mixture of adiabatic and isocurvature CMB fluctuations of the WMAP group, who set the two adiabatic spectral indices equal. Allowing n_ad1 and n_ad2 to vary independently we find that the WMAP data favor models where the two adiabatic components have opposite spectral tilts. Using the WMAP data only, the 2-sigma upper bound for the isocurvature fraction f_iso of the initial power spectrum at k_0=0.05 Mpc^{-1} increases somewhat, e.g., from 0.76 of n_ad2 = n_ad1 models to 0.84 with a prior n_iso < 1.84 for the isocurvature spectral index.

  20. Probing interaction and spatial curvature in the holographic dark energy model

    International Nuclear Information System (INIS)

    In this paper we place observational constraints on the interaction and spatial curvature in the holographic dark energy model. We consider three kinds of phenomenological interactions between holographic dark energy and matter, i.e., the interaction term Q is proportional to the energy densities of dark energy (ρΛ), matter (ρm), and matter plus dark energy (ρm+ρΛ). For probing the interaction and spatial curvature in the holographic dark energy model, we use the latest observational data including the type Ia supernovae (SNIa) Constitution data, the shift parameter of the cosmic microwave background (CMB) given by the five-year Wilkinson Microwave Anisotropy Probe (WMAP5) observations, and the baryon acoustic oscillation (BAO) measurement from the Sloan Digital Sky Survey (SDSS). Our results show that the interaction and spatial curvature in the holographic dark energy model are both rather small. Besides, it is interesting to find that there exists significant degeneracy between the phenomenological interaction and the spatial curvature in the holographic dark energy model

  1. A Hint of Poincar\\'e Dodecahedral Topology in the WMAP First Year Sky Map

    OpenAIRE

    Roukema, Boudewijn F; Lew, Bartosz; Cechowska, Magdalena; Marecki, Andrzej; Bajtlik, Stanislaw

    2004-01-01

    Luminet et al. (2003) suggested that WMAP data are better matched by a Poincar\\'e dodecahedral FLRW model of global geometry, rather than by an infinite flat model. The analysis by Cornish et al. (2003) for angular radii 25-90 degrees failed to support this. Here, a matched circles analysis specifically designed to detect dodecahedral patterns of matched circles is performed over angular radii in the range 1-40 degrees on the one-year WMAP ILC map, using a correlation statistic and an rms dif...

  2. Elastic anisotropy of crystals

    Directory of Open Access Journals (Sweden)

    Christopher M. Kube

    2016-09-01

    Full Text Available An anisotropy index seeks to quantify how directionally dependent the properties of a system are. In this article, the focus is on quantifying the elastic anisotropy of crystalline materials. Previous elastic anisotropy indices are reviewed and their shortcomings discussed. A new scalar log-Euclidean anisotropy measure AL is proposed, which overcomes these deficiencies. It is based on a distance measure in a log-Euclidean space applied to fourth-rank elastic tensors. AL is an absolute measure of anisotropy where the limiting case of perfect isotropy yields zero. It is a universal measure of anisotropy applicable to all crystalline materials. Specific examples of strong anisotropy are highlighted. A supplementary material provides an anisotropy table giving the values of AL for 2,176 crystallite compounds.

  3. Bayesian analysis of white noise levels in the 5-year WMAP data

    CERN Document Server

    Groeneboom, N E; Gorski, K; Huey, G; Jewell, J; Wandelt, B

    2009-01-01

    We develop a new Bayesian method for estimating white noise levels in CMB sky maps, and apply this algorithm to the 5-year WMAP data. We assume that the amplitude of the noise RMS is scaled by a constant value, alpha, relative to a pre-specified noise level. We then derive the corresponding conditional density, P(alpha | s, C_l, d), which is subsequently integrated into a general CMB Gibbs sampler. We first verify our code by analyzing simulated data sets, and then apply the framework to the WMAP data. For the foreground-reduced 5-year WMAP sky maps, we find that the posterior means typically range between alpha=1.005 +- 0.001 and alpha=1.010 +- 0.001 depending on differencing assembly, indicating that the noise level of these maps are underestimated by 0.5-1.0%. The same problem is not observed for the uncorrected WMAP sky maps. The only difference between these two cases is that the nominal white noise level for the foreground-reduced map is specified to be lower than that of the raw maps. This is likely in...

  4. Asymmetry and non-random orientation of the inflight effective beam pattern in the WMAP data

    International Nuclear Information System (INIS)

    Tentative evidence for statistical anisotropy in the Wilkinson Microwave Anisotropy Probe data was alleged to be due to 'insufficient handling of beam asymmetries'. In this paper, we investigate this issue and develop a method to estimate the shape of the inflight effective beam, particularly the asymmetry and azimuthal orientation. We divide the whole map into square patches and exploit the information in the Fourier space. For patches containing bright extragalactic point sources, we can directly estimate their shapes, from which the inflight effective beam can be estimated. For those without, we estimate the pattern from iso-power contours in two-dimensional Fourier space. We show that the inflight effective beam convolving the signal is indeed non-symmetric for most of the sky, and it is not randomly oriented. Around the ecliptic poles, however, the asymmetry is smaller due to the averaging effect from different orientations of the beam from the scan strategy. The orientations of the effective beam with significant asymmetry are parallel to the lines of ecliptic longitude. In the foreground-cleaned Internal Linear Combination map, however, the systematics caused by beam effect is significantly lessened.

  5. Big Bang nucleosynthesis, microwave anisotropy, and the light element abundances

    Energy Technology Data Exchange (ETDEWEB)

    Coc, A. [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, CNRS/IN2P3/UPS, Bat. 104, F-91405 Orsay Campus (France); Angulo, C. [Centre de Recherches du Cyclotron, Universite catholique de Louvain, Chemin du cyclotron 2, B-1348 Louvain-la-Neuve (Belgium); Vangioni-Flam, E. [lnstitut d' Astrophysique de Paris, CNRS, 98bis Bd. Arago, F-75014 Paris (France); Descouvemont, P. [Physique Nucleaire Theorique et Physique Mathematique, CP229, Universite Libre de Bruxelles, B-1050 Brussels (Belgium); Adahchour, A. [Physique Nucleaire Theorique et Physique Mathematique, CP229, Universite Libre de Bruxelles, B-1050 Brussels (Belgium)

    2005-04-18

    From the observations of the anisotropies of the Cosmic Microwave Background (CMB) radiation, the WMAP satellite has provided a determination of the baryonic density of the Universe, with an unprecedented precision: 4%. This imposes a careful reanalysis of the standard Big-Bang Nucleosynthesis (SBBN) calculations. In a recent paper, we used the R-matrix theory to fit S-factor data on nuclear reactions involved in Big Bang nucleosynthesis. We derived the reaction rates with associated uncertainties, which were evaluated on statistical grounds (available at http://pntpm3.ulb.ac.be/bigbang). Combining these BBN results with the {omega}bh2 value from WMAP, we deduced the light element ({sup 4}He, D, {sup 3}He and {sup 7}Li) primordial abundances and compare them with spectroscopic observations. There is a very good agreement with deuterium observed in cosmological clouds, which strengthens the confidence on the estimated baryonic density of the Universe. However, there is a discrepancy between the deduced {sup 7}Li abundance and the one observed in halo stars of our Galaxy, supposed, until now, to represent the primordial abundance of this isotope. The origin of this discrepancy, observational, nuclear or more fundamental remains to be clarified. The possible role of the up to now neglected {sup 7}Be(d,p)2{alpha} and {sup 7}Be(d,{alpha}){sup 5}Li reactions is considered and we present here a dedicated experiment performed at Louvain-la-Neuve to measure these cross sections.

  6. Big Bang nucleosynthesis, microwave anisotropy, and the light element abundances

    Science.gov (United States)

    Coc, A.; Angulo, C.; Vangioni-Flam, E.; Descouvemont, P.; Adahchour, A.

    2005-04-01

    From the observations of the anisotropies of the Cosmic Microwave Background (CMB) radiation, the WMAP satellite has provided a determination of the baryonic density of the Universe, with an unprecedented precision: 4%. This imposes a careful reanalysis of the standard Big-Bang Nucleosynthesis (SBBN) calculations. In a recent paper, we used the R-matrix theory to fit S-factor data on nuclear reactions involved in Big Bang nucleosynthesis. We derived the reaction rates with associated uncertainties, which were evaluated on statistical grounds (available at http://pntpm3.ulb.ac.be/bigbang). Combining these BBN results with the Ωbh2 value from WMAP, we deduced the light element (4He, D,3He and 7Li) primordial abundances and compare them with spectroscopic observations. There is a very good agreement with deuterium observed in cosmological clouds, which strengthens the confidence on the estimated baryonic density of the Universe. However, there is a discrepancy between the deduced 7Li abundance and the one observed in halo stars of our Galaxy, supposed, until now, to represent the primordial abundance of this isotope. The origin of this discrepancy, observational, nuclear or more fundamental remains to be clarified. The possible role of the up to now neglected 7Be(d,p)2α and 7Be(d,α)5Li reactions is considered and we present here a dedicated experiment performed at Louvain-la-Neuve to measure these cross sections.

  7. Do WMAP5 data favor neutrino mass and a coupling between Cold Dark Matter and Dark Energy?

    CERN Document Server

    Bonometto, S A; Kristiansen, J R; Mainini, R; Colombo, L P L

    2009-01-01

    We fit WMAP5 and related data by allowing for a CDM--DE coupling and non--zero neutrino masses, simultaneously. We find a significant correlation between these parameters, so that simultaneous higher coupling and \

  8. Foreground removal from WMAP 7 yr polarization maps using an MLP neural network

    DEFF Research Database (Denmark)

    Nørgaard-Nielsen, Hans Ulrik

    2012-01-01

    One of the fundamental problems in extracting the cosmic microwave background signal (CMB) from millimeter/submillimeter observations is the pollution by emission from the Milky Way: synchrotron, free-free, and thermal dust emission. To extract the fundamental cosmological parameters from CMB...... signal, it is mandatory to minimize this pollution since it will create systematic errors in the CMB power spectra. In previous investigations, it has been demonstrated that the neural network method provide high quality CMB maps from temperature data. Here the analysis is extended to polarization maps....... As a concrete example, the WMAP 7-year polarization data, the most reliable determination of the polarization properties of the CMB, has been analyzed. The analysis has adopted the frequency maps, noise models, window functions and the foreground models as provided by the WMAP Team, and no auxiliary data...

  9. Constraints on the time variation of the fine structure constant by the 5-year WMAP data

    CERN Document Server

    Nakashima, Masahiro; Yokoyama, Jun'ichi

    2008-01-01

    The constraints on the time variation of the fine structure constant at recombination epoch relative to its present value, $\\Delta\\alpha/\\alpha \\equiv (\\alpha_{\\mathrm{rec}} - \\alpha_{\\mathrm{now}})/\\alpha_{\\mathrm{now}}$, are obtained from the analysis of the 5-year WMAP cosmic microwave background data. As a result of Markov-Chain Monte-Carlo analysis, it is found that, contrary to the analysis based on the previous WMAP data, the mean value of $\\Delta\\alpha/\\alpha=-0.0009$ does not change significantly whether we use the Hubble Space Telescope (HST) measurement of the Hubble parameter as a prior or not. The resultant 95% confidence ranges of $\\Delta\\alpha/\\alpha$ are $-0.028 < \\Delta\\alpha/\\alpha < 0.026$ with HST prior and $-0.050 < \\Delta\\alpha/\\alpha < 0.042$ without HST prior.

  10. Foreground removal from WMAP 7yr polarization maps using an MLP neural network

    CERN Document Server

    Nielsen, H U Nørgaard -

    2012-01-01

    One of the fundamental problems in extracting the cosmic microwave background signal (CMB) from millimeter/submillimeter observations is the pollution by emission from the Milky Way: synchrotron, free-free, and thermal dust emission. To extract the fundamental cosmological parameters from CMB signal, it is mandatory to minimize this pollution since it will create systematic errors in the CMB power spectra. In previous investigations, it has been demonstrated that the neural network method provide high quality CMB maps from temperature data. Here the analysis is extended to polarization maps. As a concrete example, the WMAP 7-year polarization data, the most reliable determination of the polarization properties of the CMB, has been analysed. The analysis has adopted the frequency maps, noise models, window functions and the foreground models as provided by the WMAP Team, and no auxiliary data is included. Within this framework it is demonstrated that the network can extract the CMB polarization signal with no ...

  11. Cosmological parameters after WMAP5: forecasts for Planck and future galaxy surveys

    OpenAIRE

    Colombo, L. P. L.; Pierpaoli, E.; Pritchard, J. R.

    2008-01-01

    The Planck satellite is expected to improve the measurement of most cosmological parameters by several factors with respect to current WMAP results. The actual performance may depend upon various aspects of the data analysis. In this paper we analyse the impact of specifics of the data analysis on the actual final results. We also explore the synergies in combining Planck results with future galaxy surveys. We find that Planck will improve constraints on most cosmological parameters by a fact...

  12. Protecting the primordial baryon asymmetry in the seesaw model compatible with WMAP and KamLAND

    OpenAIRE

    Hasegawa, K

    2003-01-01

    We require that the primordial baryon asymmetry is not washed out in the seesaw model compatible with the recent results of WMAP and the neutrino oscillation experiments including the first results of KamLAND. We find that only the case of the normal neutrino mass hierarchy with an approximate $L_{e}$-symmetry satisfies the requirement. We further derive, depending on the signs of neutrino mass eigenvalues, three types of neutrino mass matrixes, where the values of each element are rather pre...

  13. A hint of Poincaré dodecahedral topology in the WMAP first year sky map

    Science.gov (United States)

    Roukema, B. F.; Lew, B.; Cechowska, M.; Marecki, A.; Bajtlik, S.

    2004-09-01

    It has recently been suggested by Luminet et al. (\\cite{LumNat03}) that the WMAP data are better matched by a geometry in which the topology is that of a Poincaré dodecahedral model and the curvature is ``slightly'' spherical, rather than by an (effectively) infinite flat model. A general back-to-back matched circles analysis by Cornish et al. (\\cite{CSSK03}) for angular radii in the range 25-90 °, using a correlation statistic for signal detection, failed to support this. In this paper, a matched circles analysis specifically designed to detect dodecahedral patterns of matched circles is performed over angular radii in the range 1-40\\ddeg on the one-year WMAP data. Signal detection is attempted via a correlation statistic and an rms difference statistic. Extreme value distributions of these statistics are calculated for one orientation of the 36\\ddeg ``screw motion'' (Clifford translation) when matching circles, for the opposite screw motion, and for a zero (unphysical) rotation. The most correlated circles appear for circle radii of \\alpha =11 ± 1 \\ddeg, for the left-handed screw motion, but not for the right-handed one, nor for the zero rotation. The favoured six dodecahedral face centres in galactic coordinates are (\\lII,\\bII) ≈ (252\\ddeg,+65\\ddeg), (51\\ddeg,+51\\ddeg), (144\\ddeg,+38\\ddeg), (207\\ddeg,+10\\ddeg), (271\\ddeg,+3\\ddeg), (332\\ddeg,+25\\ddeg) and their opposites. The six pairs of circles independently each favour a circle angular radius of 11 ± 1\\ddeg. The temperature fluctuations along the matched circles are plotted and are clearly highly correlated. Whether or not these six circle pairs centred on dodecahedral faces match via a 36\\ddeg rotation only due to unexpected statistical properties of the WMAP ILC map, or whether they match due to global geometry, it is clear that the WMAP ILC map has some unusual statistical properties which mimic a potentially interesting cosmological signal.

  14. Inflection point inflation: WMAP constraints and a solution to the fine-tuning problem

    OpenAIRE

    Hotchkiss, Shaun; mazumdar, Anupam; Nadathur, Seshadri

    2011-01-01

    We consider observational constraints and fine-tuning issues in a renormalizable model of inflection point inflation, with two independent parameters. We derive constraints on the parameter space of this model arising from the WMAP 7-year power spectrum. It has previously been shown that it is possible to successfully embed this potential in the MSSM. Unfortunately, to do this requires severe fine-tuning. We address this issue by introducing a hybrid field to dynamically uplift the potential ...

  15. Magnetic surface anisotropy

    Science.gov (United States)

    Rado, George T.

    1992-02-01

    Selected aspects of magnetic surface anisotropy are reviewed. The emphasis is on methods for deducing reliable surface anisotropy values from experiments such as ferromagnetic resonance at microwave frequencies and Brillouin scattering at optical frequencies. The methods used are the "general exchange boundary condition method" and the "effective volume anisotropy method". The essence of the former is the supplementing of the equation of motion of the magnetization with the general exchange boundary condition whereas the latter consists of using the "stratagem" of effective volume anisotropy. We find that use of the general exchange boundary condition method is not only preferable in principle but often actually necessary to prevent the prediction of wrong surface anisotropy values and to permit the prediction of some observable Brillouin shifts.

  16. Anisotropy-graded media: Magnetic characterization

    Science.gov (United States)

    Lu, Zhihong; Visscher, P. B.; Harrell, J. W.

    2008-04-01

    The concept of exchange-coupled media (each grain having a soft end whose exchange field helps to switch a hard end) has recently been generalized to allow a continuous gradation of anisotropy from soft to hard. We have recently shown that the "figure of merit" for such media ξ =2Eb/μ0MsHsw, proportional to the ratio of the energy barrier Eb to the switching field Hsw, cannot exceed 4 for any anisotropy profile K(r ). In the thin-wall limit (exchange constant A ≪KL2), it can be made to approach 4 by choosing a graded anisotropy K(z )∝z2. In developing such a medium, it is important to be able to experimentally probe the anisotropy distribution. In this paper, we study one method for doing this, the hard axis loop. In the absence of exchange, the second derivative of this loop gives the distribution directly; we show that even in the presence of realistic exchange, this remains approximately true and the anisotropy distribution can be extracted from the hard axis loop.

  17. Supernovae anisotropy power spectrum

    CERN Document Server

    Ghodsi, Hoda; Habibi, Farhang

    2016-01-01

    We contribute another anisotropy study to this field of research using Supernovae Type Ia (SNe Ia). In this work, we utilise the power spectrum calculation method and apply it to both the current SNe Ia data and simulation. Our simulations are constructed with the characteristics of the upcoming survey of the Large Synoptic Survey Telescope (LSST), which shall bring us the largest SNe Ia collection to date. We make predictions for the amplitude of a possible dipole anisotropy or anisotropy in higher multipole moments that would be detectable by the LSST.

  18. Constraint on inflation model from BICEP2 and WMAP 9-year data

    CERN Document Server

    Cheng, Cheng

    2014-01-01

    Even though Planck data released in 2013 (P13) is not compatible with Background Imaging of Cosmic Extragalactic Polarization (B2) and some local cosmological observations, including Supernova Legacy Survey (SNLS) samples and $H_0$ prior from Hubble Space Telescope (HST) etc, Wilkinson Microwaves Anisotropy Probe 9-year data (W9) is consistent with all of them in the base six-parameter $\\Lambda$CDM+tensor cosmology quite well. In this letter, we adopt the combinations of B2+W9 and B2+W9+SNLS+BAO+HST to constrain the cosmological parameters in the base six-parameter $\\Lambda$CDM+tensor model with $n_t=-r/8$, where r and $n_t$ are the tensor-to-scalar ratio and the tilt of relic gravitational wave spectrum, and BAO denotes Baryon Acoustic Oscillation. We find that the Harrison-Zel'dovich (HZ) scale invariant scalar power spectrum is consistent with both data combinations, $m^2\\phi^2/2$ chaotic inflation is marginally disfavored by the data at around $2\\sigma$ level, but the power-law inflation model can fit the...

  19. FERMI-LAT AND WMAP OBSERVATIONS OF THE PUPPIS A SUPERNOVA REMNANT

    International Nuclear Information System (INIS)

    We report the detection of GeV γ-ray emission from the supernova remnant (SNR) Puppis A with the Fermi Gamma-Ray Space Telescope. Puppis A is among the faintest SNRs yet detected at GeV energies, with a luminosity of only 2.7 × 1034 (D/2.2 kpc)2 erg s–1 between 1 and 100 GeV. The γ-ray emission from the remnant is spatially extended, with a morphology matching that of the radio and X-ray emission, and is well described by a simple power law with an index of 2.1. We attempt to model the broadband spectral energy distribution (SED), from radio to γ-rays, using standard nonthermal emission mechanisms. To constrain the relativistic electron population we use 7 years of Wilkinson Microwave Anisotropy Probe data to extend the radio spectrum up to 93 GHz. Both leptonic- and hadronic-dominated models can reproduce the nonthermal SED, requiring a total content of cosmic-ray electrons and protons accelerated in Puppis A of at least W CR ≈ (1-5) × 1049 erg.

  20. FERMI-LAT AND WMAP OBSERVATIONS OF THE PUPPIS A SUPERNOVA REMNANT

    Energy Technology Data Exchange (ETDEWEB)

    Hewitt, J. W. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Grondin, M.-H. [Max-Planck-Institut fuer Kernphysik, D-69029 Heidelberg (Germany); Lemoine-Goumard, M.; Reposeur, T. [Centre d' Etudes Nucleaires de Bordeaux-Gradignan, Universite Bordeaux 1, CNRS/IN2p3, F-33175 Gradignan (France); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d' Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Tanaka, T., E-mail: john.w.hewitt@nasa.gov, E-mail: marie-helene.grondin@mpi-hd.mpg.de, E-mail: lemoine@cenbg.in2p3.fr [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)

    2012-11-10

    We report the detection of GeV {gamma}-ray emission from the supernova remnant (SNR) Puppis A with the Fermi Gamma-Ray Space Telescope. Puppis A is among the faintest SNRs yet detected at GeV energies, with a luminosity of only 2.7 Multiplication-Sign 10{sup 34} (D/2.2 kpc){sup 2} erg s{sup -1} between 1 and 100 GeV. The {gamma}-ray emission from the remnant is spatially extended, with a morphology matching that of the radio and X-ray emission, and is well described by a simple power law with an index of 2.1. We attempt to model the broadband spectral energy distribution (SED), from radio to {gamma}-rays, using standard nonthermal emission mechanisms. To constrain the relativistic electron population we use 7 years of Wilkinson Microwave Anisotropy Probe data to extend the radio spectrum up to 93 GHz. Both leptonic- and hadronic-dominated models can reproduce the nonthermal SED, requiring a total content of cosmic-ray electrons and protons accelerated in Puppis A of at least W {sub CR} Almost-Equal-To (1-5) Multiplication-Sign 10{sup 49} erg.

  1. Constraint on inflation model from BICEP2 and WMAP 9-year data

    Science.gov (United States)

    Cheng, Cheng; Huang, Qing-Guo

    2015-11-01

    Even though Planck data released in 2013 (P13) is not compatible with Background Imaging of Cosmic Extragalactic Polarization (B2) and some local cosmological observations, including Supernova Legacy Survey (SNLS) samples and H0 prior from Hubble Space Telescope (HST) etc. Wilkinson Microwave Anisotropy Probe 9-year data (W9) is consistent with all of them in the base six-parameter ΛCDM + tensor cosmology quite well. In this paper, we adopt the combinations of B2+W9 and B2+W9+SNLS+BAO+HST to constrain the cosmological parameters in the base six-parameter ΛCDM + tensor model with nt = -r/8, where r and nt are the tensor-to-scalar ratio and the tilt of relic gravitational wave spectrum, and BAO denotes Baryon Acoustic Oscillation (BAO). We find that the Harrison-Zel'dovich (HZ) scale invariant scalar power spectrum is consistent with both data combinations, chaotic inflation is marginally disfavored by the data at around 2σ level, but the power-law inflation model and the inflation model with inverse power-law potential can fit the data nicely.

  2. A determination of the Spectra of Galactic components observed by WMAP

    OpenAIRE

    Davies, R. D.; Dickinson, C.; Banday, A. J.; Jaffe, T. R.; Gorski, K. M.; Davis, R J

    2005-01-01

    WMAP data when combined with ancillary data on free-free, synchrotron and dust allow an improved understanding of the spectrum of emission from each of these components. Here we examine the sky variation at intermediate latitudes using a cross-correlation technique. In particular, we compare the observed emission in 15 selected sky regions to three ``standard'' templates. The free-free emission of the diffuse ionised gas is fitted by a well-known spectrum at K and Ka band, but the derived emi...

  3. Limits on fNL parameters from WMAP 3yr data

    International Nuclear Information System (INIS)

    We analyze the 3-year WMAP data and look for a deviation from Gaussianity in the form of a 3-point function that has either of the two theoretically motivated shapes: local and equilateral. There is no evidence of departure from Gaussianity and the analysis gives the presently tightest bounds on the parameters fNLlocal and fNLequil., which define the amplitude of respectively the local and the equilateral non-Gaussianity: -36 NLlocal NLequil. < 332 at 95% C.L. (author)

  4. Constraints to Holographic Dark Energy Model via Type Ia Supernovae, Baryon Acoustic Oscillation and WMAP

    OpenAIRE

    Xu, Lixin

    2012-01-01

    In this paper, the holographic dark energy (HDE) model, where the future event horizon is taken as an IR cut-off, is confronted by using currently available cosmic observational data sets which include type Ia supernovae, baryon acoustic oscillation and cosmic microwave background radiation from full information of WMAP-7yr. Via the Markov Chain Monte Carlo method, we obtain the values of model parameter $c= 0.696_{- 0.0737- 0.132- 0.190}^{+ 0.0736+ 0.159+ 0.264}$ with $1,2,3\\sigma$ regions. ...

  5. Non-thermal WIMPs as "Dark Radiation" in Light of ATACAMA, SPT, WMAP9 and Planck

    CERN Document Server

    Kelso, Chris; Queiroz, Farinaldo S

    2013-01-01

    The Planck and WMAP9 satellites, as well as the ATACAMA and South Pole telescopes, have recently presented results on the angular power spectrum of the comic microwave background. Data tentatively point to the existence of an extra radiation component in the early universe. Here, we show that this extra component can be mimicked by ordinary WIMP dark matter particles whose majority is cold, but with a small fraction being non-thermally produced in a relativistic state. We present a few example theories where this scenario is explicitly realized, and explore the relevant parameter space consistent with BBN, CMB and Structure Formation bounds.

  6. Spectrum of the Anomalous Microwave Emission in the North Celestial Pole with WMAP 7-Year data

    CERN Document Server

    Bonaldi, Anna; 10.1155/2012/853927

    2013-01-01

    We estimate the frequency spectrum of the diffuse anomalous microwave emission (AME) on the North Celestial Pole (NCP) region of the sky with the Correlated Component Analysis (CCA) component separation method applied to WMAP 7-yr data. The NCP is a suitable region for this analysis because the AME is weakly contaminated by synchrotron and free-free emission. By modeling the AME component as a peaked spectrum we estimate the peak frequency to be $21.7\\pm0.8$\\,GHz, in agreement with previous analyses which favored $\

  7. Single Field Inflation models allowed and ruled out by the three years WMAP data

    CERN Document Server

    De Vega, H J

    2006-01-01

    We study the single field slow-roll inflation models that better fit the available CMB and LSS data including the three years WMAP data: new inflation and hybrid inflation. We study them as effective field theories in the Ginsburg-Landau context: a trinomial potential turns out to be a simple and well motivated model. The compute the spectral index n_s of the adiabatic fluctuations, the ratio r of tensor to scalar fluctuations and the running index d n_s/dln k, derive explicit formulae and provide relevant plots. In new inflation, and for the three years WMAP central value n_s = 0.95, we predict 0.031. Hybrid inflation for mu_0^2>Lambda_0 M_{Pl}^2/192 can fullfill all the present CMB+LSS data. Even if chaotic inflation predicts n_s values compatible with the data, chaotic inflation is disfavoured since it predicts a too high value for the ratio r=0.27. The model which best fits the current data and which best prepares the way to the expected data r < 0.1, is the trinomial potential with negative mass term:...

  8. Implications of WMAP observations on Li abundance and stellar evolution models

    CERN Document Server

    Richard, O; Richer, J; Richard, Olivier; Michaud, Georges; Richer, Jacques

    2004-01-01

    The WMAP determination of the baryon-to-photon ratio implies, through Big Bang nucleosynthesis, a cosmological Li abundance larger, by a factor of 2 to 3, than the Li abundance plateau observed in the oldest Pop II stars. It is however inescapable that there be a reduction by a factor of at least 1.6 to 2.0 of the surface Li abundance during the evolution of Pop II field stars with [Fe/H] < -1.5. That the observed Li be lower than cosmologically produced Li is expected from stellar evolution models. Since at turnoff most of the Li abundance reduction is caused by gravitational settling, the presence of Lithium 6 in some turnoff stars is also understood. Given that the WMAP implications for Li cosmological abundance and the Li Spite plateau can be naturally explained by gravitational settling in the presence of weak turbulence, there appears little need for exotic physics as suggested by some authors. Instead, there is a need for a better understanding of turbulent transport in the radiative zones of stars....

  9. A Hint of Poincar\\'e Dodecahedral Topology in the WMAP First Year Sky Map

    CERN Document Server

    Roukema, B F; Cechowska, M; Marecki, A; Bajtlik, S

    2004-01-01

    Luminet et al. (2003) suggested that WMAP data are better matched by a Poincar\\'e dodecahedral FLRW model of global geometry, rather than by an infinite flat model. The analysis by Cornish et al. (2003) for angular radii 25-90 degrees failed to support this. Here, a matched circles analysis specifically designed to detect dodecahedral patterns of matched circles is performed over angular radii in the range 1-40 degrees on the one-year WMAP ILC map, using a correlation statistic and an rms difference statistic. Extreme value distributions of these statistics are calculated for left-handed and right-handed 36 degree `screw motions' (Clifford translations) when matching circles and for a zero (unphysical) rotation. The most correlated circles appear for circle radii of 11\\pm1 degrees, for the left-handed screw motion, but not for the right-handed one, nor for the zero rotation. The favoured six dodecahedral face centres in galactic coordinates are (l,b)= (252, +65), (51, +51), (144,+38), (207,+10), (271,+3), (33...

  10. Analysis of complex anisotropy decays from single-frequency polarized-phasor ellipse plots

    Science.gov (United States)

    Kozer, Noga; Clayton, Andrew H. A.

    2016-06-01

    The anisotropy decay of a fluorescently-labelled macromolecule provides information on the internal and global dynamics of the macromolecule. Weber was a pioneer of fluorescent probes, polarization and polarized phase-modulation methods and revealed the power of combining or comparing these methods to disentangle complex modes of emission depolarization. In this paper we take a similar course and show that when measurements of dynamic depolarization are combined with steady-state anisotropy, complex anisotropy decays can be deduced from measurements at a single modulation frequency. Specifically, a double exponential anisotropy decay can be resolved by combining one of the polarized emission phasors with the steady-state anisotropy. The key is the polarized phasor ellipse plot which provides a convenient visualisation aid and reduces the dimensionality of the minimisation problem from three variables to one variable. We illustrate these concepts with an experimental measurement of the anisotropy decay of a small cytoplasmic fluorescent probe in live cells.

  11. Dark matter electron anisotropy. A universal upper limit

    Energy Technology Data Exchange (ETDEWEB)

    Borriello, Enrico [Universita ' ' Federico II' ' , Napoli (Italy). Dipt. di Scienze Fisiche; INFN, Sezione di Napoli (Italy); Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Maccione, Luca [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Cuoco, Alessandro [Oskar Klein Centre for Cosmoparticle Physics, Stockholm (Sweden)

    2010-12-15

    Indirect searches of particle Dark Matter (DM) with high energy Cosmic Rays (CR) are affected by large uncertainties, coming both from the DM side, and from poor understanding of the astrophysical backgrounds. We show that, on the contrary, the DM intrinsic degree of anisotropy in the arrival directions of high energy CR electrons and positrons does not suffer from these unknowns. Furthermore, if contributions from possible local sources are neglected, the intrinsic DM anisotropy sets the maximum degree of total anisotropy. As a consequence, if some anisotropy larger than the DM upper bound is detected, its origin could not be ascribed to DM, and would constitute an unambiguous evidence for the presence of astrophysical local discrete sources of high energy electrons and positrons. The Fermi-LAT will be able to probe such scenarios in the next years. (orig.)

  12. Cosmic Ray contribution to the WMAP polarization data on the Cosmic Microwave Background

    CERN Document Server

    Wibig, Tadeusz

    2015-01-01

    We have updated our analysis of the 9-year WMAP data using the collection of polarization maps looking for the presence of additional evidence for a finite 'cosmic ray foreground' for the CMB. We have given special attention to high Galactic latitudes, where the recent BICEP2 findings were reported. The method of examining the correlation with the observed gamma ray flux proposed in our earlier papers and applied to the polarization data shows that the foreground related to cosmic rays is still observed even at high Galactic altitudes and conclusions about gravitational waves are not yet secure. Theory has it that there is important information about inflationary gravitational waves in the fine structure of the CMB polarization properties (polarization vector and angle) and it is necessary to examine further the conclusions that can be gained from studies of the CMB maps, in view of the disturbing foreground effects.

  13. ANALYSIS OF WMAP 7 YEAR TEMPERATURE DATA: ASTROPHYSICS OF THE GALACTIC HAZE

    Energy Technology Data Exchange (ETDEWEB)

    Pietrobon, Davide; Gorski, Krzysztof M.; Bartlett, James; Colombo, Loris P. L.; Jewell, Jeffrey B.; Pagano, Luca; Rocha, Graca; Lawrence, Charles R. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099 (United States); Banday, A. J. [Universie de Toulouse, UPS-OMP, IRAP, Toulouse (France); Dobler, Gregory [Kavli Institute for Theoretical Physics, University of California, Santa Barbara Kohn Hall, Santa Barbara, CA 93106 (United States); Hildebrandt, Sergi R. [Division of Physics, Mathematics and Astronomy, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Eriksen, Hans Kristian [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, N-0315 Oslo (Norway); Saha, Rajib, E-mail: davide.pietrobon@jpl.nasa.gov [Physics Department, Indian Institute of Science Education and Research Bhopal, Bhopal, MP 462023 (India)

    2012-08-10

    We perform a joint analysis of the cosmic microwave background (CMB) and Galactic emission from the WMAP 7 year temperature data. Using the Commander code, based on Gibbs sampling, we simultaneously derive the CMB and Galactic components on scales larger than 1 Degree-Sign with improved sensitivity over previous work. We conduct a detailed study of the low-frequency Galactic foreground, focusing on the 'microwave haze' emission around the Galactic center. We demonstrate improved performance in quantifying the diffuse Galactic emission when including Haslam 408 MHz data and when jointly modeling the spinning and thermal dust emission. We examine whether the hypothetical Galactic haze can be explained by a spatial variation of the synchrotron spectral index, and find that the excess of emission around the Galactic center is stable with respect to variations of the foreground model. Our results demonstrate that the new Galactic foreground component-the microwave haze-is indeed present.

  14. Primordial Magnetism in the CMB: Exact Treatment of Faraday Rotation and WMAP7 Bounds

    CERN Document Server

    Pogosian, Levon; Ng, Yi-Fung; Vachaspati, Tanmay

    2011-01-01

    Faraday rotation induced B-modes can provide a distinctive signature of primordial magnetic fields because of their characteristic frequency dependence and because they are only weakly damped on small scales, allowing them to dominate B-modes from other sources. By numerically solving the full CMB radiative transport equations, we study the B-mode power spectrum induced by stochastic magnetic fields that have significant power on scales smaller than the thickness of the last scattering surface. Constraints on the magnetic field energy density and inertial scale are derived from WMAP 7-year data, and are stronger than the big bang nucleosynthesis (BBN) bound for a range of parameters. Observations of the CMB polarization at smaller angular scales are crucial to provide tighter constraints or a detection.

  15. Foreground removal from WMAP 5 yr temperature maps using an MLP neural network

    DEFF Research Database (Denmark)

    Nørgaard-Nielsen, Hans Ulrik

    2010-01-01

    Aims. One of the main obstacles for extracting the cosmic microwave background (CMB) signal from observations in the mm/sub-mm range is the foreground contamination by emission from Galactic component: mainly synchrotron, free-free, and thermal dust emission. The statistical nature of the intrinsic...... CMB signal makes it essential to minimize the systematic errors in the CMB temperature determinations. Methods. The feasibility of using simple neural networks to extract the CMB signal from detailed simulated data has already been demonstrated. Here, simple neural networks are applied to the WMAP 5......, the systematic errors, i.e. errors correlated with the Galactic foregrounds, are very small. Conclusions. With these results the neural network method is well prepared for dealing with the high-quality CMB data from the ESA Planck Surveyor satellite. © ESO, 2010....

  16. All-sky reconstruction of the primordial scalar potential from WMAP temperature data

    CERN Document Server

    Dorn, Sebastian; Enßlin, Torsten A

    2014-01-01

    An essential quantity required to understand the physics of the early Universe, in particular the inflationary epoch, is the primordial scalar potential $\\Phi$ and its statistics. We present for the first time an all-sky reconstruction of $\\Phi$ with corresponding $1\\sigma$-uncertainty from WMAP's cosmic microwave background (CMB) temperature data - a map of the very early Universe right after the inflationary epoch. This has been achieved by applying a Bayesian inference method that separates the whole inverse problem of the reconstruction into many independent ones, each of them solved by an optimal linear filter (Wiener filter). In this way, the three-dimensional potential $\\Phi$ gets reconstructed slice by slice resulting in a thick shell of nested spheres around the comoving distance to the last scattering surface. Each slice represents the primordial scalar potential $\\Phi$ projected onto a sphere with corresponding distance. Furthermore, we present an advanced method for inferring $\\Phi$ and its power ...

  17. First Observational Tests of Eternal Inflation: Analysis Methods and WMAP 7-Year Results

    CERN Document Server

    Feeney, Stephen M; Mortlock, Daniel J; Peiris, Hiranya V

    2010-01-01

    In the picture of eternal inflation, our observable universe resides inside a single bubble nucleated from an inflating false vacuum. Many of the theories giving rise to eternal inflation predict that we have causal access to collisions with other bubble universes, providing an opportunity to confront these theories with observation. We present the results from the first observational search for the effects of bubble collisions, using cosmic microwave background data from the WMAP satellite. Our search targets a generic set of properties associated with a bubble collision spacetime, which we describe in detail. We use a modular algorithm that is designed to avoid a posteriori selection effects, automatically picking out the most promising signals, performing a search for causal boundaries, and conducting a full Bayesian model selection analysis. We outline each component of this algorithm, describing its response to simulated CMB skies with and without bubble collisions. We rule out bubble collisions over a r...

  18. In-Plane Optical Anisotropy of Layered Gallium Telluride.

    Science.gov (United States)

    Huang, Shengxi; Tatsumi, Yuki; Ling, Xi; Guo, Huaihong; Wang, Ziqiang; Watson, Garrett; Puretzky, Alexander A; Geohegan, David B; Kong, Jing; Li, Ju; Yang, Teng; Saito, Riichiro; Dresselhaus, Mildred S

    2016-09-27

    Layered gallium telluride (GaTe) has attracted much attention recently, due to its extremely high photoresponsivity, short response time, and promising thermoelectric performance. Different from most commonly studied two-dimensional (2D) materials, GaTe has in-plane anisotropy and a low symmetry with the C2h(3) space group. Investigating the in-plane optical anisotropy, including the electron-photon and electron-phonon interactions of GaTe is essential in realizing its applications in optoelectronics and thermoelectrics. In this work, the anisotropic light-matter interactions in the low-symmetry material GaTe are studied using anisotropic optical extinction and Raman spectroscopies as probes. Our polarized optical extinction spectroscopy reveals the weak anisotropy in optical extinction spectra for visible light of multilayer GaTe. Polarized Raman spectroscopy proves to be sensitive to the crystalline orientation of GaTe, and shows the intricate dependences of Raman anisotropy on flake thickness, photon and phonon energies. Such intricate dependences can be explained by theoretical analyses employing first-principles calculations and group theory. These studies are a crucial step toward the applications of GaTe especially in optoelectronics and thermoelectrics, and provide a general methodology for the study of the anisotropy of light-matter interactions in 2D layered materials with in-plane anisotropy.

  19. Flow stress anisotropy

    DEFF Research Database (Denmark)

    Winther, G.

    1996-01-01

    stress Variation in the rolling plane, which may be as high as 20%, are presented. The traditional Taylor model is applied to the data to account for the effect of texture. However, texture effects alone are not enough to explain all of the observed anisotropy. New models which take the combined effects...... of texture and deformation microstructure into account are presented. The models are based on the Taylor and Sachs models but modified with an anisotropic critical shear stress to account for the effect of the microstructure. The agreement between experimental data and model predictions is definitely better...

  20. Are all modes created equal? An analysis of the WMAP 5- and 7-year data without inflationary prejudice

    Science.gov (United States)

    Gjerløw, Eirik; Elgarøy, Øystein

    2011-03-01

    We submit recent claims of hints of primordial tensor perturbations and a scale-dependent spectral index in the WMAP data to a closer scrutiny. Our approach differs in that we use different best-fit values at which to fix the parameters not to be varied, and in that we use CosmoMC, thus incorporating the WMAP likelihood code and EE and BB mode data. We introduce a new parameter to test the claims of a scale-dependent spectral index. While we do find some hints of a scale-dependent spectral index over the multipole range ℓ=2-220, the change in maximum likelihood is too small to justify introducing a new parameter. We conclude that there is no significant detection of primordial tensor perturbations, and that the assumption of a scale-independent spectral index in this multipole range has little effect on the amount of primordial gravitational waves found.

  1. Some Doubts on the Validity of the Foreground Galactic Contribution Subtraction from Microwave Anisotropies

    Indian Academy of Sciences (India)

    Martín López-Corredoira

    2007-06-01

    The Galactic foreground contamination in CMBR anisotropies, especially from the dust component, is not easily separable from the cosmological or extragalactic component. In this paper, some doubts will be raised concerning the validity of the methods used until now to remove Galactic dust emission and will show that none of them achieves its goal. First, I review the recent bibliography on the topic and discuss critically the methods of foreground subtraction: the cross-correlation with templates, analysis assuming the spectral shape of the Galactic components, the ``maximum entropy method”, ``internal linear combination”, and ``wavelet-based high resolution fitting of internal templates”. Second, I analyse the Galactic latitude dependence from WMAP data. The frequency dependence is discussed with data in the available literature. The result is that all methods of subtracting the Galactic contamination are inaccurate. The Galactic latitude dependence analysis or the frequency dependence of the anisotropies in the range 50–250 GHz put a constraint on the maximum Galactic contribution in the power spectrum to be less than ∼ 10% (68% C. L.) for an ∼ 1 degree scale, and possibly higher for larger scales. The origin of most of the signals in the CMBR anisotropies is not Galactic. In any case, the subtraction of the galaxy is not accurate enough to allow a ``precision Cosmology”; other sources of contamination (extragalactic, solar system) are also present.

  2. Protecting the primordial baryon asymmetry in the $SU(2)_{L}$ triplet Higgs model compatible with KamLAND and WMAP

    OpenAIRE

    Hasegawa, K

    2004-01-01

    We find the condition that the primordial baryon asymmetry is not washed out in the $SU(2)_{L}$ triplet Higgs model by solving the Boltzmann equation. We further require that the model is compatible with the recent results of the neutrino oscillation experiments and WMAP, and the constraints on the $\\rho$ parameter imposed by the LEP. We finally obtain the allowed region of the parameters in the model.

  3. Ferromagnetic resonance of nanocrystal chains with competitive and cooperative anisotropy

    Science.gov (United States)

    Koulialias, D.

    2015-12-01

    The formation of cellular magnetic dipoles by chain assemblies of nearly equidimensional, stable single domain magnetite nanocrystals aligned along their [111] easy axes is a common property encountered in many magnetotactic bacteria (MTB). The development of such dipoles permits the navigation of MTB along the geomagnetic field towards favourable habitats, a process also referred to as magnetotaxis. An important characteristic is the anisotropy within the chains, which mainly consists of the magnetocrystalline and the shape anisotropy. The two anisotropy contributions can be cooperative or competitive depending on the orientation with respect to the chain axis. The change in the relative orientation between the two anisotropy contributions caused by the Verwey transition TV, can be used to unambigously detect MTB and their fossil remains. Ferromagnetic resonance spectroscopy (FMR) is a well-established method to probe magnetic anisotropy in absolute units. Here, we use X- and Q-band FMR spectroscopy and numerical simulation to analyze the MTB species of Desulfovibrio magneticus RS-1 with elongated magnetosomes aligned along the [100] hard axis. In this special case, the magnetotaxis above TV is strongly affected by the shape anisotropy of the nanocrystals and it is competitive to the magnetocrystalline anisotropy. Below TV, the change of the easy axis [111] to [100] generates a cooperative system, which can be considered as the optimal case for magnetotaxis, i.e., shape and magnetocrystalline anisotropies are nearly parallel to the MTB chain axis. In summary, the nanocrystal assembly in RS-1 provides another step towards a better understanding of the physics behind magnetotaxis.

  4. Constraints on isocurvature models from the WMAP first-year data

    CERN Document Server

    Moodley, K; Dunkley, J; Ferreira, P G; Skordis, C

    2004-01-01

    We investigate the constraints imposed by the first-year WMAP CMB data extended to higher multipole by data from ACBAR, BOOMERANG, CBI and the VSA and by the LSS data from the 2dF galaxy redshift survey on the possible amplitude of primordial isocurvature modes. A flat universe with CDM and Lambda is assumed, and the baryon, CDM (CI), and neutrino density (NID) and velocity (NIV) isocurvature modes are considered. Constraints on the allowed isocurvature contributions are established from the data for various combinations of the adiabatic mode and one, two, and three isocurvature modes, with intermode cross-correlations allowed. Since baryon and CDM isocurvature are observationally virtually indistinguishable, these modes are not considered separately. We find that when just a single isocurvature mode is added, the present data allows an isocurvature fraction as large as 13+-6, 7+-4, and 13+-7 percent for adiabatic plus the CI, NID, and NIV modes, respectively. When two isocurvature modes plus the adiabatic mo...

  5. The joint large-scale foreground-CMB posteriors of the 3-year WMAP data

    CERN Document Server

    Eriksen, H K; Jewell, J B; Banday, A J; Górski, K M; Lawrence, C R

    2007-01-01

    Using a Gibbs sampling algorithm for joint CMB estimation and component separation, we compute the large-scale CMB and foreground posteriors of the 3-yr WMAP temperature data. Our parametric data model includes the cosmological CMB signal and instrumental noise, a single power law foreground component with free amplitude and spectral index for each pixel, a thermal dust template with a single free overall amplitude, and free monopoles and dipoles at each frequency. This simple model yields a surprisingly good fit to the data over the full frequency range from 23 to 94 GHz. We obtain a new estimate of the CMB sky signal and power spectrum, and a new foreground model, including a measurement of the effective spectral index over the high-latitude sky. A particularly significant result is the detection of a common spurious offset in all frequency bands of ~ -13muK, as well as a dipole in the V-band data. Correcting for these is essential when determining the effective spectral index of the foregrounds. We find th...

