1,818 research outputs found
Turnaround Time Between ILLiad’s Odyssey and Ariel Delivery Methods: A Comparison
Interlibrary loan departments are frequently looking for ways to reduce turnaround time. The advent of electronic delivery in the past decade has greatly reduced turnaround time for articles, but recent developments in this arena have the potential to decrease that time even further. The ILLiad ILL management system has an electronic delivery component, Odyssey, with a Trusted Sender setting that allows articles to be sent to patrons without borrowing staff intervention, provided the lending library is designated as a Trusted Sender, or this feature is enabled for all lenders. Using the tracking data created by the ILLiad management system, the turnaround time for two delivery methods, Ariel and Odyssey, was captured for two different academic institutions. With the Trusted Sender setting turned on, Odyssey delivery was faster than Ariel for the institutions studied
Substrate Specificity of Peptide Adsorption: A Model Study
Applying the contact density chain-growth algorithm to lattice
heteropolymers, we identify the conformational transitions of a nongrafted
hydrophobic-polar heteropolymer with 103 residues in the vicinity of a polar, a
hydrophobic, and a uniformly attractive substrate. Introducing only two system
parameters, the numbers of surface contacts and intrinsic hydrophobic contacts,
respectively, we obtain surprisingly complex temperature and solvent dependent,
substrate-specific pseudo-phase diagrams.Comment: 5 pages, 2 figure
Simplicial Quantum Gravity on a Randomly Triangulated Sphere
We study 2D quantum gravity on spherical topologies employing the Regge
calculus approach with the dl/l measure. Instead of the normally used fixed
non-regular triangulation we study random triangulations which are generated by
the standard Voronoi-Delaunay procedure. For each system size we average the
results over four different realizations of the random lattices. We compare
both types of triangulations quantitatively and investigate how the difference
in the expectation value of the squared curvature, , for fixed and random
triangulations depends on the lattice size and the surface area A. We try to
measure the string susceptibility exponents through finite-size scaling
analyses of the expectation value of an added -interaction term, using two
conceptually quite different procedures. The approach, where an ultraviolet
cut-off is held fixed in the scaling limit, is found to be plagued with
inconsistencies, as has already previously been pointed out by us. In a
conceptually different approach, where the area A is held fixed, these problems
are not present. We find the string susceptibility exponent in
rough agreement with theoretical predictions for the sphere, whereas the
estimate for appears to be too negative. However, our results
are hampered by the presence of severe finite-size corrections to scaling,
which lead to systematic uncertainties well above our statistical errors. We
feel that the present methods of estimating the string susceptibilities by
finite-size scaling studies are not accurate enough to serve as testing grounds
to decide about a success or failure of quantum Regge calculus.Comment: LaTex, 29 pages, including 9 figure
Free zero-range processes on networks
A free zero-range process (FRZP) is a simple stochastic process describing
the dynamics of a gas of particles hopping between neighboring nodes of a
network. We discuss three different cases of increasing complexity: (a) FZRP on
a rigid geometry where the network is fixed during the process, (b) FZRP on a
random graph chosen from a given ensemble of networks, (c) FZRP on a dynamical
network whose topology continuously changes during the process in a way which
depends on the current distribution of particles. The case (a) provides a very
simple realization of the phenomenon of condensation which manifests as the
appearance of a condensate of particles on the node with maximal degree. The
case (b) is very interesting since the averaging over typical ensembles of
graphs acts as a kind of homogenization of the system which makes all nodes
identical from the point of view of the FZRP. In the case (c), the distribution
of particles and the dynamics of network are coupled to each other. The
strength of this coupling depends on the ratio of two time scales: for changes
of the topology and of the FZRP. We will discuss a specific example of that
type of interaction and show that it leads to an interesting phase diagram.Comment: 11 pages, 4 figures, to appear in Proceedings of SPIE Symposium
"Fluctuations and Noise 2007", Florence, 20-24 May 200
