26,036 research outputs found
Behavioral Communities and the Atomic Structure of Networks
We develop a theory of `behavioral communities' and the `atomic structure' of
networks. We define atoms to be groups of agents whose behaviors always match
each other in a set of coordination games played on the network. This provides
a microfoundation for a method of detecting communities in social and economic
networks. We provide theoretical results characterizing such behavior-based
communities and atomic structures and discussing their properties in large
random networks. We also provide an algorithm for identifying behavioral
communities. We discuss applications including: a method of estimating
underlying preferences by observing behavioral conventions in data, and
optimally seeding diffusion processes when there are peer interactions and
homophily. We illustrate the techniques with applications to high school
friendship networks and rural village networks
Size-dependence of Strong-Coupling Between Nanomagnets and Photonic Cavities
The coherent dynamics of a coupled photonic cavity and a nanomagnet is
explored as a function of nanomagnet size. For sufficiently strong coupling
eigenstates involving highly entangled photon and spin states are found, which
can be combined to create coherent states. As the size of the nanomagnet
increases its coupling to the photonic mode also monotonically increases, as
well as the number of photon and spin states involved in the system's
eigenstates. For small nanomagnets the crystalline anisotropy of the magnet
strongly localized the eigenstates in photon and spin number, quenching the
potential for coherent states. For a sufficiently large nanomagnet the
macrospin approximation breaks down and different domains of the nanomagnet may
couple separately to the photonic mode. Thus the optimal nanomagnet size is
just below the threshold for failure of the macrospin approximation.Comment: 10 pages, 7 figure
ULAS J234311.93-005034.0: A gravitational lens system selected from UKIDSS and SDSS
We report the discovery of a new gravitational lens system. This object, ULAS
J234311.93-005034.0, is the first to be selected by using the new UKIRT
Infrared Deep Sky Survey (UKIDSS), together with the Sloan Digital Sky Survey
(SDSS). The ULAS J234311.93-005034.0 system contains a quasar at redshift 0.788
which is doubly imaged, with separation 1.4". The two quasar images have the
same redshift and similar, though not identical, spectra. The lensing galaxy is
detected by subtracting point-spread functions from R-band images taken with
the Keck telescope. The lensing galaxy can also be detected by subtracting the
spectra of the A and B images, since more of the galaxy light is likely to be
present in the latter. No redshift is determined from the galaxy, although the
shape of its spectrum suggests a redshift of about 0.3. The object's lens
status is secure, due to the identification of two objects with the same
redshift together with a lensing galaxy. Our imaging suggests that the lens is
found in a cluster environment, in which candidate arc-like structures, that
require confirmation, are visible in the vicinity. Further discoveries of
lenses from the UKIDSS survey are likely as part of this programme, due to the
depth of UKIDSS and its generally good seeing conditions.Comment: Accepted by MNRA
SAFT-γ force field for the simulation of molecular fluids: 4. A single-site coarse-grained model of water applicable over a wide temperature range
In this work, we develop coarse-grained (CG) force fields for water, where the effective CG intermolecular interactions between particles are estimated from an accurate description of the macroscopic experimental vapour-liquid equilibria data by means of a molecular-based equation of state. The statistical associating fluid theory for Mie (generalised Lennard-Jones) potentials of variable range (SAFT-VR Mie) is used to parameterise spherically symmetrical (isotropic) force fields for water. The resulting SAFT-γ CG models are based on the Mie (8-6) form with size and energy parameters that are temperature dependent; the latter dependence is a consequence of the angle averaging of the directional polar interactions present in water. At the simplest level of CG where a water molecule is represented as a single bead, it is well known that an isotropic potential cannot be used to accurately reproduce all of the thermodynamic properties of water simultaneously. In order to address this deficiency, we propose two CG potential models of water based on a faithful description of different target properties over a wide range of temperatures: our CGW1-vle model is parameterised to match the saturated-liquid density and vapour pressure; our other CGW1-ift model is parameterised to match the saturated-liquid density and vapour-liquid interfacial tension. A higher level of CG corresponding to two water molecules per CG bead is also considered: the corresponding CGW2-bio model is developed to reproduce the saturated-liquid density and vapour-liquid interfacial tension in the physiological temperature range, and is particularly suitable for the large-scale simulation of bio-molecular systems. A critical comparison of the phase equilibrium and transport properties of the proposed force fields is made with the more traditional atomistic models
Systematic study of Pt-Ru/C catalysts prepared by chemical deposition for direct methanol fuel cells