  6. Fermi-LAT and WMAP observations of the Puppis A Supernova Remnant

    CERN Document Server

    Hewitt, J W; Lemoine-Goumard, M; Reposeur, T; Ballet, J; Tanaka, T

    2012-01-01

    We report the detection of GeV \\gamma-ray emission from the supernova remnant Puppis A with the Fermi Gamma-Ray Space Telescope. Puppis A is among the faintest supernova remnants yet detected at GeV energies, with a luminosity of only 2.7x10^34 (D/2.2 kpc)^2 erg/s between 1 and 100 GeV. The \\gamma-ray emission from the remnant is spatially extended, with a morphology matching that of the radio and X-ray emission, and is well described by a simple power law with an index of 2.1. We attempt to model the broadband spectral energy distribution, from radio to \\gamma-rays, using standard nonthermal emission mechanisms. To constrain the relativistic electron population we use 7 years of WMAP data to extend the radio spectrum up to 93 GHz. Both leptonic and hadronic dominated models can reproduce the nonthermal spectral energy distribution, requiring a total content of cosmic ray (CR) electrons and protons accelerated in Puppis A of at least (1-5)x10^49 erg.

  7. Fermi-Lat and WMAP Observations of the Puppis a Supernova Remnant

    Science.gov (United States)

    Hewitt, John William; Grondin, M. H.; Lemoine-Goumard, M.; Reposeur, T.; Ballet, J.; Tanaka, T.

    2012-01-01

    We report the detection of GeV gamma-ray emission from the supernova remnant Puppis A with the Fermi Gamma-Ray Space Telescope. Puppis A is among the faintest supernova remnants yet detected at GeV energies, with a luminosity of only 2.7×10(exp 34) (D/2.2 kpc)(exp 2) erg s(exp -1) between 1 and 100 GeV. The gamma-ray emission from the remnant is spatially extended, with a morphology matching that of the radio and X-ray emission, and is well described by a simple power law with an index of 2.1. We attempt to model the broadband spectral energy distribution, from radio to gamma-rays, using standard nonthermal emission mechanisms. To constrain the relativistic electron population we use 7 years of WMAP data to extend the radio spectrum up to 93 GHz. Both leptonic and hadronic dominated models can reproduce the nonthermal spectral energy distribution, requiring a total content of cosmic ray (CR) electrons and protons accelerated in Puppis A of at least WCR is approx. (1 - 5)×10 (exp 49) erg.

  8. On the Origins of the CMB: Insight from the COBE, WMAP, and Relikt-1 Satellites

    Directory of Open Access Journals (Sweden)

    Robitaille P.-M.

    2007-01-01

    Full Text Available The powerful “Cosmic Microwave Background (CMB” signal currently associated with the origins of the Universe is examined from a historical perspective and relative to the experimental context in which it was measured. Results from the COBE satellite are reviewed, with particular emphasis on the systematic error observed in determining the CMB temperature. The nature of the microwave signal emanating from the oceans is also discussed. From this analysis, it is demonstrated that it is improper for the COBE team to model the Earth as a 285 K blackbody source. The assignment of temperatures to objects that fail to meet the requirements set forth in Kirchhoff’s law constitutes a serious overextension of the laws of thermal emission. Using this evidence, and the general rule that powerful signals are associated with proximal sources, the CMB monopole signal is reassigned to the oceans. In turn, through the analysis of COBE, WMAP, and Relikt-1 data, the dipole signal is attributed to motion through a much weaker microwave field present both at the position of the Earth and at the second Lagrange point.

  9. Inflection point inflation: WMAP constraints and a solution to the fine tuning problem

    International Nuclear Information System (INIS)

    We consider observational constraints and fine-tuning issues in a renormalizable model of inflection point inflation, with two independent parameters. We derive constraints on the parameter space of this model arising from the WMAP 7-year power spectrum. It has previously been shown that it is possible to successfully embed this potential in the MSSM. Unfortunately, to do this requires severe fine-tuning. We address this issue by introducing a hybrid field to dynamically uplift the potential with a subsequent smooth phase transition to end inflation at the necessary point. Large parameter regions exist where this drastically reduces the fine-tuning required without ruining the viability of the model. A side effect of this mechanism is that it increases the width of the slow-roll region of the potential, thus also alleviating the problem of the fine-tuning of initial conditions. The MSSM embedding we study has been previously shown to be able to explain the smallness of the neutrino masses. The hybrid transition does not spoil this feature as there exist parameter regions where the fine-tuning parameter is as large as 10−1 and the neutrino masses remain small

  10. Cosmic microwave background reconstruction from WMAP and Planck PR2 data

    Science.gov (United States)

    Bobin, J.; Sureau, F.; Starck, J.-L.

    2016-06-01

    We describe a new estimate of the cosmic microwave background (CMB) intensity map reconstructed by a joint analysis of the full Planck 2015 data (PR2) and nine years of WMAP data. The proposed map provides more than a mere update of the CMB map introduced in a previous paper since it benefits from an improvement of the component separation method L-GMCA (Local-Generalized Morphological Component Analysis), which facilitates efficient separation of correlated components. Based on the most recent CMB data, we further confirm previous results showing that the proposed CMB map estimate exhibits appealing characteristics for astrophysical and cosmological applications: i) it is a full-sky map as it did not require any inpainting or interpolation postprocessing; ii) foreground contamination is very low even on the galactic center; and iii) the map does not exhibit any detectable trace of thermal Sunyaev-Zel'dovich contamination. We show that its power spectrum is in good agreement with the Planck PR2 official theoretical best-fit power spectrum. Finally, following the principle of reproducible research, we provide the codes to reproduce the L-GMCA, which makes it the only reproducible CMB map. The reconstructed CMB map and the code are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/591/A50

  11. Fermi LAT and WMAP observations of the supernova remnant HB 21

    CERN Document Server

    Pivato, G; Tibaldo, L; Acero, F; Ballet, J; Brandt, T J; de Palma, F; Giordano, F; Janssen, G H; Johannesson, G; Smith, D A

    2013-01-01

    We present the analysis of Fermi Large Area Telescope (LAT) $\\gamma$-ray observations of HB~21 (G89.0+4.7). We detect significant $\\gamma$-ray emission associated with the remnant: the flux >100 MeV is $9.4\\pm0.8(stat)\\pm1.6(syst)\\times10^{-11}$ erg cm$^{-2}$ s$^{-1}$. HB 21 is well modeled by a uniform disk centered at $l= 88{\\deg}.75\\pm 0{\\deg}.04$, $b = +4{\\deg}.65 \\pm 0{\\deg}.06$ with a radius of $1{\\deg}.19 \\pm 0{\\deg}.06$. The $\\gamma$-ray spectrum shows clear evidence of curvature, suggesting a cutoff or break in the underlying particle population at an energy of a few GeV. We complement $\\gamma$-ray observations with the analysis of the WMAP 7-year data from 23 to 93 GHz, achieving the first detection of HB 21 at these frequencies. In combination with archival radio data, the radio spectrum shows a spectral break which helps to constrain the relativistic electron spectrum, hence parameters of simple non-thermal radiation models. In one-zone models multiwavelength data favor the origin of $\\gamma$ rays...

  12. Inflection point inflation: WMAP constraints and a solution to the fine tuning problem

    Energy Technology Data Exchange (ETDEWEB)

    Hotchkiss, Shaun [Department of Physics, University of Helsinki and Helsinki Institute of Physics, P.O. Box 64, FIN-00014 University of Helsinki (Finland); Mazumdar, Anupam [Physics Department, Lancaster University, Lancaster LA1 4YB (United Kingdom); Nadathur, Seshadri, E-mail: shaun.hotchkiss@helsinki.fi, E-mail: a.mazumdar@lancaster.ac.uk, E-mail: seshadri@thphys.ox.ac.uk [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP (United Kingdom)

    2011-06-01

    We consider observational constraints and fine-tuning issues in a renormalizable model of inflection point inflation, with two independent parameters. We derive constraints on the parameter space of this model arising from the WMAP 7-year power spectrum. It has previously been shown that it is possible to successfully embed this potential in the MSSM. Unfortunately, to do this requires severe fine-tuning. We address this issue by introducing a hybrid field to dynamically uplift the potential with a subsequent smooth phase transition to end inflation at the necessary point. Large parameter regions exist where this drastically reduces the fine-tuning required without ruining the viability of the model. A side effect of this mechanism is that it increases the width of the slow-roll region of the potential, thus also alleviating the problem of the fine-tuning of initial conditions. The MSSM embedding we study has been previously shown to be able to explain the smallness of the neutrino masses. The hybrid transition does not spoil this feature as there exist parameter regions where the fine-tuning parameter is as large as 10{sup −1} and the neutrino masses remain small.

  13. Inflection point inflation: WMAP constraints and a solution to the fine-tuning problem

    CERN Document Server

    Hotchkiss, Shaun; Nadathur, Seshadri

    2011-01-01

    We consider observational constraints and fine-tuning issues in a very generic model of inflection point inflation with two independent parameters and with quadratic, cubic and quartic self-interactions of the inflaton at sub-Planckian field values. We investigate the constraints on parameter space of this model obtained from WMAP 7-year power spectrum limits and the requirement to generate an appropriate number of e-folds of inflation, which allow inflaton mass to take values over a wide range of scales. At low scales, it is possible to realise this potential in an interesting particle physics model based on the MSSM that can also explain the smallness of the neutrino masses and provide a dark matter candidate as part of the inflaton. It is known that this low scale model of inflation requires severe fine-tuning. We address this issue by dynamically uplifting the potential with a subsequent smooth phase transition which ends inflation to drastically reduce the fine-tuning required. We demonstrate that it is ...

  14. Real space tests of the statistical isotropy and Gaussianity of the three year WMAP data

    CERN Document Server

    Lew, Bartosz

    2008-01-01

    CONTEXT: Gaussianity will become a strong observational tool allowing to constrain viable inflationary models. AIMS: In this paper, we introduce and analyze a new method for testing SI and Gaussianity and apply it to the 3 years WMAP CMB data. METHODS: We use an original pixelization scheme to divide the sky into regions of varying size and shape. We then measure the first four moments of the one-point distribution within these regions and using their simulated spatial distributions we test the statistical isotropy and Gaussianity hypotheses. By randomly varying orientations of these regions, their angular size and shape, we sample the underlying CMB field in a new manner, that offers a richer exploration of data the content. In our analysis we account for all correlations between different regions and also show the impact on the results when these correlations are neglected. The statistical significance is assessed via comparison with realistic Monte-Carlo simulations of the observed data. RESULTS: We find t...

  15. A CMB Gibbs sampler for localized secondary anisotropies

    CERN Document Server

    Bull, Philip; Eriksen, Hans Kristian; Ferreira, Pedro G; Fuskeland, Unni; Gorski, Krzysztof M; Jewell, Jeffrey B

    2014-01-01

    As well as primary fluctuations, CMB temperature maps contain a wealth of additional information in the form of secondary anisotropies. Secondary effects that can be identified with individual objects, such as the thermal and kinetic Sunyaev-Zel'dovich (SZ) effects due to galaxy clusters, are difficult to unambiguously disentangle from foreground contamination and the primary CMB, which currently inhibits their use as precision cosmological probes. We develop a Bayesian formalism for rigorously characterising anisotropies that are localised on the sky, taking the TSZ and KSZ effects as an example. Using a Gibbs sampling scheme, we are able to efficiently sample from the joint posterior distribution for a multi-component model of the sky with many thousands of correlated physical parameters. The posterior can then be exactly marginalised to estimate properties of the secondary anisotropies, fully taking into account degeneracies with the other signals in the CMB map. We show that this method is computationally...

  16. Thermal conductivity anisotropy of metasedimentary and igneous rocks

    Science.gov (United States)

    Davis, Michael G.; Chapman, David S.; van Wagoner, Thomas M.; Armstrong, Phillip A.

    2007-05-01

    Thermal conductivity anisotropy was determined for three sets of metasedimentary and igneous rocks from central Utah, USA. Most conductivity measurements were made in transient mode with a half-space, line source instrument oriented in two orthogonal directions on a flat face cut perpendicular to bedding. One orientation of the probe yields thermal conductivity parallel to bedding (kpar) directly, the other orientation of the probe measures a product of conductivities parallel and perpendicular to bedding from which the perpendicular conductivity (kperp) is calculated. Some direct measurements of kpar and kperp were made on oriented cylindrical discs using a conventional divided bar device in steady state mode. Anisotropy is defined as kpar/kperp. Precambrian argillites from Big Cottonwood Canyon have anisotropy values from 0.8 to 2.1 with corresponding conductivity perpendicular to bedding of 2.0 to 6.2 W m-1 K-1. Anisotropy values for Price Canyon sedimentary samples are less than 1.2 with a mean of 1.04 although thermal conductivity perpendicular to bedding for the samples varied from 1.3 to 5.0 W m-1 K-1. The granitic rocks were found to be essentially isotropic with thermal conductivity perpendicular to bedding having a range of 2.2 to 3.2 W m-1 K-1 and a mean of 2.68 W m-1 K-1. The results confirm the observation by Deming [1994] that anisotropy is negligible for rocks having kperp greater than 4.0 W m-1 K-1 and generally increases for low conductivity metamorphic and clay-rich rocks. There is little evidence, however, for his suggestion that thermal conductivity anisotropy of all rocks increases systematically to about 2.5 for low thermal conductivity rocks.

  17. Fermi LAT and WMAP observations of the supernova remnant HB 21

    Energy Technology Data Exchange (ETDEWEB)

    Pivato, G. [Dipartimento di Fisica e Astronomia " G. Galilei," Università di Padova, I-35131 Padova (Italy); Hewitt, J. W. [CRESST, University of Maryland, Baltimore County, Baltimore, MD 21250 (United States); Tibaldo, L. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Acero, F.; Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d' Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); De Palma, F.; Giordano, F. [Dipartimento di Fisica " M. Merlin" dell' Università e del Politecnico di Bari, I-70126 Bari (Italy); Janssen, G. H. [University of Manchester, Manchester, M13 9PL (United Kingdom); Jóhannesson, G. [Science Institute, University of Iceland, IS-107 Reykjavik (Iceland); Smith, D. A., E-mail: giovanna.pivato@pd.infn.it, E-mail: john.w.hewitt@nasa.gov, E-mail: ltibaldo@slac.stanford.edu [Centre d' Études Nucléaires de Bordeaux Gradignan, IN2P3/CNRS, Université Bordeaux 1, BP120, F-33175 Gradignan Cedex (France)

    2013-12-20

    We present the analysis of Fermi Large Area Telescope γ-ray observations of HB 21 (G89.0+4.7). We detect significant γ-ray emission associated with the remnant: the flux >100 MeV is 9.4 ± 0.8 (stat) ± 1.6 (syst) × 10{sup –11} erg cm{sup –2} s{sup –1}. HB 21 is well modeled by a uniform disk centered at l = 88.°75 ± 0.°04, b = +4.°65 ± 0.°06 with a radius of 1.°19 ± 0.°06. The γ-ray spectrum shows clear evidence of curvature, suggesting a cutoff or break in the underlying particle population at an energy of a few GeV. We complement γ-ray observations with the analysis of the WMAP 7 yr data from 23 to 93 GHz, achieving the first detection of HB 21 at these frequencies. In combination with archival radio data, the radio spectrum shows a spectral break, which helps to constrain the relativistic electron spectrum, and, in turn, parameters of simple non-thermal radiation models. In one-zone models multiwavelength data favor the origin of γ rays from nucleon-nucleon collisions. A single population of electrons cannot produce both γ rays through bremsstrahlung and radio emission through synchrotron radiation. A predominantly inverse-Compton origin of the γ-ray emission is disfavored because it requires lower interstellar densities than are inferred for HB 21. In the hadronic-dominated scenarios, accelerated nuclei contribute a total energy of ∼3 × 10{sup 49} erg, while, in a two-zone bremsstrahlung-dominated scenario, the total energy in accelerated particles is ∼1 × 10{sup 49} erg.

  18. Anisotropy in rotating drums

    Science.gov (United States)

    Povall, Timothy; McBride, Andrew; Govender, Indresan

    2015-11-01

    An anisotropic relationship between the stress and the strain rate has been observed in two-dimensional simulations of rotating drums. The objective of this work is to investigate the structure of the constitutive relation using three-dimensional discrete-element-method simulations of a rotating drum containing identical rigid spheres for a range of rotational speeds. Anisotropy is quantified from the alignment of the stress and strain rate tensors, with the strain rate computed using a least-squares fit. It is shown that in certain regions there is a strong anisotropic relationship, regardless of the speed of rotation. The effective friction coefficient is examined in order to determine the phase space in which the μ (I) rheology is valid. Lastly, a depth-averaged approach through the flowing layer is employed to determine the relationship between the velocity tangential to the equilibrium surface and the height of the flowing layer. A power-law relationship that approaches linear at high speeds is observed. Supported by NRF/DST Scarce Skills (South Africa).

  19. Anisotropy in solid inflation

    International Nuclear Information System (INIS)

    In the model of solid / elastic inflation, inflation is driven by a source that has the field theoretical description of a solid. To allow for prolonged slow roll inflation, the solid needs to be extremely insensitive to the spatial expansion. We point out that, because of this property, the solid is also rather inefficient in erasing anisotropic deformations of the geometry. This allows for a prolonged inflationary anisotropic solution, providing the first example with standard gravity and scalar fields only which evades the conditions of the so called cosmic no-hair conjecture. We compute the curvature perturbations on the anisotropic solution, and the corresponding phenomenological bound on the anisotropy. Finally, we discuss the analogy between this model and the f(φ)F2 model, which also allows for anisotropic inflation thanks to a suitable coupling between the inflaton φ and a vector field. We remark that the bispectrum of the curvature perturbations in solid inflation is enhanced in the squeezed limit and presents a nontrivial angular dependence, as had previously been found for the f(φ)F2 model

  20. Neutrino Anisotropies after Planck

    CERN Document Server

    Gerbino, Martina; Said, Najla

    2013-01-01

    We present new constraints on the rest-frame sound speed, c_eff^2, and the viscosity parameter, c_vis^2, of the Cosmic Neutrino Background from the recent measurements of the Cosmic Microwave Background anisotropies provided by the Planck satellite. While broadly consistent with the ex- pectations of c_eff^2 = c_vis^2 = 1/3 in the standard scenario, the Planck dataset hints for a higher value of the viscosity parameter, with c_vis^2 = 0.60 +/- 0.18 at 68% c.l., and a lower value of the sound speed, with c_eff^2 = 0.304 +/- 0.013 at 68% c.l.. We find a correlation between the neutrino parameters and the lensing amplitude of the temperature power spectrum A_L. When the latter parameter is allowed to vary, we find a better consistency with the standard model with c_vis^2 = 0.51 +/- 0.22, c_eff^2 = 0.311 +/- 0.019 and A_L = 1.08 +/- 0.18 at 68% c.l.. This result indicates that the anomalous large value of A_L measured by Planck could be connected to non-standard neutrino properties. Including additional datasets ...

  1. Are all perturbations created equal? An analysis of the WMAP 5- and 7-year data without inflationary prejudice

    CERN Document Server

    Gjerløw, Eirik

    2010-01-01

    We submit recent claims of a semi-significant detection of primordial tensor perturbations in the WMAP data to a closer scrutiny. Our conclusion is in brief that no such mode is present at a detectable level once the analysis is done more carefully. These claims have their root in a brief debate in the late 1990s about the standard calculation of the scalar and tensor spectra in standard inflationary theory, where Grishchuk and collaborators claimed that their amplitudes should be roughly equal. We give a brief summary of the debate and our own reasons for why the standard calculation is correct.

  2. New inflation vs. chaotic inflation, higher degree potentials and the reconstruction program in light of WMAP3

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Chiu Man; Boyanovsky, D.; de Vega, H.J.; Ho, C.M.; Sanchez, N.G.

    2007-02-12

    The cosmic microwave background power spectra are studied for different families of single field new and chaotic inflation models in the effective field theory approach to inflation. We implement a systematic expansion in 1/N(e), where N(e)~;;50 is the number of e-folds before the end of inflation. We study the dependence of the observables (n(s), r and dn(s)/dlnk) on the degree of the potential (2n) and confront them to the WMAP3 and large scale structure data: This shows in general that fourth degree potentials (n=2) provide the best fit to the data; the window of consistency with the WMAP3 and LSS data narrows for growing n. New inflation yields a good fit to the r and n(s) data in a wide range of field and parameter space. Small field inflation yields r<0.16 while large field inflation yields r>0.16 (for N(e)=50). All members of the new inflation family predict a small but negative running -4(n+1) x 10-4<=dn(s)/dlnk<=-2 x 10-4. (The values of r, n(s), dn(s)/dlnk for arbitrary N(e) follow by a simple rescaling from the N(e)=50 values.) A reconstruction program is carried out suggesting quite generally that for n(s) consistent with the WMAP3 and LSS data and r<0.1 the symmetry breaking scale for new inflation is |phi0|~;;10MPl while the field scale at Hubble crossing is lbar phi(c) rbar~;;M(Pl). The family of chaotic models features r>=0.16 (for N(e)=50) and only a restricted subset of chaotic models are consistent with the combined WMAP3 bounds on r, n(s), dn(s)/dlnk with a narrow window in field amplitude around |phi(c)|~;;15M(Pl). We conclude that a measurement of r<0.16 (for N(e)=50) distinctly rules out a large class of chaotic scenarios and favors small field new inflationary models. As a general consequence, new inflation emerges more favored than chaotic inflation.

  3. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    Duvaa, Uffe; Ørngreen, Rikke; Weinkouff Mathiasen, Anne-Gitte;

    2013-01-01

    Mobile probing is a method, developed for learning about digital work situations, as an approach to discover new grounds. The method can be used when there is a need to know more about users and their work with certain tasks, but where users at the same time are distributed (in time and space...... to mobile probing being a flexible method for uncovering the unknowns, as a way of getting rich data to the analysis and design phases. On the other hand it is difficult to engage users to give in depth explanations, which seem easier in synchronous dialogs (whether online or face2face). The development...

  4. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    Duvaa, Uffe; Ørngreen, Rikke; Weinkouff, Anne-Gitte;

    2012-01-01

    Mobile probing is a method, which has been developed for learning about digital work situations, as an approach to discover new grounds. The method can be used when there is a need to know more about users and their work with certain tasks, but where users at the same time are distributed (in time...... point to mobile probing being a flexible method for uncovering the unknowns, as a way of getting rich data to the analysis and design phases. On the other hand it is difficult to engage users to give in depth explanations, which seem easier in synchronous dialogs (whether online or face2face...

  5. Broadband optical limiter based on nonlinear photoinduced anisotropy in bacteriorhodopsin film

    Science.gov (United States)

    Huang, Yuhua; Siganakis, Georgios; Moharam, M. G.; Wu, Shin-Tson

    2004-11-01

    Nonlinear photoinduced anisotropy in a bacteriorhodopsin film was theoretically and experimentally investigated and a broadband active optical limiter was demonstrated in the visible spectral range. A diode-pumped second harmonic yttrium aluminum garnet laser was used as a pumping beam and three different wavelengths at λ =442, 532, and 655nm from different lasers were used as probing beams. The pump and probe beams overlap at the sample. When the pumping beam is absent, the probing beam cannot transmit the crossed polarizers. With the presence of the pumping beam, a portion of the probing light is detected owing to the photoinduced anisotropy. Due to the optical nonlinearity, the transmitted probing beam intensity is clamped at a certain value, which depends on the wavelength, when the pumping beam intensity exceeds 5mW/mm2. Good agreement between theory and experiment is found.

  6. Spin confinement by anisotropy modulation

    Energy Technology Data Exchange (ETDEWEB)

    Bland, J.A.C. [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom)]. E-mail: jacb1@phy.cam.ac.uk; Lew, W.S.; Li, S.P.; Lopez-Diaz, L.; Vaz, C.A.F. [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom); Natali, M.; Chen, Y. [Laboratoire de Photonique et de Nanostructures, CNRS-LPN, Marcoussis (France)

    2002-10-07

    The spin configuration in a magnet is in general a 'natural' consequence of both the intrinsic properties of the material and the sample dimensions. We demonstrate that this limitation can be overcome in a homogeneous ferromagnetic film by engineering an anisotropy contrast. Substrates with laterally modulated single-crystal and polycrystalline surface regions were used to induce selective epitaxial growth of a ferromagnetic Ni film. The resulting spatially varying magnetic anisotropy leads to regular perpendicular and in-plane magnetic domains, separated by a new type of magnetic domain wall-the 'anisotropy constrained' magnetic wall. Micromagnetic simulations indicate that the wall is asymmetric, has a small out-of-plane component and has no mobility under external perturbation. (author)

  7. Spin confinement by anisotropy modulation

    Science.gov (United States)

    Bland, J. A. C.; Lew, W. S.; Li, S. P.; Lopez-Diaz, L.; Vaz, C. A. F.; Natali, M.; Chen, Y.

    2002-10-01

    The spin configuration in a magnet is in general a `natural' consequence of both the intrinsic properties of the material and the sample dimensions. We demonstrate that this limitation can be overcome in a homogeneous ferromagnetic film by engineering an anisotropy contrast. Substrates with laterally modulated single-crystal and polycrystalline surface regions were used to induce selective epitaxial growth of a ferromagnetic Ni film. The resulting spatially varying magnetic anisotropy leads to regular perpendicular and in-plane magnetic domains, separated by a new type of magnetic domain wall-the `anisotropy constrained' magnetic wall. Micromagnetic simulations indicate that the wall is asymmetric, has a small out-of-plane component and has no mobility under external perturbation.

  8. Detection of primordial non-Gaussianity (fNL) in the WMAP 3-year data at above 99.5% confidence

    CERN Document Server

    Yadav, Amit P S

    2007-01-01

    We present evidence for the detection of primordial non-Gaussianity of the local type (fNL), using the temperature information of the Cosmic Microwave Background (CMB) from the WMAP 3-year data. We employ the bispectrum estimator of non-Gaussianity described in Yadav et al. 2007b which allows us to analyze the entirety of the WMAP data without an arbitrary cut-off in angular scale. Using the combined information from WMAP's two main science channels up to l_{max}=750 and the conservative Kp0 foreground mask we find 26.9 < fNL < 146.7 at 95% C.L., with a central value of fNL=86.8. This corresponds to a rejection of fNL=0 at more than 99.5% significance. We find that this detection is robust to variations in l_{max}, frequency and masks. We conclude that the WMAP 3-year data disfavors single field slow-roll inflation.

  9. Exhaustive Study of Cosmic Microwave Background Anisotropies in Quintessential Scenarios

    CERN Document Server

    Brax, P; Riazuelo, A; Brax, Philippe; Martin, Jerome; Riazuelo, Alain

    2000-01-01

    Recent high precision measurements of the CMB anisotropies performed by the BOOMERanG and MAXIMA-1 experiments provide an unmatched set of data allowing to probe different cosmological models. Among these scenarios, motivated by the recent measurements of the luminosity distance versus redshift relation for type Ia supernovae, is the quintessence hypothesis. It consists in assuming that the acceleration of the Universe is due to a scalar field whose final evolution is insensitive to the initial conditions. Within this framework we investigate the cosmological perturbations for two well-motivated potentials: the Ratra-Peebles and the SUGRA tracking potentials. We show that the solutions of the perturbed equations possess an attractor and that, as a consequence, the insensitivity to the initial conditions is preserved at the perturbed level. Then, we study the predictions of these two models for structure formation and CMB anisotropies and investigate the general features of the multipole moments in the presenc...

  10. Late time CMB anisotropies constrain mini-charged particles

    Energy Technology Data Exchange (ETDEWEB)

    Burrage, C.; Redondo, J.; Ringwald, A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Jaeckel, J. [Univ. of Durham, Inst. for Particle Physics Phenomenology (United Kingdom)

    2009-09-15

    Observations of the temperature anisotropies induced as light from the CMB passes through large scale structures in the late universe are a sensitive probe of the interactions of photons in such environments. In extensions of the Standard Model which give rise to mini-charged particles, photons propagating through transverse magnetic fields can be lost to pair production of such particles. Such a decrement in the photon flux would occur as photons from the CMB traverse the magnetic fields of galaxy clusters. Therefore late time CMB anisotropies can be used to constrain the properties of mini- charged particles. We outline how this test is constructed, and present new constraints on mini-charged particles from observations of the Sunyaev-Zel'dovich effect in the Coma cluster. (orig.)

  11. WMAP 3yr data with the CCA: anomalous emission and impact of component separation on the CMB power spectrum

    CERN Document Server

    Bonaldi, A; Leach, S; Stivoli, F; Baccigalupi, C; De Zotti, G

    2007-01-01

    The Correlated Component Analysis (CCA) allows us to estimate how the different diffuse emissions mix in CMB experiments, exploiting also complementary information from other surveys. It is especially useful to deal with possible additional components. An application of CCA to WMAP maps assuming that only the canonical Galactic emissions are present, highlights the widespread presence of a spectrally flat "synchrotron" component, largely uncorrelated with the synchrotron template, suggesting that an additional foreground is indeed required. We have tested various spectral shapes for such component, namely a power law as expected if it is flat synchrotron, and two spectral shapes that may fit the spinning dust emission: a parabola in the logS - log(frequency) plane, and a grey body. Quality tests applied to the reconstructed CMB maps clearly disfavour two of the models. The CMB power spectra, estimated from CMB maps reconstructed exploiting the three surviving foreground models, are generally consistent with t...

  12. Fourier-transform infrared anisotropy in cross and parallel sections of tendon and articular cartilage

    Directory of Open Access Journals (Sweden)

    Bidthanapally Aruna

    2008-10-01

    Full Text Available Abstract Background Fourier Transform Infrared Imaging (FTIRI is used to investigate the amide anisotropies at different surfaces of a three-dimensional cartilage or tendon block. With the change in the polarization state of the incident infrared light, the resulting anisotropic behavior of the tissue structure is described here. Methods Thin sections (6 μm thick were obtained from three different surfaces of the canine tissue blocks and imaged at 6.25 μm pixel resolution. For each section, infrared imaging experiments were repeated thirteen times with the identical parameters except a 15° increment of the analyzer's angle in the 0° – 180° angular space. The anisotropies of amide I and amide II components were studied in order to probe the orientation of the collagen fibrils at different tissue surfaces. Results For tendon, the anisotropy of amide I and amide II components in parallel sections is comparable to that of regular sections; and tendon's cross sections show distinct, but weak anisotropic behavior for both the amide components. For articular cartilage, parallel sections in the superficial zone have the expected infrared anisotropy that is consistent with that of regular sections. The parallel sections in the radial zone, however, have a nearly isotropic amide II absorption and a distinct amide I anisotropy. Conclusion From the inconsistency in amide anisotropy between superficial to radial zone in parallel section results, a schematic model is used to explain the origins of these amide anisotropies in cartilage and tendon.

  13. Excitonic intraband relaxation and polarization anisotropies in PTCDA on femtosecond and picosecond timescales

    International Nuclear Information System (INIS)

    We report on investigations of optical excitations in polycrystalline organic molecular crystals with quasi-1D-stacked crystal structure and negative exciton dispersion. As model system, we choose thin films of the perylene derivative 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA). Using pump-probe spectroscopy, we show how the relaxation from the absorbing state towards the border of the Brillouin zone occurs on a 120 fs timescale. Time-resolved luminescence anisotropy gives evidence that as a result of the coherent coupling between adjacent stacks, populations of the Davydov-split states that are prepared during photo-excitation relax into the emitting states in less than 5 ps. The behavior of the luminescence anisotropy can be explained by the orientation of the two PTCDA molecules in the unit cell. However, a full understanding of the ultrafast pump-probe anisotropy requires novel explanations beyond current models

  14. Global imaging of the Earth's deep interior: seismic constraints on (an)isotropy, density and attenuation

    NARCIS (Netherlands)

    Trampert, J.; Fichtner, A.

    2013-01-01

    Seismic tomography is the principal tool to probe the deep interior of the Earth. Models of seismic anisotropy induced by crystal alignment provide insight into the underlying convective motion, and variations of density allow us to discriminate between thermal and compositional heterogeneities. Thi

  15. Magnetoresistance Anisotropy in WTe2

    Science.gov (United States)

    Thoutam, Laxman Raju; Wang, Yonglei; Xiao, Zhili; Das, Saptarshi; Luican Mayer, Adina; Divan, Ralu; Crabtree, George W.; Kwok, Wai Kwong

    We report the angle dependence of the magnetoresistance in WTe2. Being a layered material, WTe2 is considered to be electronically two-dimensional (2D). Our results demonstrate that it is in fact 3D with an anisotropy of effective mass as small as 2. We measured the magnetic field dependence of the sample resistance R(H) at various angles between the applied magnetic field with respect to the c-axis of the crystal and found that they can be scaled based on the mass anisotropy, which changes from ~2 to ~5 with decreasing temperature in the Fermi liquid state. We will also discuss the origin of the turn-on temperature behavior in this material.

  16. [Cosmic Microwave Background (CMB) Anisotropies

    Science.gov (United States)

    Silk, Joseph

    1998-01-01

    One of the main areas of research is the theory of cosmic microwave background (CMB) anisotropies and analysis of CMB data. Using the four year COBE data we were able to improve existing constraints on global shear and vorticity. We found that, in the flat case (which allows for greatest anisotropy), (omega/H)0 less than 10-7, where omega is the vorticity and H is the Hubble constant. This is two orders of magnitude lower than the tightest, previous constraint. We have defined a new set of statistics which quantify the amount of non-Gaussianity in small field cosmic microwave background maps. By looking at the distribution of power around rings in Fourier space, and at the correlations between adjacent rings, one can identify non-Gaussian features which are masked by large scale Gaussian fluctuations. This may be particularly useful for identifying unresolved localized sources and line-like discontinuities. Levin and collaborators devised a method to determine the global geometry of the universe through observations of patterns in the hot and cold spots of the CMB. We have derived properties of the peaks (maxima) of the CMB anisotropies expected in flat and open CDM models. We represent results for angular resolutions ranging from 5 arcmin to 20 arcmin (antenna FWHM), scales that are relevant for the MAP and COBRA/SAMBA space missions and the ground-based interferometer. Results related to galaxy formation and evolution are also discussed.

  17. Mechanochromism, Shear Force Anisotropy, and Molecular Mechanics in Polydiacetylene Monolayers

    Energy Technology Data Exchange (ETDEWEB)

    BURNS,ALAN R.; CARPICK,R.W.; SASAKI,DARRYL Y.; SHELNUTT,JOHN A.; HADDAD,R.

    2000-08-14

    The authors use scanning probe microscopy to actuate and characterize the nanoscale mechanochromism of polydiacetylene monolayer on atomically-flat silicon oxide substrates. They find explicit evidence that the irreversible blue-to-red transformation is caused by shear forces exerted normal to the polydiacetylene polymer backbone. The anisotropic probe-induced transformation is characterized by a significant change in the tilt orientation of the side chains with respect to the surface normal. They also describe a new technique, based on shear force microscopy, that allows them to image friction anisotropy of polydiacetylene monolayer independent of scan direction. Finally, they discuss preliminary molecular mechanics modeling and electronic structure calculations that allow them to understand the correlation of mechanochromism with bond-angle changes in the conjugated polymer backbone.

  18. Lichtinduzierte Generierung und Charakterisierung optischer Anisotropie

    OpenAIRE

    Jung, Carl Christoph

    2005-01-01

    Eine Nutzung der optischen Anisotropie dünner Schichten ist vor allem für die Displaytechnologie, die optische Datenspeicherung und für optische Sicherheitselemente von hoher Bedeutung. Diese Doktorarbeit befasst sich mit theoretischen und experimentellen Untersuchung von dreidimensionaler Anisotropie und dabei insbesondere mit der Untersuchung von lichtinduzierter dreidimensionaler Anisotropie in organischen dünnen Polymer-Schichten. Die gewonnenen Erkentnisse und entwickelten Methoden könne...

  19. Flow stress anisotropy in aluminium

    DEFF Research Database (Denmark)

    Juul Jensen, D.; Hansen, N.

    1990-01-01

    The plastic anisotropy of cold-rolled high purity aluminum (99.996%) and commercially pure aluminum (99.6%) has been investigated. Sample parameters were the initial grain size and the degree of plastic strain (ϵ ... tension as a function of the angle between the tensile axis and the rolling direction. Textures were determined by neutron diffraction, and Taylor M-factors were calculated. The microstructures were studied by TEM. It was found that the flow stress varies significantly with orientation both at low...

  20. Upper bounds on signals due to WIMP self--annihilation : comments on the case of the synchrotron radiation from the galactic center and the WMAP haze

    CERN Document Server

    Bottino, A; Fornengo, N; Scopel, S

    2008-01-01

    Two recent papers reconsider the possibility that the excess of microwave emission from a region within $\\sim 20^0$ of the galactic center (the {\\it WMAP haze}), measured by WMAP, can be due to the synchrotron emission originated by neutralino self-annihilation; on the basis of this possible occurrence, also upper bounds on the neutralino self-annihilation cross--section are suggested. In the present note, we show that, when the rescaling of the galactic WIMP density is duly taken into account for subdominant WIMPs, the upper bound derivable generically for {\\it any} signal due to self-conjugate thermal WIMPs is more stringent than the one obtainable from analysis of the WMAP haze. Our upper bound disfavors the interpretation of this excess in the microwave emission from the galactic center as mainly due to neutralino self--annihilation, except possibly for neutralinos with masses $\\lsim$ 100 GeV. We also comment on the fact that an experimental upper bound which can compete with our generic upper limit, deri...

  1. On the problem of electron-induced anisotropy effect in As2S3-based glasses

    International Nuclear Information System (INIS)

    Effect of electron-induced anisotropy was observed in glassy As2S3-based samples irradiated by accelerated electrons (E=2.8 MeV) in the perpendicular plane to the probe light. Spectral and compositional dependences of this effect and its time stability at room temperature were discussed. It was supposed that the microstructural mechanism of the anisotropy effect was connected with electron-induced formation of new oriented (relatively to the electron flow) defects in the form of broken chemical bonds

  2. Probing magnetochirality

    Indian Academy of Sciences (India)

    Rupamanjari Ghosh

    2002-08-01

    Magnetochiral anisotropy refers to the phenomenon that when light is passed through a chiral medium placed in an external magnetic field, the refractive index, or equivalently, the absorption encountered by the light differs depending on whether it travels parallel or antiparallel to the magnetic field. It is a very small effect, the change in refractive index because of this effect alone being of the order of 10-11. This effect has recently been measured in an active ring laser interferometer in which the detection scheme convincingly eliminates the contributions from natural optical activity, the Faraday effect and other stray anisotropies in the system. The phenomenon is important in the context of fundamental interactions between light and matter and the governing symmetry principles, and also in biochemistry as one possible explanation for the homochirality of life.

  3. Anomalous Nernst Effect with Magnetocrystalline Anisotropy (110)

    Science.gov (United States)

    Chesman, Carlos; Costa Neto, Jose; Department of Physics-UFRN Team

    2014-03-01

    When a ferromagnetic material is submitted to a temperature gradient and the magnetic field generates voltage on the edges of the samples, this is called the Anomalous Nernst Effect (ANE). The Heusler alloys that currently exhibit this effect are the most promising for spintronics and spin caloritronics. In this study we perform a theoretical investigation of voltage curves associated to the ANE, when the material displays magnetocrystalline anisotropy for experimental results in two configurations, ANE versus applied magnetic field and planar angle variations of ANE. We analyzed three types of magnetocrystalline anisotropy: cubic anisotropy (100) with C4 symmetry, uniaxial anisotropy with C2 symmetry and cubic anisotropy (110). The aim was to prove that cubic anisotropy (110) is equivalent to anisotropy (100) combined with uniaxial anisotropy. Theoretical fitting of experimental ANE data demonstrates this total equivalence and that a new interpretation with the use of cubic anisotropy (110) may be due to the atomic arrangement of the so-called full-Heusler. Comparative analyses of Co2FeAl and Co2MnGe alloys will be presented. CNPq, CAPES, FAPERN.

  4. Probe Storage

    NARCIS (Netherlands)

    Gemelli, Marcellino; Abelmann, Leon; Engelen, Johan B.C.; Khatib, Mohammed G.; Koelmans, Wabe W.; Zaboronski, Olog; Campardo, Giovanni; Tiziani, Federico; Laculo, Massimo

    2011-01-01

    This chapter gives an overview of probe-based data storage research over the last three decades, encompassing all aspects of a probe recording system. Following the division found in all mechanically addressed storage systems, the different subsystems (media, read/write heads, positioning, data chan

  5. Scale-dependent non-Gaussianities in the WMAP data as identified by using surrogates and scaling indices

    CERN Document Server

    Raeth, C; Rossmanith, G; Modest, H; Suetterlin, R; Gorski, K M; Delabrouille, J; Morfill, G E

    2010-01-01

    We present a model-independent investigation of the WMAP data with respect to scale- dependent non-Gaussianities (NGs). To this end, we employ the method of constrained randomization. For generating so-called surrogate maps a shuffling scheme is applied to the Fourier phases of the original data, which allows to test for the presence of higher order correlations (HOCs) on well-defined scales. Using scaling indices as test statistics for the HOCs we find highly significant signatures for non-Gaussianities when considering all scales. We test for NGs in the bands l = [2,20], l = [20,60], l = [60,120] and l = [120,300]. We find highly significant signatures for both non-Gaussianities and ecliptic hemispherical asymmetries for the interval l = [2, 20]. We also obtain highly significant deviations from Gaussianity for the band l = [120,300]. The result for the full l-range can be interpreted as a superposition of the signatures found in the bands l = [2, 20] and l = [120, 300]. We find remarkably similar results w...

  6. A search for concentric rings with unusual variance in the 7-year WMAP temperature maps using a fast convolution approach

    CERN Document Server

    Bielewicz, P; Banday, A J

    2012-01-01

    We present a method for the computation of the variance of cosmic microwave background (CMB) temperature maps on azimuthally symmetric patches using a fast convolution approach. As an example of the application of the method, we show results for the search for concentric rings with unusual variance in the 7-year WMAP data. We re-analyse claims concerning the unusual variance profile of rings centred at two locations on the sky that have recently drawn special attention in the context of the conformal cyclic cosmology scenario proposed by Penrose (2009). We extend this analysis to rings with larger radii and centred on other points of the sky. Using the fast convolution technique enables us to perform this search with higher resolution and a wider range of radii than in previous studies. We show that for one of the two special points rings with radii larger than 10 degrees have systematically lower variance in comparison to the concordance LambdaCDM model predictions. However, we show that this deviation is ca...

  7. Particle physics implications of Wilkinson microwave anisotropy project measurements

    Indian Academy of Sciences (India)

    U A Yajnik

    2004-12-01

    We present an overview of the implications of the WMAP data for particle physics. The standard parameter set and characterising the inflaton potential can be related to the power-law indices characterising deviation of the CMB spectrum from the scale invariant form. Different classes of inflation potentials are in turn naturally associated with different unified schemes. At present WMAP does not exclude any but a few simple unified models. In particular, hybrid models favoured by supersymmetric unification continue to be viable. However future improvement in data leading to better determination of the `running' of power-law indices should help to narrow the possibilities for unified models. The main conclusion is that WMAP is consistent with the paradigm of GUT scale (1016 GeV) inflation.

  8. Comment on the "Excess ellipticity of hot and cold spots WMAP data?" by Berntsen, E. and Hansen, F.K

    CERN Document Server

    Kashin, A L

    2012-01-01

    The recent paper by Berntsen and Hansen devoted to the analysis of elliptic-ity of anisotropies in CMB maps, distorts some statements of previous studies, misses relevant papers, along with superficial comparison of the results (in part of definitions, the role of noise, angular resolution, model parameters).

  9. Anisotropy in solar wind plasma turbulence.

    Science.gov (United States)

    Oughton, S; Matthaeus, W H; Wan, M; Osman, K T

    2015-05-13

    A review of spectral anisotropy and variance anisotropy for solar wind fluctuations is given, with the discussion covering inertial range and dissipation range scales. For the inertial range, theory, simulations and observations are more or less in accord, in that fluctuation energy is found to be primarily in modes with quasi-perpendicular wavevectors (relative to a suitably defined mean magnetic field), and also that most of the fluctuation energy is in the vector components transverse to the mean field. Energy transfer in the parallel direction and the energy levels in the parallel components are both relatively weak. In the dissipation range, observations indicate that variance anisotropy tends to decrease towards isotropic levels as the electron gyroradius is approached; spectral anisotropy results are mixed. Evidence for and against wave interpretations and turbulence interpretations of these features will be discussed. We also present new simulation results concerning evolution of variance anisotropy for different classes of initial conditions, each with typical background solar wind parameters.

  10. CMB anisotropy science: a review

    CERN Document Server

    Challinor, Anthony

    2012-01-01

    The cosmic microwave background (CMB) provides us with our most direct observational window to the early universe. Observations of the temperature and polarization anisotropies in the CMB have played a critical role in defining the now-standard cosmological model. In this contribution we review some of the basics of CMB science, highlighting the role of observations made with ground-based and balloon-borne Antarctic telescopes. Most of the ingredients of the standard cosmological model are poorly understood in terms of fundamental physics. We discuss how current and future CMB observations can address some of these issues, focusing on two directly relevant for Antarctic programmes: searching for gravitational waves from inflation via B-mode polarization, and mapping dark matter through CMB lensing.

  11. Seepage Anisotropy of Heterogeneous Body

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Ore dumps are heterogeneous bodies with anisotropic seepage characteristics because of the ore segregation.In an indoor experiment, a dump was constructed with three strata, where the horizontal and vertical seepage experiments were carried out.Horizontals flow are regarded as phreatic plan flows without penetration.Its seepage law satifies the Dupuit equation.With parallel lay seepage model, the equivalent seepage coefficient in the horizontal flow was obtained and was equivalent to the weighted mean of the seepage coefficient of each stratum.An unsaturated flow appeared in the vertical experiment, with a hydraulic gradient of 1.The vertical flow was equivalent to the seepage model that moved in vertical bedding; its equivalent seepage coefficient depended on the stratum with the minimum seepage coefficient.That the experiment showed clear anisotropy in a heterogeneous body was obvious with an anisotropic coefficient between 63 and 155, which is 25 to 100 times larger than that of a homogeneous body.

  12. Fluorescence anisotropy of diphenylhexatriene and its cationic Trimethylamino derivative in liquid dipalmitoylphosphatidylcholine liposomes: opposing responses to isoflurane

    Directory of Open Access Journals (Sweden)

    Nelson Steven C

    2012-03-01

    Full Text Available Abstract Background The mechanism of action of volatile general anesthetics has not yet been resolved. In order to identify the effects of isoflurane on the membrane, we measured the steady-state anisotropy of two fluorescent probes that reside at different depths. Incorporation of anesthetic was confirmed by shifting of the main phase transition temperature. Results In liquid crystalline dipalmitoylphosphatidylcholine liposomes, isoflurane (7-25 mM in the bath increases trimethylammonium-diphenylhexatriene fluorescence anisotropy by ~0.02 units and decreases diphenylhexatriene anisotropy by the same amount. Conclusions The anisotropy data suggest that isoflurane decreases non-axial dye mobility in the headgroup region, while increasing it in the tail region. We propose that these results reflect changes in the lateral pressure profile of the membrane.

