A5006496542- Geomagnetism and Paleomagnetism Studies
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Cardiac electrophysiology and arrhythmias
- Magnetic and Electromagnetic Effects
- Characterization and Applications of Magnetic Nanoparticles
- Nonlinear Dynamics and Pattern Formation
- Astro and Planetary Science
- Ionosphere and magnetosphere dynamics
- stochastic dynamics and bifurcation
- Neuroscience and Neural Engineering
- Geology and Paleoclimatology Research
- Electron Spin Resonance Studies
- Cardiovascular Function and Risk Factors
- Electrochemical Analysis and Applications
- Combustion and flame dynamics
- Hydrocarbon exploration and reservoir analysis
- Fluid dynamics and aerodynamics studies
- Circadian rhythm and melatonin
- Scientific Research and Discoveries
- 3D Printing in Biomedical Research
- Combustion and Detonation Processes
- Electrostatic Discharge in Electronics
- Advanced MRI Techniques and Applications
- Heart Rate Variability and Autonomic Control
University of Glasgow
2015-2025
University of California, Los Angeles
2013-2015
Ames Research Center
2015
Stanford University
2013-2014
Nordic Institute for Theoretical Physics
2012
AlbaNova
2012
University of Liverpool
2005-2007
University of Bayreuth
2002-2006
Numerical simulations of the geodynamo have successfully represented many observable characteristics geomagnetic field, yielding insight into fundamental processes that generate magnetic fields in Earth's core. Because limited spatial resolution, however, diffusivities numerical dynamo models are much larger than those core, and consequently, questions remain about how realistic these are. The typical strategy used to address this issue has been continue increase resolution quasi-laminar...
Bistability and hysteresis of magnetohydrodynamic dipolar dynamos generated by turbulent convection in rotating spherical fluid shells is demonstrated. Hysteresis appears as a transition between two distinct regimes with rather different properties including pronounced difference the amplitude axisymmetric poloidal field component form differential rotation. The bistability occurs from onset dynamo action up to about 9 times critical value Rayleigh number for over wide range values ordinary...
For the understanding of planetary and stellar dynamos, an overview major parameter dependences convection driven dynamos in rotating spherical fluid shells is desirable. Although computationally accessible space limited, earlier work extended with emphasis on higher Prandtl numbers uniform heat flux condition at outer boundary. The transition from dominated by non-axisymmetric components magnetic field to those axisymmetric depends number as well ordinary for values rotation τ. dependence...
Convection in planetary cores can generate fluid flow and magnetic fields, a number of sophisticated codes exist to simulate the dynamic behaviour such systems. We report on first community activity compare numerical results computer designed calculate within whole sphere. The flows are incompressible rapidly rotating forcing is either due thermal convection or moving boundaries. All problems defined have solutions that allow easy comparison, since they steady, slowly drifting perfectly...
Cardiac electrophysiological heterogeneity includes: (i) regional differences in action potential (AP) waveform, (ii) AP waveform cells isolated from a single region, (iii) variability of the contribution individual ion currents with similar durations (APDs). The aim this study is to assess intra-regional differences, quantify specific channels APD via drug responses and generate population mathematical models investigate mechanisms underlying rabbit ventricular cells.APD ∼50 subregions LV...
Recent high-throughput experiments unveil substantial electrophysiological diversity among uncoupled healthy myocytes under identical conditions. To quantify inter-cell variability, the values of a subset parameters in well-regarded mathematical model action potential rabbit ventricular are estimated from fluorescence voltage measurements large number cells. Statistical inference yields population nearly 1200 cell-specific variants that, on population-level replicate experimentally measured...
Recent high-throughput experiments unveil substantial electrophysiological diversity among uncoupled healthy myocytes under identical conditions. To quantify inter-cell variability, the values of a subset parameters in well-regarded mathematical model action potential rabbit ventricular are estimated from fluorescence voltage measurements large number cells. Statistical inference yields population nearly 1200 cell-specific variants that, on population-level replicate experimentally measured...
The value of the Prandtl number $P$ exerts a strong influence on convection-driven dynamos in rotating spherical shells filled with electrically conducting fluids. Low numbers promote dynamo action through shear provided by differential rotation, while generation magnetic fields is more difficult to sustain high-Prandtl-number fluids where higher values $P_m$ are required. magnetostrophic approximation often used theory appears be valid only for relatively high and $P_m$. Dynamos minimum...
