Reconstructing the linear power spectrum of cosmological mass fluctuations

We describe an attempt to reconstruct the initial conditions for the formation of cosmological large-scale structure. The power spectrum of the primordial fluctuations is affected by bias, nonlinear evolution and redshift-space distortions, but we show how these effects can be corrected for analytically. Using eight independent datasets, we obtain excellent agreement in the estimated linear power spectra given the following conditions. First, the relative bias factors for Abell clusters, radio galaxies, optical galaxies and IRAS galaxies must be in the ratios 4.5:1.9:1.3:1. Second, the data require redshift-space distortion: \Omega^{0.6}/b_{\ss I} = 1.0 \pm 0.2. Third, low values of $\Omega$ and bias are disfavoured. The shape of the spectrum is extremely well described by a CDM transfer function with an apparent value of the fitting parameter $\Omega h =0.25$. Tilted models predict too little power at 100 Mpc wavelengths.Comment: Edinburgh Astronomy Preprint 26/93. Accepted for publication in Monthly Notices of the RAS. 13 pages of LaTeX, plus 10 PostScript figures. You will need the mn.sty style file (from babbage: get mn.sty). The figure .ps files are in the usual self-unpacking unix scrip

Measurements of orbit-lattice coupling of Er and Dy impurities in Ag and Al hosts

The magnetic resonance of dilute Dy and Er impurities has been observed in thin polycrystalline Al and Ag films on two different substrates. The films are deposited at room temperature, and the measurements are made at liquid-helium temperatures. During cooling, the difference in thermal contraction between film and substrate produces an effectively uniaxial strain in the film. This results in an anisotropic g value, which we have used to obtain lower limits on the orbit-lattice coupling coefficient for these systems. We find values for V ( Γ 3g, 2 ) from 600 to 2000 cm − 1 , somewhat smaller than observed in insulators, but of the same order of magnitude. Measurements on substrates with different thermal contractions indicate that all of the expected strain is present in these films, contrary to previous measurements on Ag: Er films grown on NaCl surfaces

Geometry of River Networks II: Distributions of Component Size and Number

The structure of a river network may be seen as a discrete set of nested sub-networks built out of individual stream segments. These network components are assigned an integral stream order via a hierarchical and discrete ordering method. Exponential relationships, known as Horton's laws, between stream order and ensemble-averaged quantities pertaining to network components are observed. We extend these observations to incorporate fluctuations and all higher moments by developing functional relationships between distributions. The relationships determined are drawn from a combination of theoretical analysis, analysis of real river networks including the Mississippi, Amazon and Nile, and numerical simulations on a model of directed, random networks. Underlying distributions of stream segment lengths are identified as exponential. Combinations of these distributions form single-humped distributions with exponential tails, the sums of which are in turn shown to give power law distributions of stream lengths. Distributions of basin area and stream segment frequency are also addressed. The calculations identify a single length-scale as a measure of size fluctuations in network components. This article is the second in a series of three addressing the geometry of river networks.Comment: 16 pages, 13 figures, 4 tables, Revtex4, submitted to PR

The development of reputational capital–How social media influencers differ from traditional celebrities

Social media influencers (SMI) have grown in importance as a promotional channel. However, little is known about how they build reputational capital and thus endorsement effectiveness, particularly compared to traditional celebrity endorsers. From a consumers' perspective, this research investigates both types of endorsers in different stages of the Celebrity Capital Life Cycle (CCLC). Across three studies, we find that parasocial relationships and interactions with consumers are paramount for SMIs reputational capital and endorsement effectiveness, yet not critical for traditional celebrities. Further, a consumer's perceived weak parasocial relationship/interaction with SMIs can be detrimental to their effectiveness yet has little impact on traditional celebrities' influence. We find that the positive effect of a SMI with high parasocial relationship/interaction with consumers on Word of Mouth (i.e., endorsers effectiveness) is mediated by expectation fulfillment and brand endorsers' credibility (i.e., reputation capital). This research discovers how important parasocial relationships with consumers are for SMIs in comparison to traditional celebrities; importantly this is the first research that empirically identifies how SMIs can gain and maintain reputation capital and subsequently be more effective as brand endorsers. Our findings have important implications for marketing professionals who are managing SMIs.fals

Nonlinear evolution of cosmological power spectra

Hamilton et al. have suggested an invaluable scaling formula which describes how the power spectra of density fluctuations evolve into the nonlinear regime of hierarchical clustering. This paper presents an extension of their method to low-density universes and universes with nonzero cosmological constant. We pay particular attention to models with large negative spectral indices, and give a spectrum-dependent fitting formula which is of significantly improved accuracy by comparison with an earlier version of this work. The tendency of nonlinear effects to increase power on small scales is stronger for spectra with more negative spectral indices, and for lower densities. However, for low-density models with a cosmological constant, the nonlinear effects are less strong than for an open universe of the same $\Omega$.Comment: MNRAS in press. 8 pages TeX including Postscript figures. Uses mn.tex and epsf.te

Dry Particle High-Impact Coating of Biopowders: Coating Strength

4th RELPOWFLO Symposium 2008, Tromso, NORWAY, JUN 10-12, 2008International audienceThe aim of this study is to develop a fundamental knowledge on dry coating, to understand the coating strength of different bio-couples with a theoretical and experimental approach and how the dry coating is affected by the size of host particle and choice of dry particle coating equipment. For this purpose, we examine the feasibility of dry coating of two different particle size distributions of Cellets particles with talc using a Nara Hybridizer NHS-0, a 1L Cyclomix, and a Turbula blender. Special care is required to choose suitable operating conditions in order to achieve surface modification without breakage phenomena. An experimental methodology based on a commercial granulometer is used to study the coating strength of the composites and allows us to study the influence of particle size. The conclusion is that the smaller the guest-to-host size ratio, the stronger the coating. This result is in agreement with the estimation of particle adhesion with the help of a van der Waals approach. The influence of the coating equipment is also studied. The Hybridizer leads with the chosen operating conditions to the stronger coating

Dry particle high coating of biopowders: An energy approach

Symposium on Science and Technology of Powders and Sintered Materials (STPMF 2009), Montpellier, FRANCE, MAY 25-27, 2009International audienceThe general aim of this paper is to study the coating strength of different composite powders with an experimental approach based on mixing energy descriptors derived from linear velocity at the end of paddles. The chosen system is Cellets particles coated with Talc particles, with two size ratios: 7 and 22. The studied processes are Nara Hybridizer NHS-0, 1 litre Hosokawa Cyclomix, Turbula mixer and finally ``Basic Mixing''. The developed energy analysis leads to quantitative comparison of the equipment and helps to show the specific dry coating improvement in term of coating strength compared to the simple ordered mixing phenomenon. According to the chosen energy descriptors, in accordance with the litterature, the Hybridizer is the higher energy system and leads with the chosen operating conditions to the stronger coating. If we compare the other processes, the increase of mixing energy always leads to an increase of coating strength as soon as breakage is avoided. This can be possible by choosing the adapted operating parameters in each system

ESR and spin-lattice relaxation of Nd3+ in a metallic host: LaRh2

We report the first ESR observation of Nd3+ in a metal: cubic LaRh2. The resonance arises from a Γ6 ground state and exhibits hyperfine splitting at low temperature, allowing for positive identification. Above about 12 K, the ESR linewidth increases exponentially with temperature. We attribute this increase to the resonance phonon relaxation process involving the first excited state at 125±10 K