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Sample records for anisotropy probe wmap

  1. Wilkinson Microwave Anisotropy Probe (WMAP) First Year Observations TE Polarization

    CERN Document Server

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

    2003-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) has mapped the full sky in Stokes I, Q, and U parameters at frequencies 23, 33, 41, 61, and 94 GHz. We detect correlations between the temperature and polarization maps significant at more than 10 standard deviations. The correlations are present in all WMAP frequency bands with similar amplitude from 23 to 94 GHz, and are consistent with a superposition of a CMB signal with a weak foreground. The fitted CMB component is robust against different data combinations and fitting techniques. On small angular scales theta 20 agree well with the signal predicted solely from the temperature power spectra, with no additional free parameters. We detect excess power on large angular scales (theta > 10 deg) compared to predictions based on the temperature power spectra alone. The excess power is well described by reionization at redshift 11 < z_r < 30 at 95% confidence, depending on the ionization history. A model-independent fit to reionization optical depth yields ...

  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. The Wilkinson Microwave Anisotropy Probe (WMAP) Source Catalog

    Science.gov (United States)

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

    2008-01-01

    We present the list of point sources found in the WMAP 5-year maps. The technique used in the first-year and three-year analysis now finds 390 point sources, and the five-year source catalog is complete for regions of the sky away from the galactic plane to a 2 Jy limit, with SNR greater than 4.7 in all bands in the least covered parts of the sky. The noise at high frequencies is still mainly radiometer noise, but at low frequencies the CMB anisotropy is the largest uncertainty. A separate search of CMB-free V-W maps finds 99 sources of which all but one can be identified with known radio sources. The sources seen by WMAP are not strongly polarized. Many of the WMAP sources show significant variability from year to year, with more than a 2:l range between the minimum and maximum fluxes.

  4. 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

  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.; Jarosik, 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.

    2013-10-01

    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 -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 eff = 3.84 ± 0.40). The model fit also implies that the age of the universe is t 0 = 13.772 ± 0.059 Gyr, and the fit Hubble constant is H 0 = 69.32 ± 0.80 km s-1 Mpc-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 (ns = 0.9608 ± 0.0080); and the universe is close to flat/Euclidean (\\Omega _k = -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-parameter ΛCDM model

  8. First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations Angular Power Spectrum

    CERN Document Server

    Hinshaw, G; Verde, L; Hill, R S; Meyer, S S; Barnes, C; Bennett, C L; Halpern, M; Jarosik, N C; Kogut, A J; Komatsu, E; Limon, M; Page, L; Tucker, G S; Weiland, J; Wollack, E; Wright, E L

    2003-01-01

    We present the angular power spectrum derived from the first-year Wilkinson Microwave Anisotropy Probe (WMAP) sky maps. We study a variety of power spectrum estimation methods and data combinations and demonstrate that the results are robust. The data are modestly contaminated by diffuse Galactic foreground emission, but we show that a simple Galactic template model is sufficient to remove the signal. Point sources produce a modest contamination in the low frequency data. After masking ~700 known bright sources from the maps, we estimate residual sources contribute ~3500 uK^2 at 41 GHz, and ~130 uK^2 at 94 GHz, to the power spectrum l*(l+1)*C_l/(2*pi) at l=1000. Systematic errors are negligible compared to the (modest) level of foreground emission. Our best estimate of the power spectrum is derived from 28 cross-power spectra of statistically independent channels. The final spectrum is essentially independent of the noise properties of an individual radiometer. The resulting spectrum provides a definitive mea...

  9. First Year Wilkinson Microwave Anisotropy Probe(WMAP) Observations: Data Processing Methods and Systematic Errors Limits

    Science.gov (United States)

    Hinshaw, G.; Barnes, C.; Bennett, C. L.; Greason, M. R.; Halpern, M.; Hill, R. S.; Jarosik, N.; Kogut, A.; Limon, M.; Meyer, S. S.

    2003-01-01

    We describe the calibration and data processing methods used to generate full-sky maps of the cosmic microwave background (CMB) from the first year of Wilkinson Microwave Anisotropy Probe (WMAP) observations. Detailed limits on residual systematic errors are assigned based largely on analyses of the flight data supplemented, where necessary, with results from ground tests. The data are calibrated in flight using the dipole modulation of the CMB due to the observatory's motion around the Sun. This constitutes a full-beam calibration source. An iterative algorithm simultaneously fits the time-ordered data to obtain calibration parameters and pixelized sky map temperatures. The noise properties are determined by analyzing the time-ordered data with this sky signal estimate subtracted. Based on this, we apply a pre-whitening filter to the time-ordered data to remove a low level of l/f noise. We infer and correct for a small (approx. 1 %) transmission imbalance between the two sky inputs to each differential radiometer, and we subtract a small sidelobe correction from the 23 GHz (K band) map prior to further analysis. No other systematic error corrections are applied to the data. Calibration and baseline artifacts, including the response to environmental perturbations, are negligible. Systematic uncertainties are comparable to statistical uncertainties in the characterization of the beam response. Both are accounted for in the covariance matrix of the window function and are propagated to uncertainties in the final power spectrum. We characterize the combined upper limits to residual systematic uncertainties through the pixel covariance matrix.

  10. First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations Determination of Cosmological Parameters

    CERN Document Server

    Spergel, D N; Peiris, H V; Komatsu, E; 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; Weiland, J L; Wollack, E; Wright, E L

    2003-01-01

    WMAP precision data enables accurate testingof cosmological models. We find that the emerging standard model of cosmology, a flat Lambda-dominated universe seeded by a nearly scale-invariant adiabatic Gaussian fluctuations, fits the WMAP data. With parameters fixed only by WMAP data, we can fit finer scale CMB measurements and measurements of large scale structure (galaxy surveys and the Lyman Alpha forest). This simple model is also consistent with a host of other astronomical measurements. We then fit the model parameters to a combination of WMAP data with other finer scale CMB experiments (ACBAR and CBI), 2dFGRS measurements and Lyman Alpha forest data to find the model's best fit cosmological parameters: h = 0.71^{+ 0.04}_{- 0.03}}, Omega_bh^2 = 0.0224+/-0.0009}, Omega_mh^2 = 0.135^{+ 0.008}_{- 0.009}}, tau = 0.17+/-0.06}, n_s(0.05 Mpc$^{-1}) = 0.93 \\pm 0.03}, and sigma_8 = 0.84+/-0.04}. WMAP's best determination of tau=0.17+/-0.04 arises directly from the TE data and not from this model fit, but they are...

  11. 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...

  12. 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...

  13. 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}).

  14. The Spectrum of the Cosmic Microwave Background Anisotropy from the Combined COBE FIRAS and WMAP Observations

    Science.gov (United States)

    Fixsen, D. J.

    2003-09-01

    The cosmic microwave background (CMB) anisotropy data from the COBE Far Infrared Absolute Spectrophotometer (FIRAS) is reanalyzed in light of the Wilkinson Microwave Anisotropy Probe (WMAP) observations. The frequency spectrum of the FIRAS signal that has the spatial distribution seen by WMAP is shown to be consistent with CMB temperature fluctuations well into the Wien region of the spectrum. The consistency of these data, from very different instruments with very different observing strategies, provides compelling support for the interpretation that the signal seen by WMAP is temperature anisotropy of cosmological origin. The data also limit rms fluctuations in the Compton y parameter, observable via the Sunyaev-Zeldovich effect, to Δy<3×10-6 (95% confidence level) on ~5° angular scales. The National Aeronautics and Space Administration Goddard Space Flight Center (NASA/GSFC) was responsible for the design, development, and operation of the Cosmic Background Explorer (COBE).

  15. Results from the Wilkinson Microwave Anisotropy Probe

    CERN Document Server

    Komatsu, Eiichiro

    2014-01-01

    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 $\\Lambda$ cold dark matter ($\\Lambda$CDM) 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 backgrou...

  16. 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.

  17. 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...

  18. Intracluster Medium through three years of WMAP

    CERN Document Server

    Afshordi, N

    2006-01-01

    Wilkinson Microwave Anisotropy Probe (WMAP) has provided us with the yet highest resolution all-sky maps of the Cosmic Microwave Background. As a result of thermal Sunyaev-Zel'dovich effect, clusters of galaxies are imprinted as tiny, poorly resolved dips on top of primary CMB anisotropies in these maps. Here, I describe different efforts to extract the physics of Intracluster Medium (ICM) from the sea of primary CMB, through combining WMAP with low-redshift galaxy or X-ray cluster surveys. This finally culminates at a mean (universal) ICM pressure profile, which is for the first time directly constrained from WMAP 3yr maps, and leads to interesting constraints on the ICM baryonic budget.

  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. WMAP Detection of Early Reionization

    Science.gov (United States)

    Kogut, A.

    2003-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) has mapped the full sky in Stokes I, Q, and U parameters at frequencies 23, 33, 41, 61, and 94 GHz. We detect correlations between the temperature and polarization maps significant at more than 10 standard deviations. The correlations are inconsistent with instrument noise and are significantly larger than the upper limits established for potential systematic errors. The correlations are present in all WMAP frequency bands with similar amplitude from 23 to 94 GHz, and are consistent with a superposition of a CMB signal with a weak foreground. The fitted CMB component is robust against different data combinations and fitting techniques. On small angular scales the WMAP data show the temperature-polarization correlation expected from adiabatic density perturbations. The data for $\\ell > 20$ agree well with the signal predicted solely from the temperature power spectra, with no additional free parameters. The existence of correlations on super-horizon scales provides significant support for inflationary cosmologies. We detect excess power on large angular scales compared to predictions based on the temperature power spectra alone. The excess power is well described by reionization at redshift $11 reionization optical depth yields results consistent with the best-fit $\\Lambda$CDM model, with best fit value $\\tau = 0.17 \\pm 0.04$ at 68\\% confidence, including systematic and foreground uncertainties. This trough in the absorption spectra of distant quasars, and implies that the universe has a complex ionization history. I will discuss the WMAP data and its implications for reionization in the early universe.

  2. WMAP - A Glimpse of the Early Universe

    Science.gov (United States)

    Wollack, Edward

    2009-01-01

    The early Universe was incredibly hot, dense, and homogeneous. A powerful probe of this time is provided by the relic radiation which we refer to today as the Cosmic Microwave Background (CMB). Images produced from this light contain the earliest glimpse of the Universe after the "Big Bang" and the signature of the evolution of its contents. By exploiting these clues, precise constraints on the age, mass density, and geometry of the early Universe can be derived. The history of this intriguing cosmological detective story will be reviewed. Recent results from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) will be presented.

  3. 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

  4. Probing dark energy perturbations: the dark energy equation of state and speed of sound as measured by WMAP

    CERN Document Server

    Bean, R; Bean, Rachel; Dore, Olivier

    2004-01-01

    We review the implications of having a non-trivial matter component in the universe and the potential for detecting such a component through the matter power spectrum and ISW effect. We adopt a phenomenological approach and consider the mysterious dark energy to be a cosmic fluid. It is thus fully characterized, up to linear order, by its equation of state and its speed of sound. Whereas the equation of state has been widely studied in the literature, less interest has been devoted to the speed of sound. Its observational consequences come predominantly from very large scale modes of dark matter perturbations ($k < 0.01 hmathrm{Mpc}^{-1}$). Since these modes have hardly been probed so far by large scale galaxy surveys, we investigate whether joint constraints that can be placed on those two quantities using the recent CMB fluctuations measurements by WMAP as well as the recently measured CMB large scale structure cross-correlation. We find only a tentative 1$sigma$ detection of the speed of sound, from CMB...

  5. Reconstruction of Gravitational Lensing Using WMAP 7-Year Data

    CERN Document Server

    Feng, Chang; Paar, Hans P; Zahn, Oliver

    2011-01-01

    Gravitational lensing by large scale structure introduces non-Gaussianity into the Cosmic Microwave Background and imprints a new observable, which can be used as a cosmological probe. We apply a four-point estimator to the Wilkinson Microwave Anisotropy Probe (WMAP) 7-year coadded temperature maps alone to reconstruct the gravitational lensing signal. The Gaussian bias is simulated and subtracted, and the higher order bias is investigated. We measure a gravitational lensing signal with a statistical amplitude of $\\mathcal {C}$ = $1.27\\pm 0.98$ using all the correlations of the W- and V-band Differencing Assemblies (DAs). We therefore conclude that WMAP 7-year data alone, can not detect lensing.

  6. 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...

  7. Particle physics implications of the WMAP neutrino mmass bound

    CERN Document Server

    Bhattacharya, G; Song, L; Weiler, Thomas J

    2003-01-01

    The recently published cosmological bound on the absolute neutrino masses obtained from the Wilkinson Microwave Anisotropy Probe (WMAP) data has important consequences for neutrino experiments. Taken at face value, the new bound excludes the determination of the absolute neutrino mass in the KATRIN experiment and excludes a neutrino oscillation interpretation of the LSND experiment. Combined with KamLAND data, the WMAP bound defines an accessible range for the neutrinoless double beta decay amplitude. The bound also impacts the Z-burst annihilation mechanism for resonant generation of extreme-energy cosmic rays on the cosmic neutrino background in two ways: it constrains the local overdensity of neutrino dark matter which is not helpful, but it also limits the resonant energy to a favorable range. Since theories with \\Delta L=1 lepton number violation such as R-parity violating SUSY generate neutrino masses radiatively, bounds on absolute neutrino masses translate into bounds on coupling products \\lambda^(')\\...

  8. WMAP Observatory Thermal Design and On-Orbit Thermal Performance

    Science.gov (United States)

    Glazer, Stuart D.; Brown, Kimberly D.; Michalek, Theodore J.; Ancarrow, Walter C.

    2003-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) observatory, launched June 30, 2001, is designed to measure the cosmic microwave background radiation with unprecedented precision and accuracy while orbiting the second Lagrange point (L2). The instrument cold stage must be cooled passively to <95K, and systematic thermal variations in selected instrument components controlled to less than 0.5 mK (rms) per spin period. This paper describes the thermal design and testing of the WMAP spacecraft and instrument. Flight thermal data for key spacecraft and instrument components are presented from launch through the first year of mission operations. Effects of solar flux variation due to the Earth's elliptical orbit about the sun, surface thermo-optical property degradations, and solar flares on instrument thermal stability are discussed.

  9. WMAP - A Portrait of the Early Universe

    Science.gov (United States)

    Wollack, Edward J.

    2008-01-01

    A host of astrophysical observations suggest that early Universe was incredibly hot, dense, and homogeneous. A powerful probe of this time is provided by the relic radiation which we refer to today as the Cosmic Microwave Background (CMB). Images produced from this light contain the earliest glimpse of the Universe after the 'Big Bang' and the signature of the evolution of its contents. By exploiting these clues, constraints on the age, mass density, and geometry of the early Universe can be derived. A brief history of the evolution of the microwave radiometer systems and map making approaches used in advancing these aspects our understanding of cosmological will be reviewed. In addition, an overview of the results from NASA's Wilkinson Microwave Anisotropy (WMAP) will be presented.

  10. 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.

  11. Follow-up observations at 16 and 33 GHz of extragalactic sources from WMAP 3-year data: I - Spectral properties

    OpenAIRE

    2009-01-01

    We present follow-up observations of 97 point sources from the Wilkinson Microwave Anisotropy Probe (WMAP) 3-year data, contained within the New Extragalactic WMAP Point Source (NEWPS) catalogue between declinations of -4 and +60 degrees; the sources form a flux-density-limited sample complete to 1.1 Jy (approximately 5 sigma) at 33 GHz. Our observations were made at 16 GHz using the Arcminute Microkelvin Imager (AMI) and at 33 GHz with the Very Small Array (VSA). 94 of the sources have relia...

  12. 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.

  13. Implications of primordial power spectra with statistical anisotropy on CMB temperature fluctuation and polarizations

    CERN Document Server

    Chang, Zhe

    2013-01-01

    Both the Wilkinson Microwave Anisotropy Probe (WMAP) and Planck observations reported the hemispherical asymmetry of the cosmic microwave background (CMB) temperature fluctuation. The hemispherical asymmetry might be stemmed from the primordial statistical anisotropy during the inflationary era of the universe. In this paper, we study possible implications of the primordial power spectra with dipolar anisotropy on the CMB temperature fluctuation and polarizations. We explicitly show that the statistical dipolar anisotropy may induce the off-diagonal (\\(\\ell'\

  14. 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.

  15. 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

  16. 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...

  17. 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

  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. 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.

  20. 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...

  1. 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.

  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. Alignment, vibronic level splitting, and coherent coupling effects on the pump-probe polarization anisotropy.

    Science.gov (United States)

    Smith, Eric R; Jonas, David M

    2011-04-28

    The pump-probe polarization anisotropy is computed for molecules with a nondegenerate ground state, two degenerate or nearly degenerate excited states with perpendicular transition dipoles, and no resonant excited-state absorption. Including finite pulse effects, the initial polarization anisotropy at zero pump-probe delay is predicted to be r(0) = 3/10 with coherent excitation. During pulse overlap, it is shown that the four-wave mixing classification of signal pathways as ground or excited state is not useful for pump-probe signals. Therefore, a reclassification useful for pump-probe experiments is proposed, and the coherent anisotropy is discussed in terms of a more general transition dipole and molecular axis alignment instead of experiment-dependent ground- versus excited-state pathways. Although coherent excitation enhances alignment of the transition dipole, the molecular axes are less aligned than for a single dipole transition, lowering the initial anisotropy. As the splitting between excited states increases beyond the laser bandwidth and absorption line width, the initial anisotropy increases from 3/10 to 4/10. Asymmetric vibrational coordinates that lift the degeneracy control the electronic energy gap and off-diagonal coupling between electronic states. These vibrations dephase coherence and equilibrate the populations of the (nearly) degenerate states, causing the anisotropy to decay (possibly with oscillations) to 1/10. Small amounts of asymmetric inhomogeneity (2 cm(-1)) cause rapid (130 fs) suppression of both vibrational and electronic anisotropy beats on the excited state, but not vibrational beats on the ground electronic state. Recent measurements of conical intersection dynamics in a silicon napthalocyanine revealed anisotropic quantum beats that had to be assigned to asymmetric vibrations on the ground electronic state only [Farrow, D. A.; J. Chem. Phys. 2008, 128, 144510]. Small environmental asymmetries likely explain the observed absence

  4. Occam's razor meets WMAP

    CERN Document Server

    Magueijo, J; Magueijo, Joao; Sorkin, Rafael D.

    2006-01-01

    Using a variety of quantitative implementations of Occam's razor we examine the low quadrupole, the ``axis of evil'' effect and other detections recently made appealing to the excellent WMAP data. We find that some razors {\\it fully} demolish the much lauded claims for departures from scale-invariance. They all reduce to pathetic levels the evidence for a low quadrupole (or any other low $\\ell$ cut-off), both in the first and third year WMAP releases. The ``axis of evil'' effect is the only anomaly examined here that survives the humiliations of Occam's razor, and even then in the category of ``strong'' rather than ``decisive'' evidence. Statistical considerations aside, differences between the various renditions of the datasets remain worrying.

  5. 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.

  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.

  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. Probing the Intergalactic Magnetic Field with the Anisotropy of the Extragalactic Gamma-ray Background

    Science.gov (United States)

    Venters, T. M.; Pavlidou, V.

    2013-01-01

    The intergalactic magnetic field (IGMF) may leave an imprint on the angular anisotropy of the extragalactic gamma-ray background through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thereby inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that current Fermi data already seem to prefer nonnegligible IGMF values. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.

  10. Cubic anomalies in WMAP

    CERN Document Server

    Land, K; Land, Kate; Magueijo, Joao

    2004-01-01

    We perform a frequentist analysis of the bispectrum of WMAP first year data. We find clear signal domination up to l=200, with overall consistency with Gaussianity except for the following features. There is a flat patch (i.e. a low chi-squared region) in the same-l components of the bispectrum spanning the range l=32-62; this may be interpreted as ruling out Gaussianity at the 99.6% confidence level. There is also an asymmetry between the North and South inter-l bispectrum components at the 99% confidence level. The preferred asymmetry axis correlates well with the (l,b)=(57,10) direction quoted in the literature for asymmetries in the power spectrum and three-point correlation function. However our analysis of the quadrupole (its bispectrum and principal axes) fail to make contact with previously claimed anomalies.

  11. 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.

  12. 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.

  13. High Galactic latitude interstellar neutral hydrogen (HI) structure and associated acoustic-scale WMAP hot spots

    CERN Document Server

    Verschuur, Gerrit L

    2007-01-01

    Associations have been found between interstellar neutral hydrogen (HI) emission morphology and small-scale structure observed by the Wilkinson Microwave Anisotropy Probe (WMAP) in a Target Area bounded by l = 60 deg & 180 deg, b = 30 deg & 70 deg. This area is marked by the presence of highly disturbed local HI and a preponderance of intermediate- and high-velocity gas and it remains to be determined whether the claimed associations are a hallmark of the presence of the anomalous velocity gas. The HI distribution toward the 33 brightest WMAP peaks in the Target Area is examined and it is demonstrated that the associations do not appear to be the result of chance coincidence. Furthermore, several important properties of diffuse interstellar neutral hydrogen structure have been identified that might otherwise have been overlooked if it were not for the fact that the continuum data focused attention on certain areas of the HI sky. Some of the most dramatic associations are illustrated. It is suggested t...

  14. 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.

  15. Anisotropies of Gravitational-Wave Standard Sirens as a New Cosmological Probe without Redshift Information.

    Science.gov (United States)

    Namikawa, Toshiya; Nishizawa, Atsushi; Taruya, Atsushi

    2016-03-25

    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, previously proposed cosmological 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, once GW observations will be well established in the future, (i) these anisotropies can be measured even at very high redshifts (z≥2), where the identification of the electromagnetic counterpart is difficult, (ii) the expected constraints on the primordial non-Gaussianity with the Einstein Telescope would be comparable to or even better than the other large-scale structure probes at the same epoch, and (iii) the cross-correlation with other cosmological observations is found to have high-statistical significance, providing additional cosmological information at very high redshifts.

  16. Application of Monte-Carlo Analyses for the Microwave Anisotropy Probe (MAP) Mission

    Science.gov (United States)

    Mesarch, Michael A.; Rohrbaugh, David; Schiff, Conrad; Bauer, Frank H. (Technical Monitor)

    2001-01-01

    The Microwave Anisotropy Probe (MAP) is the third launch in the National Aeronautics and Space Administration's (NASA's) a Medium Class Explorers (MIDEX) program. MAP will measure, in greater detail, the cosmic microwave background radiation from an orbit about the Sun-Earth-Moon L2 Lagrangian point. Maneuvers will be required to transition MAP from it's initial highly elliptical orbit to a lunar encounter which will provide the remaining energy to send MAP out to a lissajous orbit about L2. Monte-Carlo analysis methods were used to evaluate the potential maneuver error sources and determine their effect of the fixed MAP propellant budget. This paper will discuss the results of the analyses on three separate phases of the MAP mission - recovering from launch vehicle errors, responding to phasing loop maneuver errors, and evaluating the effect of maneuver execution errors and orbit determination errors on stationkeeping maneuvers at L2.

  17. 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.

  18. 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.

  19. The effect of asymmetric beams in the Wilkinson Microwave Anisotropy Probe experiment

    CERN Document Server

    Wehus, Ingunn Kathrine; Eriksen, H K; Groeneboom, Nicolaas E

    2009-01-01

    We generate simulations of the CMB temperature field as observed by the WMAP satellite, taking into account the detailed shape of the asymmetric beams and scanning strategy of the experiment, and use these to re-estimate the WMAP beam transfer functions. This method avoids the need of artificially symmetrizing the beams, as done in the baseline WMAP approach, and instead measures the total convolution effect by direct simulation. We find noticeable differences with respect to the nominal transfer functions. For instance, the nominal V1 beam under-estimates the full beam convolution by ~0.5% at l=500 and ~1.0% at l=800. Similar differences are seen for other DA's. This in turn implies that the high-l power spectrum is biased low by 1-2%, effectively tilting the spectrum slightly. Re-estimating cosmological parameters we find that the spectral index of scalar perturbations is n_s = 0.969 +- 0.014 after correcting for this effect, corresponding to a positive shift of 0.3 sigma compared to the previously released...

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

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Cheng; Huang, Qing-Guo [State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China); Ma, Yin-Zhe, E-mail: chcheng@itp.ac.cn, E-mail: huangqg@itp.ac.cn, E-mail: mayinzhe@phas.ubc.ca [Department of Physics and Astronomy, University of British Columbia, Vancouver, V6T 1Z1, BC Canada (Canada)

    2013-07-01

    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 χ{sup 2} is improved by a factor of Δχ{sup 2} = 8.44, which strongly indicates the preference of this parameter from current data. In addition, we find that the running of spectral index α{sub s} 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−n{sub s} give very tight constraints on single-field inflation models, and the models with power law potential φ{sup p} can only survive if 0.9∼WMAP data.

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

    Science.gov (United States)

    Cheng, Cheng; Huang, Qing-Guo; Ma, Yin-Zhe

    2013-07-01

    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 phip can only survive if 0.9lesssimplesssim2.1, so a large class of inflation models have already been ruled out before Planck data. Finally, we use the fNL 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.

  2. 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...

  3. The Anisotropic Line Correlation Function as a Probe of Anisotropies in Galaxy Surveys

    CERN Document Server

    Eggemeier, Alexander; Smith, Robert E; Niemeyer, Jens

    2015-01-01

    We propose an anisotropic generalisation of the line correlation function (ALCF) to separate and quantify phase information in the large-scale structure of galaxies. The line correlation function probes the strictly non-linear regime of structure formation and since phase information drops out of the power spectrum, the line correlation function provides a complementary tool to commonly used techniques based on two-point statistics. Furthermore, it is independent of linear bias as well as the Gaussian variance on the modulus of the density field and thus may also prove to be advantageous compared to the bispectrum or similar higher-order statistics for certain cases. For future applications it is vital, though, to be able to account for observational effects that cause anisotropies in the distribution of galaxies. Based on a number of numerical studies, we find that our ALCF is well suited to accomplish this task and we demonstrate how the Alcock-Paczynski effect and kinematical redshift-space distortions can...

  4. 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.

  5. Constraining anisotropic models of early Universe with WMAP9 data

    CERN Document Server

    Ramazanov, Sabir

    2013-01-01

    We constrain several models of the early Universe that predict statistical anisotropy of the CMB sky. We make use of WMAP9 maps deconvolved with beam asymmetries. As compared to previous releases of WMAP data, they do not exhibit the anomalously large quadrupole of the statistical anisotropy. This allows to strengthen limits on parameters of models established earlier in literature. In particular, the amplitude of the special quadrupole, whose direction is aligned with ecliptic poles, is now constrained as g_* =0.002 \\pm 0.041 at 95% CL (\\pm 0.020 at 68% CL). The upper limit is obtained on the total number of e-folds in anisotropic inflation with the Maxwellian term non-minimally coupled to the inflaton, namely N_{tot}

  6. Lipidic Carbo-benzenes: Molecular Probes of Magnetic Anisotropy and Stacking Properties of α-Graphyne.

    Science.gov (United States)

    Zhu, Chongwei; Rives, Arnaud; Duhayon, Carine; Maraval, Valérie; Chauvin, Remi

    2017-01-20

    Solubilization of the C18 fundamental circuit of α-graphyne has been envisaged by decoration with aliphatic chains R = n-CnH2n+1. The synthesis and characterization of p-dialkyl-tetraphenyl-carbo-benzenes (n = 2, 8, 14, 20) are thus presented and compared to the monoalkyl series produced concomitantly. In both series, a dramatic enhancement of solubility in organic solvents (CH2Cl2, CHCl3) is observed for n ≥ 8, and in the dialkyl series, the melting-decomposition temperature of the solid products is shown to decrease linearly from 208 °C for n = 2 to 149 °C for n = 20. Fluoroalkyl analogues with R = n-C8H4F13 are also described. The products display classical UV-vis electronic spectra of carbo-benzenes in solution (λmax = 445.5 ± 1 nm, ε ≈ 200 000 L·mol(-1)·cm(-1)). They are also characterized by UV-vis absorption in the solid state, which is found to be correlated with the color and crystal packing. The methylene groups of R provide an experimental probe of the magnetic anisotropy and aromaticity of the C18 ring through the progressive NMR shielding of the (1)H nuclei from ca. 4.70 to 1.25 ppm going away from the border of the ring (as far as 8 Å away). All alkyl-carbo-benzenes were also found to be highly crystalline. Seven of them have been characterized by X-ray diffraction analysis and the C18 columnar packing compared in a systematic manner. Crystals of the diethyl and bistetradecyl derivatives, containing no solvent molecule, provided the first examples of direct π-stacking of carbo-benzene rings, with inter-ring distances very close to calculated interlayer distances in AB and ABC α-graphityne (3.255 and 3.206 Å vs 3.266 and 3.201 Å, respectively).

  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. 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.

  9. 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 ...

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

    OpenAIRE

    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 particula...

  11. Radio spectra of the WMAP catalog sources

    CERN Document Server

    Trushkin, S A

    2003-01-01

    Compiled radio spectra are presented for 208 extragalactic sources from the catalog created from the WMAP satellite all-sky survey data in a range of 23-94 GHz taken during the first year of its operation in orbit. 205 out of 208 WMAP sources are reliably identified with radio sources from other catalogs, including also four out of five sources unidentified by the WMAP survey authors. We have found 203 WMAP sources to have optical identification: 141 quasars, 29 galaxies, 19 active galactic nuclei, 19 BL Lac-type objects and one planetary nebula, IC418. Simultaneous measurements of flux densities for 26 sources at five frequencies, 2.3, 3.9, 7.7, 11.2 and 21.7 GHz, were made with the radio telescope RATAN-600 in 2003 March. 25 sources were detected at all the frequencies, and only one, WMAP0517-0546, unidentified in other catalogs was not detected in our observations and is likely to be spurious. Using the database CATS we found a large number of identifications in different radio catalogs and in several long...

  12. 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...

  13. 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.

  14. Whistler anisotropy instabilities as the source of banded chorus: Van Allen Probes observations and particle-in-cell simulations.

    Science.gov (United States)

    Fu, Xiangrong; Cowee, Misa M; Friedel, Reinhard H; Funsten, Herbert O; Gary, S Peter; Hospodarsky, George B; Kletzing, Craig; Kurth, William; Larsen, Brian A; Liu, Kaijun; MacDonald, Elizabeth A; Min, Kyungguk; Reeves, Geoffrey D; Skoug, Ruth M; Winske, Dan

    2014-10-01

    Magnetospheric banded chorus is enhanced whistler waves with frequencies ωr particle-in-cell simulations in a magnetized, homogeneous, collisionless plasma to test the hypothesis that banded chorus is due to local linear growth of two branches of the whistler anisotropy instability excited by two distinct, anisotropic electron components of significantly different temperatures. The electron densities and temperatures are derived from Helium, Oxygen, Proton, and Electron instrument measurements on the Van Allen Probes A satellite during a banded chorus event on 1 November 2012. The observations are consistent with a three-component electron model consisting of a cold (a few tens of eV) population, a warm (a few hundred eV) anisotropic population, and a hot (a few keV) anisotropic population. The simulations use plasma and field parameters as measured from the satellite during this event except for two numbers: the anisotropies of the warm and the hot electron components are enhanced over the measured values in order to obtain relatively rapid instability growth. The simulations show that the warm component drives the quasi-electrostatic upper band chorus and that the hot component drives the electromagnetic lower band chorus; the gap at ∼Ω e /2 is a natural consequence of the growth of two whistler modes with different properties.

  15. Whistler anisotropy instabilities as the source of banded chorus: Van Allen Probes observations and particle-in-cell simulations

    Science.gov (United States)

    Fu, Xiangrong; Cowee, Misa M.; Friedel, Reinhard H.; Funsten, Herbert O.; Gary, S. Peter; Hospodarsky, George B.; Kletzing, Craig; Kurth, William; Larsen, Brian A.; Liu, Kaijun; MacDonald, Elizabeth A.; Min, Kyungguk; Reeves, Geoffrey D.; Skoug, Ruth M.; Winske, Dan

    2014-10-01

    Magnetospheric banded chorus is enhanced whistler waves with frequencies ωrcell simulations in a magnetized, homogeneous, collisionless plasma to test the hypothesis that banded chorus is due to local linear growth of two branches of the whistler anisotropy instability excited by two distinct, anisotropic electron components of significantly different temperatures. The electron densities and temperatures are derived from Helium, Oxygen, Proton, and Electron instrument measurements on the Van Allen Probes A satellite during a banded chorus event on 1 November 2012. The observations are consistent with a three-component electron model consisting of a cold (a few tens of eV) population, a warm (a few hundred eV) anisotropic population, and a hot (a few keV) anisotropic population. The simulations use plasma and field parameters as measured from the satellite during this event except for two numbers: the anisotropies of the warm and the hot electron components are enhanced over the measured values in order to obtain relatively rapid instability growth. The simulations show that the warm component drives the quasi-electrostatic upper band chorus and that the hot component drives the electromagnetic lower band chorus; the gap at ˜Ωe/2 is a natural consequence of the growth of two whistler modes with different properties.

