26,818 research outputs found
On the beneficial role of noise in resistive switching
We study the effect of external noise on resistive switching. Experimental
results on a manganite sample are presented showing that there is an optimal
noise amplitude that maximizes the contrast between high and low resistive
states. By means of numerical simulations, we study the causes underlying the
observed behavior. We find that experimental results can be related to general
characteristics of the equations governing the system dynamics.Comment: 4 pages, 5 figure
On the admissibility of unboundedness properties of forced deterministic and stochastic sublinear Volterra summation equations
In this paper we consider unbounded solutions of perturbed convolution
Volterra summation equations. The equations studied are asymptotically
sublinear, in the sense that the state--dependence in the summation is of
smaller than linear order for large absolute values of the state. When the
perturbation term is unbounded, it is elementary to show that solutions are
also. The main results of the paper are mostly of the following form: the
solution has an additional unboundedness property if and only if the
perturbation has property . Examples of property include monotone
growth, monotone growth with fluctuation, fluctuation on without
growth, existence of time averages. We also study the connection between the
times at which the perturbation and solution reach their running maximum, and
the connection between the size of signed and unsigned running maxima of the
solution and forcing term.Comment: 45 page
Blow-up and superexponential growth in superlinear Volterra equations
This paper concerns the finite-time blow-up and asymptotic behaviour of
solutions to nonlinear Volterra integrodifferential equations. Our main
contribution is to determine sharp estimates on the growth rates of both
explosive and nonexplosive solutions for a class of equations with nonsingular
kernels under weak hypotheses on the nonlinearity. In this superlinear setting
we must be content with estimates of the form ,
where is the blow-up time if solutions are explosive or
if solutions are global. Our estimates improve on the sharpness of results in
the literature and we also recover well-known blow-up criteria via new methods.Comment: 24 page
Subexponential Growth Rates in Functional Differential Equations
This paper determines the rate of growth to infinity of a scalar autonomous
nonlinear functional differential equation with finite delay, where the right
hand side is a positive continuous linear functional of . We assume
grows sublinearly, and is such that solutions should exhibit growth faster than
polynomial, but slower than exponential. Under some technical conditions on
, it is shown that the solution of the functional differential equation is
asymptotic to that of an auxiliary autonomous ordinary differential equation
with righthand side proportional to (with the constant of proportionality
equal to the mass of the finite measure associated with the linear functional),
provided grows more slowly than . This linear--logarithmic
growth rate is also shown to be critical: if grows more rapidly than ,
the ODE dominates the FDE; if is asymptotic to a constant multiple of ,
the FDE and ODE grow at the same rate, modulo a constant non--unit factor.Comment: 10 page
London SynEx Demonstrator Site: Impact Assessment Report
The key ingredients of the SynEx-UCL software components are:
1. A comprehensive and federated electronic healthcare record that can be used to
reference or to store all of the necessary healthcare information acquired from a
diverse range of clinical databases and patient-held devices.
2. A directory service component to provide a core persons demographic database to
search for and authenticate staff users of the system and to anchor patient
identification and connection to their federated healthcare record.
3. A clinical record schema management tool (Object Dictionary Client) that enables
clinicians or engineers to define and export the data sets mapping to individual
feeder systems.
4. An expansible set of clinical management algorithms that provide prompts to the
patient or clinician to assist in the management of patient care.
CHIME has built up over a decade of experience within Europe on the requirements
and information models that are needed to underpin comprehensive multiprofessional
electronic healthcare records. The resulting architecture models have
influenced new European standards in this area, and CHIME has designed and built
prototype EHCR components based on these models. The demonstrator systems
described here utilise a directory service and object-oriented engineering approach,
and support the secure, mobile and distributed access to federated healthcare
records via web-based services.
The design and implementation of these software components has been founded on
a thorough analysis of the clinical, technical and ethico-legal requirements for
comprehensive EHCR systems, published through previous project deliverables and
in future planned papers.
The clinical demonstrator site described in this report has provided the solid basis
from which to establish "proof of concept" verification of the design approach, and a
valuable opportunity to install, test and evaluate the results of the component
engineering undertaken during the EC funded project. Inevitably, a number of
practical implementation and deployment obstacles have been overcome through
this journey, each of those having contributed to the time taken to deliver the
components but also to the richness of the end products.
UCL is fortunate that the Whittington Hospital, and the department of cardiovascular
medicine in particular, is committed to a long-term vision built around this work. That
vision, outlined within this report, is shared by the Camden and Islington Health
Authority and by many other purchaser and provider organisations in the area, and
by a number of industrial parties. They are collectively determined to support the
Demonstrator Site as an ongoing project well beyond the life of the EC SynEx
Project.
This report, although a final report as far as the EC project is concerned, is really a
description of the first phase in establishing a centre of healthcare excellence. New
EC Fifth Framework project funding has already been approved to enable new and
innovative technology solutions to be added to the work already established in north
London
Design and implementation of a federated health record server
This paper describes the practical implementation of a federated health record serverbased on a generic and comprehensive public domain architecture and deployed in alive clinical setting.The authors, working at the Centre for Health Informatics and MultiprofessionalEducation (University College London), have built up over a decade of experiencewithin Europe on the requirements and information models that are needed to underpincomprehensive multi-professional electronic health records. This work has involvedcollaboration with a wide range of healthcare and informatics organisations and partnersin the healthcare computing industry across Europe though the EU Health Telematicsprojects GEHR, Synapses, EHCR-SupA, SynEx and Medicate. The resultingarchitecture models have influenced recent European standards in this area, such asCEN TC/251 ENV 13606. UCL has now designed and built a federated health recordserver based on these models which is now running in the Department ofCardiovascular Medicine at the Whittington Hospital in north London. A new EC FifthFramework project, 6WINIT, is enabling new and innovative IPv6 and wirelesstechnology solutions to be added to this work.The north London clinical demonstrator site has provided the solid basis from which toestablish "proof of concept" verification of the design approach, and a valuableopportunity to install, test and evaluate the results of the component engineeringundertaken during the EC funded projects
- …