168 research outputs found
Phase behavior of weakly polydisperse sticky hard spheres: Perturbation theory for the Percus-Yevick solution
We study the effects of size polydispersity on the gas-liquid phase behaviour
of mixtures of sticky hard spheres. To achieve this, the system of coupled
quadratic equations for the contact values of the partial cavity functions of
the Percus-Yevick solution is solved within a perturbation expansion in the
polydispersity, i.e. the normalized width of the size distribution. This allows
us to make predictions for various thermodynamic quantities which can be tested
against numerical simulations and experiments. In particular, we determine the
leading-order effects of size polydispersity on the cloud curve delimiting the
region of two-phase coexistence and on the associated shadow curve; we also
study the extent of size fractionation between the coexisting phases. Different
choices for the size-dependence of the adhesion strengths are examined
carefully; the Asakura-Oosawa model of a mixture of polydisperse colloids and
small polymers is studied as a specific example.Comment: 43 pages, 12 figures, and 1 tabl
Exact results at the 2-D percolation point
We derive exact expressions for the excess number of clusters b and the
excess cumulants b_n of a related quantity at the 2-D percolation point.
High-accuracy computer simulations are in accord with our predictions. b is a
finite-size correction to the Temperley-Lieb or Baxter-Temperley-Ashley formula
for the number of clusters per site n_c in the infinite system limit; the bn
correct bulk cumulants. b and b_n are universal, and thus depend only on the
system's shape. Higher-order corrections show no apparent dependence on
fractional powers of the system size.Comment: 12 pages, 2 figures, LaTeX, submitted to Physical Review Letter
Perturbed Defects and T-Systems in Conformal Field Theory
Defect lines in conformal field theory can be perturbed by chiral defect
fields. If the unperturbed defects satisfy su(2)-type fusion rules, the
operators associated to the perturbed defects are shown to obey functional
relations known from the study of integrable models as T-systems. The procedure
is illustrated for Virasoro minimal models and for Liouville theory.Comment: 24 pages, 13 figures; v2: typos corrected, in particular in (2.10)
and app. A.2, version to appear in J.Phys.
Universality of the excess number of clusters and the crossing probability function in three-dimensional percolation
Extensive Monte-Carlo simulations were performed to evaluate the excess
number of clusters and the crossing probability function for three-dimensional
percolation on the simple cubic (s.c.), face-centered cubic (f.c.c.), and
body-centered cubic (b.c.c.) lattices. Systems L x L x L' with L' >> L were
studied for both bond (s.c., f.c.c., b.c.c.) and site (f.c.c.) percolation. The
excess number of clusters per unit length was confirmed to be a
universal quantity with a value . Likewise, the
critical crossing probability in the L' direction, with periodic boundary
conditions in the L x L plane, was found to follow a universal exponential
decay as a function of r = L'/L for large r. Simulations were also carried out
to find new precise values of the critical thresholds for site percolation on
the f.c.c. and b.c.c. lattices, yielding , .Comment: 14 pages, 7 figures, LaTeX, submitted to J. Phys. A: Math. Gen, added
references, corrected typo
Theoretical studies of the historical development of the accounting discipline: a review and evidence
Many existing studies of the development of accounting thought have either been atheoretical or have adopted Kuhn's model of scientific growth. The limitations of this 35-year-old model are discussed. Four different general neo-Kuhnian models of scholarly knowledge development are reviewed and compared with reference to an analytical matrix. The models are found to be mutually consistent, with each focusing on a different aspect of development. A composite model is proposed. Based on a hand-crafted database, author co-citation analysis is used to map empirically the entire literature structure of the accounting discipline during two consecutive time periods, 1972â81 and 1982â90. The changing structure of the accounting literature is interpreted using the proposed composite model of scholarly knowledge development
Critical phenomena in complex networks
The combination of the compactness of networks, featuring small diameters,
and their complex architectures results in a variety of critical effects
dramatically different from those in cooperative systems on lattices. In the
last few years, researchers have made important steps toward understanding the
qualitatively new critical phenomena in complex networks. We review the
results, concepts, and methods of this rapidly developing field. Here we mostly
consider two closely related classes of these critical phenomena, namely