  16. PROBING THE EPOCH OF PRE-REIONIZATION BY CROSS-CORRELATING COSMIC MICROWAVE AND INFRARED BACKGROUND ANISOTROPIES

    Energy Technology Data Exchange (ETDEWEB)

    Atrio-Barandela, F. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Kashlinsky, A., E-mail: atrio@usal.es, E-mail: Alexander.Kashlinsky@nasa.gov [Observational Cosmology Lab, NASA Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States)

    2014-12-20

    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 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 Euclid CIB maps to detect the cross-power at scales ∼5'-60' with signal-to-noise ratios (S/Ns) of up to S/N ∼ 4-8 depending on the contribution to the Thomson optical depth during those pre-reionization epochs (Δτ ≅ 0.05) and the temperature of the IGM (up to ∼10{sup 4} K). Such a measurement would offer a new window to explore the emergence and physical properties of these first light sources.

  17. 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...

  18. 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...

  19. Heat assisted magnetic probe recording onto a thin film with perpendicular magnetic anisotropy

    NARCIS (Netherlands)

    Onoue, T.; Siekman, M.H.; Abelmann, L.; Lodder, J.C.

    2008-01-01

    The possibility of magnetic probe recording into a continuous perpendicular medium is discussed. By applying a current from the tip to the medium, a very localized area can be heated and bits as small as 80 nm in diameter could be written. This value is close to the calculated minimum diameter of re

  20. 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...

  1. Joint Planck and WMAP assessment of low CMB multipoles

    Science.gov (United States)

    Iqbal, Asif; Prasad, Jayanti; Souradeep, Tarun; Malik, Manzoor A.

    2015-06-01

    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 ΛCDM model. However, the lack of power in the CMB temperature anisotropies at large angular scales (low-l), as has been confirmed by the recent Planck data also (up to 0l=4), although statistically not very strong (less than 3σ), 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 feature of all the models of PPS that we consider is an infra-red cut off which leads to suppression of power at large angular scales. We consider models of PPS with maximum three extra parameters and use Akaike information criterion (AIC) and Bayesian information criterion (BIC) of model selection to compare the models. For most models, we find good constraints for the cut off scale kc, however, for other parameters our constraints are not that good. We find that sharp cut off model gives best likelihood value for the WMAP 9 year data, but is as good as power law model according to AIC. For the joint WMAP 9 + Planck data set, Starobinsky model is slightly preferred by AIC which is also able to produce CMB power suppression up to 0l<=3 to some extent. However, using BIC criteria, one finds model(s) with least number of parameters (power law model) are always preferred.

  2. Angular Anisotropies in the Cosmic Gamma-ray Background as a Probe of its Origin

    CERN Document Server

    Miniati, Francesco; Di Matteo, Tiziana

    2007-01-01

    Notwithstanding the advent of the Gamma-ray Large Area Telescope, theoretical models predict that a significant fraction of the cosmic gamma-ray background (CGB), at the level of 20% of the currently measured value, will remain unresolved. The angular power spectrum of intensity fluctuations of the CGB contains information on its origin. We show that probing the latter from a few tens of arcmin to several degree scales, together with complementary GLAST observations of gamma-ray emission from galaxy clusters and the blazars luminosity function, can discriminate between a background that originates from unresolved blazars or cosmic rays accelerated at structure formation shocks.

  3. Constraints on single-field inflation with WMAP, SPT and ACT data -- A last-minute stand before Planck

    CERN Document Server

    Cheng, Cheng; Ma, Yin-Zhe

    2013-01-01

    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 $\\chi^2$ is improved by a factor of $\\Delta \\chi^2=4.22$, which strongly indicates the preference of this parameter from current data. In addition, we find that the running of spectral index $\\alpha_s$ 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 $r-n_{s}$ give very tight constraints on single-field inflation models, and the models with power law potential $\\phi^{p}$ can only survive if $0.9 \\lesssim p \\lesssim 2.1$, so a large class of inflation models have already been ruled out before Planck data. Finally, we use the $f_{NL}$ data...

  4. Carrier-phonon interactions in hybrid halide perovskites probed with ultrafast anisotropy studies

    Science.gov (United States)

    Rivett, Jasmine P. H.; Richter, Johannes M.; Price, Michael B.; Credgington, Dan; Deschler, Felix

    2016-09-01

    Hybrid halide perovskites are at the frontier of optoelectronic research due to their excellent semiconductor properties and solution processability. For this reason, much attention has recently been focused on understanding photoexcited charge-carrier generation and recombination in these materials. Conversely, very few studies have so far been devoted to understanding carrier-carrier and carrier-phonon scattering mechanisms in these materials. This is surprising given that carrier scattering mechanisms fundamentally limit charge-carrier motilities and therefore the performance of photovoltaic devices. We apply linear polarization selective transient absorption measurements to polycrystalline CH3NH3PbBr3 hybrid halide perovskite films as an effective way of studying the scattering processes in these materials. Comparison of the photo induced bleach signals obtained when the linear polarizations of the pump and probe are aligned either parallel or perpendicular to one another, reveal a significant difference in spectral intensity and shape within the first few hundred femtoseconds after photoexcitation.

  5. 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.

  6. WMAP anomaly : Weak lensing in disguise

    CERN Document Server

    Rotti, Aditya; Souradeep, Tarun

    2011-01-01

    Statistical isotropy (SI) has been one of the simplifying assumptions in cosmological model building. Experiments like WMAP and PLANCK are attempting to test this assumption by searching for specific signals in the Cosmic Microwave Background (CMB) two point correlation function. Modifications to this correlation function due to gravitational lensing by the large scale structure (LSS) surrounding us have been ignored in this context. Gravitational lensing will induce signals which mimic isotropy violation even in an isotropic universe. The signal detected in the Bipolar Spherical Harmonic (BipoSH) coefficients $A^{20}_{ll}$ by the WMAP team may be explained by accounting for the lensing modifications to these coefficients. Further the difference in the amplitude of the signal detected in the V-band and W-band maps can be explained by accounting for the differences in the designed angular sensitivity of the instrumental beams. The arguments presented in this article have crucial implications for SI violation s...

  7. Planar current anisotropy and field dependence of J c in coated conductors assessed by scanning Hall probe microscopy

    Science.gov (United States)

    Lao, M.; Hecher, J.; Sieger, M.; Pahlke, P.; Bauer, M.; Hühne, R.; Eisterer, M.

    2017-02-01

    The local distribution of the critical current density, J c, of coated conductors and YBa2Cu3O{}7-δ (YBCO) films on single crystalline substrate was investigated by scanning Hall probe microscopy. The high spatial resolution of the measurements enabled an assessment of dependence of the local J c on the local magnetic induction, B, and electric field, E. The derived J c(B)-dependence agreed well with the global J c obtained from magnetization loops and provided values of J c at very low fields, which are inaccessible to magnetization and transport measurements. The anisotropic current flow within the film plane was investigated in YBCO films on miscut SrTiO3 substrates and a GdBa2Cu3O{}7-δ film on an MgO buffer layer prepared by inclined substrate deposition on a Hastelloy substrate. The c-axis currents calculated from the Hall maps were significantly larger than previously reported data obtained from direct transport measurements. The planar current anisotropy at 77 K was found to be highly influenced by the microstructure which can either deteriorate the current flowing across the ab-planes or cause enhanced pinning and increase the critical current flowing parallel to the ab-planes.

  8. 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...

  9. Polarization of the WMAP Point Sources

    CERN Document Server

    Lopez-Caniego, M; Gonzalez-Nuevo, J; Lanz, L; Herranz, D; De Zotti, G; Sanz, J L; Argüeso, F

    2009-01-01

    The detection of polarized sources in the WMAP 5-year data is a very difficult task. The maps are dominated by instrumental noise and only a handful of sources show up as clear peaks in the Q and U maps. Optimal linear filters applied at the position of known bright sources detect with a high level of significance a polarized flux P from many more sources, but estimates of P are liable to biases. Using a new technique, named the "filtered fusion technique", we have detected in polarization, with a significance level greater than 99.99% in at least one WMAP channel, 22 objects, 5 of which, however, do not have a plausible low radio frequency counterpart and are therefore doubtful. Estimated polarized fluxes P < 400 mJy at 23 GHz were found to be severely affected by the Eddington bias. The corresponding polarized flux limit for Planck/LFI at 30 GHz, obtained via realistic simulations, is 300 mJy. We have also obtained statistical estimates of, or upper limits to the mean polarization degrees of bright WMAP ...

  10. Probing the Anisotropy of the Milky Way Gaseous Halo-II: sightline toward Mrk509

    CERN Document Server

    Gupta, Anjali; Krongold, Yair

    2016-01-01

    Hot, million degree gas appears to pervade the Milky way halo, containing a large fraction of the Galactic missing baryons. This circumgalactic medium (CGM) is probed effectively in X-rays, both in absorption and in emission. The CGM also appears to be anisotropic, so we have started a program to determine CGM properties along several sightlines by combining absorption and emission measurements. Here we present the emission measure close to the Mrk 509 sightline using new Suzaku and XMM-Newton observations. We also present new analysis and modeling of Chandra HETG spectra to constrain the absorption parameters. The emission measure in this sightline is high, EM$=0.0165\\pm0.0008\\pm0.0006~$cm$^{-6}~$pc, five times larger than the average. The observed OVII column density N(O$_{VII}) = 2.35\\pm0.4 \\times 10^{16}$cm$^{-2}$, however, is close to the average. We find that the temperature of the emitting and absorbing gas is the same: $\\log T (\\rm K) = 6.33\\pm0.01$ and $\\log T (\\rm K)=6.33\\pm0.16$ respectively. We fi...

  11. Heat-assisted magnetic probe recording onto a thin film with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Onoue, T; Siekman, M; Abelmann, L; Lodder, J C [Systems and Materials for Information storage (SMI), MESA Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE, Enschede (Netherlands)

    2008-08-07

    The possibility of magnetic probe recording into a continuous perpendicular medium is discussed. By applying a current from the tip to the medium, a very localized area can be heated and bits as small as 80 nm in diameter could be written. This value is close to the calculated minimum diameter of reversed cylindrical domains in our perpendicular medium. A current can be injected directly from the tip to the medium by means of a current source, or one can use capacitive currents. We prefer the first method, since the current, and therefore the heating process, can be controlled more precisely. The energy required to write a bit is in the order of 1 nJ. Calculations show that most of the heat is dissipated at the tip end. Demagnetizing fields of the surrounding material play an important role and are so strong that bits can be written without applying an external field. By decreasing the film thickness, the demagnetizing fields are reduced, and selective overwriting of previously written bits could be demonstrated.

  12. 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.

  13. Hint of relic gravitational waves in the Planck and WMAP data

    CERN Document Server

    Zhao, Wen; Huang, Qing-Guo

    2014-01-01

    Relic gravitational waves (RGWs) leave well-understood imprints on the anisotropies in the temperature and polarization of cosmic microwave background (CMB) radiation. In the TT and TE information channels, which have been well observed by WMAP and Planck missions, RGWs compete with density perturbations mainly at low multipoles. It is dangerous to include high-multipole CMB data in the search for gravitational waves, as the spectral indices may not be constants. In this paper, we repeat our previous work [W.Zhao & L.P.Grishchuk, Phys.Rev.D {\\bf 82}, 123008 (2010)] by utilizing the Planck TT and WMAP TE data in the low-multipole range $\\ell\\le100$. We find that our previous result is confirmed {with higher confidence}. The constraint on the tensor-to-scalar ratio from Planck TT and WMAP TE data is $r\\in [0.06,~0.60]$ (68% C.L.) with a peak around $r\\sim 0.2$. Correspondingly, the spectral index at the pivot wavenumber $k_*=0.002$Mpc$^{-1}$ is $n_s=1.13^{+0.07}_{-0.08}$, which is larger than 1 at more than...

  14. 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...

  15. 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.

  16. 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.

  17. Complete WMAP Constraints on Bandlimited Inflationary Features

    CERN Document Server

    Dvorkin, Cora

    2011-01-01

    Using a principal component (PC) basis that accommodates order unity features in the slow roll parameters as fine as 1/10 of a decade across more than 2 decades of the inflationary expansion, we test slow roll and single field inflation with the WMAP7 data. Detection of any non-zero component would represent a violation of ordinary slow roll and indicate a feature in the inflaton potential or sound speed. Although one component shows a deviation at the 98% CL, it cannot be considered statistically significant given the 20 components tested. The maximum likelihood PC parameters only improves 2DeltalnL by 17 for the 20 parameters associated with known glitches in the WMAP power spectrum at multipoles l<60. We make model-independent predictions for the matching glitches in the polarization spectrum that would test their inflationary origin. This complete analysis for bandlimited features in the source function of generalized slow roll can be used to constrain parameters of specific models of the inflaton pote...

  18. On the bispectrum of COBE and WMAP

    CERN Document Server

    Magueijo, J; Magueijo, Jo\\~{a}o; Medeiros, Jo\\~{a}o

    2003-01-01

    The COBE-DMR 4-year maps displayed a strong non-Gaussian signal in the ``inter-scale'' components of the bispectrum: their observed values did not display the scatter expected from Gaussian maps. We re-examine this and other suggested non-Gaussian features in the light of WMAP. We find that they all disappear. Given that it was proved that COBE-DMR high noise levels and documented systematics could at most {\\it dilute} the observed non-Gaussian features, we conclude that this dataset must have contained non-negligible undocumented systematic errors. It turns out that the culprit is a combination of QuadCube pixelization and data collected during the ``eclipse season''.

  19. 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 ...

  20. Inflation Model (with doublet scalar field) consistent with Lambda CDM and WMAP cosmological observations

    CERN Document Server

    Amruth, B R; R., Amruth B.; Patwardhan, Ajay

    2006-01-01

    Cosmological inflation models with modifications to include recent cosmological observations has been an active area of research after WMAP 3 results, which have given us information about the composition of dark matter, normal matter and dark energy and the anisotropy at the 300,000 years horizon with high precision. We work on inflation models of Guth and Linde and modify them by introducing a doublet scalar field to give normal matter particles and their supersymmetric partners which result in normal and dark matter of our universe. We include the cosmological constant term as the vaccuum expectation value of the stress energy tensor, as the dark energy. We callibrate the parameters of our model using recent observations of density fluctuations. We develop a model which consistently fits with the recent observations.

  1. Mechanical Anisotropy and Pressure Induced Structural Changes in Piroxicam Crystals Probed by In Situ Indentation and Raman Spectroscopy

    Science.gov (United States)

    Manimunda, Praveena; Hintsala, Eric; Asif, Syed; Mishra, Manish Kumar

    2017-01-01

    The ability to correlate mechanical and chemical characterization techniques in real time is both lacking and powerful tool for gaining insights into material behavior. This is demonstrated through use of a novel nanoindentation device equipped with Raman spectroscopy to explore the deformation-induced structural changes in piroxicam crystals. Mechanical anisotropy was observed in two major faces ( 0bar{1}1 ) and (011), which are correlated to changes in the interlayer interaction from in situ Raman spectra recorded during indentation. The results of this study demonstrate the considerable potential of an in situ Raman nanoindentation instrument for studying a variety of topics, including stress-induced phase transformation mechanisms, mechanochemistry, and solid state reactivity under mechanical forces that occur in molecular and pharmaceutical solids.

  2. Extending the WMAP Bound on the Size of the Universe

    CERN Document Server

    Key, J S; Starkman, D N S G D; Cornish, Neil J.; Key, Joey Shapiro; Starkman, David N. Spergel & Glenn D.

    2006-01-01

    Clues to the shape of our Universe can be found by searching the CMB for matching circles of temperature patterns. A full sky search of the CMB, mapped extremely accurately by NASA's WMAP satellite, returned no detection of such matching circles and placed a lower bound on the size of the Universe at 24 Gpc. This lower bound can be extended by optimally filtering the WMAP power spectrum. More stringent bounds can be placed on specific candidate topologies by using a a combination statistic. We use optimal filtering and the combination statistic to rule out the infamous "soccer ball universe'' model.

  3. 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); Murase, Kohta [Inst. for Advanced Study, Princeton, NJ (United States); Madejski, Grzegorz M. [Stanford Univ., CA (United States); Uchiyama, Yasunobu [Stanford Univ., CA (United States); Rikkyo Univ., Tokyo (Japan)

    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 future hard X-ray all sky satellites achieve a sensitivity better than 10–12 erg cm–2 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.

  4. 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.

  5. The large-scale anomalous microwave emission revisited by WMAP

    CERN Document Server

    Lagache, G

    2003-01-01

    We present a new study of the high latitude galactic contributions to the millimeter sky, based on an analysis of the WMAP data combined with several templates of dust emission (DIRBE/COBE and FIRAS/COBE) and gas tracers (HI and Halpha). To study the IR to millimeter properties of the diffuse sky at high galactic latitude, we concentrate on the emission correlated with the HI gas. We compute the emission spectrum of the dust/free-free/synchrotron components associated with HI gas from low to large column densities. A significant residual WMAP emission over the free-free, synchrotron and the dust contribution is found from 3.2 to 9.1 mm. We show that this residual WMAP emission (normalised to 10$^{20}$ atoms/cm$^2$) (1) exhibits a constant spectrum from 3.2 to 9.1 mm and (2) significantly decreases in amplitude when N$_{HI}$ increases, contrary to the HI-normalised far-infrared emission which stays rather constant. It is thus very likely that the residual WMAP emission is not associated with the Large Grain du...

  6. 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.

  7. Probing the Anisotropy of the Milky Way Gaseous Halo-II: Sightline toward Mrk 509

    Science.gov (United States)

    Gupta, A.; Mathur, S.; Krongold, Y.

    2017-02-01

    Hot, million degree gas appears to pervade the Milky Way halo, containing a large fraction of the Galactic missing baryons. This circumgalactic medium (CGM) is probed effectively in X-rays, both in absorption and in emission. The CGM also appears to be anisotropic, so we have started a program to determine CGM properties along several sightlines by combining absorption and emission measurements. Here we present the emission measure close to the Mrk 509 sightline using new Suzaku and XMM-Newton observations. We also present new analysis and modeling of Chandra HETG spectra to constrain the absorption parameters. The emission measure in this sightline is high, EM = 0.0165 ± 0.0008 ± 0.0006 cm‑6 pc, five times larger than the average. The observed O vii column density N(O vii) = 2.35+/- 0.4× {10}16 cm‑2, however, is close to the average. We find that the temperature of the emitting and absorbing gas is the same: logT(K) = 6.33 ± 0.01 and logT(K) = 6.33 ± 0.16 respectively. We fit the observed column density and emission measure with a β-model density profile. The central density is constrained to be between n 0 = 2.8–6.0 × 10‑4 cm‑3 and the core radius of the density profile has a lower limit of 40 kpc. This shows that the hot gas is mostly in the CGM of the galaxy, not in the Galactic disk. Our derived density profile is close to the Maller & Bullock profile for adiabatic gas in hydrostatic equilibrium with an NFW dark-matter potential well. Assuming this density profile, the minimum mass of the hot CGM is 3.2× {10}10 M ⊙.

  8. WMAP 5-year constraints on α and me

    Science.gov (United States)

    Scóccola, Claudia G.; Landau, Susana J.; Vucetich, Héctor

    2010-11-01

    We have studied the role of fundamental constants in an updated recombination scenario. We focus on the time variation of the fine structure constant α, and the electron mass me in the early Universe. In the last years, helium recombination has been studied in great detail revealing the importance of taking new physical processes into account in the calculation of the recombination history. The equations to solve the detailed recombination scenario can be found for example in Wong et al. 2008. In the equation for helium recombination, a term which accounts for the semi-forbidden transition 23p-11s is added. Furthermore, the continuum opacity of HI is taken into account by a modification in the escape probability of the photons that excite helium atoms, with the fitting formulae proposed Kholupenko et al 2007. We have analized the dependences of the quantities involved in the detailed recombination scenario on α and me. We have performed a statistical analysis with COSMOMC to constrain the variation of α and me at the time of neutral hydrogen formation. The observational set used for the analysis was data from the WMAP 5-year temperature and temperature-polarization power spectrum and other CMB experiments such as CBI, ACBAR and BOOMERANG and the power spectrum of the 2dFGRS. Considering the joint variation of α and me we obtain the following bounds: -0.011 Landau et al 2008, which were obtained in the standard recombination scenario and using WMAP 3 year release data. The constraints are tighter in the current analysis, which is an expectable fact since we are working with more accurate data from WMAP. The bounds obtained are consistent with null variation, for both α and me, but in the present analysis, the 68% confidence limits on the variation of both constants have changed. In the case of α, the present limit is more consistent with null variation than the previous one, while in the case of me the single parameters limits have moved toward lower values

  9. 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.

  10. 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...

  11. 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.

  12. 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.

  13. 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.

  14. 第一讲微波背景辐射的各向异性、偏振及宇宙电离的历史%Anisotropy and polarization of the microwave background radiation, and the reionization of the universe

    Institute of Scientific and Technical Information of China (English)

    范祖辉

    2005-01-01

    文章对微波背景辐射的各向异性、偏振及宇宙电离的历史给出了评述性介绍.从大爆炸理论的预言,到观测的发现,到其各向异性及偏振的探测,微波背景辐射(CMB)向人们揭示了丰富的宇宙学信息.文章在对基本理论作了简单介绍后,着重讲述了最新的CMB的观测结果及其物理意义.特别对微波背景各向异性探测器(Wilkinson Microwave Anisotropy Probe, WMAP)的偏振观测及其对宇宙重新电离的限制给出了较详细的叙述.

  15. The Multipole Vectors of WMAP, and their frames and invariants

    CERN Document Server

    Land, K; Land, Kate; Magueijo, Joao

    2005-01-01

    We investigate the Statistical Isotropy and Gaussianity of the CMB fluctuations, using a set of multipole vector functions capable of separating these two issues. In general a multipole is broken into a frame and $2\\ell-3$ ordered invariants. The multipole frame is found to be suitably sensitive to galactic cuts. We then apply our method to real WMAP datasets; a coadded masked map, the Internal Linear Combinations map, and Wiener filtered and cleaned maps. Taken as a whole, multipoles in the range $\\ell=2-10$ or $\\ell=2-20$ show consistency with statistical isotropy, as proved by the Kolmogorov test applied to the frame's Euler angles. This result in {\\it not} inconsistent with previous claims for a preferred direction in the sky for $\\ell=2,...5$. The multipole invariants also show overall consistency with Gaussianity apart from a few anomalies of limited significance (98%), listed at the end of this paper.

  16. WMAP, Verschuur's Galactic Associations, and the Dual Proposal

    Science.gov (United States)

    Bartlett, David F.

    2009-01-01

    Gerrit Verschuur (2007,2008) has associated 21-cm emissions from neutral hydrogen in the Milky Way with the small scale (1/2 - 1 degree) continuum emissions of WMAP.This association has been challenged by Land and Slosar (2007). In this poster I will show how the dual proposal supports Verschuur. In the dual proposal there are maxima of gravitational potential spaced 400 pc apart throughout the Galaxy. ["Analogies between Electricity and Gravity, Metrologia 41, (2004) S114-S124; "Contour Map for the Gravitational Potential of the Milky Way", BAAS 38, 1148 (2006). I gratefully acknowledge using the Leyden-Argentine-Bonn all-sky survey of HI. (www.astro.uni-bonn.de).

  17. Planck and WMAP constraints on generalised Hubble flow inflationary trajectories

    CERN Document Server

    Contaldi, Carlo R

    2013-01-01

    We use the Hamilton--Jacobi formalism to constrain the space of possible single field, inflationary Hubble flow trajectories when compared to the WMAP and Planck 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 $V(\\phi)$ and also yields a prediction for, $f_{\\rm NL}$, the dimensionless amplitude of the non-Gaussian bispectrum.

  18. Review of non-Gaussianity at low and high multipoles from WMAP data

    Science.gov (United States)

    Verkhodanov, O. V.; Naselsky, P. D.; Chiang, L.-Y.; Doroshkevich, A. G.; Novikov, I. D.

    2008-09-01

    We review problems of non-Gaussianity analysis of the WMAP data. The non-Gaussianity has been detected by different methods in several multipole ranges. To our opinion, it could be due to some systematic effects of data analysis.

  19. Anomalous parity asymmetry of WMAP power spectrum data at low multpoles: is it cosmological or systematics?

    CERN Document Server

    Kim, Jaiseung

    2010-01-01

    We have investigated the odd-parity preference of the WMAP 7 year power spectrum. Our investigation shows parity asymmetry of the WMAP data (2<= l <=22) is anomalous at 4-in-1000 level. We also find it likely that low quadrupole power is part of this parity asymmetry rather than an isolated anomaly. We have investigated non-cosmological causes for the odd-parity preference, but have not found a definite non-cosmological origin. WMAP7 data possesses most anomalous odd-parity preference, while they have more accurate calibration and less foreground contamination than earlier data. Besides that, the anomaly is associated with the WMAP power spectrum data, in which most efforts have been exerted to minimize systematics. Therefore, we find it unlikely that calibration or foregrounds are the source of the anomaly. We have also considered primordial origin for the parity asymmetry. However, we find primordial origin requires violation of translational invariance on large scales.

  20. The SLUGGS survey: breaking degeneracies between dark matter, anisotropy and the IMF using globular cluster subpopulations in the giant elliptical NGC 5846

    Science.gov (United States)

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

    2014-03-01

    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 Λ cold dark matter (ΛCDM) and 7-year Wilkinson Microwave Anisotropy Probe (WMAP7) cosmology in terms of virial mass (log MDM ˜ 13.3 M⊙) and concentration (cvir ˜ 8). This is the first such analysis that solves the dynamics of the different GC subpopulations in a self-consistent manner. Our method improves the uncertainties on the halo parameter determination by a factor of 2 and opens new avenues for the use of elliptical galaxy dynamics as tests of predictions from cosmological simulations. The implied stellar mass-to-light ratio derived from the dynamical modelling is fully consistent with a Salpeter initial mass function (IMF) and rules out a bottom light IMF. The different GC subpopulations show markedly distinct orbital distributions at large radii, with red GCs having an anisotropy parameter β˜0.4 outside ˜ 3 Re (Re is the effective radius), and the blue GCs having β˜0.15 at the same radii, while centrally ( ˜ 1 Re) they are both isotropic. We discuss the implications of our findings within the two-phase formation scenario for early-type galaxies.

  1. Phase cross-correlation of the WMAP ILC map and foregrounds

    CERN Document Server

    Naselsky, P D; Verkhodanov, O V

    2003-01-01

    We present a circular cross-correlation tests for the phases of the Internal Linear Combination Map (ILC) and {\\it WMAP}'s foregrounds for all K--W frequency bands at the range of multipoles $\\ell\\le 50$. We have found significant deviations from the expected Poissonian statistics for the ILC and the foregrounds phases. Our analysis shows that the low multipole range of the ILC power spectrum contains some of the foregrounds residues.

  2. Cosmological Parameters from a re-analysis of the WMAP-7 low resolution maps

    CERN Document Server

    Finelli, F; Gruppuso, A; Paoletti, D

    2012-01-01

    Cosmological parameters from WMAP 7 year data are re-analyzed by substituting a pixel-based likelihood estimator to the one delivered publicly by the WMAP team. Our pixel based estimator handles exactly intensity and polarization in a joint manner, allowing to use low-resolution maps and noise covariance matrices in $T,Q,U$ at the same resolution, which in this work is $N_{\\rm side}=16$. We describe the features and the performances of the code implementing our pixel-based likelihood estimator. We perform a battery of tests on the application of our pixel based likelihood routine to WMAP publicly available low resolution foreground cleaned products, in combination with the WMAP high-$\\ell$ likelihood, reporting the differences on cosmological parameters evaluated by the full WMAP likelihood public package. The credible central value for the cosmological parameters change below the 1 $\\sigma$ level with respect to the evaluation by the full WMAP 7 year likelihood code, with the largest difference in a shift to...

  3. 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".

  4. Swelling-induced optical anisotropy of thermoresponsive hydrogels based on poly(2-(2-methoxyethoxy)ethyl methacrylate): deswelling kinetics probed by quantitative Mueller matrix polarimetry.

    Science.gov (United States)

    Patil, Nagaraj; Soni, Jalpa; Ghosh, Nirmalya; De, Priyadarsi

    2012-11-29

    Thermodynamically favored polymer-water interactions below the lower critical solution temperature (LCST) caused swelling-induced optical anisotropy (linear retardance) of thermoresponsive hydrogels based on poly(2-(2-methoxyethoxy)ethyl methacrylate). This was exploited to study the macroscopic deswelling kinetics quantitatively by a generalized polarimetry analysis method, based on measurement of the Mueller matrix and its subsequent inverse analysis via the polar decomposition approach. The derived medium polarization parameters, namely, linear retardance (δ), diattenuation (d), and depolarization coefficient (Δ), of the hydrogels showed interesting differences between the gels prepared by conventional free radical polymerization (FRP) and reversible addition-fragmentation chain transfer polymerization (RAFT) and also between dry and swollen state. The effect of temperature, cross-linking density, and polymerization technique employed to synthesize hydrogel on deswelling kinetics was systematically studied via conventional gravimetry and corroborated further with the corresponding Mueller matrix derived quantitative polarimetry characteristics (δ, d, and Δ). The RAFT gels exhibited higher swelling ratio and swelling-induced optical anisotropy compared to FRP gels and also deswelled faster at 30 °C. On the contrary, at 45 °C, deswelling was significantly retarded for the RAFT gels due to formation of a skin layer, which was confirmed and quantified via the enhanced diattenuation and depolarization parameters.

  5. Evidence for a Galactic Sunyaev-Zel'dovich-like Signal in WMAP Data

    CERN Document Server

    Joudaki, Shahab; Amblard, Alexandre; Cooray, Asantha

    2010-01-01

    The Sunyaev-Zel'dovich (SZ) effect has a distinct spectral signature that allows its separation from fluctuations in the cosmic microwave background (CMB) and foregrounds. Using CMB anisotropies measured in Wilkinson Microwave Anisotropy Probe's five-year maps, we constrain the SZ fluctuations at large, degree angular scales corresponding to multipoles in the range from 10 to 400. While we do not find any evidence for SZ fluctuations at multipoles greater than 50, we do find evidence for an SZ-like signal at ten degrees angular scales. We have failed to explain it as a residual from known Galactic foregrounds. If this signal is in fact the SZ effect associated with electrons of ~1 keV in the outskirts of the Galactic halo, the required column density of electrons is ~1.5 x 10^(22) cm^(-2). The ten degrees angular scale SZ signal is consistent with the FIRAS bound on the CMB spectral distortions.

  6. 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 ...

  7. Revisiting the WMAP - NVSS angular cross correlation. A skeptic view

    CERN Document Server

    Hernandez-Monteagudo, Carlos

    2009-01-01

    In the context of the study of the ISW, we revisit the angular cross correlation of WMAP CMB data with the NVSS radio survey. We compute 2-point cross functions between the two surveys in real and in Fourier space, paying particular attention on the dependence of results on the flux of NVSS radio sources, the angular scales where correlations arise and the comparison with theoretical expectations. We reproduce previous results that claim an excess of correlation in the angular correlation function (ACF), and we also find some (low significance) similarity between the CMB and radio galaxy data in the multipole range $\\el \\in $ [10, 25]. However, the S/N in the ACFs increases with higher flux thresholds for NVSS sources, but drops a $\\sim$ 30 - 50% in separations of the order of a pixel size, suggesting some residual point source contribution. When restricting our analyses to multipoles $\\el \\gt $60, we fail to find any evidence for cross correlation in the range $\\el \\in [2,10]$, where according to the model p...

  8. Dark energy constraints and correlations with systematics from CFHTLS weak lensing, SNLS supernovae Ia and WMAP5

    CERN Document Server

    Kilbinger, M; Guy, J; Astier, Pierre; Tereno, I; Fu, L; Wraith, D; Coupon, J; Mellier, Y; Balland, C; Bouchet, F R; Hamana, T; Hardin, D; McCracken, H J; Pain, R; Regnault, N; Schultheiss, M; Yahagi, H

    2008-01-01

    We combine measurements of weak gravitational lensing from the CFHTLS-Wide survey, supernovae Ia from CFHT SNLS and CMB anisotropies from WMAP5 to obtain joint constraints on cosmological parameters, in particular, the dark energy equation of state parameter w. We assess the influence of systematics in the data on the results and look for possible correlations with cosmological parameters. We implement an MCMC algorithm to sample the parameter space of a flat CDM model with a dark-energy component of constant w. Systematics in the data are parametrised and included in the analysis. We determine the influence of photometric calibration of SNIa data on cosmological results by calculating the response of the distance modulus to photometric zero-point variations. The weak lensing data set is tested for anomalous field-to-field variations and a systematic shape measurement bias for high-z galaxies. Ignoring photometric uncertainties for SNLS biases cosmological parameters by at most 20% of the statistical errors, ...

  9. 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.

  10. 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.

  11. 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...

  12. Anisotropy in conductance of a quasi-one-dimensional metallic surface state measured by a square micro-four-point probe method.

    Science.gov (United States)

    Kanagawa, Taizo; Hobara, Rei; Matsuda, Iwao; Tanikawa, Takehiro; Natori, Akiko; Hasegawa, Shuji

    2003-07-18

    We have devised a "square micro-four-point probe method" using an independently driven ultrahigh-vacuum four-tip scanning tunneling microscope, and succeeded for the first time to directly measure anisotropic electrical conductance of a single-atomic layer on a solid surface. A quasi-one-dimensional metal of a single-domain Si(111)4 x 1-In had a surface-state conductance along the metallic atom chains (sigma(axially)) to be 7.2(+/-0.6) x 10(-4) S/square at room temperature, which was larger than that in the perpendicular direction (sigma(radially)) by approximately 60 times. The sigma(axially) was consistently interpreted by a Boltzmann equation with the anisotropic surface-state band dispersion, while the sigma(radially) was dominated by a surface-space-charge-layer conductance.

