1,494 research outputs found
Building Data-Driven Pathways From Routinely Collected Hospital Data:A Case Study on Prostate Cancer
Background: Routinely collected data in hospitals is complex, typically heterogeneous, and scattered across multiple Hospital Information Systems (HIS). This big data, created as a byproduct of health care activities, has the potential to provide a better understanding of diseases, unearth hidden patterns, and improve services and cost. The extent and uses of such data rely on its quality, which is not consistently checked, nor fully understood. Nevertheless, using routine data for the construction of data-driven clinical pathways, describing processes and trends, is a key topic receiving increasing attention in the literature. Traditional algorithms do not cope well with unstructured processes or data, and do not produce clinically meaningful visualizations. Supporting systems that provide additional information, context, and quality assurance inspection are needed. Objective: The objective of the study is to explore how routine hospital data can be used to develop data-driven pathways that describe the journeys that patients take through care, and their potential uses in biomedical research; it proposes a framework for the construction, quality assessment, and visualization of patient pathways for clinical studies and decision support using a case study on prostate cancer. Methods: Data pertaining to prostate cancer patients were extracted from a large UK hospital from eight different HIS, validated, and complemented with information from the local cancer registry. Data-driven pathways were built for each of the 1904 patients and an expert knowledge base, containing rules on the prostate cancer biomarker, was used to assess the completeness and utility of the pathways for a specific clinical study. Software components were built to provide meaningful visualizations for the constructed pathways. Results: The proposed framework and pathway formalism enable the summarization, visualization, and querying of complex patient-centric clinical information, as well as the computation of quality indicators and dimensions. A novel graphical representation of the pathways allows the synthesis of such information. Conclusions: Clinical pathways built from routinely collected hospital data can unearth information about patients and diseases that may otherwise be unavailable or overlooked in hospitals. Data-driven clinical pathways allow for heterogeneous data (ie, semistructured and unstructured data) to be collated over a unified data model and for data quality dimensions to be assessed. This work has enabled further research on prostate cancer and its biomarkers, and on the development and application of methods to mine, compare, analyze, and visualize pathways constructed from routine data. This is an important development for the reuse of big data in hospitals
Irreversibility in response to forces acting on graphene sheets
The amount of rippling in graphene sheets is related to the interactions with
the substrate or with the suspending structure. Here, we report on an
irreversibility in the response to forces that act on suspended graphene
sheets. This may explain why one always observes a ripple structure on
suspended graphene. We show that a compression-relaxation mechanism produces
static ripples on graphene sheets and determine a peculiar temperature ,
such that for the free-energy of the rippled graphene is smaller than
that of roughened graphene. We also show that depends on the structural
parameters and increases with increasing sample size.Comment: 4 pages, 4 Figure
Solvent-free coarse-grained lipid model for large-scale simulations
A coarse-grained molecular model, which consists of a spherical particle and
an orientation vector, is proposed to simulate lipid membrane on a large length
scale. The solvent is implicitly represented by an effective attractive
interaction between particles. A bilayer structure is formed by
orientation-dependent (tilt and bending) potentials. In this model, the
membrane properties (bending rigidity, line tension of membrane edge, area
compression modulus, lateral diffusion coefficient, and flip-flop rate) can be
varied over broad ranges. The stability of the bilayer membrane is investigated
via droplet-vesicle transition. The rupture of the bilayer and worm-like
micelle formation can be induced by an increase in the spontaneous curvature of
the monolayer membrane.Comment: 13 pages, 19 figure
The lamellar-to-isotropic transition in ternary amphiphilic systems
We study the dependence of the phase behavior of ternary amphiphilic systems
on composition and temperature. Our analysis is based on a curvature elastic
model of the surfactant film with sufficiently large spontaneous curvature and
sufficiently negative saddle-splay modulus that the stable phases are the
lamellar phase and a droplet microemulsion. In addition to the curvature
energy, we consider the contributions to the free energy of the long-ranged van
der Waals interaction and of the undulation modes. We find that for bending
rigidities of order k_B T, the lamellar phase extends further and further into
the water apex of the phase diagram as the phase inversion temperature is
approached, in good agreement with experimental results.Comment: LaTeX2e, 11 pages with references and 2 eps figures included,
submitted to Europhys. Let
The isotropic-nematic interface in suspensions of hard rods: Mean-field properties and capillary waves
We present a study of the isotropic-nematic interface in a system of hard
spherocylinders. First we compare results from Monte Carlo simulations and
Onsager density functional theory for the interfacial profiles of the
orientational order parameter and the density. Those interfacial properties
that are not affected by capillary waves are in good agreement, despite the
fact that Onsager theory overestimates the coexistence densities. Then we show
results of a Monte Carlo study of the capillary waves of the interface. In
agreement with recent theoretical investigations (Eur.Phys.J. E {\bf 18} 407
(2005)) we find a strongly anistropic capillary wave spectrum. For the
wave-numbers accessed in our simulations, the spectrum is quadratic,
i.e.elasticity does not play a role. We conjecture that this effect is due to
the strong bending rigidity of the director field in suspensions of
spherocylinders.Comment: 8 pages, 10 figure
Shape of a liquid front upon dewetting
We examine the profile of a liquid front of a film that is dewetting a solid
substrate. Since volume is conserved, the material that once covered the
substrate is accumulated in a rim close to the three phase contact line.