  13. Primordial anisotropies in gauged hybrid inflation

    International Nuclear Information System (INIS)

    We study primordial anisotropies generated in the model of gauged hybrid inflation in which the complex waterfall field is charged under a U(1)gauge field. Primordial anisotropies are generated either actively during inflation or from inhomogeneities modulating the surface of end of inflation during waterfall transition. We present a consistent δN mechanism to calculate the anisotropic power spectrum and bispectrum. We show that the primordial anisotropies generated at the surface of end of inflation do not depend on the number of e-folds and therefore do not produce dangerously large anisotropies associated with the IR modes. Furthermore, one can find the parameter space that the anisotropies generated from the surface of end of inflation cancel the anisotropies generated during inflation, therefore relaxing the constrains on model parameters imposed from IR anisotropies. We also show that the gauge field fluctuations induce a red-tilted power spectrum so the averaged power spectrum from the gauge field can change the total power spectrum from blue to red. Therefore, hybrid inflation, once gauged under a U(1) field, can be consistent with the cosmological observations

  14. Anisotropy of rare-earth magnets

    Institute of Scientific and Technical Information of China (English)

    R.Skomski; D.J.Sellmyer

    2009-01-01

    Rare-earth intermetallics such as Nd2FeI4B and Sm-Co are widely used as high-performance permanent magnets,because they combine high magnetocrystalline anisotropy with reasonable magnetization and Curie temperature.The anisotropy is a combined effect of spin-orbit coupling and electrostatic crystal-field interactions.The main contribution comes from the rare-earth 4f electrons,which are well-screened from the crystalline environment but exhibit a strong spin-orbit coupling.In this limit,the magnetocrystalline anisotropy has a very transparent physical interpretation,the anisotropy energy essentially being equal to the energy of Hund's-rules 4f ion in the crystal field.The corresponding expression for the lowest-order uniaxial anisotropy constant K1 is used to discuss rare-earth substitutions,which have recently attracted renewed interest due to shifts in the rare-earth production and demand.Specific phenomena reviewed in this article are the enhancement of the anisotropy of Sm2Fe17 due to interstitial nitrogen,the use of Sm-Co magnets for high-temperature applications,and the comparison of rare-earth single-ion anisotropy with other single-ion and two-ion mechanisms.

  15. Probing Capacity

    CERN Document Server

    Asnani, Himanshu; Weissman, Tsachy

    2010-01-01

    We consider the problem of optimal probing of states of a channel by transmitter and receiver for maximizing rate of reliable communication. The channel is discrete memoryless (DMC) with i.i.d. states. The encoder takes probing actions dependent on the message. It then uses the state information obtained from probing causally or non-causally to generate channel input symbols. The decoder may also take channel probing actions as a function of the observed channel output and use the channel state information thus acquired, along with the channel output, to estimate the message. We refer to the maximum achievable rate for reliable communication for such systems as the 'Probing Capacity'. We characterize this capacity when the encoder and decoder actions are cost constrained. To motivate the problem, we begin by characterizing the trade-off between the capacity and fraction of channel states the encoder is allowed to observe, while the decoder is aware of channel states. In this setting of 'to observe or not to o...

  16. DNA probes

    International Nuclear Information System (INIS)

    The creation of DNA probes for detection of specific nucleotide segments differs from ligand detection in that it is a chemical rather than an immunological reaction. Complementary DNA or RNA is used in place of the antibody and is labelled with 32P. So far, DNA probes have been successfully employed in the diagnosis of inherited disorders, infectious diseases, and for identification of human oncogenes. The latest approach to the diagnosis of communicable and parasitic infections is based on the use of deoxyribonucleic acid (DNA) probes. The genetic information of all cells is encoded by DNA and DNA probe approach to identification of pathogens is unique because the focus of the method is the nucleic acid content of the organism rather than the products that the nucleic acid encodes. Since every properly classified species has some unique nucleotide sequences that distinguish it from every other species, each organism's genetic composition is in essence a finger print that can be used for its identification. In addition to this specificity, DNA probes offer other advantages in that pathogens may be identified directly in clinical specimens

  17. Magnetic Domain Confinement by Anisotropy Modulation

    Science.gov (United States)

    Li, S. P.; Lew, W. S.; Bland, J. A.; Lopez-Diaz, L.; Vaz, C. A.; Natali, M.; Chen, Y.

    2002-02-01

    The spin configuration in a magnet is in general a ``natural'' consequence of both the intrinsic properties of the material and the sample dimensions. We demonstrate that this limitation can be overcome in a homogeneous ferromagnetic film by engineering an anisotropy contrast. Substrates with laterally modulated single-crystal and polycrystalline surface regions were used to induce selective epitaxial growth of a ferromagnetic Ni film. The resulting spatially varying magnetic anisotropy leads to regular perpendicular and in-plane magnetic domains, separated by a new type of magnetic wall-the ``anisotropy constrained'' magnetic wall.

  18. Apparent resistivity of azimuthal anisotropy layered media

    Institute of Scientific and Technical Information of China (English)

    阮爱国; 毛桐恩; 李清河; 葛双成

    2002-01-01

    The electric field, equations of boundary conditions and calculation formula of apparent resistivity are derived for azimuthal anisotropy layered media with DC method based on anisotropic Ohm(s law. Taking Schlumberger symmetric system as an example and using recurrence formula of nuclear function, the paper theoretically simulates a model of four layers with the same anisotropy coefficient for each layer. The deep sounding curves of resistivity and the pattern of contours are obtained for the model. The results shows the theoretical formula of this paper is correct, the deep sounding curves not only exhibit the difference of resistivity among layers but also indicate the anisotropy characteristics of layers.

  19. Effect of anisotropy on small magnetic clusters

    CERN Document Server

    Hucht, Alfred; Sil, Shreekantha; Entel, Peter; 10.1103/PhysRevB.84.104438

    2012-01-01

    The effect of dipolar interaction and local uniaxial anisotropy on the magnetic response of small spin clusters where spins are located on the vertices of icosahedron, cuboctahedron, tetrahedron and square geometry have been investigated. We consider the ferromagnetic and antiferromagnetic spin-1/2 and spin-1 Heisenberg model with uniaxial anisotropy and dipolar interaction and apply numerical exact diagonalization technique in order to study the influence of frustration and anisotropy on the ground state properties of the spin-clusters. The ground state magnetization, spin-spin correlation and several thermodynamic quantities such as entropy and specific heat are calculated as a function of temperature and magnetic field.

  20. Report on 3- and 4-Point Correlation Statistics in COBE DMR Anisotropy Maps

    Science.gov (United States)

    Hinshaw, Gary; Gorski, Krzystof M.; Bennett, Charles L.; Banday, Anthony J.

    1996-01-01

    As part of the work performed under this contract, we have computed the 3- and 4-point correlation functions of the COBE-DMR 2-year and 4-year anisotropy maps. The results of our work showed that the 3-point correlation function is consistent with zero and that the 4-point function is not a very sensitive probe of non-Gaussian behavior in the COBE-DMR data.

  1. Influence of interface exchange coupling in perpendicular anisotropy [Pt/Co]50/TbFe bilayers

    OpenAIRE

    Mangin, S.; Hauet, Thomas; Fischer, P.; Kim, D. H.; Kortright, J.B.; Chesnel, K.; Arenholz, E.; Fullerton, Eric E.

    2008-01-01

    International audience We present the magnetization evolution of perpendicular anisotropy TbFe and ͓Co/ Pt͔ 50 thin films either in direct contact resulting in antiferromagnetic interfacial coupling or separated by a thick decoupling Pt layer. Magnetometry and x-ray magnetic circular dichroism spectroscopy determine the spatially averaged magnetic properties. Resonant magnetic x-ray small-angle scattering and magnetic soft x-ray transmission microscopy probed the domain configurations and ...

  2. Exhaustive study of cosmic microwave background anisotropies in quintessential scenarios

    Science.gov (United States)

    Brax, Philippe; Martin, Jérôme; Riazuelo, Alain

    2000-11-01

    Recent high-precision measurements of the CMB anisotropies performed by the BOOMERanG and MAXIMA-1 experiments provide an unmatched set of data allowing us to probe different cosmological models. Among these scenarios, motivated by the recent measurements of the luminosity distance versus redshift relation for type Ia supernovas, is the quintessence hypothesis. It consists of assuming that the acceleration of the Universe is due to a scalar field whose final evolution is insensitive to the initial conditions. Within this framework we investigate the cosmological perturbations for two well-motivated potentials: the Ratra-Peebles and the SUGRA tracking potentials. We show that the solutions of the perturbed equations possess an attractor and that, as a consequence, the insensitivity to the initial conditions is preserved at the perturbed level. Then, we study the predictions of these two models for structure formation and CMB anisotropies and investigate the general features of the multipole moments in the presence of quintessence. We also compare the CMB multipoles calculated with the help of a full Boltzmann code with the BOOMERanG and MAXIMA-1 data. We pay special attention to the location of the second peak and demonstrate that it significantly differs from the location obtained in the cosmological constant case. Finally, we argue that the SUGRA potential is compatible with all the recent data with standard values of the cosmological parameters. In particular, it fits the MAXIMA-1 data better than a cosmological constant or the Ratra-Peebles potential.

  3. Cellulose and the Control of Growth Anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Tobias I. Baskin

    2004-04-01

    The authors research aims to understand morphogenesis, focusing on growth anisotropy, a process that is crucial to make organs with specific and heritable shapes. For the award, the specific aims were to test hypotheses concerning how growth anisotropy is controlled by cell wall structure, particularly by the synthesis and alignment of cellulose microfibrils, the predominant mechanical element in the cell wall. This research has involved characterizing the basic physiology of anisotropic expansion, including measuring it at high resolution; and second, characterizing the relationship between growth anisotropy, and cellulose microfibrils. Important in this relationship and also to the control of anisotropic expansion are structures just inside the plasma membrane called cortical microtubules, and the research has also investigated their contribution to controlling anisotropy and microfibril alignment. In addition to primary experimental papers, I have also developed improved methods relating to these objectives as well as written relevant reviews. Major accomplishments in each area will now be described.

  4. The Intrinsic Quasar Luminosity Function: Accounting for Accretion Disk Anisotropy

    CERN Document Server

    DiPompeo, M A; Brotherton, M S; Runnoe, J C; Green, R F

    2014-01-01

    Quasar luminosity functions are a fundamental probe of the growth and evolution of supermassive black holes. Measuring the intrinsic luminosity function is difficult in practice, due to a multitude of observational and systematic effects. As sample sizes increase and measurement errors drop, characterizing the systematic effects is becoming more important. It is well known that the continuum emission from the accretion disk of quasars is anisotropic --- in part due to its disk-like structure --- but current luminosity function calculations effectively assume isotropy over the range of unobscured lines of sight. Here, we provide the first steps in characterizing the effect of random quasar orientations and simple models of anisotropy on observed luminosity functions. We find that the effect of orientation is not insignificant and exceeds other potential corrections such as those from gravitational lensing of foreground structures. We argue that current observational constraints may overestimate the intrinsic l...

  5. Conductivity-type anisotropy in molecular solids

    OpenAIRE

    Ostrick, J. R.; Dodabalapur, A.; Torsi, L.; Lovinger, A, J.; Kwock, E. W.; Miller, T. M.; Galvin, M; Berggren, Magnus; Katz, H. E.

    1997-01-01

    Thin polycrystalline films of perylenetetracarboxylic dianyhydride (PTCDA), an organic molecular solid, exhibits substantial anisotropies in its electronic transport properties. Only electrons transport in the directions along molecular planes, while mainly holes transport in the direction normal to molecular planes. A series of measurements on both field effect transistors with PTCDA active layers and light emitting diodes with PTCDA transport layers documents the anisotropy seen in the elec...

  6. A read and write element for magnetic probe recording

    NARCIS (Netherlands)

    Craus, C.B.; Onoue, T.; Ramstöck, K.; Geerts, W.J.M.A.; Siekman, M.H.; Abelmann, L.; Lodder, J.C.

    2005-01-01

    We present our results on the development of magnetic sensors for application in magnetic probe recording. Successful writing experiments on a magnetic medium with perpendicular anisotropy show that magnetic domains of 130 nm can be reversed in a heat-assisted process. For reading purposes we propos

  7. Friction anisotropy in boronated graphite

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, N., E-mail: niranjan@igcar.gov.in [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Radhika, R. [Crystal Growth Centre, Anna University, Chennai (India); Kozakov, A.T. [Research Institute of Physics, Southern Federal University, Rostov-on-Don (Russian Federation); Pandian, R. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Chakravarty, S. [UGC-DAE CSR, Kalpakkam (India); Ravindran, T.R.; Dash, S.; Tyagi, A.K. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India)

    2015-01-01

    Graphical abstract: - Highlights: • Friction anisotropy in boronated graphite is observed in macroscopic sliding condition. • Low friction coefficient is observed in basal plane and becomes high in prismatic direction. • 3D phase of boronated graphite transformed into 2D structure after friction test. • Chemical activity is high in prismatic plane forming strong bonds between the sliding interfaces. - Abstract: Anisotropic friction behavior in macroscopic scale was observed in boronated graphite. Depending upon sliding speed and normal loads, this value was found to be in the range 0.1–0.35 in the direction of basal plane and becomes high 0.2–0.8 in prismatic face. Grazing-incidence X-ray diffraction analysis shows prominent reflection of (0 0 2) plane at basal and prismatic directions of boronated graphite. However, in both the wear tracks (1 1 0) plane become prominent and this transformation is induced by frictional energy. The structural transformation in wear tracks is supported by micro-Raman analysis which revealed that 3D phase of boronated graphite converted into a disordered 2D lattice structure. Thus, the structural aspect of disorder is similar in both the wear tracks and graphite transfer layers. Therefore, the crystallographic aspect is not adequate to explain anisotropic friction behavior. Results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy shows weak signature of oxygen complexes and functional groups in wear track of basal plane while these species dominate in prismatic direction. Abundance of these functional groups in prismatic plane indicates availability of chemically active sites tends to forming strong bonds between the sliding interfaces which eventually increases friction coefficient.

  8. Friction anisotropy in boronated graphite

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Friction anisotropy in boronated graphite is observed in macroscopic sliding condition. • Low friction coefficient is observed in basal plane and becomes high in prismatic direction. • 3D phase of boronated graphite transformed into 2D structure after friction test. • Chemical activity is high in prismatic plane forming strong bonds between the sliding interfaces. - Abstract: Anisotropic friction behavior in macroscopic scale was observed in boronated graphite. Depending upon sliding speed and normal loads, this value was found to be in the range 0.1–0.35 in the direction of basal plane and becomes high 0.2–0.8 in prismatic face. Grazing-incidence X-ray diffraction analysis shows prominent reflection of (0 0 2) plane at basal and prismatic directions of boronated graphite. However, in both the wear tracks (1 1 0) plane become prominent and this transformation is induced by frictional energy. The structural transformation in wear tracks is supported by micro-Raman analysis which revealed that 3D phase of boronated graphite converted into a disordered 2D lattice structure. Thus, the structural aspect of disorder is similar in both the wear tracks and graphite transfer layers. Therefore, the crystallographic aspect is not adequate to explain anisotropic friction behavior. Results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy shows weak signature of oxygen complexes and functional groups in wear track of basal plane while these species dominate in prismatic direction. Abundance of these functional groups in prismatic plane indicates availability of chemically active sites tends to forming strong bonds between the sliding interfaces which eventually increases friction coefficient

  9. Does deformation saturate seismic anisotropy?

    Science.gov (United States)

    Tatham, D. J.; Lloyd, G. E.; Butler, R. W.; Casey, M.

    2006-12-01

    The progressive simple shear deformation that characterizes ductile fault zones in the crust involves both rotation and intensification of the strain ellipsoid. These mathematic predictions have been confirmed repeatedly by finite strain determinations in outcrop studies of natural shear zones and used to test geodynamic models of mountain belts. Seismic anisotropy (SA) methods offer the opportunity to pursue these approaches in situ. First however, we must calibrate the magnitude and orientation of the SA ellipsoid against naturally deformed tectonites of known strain state and microstructure. Here we present data from a field analogue of mafic ductile crust in an amphibolite-facies shear zone developed in a deformed mafic dyke embedded within the Lewisian Gneiss (Badcall, NW Scotland). Deflection of pre-existing linear and planar elements and attenuation of the dyke into the shear zone are used to determine the strain gradient. Specimens collected along this gradient were used to establish the geometric fabric intensity defined by different minerals (hornblende grain alignment and ellipticity of plagioclase clots). Finally, petrophysical properties were calculated for the specimens using the SEM-EBSD measured populations of lattice preferred orientations (LPO) for all mineral phases. It is the hornblende-plagioclase LPO, combined in their modal proportions and modulated by the individual mineral single crystal elastic properties, which define the SA profile across the shear zone. Hornblende develops a strong preferred dimensional orientation and hence LPO at shear strains of about 2, whereas the plagioclase LPO remains close to random regardless of bulk strain. The modelled SA of the samples is dominated therefore by the amphibole LPO. Although the values of bulk shear strain vary across the shear zone (0 at the margins to greater than 12 in the centre), the calculated intensity of SA saturates at a shear strain of about 2. These results, if typical of large

  10. The SLUGGS Survey: Breaking degeneracies between dark matter, anisotropy and the IMF using globular cluster subpopulations in the giant elliptical NGC 5846

    CERN Document Server

    Napolitano, Nicola R; Romanowsky, Aaron J; Forbes, Duncan A; Brodie, Jean P; Foster, Caroline

    2014-01-01

    We study the mass and anisotropy distribution of the giant elliptical galaxy NGC 5846 using stars, as well as the red and blue globular cluster (GC) subpopulations. We break degeneracies in the dynamical models by taking advantage of the different phase space distributions of the two GC subpopulations to unambiguously constrain the mass of the galaxy and the anisotropy of the GC system. Red GCs show the same spatial distribution and behaviour as the starlight, whereas blue GCs have a shallower density profile, a larger velocity dispersion and a lower kurtosis, all of which suggest a different orbital distribution. We use a dispersion-kurtosis Jeans analysis and find that the solutions of separate analyses for the two GC subpopulations overlap in the halo parameter space. The solution converges on a massive dark matter halo, consistent with expectations from $\\Lambda$CDM and WMAP7 cosmology in terms of virial mass ($\\log M_{DM} \\sim13.3 M_{sun}$) and concentration ($c_{vir}\\sim8$). This is the first such analy...

  11. On the problem of electron-induced anisotropy effect in As{sub 2}S{sub 3}-based glasses

    Energy Technology Data Exchange (ETDEWEB)

    Balitska, V.O.; Shpotyuk, O.I. E-mail: karat@ipm.lviv.ua

    2000-05-02

    Effect of electron-induced anisotropy was observed in glassy As{sub 2}S{sub 3}-based samples irradiated by accelerated electrons (E=2.8 MeV) in the perpendicular plane to the probe light. Spectral and compositional dependences of this effect and its time stability at room temperature were discussed. It was supposed that the microstructural mechanism of the anisotropy effect was connected with electron-induced formation of new oriented (relatively to the electron flow) defects in the form of broken chemical bonds.

  12. The expected anisotropy in solid inflation

    Energy Technology Data Exchange (ETDEWEB)

    Bartolo, Nicola; Ricciardone, Angelo [Dipartimento di Fisica e Astronomia ' ' G. Galilei' ' , Università degli Studi di Padova, via Marzolo 8, I-35131, Padova (Italy); Peloso, Marco; Unal, Caner, E-mail: nicola.bartolo@pd.infn.it, E-mail: peloso@physics.umn.edu, E-mail: angelo.ricciardone@pd.infn.it, E-mail: unal@physics.umn.edu [School of Physics and Astronomy, University of Minnesota, 116 Church Street S.E., Minneapolis 55455 (United States)

    2014-11-01

    Solid inflation is an effective field theory of inflation in which isotropy and homogeneity are accomplished via a specific combination of anisotropic sources (three scalar fields that individually break isotropy). This results in specific observational signatures that are not found in standard models of inflation: a non-trivial angular dependence for the squeezed bispectrum, and a possibly long period of anisotropic inflation (to drive inflation, the ''solid'' must be very insensitive to any deformation, and thus background anisotropies are very slowly erased). In this paper we compute the expected level of statistical anisotropy in the power spectrum of the curvature perturbations of this model. To do so, we account for the classical background values of the three scalar fields that are generated on large (superhorizon) scales during inflation via a random walk sum, as the perturbation modes leave the horizon. Such an anisotropy is unavoidably generated, even starting from perfectly isotropic classical initial conditions. The expected level of anisotropy is related to the duration of inflation and to the amplitude of the squeezed bispectrum. If this amplitude is close to its current observational limit (so that one of the most interesting predictions of the model can be observed in the near future), we find that a level of statistical anisotropy F{sup 2} gives frozen and scale invariant vector perturbations on superhorizon scales.

  13. Surface anisotropy characterisation with meteosat observations

    Science.gov (United States)

    Lattanzio, A.; Govaerts, Y. M.; Pinty, B.

    Surface albedo, or more precisely Directional Hemispherical Reflectance (DHR), is the integral the Bi-directional Reflectance Factor (BRF) of the surface over all angles of the upward hemisphere. The retrieval of the DHR trough space observations requires accounting for the scattering and absorption processes in the atmosphere as well as for the angular anisotropy of the surface, the two systems being radiatively coupled. The accuracy achieved in the albedo estimation depends thus on the density of the angular sampling and the reliability of the atmospheric correction. Pinty et al. demonstrated the possibility to derive reliable surface albedo from observations acquired by Meteosat, the European meteorological geostationary satellite. The purpose of this presentation is to analyse the accuracy of this new Meteosat Surface Albedo (MSA) product, including the effects due to instrument changes and associated calibration uncertainties. In particular, the consistency of the surface anisotropy characterisation is examined in detail. To this end, observations acquired by two adjacent geostationary spacecrafts, i.e., Meteosat-7 and Meteosat-5 have been processed with the MSA algorithm. These satellites are located respectively at 0 and 63 degrees East. Data acquired by these two instruments overlap over a large area encompassing most of Africa and the Arabian Peninsula. The consistency of the surface anisotropy retrieval is evaluated through a reconstruction of the Meteosat-5 (-7) observations with the Meteosat-7 (-5) surface anisotropy characterisation. No differences larger than the calibration uncertainties have been found, which indicates that the MSA algorithm accounts correctly for the surface anisotropy and instrument differences.

  14. The expected anisotropy in solid inflation

    International Nuclear Information System (INIS)

    Solid inflation is an effective field theory of inflation in which isotropy and homogeneity are accomplished via a specific combination of anisotropic sources (three scalar fields that individually break isotropy). This results in specific observational signatures that are not found in standard models of inflation: a non-trivial angular dependence for the squeezed bispectrum, and a possibly long period of anisotropic inflation (to drive inflation, the ''solid'' must be very insensitive to any deformation, and thus background anisotropies are very slowly erased). In this paper we compute the expected level of statistical anisotropy in the power spectrum of the curvature perturbations of this model. To do so, we account for the classical background values of the three scalar fields that are generated on large (superhorizon) scales during inflation via a random walk sum, as the perturbation modes leave the horizon. Such an anisotropy is unavoidably generated, even starting from perfectly isotropic classical initial conditions. The expected level of anisotropy is related to the duration of inflation and to the amplitude of the squeezed bispectrum. If this amplitude is close to its current observational limit (so that one of the most interesting predictions of the model can be observed in the near future), we find that a level of statistical anisotropy F2 gives frozen and scale invariant vector perturbations on superhorizon scales

  15. Measurements of magnetic anisotropy in sickle cells

    International Nuclear Information System (INIS)

    Room temperature magnetic measurements in deoxigenated sickle cells showed the existence of magnetic anisotropy, Δchi=1,29 x 10-3. This effect was supposed paramagnetic and considered to be due to the iron atoms of the hemoglobin molecules which are one over the other, forming ordered chains inside the erythrocytes. Low temperature (liquid He - 4,2K) measurements of the magnetic anisotropy of sickle cells and normal red blood cells diluted in a cryoprotector was made to confirm the paramagnetic origin of the fenomena. For that purpose it was used a superconductor magnetometer coupled to a SQUID, developed in the 'Laboratorio do Estado Solido do Departamento de Fisica da PUC-RJ'. The results obtained seem to confirm the expected paramagnetic anisotropy and, furthermore, suggest the presence of magnetic interactions among the iron atoms in the sickle cells samples. (Author)

  16. Large Friction Anisotropy of a Polydiacetylene Monolayer

    International Nuclear Information System (INIS)

    Friction force microscopy measurements of a polydiacetylene monolayer film reveal a 300% friction anisotropy that is correlated with the film structure. The film consists of a monolayer of the red form of N-(2-ethanol)- 10,12 pentacosadiynamide, prepared on a Langmuir trough and deposited on a mica substrate. As confirmed by atomic force microscopy and fluorescence microscopy, the monolayer consists of domains of linearly oriented conjugated backbones with pendant hydrocarbon side chains above and below the backbones. Maximum friction occurs when the sliding direction is perpendicular to the backbone. We propose that the backbones impose anisotropic packing of the hydrocarbon side chains which leads to the observed friction anisotropy. Friction anisotropy is therefore a sensitive, optically-independent indicator of polymer backbone direction and monolayer structural properties

  17. Hydraulic Conductivity Anisotropy of Heterogeneous Unsaturated Soils

    Science.gov (United States)

    Sun, Dongmin; Zhu, Jianting

    2010-05-01

    The effects of saturation degree (or capillary pressure) on hydraulic conductivity anisotropy in unsaturated soils have not been fully understood. This study developed an approach based on a conceptualization of combining the neural network based pedo-transfer function (PTF) results with the thin layer concept to explore the capillary pressure-dependent anisotropy in relation to soil texture and soil bulk density. The main objective is to examine how anisotropy characteristics are related to the relationships between hydraulic parameters and the basic soil attributes such as texture and bulk density. The hydraulic parameters are correlated with the texture and bulk density based on the pedo-transfer function (PTF) results. It is demonstrated that non-monotonic behavior of the unsaturated soil anisotropy in relation to the capillary pressure is only observed when the saturated hydraulic conductivity and the shape parameter are both related to the mean particle diameter. When only one hydraulic parameter is related to the grain diameter or when both are not related to the same attribute simultaneously, the unsaturated soil anisotropy increases monotonically with the increasing capillary pressure head. Therefore, it is suggested that this behavior is mainly due to the coupled dependence of the layer saturated hydraulic conductivities and the shape factors on the texture and bulk density. The correlation between the soil grain diameter and bulk density decreases the anisotropy effects of the unsaturated layered soils. The study illustrates that the inter-relationships of soil texture, bulk density, and hydraulic properties may cause vastly different characteristics of anisotropic unsaturated soils.

  18. Probing the Frontiers of QCD

    CERN Document Server

    Horowitz, W A

    2010-01-01

    With the energy scales opened up by RHIC and LHC the age of high-pT physics is upon us. This has created new opportunities and novel mysteries, both of which will be explored in this thesis. The possibility now exists experimentally to exploit these high momentum particles to uniquely probe the unprecedented state of matter produced in heavy ion collisions. At the same time naive theoretical expectations have been dashed by data. The first puzzle we confront is that of the enormous intermediate-pT azimuthal anisotropy, or v2, of jets observed at RHIC. The second puzzle is the surprisingly similar suppression of light mesons and nonphotonic electrons, which precludes perturbative predictions predicated on gluon bremsstrahlung radiation as the dominant energy loss channel. Near qualitative agreement results from including collisional energy loss and integrating over the fluctuating jet pathlengths. Another conjecture for heavy quark energy loss comes via explicit construction using the AdS/CFT correspondence; t...

  19. Mobility anisotropy of two-dimensional semiconductors

    CERN Document Server

    Lang, Haifeng; Liu, Zhirong

    2016-01-01

    The carrier mobility of anisotropic two-dimensional (2D) semiconductors under longitudinal acoustic (LA) phonon scattering was theoretically studied with the deformation potential theory. Based on Boltzmann equation with relaxation time approximation, an analytic formula of intrinsic anisotropic mobility was deduced, which shows that the influence of effective mass to the mobility anisotropy is larger than that of deformation potential constant and elastic modulus. Parameters were collected for various anisotropic 2D materials (black phosphorus, Hittorf's phosphorus, BC$_2$N, MXene, TiS$_3$, GeCH$_3$) to calculate their mobility anisotropy. It was revealed that the anisotropic ratio was overestimated in the past.

  20. Non-destructive label-free continuous monitoring of in vitro chondrogenesis via electrical conductivity and its anisotropy.

    Science.gov (United States)

    Oh, Tong In; Kim, Changhwan; Karki, Bishal; Son, Youngsook; Lee, EunAh; Woo, Eung Je

    2015-02-01

    Non-destructive label-free continuous monitoring of in vitro tissue culture is an unmet demand in tissue engineering. Noting that different compositions of cartilage lead to different electrical tissue properties, we propose a new method to measure the electrical conductivity and its anisotropy during in vitro chondrogenesis. We used a conductivity tensor probe with 17 electrodes and a bio-impedance spectroscopy (BIS) device to measure the conductivity values and the anisotropy ratios at the bottom and top surfaces of the tissue samples during the culture period of 6 weeks. Clearly distinguishing glycosaminoglycans (GAGs), collagen, and also various mixtures of them, the measured conductivity value and the estimated tissue anisotropy provide diagnostic information of the depth-dependent tissue structure and compositions. Continuously monitoring the individual tissue during the entire chondrogenesis process without any adverse effect, the proposed method may significantly increase the productivity of cartilage tissue engineering.

  1. Steady-state acceptor fluorescence anisotropy imaging under evanescent excitation for visualisation of FRET at the plasma membrane.

    Directory of Open Access Journals (Sweden)

    Viviane Devauges

    Full Text Available We present a novel imaging system combining total internal reflection fluorescence (TIRF microscopy with measurement of steady-state acceptor fluorescence anisotropy in order to perform live cell Förster Resonance Energy Transfer (FRET imaging at the plasma membrane. We compare directly the imaging performance of fluorescence anisotropy resolved TIRF with epifluorescence illumination. The use of high numerical aperture objective for TIRF required correction for induced depolarization factors. This arrangement enabled visualisation of conformational changes of a Raichu-Cdc42 FRET biosensor by measurement of intramolecular FRET between eGFP and mRFP1. Higher activity of the probe was found at the cell plasma membrane compared to intracellularly. Imaging fluorescence anisotropy in TIRF allowed clear differentiation of the Raichu-Cdc42 biosensor from negative control mutants. Finally, inhibition of Cdc42 was imaged dynamically in live cells, where we show temporal changes of the activity of the Raichu-Cdc42 biosensor.

  2. Orientational dynamics of ferrofluids with finite magnetic anisotropy of the particles: relaxation of magneto-birefringence in crossed fields.

    Science.gov (United States)

    Raikher, Yu L; Stepanov, V I; Bacri, J-C; Perzynski, R

    2002-08-01

    Dynamic birefringence in a ferrofluid subjected to crossed bias (constant) and probing (pulse or ac) fields is considered, assuming that the nanoparticles have finite magnetic anisotropy. This is done on the basis of the general Fokker-Planck equation that takes into account both internal magnetic and external mechanical degrees of freedom of the particle. We describe the orientation dynamics in terms of the integral relaxation time of the macroscopic orientation order parameter. To account for an arbitrary relation between the bias (external) and anisotropy (internal) fields, an interpolation expression for the integral relaxation time is proposed and justified. A developed description is used to interpret the measurements of birefringence relaxation in magnetic fluids with nanoparticles of high (cobalt ferrite) and low (maghemite) anisotropy. The proposed theory appears to be in full qualitative agreement with all the experimental data available. PMID:12241160

  3. Measuring the thermal Sunyaev-Zel'dovich effect through the cross correlation of Planck and WMAP maps with ROSAT galaxy cluster catalogs

    Energy Technology Data Exchange (ETDEWEB)

    Hajian, Amir; Bond, J. Richard [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8 (Canada); Battaglia, Nicholas [McWilliams Center for Cosmology, Wean Hall, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, PA 15213 (United States); Spergel, David N. [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States); Pfrommer, Christoph [Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, D-69118 Heidelberg (Germany); Sievers, Jonathan L., E-mail: ahajian@cita.utoronto.ca, E-mail: nbattaglia@cmu.edu, E-mail: dns@astro.princeton.edu, E-mail: bond@cita.utoronto.ca, E-mail: christoph.pfrommer@h-its.org, E-mail: sievers@cita.utoronto.ca [Astrophysics and Cosmology Research Unit, University of Kwazulu-Natal, Westville, Durban 4000 (South Africa)

    2013-11-01

    We measure a significant correlation between the thermal Sunyaev-Zel'dovich effect in the Planck and WMAP maps and an X-ray cluster map based on ROSAT. We use the 100, 143 and 343 GHz Planck maps and the WMAP 94 GHz map to obtain this cluster cross spectrum. We check our measurements for contamination from dusty galaxies using the cross correlations with the 217, 545 and 857 GHz maps from Planck. Our measurement yields a direct characterization of the cluster power spectrum over a wide range of angular scales that is consistent with large cosmological simulations. The amplitude of this signal depends on cosmological parameters that determine the growth of structure (σ{sub 8} and Ω M) and scales as σ{sub 8}{sup 7.4} and Ω M{sup 1.9} around the multipole (ℓ) ∼ 1000. We constrain σ{sub 8} and Ω M from the cross-power spectrum to be σ{sub 8}(Ω M/0.30){sup 0.26} = 0.8±0.02. Since this cross spectrum produces a tight constraint in the σ{sub 8} and Ω M plane the errors on a σ{sub 8} constraint will be mostly limited by the uncertainties from external constraints. Future cluster catalogs, like those from eRosita and LSST, and pointed multi-wavelength observations of clusters will improve the constraining power of this cross spectrum measurement. In principle this analysis can be extended beyond σ{sub 8} and Ω M to constrain dark energy or the sum of the neutrino masses.

  4. Angular anisotropy representation by probability tables

    International Nuclear Information System (INIS)

    In this paper, we improve point-wise or group-wise angular anisotropy representation by using probability tables. The starting point of this study was to give more flexibility (sensitivity analysis) and more accuracy (ray effect) to group-wise anisotropy representation by Dirac functions, independently introduced at CEA (Mao, 1998) and at IRSN (Le Cocq, 1998) ten years ago. Basing ourselves on our experience of cross-section description, acquired in CALENDF (Sublet et al., 2006), we introduce two kinds of moment based probability tables, Dirac (DPT) and Step-wise (SPT) Probability Tables where the angular probability distribution is respectively represented by Dirac functions or by a step-wise function. First, we show how we can improve equi-probable cosine representation of point-wise anisotropy by using step-wise probability tables. Then we show, by Monte Carlo techniques, how we can obtain a more accurate description of group-wise anisotropy than the one usually given by a finite expansion on a Legendre polynomial basis (that can induce negative values) and finally, we describe it by Dirac probability tables. This study is carried out in the framework of GALILEE project R and D activities (Coste-Delclaux, 2008). (authors)

  5. Azimuthal anisotropy of jet quenching at LHC

    Indian Academy of Sciences (India)

    I P Lokhtin; S V Petrushanko; L I Sarycheva; A M Snigirev

    2003-05-01

    We analyze the azimuthal anisotropy of jet spectra due to energy loss of hard partons in quark–gluon plasma, created initially in nuclear overlap zone in collisions with non-zero impact parameter. The calculations are performed for semi-central Pb–Pb collisions at LHC energy.

  6. Impact of rock anisotropy on fracture development

    Institute of Scientific and Technical Information of China (English)

    Lianbo Zeng; Jiyong Zhao; Shengju Zhu; Weiliang Xiong; Yonghong He; Jianwen Chen

    2008-01-01

    Experiments on uniaxial and triaxial rock mechanics and rock acoustic emissions have been conducted for research on the impact of rock anisotropy on the development of the fractures of different directions by taking as an example the ultra-low-permeability sandstone reservoir in the Upper Triassic Yanchang Formation within the Ordos Basin. The experimental results prove the existence of anisotropy of the rock mechanical property in the different directions on the plane, which is the chief reason for the production of impacts on the development of different assemblages of fractures in the geological periods. The rock anisotropy usually restricts the development of one assemblage of conjugate shear fractures. The fractures in the Yanchang Formation within the Ordos Basin are mainly shear fractures that formed under two tectonic actions. Theoretically, here, four assemblages of shear fractures should have developed, but due to the effect of a strong rock anisotropy, in each period one assemblage of fractures chiefly developed. Thus, two assemblages of fractures are usually developed in every part at present.

  7. Effective anisotropy through traveltime and amplitude matching

    KAUST Repository

    Wang, Hui

    2014-08-05

    Introducing anisotropy to seismic wave propagation reveals more realistic physics of our Earth\\'s subsurface as compared to the isotropic assumption. However wavefield modeling, the engine of seismic inverse problems, in anisotropic media still suffers from computational burdens, in particular with complex anisotropy such as transversely isotropic (TI) and Orthorhombic anisotropy. We develop effective isotropic velocity and density models to package the effects of anisotropy such that the wave propagation behavior using these effective models approximate those of the original anisotropic model. We build these effective models through the high frequency asymptotic approximation based on the eikonal and transport equations. We match the geometrical behavior of the wave-fields, given by traveltimes, from the anisotropic and isotropic eikonal equations. This matching yields the effective isotropic velocity that approximates the kinematics of the anisotropic wavefield. Equivalently, we calculate the effective densities by equating the anisotropic and isotropic transport equations. The effective velocities and densities are then fed into the isotropic acoustic variable density wave equation to obtain cheaper anisotropic wavefields. We justify our approach by testing it on an elliptical anisotropic model. The numerical results demonstrate a good matching of both traveltime and amplitude between anisotropic and effective isotropic wavefields.

  8. Magnetic anisotropy in rare-earth metals

    DEFF Research Database (Denmark)

    Nielsen, Mourits; Bjerrum Møller, Hans; Lindgård, Per-Anker;

    1970-01-01

    The magnetic field dependence of the energy of long- wavelength magnons in Tb-10%Ho has been studied by inelastic neutron scattering. The results agree with the `frozen-lattice' model, provided that the second-order magnetoelastic effect is taken into account. The planar anisotropy is almost...

  9. Plastic Anisotropy Prediction by Ultrasonic Texture Data

    OpenAIRE

    Serebryany, V. N.

    1996-01-01

    The plastic anisotropy parameters (R coefficient and height of ears of the drawn cup) have been calculated from ultrasonic orientation distribution function (ODF) coefficients on the basis of Taylor theory for low carbon steel and aluminium alloy sheets. The ODF coefficients were defined by Sayers method and using the iterative procedure on the basis of measurement of bulk longitudinal and shear wave time delays.

  10. Anisotropy of Wood in the Microwave Region

    Science.gov (United States)

    Ziherl, Sasa; Bajc, Jurij; Urankar, Bernarda; Cepic, Mojca

    2010-01-01

    Wood is transparent for microwaves and due to its anisotropic structure has anisotropic dielectric properties. A laboratory experiment that allows for the qualitative demonstration and quantitative measurements of linear dichroism and birefringence in the microwave region is presented. As the proposed experiments are based on the anisotropy (of…

  11. Gold Spiky Nanodumbbells: Anisotropy in Gold Nanostars

    OpenAIRE

    Novikov, Sergey M.; Sánchez-Iglesias, Ana; Schmidt, Mikołaj K.; Chuvilin, Andrey; Aizpurua, Javier; Grzelczak, Marek; Liz-Marzán, Luis M.

    2013-01-01

    A new type of gold nanoparticle—called “spiky nanodumbbells”—is introduced. These particles combine the anisotropy of nanorods with sharp nanoscale features of nanostars, which are important for SERS applications. Both the morphology and the optical response of the particles are characterized in detail, and the experimental results are compared with FDTD simulations, showing good agreement.

  12. Surface stress anisotropy of Ge(001)

    NARCIS (Netherlands)

    Middel, M.T.; Zandvliet, H.J.W.; Poelsema, Bene

    2002-01-01

    By analyzing the equilibrium shape of vacancy islands on the Ge(001) surface we have determined the surface stress anisotropy, i.e., the difference between the compressive stress component along the substrate dimer rows and the tensile stress component perpendicular to the substrate dimer rows. In o

  13. Gaussian Anisotropy In Strange Quark Stars

    CERN Document Server

    Panahi, H; Eghdami, I

    2015-01-01

    In this paper for studying the anisotropic strange quark stars, we assume that the radial pressure inside the anisotropic star is a superposition of pressure in an isotropic case plus a Gaussian perturbation term. Considering a proportionality between electric charge density and the density of matter, we solve the TOV equation for different cases numerically. Our results indicate that anisotropy increases the maximum mass $M_{max}$ and also its corresponding radius $R$ for a typical strange quark star. According to our calculations, an anisotropy amplitude of $A=3\\times10^{33}Nm^{-2}$ with a standard deviation of $\\sigma=3\\times10^{3}m$ leads to a neutron star of 1.97$M_{\\odot}$. Furthermore, electric charge not only increases the maximum mass and its corresponding radius, but also raises up the anisotropy factor. We can see that the tangential pressure $p_{t}$ and anisotropy factor $\\Delta$ unlike the radial pressure $p_{r}$ have a maximum on the surface and this maximum increases by adding electric charge e...

  14. Morphological diagram of diffusion driven aggregate growth in plane: Competition of anisotropy and adhesion

    Science.gov (United States)

    Menshutin, A. Yu.; Shchur, L. N.

    2011-09-01

    Two-dimensional structures grown with Witten and Sander algorithm are investigated. We analyze clusters grown off-lattice and clusters grown with antenna method with N=3,4,5,6,7 and 8 allowed growth directions. With the help of variable probe particles technique we measure fractal dimension of such clusters D(N) as a function of their size N. We propose that in the thermodynamic limit of infinite cluster size the aggregates grown with high degree of anisotropy ( N=3,4,5) tend to have fractal dimension D equal to 3/2, while off-lattice aggregates and aggregates with lower anisotropy ( N>6) have D≈1.710. Noise-reduction procedure results in the change of universality class for DLA. For high enough noise-reduction value clusters with N⩾6 have fractal dimension going to 3/2 when N→∞.

  15. Magnetic Anisotropy and Magnetization Switching in Ferromagnetic GaMnAs

    Science.gov (United States)

    Limmer, W.; Daeubler, J.; Glunk, M.; Hummel, T.; Schoch, W.; Schwaiger, S.; Tabor, M.; Sauer, R.

    Characteristic features of diluted ferromagnetic semiconductors such as the anisotropic magnetoresistance or the spin polarization of charge carriers are intimately connected with a macroscopic magnetization. Since the orientation of the magnetization is controlled by magnetic anisotropy (MA), a detailed knowledge of this anisotropy is indispensable for the design of novel spintronic devices. In this article, angle-dependent magnetotransport is demonstrated to be an excellent tool for probing MA as an alternative to the standard ferromagnetic-resonance method. Moreover, its ability to trace the motion of the magnetization vector in a variable external magnetic field makes it ideally suitable for studying magnetization switching, a potential basic effect in future logical devices. The MA of a series of differently strained GaMnAs samples is analyzed by means of model calculations in a single-domain picture based on a series expansion of the resistivity tensor and a numerical minimization of the free enthalpy.

  16. Is there evidence for anomalous dipole anisotropy in the large-scale structure?

    CERN Document Server

    Bengaly,, C A P; Alcaniz, J S; Xavier, H S; Novaes, C P

    2016-01-01

    We probe the anisotropy of the large-scale structure (LSS) with the WISE-2MASS catalogue. This analysis is performed by a directional comparison of the galaxy number counts through the entire celestial sphere once systematic effects, such as star-galaxy separation and foregrounds contamination, are properly taken into account. We find a maximal hemispherical asymmetry whose dipolar component is $A = 0.0507 \\pm 0.0014$ toward the $(l,b) = (323^{\\circ},-5^{\\circ})$ direction. This result is consistent with previous estimations of our proper motion in low and intermediate redshifts, as those carried out with Type Ia Supernovae and similar LSS catalogues.Furthermore, this dipole amplitude obtained is statistically consistent with mock catalogues simulated according to the $\\Lambda$CDM matter density expected fluctuations, in addition to observational biases such as the incomplete celestial coverage, anisotropic sky exposure. Our results suggest, therefore, that there is no strong evidence for anomalous anisotropy...

  17. Tuning the Magnetic Anisotropy at a Molecule-Metal Interface

    DEFF Research Database (Denmark)

    Bairagi, K.; Bellec, A.; Repain, V.;

    2015-01-01

    We demonstrate that a C60 overlayer enhances the perpendicular magnetic anisotropy of a Co thin film, inducing an inverse spin reorientation transition from in plane to out of plane. The driving force is the C60/Co interfacial magnetic anisotropy that we have measured quantitatively in situ as a ......) surface decreases the perpendicular magnetic anisotropy. These results open the way to tailor the interfacial magnetic anisotropy in organic-material-ferromagnet systems....

  18. Synthesis of transport layers with controlled anisotropy and application thereof to study proton exchange membrane fuel cell performance

    Science.gov (United States)

    Todd, Devin; Mérida, Walter

    2016-04-01

    We report on a novel method for the synthesis of fibre-based proton exchange membrane (PEM) fuel cell porous transport layers (PTLs) with controllable fibre alignment. We also report the first application of such layers as diagnostics tools to probe the effect of within-plane PTL anisotropy upon PEM fuel cell performance. These structures are realized via adaptation of electrospinning technology. Electrospun layers with progressive anisotropy magnitude are produced and evaluated. This novel approach is distinguished from the state-of-the-art because an equivalent study using commercially available materials is impossible due to lack of structurally similar substrates with different anisotropies. The anisotropy is visualized via scanning electron microscopy, and quantified using electrical resistivity. The capacity is demonstrated to achieve fibre alignment, and the associated impact on transport properties. A framework is presented for assessing the in-situ performance, whereby transport layer orientation versus bipolar plate flow-field geometry is manipulated. While an effect upon the commercial baseline cannot be discerned, electrospun transport layers with greater anisotropy magnitude suggest greater sensitivity to orientation; where greater performance is obtained with fibres cross-aligned to flow-field channels. Our approach of electrospun transport enables deterministic structures by which fuel cell performance can be explained and optimized.