  13. 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.

  14. Sunyaev-Zeldovich effect in WMAP and its effect on cosmological parameters

    CERN Document Server

    Huffenberger, Kevin M; Makarov, A; Huffenberger, Kevin M.; Seljak, Uros; Makarov, Alexey

    2004-01-01

    We use multi-frequency information in first year WMAP data to search for the Sunyaev-Zeldovich (SZ) effect. WMAP has sufficiently broad frequency coverage to constrain SZ without the addition of higher frequency data: the SZ power spectrum amplitude is expected to increase 50% from W to Q frequency band. This, in combination with the low noise in WMAP, allows us to strongly constrain the SZ contribution. We derive an optimal frequency combination of WMAP cross-spectra to extract SZ in the presence of noise, CMB, and radio point sources, which are marginalized over. We find that the SZ contribution is less than 2% (95% c.l.) at the first acoustic peak in W band. Under the assumption that the removed radio point sources are not correlated with SZ this limit implies sigma_8<1.07 at 95% c.l. We investigate the effect on the cosmological parameters of allowing an SZ component. We run Monte Carlo Markov Chains with and without an SZ component and find that the addition of SZ does not affect any of the cosmologic...

  15. 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.

  16. Constraints on CPT violation from WMAP three year polarization data: a wavelet analysis

    CERN Document Server

    Cabella, Paolo; Silk, Joseph

    2007-01-01

    We perform a wavelet analysis of the temperature and polarization maps of the Cosmic Microwave Background (CMB) delivered by the WMAP experiment in search for a parity violating signal. Such a signal could be seeded by new physics beyond the standard model, for which the Lorentz and CPT symmetries may not hold. Under these circumstances, the linear polarization direction of a CMB photon may get rotated during its cosmological journey, a phenomenon also called cosmological birefringence. Recently, Feng et al. have analyzed a subset the WMAP and BOOMERanG 2003 angular power spectra of the CMB, deriving a constraint that mildly favors a non zero rotation. By using wavelet transforms we set a tighter limit on the CMB photon rotation angle \\Delta\\alpha= -2.5 \\pm 3.0 (\\Delta\\alpha= -2.5 \\pm 6.0) at the one (two) \\sigma level, consistent with a null detection.

  17. 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.

  18. 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 ...

  19. Information Gains from Cosmological Probes

    CERN Document Server

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

    2015-01-01

    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 $\\Lambda$CDM 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 ...

  20. 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.

  1. 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.

  2. 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...

  3. Cross-correlation of the CMB and foregrounds phases derived from the WMAP data

    CERN Document Server

    Naselsky, P D; Verkhodanov, O V

    2004-01-01

    We present circular and linear cross-correlation tests and the "friend-of-friend" analysis for phases of the Internal Linear Combination Map (ILC) and the WMAP foregrounds for all K--W frequency bands at the range of multipoles $\\ell\\le100$. We compare also Tegmark, de Oliveira-Costa and Hamilton (2003) and Naselsky et al. (2003) cleaned maps with corresponding foregrounds. We have found significant deviations from the expected Poissonian statistics for all the cleaned maps and foregrounds. Our analysis shows that, for a low multipole range of the cleaned maps, power spectra contains some of the foregrounds residuals mainly from the W band.

  4. 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...

  5. 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 $\

  6. 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.

  7. 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.

  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. Template fitting of WMAP 7-year data: anomalous dust or flattening synchrotron emission?

    CERN Document Server

    Peel, M W; Davies, R D; Banday, A J; Jaffe, T R; Jonas, J L

    2011-01-01

    Anomalous microwave emission at 20-40GHz has been detected across our Galactic sky. It is highly correlated with thermal dust emission and hence it is thought to be due to spinning dust grains. Alternatively, this emission could be due to synchrotron radiation with a flattening (hard) spectral index. We cross-correlate synchrotron, free- free and thermal dust templates with the WMAP 7-year maps using synchrotron templates at both 408MHz and 2.3GHz to assess the amount of flat synchrotron emission that is present, and the impact that this has on the correlations with the other components. We find that there is only a small amount of flattening visible in the synchrotron spectral indices by 2.3GHz, of around \\Delta{\\beta} \\approx 0.05, and that the significant level of dust-correlated emission in the lowest WMAP bands is largely unaffected by the choice of synchrotron template, particularly at high latitudes (it decreases by only ~7 per cent when using 2.3 GHz rather than 408 MHz). This agrees with expectation ...

  10. Foreground Analysis Using Cross-Correlations of External Templates on the 7-year WMAP data

    CERN Document Server

    Ghosh, Tuhin; Jaffe, Tess; Dickinson, Clive; Davies, Rod; Davis, Richard; Gorski, Krzysztof

    2012-01-01

    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 and high latitudes using a cross-correlation technique. In particular, we compare the observed emission in several large partitions of the sky plus 33 selected sky regions to three "standard" templates. The regions are selected using a criterion based on the morphology of these template maps. The synchrotron emission shows evidence of steepening between GHz frequencies and the \\emph{WMAP} bands. There are indications of spectral index variations across the sky but the current data are not precise enough to accurately quantify this from region-to-region. The emission correlated with the $H_{\\alpha}$ template shows clear evidence of deviation from a free-free spectrum. The emission can be decomposed into a contribution from both free-free and spinning dust in the warm ionised medium of the Galax...

  11. 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:...

  12. Optical-reflectance anisotropy in epitaxial metastable (GaAs) sub 1 minus x (Si sub 2 ) sub x (001) alloys: A probe for the zinc-blende--to--diamond structural transition

    Energy Technology Data Exchange (ETDEWEB)

    Lastras-Martriaanez, A.; Rodriguez-Pedroza, G. (Instituto de Fisica, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, San Luis Potosi, San Luis Potosi, Mexico (MX)); Mei, D.H.; Kramer, B.; Lubben, D.; Greene, J.E. (Department of Materials Science, The Coordinated Science Laboratory, the Materials Research Laboratory, University of Illinois, 1101 West Springfield Ave., Urbana, Illinois 61801 (USA))

    1991-06-15

    Anisotropy in the above-band-gap optical reflectance along the (110) and (1{bar 1}0) directions has been used to investigate long-range atomic ordering in metastable epitaxial (GaAs){sub 1{minus}{ital x}}(Si{sub 2}){sub {ital x}}(001) alloys as a function of Si concentration {ital x}. The amplitude of the differentiated reflectance-difference signal was found to decrease monotonically with increasing {ital x} and reach zero, corresponding to the critical concentration for the zinc-blende--to--diamond transition, at {ital x}{congruent}0.37, consistent with x-ray-diffraction results. The highest sensitivity in the optical-anisotropy spectra was obtained in the spectral region near the {ital E}{sub 0}{sup {prime}} critical point (4.5 eV in GaAs).

  13. 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....

  14. 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.

  15. WMAP 5-year constraints on time variation of $\\alpha$ and $m_e$

    CERN Document Server

    Scóccola, Claudia G; Vucetich, Hector

    2009-01-01

    We studied the role of fundamental constants in an updated recombination scenario, focusing on the time variation of the fine structure constant \\alpha and the electron mass m_e in the early Universe. Using CMB data including WMAP 5-yr release, and the 2dFGRS power spectrum, we put bounds on variations of these constants, when both constants are allowed to vary, and in the case that only one of them is variable. In particular, we have found that -0.019 < \\Delta \\alpha / \\alpha_0 < 0.017 (95% c.l.), in our joint estimation of \\alpha and cosmological parameters. Finally, we analyze how the constraints depends on the recombination scenario.

  16. 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.

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

    CERN Document Server

    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. Therefore one can conclude that at lest $3\\sigma$ level the future Universe will be dominated by phantom like dark energy. It is not consistent with positive energy condition, however this condition must be satisfied to derive the holographic bound. It implies that the current cosmic observational data points disfavor the HDE model.

  18. 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...

  19. 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...... is included. Within this framework it is demonstrated that the network can extract the CMB polarization signal with no sign of pollution by the polarized foregrounds. The errors in the derived polarization power spectra are improved compared to the errors derived by the WMAP Team....

  20. 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.)

  1. Cosmological Perturbation Theory to second order for curvature, density, and gravity waves on FRW background; and the WMAP results of inhomogeneity and clustering in the early universe

    CERN Document Server

    Patwardhan, Ajay; Kumar, M S R

    2008-01-01

    The second order perturbation calculations for gravity wave and Einstein equation for space time and matter are presented for the FRW metric cosmological model. While exact equations are found, suitable approximations are made to obtain definite results. In the gravity wave case the small wavelength case allows nearly locally flat background for obtaining a fit to the WMAP data. In the density and curvature case the FRW background is retained for the length scale of WMAP. Clustering and inhomogeneity are understood. The gravity wave ripples from Big Bang couple nonlinearly and redistribute the modes to higher values of 'l' giving consistency with the WMAP results. The order by order consistency of Einstein equations relate the second order perturbations in the curvature and density and the wrinkles in spacetime caused by the gravity wave modes reorganize these distributions. The radiation data of WMAP gives the picture of a FRW spacetime deformed and wrinkled consistent with matter distribution to one hundred...

  2. 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.

  3. WMAP 5-year constraints on time variation of $\\alpha$ and $m_e$ in a detailed recombination scenario

    CERN Document Server

    Scóccola, Claudia G; Vucetich, Hector

    2008-01-01

    We study the role of fundamental constants in an updated recombination scenario. We focus on the time variation of the fine structure constant, and the electron mass in the early Universe, and put bounds on these quantities by using data from CMB including WMAP 5-yr release and the 2dFGRS power spectrum. We analyze how the constraints are modified when changing the recombination scenario.

  4. Anomalous parity asymmetry of WMAP 7-year power spectrum data at low multipoles: Is it cosmological or systematics?

    Science.gov (United States)

    Kim, Jaiseung; Naselsky, Pavel

    2010-09-01

    It is natural to assume a parity-neutral Universe and accordingly no particular parity preference in the cosmic microwave background sky. However, our investigation based on the WMAP 7-year power spectrum shows there exists a large-scale odd-parity preference with high statistical significance. We also find that the odd-parity preference in WMAP7 data is slightly higher than earlier releases. We have investigated possible origins, and ruled out various noncosmological origins. We also find that the primordial origin requires |Re[Φ(k)]|≪|Im[Φ(k)]| for k≲22/η0, where η0 is the present conformal time. In other words, it requires translational invariance in the primordial Universe to be violated on scales larger than 4Gpc. The Planck surveyor, which possesses wide frequency coverage and systematics distinct from the WMAP, may allow us to resolve the mystery of the anomalous odd-parity preference. Furthermore, polarization maps of large-sky coverage will reduce degeneracy in cosmological origins.

  5. Polarimetry-based method to extract geometry-independent metrics of tissue anisotropy.

    Science.gov (United States)

    Wallenburg, Marika A; Wood, Michael F G; Ghosh, Nirmalya; Vitkin, I Alex

    2010-08-01

    Recently, we have used polarimetry as a method for assessing the linear retardance of infarcted myocardium. While linear retardance reflects tissue anisotropy, experimental geometry has a confounding effect due to dependence of the linear retardance on the orientation of the sample with respect to the probing beam. Here, polarimetry imaging of an 8mm diameter birefringent polystyrene sphere of known anisotropy axis was used to test a dual-projection method by which the anisotropy axis and its true magnitude can be reconstructed, thus eliminating the confounding effect of anisotropy axis orientation. Feasibility is demonstrated in ex-vivo tissue imaging.

  6. 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.

  7. 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.

  8. 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...

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

    Directory of Open Access Journals (Sweden)

    Anna Bonaldi

    2012-01-01

    Full Text Available 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±0.8 GHz, in agreement with previous analyses which favored νp < 23 GHz. The ability of our method to correctly recover the position of the peak is verified through simulations. We compare the estimated AME spectrum with theoretical spinning dust models to constrain the hydrogen density nH. The best results are obtained with densities around 0.2–0.3 cm−3, typical of warm ionised medium (WIM to warm neutral medium (WNM conditions. The degeneracy with the gas temperature prevents an accurate determination of nH, especially for low hydrogen ionization fractions, where densities of a few cm−3 are also allowed.

  10. 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.

  11. Constraints on variation in $\\alpha$ and $m_e$ from WMAP 7-year data

    CERN Document Server

    Landau, Susana J

    2010-01-01

    We update the constraints on the time variation of the fine structure constant $\\alpha$ and the electron mass $m_e$, using the latest CMB data, including the 7-yr release of WMAP. We made statistical analyses of the variation of each one of the constants and of their joint variation, together with the basic set of cosmological parameters. We used a modified version of CAMB and COSMOMC to account for these possible variations. We present bounds on the variation of the constants for different data sets, and show how results depend on them. When using the latest CMB data plus the power spectrum from Sloan Digital Sky Survey LRG, we find that $\\alpha / \\alpha_0=0.986 \\pm 0.007$ at 1-$\\sigma$ level, when the 6 basic cosmological parameters were fitted, and only variation in $\\alpha$ was allowed. The constraints in the case of variation in both constants are $ \\alpha / \\alpha_0= 0.986 \\pm 0.009$ and $m_e / m_{e0} = 0.999 \\pm 0.035$. In the case of only variation in $m_e$, the bound is $m_e /m_{e0}=0.964 \\pm 0.025$.

  12. 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...

  13. Evolution of the CMB Power Spectrum Across WMAP Data Releases: A Nonparametric Analysis

    CERN Document Server

    Aghamousa, Amir; Souradeep, Tarun

    2011-01-01

    We present a comparative analysis of the WMAP 1-, 3-, 5-, and 7-year data releases for the CMB angular power spectrum, with respect to the following three key questions: (a) How well is the angular power spectrum determined by the data alone? (b) How well is the Lambda-CDM model supported by a model-independent, data-driven analysis? (c) What are the realistic uncertainties on peak/dip locations and heights? Our analysis is based on a nonparametric function estimation methodology [1,2]. Our results show that the height of the power spectrum is well determined by data alone for multipole index l approximately less than 600 (1-year), 800 (3-year), and 900 (5- and 7-year data realizations). We also show that parametric fits based on the Lambda-CDM model are remarkably close to our nonparametric fit in l-regions where the data are sufficiently precise. A contrasting example is provided by an H-Lambda-CDM model: As the data become precise with successive data realizations, the H-Lambda-CDM angular power spectrum g...

  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. 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.

  16. 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...

  17. 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.

  18. Subminiature Hot-Wire Probes

    Science.gov (United States)

    Westphal, R. V.; Lemos, F. R.; Ligrani, P. M.

    1989-01-01

    Class of improved subminiature hot-wire flow-measuring probes developed. Smaller sizes yield improved resolution in measurements of practical aerodynamic flows. Probe made in one-wire, two-perpendicular-wire, and three-perpendicular-wire version for measurement of one, two, or all three components of flow. Oriented and positioned on micromanipulator stage and viewed under microscope during fabrication. Tested by taking measurements in constant-pressure turbulent boundary layer. New probes give improved measurements of turbulence quantities near surfaces and anisotropies of flows strongly influence relative errors caused by phenomena related to spatial resolution.

  19. 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.

  20. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    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......). Mobile probing was inspired by the cultural probe method, and was influenced by qualitative interview and inquiry approaches. The method has been used in two subsequent projects, involving school children (young adults at 15-17 years old) and employees (adults) in a consultancy company. Findings 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). The development...

  1. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    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...... and space). Mobile probing was inspired by the cultural probe method, and was influenced by qualitative interview and inquiry approaches. The method has been used in two subsequent projects, involving school children (young adults at 15-17 years old) and employees (adults) in a consultancy company. Findings...... 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...

  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. 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.

  4. Seasonal anisotropy in handedness.

    Science.gov (United States)

    Jones, Gregory V; Martin, Maryanne

    2008-01-01

    The preference for using either the left or the right hand has been linked to important human characteristics such as language lateralisation within the cerebral hemispheres, and evidence has been reported that the proportions of different types of handedness may be influenced by factors such as levels of maternal hormones and anxiety. Under such influences, it is possible in principle that distributions of handedness provide evidence of seasonal anisotropy, that is, variation in the direction of handedness for births in different parts of the year. The results of a number of studies are compared here, and shown to provide evidence of a significant tendency for the incidence of left-handed people to be higher among those born in the spring and ensuing months (March-July in the northern hemisphere) than among those born in the remainder of the year, at least among the male population.

  5. CMB statistical anisotropy from noncommutative gravitational waves

    CERN Document Server

    Shiraishi, Maresuke; Ricciardone, Angelo; Arroja, Frederico

    2014-01-01

    Primordial statistical anisotropy is a key indicator to investigate early Universe models and has been probed by the cosmic microwave background (CMB) anisotropies. In this paper, we examine tensor-mode CMB fluctuations generated from anisotropic gravitational waves, parametrised by $P_h({\\bf k}) = P_h^{(0)}(k) [ 1 + \\sum_{LM} f_L(k) g_{LM} Y_{LM} (\\hat{\\bf k}) ]$, where $P_h^{(0)}(k)$ is the usual scale-invariant power spectrum. Such anisotropic tensor fluctuations may arise from an inflationary model with noncommutativity of fields. It is verified that in this model, an isotropic component and a quadrupole asymmetry with $f_0(k) = f_2(k) \\propto k^{-2}$ are created and hence highly red-tilted off-diagonal components arise in the CMB power spectra, namely $\\ell_2 = \\ell_1 \\pm 2$ in $TT$, $TE$, $EE$ and $BB$, and $\\ell_2 = \\ell_1 \\pm 1$ in $TB$ and $EB$. We find that B-mode polarisation is more sensitive to such signals than temperature and E-mode polarisation due to the smallness of large-scale cosmic varian...

  6. Polarization singularity anisotropy: determining monstardom

    CERN Document Server

    Dennis, Mark R

    2008-01-01

    C points, that is isolated points of circular polarization in transverse fields of varying polarization, are classified morphologically into three distinct types, known as lemons, stars and monstars. These morphologies are interpreted here according to two natural parameters associated with the singularity, namely the anisotropy of the C point, and the polarization azimuth on the anisotropy axis. In addition to providing insight into singularity morphology, this observation applies to the densities of the various morphologies in isotropic random polarization speckle fields.

  7. Magnetic anisotropy and porosity of Antarctic chondrites

    OpenAIRE

    Hamano,Yozo/Yomogida,Kiyoshi

    1982-01-01

    Magnetic susceptibility anisotropy and porosity were measured in eleven Antarctic meteorites. These meteorites are ordinary chondrites (H and L type) in various metamorphic stages. Large magnetic anisotropy has been observed in most of the chondrites. The foliation type of the anisotropy, inferred from the shape of the susceptibility ellipsoid indicates that a uniaxial compressional type deformation is responsible for the anisotropy. The degree of the anisotropy and the porosity do not correl...

  8. Magnetization switching behavior with competing anisotropies in epitaxial Co3FeN /MnN exchange-coupled bilayers

    Science.gov (United States)

    Hajiri, T.; Yoshida, T.; Jaiswal, S.; Filianina, M.; Borie, B.; Ando, H.; Asano, H.; Zabel, H.; Kläui, M.

    2016-11-01

    We report unusual magnetization switching processes and angular-dependent exchange bias effects in fully epitaxial Co3FeN /MnN bilayers, where magnetocrystalline anisotropy and exchange coupling compete, probed by longitudinal and transverse magneto-optic Kerr effect (MOKE) magnetometry. The MOKE loops show multistep jumps corresponding to the nucleation and propagation of 90∘ domain walls in as-grown bilayers. By inducing exchange coupling, we confirm changes of the magnetization switching process due to the unidirectional anisotropy field of the exchange coupling. Taking into account the experimentally obtained values of the fourfold magnetocrystalline anisotropy, the unidirectional anisotropy field, the exchange-coupling constant, and the uniaxial anisotropy including its direction, the calculated angular-dependent exchange bias reproduces the experimental results. These results demonstrate the essential role of the competition between magnetocrystalline anisotropy and exchange coupling for understanding and tailoring exchange-coupling phenomena usable for engineering switching in fully epitaxial bilayers made of tailored materials.

  9. Effect of induced shape anisotropy on magnetic properties of ferromagnetic cobalt nanocubes.

    Science.gov (United States)

    Srikala, D; Singh, V N; Banerjee, A; Mehta, B R

    2010-12-01

    We report on the synthesis of ferromagnetic cobalt nanocubes of various sizes using thermal pyrolysis method and the effect of shape anisotropy on the static and dynamic magnetic properties were studied. Shape anisotropy of approximately 10% was introduced in nanocubes by making nanodiscs using a linear chain amine surfactant during synthesis process. It has been observed that, ferromagnetism persisted above room temperature and a sharp drop in magnetic moment at low temperatures in zero-field cooled magnetization may be associated with the spin disorder due to the effective anisotropy present in the system. Dynamic magnetic properties were studied using RF transverse susceptibility measurements at different temperatures and the singularities due to anisotropy fields were probed at low temperatures. Symmetrically located broad peaks are observed in the frozen state at the effective anisotropy fields and the peak structure is strongly affected by shape anisotropy and temperature. Irrespective of size the shape anisotropy gave rise to higher coercive fields and larger transverse susceptibility ratio at all temperatures. The role of shape anisotropy and the size of the particles on the observed magnetic behaviour were discussed.

  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. CMB statistical anisotropy from noncommutative gravitational waves

    Energy Technology Data Exchange (ETDEWEB)

    Shiraishi, Maresuke; Ricciardone, Angelo [Dipartimento di Fisica e Astronomia ' ' G. Galilei' ' , Università degli Studi di Padova, via Marzolo 8, I-35131, Padova (Italy); Mota, David F. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, N-0315 Oslo (Norway); Arroja, Frederico, E-mail: maresuke.shiraishi@pd.infn.it, E-mail: d.f.mota@astro.uio.no, E-mail: angelo.ricciardone@pd.infn.it, E-mail: arroja@pd.infn.it [INFN, Sezione di Padova, via Marzolo 8, I-35131, Padova (Italy)

    2014-07-01

    Primordial statistical anisotropy is a key indicator to investigate early Universe models and has been probed by the cosmic microwave background (CMB) anisotropies. In this paper, we examine tensor-mode CMB fluctuations generated from anisotropic gravitational waves, parametrised by P{sub h}(k) = P{sub h}{sup (0)}(k) [ 1 + ∑{sub LM} f{sub L}(k) g{sub LM} Y{sub LM} ( k-circumflex )], where P{sub h}{sup (0)}(k) is the usual scale-invariant power spectrum. Such anisotropic tensor fluctuations may arise from an inflationary model with noncommutativity of fields. It is verified that in this model, an isotropic component and a quadrupole asymmetry with f{sub 0}(k) = f{sub 2}(k) ∝ k{sup -2} are created and hence highly red-tilted off-diagonal components arise in the CMB power spectra, namely ℓ{sub 2} = ℓ{sub 1} ± 2 in TT, TE, EE and BB, and ℓ{sub 2} = ℓ{sub 1} ± 1 in TB and EB. We find that B-mode polarisation is more sensitive to such signals than temperature and E-mode polarisation due to the smallness of large-scale cosmic variance and we can potentially measure g{sub 00} = 30 and g{sub 2M} = 58 at 68% CL in a cosmic-variance-limited experiment. Such a level of signal may be measured in a PRISM like experiment, while the instrumental noise contaminates it in the Planck experiment. These results imply that it is impossible to measure the noncommutative parameter if it is small enough for the perturbative treatment to be valid. Our formalism and methodology for dealing with the CMB tensor statistical anisotropy are general and straightforwardly applicable to other early Universe models.

  12. 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 < 3.00). Flow stresses (0.2% offset) were measured at room temperature by uniaxial t...

  13. 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.

  14. 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...

  15. 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...

  16. The galaxy cluster Ysz-Lx and Ysz-M relations from the WMAP 5-yr data

    CERN Document Server

    Melin, J -B; Delabrouille, J; Arnaud, M; Piffaretti, R; Pratt, G W

    2010-01-01

    We use multifrequency matched filters to estimate, in the WMAP 5-year data, the Sunyaev-Zel'dovich (SZ) fluxes of 893 ROSAT NORAS/REFLEX clusters spanning the luminosity range Lx,[0.1-2.4]keV = 2 10^{41} - 3.5 10^{45} erg s^{-1}. The filters are spatially optimised by using the universal pressure profile recently obtained from combining XMM-Newton observations of the REXCESS sample and numerical simulations. Although the clusters are individually only marginally detected, we are able to firmly measure the SZ signal (>10 sigma) when averaging the data in luminosity/mass bins. The comparison between the bin-averaged SZ signal versus luminosity and X-ray model predictions shows excellent agreement, implying that there is no deficit in SZ signal strength relative to expectations from the X-ray properties of clusters. Using the individual cluster SZ flux measurements, we directly constrain the Y500-Lx and Y500-M500 relations, where Y500 is the Compton y-parameter integrated over a sphere of radius r500. The Y500-M...

  17. 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.

  18. 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

  19. Cultural probes

    DEFF Research Database (Denmark)

    Madsen, Jacob Østergaard

    2016-01-01

    The aim of this study was thus to explore cultural probes (Gaver, Boucher et al. 2004), as a possible methodical approach, supporting knowledge production on situated and contextual aspects of occupation.......The aim of this study was thus to explore cultural probes (Gaver, Boucher et al. 2004), as a possible methodical approach, supporting knowledge production on situated and contextual aspects of occupation....

  20. Extension of the standard cosmological model: anisotropy, rotation, and magnetic field

    CERN Document Server

    Demia'nski, M

    2007-01-01

    We show that the difference between the theoretically expected and measured by WMAP amplitude of the quadrupole fluctuations of CMB can be related to the impact of the anisotropic curvature of the homogeneous universe dominated by the dark energy. In such universe the matter expansion becomes practically isotropic just after the period of inflation and only at small redshifts the anisotropic expansion is generated again by the curvature. For the simplest model we found that the required deviations from the spatially flat universe are small, $\\Omega_K=1-\\Omega_m- \\Omega_\\Lambda \\leq 10^{-4}$. For such models the correlations of large scale perturbations and distortions of their Gaussianity are possible. Such models are also compatible with existence of a homogeneous magnetic field and matter rotation which contribute to the low $\\ell$ anisotropy and can be considered as ``hidden parameters'' of the model. Their influence can be observed as, for example, the Faraday rotation of the CMB and light of the farthest...

  1. Probing the High-Redshift Universe Using Fluctuations in the Cosmic Microwave and Infrared Backgrounds

    Science.gov (United States)

    Smidt, Joseph Michael

    Background (CIB) continues to be one of the best probes of physics at the early stages of the universe. If the CMB were a purely Gaussian field, all statistical information would be contained in the power spectrum or two-point correlation function. However, non-Gaussianities ensure that new physics may be extracted from higher n-point correlation functions including the bispectrum and trispectrum of the CMB. In this thesis discuss new estimators we have formulated to probe primordial non-Gaussianity in the bispectrum and trispectrum of CMB data and the constraints we have made using WMAP data while discussing implications for inflationary models. I discuss how these same methods may be used to probe CMB Lensing. Finally, I discuss how upcoming measurements of near and far-infrared CIB fluctuations may be used to constrain the redshift of reionization and clustering of various populations of galaxies. Some preliminary results involving CANDELS, Spitzer SDWFS, CIBER and Herschel datasets is presented.

  2. 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.

  3. Galaxy clusters and microwave background anisotropy

    CERN Document Server

    Quilis, V; Sáez, D

    1995-01-01

    Previous estimates of the microwave background anisotropies produced by freely falling spherical clusters are discussed. These estimates are based on the Swiss-Cheese and Tolman-Bondi models. It is proved that these models give only upper limits to the anisotropies produced by the observed galaxy clusters. By using spherically symmetric codes including pressureless matter and a hot baryonic gas, new upper limits are obtained. The contributions of the hot gas and the pressureless component to the total anisotropy are compared. The effects produced by the pressure are proved to be negligible; hence, estimations of the cluster anisotropies based on N-body simulations are hereafter justified. After the phenomenon of violent relaxation, any realistic rich cluster can only produce small anisotropies with amplitudes of order 10^{-7}. During the rapid process of violent relaxation, the anisotropies produced by nonlinear clusters are expected to range in the interval (10^{-6},10^{-5}). The angular scales of these anis...

  4. Quantitative assessment of diffusional kurtosis anisotropy.

    Science.gov (United States)

    Glenn, G Russell; Helpern, Joseph A; Tabesh, Ali; Jensen, Jens H

    2015-04-01

    Diffusional kurtosis imaging (DKI) measures the diffusion and kurtosis tensors to quantify restricted, non-Gaussian diffusion that occurs in biological tissue. By estimating the kurtosis tensor, DKI accounts for higher order diffusion dynamics, when compared with diffusion tensor imaging (DTI), and consequently can describe more complex diffusion profiles. Here, we compare several measures of diffusional anisotropy which incorporate information from the kurtosis tensor, including kurtosis fractional anisotropy (KFA) and generalized fractional anisotropy (GFA), with the diffusion tensor-derived fractional anisotropy (FA). KFA and GFA demonstrate a net enhancement relative to FA when multiple white matter fiber bundle orientations are present in both simulated and human data. In addition, KFA shows net enhancement in deep brain structures, such as the thalamus and the lenticular nucleus, where FA indicates low anisotropy. Thus, KFA and GFA provide additional information relative to FA with regard to diffusional anisotropy, and may be particularly advantageous for the assessment of diffusion in complex tissue environments.

  5. Magnetic Anisotropy in the Radula of Chiton

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jian-Gao; QIAN Xia; LIU Wei; LIU Chuan-lin; ZHAN Wen-Shan

    2000-01-01

    Radular teeth of chitons were studied by using magnetic torque-meter and transmission electron microscopy (TEM). The magnetic torque curves give clear evidence of presence of strong uni-axial magnetic anisotropy. The easy axis is along the length direction of tongue-like radula. The TEM pattern shows that long chip-like magnetite nano-scaled particles packed in the radular teeth with both uni-axial shape anisotropy and magneto-crystalline anisotropy.

  6. Magnetic Anisotropy in the Radula of Chiton

    Science.gov (United States)

    Zhao, Jian-Gao; Qian, Xia; Liu, Wei; Liu, Chuan-Lin; Zhan, Wen-Shan

    2000-07-01

    Radular teeth of chitons were studied by using magnetic torque-meter and transmission electron microscopy (TEM). The magnetic torque curves give clear evidence of presence of strong uni-axial magnetic anisotropy. The easy axis is along the length direction of tongue-like radula. The TEM pattern shows that long chip-like magnetite nano-scaled particles packed in the radular teeth with both uni-axial shape anisotropy and magneto-crystalline anisotropy.

  7. Statistical Anisotropy from Anisotropic Inflation

    CERN Document Server

    Soda, Jiro

    2012-01-01

    We review an inflationary scenario with the anisotropic expansion rate. An anisotropic inflationary universe can be realized by a vector field coupled with an inflaton, which can be regarded as a counter example to the cosmic no-hair conjecture. We show generality of anisotropic inflation and derive a universal property. We formulate cosmological perturbation theory in anisotropic inflation. Using the formalism, we show anisotropic inflation gives rise to the statistical anisotropy in primordial fluctuations. We also explain a method to test anisotropic inflation using the cosmic microwave background radiation (CMB).

  8. Formation of Magnetic Anisotropy by Lithography.

    Science.gov (United States)

    Kim, Si Nyeon; Nam, Yoon Jae; Kim, Yang Doo; Choi, Jun Woo; Lee, Heon; Lim, Sang Ho

    2016-05-24

    Artificial interface anisotropy is demonstrated in alternating Co/Pt and Co/Pd stripe patterns, providing a means of forming magnetic anisotropy using lithography. In-plane hysteresis loops measured along two principal directions are explained in depth by two competing shape and interface anisotropies, thus confirming the formation of interface anisotropy at the Co/Pt and Co/Pd interfaces of the stripe patterns. The measured interface anisotropy energies, which are in the range of 0.2-0.3 erg/cm(2) for both stripes, are smaller than those observed in conventional multilayers, indicating a decrease in smoothness of the interfaces when formed by lithography. The demonstration of interface anisotropy in the Co/Pt and Co/Pd stripe patterns is of significant practical importance, because this setup makes it possible to form anisotropy using lithography and to modulate its strength by controlling the pattern width. Furthermore, this makes it possible to form more complex interface anisotropy by fabricating two-dimensional patterns. These artificial anisotropies are expected to open up new device applications such as multilevel bits using in-plane magnetoresistive thin-film structures.

  9. Surface magnetic anisotropy in amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tejedor, M.; Rubio, H.; Elbaile, L.; Iglesias, R. (Univ. de Oviedo (Spain). Dept. de Fisica)

    1993-11-01

    The total in-plane magnetic anisotropy and the in-plane surface magnetic anisotropy constants have been measured in nearly-zero magnetostrictive amorphous ribbons in as-quenched state. The magnetostatic energy of a two-dimensional square-lattice of parallelepipeds or ellipsoids, whose dimensions are determined by the parameters characterizing the roughness, is evaluated. From the results obtained, they can conclude that the in-plane surface anisotropy can be magnetostatic in origin but it has little influence on the total in-plane magnetic anisotropy of the ribbon.

