Imperial College London

DrJenniferTweedy

Faculty of EngineeringDepartment of Bioengineering

Senior Lecturer
 
 
 
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Contact

 

+44 (0)20 7594 3663j.siggers Website

 
 
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Location

 

4.30Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

55 results found

Argungu M, Tweedy JH, Microcirculation of blood and interstitial fluid in a poroelastic model of theliver, 6th Bio Conference on Poromechanics 2017, Publisher: ASCE

Cirrhosis is a life-threatening condition that represents a leading cause of deathin the western world. In this condition the structure of the liver tissue is altered bythe development of fibrosis, which means it becomes stiffer and its permeability toblood and interstitial flow within the tissue that are vital to its function are reduced.We develop a new mathematical model based on those by Bonfiglio et al (2010) andSiggers et al (2014), which we use to investigate the changes in liver volume, bloodflow and lymphatic uptake, which measures interstitial flow, that occur as the tissuebecomes progressively stiffer. Our results suggest that the typical changes that developduring cirrhosis have a significant effect on the permeability properties, highlightingthe seriousness of this condition.

CONFERENCE PAPER

Schobesberger S, Jonsson P, Buzuk A, Korchev Y, Siggers J, Gorelik Jet al., Precise, nanoscale, voltage-driven application of bio-active substances onto cardiomyocyte surface with organized topography, Biophysical Journal, ISSN: 1542-0086

With Scanning Ion Conductance Microscopy (SICM), a non-contact scanning probe technique, it is possible to obtain information about both the surface topography of live cells and to apply molecules onto specific nanoscale structures. The technique is therefore widely used to apply chemical compounds and to study the properties of molecules on the surface of various cell types. The heart muscle cells, the cardiomyocytes, possess a highly elaborate, unique surface topography including T-tubule openings leading into a cell internal system which exclusively har-bors many proteins necessary for the cells physiological function. Here we applied Isoproterenol into these surface openings by changing the applied voltage over the SICM nanopipette. To determine the grade of precision of our application we used finite element simulations to inves-tigate how the concentration profile varies over the cell surface. We first obtained topography scans of the cardiomyocytes using SICM and then determined the electrophoretic mobility of Isoproterenol in a high ion solution to be -7×10-9 m2/Vs. The simulations showed that the delivery to the T-tubule opening is highly confined to the underlying Z-groove and especially to the first T-tubule opening, where the concen-tration is approximately 6.5 times higher compared to on a flat surface under the same delivery settings. Delivery to the crest, instead of the T-tubule opening, resulted in a much lower concentration, emphasizing the importance of topography on agonist delivery. In conclusion SICM, unlike other techniques, can reliably deliver precise quantities of compounds to the T-tubules of cardiomyocytes

JOURNAL ARTICLE

Tweedy JH, Argungu M, Microcirculation of blood and interstitial fluid in a poroelastic model of the liver, Conference Proceedings of 6th Biot Conference on Poromechanics (ASCE)

JOURNAL ARTICLE

Tweedy JH, Dvoriashyna M, Repetto R, Aqueous humor flow in the posterior chamber of the eye with iridotomy, Summer Biomechanics, Bioengineering and Biotransport Conference 2016

CONFERENCE PAPER

Tweedy JH, Pralits JO, Repetto R, Soleri Pet al., Flow in the anterior chamber of the eye with an implanted iris-fixated artificial lens, Mathematical Medicine and Biology-a Journal of the IMA, ISSN: 1477-8599

Flow in the aqueous humour that fills the anterior chamber of the eye occurs in response to the production and drainage of the aqueous humour, and also due to buoyancy effects produced by thermal gradients. Phakic intraocular lenses (pIOLs) are manufactured lenses that are surgically inserted in the eyes of patients to correct refractive errors. Their presence has a dramatic effect on the circulation of the aqueous humour, resulting a very different flow in the anterior chamber, the effects of which have not been extensively investigated. In this article we use a simplified mathematical model to analyse the flow, in order to assess the effect of the implanted lens on the pressure drop required to drive the flow and also on the wall shear stress experienced by the corneal endothelial cells and the cells of the iris. A high pressure drop could result in an increased risk of glaucoma, whilst raised shear stress on the cornea could result in a reduction in the density of endothelial cells there, and on the iris it could result in the detachment of pigment cells, which block the outflow of the eye, also leading to glaucoma. Our results confirm those of previous fully numerical studies, and show that, although the presence of the lens causes significant differences in the flow topology and direction, the typical magnitudes of the shear stress are not significantly changed from the natural case. Our semi-analytical solution allows us to perform a thorough study of the dependence of the results on the controlling parameters and also to understand the basic physical mechanisms underlying flow characteristics.

