1,926 research outputs found
An Energy-Minimization Finite-Element Approach for the Frank-Oseen Model of Nematic Liquid Crystals: Continuum and Discrete Analysis
This paper outlines an energy-minimization finite-element approach to the
computational modeling of equilibrium configurations for nematic liquid
crystals under free elastic effects. The method targets minimization of the
system free energy based on the Frank-Oseen free-energy model. Solutions to the
intermediate discretized free elastic linearizations are shown to exist
generally and are unique under certain assumptions. This requires proving
continuity, coercivity, and weak coercivity for the accompanying appropriate
bilinear forms within a mixed finite-element framework. Error analysis
demonstrates that the method constitutes a convergent scheme. Numerical
experiments are performed for problems with a range of physical parameters as
well as simple and patterned boundary conditions. The resulting algorithm
accurately handles heterogeneous constant coefficients and effectively resolves
configurations resulting from complicated boundary conditions relevant in
ongoing research.Comment: 31 pages, 3 figures, 3 table
Computing equilibrium states of cholesteric liquid crystals in elliptical channels with deflation algorithms
We study the problem of a cholesteric liquid crystal confined to an
elliptical channel. The system is geometrically frustrated because the
cholesteric prefers to adopt a uniform rate of twist deformation, but the
elliptical domain precludes this. The frustration is resolved by deformation of
the layers or introduction of defects, leading to a particularly rich family of
equilibrium configurations. To identify the solution set, we adapt and apply a
new family of algorithms, known as deflation methods, that iteratively modify
the free energy extremisation problem by removing previously known solutions. A
second algorithm, deflated continuation, is used to track solution branches as
a function of the aspect ratio of the ellipse and preferred pitch of the
cholesteric.Comment: 9 pages, 6 figure
Nonlinear Methods for Shape Optimization Problems in Liquid Crystal Tactoids
Anisotropic fluids, such as nematic liquid crystals, can form non-spherical
equilibrium shapes known as tactoids. Predicting the shape of these structures
as a function of material parameters is challenging and paradigmatic of a
broader class of problems that combine shape and order. Here, we develop a
discrete shape optimization approach with finite elements to find the
configuration of a two-dimensional tactoid using the Landau de Gennes framework
and a Q-tensor representation. Efficient solution of the resulting constrained
energy minimization problem is achieved using a quasi-Newton and nested
iteration algorithm. Numerical validation is performed with benchmark solutions
and compared against experimental data and earlier work. We explore physically
motivated subproblems, whereby the shape and order are separately held fixed,
to explore the role of both and examine material parameter dependence of the
convergence. Nested iteration significantly improves both the computational
cost and convergence of numerical solutions of these highly deformable
materials
A finite element based formulation for sensitivity studies of piezoelectric systems
Sensitivity Analysis is a branch of numerical analysis which aims to quantify the affects that variability in the parameters of a numerical model have on the model output. A finite element based sensitivity analysis formulation for piezoelectric media is developed here and implemented to simulate the operational and sensitivity characteristics of a piezoelectric based distributed mode actuator (DMA). The work acts as a starting point for robustness analysis in the DMA technology
Animal, Plant, Collagen and Blended Dietary Proteins: Effects on Musculoskeletal Outcomes
This is the final version. Available from MDPI via the DOI in this record.Dietary protein is critical for the maintenance of musculoskeletal health, whereappropriate intake (i.e., source, dose, timing) can mitigate declines in muscle and bone mass and/orfunction. Animal-derived protein is a potent anabolic source due to rapid digestion and absorptionkinetics stimulating robust increases in muscle protein synthesis and promoting bone accretion andmaintenance. However, global concerns surrounding environmental sustainability has led to anincreasing interest in plant- and collagen-derived protein as alternative or adjunct dietary sources.This is despite the lower anabolic profile of plant and collagen protein due to the inferior essentialamino acid profile (e.g., lower leucine content) and subordinate digestibility (versus animal). Thisreview evaluates the efficacy of animal-, plant- and collagen-derived proteins in isolation, and asprotein blends, for augmenting muscle and bone metabolism and health in the context of ageing,exercise and energy restriction.Medical Research Council (MRC)National Institute for Health Researc
Mechanism, dynamics, and biological existence of multistability in a large class of bursting neurons
Multistability, the coexistence of multiple attractors in a dynamical system,
is explored in bursting nerve cells. A modeling study is performed to show that
a large class of bursting systems, as defined by a shared topology when
represented as dynamical systems, is inherently suited to support
multistability. We derive the bifurcation structure and parametric trends
leading to multistability in these systems. Evidence for the existence of
multirhythmic behavior in neurons of the aquatic mollusc Aplysia californica
that is consistent with our proposed mechanism is presented. Although these
experimental results are preliminary, they indicate that single neurons may be
capable of dynamically storing information for longer time scales than
typically attributed to nonsynaptic mechanisms.Comment: 24 pages, 8 figure
Communication disability in low and middle-income countries: a call to action
Communication disability is a common but under-reported and often neglected part of health, rehabilitation and disability services, despite communication being a human right.
Communication disability has far-reaching impacts throughout life.
Innovation is required in contexts where services for people with communication disability are limited—particularly low and middle-income countries.
Local and national governments, funders/commissioners, communication disability experts, universities, non-government organisations, communities, health, social care, rehabilitation services and education sectors all have a role to play in putting communication disability on the global disability/(re)habilitation agenda
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