1,560 research outputs found
Theory of Double-Sided Flux Decorations
A novel two-sided Bitter decoration technique was recently employed by Yao et
al. to study the structure of the magnetic vortex array in high-temperature
superconductors. Here we discuss the analysis of such experiments. We show that
two-sided decorations can be used to infer {\it quantitative} information about
the bulk properties of flux arrays, and discuss how a least squares analysis of
the local density differences can be used to bring the two sides into registry.
Information about the tilt, compressional and shear moduli of bulk vortex
configurations can be extracted from these measurements.Comment: 17 pages, 3 figures not included (to request send email to
[email protected]
Spin Reduction Transition in Spin-3/2 Random Heisenberg Chains
Random spin-3/2 antiferromagnetic Heisenberg chains are investigated using an
asymptotically exact renormalization group. Randomness is found to induce a
quantum phase transition between two random-singlet phases. In the strong
randomness phase the effective spins at low energies are S_eff=3/2, while in
the weak randomness phase the effective spins are S_eff=1/2. Separating them is
a quantum critical point near which there is a non-trivial mixture of S=1/2,
S=1, and S=3/2 effective spins at low temperatures.Comment: 4 pages, 3 figures. Typos correcte
Airy processes and variational problems
We review the Airy processes; their formulation and how they are conjectured
to govern the large time, large distance spatial fluctuations of one
dimensional random growth models. We also describe formulas which express the
probabilities that they lie below a given curve as Fredholm determinants of
certain boundary value operators, and the several applications of these
formulas to variational problems involving Airy processes that arise in
physical problems, as well as to their local behaviour.Comment: Minor corrections. 41 pages, 4 figures. To appear as chapter in "PASI
Proceedings: Topics in percolative and disordered systems
Modelling the influence of RKIP on the ERK signalling pathway using the stochastic process algebra PEPA
This paper examines the influence of the Raf Kinase Inhibitor Protein (RKIP) on the Extracellular signal Regulated Kinase (ERK) signalling pathway [5] through modelling in a Markovian process algebra, PEPA [11]. Two models of the system are presented, a reagent-centric view and a pathway-centric view. The models capture functionality at the level of subpathway, rather than at a molecular level. Each model affords a different perspective of the pathway and analysis. We demonstrate the two models to be formally equivalent using the timing-aware bisimulation defined over PEPA models and discuss the biological significance
Sustainable synthesis of enantiopure fluorolactam derivatives by a selective direct fluorination – amidase strategy
Pharmaceutically important chiral fluorolactam derivatives bearing a fluorine atom at a stereogenic centre were synthesized by a route involving copper catalyzed selective direct fluorination using fluorine gas for the construction of the key C–F bond and a biochemical amidase process for the crucial asymmetric cyclisation stage. A comparison of process green metrics with reported palladium catalyzed enantioselective fluorination methodology shows the fluorination-amidase route to be very efficient and more suitable for scale-up
Test of Replica Theory: Thermodynamics of 2D Model Systems with Quenched Disorder
We study the statistics of thermodynamic quantities in two related systems
with quenched disorder: A (1+1)-dimensional planar lattice of elastic lines in
a random potential and the 2-dimensional random bond dimer model. The first
system is examined by a replica-symmetric Bethe ansatz (RBA) while the latter
is studied numerically by a polynomial algorithm which circumvents slow glassy
dynamics. We establish a mapping of the two models which allows for a detailed
comparison of RBA predictions and simulations. Over a wide range of disorder
strength, the effective lattice stiffness and cumulants of various
thermodynamic quantities in both approaches are found to agree excellently. Our
comparison provides, for the first time, a detailed quantitative confirmation
of the replica approach and renders the planar line lattice a unique testing
ground for concepts in random systems.Comment: 16 pages, 14 figure
Healthy volunteers in US phase I clinical trials: Sociodemographic characteristics and participation over time
Background Increasing the diversity of research participants is an important focus of clinical trials. However, little is known regarding who enrolls as healthy volunteers in Phase I clinical trials, which test the safety and tolerability of investigational new drugs. Despite the risk, healthy volunteers can derive no medical benefit from their participation, and they are financially compensated for enrolling. Objective This study’s purpose is to describe sociodemographic characteristics and clinical trial participation histories of healthy people who enroll in US Phase I trials. Methods The HealthyVOICES Project (HVP) is a longitudinal study of healthy individuals who have enrolled in Phase I trials. We describe self-reported sociodemographic information and Phase I trial history from HVP recruitment (May-December 2013) through the project’s end three years later (December 2016). Trial experiences are presented as medians and quartiles. Results The HVP included 178 participants. Nearly three-fourths of participants were male, and two-thirds were classified as racial and ethnic minorities. We found that some groups of participants were more likely to have completed a greater number of clinical trials over a longer timeframe than others. Those groups included participants who were male, Black, Hispanic, 30-39-years-old, unemployed, had received vocational training in a trade, or had annual household incomes of less than $25,000. Additionally, the greater the number of clinical trials participants had completed, the more likely they were to continue screening for new trials over the course of three years. Participants who pursued clinical trials as a full-time job participated in the greatest number of trials and were the most likely to continuing screening over time. Implications Participation as a healthy volunteer in US Phase I trials is driven by social inequalities. Disadvantaged groups tend to participate in a greater number of clinical trials and participate longer than more privileged groups
High resolution studies of low-energy electron attachment to SF5Cl: Product anions and absolute cross sections
Low energy electron attachment to SFCl was studied at high energy resolution by mass spectrometric detection of the product anions. Two variants of the laser photoelectron attachment (LPA) technique (Kaiserslautern) were used for determining the threshold behaviour of the yield for SF formation at about 1 meV resolution, and to investigate the relative cross sections for Cl, FCl, and SF formation towards higher energies (up to 1 eV) at about 20 meV resolution. Thermal swarm measurements (Birmingham) were used to place the relative LPA cross sections on an absolute scale. A trochoidal electron monochromator (Innsbruck) was used for survey measurements of the relative cross sections for the different product anions over the energy range of 0-14 eV with a resolution of 0.30 eV. Combined with earlier beam data (taken at Berlin, J. Chem. Phys. 88 (1988) 149), the present experimental results provide a detailed set of partial cross sections for anion formation in low-energy electron collisions with SFCl
Tensionless structure of glassy phase
We study a class of homogeneous finite-dimensional Ising models which were
recently shown to exhibit glassy properties. Monte Carlo simulations of a
particular three-dimensional model in this class show that the glassy phase
obtained under slow cooling is dominated by large scale excitations whose
energy scales with their size as with
. Simulations suggest that in another model of this class,
namely the four-spin model, energy is concentrated mainly in linear defects
making also in this case domain walls tensionless. Two-dimensinal variants of
these models are trivial and energy of excitations scales with the exponent
.Comment: 5 page
From Vicious Walkers to TASEP
We propose a model of semi-vicious walkers, which interpolates between the
totally asymmetric simple exclusion process and the vicious walkers model,
having the two as limiting cases. For this model we calculate the asymptotics
of the survival probability for particles and obtain a scaling function,
which describes the transition from one limiting case to another. Then, we use
a fluctuation-dissipation relation allowing us to reinterpret the result as the
particle current generating function in the totally asymmetric simple exclusion
process. Thus we obtain the particle current distribution asymptotically in the
large time limit as the number of particles is fixed. The results apply to the
large deviation scale as well as to the diffusive scale. In the latter we
obtain a new universal distribution, which has a skew non-Gaussian form. For
particles its asymptotic behavior is shown to be
as and
as .Comment: 37 pages, 4 figures, Corrected reference
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