Theoretically, such a profile of a Newtonian liquid resembles an exponentially
decaying harmonic oscillation that relaxes into the prepared film thickness.
For the first time, we were able to observe this behavior experimentally. A
non-Newtonian liquid - a polymer melt - however, behaves differently. Here,
viscoelastic properties come into play. We will demonstrate that by analyzing
the shape of the rim profile. On a nm scale, we gain access to the rheology of
a non-Newtonian liquid.Comment: 4 pages, 4 figure
Liquid drops on a surface: using density functional theory to calculate the binding potential and drop profiles and comparing with results from mesoscopic modelling
The contribution to the free energy for a film of liquid of thickness on
a solid surface, due to the interactions between the solid-liquid and
liquid-gas interfaces is given by the binding potential, . The precise
form of determines whether or not the liquid wets the surface. Note that
differentiating gives the Derjaguin or disjoining pressure. We develop a
microscopic density functional theory (DFT) based method for calculating
, allowing us to relate the form of to the nature of the molecular
interactions in the system. We present results based on using a simple lattice
gas model, to demonstrate the procedure. In order to describe the static and
dynamic behaviour of non-uniform liquid films and drops on surfaces, a
mesoscopic free energy based on is often used. We calculate such
equilibrium film height profiles and also directly calculate using DFT the
corresponding density profiles for liquid drops on surfaces. Comparing
quantities such as the contact angle and also the shape of the drops, we find
good agreement between the two methods. We also study in detail the effect on
of truncating the range of the dispersion forces, both those between the
fluid molecules and those between the fluid and wall. We find that truncating
can have a significant effect on and the associated wetting behaviour of
the fluid.Comment: 16 pages, 13 fig
Zero-range processes with saturated condensation: the steady state and dynamics
We study a class of zero-range processes in which the real-space condensation
phenomenon does not occur and is replaced by a saturated condensation: that is,
an extensive number of finite-size "condensates" in the steady state. We
determine the conditions under which this occurs, and investigate the dynamics
of relaxation to the steady state. We identify two stages: a rapid initial
growth of condensates followed by a slow process of activated evaporation and
condensation. We analyze these nonequilibrium dynamics with a combination of
meanfield approximations, first-passage time calculations and a
fluctuation-dissipation type approach.Comment: 21 pages, 12 figure
Universal reduction of pressure between charged surfaces by long-wavelength surface charge modulation
We predict theoretically that long-wavelength surface charge modulations
universally reduce the pressure between the charged surfaces with counterions
compared with the case of uniformly charged surfaces with the same average
surface charge density. The physical origin of this effect is the fact that
surface charge modulations always lead to enhanced counterion localization near
the surfaces, and hence, fewer charges at the midplane. We confirm the last
prediction with Monte Carlo simulations.Comment: 8 pages 1 figure, Europhys. Lett., in pres
Capillary Waves in a Colloid-Polymer Interface
The structure and the statistical fluctuations of interfaces between
coexisting phases in the Asakura-Oosawa (AO) model for a colloid--polymer
mixture are analyzed by extensive Monte Carlo simulations. We make use of a
recently developed grand canonical cluster move with an additional constraint
stabilizing the existence of two interfaces in the (rectangular) box that is
simulated. Choosing very large systems, of size LxLxD with L=60 and D=120,
measured in units of the colloid radius, the spectrum of capillary wave-type
interfacial excitations is analyzed in detail. The local position of the
interface is defined in terms of a (local) Gibbs surface concept. For small
wavevectors capillary wave theory is verified quantitatively, while for larger
wavevectors pronounced deviations show up. For wavevectors that correspond to
the typical distance between colloids in the colloid-rich phase, the
interfacial fluctuations exhibit the same structure as observed in the bulk
structure factor. When one analyzes the data in terms of the concept of a
wavevector-dependent interfacial tension, a monotonous decrease of this
quantity with increasing wavevector is found. Limitations of our analysis are
critically discussed.Comment: 12 pages, 15 figure
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