  10. Azimuthal anisotropy measurements by STAR

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Li

    2014-06-15

    The recent study of centrality and transverse momentum (p{sub T}) dependence of inclusive charged hardron elliptic anisotropy (v{sub 2}) at midrapidity (|η|<1.0) in Au+Au collision at √(s{sub NN})=7.7,11.5,19.6,27, and39 GeV in STAR Beam Energy Scan program is presented. We show that the observed increase of inclusive v{sub 2} is mainly due to the average p{sub T} increase with energy. In Au+Au 200 GeV collisions, the triangular anisotropy (v{sub 3}) measurements highly depend on measurement methods; v{sub 3} is strongly dependent on Δη. The difference between two- and four-particle cumulants v{sub 2}{2} and v{sub 2}{4} for Au+Au and Cu+Cu collision at √(s{sub NN})=62.4 and 200 GeV is used to explore flow fluctuations. Furthermore, by exploiting the symmetry of average flow in pseudorapidity η about midrapidity, the Δη-dependent and independent components are separated using v{sub 2}{2} and v{sub 2}{4}.

  11. Measurements of the anisotropy in permalloy

    NARCIS (Netherlands)

    Eijkel, Kees J.

    1988-01-01

    A measurement system is described, which accurately determines the anisotropy field H/sub k/ and the orientation of the easy-axis in a permalloy film or in any material showing magnetization induced resistance anisotropy. An accuracy of 0.1% in H/sub k/ and 0.1 degrees in easy-axis orientation is re

  12. Optical and diamagnetic anisotropy of graphene oxide

    Science.gov (United States)

    Exarhos, A. L.; Vora, P. M.; Lou, Z.; Johnson, A. T.; Kikkawa, J. M.

    2009-03-01

    We have recently shown that graphene oxide (GO) emits a broad photoluminescence (PL) band in both solid and aqueous preparations. The origin of this PL is not yet well understood, but for absorptive and emissive optical processes originating in the two dimensional GO plane, one expects an in-plane polarization. Studies of optical anisotropy can therefore help to clarify the origin of the PL. Here we use a method of optical nanomagnetometry (Torrens, et al, JACS 129, p. 252 (2007)) to extract these quantities, also determining the magnetic anisotropy. We find that when aqueous preparations of GO are placed in a magnetic field, diamagnetically induced alignment leads to marked linear polarization anisotropy of absorbance and photoluminescence. By taking six optical measurements at each magnetic field, we are able to extract the intrinsic polarization anisotropies of optical absorption and emission of GO flakes and to quantify the orbital diamagnetic anisotropy. We discuss how these quantities give insight into electronic delocalization in these systems.

  13. 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.

  14. Conductivity Probe

    Science.gov (United States)

    2008-01-01

    The Thermal and Electrical Conductivity Probe (TECP) for NASA's Phoenix Mars Lander took measurements in Martian soil and in the air. The needles on the end of the instrument were inserted into the Martian soil, allowing TECP to measure the propagation of both thermal and electrical energy. TECP also measured the humidity in the surrounding air. The needles on the probe are 15 millimeters (0.6 inch) long. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  15. 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.

  16. 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.

  17. 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.

  18. Pollution Probe.

    Science.gov (United States)

    Chant, Donald A.

    This book is written as a statement of concern about pollution by members of Pollution Probe, a citizens' anti-pollution group in Canada. Its purpose is to create public awareness and pressure for the eventual solution to pollution problems. The need for effective government policies to control the population explosion, conserve natural resources,…

  19. A minimal empirical model for the cosmic far-infrared background anisotropies

    CERN Document Server

    Wu, Hao-Yi

    2016-01-01

    Cosmic far-infrared background (CFIRB) probes unresolved dusty star-forming galaxies across cosmic time and is complementary to ultraviolet/optical probes of galaxy evolution. In this work, we interpret the observed CFIRB anisotropies using an empirical model based on recent galaxy survey results, including stellar mass functions, star-forming main sequence, and dust attenuation. Without introducing new parameters, our model agrees well with the CFIRB anisotropies observed by Planck and the submillimeter number counts observed by Herschel. We find that the commonly used linear relation between infrared luminosity and star-formation rate over-produces the observed CFIRB amplitudes, and lower infrared luminosities from low-mass galaxies are required. Our results indicate that CFIRB not only provides a consistency check for galaxy evolution models but also informs the star-formation rate and dust content for low-mass galaxies.

  20. 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.

  1. 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.

  2. Exchange anisotropy pinning of a standing spin-wave mode

    Science.gov (United States)

    Magaraggia, R.; Kennewell, K.; Kostylev, M.; Stamps, R. L.; Ali, M.; Greig, D.; Hickey, B. J.; Marrows, C. H.

    2011-02-01

    Standing spin waves in a thin film are used as sensitive probes of interface pinning induced by an antiferromagnet through exchange anisotropy. Using coplanar waveguide ferromagnetic resonance, pinning of the lowest energy spin-wave thickness mode in Ni80Fe20/Ir25Mn75 exchange-biased bilayers was studied for a range of Ir25Mn75 thicknesses. We show that pinning of the standing mode can be used to amplify, relative to the fundamental resonance, frequency shifts associated with exchange bias. The shifts provide a unique “fingerprint” of the exchange bias and can be interpreted in terms of an effective ferromagnetic film thickness and ferromagnet-antiferromagnet interface anisotropy. Thermal effects are studied for ultrathin antiferromagnetic Ir25Mn75 thicknesses, and the onset of bias is correlated with changes in the pinning fields. The pinning strength magnitude is found to grow with cooling of the sample, while the effective ferromagnetic film thickness simultaneously decreases. These results suggest that exchange bias involves some deformation of magnetic order in the interface region.

  3. 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...

  4. 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...

  5. Spatial Periodicity of Galaxy Number Counts, CMB Anisotropy, and SNIa Hubble Diagram Based on the Universe Accompanied by a Non-Minimally Coupled Scalar Field

    CERN Document Server

    Hirano, Koichi; Komiya, Zen

    2008-01-01

    We have succeeded in establishing a cosmological model with a non-minimally coupled scalar field $\\phi$ that can account not only for the spatial periodicity or the {\\it picket-fence structure} exhibited by the galaxy $N$-$z$ relation of the 2dF survey but also for the spatial power spectrum of the cosmic microwave background radiation (CMB) temperature anisotropy observed by the WMAP satellite. The Hubble diagram of our model also compares well with the observation of Type Ia supernovae. The scalar field of our model universe starts from an extremely small value at around the nucleosynthesis epoch, remains in that state for sufficiently long periods, allowing sufficient time for the CMB temperature anisotropy to form, and then starts to grow in magnitude at the redshift $z$ of $\\sim 1$, followed by a damping oscillation which is required to reproduce the observed picket-fence structure of the $N$-$z$ relation. To realize such behavior of the scalar field, we have found it necessary to introduce a new form of...

  6. Elastic anisotropy of Earth's inner core.

    Science.gov (United States)

    Belonoshko, Anatoly B; Skorodumova, Natalia V; Rosengren, Anders; Johansson, Börje

    2008-02-08

    Earth's solid-iron inner core is elastically anisotropic. Sound waves propagate faster along Earth's spin axis than in the equatorial plane. This anisotropy has previously been explained by a preferred orientation of the iron alloy hexagonal crystals. However, hexagonal iron becomes increasingly isotropic on increasing temperature at pressures of the inner core and is therefore unlikely to cause the anisotropy. An alternative explanation, supported by diamond anvil cell experiments, is that iron adopts a body-centered cubic form in the inner core. We show, by molecular dynamics simulations, that the body-centered cubic iron phase is extremely anisotropic to sound waves despite its high symmetry. Direct simulations of seismic wave propagation reveal an anisotropy of 12%, a value adequate to explain the anisotropy of the inner core.

  7. Anisotropy and Corotation of Galactic Cosmic Rays

    CERN Document Server

    Amenomori, M; Bi, X J; Chen, D; Cui, S W; Danzengluobu; Ding, L K; Ding, X H; Feng Cun Feng; Zhaoyang Feng; Feng, Z Y; Gao, X Y; Geng, Q X; Guo, H W; He, H H; He, M; Hibino, K; Hotta, N; Haibing, H; Hu, H B; Huang, J; Huang, Q; Jia, H Y; Kajino, F; Kasahara, K; Katayose, Y; Kato, C; Kawata, K; Labaciren; Le, G M; Li, A F; Li, J Y; Lou, Y Q; Lü, H; Lu, S L; Meng, X R; Mizutani, K; Mu, J; Munakata, K; Nagai, A; Nanjo, H; Nishizawa, M; Ohnishi, M; Ohta, I; Onuma, H; Ouchi, T; Ozawa, S; Ren, J R; Saitô, T; Saito, T Y; Sakata, M; Sako, T K; Sasaki, T; Shibata, M; Shiomi, A; Shirai, T; Sugimoto, H; Takita, M; Tan, Y H; Tateyama, N; Torii, S; Tsuchiya, H; Udo, S; Wang, B; Wang, H; Wang, X; Wang, Y G; Wu, H R; Xue Liang; Yamamoto, Y; Yan, C T; Yang, X C; Yasue, S; Ye, Z H; Yu, G C; Yuan, A F; Yuda, T; Zhang, H M; Zhang, J L; Zhang, N J; Zhang, X Y; Zhang, Y; Zhaxisangzhu; Zhou, X X

    2006-01-01

    The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments.

  8. Microwave Background Anisotropies from Scaling Seed Perturbations

    CERN Document Server

    Durrer, R; Durrer, Ruth; Sakellariadou, Mairi

    1997-01-01

    We study microwave background anisotropies induced by scaling seed perturbations in a universe dominated by cold dark matter. Using a gauge invariant linear perturbation analysis, we solve the perturbation equations on super-horizon scales, for CMB anisotropies triggered by generic gravitational seeds. We find that perturbations induced by seeds -- under very mild restrictions -- are nearly isocurvature. Thus, compensation, which is mainly the consequence of physically sensible initial conditions, is very generic. We then restrict our study to the case of scaling sources, motivated by global scalar fields. We parameterize the energy momentum tensor of the source by ``seed functions'' and calculate the Sachs-Wolfe and acoustic contributions to the CMB anisotropies. We discuss the dependence of the anisotropy spectrum on the parameters of the model considered. Even within the restricted class of models investigated in this work, we find a surprising variety of results for the position and height of the first ac...

  9. Magnetic anisotropies of rare-earth compounds

    Science.gov (United States)

    Loewenhaupt, M.; Rotter, M.; Kramp, S.

    2000-03-01

    There are two kinds of magnetic anisotropy in rare-earth compounds: the single-ion anisotropy caused by the crystal field (CF) and the anisotropy of the two-ion interactions. Both types of anisotropy have to be considered to arrive at a consistent description of the magnetic properties of the orthorhombic intermetallic compound NdCu 2. From the analysis of NdCu 2 we can derive predictions for the type of ordering in other isostructural RCu 2 compounds, that agree well with experimental results: If the magnetic moments point into the crystallographic b-direction, an ordering wave vector of (2/3 0 0) is expected. If the moments are oriented perpendicular to b then the ordering wave vector is (2/3 1 0) .

  10. Higher order anisotropies in the Buda-Lund model -- disentangling flow and density field anisotropies

    CERN Document Server

    Lökös, Sándor; Csörgő, Tamás; Tomášik, Boris

    2016-01-01

    The Buda-Lund hydro model describes an expanding ellipsoidal fireball, and fits the observed elliptic flow and oscillating HBT radii successfully. Due to fluctuations in energy depositions, the fireball shape however fluctuates on an event-by-event basis. The transverse plane asymmetry can be translated into a series of multipole anisotropy coefficients. These anisotropies then result in measurable momentum-space anisotropies, to be measured with respect to their respective symmetry planes. In this paper we detail an extension of the Buda-Lund model to multipole anisotropies and investigate the resulting flow coefficients and oscillations of HBT radii.

  11. Higher-order anisotropies in the Buda-Lund model: Disentangling flow and density field anisotropies

    Energy Technology Data Exchange (ETDEWEB)

    Loekoes, Sandor [Eoetvoes Lorand University, Budapest (Hungary); Csanad, Mate [Eoetvoes Lorand University, Budapest (Hungary); Stony Brook University, Stony Brook, NY (United States); Tomasik, Boris [Univerzita Mateja Bela, Banska Bystrica (Slovakia); Czech Technical University in Prague, FNSPE, Prague (Czech Republic); Csoergo, Tamas [Wigner RCP, Budapest (Hungary); KRF, Gyoengyoes (Hungary)

    2016-10-15

    The Buda-Lund hydro model describes an expanding ellipsoidal fireball, and fits the observed elliptic flow and oscillating HBT radii successfully. Due to fluctuations in energy depositions, the fireball shape however fluctuates on an event-by-event basis. The transverse plane asymmetry can be translated into a series of multipole anisotropy coefficients. These anisotropies then result in measurable momentum-space anisotropies, to be measured with respect to their respective symmetry planes. In this paper we detail an extension of the Buda-Lund model to multipole anisotropies and investigate the resulting flow coefficients and oscillations of HBT radii. (orig.)

  12. 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.

  13. Mantle wedge dynamics from seismic anisotropy (Invited)

    Science.gov (United States)

    Long, M. D.; Wirth, E. A.

    2013-12-01

    The mantle wedge above subducting slabs plays a critical role in many of the physical processes associated with subduction, including water transport into the upper mantle and the generation and transport of melts. Our understanding of mantle wedge dynamics is incomplete; in particular, the mantle flow field above subducting slabs remains poorly understood. Because seismic anisotropy is a consequence of deformation, observations of anisotropy (such as shear wave splitting and P-to-SH converted waves) can constrain the geometry of the wedge flow field. Additionally, because the presence of water (either in nominally anhydrous minerals or as hydrous phases) can have a large effect on anisotropic structure, a detailed understanding of mantle wedge anisotropy can help to constrain processes related to water cycling in subduction systems. We present a global, synoptic view of anisotropy observations in subduction zone mantle wedges, compiled from a large number of individual studies, with the goal of understanding the first-order controls on wedge anisotropy and flow patterns. This compilation allows us to explicitly test the predictions made by many different conceptual models for wedge anisotropy, as well as to explore the relationships between observed anisotropy parameters and other parameters that describe subduction. We find that no simple model can explain all of the trends observed in the global data set. Mantle wedge flow is likely controlled by a combination of downdip motion of the slab, trench migration, ambient mantle flow, small-scale convection, proximity to slab edges, and slab morphology, with the relative contributions of these in any given subduction system controlled by the subduction kinematics and mantle rheology. There is also a likely contribution from B-type olivine and/or serpentinite fabric in many subduction zones, governed by the local thermal structure and volatile distribution.

  14. 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.

  15. Magnetic Barkhausen Noise Measurements Using Tetrapole Probe Designs

    Science.gov (United States)

    McNairnay, Paul

    A magnetic Barkhausen noise (MBN) testing system was developed for Defence Research and Development Canada (DRDC) to perform MBN measurements on the Royal Canadian Navy's Victoria class submarine hulls that can be correlated with material properties, including residual stress. The DRDC system was based on the design of a MBN system developed by Steven White at Queen's University, which was capable of performing rapid angular dependent measurements through the implementation of a flux controlled tetrapole probe. In tetrapole probe designs, the magnetic excitation field is rotated in the surface plane of the sample under the assumption of linear superposition of two orthogonal magnetic fields. During the course of this work, however, the validity of flux superposition in ferromagnetic materials, for the purpose of measuring MBN, was brought into question. Consequently, a study of MBN anisotropy using tetrapole probes was performed. Results indicate that MBN anisotropy measured under flux superposition does not simulate MBN anisotropy data obtained through manual rotation of a single dipole excitation field. It is inferred that MBN anisotropy data obtained with tetrapole probes is the result of the magnetic domain structure's response to an orthogonal magnetization condition and not necessarily to any bulk superposition magnetization in the sample. A qualitative model for the domain configuration under two orthogonal magnetic fields is proposed to describe the results. An empirically derived fitting equation, that describes tetrapole MBN anisotropy data, is presented. The equation describes results in terms of two largely independent orthogonal fields, and includes interaction terms arising due to competing orthogonally magnetized domain structures and interactions with the sample's magnetic easy axis. The equation is used to fit results obtained from a number of samples and tetrapole orientations and in each case correctly identifies the samples' magnetic easy axis.

  16. 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.

  17. Magnetic anisotropy and the phase diagram of chiral MnSb2O6

    Science.gov (United States)

    Werner, J.; Koo, C.; Klingeler, R.; Vasiliev, A. N.; Ovchenkov, Y. A.; Polovkova, A. S.; Raganyan, G. V.; Zvereva, E. A.

    2016-09-01

    The magnetic phase diagram and low-energy magnon excitations of structurally and magnetically chiral MnSb2O6 are reported. The specific heat and the static magnetization are investigated in magnetic fields up to 9 and 30 T, respectively, while the dynamic magnetic properties are probed by X-band as well as tunable high-frequency electron spin-resonance spectroscopy. Below TN=11.5 K, we observe antiferromagnetic resonance modes which imply small but finite planar anisotropy showing up in a zero-field splitting of 20 GHz. The data are well described by means of an easy-plane two-sublattice model with the anisotropy field BA=0.02 T. The exchange field BE=13 T is obtained from the saturation field derived from the pulsed-field magnetization. A crucial role of the small anisotropy for the spin structure is reflected by competing antiferromagnetic phases appearing, at T =2 K, in small magnetic fields at BC 1 ≈0.5 T and BC 2=0.9 T. We discuss the results in terms of spin reorientation and of small magnetic fields favoring helical spin structure over the cycloidal ground state which, at B =0 , is stabilized by the planar anisotropy. Above TN, short-range magnetic correlations up to ≳60 K and magnetic entropy changes well above TN reflect the frustrated triangular arrangement of Mn2 + ions in MnSb2O6 .

  18. Interpreting Power Anisotropy Measurements in Plasma Turbulence

    CERN Document Server

    Chen, C H K; Horbury, T S; Schekochihin, A A

    2009-01-01

    A relationship between power anisotropy and wavevector anisotropy in turbulent fluctuations is derived. This can be used to interpret plasma turbulence measurements, for example in the solar wind. If fluctuations are anisotropic in shape then the ion gyroscale break point in spectra in the directions parallel and perpendicular to the magnetic field would not occur at the same frequency, and similarly for the electron gyroscale break point. This is an important consideration when interpreting solar wind observations in terms of anisotropic turbulence theories. Model magnetic field power spectra are presented assuming a cascade of critically balanced Alfven waves in the inertial range and kinetic Alfven waves in the dissipation range. The variation of power anisotropy with scale is compared to existing solar wind measurements and the similarities and differences are discussed.

  19. CMB Anisotropies Total Angular Momentum Method

    CERN Document Server

    Hu, W; Hu, Wayne; White, Martin

    1997-01-01

    A total angular momentum representation simplifies the radiation transport problem for temperature and polarization anisotropy in the CMB. Scattering terms couple only the quadrupole moments of the distributions and each moment corresponds directly to the observable angular pattern on the sky. We develop and employ these techniques to study the general properties of anisotropy generation from scalar, vector and tensor perturbations to the metric and the matter, both in the cosmological fluids and from any seed perturbations (e.g.~defects) that may be present. The simpler, more transparent form and derivation of the Boltzmann equations brings out the geometric and model-independent aspects of temperature and polarization anisotropy formation. Large angle scalar polarization provides a robust means to distinguish between isocurvature and adiabatic models for structure formation in principle. Vector modes have the unique property that the CMB polarization is dominated by magnetic type parity at small angles and ...

  20. The expected anisotropy in solid inflation

    CERN Document Server

    Bartolo, Nicola; Ricciardone, Angelo; Unal, Caner

    2014-01-01

    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 initia...

  1. Radial anisotropy ambient noise tomography of volcanoes

    Science.gov (United States)

    Mordret, Aurélien; Rivet, Diane; Shapiro, Nikolai; Jaxybulatov, Kairly; Landès, Matthieu; Koulakov, Ivan; Sens-Schönfelder, Christoph

    2016-04-01

    The use of ambient seismic noise allows us to perform surface-wave tomography of targets which could hardly be imaged by other means. The frequencies involved (~ 0.5 - 20 s), somewhere in between active seismic and regular teleseismic frequency band, make possible the high resolution imaging of intermediate-size targets like volcanic edifices. Moreover, the joint inversion of Rayleigh and Love waves dispersion curves extracted from noise correlations allows us to invert for crustal radial anisotropy. We present here the two first studies of radial anisotropy on volcanoes by showing results from Lake Toba Caldera, a super-volcano in Indonesia, and from Piton de la Fournaise volcano, a hot-spot effusive volcano on the Réunion Island (Indian Ocean). We will see how radial anisotropy can be used to infer the main fabric within a magmatic system and, consequently, its dominant type of intrusion.

  2. 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.

  3. ANISOTROPY DETERMINATIONS IN EXCHANGE SPRING MAGNETS.

    Energy Technology Data Exchange (ETDEWEB)

    LEWIS,L.H.; HARLAND,C.L.

    2002-08-18

    Ferromagnetic nanocomposites, or ''exchange spring'' magnets, possess a nanoscaled microstructure that allows intergrain magnetic exchange forces to couple the constituent grains and alter the system's effective magnetic anisotropies. While the effects of the anisotropy alterations are clearly seen in macroscopic magnetic measurement, it is extremely difficult to determine the detailed effects of the system's exchange coupling, such as the interphase exchange length, the inherent domain wall widths or the effective anisotropies of the system. Clarification of these materials parameters may be obtained from the ''micromagnetic'' phenomenological model, where the assumption of magnetic reversal initiating in the magnetically-soft regions of the exchange-spring maqet is explicitly included. This approach differs from that typically applied by other researchers and allows a quantitative estimate of the effective anisotropies of an exchange spring system. Hysteresis loops measured on well-characterized nanocomposite alloys based on the composition Nd{sub 2}Fe{sub 14}B + {alpha}-Fe at temperatures above the spin reorientation temperature were analyzed within the framework of the micromagnetic phenomenological model. Preliminary results indicate that the effective anisotropy constant in the material is intermediate to that of bulk {alpha}-Fe and bulk Nd{sub 2}Fe{sub 14}B and increases with decreasing temperature. These results strongly support the idea that magnetic reversal in nanocomposite systems initiates in the lower-anisotropy regions of the system, and that the soft-phase regions become exchange-hardened by virtue of their proximity to the magnetically-hard regions.

  4. Anisotropy of the Topopah Spring Member Tuff

    Energy Technology Data Exchange (ETDEWEB)

    Martin, R.J. III; Boyd, P.J.; Haupt, R.W. [New England Research, Inc., White River Junction, VT (United States); Price, R.H. [Sandia National Labs., Albuquerque, NM (United States)

    1992-07-01

    Mechanical properties of the tuffaceous rocks within Yucca Mountain are needed for near and far-field modeling of the potential nuclear waste repository. If the mechanical properties are significantly anisotropic (i.e., direction-dependent), a more complex model is required. Relevant data from tuffs tested in earlier studies indicate that elastic and strength properties are anisotropic. This scoping study confirms the elastic anisotropy and concludes some tuffs are transversely isotropic. An approach for sampling and testing the rock to determine the magnitude of the anisotropy is proposed.

  5. 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.

  6. Planck intermediate results: XVII. Emission of dust in the diffuse interstellar medium from the far-infrared to microwave frequencies

    DEFF Research Database (Denmark)

    Bartlett, J.G.; Cardoso, J.-F.; Delabrouille, J.

    2014-01-01

    and microwave backgrounds. We cross-correlate sky maps from Planck, the Wilkinson Microwave Anisotropy Probe (WMAP), and the diffuse infrared background experiment (DIRBE), at 17 frequencies from 23 to 3000 GHz, with the Parkes survey of the 21 cm line emission of neutral atomic hydrogen, over a contiguous area...

  7. 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.

  8. 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.

  9. Origin of Perpendicular Magnetic Anisotropy and Large Orbital Moment in Fe Atoms on MgO.

    Science.gov (United States)

    Baumann, S; Donati, F; Stepanow, S; Rusponi, S; Paul, W; Gangopadhyay, S; Rau, I G; Pacchioni, G E; Gragnaniello, L; Pivetta, M; Dreiser, J; Piamonteze, C; Lutz, C P; Macfarlane, R M; Jones, B A; Gambardella, P; Heinrich, A J; Brune, H

    2015-12-04

    We report on the magnetic properties of individual Fe atoms deposited on MgO(100) thin films probed by x-ray magnetic circular dichroism and scanning tunneling spectroscopy. We show that the Fe atoms have strong perpendicular magnetic anisotropy with a zero-field splitting of 14.0±0.3  meV/atom. This is a factor of 10 larger than the interface anisotropy of epitaxial Fe layers on MgO and the largest value reported for Fe atoms adsorbed on surfaces. The interplay between the ligand field at the O adsorption sites and spin-orbit coupling is analyzed by density functional theory and multiplet calculations, providing a comprehensive model of the magnetic properties of Fe atoms in a low-symmetry bonding environment.

  10. Skewness in the Cosmic Microwave Background Anisotropy from Inflationary Gravity Wave Background

    CERN Document Server

    Bharadwaj, S; Souradeep, T; Bharadwaj, Somnath; Munshi, Dipak; Souradeep, Tarun

    1997-01-01

    In the context of inflationary scenarios, the observed large angle anisotropy of the Cosmic Microwave Background (CMB) temperature is believed to probe the primordial metric perturbations from inflation. Although the perturbations from inflation are expected to be gaussian random fields, there remains the possibility that nonlinear processes at later epochs induce ``secondary'' non-gaussian features in the corresponding CMB anisotropy maps. The non-gaussianity induced by nonlinear gravitational instability of scalar (density) perturbations has been investigated in existing literature. In this paper, we highlight another source of non-gaussianity arising out of higher order scattering of CMB photons off the metric perturbations. We provide a simple and elegant formalism for deriving the CMB temperature fluctuations arising due to the Sachs-Wolfe effect beyond the linear order. In particular, we derive the expression for the second order CMB temperature fluctuations. The multiple scattering effect pointed out i...

  11. 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...

  12. 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.

  13. Strain-activated structural anisotropy in BaFe2As2

    Science.gov (United States)

    Chen, Xiang; Harriger, Leland; Sefat, Athena; Birgeneau, R. J.; Wilson, Stephen D.

    2016-04-01

    High-resolution single crystal neutron diffraction measurements are presented probing the magnetostructural response to uniaxial pressure in the iron pnictide parent system BaFe2As2 . Scattering data reveal a strain-activated, anisotropic broadening of nuclear Bragg reflections, which increase upon cooling below the resolvable onset of global orthorhombicity. This anisotropy in lattice coherence continues to build until a lower temperature scale—the first-order onset of antiferromagnetism—is reached. Our data suggest that antiferromagnetism and strong magnetoelastic coupling drive the strain-activated lattice response in this material and that the development of anisotropic lattice correlation lengths under strain is a possible origin for the high temperature transport anisotropy in this compound.

  14. Origin of Perpendicular Magnetic Anisotropy and Large Orbital Moment in Fe Atoms on MgO

    Science.gov (United States)

    Baumann, S.; Donati, F.; Stepanow, S.; Rusponi, S.; Paul, W.; Gangopadhyay, S.; Rau, I. G.; Pacchioni, G. E.; Gragnaniello, L.; Pivetta, M.; Dreiser, J.; Piamonteze, C.; Lutz, C. P.; Macfarlane, R. M.; Jones, B. A.; Gambardella, P.; Heinrich, A. J.; Brune, H.

    2015-12-01

    We report on the magnetic properties of individual Fe atoms deposited on MgO(100) thin films probed by x-ray magnetic circular dichroism and scanning tunneling spectroscopy. We show that the Fe atoms have strong perpendicular magnetic anisotropy with a zero-field splitting of 14.0 ±0.3 meV /atom . This is a factor of 10 larger than the interface anisotropy of epitaxial Fe layers on MgO and the largest value reported for Fe atoms adsorbed on surfaces. The interplay between the ligand field at the O adsorption sites and spin-orbit coupling is analyzed by density functional theory and multiplet calculations, providing a comprehensive model of the magnetic properties of Fe atoms in a low-symmetry bonding environment.

  15. 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.

  16. 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.

  17. 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...

  18. Heterogeneity and anisotropy of Earth's inner core

    NARCIS (Netherlands)

    Deuss, Arwen

    2014-01-01

    Seismic observations provide strong evidence that Earth's inner core is anisotropic, with larger velocity in the polar than in the equatorial direction. The top 60-80 km of the inner core is isotropic; evidence for an innermost inner core is less compelling. The anisotropy is most likely due to alig

  19. Anisotropy of a cubic ferromagnet at criticality

    Science.gov (United States)

    Kudlis, A.; Sokolov, A. I.

    2016-10-01

    Critical fluctuations change the effective anisotropy of cubic ferromagnet near the Curie point. If the crystal undergoes phase transition into orthorhombic phase and the initial anisotropy is not too strong, reduced anisotropy of nonlinear susceptibility acquires at Tc the universal value δ4*=2/v* 3 (u*+v*) where u* and v* are coordinates of the cubic fixed point on the flow diagram of renormalization group equations. In the paper, the critical value of the reduced anisotropy is estimated within the pseudo-ɛ expansion approach. The six-loop pseudo-ɛ expansions for u*, v*, and δ4* are derived for the arbitrary spin dimensionality n . For cubic crystals (n =3 ) higher-order coefficients of the pseudo-ɛ expansions obtained turn out to be so small that use of simple Padé approximants yields reliable numerical results. Padé resummation of the pseudo-ɛ series for u*, v*, and δ4* leads to the estimate δ4*=0.079 ±0.006 , indicating that detection of the anisotropic critical behavior of cubic ferromagnets in physical and computer experiments is certainly possible.

  20. 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…

  1. 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.

  2. 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...

  3. Magnetization of superparamagnetics in the state of mechanical anisotropy

    OpenAIRE

    Ugulava, Archil; Chkhaidze, Simon; Kekutia, Shalva; Rostomashvili, Zurab

    2015-01-01

    The internal energy of magnetic anisotropy for some nanoparticles dominates over the thermal energy even at room temperature. Strong magnetic anisotropy of nanoparticles can significantly affect the process of magnetization of the magnetic fluid. This influence is substantial if the system of nanoparticles is in a state of mechanical anisotropy in which the anisotropy axes of the particles have the same direction. In this work, it is shown that the magnetization curve of the magnetic fluid in...

  4. Surface contribution to the anisotropy of magnetic nanoparticles

    OpenAIRE

    Garanin, D. A.; Kachkachi, H.

    2002-01-01

    We calculate the contribution of the Neel surface anisotropy to the effective anisotropy of magnetic nanoparticles of spherical shape cut out of a simple cubic lattice. The effective anisotropy arises because deviations of atomic magnetizations from collinearity and thus the energy depends on the orientation of the global magnetization. The result is second order in the Neel surface anisotropy, scales with the particle volume and has cubic symmetry with preferred directions [+-1,+-1,+-1].

  5. Pn Anisotropy in Old Pacific Lithosphere

    Science.gov (United States)

    Shintaku, N.; Forsyth, D. W.; Weeraratne, D. S.

    2012-12-01

    Pn is the high frequency, scattered P phase guided for great distances within old oceanic lithosphere, which is also known as Po. Two arrays of ocean bottom seismometers were deployed on old (~150-160Ma) seafloor in the northwestern Pacific south of Shatsky Rise for the PLATE experiment (Pacific Lithosphere Anisotropy and Thickness Experiment). More than 5 or 6 Pn phases per day are recorded on these ocean bottom seismometers generated by earthquakes in western Pacific subduction zones during one year of deployment; we used 512 Pn phases from earthquakes with locations reported in routine bulletins. Each array was deployed on a separate limb of a magnetic bight, formed at a ridge-ridge-ridge triple junction. The spreading rates on both limbs were ~ 70mm/yr, and the current plate motion direction in the hotspot coordinate frame is WNW. Our overall goal is to identify the pattern of fossil anisotropy in the old oceanic lithosphere, and dynamically generated anisotropy in underlying asthenosphere using both body waves and surface waves. Using high frequency waves (3-10 Hz), we look at variations of Pn velocities as a function of backazimuth. In the western array, where the spreading direction is parallel to the absolute plate motion direction, we find clear Pn anisotropy with velocities varying from ~8.5 km/s in the spreading direction to ~ 8.0 km/s perpendicular to the spreading direction. However, in the eastern array where the fossil spreading direction is perpendicular to the current plate motion, the velocity variations as a function of backazimuth are much less obvious. This may be due to heterogeneity of anisotropy in the oceanic lithosphere, with the fast direction changing from the fossil direction at shallow levels to the absolute direction at greater depth.

  6. Multi-scale characterization of topographic anisotropy

    Science.gov (United States)

    Roy, S. G.; Koons, P. O.; Osti, B.; Upton, P.; Tucker, G. E.

