422 research outputs found
Reference materials for phase equilibrium studies. 1. Liquid–liquid equilibria (IUPAC Technical Report)
This article is the first of three projected IUPAC Technical Reports resulting from IUPAC Project 2011-037-2-100 (Reference Materials for Phase Equilibrium Studies). The goal of this project is to select reference systems with critically evaluated property values for the validation of instruments and techniques used in phase equilibrium studies of mixtures. This report proposes seven systems for liquid–liquid equilibrium studies, covering the four most common categories of binary mixtures: aqueous systems of moderate solubility, non-aqueous systems, systems with low solubility, and systems with ionic liquids. For each system, the available literature sources, accepted data, smoothing equations, and estimated uncertainties are given
Current reversal with type-I intermittency in deterministic inertia ratchets
The intermittency is investigated when the current reversal occurs in a
deterministic inertia ratchet system. To determine which type the intermittency
belongs to, we obtain the return map of velocities of particle using
stroboscopic recording, and numerically calculate the distribution of average
laminar length . The distribution follows the scaling law of , the characteristic relation of type-I
intermittency.Comment: 4 pages, 7 figure
Food and Nutrition Extension Programs: Next Generation Impact Evaluation
Grassroots stakeholder input results in relevant and timely Extension programs, but presents a challenge for performance measurement using common indicators. A balanced approach to program evaluation and reporting that is adequately valid and reliable while honoring the Extension culture of service is most likely to be successful. This article reviews recent advances in evaluation methodology of food and nutrition programs. It further describes how this evidence base informs the current set of national Extension program outcomes and indicators. Evaluation work is an essential step in documenting the public value of Extension programs
Dynamic Vortex Phases and Pinning in Superconductors with Twin Boundaries
We investigate the pinning and driven dynamics of vortices interacting with
twin boundaries using large scale molecular dynamics simulations on samples
with near one million pinning sites. For low applied driving forces, the vortex
lattice orients itself parallel to the twin boundary and we observe the
creation of a flux gradient and vortex free region near the edges of the twin
boundary. For increasing drive, we find evidence for several distinct dynamical
flow phases which we characterize by the density of defects in the vortex
lattice, the microscopic vortex flow patterns, and orientation of the vortex
lattice. We show that these different dynamical phases can be directly related
to microscopically measurable voltage - current V(I) curves and voltage noise.
By conducting a series of simulations for various twin boundary parameters we
derive several vortex dynamic phase diagrams.Comment: 5 figures, to appear in Phys. Rev.
Adaptive Mesh Refinement for Characteristic Grids
I consider techniques for Berger-Oliger adaptive mesh refinement (AMR) when
numerically solving partial differential equations with wave-like solutions,
using characteristic (double-null) grids. Such AMR algorithms are naturally
recursive, and the best-known past Berger-Oliger characteristic AMR algorithm,
that of Pretorius & Lehner (J. Comp. Phys. 198 (2004), 10), recurses on
individual "diamond" characteristic grid cells. This leads to the use of
fine-grained memory management, with individual grid cells kept in
2-dimensional linked lists at each refinement level. This complicates the
implementation and adds overhead in both space and time.
Here I describe a Berger-Oliger characteristic AMR algorithm which instead
recurses on null \emph{slices}. This algorithm is very similar to the usual
Cauchy Berger-Oliger algorithm, and uses relatively coarse-grained memory
management, allowing entire null slices to be stored in contiguous arrays in
memory. The algorithm is very efficient in both space and time.
I describe discretizations yielding both 2nd and 4th order global accuracy.
My code implementing the algorithm described here is included in the electronic
supplementary materials accompanying this paper, and is freely available to
other researchers under the terms of the GNU general public license.Comment: 37 pages, 15 figures (40 eps figure files, 8 of them color; all are
viewable ok in black-and-white), 1 mpeg movie, uses Springer-Verlag svjour3
document class, includes C++ source code. Changes from v1: revised in
response to referee comments: many references added, new figure added to
better explain the algorithm, other small changes, C++ code updated to latest
versio
Modeling DNA Structure, Elasticity and Deformations at the Base-pair Level
We present a generic model for DNA at the base-pair level. We use a variant
of the Gay-Berne potential to represent the stacking energy between neighboring
base-pairs. The sugar-phosphate backbones are taken into account by semi-rigid
harmonic springs with a non-zero spring length. The competition of these two
interactions and the introduction of a simple geometrical constraint leads to a
stacked right-handed B-DNA-like conformation. The mapping of the presented
model to the Marko-Siggia and the Stack-of-Plates model enables us to optimize
the free model parameters so as to reproduce the experimentally known
observables such as persistence lengths, mean and mean squared base-pair step
parameters. For the optimized model parameters we measured the critical force
where the transition from B- to S-DNA occurs to be approximately . We
observe an overstretched S-DNA conformation with highly inclined bases that
partially preserves the stacking of successive base-pairs.Comment: 15 pages, 25 figures. submitted to PR
A Conflict Model for Strategists and Managers
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67210/2/10.1177_000276427201500604.pd
Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV
We report a measurement of the longitudinal double-spin asymmetry A_LL and
the differential cross section for inclusive Pi0 production at midrapidity in
polarized proton collisions at sqrt(s) = 200 GeV. The cross section was
measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be
in good agreement with a next-to-leading order perturbative QCD calculation.
The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T <
11 GeV/c and excludes a maximal positive gluon polarization in the proton. The
mean transverse momentum fraction of Pi0's in their parent jets was found to be
around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC
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