In this research, the activity and stability for methanol electro-oxidation on Pt-Ru/C catalysts was increased by optimising the catalyst preparation method. The Pt-Ru/C catalysts were synthesised using Pt(acac)2 and Ru(acac)3 precursors for chemical deposition of the metals. Performance of the catalyst was examined by cyclic voltammetry and chronoamperometry in a methanol-containing electrolyte. TEM, EDS, X-ray photoelectron spectroscopy and XRD were used to physically characterise the catalysts. The parameters investigated were precursor decomposition phase, synthesis temperature and Pt/Ru ratio. Precursor deposition from the liquid phase was more active for methanol electro-oxidation, predominantly due to particle size and degree of alloying achieved during this precursor decomposition phase. Synthesis temperature affected the particle size, active surface area, ruthenium oxidation state and degree of alloying which in turn affected catalyst stability and activity for methanol electro-oxidation. The Pt/Ru ratio greatly affects the performance of the catalyst. The catalyst with the highest activity for methanol electro-oxidation was the catalyst synthesised at 350 °C with a Pt/Ru ratio of 50:50
Addition theorems for spin spherical harmonics. II Results
Based on the results of part I, we obtain the general form of the addition
theorem for spin spherical harmonics and give explicit results in the cases
involving one spin- and one spin- spherical harmonics with ,
1, 3/2, and , 1. We obtain also a fully general addition theorem for
one scalar and one tensor spherical harmonic of arbitrary rank. A variety of
bilocal sums of ordinary and spin spherical harmonics are given in explicit
form, including a general explicit expression for bilocal spherical harmonics
Rotating Bose-Einstein condensates: Closing the gap between exact and mean-field solutions
When a Bose-Einstein condensed cloud of atoms is given some angular momentum,
it forms vortices arranged in structures with a discrete rotational symmetry.
For these vortex states, the Hilbert space of the exact solution separates into
a "primary" space related to the mean-field Gross-Pitaevskii solution and a
"complementary" space including the corrections beyond mean-field. Considering
a weakly-interacting Bose-Einstein condensate of harmonically-trapped atoms, we
demonstrate how this separation can be used to close the conceptual gap between
exact solutions for systems with only a few atoms and the thermodynamic limit
for which the mean-field is the correct leading-order approximation. Although
we illustrate this approach for the case of weak interactions, it is expected
to be more generally valid.Comment: 8 pages, 5 figure
Microscopic Conductivity of Lattice Fermions at Equilibrium - Part I: Non-Interacting Particles
We consider free lattice fermions subjected to a static bounded potential and
a time- and space-dependent electric field. For any bounded convex region
() of space, electric fields
within drive currents. At leading order, uniformly
with respect to the volume of and
the particular choice of the static potential, the dependency on
of the current is linear and described by a conductivity distribution. Because
of the positivity of the heat production, the real part of its Fourier
transform is a positive measure, named here (microscopic) conductivity measure
of , in accordance with Ohm's law in Fourier space. This finite
measure is the Fourier transform of a time-correlation function of current
fluctuations, i.e., the conductivity distribution satisfies Green-Kubo
relations. We additionally show that this measure can also be seen as the
boundary value of the Laplace-Fourier transform of a so-called quantum current
viscosity. The real and imaginary parts of conductivity distributions satisfy
Kramers-Kronig relations. At leading order, uniformly with respect to
parameters, the heat production is the classical work performed by electric
fields on the system in presence of currents. The conductivity measure is
uniformly bounded with respect to parameters of the system and it is never the
trivial measure . Therefore, electric fields generally
produce heat in such systems. In fact, the conductivity measure defines a
quadratic form in the space of Schwartz functions, the Legendre-Fenchel
transform of which describes the resistivity of the system. This leads to
Joule's law, i.e., the heat produced by currents is proportional to the
resistivity and the square of currents
The role of emotional intelligence and personality in moral reasoning
In this study we investigated the potential role of Emotional Intelligence (EI) in Moral Reasoning (MR). A sample of 131undergraduate students completed a battery of psychological tests, which included measures of Emotional Intelligence, Moral Reasoning and the Big Five dimensions of personality. Results demonstrated support for a proposed model of the relationship between Emotional Intelligence, personality and Moral Reasoning. Specifically, Emotional Intelligence was found to be a significant predictor of four of the Big Five personality dimensions (Extraversion, Openness, Neuroticism, Agreeableness), which in turn were significant predictors of Moral Reasoning. These results have important implications in regards to our current understanding of the relationships between Emotional Intelligence, Moral Reasoning and personality. We emphasize the need to incorporate the constructs of Emotional Intelligence and Moral Reasoning into a broader, explanatory personality framework.
ISBN: 978192151366
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