Balls-in-boxes condensation on networks
We discuss two different regimes of condensate formation in zero-range
processes on networks: on a q-regular network, where the condensate is formed
as a result of a spontaneous symmetry breaking, and on an irregular network,
where the symmetry of the partition function is explicitly broken. In the
latter case we consider a minimal irregularity of the q-regular network
introduced by a single Q-node with degree Q>q. The statics and dynamics of the
condensation depends on the parameter log(Q/q), which controls the exponential
fall-off of the distribution of particles on regular nodes and the typical time
scale for melting of the condensate on the Q-node which increases exponentially
with the system size . This behavior is different than that on a q-regular
network where log(Q/q)=0 and where the condensation results from the
spontaneous symmetry breaking of the partition function, which is invariant
under a permutation of particle occupation numbers on the q-nodes of the
network. In this case the typical time scale for condensate melting is known to
increase typically as a power of the system size.Comment: 7 pages, 3 figures, submitted to the "Chaos" focus issue on
"Optimization in Networks" (scheduled to appear as Volume 17, No. 2, 2007
Cross-correlations in scaling analyses of phase transitions
Thermal or finite-size scaling analyses of importance sampling Monte Carlo
time series in the vicinity of phase transition points often combine different
estimates for the same quantity, such as a critical exponent, with the intent
to reduce statistical fluctuations. We point out that the origin of such
estimates in the same time series results in often pronounced
cross-correlations which are usually ignored even in high-precision studies,
generically leading to significant underestimation of statistical fluctuations.
We suggest to use a simple extension of the conventional analysis taking
correlation effects into account, which leads to improved estimators with often
substantially reduced statistical fluctuations at almost no extra cost in terms
of computation time.Comment: 4 pages, RevTEX4, 3 tables, 1 figur
Monte Carlo study of the evaporation/condensation transition on different Ising lattices
In 2002 Biskup et al. [Europhys. Lett. 60, 21 (2002)] sketched a rigorous
proof for the behavior of the 2D Ising lattice gas, at a finite volume and a
fixed excess \delta M of particles (spins) above the ambient gas density
(spontaneous magnetisation). By identifying a dimensionless parameter \Delta
(\delta M) and a universal constant \Delta_c, they showed in the limit of large
system sizes that for \Delta < \Delta_c the excess is absorbed in the
background (``evaporated'' system), while for \Delta > \Delta_c a droplet of
the dense phase occurs (``condensed'' system).
To check the applicability of the analytical results to much smaller,
practically accessible system sizes, we performed several Monte Carlo
simulations for the 2D Ising model with nearest-neighbour couplings on a square
lattice at fixed magnetisation M. Thereby, we measured the largest minority
droplet, corresponding to the condensed phase, at various system sizes (L=40,
>..., 640). With analytic values for for the spontaneous magnetisation m_0, the
susceptibility \chi and the Wulff interfacial free energy density \tau_W for
the infinite system, we were able to determine \lambda numerically in very good
agreement with the theoretical prediction.
Furthermore, we did simulations for the spin-1/2 Ising model on a triangular
lattice and with next-nearest-neighbour couplings on a square lattice. Again,
finding a very good agreement with the analytic formula, we demonstrate the
universal aspects of the theory with respect to the underlying lattice. For the
case of the next-nearest-neighbour model, where \tau_W is unknown analytically,
we present different methods to obtain it numerically by fitting to the
distribution of the magnetisation density P(m).Comment: 14 pages, 17 figures, 1 tabl
Simplified Transfer Matrix Approach in the Two-Dimensional Ising Model with Various Boundary Conditions
A recent simplified transfer matrix solution of the two-dimensional Ising
model on a square lattice with periodic boundary conditions is generalized to
periodic-antiperiodic, antiperiodic-periodic and antiperiodic-antiperiodic
boundary conditions. It is suggested to employ linear combinations of the
resulting partition functions to investigate finite-size scaling. An exact
relation of such a combination to the partition function corresponding to
Brascamp-Kunz boundary conditions is found.Comment: Phys.Rev.E, to be publishe
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