1,709 research outputs found
Clinical leadership and prevention in practice: is a needs led preventive approach to the delivery of care to improve quality, outcomes and value in primary dental care practice a realistic concept?
Eigenmodes of Decay and Discrete Fragmentation Processes
Linear rate equations are used to describe the cascading decay of an initial
heavy cluster into fragments. This representation is based upon a triangular
matrix of transition rates. We expand the state vector of mass multiplicities,
which describes the process, into the biorthonormal basis of eigenmodes
provided by the triangular matrix. When the transition rates have a scaling
property in terms of mass ratios at binary fragmentation vertices, we obtain
solvable models with explicit mathematical properties for the eigenmodes. A
suitable continuous limit provides an interpolation between the solvable
models. It gives a general relationship between the decay products and the
elementary transition rates.Comment: 6 pages, plain TEX, 2 figures available from the author
Widespread dysregulation of MiRNAs by MYCN amplification and chromosomal imbalances in neuroblastoma: association of miRNA expression with survival
MiRNAs regulate gene expression at a post-transcriptional level and their dysregulation can play major roles in the pathogenesis of many different forms of cancer, including neuroblastoma, an often fatal paediatric cancer originating from precursor cells of the sympathetic nervous system. We have analyzed a set of neuroblastoma (n = 145) that is broadly representative of the genetic subtypes of this disease for miRNA expression (430 loci by stem-loop RT qPCR) and for DNA copy number alterations (array CGH) to assess miRNA involvement in disease pathogenesis. The tumors were stratified and then randomly split into a training set (n = 96) and a validation set (n = 49) for data analysis. Thirty-seven miRNAs were significantly over-or under-expressed in MYCN amplified tumors relative to MYCN single copy tumors, indicating a potential role for the MYCN transcription factor in either the direct or indirect dysregulation of these loci. In addition, we also determined that there was a highly significant correlation between miRNA expression levels and DNA copy number, indicating a role for large-scale genomic imbalances in the dysregulation of miRNA expression. In order to directly assess whether miRNA expression was predictive of clinical outcome, we used the Random Forest classifier to identify miRNAs that were most significantly associated with poor overall patient survival and developed a 15 miRNA signature that was predictive of overall survival with 72.7% sensitivity and 86.5% specificity in the validation set of tumors. We conclude that there is widespread dysregulation of miRNA expression in neuroblastoma tumors caused by both over-expression of the MYCN transcription factor and by large-scale chromosomal imbalances. MiRNA expression patterns are also predicative of clinical outcome, highlighting the potential for miRNA mediated diagnostics and therapeutics
Dental fluorosis in populations from Chiang Mai, Thailand with different fluoride exposures - Paper 2: The ability of fluorescence imaging to detect differences in fluorosis prevalence and severity for different fluoride intakes from water
BACKGROUND: To assess the ability of fluorescence imaging to detect a dose response relationship between fluorosis severity and different levels of fluoride in water supplies compared to remote photographic scoring in selected populations participating in an observational, epidemiological survey in Chiang Mai, Thailand. METHODS: Subjects were male and female lifetime residents aged 8-13 years. For each child the fluoride content of cooking water samples (CWS) was assessed to create categorical intervals of water fluoride concentration. Fluorescence images were taken of the maxillary central incisors and analyzed for dental fluorosis using two different software techniques. Output metrics for the fluorescence imaging techniques were compared to TF scores from blinded photographic scores obtained from the survey. RESULTS: Data from 553 subjects were available. Both software analysis techniques demonstrated significant correlations with the photographic scores. The metrics for area effected by fluorosis and the overall fluorescence loss had the strongest association with the photographic TF score (Spearman’s rho 0.664 and 0.652 respectively). Both software techniques performed well for comparison of repeat fluorescence images with ICC values of 0.95 and 0.85 respectively. CONCLUSIONS: This study supports the potential use of fluorescence imaging for the objective quantification of dental fluorosis. Fluorescence imaging was able to discriminate between populations with different fluoride exposures on a comparable level to remote photographic scoring with acceptable levels of repeatability
Universal fluctuations in heavy-ion collisions in the Fermi energy domain
We discuss the scaling laws of both the charged fragments multiplicity
fluctuations and the charge of the largest fragment fluctuations for Xe+Sn
collisions in the range of bombarding energies between 25 MeV/A and 50 MeV/A.