JOURNAL ARTICLE

Roney CH, Cantwell CD, Bayer JD, Qureshi NA, Lim PB, Tweedy JH, Kanagaratnam P, Peters NS, Vigmond EJ, Ng FSet al., 2017, Spatial Resolution Requirements for Accurate Identification of Drivers of Atrial Fibrillation, CIRCULATION-ARRHYTHMIA AND ELECTROPHYSIOLOGY, Vol: 10, ISSN: 1941-3149

JOURNAL ARTICLE

Roney CH, Cantwell CD, Qureshi NA, Chowdhury RA, Dupont E, Lim PB, Vigmond EJ, Tweedy JH, Ng FS, Peters NSet al., 2017, Rotor Tracking Using Phase of Electrograms Recorded During Atrial Fibrillation, ANNALS OF BIOMEDICAL ENGINEERING, Vol: 45, Pages: 910-923, ISSN: 0090-6964

JOURNAL ARTICLE

Baksi AJ, Davies JE, Hadjiloizou N, Baruah R, Unsworth B, Foale RA, Korolkova O, Siggers JH, Francis DP, Mayet J, Parker KH, Hughes ADet al., 2016, Attenuation of reflected waves in man during retrograde propagation from femoral artery to proximal aorta, INTERNATIONAL JOURNAL OF CARDIOLOGY, Vol: 202, Pages: 441-445, ISSN: 0167-5273

JOURNAL ARTICLE

Ali RL, Cantwell CD, Qureshi NA, Roney CH, Lim PB, Sherwin SJ, Siggers JH, Peters NSet al., 2015, Automated fiducial point selection for reducing registration error in the co-localisation of left atrium electroanatomic and imaging data, 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Publisher: IEEE, Pages: 1989-1992, ISSN: 1557-170X

CONFERENCE PAPER

Cantwell CD, Roney CH, Ng FS, Siggers JH, Sherwin SJ, Peters NSet al., 2015, Techniques for automated local activation time annotation and conduction velocity estimation in cardiac mapping, COMPUTERS IN BIOLOGY AND MEDICINE, Vol: 65, Pages: 229-242, ISSN: 0010-4825

JOURNAL ARTICLE

Dehbi H-M, Jones S, Sohaib SMA, Finegold JA, Siggers JH, Stegemann B, Whinnett ZI, Francis DPet al., 2015, A novel curve fitting method for AV optimisation of biventricular pacemakers, PHYSIOLOGICAL MEASUREMENT, Vol: 36, Pages: 1889-1900, ISSN: 0967-3334

JOURNAL ARTICLE

Repetto R, Khongar PD, Pralits JO, Siggers JH, Soleri Pet al., 2015, Numerical simulations of flow and mass transport processes in the anterior chamber in the presence of an iris-fixated intraocular lens, Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology (ARVO), Publisher: ASSOC RESEARCH VISION OPHTHALMOLOGY INC, ISSN: 0146-0404

CONFERENCE PAPER

Repetto R, Pralits JO, Siggers JH, Soleri Pet al., 2015, Phakic iris-fixated intraocular lens placement in the anterior chamber: effects on aqueous flow., Investigative Ophthalmology & Visual Science, Vol: 56, Pages: 3061-3068, ISSN: 1552-5783

PURPOSE: Phakic intraocular lenses (pIOLs) are used for correcting vision; in this paper we investigate the fluid dynamical effects of an iris-fixated lens in the anterior chamber. In particular, we focus on changes in the wall shear stress (WSS) on the cornea and iris, which could be responsible for endothelial and pigment cell loss, respectively, and also on the possible increase of the intraocular pressure, which is known to correlate with the incidence of secondary glaucoma. METHODS: We use a mathematical model to study fluid flow in the anterior chamber in the presence of a pIOL. The governing equations are solved numerically using the open source software OpenFOAM. We use an idealized standard geometry for the anterior chamber and a realistic geometric description of the pIOL. RESULTS: We consider separately the main mechanisms that produce fluid flow in the anterior chamber. The numerical simulations allow us to obtain a detailed description of the velocity and pressure distribution in the anterior chamber, and indicated that implantation of the pIOL significantly modifies the fluid dynamics in the anterior chamber. However, lens implantation has negligible influence on the intraocular pressure and does not produce a significant increase of the shear stress on the cornea, while the shear stress on the iris, although increased, is not enough to cause detachment of cells. CONCLUSIONS: We conclude that alterations in the fluid dynamics in the anterior chamber as a result of lens implantation are unlikely to be the cause of medical complications associated with its use.

JOURNAL ARTICLE

Roney CH, Tzortzis KN, Cantwell CD, Qureshi NA, Ali RL, Lim PB, Siggers JH, Ng FS, Peters NSet al., 2015, A Technique for Visualising Three-Dimensional Left Atrial Cardiac Activation Data in Two Dimensions with Minimal Distance Distortion, 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Publisher: IEEE, Pages: 7296-7299, ISSN: 1557-170X

CONFERENCE PAPER

Ali RL, Cantwell CD, Roney CH, Qureshi NA, Lim PB, Siggers JH, Sherwin SJ, Peters NSet al., 2014, A novel method for quantifying localised correlation of late-gadolinium intensity with conduction velocity, 41st Computing in Cardiology Conference (CinC), Publisher: IEEE, Pages: 193-196, ISSN: 0276-6574