    2016-05-01

    We present the every-direction variogram analysis (EVA) method for quantifying orientation and scale dependence of topographic anisotropy to aid in differentiation of the fluvial and tectonic contributions to surface evolution. Using multi-directional variogram statistics to track the spatial persistence of elevation values across a landscape, we calculate anisotropy as a multiscale, direction-sensitive variance in elevation between two points on a surface. Tectonically derived topographic anisotropy is associated with the three-dimensional kinematic field, which contributes (1) differential surface displacement and (2) crustal weakening along fault structures, both of which amplify processes of surface erosion. Based on our analysis, tectonic displacements dominate the topographic field at the orogenic scale, while a combination of the local displacement and strength fields are well represented at the ridge and valley scale. Drainage network patterns tend to reflect the geometry of underlying active or inactive tectonic structures due to the rapid erosion of faults and differential uplift associated with fault motion. Regions that have uniform environmental conditions and have been largely devoid of tectonic strain, such as passive coastal margins, have predominantly isotropic topography with typically dendritic drainage network patterns. Isolated features, such as stratovolcanoes, are nearly isotropic at their peaks but exhibit a concentric pattern of anisotropy along their flanks. The methods we provide can be used to successfully infer the settings of past or present tectonic regimes, and can be particularly useful in predicting the location and orientation of structural features that would otherwise be impossible to elude interpretation in the field. Though we limit the scope of this paper to elevation, EVA can be used to quantify the anisotropy of any spatially variable property.

  7. What does anisotropy measure? Insights from increased and decreased anisotropy in selective fiber tracts in schizophrenia.

    Directory of Open Access Journals (Sweden)

    Gabriel A De Erausquin

    2013-03-01

    Full Text Available Schizophrenia is a common, severe and chronically disabling mental illness of unknown cause. Recent MRI studies have focused attention on white matter abnormalities in schizophrenia using diffusion tensor imaging (DTI. Indices commonly derived from DTI include (a mean diffusivity, independent of direction, (b fractional anisotropy (FA or relative anisotropy (RA, (c axial diffusivity, and (d radial diffusivity. In cerebral white matter, contributions to these indices come from fiber arrangements, degree of myelination, and axonal integrity. Relatively pure deficits in myelin result in a modest increase in radial diffusivity, without affecting axial diffusivity and with preservation of anisotropy. Although schizophrenia is not characterized by gross abnormalities of white matter, it does involve a profound dysregulation of myelin-associated gene expression, reductions in oligodendrocyte numbers, and marked abnormalities in the ultrastructure of myelin sheaths. Since each oligodendrocyte myelinates as many as 40 axon segments, changes in the number of oligodendrocytes, and/or in the integrity of myelin sheaths, and/or axoglial contacts can have a profound impact on signal propagation and the integrity of neuronal circuits. Whereas a number of studies have revealed inconsistent decreases in anisotropy in schizophrenia, we and others have found increased fractional anisotropy in key subcortical tracts associated with the circuits underlying symptom generation in schizophrenia. We review data revealing increased anisotropy in dopaminergic tracts in the mesencephalon of schizophrenics and their unaffected relatives, and discuss the possible biological underpinnings and physiological significance of this finding.

  8. 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.

  9. 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.

  10. Probe tip heating assembly

    Science.gov (United States)

    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.

  11. Constraints on the Holographic Dark Energy Model from Type Ia Supernovae, WMAP7, Baryon Acoustic Oscillation and Redshift-Space Distortion

    CERN Document Server

    Xu, Lixin

    2013-01-01

    In this paper, we use the joint measurement of geometry and growth rate from matter density perturbations to constrain the holographic dark energy model. The geometry measurement includes type Ia supernovae (SN Ia) Union2.1, full information of cosmic microwave background (CMB) from WMAP-7yr and baryon acoustic oscillation (BAO). For the growth rate of matter density perturbations, the results $f(z)\\sigma_8(z)$ measured from the redshift-space distortion (RSD) in the galaxy power spectrum are employed. Via the Markov Chain Monte Carlo method, we try to constrain the model parameters space. The jointed constraint shows that $c=0.750_{- 0.0999- 0.173- 0.226}^{+ 0.0976+ 0.215+ 0.319}$ and $\\sigma_8=0.763_{- 0.0465- 0.0826- 0.108}^{+ 0.0477+ 0.0910+ 0.120}$ with $1,2,3\\sigma$ regions. After marginalizing the other irrelevant model parameters, we show the evolution of the equation of state of HDE with respect to the redshift $z$. Though the current cosmic data points favor a phantom like HDE Universe for the mean ...

  12. Magnetic anisotropy of grain boundaries in nanocrystalline Ni

    Science.gov (United States)

    Bian, Q.; Niewczas, M.

    2017-01-01

    Temperature-dependent magnetic anisotropy due to grain boundaries in nanocrystalline Ni has been studied by simulating experimental magnetization data with the stochastic Landau-Lifshitz-Gilbert theory. In the model the grain boundary magnetic anisotropy energy is expressed as the sum of the uniaxial anisotropy and the cubic anisotropy, characterized by Kua and Kca anisotropy constants. By comparing the calculated magnetization with the experimental magnetization measurements at finite temperatures, the values of Kua and Kca can be determined. For nanocrystalline Ni it is found that with increasing temperature Kua decreases and Kca increases. At low temperatures Kua dominates the grain boundary anisotropy energy, whereas Kca is very small and it can be neglected. At room temperature Kua and Kca are of the same order with the corresponding ratio Kua /Kca ≈ 1.9 , both coefficients are much larger than the magnetocrystalline anisotropy constant.

  13. Perpendicular magnetic anisotropy of two-dimensional Rashba ferromagnets

    Science.gov (United States)

    Kim, Kyoung-Whan; Lee, Kyung-Jin; Lee, Hyun-Woo; Stiles, M. D.

    2016-11-01

    We compute the magnetocrystalline anisotropy energy within two-dimensional Rashba models. For a ferromagnetic free-electron Rashba model, the magnetic anisotropy is exactly zero regardless of the strength of the Rashba coupling, unless only the lowest band is occupied. For this latter case, the model predicts in-plane anisotropy. For a more realistic Rashba model with finite band width, the magnetic anisotropy evolves from in-plane to perpendicular and back to in-plane as bands are progressively filled. This evolution agrees with first-principles calculations on the interfacial anisotropy, suggesting that the Rashba model captures energetics leading to anisotropy originating from the interface provided that the model takes account of the finite Brillouin zone. The results show that the electron density modulation by doping or an external voltage is more important for voltage-controlled magnetic anisotropy than the modulation of the Rashba parameter.

  14. 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.

  15. Microwave Anisotropies from Texture Seeded Structure Formation

    CERN Document Server

    Durrer, R; Zhou, Z H

    1994-01-01

    The cosmic microwave anisotropies in a scenario of large scale structure formation with cold dark matter and texture are discussed and compared with recent observational results of the COBE satellite. A couple of important statistical parameters are determined. The fluctuations are slightly non gaussian. The quadrupole anisotropy is $1.5\\pm 1.2\\times 10^{-5}$ and the fluctuations on a angular scale of 10 degrees are $ (3.8\\pm 2.6)\\times 10^{-5}$. The COBE are within about one standard deviation of the typical texture + CDM model discussed in this paper. Furthermore, we calculate fluctuations on intermediate scales (about 2 degrees) with the result $\\De T/T(\\theta \\sim 2^o) = 3.9\\pm 0.8)\\times 10^{-5}$. Collapsing textures are modeled by spherically symmetric field configurations. This leads to uncertainties of about a factor of~2.

  16. CMB anisotropies from primordial inhomogeneous magnetic fields

    CERN Document Server

    Lewis, A

    2004-01-01

    Primordial inhomogeneous magnetic fields of the right strength can leave a signature on the CMB temperature anisotropy and polarization. Potentially observable contributions to polarization B-modes are generated by vorticity and gravitational waves sourced by the magnetic anisotropic stress. We compute the corresponding CMB transfer functions in detail including the effect of neutrinos. The shear rapidly causes the neutrino anisotropic stress to cancel the stress from the magnetic field, suppressing the production of gravitational waves and vorticity on super-horizon scales after neutrino decoupling. A significant large scale signal from tensor modes can only be produced before neutrino decoupling, and the actual amplitude is somewhat uncertain. Plausible values suggest primordial nearly scale invariant fields of ~ 10^(-10)G today may be observable from their large scale tensor anisotropy. They can be distinguished from primordial gravitational waves by their non-Gaussianity. Vector mode vorticity sources B-m...

  17. Random anisotropy induced by structural disorder

    Science.gov (United States)

    Martinez, B.; Labarta, A.; Badia, F.; Tejada, J.

    1992-02-01

    As a direct consequence of the structural disorder, inherent to the amorphous state, local electrostatic fields are highly irregular. Due to the interplay between those highly irregular local electrostatic fields and the aspherical 4f electron clouds of the rare earth atoms, local anisotropy axis, directed along directions that vary randomly in space, may be generated. These directions are determined by the local arrangement of atoms; therefore, some information about amorphous structure may be obtained through the study of the magnetization curve.

  18. Shape-induced anisotropy in antiferromagnetic nanoparticles

    OpenAIRE

    H. Gomonay; Kondovych, S.; Loktev, V.

    2013-01-01

    High fraction of the surface atoms considerably enhances the influence of size and shape on the magnetic and electronic properties of nanoparticles. Shape effects in ferromagnetic nanoparticles are well understood and allow to set and control the parameters of a sample that affect its magnetic anisotropy during production. In the present paper we study the shape effects in the other widely used magnetic materials -- antiferromagnets, -- which possess vanishingly small or zero macroscopic magn...

  19. Pn anisotropy in Mesozoic western Pacific lithosphere

    Science.gov (United States)

    Shintaku, Natsumi; Forsyth, Donald W.; Hajewski, Christina J.; Weeraratne, Dayanthie S.

    2014-04-01

    Pn is the high-frequency, scattered P phase guided for great distances within the old oceanic lithosphere. Two arrays of ocean bottom seismometers were deployed on old (150-160 Ma) seafloor in the northwestern Pacific south of Shatsky Rise for the Pacific Lithosphere Anisotropy and Thickness Experiment. We use Pn phases from 403 earthquakes during the 1 year of deployment to measure apparent velocities across the arrays. Each array was deployed on a separate limb of a magnetic bight, formed near a fast-spreading, ridge-ridge-ridge triple junction. Using high-frequency waves (5-10 Hz), we look at variations of Pn velocities as a function of azimuth. In the western array, we find Pn anisotropy with velocities ranging from ~8.7 km/s in the back azimuth (θ) direction of 310° to ~7.7 km/s at ~350°. In the eastern array, the velocity ranges from ~8.5 km/s in back azimuth direction of ~210° to ~7.7 km/s at 260° and ~310°. We observe rapid velocity changes with azimuth in the both arrays requiring sinusoidal variations of roughly equal amplitude as a function of both 2θ and 4θ, which is not expected for the orthorhombic symmetry of olivine or orthopyroxene. The fastest directions on the two limbs are roughly orthogonal to each other suggesting the dominance of fossil anisotropy, but the fast directions of the 2θ components are skewed counterclockwise from the spreading directions. We speculate that the rapid azimuthal variations may be caused by vertical stratification with changing anisotropy with depth in the oceanic lithosphere.

  20. 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...

  1. CMB anisotropies: Total angular momentum method

    Science.gov (United States)

    Hu, Wayne; White, Martin

    1997-07-01

    A total angular momentum representation simplifies the radiation transport problem for temperature and polarization anisotropy in the cosmic microwave background (CMB). Scattering terms couple only the quadrupole moments of the distributions and each moment corresponds directly to the observable angular pattern on the sky. We develop and employ these techniques to study the general properties of anisotropy generation from scalar, vector, and tensor perturbations to the metric and the matter, both in the cosmological fluids and from any seed perturbations (e.g., defects) that may be present. The simpler, more transparent form and derivation of the Boltzmann equations brings out the geometric and model-independent aspects of temperature and polarization anisotropy formation. Large angle scalar polarization provides a robust means to distinguish between isocurvature and adiabatic models for structure formation in principle. Vector modes have the unique property that the CMB polarization is dominated by magnetic-type parity at small angles (a factor of 6 in power compared with 0 for the scalars and 8/13 for the tensors) and hence potentially distinguishable independent of the model for the seed. The tensor modes produce a different sign from the scalars and vectors for the temperature-polarization correlations at large angles. We explore conditions under which one perturbation type may dominate over the others including a detailed treatment of the photon-baryon fluid before recombination.

  2. Anisotropy analyses of population distribution patterns

    Institute of Scientific and Technical Information of China (English)

    WANG Benyang; YU Shixiao; WANG Yongfan

    2007-01-01

    Direction-dependence,or anisotropy,of spatial distribution patterns of vegetation is rarely explored due to neglect of this ecological phenomenon and the paucity of methods dealing with this issue.This paper proposes a new approach to anisotropy analysis of spatial distribution patterns of plant populations on the basis of the data resampling technique (DRT) combined with Ripley's L index.Using the ArcView Geographic Information System (GIS) platform,a case study was carried out by selecting the population of Pinus massoniana from a needle- and broad-leaved mixed forest community in the Heishiding Nature Reserve,Guangdong Province.Results showed that the spatial pattern of the P massoniana population was typically anisotropic with different patterns in different directions.The DRT was found to be an effective approach to the anisotropy analysis of spatial patterns of plant populations.By employing resampling sub-datasets from the original dataset in different directions,we could overcome the difficulty in the direct use of current non-angular methods of pattern analysis.

  3. Effective surface anisotropy in polycrystalline ferromagnetic nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Holanda, J.; Campos, C.L.A.V.; Franca, C.A.; Padrón-Hernández, E., E-mail: padron@df.ufpe.br

    2014-12-25

    Highlights: • Here we make a mixing of two models. A macroscopic and a microscopic model. • The principal idea in this paper is to write the free magnetic energy for a soft magnetic cylindrical nanowire and make the comparison with our previous models. • The model is tested to determine the effective constant in Ni nanowires. - Abstract: Here we express the effective surface anisotropy for soft ferromagnetic nanowires as the function of the micro-structural behaviors. Many papers about these systems determine the reversal modes for the magnetization to explain magnetic properties of the nanowires. Our previous works related morphological structure with magnetic properties. The principal idea in this paper is to write the free magnetic energy for a soft magnetic cylindrical nanowire and make the comparison with our previous models. In this way we include the macroscopic effective anisotropy due to the disordered atoms and ignoring other microstructure terms related in our previous works. From this idea and our last model to these systems, we made an association that permit to express the effective anisotropy in function of the principal morphological characteristics of nanowires. The model is tested to determine the numerical value of the mentioned constant in Ni nanowires obtained by electrodeposition in porous anodic aluminum oxide membranes using the Transmission Electron Microscopy.

  4. Dynamical anisotropy of the optical propagation paths

    Science.gov (United States)

    Arsenyan, Tatiana I.; Pisklin, Maksim V.; Suhareva, Natalia A.; Zotov, Aleksey M.

    2015-11-01

    Dynamics of laser beam intensity profile spatial modulations over a model tropospheric path with the controlled meteorological parameters was studied. Influence of the underlying surface temperature as well as the side wind load were considered. The increase of dynamic anisotropic disturbances saturation with the path length was observed. Spatio-temporal correlation characteristics of the directivity pattern in the signal beam registration plane were obtained. Proposed method of the experimental samples analysis on the base of chronogram with the following definition of the dynamic structure tensors array allows to estimate local and averaged projections of the flow velocities over the chosen spatio-temporal region and to restore their geometry in the zone of intersection with the signal beam. Additional characteristics suggested for the diagonalized local structure tensors such as local energy capacity and local structuredness are informative for the estimation of the inhomogeneities spatial dimensions, time of access through the section considered, the dynamics of energetic jets. The concepts of rotational and translational dynamic anisotropy are introduced to discriminate the types of the changes of the local ellipsoids axes orientation as well as their values. Rotational anisotropy shows itself in the changes of the local ellipsoids orientation, thus characterizing the illumination variation over the beam cross-section. Translational anisotropy describes the difference between the axes values for local ellipsoids.

  5. 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

  6. 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.

  7. β - Ag2Te: A topological insulator with strong anisotropy

    Science.gov (United States)

    Wang, Lan; Sulaev, Azat; Ren, Peng; Xia, Bin; Lin, Qinghua; Yu, Ting; Qiu, Caiyu; Zhang, Shuang-Yuan; Han, Ming-Yong; Li, Zhipeng; Zhu, Wei Guang; Wu, Qingyu; Feng, Yuan Ping; Shen, Lei; Shen, Shun-Qing

    2013-03-01

    We present evidence of topological surface states in β-Ag2Te through first-principles calculations, periodic quantum interference effect and ambipolar electric field effect in single crystalline nanoribbon. Our first-principles calculations show that β-Ag2Te is a topological insulator with a gapless Dirac cone with strong anisotropy. To experimentally probe the topological surface state, we synthesized high quality β-Ag2Te nanoribbons and performed electron transport measurements. The coexistence of pronounced Aharonov-Bohm oscillations and weak Altshuler-Aronov-Spivak oscillations clearly demonstrates coherent electron transport around the perimeter of β-Ag2Te nanoribbon and therefore the existence of topological surface states, which is further supported by the ambipolar electric field effect for devices fabricated by β-Ag2Te nanoribbons. The experimentally confirmed topological surface states and the theoretically predicted isotropic Dirac cone of β-Ag2Te suggest that the material may be a promising material for fundamental study and future spintronic devices. RCA-08/018 (Singapore), MOE2010-T2-2-059 (Singapore), HKU705150P (Hong Kong), NTU-SUG M4080513

  8. Magneto-optical investigation of the shape anisotropy of individual micron-sized magnetic elements

    Science.gov (United States)

    Sebastian, T.; Conca, A.; Wolf, G.; Schultheiss, H.; Leven, B.; Hillebrands, B.

    2011-10-01

    In this work, the anisotropy of individual microstructured magnetic elements has been investigated. The investigated elements are of elliptical shape with different sizes and aspect ratios (AR), structured from a 5-nm-thick permalloy (Ni80 Fe20) film. For the measurements, a new magneto-optical Kerr effect (MOKE) magnetometer was used. To allow for the investigation of individual microstructured elements, a micro-focused probing laser beam (spatial resolution ≈1μm) has been combined with a self-stabilizing positioning system of high accuracy, including a rotating unit. Hysteresis loops can be taken for varying orientation of the symmetry axes of the magnetic elements relative to the applied field. For the characterization of the anisotropy, the coercive field as a function of the magnetization direction is extracted from the corresponding hysteresis loops. These results make a quantitative and systematic study of the influence of the shape anisotropy on the magnetic behavior of microstructures possible. The experimental data has been compared to an extended Stoner-Wohlfarth model.

  9. 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.

  10. 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....

  11. The calibration of (multi-)hot-wire probes. 2. Velocity-calibration

    NARCIS (Netherlands)

    Dijk, van A.; Nieuwstadt, F.T.M.

    2004-01-01

    We review a set of velocity calibration methods for one popular configuration of a four-hot-wire probe with the aim of finding a method of estimating with 10% accuracy (based on full scale) the mean flow vector, the rms of the turbulent velocity component and the associated linearized anisotropy inv

  12. 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.

  13. 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...

  14. Competing magnetic anisotropies in obliquely deposited thin permalloy film

    Energy Technology Data Exchange (ETDEWEB)

    Belyaev, B.A. [Siberian Federal University, 79, pr. Svobodnyi, Krasnoyarsk 660041 (Russian Federation); Kirensky Institute of Physics, Siberian Branch of the Russian Academy of Sciences, 50/38, Akademgorodok, Krasnoyarsk 660036 (Russian Federation); Reshetnev Siberian State Aerospace University, 31, pr. Imeni Gazety “Krasnoyarskii Rabochii”, Krasnoyarsk 660014 (Russian Federation); Izotov, A.V. [Siberian Federal University, 79, pr. Svobodnyi, Krasnoyarsk 660041 (Russian Federation); Kirensky Institute of Physics, Siberian Branch of the Russian Academy of Sciences, 50/38, Akademgorodok, Krasnoyarsk 660036 (Russian Federation); Solovev, P.N., E-mail: platon.solovev@gmail.com [Siberian Federal University, 79, pr. Svobodnyi, Krasnoyarsk 660041 (Russian Federation)

    2016-01-15

    Distribution of the magnetic anisotropy in thin film prepared by thermal vacuum oblique deposition of permalloy with small off-normal angle of incident in the presence of an external magnetic field has been studied by ferromagnetic resonance technique. On local area of the sample, a mutual compensation of near orthogonal in-plane uniaxial magnetic anisotropies induced by oblique deposition and by applied magnetic field has been found. Moreover, in addition to the uniaxial (twofold) magnetic anisotropy, fourfold and sixfold magnetic anisotropies have been observed in the sample. To explain the obtained high-order anisotropies, we assumed that the sample has exchange coupled adjacent regions or phases with different parameters of magnetic anisotropy. The results of the micromagnetic analysis of a two-layer model of the sample confirm the hypothesis.

  15. Properties of Ultrasound Probes

    OpenAIRE

    Rusina, M.

    2015-01-01

    This work deals with the measurement properties of ultrasound probes. Ultrasound probes and their parameters significantly affect the quality of the final image. In this work there are described the possibility of measuring the spatial resolution, sensitivity of the probe and measuring the length of the dead zone. Ultrasound phantom ATS Multi Purpose Phantom Type 539 was used for measurements.

  16. 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.

  17. Programming magnetic anisotropy in polymeric microactuators.

    Science.gov (United States)

    Kim, Jiyun; Chung, Su Eun; Choi, Sung-Eun; Lee, Howon; Kim, Junhoi; Kwon, Sunghoon

    2011-10-01

    Polymeric microcomponents are widely used in microelectromechanical systems (MEMS) and lab-on-a-chip devices, but they suffer from the lack of complex motion, effective addressability and precise shape control. To address these needs, we fabricated polymeric nanocomposite microactuators driven by programmable heterogeneous magnetic anisotropy. Spatially modulated photopatterning was applied in a shape-independent manner to microactuator components by successive confinement of self-assembled magnetic nanoparticles in a fixed polymer matrix. By freely programming the rotational axis of each component, we demonstrate that the polymeric microactuators can undergo predesigned, complex two- and three-dimensional motion.

  18. A Complete Treatment of CMB Anisotropies in a FRW Universe

    CERN Document Server

    Hu, W; White, M; Zaldarriaga, M; Hu, Wayne; Seljak, Uros; White, Martin; Zaldarriaga, Matias

    1998-01-01

    We generalize the total angular momentum method for computing Cosmic Microwave Background anisotropies to Friedman-Robertson-Walker (FRW) spaces with arbitrary geometries. This unifies the treatment of temperature and polarization anisotropies generated by scalar, vector and tensor perturbations of the fluid, seed, or a scalar field, in a universe with constant comoving curvature. The resulting formalism generalizes and simplifies the calculation of anisotropies and, in its integral form, allows for a fast calculation of model predictions in linear theory for any FRW metric. With this work, the perturbation theory of CMB temperature and polarization anisotropy formation through gravitational instability in an FRW universe may be considered complete.

  19. Effects of anisotropy on the two-dimensional inversion procedure

    Science.gov (United States)

    Heise, Wiebke; Pous, Jaume

    2001-12-01

    In this paper we show some of the effects that appear in magnetotelluric measurements over 2-D anisotropic structures, and propose a procedure to recover the anisotropy using 2-D inversion algorithms for isotropic models. First, we see how anisotropy affects the usual interpretation steps: dimensionality analysis and 2-D inversion. Two models containing general 2-D azimuthal anisotropic features were chosen to illustrate this approach: an anisotropic block and an anisotropic layer, both forming part of general 2-D models. In addition, a third model with dipping anisotropy was studied. For each model we examined the influence of various anisotropy strikes and resistivity contrasts on the dimensionality analysis and on the behaviour of the induction arrows. We found that, when the anisotropy ratio is higher than five, even if the strike is frequency-dependent it is possible to decide on a direction close to the direction of anisotropy. Then, if the data are rotated to this angle, a 2-D inversion reproduces the anisotropy reasonably well by means of macro-anisotropy. This strategy was tested on field data where anisotropy had been previously recognized.

  20. 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.

  1. 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.

  2. 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.

  3. Theoretical Compton profile anisotropies in molecules and solids. VI. Compton profile anisotropies and chemical binding

    Energy Technology Data Exchange (ETDEWEB)

    Matcha, R.L.; Pettitt, B.M.

    1979-03-15

    An interesting empirical relationship between zero point Compton profile anisotropies ..delta..J (0) and nuclear charges is noted. It is shown that, for alkali halide molecules AB, to a good approximation ..delta..J (0) =N ln(Z/sub b//Z/sub a/).

  4. 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.

  5. The nature versus nurture of anisotropies

    CERN Document Server

    Hu, W

    1994-01-01

    With the rapidly growing number of cosmic microwave background measurements on various scales, there is real hope that the number of acceptable models for structure formation will be limited to a very few in the near future. Yet any given model can always be saved by introducing and tuning extraneous free parameters. To better understand this question of ``nature versus nurture'' for temperature fluctuations, it is useful to know not only the general features of anisotropy predictions but also their causes. Extracting the physical content of our other works, we present here a {\\it simple} account of cosmic microwave background anisotropies on all scales. In particular, we show that analytic approximations can trace the structure of the so-called ``Doppler peaks,'' which arise due to the {\\it adiabatic} oscillations in the photon-baryon fluid. We also show how the finite thickness of the last scattering surface and the Silk damping mechanism can be described in a unified way by photon diffusion. In order to pr...

  6. Anisotropy Studies with the Pierre Auger Observatory

    CERN Document Server

    Santos, E M

    2009-01-01

    An anisotropy signal for the arrival directions of ultra-high energy cosmic rays (UHECR) of more than 99% confidence level was established using data collected by the Pierre Auger Observatory. Cosmic rays with energy above $\\sim 6 \\times 10^{19}$ eV show a correlation with the positions of extragalactic nearby active galactic nuclei (AGN), being maximum for sources at less than $\\sim$100 Mpc and angular separation of a few degrees. The evolution of the correlation signal with the energy shows that the departure from anisotropy coincides with the flux suppression observed in the spectrum, being therefore consistent with the hypothesis that the correlated events have their origin in extragalactic sources close enough to avoid significant interaction with the cosmic microwave background (the Greisen-Zatsepin-Kuz'min effect). Even though the observed signal cannot unambiguously identify AGNs as the production sites of UHECRs, the potential sources have to be distributed in a similar way. A number of additional st...

  7. A fully covariant description of CMB anisotropies

    CERN Document Server

    Dunsby, P K S

    1997-01-01

    Starting from the exact non-linear description of matter and radiation, a fully covariant and gauge-invariant formula for the observed temperature anisotropy of the cosmic microwave background (CBR) radiation, expressed in terms of the electric ($E_{ab}$) and magnetic ($H_{ab}$) parts of the Weyl tensor, is obtained by integrating photon geodesics from last scattering to the point of observation today. This improves and extends earlier work by Russ et al where a similar formula was obtained by taking first order variations of the redshift. In the case of scalar (density) perturbations, $E_{ab}$ is related to the harmonic components of the gravitational potential $\\Phi_k$ and the usual dominant Sachs-Wolfe contribution $\\delta T_R/\\bar{T}_R\\sim\\Phi_k$ to the temperature anisotropy is recovered, together with contributions due to the time variation of the potential (Rees-Sciama effect), entropy and velocity perturbations at last scattering and a pressure suppression term important in low density universes. We a...

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Anisotropy and Crystalline Structure in Polyaniline Films

    Science.gov (United States)

    Minto, C. D. G.; Vaughan, A. S.

    1996-03-01

    Films of polyaniline -- camphor sulphonic acid cast from m-cresol exhibit transport properties characteristic of a material stradelling the metal/insulator transition. This improvement in properties over traditional methods of polyaniline production has been suggested as being caused by the macromolecule adopting an expanded coil configuration in this solvent. Such films have been shown to be semi--crystalline and are presumed to be completely isotropic. We present here new results which demonstrate that such films are in fact appreciably aligned. X-ray scattering is utilised to expose the presence of molecular anisotropy within such films, the polymers forming a stacked structure with the molecules preferentially oriented parallel to the plane of the film. Similar measurements confirm that the molecules are randomly oriented within this plane. Such alignment considerably improves the transport properties. Anisotropy and the crystalline structure within these films, those cast from chloroform and those using the isolated enantiomeric counter ion are quantified and discussed. The results demonstrate that improved transport properties have arisen as a result of both polymer--solvent interactions and as a result of improved chain alignment.

  13. Spectroscopic probing of location and dynamics of an environment-sensitive intramolecular charge transfer probe within liposome membranes.

    Science.gov (United States)

    Paul, Bijan Kumar; Guchhait, Nikhil

    2011-11-15

    The present work demonstrates the interaction of an intramolecular charge transfer (ICT) probe 5-(4-dimethylamino-phenyl)-penta-2,4-dienoic acid methyl ester (DPDAME) with liposome membranes of dimyristoyl-L-α-phosphatidylcholine (DMPC) and dimyristoyl-L-α-phosphatidylglycerol (DMPG) studied by steady-state absorption, emission and time-resolved emission techniques. A huge hypsochromic shift together with remarkable enhancement of fluorescence quantum yield of the polarity sensitive ICT emission of DPDAME upon interaction with the lipids has been rationalized in terms of incorporation of the probe into hydrophobic interior of the lipids. Compelling evidences for penetration of the probe into the hydrocarbon interior of the lipids have been deduced from intertwining different experimental results e.g., micropolarity in the immediate vicinity of the probe in lipid environments, steady-state anisotropy, red-edge excitation shift (REES), fluorescence quenching experiments and time-resolved measurements. The rotational relaxation dynamics study of the membrane-bound probe unveils the impartation of high degree of motional rigidity. Wavelength-selective emission behaviour paves way for monitoring of solvent-relaxation in the membranes. Overall, the ICT probe DPDAME displays its commendable sensitivity in deciphering the microheterogeneous environments of liposomal membranes of DMPC and DMPG and promises a new membrane-polarity sensitizing probe.

  14. 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...

  15. 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.

  16. STUDYING THE INTERSTELLAR MAGNETIC FIELD FROM ANISOTROPIES IN VELOCITY CHANNELS

    Energy Technology Data Exchange (ETDEWEB)

    Esquivel, A. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, 04510 México D.F., México (Mexico); Lazarian, A. [Astronomy Department, University of Wisconsin–Madison, 475 N. Charter Street, Madison, WI (United States); Pogosyan, D., E-mail: esquivel@nucleares.unam.mx, E-mail: lazarian@astro.wisc.edu, E-mail: pogosyan@ualberta.ca [Physics Department, University of Alberta, Edmonton, AB (Canada)

    2015-11-20

    Turbulence in the interstellar medium is anisotropic due to the ubiquitous magnetic fields. This anisotropy depends on the strength of the magnetic field and leaves an imprint on observations of spectral line maps. We use a grid of ideal magnetohydrodynamic simulations of driven turbulence and produce synthetic position–position–velocity maps to study the turbulence anisotropy in velocity channels of various resolutions. We found that the average structure function of velocity channels is aligned with the projection of the magnetic field on the plane of the sky. We also found that the degree of such anisotropy increases with the magnitude of the magnetic field. For thick velocity channels (low velocity resolution), the anisotropy is dominated by density, and the degree of anisotropy in these maps allows one to distinguish sub-Alfvénic and super-Alfvénic turbulence regimes, but it also depends strongly on the sonic Mach number. For thin channels (high velocity resolution), we find that the anisotropy depends less on the sonic Mach number. An important limitation of this technique is that it only gives a lower limit on the magnetic field strength because the anisotropy is related only to the magnetic field component on the plane of the sky. It can, and should, be used in combination with other techniques to estimate the magnetic field, such as the Fermi-Chandrasekhar method, anisotropies in centroids, Faraday rotation measurements, or direct line-of-sight determinations of the field from Zeeman effect observations.

  17. Effects of Surface Anisotropy on Magnetic Vortex Core

    OpenAIRE

    Pylypovskyi, Oleksandr V.; Sheka, Denis D.; Kravchuk, Volodymyr P.; Gaididei, Yuri

    2013-01-01

    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.

  18. Ultrasonic velocity and attenuation anisotropy of shales, Whitby, United Kingdom

    NARCIS (Netherlands)

    Zhubayev, A.; Houben, M.E.; Smeulders, D.M.J.; Barnhoorn, A.

    2015-01-01

    We have conducted ultrasonic experiments, between 0.3 and 1 MHz, to measure velocity and attenuation (Q−1) anisotropy of P- and S-waves in dry Whitby Mudstone samples as a function of stress. We found the degree of anisotropy to be as large as 70% for velocity and attenuation. The sensitivity of P-w

  19. Ultrasonic velocity and attenuation anisotropy of shales, Whitby, United Kingdom

    NARCIS (Netherlands)

    Zhubayev, Alimzhan; Houben, M.E.; Smeulders, David; Barnhoorn, A.

    2016-01-01

    We have conducted ultrasonic experiments, between 0.3 and 1 MHz, to measure velocity and attenuation (Q−1) anisotropy of P- and S-waves in dry Whitby Mudstone samples as a function of stress. We found the degree of anisotropy to be as large as 70% for velocity and attenuation. The sensitivity of P-w

  20. 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...

  1. Reorientation of magnetic anisotropy in obliquely sputtered metallic thin films

    NARCIS (Netherlands)

    Lisfi, A.; Lodder, J.C.; Wormeester, H.; Poelsema, B.