  19. Evolution of Tidally Truncated Globular Clusters with Anisotropy

    CERN Document Server

    Takahashi, K; Inagaki, S

    1997-01-01

    The evolution of tidally truncated globular clusters is investigated by integrating two-dimensional Fokker-Planck equation that allows the development of velocity anisotropy. We start from the isotropic Plummer model with tidal cut off and followed the evolution through the corecollapse. The heating by three-binary is included to obtain the evolution past the corecollapse. The anisotropy in velocity dispersion develops during the precollapse evolution. However, the anisotropy becomes highly depressed during the post-collapse evolution because of rapid loss of radial orbits. Maximum radial anisotropy appears just after the beginning of the expansion, and degree of anisotropy decreases slowly as the total mass of the cluster decreases. Thus it may be possible to determine the evolutionary status of a cluster if the velocity anisotropy can be measured in the sense that the postcollapse clusters always have very little degree of anisotropy. The structure of the post-collapse cluster can be well fitted to King mod...

  20. Coherent control of the optical nonlinear and luminescence anisotropies in molecular thin films by multiphoton excitations.

    Science.gov (United States)

    Bidault, Sébastien; Brasselet, Sophie; Zyss, Joseph

    2004-06-01

    Photoinduced orientational distributions are implemented with one- and two-photon absorption interference in polymer films containing chromophores that exhibit luminescent and nonlinear properties. The odd- and even-order parameters of the final distribution are probed by simultaneous measurement of second-harmonic generation (SHG) and two-photon fluorescence (TPF). We show the possibility of engineering local SHG and TPF anisotropies by controlling the polarization states and intensities of the writing optical fields. Complex multipolar orders are modeled with an irreducible spherical tensor-based formalism jointly applied to the molecular polarizabilities and field tensors. PMID:15214309

  1. First-order reversal curve analysis of graded anisotropy FePtCu films

    Science.gov (United States)

    Bonanni, Valentina; Fang, Yeyu; Dumas, Randy K.; Zha, Chaolin; Bonetti, Stefano; Nogués, Josep; Åkerman, Johan

    2010-11-01

    The reversal mechanisms of graded anisotropy FePtCu films have been investigated by alternating gradient magnetometer (AGM) and magneto-optical Kerr effect (MOKE) measurements with first-order reversal curve (FORC) techniques. The AGM-FORC analysis, which clearly shows the presence of soft and hard components, is unable to resolve how these phases are distributed throughout the film thickness. MOKE-FORC measurements, which preferentially probe the surface of the film, reveal that the soft components are indeed located toward the top surface. Combining AGM-FORC with the inherent surface sensitivity of MOKE-FORC analysis allows for a comprehensive analysis of heterogeneous systems such as graded materials.

  2. Reduction of anisotropy influence and contacting effects in in-vitro bioimpedance measurements

    International Nuclear Information System (INIS)

    Experimental procedure is a decisive part in in-vitro bioimpedance measurement in order to get reproducible measurements. An electrode configuration is proposed to avoid several disadvantages produced by needle electrodes and circular non-penetrating electrode. The proposed electrode geometry reduces the influence of anisotropy and allows simultaneously a good probe contacting. We propose an experimental method to avoid the appearance of bacteria and to reduce water loss in meat during experiment post-mortem. The results show that electrode configuration with the developed experimental method have ensured reproducible measurements during a long period of 14 days post-mortem.

  3. Reduction of anisotropy influence and contacting effects in in-vitro bioimpedance measurements

    Science.gov (United States)

    Guermazi, M.; Kanoun, O.; Derbel, N.

    2013-04-01

    Experimental procedure is a decisive part in in-vitro bioimpedance measurement in order to get reproducible measurements. An electrode configuration is proposed to avoid several disadvantages produced by needle electrodes and circular non-penetrating electrode. The proposed electrode geometry reduces the influence of anisotropy and allows simultaneously a good probe contacting. We propose an experimental method to avoid the appearance of bacteria and to reduce water loss in meat during experiment post-mortem. The results show that electrode configuration with the developed experimental method have ensured reproducible measurements during a long period of 14 days post-mortem.

  4. Nonlinear photoinduced anisotropy and modifiable optical image display in a bacteriorhodopsin/polymer composite film

    Science.gov (United States)

    Wei, Lai; Luo, Jia; Zhu, Jiang; Lu, Ming; Zhao, You-yuan; Ma, De-wang; Ding, Jian-dong

    2007-04-01

    The nonlinear photoinduced anisotropy with large birefringence in a bacteriorhodopsin/polymer composite (bR/PC) film was observed. The contrast ratio, a ratio of the maximum to the minimum intensity of transmitted probe light through the bR/PC film within the linear gray scale range could reach ˜350:1. An all-optical image display in different colors was performed. The intensity of the transmitted signal could be modulated by adjusting the multibeam polarization states and intensities. Therefore, the positive image, negative image, and image erasure in display were demonstrated.

  5. Anisotropies in the cosmic microwave background: Theory

    Energy Technology Data Exchange (ETDEWEB)

    Dodelson, S.

    1998-02-01

    Anisotropies in the Cosmic Microwave Background (CMB) contain a wealth of information about the past history of the universe and the present values of cosmological parameters. I online some of the theoretical advances of the last few years. In particular, I emphasize that for a wide class of cosmological models, theorists can accurately calculate the spectrum to better than a percent. The spectrum of anisotropies today is directly related to the pattern of inhomogeneities present at the time of recombination. This recognition leads to a powerful argument that will enable us to distinguish inflationary models from other models of structure formation. If the inflationary models turn out to be correct, the free parameters in these models will be determined to unprecedented accuracy by the upcoming satellite missions.

  6. Two-photon fluorescence anisotropy imaging

    Science.gov (United States)

    Li, Wei; Wang, Yi; Shao, Hanrong; He, Yonghong; Ma, Hui

    2006-09-01

    We have developed a novel method for imaging the fluorescence intensity and anisotropy by two-photon fluorescence microscopy and tested its capability in biological application. This method is applied to model sample including FITC and FITC-CD44 antibody solution and also FITC-CD44 stained cells. The fluorescence anisotropy (FA) of FITC-CD44ab solution is higher than the FITC solution with the same concentration. The fluorescence in cell sample has even higher FA than in solution because the rotation diffusion is restrained in membrane. The method is employed to study the effect of berberine a kind of Chinese medicine, on tumor metastasis. The results indicated that tumor cell membrane fluidity is decreasing with increasing the concentration of berberine in culture medium.

  7. Microwave background anisotropies in quasiopen inflation

    CERN Document Server

    García-Bellido, J; Montes, X; Garcia-Bellido, Juan; Garriga, Jaume; Montes, Xavier

    1999-01-01

    Quasiopenness seems to be generic to multi-field models of single-bubble open inflation. Instead of producing infinite open universes, these models actually produce an ensemble of very large but finite inflating islands. In this paper we study the possible constraints from CMB anisotropies on existing models of open inflation. The effect of supercurvature anisotropies combined with the quasiopenness of the inflating regions make some models incompatible with observations, and severely reduces the parameter space of others. Supernatural open inflation and the uncoupled two-field model seem to be ruled out due to these constraints for values of $\\Omega_0\\lesssim0.98$. Others, such as the open hybrid inflation model with suitable parameters for the slow roll potential can be made compatible with observations.

  8. Texture-induced microwave background anisotropies

    CERN Document Server

    Borrill, J; Liddle, A R; Stebbins, A J; Veeraraghavan, S; Julian Borrill; Edmund J Copeland; Andrew R Liddle; Albert Stebbins; Shoba Veeraraghavan

    1994-01-01

    We use numerical simulations to calculate the cosmic microwave background anisotropy induced by the evolution of a global texture field, with special emphasis on individual textures. Both spherically symmetric and general configurations are analysed, and in the latter case we consider field configurations which exhibit unwinding events and also ones which do not. We compare the results given by evolving the field numerically under both the expanded core (XCORE) and non-linear sigma model (NLSM) approximations with the analytic predictions of the NLSM exact solution for a spherically symmetric self-similar (SSSS) unwinding. We find that the random unwinding configuration spots' typical peak height is 60-75% and angular size typically only 10% of those of the SSSS unwinding, and that random configurations without an unwinding event nonetheless may generate indistinguishable hot and cold spots. The influence of these results on analytic estimates of texture induced microwave anisotropies is examined, and compari...

  9. CMB anisotropies in the weak coupling limit

    CERN Document Server

    Hu, W; Hu, Wayne; White, Martin

    1995-01-01

    We present a new, more powerful and accurate, analytic treatment of cosmic microwave background (CMB) anisotropies in the weakly coupled regime. Three applications are presented: gravitational redshifts in a time dependent potential, the Doppler effect in reionized scenarios, and the Vishniac effect. The Vishniac effect can dominate primary anisotropies at small angles even in late and minimally reionized models in flat dark-matter dominated universes with Harrison-Zel'dovich initial conditions. The techniques developed here refine previous calculations yielding a larger coherence angle for the Vishniac effect and moreover can be applied to non-trivial ionization histories. These analytic expressions may be used to modify results for the standard cold dark matter model to its cosmological constant and reionized extensions without detailed and time consuming recalculation.

  10. Physics of the cosmic microwave background anisotropy

    CERN Document Server

    Bucher, Martin

    2015-01-01

    Observations of the cosmic microwave background (CMB), especially of its frequency spectrum and its anisotropies, both in temperature and in polarization, have played a key role in the development of modern cosmology and our understanding of the very early universe. We review the underlying physics of the CMB and how the primordial temperature and polarization anisotropies were imprinted. Possibilities for distinguishing competing cosmological models are emphasized. The current status of CMB experiments and experimental techniques with an emphasis toward future observations, particularly in polarization, is reviewed. The physics of foreground emissions, especially of polarized dust, is discussed in detail, since this area is likely to become crucial for measurements of the B modes of the CMB polarization at ever greater sensitivity.

  11. Reionization Revisited: Secondary CMB Anisotropies and Polarization

    OpenAIRE

    Hu, Wayne

    1999-01-01

    Secondary CMB anisotropies and polarization provide a laboratory to study structure formation in the reionized epoch. We consider the kinetic Sunyaev-Zel'dovich effect from mildly nonlinear large-scale structure and show that it is a natural extension of the perturbative Vishniac effect. If the gas traces the dark matter to overdensities of order 10, as expected from simulations, this effect is at least comparable to the Vishniac effect at arcminute scales. On smaller scales, it may be used t...

  12. Relativistic Density Functional Treatment of Magnetic Anisotropy

    OpenAIRE

    Zhang, Hongbin

    2009-01-01

    Spin-orbit coupling (SOC) reduces the spatial symmetry of ferromagnetic solids. That is, the physical properties of ferromagnetic materials are anisotropic, depending on the magnetization direction. In this thesis, by means of numerical calculations with full-relativistic density functional theory, we studied two kinds of physical properties: surface magnetic anisotropy energy (MAE) and anisotropic thermoelectric power due to Lifshitz transitions. After a short introduction to ...

  13. Interferometric Observation of Cosmic Microwave Background Anisotropies

    CERN Document Server

    White, M; Dragovan, M; White, Martin; Carlstrom, John E.; Dragovan, Mark

    1999-01-01

    We present a formalism for analyzing interferometric observations of Cosmic Microwave Background (CMB) anisotropy and polarization data. The formalism is based upon the ell-space expansion of the angular power spectrum favoured in recent years. Explicit discussions of maximum likelihood analysis, power spectrum reconstruction, parameter estimation, imaging and polarization are given. As an example, several calculations for the Degree Angular Scale Interferometer (DASI) and Cosmic Background Interferometer (CBI) experiments are presented.

  14. Mid mantle seismic anisotropy around subduction zones

    Science.gov (United States)

    Faccenda, M.

    2014-02-01

    There is increasing evidence for mid mantle seismic anisotropy around subduction zones whose interpretation remains elusive. In this study I estimate the strain-induced mid mantle fabric and associated seismic anisotropy developing in 3D petrological-thermo-mechanical subduction models where the slab is either stagnating over the 660 km discontinuity or penetrating into the lower mantle. The modelling of synthetic lattice-preferred-orientation (LPO) development of wadsleyite and perovskite has been calibrated with results from deformational experiments and ab-initio atomic scale models, and the single crystal elastic tensor of the different mineral phases is scaled by local P-T conditions. The lower transition zone (ringwoodite + garnet) is assumed to be isotropic. Mid mantle fabric develops in proximity of the subducting slab where deformation and stresses are high, except at depths where upwelling or downwelling material undergoes phase transformations, yielding to LPO reset. The upper transition zone (wadsleyite + garnet) is characterized by weak transverse isotropy (2-3%) with symmetry axes oriented and fast S wave polarized dip-normal. A slightly stronger transverse isotropy develops in the lower mantle (perovskite + periclase), where the symmetry axes, the polarization of the fast S wave and the maximum Vp and dVs are parallel to the slab dip and subduction direction. For stagnating slab models this translates into negative and positive radial anisotropy in the upper transition zone and lower mantle back-arc, respectively, minimum delay times for vertically travelling shear waves and large shear wave splitting for waves propagating horizontally in the lower mantle. These results may help in reconciling the seismic anisotropy patterns observed in some subduction zones with subduction-induced deformation, such as those measured in the mid mantle between the Australian plate and the New Hebrides-Tonga-Kermadec trenches that I interpret as related to stagnating

  15. Cosmic microwave background radiation: anisotropies and polarization

    Energy Technology Data Exchange (ETDEWEB)

    Goncalves, Sergio Vitorino de Borba; Guaitolini Junior, J.T. [Universidade Federal do Espirito Santo (UFES), ES (Brazil). Dept. de Fisica

    2011-07-01

    Full text: The development of cosmological models which describe correctly the universe we live in is becoming more reliable, as the improvement of the measure tools provides us with more accurate information. The Cosmic Microwave Background Radiation (CMB) was discovered accidentally by Arno Penzias and Robert Wilson in early 60s, becoming a strong evidence in favor of the Big Bang model. This radiation, typical of a blackbody with maximum intensity in the microwave band, was already predicted by Gamov, Alpher and Herman and it's originated from the uncoupling between radiation and matter in recombination, at z = 1088. Nowadays, since no other observable in Cosmology provides us with information of such a distant past, studying CMB is of great importance for the process of the comprehension of the universe. The detection of small anisotropies at the temperatures distribution, which remain even after considering the universe recent phenomena and effects of referential movements, evidenced that the primordial universe was closer to the thermodynamic equilibrium and that the appearance of small inhomogeneities were the beginning of the formation of the structures we see today. These small anisotropies are important because from them it is possible to observe polarization at CMB. In a universe so perfectly homogeneous and isotropic, polarization would never exist. In this work, we calculate the behavior of light propagation in a disturbed universe, obtaining anisotropies from the potential variation at the radiation way and from the peculiar velocity of matter which spread radiation in our direction. At this point, the next purpose is to theoretically calculate these anisotropies in an alternative cosmological example, such as in Brans-Dicke theory or a model of an universe filled with a viscous fluid. Besides, with the Stokes Parameters describing the radiation field, we study the CMB polarization, in particular analyzing the polarization tensor in a 2-sphere as

  16. Gaussian Anisotropy In Strange Quark Stars

    OpenAIRE

    Panahi, H.; Monadi, R.; Eghdami, I.

    2015-01-01

    In this paper for studying the anisotropic strange quark stars, we assume that the radial pressure inside the anisotropic star is a superposition of pressure in an isotropic case plus a Gaussian perturbation term. Considering a proportionality between electric charge density and the density of matter, we solve the TOV equation for different cases numerically. Our results indicate that anisotropy increases the maximum mass $M_{max}$ and also its corresponding radius $R$ for a typical strange q...

  17. Proximal Probes Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Proximal Probes Facility consists of laboratories for microscopy, spectroscopy, and probing of nanostructured materials and their functional properties. At the...

  18. Anisotropy and micromagnetics in complex oxide thin films

    Science.gov (United States)

    Wynn, Thomas Andrew

    maintained a [110] easy axis. To examine magnetocrystalline effects at further reduced length scales, a series of two-micron micromagnets of various shapes and orientations were patterned via argon ion implantation into LSMO thin films deposited on a SrTiO 3 substrates. The magnetic ground state was observed via x-ray photoemission electron microscopy (X-PEEM), directly probing the competition between magnetocrystalline and shape anisotropies. Analysis of the images showed that the domain patterns consisted of a superposition of Landau and vortex patterns. A metric, named the vortex fraction, was formulated to quantify this behavior as a function of temperature and radius in circular micromagnets. Vortex fractions were used to compare X-PEEM images to simulations performed by the Object Oriented Micromagnetics Framework (OOMMF) and MuMax3 micromagnetics simulation software; results allowed for the extraction of magnetocrystalline anisotropy constant at sub-micron length scales from X-PEEM data. These results illustrate the potential for tuning magnetic ground states for future spintronic devices.

  19. Getting Anisotropy in the Seismic Data Processing

    Directory of Open Access Journals (Sweden)

    Edenia de la Caridad Camejo Cordero

    2013-06-01

    Full Text Available In a conventional processing of seismic data (processing of only one type of wave, P or S, to getimages for hydrocarbons exploration, an isotropic model of the earth is assumed. Studies havedemonstrated that in areas with evidences of anisotropy, the conventional process of time migrationproduces images with poor resolution or erroneous lateral localization of structural events with highinclinations, due to variations in the elastic properties according to the direction of propagation of theseismic waves. At present this topic is of great importance in seismic acquisitions because of thevast employ of the far offset (large distances source–receptor. To, compensate this negative effectsis a priority objective to improve the seismic information. To obtain the anisotropy first started from asequence of high density processing that takes into consideration the characteristics of the earth;and data can be analyzed in all volume. As a final result; getting the comparison between the timemigration stack, with the application of standard normal Moveout correction (NMO and the others,that takes into consideration the obtained anisotropy values, allowing an improvement in the continuityof the reflectors in the seismic images, and at the same time a more reliable interpretation, with theconsequent decrease of the uncertainty and the risks in the oil exploration.

  20. Anisotropy of ice Ih: Developement of fabric and effects of anisotropy on deformation

    Science.gov (United States)

    Thorsteinsson, Throstur

    The anisotropy arising from preferred crystal orientation of ice I h is examined. To understand plastic anisotropy of polycrystalline materials it is necessary to examine the behavior at the single crystal level. Ice crystals have extremely strong plastic anisotropy that strongly influences the bulk behavior. There are several ways to relate single crystal deformation to the bulk behavior. Two approaches are used here. The first one is to assume a homogeneous stress throughout the bulk, which allows us to derive analytical relations between stress and strain rate. The anisotropy affects the strain rate-stress relationship significantly. For example strongly anisotropic ice, with a vertically symmetric fabric, can deform transversely to the applied stress in pure shear, be nearly undeformable in vertical compression, and shear easily in simple shear. The second approach takes the interaction between neighboring crystals into account, and recrystallization processes are also considered. Comparison of fabric evolution using the model and fabric from the GRIP ice core indicates that nearest neighbor interaction is necessary to explain observations. Quantification of the interaction is complicated by recrystallization processes. A consistent method of characterizing measured fabric is needed to verify models of fabric development. Here the elastic anisotropy of ice plays a central role, and relations between fabric and elastic wave velocities are used to characterize fabric. As always, several other methods are possible, but comparison indicates that sonic measurements give an accurate estimate for deformation effects from vertically symmetric fabric especially in simple shear. The deformation of the borehole at Dye 3, Greenland, has been measured with borehole inclinometry. Sonic velocity measurements done in the borehole allow us to model the deformation using an anisotropic flow law. Anisotropy alone cannot explain all the deformation. The additional processes

  1. The intrinsic quasar luminosity function: Accounting for accretion disk anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    DiPompeo, M. A.; Myers, A. D.; Brotherton, M. S. [University of Wyoming, Department of Physics and Astronomy 3905, 1000 East University, Laramie, WY 82071 (United States); Runnoe, J. C. [Penn State University, Department of Astronomy and Astrophysics, 413 Davey Lab, University Park, PA 16802 (United States); Green, R. F. [Large Binocular Telescope Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

    2014-05-20

    Quasar luminosity functions are a fundamental probe of the growth and evolution of supermassive black holes. Measuring the intrinsic luminosity function is difficult in practice, due to a multitude of observational and systematic effects. As sample sizes increase and measurement errors drop, characterizing the systematic effects is becoming more important. It is well known that the continuum emission from the accretion disk of quasars is anisotropic—in part due to its disk-like structure—but current luminosity function calculations effectively assume isotropy over the range of unobscured lines of sight. Here, we provide the first steps in characterizing the effect of random quasar orientations and simple models of anisotropy on observed luminosity functions. We find that the effect of orientation is not insignificant and exceeds other potential corrections such as those from gravitational lensing of foreground structures. We argue that current observational constraints may overestimate the intrinsic luminosity function by as much as a factor of ∼2 on the bright end. This has implications for models of quasars and their role in the universe, such as quasars' contribution to cosmological backgrounds.

  2. Probing axial orientation of collagen fibers with Brillouin microspectroscopy

    Science.gov (United States)

    Meng, Zhaokai; Yakovlev, Vladislav V.

    2015-03-01

    Collagen is an important structural component in many biological tissues including bone, teeth, skin, and vascular endothelial layer. Its fibrillar arrangement can produce tissues with distinct anisotropies and is responsible for its unique elastic properties. However, current methods of retrieving orientation of those fibers show low sensitivity to the out-of-plane orientations. In this report, we employed Brillouin microspectroscopy to probe the local sound velocity, which, in its turn, is found to have a strong correlation to the local fibrillar arrangements.

  3. Optical anisotropy in packed isotropic spherical particles: indication of nanometer scale anisotropy in packing structure.

    Science.gov (United States)

    Yamaguchi, Kohei; Inasawa, Susumu; Yamaguchi, Yukio

    2013-02-28

    We investigated the origin of birefringence in colloidal films of spherical silica particles. Although each particle is optically isotropic in shape, colloidal films formed by drop drying demonstrated birefringence. While periodic particle structures were observed in silica colloidal films, no regular pattern was found in blended films of silica and latex particles. However, since both films showed birefringence, regular film structure patterns were not required to exhibit birefringence. Instead, we propose that nanometer-scale film structure anisotropy causes birefringence. Due to capillary flow from the center to the edge of a cast suspension, particles are more tightly packed in the radial direction. Directional packing results in nanometer-scale anisotropy. The difference in the interparticle distance between radial and circumferential axes was estimated to be 10 nm at most. Nanometer-scale anisotropy in colloidal films and the subsequent optical properties are discussed.

  4. Fabrication of electrodeposited Co nanowire arrays with perpendicular anisotropy

    International Nuclear Information System (INIS)

    Co nanowire arrays have been electrodeposited into polycarbonate membranes with nanosized pores at different voltages. By means of X-ray diffraction, electron diffraction, vibrating sample magnetometer, their microstructures and magnetic properties were investigated at full length. The sample prepared at -1.2 V, 250 mA/cm2 shows perpendicular anisotropy, but the one deposited at -1.0V, 125 mA/cm2 has no perpendicular anisotropy. This different magnetic behavior can be explained from their different microstructures. X-ray diffraction and electron diffraction evidence that the former sample is amorphous, and the latter is polycrystalline. In the polycrystalline sample, due to the competition of shape anisotropy and magnetocrystal anisotropy, the sample does not display perpendicular anisotropy. But magnetocrystal anisotropy is very small in amorphous sample, therefore, shape anisotropy plays a dominant role which leads to strong perpendicular anisotropy because of shape anisotropy. Furthermore, applying a magnetic field during deposition, Co grains will preferentially grow with c-axis along the wire axis, which also leads to strong perpendicular anisotropy

  5. An approach to directly probe simultaneity

    Science.gov (United States)

    Kipreos, Edward T.; Balachandran, Riju S.

    2016-08-01

    The theory of special relativity derives from the Lorentz transformation. The Lorentz transformation implies differential simultaneity and light speed isotropy. Experiments to probe differential simultaneity should be able to distinguish the Lorentz transformation from a kinematically-similar alternate transformation that predicts absolute simultaneity, the absolute Lorentz transformation. Here, we describe how published optical tests of light speed isotropy/anisotropy cannot distinguish between the two transformations. We show that the shared equations of the two transformations, from the perspective of the “stationary” observer, are sufficient to predict null results in optical resonator experiments and in tests of frequency changes in one-way light paths. In an influential 1910 exposition on differential simultaneity, Comstock described how a “stationary” observer would observe different clock readings for spatially-separated “moving” clocks. The difference in clock readings is an integral aspect of differential simultaneity. We derive the equation for the difference in clock readings and show that it is equivalent to the Sagnac correction that describes light speed anisotropies in satellite communications. We describe an experimental strategy that can measure the differences in spatially-separated clock times to allow a direct probe of the nature of simultaneity.

  6. Dual-probe spectroscopic fingerprints of defects in graphene

    DEFF Research Database (Denmark)

    Settnes, Mikkel; Power, Stephen; Petersen, Dirch Hjorth;

    2014-01-01

    (e.g., an extended graphene sheet). Applying this method, we study the transport anisotropies in pristine graphene sheets, and analyze the spectroscopic fingerprints arising from quantum interference around single-site defects, such as vacancies and adatoms. Furthermore, we demonstrate that the dual......Recent advances in experimental techniques emphasize the usefulness of multiple scanning probe techniques when analyzing nanoscale samples. Here, we analyze theoretically dual-probe setups with probe separations in the nanometer range, i.e., in a regime where quantum coherence effects can......-probe setup is a useful tool for characterizing the electronic transport properties of extended defects or designed nanostructures. In particular, we show that nanoscale perforations, or antidots, in a graphene sheet display Fano-type resonances with a strong dependence on the edge geometry of the perforation....

  7. Probe tip heating assembly

    Energy Technology Data Exchange (ETDEWEB)

    Schmitz, Roger William; Oh, Yunje

    2016-10-25

    A heating assembly configured for use in mechanical testing at a scale of microns or less. The heating assembly includes a probe tip assembly configured for coupling with a transducer of the mechanical testing system. The probe tip assembly includes a probe tip heater system having a heating element, a probe tip coupled with the probe tip heater system, and a heater socket assembly. The heater socket assembly, in one example, includes a yoke and a heater interface that form a socket within the heater socket assembly. The probe tip heater system, coupled with the probe tip, is slidably received and clamped within the socket.

  8. Detecting 3D vegetation structure with the Galileo space probe: Can a distant probe detect vegetation structure on Earth?

    CERN Document Server

    Doughty, Christopher E

    2016-01-01

    Sagan et al. (1993) used the Galileo space probe data and first principles to find evidence of life on Earth. Here we ask whether Sagan et al. (1993) could also have detected whether life on Earth had three-dimensional structure, based on the Galileo space probe data. We reanalyse the data from this probe to see if structured vegetation could have been detected in regions with abundant photosynthetic pigments through the anisotropy of reflected shortwave radiation. We compare changing brightness of the Amazon forest (a region where Sagan et al. (1993) noted a red edge in the reflectance spectrum, indicative of photosynthesis) as the planet rotates to a common model of reflectance anisotropy and found measured increase of surface reflectance of 0.019 versus a 0.007 predicted from only anisotropic effects. We hypothesize the difference was due to minor cloud contamination. However, the Galileo dataset had only a small change in phase angle (sun-satellite position) which reduced the observed anisotropy signal an...

  9. Cosmic Microwave Background and Supernova Constraints on Quintessence: Concordance Regions and Target Models

    OpenAIRE

    Caldwell, Robert R.; Doran, Michael

    2003-01-01

    We perform a detailed comparison of the Wilkinson Microwave Anisotropy Probe (WMAP) measurements of the cosmic microwave background (CMB) temperature and polarization anisotropy with the predictions of quintessence cosmological models of dark energy. We consider a wide range of quintessence models, including: a constant equation-of-state; a simply-parametrized, time-evolving equation-of-state; a class of models of early quintessence; scalar fields with an inverse-power law potential. We also ...

  10. Extending Velocity Channel Analysis for Studying Turbulence Anisotropies

    CERN Document Server

    Kandel, Dinesh; Pogosyan, Dmitri

    2016-01-01

    We extend the analysis of the fluctuations in the velocity slices of Position-Position- Velocity (PPV) spectroscopic data from Doppler broadened lines, i.e. Velocity Channel Analysis (VCA) introduced by Lazarian & Pogosyan (2000), to study anisotropy of the underlying velocity and density turbulence statistics that arises from the presence of magnetic field. In particular, we study analytically how the measurable anisotropy of the statistics of the channel map fluctuations changes with the thickness of velocity channels. In agreement with the earlier VCA studies we find that the anisotropy of the thick channels reflects the anisotropy of the density field, while the relative contribution of density and velocity fluctuations to the thin velocity channels depends on the density spectral slope. We show that the anisotropies arising from Alfven, slow and fast modes are different, in particular, the anisotropy in PPV created by fast modes is opposite to that created by Alfven and slow modes and this can be use...

  11. Follow-up observations at 16 and 33 GHz of extragalactic sources from WMAP 3-year data: II - Flux-density variability

    CERN Document Server

    Franzen, Thomas M O; Davies, Rod D; Davis, Richard J; Feroz, Farhan; Genova-Santos, Ricardo; Grainge, Keith J B; Green, David A; Hobson, Michael P; Hurley-Walker, Natasha; Lasenby, Anthony N; Lopez-Caniego, Marcos; Olamaie, Malak; Padilla-Torres, Carmen P; Pooley, Guy G; Rebolo, Rafael; Rodriguez-Gonzalvez, Carmen; Saunders, Richard D E; Scaife, Anna M M; Scott, Paul F; Shimwell, Timothy W; Titterington, David J; Waldram, Elizabeth M; Watson, Robert A; Zwart, Jonathan T L

    2009-01-01

    Using the Arcminute Microkelvin Imager (AMI) at 16 GHz and the Very Small Array (VSA) at 33 GHz to make follow-up observations of sources in the New Extragalactic WMAP Point Source Catalogue, we have investigated the flux-density variability in a complete sample of 97 sources over timescales of a few months to approximately 1.5 years. We find that 53 per cent of the 93 sources, for which we have multiple observations, are variable, at the 99 per cent confidence level, above the flux density calibration uncertainties of approximately 4 per cent at 16 GHz; the fraction of sources having varied by more than 20 per cent is 15 per cent at 16 GHz and 20 per cent at 33 GHz. Not only is this common occurrence of variability at high frequency of interest for source physics, but strategies for coping with source contamination in CMB work must take this variability into account. There is no strong evidence of a correlation between variability and flux density for the sample as a whole. Using a maximum-likelihood method,...

  12. Lichtinduzierte Generierung und Charakterisierung optischer Anisotropie. - [überarb. Diss.

    OpenAIRE

    Jung, Carl Christoph

    2005-01-01

    Eine Nutzung der optischen Anisotropie dünner Schichten ist vor allem für die Displaytechnologie, die optische Datenspeicherung und für optische Sicherheitselemente von hoher Bedeutung. Diese Doktorarbeit befasst sich mit theoretischen und experimentellen Untersuchung von dreidimensionaler Anisotropie und dabei insbesondere mit der Untersuchung von lichtinduzierter dreidimensionaler Anisotropie in organischen dünnen Polymer-Schichten. Die gewonnenen Erkentnisse und entwickelten Methoden könne...

  13. Anisotropy in cohesive, frictional granular media

    International Nuclear Information System (INIS)

    The modelling of cohesive, frictional granular materials with a discrete particle molecular dynamics is reviewed. From the structure of the quasi-static granular solid, the fabric, stress, and stiffness tensors are determined, including both normal and tangential forces. The influence of the material properties on the flow behaviour is also reported, including relations between the microscopic attractive force and the macroscopic cohesion as well as the dependence of the macroscopic friction on the microscopic contact friction coefficient. Related to the dynamics, the anisotropy of both structure and stress are exponentially approaching the maximum

  14. Three-layer model for exchange anisotropy

    Science.gov (United States)

    Rezende, S. M.; Azevedo, A.; de Aguiar, F. M.; Fermin, J. R.; Egelhoff, W. F.; Parkin, S. S.

    2002-08-01

    Recent x-ray absorption measurements have indicated that the interface between the antiferromagnetic (AF) and the ferromagnetic (FM) layers in AF/FM bilayers instead of being abrupt, consists of a thin layer with uncompensated spins. Here the effect of an interfacial layer between the AF and FM layers on the ferromagnetic resonance response is investigated using a three-layer model for the exchange anisotropy. The calculated dependence of the resonance field with the azimuthal angle of the in-plane external field agrees quite well with experimental data in several samples, lending support to the existence of the uncompensated interfacial layer.

  15. Cosmology with cosmic microwave background anisotropy

    Indian Academy of Sciences (India)

    Tarun Sourdeep

    2006-10-01

    Measurements of CMB anisotropy and, more recently, polarization have played a very important role in allowing precise determination of various parameters of the `standard' cosmological model. The expectation of the paradigm of inflation and the generic prediction of the simplest realization of inflationary scenario in the early Universe have also been established - `acausally' correlated initial perturbations in a flat, statistically isotropic Universe, adiabatic nature of primordial density perturbations. Direct evidence for gravitational instability mechanism for structure formation from primordial perturbations has been established. In the next decade, future experiments promise to strengthen these deductions and uncover the remaining crucial signature of inflation - the primordial gravitational wave background.

  16. Molecular anisotropy effects in carbon K-edge scattering: depolarized diffuse scattering and optical anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Stone, Kevin H.

    2014-07-14

    Some polymer properties, such as conductivity, are very sensitive to short- and intermediate-range orientational and positional ordering of anisotropic molecular functional groups, and yet means to characterize orientational order in disordered systems are very limited. We demonstrate that resonant scattering at the carbon K-edge is uniquely sensitive to short-range orientation correlations in polymers through depolarized scattering at high momentum transfers, using atactic polystyrene as a well-characterized test system. Depolarized scattering is found to coexist with unpolarized fluorescence, and to exhibit pronounced anisotropy. We also quantify the spatially averaged optical anisotropy from low-angle reflectivity measurements, finding anisotropy consistent with prior visible, x-ray absorption, and theoretical studies. The average anisotropy is much smaller than that in the depolarized scattering and the two have different character. Both measurements exhibit clear spectral signatures from the phenyl rings and the polyethylene-like backbone. Discussion focuses on analysis considerations and prospects for using this depolarized scattering for studies of disorder in soft condensed matter.

  17. Computing magnetic anisotropy constants of single molecule magnets

    Indian Academy of Sciences (India)

    S Ramasesha; Shaon Sahoo; Rajamani Raghunathan; Diptiman Sen

    2009-09-01

    We present here a theoretical approach to compute the molecular magnetic anisotropy parameters, and for single molecule magnets in any given spin eigenstate of exchange spin Hamiltonian. We first describe a hybrid constant -valence bond (VB) technique of solving spin Hamiltonians employing full spatial and spin symmetry adaptation and we illustrate this technique by solving the exchange Hamiltonian of the Cu6Fe8 system. Treating the anisotropy Hamiltonian as perturbation, we compute the and values for various eigenstates of the exchange Hamiltonian. Since, the dipolar contribution to the magnetic anisotropy is negligibly small, we calculate the molecular anisotropy from the single-ion anisotropies of the metal centers. We have studied the variation of and by rotating the single-ion anisotropies in the case of Mn12Ac and Fe8 SMMs in ground and few low-lying excited states of the exchange Hamiltonian. In both the systems, we find that the molecular anisotropy changes drastically when the single-ion anisotropies are rotated. While in Mn12Ac SMM values depend strongly on the spin of the eigenstate, it is almost independent of the spin of the eigenstate in Fe8 SMM. We also find that the value is almost insensitive to the orientation of the anisotropy of the core Mn(IV) ions. The dependence of on the energy gap between the ground and the excited states in both the systems has also been studied by using different sets of exchange constants.

  18. The study of the shape anisotropy in patterned permalloy films

    Institute of Scientific and Technical Information of China (English)

    Zhang Dong; Zhai Ya; Zhai Hong-Ru

    2007-01-01

    In this paper a systematic ferromagnetic resonance study shows that an in-plane magnetic anisotropy in the patterned micron octagon permalloy (Ni80Fe20) elements is mainly determined by the element geometry. The easy-axis is along the edge of the elements, and the hard-axis is along the diagonal. The shape anisotropy of the octagon elements is determined by square and equilateral octagon, and the theoretical calculation was studied on the shape anisotropy. The shape anisotropy of rectangular was calculated by using the same theory.

  19. Texture and anisotropy analysis of Qusaiba shales

    KAUST Repository

    Kanitpanyacharoen, Waruntorn

    2011-02-17

    Scanning and transmission electron microscopy, synchrotron X-ray diffraction, microtomography and ultrasonic velocity measurements were used to characterize microstructures and anisotropy of three deeply buried Qusaiba shales from the Rub\\'al-Khali basin, Saudi Arabia. Kaolinite, illite-smectite, illite-mica and chlorite show strong preferred orientation with (001) pole figure maxima perpendicular to the bedding plane ranging from 2.4-6.8 multiples of a random distribution (m.r.d.). Quartz, feldspars and pyrite crystals have a random orientation distribution. Elastic properties of the polyphase aggregate are calculated by averaging the single crystal elastic properties over the orientation distribution, assuming a nonporous material. The average calculated bulk P-wave velocities are 6.2 km/s (maximum) and 5.5 km/s (minimum), resulting in a P-wave anisotropy of 12%. The calculated velocities are compared with those determined from ultrasonic velocity measurements on a similar sample. In the ultrasonic experiment, which measures the effects of the shale matrix as well as the effects of porosity, velocities are smaller (P-wave maximum 5.3 km/s and minimum 4.1 km/s). The difference between calculated and measured velocities is attributed to the effects of anisotropic pore structure and to microfractures present in the sample, which have not been taken into account in the matrix averaging. © 2011 European Association of Geoscientists & Engineers.

  20. The Anisotropy of Replicated Aluminum Foams

    Directory of Open Access Journals (Sweden)

    Eugeny L. Furman

    2014-01-01

    Full Text Available The replication casting process gives the open-cell aluminum foams that can be used in many industrial applications as well as in filtering technology. The essential requirement for filters is the uniformity of filtering degree which is defined by the minimal pore size. However the structure of replication castings is often inhomogeneous and the minimal pore radius is decreasing in the direction of melt infiltration. The objective of this investigation is to study the dynamics of melt impregnation of the porous medium by vacuum suction to identify the possibility of reducing the anisotropy. Theoretical data illustrate the processes at the boundary between melt and gas medium. The experiments were carried out using the replication aluminum samples produced according to commercial technology. It was found that the permeability coefficient varies throughout the height of castings. A method for estimation of pressure on the line of melt movement was proposed. The resistance of NaCl layer and circular vents of the mold causes the inhomogeneity of castings. Finally the ways of minimizing the anisotropy were offered.

  1. Electromagnetic Instabilities Excited by Electron Temperature Anisotropy

    Institute of Scientific and Technical Information of China (English)

    陆全明; 王连启; 周艳; 王水

    2004-01-01

    One-dimensional particle-in-cell simulations are performed to investigate the nonlinear evolution of electromagnetic instabilities excited by the electron temperature anisotropy in homogeneous plasmas with different parameters. The results show that the electron temperature anisotropy can excite the two right-hand electromagnetic instabilities, one has the frequency higher than Ωe, the other is the whistler instability with larger amplitude,and its frequency is below Ωe. Their dispersion relations are consistent with the prediction from the cold plasma theory. In the initial growth stage (prediction from linear theory), the frequency of the dominant mode (the mode whose amplitude is large enough) of the whistler wave almost does not change, but in the saturation stage the situation is different. In the case that the ratio of electron plasma frequency to cyclotron frequency is larger than 1, the frequency of the dominant mode of the whistler wave drifts from high to low continuously. However, for the case of the ratio smaller than 1, besides the original dominant mode of the whistler wave whose frequency is about 2.6ωe, another dominant mode whose frequency is about 1.55ωe also begins to be excited at definite time,and its amplitude increases with time until it exceeds the original dominant mode.

  2. Anisotropy in thin Canning sheet metals

    Science.gov (United States)

    Rees, D. W. A.

    2003-03-01

    The in-plane anisotropy of ductile sheet metal may be characterised by r-values within a uniform tensile strain range. In iow ductiiity material, tensile failure occurs by the formation of an inciined groove within which the plasticity is localised. Under these conditions, where lateral and axial displacements cannot determine an r-value reliably, the inclination of the local groove is used. Anisotropy is characterised from an orthotropic yield criterion within three r-values, found from tension tests at 0^{circ}, 45^{circ} and 90^{circ} to the roll. Application to bi-axial stress states are made from elliptical bulge forming. The theory may reprcduce the pressure-height curves and pole strain paths provided an equivalence exists between flow curves from tension and bulge tests. Otherwise, the circular bulge test is better for providing the hardening parameters and fracture strain for use in in biaxial stress applications. There appears to be no advantage in using other non-quadratic yield criteria except by the addition of linear and cubic terms.

  3. Scanning anisotropy parameters in complex media

    KAUST Repository

    Alkhalifah, Tariq Ali

    2011-03-21

    Parameter estimation in an inhomogeneous anisotropic medium offers many challenges; chief among them is the trade-off between inhomogeneity and anisotropy. It is especially hard to estimate the anisotropy anellipticity parameter η in complex media. Using perturbation theory and Taylor’s series, I have expanded the solutions of the anisotropic eikonal equation for transversely isotropic (TI) media with a vertical symmetry axis (VTI) in terms of the independent parameter η from a generally inhomogeneous elliptically anisotropic medium background. This new VTI traveltime solution is based on a set of precomputed perturbations extracted from solving linear partial differential equations. The traveltimes obtained from these equations serve as the coefficients of a Taylor-type expansion of the total traveltime in terms of η. Shanks transform is used to predict the transient behavior of the expansion and improve its accuracy using fewer terms. A homogeneous medium simplification of the expansion provides classical nonhyperbolic moveout descriptions of the traveltime that are more accurate than other recently derived approximations. In addition, this formulation provides a tool to scan for anisotropic parameters in a generally inhomogeneous medium background. A Marmousi test demonstrates the accuracy of this approximation. For a tilted axis of symmetry, the equations are still applicable with a slightly more complicated framework because the vertical velocity and δ are not readily available from the data.

  4. Anisotropy and Heterogeneity Interaction in Shear Zones

    Science.gov (United States)

    Dabrowski, M.; Schmid, D. W.

    2009-04-01

    Rocks are heterogeneous on many different scales and deformation may introduce a coexistence of heterogeneity and anisotropy in shear zones. A competent inclusion embedded in a laminated matrix is a typical example. Indisputably, the presence of a mechanical heterogeneity leads to a flow perturbation and consequently to a deflection of the lamination in its vicinity. Assuming a passive response of the matrix phase, the pattern formation around rigid objects has been modeled in two and three dimensions using analytical solutions. Yet, the laminas may be mechanically distinct, leading to an effectively anisotropic rheology of the matrix. The feedback of an evolving matrix structure on the inclusion motion cannot be precluded in this case. In our study elliptical inclusions of varying aspect ratios are embedded in a laminated linear viscous host and subject to a large simple shear deformation in finite element numerical simulations. Increasing the viscosity ratio of the weak and strong lamina significantly changes the pattern characteristics in the matrix. The structural evolution around an inclusion proves to have a major impact on the inclusion motion, leading to the stabilization of elongated inclusions at antithetic orientations. We provide a comparison of two different modeling approaches. In the first approach discrete layers are introduced in the matrix and the large strain evolution of individual minute layers is resolved. Next, the matrix is modeled as an anisotropic medium using an evolving director field that locally describes the anisotropy direction. The length scale of layering can be restored in this model using the micropolar medium formulation.

  5. THE ORNL ATOM PROBE

    OpenAIRE

    Miller, M

    1986-01-01

    The ORNL Atom Probe is a microanalytical tool for studies in materials science. The instrument is a combination of a customized version of the vacuum system of the VG FIM-100 atom probe, an ORNL-designed microcomputer-controlled digital timing system, and a double curved CEMA Imaging Atom Probe detector. The atom probe combines four instruments into one - namely a field ion microscope, an energy compensated time-of-flight mass spectrometer, an imaging atom probe, and a pulsed laser atom probe.

  6. Mobile Game Probes

    DEFF Research Database (Denmark)

    Borup Lynggaard, Aviaja

    2006-01-01

    This paper will examine how probes can be useful for game designers in the preliminary phases of a design process. The work is based upon a case study concerning pervasive mobile phone games where Mobile Game Probes have emerged from the project. The new probes are aimed towards a specific target...... group and the goal is to specify the probes so they will cover the most relevant areas for our project. The Mobile Game Probes generated many interesting results and new issues occurred, since the probes came to be dynamic and favorable for the process in new ways....

  7. Exonuclease III-assisted graphene oxide amplified fluorescence anisotropy strategy for ricin detection.

    Science.gov (United States)

    Xiao, Xue; Tao, Jing; Zhang, Hong Zhi; Huang, Cheng Zhi; Zhen, Shu Jun

    2016-11-15

    Graphene oxide (GO) is an excellent fluorescence anisotropy (FA) amplifier. However, in the conventional GO amplified FA strategy, one target can only induce the FA change of one fluorophore on probe, which limits the detection sensitivity. Herein, we developed an exonuclease III (Exo III) aided GO amplified FA strategy by using aptamer as an recognition element and ricin B-chain as a proof-of-concept target. The aptamer was hybridized with a blocker sequence and linked onto the surface of magnetic beads (MBs). Upon the addition of ricin B-chain, blocker was released from the surface of MBs and hybridized with the dye-modified probe DNA on the surface of GO through the toehold-mediated strand exchange reaction. The formed blocker-probe DNA duplex triggered the Exo III-assisted cyclic signal amplification by repeating the hybridization and digestion of probe DNA, liberating the fluorophore with several nucleotides (low FA value). Thus, ricin B-chain could be sensitively detected by the significantly decreased FA. The linear range was from 1.0μg/mL to 13.3μg/mL and the limit of detection (LOD) was 400ng/mL. This method improved the sensitivity of FA assay and it could be generalized to any kind of target detection based on the use of an appropriate aptamer. PMID:27295569

  8. The Cosmic Microwave Background Radiation-A Unique Window on the Early Universe

    Science.gov (United States)

    Hinshaw, Gary

    2010-01-01

    The cosmic microwave background radiation is the remnant heat from the Big Bang. It provides us with a unique probe of conditions in the early universe, long before any organized structures had yet formed. The anisotropy in the radiation's brightness yields important clues about primordial structure and additionally provides a wealth of information about the physics of the early universe. Within the framework of inflationary dark matter models, observations of the anisotropy on sub-degree angular scales reveals the signatures of acoustic oscillations of the photon-baryon fluid at a redshift of 11 00. Data from the first seven years of operation of the Wilkinson Microwave Anisotropy Probe (WMAP) satellite provide detailed full-sky maps of the cosmic microwave background temperature and polarization anisotropy. Together, the data provide a wealth of cosmological information, including the age of the universe, the epoch when the first stars formed, and the overall composition of baryonic matter, dark matter, and dark energy. The results also provide constraints on the period of inflationary expansion in the very first moments of time. WMAP, part of NASA's Explorers program, was launched on June 30, 2001. The WMAP satellite was produced in a partnership between the Goddard Space Flight Center and Princeton University. The WMAP team also includes researchers at the Johns Hopkins University; the Canadian Institute of Theoretical Astrophysics; University of Texas; Oxford University; University of Chicago; Brown University; University of British Columbia; and University of California, Los Angeles.

