3,287 research outputs found
Domain and droplet sizes in emulsions stabilized by colloidal particles
Particle-stabilized emulsions are commonly used in various industrial
applications. These emulsions can present in different forms, such as Pickering
emulsions or bijels, which can be distinguished by their different topologies
and rheology. We numerically investigate the effect of the volume fraction and
the uniform wettability of the stabilizing spherical particles in mixtures of
two fluids. For this, we use the well-established three-dimensional lattice
Boltzmann method, extended to allow for the added colloidal particles with
non-neutral wetting properties. We obtain data on the domain sizes in the
emulsions by using both structure functions and the Hoshen-Kopelman (HK)
algorithm, and demonstrate that both methods have their own (dis-)advantages.
We confirm an inverse dependence between the concentration of particles and the
average radius of the stabilized droplets. Furthermore, we demonstrate the
effect of particles detaching from interfaces on the emulsion properties and
domain size measurements.Comment: 9 pages, 9 figure
Estimating the expected cost of equity capital using consensus forecasts
In this study, we develop a technique for estimating a firm’s expected cost of equity capital derived from analyst consensus forecasts and stock prices. Building on the work of Gebhardt/Lee/-Swaminathan (2001) and Easton/Taylor/Shroff/Sougiannis (2002), our approach allows daily estimation, using only publicly available information at that date. We then estimate the expected cost of equity capital at the market, industry and individual firm level using historical German data from 1989-2002 and examine firm characteristics which are systematically related to these estimates. Finally, we demonstrate the applicability of the concept in a contemporary case study for DaimlerChrysler and the European automobile industry
Timescales of emulsion formation caused by anisotropic particles
Particle stabilized emulsions have received an enormous interest in the
recent past, but our understanding of the dynamics of emulsion formation is
still limited. For simple spherical particles, the time dependent growth of
fluid domains is dominated by the formation of droplets, particle adsorption
and coalescence of droplets (Ostwald ripening), which eventually can be almost
fully blocked due to the presence of the particles. Ellipsoidal particles are
known to be more efficient stabilizers of fluid interfaces than spherical
particles and their anisotropic shape and the related additional rotational
degrees of freedom have an impact on the dynamics of emulsion formation. In
this paper, we investigate this point by means of simple model systems
consisting of a single ellipsoidal particle or a particle ensemble at a flat
interface as well as a particle ensemble at a spherical interface. By applying
combined multicomponent lattice Boltzmann and molecular dynamics simulations we
demonstrate that the anisotropic shape of ellipsoidal particles causes two
additional timescales to be of relevance in the dynamics of emulsion formation:
a relatively short timescale can be attributed to the adsorption of single
particles and the involved rotation of particles towards the interface. As soon
as the interface is jammed, however, capillary interactions between the
particles cause a local reordering on very long timescales leading to a
continuous change in the interface configuration and increase of interfacial
area. This effect can be utilized to counteract the thermodynamic instability
of particle stabilized emulsions and thus offers the possibility to produce
emulsions with exceptional stability.Comment: 14 pages, 14 figure
Achieving diffraction-limited resolution in soft-X-ray Fourier-transform holography
The spatial resolution of microscopic images acquired via X-ray Fourier-transform holography is limited by the source size of the reference wave and by the numerical aperture of the detector. We analyze the interplay between both influences and show how they are matched in practice. We further identify, how high spatial frequencies translate to imaging artifacts in holographic reconstructions where mainly the reference beam limits the spatial resolution. As a solution, three methods are introduced based on numerical post-processing of the reconstruction. The methods comprise apodization of the hologram, refocusing via wave propagation, and deconvolution using the transfer function of the imaging system. In particular for the latter two, we demonstrate that image details smaller than the source size of the reference beam can be recovered up to the diffraction limit of the hologram. Our findings motivate the intentional application of a large reference-wave source enhancing the image contrast in applications with low photon numbers such as single-shot experiments at free-electron lasers or imaging at laboratory sources.BMBF, 05K10KTB, Verbundprojekt: FSP 301 - FLASH: Nanoskopische Systeme. Teilprojekt 1.1: Universelle Experimentierkammer für Streuexperimente mit kohärenten Femtosekunden-Röntgenpulsen Multi Purpose Coherent Scattering Chamber for FLASH and XFEL 'MPscatt
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