337 research outputs found
Replica Symmetry Breaking in Attractor Neural Network Models
The phenomenon of replica symmetry breaking is investigated for the retrieval
phases of Hopfield-type network models. The basic calculation is done for the
generalized version of the standard model introduced by Horner [1] and by
Perez-Vicente and Amit [2] which can exhibit low mean levels of neural
activity. For a mean activity the Hopfield model is recovered. In
this case, surprisingly enough, we cannot confirm the well known one step
replica symmetry breaking (1RSB) result for the storage capacity which was
presented by Crisanti, Amit and Gutfreund [3] (\alpha_c^{\hbox{\mf
1RSB}}\simeq 0.144). Rather, we find that 1RSB- and 2RSB-Ans\"atze yield only
slightly increased capacities as compared to the replica symmetric value
(\alpha_c^{\hbox{\mf 1RSB}}\simeq 0.138\,186 and \alpha_c^{\hbox{\mf
2RSB}}\simeq 0.138\,187 compared to \alpha_c^{\hbox{\mf RS}}\simeq
0.137\,905), significantly smaller also than the value \alpha_c^{\hbox{\mf
sim}} = 0.145\pm 0.009 reported from simulation studies. These values still
lie within the recently discovered reentrant phase [4]. We conjecture that in
the infinite Parisi-scheme the reentrant behaviour disappears as is the case in
the SK-spin-glass model (Parisi--Toulouse-hypothesis). The same qualitative
results are obtained in the low activity range.Comment: Latex file, 20 pages, 8 Figures available from the authors upon
request, HD-TVP-94-
Dental anomalies in craniofacial microsomia: A systematic review
Objective: To provide an overview on the prevalence and types of dental anomalies in patients with craniofacial microsomia (CFM). Eligibility criteria: Inclusion criteria were CFM and dental anomalies. The following data were extracted: number of patients, methodology, mean age, sex, affected side, severity of mandibular hypoplasia, dentition stage and dental
Ocular and adnexal anomalies in craniofacial microsomia: a systematic review
Ocular anomalies may occur in craniofacial microsomia (CFM). The aim of this systematic review was to review the literature on ocular anomalies and their incidence, in order to estimate the need for ophthalmological screening in CFM patients. Online databases were searched, and data on the number of patients, type and incidence of ocular anomalies, and visual acuity were extracted. Four subgroups of ocular and adnexal anomalies were identified, to provide an overview of the different anomalies. Twenty-five papers analysing 1419 patients in total were included. Ocular anomalies were documented in 6.7–100% of patients. The most reported type I ocular anomalies were eyelid coloboma, lipodermoids, and orbital dystopia. The most reported type II ocular anomalies were epibulbar dermoid, microphthalmia, and anophthalmia. Ptosis
Partnership or insanity: why do health partnerships do the same thing over and over again and expect a different result?
Objectives
The paper reports on an empirical study of Health and Wellbeing Boards (HWBs) in England. Established by the Health and Social Care Act 2012, HWBs act as place-based hubs for leaders in health, social care, local government and other sectors to come together to address health improvement and the wider determinants of health.
Methods
We conducted a three-year study of HWBs (2015–2017) in five localities across England. This involved collecting qualitative data from semi-structured interviews with key actors in the HWBs at strategic and operational levels, and focus group sessions with voluntary-sector participants at each HWB.
Results
HWBs have largely followed the path of previous partnerships in terms of a lack of clear aims and objectives, lack of ownership and accountability by partners, and an absence of any significant impact on health outcomes.