  9. Measurements of cosmic ray anisotropies from Pioneers 10 and 11

    International Nuclear Information System (INIS)

    Cosmic ray anisotropy measurements are performed by the University of California, San Diego experiments on Pioneers 10 and 11. A directional Cerenkov counter sensitive to protons and α particles with kinetic energies >= 480 MeV/nucleon is used to determine east-west and north-south anisotropies. (orig./WBU)

  10. Anisotropy of synthetic diamond in catalytic etching using iron powder

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Junsha [College of Materials Science and Engineering, Hunan University, Hunan 410082 (China); Department of Mechanical Engineering, Keio University, Yokohama 223-8522 (Japan); Wan, Long, E-mail: wanlong1799@163.com [College of Materials Science and Engineering, Hunan University, Hunan 410082 (China); Chen, Jing [College of Materials Science and Engineering, Hunan University, Hunan 410082 (China); Yan, Jiwang [Department of Mechanical Engineering, Keio University, Yokohama 223-8522 (Japan)

    2015-08-15

    Highlights: • Synthetic diamond crystallites were etched using iron without requiring hydrogen. • The effect of temperature on the etching behaviour was demonstrated. • The anisotropy of etching on different crystal planes was investigated. • The extent of etching on diamond surface was examined quantitatively. • A schematic model for diamond etching by iron is being proposed. - Abstract: This paper demonstrated a novel technique for catalytic etching of synthetic diamond crystallites using iron (Fe) powder without flowing gas. The effect of temperature on the etching behaviour on different crystal planes of diamond was investigated. The surface morphology and surface roughness of the processed diamond were examined by scanning electron microscope (SEM) and laser-probe surface profiling. In addition, the material composition of the Fe-treated diamond was characterized using micro-Raman spectroscopy and the distribution of chemical elements and structural changes on Fe-loaded diamond surfaces were analyzed by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), respectively. Results showed that at the same temperature the {1 0 0} plane was etched faster than the {1 1 1} plane, and that the etching rate of both {1 0 0} and {1 1 1} plane increased with temperature. The etch pits on {1 0 0} plane were reversed pyramid with flat {1 1 1} walls, while the etch holes on {1 1 1} plane were characterized with flat bottom. It was also demonstrated that graphitization of diamond and subsequent carbon diffusion in molten iron were two main factors resulting in the removal of carbon from the diamond surface.

  11. Carrier-dependent magnetic anisotropy of Gd-adsorbed graphene

    Science.gov (United States)

    Lu, Yuan; Zhou, Tie-ge; Shao, Bin; Zuo, Xu; Feng, Min

    2016-05-01

    Using first-principles calculation based on density functional theory, we study the magnetic anisotropy of Gd-adsorbed graphene and its dependence on carrier accumulation. We show that carrier accumulation not only impacts the magnitude of magnetic anisotropy but also switches its sign. Hole accumulation enhances the perpendicular anisotropy up to ˜16 meV per Gd atom, while electron accumulation switches the anisotropy from perpendicular to in-plane direction. Moreover, we find that the first order perturbation of spin-orbit coupling interaction induces a pseudo-gap at Γ for the perpendicular magnetization, which leads to the the anomalous magnetic anisotropy for the neutral composite. Our findings pave the way for magneto-electric materials based on rare-earth-decorated graphene for voltage-controlled spintronics.

  12. Intrinsic anisotropy-defined magnetization reversal in submicron ring magnets

    Science.gov (United States)

    Li, S. P.; Lew, W. S.; Bland, J. A. C.; Natali, M.; Lebib, A.; Chen, Y.

    2002-12-01

    We report a study of the effect of magnetocrystalline anisotropy in the magnetization reversal of submicron Co rings fabricated by nanoimprint lithography. For weak magnetocrystalline anisotropy, the complete reversal takes place via a transition from saturation at large negative fields, into a vortex configuration at small fields, and back to reverse saturation at large positive fields. When the anisotropy strength is increased to a critical value, the intermediate vortex configuration no longer exists in the magnetization reversal along the easy axis; instead, the reversal occurs through a rapid jump. However, when the applied field direction is far from the easy axis, the presence of the magnetocrystalline anisotropy favors local vortex nucleation, and this leads to a similar switching process as found for low anisotropy. Micromagnetic simulations indicate that the magnetization reversal process of the rings, starts from a buckling-like reverse domain nucleation, followed by local vortex formation and an avalanche process of local vortex nucleation.

  13. Perpendicular magnetic anisotropy of Co85Cr15/Pt multilayers

    Institute of Scientific and Technical Information of China (English)

    Pol Hwang; Baohe Li; Tao Yang; Zhonghai Zhai; Fengwu Zhu

    2004-01-01

    The CoCr/Pt bilayers and (CoCr/Pt)20 multilayers with Pt underlayer were prepared by DC magnetron sputtering. The effects of prepared condition on perpendicular magnetic anisotropy were investigated. The results show that the thickness of Pt underlayer has a great effect on the microstructure and perpendicular magnetic anisotropy of CoCr/Pt bilayers and (CoCr/Pt)20 multilayers.When the thickness of Pt underlayer increases, Pt(111) and CoCr(002) peaks of both CoCr/Pt bilayers and (CoCr/Pt)20 multilayers increase and the bilayer periodicity of the multilayers is improved. The effective magnetic anisotropy of (CoCr/Pt)20 multilayers with Pt underlayer was much larger than that of CoCr/Pt bilayers. The (CoCr/Pt)20 multilayers has a stronger perpendicular magnetic anisotropy than that of CoCr/Pt bilayers. This is ascribed to the interface magnetic anisotropy of the multilayers.

  14. Polarization and dilepton anisotropy in pion-nucleon collisions

    CERN Document Server

    Speranza, Enrico; Friman, Bengt

    2016-01-01

    Hadronic polarization and the related anisotropy of the dilepton angular distribution are studied for the reaction $\\pi N \\rightarrow Ne^+ e^-$. We employ consistent effective interactions for baryon resonances up to spin-5/2, where non-physical degrees of freedom are eliminated, to compute the anisotropy coefficients for isolated intermediate baryon resonances. It is shown that the spin and parity of the intermediate baryon resonance is reflected in the angular dependence of the anisotropy coefficient. We then compute the anisotropy coefficient including the $N(1520)$ and $N(1440)$ resonances, which are essential at the collision energy of the recent data obtained by the HADES collaboration on this reaction. We conclude that the anisotropy coefficient provides useful constraints for unravelling the resonance contributions to this process.

  15. Carrier-dependent magnetic anisotropy of Gd-adsorbed graphene

    Directory of Open Access Journals (Sweden)

    Yuan Lu

    2016-05-01

    Full Text Available Using first-principles calculation based on density functional theory, we study the magnetic anisotropy of Gd-adsorbed graphene and its dependence on carrier accumulation. We show that carrier accumulation not only impacts the magnitude of magnetic anisotropy but also switches its sign. Hole accumulation enhances the perpendicular anisotropy up to ∼16 meV per Gd atom, while electron accumulation switches the anisotropy from perpendicular to in-plane direction. Moreover, we find that the first order perturbation of spin-orbit coupling interaction induces a pseudo-gap at Γ for the perpendicular magnetization, which leads to the the anomalous magnetic anisotropy for the neutral composite. Our findings pave the way for magneto-electric materials based on rare-earth-decorated graphene for voltage-controlled spintronics.

  16. Determination of the magnetic anisotropy constant of Cu/Fe/SiO2/Si by a magneto-optical Kerr effect susceptometer

    International Nuclear Information System (INIS)

    The magneto-optical Kerr effect susceptometry technique is proposed to determine the uniaxial magnetic anisotropy (UMA) constant Ku. The magnetic properties of Cu/Fe/SiO2/Si grown by dc magnetron sputtering were investigated. The in-plane uniaxial magnetic anisotropy was probed by the magneto-optical Kerr effect (MOKE). The value of UMA, Ku = 2.5 ×103 J/m3, was simulated from the field dependence of ac susceptibility along the hard axis according to the Stoner—Wohlfarth (S—W) model, which is consistent with Ku = 2.7 × 103 J/m3 calculated from the magnetic hysteresis loops. Our results show that the magneto-optical Kerr effect susceptometry can be employed to determine the magnetic anisotropy constant owing to its high sensitivity. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  17. CMB Anisotropies from a Gradient Mode

    CERN Document Server

    Mirbabayi, Mehrdad

    2014-01-01

    A pure gradient mode must have no observable dynamical effect at linear level. We confirm this by showing that its contribution to the dipolar power asymmetry of CMB anisotropies vanishes, if Maldacena's consistency condition is satisfied. To this end, the existing second order Sachs-Wolfe formula in the squeezed limit is extended to include a gradient in the long mode and to account for the change in the location of the last scattering surface induced by this mode. At second order, a gradient mode generated in Single-field inflation is shown to induce a quadrupole moment. For instance in a matter-dominated model it is equal to 5/18 times the square of the linear gradient part. This quadrupole can be cancelled by superposing a quadratic perturbation. The result is shown to be a non-linear extension of Weinberg's adiabatic modes: a long-wavelength physical mode which looks locally like a coordinate transformation.

  18. Fine structure constant variation or spacetime anisotropy?

    International Nuclear Information System (INIS)

    Recent observations on the quasar absorption spectra supply evidence for the variation of the fine structure constant α. In this paper, we propose another interpretation of the observational data on the quasar absorption spectra: a scenario with spacetime inhomogeneity and anisotropy. Maybe the spacetime is characterized by the Finsler geometry instead of the Riemann one. The Finsler geometry admits fewer symmetries than the Riemann geometry does. We investigate the Finslerian geodesic equations in the Randers spacetime (a special Finsler spacetime). It is found that the cosmological redshift in this spacetime deviates from the one in general relativity. The modification term to the redshift could be generally revealed as a monopole plus dipole function of spacetime locations and directions. We suggest that this modification corresponds to the spatial monopole and dipole of α variation in the quasar absorption spectra. (orig.)

  19. Anisotropy of light propagation in human skin

    Science.gov (United States)

    Nickell, Stephan; Hermann, Marcus; Essenpreis, Matthias; Farrell, Thomas J.; Krämer, Uwe; Patterson, Michael S.

    2000-10-01

    Using spatially resolved, steady state diffuse reflectometry, a directional dependence was found in the propagation of visible and near infrared light through human skin in vivo. The skin's reduced scattering coefficient µ's varies by up to a factor of two between different directions of propagation at the same position. This anisotropy is believed to be caused by the preferential orientation of collagen fibres in the dermis, as described by Langer's skin tension lines. Monte Carlo simulations that examine the effect of partial collagen fibre orientation support this hypothesis. The observation has consequences for non-invasive diagnostic methods relying on skin optical properties, and it could be used non-invasively to determine the direction of lines of cleavage in order to minimize scars due to surgical incisions.

  20. Time resolved multiphoton excited fluorescence probes in model membranes

    CERN Document Server

    Bai, Y

    2000-01-01

    Using the time-correlated single-photon counting technique, this thesis reports on a time-resolved fluorescence study of several fluorescent probes successfully employed in membrane research. Concentration and temperature effects on fluorescence anisotropy parameters are demonstrated by DPH, p-terphenyl, alpha-NPO and PPO in DPPC lipid bilayers. Fluorescence anisotropy has shown that trans-stilbene and Rhd 800 have a two-site location in membranes. Multiphoton induced fluorescence of DPH, p-terphenyl, alpha-NPO and v-biphenyl in liposomes was measured using 800nm excitation with a femtosecond Ti:Sapphire laser. P-terphenyl, alpha-NPO and v-biphenyl are new probes for membranes. Comparison of one and multiphoton excitation results has demonstrated higher initial anisotropy with multiphoton excitation than with one-photon excitation. The rotational times were identical for one and multiphoton excitation, indicating the absence of significant local heating or sample perturbation. Excimer formation of alpha-NPO w...

  1. Direct measurement of the magnetic anisotropy field in Mn-Ga and Mn-Co-Ga Heusler films

    Science.gov (United States)

    Fowley, Ciarán; Ouardi, Siham; Kubota, Takahide; Yildirim, Oguz; Neudert, Andreas; Lenz, Kilian; Sluka, Volker; Lindner, Jürgen; Law, Joseph M.; Mizukami, Shigemi; Fecher, Gerhard H.; Felser, Claudia; Deac, Alina M.

    2015-04-01

    The static and dynamic magnetic properties of tetragonally distorted Mn-Ga based alloys were investigated. Static properties are determined in magnetic fields up to 6.5 T using SQUID magnetometry. For the pure Mn1.6Ga film, the saturation magnetisation is 0.36 MA m-1 and the coercivity is 0.29 T. Partial substitution of Mn by Co results in Mn2.6Co0.3Ga1.1. The saturation magnetisation of those films drops to 0.2 MA m-1 and the coercivity is increased to 1 T. The time-resolved magneto-optical Kerr effect (TR-MOKE) is used to probe the high-frequency dynamics of Mn-Ga. The ferromagnetic resonance frequency extrapolated to zero-field is found to be 125 GHz with a Gilbert damping, α, of 0.019. The anisotropy field is determined from both SQUID and TR-MOKE to be 4.5 T, corresponding to an effective anisotropy density of 0.81 MJ m-3. Given the large anisotropy field of the Mn2.6Co0.3Ga1.1 film, pulsed magnetic fields up to 60 T are used to determine the field strength required to saturate the film in the plane. For this, the extraordinary Hall effect was employed as a probe of the local magnetisation. By integrating the reconstructed in-plane magnetisation curve, the effective anisotropy energy density for Mn2.6Co0.3Ga1.1 is determined to be 1.23 MJ m-3.

  2. Traversing probe system

    International Nuclear Information System (INIS)

    This invention comprises a rotatable annular probe-positioner which carries at least one radially disposed sensing probe, such as a Pitot tube having a right-angled tip. The positioner can be coaxially and rotatably mounted within a compressor casing or the like and then actuated to orient the sensing probe as required to make measurements at selected stations in the annulus between the positioner and compressor casing. The positioner can be actuated to (a) selectively move the probe along its own axis, (b) adjust the yaw angle of the right-angled probe tip, and (c) revolve the probe about the axis common to the positioner and casing. A cam plate engages a cam-follower portion of the probe and normally rotates with the positioner. The positioner includes a first-motor-driven ring gear which effects slidable movement of the probe by rotating the positioner at a time when an external pneumatic cylinder is actuated to engage the cam plate and hold it stationary. When the pneumatic cylinder is not actuated, this ring gear can be driven to revolve the positioner and thus the probe to a desired circumferential location about the above-mentioned common axis. A second motor-driven ring gear included in the positioner can be driven to rotate the probe about its axis, thus adjusting the yaw angle of the probe tip. The positioner can be used in highly corrosive atmosphere, such as gaseous uranium hexafluoride. 10 claims, 6 figures

  3. Daytime Thermal Anisotropy of Urban Neighbourhoods: Morphological Causation

    Directory of Open Access Journals (Sweden)

    E. Scott Krayenhoff

    2016-01-01

    Full Text Available Surface temperature is a key variable in boundary-layer meteorology and is typically acquired by remote observation of emitted thermal radiation. However, the three-dimensional structure of cities complicates matters: uneven solar heating of urban facets produces an “effective anisotropy” of surface thermal emission at the neighbourhood scale. Remotely-sensed urban surface temperature varies with sensor view angle as a consequence. The authors combine a microscale urban surface temperature model with a thermal remote sensing model to predict the effective anisotropy of simplified neighbourhood configurations. The former model provides detailed surface temperature distributions for a range of “urban” forms, and the remote sensing model computes aggregate temperatures for multiple view angles. The combined model’s ability to reproduce observed anisotropy is evaluated against measurements from a neighbourhood in Vancouver, Canada. As in previous modeling studies, anisotropy is underestimated. Addition of moderate coverages of small (sub-facet scale structure can account for much of the missing anisotropy. Subsequently, over 1900 sensitivity simulations are performed with the model combination, and the dependence of daytime effective thermal anisotropy on diurnal solar path (i.e., latitude and time of day and blunt neighbourhood form is assessed. The range of effective anisotropy, as well as the maximum difference from nadir-observed brightness temperature, peak for moderate building-height-to-spacing ratios (H/W, and scale with canyon (between-building area; dispersed high-rise urban forms generate maximum anisotropy. Maximum anisotropy increases with solar elevation and scales with shortwave irradiance. Moreover, it depends linearly on H/W for H/W < 1.25, with a slope that depends on maximum off-nadir sensor angle. Decreasing minimum brightness temperature is primarily responsible for this linear growth of maximum anisotropy. These

  4. Probing primordial features with future galaxy surveys

    CERN Document Server

    Ballardini, Mario; Fedeli, Cosimo; Moscardini, Lauro

    2016-01-01

    We study the capability of future measurements of the galaxy clustering power spectrum to probe departures from a power-law spectrum for primordial fluctuations. On considering the information from the galaxy clustering power spectrum up to quasi-linear scales, i.e. $k<0.1$ h Mpc$^{-1}$, we present forecasts for DESI, Euclid and SPHEREx in combination with CMB measurements. As examples of departures in the primordial power spectrum from a simple power-law, we consider four $Planck$ 2015 best-fits motivated by inflationary models with different breaking of the slow-roll approximation. These four representative models provide an improved fit to CMB temperature anisotropies, although not at statistical significant level. As for other extensions in the matter content of the simplest $\\Lambda$CDM model, the complementarity of the information in the resulting matter power spectrum expected from these galaxy surveys and in the primordial power spectrum from CMB anisotropies can be effective in constraining cosmol...

  5. Probing the dark energy methods and strategies

    CERN Document Server

    Huterer, D; Huterer, Dragan; Turner, Michael S.

    2001-01-01

    The presence of dark energy in the Universe is inferred directly from the accelerated expansion of the Universe, and indirectly, from measurements of cosmic microwave background (CMB) anisotropy. Dark energy contributes about 2/3 of the critical density, is very smoothly distributed, and has large negative pressure. Its nature is very much unknown. Most of its discernible consequences follow from its effect on evolution of the expansion rate of the Universe, which in turn affects the growth of density perturbations and the age of the Universe, and can be probed by the classical kinematic cosmological tests. Absent a compelling theoretical model (or even a class of models), we describe the dark energy by an effective equation-of-state w=p_X/\\rho_X which is allowed to vary with time. We describe and compare different approaches for determining w(t), including magnitude-redshift (Hubble) diagram, number counts of galaxies and clusters, and CMB anisotropy, focusing particular attention on the use of a sample of s...

  6. Anisotropy Graded Media: Extending the Superparamagnetic Limit (abstract)

    Science.gov (United States)

    Horton, K. Renee; Kang, S.; Harrell, J. W.

    2009-04-01

    The maximum storage density in magnetic media is limited by the superparamagnetic size of the grains that make up the bits. The superparamagnetic size can be reduced by increasing the anisotropy of the grains; however, in conventional media, in which the anisotropy of the grains is uniform, this leads to a proportionate increase in the switching field. The switching field, however, is limited by the maximum magnetization of the core material in the write head. Recent calculations have shown that the switching field can be significantly reduced relative to the thermal stability of the grains if the anisotropy is made to vary appropriately from the bottom to the top of the grain. In this project we propose to test this concept by fabricating and characterizing anisotropy graded films. We will use the hcp CoPtX system, with X = Cr or Ru, where the anisotropy gradient is obtained by grading the composition. Both sheet films and granular films will be fabricated. The anisotropy gradients will be determined by analyzing magnetization curves. Dynamic coercivity measurements will be used to determine the short-time coercivity and the zero-field energy barrier in the granular films. These results will be compared with similar measurements on films with uniform anisotropy films in order to test the predictions for graded media.

  7. The COBE cosmic 3 K anisotropy experiment: A gravity wave and cosmic string probe

    Science.gov (United States)

    Bennett, Charles L.; Smoot, George F.

    1989-01-01

    Among the experiments to be carried into orbit next year, by the COBE satellite, are differential microwave radiometers. They will make sensitive all-sky maps of the temperature of the cosmic microwave background radiation at three frequencies, giving dipole, quadrupole, and higher order multipole measurements of the background radiation. The experiment will either detect, or place significant constraints on, the existence of cosmic strings and long wavelength gravity waves.

  8. Large anisotropy of electron and hole g factors in infrared-emitting InAs/InAlGaAs self-assembled quantum dots

    Science.gov (United States)

    Belykh, V. V.; Yakovlev, D. R.; Schindler, J. J.; Zhukov, E. A.; Semina, M. A.; Yacob, M.; Reithmaier, J. P.; Benyoucef, M.; Bayer, M.

    2016-03-01

    A detailed study of the g -factor anisotropy of electrons and holes in InAs/In0.53Al0.24Ga0.23As self-assembled quantum dots emitting in the telecom spectral range of 1.5 -1.6 μ m (around 0.8 eV photon energy) is performed by time-resolved pump-probe ellipticity technique using a superconducting vector magnet. All components of the g -factor tensors are measured, including their spread in the quantum dot (QD) ensemble. Surprisingly, the electron g factor shows a large anisotropy changing from ge ,x=-1.63 to ge ,z=-2.52 between directions perpendicular and parallel to the dot growth axis, respectively, at an energy of 0.82 eV. The hole g -factor anisotropy at this energy is even stronger: | gh,x|=0.64 and | gh,z|=2.29 . On the other hand, the in-plane anisotropies of electron and hole g factors are small. The pronounced out-of-plane anisotropy is also observed for the spread of the g factors, determined from the spin dephasing time. The hole longitudinal g factors are described with a theoretical model that allows us to estimate the QD parameters. We find that the QD height-to-diameter ratio increases while the indium composition decreases with increasing QD emission energy.

  9. An approach to directly probe simultaneity

    CERN Document Server

    Kipreos, Edward T

    2016-01-01

    The theory of special relativity derives from the Lorentz transformation. The Lorentz transformation implies differential simultaneity and light speed isotropy. Experiments to probe differential simultaneity should be able to distinguish the Lorentz transformation from a kinematically-similar alternate transformation that predicts absolute simultaneity, the absolute Lorentz transformation. Here, we describe how published optical tests of light speed isotropy/anisotropy cannot distinguish between the two transformations. We show that the shared equations of the two transformations, from the perspective of the "stationary" observer, are sufficient to predict null results in optical resonator experiments and in tests of frequency changes in one-way light paths. In an influential 1910 exposition on differential simultaneity, Comstock described how a "stationary" observer would observe different clock readings for spatially-separated "moving" clocks. The difference in clock readings is an integral aspect of differ...

  10. Probing SZ Source Detection with Gasdynamical Simulations

    CERN Document Server

    Bond, J R; Wadsley, J W; Gladders, M D; Ruetalo, Marcelo I.; Wadsley, James W.; Gladders, Michael D.

    2001-01-01

    The huge worldwide investment in CMB experiments should make the Sunyaev-Zeldovich (SZ) effect a key probe of the cosmic web in the near future. For the promise to be realized, substantial development of simulation and analysis tools to relate observation to theory is needed. The high nonlinearity and dissipative/feedback gas physics lead to highly non-Gaussian patterns that are much more difficult to analyze than Gaussian primary anisotropies for which the procedures are reasonably well developed. Historical forecasts for what CMB experiments might see used semi-analytic tools, including large scale map constructions, with localized and simplified pressure structures distributed on a point process of (clustered) sources. Hydro studies beyond individual cluster/supercluster systems were inadequate, but now large-volume simulations with high resolution are beginning to shift the balance. We illustrate this by applying ``Gasoline'' (parallelized Tree+SPH) computations to construct SZ maps and derive statistical...

  11. Nanopatterning reconfigurable magnetic landscapes via thermally assisted scanning probe lithography

    Science.gov (United States)

    Albisetti, E.; Petti, D.; Pancaldi, M.; Madami, M.; Tacchi, S.; Curtis, J.; King, W. P.; Papp, A.; Csaba, G.; Porod, W.; Vavassori, P.; Riedo, E.; Bertacco, R.

    2016-06-01

    The search for novel tools to control magnetism at the nanoscale is crucial for the development of new paradigms in optics, electronics and spintronics. So far, the fabrication of magnetic nanostructures has been achieved mainly through irreversible structural or chemical modifications. Here, we propose a new concept for creating reconfigurable magnetic nanopatterns by crafting, at the nanoscale, the magnetic anisotropy landscape of a ferromagnetic layer exchange-coupled to an antiferromagnetic layer. By performing localized field cooling with the hot tip of a scanning probe microscope, magnetic structures, with arbitrarily oriented magnetization and tunable unidirectional anisotropy, are reversibly patterned without modifying the film chemistry and topography. This opens unforeseen possibilities for the development of novel metamaterials with finely tuned magnetic properties, such as reconfigurable magneto-plasmonic and magnonic crystals. In this context, we experimentally demonstrate spatially controlled spin wave excitation and propagation in magnetic structures patterned with the proposed method.

  12. Growth of Co Nanomagnet Arrays with Enhanced Magnetic Anisotropy

    Science.gov (United States)

    Fernández, Laura; Ilyn, Maxim; Magaña, Ana; Vitali, Lucia; Ortega, José Enrique

    2016-01-01

    A trigon structure formed by submonolayer gadolinium deposition onto Au(111) is revealed as a robust growth template for Co nanodot arrays. Scanning Tunneling Microscopy and X‐Ray Magnetic Circular Dichroism measurements evidence that the Co nanoislands behave as independent magnetic entities with an out‐of‐plane easy axis of anisotropy and enhanced magnetic anisotropy values, as compared to other self‐organized Co nanodot superlattices. The large strain induced by the lattice mismatch at the interface between Co and trigons is discussed as the main reason for the increased magnetic anisotropy of the nanoislands. PMID:27711268

  13. Effects of surface anisotropy on magnetic vortex core

    Energy Technology Data Exchange (ETDEWEB)

    Pylypovskyi, Oleksandr V., E-mail: engraver@univ.net.ua [Taras Shevchenko National University of Kiev, 01601 Kiev (Ukraine); Sheka, Denis D. [Taras Shevchenko National University of Kiev, 01601 Kiev (Ukraine); Kravchuk, Volodymyr P.; Gaididei, Yuri [Institute for Theoretical Physics, 03143 Kiev (Ukraine)

    2014-06-01

    The vortex core shape in the three dimensional Heisenberg magnet is essentially influenced by a surface anisotropy. We predict that depending of the surface anisotropy type there appears barrel- or pillow-shaped deformation of the vortex core along the magnet thickness. Our theoretical study is well confirmed by spin–lattice simulations. - Highlights: • The shape of magnetic vortex core is essentially influenced by SA (surface anisotropy). • We predict barrel- or pillow-shaped deformation of the vortex depending on SA. • The variational approach fully describes the vortex core deformation. • We performed spin–lattice simulations to detect SA influence on the vortex core.

  14. A Theoretical Diagnosis on Light Speed Anisotropy from GRAAL Experiment

    CERN Document Server

    Lingli, Zhou

    2012-01-01

    The light speed anisotropy, i.e., the variation of the light speed with respect to direction in an "absolute" reference frame, is a profound issue in physics. The one-way experiment, performed at the GRAAL facility of the European Synchrotron Radiation Facility (ESRF) in Grenoble, reported results on the light speed anisotropy by Compton scattering of laser photons on high-energy electrons. We show in this paper that the azimuthal distribution of the GRAAL experiment data can be elegantly reproduced by a new theory of Lorentz invariance violation or space-time anisotropy, based on a general principle of physical independence of the mathematical background manifold.

  15. Anisotropies of Gravitational Wave Backgrounds: A Line Of Sight Approach

    CERN Document Server

    Contaldi, Carlo R

    2016-01-01

    In the weak field regime, gravitational waves can be considered as being made up of collisionless, relativistic tensor modes that travel along null geodesics of the perturbed background metric. We work in this geometric optics picture to calculate the anisotropies in gravitational wave backgrounds resulting from astrophysical and cosmological sources. Our formalism yields expressions for the angular power spectrum of the anisotropies. We show how the anisotropies are sourced by intrinsic, Doppler, Sachs-Wolfe, and Integrated Sachs-Wolfe terms in analogy with Cosmic Microwave Background photons.

  16. Review of the anisotropy working group at UHECR-2012

    Directory of Open Access Journals (Sweden)

    Ivanov A.

    2013-06-01

    Full Text Available The study of ultra-high energy cosmic rays (UHECRs has recently experienced a jump in statistics as well as improved instrumentation. This has allowed a better sensitivity in searching for anisotropies in the arrival directions of cosmic rays. In this written version of the presentation given by the inter-collaborative “Anisotropy Working Group” at the International Symposium on Future Directions in UHECR physics at CERN in February 2012, we report on the current status for anisotropy searches in the arrival directions of UHECRs.

  17. Irreversible magnetic processes under biaxial and uniaxial magnetic anisotropies

    Science.gov (United States)

    Pokharel, S.; Akioya, O.; Alqhtany, N. H.; Dickens, C.; Morgan, W.; Wuttig, M.; Lisfi, A.

    2016-05-01

    Irreversible magnetic processes have been investigated in magnetic systems with two different anisotropy symmetries (uniaxial and biaxial) through angular measurement of the switching field, the irreversible susceptibility and the magnetic viscosity. These two systems consist of two-dimensional cobalt ferrite hetero-structures epitaxially grown on (100) and (110) MgO substrate. It is found that for uniaxial anisotropy the irreversible characteristics of the magnetization are large and display a strong angular dependence, which exhibits its maximum at the easy axis and drops quickly to vanish at the hard axis. However, for biaxial anisotropy the magnetization irreversible characteristics are considerably reduced and are less sensitive to the field angle.

  18. Small molecule aptamer assays based on fluorescence anisotropy signal-enhancer oligonucleotides.

    Science.gov (United States)

    Perrier, Sandrine; Bouilloud, Prisca; De Oliveira Coelho, Gisella; Henry, Mickael; Peyrin, Eric

    2016-08-15

    Herein, we design novel fluorescence anisotropy (FA) aptamer sensing platforms dedicated to small molecule detection. The assay strategy relied on enhanced fluctuations of segmental motion dynamics of the aptamer tracer mediated by an unlabelled, partially complementary oligonucleotide. The signal-enhancer oligonucleotide (SEO) essentially served as a free probe fraction revealer. By targeting specific regions of the signalling functional nucleic acid, the SEO binding to the unbound aptamer triggered perturbations of both the internal DNA flexibility and the localized dye environment upon the free probe to duplex structure transition. This potentiating effect determined increased FA variations between the duplex and target bound states of the aptameric probe. FA assay responses were obtained with both pre-structured (adenosine) and unstructured (tyrosinamide) aptamers and with dyes of different photochemical properties (fluorescein and texas red). The multiplexed analysis ability was further demonstrated through the simultaneous multicolour detection of the two small targets. The FA method appears to be especially simple, sensitive and widely applicable. PMID:27085946

  19. A sensitive fluorescence anisotropy method for detection of lead (II) ion by a G-quadruplex-inducible DNA aptamer

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Dapeng [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085 (China); Yin, Lei; Meng, Zihui [School of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing, 100081 (China); Yu, Anchi [Department of Chemistry, Renmin University of China, Beijing, 100872 (China); Guo, Lianghong [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085 (China); Wang, Hailin, E-mail: hlwang@rcees.ac.cn [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085 (China)

    2014-02-17

    Graphical abstract: -- Highlights: •A fluorescence anisotropy approach for detection of Pb{sup 2+} was developed. •The strategy was based on binding-induced allosteric conformational change of aptamer probe. •The sensing mechanism was established by testing the photoinduced electron transfer interaction. -- Abstract: Sensitive and selective detection of Pb{sup 2+} is of great importance to both human health and environmental protection. Here we propose a novel fluorescence anisotropy (FA) approach for sensing Pb{sup 2+} in homogeneous solution by a G-rich thrombin binding aptamer (TBA). The TBA labeled with 6-carboxytetramethylrhodamine (TMR) at the seventh thymine nucleotide was used as a fluorescent probe for signaling Pb{sup 2+}. It was found that the aptamer probe had a high FA in the absence of Pb{sup 2+}. This is because the rotation of TMR is restricted by intramolecular interaction with the adjacent guanine bases, which results in photoinduced electron transfer (PET). When the aptamer probe binds to Pb{sup 2+} to form G-quadruplex, the intramolecular interaction should be eliminated, resulting in faster rotation of the fluorophore TMR in solution. Therefore, FA of aptamer probe is expected to decrease significantly upon binding to Pb{sup 2+}. Indeed, we observed a decrease in FA of aptamer probe upon Pb{sup 2+} binding. Circular dichroism, fluorescence spectra, and fluorescence lifetime measurement were used to verify the reliability and reasonability of the sensing mechanism. By monitoring the FA change of the aptamer probe, we were able to real-time detect binding between the TBA probe and Pb{sup 2+}. Moreover, the aptamer probe was exploited as a recognition element for quantification of Pb{sup 2+} in homogeneous solution. The change in FA showed a linear response to Pb{sup 2+} from 10 nM to 2.0 μM, with 1.0 nM limit of detection. In addition, this sensing system exhibited good selectivity for Pb{sup 2+} over other metal ions. The method is simple

  20. Exchange bias for ferromagnetic/antiferromagnetic bilayers with the uniaxial anisotropy being misaligned with the exchange anisotropy

    Institute of Scientific and Technical Information of China (English)

    BAI YuHao; YUN GuoHong

    2009-01-01

    Using the principle of minimal energy and S-W model, the exchange bias for ferromagnetic/antiferromagnetic bilayers has been investigated when the uniaxial anisotropy is misaligned with the exchange anisotropy. According to the relation between the energy of the bilayer and the orientation of ferromagnetic magnetization, it is found that the bilayer will be in the monostable state or bistable state when the external field is absent in the initial magnetization state. The monostable state or bistable state of the bilayer, which determines the angular dependence of exchange bias directly, is controlled by the competition between the exchange anisotropy and uniaxial anisotropy. When the applied field is parallel to the intrinsic easy axes and intrinsic hard axes, one of the switching fields of the hysteresis loop shows an abrupt change, while the other keep continuous by analyzing the magnetization reversal processes. Consequently, the exchange bias field and the coercivity will show a jump phenomenon.The numerical calculations indicate that both the magnitude and direction of the exchange anisotropy will significantly affect the angular dependence of exchange bias. The jump phenomenon of exchange bias is an intrinsic property of the bilayer, which is dependent on the interracial exchange-coupling constant, the orientation of the exchange anisotropy, the thickness and uniaxial anisotropy constant of the ferromagnetic layer.

  1. Exchange bias for ferromagnetic/antiferromagnetic bilayers with the uniaxial anisotropy being misaligned with the exchange anisotropy

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Using the principle of minimal energy and S-W model,the exchange bias for ferromagnetic/antiferro-magnetic bilayers has been investigated when the uniaxial anisotropy is misaligned with the exchange anisotropy. According to the relation between the energy of the bilayer and the orientation of ferro-magnetic magnetization,it is found that the bilayer will be in the monostable state or bistable state when the external field is absent in the initial magnetization state. The monostable state or bistable state of the bilayer,which determines the angular dependence of exchange bias directly,is controlled by the competition between the exchange anisotropy and uniaxial anisotropy. When the applied field is parallel to the intrinsic easy axes and intrinsic hard axes,one of the switching fields of the hysteresis loop shows an abrupt change,while the other keep continuous by analyzing the magnetization reversal processes. Consequently,the exchange bias field and the coercivity will show a jump phenomenon. The numerical calculations indicate that both the magnitude and direction of the exchange anisotropy will significantly affect the angular dependence of exchange bias. The jump phenomenon of exchange bias is an intrinsic property of the bilayer,which is dependent on the interfacial exchange-coupling constant,the orientation of the exchange anisotropy,the thickness and uniaxial anisotropy constant of the ferromagnetic layer.

  2. Taking the Measure of the Universe

    Science.gov (United States)

    Bennett, Charles L.; Hinshaw, Gary

    2003-01-01

    The first findings from a year of operations by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite provide the first detailed full sky picture of the afterglow of the Big Bang. The patterns in this picture encode a wealth of cosmological information, including the age of the universe, the epoch when the first stars formed, and the overall composition of normal matter, dark matter, and dark energy. The results have tantalizing implications for the period of inflationary expansion in the very first moments of time. These and other aspects of the mission will be discussed. The WMAP satellite was built in a close partnership between Princeton University and the Goddard Space Flight Center.

  3. Detecting candidate cosmic bubble collisions with optimal filters

    CERN Document Server

    McEwen, J D; Johnson, M C; Peiris, H V

    2012-01-01

    We review an optimal-filter-based algorithm for detecting candidate sources of unknown and differing size embedded in a stochastic background, and its application to detecting candidate cosmic bubble collision signatures in Wilkinson Microwave Anisotropy Probe (WMAP) 7-year observations. The algorithm provides an enhancement in sensitivity over previous methods by a factor of approximately two. Moreover, it is optimal in the sense that no other filter-based approach can provide a superior enhancement of these signatures. Applying this algorithm to WMAP 7-year observations, eight new candidate bubble collision signatures are detected for follow-up analysis.

  4. CMB anisotropies from a gradient mode

    Science.gov (United States)

    Mirbabayi, Mehrdad; Zaldarriaga, Matias

    2015-03-01

    A linear gradient mode must have no observable dynamical effect on short distance physics. We confirm this by showing that if there was such a gradient mode extending across the whole observable Universe, it would not cause any hemispherical asymmetry in the power of CMB anisotropies, as long as Maldacena's consistency condition is satisfied. To study the effect of the long wavelength mode on short wavelength modes, we generalize the existing second order Sachs-Wolfe formula in the squeezed limit to include a gradient in the long mode and to account for the change in the location of the last scattering surface induced by this mode. Next, we consider effects that are of second order in the long mode. A gradient mode Φ = qṡx generated in Single-field inflation is shown to induce an observable quadrupole moment. For instance, in a matter-dominated model it is equal to Q = 5(qṡx)2/18. This quadrupole can be canceled by superposition of a quadratic perturbation. The result is shown to be a nonlinear extension of Weinberg's adiabatic modes: a long-wavelength physical mode which looks locally like a coordinate transformation.

  5. Twinning anisotropy of tantalum during nanoindentation

    Energy Technology Data Exchange (ETDEWEB)

    Goel, Saurav, E-mail: S.GOEL@qub.ac.uk [School of Mechanical and Aerospace Engineering, Queen' s University, Belfast, BT9 5AH (United Kingdom); Beake, Ben [Micro Materials Limited, Willow House, Yale Business Village, Ellice Way, Wrexham LL13 7YL (United Kingdom); Dalton Research Institute, Manchester Metropolitan University, Manchester, M15GD (United Kingdom); Chan, Chi-Wai [School of Mechanical and Aerospace Engineering, Queen' s University, Belfast, BT9 5AH (United Kingdom); Haque Faisal, Nadimul [School of Engineering, Robert Gordon University, Garthdee Road, Aberdeen AB10 7GJ (United Kingdom); Dunne, Nicholas [School of Mechanical and Aerospace Engineering, Queen' s University, Belfast, BT9 5AH (United Kingdom)

    2015-03-11

    Unlike other BCC metals, the plastic deformation of nanocrystalline Tantalum (Ta) during compression is regulated by deformation twinning. Whether or not this twinning exhibits anisotropy was investigated through simulation of displacement-controlled nanoindentation test using molecular dynamics (MD) simulation. MD data was found to correlate well with the experimental data in terms of surface topography and hardness measurements. The mechanism of the transport of material was identified due to the formation and motion of prismatic dislocations loops (edge dislocations) belonging to the 1/2〈111〉 type and 〈100〉 type Burgers vector family. Further analysis of crystal defects using a fully automated dislocation extraction algorithm (DXA) illuminated formation and migration of twin boundaries on the (110) and (111) orientation but not on the (010) orientation and most importantly after retraction all the dislocations disappeared on the (110) orientation suggesting twinning to dominate dislocation nucleation in driving plasticity in tantalum. A significant finding was that the maximum shear stress (critical Tresca stress) in the deformation zone exceeded the theoretical shear strength of Ta (Shear modulus/2π~10.03 GPa) on the (010) orientation but was lower than it on the (110) and the (111) orientations. In light of this, the conventional lore of assuming the maximum shear stress being 0.465 times the mean contact pressure was found to break down at atomic scale.

  6. Studies of anisotropy of iron based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, Jason A. [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    To study the electronic anisotropy in iron based superconductors, the temperature dependent London penetration depth, Δλ(T), have been measured in several compounds, along with the angular dependent upper critical field, Hc2(T). Study was undertaken on single crystals of Ba(Fe1-xCox)2As2 with x=0.108 and x=0.127, in the overdoped range of the doping phase diagram, characterized by notable modulation of the superconducting gap. Heavy ion irradiation with matching field doses of 6 T and 6.5 T respectively, were used to create columnar defects and to study their effect on the temperature Δλ(T). The variation of the low-temperature penetration depth in both pristine and irradiated samples was fitted with a power-law function Δλ(T) = ATn. Irradiation increases the magnitude of the pre-factor A and decreases the exponent n, similar to the effect on the optimally doped samples. This finding supports the universal s ± scenario for the whole doping range.

  7. Surface-Charge Anisotropy of Scheelite Crystals.

    Science.gov (United States)

    Gao, Zhiyong; Hu, Yuehua; Sun, Wei; Drelich, Jaroslaw W

    2016-06-28

    Atomic force microscopy was employed to measure the colloidal interactions between silicon nitride cantilever tips and scheelite crystal surfaces in 1 mM KCl solutions of varying pH. By fitting the Derjguin-Landau-Verwey-Overbeek (DLVO) theoretical model to the recorded force-distance curves, the surface-charge density and surface-potential values were calculated for three crystallographic surfaces including {112}, {101}, and {001}. The calculated surface-potential values were negative in both acidic and basic solutions and varied among crystallographic surfaces. The determined surface-potential values were within zeta-potential values reported in the literature for powdered scheelite minerals. The surface {101} was the most negatively charged surface, followed by {112} and {001}. The surface potential for {001} was only slightly affected by pH, whereas the surface potential for both {112} and {101} increased with increasing pH. Anisotropy in surface-charge density was analyzed in relation to the surface density of active oxygen atoms, that is, the density of oxygen atoms with one or two broken bond(s) within tungstate ions located in the topmost surface layer. On a surface with a higher surface density of active oxygen atoms, a larger number of OH(-) are expected to adsorb through hydrogen bonding, leading to a more negatively charged surface. PMID:27269369

  8. Role of structural anisotropy of biological tissues in poroelastic wave propagation.

    Science.gov (United States)

    Cardoso, Luis; Cowin, Stephen C

    2012-01-01

    Ultrasound waves have a broad range of clinical applications as a non-destructive testing approach in imaging and in the diagnoses of medical conditions. Generally, biological tissues are modeled as an homogenized equivalent medium with an apparent density through which a single wave propagates. Only the first wave arriving at the ultrasound probe is used for the measurement of the speed of sound. However, the existence of a second wave in tissues such as cancellous bone has been reported and its existence is an unequivocal signature of Biot type poroelastic media. To account for the fact that ultrasound is sensitive to microarchitecture as well as density, a fabric-dependent anisotropic poroelastic ultrasound (PEU) propagation theory was recently developed. Key to this development was the inclusion of the fabric tensor - a quantitative stereological measure of the degree of structural anisotropy of bone - into the linear poroelasticity theory. In the present study, this framework is extended to the propagation of waves in several soft and hard tissues. It was found that collagen fibers in soft tissues and the mineralized matrix in hard tissues are responsible for the anisotropy of the solid tissue constituent through the fabric tensor in the model. PMID:22162897

  9. Strain-induced Fermi contour anisotropy of GaAs (311)A 2D holes

    Science.gov (United States)

    Shabani, Javad; Shayegan, Mansour; Winkler, Roland

    2008-03-01

    There is considerable current interest in electronic properties of two-dimensional (2D) carriers whose energy bands are spin-split at finite values of in-plane wave vector, thanks to the spin-orbit interaction and the lack of inversion symmetry. We report experimental and theoretical results revealing that the spin-subband Fermi contours of the heavy and light heavy-holes (HHh and HHl) can be tuned in high mobility GaAs (311)A 2D hole systems via the application of symmetry-breaking in-plane strain. Our calculations show that the HHl spin-subband Fermi contour is circular but the HHh spin-subband Fermi contour is distorted. Experimentally, we probe the Fermi contour anisotropy by measuring the magneto-resistance commensurability peaks induced by square arrays of antidots. When the spin splitting is sufficiently large, the magneto-resistance trace exhibits two peaks, providing clear evidence for spin-resolved ballistic transport. The experimental results are in good agreement with the calculations, and confirm that the majority spin-subband (HHh) has a severely distorted Fermi contour whose anisotropy can be tuned with strain while Fermi contour of the minority spin-subband (HHl) remains nearly isotropic.

  10. Is there evidence for anomalous dipole anisotropy in the large-scale structure?

    Science.gov (United States)

    Bengaly, C. A. P.; Bernui, A.; Alcaniz, J. S.; Xavier, H. S.; Novaes, C. P.

    2016-09-01

    We probe the anisotropy of the large-scale structure (LSS) with the WISE-2MASS catalogue. This analysis is performed by a directional comparison of the galaxy number counts through the entire celestial sphere once systematic effects, such as star-galaxy separation and foregrounds contamination, are properly taken into account. We find a maximal hemispherical asymmetry whose dipolar component is A = 0.0507 ± 0.0014 toward the (l, b) = (323°, -5°) direction, whose result is consistent with previous estimations of our proper motion in low and intermediate redshifts, as those carried out with Type Ia Supernovae and similar LSS catalogues. Furthermore, this dipole amplitude is statistically consistent (p-value = 0.061) with mock catalogues simulated according to the expected ΛCDM matter density fluctuations, in addition to observational biases such as the incomplete celestial coverage and anisotropic sky exposure. Our results suggest, therefore, that there is no strong evidence for anomalous anisotropy in the LSS, given the limitations and systematics of current data, in the concordance model scenario.

  11. Effects of electron temperature anisotropy on proton mirror instability evolution

    Science.gov (United States)

    Ahmadi, Narges; Germaschewski, Kai; Raeder, Joachim

    2016-06-01

    Proton mirror modes are large amplitude nonpropagating structures frequently observed in the magnetosheath. It has been suggested that electron temperature anisotropy can enhance the proton mirror instability growth rate while leaving the proton cyclotron instability largely unaffected, therefore causing the proton mirror instability to dominate the proton cyclotron instability in Earth's magnetosheath. Here we use particle-in-cell simulations to investigate the electron temperature anisotropy effects on proton mirror instability evolution. Contrary to the hypothesis, electron temperature anisotropy leads to excitement of the electron whistler instability. Our results show that the electron whistler instability grows much faster than the proton mirror instability and quickly consumes the electron-free energy so that there is no electron temperature anisotropy left to significantly impact the evolution of the proton mirror instability.