    2002-01-01

    Reorientation in the magnetic anisotropy as a function of film thickness has been observed in Co-Ni and Co thin films, obliquely sputtered on a polyethylene terephthalate substrate at a large incidence angle (70°). This effect is a consequence of the low magnetocrystalline anisotropy of the films (f

  2. Anisotropy Spectra for Enantiomeric Differentiation of Biomolecular Building Blocks

    DEFF Research Database (Denmark)

    Evans, Amanda C.; Meinert, Cornelia; Bredehoft, Jan H.;

    2013-01-01

    light. This chapter will: (1) present the theory and configuration of anisotropy spectroscopy; (2) explain experimentally recorded anisotropy spectra of selected chiral biomolecules such as amino acids; and (3) discuss the relevance of these spectra for the investigation of the origin of the molecular...

  3. 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...

  4. Modeling Scattering Polarization for Probing Solar Magnetism

    CERN Document Server

    Bueno, Javier Trujillo

    2011-01-01

    This paper considers the problem of modeling the light polarization that emerges from an astrophysical plasma composed of atoms whose excitation state is significantly influenced by the anisotropy of the incident radiation field. In particular, it highlights how radiative transfer simulations in three-dimensional models of the quiet solar atmosphere may help us to probe its thermal and magnetic structure, from the near equilibrium photosphere to the highly non-equilibrium upper chromosphere. The paper finishes with predictions concerning the amplitudes and magnetic sensitivities of the linear polarization signals produced by scattering processes in two transition region lines, which should encourage us to develop UV polarimeters for sounding rockets and space telescopes with the aim of opening up a new diagnostic window in astrophysics.

  5. 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...

  6. 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...

  7. Dispersion of the electron g factor anisotropy in InAs/InP self-assembled quantum dots

    Science.gov (United States)

    Belykh, V. V.; Yakovlev, D. R.; Schindler, J. J.; van Bree, J.; Koenraad, P. M.; Averkiev, N. S.; Bayer, M.; Silov, A. Yu.

    2016-08-01

    The electron g factor in an ensemble of InAs/InP quantum dots with emission wavelengths around 1.4 μm is measured using time-resolved pump-probe Faraday rotation spectroscopy in different magnetic field orientations. Thereby, we can extend recent single dot photoluminescence measurements significantly towards lower optical transition energies through 0.86 eV. This allows us to obtain detailed insight into the dispersion of the recently discovered g factor anisotropy in these infrared emitting quantum dots. We find with decreasing transition energy over a range of 50 meV a strong enhancement of the g factor difference between magnetic field normal and along the dot growth axis, namely, from 1 to 1.7. We argue that the g factor cannot be solely determined by the confinement energy, but the dot asymmetry underlying this anisotropy therefore has to increase with increasing dot size.

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

    Science.gov (United States)

    Bairagi, K; Bellec, A; Repain, V; Chacon, C; Girard, Y; Garreau, Y; Lagoute, J; Rousset, S; Breitwieser, R; Hu, Yu-Cheng; Chao, Yen Cheng; Pai, Woei Wu; Li, D; Smogunov, A; Barreteau, C

    2015-06-19

    We demonstrate that a C(60) 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 (60)/Co interfacial magnetic anisotropy that we have measured quantitatively in situ as a function of the (60) coverage. Comparison with state-of-the-art ab initio calculations show that this interfacial anisotropy mainly arises from the local hybridization between (60) p(z) and Co d(z(2)) orbitals. By generalizing these arguments, we also demonstrate that the hybridization of (60) with a Fe(110) surface decreases the perpendicular magnetic anisotropy. These results open the way to tailor the interfacial magnetic anisotropy in organic-material-ferromagnet systems.

  9. 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.

  10. 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.

  11. 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.

  12. Statistical anisotropy in the inflationary universe

    CERN Document Server

    Shtanov, Yuri

    2009-01-01

    During cosmological inflation, quasiclassical perturbations are permanently generated on super-Hubble spatial scales, their power spectrum being determined by the fundamental principles of quantum field theory. By the end of inflation, they serve as primeval seeds for structure formation in the universe. At early stages of inflation, such perturbations break homogeneity and isotropy of the inflationary background. In the present paper, we perturbatively take into account this quasiclassical background inhomogeneity of the inflationary universe while considering the evolution of small-scale (sub-Hubble) quantum modes. As a result, the power spectrum of primordial perturbations develops statistical anisotropy, which can subsequently manifest itself in the large-scale structure and cosmic microwave background. The statistically anisotropic contribution to the primordial power spectrum is predicted to have almost scale-invariant form dominated by a quadrupole. Theoretical expectation of the magnitude of this anis...

  13. Rational approach to anisotropy of sand

    Science.gov (United States)

    Wu, Wei

    1998-11-01

    The paper presents a constitutive model for the three-dimensional deformation-strength behaviour of inherently anisotropic sand. Based on non-linear tensorial functions, the model is developed without recourse to the concepts in plasticity theory such as yield surface and plastic potential. Benefited from the fact that no decomposition of strain into elastic and plastic parts is assumed, a unified treatment of anisotropic behaviour of deformation and strength is achieved. Anisotropy is characterized by a vector normal to the bedding plane. The extension of the constitutive model is furnished by incorporating the vector under consideration of the principle of objectivity and the condition of material symmetry. Distinct features of the model are its elegant formulation and its simple structure involving few material parameters. Model performance and comparison with experiments show that the model is capable of capturing the salient behaviour of anisotropic sand.

  14. PAPPA: Primordial Anisotropy Polarization Pathfinder Array

    CERN Document Server

    Kogut, A; Fixsen, D; Hinshaw, G F; Limon, M; Moseley, S H; Phillips, N; Sharp, E; Wollack, E J; U-Yen, K; Cao, N; Stevenson, T; Hsieh, W; Devlin, M; Dicker, S; Semisch, C; Irwin, K

    2006-01-01

    The Primordial Anisotropy Polarization Pathfinder Array (PAPPA) is a balloon-based instrument to measure the polarization of the cosmic microwave background and search for the signal from gravity waves excited during an inflationary epoch in the early universe. PAPPA will survey a 20 x 20 deg patch at the North Celestial Pole using 32 pixels in 3 passbands centered at 89, 212, and 302 GHz. Each pixel uses MEMS switches in a superconducting microstrip transmission line to combine the phase modulation techniques used in radio astronomy with the sensitivity of transition-edge superconducting bolometers. Each switched circuit modulates the incident polarization on a single detector, allowing nearly instantaneous characterization of the Stokes I, Q, and U parameters. We describe the instrument design and status.

  15. 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.

  16. 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.

  17. Nanomagnets with high shape anisotropy and strong crystalline anisotropy: perspectives on magnetic force microscopy.

    Science.gov (United States)

    Campanella, H; Jaafar, M; Llobet, J; Esteve, J; Vázquez, M; Asenjo, A; del Real, R P; Plaza, J A

    2011-12-16

    We report on a new approach for magnetic imaging, highly sensitive even in the presence of external, strong magnetic fields. Based on FIB-assisted fabricated high-aspect-ratio rare-earth nanomagnets, we produce groundbreaking magnetic force tips with hard magnetic character where we combine a high aspect ratio (shape anisotropy) together with strong crystalline anisotropy (rare-earth-based alloys). Rare-earth hard nanomagnets are then FIB-integrated to silicon microcantilevers as highly sharpened tips for high-field magnetic imaging applications. Force resolution and domain reversing and recovery capabilities are at least one order of magnitude better than for conventional magnetic tips. This work opens new, pioneering research fields on the surface magnetization process of nanostructures based either on relatively hard magnetic materials-used in magnetic storage media-or on materials like superparamagnetic particles, ferro/antiferromagnetic structures or paramagnetic materials.

  18. Theoretical Compton profile anisotropies in molecules and solids. IV. Parallel--perpendicular anisotropies in alkali fluoride molecules

    Energy Technology Data Exchange (ETDEWEB)

    Matcha, R.L.; Pettitt, B.M.; Ramirez, B.I.; McIntire, W.R.

    1979-07-15

    Calculations of Compton profiles and parallel--perpendicular anisotropies in alkali fluorides are presented and analyzed in terms of molecular charge distributions and wave function character. It is found that the parallel profile associated with the valence pi orbital is the principal factor determining the relative shapes of the total profile anisotropies in the low momentum region.

  19. Astrophysical Probes of New Models of Dark Matter

    Science.gov (United States)

    Zurek, Kathryn

    One of the most pressing and relevant cosmological questions is on the nature of the dark matter. I propose a comprehensive program at the boundary of astrophysics and cosmology with particle physics, focused on the question on the nature of the Dark Matter (DM). Research at the boundary of the two fields is critically important as a plethora of experiments in both particle physics and astrophysics, such as direct and indirect detection of Dark Matter (DM) by the Fermi Gamma Ray Space Telescope (FGST), AMS-02, and Cosmic Microwave Background probes such as Planck, come online. At the same time, data from the Large Hadron Collider (LHC) will probe fundamental questions about Electroweak Symmetry Breaking and its implications for astrophysics and cosmology, as concerns especially the nature of the DM and the generation of the baryon asymmetry. Physics beyond the Standard Model (SM) is required to explain the astrophysical observation that DM dominates over ordinary matter by a ratio 5:1, as we learned through WMAP, as well as large scale structure surveys. Despite lacking an understanding of the properties of the DM, its presence is crucial for the formation of structure in the universe. Particle physics provides a framework for understanding what the DM could be. This proposal centers on building new models of DM, as well as studying their signatures both in the galaxy and on earth. While particle physics has provided a few popular candidates for DM (such as the supersymmetric neutralino), whose signatures have been extensively studied in the literature, it is important to consider other theoretically motivated candidates which provide distinct signatures. This proposal focuses on such new models of DM, especially models of DM from hidden sectors. For example, recently, the PAMELA experiment has observed a rise in the ratio of positron to electron flux at high energies. The flux may likely come from astrophysical objects nearby, such as pulsars. An intriguing

  20. Determination of elastic anisotropy of rocks from P- and S-wave velocities: numerical modelling and lab measurements

    Science.gov (United States)

    Svitek, Tomáš; Vavryčuk, Václav; Lokajíček, Tomáš; Petružálek, Matěj

    2014-12-01

    The most common type of waves used for probing anisotropy of rocks in laboratory is the direct P wave. Information potential of the measured P-wave velocity, however, is limited. In rocks displaying weak triclinic anisotropy, the P-wave velocity depends just on 15 linear combinations of 21 elastic parameters, called the weak-anisotropy parameters. In strong triclinic anisotropy, the P-wave velocity depends on the whole set of 21 elastic parameters, but inversion for six of them is ill-conditioned and these parameters are retrieved with a low accuracy. Therefore, in order to retrieve the complete elastic tensor accurately, velocities of S waves must also be measured and inverted. For this purpose, we developed a lab facility which allows the P- and S-wave ultrasonic sounding of spherical rock samples in 132 directions distributed regularly over the sphere. The velocities are measured using a pair of P-wave sensors with the transmitter and receiver polarized along the radial direction and using two pairs of S-wave sensors with the transmitter and receiver polarized tangentially to the spherical sample in mutually perpendicular directions. We present inversion methods of phase and ray velocities for elastic parameters describing general triclinic anisotropy. We demonstrate on synthetic tests that the inversion becomes more robust and stable if the S-wave velocities are included. This applies even to the case when the velocity of the S waves is measured in a limited number of directions and with a significantly lower accuracy than that of the P wave. Finally, we analyse velocities measured on a rock sample from the Outokumpu deep drill hole, Finland. We present complete sets of elastic parameters of the sample including the error analysis for several levels of confining pressure ranging from 0.1 to 70 MPa.

  1. Origin of magnetization-induced anisotropy of magnetic films

    Institute of Scientific and Technical Information of China (English)

    Jin Han-Min; Chong-Oh Kim; Taek-Dong Lee; Hyo-Jin Kim

    2007-01-01

    It is proposed that the magnetization-induced anisotropy of magnetic films of cubic crystal structure originates from the anisotropy of atomic pair ordering, shape anisotropy, and strain anisotropy resulting from the constraint of the magnetostriction strain imposed on the film by the substrate. Calculated are the three anisotropy constants and their sum K vs temperature for Ni, Fe, and 55%Ni-Fe films; the room temperature (RT) constants vs the substrate temperature Tt during deposition or annealing after deposition for Ni and 50%Ni-Co films; the RT constants vs composition fraction for Fe-Ni films with Tt = RT, 250℃ and 450℃, Co-Ni films at Tt = RT, 100℃ and 320℃, and Fe-Co films with Tt = RT and 300℃; the spread of RT K vs composition fraction for Fe-Ni films; and RT △K/K vs composition fraction for Fe-Ni and Co-Ni films, where △K denotes the variation of K of the film that is detached from its substrate. The calculated curves well accord with the measurements. The irrelevancy of K to the substrate material and the fast kinetics of the annealing in a field applied in the direction of the hard axis are explained reasonably.The anisotropies of Fe and Ni films originate mainly from the shape anisotropy and the strain anisotropy, respectively. The major anisotropy component in many cases depends not only on composition fraction but also on Tt . For example, the RT anisotropy of 40-70%Ni-Fe films, when Tt is RT, mostly comes from the anisotropy of atomic pair ordering while it stems mostly from the shape anisotropy when Tt is 450 ℃. The most important cause of the spread in values of K is the spread of the intrinsic anisotropic stresses superimposed on the intrinsic isotropic planar stress. It is suggested that the field cooling induced magnetic anisotropy originating from the induced crystal texture observed in the bulk alloys is also a major origin for Co and Co-rich alloy films of hexagonal crystal structure.

  2. Laboratory measurements of the viscous anisotropy of olivine aggregates.

    Science.gov (United States)

    Hansen, L N; Zimmerman, M E; Kohlstedt, D L

    2012-12-20

    A marked anisotropy in viscosity develops in Earth's mantle as deformation strongly aligns the crystallographic axes of the individual grains that comprise the rocks. On the basis of geodynamic simulations, processes significantly affected by viscous anisotropy include post-glacial rebound, foundering of lithosphere and melt production above subduction zones. However, an estimate of the magnitude of viscous anisotropy based on the results of deformation experiments on single crystals differs by three orders of magnitude from that obtained by grain-scale numerical models of deforming aggregates with strong crystallographic alignment. Complicating matters, recent experiments indicate that deformation of the uppermost mantle is dominated by dislocation-accommodated grain-boundary sliding, a mechanism not activated in experiments on single crystals and not included in numerical models. Here, using direct measurements of the viscous anisotropy of highly deformed polycrystalline olivine, we demonstrate a significant directional dependence of viscosity. Specifically, shear viscosities measured in high-strain torsion experiments are 15 times smaller than normal viscosities measured in subsequent tension tests performed parallel to the torsion axis. This anisotropy is approximately an order of magnitude larger than that predicted by grain-scale simulations. These results indicate that dislocation-accommodated grain-boundary sliding produces an appreciable anisotropy in rock viscosity. We propose that crystallographic alignment imparts viscous anisotropy because the rate of deformation is limited by the movement of dislocations through the interiors of the crystallographically aligned grains. The maximum degree of anisotropy is reached at geologically low shear strain (of about ten) such that deforming regions of the upper mantle will exhibit significant viscous anisotropy.

  3. Crustal radial anisotropy beneath Cameroon from ambient noise tomography

    Science.gov (United States)

    Ojo, Adebayo Oluwaseun; Ni, Sidao; Li, Zhiwei

    2017-01-01

    To increase the understanding of crustal deformation and crustal flow patterns due to tectonic processes in Cameroon, we study the lateral variability of the crustal isotropic velocity and radial anisotropy estimated using Ambient Noise Tomography (ANT). Rayleigh and Love wave Noise Correlation Functions (NCFs) were retrieved from the cross-correlation of seismic ambient noise data recorded in Cameroon, and phase velocities at periods of 8 to 30 s were measured to perform surface wave tomography. Joint inversion of Rayleigh and Love wave data for isotropic velocity models could not fit the observed dispersions simultaneously. We attribute the Love-Rayleigh discrepancy to the presence of radial anisotropy in the crust and estimated its magnitude. Our 3-D radial anisotropic model reveals the spatial variation of strong to weak positive (Vsh > Vsv) and negative (Vsv > Vsh) radial anisotropy in the crust. We observe negative radial anisotropy in the upper crust that is associated mainly with the location of a previously reported mantle plume. The anisotropy could be attributed to the vertical alignment of fossil microcracks or metamorphic foliations due to the upwelling of plume material. A strong positive radial anisotropy is centered at the location of an inferred boundary between the Congo Craton and the Oubanguides Belt that might be related to the preferred orientation of crustal anisotropic minerals associated with shearing in this fault zone. The middle crust is characterized by a widespread negative radial anisotropy that is likely caused by the flow-induced alignment of anisotropic minerals that crystallized during magma intrusion. The magnitude of the radial anisotropy varies systematically from predominantly negative in the middle crust to positive in the lower crust. The imaged patterns of the isotropic velocity and radial anisotropy are consistent with previous studies and agree with regional tectonics.

  4. 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

  5. Complete treatment of CMB anisotropies in a FRW universe

    Science.gov (United States)

    Hu, Wayne; Seljak, Uroš; White, Martin; Zaldarriaga, Matias

    1998-03-01

    We generalize the total angular momentum method for computing cosmic microwave background anisotropies to Friedmann-Robertson-Walker (FRW) spaces with arbitrary geometries. This unifies the treatment of temperature and polarization anisotropies generated by scalar, vector and tensor perturbations of the fluid, seed, or a scalar field, in a universe with constant comoving curvature. The resulting formalism generalizes and simplifies the calculation of anisotropies and, in its integral form, allows for a fast calculation of model predictions in linear theory for any FRW metric.

  6. 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.

  7. Cubic versus spherical magnetic nanoparticles: the role of surface anisotropy.

    Science.gov (United States)

    Salazar-Alvarez, G; Qin, J; Sepelák, V; Bergmann, I; Vasilakaki, M; Trohidou, K N; Ardisson, J D; Macedo, W A A; Mikhaylova, M; Muhammed, M; Baró, M D; Nogués, J

    2008-10-08

    The magnetic properties of maghemite (gamma-Fe2O3) cubic and spherical nanoparticles of similar sizes have been experimentally and theoretically studied. The blocking temperature, T(B), of the nanoparticles depends on their shape, with the spherical ones exhibiting larger T(B). Other low temperature properties such as saturation magnetization, coercivity, loop shift or spin canting are rather similar. The experimental effective anisotropy and the Monte Carlo simulations indicate that the different random surface anisotropy of the two morphologies combined with the low magnetocrystalline anisotropy of gamma-Fe2O3 is the origin of these effects.

  8. 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.

  9. 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

  10. Canonical Transform Method for Treating Strongly Anisotropy Magnets

    DEFF Research Database (Denmark)

    Cooke, J. F.; Lindgård, Per-Anker

    1977-01-01

    An infinite-order perturbation approach to the theory of magnetism in magnets with strong single-ion anisotropy is given. This approach is based on a canonical transformation of the system into one with a diagonal crystal field, an effective two-ion anisotropy, and reduced ground-state corrections....... A matrix-element matching procedure is used to obtain an explicit expression for the spin-wave energy to second order. The consequences of this theory are illustrated by an application to a simple example with planar anisotropy and an external magnetic field. A detailed comparison between the results...

  11. CPO-induced seismic anisotropy in UHP eclogites

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Ultrahigh-pressure (UHP) eclogites often show strong plastic deformation and anisotropy of seismic properties. We report in this paper the seismic velocity and anisotropy of eclogite calculated from the crystallographic preferred orientations (CPOs) of constituent minerals (garnet, omphacite, quartz and rutile) and single crystal elastic properties. We also compared the calculated results with the measured results in similar eclogites. Our results suggest that (1) Except that garnet is a seismically quasi-isotropic mineral, omphacite, quartz, coesite and rutile all have strong seismic anisotropies (AVp = 23.0%―40.9%, Max. AVs = 18.5%―47.1%). They are the major sources for anisotropy in eclogite. The average seismic velocities are fast in garnet and rutile, moderate in omphacite and coesite, and slow in quartz. (2) The deformed eclogites have the maximum Vp (8.33―8.75 km/s) approximately parallel to foliation and lineation, the minimum Vp (8.25―8.62 km/s) approximately normal to foliation and lineation and the Vp anisotropies of 1.0―1.7%. Their Vs are 4.93―4.97 km/s. The corresponding maximum anisotropies (0.73%―1.78%) of Vs are at 45° to both foliation and lineation and the minimum anisotropies at positions normal to lineation on the foliation plane. The Vs1 polarization planes are approximately parallel to foliation. The mean Vp and Vs of eclogite under UHP peak metamorphism conditions (P = 3―5 GPa, T = 900―1100℃) are estimated to be 3.4%―7.2% and 6.3%―12.1% higher than those at ambient pressure and temperature conditions, respectively. (3) Omphacite component dominates the anisotropy of eclogite while garnet component reduces the anisotropy and increases the seismic velocities. Quartz component has a small effect on the anisotropy but reduces the seismic velocities of eclogite. The effect of rutile component is negligible on seismic properties of eclogite due to its trivial volume fraction. (4) The increase of volume fraction of omphacite

  12. 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.

  13. Texture induced magnetic anisotropy in Fe3O4 films

    Science.gov (United States)

    Liu, Er; Huang, Zhaocong; Zheng, Jian-Guo; Yue, Jinjin; Chen, Leyi; Wu, Xiumei; Sui, Yunxia; Zhai, Ya; Tang, Shaolong; Du, Jun; Zhai, Hongru

    2015-10-01

    This letter reports a free energy density model for textured films in which the related physical concept and expression of magneto-texture anisotropy energy are presented. The structural characterization and out-of-plane angular dependence ferromagnetic resonance of strongly textured Fe3O4 films were systematically investigated. We found that the typical free energy density model for polycrystalline film cannot be applied to the textured films. With the introduction of magneto-texture anisotropy energy in the free energy density model for thin films, we simulated and quantitatively determined the competing anisotropies in (111)-textured Fe3O4 films.

  14. 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.

  15. Anisotropy in the paramagnetic phase of RAl/sub 2/ cubic intermetallic compounds (R = Tb, Dy, and Er)

    Energy Technology Data Exchange (ETDEWEB)

    del Moral, A.; Ibarra, M.R.; Abell, J.S.; Montenegro, J.F.D.

    1987-05-01

    In this paper it is shown that the anisotropy in the paramagnetic phase is a useful characteristic when used to single out high-rank susceptibility tensor components in the paramagnetic regime of cubic crystals. Application of this technique to RAl/sub 2/ compounds (R = Tb,Dy,Er) allows the determination of longitudinal and transverse (in the form of linear combinations) fourth- and sixth-rank paramagnetic susceptibilities. The use of the fourth-rank longitudinal susceptibility allows quadrupolar pair interactions in these compounds to be probed.

  16. Response of an environment-sensitive intramolecular charge transfer probe towards solubilization of liposome membranes by a non-ionic detergent: Association and dissociation kinetics

    Science.gov (United States)

    Paul, Bijan Kumar; Guchhait, Nikhil

    2012-10-01

    The present report describes an endeavor to follow the solubilization of DMPC and DMPG liposome membranes by a non-ionic detergent Triton X-100 on the lexicon of environment-sensitive intramolecular charge transfer (ICT) photophysics of an extrinsic molecular probe 5-(4-dimethylamino-phenyl)-penta-2, 4-dienoic acid methyl ester (DPDAME). The prospective applicability of the probe to function as a reporter for detergent-sequestered solubilization of liposome membranes is argued on the basis of comparison of the spectral properties of the probe in various environments. Fluorescence anisotropy study delineates the degree of motional restriction imposed on the probe in different microheterogeneous assemblies. The kinetics of association of the probe with the liposome membranes and the dissociation kinetics of TX-100-sequestered solubilization process of the liposomes have been monitored by the stopped-flow fluorescence technique and the results are rationalized in relevance to fluorescence anisotropy study.

  17. Pioneer Jupiter orbiter probe mission 1980, probe description

    Science.gov (United States)

    Defrees, R. E.

    1974-01-01

    The adaptation of the Saturn-Uranus Atmospheric Entry Probe (SUAEP) to a Jupiter entry probe is summarized. This report is extracted from a comprehensive study of Jovian missions, atmospheric model definitions and probe subsystem alternatives.

  18. 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.

  19. 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.

  20. Fluorescence characteristics of hydrophobic partial agonist probes of the cholecystokinin receptor.

    Science.gov (United States)

    Harikumar, Kaleeckal G; Pinon, Delia I; Miller, Laurence J

    2006-04-01

    Fluorescence spectroscopic studies are powerful tools for the evaluation of receptor structure and the dynamic changes associated with receptor activation. Here, we have developed two chemically distinct fluorescent probes of the cholecystokinin (CCK) receptor by attaching acrylodan or a nitrobenzoxadiazole moiety to the amino terminus of a partial agonist CCK analogue. These two probes were able to bind to the CCK receptor specifically and with high affinity, and were able to elicit only submaximal intracellular calcium responses typical of partial agonists. The fluorescence characteristics of these probes were compared with those previously reported for structurally-related full agonist and antagonist probes. Like the previous probes, the partial agonist probes exhibited longer fluorescence lifetimes and increased anisotropy when bound to the receptor than when free in solution. The receptor-bound probes were not easily quenched by potassium iodide, suggesting that the fluorophores were protected from the extracellular aqueous milieu. The fluorescence characteristics of the partial agonist probes were quite similar to those of the analogous full agonist probes and quite distinct from the analogous antagonist probes. These data suggest that the partially activated conformational state of this receptor is more closely related to its fully active state than to its inactive state.

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

    Science.gov (United States)

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

    2017-01-01

    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 ± 0.0014 towards 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 Λ cold dark 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.

  2. On the Observation of the Cosmic Ray Anisotropy below 10$^{15}$ eV

    CERN Document Server

    Di Sciascio, G

    2014-01-01

    The measurement of the anisotropy in the arrival direction of cosmic rays is complementary to the study of their energy spectrum and chemical composition to understand their origin and propagation. It is also a tool to probe the structure of the magnetic fields through which cosmic rays travel. As cosmic rays are mostly charged nuclei, their trajectories are deflected by the action of galactic magnetic field they propagate through before reaching the Earth atmosphere, so that their detection carries directional information only up to distances as large as their gyro-radius. If cosmic rays below $10^{15}{\\rm\\,eV}$ are considered and the local galactic magnetic field ($\\sim3{\\rm\\,\\mu G}$) is accounted for, gyro-radii are so short that isotropy is expected. At most, a weak di-polar distribution may exist, reflecting the contribution of the closest CR sources. However, a number of experiments observed an energy-dependent \\emph{"large scale"} anisotropy in the sidereal time frame with an amplitude of about 10$^{-4...

  3. Liposome fluidization and melting point depression by pressurized CO2 determined by fluorescence anisotropy.

    Science.gov (United States)

    Bothun, Geoffrey D; Knutson, Barbara L; Strobel, Herbert J; Nokes, Sue E

    2005-01-18

    The influence of CO2 on the bilayer fluidity of liposomes, which are representative of model cellular membranes, was examined for the first time at the elevated pressures (up to 13.9 MPa) associated with CO2-based processing of liposomes and microbial sterilization. Fluidization and melting point depression of aqueous dipalmitoylphosphatidylcholine (DPPC) liposomes by pressurized CO2 (present as an excess phase) were studied by steady-state fluorescence anisotropy using the membrane probe 1,6-diphenyl-1,3,5-hexatriene (DPH). Isothermal experiments revealed reversible, pressure-dependent fluidization of DPPC bilayers at temperatures corresponding to near-gel (295 K) and fluid (333 K) phases at atmospheric pressure, where the gel-to-fluid phase transition (Tm) occurs at approximately 315 K. Isobaric measurements (PCO2 =1.8, 7.0, and 13.9 MPa) of DPH anisotropy demonstrate substantial melting point depression (DeltaTm = -4.8 to -18.5 K) and a large broadening of the gel-fluid phase transition region, which were interpreted using conventional theories of melting point depression. Liposome fluidity is influenced by CO2 accumulation in the hydrocarbon core and polar headgroup region, as well as the formation of carbonic acid and/or the presence of buffering species under elevated CO2 pressure.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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...

  10. 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.

  11. Control of magnetic domains in Co/Pd multilayered nanowires with perpendicular magnetic anisotropy.

    Science.gov (United States)

    Noh, Su Jung; Miyamoto, Yasuyoshi; Okuda, Mitsunobu; Hayashi, Naoto; Kim, Young Keun

    2012-01-01

    Magnetic domain wall (DW) motion induced by spin transfer torque in magnetic nanowires is of emerging technological interest for its possible applications in spintronic memory or logic devices. Co/Pd multilayered magnetic nanowires with perpendicular magnetic anisotropy were fabricated on the surfaces of Si wafers by ion-beam sputtering. The nanowires had different sized widths and pinning sites formed by an anodic oxidation method via scanning probe microscopy (SPM) with an MFM tip. The magnetic domain structure was changed by an anodic oxidation method. To discover the current-induced DW motion in the Co/Pd nanowires, we employed micromagnetic modeling based on the Landau-Lifschitz-Gilbert (LLG) equation. The split DW motions and configurations due to the edge effects of pinning site and nanowire appeared.

  12. Microstructural, Magnetic Anisotropy, and Magnetic Domain Structure Correlations in Epitaxial FePd Thin Films with Perpendicular Magnetic Anisotropy

    Science.gov (United States)

    Skuza, J. R.; Clavero, C.; Yang, K.; Wincheski, B.; Lukaszew, R. A.

    2009-01-01

    L1(sub 0)-ordered FePd epitaxial thin films were prepared using dc magnetron sputter deposition on MgO (001) substrates. The films were grown with varying thickness and degree of chemical order to investigate the interplay between the microstructure, magnetic anisotropy, and magnetic domain structure. The experimentally measured domain size/period and magnetic anisotropy in this high perpendicular anisotropy system were found to be correlated following the analytical energy model proposed by Kooy and Enz that considers a delicate balance between the domain wall energy and the demagnetizing stray field energy.

  13. 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.

  14. Patchy polymer colloids with tunable anisotropy dimensions.

    Science.gov (United States)

    Kraft, Daniela J; Hilhorst, Jan; Heinen, Maria A P; Hoogenraad, Mathijs J; Luigjes, Bob; Kegel, Willem K

    2011-06-09

    We present the synthesis of polymer colloids with continuously tunable anisotropy dimensions: patchiness, roughness, and branching. Our method makes use of controlled fusion of multiple protrusions on highly cross-linked polymer particles produced by seeded emulsion polymerization. Carefully changing the synthesis conditions, we can tune the number of protrusions, or branching, of the obtained particles from spheres with one to three patches to raspberry-like particles with multiple protrusions. In addition to that, roughness is generated on the seed particles by adsorption of secondary nucleated particles during synthesis. The size of the roughness relative to the smooth patches can be continuously tuned by the initiator, surfactant, and styrene concentrations. Seed colloids chemically different from the protrusions induce patches of different chemical nature. The underlying generality of the synthesis procedure allows for application to a variety of seed particle sizes and materials. We demonstrate the use of differently sized polyNIPAM (poly-N-isopropylacrylamide), as well as polystyrene and magnetite filled polyNIPAM seed particles, the latter giving rise to magnetically anisotropic colloids. The high yield together with the uniform, anisotropic shape make them interesting candidates for use as smart building blocks in self-assembling systems.

  15. Nanoscale magnetic ratchets based on shape anisotropy

    Science.gov (United States)

    Cui, Jizhai; Keller, Scott M.; Liang, Cheng-Yen; Carman, Gregory P.; Lynch, Christopher S.

    2017-02-01

    Controlling magnetization using piezoelectric strain through the magnetoelectric effect offers several orders of magnitude reduction in energy consumption for spintronic applications. However strain is a uniaxial effect and, unlike directional magnetic field or spin-polarized current, cannot induce a full 180° reorientation of the magnetization vector when acting alone. We have engineered novel ‘peanut’ and ‘cat-eye’ shaped nanomagnets on piezoelectric substrates that undergo repeated deterministic 180° magnetization rotations in response to individual electric-field-induced strain pulses by breaking the uniaxial symmetry using shape anisotropy. This behavior can be likened to a magnetic ratchet, advancing magnetization clockwise with each piezostrain trigger. The results were validated using micromagnetics implemented in a multiphysics finite elements code to simulate the engineered spatial and temporal magnetic behavior. The engineering principles start from a target device function and proceed to the identification of shapes that produce the desired function. This approach opens a broad design space for next generation magnetoelectric spintronic devices.

  16. 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.

  17. Loop quantum cosmology: Anisotropies and inhomogeneities

    Science.gov (United States)

    Wilson-Ewing, Edward

    In this dissertation we extend the improved dynamics of loop quantum cosmology from the homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker space-times to cosmological models which allow anisotropies and inhomogeneities. Specifically, we consider the cases of the homogeneous but anisotropic Bianchi type I, II and IX models with a massless scalar field as well as the vacuum, inhomogeneous, linearly polarized Gowdy T3 model. For each case, we derive the Hamiltonian constraint operator and study its properties. In particular, we show how in all of these models the classical big bang and big crunch singularities are resolved due to quantum gravity effects. Since the Bianchi models play a key role in the Belinskii, Khalatnikov and Lifshitz conjecture regarding the nature of generic space-like singularities in general relativity, the quantum dynamics of the Bianchi cosmologies are likely to provide considerable intuition about the fate of such singularities in quantum gravity. In addition, the results obtained here provide an important step toward the full loop quantization of cosmological space-times that allow generic inhomogeneities; this would provide falsifiable predictions that could be compared to observations.

