291 research outputs found
A necklace of Wulff shapes
In a probabilistic model of a film over a disordered substrate, Monte-Carlo
simulations show that the film hangs from peaks of the substrate. The film
profile is well approximated by a necklace of Wulff shapes. Such a necklace can
be obtained as the infimum of a collection of Wulff shapes resting on the
substrate. When the random substrate is given by iid heights with exponential
distribution, we prove estimates on the probability density of the resulting
peaks, at small density
Whole-genome sequencing to explore nosocomial transmission and virulence in neonatal methicillin-susceptible Staphylococcus aureus bacteremia
BACKGROUND: Neonatal Staphylococcus aureus (S. aureus) bacteremia is an important cause of morbidity and mortality. In this study, we examined whether methicillin-susceptible S. aureus (MSSA) transmission and genetic makeup contribute to the occurrence of neonatal S. aureus bacteremia. METHODS: A retrospective, single-centre study was performed. All patients were included who suffered from S. aureus bacteremia in the neonatal intensive care unit (NICU), Erasmus MC-Sophia, Rotterdam, the Netherlands, between January 2011 and November 2017. Whole-genome sequencing (WGS) was used to characterize the S. aureus isolates, as was also done in comparison to reference genomes. Transmission was considered likely in case of genetically indistinguishable S. aureus isolates. RESULTS: Excluding coagulase-negative staphylococci (CoNS), S. aureus was the most common cause of neonatal bacteremia. Twelve percent (n = 112) of all 926 positive blood cultures from neonates grew S. aureus. Based on core genome multilocus sequence typing (cgMLST), 12 clusters of genetically indistinguishable MSSA isolates were found, containing 33 isolates in total (2-4 isolates per cluster). In seven of these clusters, at least two of the identified MSSA isolates were collected within a time period of one month. Six virulence genes were present in 98-100% of all MSSA isolates. In comparison to S. aureus reference genomes, toxin genes encoding staphylococcal enterotoxin A (sea) and toxic shock syndrome toxin 1 (tsst-1) were present more often in the genomes of bacteremia isolates. CONCLUSION: Transmission of MSSA is a contributing factor to the occurrence of S. aureus bacteremia in neonates. Sea and tsst-1 might play a role in neonatal S. aureus bacteremia
Rigorous Probabilistic Analysis of Equilibrium Crystal Shapes
The rigorous microscopic theory of equilibrium crystal shapes has made
enormous progress during the last decade. We review here the main results which
have been obtained, both in two and higher dimensions. In particular, we
describe how the phenomenological Wulff and Winterbottom constructions can be
derived from the microscopic description provided by the equilibrium
statistical mechanics of lattice gases. We focus on the main conceptual issues
and describe the central ideas of the existing approaches.Comment: To appear in the March 2000 special issue of Journal of Mathematical
Physics on Probabilistic Methods in Statistical Physic
Vicinal Surface with Langmuir Adsorption: A Decorated Restricted Solid-on-solid Model
We study the vicinal surface of the restricted solid-on-solid model coupled
with the Langmuir adsorbates which we regard as two-dimensional lattice gas
without lateral interaction. The effect of the vapor pressure of the adsorbates
in the environmental phase is taken into consideration through the chemical
potential. We calculate the surface free energy , the adsorption coverage
, the step tension , and the step stiffness by
the transfer matrix method combined with the density-matrix algorithm. Detailed
step-density-dependence of and is obtained. We draw the roughening
transition curve in the plane of the temperature and the chemical potential of
adsorbates. We find the multi-reentrant roughening transition accompanying the
inverse roughening phenomena. We also find quasi-reentrant behavior in the step
tension.Comment: 7 pages, 12 figures (png format), RevTeX 3.1, submitted to Phys. Rev.
Regularity Properties and Pathologies of Position-Space Renormalization-Group Transformations
We reconsider the conceptual foundations of the renormalization-group (RG)
formalism, and prove some rigorous theorems on the regularity properties and
possible pathologies of the RG map. Regarding regularity, we show that the RG
map, defined on a suitable space of interactions (= formal Hamiltonians), is
always single-valued and Lipschitz continuous on its domain of definition. This
rules out a recently proposed scenario for the RG description of first-order
phase transitions. On the pathological side, we make rigorous some arguments of
Griffiths, Pearce and Israel, and prove in several cases that the renormalized
measure is not a Gibbs measure for any reasonable interaction. This means that
the RG map is ill-defined, and that the conventional RG description of
first-order phase transitions is not universally valid. For decimation or
Kadanoff transformations applied to the Ising model in dimension ,
these pathologies occur in a full neighborhood of the low-temperature part of the first-order
phase-transition surface. For block-averaging transformations applied to the
Ising model in dimension , the pathologies occur at low temperatures
for arbitrary magnetic-field strength. Pathologies may also occur in the
critical region for Ising models in dimension . We discuss in detail
the distinction between Gibbsian and non-Gibbsian measures, and give a rather
complete catalogue of the known examples. Finally, we discuss the heuristic and
numerical evidence on RG pathologies in the light of our rigorous theorems.Comment: 273 pages including 14 figures, Postscript, See also
ftp.scri.fsu.edu:hep-lat/papers/9210/9210032.ps.
