670 research outputs found
Effective capillary interaction of spherical particles at fluid interfaces
We present a detailed analysis of the effective force between two smooth
spherical colloids floating at a fluid interface due to deformations of the
interface. The results hold in general and are applicable independently of the
source of the deformation provided the capillary deformations are small so that
a superposition approximation for the deformations is valid. We conclude that
an effective long--ranged attraction is possible if the net force on the system
does not vanish. Otherwise, the interaction is short--ranged and cannot be
computed reliably based on the superposition approximation. As an application,
we consider the case of like--charged, smooth nanoparticles and
electrostatically induced capillary deformation. The resulting long--ranged
capillary attraction can be easily tuned by a relatively small external
electrostatic field, but it cannot explain recent experimental observations of
attraction if these experimental systems were indeed isolated.Comment: 23 page
Interplay between elastic fields due to gravity and a partial dislocation for a hard-sphere crystal coherently grown under gravity: driving force for defect disappearance
We previously observed that an intrinsic staking fault shrunk through a glide
of a Shockley partial dislocation terminating its lower end in a hard-sphere
crystal under gravity coherently grown in by Monte Carlo simulations
[Mori et al., Molec. Phys. 105, 1377 (2007)]; it was an answer to a one-decade
long standing question why the stacking disorder in colloidal crystals reduced
under gravity [Zhu et al., Nature 387, 883 (1997)]. Here, we present an elastic
energy calculation; in addition to the self-energy of the partial dislocation
[Mori et al., Prog. Theor. Phys. Suppl. 178, 33 (2009)] we calculate the
cross-coupling term between elastic field due to gravity and that due to a
Shockley partial dislocation. The cross term is a increasing function of the
linear dimension R over which the elastic field expands, showing that a driving
force arises for the partial dislocation moving toward the upper boundary of a
grain.Comment: 8pages, 4figures, to be published in Molecular Physic
Manipulation of Optimal Matchings via Predonation of Endowment
In this paper we answer a question posed by Sertel and Sanver (2002) on the manipulability of optimal matching rules in matching problems with endowments. We characterize the classes of consumption rules under which optimal matching rules can be manipulated via predonation of endowment.G. Fiestras-Janeiro received financial support from the Spanish Ministerio de Ciencia y Tecnología and the FEDER through projects PB98-0613-C02-02 and BEC2002-04102-C02-02, and from the Xunta de Galicia through grant PGIDT00PXI20703PN. The work of F. Klijn is partially supported by Research Grant BEC2002-02130 from the Spanish Ministerio de Ciencia y Tecnología and by a Marie Curie Fellowship of the European Community programme “Improving Human Research Potential and the Socioeconomic Knowledge Base” under contract number HPMF-CT-2001-01232. The work of E. Sánchez is supported by project BEC2002-04102-C02-02 from the Spanish Ministerio de Ciencia y Tecnología and the FEDER
Resonance-Induced Effects in Photonic Crystals
For the case of a simple face-centered-cubic photonic crystal of homogeneous
dielectric spheres, we examine to what extent single-sphere Mie resonance
frequencies are related to band gaps and whether the width of a gap can be
enlarged due to nearby resonances. Contrary to some suggestions, no spectacular
effects may be expected. When the dielectric constant of the spheres
is greater than the dielectric constant of the
background medium, then for any filling fraction there exists a critical
above which the lowest lying Mie resonance frequency falls inside
the lowest stop gap in the (111) crystal direction, close to its midgap
frequency. If , the correspondence between Mie
resonances and both the (111) stop gap and a full gap does not follow such a
regular pattern. If the Mie resonance frequency is close to a gap edge, one can
observe a resonance-induced widening of a relative gap width by .Comment: 14 pages, 3 figs., RevTex. For more info look at
http://www.amolf.nl/external/wwwlab/atoms/theory/index.htm
A simple formula for the L-gap width of a face-centered-cubic photonic crystal
The width of the first Bragg's scattering peak in the (111)
direction of a face-centered-cubic lattice of air spheres can be well
approximated by a simple formula which only involves the volume averaged
and over the lattice unit cell, being the
(position dependent) dielectric constant of the medium, and the effective
dielectric constant in the long-wavelength limit approximated
by Maxwell-Garnett's formula. Apparently, our formula describes the asymptotic
behaviour of the absolute gap width for high dielectric contrast
exactly. The standard deviation steadily decreases well below
1% as increases. For example for the sphere filling
fraction and . On the interval , our
formula still approximates the absolute gap width (the relative
gap width ) with a reasonable precision, namely with a standard
deviation 3% (4.2%) for low filling fractions up to 6.5% (8%) for the
