3,493 research outputs found
Preferential attachment of communities: the same principle, but a higher level
The graph of communities is a network emerging above the level of individual
nodes in the hierarchical organisation of a complex system. In this graph the
nodes correspond to communities (highly interconnected subgraphs, also called
modules or clusters), and the links refer to members shared by two communities.
Our analysis indicates that the development of this modular structure is driven
by preferential attachment, in complete analogy with the growth of the
underlying network of nodes. We study how the links between communities are
born in a growing co-authorship network, and introduce a simple model for the
dynamics of overlapping communities.Comment: 7 pages, 3 figure
The Genetic and Environmental Sources of Resemblance Between Normative Personality and Personality Disorder Traits
Recent work has suggested a high level of congruence between normative personality, most typically represented by the big five factors, and abnormal personality traits. In 2,293 Norwegian adult twins ascertained from a population-based registry, the authors evaluated the degree of sharing of genetic and environmental influences on normative personality, assessed by the Big Five Inventory (BFI), and personality disorder traits (PDTs), assessed by the Personality Inventory for DSM-S-Norwegian Brief Form (PID-5NBF). For four of the five BFI dimensions, the strongest genetic correlation was observed with the expected PID-5-NBF dimension (e.g., neuroticism with negative affectivity [+], conscientiousness with disinhibition [-]). However, neuroticism, conscientiousness, and agreeableness had substantial genetic correlations with other PID-S-NBF dimensions (e.g., neuroticism with compulsivity [+], agreeableness with detachment [-]). Openness had no substantial genetic correlations with any PID-5-NBF dimension. The proportion of genetic risk factors shared in aggregate between the BFI traits and the PID-5-NBF dimensions was quite high for conscientiousness and neuroticism, relatively robust for extraversion and agreeableness, but quite low for openness. Of the six PID-S-NBF dimensions, three (negative affectivity, detachment, and disinhibition) shared, in aggregate, most of their genetic risk factors with normative personality traits. Genetic factors underlying psychoticism, antagonism, and compulsivity were shared to a lesser extent, suggesting that they are influenced by etiological factors not well indexed by the BFI
A direct D-bar reconstruction algorithm for recovering a complex conductivity in 2-D
A direct reconstruction algorithm for complex conductivities in
, where is a bounded, simply connected Lipschitz
domain in , is presented. The framework is based on the
uniqueness proof by Francini [Inverse Problems 20 2000], but equations relating
the Dirichlet-to-Neumann to the scattering transform and the exponentially
growing solutions are not present in that work, and are derived here. The
algorithm constitutes the first D-bar method for the reconstruction of
conductivities and permittivities in two dimensions. Reconstructions of
numerically simulated chest phantoms with discontinuities at the organ
boundaries are included.Comment: This is an author-created, un-copyedited version of an article
accepted for publication in [insert name of journal]. IOP Publishing Ltd is
not responsible for any errors or omissions in this version of the manuscript
or any version derived from it. The Version of Record is available online at
10.1088/0266-5611/28/9/09500
Diamagnetic Susceptibility and Current Distributions in Granular Superconductors at Percolation
Comments: 4 pages RevTeX, 4 Postscript figures. References added. We study a
two-dimensional granular superconducting network at the percolation threshold
under the influence of an external perpendicular magnetic field. By numerical
simulations on the full nonlinear problem, we determine the scaling exponent
for the magnetic susceptibility. Further, we report on the scaling properties
of the current distribution. The scaling of the current is found to be
independent of the value of the magnetic field. Our results are in
contradiction with previous numerical results based on linearized equations. We
find a value for the susceptibility exponent which does not agree with existing
theoretical suggestions, but agrees perfectly with renormalization group
calculations
The pre-WDVV ring of physics and its topology
We show how a simplicial complex arising from the WDVV
(Witten-Dijkgraaf-Verlinde-Verlinde) equations of string theory is the
Whitehouse complex. Using discrete Morse theory, we give an elementary proof
that the Whitehouse complex is homotopy equivalent to a wedge of
spheres of dimension . We also verify the Cohen-Macaulay
property. Additionally, recurrences are given for the face enumeration of the
complex and the Hilbert series of the associated pre-WDVV ring.Comment: 13 pages, 4 figures, 2 table
Neutron Resonance Spectroscopy of 106Pd, and 108Pd from 20–2000 eV
Parity nonconserving asymmetries have been measured in p-wave resonances of 106Pd and 108Pd. The data analysis requires knowledge of the neutron resonance parameters. Transmission and capture γ-ray yields were measured for En=20–2000 eV with the time-of-flight method at the Los Alamos Neutron Science Center (LANSCE). A total of 28 resonances in 106Pd and 32 resonances in 108Pd were studied. The resonance parameters for 106Pd are new for all except one resonance. In 108Pd six new resonances were observed and the precision improved for many of the resonance parameters. A Bayesian analysis was used to assign orbital angular momentum for the resonances studied
Parity Nonconservation in 106Pd and 108Pd Neutron Resonances
Parity nonconservation (PNC) has been studied in the neutron p-wave resonances of 106Pd and 108Pd in the energy range of 20 to 2000 eV. Longitudinal asymmetries in p-wave capture cross sections are measured using longitudinally polarized neutrons incident on ∼20-g metal-powder targets at LANSCE. A CsI γ-ray detector array measures capture cross section asymmetries as a function of neutron energy which is determined by the neutron time-of-flight method. A total of 21 p-wave resonances in 106Pd and 21 p-wave resonances in 108Pd were studied. One statistically significant PNC effect was observed in106Pd, and no effects were observed in 108Pd. For 106Pd a weak spreading width of Γw=34-28+47×10-7 eV was obtained. For 108Pd an upper limit on the weak spreading width of Γw\u3c12×10-7 eV was determined at the 68% confidence level
Parity Violation in Neutron Resonances in 107,109Ag
Parity nonconservation (PNC) was studied in p-wave resonances in Ag by measuring the helicity dependence of the neutron total cross section. Transmission measurements on natural Ag were performed in the energy range 32 to 422 eV with the time-of-flight method at the Manuel Lujan Neutron Scattering Center at Los Alamos National Laboratory. A total of 15 p-wave neutron resonances were studied in 107Ag and ninep-wave resonances in 109Ag. Statistically significant asymmetries were observed for eight resonances in 107Ag and for four resonances in109Ag. An analysis treating the PNC matrix elements as random variables yields a weak spreading width of Γw=(2.67-1.21+2.65)×10-7 eV for107Ag and Γw=(1.30-0.74+2.49)×10-7 eV for 109Ag
Quantum Drag Forces on a Sphere Moving Through a Rarefied Gas
As an application of quantum fluid mechanics, we consider the drag force
exerted on a sphere by an ultra-dilute gas. Quantum mechanical diffraction
scattering theory enters in that regime wherein the mean free path of a
molecule in the gas is large compared with the sphere radius. The drag force is
computed in a model specified by the ``sticking fraction'' of events in which a
gaseous molecule is adsorbed by the spherical surface. Classical inelastic
scattering theory is shown to be inadequate for physically reasonable sticking
fraction values. The quantum mechanical scattering drag force is exhibited
theoretically and compared with experimental data.Comment: 5 pages no figure
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