structural phase transitions in the network architectures and transitions in
cooperative models on networks as substrates. We also discuss systems where a
network and interacting agents on it influence each other. We overview a wide
range of critical phenomena in equilibrium and growing networks including the
birth of the giant connected component, percolation, k-core percolation,
phenomena near epidemic thresholds, condensation transitions, critical
phenomena in spin models placed on networks, synchronization, and
self-organized criticality effects in interacting systems on networks. We also
discuss strong finite size effects in these systems and highlight open problems
and perspectives.Comment: Review article, 79 pages, 43 figures, 1 table, 508 references,
extende
Weaned age variation in the Virunga mountain gorillas (Gorilla beringei beringei)
The final publication is available at Springer via http://dx.doi.org/10.1007/s00265-016-2066-6Weaning marks an important milestone during life history in mammals indicating nutritional independence from the mother. Age at weaning is a key measure of maternal investment and care, affecting female reproductive rates, offspring survival and ultimately the viability of a population. Factors explaining weaned age variation in the endangered mountain gorilla are not yet well understood. This study investigated the impact of group size, group type (one-male versus multi-male), offspring sex, as well as maternal age, rank, and parity on weaned age variation in the Virunga mountain gorilla population. The status of nutritional independence was established in 69 offspring using long-term suckling observations. A Cox-regression with mixed effects was applied to model weaned age and its relationship with covariates. Findings indicate that offspring in one-male groups are more likely to be weaned earlier than offspring in multi-male groups, which may reflect a female reproductive strategy to reduce higher risk of infanticide in one-male groups. Inferior milk production capacity and conflicting resource allocation between their own and offspring growth may explain later weaning in primiparous mothers compared to multiparous mothers. Sex-biased weaned age related to maternal condition defined by parity, rank, and maternal age will be discussed in the light of the Trivers-Willard hypothesis. Long-term demographic records revealed no disadvantage of early weaning for mother or offspring. Population growth and two peaks in weaned age within the Virunga population encourage future studies on the potential impact of bamboo shoots as a weaning food and other environmental factors on weaning
The RUDY study platform â a novel approach to patient driven research in rare musculoskeletal diseases
Background: Research into rare diseases is becoming more common, with recognition of the significant diagnostic and therapeutic care gaps. Registries are considered a key research methodology to address rare diseases. This report describes the structure of the Rare UK Diseases Study (RUDY) platform that aims to improve research processes and address many of the challenges of carrying out rare musculoskeletal disease research.
RUDY is an internet-based platform with online registration, initial verbal consent, online capture of patient reported outcome measures and events within a dynamic consent framework. The database structure, security and governance framework are described.
Results: There have been 380 participants recruited into RUDY with completed questionnaire rates in excess of 50 %. There has been one withdrawal and two participants have amended their consent options.
Conclusions: The strengths of RUDY include low burden for the clinical team, low research administration costs with high participant recruitment and ease of data collection and access. This platform has the potential to be used as the model for other rare diseases globally
Identification of modifiable factors associated with owner-reported equine laminitis in Britain using a web-based cohort study approach
Equine laminitis is a complex disease that manifests as pain and lameness in the feet, often with debilitating consequences. There is a paucity of data that accounts for the multifactorial nature of laminitis and considers time-varying covariates that may be associated with disease development; particularly those that are modifiable and present potential interventions. A previous case-control study identified a number of novel, modifiable factors associated with laminitis which warranted further investigation and corroboration. The aim of this study was to identify factors associated with equine laminitis in horses/ponies in Great Britain (GB) using a prospective, web-based cohort study design, with particular interest in evaluating modifiable factors previously identified in the case-control study
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