Patterns of convection in internally heated, self-gravitating rotating spherical fluid shells are investigated through numerical simulations. While turbulent states primary interest planetary and stellar applications the present paper emphasizes more regular dynamical features at Rayleigh numbers not far above threshold which similar to those might be observed laboratory or space experiments. Amplitude vacillations spatial modulations columns common moderate large Prandtl numbers. In low...
It is frequently considered that many planetary magnetic fields originate as a result of convection within cores. Buoyancy forces responsible for driving the generate fluid flow able to induce fields; numerous sophisticated computer codes are simulate dynamic behaviour such systems. This paper reports results community activity aimed at comparing numerical several different types capable solving equations momentum transfer, field generation and heat transfer in setting spherical shell,...
Numerical MHD simulations play an increasingly important role for understanding the mechanisms of stellar magnetism. We present convection and dynamos in density-stratified rotating spherical fluid shells. employ a new 3D simulation code obtaining solution physically consistent anelastic model process with minimum number parameters. The reported dynamo extend into "buoyancy-dominated" regime where buoyancy forcing is dominant while Coriolis force no longer balanced by pressure gradients,...
Aims: To investigate the relationship between surges and magnetic reconnection during emergence of small-scale active regions. In particular, to examine how large-scale geometry field, shaped by different phases reconnection, guides flowing surges. Methods: We present three flux models. The first model, simplest, consists a region emerging into horizontal ambient field that is initially parallel top region. second model same as but with an extra smaller which perturbs main This added create...
We describe a novel mathematical model for blood flow, delivery of nanoparticles, and heat transport in vascularised tumour tissue. The model, which is derived via the asymptotic homogenisation technique, provides link between macroscale behaviour system its underlying, tortuous micro-structure, as parametrised Penta Ambrosi (2015). It consists double Darcy's law, coupled with advection-diffusion-reaction describing transport, an equation adhesion particles. Particles are assumed...
The onset of convection in the form inertial waves a rotating fluid sphere is studied through perturbation analysis an extension earlier work by Zhang (1994). Explicit expressions for dependence Rayleigh number on azimuthal wavenumber are derived and new results case nearly thermally insulating boundary obtained.
Some concepts used in the theory of convection-driven dynamos rotating spherical fluid shells are discussed. The analogy between imposed magnetic fields and those generated by dynamo action is evaluated role Elsasser number considered. Eddy diffusivities essential ingredients numerical simulations, but their effects could be misleading. New aspects simultaneous existence different states described.
Abstract Human induced pluripotent stem cell‐derived cardiomyocytes (hiPSC‐CM) in monolayers interact mechanically via cell–cell and cell–substrate adhesion. Spatiotemporal features of contraction were analysed hiPSC‐CM (1) attached to glass or plastic (Young's modulus (E) >1 GPa), (2) detached (substrate‐free) (3) a flexible collagen hydrogel (E = 22 kPa). The effects isoprenaline on compared between rigid substrates. To clarify the underlying mechanisms, further gene expression...
We analyse small parameters in selected models of biological excitability, including Hodgkin–Huxley (Hodgkin & Huxley 1952 J. Physiol. 117 , 500–544) model nerve axon, Noble (Noble 1962 160 317–352) heart Purkinje fibres and Courtemanche et al . (Courtemanche 1998 Am. 275 H301–H321) human atrial cells. Some the are responsible for differences characteristic time-scales dynamic variables, as traditional singular perturbation approaches. Others appear a way which makes standard approaches...
A general reformulation of the Reynolds stresses created by two-dimensional waves breaking a translational or rotational invariance is described. This emphasizes importance geometrical factor: slope separatrices wave flow. Its physical relevance illustrated two model systems: destabilizing open shear flows; and thermal Rossby in spherical shell convection with rotation. In case shear-flow waves, new expression Reynolds–Orr amplification mechanism obtained, good understanding form mean...
We consider the problem of ignition propagating waves in one-dimensional bistable or excitable systems by an instantaneous spatially extended stimulus. Earlier we proposed a method (Idris and Biktashev, PRL, vol 101, 2008, 244101) for analytical description threshold conditions based on approximation (center-)stable manifold certain critical solution. Here generalize this to address wider class systems, such as multicomponent reaction-diffusion with non-self-adjoint linearized operators,...