  18. $\\Lambda$-inflation and CMB anisotropy

    CERN Document Server

    Lukash, V N

    2000-01-01

    We explore a broad class of three-parameter inflationary models, called the cosmic gravitational waves consistent with the Harrison-Zel'dovich spectrum of primordial cosmological perturbations, the non-power-law wing-like spectrum of matter density perturbations, high efficiency of these models to meet current observational tests, and others. We show that a parity contribution of the gravitational waves and adiabatic density perturbations into the large-scale temperature anisotropy, T/S $\\sim 1$, is a common feature of are reached in models where (i) the local spectrum shape of density perturbations is flat or slightly red ($n_S{}_\\sim^< 1$), and (ii) the residual potential energy of the inflaton is near the GUT scale ($V_0^{{1/4}} \\sim 10^{16} GeV$). The conditions to find large T/S in the paradigm of cosmic inflation and the relationship of T/S to the ratio of the power spectra, $r$, and to the inflationary $\\gamma$ and Hubble parameters, are discussed. We argue that a simple estimate, T/S$\\simeq 3r\\sime...

  19. Anisotropy in the Interaction of Ultracold Dysprosium

    CERN Document Server

    Kotochigova, Svetlana

    2011-01-01

    The nature of the interaction between ultracold atoms with a large orbital and spin angular momentum has attracted considerable attention. It was suggested that such interactions can lead to the realization of exotic states of highly correlated matter. Here, we report on a theoretical study of the competing anisotropic dispersion, magnetic dipole-dipole, and electric quadrupole-quadrupole forces between two dysprosium atoms. Each dysprosium atom has an orbital angular momentum L=6 and magnetic moment $\\mu=10\\mu_B$. We show that the dispersion coefficients of the ground state adiabatic potentials lie between 1865 a.u. and 1890 a.u., creating a non-negligible anisotropy with a spread of 25 a.u. and that the electric quadrupole-quadrupole interaction is weak compared to the other interactions. We also find that for interatomic separations $R< 50\\,a_0$ both the anisotropic dispersion and magnetic dipole-dipole potential are larger than the atomic Zeeman splittings for external magnetic fields of order 10 G to ...

  20. Anisotropy of the magnetic susceptibility of gallium

    Science.gov (United States)

    Pankey, T.

    1960-01-01

    The bulk magnetic susceptibilities of single gallium crystals and polycrystalline gallium spheres were measured at 25??C. The following anisotropic diamagnetic susceptibilities were found: a axis (-0.119??0. 001)??10-6 emu/g, b axis (-0.416??0.002)??10 -6 emu/g, and c axis (-0.229??0.001) emu/g. The susceptibility of the polycrystalline spheres, assumed to be the average value for the bulk susceptibility of gallium, was (-0.257??0.003)??10-6 emu/g at 25??C, and (-0.299??0.003)??10-6 emu/g at -196??C. The susceptibility of liquid gallium was (0.0031??0.001) ??10-6 emu/g at 30??C and 100??C. Rotational diagrams of the susceptibilities in the three orthogonal planes of the unit cell were not sinusoidal. The anisotropy in the single crystals was presumably caused by the partial overlap of Brillouin zone boundaries by the Fermi-energy surface. The large change in susceptibility associated with the change in state was attributed to the absence of effective mass influence in the liquid state. ?? 1960 The American Institute of Physics.

  1. 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.

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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.

  7. 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...

  8. 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.

  9. Is the magnetic anisotropy proportional to the orbital moment?

    Energy Technology Data Exchange (ETDEWEB)

    Skomski, R; Kashyap, A; Enders, A

    2011-04-01

    The relation between orbital moment and magnetic anisotropy is investigated by model calculations, which show that only a part of the spin-orbit coupling contributes to the anisotropy. A large part of the anisotropy energy, about 50% for iron series elements and nearly 100% for rare-earths, is stored in the nonrelativistic part of the Hamiltonian. A feature important for x-ray magnetic circular dichroism is that the orbital moment of heavy atoms rotates with the spin moment, whereas in light atoms, the orbital moment is recreated in each different direction. In the discussion, we consider three examples of current interest in different areas of magnetism, namely, spin-orbit coupling in Gd3+ and Eu2+, surface anisotropy of Nd2Fe14B, and multiferroic magnetization switching using rare-earths. (C) 2011 American Institute of Physics. [doi:10.1063/1.3562445

  10. 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.

  11. Friction Anisotropy: A unique and intrinsic property of decagonal quasicrystals

    Energy Technology Data Exchange (ETDEWEB)

    Mulleregan, Alice; Park, Jeong Young; Salmeron, Miquel; Ogetree, D.F.; Jenks, C.J.; Thiel, P.A.; Brenner, J.; Dubois, J.M.

    2008-06-25

    We show that friction anisotropy is an intrinsic property of the atomic structure of Al-Ni-Co decagonal quasicrystals and not only of clean and well-ordered surfaces that can be prepared in vacuum [J.Y. Park et al., Science (2005)]. Friction anisotropy is manifested both in nanometer size contacts obtained with sharp atomic force microscope (AFM) tips as well as in macroscopic contacts produced in pin-on-disc tribometers. We show that the friction anisotropy, which is not observed when an amorphous oxide film covers the surface, is recovered when the film is removed due to wear. Equally important is the loss of the friction anisotropy when the quasicrystalline order is destroyed due to cumulative wear. These results reveal the intimate connection between the mechanical properties of these materials and their peculiar atomic structure.

  12. CoTaZr/Pd multilayer with perpendicular magnetic anisotropy

    Directory of Open Access Journals (Sweden)

    Yong Chang Lau

    2013-08-01

    Full Text Available We report a novel perpendicularly magnetized thin film [Co91.5Ta4.5Zr4/Pd]5 multilayer, which exhibits strong perpendicular magnetic anisotropy when grown on 5 nm of Pd and Ru seed layers. The Pd-seeded multilayer annealed at 300 °C shows an effective uniaxial anisotropy constant, Keff = 1.1 MJ m−3, with an anisotropy field as high as 1.6 T. The perpendicular anisotropy is sustained on annealing at 400 °C for 1 h. X-ray diffraction on multilayers with 30 repeats suggests that the use of amorphous CoTaZr reduces the stress of the stack, compared to [Co/Pd] multilayer.

  13. Cosmic microwave background anisotropies seeded by incoherent sources

    CERN Document Server

    Riazuelo, A; Riazuelo, Alain; Deruelle, Nathalie

    2000-01-01

    The cosmic microwave background anisotropies produced by active seeds, such as topological defects, have been computed recently for a variety of models by a number of authors. In this paper we show how the generic features of the anisotropies caused by active, incoherent, seeds (that is the absence of acoustic peaks at small scales) can be obtained semi-analytically, without entering into the model dependent details of their formation, structure and evolution.

  14. 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.

  15. 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 <γ< -2.6. Conclusions: 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.

  16. Spatially frustrated S = 1 Heisenberg antiferromagnet with single ion anisotropy

    Science.gov (United States)

    Pires, A. S. T.

    2016-10-01

    Using the SU(3) Schwinger boson formalism, I study the S = 1 square lattice Heisenberg antiferromagnet, at zero temperature, with spatially anisotropic nearest-neighbor couplings frustrated by a next-nearest neighbor interaction and single ion anisotropy. The phase diagram at zero temperature is presented. My calculations show two magnetically ordered phases separated by a quantum-disordered region for all values of the anisotropy.

  17. 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.

  18. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Santos-Lima, R. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Potsdam Univ. (Germany). Inst. fuer Physik und Astronomie; Univ. de Sao Paulo (Brazil). Inst. de Astronomia, Geofisica e Ciencias Atmosfericas; Yan, H. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Potsdam Univ. (Germany). Inst. fuer Physik und Astronomie; Gouveia Dal Pino, E.M. de [Univ. de Sao Paulo (Brazil). Inst. de Astronomia, Geofisica e Ciencias Atmosfericas; Lazarian, A. [Wisconsin Univ., Madison, WI (United States). Dept. of Astronomy

    2016-05-15

    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 pressure magnetohydrodynamic (AMHD) turbulence shows a very different statistical behaviour from the standard MHD one and is unable to amplify seed magnetic fields, in disagreement with previous cosmological MHD simulations which are successful to explain the observed magnetic fields in the ICM. On the other hand, temperature anisotropies can also drive plasma instabilities which can relax the anisotropy. This work aims to compare the relaxation rate with the growth rate of the anisotropies driven by the turbulence. We employ quasilinear theory to estimate the ions scattering rate due to the parallel firehose, mirror, and ion-cyclotron instabilities, for a set of plasma parameters resulting from AMHD simulations of the turbulent ICM. We show that the ICM turbulence can sustain only anisotropy levels very close to the instabilities thresholds. We argue that the AMHD model which bounds the anisotropies at the marginal stability levels can describe the Alfvenic turbulence cascade in the ICM.

  20. 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.)

  1. Analysis of North Sky Cosmic Ray Anisotropy with Atmospheric Neutrinos

    Science.gov (United States)

    Wills, Elizabeth; IceCube Collaboration

    2017-01-01

    Since the discovery of Cosmic Ray anisotropy, no experiment has definitively discovered the source of this unexpected phenomenon. Studying the cosmic rays' neutral daughter particles with pointing capabilities, like neutrinos, could shed new light. This can be done at two levels; a source which produces cosmic rays must also produce high energy astrophysical neutrinos, and low energy atmospheric neutrinos are made when the cosmic rays interact with the atmosphere. This analysis focuses on atmospheric neutrinos detected by IceCube, a Cherenkov detector instrumenting a kilometer cubed of glacial ice at the South Pole. The anisotropy and its energy dependence have been studied in the Southern sky using atmospheric muons by IceCube. In the North, gamma ray detectors, such as HAWC, and Argo-YBJ, have observed this anisotropy in cosmic ray showers. Thus far, no single- detector full-sky map exists of the anisotropy. Using IceCube's neutrino data, we can complement these studies with an exploration of the northern sky anisotropy at higher energies of cosmic rays. This could bring us much closer to understanding the complete picture of this anisotropy across energy levels and the whole sky.

  2. 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.

  3. 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.

  4. 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.

  5. 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)

  6. 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.

  7. Application of the anisotropy field distribution method to arrays of magnetic nanowires

    OpenAIRE

    De La Torre Medina, Joaquin; Darques, Michaël; Piraux, Luc; Encinas, Armando

    2009-01-01

    The applicability of the anisotropy field distribution method and the conditions required for an accurate determination of the effective anisotropy field in arrays of magnetic nanowires have been evaluated. In arrays of magnetic nanowires that behave as ideal uniaxial systems having only magnetostatic contributions to the effective anisotropy field, i.e., shape anisotropy and magnetostatic coupling, the method yields accurate values of the average anisotropy field at low-moderate dipolar coup...

  8. 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...

  9. 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...

  10. Anisotropy spectra for enantiomeric differentiation of biomolecular building blocks.

    Science.gov (United States)

    Evans, A C; Meinert, C; Bredehöft, J H; Giri, C; Jones, N C; Hoffmann, S V; Meierhenrich, U J

    2013-01-01

    All biopolymers are composed of homochiral building blocks, and both D-sugars and L-amino acids uniquely constitute life on Earth. These monomers were originally enantiomerically differentiated under prebiotic conditions. Particular progress has recently been made in support of the photochemical model for this differentiation: the interaction of circularly polarized light with racemic molecules is currently thought to have been the original source for life's biological homochirality. The differential asymmetric photoreactivity of particular small molecules can be characterized by both circular dichroism and anisotropy spectroscopy. Anisotropy spectroscopy, a novel derivative of circular dichroism spectroscopy, records the anisotropy factor g = Δε/ε as a function of the wavelength. Anisotropy spectroscopy promisingly affords the wavelength-dependent determination of the enantiomeric excess (ee) inducible into chiral organic molecules by photochemical irradiation with circularly polarized light. Anisotropy spectra of small molecules therefore provide unique means for characterizing the different photochemical behaviors between enantiomers upon exposure to various wavelengths of circularly polarized light. This chapter will: (1) present the theory and configuration of anisotropy spectroscopy; (2) explain experimentally recorded anisotropy spectra of selected chiral biomolecules such as amino acids; and (3) discuss the relevance of these spectra for the investigation of the origin of the molecular homochirality observed in living organisms. This review describes a new chiroptical technique that is of significance for advances in asymmetric photochemistry and that is also highly relevant for the European Space Agency Rosetta Mission, which will determine enantiomeric excesses (ees) in chiral organic molecules in cometary ices when it lands on Comet 67P/Churyumov-Gerasimenko in November 2014.

  11. 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.

  12. 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.

  13. 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...

  14. 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.

  15. Scaling of coercivity in a 3d random anisotropy model

    Energy Technology Data Exchange (ETDEWEB)

    Proctor, T.C., E-mail: proctortc@gmail.com; Chudnovsky, E.M., E-mail: EUGENE.CHUDNOVSKY@lehman.cuny.edu; Garanin, D.A.

    2015-06-15

    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.

  16. Concepts for integrating plastic anisotropy into metal forming simulations

    Energy Technology Data Exchange (ETDEWEB)

    Raabe, D.; Roters, F. [Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf (Germany). Abt. fuer Mikrostrukturphysik; Klose, P.; Engl, B.; Imlau, K.P.; Friedel, F. [Research and Development, Quality Engineering, and Materials Testing, Thyssen Krupp Stahl AG, Duisburg (Germany)

    2002-04-01

    Modern metal forming and crash simulations are usually based on the finite element method. Aims of such simulations are typically the prediction of the material shape, failure, and mechanical properties during deformation. Further goals lie in the computer assisted lay-out of manufacturing tools used for intricate processing steps. Any such simulation requires that the material under investigation is specified in terms of its respective constitutive behavior. Modern finite element simulations typically use three sets of material input data, covering hardening, forming limits, and anisotropy. The current article is about the latter aspect. It reviews different empirical and physically based concepts for the integration of the elastic-plastic anisotropy into metal forming finite element simulations. Particular pronunciation is placed on the discussion of the crystallographic anisotropy of polycrystalline material rather than on aspects associated with topological or morphological microstructure anisotropy. The reviewed anisotropy concepts are empirical yield surface approximations, yield surface formulations based on crystallographic homogenization theory, combinations of finite element and homogenization approaches, the crystal plasticity finite element method, and the recently introduced texture component crystal plasticity finite element method. The paper presents the basic physical approaches behind the different methods and discusses engineering aspects such as scalability, flexibility, and texture update in the course of a forming simulation. (orig.)

  17. Origin of azimuthal seismic anisotropy in oceanic plates and mantle

    Science.gov (United States)

    Becker, Thorsten W.; Conrad, Clinton P.; Schaeffer, Andrew J.; Lebedev, Sergei

    2014-09-01

    Seismic anisotropy is ubiquitous in the Earth's mantle but strongest in its thermo-mechanical boundary layers. Azimuthal anisotropy in the oceanic lithosphere and asthenosphere can be imaged by surface waves and should be particularly straightforward to relate to well-understood plate kinematics and large-scale mantle flow. However, previous studies have come to mixed conclusions as to the depth extent of the applicability of paleo-spreading and mantle flow models of anisotropy, and no simple, globally valid, relationships exist. Here, we show that lattice preferred orientation (LPO) inferred from mantle flow computations produces a plausible global background model for asthenospheric anisotropy underneath oceanic lithosphere. The same is not true for absolute plate motion (APM) models. A ˜200 km thick layer where the flow model LPO matches observations from tomography lies just below the ˜1200 °C isotherm of a half-space cooling model, indicating strong temperature-dependence of the processes that control the development of azimuthal anisotropy. We infer that the depth extent of shear, and hence the thickness of a relatively strong oceanic lithosphere, can be mapped this way. These findings for the background model, and ocean-basin specific deviations from the half-space cooling pattern, are found in all of the three recent and independent tomographic models considered. Further exploration of deviations from the background model may be useful for general studies of oceanic plate formation and dynamics as well as regional-scale tectonic analyses.

  18. A Investigation of the Elastic and Dielectric Anisotropy of Paper.

    Science.gov (United States)

    Fleischman, Elmer Henry, Jr.

    This investigation was undertaken to learn more about the way in which fiber orientation and drying restraint affect the elastic and dielectric properties in all three principal directions of paper. It was found that both variables affect the in -plane elastic anisotropy by similar magnitudes. What was surprising, however, was that wet straining has the greatest effect in the z-direction. The z-direction stiffness was reduced 50% as a result of only a moderate 2.4% wet strain in the plane of the sheet. On the other hand, the dielectric anisotropy was affected very little by wet straining. In fact, the dielectric results could be explained in terms of mixture theories. The anisotropy in the dielectric constant when measured at microwave frequencies could largely be explained as being the result of fiber orientation alone without having to assume that the fiber has an anisotropic dielectric constant. From comparison of the elastic and dielectric results, it may be concluded that the mechanism by which wet straining enhances the elastic anisotropy does not involve a large fiber orientation in the direction of wet straining. From a practical standpoint, one could use the dielectric anisotropy measured at microwave frequencies as a measure of the fiber orientation distribution in the sheet. On the basis of the results presented here, this measurement should be quite insensitive to any stresses imposed on the sheet as it dries.

  19. Magnetic anisotropy of ultrafine 316L stainless steel fibers

    Science.gov (United States)

    Shyr, Tien-Wei; Huang, Shih-Ju; Wur, Ching-Shuei

    2016-12-01

    An as-received 316L stainless steel fiber with a diameter of 20 μm was drawn using a bundle drawing process at room temperature to form ultrafine stainless steel fibers with diameters of 12, 8, and 6 μm. The crystalline phases of the fibers were analyzed using the X-ray diffraction (XRD) profile fitting technique. The grain sizes of γ-austenite and α‧-martensite were reduced to nanoscale sizes after the drawing process. XRD analysis and focused ion beam-scanning electron microscope observations showed that the newly formed α‧-martensitic grains were closely arrayed in the drawing direction. The magnetic property was measured using a superconducting quantum interference device vibrating sample magnetometer. The magnetic anisotropy of the fibers was observed by applying a magnetic field parallel and perpendicular to the fiber axis. The results showed that the microstructure anisotropy including the shape anisotropy, magnetocrystalline anisotropy, and the orientation of the crystalline phases strongly contributed to the magnetic anisotropy.

  20. 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...

  1. Plasmon-induced optical anisotropy in hybrid graphene-metal nanoparticle systems.

    Science.gov (United States)

    Gilbertson, Adam M; Francescato, Yan; Roschuk, Tyler; Shautsova, Viktoryia; Chen, Yiguo; Sidiropoulos, Themistoklis P H; Hong, Minghui; Giannini, Vincenzo; Maier, Stefan A; Cohen, Lesley F; Oulton, Rupert F

    2015-05-13

    Hybrid plasmonic metal-graphene systems are emerging as a class of optical metamaterials that facilitate strong light-matter interactions and are of potential importance for hot carrier graphene-based light harvesting and active plasmonic applications. Here we use femtosecond pump-probe measurements to study the near-field interaction between graphene and plasmonic gold nanodisk resonators. By selectively probing the plasmon-induced hot carrier dynamics in samples with tailored graphene-gold interfaces, we show that plasmon-induced hot carrier generation in the graphene is dominated by direct photoexcitation with minimal contribution from charge transfer from the gold. The strong near-field interaction manifests as an unexpected and long-lived extrinsic optical anisotropy. The observations are explained by the action of highly localized plasmon-induced hot carriers in the graphene on the subresonant polarizability of the disk resonator. Because localized hot carrier generation in graphene can be exploited to drive electrical currents, plasmonic metal-graphene nanostructures present opportunities for novel hot carrier device concepts.

  2. Assessment of the mode of action of polyhexamethylene biguanide against Listeria innocua by Fourier transformed infrared spectroscopy and fluorescence anisotropy analysis.

    Science.gov (United States)

    Chadeau, Elise; Dumas, Emilie; Adt, Isabelle; Degraeve, Pascal; Noël, Claude; Girodet, Christophe; Oulahal, Nadia

    2012-12-01

    Polyhexamethylene biguanide (PHMB) is a cationic biocide. The antibacterial mode of action of PHMB (at concentrations not exceeding its minimal inhibitory concentration) upon Listeria innocua LRGIA 01 was investigated by Fourier transformed infrared spectroscopy and fluorescence anisotropy analysis. Fourier transformed infrared spectra of bacteria treated with or without PHMB presented some differences in the lipids region: the CH(2)/CH(3) (2924 cm(-1)/2960 cm(-1)) band areas ratio significantly increased in the presence of PHMB. Since this ratio generally reflects membrane phospholipids and membrane microenvironment of the cells, these results suggest that PHMB molecules interact with membrane phospholipids and, thus, affect membrane fluidity and conformation. To assess the hypothesis of PHMB interaction with L. innocua membrane phospholipids and to clarify the PHMB mode of action, we performed fluorescence anisotropy experiments. Two probes, 1,6-diphenyl-1,3,5-hexatriene (DPH) and its derivative 1-[4-(trimethyl-amino)-phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH), were used. DPH and TMA-DPH incorporate inside and at the surface of the cytoplasmic membrane, respectively. When PHMB was added, an increase of TMA-DPH fluorescence anisotropy was observed, but no changes of DPH fluorescence anisotropy occurred. These results are consistent with the hypothesis that PHMB molecules perturb L. innocua LRGIA 01 cytoplasmic membrane by interacting with the first layer of the membrane lipid bilayer.

  3. 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.

  4. Cosmic Ray Small Scale Anisotropies and Local Turbulent Magnetic Fields

    CERN Document Server

    López-Barquero, Vanessa; Xu, S; Desiati, P; Lazarian, A

    2015-01-01

    Cosmic ray anisotropy is observed in a wide energy range and at different angular scales by a variety of experiments. However, a comprehensive and satisfactory explanation has been elusive for over a decade now. The arrival distribution of cosmic rays on Earth is the convolution of the distribution of their sources and of the effects of geometry and properties of the magnetic field through which particles propagate. It is generally believed that the anisotropy topology at the largest angular scale is adiabatically shaped by diffusion in the structured interstellar magnetic field. On the contrary, the medium and small angular scale structure could be an effect of non diffusive propagation of cosmic rays in perturbed magnetic fields. In particular, a possible explanation of the observed small scale anisotropy observed at TeV energy scale, may come from the effect of particle scattering in turbulent magnetized plasmas. We perform numerical integration of test particle trajectories in low-$\\beta$ compressible mag...

  5. Predicted Impacts of Proton Temperature Anisotropy on Solar Wind Turbulence

    CERN Document Server

    Klein, Kristopher G

    2015-01-01

    Particle velocity distributions measured in the weakly collisional solar wind are frequently found to be non-Maxwellian, but how these non-Maxwellian distributions impact the physics of plasma turbulence in the solar wind remains unanswered. Using numerical solutions of the linear dispersion relation for a collisionless plasma with a bi-Maxwellian proton velocity distribution, we present a unified framework for the four proton temperature anisotropy instabilities, identifying the associated stable eigenmodes, highlighting the unstable region of wavevector space, and presenting the properties of the growing eigenfunctions. Based on physical intuition gained from this framework, we address how the proton temperature anisotropy impacts the nonlinear dynamics of the \\Alfvenic fluctuations underlying the dominant cascade of energy from large to small scales and how the fluctuations driven by proton temperature anisotropy instabilities interact nonlinearly with each other and with the fluctuations of the large-scal...

  6. 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.

  7. Spin anisotropy and slow dynamics in spin glasses.

    Science.gov (United States)

    Bert, F; Dupuis, V; Vincent, E; Hammann, J; Bouchaud, J-P

    2004-04-23

    We report on an extensive study of the influence of spin anisotropy on spin glass aging dynamics. New temperature cycle experiments allow us to compare quantitatively the memory effect in four Heisenberg spin glasses with various degrees of random anisotropy and one Ising spin glass. The sharpness of the memory effect appears to decrease continuously with the spin anisotropy. Besides, the spin glass coherence length is determined by magnetic field change experiments for the first time in the Ising sample. For three representative samples, from Heisenberg to Ising spin glasses, we can consistently account for both sets of experiments (temperature cycle and magnetic field change) using a single expression for the growth of the coherence length with time.

  8. SIMULTANEOUS MEASUREMENT OF CIRCULAR DICHROISM AND FLUORESCENCE POLARIZATION ANISOTROPY.

    Energy Technology Data Exchange (ETDEWEB)

    SUTHERLAND,J.C.

    2002-01-19

    Circular dichroism and fluorescence polarization anisotropy are important tools for characterizing biomolecular systems. Both are used extensively in kinetic experiments involving stopped- or continuous flow systems as well as titrations and steady-state spectroscopy. This paper presents the theory for determining circular dichroism and fluorescence polarization anisotropy simultaneously, thus insuring the two parameters are recorded under exactly the same conditions and at exactly the same time in kinetic experiments. The approach to measuring circular dichroism is that used in almost all conventional dichrographs. Two arrangements for measuring fluorescence polarization anisotropy are described. One uses a single fluorescence detector and signal processing with a lock-in amplifier that is similar to the measurement of circular dichroism. The second approach uses classic ''T'' format detection optics, and thus can be used with conventional photon-counting detection electronics. Simple extensions permit the simultaneous measurement of the absorption and excitation intensity corrected fluorescence intensity.

  9. Evidence for an anisotropy of the speed of light

    CERN Document Server

    de Aragao, C M L; Grillo, A

    2005-01-01

    By comparing with the most recent experimental results, we point out the model dependence of the present bounds on the anisotropy of the speed of light. In fact, by replacing the CMB with a class of preferred frames that can better account for the experimental data, one obtains values of the RMS anisotropy parameter (1/2 -beta + delta) that are one order of magnitude larger than the presently quoted ones. The resulting non-zero anisotropy can be understood starting from the observation that the speed of light in the Earth's gravitational field is not the basic parameter c=1 entering Lorentz transformations. In this sense, light can propagate isotropically only in one `preferred' frame.

  10. Effects of spacetime anisotropy on the galaxy rotation curves

    CERN Document Server

    Chang, Zhe; Li, Xin; Lin, Hai-Nan; Wang, Sai

    2013-01-01

    The observations on galaxy rotation curves show significant discrepancies from the Newtonian theory. This issue could be explained by the effect of the anisotropy of the spacetime. Conversely, the spacetime anisotropy could also be constrained by the galaxy rotation curves. Finsler geometry is a kind of intrinsically anisotropic geometry. In this paper, we study the effect of the spacetime anisotropy at the galactic scales in the Finsler spacetime. It is found that the Finslerian model has close relations with the Milgrom's MOND. By performing the best-fit procedure to the galaxy rotation curves, we find that the anisotropic effects of the spacetime become significant when the Newtonian acceleration \\(GM/r^2\\) is smaller than the critical acceleration \\(a_0\\). Interestingly, the critical acceleration \\(a_0\\), although varies between different galaxies, is in the order of magnitude \\(cH_0/2\\pi\\sim 10^{-10} \\rm{m\\,\\, s^{-2}}\\).

  11. Fire Hose instability driven by alpha particle temperature anisotropy

    CERN Document Server

    Matteini, Lorenzo; Schwartz, Steven; Landi, Simone

    2015-01-01

    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, the instability can be triggered also 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 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...

  12. 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.

  13. Determination of magnetic anisotropy of magnetically hard materials

    Science.gov (United States)

    Richter, H. J.

    1990-03-01

    The determination of the first-order anisotropy field strength using the torsion pendulum method is described. Since the applied field need not necessarily be in the range of the anisotropy field, this method is particularly useful for characterizing modern permanent magnet materials which have a very high uniaxial anisotropy. The method requires oriented samples. Measurements were made on polycrystalline samples of NdFeB, SmCo, and barium ferrite. The method is described and error sources are discussed. It is pointed out that the torsion pendulum method is closely related to reversible transverse susceptibility measurements. It is shown both experimentally and theoretically, that using susceptibility measurements similar results can be obtained. The susceptibility method is, however, not applicable to conducting materials at present.

  14. 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...

  15. Determination of metal ions by fluorescence anisotropy exhibits a broad dynamic range

    Science.gov (United States)

    Thompson, Richard B.; Maliwal, Badri P.; Fierke, Carol A.

    1998-05-01

    Recently, we have shown that metal ions free in solution may be determined at low levels by fluorescence anisotropy (polarization) measurements. Anisotropy measurements enjoy the advantages of wavelength ratiometric techniques for determining metal ions such as calcium, because anisotropy measurements are ratiometric as well. Furthermore, fluorescence anisotropy may be imaged in the microscope. An advantage of anisotropy not demonstrated for wavelength ratiometric approaches using indicators such as Fura-2 and Indo-1 is that under favorable circumstances anisotropy-based determinations exhibit a much broader dynamic range in metal ion concentration. Determinations of free Zn(II) in the picomolar range are demonstrated.

  16. 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.

  17. 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

  18. 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.

  19. Aligned submicron grains in archeological potteries with high TRM anisotropy

    Science.gov (United States)

    Fukuma, K.; Ooga, M.; Isobe, H.

    2010-12-01

    Potteries have been often used to obtain archeointensity data because of the extremely high success rates in Thellier experiments. Since high anisotropy of thermoremanent magnetization (TRM) are commonly observed for potteries, anisotropy correction is routinely applied to make archeointensity data reliable. Such a TRM anisotropy is characterized by the foliated structure parallel to the surface and has been interpreted to reflect aligned magnetic minerals during molding. However, the high thermal stability and the higher degrees of TRM anisotropies than those of low-field susceptibility suggest that pottery TRM resides in fine-grained magnetic minerals formed during firing. Molding is not sufficient to explain highly anisotropic TRM of potteries. We measured TRM susceptibility tensors on potteries manufactured from 14th to 17th centuries in Japan. These potteries were fired up to about 1200°C resulting in partial vitrification. The ratios of maximum and minimum eigenvalues of the TRM susceptibility tensors are well distributed and reaches 1.8 for most anisotropic samples. The Curie temperature ranges from 500°C to 550°C implying titanium-poor titanomagnetite as TRM carriers, and the narrow unblocking temperature indicates that the low-titanium titanomagnetites are in or close to the single-domain size range. Submicron titanomagnetite grains were commonly observed on the polished sections under a FE-SEM. Some of the grains occur as inclusions in iron-bearing silicates such as pyroxene or hornblende, and other grains reside in glass matrix. In addition, vesiculated clay minerals contain highly elongated titanomagnetite grains. Such clay minerals seem stretched parallel to the pottery surface and inside titanomagnetite grains are also elongated along the surface. Relative abundance of titanomagnetite inclusions in silicates or glass against in clay minerals should control the degree of TRM anisotropy. Foliated TRM anisotropies originate from both alignment of clay

  20. Probing The New Cosmology

    CERN Document Server

    Zentner, A R

    2003-01-01

    Improvements in observational techniques have transformed cosmology into a field inundated with ever-expanding, high-quality data sets and driven cosmology toward a standard model where the classic cosmological parameters are accurately measured. I briefly discuss some of the methods used to determine cosmological parameters, particularly primordial nucleosynthesis, the magnitude- redshift relation of supernovae, and cosmic microwave background anisotropy. I demonstrate how cosmological data can be used to complement particle physics and constrain extensions to the Standard Model. Specifically, I present bounds on light particle species and the properties of unstable, weakly-interacting, massive particles. Despite the myriad successes of the emerging standard cosmological model, unanswered questions linger. Numerical simulations of structure formation predict galactic central densities that are considerably higher than observed. They also reveal hundreds of satellites orbiting Milky Way-like galaxies while th...

  1. 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.

  2. Seismic anisotropy: tracing plate dynamics in the mantle.

    Science.gov (United States)

    Park, Jeffrey; Levin, Vadim

    2002-04-19

    Elastic anisotropy is present where the speed of a seismic wave depends on its direction. In Earth's mantle, elastic anisotropy is induced by minerals that are preferentially oriented in a directional flow or deformation. Earthquakes generate two seismic wave types: compressional (P) and shear (S) waves, whose coupling in anisotropic rocks leads to scattering, birefringence, and waves with hybrid polarizations. This varied behavior is helping geophysicists explore rock textures within Earth's mantle and crust, map present-day upper-mantle convection, and study the formation of lithospheric plates and the accretion of continents in Earth history.