  12. Effects of electron temperature anisotropy on proton mirror instability evolution

    CERN Document Server

    Ahmadi, Narges; Raeder, Joachim

    2016-01-01

    Proton mirror modes are large amplitude nonpropagating structures frequently observed in the magnetosheath. It has been suggested that electron temperature anisotropy can enhance the proton mirror instability growth rate while leaving the proton cyclotron instability largely unaffected, therefore causing the proton mirror instability to dominate the proton cyclotron instability in Earth's magnetosheath. Here, we use particle-in-cell simulations to investigate the electron temperature anisotropy effects on proton mirror instability evolution. Contrary to the hypothesis, electron temperature anisotropy leads to excitement of the electron whistler instability. Our results show that the electron whistler instability grows much faster than the proton mirror instability and quickly consumes the electron free energy, so that there is no electron temperature anisotropy left to significantly impact the evolution of the proton mirror instability.

  13. Tuning Exchange Anisotropy of Exchange-Biased System

    Institute of Scientific and Technical Information of China (English)

    XU Yan; HU Jing-Guo; R.L.Stamps

    2008-01-01

    Exchange anisotropy in FM/AFM bilayers has given a lot of static magnetization properties such as enhanced coercivity and magnetization loop shifts.These phenomena are primarily from the effective anisotropies intro-duced into a ferromagnet by exchange coupling with a strongly anisotropic antiferromagnet.These effective anisotropies can also be used to explain the dynamic consequences of exchange-biased bilayers.In this article,the dynamic con-sequences such as exchange-induced susceptibility,exchange-induced permeability,and the corresponding domain wall characteristics in the exchange-biased structures of ferromagnet/antiferromagnetl/antiferromagnet2 are studied.The results show that the second antiferromagnetic layer can largely affect the dynamic consequences of exchange-biased bilayers.Especially in the ease of critical temperature,the effects become more obvious.Practically,the exchange anisotropy of biased bilayer system can be tuned by exchange coupling with the second antiferromagnetic layer.

  14. Axisymmetric equilibria with pressure anisotropy and plasma flow

    CERN Document Server

    Evangelias, Achilleas

    2016-01-01

    In this Master thesis we investigate the influence of pressure anisotropy and incompressible flow of arbitrary direction on the equilibrium properties of magnetically confined, axisymmetric toroidal plasmas. The main novel contribution is the derivation of a pertinent generalised Grad-Shafranov equation. This equation includes six free surface functions and recovers known Grad-Shafranov-like equations in the literature as well as the usual static, isotropic one. The form of the generalised equation indicates that pressure anisotropy and flow act additively on equilibrium. In addition, two sets of analytical solutions, an extended Solovev one with a plasma reaching the separatrix and an extended Hernegger-Maschke one for a plasma surrounded by a fixed boundary possessing an X-point, are constructed, particularly in relevance to the ITER and NSTX tokamaks. Furthermore, the impacts both of pressure anisotropy, through an anisotropy function assumed to be uniform on the magnetic surfaces, and plasma flow, via the...

  15. Issues on generating primordial anisotropies at the end of inflation

    International Nuclear Information System (INIS)

    We revisit the idea of generating primordial anisotropies at the end of inflation in models of inflation with gauge fields. To be specific we consider the charged hybrid inflation model where the waterfall field is charged under a U(1) gauge field so the surface of end of inflation is controlled both by inflaton and the gauge fields. Using δN formalism properly we find that the anisotropies generated at the end of inflation from the gauge field fluctuations are exponentially suppressed on cosmological scales. This is because the gauge field evolves exponentially during inflation while in order to generate appreciable anisotropies at the end of inflation the spectator gauge field has to be frozen. We argue that this is a generic feature, that is, one can not generate observable anisotropies at the end of inflation within an FRW background

  16. Microstructure, Slip Systems and Yield Stress Anisotropy in Plastic Deformation

    DEFF Research Database (Denmark)

    Winther, Grethe; You, Ze Sheng; Lu, Lei

    The highly anisotropic microstructures in nanotwinned copper produced by electrodeposition provide an excellent opportunity to evaluate models for microstructurally induced mechanical anisotropy. A crystal plasticity model originally developed for the integration of deformation induced dislocation...

  17. Polarimetric investigation of materials with both linear and circular anisotropy

    DEFF Research Database (Denmark)

    Naydenova, I.; Nikolova, L.; Todorov, T.;

    1997-01-01

    We investigate light propagation through materials with both linear and circular anisotropy and find the relation of the amplitude and polarization transfer functions to the four anisotropic characteristics: linear circular birefringence, and linear and circular dichroism. We determine these four...

  18. A solution to the cosmic ray anisotropy problem

    Science.gov (United States)

    Mertsch, P.; Funk, S.

    2015-10-01

    Observations of the cosmic ray (CR) anisotropy are widely advertised as a means of finding nearby sources. This idea has recently gained currency after the discovery of a rise in the positron fraction and is the goal of current experimental efforts, e.g., with AMS-02 on the International Space Station. Yet, even the anisotropy observed for hadronic CRs is not understood, in the sense that isotropic diffusion models overpredict the dipole anisotropy in the TeV-PeV range by almost two orders of magnitude. Here, we consider two additional effects normally not considered in isotropic diffusion models: anisotropic diffusion due to the presence of a background magnetic field and intermittency effects of the turbulent magnetic fields. We numerically explore these effect by tracking test-particles through individual realisations of the turbulent field. We conclude that a large misalignment between the CR gradient and the background field can explain the observed low level of anisotropy.

  19. Axisymmetric equilibria with pressure anisotropy and plasma flow

    CERN Document Server

    Evangelias, A

    2016-01-01

    A generalised Grad-Shafranov equation that governs the equilibrium of an axisymmetric toroidal plasma with anisotropic pressure and incompressible flow of arbitrary direction is derived. This equation includes six free surface functions and recovers known Grad-Shafranov-like equations in the literature as well as the usual static, isotropic one. The form of the generalised equation indicates that pressure anisotropy and flow act additively on equilibrium. In addition, two sets of analytical solutions, an extended Solovev one with a plasma reaching the separatrix and an extended Hernegger-Maschke one for a plasma surrounded by a fixed boundary possessing an X-point, are constructed, particularly in relevance to the ITER and NSTX tokamaks. Furthermore, the impacts both of pressure anisotropy and plasma flow on these equilibria are examined. It turns out that depending on the maximum value and the shape of an anisotropy function, the anisotropy can act either paramagnetically or diamagnetically. Also, in most of...

  20. Electric Field Induced Magnetic Anisotropy in a Ferromagnet

    Energy Technology Data Exchange (ETDEWEB)

    Gamble, S. J.

    2010-02-24

    We report the first observation of a transient all electric field induced magnetic anisotropy in a thin film metallic ferromagnet. We generate the anisotropy with a strong (-10{sup 9} V/m) and short (70 fs) {rvec E}-field pulse. This field is large enough to distort the valence charge distribution in the metal, yet its duration is too brief to change the atomic positions. This pure electronic structure alteration of the sample generates a new type of transient anisotropy axis and strongly influences the magnetization dynamics. The successful creation of such an anisotropy opens the possibility for all {rvec E}-field induced magnetization reversal in thin metallic films - a greatly desired yet unachieved process.

  1. Limits on the ions temperature anisotropy in turbulent intracluster medium

    CERN Document Server

    Santo-Lima, R; Pino, E M de Gouveia Dal; Lazarian, A

    2016-01-01

    Turbulence in the weakly collisional intracluster medium of galaxies (ICM) is able to generate strong thermal velocity anisotropies in the ions (with respect to the local magnetic field direction), if the magnetic moment of the particles is conserved in the absence of Coulomb collisions. In this scenario, the anisotropic MHD turbulence shows a very different statistical behaviour from the isotropic (standard) one and is unable to amplify seed magnetic fields, in disagreement with previous cosmological MHD simulations which are able to explain the observed magnetic fields in the ICM. On the other hand, temperature anisotropy can also drive kinetic instabilities which grow faster near the ions kinetic scales. Observations from the solar wind suggest that these micro- instabilities scatter the ions, thus relaxing the anisotropy. This work aims to compare this relaxation rate with the growth rate of the anisotropies driven by the turbulence. We employ quasilinear theory to estimate the scattering rate provided by...

  2. Low-temperature magnetic anisotropy in micas and chlorite

    DEFF Research Database (Denmark)

    Biedermann, Andrea R.; Bender Koch, Christian; Lorenz, Wolfram E A;

    2014-01-01

    of magnetic susceptibility. Because diamagnetic and paramagnetic susceptibility are both linearly dependent on field, separation of the anisotropic contributions requires understanding how the degree of anisotropy of the paramagnetic susceptibility changes as a function of temperature. Note that diamagnetic...... of approximately 6.3-8.7 for individual samples of muscovite, phlogopite and chlorite on cooling from RT to 77 K and between 11.2 and 12.4 for biotite. A decrease in temperature enhances the paramagnetic anisotropy in a mineral. Biotite exhibits a relatively stronger enhancement due to the onset of magnetic......Phyllosilicates, such as micas and chlorite, are common rock-forming minerals and often show preferred orientation in deformed rocks. In combination with single-crystal anisotropy, this leads to anisotropy of physical properties in the rock, such as magnetic susceptibility. In order to effectively...

  3. Primordial Statistical Anisotropies: The Effective Field Theory Approach

    CERN Document Server

    Abolhasani, Ali Akbar; Emami, Razieh; Firouzjahi, Hassan

    2015-01-01

    In this work we present the effective field theory of primordial statistical anisotropies generated during anisotropic inflation involving a background $U(1)$ gauge field. Besides the usual Goldstone boson associated with the breaking of time diffeomorphism we have two additional Goldstone bosons associated with the breaking of spatial diffeomorphisms. We further identify these two new Goldstone bosons with the expected two transverse degrees of the $U(1)$ gauge field fluctuations. Upon defining the appropriate unitary gauge, we present the most general quadratic action which respects the remnant symmetry in the unitary gauge. The interactions between various Goldstone bosons leads to statistical anisotropy in curvature perturbation power spectrum. Calculating the general results for power spectrum anisotropy, we recover the previously known results in specific models of anisotropic inflation. In addition, we present novel results for statistical anisotropy in models with non-trivial sound speed for inflaton ...

  4. ORIGIN OF COBALT ANISOTROPY IN RARE EARTH-COBALT INTERMETALLICS

    OpenAIRE

    Ballou, Rafik; Lemaire, R.

    1988-01-01

    The strong cobalt anisotropies in rare earth-cobalt intermetallics are shown to arise from orbitally selective 3d band energy dispersion due to either chain like or layered like cobalt staking rather than from usual crystal field effect.

  5. TeV Cosmic-Ray Anisotropy from the Magnetic Field at the Heliospheric Boundary

    CERN Document Server

    López-Barquero, Vanessa; Desiati, P; Lazarian, A; Pogorelov, N V; Yan, H

    2016-01-01

    We performed numerical calculations to test the suggestion by Desiati & Lazarian (2013) that the anisotropies of TeV cosmic rays may arise from their interactions with the heliosphere. For this purpose, we used a magnetic field model of the heliosphere and performed direct numerical calculations of particle trajectories. Unlike earlier papers testing the idea, we did not employ time-reversible techniques that are based on Liouville's theorem. We showed numerically that for scattering by the heliosphere the conditions of Liouville's theorem are not satisfied and the adiabatic approximation and time-reversibility of the particle trajectories are not valid. Our results indicate sensitivity to the magnetic structure of the heliospheric magnetic field, and we expect that this will be useful for probing this structure in future research.

  6. Recovering hidden signals of statistical anisotropy from a masked or partial CMB sky

    CERN Document Server

    Aluri, Pavan K; Rotti, Aditya; Souradeep, Tarun

    2015-01-01

    Any isotropy violating phenomena on cosmic microwave background (CMB) induces off-diagonal correlations in the two-point function. These correlations themselves can be used to estimate the underlying anisotropic signals. Masking due to residual foregrounds, or availability of partial sky due to survey limitation, are unavoidable circumstances in CMB studies. But, masking induces additional correlations, and thus complicates the recovery of such signals. In this work, we discuss a procedure based on bipolar spherical harmonic (BipoSH) formalism to comprehensively addresses any spurious correlations induced by masking and successfully recover hidden signals of anisotropy in observed CMB maps. This method is generic, and can be applied to recover a variety of isotropy violating phenomena. Here, we illustrate the procedure by recovering the subtle Doppler boost signal from simulated boosted CMB skies, which has become possible with the unprecedented full-sky sensitivity of PLANCK probe.

  7. Time delay anisotropy in photoelectron emission from the isotropic ground state of helium

    CERN Document Server

    Heuser, Sebastian; Cirelli, Claudio; Sabbar, Mazyar; Boge, Robert; Lucchini, Matteo; Gallmann, Lukas; Ivanov, Igor; Kheifets, Anatoli S; Dahlström, J Marcus; Lindroth, Eva; Argenti, Luca; Martín, Fernando; Keller, Ursula

    2015-01-01

    Time delays of electrons emitted from an isotropic initial state and leaving behind an isotropic ion are assumed to be angle-independent. Using an interferometric method involving XUV attosecond pulse trains and an IR probe field in combination with a detection scheme, which allows for full 3D momentum resolution, we show that time delays between electrons liberated from the $1s^{2}$ spherically symmetric ground state of He depend on the emission direction of the electrons with respect to the linear polarization axis of the ionizing XUV light. Such time delays can exhibit values as large as 60 attoseconds. With the help of refined theoretical models we can attribute the observed anisotropy to the interplay between different final quantum states, which arise naturally when two photons are involved in the photoionization process. Since most measurement techniques tracing attosecond electron dynamics have involved at least two photons so far, this is a general, significant, and initially unexpected effect that m...

  8. Influence of interface exchange coupling in perpendicular anisotropy [Pt/Co]50/TbFe bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Mangin, S.; Hauet, T.; Fischer, P.; Kim, D.H.; Kortright, J.B.; Chesnel, K.; Arenholz, E.; Fullerton, Eric E.

    2007-10-10

    We present the magnetization evolution of perpendicular anisotropy TbFe and [Co/Pt]{sub 50} thin films either in direct contact resulting in antiferromagnetic interfacial coupling or separated by a thick Pt layer. Magnetometry and x-ray magnetic circular dichroism spectroscopy determine the spatially averaged magnetic properties. Resonant magnetic x-ray small-angle scattering and magnetic soft X-ray transmission microscopy probed the domain configurations and correlations in the reversal processes. While the Co/Pt multilayer reverses by domain propagation, the TbFe magnetization reversal is found to be dominated either by coherent magnetization reversal processes or by lateral domain formation depending on the interface exchange coupling. In the presence of lateral domains, dipolar field induced domain replication phenomena are observed.

  9. Anisotropies of the lower and upper critical fields in MgB2 single crystals.

    Science.gov (United States)

    Lyard, L; Szabó, P; Klein, T; Marcus, J; Marcenat, C; Kim, K H; Kang, B W; Lee, H S; Lee, S I

    2004-02-01

    The temperature dependence of the upper (H(c2)) and lower (H(c1)) critical fields has been deduced from Hall probe magnetization measurements of high quality MgB2 single crystals along the two main crystallographic directions. We show that Gamma(H(c2))=H(c2 axially ab)/H(c2 axially c) and Gamma(H(c1))=H(c1 axially c)/H(c1 axially ab) differ significantly at low temperature (being approximately 5 and approximately 1, respectively) and have opposite temperature dependencies. We suggest that MgB2 can be described by a single field dependent anisotropy parameter gamma(H) (=lambda(c)/lambda(ab)=xi(ab)/xi(c)) that increases from Gamma(H(c1)) at low field to Gamma(H(c2)) at high field.

  10. Anisotropy signature in extended images from reverse-time migration

    KAUST Repository

    Sava, Paul

    2012-11-04

    Reverse-time migration can accurately image complex geologic structures in anisotropic media. Extended images at selected locations in the earth, i.e. at common-image-point gathers (CIPs), carry enough information to characterize the angle-dependent illumination and to provide measurements for migration velocity analysis. Furthermore, inaccurate anisotropy leaves a distinctive signature in CIPs, which can be used to evaluate anisotropy through techniques similar to the ones used in conventional wavefield tomography.

  11. Effective anisotropy gradient in pressure graded [Co/Pd] multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Kirby, B. J., E-mail: bkirby@nist.gov; Maranville, B. B. [Center for Neutron Research, NIST, Gaithersburg, Maryland 20899 (United States); Greene, P. K.; Liu, Kai [Physics Department, University of California, Davis, California 95616 (United States); Davies, J. E. [Advanced Technology Group, NVE Corporation, Eden Prarie, Minneapolis 55344 (United States)

    2015-02-14

    We have used polarized neutron reflectometry to show that controlled variation of growth pressure during deposition of Co/Pd multilayers can be used to achieve a significant vertical gradient in the effective anisotropy. This gradient is strongly dependent on deposition order (low to high pressure or vice versa), and is accompanied by a corresponding gradient in saturation magnetization. These results demonstrate pressure-grading as an attractively simple technique for tailoring the anisotropy profile of magnetic media.

  12. Anisotropies in the HI gas distribution toward 3C 196

    Science.gov (United States)

    Kalberla, P. M. W.; Kerp, J.

    2016-10-01

    Context. The local Galactic Hi gas was found to contain cold neutral medium (CNM) filaments that are aligned with polarized dust emission. These filaments appear to be dominated by the magnetic field and in this case turbulence is expected to show distinct anisotropies. Aims: We use the Galactic Effelsberg-Bonn Hi Survey (EBHIS) to derive 2D turbulence spectra for the Hi distribution in direction to 3C 196 and two more comparison fields. Methods: Prior to Fourier transform we apply a rotational symmetric 50% Tukey window to apodize the data. We derive average as well as position angle dependent power spectra. Anisotropies in the power distribution are defined as the ratio of the spectral power in orthogonal directions. Results: We find strong anisotropies. For a narrow range in position angle, in direction perpendicular to the filaments and the magnetic field, the spectral power is on average more than an order of magnitude larger than parallel. In the most extreme case the anisotropy reaches locally a factor of 130. Anisotropies increase on average with spatial frequency as predicted by Goldreich & Sridhar (1995, ApJ, 438, 763), at the same time the Kolmogorov spectral index remains almost unchanged. The strongest anisotropies are observable for a narrow range in velocity and decay with a power law index close to -8/3, almost identical to the average isotropic spectral index of -2.9 Hi filaments, associated with linear polarization structures in LOFAR observations in direction to 3C 196, show turbulence spectra with marked anisotropies. Decaying anisotropies appear to indicate that we witness an ongoing shock passing the Hi and affecting the observed Faraday depth.

  13. Magnetic anisotropies of late transition metal atomic clusters

    OpenAIRE

    Fernández-Seivane, Lucas; Ferrer, Jaime

    2006-01-01

    We analyze the impact of the magnetic anisotropy on the geometric structure and magnetic ordering of small atomic clusters of palladium, iridium, platinum and gold, using Density Functional Theory. Our results highlight the absolute need to include self-consistently the spin orbit interaction in any simulation of the magnetic properties of small atomic clusters, and a complete lack of universality in the magnetic anisotropy of small-sized atomic clusters.

  14. In-plane anisotropy of 1545 aluminum alloy sheet

    Institute of Scientific and Technical Information of China (English)

    PENG Yong-yi; YIN Zhi-min; YANG Jin; DU Yu-xuan

    2005-01-01

    The microstructures and the tensile mechanical properties in the rolling plane of 1545 aluminum alloy sheet at different orientations with respect to the rolling direction were studied by means of tensile test,X-ray diffractometer(XRD),optical microscope and transmission electron microscope.The in-plane anisotropy of tensile mechanical properties was calculated and the inverse pole figures of the rolling plane,transversal section and longitudinal section were obtained by Harris method.The results show that the 1545 Al alloy sheet has remarkable in-plane anisotropy of mechanical properties and the main texture component is{110}texture.On the basis of the model that regards the sheet containing only{110}texture as a monocrystal,the relationship of in-plane anisotropy and the anisotropy of crystallography was analyzed.The study shows that it is the combined effects of the anisotropy of crystallography and microstructures that cause the in-plane anisotropy of mechanical properties,but the main cause is the crystallographic texture.

  15. Anisotropy of eddy variability in the global ocean

    Science.gov (United States)

    Stewart, K. D.; Spence, P.; Waterman, S.; Sommer, J. Le; Molines, J.-M.; Lilly, J. M.; England, M. H.

    2015-11-01

    The anisotropy of eddy variability in the global ocean is examined in geostrophic surface velocities derived from satellite observations and in the horizontal velocities of a 1/12° global ocean model. Eddy anisotropy is of oceanographic interest as it is through anisotropic velocity fluctuations that the eddy and mean-flow fields interact dynamically. This study is timely because improved observational estimates of eddy anisotropy will soon be available with Surface Water and Ocean Topography (SWOT) altimetry data. We find there to be good agreement between the characteristics and distributions of eddy anisotropy from the present satellite observations and model ocean surface. In the model, eddy anisotropy is found to have significant vertical structure and is largest close to the ocean bottom, where the anisotropy aligns with the underlying isobaths. The highly anisotropic bottom signal is almost entirely contained in the barotropic variability. Upper-ocean variability is predominantly baroclinic and the alignment is less sensitive to the underlying bathymetry. These findings offer guidance for introducing a parameterization of eddy feedbacks, based on the eddy kinetic energy and underlying bathymetry, to operate on the barotropic flow and better account for the effects of barotropic Reynolds stresses unresolved in coarse-resolution ocean models.

  16. Slow shock formation and temperature anisotropy in collisionless magnetic reconnection

    Science.gov (United States)

    Higashimori, K.; Hoshino, M.

    2011-12-01

    We perform a two-dimensional simulation by using an electromagnetic hybrid code to study the formation of slow-mode shocks in collisionless magnetic reconnection in low beta plasmas, and we argue that one of important agents of the formation of slow shocks is the ion temperature anisotropy enhanced at the shock downstream region. As magnetic reconnection develops, it is known that the parallel temperature along the magnetic field becomes large in association with the anisotropic PSBL ion beams, and this temperature anisotropy has a tendency to suppress the formation of slow shock. Although preceding studies on magnetic reconnection with kinetic codes have shown such ion temperature anisotropy along the reconnection layer, the direct relation between formation of slow shocks and the ion temperature anisotropy has not been investigated. Based on our simulation result, we found that the slow shock formation is suppressed due to the large temperature anisotropy near the X-type region, but the downstream ion temperature anisotropy relaxes with increasing the distance from the magnetic neutral point. As a result, two pairs of current structures, which are the strong evidence of dissipation of magnetic field in slow shocks, are formed at the distance |x| > 115 λ i from the neutral point.

  17. Physical modelling of elastic anisotropy in porous media

    Energy Technology Data Exchange (ETDEWEB)

    Furre, Anne-Kari

    1997-12-31

    During the last decades, anisotropy has become increasingly interesting in hydrocarbon prospecting. Knowledge of anisotropy in the subsurface can improve reservoir production and data interpretation. This thesis presents experimental studies of three different artificial anisotropic media: layered materials, isotropic matrix with stress-induced fractures, and layered media with controlled crack patterns at an oblique angle relative to layering. Layered media were constructed by varying grain size distributions for different layers, which resulted in acoustic and permeability anisotropy. The thin layer materials could be described by Backus modelling provided the wavelength was much larger than the layer periods. Frequency dependent scattering was observed for waves travelling normal to the layers. Saturated wave velocities were consistent with transverse isotropic Biot theory, but because the permeability anisotropy was small, no flow dependent attenuation anisotropy was observed. When sandstones were cemented under stress and then released, to simulate a vertical core or uplift process, predominantly horizontal cracks developed in the samples. On reloading to the cementing stress level, the velocities were below the initial values, which supports the theories of crack growth. In further triaxial tests on the same material a stress-dependent anisotropy occurred similar to what is often seen in natural samples taken from large depths. 70 refs., 200 figs., 56 tabs.

  18. Magnetic anisotropies of (Ga,Mn)As films and nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Frank

    2011-02-02

    In this work the magnetic anisotropies of the diluted magnetic semiconductor (Ga,Mn)As were investigated experimentally. (Ga,Mn)As films show a superposition of various magnetic anisotropies which depend sensitively on various parameters such as temperature, carrier concentration or lattice strain. However, the anisotropies of lithographically prepared (Ga,Mn)As elements differ significantly from an unpatterned (Ga,Mn)As film. In stripe-shaped structures this behaviour is caused by anisotropic relaxation of the compressive lattice strain. In order to determine the magnetic anisotropies of individual (Ga,Mn)As nanostructures a combination of ferromagnetic resonance and time-resolved scanning Kerr microscopy was employed in this thesis. In addition, local changes of the magnetic anisotropy in circular and rectangular structures were visualized by making use of spatially resolved measurements. Finally, also the influence of the laterally inhomogeneous magnetic anisotropies on the static magnetic properties, such as coercive fields, was investigated employing spatially resolved static MOKE measurements on individual (Ga,Mn)As elements. (orig.)

  19. Colossal anisotropy of the magnetic properties of doped lithium nitrodometalates

    Energy Technology Data Exchange (ETDEWEB)

    Antropov, Vladimir P [Ames Laboratory; Antonov, Victor N [Ames Laboratory

    2014-09-01

    We present a first-principles investigation of the electronic structure and physical properties of doped lithium nitridometalates Li2(Li1-xMx)N (LiMN) with M = Cr, Mn, Fe, Co, and Ni. The diverse properties include the equilibrium magnetic moments, magneto-crystalline anisotropy, magneto-optical Kerr spectra, and x-ray magnetic circular dichroism. We explain the colossal magnetic anisotropy in LiFeN by its unique electronic structure which ultimately leads to a series of unusual physical properties. The most unique property is a complete suppression of relativistic effects and freezing of orbital moments for in-plane orientation of the magnetization. This leads to the colossal spatial anisotropy of many magnetic properties including energy, Kerr, and dichroism effects. LiFeN is identified as an ultimate single-ion anisotropy system where a nearly insulating state can be produced by a spin orbital coupling alone. A very nontrivial strongly fluctuating and sign changing character of the magnetic anisotropy with electronic 3d-atomic doping is predicted theoretically. A large and highly anisotropic Kerr effect due to the interband transitions between atomic-like Fe 3d bands is found for LiFeN. A giant anisotropy of the x-ray magnetic circular dichroism for the Fe K spectrum and a very weak one for the Fe L2,3 spectra in LiFeN are also predicted.

  20. Characterization of optical anisotropy in quantum wells under compressive anisotropic in-plane strain

    Science.gov (United States)

    Biermann, Mark L.; Walters, Matthew; Diaz-Barriga, James; Rabinovich, W. S.

    2003-10-01

    Anisotropic in-plane strain in quantum wells leads to an optical polarization anisotropy that can be exploited for device applications. We have determined that for many anisotropic compressive strain cases, the dependence of the optical anisotropy is linear in the strain anisotropy. This result holds for a variety of well and barrier materials and widths and for various overall strain conditions. Further, the polarization anisotropy per strain anisotropy varies as the reciprocal of the energy separation of the relevant hole sub-bands. Hence, a general result for the polarization anisotropy per strain anisotropy is avialable for cases of compressive anisotropic in-plane strain.

  1. Characterization of optical anisotropy in quantum wells under compressive anisotropic in-plane strain

    Energy Technology Data Exchange (ETDEWEB)

    Biermann, Mark L [Physics Department, 566 Brownson Rd., U.S. Naval Academy, Annapolis, MD 21402 (United States); Walters, Matthew [Physics Department, 566 Brownson Rd., U.S. Naval Academy, Annapolis, MD 21402 (United States); Diaz-Barriga, James [Physics Department, 566 Brownson Rd., U.S. Naval Academy, Annapolis, MD 21402 (United States); Rabinovich, W S [Naval Research Laboratory, Code 5652, 4555 Overlook Ave. SW, Washington, DC 20375-5320 (United States)

    2003-10-21

    Anisotropic in-plane strain in quantum wells leads to an optical polarization anisotropy that can be exploited for device applications. We have determined that for many anisotropic compressive strain cases, the dependence of the optical anisotropy is linear in the strain anisotropy. This result holds for a variety of well and barrier materials and widths and for various overall strain conditions. Further, the polarization anisotropy per strain anisotropy varies as the reciprocal of the energy separation of the relevant hole sub-bands. Hence, a general result for the polarization anisotropy per strain anisotropy is available for cases of compressive anisotropic in-plane strain.

  2. Can modified gravity models reconcile the tension between CMB anisotropy and lensing maps in Planck-like observations?

    CERN Document Server

    Hu, Bin

    2015-01-01

    Planck-2015 data seem to favour a large value of the lensing amplitude parameter, $A_{\\rm L}=1.22\\pm0.10$, in CMB spectra. This result is in $2\\sigma$ tension with the lensing reconstruction result, $A_{\\rm L}^{\\phi\\phi}=0.95\\pm0.04$. In this paper, we simulate several CMB anisotropy and CMB lensing spectra based on Planck-2015 best-fit cosmological parameter values and Planck blue book beam and noise specifications. We analyse several modified gravity models within the effective field theory framework against these simulations and find that models whose effective Newton constant is enhanced can modulate the CMB anisotropy spectra in a way similar to that of the $A_{\\rm L}$ parameter. However, in order to lens the CMB anisotropies sufficiently, like in the Planck-2015 results, the growth of matter perturbations is substantially enhanced and gives a high $\\sigma_8$ value. This in turn proves to be problematic when combining these data to other probes, like weak lensing from CFHTLenS, that favour a smaller ampl...

  3. Global inversion for anisotropy during full-waveform inversion

    Science.gov (United States)

    Debens, H. A.; Warner, M.; Umpleby, A.

    2015-12-01

    Full-waveform inversion (FWI) is a powerful tool for quantitative estimation of high-resolution high-fidelity models of subsurface seismic parameters, typically P-wave velocity. The solution to FWI's posed nonlinear inverse problem is obtained via an iterative series of linearized local updates to a start model, assuming this model lies within the basin of attraction to the global minimum. Thanks to many successful published applications to three-dimensional (3D) field datasets, its advance has been rapid and driven in large-part by the oil and gas industry. The consideration of seismic anisotropy during FWI is of vital importance, as it holds influence over both the kinematics and dynamics of seismic waveforms. If not appropriately taken into account then inadequacies in the anisotropy model are likely to manifest as significant error in the recovered velocity model. Conventionally, anisotropic FWI employs either an a priori anisotropy model, held fixed during FWI, or it uses a multi-parameter local inversion scheme to recover the anisotropy as part of the FWI; both of these methods can be problematic. Constructing an anisotropy model prior to FWI often involves intensive (and hence expensive) iterative procedures, such as travel-time tomography or moveout velocity analysis. On the other hand, introducing multiple parameters to FWI itself increases the complexity of what is already an underdetermined inverse problem. We propose that global rather than local FWI can be used to recover the long-wavelength acoustic anisotropy model, and that this can then be followed by more-conventional local FWI to recover the detailed model. We validate this approach using a full 3D field dataset, demonstrating that it avoids problems associated to crosstalk that can bedevil local inversion schemes, and reconciles well with in situ borehole measurements. Although our approach includes a global inversion for anisotropy, it is nonetheless affordable and practical for 3D field data.

  4. Equatorial anisotropy of the Earth's inner-inner core

    Science.gov (United States)

    Song, X.; Wang, T.; Xia, H.

    2015-12-01

    Anisotropy of Earth's inner core is a key to understand its evolution and the generation of the Earth's magnetic field. All the previous inner core anisotropy models have assumed a cylindrical anisotropy with the symmetry axis parallel (or nearly parallel) to the Earth's spin axis. However, we have recently found that the fast axis in the inner part of the inner core is close to the equator from inner-core waves extracted from earthquake coda. We obtained inner core phases, PKIIKP2 and PKIKP2 (round-trip phases between the station and its antipode that passes straight through the center of the Earth and that is reflected from the inner core boundary, respectively), from stackings of autocorrelations of the coda of large earthquakes (10,000~40,000 s after Mw>=7.0 earthquakes) at seismic station clusters around the world. We observed large variation of up to 10 s along equatorial paths in the differential travel times PKIIKP2 - PKIKP2, which are sensitive to inner-core structure. The observations can be explained by a cylindrical anisotropy in the inner inner core (IIC) (with a radius of slightly less than half the inner core radius) that has a fast axis aligned near the equator and a cylindrical anisotropy in the outer inner core (OIC) that has a fast axis along the north-south direction. We have obtained more observations using the combination of autocorrelations and cross-correlations at low-latitude station arrays. The results further confirm that the IIC has an equatorial anisotropy and a pattern different from the OIC. The equatorial fast axis of the IIC is near the Central America and the Southeast Asia. The drastic change in the fast axis and the form of anisotropy from the IIC to the OIC may suggest a phase change of the iron or a major shift in the crystallization and deformation during the formation and growth of the inner core.

  5. Laser-induced nuclear orientation and gamma anisotropy in sodium

    International Nuclear Information System (INIS)

    The use of laser optical pumping to induce nuclear orientation in several isotopes and one isomer of atomic sodium vapor is described. Essentially complete nuclear polarization, P > 90%, has been achieved in stable 23Na when pumping with modest laser intensities (I approx. = 10 mW/cm2). The volume of the sample cell was approximately 10 cc, and was filled with a sodium density of about 10'' atoms/cc. Complete coverage of the Doppler distribution was accomplished with the use of trace amounts (less than or equal to 1 torr) of argon buffer gas to induce velocity changing collisions. A theoretical model which accurately predicts the amount of polarization is developed. The orientation of nuclei which are unstable to gamma decay can manifest itself in anisotropic gamma ray emission. This anisotropy can be used to measure isotope and isomer shifts, from which nuclear properties can be derived. Gamma anisotropy was observed in two systems, 22Na and /sup 24m/Na. From the observed anisotropy in /sup 24m/Na, a negative sign for the g factor is determined. Values are derived for the magnetic moment, μ = 2.56 +- 0.64 nm, and the isomer shift, deltaν/sub 24m/ = 288 +- 191 MHz (D1 line). A model is described which relates various laser and fubber gas parameters to the observed gamma anisotropy lineshape. This model facilitates the extraction of physical parameters from knowledge of the laser frequency at which the anisotropy is a maximum

  6. Performance of ERNE in particle flux anisotropy measurement

    Directory of Open Access Journals (Sweden)

    E. Riihonen

    Full Text Available The HED particle detector of the ERNE experiment to be flown on the SOHO spacecraft is unique compared to the earlier space-born detectors in its high directional resolution (better than 2°, depending on the track inclination. Despite the fixed view cone due to the three-axis stabilization of the spacecraft, the good angular and temporal resolution of the detector provides a new kind of opportunity for monitoring in detail the development of the anisotropies pertaining, for example, to the onset of SEP events, or passage of shock fronts related to gradual events. In order to optimize the measurement parameters, we have made a preflight simulation study of the HED anisotropy measurement capabilities. The purpose was to prove the feasibility of the selected measurement method and find the physical limits for the HED anisotropy detection. The results show HED to be capable of detecting both strong anisotropies related to impulsive events, and smoother anisotropies associated with gradual events.

  7. Scaling of coercivity in a 3d random anisotropy model

    International Nuclear Information System (INIS)

    The random-anisotropy Heisenberg model is numerically studied on lattices containing over ten million spins. The study is focused on hysteresis and metastability due to topological defects, and is relevant to magnetic properties of amorphous and sintered magnets. We are interested in the limit when ferromagnetic correlations extend beyond the size of the grain inside which the magnetic anisotropy axes are correlated. In that limit the coercive field computed numerically roughly scales as the fourth power of the random anisotropy strength and as the sixth power of the grain size. Theoretical arguments are presented that provide an explanation of numerical results. Our findings should be helpful for designing amorphous and nanosintered materials with desired magnetic properties. - Highlights: • We study the random-anisotropy model on lattices containing up to ten million spins. • Irreversible behavior due to topological defects (hedgehogs) is elucidated. • Hysteresis loop area scales as the fourth power of the random anisotropy strength. • In nanosintered magnets the coercivity scales as the six power of the grain size

  8. Axisymmetric equilibria with pressure anisotropy and plasma flow

    Science.gov (United States)

    Evangelias, A.; Throumoulopoulos, G. N.

    2016-04-01

    A generalised Grad-Shafranov equation that governs the equilibrium of an axisymmetric toroidal plasma with anisotropic pressure and incompressible flow of arbitrary direction is derived. This equation includes six free surface functions and recovers known Grad-Shafranov-like equations in the literature as well as the usual static, isotropic one. The form of the generalised equation indicates that pressure anisotropy and flow act additively on equilibrium. In addition, two sets of analytical solutions, an extended Solovev one with a plasma reaching the separatrix and an extended Hernegger-Maschke one for a plasma surrounded by a fixed boundary possessing an X-point, are constructed, particularly in relevance to the ITER and NSTX tokamaks. Furthermore, the impacts both of pressure anisotropy and plasma flow on these equilibria are examined. It turns out that depending on the maximum value and the shape of an anisotropy function, the anisotropy can act either paramagnetically or diamagnetically. Also, in most of the cases considered both the anisotropy and the flow have stronger effects on NSTX equilibria than on ITER ones.

  9. Phenomenological description of anisotropy effects in some ferromagnetic superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Shopova, Diana V., E-mail: sho@issp.bas.bg [TCCM Research Group, Institute of Solid State Physics, Bulgarian Academy of Sciences, BG-1784 Sofia (Bulgaria); Todorov, Michail D. [Department of Applied Mathematics and Computer Science, Technical University of Sofia, 1000 Sofia (Bulgaria)

    2015-07-03

    We study phenomenologically the role of anisotropy in ferromagnetic superconductors UGe{sub 2}, URhGe, and UCoGe for the description of their phase diagrams. We use the Ginzburg–Landau free energy in its uniform form as we will consider only spatially independent solutions. This is an expansion of previously derived results where the effect of Cooper-pair and crystal anisotropies is not taken into account. The three compounds are separately discussed with the special stress on UGe{sub 2}. The main effect comes from the strong uniaxial anisotropy of magnetization while the anisotropy of Cooper pairs and crystal anisotropy only slightly change the phase diagram in the vicinity of Curie temperature. The limitations of this approach are also discussed. - Highlights: • Anisotropic Landau energy for description of ferromagnetic superconductors is proposed. • Meissner phases are described with their existence and stability conditions. • The application of the model to UGe{sub 2} is discussed. • The limitations to apply the model for description of experimental data are explained.

  10. Anisotropies in the HI gas distribution toward 3C196

    CERN Document Server

    Kalberla, P M W

    2016-01-01

    The local Galactic HI gas was found to contain cold neutral medium (CNM) filaments that are aligned with polarized dust emission. These filaments appear to be dominated by the magnetic field and in this case turbulence is expected to show distinct anisotropies. We use the Galactic Effelsberg--Bonn HI Survey (EBHIS) to derive 2D turbulence spectra for the HI distribution in direction to 3C196 and two more comparison fields. Prior to Fourier transform we apply a rotational symmetric 50% Tukey window to apodize the data. We derive average as well as position angle dependent power spectra. Anisotropies in the power distribution are defined as the ratio of the spectral power in orthogonal directions. We find strong anisotropies. For a narrow range in position angle, in direction perpendicular to the filaments and the magnetic field, the spectral power is on average more than an order of magnitude larger than parallel. In the most extreme case the anisotropy reaches locally a factor of 130. Anisotropies increase on...

  11. Anisotropy vs chemical composition at ultra-high energies

    CERN Document Server

    Lemoine, Martin

    2009-01-01

    This paper proposes and discusses a test of the chemical composition of ultra-high energy cosmic rays that relies on the anisotropy patterns measured as a function of energy. In particular, we show that if one records an anisotropy signal produced by heavy nuclei of charge Z above an energy E_{thr}, one should record an even stronger (possibly much stronger) anisotropy at energies >E_{thr}/Z due to the proton component that is expected to be associated with the sources of the heavy nuclei. This conclusion remains robust with respect to the parameters characterizing the sources and it does not depend at all on the modelling of astrophysical magnetic fields. As a concrete example, we apply this test to the most recent data of the Pierre Auger Observatory. Assuming that the anisotropy reported above 55EeV is not a statistical accident, and that no significant anisotropy has been observed at energies 10^{45}Z^{-2}erg/s. Using this bound in conjunction with the above conclusions, we argue that the current PAO data...

  12. Anisotropy of magnetoviscous effect in structure-forming ferrofluids

    Science.gov (United States)

    Sreekumari, Aparna; Ilg, Patrick

    2015-07-01

    The magnetoviscous effect, change in viscosity with change in magnetic field strength, and the anisotropy of the magnetoviscous effect, change in viscosity with orientation of magnetic field, have been a focus of interest for four decades. A satisfactory understanding of the microscopic origin of anisotropy of the magnetoviscous effect in magnetic fluids is still a matter of debate and a field of intense research. Here, we present an extensive simulation study to understand the relation between the anisotropy of the magnetoviscous effect and the underlying change in microstructures of ferrofluids. Our results indicate that field-induced chainlike structures respond very differently depending on their orientation relative to the direction of an externally applied shear flow, which leads to a pronounced anisotropy of viscosity. In this work, we focus on three exemplary values of dipolar interaction strengths which correspond to weak, intermediate, and strong interactions between dipolar colloidal particles. We compare our simulation results with an experimental study on cobalt-based ferrofluids as well as with an existing theoretical model called the chain model. A nonmonotonic behavior in the anisotropy of the magnetoviscous effect is observed with increasing dipolar interaction strength and is explained in terms of microstructure formation.

  13. An Ultrasonographic Periodontal Probe

    Science.gov (United States)

    Bertoncini, C. A.; Hinders, M. K.

    2010-02-01

    Periodontal disease, commonly known as gum disease, affects millions of people. The current method of detecting periodontal pocket depth is painful, invasive, and inaccurate. As an alternative to manual probing, an ultrasonographic periodontal probe is being developed to use ultrasound echo waveforms to measure periodontal pocket depth, which is the main measure of periodontal disease. Wavelet transforms and pattern classification techniques are implemented in artificial intelligence routines that can automatically detect pocket depth. The main pattern classification technique used here, called a binary classification algorithm, compares test objects with only two possible pocket depth measurements at a time and relies on dimensionality reduction for the final determination. This method correctly identifies up to 90% of the ultrasonographic probe measurements within the manual probe's tolerance.

  14. Hard probes 2006 Asilomar

    CERN Multimedia

    2006-01-01

    "The second international conference on hard and electromagnetic probes of high-energy nuclear collisions was held June 9 to 16, 2006 at the Asilomar Conference grounds in Pacific Grove, California" (photo and 1/2 page)

  15. Optical activity of chitosan films with induced anisotropy

    Science.gov (United States)

    Gegel, Natalia O.; Shipovskaya, Anna B.

    2016-04-01

    The optical anisotropy and optical activity of salt and basic chitosan films, both initial and modified in formic acid vapor were studied. The modification of such films was found to be accompanied by induced time-stable optical anisotropy, by varying the values of specific optical rotation [α] and an inversion of the sign of [α]. The angular dependences (indicatrices) of the specific optical rotation of films on the orientation angle of the sample relative to the direction of the polarization vector of the incident light beam in a plane perpendicular to the beam were obtained. The indicatrices of the initial chitosan films have an almost symmetrical character while those of the films modified in formic acid vapor are irregular. It is concluded of the formation of a vitrified cholesteric mesophase in the chitosan films with induced optical anisotropy.

  16. Violating the General Density-Slope Anisotropy Inequality

    CERN Document Server

    Barber, Jeremy A

    2014-01-01

    We examine the robustness of the well-known empirical relationship between the density slope and the velocity anisotropy of collisionless systems. This relation, known as the Global Density-Slope Anisotropy Inequality (GDSAI) (Ciotti & Morganti, 2010), posits that no collisionless system with a globally positive distribution function exists where the anisotropy exceeds half of the power-law of the density slope. We significantly extend previous indications that the GDSAI is not a universal rule by identifying a class of models where violation occurs. These models possess a globally positive DF, have an isotropic central core, but are not guaranteed to be stable. Our analysis suggests that stability criteria provide a stronger basis for determining if a DF represents an equilibrium solution for a collisionless system.

  17. Ion temperature anisotropy limitation in high beta plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Scime, Earl E. [West Virginia University, Morgantown, West Virginia 26506 (United States); Keiter, Paul A. [West Virginia University, Morgantown, West Virginia 26506 (United States); Balkey, Matthew M. [West Virginia University, Morgantown, West Virginia 26506 (United States); Boivin, Robert F. [West Virginia University, Morgantown, West Virginia 26506 (United States); Kline, John L. [West Virginia University, Morgantown, West Virginia 26506 (United States); Blackburn, Melanie [West Virginia University, Morgantown, West Virginia 26506 (United States); Gary, S. Peter [Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States)

    2000-05-01

    Measurements of parallel and perpendicular ion temperatures in the Large Experiment on Instabilities and Anisotropies (LEIA) space simulation chamber display an inverse correlation between the upper bound on the ion temperature anisotropy and the parallel ion beta ({beta}=8{pi}nkT/B{sup 2}). Fluctuation measurements indicate the presence of low frequency, transverse, electromagnetic waves with wave numbers and frequencies that are consistent with predictions for Alfven Ion Cyclotron instabilities. These observations are also consistent with in situ spacecraft measurements in the Earth's magnetosheath and with a theoretical/computational model that predicts that such an upper bound on the ion temperature anisotropy is imposed by scattering from enhanced fluctuations due to growth of the Alfven ion cyclotron instability. (c) 2000 American Institute of Physics.

  18. The investigations of anisotropy in orientations of galaxies

    CERN Document Server

    Godlowski, Wlodzimierz; Pajowska, Paulina; Flin, Piotr

    2013-01-01

    In 1994 Parnovsky, Karachentsev and Karachentseva suggested a modified method for investigation of the orientations of galaxies. Using this method they analyzed galaxies from the UGC and ESO catalogues, as well as from their's own catalogue inclusive of flat, edge-on galaxies. They found statistically significant anisotropy in the galaxies orientations'. In 1995 Flin suggested that this anisotropy has to be specific to LOcal Supercluster (LSC) In the present paper, using the method proposed by Parnovsky, Karachentsev and Karachentseva in 1994, we analyzed orientation of galaxies in the sample of galaxies belonging to LSC founding only a weak anisotropy. The relation of this method to Hawley and Peebles (1975) method of the investigation of the orientation of galaxies was discussed as well.

  19. Dynamics of low anisotropy morphologies in directional solidification.

    Science.gov (United States)

    Utter, B; Bodenschatz, E

    2002-11-01

    We report experimental results on quasi-two-dimensional diffusion limited growth in directionally solidified succinonitrile with small amounts of poly(ethylene oxide), acetone, or camphor as a solute. Seaweed growth, or dense branching morphology, is selected by growing grains close to the [111] plane, where the in-plane surface tension is nearly isotropic. The observed growth morphologies are very sensitive to small anisotropies in surface tension caused by misorientations from the [111] plane. Different seaweed morphologies are found, including the degenerate, the stabilized, and the strongly tilted seaweeds. The degenerate seaweeds show a limited fractal scaling range and, with increased undercooling, suggests a transition from "fractal" to "compact" seaweed. Strongly tilted seaweeds demonstrate a significant twofold anisotropy. In addition, seaweed-dendrite transitions are observed in low anisotropy growth.