European ADPKD Forum multidisciplinary position statement on autosomal dominant polycystic kidney disease care
Autosomal dominant polycystic kidney disease (ADPKD) is a chronic, progressive condition characterised by the development and growth of cysts in the kidneys and other organs and by additional systemic manifestations. Individuals with ADPKD should have access to life-long, multidisciplinary, specialist and patient-centred care involving: 1) A holistic and comprehensive assessment of the manifestations, complications, prognosis and impact of the disease (in physical, psychological and social terms) on the patient and their family; 2) Access to treatment to relieve symptoms, manage complications, preserve kidney function, lower the risk of cardiovascular disease, and maintain quality of life; 3) Information and support to help patients and their families act as fully informed and active partners in care, i.e. to maintain self-management approaches, deal with the impact of the condition, and participate in decision-making regarding healthcare policies, services and research. Building on discussions at an international Roundtable of specialists and patient advocates involved in ADPKD care, this paper sets out 1) The principles for a patient-centred, holistic approach to the organisation and delivery of ADPKD care in practice, with a focus on multi-specialist collaboration and shared-decision making, 2) The rationale and knowledge base for a Route Map for ADPKD care intended to help patients navigate the services available to them and to help stakeholders and decision-makers take practical steps to ensure that all patients with ADPKD can access the comprehensive multi-specialist care to which they are entitled. Further multispecialty collaboration is encouraged to design and implement these services, and to work with patient organisations to promote awareness building, education, and research
Environmental Policy Design and the Fragmentation of International Markets for Innovation
It has long been argued that the implementation of market-based environmental policy instruments such as environmentally-related taxes and tradable permits is likely to lead to greater technological innovation than more direct forms of regulation such as technology-based standards. One of the principle reasons for such an assertion is that they give firms greater flexibility? to identify the optimal means of innovating to meet the given environmental objective. Thus, it can be argued that the benefits of (some) market-based instruments can also be true of well-designed performance standards. While the theoretical case for the use of flexible policy instruments is well-developed, empirical evidence remains limited. Drawing upon a database of patent applications from a cross-section of countries evidence is provided for the positive effect of flexibility? of the domestic environmental policy regime on the propensity for the inventions induced to be diffused widely in the world economy. For a given level of policy stringency, countries with more flexible environmental policies are more likely to generate innovations which are diffused widely and are more likely to benefit from innovations generated elsewhere. And while the focus of this paper is on the specific case of environmental policy, the discussion is equally applicable to aspects of product and labour market regulation which have implications for technological innovation, such as product and workplace safety
Feeder layer- and animal product-free culture of neonatal foreskin keratinocytes: improved performance, usability, quality and safety
Since 1987, keratinocytes have been cultured at the Queen Astrid Military Hospital. These keratinocytes have been used routinely as auto and allografts on more than 1,000 patients, primarily to accelerate the healing of burns and chronic wounds. Initially the method of Rheinwald and Green was used to prepare cultured epithelial autografts, starting from skin samples from burn patients and using animal-derived feeder layers and media containing animal-derived products. More recently we systematically optimised our production system to accommodate scientific advances and legal changes. An important step was the removal of the mouse fibroblast feeder layer from the cell culture system. Thereafter we introduced neonatal foreskin keratinocytes (NFK) as source of cultured epithelial allografts, which significantly increased the consistency and the reliability of our cell production. NFK master and working cell banks were established, which were extensively screened and characterised. An ISO 9001 certified Quality Management System (QMS) governs all aspects of testing, validation and traceability. Finally, as far as possible, animal components were systematically removed from the cell culture environment. Today, quality controlled allograft production batches are routine and, due to efficient cryopreservation, stocks are created for off-the-shelf use. These optimisations have significantly increased the performance, usability, quality and safety of our allografts. This paper describes, in detail, our current cryopreserved allograft production process
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