We show close to E_{lab}=32 MeV/A the transition in the fluctuation regime of
the charge of the largest fragment which is compatible with the transition from
the ordered to disordered phase of excited nuclear matter. The size (charge) of
the largest fragment is closely related to the order parameter characterizing
this process.Comment: 4 pages, 3 figure
14-19 education reform under New Labour : an exploration of how politics and the economy combine with educational goals to affect policy
The area of 14-19 education and training was a significant priority for the Labour Government of Tony Blair and New Labour. Reforms such as the 14-19 White Paper (Feb 2005) were seen as key to this government’s ‘third term’ agenda. This research has at its heart the desire to identify the true drivers for 14-19 education and training reform, and critically analyse the results against alternative ‘aims’ of education. Much of current policy for this phase of education mentions the economic imperative of providing young people with the skills which both they and businesses need to compete in the global economy. This research intends to question the fact that economic goals appear to be inexorably entwined with this area of education, and analyse if this is an
appropriate philosophy on which to base reform of the 14-19 phase. To achieve this, document analysis was used to identify the drivers for education reform contained within five policy documents in an attempt to understand the goals of New Labour’s 14-
19 education and training reform policy between May 1997 and February 2005. The conclusions which came from this analysis point to a consistency in the 14-19 reform programme of New Labour around the theme of the economy, with much of the content of the reforms focusing on adapting the phase in order to promote economic objectives. It is argued that by accepting economic objectives as a basis for educational reform,
New Labour confused the influence of the economy for an educational aim
Thermal Degradation of Adsorbed Bottle-Brush Macromolecules: Molecular Dynamics Simulation
The scission kinetics of bottle-brush molecules in solution and on an
adhesive substrate is modeled by means of Molecular Dynamics simulation with
Langevin thermostat. Our macromolecules comprise a long flexible polymer
backbone with segments, consisting of breakable bonds, along with two side
chains of length , tethered to each segment of the backbone. In agreement
with recent experiments and theoretical predictions, we find that bond cleavage
is significantly enhanced on a strongly attractive substrate even though the
chemical nature of the bonds remains thereby unchanged.
We find that the mean bond life time decreases upon adsorption by
more than an order of magnitude even for brush molecules with comparatively
short side chains $N=1 \div 4$. The distribution of scission probability along
the bonds of the backbone is found to be rather sensitive regarding the
interplay between length and grafting density of side chains. The life time
declines with growing contour length as ,
and with side chain length as . The probability
distribution of fragment lengths at different times agrees well with
experimental observations. The variation of the mean length of the
fragments with elapsed time confirms the notion of the thermal degradation
process as a first order reaction.Comment: 15 pages, 7 figure
Mass loss rates and the mass evolution of star clusters
We describe the interplay between stellar evolution and dynamical mass loss
of evolving star clusters, based on the principles of stellar evolution and
cluster dynamics and on a grid of N-body simulations of cluster models. The
cluster models have different initial masses, different orbits, including
elliptical ones, and different initial density profiles. We use two sets of
cluster models: initially Roche-lobe filling and Roche-lobe underfilling. We
identify four distinct mass loss effects: (1) mass loss by stellar evolution,
(2) loss of stars induced by stellar evolution and (3) relaxation-driven mass
loss before and (4) after core collapse. Both the evolution-induced loss of
stars and the relaxation-driven mass loss need time to build up. This is
described by a delay-function of a few crossing times for Roche-lobe filling
clusters and a few half mass relaxation times for Roche-lobe underfilling
clusters. The relaxation-driven mass loss can be described by a simple power
law dependence of the mass dM/dt =-M^{1-gamma}/t0, (with M in Msun) where t0
depends on the orbit and environment of the cluster. Gamma is 0.65 for clusters
with a King-parameter W0=5 and 0.80 for more concentrated clusters with W0=7.
For initially Roche-lobe underfilling clusters the dissolution is described by
the same gamma=0.80. The values of the constant t0 are described by simple
formulae that depend on the orbit of the cluster. The mass loss rate increases
by about a factor two at core collapse and the mass dependence of the
relaxation-driven mass loss changes to gamma=0.70 after core collapse. We also
present a simple recipe for predicting the mass evolution of individual star
clusters with various metallicities and in different environments, with an
accuracy of a few percent in most cases. This can be used to predict the mass
evolution of cluster systems.Comment: 25 pages, 17 figures, 4 tables, 2 appendices; accepted for
publication in MNRA
Kinetics of fragmentation-annihilation processes
We investigate the kinetics of systems in which particles of one species
undergo binary fragmentation and pair annihilation. In the latter, nonlinear
process, fragments react at collision to produce an inert species, causing loss
of mass. We analyse these systems in the reaction-limited regime by solving a
continuous model within the mean-field approximation. The rate of
fragmentation, for a particle of mass to break into fragments of masses
and , has the form (), and the annihilation
rate is constant and independent of the masses of the reactants. We find that
the asymptotic regime is characterized by the annihilation of small-mass
clusters. The results are compared with those for a model with linear mass-loss
(i.e.\ with a sink). We also study more complex models, in which the processes
of fragmentation and annihilation are controlled by mutually-reacting
catalysts. Both pair- and linear-annihilation are considered. Depending on the
specific model and initial densities of the catalysts, the time-decay of the
cluster-density can now be very unconventional and even non-universal. The
interplay between the intervening processes and the existence of a scaling
regime are determined by the asymptotic behaviour of the average-mass and of
the mass-density, which may either decay indefinitely or tend to a constant
value. We discuss further developments of this class of models and their
potential applications.Comment: 16 pages(LaTeX), submitted to Phys. Rev.
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