close-packed case. Differences between the case of air spheres in a dielectric
and dielectric spheres in air are briefly discussed.Comment: 13 pages, 4 figs., RevTex, two references added. For more info see
http://www.amolf.nl/external/wwwlab/atoms/theory/index.htm
Emission Spectrum of a Dipole in a Semi-infinite Periodic Dielectric Structure: Effect of the Boundary
The emission spectrum of a dipole embedded in a semi-infinite photonic
crystal is calculated. For simplicity we study the case in which the dielectric
function is sinusoidally modulated only along the direction perpendicular to
the boundary surface plane. In addition to oscillations of the emission rate
with the distance of the dipole from the interface we also observed that the
shape of the emission spectrum srongly depends on the \em initial \em phase
of the dielectric modulation. When the direction of light propagation inside
the periodic structure is not normal to the boundary surface plane we observed
aditional singularities in the emission spectrum, which arise due to different
angle-dependence of the Bragg stop-band for and polarizations.Comment: 14 pages, 6 figures, to appear in Phys Rev
Multi-product inventory managmement model with a multiple periodicity
Inventory management is of great interest to various spheres of activity. This theory is a new industry that arose in connection with the need of optimal regulation of reserves. Over the past decades, significant progress has been made in the development of various mathematical models for managing commodity and noncommodity inventories. Despite the fact that this topic is quite popular in the literature, the question of purchasing resources in conditions of their deficit remains topical. The study is devoted to the development of a multi-product inventory management model with a multiple periodicity
Ordered droplet structures at the liquid crystal surface and elastic-capillary colloidal interactions
We demonstrate a variety of ordered patterns, including hexagonal structures
and chains, formed by colloidal particles (droplets) at the free surface of a
nematic liquid crystal (LC). The surface placement introduces a new type of
particle interaction as compared to particles entirely in the LC bulk. Namely,
director deformations caused by the particle lead to distortions of the
interface and thus to capillary attraction. The elastic-capillary coupling is
strong enough to remain relevant even at the micron scale when its
buoyancy-capillary counterpart becomes irrelevant.Comment: 10 pages, 3 figures, to be published in Physical Review Letter
Conservation genomic analysis of domestic and wild pig populations from the Iberian Peninsula
Abstract Background Inbreeding is among the major concerns in management of local livestock populations. The effective population size of these populations tends to be small, which enhances the risk of fitness reduction and extinction. High-density SNP data make it possible to undertake novel approaches in conservation genetics of endangered breeds and wild populations.A total of 97 representative samples of domestic and wild pig populations from the Iberian Peninsula, subjected to different levels of threat with extinction, were genotyped with a 60 K SNP panel. Data analyses based on: (i) allele frequency differences; (ii) linkage disequilibrium and (iii) runs of homozygosity were integrated to study population relationships, inbreeding and demographic history. Results The domestic pigs analyzed belonged to local Spanish and Portuguese breeds: Iberian ─ including the variants Retinto Iberian, Negro Iberian and Manchado de Jabugo ─, Bisaro and Chato Murciano. The population structure and persistence of phase analysis suggested high genetic relations between Iberian variants, with recent crossbreeding of Manchado de Jabugo with other pig populations. Chato Murciano showed a high frequency of long runs of homozygosity indicating recent inbreeding and reflecting the recent bottleneck reported by historical records. The Chato Murciano and the Manchado de Jabugo breeds presented the lowest effective population sizes in accordance with their status of highly inbred breeds. The Iberian wild boar presented a high frequency of short runs of homozygosity indicating past small population size but no signs of recent inbreeding. The Iberian breed showed higher genetic similarities with Iberian wild boar than the other domestic breeds. Conclusions High-density SNP data provided a consistent overview of population structure, demographic history and inbreeding of minority breeds and wild pig populations from the Iberian Peninsula. Despite the very different background of the populations used, we found a good agreement between the different analyses. Our results are also in agreement with historical reports and provide insight in the events that shaped the current genetic variation of pig populations from the Iberian Peninsula. The results exposed will aid to design and implement strategies for the future management of endangered minority pig breeds and wild populations.This project was financially supported by European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013)/ERC grant #ERC-2009-AdG: 249894 (Sel Sweep project).Peer Reviewe
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