Conclusions
Many of the features of unsuccessful partnership working were largely displayed by HWBs. Boards require more executive power and ownership from the bottom up if they are to have any real impact
Dental anomalies in craniofacial microsomia: A systematic review
Objective: To provide an overview on the prevalence and types of dental anomalies in
patients with craniofacial microsomia (CFM). Eligibility criteria: Inclusion criteria were
CFM and dental anomalies. The following data were extracted: number of patients,
methodology, mean age, sex, affected side, severity of mandibular hypoplasia, dentition stage and dental anomalies. Information sources: Cochrane, EMBASE, PubMed,
MEDLINE Ovid, Web of Science, CINAHL EBSCOhost and Google Scholar, searched
until the 30 August 2019. Risk of bias: The quality was examined with the OCEBM
Levels of Evidence. Included studies: In total, 13 papers were included: four retrospective cohort studies, four prospective cohort studies, four case-control studies
and one case series. Synthesis of results: The studies reported information on dental
agenesis, delayed dental development, tooth size anomalies, tooth morphology and
other dental anomalies. Description of the effect: Dental anomalies are more often
diagnosed in patients with CFM than in healthy controls and occur more often on
the affected than on the non-affected side. Strengths and limitations of evidence:
This is the first systematic review study on dental anomalies in CFM. However, most
articles were of low quality. Interpretation: Dental anomalies are common in CFM,
which might be linked to the development of CFM. The pathophysiology of CFM is
not entirely clear, and further research is needed
High-Energy Aspects of Solar Flares: Overview of the Volume
In this introductory chapter, we provide a brief summary of the successes and
remaining challenges in understanding the solar flare phenomenon and its
attendant implications for particle acceleration mechanisms in astrophysical
plasmas. We also provide a brief overview of the contents of the other chapters
in this volume, with particular reference to the well-observed flare of 2002
July 23Comment: This is the introductory article for a monograph on the physics of
solar flares, inspired by RHESSI observations. The individual articles are to
appear in Space Science Reviews (2011
Recent Advances in Understanding Particle Acceleration Processes in Solar Flares
We review basic theoretical concepts in particle acceleration, with
particular emphasis on processes likely to occur in regions of magnetic
reconnection. Several new developments are discussed, including detailed
studies of reconnection in three-dimensional magnetic field configurations
(e.g., current sheets, collapsing traps, separatrix regions) and stochastic
acceleration in a turbulent environment. Fluid, test-particle, and
particle-in-cell approaches are used and results compared. While these studies
show considerable promise in accounting for the various observational
manifestations of solar flares, they are limited by a number of factors, mostly
relating to available computational power. Not the least of these issues is the
need to explicitly incorporate the electrodynamic feedback of the accelerated
particles themselves on the environment in which they are accelerated. A brief
prognosis for future advancement is offered.Comment: This is a chapter in a monograph on the physics of solar flares,
inspired by RHESSI observations. The individual articles are to appear in
Space Science Reviews (2011
Acceleration of Relativistic Protons during the 20 January 2005 Flare and CME
The origin of relativistic solar protons during large flare/CME events has
not been uniquely identified so far.We perform a detailed comparative analysis
of the time profiles of relativistic protons detected by the worldwide network
of neutron monitors at Earth with electromagnetic signatures of particle
acceleration in the solar corona during the large particle event of 20 January
2005. The intensity-time profile of the relativistic protons derived from the
neutron monitor data indicates two successive peaks. We show that microwave,
hard X-ray and gamma-ray emissions display several episodes of particle
acceleration within the impulsive flare phase. The first relativistic protons
detected at Earth are accelerated together with relativistic electrons and with
protons that produce pion decay gamma-rays during the second episode. The
second peak in the relativistic proton profile at Earth is accompanied by new
signatures of particle acceleration in the corona within approximatively 1
solar radius above the photosphere, revealed by hard X-ray and microwave
emissions of low intensity, and by the renewed radio emission of electron beams
and of a coronal shock wave. We discuss the observations in terms of different
scenarios of particle acceleration in the corona.Comment: 22 pages, 5 figure
Shrinking a large dataset to identify variables associated with increased risk of Plasmodium falciparum infection in Western Kenya
Large datasets are often not amenable to analysis using traditional single-step approaches. Here, our general objective was to apply imputation techniques, principal component analysis (PCA), elastic net and generalized linear models to a large dataset in a systematic approach to extract the most meaningful predictors for a health outcome. We extracted predictors for Plasmodium falciparum infection, from a large covariate dataset while facing limited numbers of observations, using data from the People, Animals, and their Zoonoses (PAZ) project to demonstrate these techniques: data collected from 415 homesteads in western Kenya, contained over 1500 variables that describe the health, environment, and social factors of the humans, livestock, and the homesteads in which they reside. The wide, sparse dataset was simplified to 42 predictors of P. falciparum malaria infection and wealth rankings were produced for all homesteads. The 42 predictors make biological sense and are supported by previous studies. This systematic data-mining approach we used would make many large datasets more manageable and informative for decision-making processes and health policy prioritization
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