  20. Finite-size anisotropy in statistically uniform porous media

    CERN Document Server

    Koza, Zbigniew; Khalili, Arzhang

    2009-01-01

    Anisotropy of the permeability tensor in statistically uniform porous media of sizes used in typical computer simulations is studied. Although such systems are assumed to be isotropic by default, we show that de facto their anisotropic permeability can give rise to significant changes of transport parameters such as permeability and tortuosity. The main parameter controlling the anisotropy is $a/L$, being the ratio of the obstacle to system size. Distribution of the angle $\\alpha$ between the external force and the volumetric fluid stream is found to be approximately normal, and the standard deviation of $\\alpha$ is found to decay with the system size as $(a/L)^{d/2}$, where $d$ is the space dimensionality. These properties can be used to estimate both anisotropy-related statistical errors in large-scale simulations and the size of the representative elementary volume.

  1. Angular anisotropy of the fusion-fission and quasifission fragments

    CERN Document Server

    Nasirov, A K; Utamuratov, R K; Fazio, G; Giardina, G; Hanappe, F; Mandaglio, G; Manganaro, M; Scheid, W

    2007-01-01

    The anisotropy in the angular distribution of the fusion-fission and quasifission fragments for the $^{16}$O+$^{238}$U, $^{19}$F+$^{208}$Pb and $^{32}$S+$^{208}$Pb reactions is studied by analyzing the angular momentum distributions of the dinuclear system and compound nucleus which are formed after capture and complete fusion, respectively. The orientation angles of axial symmetry axes of colliding nuclei to the beam direction are taken into account for the calculation of the variance of the projection of the total spin onto the fission axis. It is shown that the deviation of the experimental angular anisotropy from the statistical model picture is connected with the contribution of the quasifission fragments which is dominant in the $^{32}$S+$^{208}$Pb reaction. Enhancement of anisotropy at low energies in the $^{16}$O+$^{238}$U reaction is connected with quasifission of the dinuclear system having low temperature and effective moment of inertia.

  2. Interplay between anisotropy and spatial dispersion in metamaterial waveguide

    CERN Document Server

    Koshelev, Kirill L

    2016-01-01

    We analyze spectrum of waveguide modes of an arbitrary uniaxial anisotropic metamaterial slab with non-local electromagnetic response whose permittivity tensor could be described within Drude approximation. Spatial dispersion was introduced within the hydrodynamical model. Both anisotropy and spatial dispersion were considered as perturbations. This helps to distinguish their effect on the spectrum of the slab and to analyze lifting of the degeneracy of eigenmodes at plasma frequency in detail. Spatial dispersion is shown to result in break of the singularity in the den- sity of optical states in the hyperbolic regime and in suppression of negative dispersion induced by anisotropy. Mutual effect of spatial dispersion and anisotropy can bring light to a complete stop at certain frequencies.

  3. Polarization of thermal bremsstrahlung emission due to electron pressure anisotropy

    CERN Document Server

    Komarov, S; Churazov, E; Schekochihin, A

    2016-01-01

    Astrophysical plasmas are typically magnetized, with the Larmor radii of the charged particles many orders of magnitude smaller than their collisional mean free paths. The fundamental properties of such plasmas, e.g., conduction and viscosity, may depend on the instabilities driven by the anisotropy of the particle distribution functions and operating at scales comparable to the Larmor scales. We discuss a possibility that the pressure anisotropy of thermal electrons could produce polarization of thermal bremsstrahlung emission. In particular, we consider coherent large-scale motions in galaxy clusters to estimate the level of anisotropy driven by stretching of the magnetic-field lines by plasma flow and by heat fluxes associated with thermal gradients. Our estimate of the degree of polarization is $\\sim 0.1 \\%$ at energies $\\gtrsim kT$. While this value is too low for the forthcoming generation of X-ray polarimeters, it is potentially an important proxy for the processes taking place at extremely small scale...

  4. Study of the Experimental Probe of Inflationary Cosmology (EPIC)-Intemediate Mission for NASA's Einstein Inflation Probe

    CERN Document Server

    Bock, James; Amblard, Alex; Baumann, Daniel; Betoule, Marc; Chui, Talso; Colombo, Loris; Cooray, Asantha; Crumb, Dustin; Day, Peter; Dickinson, Clive; Dowell, Darren; Dragovan, Mark; Golwala, Sunil; Gorski, Krzysztof; Hanany, Shaul; Holmes, Warren; Irwin, Kent; Johnson, Brad; Keating, Brian; Kuo, Chao-Lin; Lee, Adrian; Lange, Andrew; Lawrence, Charles; Meyer, Steve; Miller, Nate; Nguyen, Hien; Pierpaoli, Elena; Ponthieu, Nicolas; Puget, Jean-Loup; Raab, Jeff; Richards, Paul; Satter, Celeste; Seiffert, Mike; Shimon, Meir; Tran, Huan; Williams, Brett; Zmuidzinas, Jonas

    2009-01-01

    Measurements of Cosmic Microwave Background (CMB) anisotropy have served as the best experimental probe of the early universe to date. The inflationary paradigm, inspired in part by the extreme isotropy of the CMB, is now a cornerstone in modern cosmology. Inflation has passed a series of rigorous experimental tests, but we still do not understand the physical mechanism or energy scale behind inflation. A general prediction of inflation and one that can provide certain insights into inflationary physics is a background of primordial gravitational waves. These perturbations leave a distinct signature in the CMB B-modes of polarization. The EPIC (Experimental Probe of Inflationary Cosmology) study team has investigated several CMB polarization mission concepts to carry out a definitive measurement of the inflationary B-mode polarization spectrum. In this report we study a mission with an aperture intermediate between the two missions discussed in our previous report. EPIC-IM's increased aperture allows access t...

  5. Studies of anisotropy of iron based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, Jason [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    To study the electronic anisotropy in iron based superconductors, the temperature dependent London penetration depth, Δλ (T), have been measured in several compounds, along with the angular dependent upper critical field, Hc2(T). Study was undertaken on single crystals of Ba(Fe1-xCox)2As2 with x=0.108 and x=0.127, in the overdoped range of the doping phase diagram, characterized by notable modulation of the superconducting gap. Heavy ion irradiation with matching field doses of 6 T and 6.5 T respectively, were used to create columnar defects and to study their effect on the temperature Δλ (T). The variation of the low-temperature penetration depth in both pristine and irradiated samples was fitted with a power-law function Δλ (T) = ATn. Irradiation increases the magnitude of the pre-factor A and decreases the exponent n, similar to the effect on the optimally doped samples. This finding supports the universal s± scenario for the whole doping range. Knowing that the s± gap symmetry exists across the superconducting dome for the electron doped systems, we next looked at λ (T), in optimally - doped, SrFe2(As1-xPx)2, x =0.35. Both, as-grown (Tc ~ 25 K) and annealed (Tc ~ 35 K) single crystals of SrFe2(As1-xPx)2 were measured. Annealing decreases the absolute value of the London penetration depth from λ(0) = 300 ± 10 nm in as-grown samples to λ (0) = 275±10 nm. At low temperatures, λ (T) ~ T indicates a superconducting gap with line nodes. Analysis of the full-temperature range superfluid density is consistent with the line nodes, but differs from the simple single-gap d-wave. The observed behavior is very similar to that of BaFe2(As1-xPx)2, showing that isovalently substituted pnictides are inherently different from

  6. Seismic anisotropy in granite at the Underground Research Laboratory, Manitoba

    International Nuclear Information System (INIS)

    The Shear-Wave Experiment at Atomic Energy of Canada Limited's Underground Research Laboratory was probably the first controlled-source shear-wave survey in a mine environment. Taking place in conjunction with the excavation of the Mine-by test tunnel at 420 m depth, the shear-wave experiment was designed to measure the in situ anisotropy of the rockmass and to use shear waves to observe excavation effects using the greatest variety of raypath directions of any in situ shear-wave survey to date. Inversion of the shear-wave polarizations shows that the anisotropy of the in situ rockmass is consistent with hexagonal symmetry with an approximate fabric orientation of strike 023degree and dip 35degree. The in situ anisotropy is probably due to microcracks with orientations governed by the in situ stress field and to mineral alignment within the weak gneissic layering. However, there is no unique interpretation as to the cause of the in situ anisotropy as the fabric orientation agrees approximately with both the orientation expected from extensive-dilatancy anisotropy and that of the gneissic layering. Eight raypaths with shear waves propagating wholly or almost wholly through granodiorite, rather than granite, do not show the expected shear-wave splitting and indicate a lower in situ anisotropy, which may be due to the finer grain size and/or the absence of gneissic layering within the granodiorite. These results suggest that shear waves may be used to determine crack and mineral orientations and for remote monitoring of a rockmass. This has potential applications in mining and waste monitoring

  7. FIRE HOSE INSTABILITY DRIVEN BY ALPHA PARTICLE TEMPERATURE ANISOTROPY

    Energy Technology Data Exchange (ETDEWEB)

    Matteini, L.; Schwartz, S. J. [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Hellinger, P. [Astronomical Institute, CAS, Prague (Czech Republic); Landi, S. [Dipartimento di Fisica e Astronomia, Università di Firenze, Firenze (Italy)

    2015-10-10

    We investigate properties of a solar wind-like plasma, including a secondary alpha particle population exhibiting a parallel temperature anisotropy with respect to the background magnetic field, using linear and quasi-linear predictions and by means of one-dimensional hybrid simulations. We show that anisotropic alpha particles can drive a parallel fire hose instability analogous to that generated by protons, but that, remarkably, can also be triggered when the parallel plasma beta of alpha particles is below unity. The wave activity generated by the alpha anisotropy affects the evolution of the more abundant protons, leading to their anisotropic heating. When both ion species have sufficient parallel anisotropies, both of them can drive the instability, and we observe the generation of two distinct peaks in the spectra of the fluctuations, with longer wavelengths associated to alphas and shorter ones to protons. If a non-zero relative drift is present, the unstable modes propagate preferentially in the direction of the drift associated with the unstable species. The generated waves scatter particles and reduce their temperature anisotropy to a marginally stable state, and, moreover, they significantly reduce the relative drift between the two ion populations. The coexistence of modes excited by both species leads to saturation of the plasma in distinct regions of the beta/anisotropy parameter space for protons and alpha particles, in good agreement with in situ solar wind observations. Our results confirm that fire hose instabilities are likely at work in the solar wind and limit the anisotropy of different ion species in the plasma.

  8. Three dimensional solar anisotropy of galactic cosmic rays near the recent solar minimum 23/24

    CERN Document Server

    Modzelewska, R

    2015-01-01

    Three dimensional (3D) galactic cosmic ray (GCR) anisotropy has been studied for 2006- 2012. The GCR anisotropy, both in the ecliptic plane and in polar direction, were obtained based on the neutron monitors (NMs) and Nagoya muon telescopes (MT) data. We analyze two dimensional (2D) GCR anisotropy in the ecliptic plane and north-south anisotropy normal to the ecliptic plane. We reveal quasi-periodicities - the annual and 27-days waves in the GCR anisotropy in 2006-2012. We investigate the relationship of the 27-day variation of the GCR anisotropy in the ecliptic plane and in the polar direction with the parameters of solar activity and solar wind.

  9. Anisotropy without tensors: a novel approach using geometric algebra.

    Science.gov (United States)

    Matos, Sérgio A; Ribeiro, Marco A; Paiva, Carlos R

    2007-11-12

    The most widespread approach to anisotropic media is dyadic analysis. However, to get a geometrical picture of a dielectric tensor, one has to resort to a coordinate system for a matrix form in order to obtain, for example, the index-ellipsoid, thereby obnubilating the deeper coordinate-free meaning of anisotropy itself. To overcome these shortcomings we present a novel approach to anisotropy: using geometric algebra we introduce a direct geometrical interpretation without the intervention of any coordinate system. By applying this new approach to biaxial crystals we show the effectiveness and insight that geometric algebra can bring to the optics of anisotropic media.

  10. Electronic nematic phase transition in the presence of anisotropy

    OpenAIRE

    Yamase, Hiroyuki

    2014-01-01

    We study the phase diagram of electronic nematic instability in the presence of xy anisotropy. While a second order transition cannot occur in this case, mean-field theory predicts that a first order transition occurs near van Hove filling and its phase boundary forms a wing structure, which we term a Griffiths wing, referring to his original work of He3-He4 mixtures. When crossing the wing, the anisotropy of the electronic system exhibits a discontinuous change, leading to a meta-nematic tra...

  11. Nanopatterned CoPt alloys with perpendicular magnetic anisotropy

    Science.gov (United States)

    Makarov, D.; Bermúdez-Ureña, E.; Schmidt, O. G.; Liscio, F.; Maret, M.; Brombacher, C.; Schulze, S.; Hietschold, M.; Albrecht, M.

    2008-10-01

    CoPt alloy films with perpendicular magnetic anisotropy were grown on SiO2 nanoparticle arrays with particle sizes as small as 10 nm. In order to induce perpendicular magnetic anisotropy in the CoPt film, a MgO seed layer was sputter deposited. Despite the fact that neighboring CoPt film caps are interconnected, individual caps appear as single domain and for most of them their magnetization orientation can be reversed individually. This behavior might be caused by domain wall nucleation and pinning preferentially at the rim of each cap. Thus, arrays of magnetic caps with defined pinning sites can be considered as a percolated perpendicular medium.

  12. Perpendicular Magnetic Anisotropy in CoFeB/Pd Bilayers

    OpenAIRE

    COEY, JOHN; FOWLEY, CIARAN; OGUZ, KAAN; Rode, Karsten; Kurt, Huseyin

    2010-01-01

    PUBLISHED Perpendicular magnetic anisotropy is observed in ultrathin (0.6 nm) amorphous Co40Fe40B20 when sputtered on an MgO (001) buffer layer and capped with Pd. The layers are superparamagnetic with a blocking temperature of similar to 230 K, below which they show an exponential temperature dependence of coercivity. Perpendicular magnetic anisotropy is observed in the as-deposited state and the mechanism is different from that of CoFeB/Pt, which requires postannealing. These ultrathin l...

  13. Anisotropy of mechanical properties of zirconium and zirconium alloys

    International Nuclear Information System (INIS)

    In studies of technological applications of zirconium to fuel elements of nuclear reactor, it was found that the use of plasticity equations for isotropic materials is not in agreement with experimental results, because of the strong anisotropy of zirconium. The present review describes recent progress on the knowledge of the influence of anisotropy on mechanical properties, after Douglass' review in 1971. The review was written to be selfconsistent, changing drastically the presentation of some of the referenced papers. It is also suggested some particular experiments to improve developments in this area

  14. Topographical Anisotropy and Wetting of Ground Stainless Steel Surfaces

    Directory of Open Access Journals (Sweden)

    Cornelia Bellmann

    2012-12-01

    Full Text Available Microscopic and physico-chemical methods were used for a comprehensive surface characterization of different mechanically modified stainless steel surfaces. The surfaces were analyzed using high-resolution confocal microscopy, resulting in detailed information about the topographic properties. In addition, static water contact angle measurements were carried out to characterize the surface heterogeneity of the samples. The effect of morphological anisotropy on water contact angle anisotropy was investigated. The correlation between topography and wetting was studied by means of a model of wetting proposed in the present work, that allows quantifying the air volume of the interface water drop-stainless steel surface.

  15. Dielectric and magnetic anisotropy of a nematic ytterbium complex

    International Nuclear Information System (INIS)

    The sign and the magnitude of the dielectric anisotropy of an ytterbium-based paramagnetic nematic liquid crystal complex, namely, tris[1-(4-(4-propylcyclohexyl)phenyl)octane-1,3-dione]-[5,5'-di (heptadecile)-2,2'-bipyridine]ytterbium, are determined. The temperature dependence of the permittivity components of the complex is obtained in the temperature range of a nematic phase. The sign of the anisotropy of the magnetic susceptibility of this compound is experimentally determined

  16. Dielectric and magnetic anisotropy of a nematic ytterbium complex

    Energy Technology Data Exchange (ETDEWEB)

    Dobrun, L. A., E-mail: l.dobrun@spbu.ru; Sakhatskii, A. S.; Kovshik, A. P.; Ryumtsev, E. I.; Kolomiets, I. P. [St. Petersburg State University (Russian Federation); Knyazev, A. A.; Galyametdinov, Yu. G. [Kazan National Research Technological University (Russian Federation)

    2015-05-15

    The sign and the magnitude of the dielectric anisotropy of an ytterbium-based paramagnetic nematic liquid crystal complex, namely, tris[1-(4-(4-propylcyclohexyl)phenyl)octane-1,3-dione]-[5,5'-di (heptadecile)-2,2'-bipyridine]ytterbium, are determined. The temperature dependence of the permittivity components of the complex is obtained in the temperature range of a nematic phase. The sign of the anisotropy of the magnetic susceptibility of this compound is experimentally determined.

  17. Fabrication of epitaxial Fe nanodot arrays and anisotropy engineering

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, H. M.; Kim, S. H.; Lee, H. S.; Lee, J. [Yonsei University, Seoul (Korea, Republic of)

    2010-04-15

    Arrays of Fe nanodots were fabricated from an epitaxial Fe (20 nm) film on Cu (001)/Si(001) by using laser interference lithography and chemical wet etching. The nanodots were aligned parallel to the two magnetic hard directions of the film and were arranged on rectangular lattices of different periods in order to engineer the magnetic anisotropy of the system by using the shape of array. As the separation between dots along one direction decrease from 550 nm to 150 nm, the dipole interaction effect became strong, and finally a uniaxial magnetic anisotropy were realized.

  18. Search for Large Scale Anisotropies with the Pierre Auger Observatory

    Science.gov (United States)

    Bonino, R.; Pierre Auger Collaboration

    The Pierre Auger Observatory studies the nature and the origin of Ultra High Energy Cosmic Rays (>3\\cdot1018 eV). Completed at the end of 2008, it has been continuously operating for more than six years. Using data collected from 1 January 2004 until 31 March 2009, we search for large scale anisotropies with two complementary analyses in different energy windows. No significant anisotropies are observed, resulting in bounds on the first harmonic amplitude at the 1% level at EeV energies.

  19. Anisotropy in layered half-metallic Heusler alloy superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Azadani, Javad G.; Munira, Kamaram; Sivakumar, Chockalingam; Butler, William H. [Center for Materials for Information Technology, University of Alabama, Tuscaloosa, Alabama 35487 (United States); Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487 (United States); Romero, Jonathon [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487 (United States); Ma, Jianhua; Ghosh, Avik W. [Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States)

    2016-01-28

    We show that when two Heusler alloys are layered in the [001], [110], or [111] directions for various thicknesses to form a superlattice, the Slater-Pauling rule may still be satisfied and the resulting superlattice is often half-metallic with gaps comparable to or larger than those of its constituents. In addition, uniaxial magnetocrystalline anisotropy is induced because of the differences in the electronic structure of the two Heuslers in the superlattice. Various full-full, full-half, and half-half Heusler superlattices are studied, and potential half-metallic superlattices with perpendicular magnetocrystalline anisotropy are identified.

  20. Small-angle anisotropies in the CMBR from active sources

    CERN Document Server

    Battye, R A

    1997-01-01

    We consider the effects of photon diffusion on the small-angle microwave background anisotropies due to active source models. We find that fluctuations created just before the time of last scattering allow anisotropy to be created on scales much smaller than allowed by standard Silk damping. Using simple models for string and texture structure functions as examples, we illustrate the differences in the angular power spectrum at scales of order a few arcminutes. In particular, we find that the Doppler peak heights are modified by 10-50% and the small-angle fall-off is power law rather than exponential.

  1. Random-anisotropy Blume-Emery-Griffiths model

    Science.gov (United States)

    Maritan, Amos; Cieplak, Marek; Swift, Michael R.; Toigo, Flavio; Banavar, Jayanth R.

    1992-01-01

    The results are described of studies of a random-anisotropy Blume-Emery-Griffiths spin-1 Ising model using mean-field theory, transfer-matrix calculations, and position-space renormalization-group calculations. The interplay between the quenched randomness of the anisotropy and the annealed disorder introduced by the spin-1 model leads to a rich phase diagram with a variety of phase transitions and reentrant behavior. The results may be relevant to the study of the phase separation of He-3 - He-4 mixtures in porous media in the vicinity of the superfluid transition.

  2. Galactic foreground contribution to the BEAST CMB Anisotropy Maps

    OpenAIRE

    Mejía, Jorge; Bersanelli, Marco; Burigana, Carlo; Childers, Jeff; Figueiredo, Newton; Kangas, Miikka; Lubin, Philip; Maino, Davide; Mandolesi, Nazzareno; Marvil, Josh; Meinhold, Peter; O'Dwyer, Ian; O'Neill, Hugh,; Platania, Paola; Seiffert, Michael

    2004-01-01

    We report limits on the Galactic foreground emission contribution to the Background Emission Anisotropy Scanning Telescope (BEAST) Ka- and Q-band CMB anisotropy maps. We estimate the contribution from the cross-correlations between these maps and the foreground emission templates of an H${\\alpha}$ map, a de-striped version of the Haslam et al. 408 MHz map, and a combined 100 $\\mu$m IRAS/DIRBE map. Our analysis samples the BEAST $\\sim10^\\circ$ declination band into 24 one-hour (RA) wide sector...

  3. Evaluation of a multi-electrode bioimpedance spectroscopy tensor probe to detect the anisotropic conductivity spectra of biological tissues

    International Nuclear Information System (INIS)

    This paper presents bioimpedance spectroscopy measurements of anisotropic tissues using a 16 electrode probe and reconstruction method of estimating the anisotropic impedance spectrum in a local region just underneath the center of the probe. This may enable in-vivo surface bioimpedance measurements with similar performance to the ex-vivo gold standard that requires excising and placing the entire tissue sample in a unit measurement cell with uniform electric field. The multiple surface electrodes enable us to create a focused current pattern so that the resulting measured voltage is more sensitive to a local region and less sensitive to other areas. This is exploited in a reconstruction method to provide improved bioimpedance and anisotropy measurements. In this paper, we describe the current pattern for localized electrical energy concentration, performance with the spring loaded pin electrodes, data calibration and experimental results on anisotropic agar phantoms and different tissue types. The anisotropic conductivity spectra are able to differentiate insulating films of different thickness and detect their orientation. Bioimpedance spectra of biological tissues are in agreement with published data and reference instruments. The anisotropy expressed as the ratio of eigenvalues and the orientation of eigenfunctions were reconstructed at 45° intervals. This information is used to predict the underlying anisotropy of the region under the probe. Tissue measurements clearly demonstrate the expected higher anisotropy of muscle tissue compared to liver tissue and spectral changes. (paper)

  4. Evaluation of a multi-electrode bioimpedance spectroscopy tensor probe to detect the anisotropic conductivity spectra of biological tissues

    Science.gov (United States)

    Karki, Bishal; Wi, Hun; McEwan, Alistair; Kwon, Hyeuknam; In Oh, Tong; Woo, Eung Je; Seo, Jin Keun

    2014-07-01

    This paper presents bioimpedance spectroscopy measurements of anisotropic tissues using a 16 electrode probe and reconstruction method of estimating the anisotropic impedance spectrum in a local region just underneath the center of the probe. This may enable in-vivo surface bioimpedance measurements with similar performance to the ex-vivo gold standard that requires excising and placing the entire tissue sample in a unit measurement cell with uniform electric field. The multiple surface electrodes enable us to create a focused current pattern so that the resulting measured voltage is more sensitive to a local region and less sensitive to other areas. This is exploited in a reconstruction method to provide improved bioimpedance and anisotropy measurements. In this paper, we describe the current pattern for localized electrical energy concentration, performance with the spring loaded pin electrodes, data calibration and experimental results on anisotropic agar phantoms and different tissue types. The anisotropic conductivity spectra are able to differentiate insulating films of different thickness and detect their orientation. Bioimpedance spectra of biological tissues are in agreement with published data and reference instruments. The anisotropy expressed as the ratio of eigenvalues and the orientation of eigenfunctions were reconstructed at 45° intervals. This information is used to predict the underlying anisotropy of the region under the probe. Tissue measurements clearly demonstrate the expected higher anisotropy of muscle tissue compared to liver tissue and spectral changes.

  5. Magnetic anisotropy in GaMnAs; Magnetische Anisotropie in GaMnAs

    Energy Technology Data Exchange (ETDEWEB)

    Daeubler, Joachim

    2009-07-02

    The goal of the present work was the detailed investigation of the impact of parameters like vertical strain, hole concentration, substrate orientation and patterning on the MA in GaMnAs. At first a method is introduced enabling us to determine the MA from angle-dependent magnetotransport measurements. This method was used to analyze the impact of vertical strain {epsilon}{sub zz} on the MA in a series of GaMnAs layers with a Mn content of 5% grown on relaxed InGaAs-templates. While hole concentration and Curie temperature were found to be unaffected by vertical strain, a significant dependence of the MA on {epsilon}{sub zz} was found. The most pronounced dependence was observed for the anisotropy parameter B{sub 2} {sub perpendicular} {sub to}, representing the intrinsic contribution to the MA perpendicular to the layer plane. For this parameter a linear dependence on {epsilon}{sub zz} was found, resulting in a strain-induced transition of the magnetic easy axis with increasing strain from in-plane to out-of-plane at {epsilon}{sub zz} {approx} -0.13%. Post-growth annealing of the samples leads to an outdiffusion and/or regrouping of the highly mobile Mn interstitial donor defects, resulting in an increase in both p and T{sub C}. For the annealed samples, the transition from in-plane to out-of-plane easy axis takes place at {epsilon}{sub zz} {approx} -0.07%. From a comparison of as-grown and annealed samples, B{sub 2} {sub perpendicular} {sub to} was found to be proportional to both p and {epsilon}{sub zz}, B{sub 2} {sub perpendicular} {sub to} {proportional_to} p .{epsilon}{sub zz}. To study the influence of substrate orientation on the magnetic properties of GaMnAs, a series of GaMnAs layers with Mn contents up to 5% was grown on (001)- and (113)A-oriented GaAs substrates. The hole densities and Curie temperatures, determined from magnetotransport measurements, are drastically reduced in the (113)A layers. The differences in the magnetic properties of (113)A- and

  6. Model for resonant plasma probe.

    Energy Technology Data Exchange (ETDEWEB)

    Warne, Larry Kevin; Johnson, William Arthur; Hebner, Gregory Albert; Jorgenson, Roy E.; Coats, Rebecca Sue

    2007-04-01

    This report constructs simple circuit models for a hairpin shaped resonant plasma probe. Effects of the plasma sheath region surrounding the wires making up the probe are determined. Electromagnetic simulations of the probe are compared to the circuit model results. The perturbing effects of the disc cavity in which the probe operates are also found.

  7. A small dimension intraoperative probe

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This article introduces the usage of the intraoperative probe in surgical based on RGS and proposes one method to design the probe. Also, a charge-sensitive preamplifier used in semiconductor detector was constructed which can reduce the dimension of the probe. At last the probe is tested by some animal experiments. Results showed that the property of this system are reliable.

  8. The local dust foregrounds in the microwave sky: I. Thermal emission spectra

    CERN Document Server

    Dikarev, V; Solanki, S; Krüger, H; Krivov, A

    2009-01-01

    Analyses of the cosmic microwave background (CMB) radiation maps made by the Wilkinson Microwave Anisotropy Probe (WMAP) have revealed anomalies not predicted by the standard inflationary cosmology. In particular, the power of the quadrupole moment of the CMB fluctuations is remarkably low, and the quadrupole and octopole moments are aligned mutually and with the geometry of the Solar system. It has been suggested in the literature that microwave sky pollution by an unidentified dust cloud in the vicinity of the Solar system may be the cause for these anomalies. In this paper, we simulate the thermal emission by clouds of spherical homogeneous particles of several materials. Spectral constraints from the WMAP multi-wavelength data and earlier infrared observations on the hypothetical dust cloud are used to determine the dust cloud's physical characteristics. In order for its emissivity to demonstrate a flat, CMB-like wavelength dependence over the WMAP wavelengths (3 through 14 mm), and to be invisible in the...

  9. Symmetry and Antisymmetry of the CMB Anisotropy Pattern

    Directory of Open Access Journals (Sweden)

    Jaiseung Kim

    2012-01-01

    Full Text Available Given an arbitrary function, we may construct symmetric and antisymmetric functions under a certain operation. Since statistical isotropy and homogeneity of our Universe has been a fundamental assumption of modern cosmology, we do not expect any particular symmetry or antisymmetry in our Universe. Besides fundamental properties of our Universe, we may also figure our contamination and improve the quality of the CMB data products, by matching the unusual symmetries and antisymmetries of the CMB data with known contaminantions. If we let the operation to be a coordinate inversion, the symmetric and antisymmetric functions have even and odd-parity respectively. The investigation on the parity of the recent CMB data shows a large-scale odd-parity preference, which is very unlikely in the statistical isotropic and homogeneous Universe. We investigated the association of the WMAP systematics with the anomaly, but did not find a definite non-cosmological cause. Besides the parity anomaly, there is anomalous lack of large-scale correlation in CMB data. We show that the odd-parity preference at low multipoles is, in fact, phenomenologically identical with the lack of large-angle correlation.

  10. Anisotropy in the electronic states of self-assembled quantum dots

    International Nuclear Information System (INIS)

    Full text: Self-assembled quantum dots (QD) are semiconductor nanostructures that have been widely reported for use in technological devices such as optical memories and detectors. Besides this commercial potential, their zero-dimensional characteristics unveil a vast realm of fundamental physics to be explored in condensed matter physics. An example is the tailorable InAsP QD system, which allows one to control emission energy and QD sizes, among other properties. In this work we use polarized optical techniques in order to determine the origin of some structures previously identified via photoluminescence (PL) and photomodulated transmission (PT). We show that by varying the linear polarization of either excitation beam (PL) or probe beam (PT) it was possible to identify both QD and wetting layer (WL) contributions for the optical spectra of InAsP QDs. PT shows clearly that lower energy spectral structures present an anisotropy as a function of the polarization direction, which can be associated to QD recombination, since some degree of spatial anisotropy is expected for these nanostructures. WL contributions, however, appears at higher energies and shows isotropic behavior as a function of linear polarization, a characteristics of a two-dimensional layer. Polarized PL measurements seem to confirm the above identification, however a slightly dependence on WL intensity as a function of excitation polarization was found; it might be related to the diffraction grating polarization response of our spectrometer, and this is under investigation at the moment. Higher states for both WL and QD, although faint in the spectra, are present for samples with deeper confining potentials. (author)

  11. Multispectral imaging probe

    Science.gov (United States)

    Sandison, David R.; Platzbecker, Mark R.; Descour, Michael R.; Armour, David L.; Craig, Marcus J.; Richards-Kortum, Rebecca

    1999-01-01

    A multispectral imaging probe delivers a range of wavelengths of excitation light to a target and collects a range of expressed light wavelengths. The multispectral imaging probe is adapted for mobile use and use in confined spaces, and is sealed against the effects of hostile environments. The multispectral imaging probe comprises a housing that defines a sealed volume that is substantially sealed from the surrounding environment. A beam splitting device mounts within the sealed volume. Excitation light is directed to the beam splitting device, which directs the excitation light to a target. Expressed light from the target reaches the beam splitting device along a path coaxial with the path traveled by the excitation light from the beam splitting device to the target. The beam splitting device directs expressed light to a collection subsystem for delivery to a detector.

  12. Anisotropy of sublimation from equivalent crystal faces of carbon-containing tungsten monocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Dekhtyar, I.Ya.; Kolesnik, V.N.; Ovsienko, D.E.; Patoka, V.I.; Silant' ev, V.I.; Sosnina, E.I. (AN Ukrainskoj SSR, Kiev. Inst. Metallofiziki)

    1981-08-01

    Anisotropy of sublimation parameters was found in equivalent faces (100) or (1O0) of W single crystals oriented perpendicular or parallel to the growth direction. The anisotropy value depends on C concentration in W single crystals.

  13. Anisotropy of sublimation from equivalent crystal faces of carbon-containing tungsten monocrystals

    International Nuclear Information System (INIS)

    Anisotropy of sublimation parameters was found in equivalent faces (100) or (1O0) of W single crystals oriented perpendicular or parallel to the growth direction. The anisotropy value depends on C concentration in W single crystals

  14. Experimental Study of Rock Drill-ability Anisotropy by Acoustic Velocity

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Rock drill-ability anisotropy has significant effects on directional drilling and deviation control. Its evaluation is an important but difficult research subject. Definitions of drill-ability anisotropy and acoustic anisotropy of rock are given in this paper. The acoustic velocities and the drill-ability parameters of several rock samples from the Engineering Center for Chinese Continental Scientific Drilling (CCSD) are respectively measured with the device for testing the rock drill-ability and the ultrasonic testing system in laboratory, so that their drill-ability anisotropy and acoustic anisotropy are respectively calculated and discussed in detail by using the experimental data. On the basis of these experimental results and calculations, correlations between drill-ability anisotropy and acoustic anisotropy of the rock samples are illustrated through regression analyses. Thus, a mathematical model developed may be used to evaluate the rock drill-ability anisotropy with the acoustic logging or seismic data to a certain extent.

  15. Large-Angular Scales CMB Anisotropy from Excited Initial Mode

    CERN Document Server

    Sojasi, A; Yusofi, E

    2015-01-01

    According to the inflationary cosmology, the CMB anisotropy gives an opportunity to test predictions of the new physics hypothesis. Initial state of quantum fluctuations is one of the important options at high energy scale, which can affect on the observables such as CMB power spectrum. In this study a quasi-de Sitter inflationary background with approximate de Sitter mode function built over the Bunch-Davies mode is applied to investigate the scale-dependency of the CMB anisotropy. Indeed, considering the recent Planck constraint on spectral index, motivated us to examine the effect of new excited mode function (instead of pure de Sitter mode) on the CMB anisotropy in large-angular scales. In so doing, it was revealed that the angular scale-invariance in the CMB temperature fluctuations is broken and in the limit $ \\ell<200 $ the tiny deviation is appeared. Also, it was shown that the power spectrum of CMB anisotropy is dependent on the slow-roll parameter $\\epsilon $.

  16. The large scale microwave background anisotropy in decaying particle cosmology

    International Nuclear Information System (INIS)

    We investigate the large-scale anisotropy of the microwave background radiation in cosmological models with decaying particles. The observed value of the quadrupole moment combined with other constraints gives an upper limit on the redshift of the decay z/sub d/ < 3-5. 12 refs., 2 figs

  17. Diamagnetic Anisotropy: Two Iron Complexes as Laboratory Examples

    Science.gov (United States)

    Fernandez, Ignacio; Sanchez, Jorge Fernando Fernandez

    2010-01-01

    There are relatively few experiments describing the NMR properties of bis(amine) iron(II) phthalocyanine complexes. Several features make this experiment attractive: First, it nicely illustrates the diamagnetic anisotropy phenomena, providing both students and teachers an opportunity to gain insight into aspects such as phase correction and…

  18. Resolution of reservoir scale electrical anisotropy from marine CSEM data

    Energy Technology Data Exchange (ETDEWEB)

    Brown, V.; Hoversten, G.M.; Key, K.; Chen, J.

    2011-10-01

    A combination of 1D and 3D forward and inverse solutions is used to quantify the sensitivity and resolution of conventional controlled source electromagnetic (CSEM) data collected using a horizontal electric dipole source to transverse electrical anisotropy located in a deep-water exploration reservoir target. Since strongly anisotropic shale layers have a vertical resistivity that can be comparable to many reservoirs, we examine how CSEM can discriminate confounding shale layers through their characteristically lower horizontal resistivity. Forward modeling demonstrates that the sensitivity to reservoir level anisotropy is very low compared to the sensitivity to isotropic reservoirs, especially when the reservoir is deeper than about 2 km below the seabed. However, for 1D models where the number of inversion parameters can be fixed to be only a few layers, both vertical and horizontal resistivity of the reservoir can be well resolved using a stochastic inversion. We find that the resolution of horizontal resistivity increases as the horizontal resistivity decreases. We show that this effect is explained by the presence of strong horizontal current density in anisotropic layers with low horizontal resistivity. Conversely, when the reservoir has a vertical to horizontal resistivity ratio of about 10 or less, the current density is vertically polarized and hence has little sensitivity to the horizontal resistivity. Resistivity anisotropy estimates from 3D inversion for 3D targets suggest that resolution of reservoir level anisotropy for 3D targets will require good a priori knowledge of the background sediment conductivity and structural boundaries.

  19. K Variations and Anisotropy: Microstructure Effect and Numerical Predictions

    Institute of Scientific and Technical Information of China (English)

    李旭东; 李华清

    2003-01-01

    Computer experiments were performed on simulated polycrystalline material samples that possess locally anisotropic microstructures to investigate stress intensity factor ( K ) variations and anisotropy along fronts of microcracks of different sizes. The anisotropic K , arising from inhomogeneous stresses in broken grains, was determined for planar microcracks by using a weight function-based numerical technique. It has been found that the grain-orientation-geometry-induced local anisotropy produces large variations in K along front of microcracks, when the crack size is of the order of few grain diameters. Synergetic effect of grain orientation and geometry of broken grains control K variations and evolution along the microcrack front. The K variations may diminish at large crack sizes, signifying a shift of K calculation to bulk stress dependence from local stress dependence. Local grain geometry and texture may lead to K anisotropy, producing unusually higher/lower K at a segment of the crack front. Either K variation or anisotropy cannot be ignored when assessing a microcrack.

  20. Effect of earthquake locations on Rayleigh wave azimuthal anisotropy

    Science.gov (United States)

    Ma, Z.; Masters, G.

    2013-12-01

    We have compiled a large dataset for Rayleigh wave phase arrival times from 5mHz to 35mHz by using cluster analysis method. Estimation of source phase is improved by using a second order approximation of the associated Legendre functions. Currently, we have about 300,000 measurements for 5mHz, 600,000 for 10mHz, 400,000 for 20mHz and 280,000 for 35mHz. We use our new dataset to invert for the 2-phi terms of Rayleigh wave azimuthal anisotropy. We have found differences in the inverted fast directions when using PDE versus CMT source locations, especially near subduction zones where most earthquakes happen. Allowing small changes in earthquake locations (latitude and longitude) in our inversion greatly reduces such discrepancies. Residue patterns and checkerboard tests both indicate that the azimuthal anisotropy patterns in ocean basins are likely coherent over large distances, especially in the Pacific. To model the change of anisotropy amplitudes in the Pacific for different frequencies, we follow the approach proposed by Montagner and Nataf (1986). Values of elastic constants are compiled from Anderson and Isaak (1995) and Abramson et al (1997). The depth extent of anisotropy will be discussed.

  1. A CMB GIBBS SAMPLER FOR LOCALIZED SECONDARY ANISOTROPIES

    Energy Technology Data Exchange (ETDEWEB)

    Bull, Philip; Eriksen, Hans Kristian; Fuskeland, Unni [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, N-0315 Oslo (Norway); Wehus, Ingunn K.; Ferreira, Pedro G. [Astrophysics, University of Oxford, DWB, Keble Road, Oxford OX1 3RH (United Kingdom); Górski, Krzysztof M.; Jewell, Jeffrey B., E-mail: p.j.bull@astro.uio.no [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2015-07-20

    In addition to primary fluctuations, cosmic microwave background (CMB) temperature maps contain a wealth of additional information in the form of secondary anisotropies. However, secondary effects that can be identified with individual objects, such as the thermal and kinetic Sunyaev–Zel’dovich (TSZ–KSZ) effects due to galaxy clusters, are difficult to unambiguously disentangle from foreground contamination and the primary CMB. We develop a Bayesian formalism to rigorously characterize anisotropies that are localized on the sky, taking the TSZ and KSZ effects as an example. Using a Gibbs sampling scheme, we are able to efficiently sample from the joint posterior distribution for a multi-component model of the sky with many thousands of correlated physical parameters. The posterior can then be exactly marginalized to estimate the properties of the secondary anisotropies, fully taking into account degeneracies with the other signals in the CMB map. We show that this method is computationally tractable using a simple implementation based on the existing Commander component separation code and discuss how other types of secondary anisotropy can be accommodated within our framework.

  2. Exotic skyrmion crystals in chiral magnets with compass anisotropy

    Science.gov (United States)

    Chen, J. P.; Zhang, Dan-Wei; Liu, J. -M.

    2016-01-01

    The compass-type anisotropy appears naturally in diverse physical contexts with strong spin-orbit coupling (SOC) such as transition metal oxides and cold atomic gases etc, and it has been receiving substantial attention. Motivated by recent studies and particularly recent experimental observations on helimagnet MnGe, we investigate the critical roles of this compass-type anisotropy in modulating various spin textures of chiral magnets with strong SOC, by Monte Carlo simulations based on a classical Heisenberg spin model with Dzyaloshinsky-Moriya interaction and compass anisotropy. A phase diagram with emergent spin orders in the space of compass anisotropy and out-of-plane magnetic field is presented. In this phase diagram, we propose that a hybrid super-crystal structure consisting of alternating half-skyrmion and half-anti-skyrmion is the possible zero-field ground state of MnGe. The simulated evolution of the spin structure driven by magnetic field is in good accordance with experimental observations on MnGe. Therefore, this Heisenberg spin model successfully captures the main physics responsible for the magnetic structures in MnGe, and the present work may also be instructive to research on the magnetic states in other systems with strong SOC. PMID:27377149

  3. Anisotropy signature in reverse-time migration extended images

    KAUST Repository

    Sava, Paul C.

    2014-11-04

    Reverse-time migration can accurately image complex geologic structures in anisotropic media. Extended images at selected locations in the Earth, i.e., at common-image-point gathers, carry rich information to characterize the angle-dependent illumination and to provide measurements for migration velocity analysis. However, characterizing the anisotropy influence on such extended images is a challenge. Extended common-image-point gathers are cheap to evaluate since they sample the image at sparse locations indicated by the presence of strong reflectors. Such gathers are also sensitive to velocity error that manifests itself through moveout as a function of space and time lags. Furthermore, inaccurate anisotropy leaves a distinctive signature in common-image-point gathers, which can be used to evaluate anisotropy through techniques similar to the ones used in conventional wavefield tomography. It specifically admits a V-shaped residual moveout with the slope of the "V" flanks depending on the anisotropic parameter η regardless of the complexity of the velocity model. It reflects the fourth-order nature of the anisotropy influence on moveout as it manifests itself in this distinct signature in extended images after handling the velocity properly in the imaging process. Synthetic and real data observations support this assertion.

  4. Large-Angular-Scale Anisotropy in the Cosmic Background Radiation

    Science.gov (United States)

    Gorenstein, M. V.; Smoot, G. F.

    1980-05-01

    We report the results of an extended series of airborne measurements of large-angular-scale anisotropy in the 3 K cosmic background radiation. Observations were carried out with a dual-antenna microwave radiometer operating at 33 GHz (.089 cm wavelength) flown on board a U-2 aircraft to 20 km altitude. In eleven flights, between December 1976 and May 1978, the radiometer measured differential intensity between pairs of directions distributed over most of the northern hemisphere with an rms sensitivity of 47 mK Hz{sup 1�}. The measurements how clear evidence of anisotropy that is readily interpreted as due to the solar motion relative to the sources of the radiation. The anisotropy is well fit by a first order spherical harmonic of amplitude 360{+ or -}50km sec{sup -1} toward the direction 11.2{+ or -}0.5 hours of right ascension and 19 {+ or -}8 degrees declination. A simultaneous fit to a combined hypotheses of dipole and quadrupole angular distributions places a 1 mK limit on the amplitude of most components of quadrupole anisotropy with 90% confidence. Additional analysis places a 0.5 mK limit on uncorrelated fluctuations (sky-roughness) in the 3 K background on an angular scale of the antenna beam width, about 7 degrees.

  5. The importance of anisotropy for relativistic fluids with spherical symmetry

    OpenAIRE

    Ivanov, B. V.

    2010-01-01

    It is shown that an effective anisotropic spherically symmetric fluid model with heat flow can absorb the addition to a perfect fluid of pressure anisotropy, heat flow, bulk and shear viscosity, electric field and null fluid. In most cases the induction of effective heat flow can be avoided.

  6. Flow stress anisotropy caused by geometrically necessary boundaries

    DEFF Research Database (Denmark)

    Hansen, N.; Juul Jensen, D.

    1992-01-01

    The microstructural anisotropy of deformed metal is related to the formation of geometrically necessary boundaries such as dense dislocation walls and microbands. These boundaries have a macroscopic orientation with respect to the sample axes and they can resist slip due to a high concentration of...

  7. Photoinduced Circular Anisotropy in Side-Chain Azobenzene Polyesters

    DEFF Research Database (Denmark)

    Nikolova, L.; Todorov, T.; Ivanov, M.;

    1997-01-01

    We report for the first time the inducing of large circular anisotropy in previously unoriented films of side-chain azobenzene polyesters on illumination with circularly polarized light at a wavelength of 488 nm. The circular dichroism and optical activity are measured simultaneously in real time...

  8. Window Function for Non-Circular Beam CMB Anisotropy Experiment

    OpenAIRE

    Souradeep, Tarun; Ratra, Bharat

    2001-01-01

    We develop computationally rapid methods to compute the window function for a cosmic microwave background anisotropy experiment with a non-circular beam which scans over large angles on the sky. To concretely illustrate these methods we compute the window function for the Python V experiment which scans over large angles on the sky with an elliptical Gaussian beam.

  9. Measurement of anisotropy constant in US with polarized neutrons

    DEFF Research Database (Denmark)

    Lander, G.H.; Brooks, M.S.S.; Lebech, B.;

    1991-01-01

    Uranium compounds can have an anisotropy that is considerably greater than that found in rare‐earth compounds. Early estimates of K1 in ferromagnetic US (Tc = 178 K), for example, were that K1 ≳ 108 erg/cm3. We have re‐examined this cubic material and determined K1 in the range of reduced moment (μ...

  10. Exotic skyrmion crystals in chiral magnets with compass anisotropy

    Science.gov (United States)

    Chen, J. P.; Zhang, Dan-Wei; Liu, J.-M.

    2016-07-01

    The compass-type anisotropy appears naturally in diverse physical contexts with strong spin-orbit coupling (SOC) such as transition metal oxides and cold atomic gases etc, and it has been receiving substantial attention. Motivated by recent studies and particularly recent experimental observations on helimagnet MnGe, we investigate the critical roles of this compass-type anisotropy in modulating various spin textures of chiral magnets with strong SOC, by Monte Carlo simulations based on a classical Heisenberg spin model with Dzyaloshinsky-Moriya interaction and compass anisotropy. A phase diagram with emergent spin orders in the space of compass anisotropy and out-of-plane magnetic field is presented. In this phase diagram, we propose that a hybrid super-crystal structure consisting of alternating half-skyrmion and half-anti-skyrmion is the possible zero-field ground state of MnGe. The simulated evolution of the spin structure driven by magnetic field is in good accordance with experimental observations on MnGe. Therefore, this Heisenberg spin model successfully captures the main physics responsible for the magnetic structures in MnGe, and the present work may also be instructive to research on the magnetic states in other systems with strong SOC.