  3. Seismic lamination and anisotropy of the Lower Continental Crust

    Science.gov (United States)

    Meissner, Rolf; Rabbel, Wolfgang; Kern, Hartmut

    2006-04-01

    Seismic lamination in the lower crust associated with marked anisotropy has been observed at various locations. Three of these locations were investigated by specially designed experiments in the near vertical and in the wide-angle range, that is the Urach and the Black Forrest area, both belonging to the Moldanubian, a collapsed Variscan terrane in southern Germany, and in the Donbas Basin, a rift inside the East European (Ukrainian) craton. In these three cases, a firm relationship between lower crust seismic lamination and anisotropy is found. There are more cases of lower-crustal lamination and anisotropy, e.g. from the Basin and Range province (western US) and from central Tibet, not revealed by seismic wide-angle measurements, but by teleseismic receiver function studies with a P-S conversion at the Moho. Other cases of lamination and anisotropy are from exhumed lower crustal rocks in Calabria (southern Italy), and Val Sesia and Val Strona (Ivrea area, Northern Italy). We demonstrate that rocks in the lower continental crust, apart from differing in composition, differ from the upper mantle both in terms of seismic lamination (observed in the near-vertical range) and in the type of anisotropy. Compared to upper mantle rocks exhibiting mainly orthorhombic symmetry, the symmetry of the rocks constituting the lower crust is either axial or orthorhombic and basically a result of preferred crystallographic orientation of major minerals (biotite, muscovite, hornblende). We argue that the generation of seismic lamination and anisotropy in the lower crust is a consequence of the same tectonic process, that is, ductile deformation in a warm and low-viscosity lower crust. This process takes place preferably in areas of extension. Heterogeneous rock units are formed that are generally felsic in composition, but that contain intercalations of mafic intrusions. The latter have acted as heat sources and provide the necessary seismic impedance contrasts. The observed

  4. 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.

  5. Modified temperature-anisotropy instability thresholds in the solar wind.

    Science.gov (United States)

    Schlickeiser, R; Michno, M J; Ibscher, D; Lazar, M; Skoda, T

    2011-11-11

    The proton and electron temperature anisotropies in the solar wind are constrained by the instability thresholds for temperature-anisotropy-driven kinetic plasma instabilities. The modifications to the marginal instability conditions from accounting for the influence of damping connected with the collisional effects in the solar wind plasma are calculated for right- and left-handed polarized parallel propagating Alfvén waves and mirror and firehose fluctuations. These modifications provide tighter threshold constraints compared to the marginal thresholds but do not fully explain the observations at small values of the parallel plasma beta.

  6. 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.

  7. Measuring the cosmological lepton asymmetry through the CMB anisotropy

    CERN Document Server

    Kinney, W H; Kinney, William H.; Riotto, Antonio

    1999-01-01

    A large lepton asymmetry in the Universe is still a viable possibility and leads to many interesting phenomena such as gauge symmetry nonrestoration at high temperature. We show that a large lepton asymmetry changes the predicted cosmic microwave background (CMB) anisotropy and that any degeneracy in the relic neutrino sea will be measured to a precision of 1% or better when the CMB anisotropy is measured at the accuracy expected to result from the planned satellite missions MAP and Planck. In fact, the current measurements already put an upper limit on the lepton asymmetry of the Universe which is stronger than the one coming from considerations of primordial nucleosynthesis and structure formation.

  8. 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.

  9. 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.

  10. 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.

  11. Magnetic Moment and Anisotropy of Individual Co Atoms on Graphene

    Science.gov (United States)

    Donati, F.; Dubout, Q.; Autès, G.; Patthey, F.; Calleja, F.; Gambardella, P.; Yazyev, O. V.; Brune, H.

    2013-12-01

    We report on the magnetic properties of single Co atoms on graphene on Pt(111). By means of scanning tunneling microscopy spin-excitation spectroscopy, we infer a magnetic anisotropy of K=-8.1meV with out-of-plane hard axis and a magnetic moment of 2.2μB. Co adsorbs on the sixfold graphene hollow site. Upon hydrogen adsorption, three differently hydrogenated species are identified. Their magnetic properties are very different from those of clean Co. Ab initio calculations support our results and reveal that the large magnetic anisotropy stems from strong ligand field effects due to the interaction between Co and graphene orbitals.

  12. 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.

  13. 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...

  14. Endocavity Ultrasound Probe Manipulators.

    Science.gov (United States)

    Stoianovici, Dan; Kim, Chunwoo; Schäfer, Felix; Huang, Chien-Ming; Zuo, Yihe; Petrisor, Doru; Han, Misop

    2013-06-01

    We developed two similar structure manipulators for medical endocavity ultrasound probes with 3 and 4 degrees of freedom (DoF). These robots allow scanning with ultrasound for 3-D imaging and enable robot-assisted image-guided procedures. Both robots use remote center of motion kinematics, characteristic of medical robots. The 4-DoF robot provides unrestricted manipulation of the endocavity probe. With the 3-DoF robot the insertion motion of the probe must be adjusted manually, but the device is simpler and may also be used to manipulate external-body probes. The robots enabled a novel surgical approach of using intraoperative image-based navigation during robot-assisted laparoscopic prostatectomy (RALP), performed with concurrent use of two robotic systems (Tandem, T-RALP). Thus far, a clinical trial for evaluation of safety and feasibility has been performed successfully on 46 patients. This paper describes the architecture and design of the robots, the two prototypes, control features related to safety, preclinical experiments, and the T-RALP procedure.

  15. 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…

  16. Structural and Magnetic Anisotropy in Amorphous Terbium-Iron Thin Films

    Science.gov (United States)

    Hufnagel, Todd Clayton

    1995-01-01

    High density, removable media magnetooptic disk drives have recently begun to make significant gains in the information mass storage market. The media in these disks are amorphous rare-earth/transition-metal (RE-TM) alloys. One vital property of these materials is a large perpendicular magnetic anisotropy; that is, an easy axis of magnetization which is perpendicular to the plane of the film. A variety of theories, sometimes contradictory, have been proposed to account for this surprising presence of an anisotropic property in an amorphous material. Recent research indicates that there is an underlying atomic-scale structural anisotropy which is responsible for the observed magnetic anisotropy. Several different types of structural anisotropy have been proposed to account for the observed magnetic anisotropy, including pair-ordering anisotropy (anisotropic chemical short-range order) and bond orientation anisotropy (an anisotropy in coordination number or distances independent of chemical ordering). We have studied the structural origins of perpendicular magnetic anisotropy in amorphous Tb-Fe thin films by employing high-energy and anomalous dispersion x-ray scattering. The as-deposited films show a clear structural anisotropy, with a preference for Tb-Fe near neighbors to align in the out-of-plane direction. These films also have a large perpendicular magnetic anisotropy. Upon annealing, the magnetic anisotropy energy drops significantly, and we see a corresponding reduction in the structural anisotropy. The radial distribution functions indicate that the number of Tb-Fe near-neighbors increases in the in-plane direction, but does not change in the out-of-plane direction. Therefore, the distribution of Tb-Fe near-neighbors becomes more uniform upon annealing. We propose that the observed reduction in perpendicular magnetic anisotropy energy is a result of this change in structure. Our results support the pair -ordering anisotropy model of the structural anisotropy

  17. Simultaneous Measurement of Elastic and Electrical Anisotropy of Shales under Elevated Pressure: A Preliminary Study

    Science.gov (United States)

    Ou, L.; Niu, Q.; Prasad, M.

    2015-12-01

    Low-porosity shales are generally considered as transverse isotropic (TI) material, both elastically and electrically. We explore the correlation of elastic and electrical anisotropy of shales to mineralogy and organic richness. Both, elastic and electrical anisotropies in rocks are known to be functions of clay and kerogen contents. The elastic anisotropy in clay- and organic-rich shales is related to their laminated and lenticular texture that is enhanced with compaction and diagenesis leading. The correlation of complex resistivity and anisotropy in shales with clay content has theoretically modeled using cation exchange capacity of the clay minerals. Although, it is appear likely that elastic and electrical anisotropy might be controlled by similar petrophyiscal properties, very little research exists that explores the relationship between these two anisotropies and how petrophysical properties might influence them. We present an experimental data of elastic and electrical anisotropy in shales acquired with a new system that allows simultaneous measurements of acoustic velocities and complex resistivities under hydrostatic pressure in three directions: parallel, 45° and perpendicular to any orientation, such as bedding planes. Our results of five shale samples show: Elastic and electrical anisotropy are inversely related to pressure Electrical anisotropy is generally higher than elastic anisotropy Electrical anisotropy is more sensitive to pressure change Complex resistivity anisotropy for in-phase resistivity and phase is highly frequency dependent In future, we plan to measure shale samples with varying clay and organic contents and correlate anisotropy to petrophysical properties.

  18. 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

  19. EDITORIAL: Probing the nanoworld Probing the nanoworld

    Science.gov (United States)

    Miles, Mervyn

    2009-10-01

    In nanotechnology, it is the unique properties arising from nanometre-scale structures that lead not only to their technological importance but also to a better understanding of the underlying science. Over the last twenty years, material properties at the nanoscale have been dominated by the properties of carbon in the form of the C60 molecule, single- and multi-wall carbon nanotubes, nanodiamonds, and recently graphene. During this period, research published in the journal Nanotechnology has revealed the amazing mechanical properties of such materials as well as their remarkable electronic properties with the promise of new devices. Furthermore, nanoparticles, nanotubes, nanorods, and nanowires from metals and dielectrics have been characterized for their electronic, mechanical, optical, chemical and catalytic properties. Scanning probe microscopy (SPM) has become the main characterization technique and atomic force microscopy (AFM) the most frequently used SPM. Over the past twenty years, SPM techniques that were previously experimental in nature have become routine. At the same time, investigations using AFM continue to yield impressive results that demonstrate the great potential of this powerful imaging tool, particularly in close to physiological conditions. In this special issue a collaboration of researchers in Europe report the use of AFM to provide high-resolution topographical images of individual carbon nanotubes immobilized on various biological membranes, including a nuclear membrane for the first time (Lamprecht C et al 2009 Nanotechnology 20 434001). Other SPM developments such as high-speed AFM appear to be making a transition from specialist laboratories to the mainstream, and perhaps the same may be said for non-contact AFM. Looking to the future, characterisation techniques involving SPM and spectroscopy, such as tip-enhanced Raman spectroscopy, could emerge as everyday methods. In all these advanced techniques, routinely available probes will

  20. Residual electric fields of InGaAs/AlAs/AlAsSb (001) coupled double quantum wells structures assessed by photoreflectance anisotropy

    Science.gov (United States)

    González-Fernández, J. V.; Herrera-Jasso, R.; Ulloa-Castillo, N. A.; Ortega-Gallegos, J.; Castro-García, R.; Lastras-Martínez, L. F.; Lastras-Martínez, A.; Balderas-Navarro, R. E.; Mozume, T.; Gozu, S.

    2016-12-01

    We report on photoreflectance anisotropy (PRA) spectroscopy of InGaAs/AlAs/AlAsSb coupled double quantum wells (CDQWs) with extremely thin coupling AlAs barriers grown by molecular beam epitaxy (MBE), with no intentional doping. By probing the in-plane interfacial optical anisotropies (OAs), it is shown that PRA spectroscopy has the ability to detect and distinguish semiconductor layers with quantum dimensions, as the anisotropic photoreflectance (PR) signal stems entirely from buried quantum wells (QWs). In order to account for the experimental PRA spectra, a theoretical model at k = 0, based on a linear electro-optic effect through a piezoelectric shear strain, has been employed to quantify the internal electric fields across the QWs. The dimensionalities of the PR lineshapes were tested by using reciprocal (Fourier) space analysis. Such a complementary test is used in order to correctly employ the PRA model developed here.

  1. Selective-resputtering-induced perpendicular magnetic anisotropy in amorphous TbFe films.

    Science.gov (United States)

    Harris, V G; Pokhil, T

    2001-08-06

    Perpendicular magnetic anisotropy energy in rf magnetron sputtered amorphous TbFe films is measured to increase exponentially with pair-order anisotropy induced by the selective resputtering of surface adatoms during film growth.

  2. The effect of stress and magnetostriction on the anisotropy of CoNi/Pt multilayers

    NARCIS (Netherlands)

    Drent, van W.P.; Bijker, M.D.; Lodder, J.C.

    1996-01-01

    An attempt is made to correlate the effective magnetic anisotropy of sputtered CoNi/Pt multilayers to the average stress in the thin film. It was found that compressive film stress decreases the perpendicular magnetic anisotropy.

  3. 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.

  4. Calibration Fixture For Anemometer Probes

    Science.gov (United States)

    Lewis, Charles R.; Nagel, Robert T.

    1993-01-01

    Fixture facilitates calibration of three-dimensional sideflow thermal anemometer probes. With fixture, probe oriented at number of angles throughout its design range. Readings calibrated as function of orientation in airflow. Calibration repeatable and verifiable.

  5. Large-scale microwave anisotropy from gravitating seeds

    Science.gov (United States)

    Veeraraghavan, Shoba; Stebbins, Albert

    1992-01-01

    Topological defects could have seeded primordial inhomogeneities in cosmological matter. We examine the horizon-scale matter and geometry perturbations generated by such seeds in an expanding homogeneous and isotropic universe. Evolving particle horizons generally lead to perturbations around motionless seeds, even when there are compensating initial underdensities in the matter. We describe the pattern of the resulting large angular scale microwave anisotropy.

  6. 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.

  7. Second order anisotropy contribution in perpendicular magnetic tunnel junctions.

    Science.gov (United States)

    Timopheev, A A; Sousa, R; Chshiev, M; Nguyen, H T; Dieny, B

    2016-06-01

    Hard-axis magnetoresistance loops were measured on perpendicular magnetic tunnel junction pillars of diameter ranging from 50 to 150 nm. By fitting these loops to an analytical model, the effective anisotropy fields in both free and reference layers were derived and their variations in temperature range between 340 K and 5 K were determined. It is found that a second-order anisotropy term of the form -K2cos(4)θ must be added to the conventional uniaxial -K1cos(2)θ term to explain the experimental data. This higher order contribution exists both in the free and reference layers. At T = 300 K, the estimated -K2/K1 ratios are 0.1 and 0.24 for the free and reference layers, respectively. The ratio is more than doubled at low temperatures changing the ground state of the reference layer from "easy-axis" to "easy-cone" regime. The easy-cone regime has clear signatures in the shape of the hard-axis magnetoresistance loops. The existence of this higher order anisotropy was also confirmed by ferromagnetic resonance experiments on FeCoB/MgO sheet films. It is of interfacial nature and is believed to be due to spatial fluctuations at the nanoscale of the first order anisotropy parameter at the FeCoB/MgO interface.

  8. On Anisotropy of Ultra-High Energy Cosmic-Rays

    CERN Document Server

    Kashti, Tamar

    2009-01-01

    We briefly summarize our study on anisotropy of Ultra-High Energy Cosmic-Rays (UHECRs), in which we define a statistics that measures the correlation between UHECRs and Large Scale Structure (LSS). We also comment here on recently published paper by Koers and Tinyakov that compared our statistics to improved KS statistics.

  9. Predicted impacts of proton temperature anisotropy on solar wind turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Klein, K. G., E-mail: kristopher.klein@unh.edu [Space Science Center, University of New Hampshire, Durham, New Hampshire 03824 (United States); Howes, G. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States)

    2015-03-15

    Particle velocity distributions measured in the weakly collisional solar wind are frequently found to be non-Maxwellian, but how these non-Maxwellian distributions impact the physics of plasma turbulence in the solar wind remains unanswered. Using numerical solutions of the linear dispersion relation for a collisionless plasma with a bi-Maxwellian proton velocity distribution, we present a unified framework for the four proton temperature anisotropy instabilities, identifying the associated stable eigenmodes, highlighting the unstable region of wavevector space and presenting the properties of the growing eigenfunctions. Based on physical intuition gained from this framework, we address how the proton temperature anisotropy impacts the nonlinear dynamics of the Alfvénic fluctuations underlying the dominant cascade of energy from large to small scales and how the fluctuations driven by proton temperature anisotropy instabilities interact nonlinearly with each other and with the fluctuations of the large-scale cascade. We find that the nonlinear dynamics of the large-scale cascade is insensitive to the proton temperature anisotropy and that the instability-driven fluctuations are unlikely to cause significant nonlinear evolution of either the instability-driven fluctuations or the turbulent fluctuations of the large-scale cascade.

  10. Predicted impacts of proton temperature anisotropy on solar wind turbulence

    Science.gov (United States)

    Klein, K. G.; Howes, G. G.

    2015-03-01

    Particle velocity distributions measured in the weakly collisional solar wind are frequently found to be non-Maxwellian, but how these non-Maxwellian distributions impact the physics of plasma turbulence in the solar wind remains unanswered. Using numerical solutions of the linear dispersion relation for a collisionless plasma with a bi-Maxwellian proton velocity distribution, we present a unified framework for the four proton temperature anisotropy instabilities, identifying the associated stable eigenmodes, highlighting the unstable region of wavevector space and presenting the properties of the growing eigenfunctions. Based on physical intuition gained from this framework, we address how the proton temperature anisotropy impacts the nonlinear dynamics of the Alfvénic fluctuations underlying the dominant cascade of energy from large to small scales and how the fluctuations driven by proton temperature anisotropy instabilities interact nonlinearly with each other and with the fluctuations of the large-scale cascade. We find that the nonlinear dynamics of the large-scale cascade is insensitive to the proton temperature anisotropy and that the instability-driven fluctuations are unlikely to cause significant nonlinear evolution of either the instability-driven fluctuations or the turbulent fluctuations of the large-scale cascade.

  11. 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.

  12. 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...

  13. 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.

  14. 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/...

  15. Permalloy multilayers to reduce the effects of uniaxial anisotropy

    NARCIS (Netherlands)

    Wieberdink, J.; Eijkel, Kees J.M.

    1989-01-01

    The anisotropic magnetoresistance effect of Permalloy (Ni0.82 Fe0.18) is used in a contactless angle detector. The uniaxial magnetic anisotropy in a Permalloy thin film causes a difference between the direction of magnetization and the magnetic field direction. This leads to a systematic error in th

  16. Magnetocrystalline anisotropy and the magnetocaloric effect in Fe2P

    NARCIS (Netherlands)

    Caron, L.; Hudl, M.; Höglin, V.; Dung, N.H.; Gomez, C.P.; Sahlberg, M.; Brück, E.; Andersson, Y.; Nordblad, P.

    2013-01-01

    Magnetic and magnetocaloric properties of high-purity, giant magnetocaloric polycrystalline and single-crystalline Fe2P are investigated. Fe2P displays a moderate magnetic entropy change, which spans over 70 K and the presence of strong magnetization anisotropy proves this system is not fully itiner

  17. 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.

  18. The anisotropy of multi-TeV cosmic rays

    Science.gov (United States)

    Dingus, Brenda

    2013-02-01

    The arrival directions of cosmic rays will be isotropized by the deflection of these charged particles in the Galactic magnetic fields. For example, a 10 TeV proton in a typical Galactic field of 2 micro Gauss has a gyroradius of only 0.005 parsec (=1000 AU) which is much smaller than the distance to any postulated sources. However, observations of TeV cosmic rays by Milagro, Tibet III, ARGO, and IceCube, show anisotropies on both large and small angular scales. These observations require the detection of large numbers of cosmic rays because the anisotropies are less than a few parts in 1000. The large angular scale anisotropies, such as a dipole, could point to diffusion from a nearby source, but the smaller scale anisotropies of extent ~10 degrees are much more difficult to explain. Possibilities that have been explored in the literature include magnetic funneling of cosmic rays from nearby sources and acceleration by magnetic reconnection in the heliosphere's magnetotail. No matter what the mechanism, these observations provide new information about cosmic ray production, nearby magnetic fields, and how the cosmic rays observed at Earth are affected by their propagation.

  19. Contribution of Long Wavelength Gravitational Waves to the CMB Anisotropy

    CERN Document Server

    White, M

    1992-01-01

    We present an in depth discussion of the production of gravitational waves from an inflationary phase that could have occurred in the early universe, giving derivations for the resulting spectrum and energy density. We also consider the large-scale anisotropy in the cosmic microwave background radiation coming from these waves. Assuming that the observed quadrupole anisotropy comes mostly from gravitational waves (consistent with the predictions of a flat spectrum of scalar density perturbations and the measured dipole anisotropy) we describe in detail how to derive a value for the scale of inflation of $(1.5-5)\\times 10^{16}$GeV, which is at a particularly interesting scale for particle physics. This upper limit corresponds to a 95\\% confidence level upper limit on the scale of inflation assuming only that the quadrupole anisotropy from gravitational waves is not cancelled by another source. Direct detection of gravitational waves produced by inflation near this scale will have to wait for the next generatio...

  20. 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.

  1. Geodynamics of southeastern Tibet from seismic anisotropy and geodesy

    NARCIS (Netherlands)

    Sol, S; Meltzer, A.; Burgmann, R.; Hilst, R.D. van der; King, R.; Chen, Z.; Koons, P.; Lev, E.; Liu, Y.P.; Zeitler, P.K.; Zhang, X.; Zhang, J.; Zurek, B.

    2007-01-01

    Ongoing plate convergence between India and Eurasia provides a natural laboratory for studying the dynamics of continental collision, a first-order process in the evolution of continents, regional climate, and natural hazards. In southeastern Tibet, the fast directions of seismic anisotropy determin

  2. 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...... of the order parameter. Journal of Applied Physics is copyrighted by The American Institute of Physics....

  3. In-plane magnetic anisotropy along the width in amorphous magnetic ribbons

    Energy Technology Data Exchange (ETDEWEB)

    Tejedor, M.; Garcia, J.A.; Carrizo, J.; Elbaile, L. E-mail: elbaile@pinon.ccu.uniovi.es; Santos, J.D.; Mira, J.; Rivas, J

    2004-05-01

    A study about the variation of the in-plane magnetic anisotropy along the width of the ribbon is carried out in Co- and Fe-based amorphous magnetic ribbons. From the measurements of the anisotropy in as-quenched, mechanical polished and annealed samples the origin of the lack of homogeneity of the in-plane magnetic anisotropy in wide amorphous ribbons is determined. In addition a shape magnetic anisotropy that we think is originated by the edge effect was found.

  4. 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.

  5. Introducing the concept of anisotropy at different scales for modeling optical turbulence.

    Science.gov (United States)

    Toselli, Italo

    2014-08-01

    In this paper, the concept of anisotropy at different atmospheric turbulence scales is introduced. A power spectrum and its associated structure function with inner and outer scale effects and anisotropy are also shown. The power spectrum includes an effective anisotropic parameter ζ(eff) to describe anisotropy, which is useful for modeling optical turbulence when a non-Kolmogorov power law and anisotropy along the direction of propagation are present.

  6. Ab initio studies of magnetic anisotropy energy in highly Co-doped ZnO

    Science.gov (United States)

    Łusakowski, A.; Szuszkiewicz, W.

    2017-03-01

    Density functional theory (DFT) calculations of the energy of magnetic anisotropy for diluted magnetic semiconductor (Zn,Co)O were performed using OpenMX package with fully relativistic pseudopotentials. The analysis of the band spin-orbit interaction and the magnetic ion's surrounding on magnetic anisotropy have been provided. As a result, the calculations show that the magnetic anisotropy in (Zn,Co)O solid solution, mainly of the single ion anisotropy type has been caused by Co ions.

  7. Probing properties of cold radiofrequency plasma with polymer probe

    Science.gov (United States)

    Bormashenko, E.; Chaniel, G.; Multanen, V.

    2015-01-01

    The probe intended for the characterization of cold plasma is introduced. The probe allows the estimation of Debye length of cold plasma. The probe is based on the pronounced modification of surface properties (wettability) of polymer films by cold plasmas. The probe was tested with the cold radiofrequency inductive air plasma discharge. The Debye length and the concentration of charge carriers were estimated for various gas pressures. The reported results coincide reasonably with the corresponding values established by other methods. The probe makes possible measurement of characteristics of cold plasmas in closed chambers.

  8. Probing Properties of Cold Radiofrequency Plasma with Polymer Probe

    CERN Document Server

    Bormashenko, Edward; Multanen, Victor

    2014-01-01

    The probe intended for the characterization of cold plasma is introduced. The probe allows estimation of the Debye length of the cold plasma. The probe is based on the pronounced modification of surface properties (wettability) of polymer films by cold plasmas. The probe was tested with the cold radiofrequency inductive air plasma discharge. The Debye length and the concentration of charge carriers were estimated for various gas pressures. The reported results coincide reasonably with the corresponding values established by other methods. The probe makes possible measurement of characteristics of cold plasmas in closed chambers.

  9. Phoenix Conductivity Probe

    Science.gov (United States)

    2008-01-01

    This image taken by the Surface Stereo Imager on Sol 49, or the 49th Martian day of the mission (July 14, 2008), shows thermal and electrical conductivity probe on NASA's Phoenix Mars Lander's Robotic Arm. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is led by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  10. Velocity Anisotropy in Self-gravitating Molecular Clouds. I. Simulation

    Science.gov (United States)

    Otto, Frank; Ji, Weiguang; Li, Hua-bai

    2017-02-01

    The complex interplay between turbulence, magnetic fields, and self-gravity leads to the formation of molecular clouds out of the diffuse interstellar medium (ISM). One avenue of studying this interplay is by analyzing statistical features derived from observations, where the interpretation of these features is greatly facilitated by comparisons with numerical simulations. Here we focus on the statistical anisotropy present in synthetic maps of velocity centroid data, which we derive from three-dimensional magnetohydrodynamic simulations of a turbulent, magnetized, self-gravitating patch of ISM. We study how the orientation and magnitude of the velocity anisotropy correlate with the magnetic field and with the structures generated by gravitational collapse. Motivated by recent observational constraints, our simulations focus on the supersonic (sonic Mach number { M }≈ 2{--}17) but sub- to trans-alfvénic (alfvénic Mach number {{ M }}{{A}}≈ 0.2{--}1.2) turbulence regime, and we consider clouds that are barely to mildly magnetically supercritical (mass-to-flux ratio equal to once or twice the critical value). Additionally we explore the impact of the turbulence driving mechanism (solenoidal or compressive) on the velocity anisotropy. While we confirm previous findings that the velocity anisotropy generally aligns well with the plane-of-sky magnetic field, our inclusion of the effects of self-gravity reveals that in regions of higher column density, the velocity anisotropy may be destroyed or even reoriented to align with the gravitationally formed structures. We provide evidence that this effect is not necessarily due to the increase of {{ M }}{{A}} inside the high-density regions.

  11. Nanoscale thermal probing

    Directory of Open Access Journals (Sweden)

    Yanan Yue

    2012-03-01

    Full Text Available Nanoscale novel devices have raised the demand for nanoscale thermal characterization that is critical for evaluating the device performance and durability. Achieving nanoscale spatial resolution and high accuracy in temperature measurement is very challenging due to the limitation of measurement pathways. In this review, we discuss four methodologies currently developed in nanoscale surface imaging and temperature measurement. To overcome the restriction of the conventional methods, the scanning thermal microscopy technique is widely used. From the perspective of measuring target, the optical feature size method can be applied by using either Raman or fluorescence thermometry. The near-field optical method that measures nanoscale temperature by focusing the optical field to a nano-sized region provides a non-contact and non-destructive way for nanoscale thermal probing. Although the resistance thermometry based on nano-sized thermal sensors is possible for nanoscale thermal probing, significant effort is still needed to reduce the size of the current sensors by using advanced fabrication techniques. At the same time, the development of nanoscale imaging techniques, such as fluorescence imaging, provides a great potential solution to resolve the nanoscale thermal probing problem.

  12. Einstein Inflationary Probe (EIP)

    Science.gov (United States)

    Hinshaw, Gary

    2004-01-01

    I will discuss plans to develop a concept for the Einstein Inflation Probe: a mission to detect gravity waves from inflation via the unique signature they impart to the cosmic microwave background (CMB) polarization. A sensitive CMB polarization satellite may be the only way to probe physics at the grand-unified theory (GUT) scale, exceeding by 12 orders of magnitude the energies studied at the Large Hadron Collider. A detection of gravity waves would represent a remarkable confirmation of the inflationary paradigm and set the energy scale at which inflation occurred when the universe was a fraction of a second old. Even a strong upper limit to the gravity wave amplitude would be significant, ruling out many common models of inflation, and pointing to inflation occurring at much lower energy, if at all. Measuring gravity waves via the CMB polarization will be challenging. We will undertake a comprehensive study to identify the critical scientific requirements for the mission and their derived instrumental performance requirements. At the core of the study will be an assessment of what is scientifically and experimentally optimal within the scope and purpose of the Einstein Inflation Probe.

  13. The magnetic properties of the spin-1 Heisenberg antiferromagnetic chain with single-ion anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Gangsan; Zhu, Rengui, E-mail: rgzhu@mail.ahnu.edu.cn

    2015-02-15

    The magnetic properties of the spin-1 Heisenberg antiferromagnetic chain with exchange anisotropy and single-ion anisotropy are studied by the double-time Green's function method. The determinative equations for the critical temperature, the magnetization, and the zero-field susceptibility are derived analytically. The effects of the anisotropies on the magnetic properties are presented.

  14. The effect of optical anisotropies on building glass façades and its measurement methods

    Directory of Open Access Journals (Sweden)

    M. Illguth

    2015-06-01

    Furthermore a method for the quantitative measurement of anisotropies is proposed and prescribed in detail. This method can assist in the quality assurance process. Measurements are showing that probably the best tempered glass offers slight anisotropies and that under unfavorable conditions these anisotropies can become evident.

  15. Ab initio modelling of magnetic anisotropy in Sr3NiPtO6

    NARCIS (Netherlands)

    Pradipto, A. -M.; Broer, R.; Picozzi, S.

    2016-01-01

    First principles calculations in the framework of Density Functional Theory (DFT) and wavefunction-based correlated methods have been performed to investigate in detail the magnetic anisotropy in Sr3NiPtO6. This material is known for the easy-plane anisotropy with a large anisotropy constant of abou

  16. 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.

  17. Nine New Fluorescent Probes

    Science.gov (United States)

    Lin, Tsung-I.; Jovanovic, Misa V.; Dowben, Robert M.

    1989-06-01

    Absorption and fluorescence spectroscopic studies are reported here for nine new fluorescent probes recently synthesized in our laboratories: four pyrene derivatives with substituents of (i) 1,3-diacetoxy-6,8-dichlorosulfonyl, (ii) 1,3-dihydroxy-6,8-disodiumsulfonate, (iii) 1,3-disodiumsulfonate, and (iv) l-ethoxy-3,6,8-trisodiumsulfonate groups, and five [7-julolidino] coumarin derivatives with substituents of (v) 3-carboxylate-4-methyl, (vi) 3- methylcarboxylate, (vii) 3-acetate-4-methyl, (viii) 3-propionate-4-methyl, and (ix) 3-sulfonate-4-methyl groups. Pyrene compounds i and ii and coumarin compounds v and vi exhibit interesting absorbance and fluorescence properties: their absorption maxima are red shifted compared to the parent compound to the blue-green region, and the band width broadens considerably. All four blue-absorbing dyes fluoresce intensely in the green region, and the two pyrene compounds emit at such long wavelengths without formation of excimers. The fluorescence properties of these compounds are quite environment-sensitive: considerable spectral shifts and fluorescence intensity changes have been observed in the pH range from 3 to 10 and in a wide variety of polar and hydrophobic solvents with vastly different dielectric constants. The high extinction and fluorescence quantum yield of these probes make them ideal fluorescent labeling reagents for proteins, antibodies, nucleic acids, and cellular organelles. The pH and hydrophobicity-dependent fluorescence changes can be utilized as optical pH and/or hydrophobicity indicators for mapping environmental difference in various cellular components in a single cell. Since all nine probes absorb in the UV, but emit at different wavelengths in the visible, these two groups of compounds offer an advantage of utilizing a single monochromatic light source (e.g., a nitrogen laser) to achieve multi-wavelength detection for flow cytometry application. As a first step to explore potential application in

  18. 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

  19. Development of Mackintosh Probe Extractor

    Science.gov (United States)

    Rahman, Noor Khazanah A.; Kaamin, Masiri; Suwandi, Amir Khan; Sahat, Suhaila; Jahaya Kesot, Mohd

    2016-11-01

    Dynamic probing is a continuous soil investigation technique, which is one of the simplest soil penetration test. It basically consist of repeatedly driving a metal tipped probe into the ground using a drop weight of fixed mass and travel. Testing was carried out continuously from ground level to the final penetration depth. Once the soil investigation work done, it is difficult to pull out the probe rod from the ground, due to strong soil structure grip against probe cone and prevent the probe rod out from the ground. Thus, in this case, a tool named Extracting Probe was created to assist in the process of retracting the probe rod from the ground. In addition, Extracting Probe also can reduce the time to extract the probe rod from the ground compare with the conventional method. At the same time, it also can reduce manpower cost because only one worker involve to handle this tool compare with conventional method used two or more workers. From experiment that have been done we found that the time difference between conventional tools and extracting probe is significant, average time difference is 155 minutes. In addition the extracting probe can reduce manpower usage, and also labour cost for operating the tool. With all these advantages makes this tool has the potential to be marketed.

  20. Probe-based data storage

    CERN Document Server

    Koelmans, Wabe W; Abelmann, L

    2015-01-01

    Probe-based data storage attracted many researchers from academia and industry, resulting in unprecendeted high data-density demonstrations. This topical review gives a comprehensive overview of the main contributions that led to the major accomplishments in probe-based data storage. The most investigated technologies are reviewed: topographic, phase-change, magnetic, ferroelectric and atomic and molecular storage. Also, the positioning of probes and recording media, the cantilever arrays and parallel readout of the arrays of cantilevers are discussed. This overview serves two purposes. First, it provides an overview for new researchers entering the field of probe storage, as probe storage seems to be the only way to achieve data storage at atomic densities. Secondly, there is an enormous wealth of invaluable findings that can also be applied to many other fields of nanoscale research such as probe-based nanolithography, 3D nanopatterning, solid-state memory technologies and ultrafast probe microscopy.