An efficient full space-time discretization method for subject-specific hemodynamic simulations of cerebral arterial blood flow with distensible wall mechanics.

A computationally inexpensive mathematical solution approach using orthogonal collocations for space discretization with temporal Fourier series is proposed to compute subject-specific blood flow in distensible vessels of large cerebral arterial networks. Several models of wall biomechanics were considered to assess their impact on hemodynamic predictions. Simulations were validated against in vivo blood flow measurements in six human subjects.

A thermoelastic deformation model of tissue contraction during thermal ablation.

Purpose: Thermal ablation is an energy-based ablation technique widely used during minimally invasive cancer treatment. Simulations are used to predict the dead tissue post therapy. However, one difficulty with the simulations is accurately predicting the ablation zone in post-procedural images due to the contraction of tissue as a result of exposure to elevated temperatures.

Mathematical model of the post-ablation enhancement zone as a tissue-level oedematic response.

Purpose: A hyperdense rim is commonly observed at the periphery of ablation zones during post-ablation imaging (e.g. ultrasound) in tumours.

A model of tissue contraction during thermal ablation.

A model of a globular protein is used to describe the contraction of tissue exposed to elevated temperatures. This will be useful in predicting the contraction of tissue that is observed during thermal ablation of tumours, which is a problem when trying to determine the ablation zone in post-operative images. The transitions between the states of the protein can be related to a change in the length of the molecule, which can be directly observed as a change in the length of the tissue.

Modelling the effects of cerebral microvasculature morphology on oxygen transport.

The cerebral microvasculature plays a vital role in adequately supplying blood to the brain. Determining the health of the cerebral microvasculature is important during pathological conditions, such as stroke and dementia. Recent studies have shown the complex relationship between cerebral metabolic rate and transit time distribution, the transit times of all the possible pathways available dependent on network topology.

A generalized mathematical framework for estimating the residue function for arbitrary vascular networks.

The microvasculature plays a vital part in the cardiovascular system. Any impairment to its function can lead to significant pathophysiological effects, particularly in organs such as the brain where there is a very tight coupling between structure and function. However, it is extremely difficult to quantify the health of the microvasculature in vivo, other than by assessing perfusion, using techniques such as arterial spin labelling.

Multi-spatial-frequency and phase-shifting profilometry using a liquid crystal phase modulator.

Optical profilometry is widely applied for measuring the morphology of objects by projecting predetermined patterns on them. In this technique, the compact size is one of the interesting issues for practical applications. The generation of pattern by the interference of coherent light sources has a potential to reduce the dimension of the illumination part.

Modelling of pH dynamics in brain cells after stroke.

The identification of salvageable brain tissue is a major challenge at stroke presentation. Standard techniques used in this context, such as the perfusion-diffusion mismatch, remain controversial. There is thus a need for new methods to help guide treatment.

A vertical-field-driven polymer-stabilized blue phase liquid crystal mode to obtain a higher transmittance and lower driving voltage.

We demonstrate a vertical-field-driven polymer-stabilized blue phase liquid crystal (PS-BPLC) mode for solving low transmittance and high driving voltage problems in conventional in-plane-switching (IPS) PS-BPLC modes. By controlling the ray directions of incident beams by means of two prism sheets attached to the top and bottom substrates, continuous grayscale properties can be achieved with a vertical field, where the transmittance of the proposed structure can be increased to become twice as high as that of a IPS PS-BPLC cell, and its driving voltage can also be lowered by about 20 V. With the vertical-field-driven PS-BPLC mode, the hysteresis problem of the IPS PS-BPLC mode can also be solved due to a reduction of the electric field required to achieve sufficient field-induced retardation.

Optical detection of volatile organic compounds using selective tensile effects of a polymer-coated fiber Bragg grating.

We demonstrated a novel selective chemical sensing approach by incorporating a poly(dimethylsiloxane) (PDMS)-coated fiber Bragg grating (FBG) structure for optically detecting various volatile organic compounds (VOC's). When the proposed structure is exposed to a nonpolar solvent, a tensile stress is induced between the coated PDMS and the optical fiber by a VOC-dependent swelling effect of the PDMS, which results in a Bragg wavelength shift dependent on the concentration and the type of VOC's. Because of no need of an etching process of a fiber cladding, the proposed PDMS-coated FBG can be used as a simple, convenient, and durable chemical sensing element with a high sensitivity, compared with conventional FBG sensors requiring an evanescent wave coupling.

Quantification of the effects of vasomotion on mass transport to tissue from axisymmetric blood vessels.

The process known as vasomotion, rhythmic oscillations in vessel diameter, has been proposed to act as a protective mechanism for tissue under conditions of reduced perfusion, since it is frequently only observed experimentally when perfusion levels are reduced. This could be due to a resultant increase in oxygen transport from the vasculature to the surrounding tissue, either directly or indirectly. It is thus potentially of significant clinical interest as a warning signal for ischemia.

The effects of non-linearities on shear stress in periodic flow in axi-symmetric vessels.

In this paper, a power series and a Fourier series approach is used to solve the governing equations of motion in an elastic axi-symmetric vessel, assuming that blood is an incompressible Newtonian fluid. The time averaged flow has shown to be greater than the steady state flow leading to a larger wall shear stress. Oscillations can also be observed, which is not present in the steady state solution.

Variable wavelength surface plasmon resonance (SPR) in biosensing.

In this study, we fabricated a novel variable wavelength surface plasmon resonance (SPR) sensor, which detects resonance conditions such as a maximum attenuation wavelength, measuring change of microscopic refractive index. Such a change was measured to detect a salmonella antigen-antibody reaction and a penicillinase-penicillin reaction. Our experiments were performed after immobilizing a salmonella antibody on the sensor chip.