2,926 research outputs found
The Role of Spin Anisotropy in the Unbinding of Interfaces
We study the ground state of a classical X-Y model with -fold spin
anisotropy in a uniform external field, . An interface is introduced
into the system by a suitable choice of boundary conditions. For large , as
, we prove using an expansion in that the interface unbinds
from the surface through an infinite series of layering transitions. Numerical
work shows that the transitions end in a sequence of critical end points.Comment: 7 pages RevTeX, plus 1 postscript figure available from the authors
OUTP-94-41
Holographic field theory models of dark energy in interaction with dark matter
We discuss two lagrangian interacting dark energy models in the context of
the holographic principle. The potentials of the interacting fields are
constructed. The models are compared with CMB distance information, baryonic
acoustic oscilations, lookback time and the Constitution supernovae sample. For
both models the results are consistent with a non vanishing interaction between
dark sectors - with more than three standard deviations of confidence for one
of them. Moreover, in both cases, the sign of coupling is consistent with dark
energy decaying into dark matter, alleviating the coincidence problem.Comment: arXiv admin note: substantial text overlap with arXiv:0912.399
Development of an automated microscale platform for conjugate vaccine production in E. coli
The current state-of-the-art for the production of glycoconjugate vaccines is a lengthy and complex series of process steps. An exciting alternative is Protein Glycan Coupling Technology (PGCT), where glycoconjugates are produced in vivo 1,2. This offers a significant reduction in the time and cost burden of glycoconjugate production, making this technology much more feasible for providing vaccines in developing countries. Current research seeks to apply this technology for pneumococcal vaccines 2, however much process optimisation must be done before this is achievable. This work seeks to provide an automated screening platform at the microscale, enabling the rapid screening of different process variables at considerably smaller volumes
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Surface spin-flop phases and bulk discommensurations in antiferromagnets
Phase diagrams as a function of anisotropy D and magnetic field H are
obtained for discommensurations and surface states for a model antiferromagnet
in which is parallel to the easy axis. The surface spin-flop phase exists
for all . We show that there is a region where the penetration length of the
surface spin-flop phase diverges. Introducing a discommensuration of even
length then becomes preferable to reconstructing the surface. The results are
used to clarify and correct previous studies in which discommensurations have
been confused with genuine surface spin-flop states.Comment: 4 pages, RevTeX, 2 Postscript figure
Role of Secondary Motifs in Fast Folding Polymers: A Dynamical Variational Principle
A fascinating and open question challenging biochemistry, physics and even
geometry is the presence of highly regular motifs such as alpha-helices in the
folded state of biopolymers and proteins. Stimulating explanations ranging from
chemical propensity to simple geometrical reasoning have been invoked to
rationalize the existence of such secondary structures. We formulate a
dynamical variational principle for selection in conformation space based on
the requirement that the backbone of the native state of biologically viable
polymers be rapidly accessible from the denatured state. The variational
principle is shown to result in the emergence of helical order in compact
structures.Comment: 4 pages, RevTex, 4 eps figure
A complete devil's staircase in the Falicov-Kimball model
We consider the neutral, one-dimensional Falicov-Kimball model at zero
temperature in the limit of a large electron--ion attractive potential, U. By
calculating the general n-ion interaction terms to leading order in 1/U we
argue that the ground-state of the model exhibits the behavior of a complete
devil's staircase.Comment: 6 pages, RevTeX, 3 Postscript figure
Intrafamily and intragenomic conflicts in human warfare
A.J.C.M. is supported by a Ph.D. studentship from the School of Biology, University of St Andrews, and A.G. is supported by a Natural Environment Research Council Independent Research Fellowship (NE/K009524/1).Recent years have seen an explosion of multidisciplinary interest in ancient human warfare. Theory has emphasised a key role for kin-selected cooperation, modulated by sex-specific demography, in explaining intergroup violence. However, conflicts of interest remain a relatively underexplored factor in the evolutionary-ecological study of warfare, with little consideration given to which parties influence the decision to go to war and how their motivation may differ. We develop a mathematical model to investigate the interplay between sex-specific demography and human warfare, showing that: the ecology of warfare drives the evolution of sex-biased dispersal; sex-biased dispersal modulates intrafamily and intragenomic conflicts in relation to warfare; intragenomic conflict drives parent-of-origin-specific patterns of gene expression – i.e. 'genomic imprinting' – in relation to warfare phenotypes; and an ecological perspective of conflicts at the levels of the gene, individual and social group yields novel predictions as to pathologies associated with mutations and epimutations at loci underpinning human violence.Publisher PDFPeer reviewe
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