  11. Extracting the jet azimuthal anisotropy from higher order cumulants

    CERN Document Server

    Lokhtin, Igor P; Snigirev, A M

    2003-01-01

    We analyze the method for calculation of a coefficient of jet azimuthal anisotropy without reconstruction of the nuclear reaction plane considering the higher order correlators between the azimuthal position of jet axis and the angles of particles not incorporated in the jet. The reliability of this technique in the real physical situation under LHC conditions is illustrated.

  12. AMiBA-array for microwave background anisotropy

    Science.gov (United States)

    Kesteven, M.

    2002-03-01

    AMiBA is a 90 GHz interferometric array of the ASIAA (Academia Sinica, Institue of Astronomy and Astrophysics). It will make a detailed study of the polarization of the CMB anisotropy; it will also undertake a survey of Sunyaev-Zel'dovich clusters. It is under construction at present, with an expected completion date of late 2003. .

  13. Influence of magnetic anisotropy on the superferromagnetic ordering in nanocomposites

    DEFF Research Database (Denmark)

    Mørup, Steen; Christiansen, Gunnar Dan

    1993-01-01

    Magnetic interaction between ultrafine particles may result in superferromagnetism, i.e., ordering of the magnetic moments of particles which would be superparamagnetic if they were noninteracting. In this article we discuss the influence of the magnetic anisotropy on the temperature dependence o...

  14. On the magnetocrystalline anisotropy of greigite (Fe3S4)

    Science.gov (United States)

    Winklhofer, Michael; Chang, Liao; Eder, Stephan H. K.

    2014-04-01

    ferrimagnetic mineral greigite (cubic Fe3S4) is well known as an intracellular biomineralization product in magnetic bacteria and as a widely occurring authigenic mineral in anoxic sediments. Due to the lack of suitable single-crystal specimens, the magnetic anisotropy parameters of greigite have remained poorly constrained, to the point where not even the easy axis of magnetization is known. Here we report on an effort to determine the anisotropy parameters on the basis of ferromagnetic resonance (FMR) powder spectroscopy on hydrothermally synthesized, chemically pure greigite microcrystals dispersed in a nonmagnetic matrix. In terms of easy axis orientations, the FMR data are consistent with or , or less likely, a more general type. With a g factor of 2.09, the anisotropy field is about 90 mT and in some samples may reach 125 mT, compared to 30 mT for cubic magnetite. This confirms the dominating role of cubic anisotropy on the magnetic properties of greigite, which we show to be responsible for large SIRM/k values. K1 is in the range -15 … -23 J/m3 () or +10 … +15 kJ/m3 (), yielding upper limits of 44 or 34 nm for the superparamagnetic grain size, respectively.

  15. On the magnetocrystalline anisotropy of greigite (Fe3S 4)

    NARCIS (Netherlands)

    Winklhofer, M.; Chang, L.; Eder, S.H.K.

    2014-01-01

    The ferrimagnetic mineral greigite (cubic Fe3S4) is well known as an intracellular biomineralization product in magnetic bacteria and as a widely occurring authigenic mineral in anoxic sediments. Due to the lack of suitable single-crystal specimens, the magnetic anisotropy parameters of greigite hav

  16. Giant and Tunable Anisotropy of Nanoscale Friction in Graphene

    Science.gov (United States)

    Almeida, Clara M.; Prioli, Rodrigo; Fragneaud, Benjamin; Cançado, Luiz Gustavo; Paupitz, Ricardo; Galvão, Douglas S.; de Cicco, Marcelo; Menezes, Marcos G.; Achete, Carlos A.; Capaz, Rodrigo B.

    2016-08-01

    The nanoscale friction between an atomic force microscopy tip and graphene is investigated using friction force microscopy (FFM). During the tip movement, friction forces are observed to increase and then saturate in a highly anisotropic manner. As a result, the friction forces in graphene are highly dependent on the scanning direction: under some conditions, the energy dissipated along the armchair direction can be 80% higher than along the zigzag direction. In comparison, for highly-oriented pyrolitic graphite (HOPG), the friction anisotropy between armchair and zigzag directions is only 15%. This giant friction anisotropy in graphene results from anisotropies in the amplitudes of flexural deformations of the graphene sheet driven by the tip movement, not present in HOPG. The effect can be seen as a novel manifestation of the classical phenomenon of Euler buckling at the nanoscale, which provides the non-linear ingredients that amplify friction anisotropy. Simulations based on a novel version of the 2D Tomlinson model (modified to include the effects of flexural deformations), as well as fully atomistic molecular dynamics simulations and first-principles density-functional theory (DFT) calculations, are able to reproduce and explain the experimental observations.

  17. Galactic foreground contribution to the BEAST CMB Anisotropy Maps

    CERN Document Server

    Mejia, J; Burigana, C; Childers, J; Figueiredo, N; Kangas, M; Lubin, P; Maino, D; Mandolesi, N; Marvil, J; Meinhold, P; O'Dwyer, I; O'Neill, H; Platania, P; Seiffert, M; Stebor, N; Tello, C A S; Villela, T; Wandelt, B; Wünsche, C A; Mej\\'{\\i}a, Jorge; Bersanelli, Marco; Burigana, Carlo; Childers, Jeff; Figueiredo, Newton; Kangas, Miikka; Lubin, Philip; Maino, Davide; Mandolesi, Nazzareno; Marvil, Josh; Meinhold, Peter; Dwyer, Ian O'; Neill, Hugh O'; Platania, Paola; Seiffert, Michael; Stebor, Nathan; Tello, Camilo; Villela, Thyrso; Wandelt, Benjamin; Wuensche, Carlos Alexandre

    2004-01-01

    We report limits on the Galactic foreground emission contribution to the Background Emission Anisotropy Scanning Telescope (BEAST) Ka- and Q-band CMB anisotropy maps. We estimate the contribution from the cross-correlations between these maps and the foreground emission templates of an H${\\alpha}$ map, a de-striped version of the Haslam et al. 408 MHz map, and a combined 100 $\\mu$m IRAS/DIRBE map. Our analysis samples the BEAST $\\sim10^\\circ$ declination band into 24 one-hour (RA) wide sectors with $\\sim7900$ pixels each, where we calculate: (a) the linear correlation coefficient between the anisotropy maps and the templates; (b) the coupling constants between the specific intensity units of the templates and the antenna temperature at the BEAST frequencies and (c) the individual foreground contributions to the BEAST anisotropy maps. The peak sector contributions of the contaminants in the Ka-band are of 56.5% free-free with a coupling constant of $8.3\\pm0.4$ $\\mu$K/R, and 67.4% dust with $45.0\\pm2.0$ $\\mu$K/...

  18. The local dust foregrounds in the microwave sky: I. Thermal emission spectra

    OpenAIRE

    Dikarev, V.; Preuss, O.; Solanki, S.; Krueger, H.; Krivov, A

    2009-01-01

    Analyses of the cosmic microwave background (CMB) radiation maps made by the Wilkinson Microwave Anisotropy Probe (WMAP) have revealed anomalies not predicted by the standard inflationary cosmology. In particular, the power of the quadrupole moment of the CMB fluctuations is remarkably low, and the quadrupole and octopole moments are aligned mutually and with the geometry of the Solar system. It has been suggested in the literature that microwave sky pollution by an unidentified dust cloud in...

  19. An exact inflationary solution in the chaotic model with non-minimal coupling

    Institute of Scientific and Technical Information of China (English)

    Liu Xiong-Wei; Yang Shu-Zheng; Chen Shi-Wu; Lin Kai

    2009-01-01

    This paper presents a new exact inflationary solution to the non-minimally coupled scalar field.The inflation The spectral index of the scalar density fluctuations ns is consistent with the result of WMAP3(Wilkinson Microwave Anisotropy Probe 3)for ACDM(Lambda-Cold Dark Matter).This model relaxes the constraint to the quartic coupling constant.And it can enter smoothly into a radiation-dominated stage when inflation ends.

  20. A curved vitrectomy probe.

    Science.gov (United States)

    Chalam, K V; Shah, Vinay A; Tripathi, Ramesh C

    2004-01-01

    A curved vitrectomy probe for better accessibility of the peripheral retina in phakic eyes is described. The specially designed curved vitrectomy probe has a 20-gauge pneumatic cutter. The radius of curvature at the shaft is 19.4 mm and it is 25 mm long. The ora serrata is accessed through a 3.0- or 4.0-mm sclerotomy in phakic eyes without touching the crystalline lens. Use of this instrument avoids inadvertent trauma to the clear lens in phakic eyes requiring vitreous base excision. This curved vitrectomy instrument complements wide-angle viewing systems and endoscopes for safe surgical treatment of peripheral retinal pathology in phakic eyes. PMID:15185799

  1. Magnetism of One-Dimensional Dipolar-Interaction Spin Chains with Perpendicular Anisotropy*

    Institute of Scientific and Technical Information of China (English)

    ZHANG Kai-Cheng; ZHU Yan

    2011-01-01

    We have investigated the magnetism of one-dimensional dipolar-interaction spin chains with perpendicular anisotropy by simulation.The behaviors of the magnetizations and the orientation correlations change dramatically as the anisotropy increases to the critical value.The domain length can be controlled by adjusting the temperature and the external field as well as the anisotropy.These properties are interesting and arise from the competition between the anisotropy and the interaction along the chain.

  2. Anisotropy in broad component of H$\\alpha$ line in the magnetospheric device RT-1

    CERN Document Server

    Kawazura, Yohei; Yoshida, Zensho; Nishiura, Masaki; Nogami, Tomoaki; Kashyap, Ankur; Yano, Yoshihisa; Saitoh, Haruhiko; Yamasaki, Miyuri; Mushiake, Toshiki; Nakatsuka, Masataka

    2016-01-01

    Temperature anisotropy in broad component of H$\\alpha$ line was found in the ring trap 1 (RT-1) device by Doppler spectroscopy. Since hot hydrogen neutrals emitting a broad component are mainly produced by charge exchange between neutrals and protons, the anisotropy in the broad component is the evidence of proton temperature anisotropy generated by betatron acceleration.

  3. Probing the Solar System

    Science.gov (United States)

    Wilkinson, John

    2013-01-01

    Humans have always had the vision to one day live on other planets. This vision existed even before the first person was put into orbit. Since the early space missions of putting humans into orbit around Earth, many advances have been made in space technology. We have now sent many space probes deep into the Solar system to explore the planets and…

  4. One-Probe Search

    DEFF Research Database (Denmark)

    Östlin, Anna; Pagh, Rasmus

    2002-01-01

    We consider dictionaries that perform lookups by probing a single word of memory, knowing only the size of the data structure. We describe a randomized dictionary where a lookup returns the correct answer with probability 1 - e, and otherwise returns don't know. The lookup procedure uses an expan...

  5. Anisotropy above and below the subducting Nazca lithosphere

    Science.gov (United States)

    MacDougall, J. G.; Fischer, K. M.; Anderson, M. L.; Kincaid, C. R.

    2011-12-01

    The goal of this study is to constrain mantle flow above and below the subducting Nazca plate at latitudes of 30°-41° S. In this segment of the South American subduction zone, slab dip varies from flat slab subduction in the north to a dip of ~40° in the south, where the segment ends at a slab gap associated with Chile Ridge. We measured shear-wave splitting in over 280 S arrivals from local earthquakes recorded by the 2010 Chile RAMP IRIS/PASSCAL array (aftershock locations from Lange et al., 2010), the 2000-2002 CHARGE IRIS/PASSCAL array, and permanent stations PLCA (USGS/GTSN) and PEL (Geoscope). We also resolved splitting in 17 SK(K)S phases at PLCA and permanent station TRQA (IRIS/GSN). Splitting parameters for a subset of phases were determined using a range of filters; most were stable as a function of frequency. The results reported below correspond to a 0.05-2 Hz bandpass filter. Local S lag times range from 0.1-0.9 seconds. For back-arc stations above the area of steep subduction, lag times correlate with path length in the mantle wedge, indicating that wedge anisotropy dominates. Lag times from the Chile RAMP stations, which are located in the forearc between 33°S and 39°S and in general correspond to shorter paths, span a narrower range (0.1-0.4 seconds). Splitting fast polarizations at back-arc stations show a coherent variation with latitude. Fast polarizations vary from NE at 40°-41°S, to N (roughly slab-strike parallel) at 35°-36°S, to NE-ESE at 30°-33°S, curving as the slab flattens. Modeling of these local S splitting results reveals that the fast symmetry axis of anisotropy is sub-parallel to the overall trend of fast polarization directions at each station, and that the strength of anisotropy is equivalent to 10-30% of single crystal olivine anisotropy. At forearc stations, we observe roughly trench-parallel fast polarization directions (largely N-NE) with the exception of two areas of localized, yet robust trench-normal trends (E

  6. Stress, strain rate and anisotropy in Kyushu, Japan

    Science.gov (United States)

    Savage, M. K.; Aoki, Y.; Unglert, K.; Ohkura, T.; Umakoshi, K.; Shimizu, H.; Iguchi, M.; Tameguri, T.; Ohminato, T.; Mori, J.

    2016-04-01

    Seismic anisotropy, the directional dependence of wave speeds, may be caused by stress-oriented cracks or by strain-oriented minerals, yet few studies have quantitatively compared anisotropy to stress and strain over large regions. Here we compare crustal stress and strain rates on the Island of Kyushu, Japan, as measured from inversions of focal mechanisms, GPS and shear wave splitting. Over 85,000 shear wave splitting measurements from local and regional earthquakes are obtained from the NIED network between 2004 and 2012, and on Aso, Sakurajima, Kirishima and Unzen volcano networks. Strain rate measurements are made from the Japanese Geonet stations. JMA-determined S arrival times processed with the MFAST shear wave splitting code measure fast polarisations (Φ), related to the orientation of the anisotropic medium and time delays (dt), related to the path length and the percent anisotropy. We apply the TESSA 2-D delay time tomography and spatial averaging code to the highest quality events, which have nearly vertical incidence angles, separating the 3455 shallow (depth = 40 km) earthquakes. Using square grids with 30 km sides for all the inversions, the best correlations are observed between splitting from shallow earthquakes and stress. Axes of maximum horizontal stress (SHmax) and Φ correlate with a coefficient c of 0.56, significant at the 99% confidence level. Their mean difference is 31.9°. Axes of maximum compressional strain rate and SHmax are also well aligned, with an average difference of 28°, but they do not correlate with each other, meaning that where they differ, the difference is not systematic. Anisotropy strength is negatively correlated with the stress ratio parameter determined from focal mechanism inversion (c = - 0.64; significant at the 99% confidence level). The anisotropy and stress results are consistent with stress-aligned microcracks in the crust in a dominantly strike-slip regime. Eigenvalues of maximum horizontal strain rate

  7. Downscaling Smooth Tomographic Models: Separating Intrinsic and Apparent Anisotropy

    Science.gov (United States)

    Bodin, Thomas; Capdeville, Yann; Romanowicz, Barbara

    2016-04-01

    In recent years, a number of tomographic models based on full waveform inversion have been published. Due to computational constraints, the fitted waveforms are low pass filtered, which results in an inability to map features smaller than half the shortest wavelength. However, these tomographic images are not a simple spatial average of the true model, but rather an effective, apparent, or equivalent model that provides a similar 'long-wave' data fit. For example, it can be shown that a series of horizontal isotropic layers will be seen by a 'long wave' as a smooth anisotropic medium. In this way, the observed anisotropy in tomographic models is a combination of intrinsic anisotropy produced by lattice-preferred orientation (LPO) of minerals, and apparent anisotropy resulting from the incapacity of mapping discontinuities. Interpretations of observed anisotropy (e.g. in terms of mantle flow) requires therefore the separation of its intrinsic and apparent components. The "up-scaling" relations that link elastic properties of a rapidly varying medium to elastic properties of the effective medium as seen by long waves are strongly non-linear and their inverse highly non-unique. That is, a smooth homogenized effective model is equivalent to a large number of models with discontinuities. In the 1D case, Capdeville et al (GJI, 2013) recently showed that a tomographic model which results from the inversion of low pass filtered waveforms is an homogenized model, i.e. the same as the model computed by upscaling the true model. Here we propose a stochastic method to sample the ensemble of layered models equivalent to a given tomographic profile. We use a transdimensional formulation where the number of layers is variable. Furthermore, each layer may be either isotropic (1 parameter) or intrinsically anisotropic (2 parameters). The parsimonious character of the Bayesian inversion gives preference to models with the least number of parameters (i.e. least number of layers, and

  8. The influence of anisotropy on preferential flow in landslides

    Science.gov (United States)

    Cristiano, Elena; Barontini, Stefano; Bogaard, Thom A.; Shao, Wei

    2015-04-01

    Infiltration is one of the most important landslides triggering mechanisms and it is controlled by the hydraulic characteristics of the soil, which depends on the degree of saturation, the existence of preferential flow paths and by anisotropy. Many soils, indeed, exhibit a certain degree of anisotropy due to the stratification associated with soil forming process. Recently, various authors investigated the effect of rainfall in layered soils and its effect on rainfall triggered landslides by means of experimental, conceptual, numerical and theoretical approaches. However, the combined effect of anisotropy and preferential flow on infiltration process and related to rainfall induced landslides has, according to the authors best knowledge, not been studied yet. Aiming at better understanding the soil hydrological processes which take place during an infiltration process, the stability of a synthetic hill slope is numerically investigated. The geometry we considered for the model is a slope with two different layers: the upper soil layer consists of sandy loam, while the lower soil layer is made out of clay. The geometry was studied using both a single permeability and a dual permeability model. In the first case the hydraulic conductivity at saturation was considered isotropic, equal in all directions. Then the vertical component of the hydraulic conductivity tensor at saturation was reduced, while in the third scenario the horizontal component was reduced. In this way the anisotropy effects on both the principal directions were studied. In the dual permeability model, the influence of the anisotropy was considered only in the preferential flow domain, and the hydraulic conductivity at saturation of the soil matrix domain was defined as being isotropic. In order to evaluate also the effects of rainfall intensity on the slope, two different rainfall events were studied: a low intensity rainfall with a long time duration (2 mmh-1,150 h) and an high intensity rainfall

  9. Spectroscopic ellipsometry investigations of optical anisotropy in obliquely deposited hafnia thin films

    Science.gov (United States)

    Tokas, R. B.; Jena, Shuvendu; Haque, S. Maidul; Rao, K. Divakar; Thakur, S.; Sahoo, N. K.

    2016-05-01

    In present work, HfO2 thin films have been deposited at various oblique incidences on Si substrates by electron beam evaporation. These refractory oxide films exhibited anisotropy in refractive index predictably due to special columnar microstructure. Spectroscopic ellipsometry being a powerful tool for optical characterization has been employed to investigate optical anisotropy. It was observed that the film deposited at glancing angle (80°) exhibits the highest optical anisotropy. Further, anisotropy was noticed to decrease with lower values of deposition angles while effective refractive index depicts opposite trend. Variation in refractive index and anisotropy has been explained in light of atomic shadowing during growth of thin films at oblique angles.

  10. Anisotropy magnetic susceptibility measurements of vulcanic rock from merapi mountain in central Java

    International Nuclear Information System (INIS)

    Anisotropy Magnetic susceptibility indicated a differences of Magnetic susceptibility value of a sample due to the direction or orientation of magnetic field on it. The 22 sample's were taken from lour area around Merapi mountain in central Java and their Anisotropy Magnetic susceptibility were measured by using MS2 Bartington. The 22 sample's shown a high susceptibility value about 8037.5 x 105. Eleven sample's have high anisotropy ( it's anisotropy degree about 16% ). The rest of the sample have an anisotropy degree less than 6% (sample's from pasar bubar, Kali Kuning, Kali Gendong, Kali Gendol Utara). This result give an indication that a part of the sample's can be used for paleomagnetic

  11. Cleavable DNA-protein hybrid molecular beacon: A novel efficient signal translator for sensitive fluorescence anisotropy bioassay.

    Science.gov (United States)

    Hu, Pan; Yang, Bin

    2016-01-15

    Due to its unique features such as high sensitivity, homogeneous format, and independence on fluorescent intensity, fluorescence anisotropy (FA) assay has become a hotspot of study in oligonucleotide-based bioassays. However, until now most FA probes require carefully customized structure designs, and thus are neither generalizable for different sensing systems nor effective to obtain sufficient signal response. To address this issue, a cleavable DNA-protein hybrid molecular beacon was successfully engineered for signal amplified FA bioassay, via combining the unique stable structure of molecular beacon and the large molecular mass of streptavidin. Compared with single DNA strand probe or conventional molecular beacon, the DNA-protein hybrid molecular beacon exhibited a much higher FA value, which was potential to obtain high signal-background ratio in sensing process. As proof-of-principle, this novel DNA-protein hybrid molecular beacon was further applied for FA bioassay using DNAzyme-Pb(2+) as a model sensing system. This FA assay approach could selectively detect as low as 0.5nM Pb(2+) in buffer solution, and also be successful for real samples analysis with good recovery values. Compatible with most of oligonucleotide probes' designs and enzyme-based signal amplification strategies, the molecular beacon can serve as a novel signal translator to expand the application prospect of FA technology in various bioassays.

  12. Cleavable DNA-protein hybrid molecular beacon: A novel efficient signal translator for sensitive fluorescence anisotropy bioassay.

    Science.gov (United States)

    Hu, Pan; Yang, Bin

    2016-01-15

    Due to its unique features such as high sensitivity, homogeneous format, and independence on fluorescent intensity, fluorescence anisotropy (FA) assay has become a hotspot of study in oligonucleotide-based bioassays. However, until now most FA probes require carefully customized structure designs, and thus are neither generalizable for different sensing systems nor effective to obtain sufficient signal response. To address this issue, a cleavable DNA-protein hybrid molecular beacon was successfully engineered for signal amplified FA bioassay, via combining the unique stable structure of molecular beacon and the large molecular mass of streptavidin. Compared with single DNA strand probe or conventional molecular beacon, the DNA-protein hybrid molecular beacon exhibited a much higher FA value, which was potential to obtain high signal-background ratio in sensing process. As proof-of-principle, this novel DNA-protein hybrid molecular beacon was further applied for FA bioassay using DNAzyme-Pb(2+) as a model sensing system. This FA assay approach could selectively detect as low as 0.5nM Pb(2+) in buffer solution, and also be successful for real samples analysis with good recovery values. Compatible with most of oligonucleotide probes' designs and enzyme-based signal amplification strategies, the molecular beacon can serve as a novel signal translator to expand the application prospect of FA technology in various bioassays. PMID:26592607

  13. Crustal anisotropy of Taihang Mountain Range using azimuthal variation of receiver functions

    Institute of Scientific and Technical Information of China (English)

    TIAN Bao-feng; LI Juan; YAO Zhen-xing

    2008-01-01

    We discussed the possibility of studying crust anisotropy by analyzing azimuthal variation of the receiver functions and presented a technique for computing the transmission response of a flat-layered medium with arbitrarily ori- ented hexagonally symmetric anisotropy using the reflectivity algorithm. Using this method we investigated the crust anisotropy of Taihang Mountain Range (TMR). Our result shows that there is significant anisotropy with a slow symmetry axis in the upper crust and a fast symmetry axis in the lower crust. The anisotropy magnitude of about 8%~15% is found in the upper crust and a smaller magnitude of about 3%~5% in the lower crust. Orienta- tion of the symmetry axes and the depth of anisotropy appearance as deduced from the seismic records of four individual seismic stations are different from each other. The crust anisotropy beneath the four stations may be associated with the local crustal fabrics in a small area.

  14. Monte Carlo simulations of medium-scale CMB anisotropy

    CERN Document Server

    Kogut, A J

    1996-01-01

    Recent detections of cosmic microwave background (CMB) anisotropy at half-degree angular scales show considerable scatter in the reported amplitude even at similar angular resolution. We use Monte Carlo techniques to simulate the current set of medium-scale CMB observations, including all relevant aspects of sky coverage and measurement technique. The scatter in the reported amplitudes is well within the range expected for the standard cold dark matter (CDM) cosmological model, and results primarily from the restricted sky coverage of each experiment. Within the context of standard CDM current observations of CMB anisotropy support the detection of a ``Doppler peak'' in the CMB power spectrum consistent with baryon density 0.01 < Omega_b < 0.13 (95% confidence) for Hubble constant H_0 = 50 km/s/Mpc. The uncertainties are approximately evenly divided between instrument noise and cosmic variance arising from the limited sky coverage.

  15. Effects of plastic anisotropy on crack-tip behaviour

    DEFF Research Database (Denmark)

    Legarth, Brian Nyvang; Tvergaard, Viggo; Kuroda, Mitsutoshi

    2002-01-01

    For a crack in a homogeneous material the effect of plastic anisotropy on crack-tip blunting and on the near-tip stress and strain fields is analyzed numerically. The full finite strain analyses are carried out for plane strain under small scale yielding conditions, with purely symmetric mode I...... loading remote from the crack-tip. In cases where the principal axes of the anisotropy are inclined to the plane of the crack it is found that the plastic zones as well as the stress and strain fields just around the blunted tip of the crack become non-symmetric. In these cases the peak strain...... on the blunted tip occurs off the center line of the crack, thus indicating that the crack may want to grow in a different direction. When the anisotropic axes are parallel to the crack symmetry is retained, but the plastic zones and the near-tip fields still differ from those predicted by standard isotropic...

  16. 3D analyses of cavitation instabilities accounting for plastic anisotropy

    DEFF Research Database (Denmark)

    Legarth, Brian Nyvang; Tvergaard, Viggo

    2010-01-01

    , and the main focus is on the effect of different degrees of plastic anisotropy. Loading cases are considered, where all the macroscopic principal stresses differ. The numerical quasi‐static solutions are obtained by a full transient analysis of the equations of motion, in which the loading is applied so slowly......Full three dimensional cell model analyses are carried out for a solid containing a single small void, in order to determine the critical stress levels for the occurrence of cavitation instabilities. The material models applied are elastic‐viscoplastic, with a small rate‐hardening exponent...... that the quasi‐static solution is well approximated. A special procedure is used to strongly reduce the loading rate a little before the instability occurs. It is found that plastic anisotropy has a significant effect on the level of the critical stress for cavitation instabilities....

  17. CMB anisotropy induced by tachyonic perturbations of dark energy

    CERN Document Server

    Libanov, M V; Sazhina, O S; Sazhin, M V

    2008-01-01

    We study effects of possible tachyonic perturbations of dark energy on the CMB temperature anisotropy. Motivated by some models of phantom energy, we consider both Lorentz-invariant and Lorentz-violating dispersion relations for tachyonic perturbations. We show that in the Lorentz-violating case, the shape of the CMB anisotropy spectrum generated by the tachyonic perturbations is very different from that due to adiabatic scalar perturbations and, if sizeable, it would be straightforwardly distinguished from the latter. The tachyonic contribution improves slightly the agreement between the theory and data; however, this improvement is not statistically significant, so our analysis results in limits on the time scale of the tachyonic instability. In the Lorentz-invariant case, tachyonic contribution is a rapidly decaying function of the multipole number $l$, so that the entire observed dipole can be generated without conflicting the data at higher multipoles. On the conservative side, our comparison with the da...

  18. Plastic anisotropy of straight and cross rolled molybdenum sheets

    Energy Technology Data Exchange (ETDEWEB)

    Oertel, C.-G. [Institut fuer Strukturphysik, Technische Universitaet Dresden, D-01062 Dresden (Germany)], E-mail: oertel@physik.tu-dresden.de; Huensche, I.; Skrotzki, W. [Institut fuer Strukturphysik, Technische Universitaet Dresden, D-01062 Dresden (Germany); Knabl, W.; Lorich, A.; Resch, J. [PLANSEE Metall GmbH, A-6600 Reutte, Tyrol (Austria)

    2008-06-15

    The microstructure, texture and mechanical properties of molybdenum sheets produced by different rolling processes were investigated by orientation imaging in the scanning electron microscope, X-ray diffraction and tensile tests, respectively. For comparable recrystallization degree of the sheets investigated, straight rolling with low reduction ratio produces {alpha}-fiber textures with a maximum at {l_brace}100{r_brace} <110>. At higher rolling degrees the maximum shifts to {l_brace}112{r_brace} <110>. Cross rolling increases the rotated cube component {l_brace}100{r_brace} <110>. The strong differences in the texture measured are reflected in the plastic anisotropy characterized by differences in the yield stress and Lankford parameter which were measured along directions in the rolling plane at angles of 0 deg., 45 deg. and 90 deg. with the rolling direction. The Taylor-Bishop-Hill theory is used successfully to qualitatively explain the plastic anisotropy.

  19. Large scale cosmic-ray anisotropy with KASCADE

    CERN Document Server

    Antoni, T; Badea, A F; Bekk, K; Bercuci, A; Blümer, H; Bozdog, H; Brancus, I M; Büttner, C; Daumiller, K; Doll, P; Engel, R; Engler, J; Fessler, F; Gils, H J; Glasstetter, R; Haungs, A; Heck, D; Hörandel, J R; Kampert, K H; Klages, H O; Maier, G; Mathes, H J; Mayer, H J; Milke, J; Müller, M; Obenland, R; Oehlschläger, J; Ostapchenko, S; Petcu, M; Rebel, H; Risse, A; Risse, M; Roth, M; Schatz, G; Schieler, H; Scholz, J; Thouw, T; Ulrich, H; Van, J; Buren; Vardanyan, A S; Weindl, A; Wochele, J; Zabierowski, J

    2004-01-01

    The results of an analysis of the large scale anisotropy of cosmic rays in the PeV range are presented. The Rayleigh formalism is applied to the right ascension distribution of extensive air showers measured by the KASCADE experiment.The data set contains about 10^8 extensive air showers in the energy range from 0.7 to 6 PeV. No hints for anisotropy are visible in the right ascension distributions in this energy range. This accounts for all showers as well as for subsets containing showers induced by predominantly light respectively heavy primary particles. Upper flux limits for Rayleigh amplitudes are determined to be between 10^-3 at 0.7 PeV and 10^-2 at 6 PeV primary energy.

  20. Backscatter, anisotropy, and polarization of solar hard X-rays

    Science.gov (United States)

    Bai, T.; Ramaty, R.

    1978-01-01

    The problems of anisotropy, polarization, center-to-limb variation of the X-ray spectrum, and Compton backscatter are investigated in a study of solar hard X-rays. Effect of backscatter are found particularly important for anisotropic sources which emit hard X-rays predominantly toward the photosphere; for such anisotropic primary X-ray sources, the observed X-ray flux near 30 keV does not depend significantly on the position of the flare. In addition, the degree of polarization of the sum of the primary and reflected X-rays with energies in the 15 to 30 keV range may be as high as 30%. Determination of the height and anisotropy of the primary X-ray sources from study of the albedo patch is also discussed.

  1. Three-dimensional mapping of single-atom magnetic anisotropy.

    Science.gov (United States)

    Yan, Shichao; Choi, Deung-Jang; Burgess, Jacob A J; Rolf-Pissarczyk, Steffen; Loth, Sebastian

    2015-03-11

    Magnetic anisotropy plays a key role in the magnetic stability and spin-related quantum phenomena of surface adatoms. It manifests as angular variations of the atom's magnetic properties. We measure the spin excitations of individual Fe atoms on a copper nitride surface with inelastic electron tunneling spectroscopy. Using a three-axis vector magnet we rotate the magnetic field and map out the resulting variations of the spin excitations. We quantitatively determine the three-dimensional distribution of the magnetic anisotropy of single Fe atoms by fitting the spin excitation spectra with a spin Hamiltonian. This experiment demonstrates the feasibility of fully mapping the vector magnetic properties of individual spins and characterizing complex three-dimensional magnetic systems.

  2. Structural Anisotropy in Polar Fluids Subjected to Periodic Boundary Conditions

    Science.gov (United States)

    2011-01-01

    A heuristic model based on dielectric continuum theory for the long-range solvation free energy of a dipolar system possessing periodic boundary conditions (PBCs) is presented. The predictions of the model are compared to simulation results for Stockmayer fluids simulated using three different cell geometries. The boundary effects induced by the PBCs are shown to lead to anisotropies in the apparent dielectric constant and the long-range solvation free energy of as much as 50%. However, the sum of all of the anisotropic energy contributions yields a value that is very close to the isotropic one derived from dielectric continuum theory, leading to a total system energy close to the dielectric value. It is finally shown that the leading-order contribution to the energetic and structural anisotropy is significantly smaller in the noncubic simulation cell geometries compared to when using a cubic simulation cell. PMID:22303290

  3. Non-elliptic wavevector anisotropy for magnetohydrodynamic turbulence

    Science.gov (United States)

    Narita, Y.

    2015-11-01

    A model of non-elliptic wavevector anisotropy is developed for the inertial-range spectrum of magnetohydrodynamic turbulence and is presented in the two-dimensional wavevector domain spanning the directions parallel and perpendicular to the mean magnetic field. The non-elliptic model is a variation of the elliptic model with different scalings along the parallel and the perpendicular components of the wavevectors to the mean magnetic field. The non-elliptic anisotropy model reproduces the smooth transition of the power-law spectra from an index of -2 in the parallel projection with respect to the mean magnetic field to an index of -5/3 in the perpendicular projection observed in solar wind turbulence, and is as competitive as the critical balance model to explain the measured frequency spectra in the solar wind. The parameters in the non-elliptic spectrum model are compared with the solar wind observations.

  4. Effect of anisotropy on HBT radii using leptonpair interferometry

    CERN Document Server

    Mohanty, Payal; Roy, Pradip K

    2014-01-01

    The effect of initial state momentum-space anisotropy on invariant mass dependence of HBT radii extracted from the leptonpair interferometry is presented here. We have studied the Bose-Einstein Correlation Function (BECF) for two identical virtual photons decaying to leptonpairs at most central collision of LHC energy having fixed transverse momentum of one of the virtual photons ($k_{1T}$= 2 GeV). The {\\em free streaming interpolating} model with fixed initial condition has been used for the evolution in anisotropic Quark Gluon Plasma (aQGP) and the relativistic (1+2)d hydrodynamics model with cylindrical symmetry and longitudinal boost invariance has been used for both isotropic Quark Gluon Plasma (iQGP) and hadronic phases. We found a significant change in the spatial and temporal dimension of the evolving system in presence of initial state momentum-space anisotropy.

  5. Large scale anisotropy studies with the Pierre Auger Observatory

    Energy Technology Data Exchange (ETDEWEB)

    Bonino, R., E-mail: rbonino@to.infn.it [Istituto Nazionale di Astrofisica - IFSI, c.so Fiume 4, 10133 Torino (Italy); INFN sezione di Torino, v. P. Giuria 1, 10125 Torino (Italy)

    2012-11-11

    Completed at the end of 2008, the Pierre Auger Observatory has been continuously operating for more than seven years. We present here the analysis techniques and the results about the search for large scale anisotropies in the sky distribution of cosmic rays, reporting both the phase and the amplitude measurements of the first harmonic modulation in right ascension in different energy ranges above 2.5 Multiplication-Sign 10{sup 17} eV. Thanks to the collected statistics, a sensitivity of 1% at EeV energies can be reached. No significant anisotropies have been observed, upper limits on the amplitudes have been derived and are here compared with the results of previous experiments and with some theoretical expectations.

  6. Large scale anisotropy studies with the Pierre Auger Observatory

    Science.gov (United States)

    Bonino, R.

    2012-11-01

    Completed at the end of 2008, the Pierre Auger Observatory has been continuously operating for more than seven years. We present here the analysis techniques and the results about the search for large scale anisotropies in the sky distribution of cosmic rays, reporting both the phase and the amplitude measurements of the first harmonic modulation in right ascension in different energy ranges above 2.5×1017 eV. Thanks to the collected statistics, a sensitivity of 1% at EeV energies can be reached. No significant anisotropies have been observed, upper limits on the amplitudes have been derived and are here compared with the results of previous experiments and with some theoretical expectations.

  7. Anisotropy minimization via least squares method for transformation optics.

    Science.gov (United States)

    Junqueira, Mateus A F C; Gabrielli, Lucas H; Spadoti, Danilo H

    2014-07-28

    In this work the least squares method is used to reduce anisotropy in transformation optics technique. To apply the least squares method a power series is added on the coordinate transformation functions. The series coefficients were calculated to reduce the deviations in Cauchy-Riemann equations, which, when satisfied, result in both conformal transformations and isotropic media. We also present a mathematical treatment for the special case of transformation optics to design waveguides. To demonstrate the proposed technique a waveguide with a 30° of bend and with a 50% of increase in its output width was designed. The results show that our technique is simultaneously straightforward to be implement and effective in reducing the anisotropy of the transformation for an extremely low value close to zero.

  8. Deciphering the Dipole Anisotropy of Galactic Cosmic Rays

    CERN Document Server

    Ahlers, Markus

    2016-01-01

    Recent measurements of the dipole anisotropy in the arrival directions of Galactic cosmic rays (CRs) indicate a strong energy dependence of the dipole amplitude and phase in the TeV-PeV range. We argue here that these observations can be well understood within standard diffusion theory as a combined effect of (i) one or more local sources at Galactic longitude 120deg < l < 300deg dominating the CR gradient below 0.1-0.3 PeV, (ii) the presence of a strong ordered magnetic field in our local environment, (iii) the relative motion of the solar system, and (iv) the limited reconstruction capabilities of ground-based observatories. We show that an excellent candidate of the local CR source responsible for the dipole anisotropy at 1-100 TeV is the Vela supernova remnant.

  9. Controlling magnetic anisotropy in epitaxial FePt(001) films

    International Nuclear Information System (INIS)

    Epitaxial equiatomic Fe50Pt50 thin films with a variable order parameter ranging from 0 to 0.9 and Fe100-xPtx thin films with x ranging from 33 to 50 were deposited on MgO (001) substrates by dc sputtering. A seed layer consisting of nonmagnetic Cr (4 nm)/Pt (12 nm) was used to promote the crystallinity of the magnetic films. The crystal structure and magnetic properties were gauged using x-ray diffraction and magnetometry. The magnetic anisotropy can be controlled by changing the order parameter. For Fe100-xPtx films, the increase in Fe composition leads to an increase in coercivity in the hard axis loop and causes a loss of perpendicular anisotropy.

  10. Lateral-drag Casimir forces induced by anisotropy

    CERN Document Server

    Nefedov, Igor S

    2016-01-01

    We predict the existence of lateral drag forces near the flat surface of an absorbing slab of an anisotropic material. The forces originate from the fluctuations of the electromagnetic field, when the anisotropy axis of the material forms a certain angle with the surface. In this situation, the spatial spectra of the fluctuating electromagnetic fields becomes asymmetric, different for positive and negative transverse wave vectors components. Differently from the case of van der Waals interactions in which the forward-backward symmetry is broken due to the particle movement or in quantum noncontact friction where it is caused by the mutual motion of the bodies, in our case the lateral motion results merely from the anisotropy of the slab. This new effect, of particular significance in hyperbolic materials, could be used for the manipulation of nanoparticles.

  11. Dynamical Condensation in a Holographic Superconductor Model with Anisotropy

    CERN Document Server

    Bai, Xiaojian; Park, Miok; Sunly, Khimphun

    2014-01-01

    We study dynamical condensation process in a holographic superconductor model with anisotropy. The time-dependent numerical solution is constructed for the Einstein-Maxwell-dilaton theory with complex scalar in asymptotic AdS spacetime. The introduction of dilaton field generates the anisotropy in boundary spatial directions. In analogy of isotropic case, we have two black hole solutions below certain critical temperature $T_c$, the anisotropic charged black hole with and without scalar hair, corresponding respectively to the supercooled normal phase and superconducting phase in the boundary theory. The instability of the supercooled anisotropic black hole will drive a small perturbation of the scalar field to rise exponentially, until the final stable hairy black hole configuration is reached. Via AdS/CFT correspondence, we extract time evolution of the condensate operator and anisotropic pressure of the boundary system. Both of them experience exponential growth and subsequent saturation, but with different...

  12. Mechanical behaviour of ferritic ODS steels - Temperature dependancy and anisotropy

    Science.gov (United States)

    Fournier, B.; Steckmeyer, A.; Rouffie, A.-L.; Malaplate, J.; Garnier, J.; Ratti, M.; Wident, P.; Ziolek, L.; Tournie, I.; Rabeau, V.; Gentzbittel, J. M.; Kruml, T.; Kubena, I.

    2012-11-01

    Ferritic 14%Cr and 18%Cr ODS steels produced at CEA in round bars or plates were tested mechanically. The present paper reports results obtained in tension, impact, fatigue, creep and toughness tests. These tests were carried out at various temperatures and in different directions. These materials show a pronounced anisotropy at all tested temperatures. No matter the loading, the transversal direction is always found to be far less resistant than the longitudinal one. This anisotropy is mainly observed in terms of damage mechanisms, with intergranular fracture preferentially occurring along the extrusion direction. This intergranular fracture mode leads to very low and anisotropic toughness values and to the absence of tertiairy creep stage, pointing out the unstable nature of fracture, even at high temperature. The unrealistically high values of the Norton exponent measured in creep suggests the existence of a threshold stress, which is consistent with the mainly kinematic nature of the stress as revealed by fatigue tests.

  13. Anisotropies in the cosmic microwave background an analytic approach

    CERN Document Server

    Hu, W; Wayne Hu; Naoshi Sugiyama

    1994-01-01

    We introduce a simple yet powerful {\\it analytic} method which obtains the structure of cosmic microwave background anisotropies to better than 5-10\\% in temperature fluctuations on {\\it all} scales. It is applicable to {\\it any} model in which the potential fluctuations at recombination are both linear and known. Moreover, it recovers and explains the presence of the ``Doppler peaks'' at degree scales as {\\it driven} acoustic oscillations of the photon-baryon fluid. We treat in detail such subtleties as the time dependence of the gravitational driving force, anisotropic stress from the neutrino quadrupole, and damping during the recombination process, again all from an analytic standpoint. We apply this formalism to the standard cold dark matter model to gain physical insight into the anisotropies, including the dependence of the peak locations and heights on cosmological parameters such as \\Omega_b and h, as well as model parameters such as the ionization history. Damping due to the finite thickness of the ...

  14. Optimization of artificial flockings by means of anisotropy measurements

    CERN Document Server

    Makiguchi, Motohiro

    2010-01-01

    An effective procedure to determine the optimal parameters appearing in artificial flockings is proposed in terms of optimization problems. We numerically examine genetic algorithms (GAs) to determine the optimal set of such parameters such as the weights for three essential interactions in BOIDS by Reynolds (1987) under `zero-collision' and `no-breaking-up' constraints. As a fitness function (the energy function) to be maximized by the GA, we choose the so-called the $\\textyen gamma$-value of anisotropy which can be observed empirically in typical flocks of starling. We confirm that the GA successfully finds the solution having a large $\\textyen gamma$-value leading-up to a strong anisotropy. The numerical experience shows that the procedure might enable us to make more realistic and efficient artificial flocking of starling even in our personal computers.

  15. Differential expansion of space and the Hubble flow anisotropy

    CERN Document Server

    Bolejko, Krzysztof; Wiltshire, David L

    2015-01-01

    The Universe on scales $10-100~h^{-1}$ Mpc is dominated by a cosmic web of voids, filaments, sheets and knots of galaxy clusters. These structures participate differently in the global expansion of the Universe: from non-expanding clusters to the above average expansion rate of voids. In this paper we characterize Hubble expansion anisotropies in the COMPOSITE sample of 4534 galaxies and clusters. We concentrate on the dipole and quadrupole in the rest frame of the Local Group. These both have statistically significant amplitudes. These anisotropies, and their redshift dependence, cannot be explained solely by a boost of the Local Group in the Friedmann-Lema\\^{i}tre-Robertson-Walker (FLRW) model which expands isotropically in the rest frame of the cosmic microwave background (CMB) radiation. We simulate the local expansion of the Universe with inhomogeneous Szekeres models, which match the standard FLRW model on $> 100~ h^{-1}$ Mpc scales but exhibit nonkinematic differential expansion on small scales. We res...

  16. ATA probe beam experiment

    International Nuclear Information System (INIS)

    The philosophy of these tests is to measure the motion of a low current, small diameter electron beam in the accelerator before running high current. By using low current, we can study particle motion in the applied fields without any extra complications associated with the self-forces of high currents. With the steering magnets off, we have measured the transverse drift of the probe beam. Also, we have used the probe beam to optimize the current in the steering magnets to compensate for the drift. There have been concurrent efforts to locate the source of the error field which is presumed to cause the drift. So far, the source has not been established but the search is continuing

  17. Scanning Probe Microscopy and Spectroscopy

    Science.gov (United States)

    Wiesendanger, Roland

    1994-09-01

    Preface; List of acronyms; Introduction; Part I. Experimental Methods and Theoretical Background of Scanning Probe Microscopy and Spectroscopy: 1. Scanning tunnelling microscopy; 2. Scanning force microscopy; 3. Related scanning probe techniques; Part II. Applications of Scanning Probe Microscopy and Spectroscopy: 4. Condensed matter physics; 5. Chemistry; 6. Organic materials; 7. Metrology and standards; 8. Nanotechnology; References; Index.

  18. Ultrasonic temperature measuring probe

    International Nuclear Information System (INIS)

    The temperature measuring probe made of sensor wire and the tube encasing it is suited for being used in fuel columns at temperatures above 20000C. The thermal expansion coefficient, the linear dimensions, and the fastening points are chosen in such manner that the temperature fluctuations occuring during operation produce such relative variations in length that formation of bridges between sensor wire and encasing tube are suppressed already in the initial stage. (DG) 891 HP/DG 892 MKO

  19. Artificially engineered Heusler ferrimagnetic superlattice exhibiting perpendicular magnetic anisotropy

    OpenAIRE

    Q. L. Ma; Zhang, X. M.; Miyazaki, T.; Mizukami, S.

    2015-01-01

    To extend density limits in magnetic recording industry, two separate strategies were developed to build the storage bit in last decade, introduction of perpendicular magnetic anisotropy (PMA) and adoption of ferrimagnetism/antiferromagnetism. Meanwhile, these properties significantly improve device performance, such as reducing spin-transfer torque energy consumption and decreasing signal-amplitude-loss. However, materials combining PMA and antiferromagnetism rather than transition-metal/rar...

  20. Flow anisotropies due to momentum deposition from hard partons

    CERN Document Server

    Tomasik, Boris

    2015-01-01

    In nuclear collisions at the LHC large number of hard partons are created in initial partonic interactions, so that it is reasonable to suppose that they do not thermalise immediately but deposit their energy and momentum later into the evolving hot quark-gluon fluid. We show that this mechanism leads to contribution to flow anisotropies at all orders which are non-negligible and should be taken into account in realistic simulations.