CONFERENCE PAPER

Debbaut C, Vierendeels J, Siggers JH, Repetto R, Monbaliu D, Segers Pet al., 2014, A 3D porous media liver lobule model: the importance of vascular septa and anisotropic permeability for homogeneous perfusion, COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING, Vol: 17, Pages: 1295-1310, ISSN: 1025-5842

JOURNAL ARTICLE

Park CM, Korolkova O, Davies JE, Parker KH, Siggers JH, March K, Tillin T, Chaturvedi N, Hughes ADet al., 2014, Arterial pressure: agreement between a brachial cuff-based device and radial tonometry, JOURNAL OF HYPERTENSION, Vol: 32, Pages: 865-872, ISSN: 0263-6352

JOURNAL ARTICLE

Repetto R, Siggers JH, Meskauskas J, 2014, Steady streaming of a viscoelastic fluid within a periodically rotating sphere, JOURNAL OF FLUID MECHANICS, Vol: 761, ISSN: 0022-1120

JOURNAL ARTICLE

Roney CH, Cantwell CD, Qureshi NA, Ali RL, Chang ETY, Lim PB, Sherwin SJ, Peters NS, Siggers JH, Ng FSet al., 2014, An Automated Algorithm for Determining Conduction Velocity, Wavefront Direction and Origin of Focal Cardiac Arrhythmias Using a Multipolar Catheter, 36th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society (EMBC), Publisher: IEEE, Pages: 1583-1586, ISSN: 1557-170X

CONFERENCE PAPER

Roney CH, Cantwell CD, Siggers JH, Ng FS, Peters NSet al., 2014, A Novel Method for Rotor Tracking Using Bipolar Electrogram Phase, 41st Computing in Cardiology Conference (CinC), Publisher: IEEE, Pages: 233-236, ISSN: 0276-6574

CONFERENCE PAPER

Siggers JH, Leungchavaphongse K, Ho CH, Repetto Ret al., 2014, Mathematical model of blood and interstitial flow and lymph production in the liver, BIOMECHANICS AND MODELING IN MECHANOBIOLOGY, Vol: 13, Pages: 363-378, ISSN: 1617-7959

JOURNAL ARTICLE

Bonfiglio A, Repetto R, Siggers JH, Stocchino Aet al., 2013, Investigation of the motion of a viscous fluid in the vitreous cavity induced by eye rotations and implications for drug delivery, PHYSICS IN MEDICINE AND BIOLOGY, Vol: 58, Pages: 1969-1982, ISSN: 0031-9155

JOURNAL ARTICLE

Putra NK, Dickinson RJ, Siggers JH, 2013, Image Processing as the Validation Method of Droplet Dispersion Modeling Process, 3rd International Conference on Instrumentation, Communications, Information Technology, and Biomedical Engineering (ICICI-BME), Publisher: IEEE, Pages: 242-245, ISSN: 2158-0456

CONFERENCE PAPER

Setchi A, Mestel AJ, Parker KH, Siggers JHet al., 2013, Low-Reynolds-number flow through two-dimensional shunts, JOURNAL OF FLUID MECHANICS, Vol: 723, Pages: 21-39, ISSN: 0022-1120

JOURNAL ARTICLE

Setchi A, Mestel AJ, Siggers JH, Parker KH, Tan MW, Wong Ket al., 2013, Mathematical model of flow through the patent ductus arteriosus, JOURNAL OF MATHEMATICAL BIOLOGY, Vol: 67, Pages: 1487-1506, ISSN: 0303-6812

JOURNAL ARTICLE

Alastruey J, Siggers JH, Peiffer V, Doorly DJ, Sherwin SJet al., 2012, Reducing the data: Analysis of the role of vascular geometry on blood flow patterns in curved vessels, PHYSICS OF FLUIDS, Vol: 24, ISSN: 1070-6631

JOURNAL ARTICLE

Bell CG, Anastassiou CA, O'Hare D, Parker KH, Siggers JHet al., 2012, Theoretical treatment of high-frequency, large-amplitude ac voltammetry applied to ideal surface-confined redox systems, ELECTROCHIMICA ACTA, Vol: 64, Pages: 71-80, ISSN: 0013-4686

JOURNAL ARTICLE

Bell CG, Howell PD, Stone HA, Lim W-J, Siggers JHet al., 2012, The long-time chronoamperometric current at an inlaid disk electrode, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, Vol: 673, Pages: 48-57, ISSN: 1572-6657

JOURNAL ARTICLE

Bonfiglio A, Stocchino A, Repetto R, Siggers JHet al., 2012, IN-VITRO SIMULATIONS OF DRUG DELIVERY IN THE VITREOUS CHAMBER OF THE EYE, ASME Summer Bioengineering Conference (SBC), Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 1171-1172

CONFERENCE PAPER

Meskauskas J, Repetto R, Siggers JH, 2012, Shape Change of the Vitreous Chamber Influences Retinal Detachment and Reattachment Processes: Is Mechanical Stress during Eye Rotations a Factor?, INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE, Vol: 53, Pages: 6271-6281, ISSN: 0146-0404

JOURNAL ARTICLE

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