2,473 research outputs found
Nonlinear preferential rewiring in fixed-size networks as a diffusion process
We present an evolving network model in which the total numbers of nodes and
edges are conserved, but in which edges are continuously rewired according to
nonlinear preferential detachment and reattachment. Assuming power-law kernels
with exponents alpha and beta, the stationary states the degree distributions
evolve towards exhibit a second order phase transition - from relatively
homogeneous to highly heterogeneous (with the emergence of starlike structures)
at alpha = beta. Temporal evolution of the distribution in this critical regime
is shown to follow a nonlinear diffusion equation, arriving at either pure or
mixed power-laws, of exponents -alpha and 1-alpha
Technical note: Lithium isotopes in dolostone as a palaeo-environmental proxy - an experimental approach
Lithium (Li) isotopes in marine carbonates have considerable potential as a proxy to constrain past changes in silicate weathering fluxes and improve our understanding of Earth\u27s climate. To date the majority of Li isotope studies on marine carbonates have focussed on calcium carbonates. The determination of the Li isotope fractionation between dolomite and a dolomitizing fluid would allow us to extend investigations to deep times (i.e. Precambrian) when dolostones were the most abundant marine carbonate archives. Dolostones often contain a significant proportion of detrital silicate material, which dominates the Li budget; thus, pretreatment needs to be designed so that only the isotope composition of the carbonate-associated Li is measured. This study aims to serve two main goals: (1) to determine the Li isotope fractionation between Ca-Mg carbonates and solution, and (2) to develop a method for leaching the carbonate-associated Li out of dolostone while not affecting the Li contained within the detrital portion of the rock. We synthesized Ca-Mg carbonates at high temperatures (150 to 220ââC) and measured the Li isotope composition (ÎŽ7Li) of the precipitated solids and their respective reactive solutions. The relationship of the Li isotope fractionation factor with temperature was obtained ..
Systematic Improvement of Classical Nucleation Theory
We reconsider the applicability of classical nucleation theory (CNT) to the
calculation of the free energy of solid cluster formation in a liquid and its
use to the evaluation of interface free energies from nucleation barriers.
Using two different freezing transitions (hard spheres and NaCl) as test cases,
we first observe that the interface-free-energy estimates based on CNT are
generally in error. As successive refinements of nucleation-barrier theory, we
consider corrections due to a non-sharp solid-liquid interface and to a
non-spherical cluster shape. Extensive calculations for the Ising model show
that corrections due to a non-sharp and thermally fluctuating interface account
for the barrier shape with excellent accuracy. The experimental solid
nucleation rates that are measured in colloids are better accounted for by
these non-CNT terms, whose effect appears to be crucial in the interpretation
of data and in the extraction of the interface tension from them.Comment: 20 pages (text + supplementary material
The Intrinsic Fundamental Group of a Linear Category
We provide an intrinsic definition of the fundamental group of a linear
category over a ring as the automorphism group of the fibre functor on Galois
coverings. If the universal covering exists, we prove that this group is
isomorphic to the Galois group of the universal covering. The grading deduced
from a Galois covering enables us to describe the canonical monomorphism from
its automorphism group to the first Hochschild-Mitchell cohomology vector
space.Comment: Final version, to appear in Algebras and Representation Theor
Excimer Laser-produced Biodegradable Photopolymer Scaffolds Do Not Induce Immune Rejection In Vivo
Following our previous works of in-vitro tests, the biocompatibility of photopolymer scaffolds was tested against immune responses in vivo. Neither relevant immune reactions nor the rejection of implanted scaffolds was detected, being an essential step for in vivo implantation of excimer laser-prepared scaffolds. The scaffolds were fabricated by UV excimer laser photocuring at 308 nm. After two weeks of transplantation neither inflammatory response nor reactive immune activation was detected based on the chemokine and cytokine profile. As a sign of biodegradability of the scaf-folds, we detected macrophage infiltration and phagocytosis of the biopolymer at the site of implan-tation. Our results suggest that poly(propylene fumarate) (PPF): diethyl fumarate (DEF) (7 : 3 w/w) scaffolds have appropriate properties for in vivo applications
Excimer laser-produced biodegradable photopolymer scaffolds do not induce immune rejection in vivo - ResearchGate. Available from: http://www.researchgate.net/publication/268523447_Excimer_laser-produced_biodegradable_photopolymer_scaffolds_do_not_induce_immune_rejection_in_vivo [accessed Aug 17, 2015]
Sequence analysis of 16S rRNA, gyrB and catA genes and DNA-DNA hybridization reveal that Rhodococcus jialingiae is a later synonym of Rhodococcus qingshengii
The results of 16S rRNA, gyrB and catA gene sequence comparisons and reasserted DNAâDNA hybridization unambiguously proved that
Rhodococcus jialingiae
Wang et al. 2010 and
Rhodococcus qingshengii
Xu et al. 2007 represent a single species. On the basis of priority
R. jialingiae
must be considered a later synonym of
R. qingshengii
.</jats:p
Summing Over Inequivalent Maps in the String Theory Interpretation of Two Dimensional QCD
Following some recent work by Gross, we consider the partition function for
QCD on a two dimensional torus and study its stringiness. We present strong
evidence that the free energy corresponds to a sum over branched surfaces with
small handles mapped into the target space. The sum is modded out by all
diffeomorphisms on the world-sheet. This leaves a sum over disconnected classes
of maps. We prove that the free energy gives a consistent result for all smooth
maps of the torus into the torus which cover the target space times, where
is prime, and conjecture that this is true for all coverings. Each class
can also contain integrations over the positions of branch points and small
handles which act as ``moduli'' on the surface. We show that the free energy is
consistent for any number of handles and that the first few leading terms are
consistent with contributions from maps with branch points.Comment: 17 pages, 5 eps figures contained in a uuencoded file, UVA-HET-92-1
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