Modelling Dynamically Re-sizeable Electrodes (DRE) for Targeted Transcutaneous Measurements in Impedance Plethysmography

Impedance plethysmography of extremities typically uses band electrodes around limbs to monitor changes in blood volume. This often causes monitored blood variations to only generate minuscule impedance values relative to the measured baseline, attributed to the tissue surrounding the artery or vein of interest. Smaller, ECG type electrodes can provide a larger signal, however their output is very easily affected by the placement of the electrodes relative to the targeted vasculature. This paper presents a novel method to adjust the active surface of electrodes, introducing Dynamically Re-sizeable Electrodes (DRE), to only target the exact area of interest, forming localised electrodes, without having to manually re-position them. Elongated rectangular electrodes were partitioned into smaller electrode segments, interconnected through custom circuitry. For the development and assessment of the DRE system, work was carried out both experimentally in-vitro on gelatine phantoms using custom switching circuits and through finite element modelling (FEM) simulations in COMSOL. A scanning sequence made use of DRE in single segment variable tetra-pole (SSVT) mode proved capable to identify the transcutaneous location of the blood vessel of interest and the specific electrode segments located in its vicinity. Impedance measurements were then taken using these segments connected to form localised electrodes only placed over the targeted vessel. The resulting localised electrodes exhibited up to 28% increased sensitivity to blood variations relative to larger electrodes

Improved Perturbation Theory for Improved Lattice Actions

We study a systematic improvement of perturbation theory for gauge fields on the lattice; the improvement entails resumming, to all orders in the coupling constant, a dominant subclass of tadpole diagrams. This method, originally proposed for the Wilson gluon action, is extended here to encompass all possible gluon actions made of closed Wilson loops; any fermion action can be employed as well. The effect of resummation is to replace various parameters in the action (coupling constant, Symanzik coefficients, clover coefficient) by ``dressed'' values; the latter are solutions to certain coupled integral equations, which are easy to solve numerically. Some positive features of this method are: a) It is gauge invariant, b) it can be systematically applied to improve (to all orders) results obtained at any given order in perturbation theory, c) it does indeed absorb in the dressed parameters the bulk of tadpole contributions. Two different applications are presented: The additive renormalization of fermion masses, and the multiplicative renormalization Z_V (Z_A) of the vector (axial) current. In many cases where non-perturbative estimates of renormalization functions are also available for comparison, the agreement with improved perturbative results is significantly better as compared to results from bare perturbation theory.Comment: 17 pages, 3 tables, 6 figure

A wideband low-distortion CMOS current driver for tissue impedance analysis

Bioimpedance measurements are performed in a variety of medical applications including cancer detection in tissue. Such applications require wideband (typically 1 MHz) accurate ac current drivers with high output impedance and low distortion. This paper presents an integrated current driver that fulfills these requirements. The circuit uses negative feedback to accurately set the output current amplitude into the load. It was fabricated in a 0.35- μm complementary metal–oxide–semiconductor (CMOS) process technology, occupies a core area of 0.4 mm, and operates from ±2.5-V power supplies. For a maximum output current of 1mA p-p, the measured total harmonic distortion is below 0.1%, and the variability of the output current with respect to the load is below 0.5% up to 800 kHz increasing to 0.86% at 1 MHz. The current driver was tested for the detection of cancer sites from postoperative human colon specimens. The circuit is intended for use in active electrode applications

Turbulent Flows and Pollution Dispersion around Tall Buildings Using Adaptive Large Eddy Simulation (LES)

The motivation for this work stems from the increased number of high-rise buildings/skyscrapers all over the world, and in London, UK, and hence the necessity to see their effect on the local environment. We concentrate on the mean velocities, Reynolds stresses, turbulent kinetic energies (TKEs) and tracer concentrations. We look at their variations with height at two main locations within the building area, and downstream the buildings. The pollution source is placed at the top of the central building, representing an emission from a Combined Heat and Power (CHP) plant. We see how a tall building may have a positive effect at the lower levels, but a negative one at the higher levels in terms of pollution levels. Mean velocities at the higher levels (over 60 m in real life) are reduced at both locations (within the building area and downstream it), whilst Reynolds stresses and TKEs increase. However, despite the observed enhanced turbulence at the higher levels, mean concentrations increase, indicating that the mean flow has a greater influence on the dispersion. At the lower levels (Z < 60 m), the presence of a tall building enhanced dispersion (hence lower concentrations) for many of the configurations

Exploring the efficacy of low-level laser therapy and exercise for knee osteoarthritis

Background: Knee Osteoarthritis (KOA) is a prevalent, chronic disorder with excessive functional, social and economic burdens. The goal of treatment is to alleviate the symptoms and slow the progression. Documenting the effects of exercise and LLLT as co-modalities in the management of KOA allows practitioners to implement this management tool as part of KOA rehabilitation, resulting in the earlier discharge from a supervised rehabilitation setting.Objective: The purpose of this study was to determine the effect of low-level laser therapy (LLLT) in the treatment of knee osteoarthritis (KOA). A randomised controlled trial (RCT) was conducted on 111 participants (aged between 40-75 years) diagnosed with KOA. Participants were randomised into an exercise (n=39), LLLT (n=40), or a combined exercise-LLLT (n=32) group.Methods: The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scale was used to assess pain and functionality. Knee range of motion was assessed using a goniometer, and the one-minute timed sit–to-stand test measured physical functionality at four time points: (T1) baseline, (T2) post 12-session intervention, (T3) one-month post intervention and (T4) three-month’s post intervention. Knee circumference was measured using a measuring tape.Results: WOMAC pain and functionality scale and knee circumference scores decreased in all three groups (P&lt;0.05), but the combined exercise-LLLT group demonstrated better outcomes than the LLLT or exercise alone groups respectively. The combined exercise-LLLT group showed better acute and long-term benefits with participants experiencing a 3.5 centimetre decrease in knee circumference, 24 point improvement in the WOMAC pain and functionality scale, and a four repetition increase in physical functionality.Conclusion: The findings suggest that LLLT is a viable tool for managing KOA when used in conjunction with physical exercise. Keywords: photobiomodulation, physical therapy, degenerative joint diseas

Towards an optimized tetrapolar electrical impedance lithium detection probe for bipolar disorder: A simulation study

Bipolar disorder is characterized as a manic-depressive syndrome with severe risks to the individual. Bipolar patients' therapy involves administration of lithium which has proven to be effective for mood stabilization. The therapeutic concentration window for lithium in blood plasma is typically between 0.6-1.5 mM and is of vital importance that concentrations do not exceed the 1.5mM as it can be toxic. Accurate monitoring of the concentration changes of Lithium in blood, down to levels of approximately 0.2mM is vital since toxicity levels are in close proximity to therapeutic levels. This paper aims to study the sensitivity of tetrapolar electrical impedance measurements when used to monitor changes in the conductivity of a solution/sample as in the case of changes in Lithium concentration in blood

Neutron-Star-Merger Equation of State

In this work, we discuss the dense matter equation of state (EOS) for the extreme range of conditions encountered in neutron stars and their mergers. The calculation of the properties of such an EOS involves modeling different degrees of freedom (such as nuclei, nucleons, hyperons, and quarks), taking into account different symmetries, and including finite density and temperature effects in a thermodynamically consistent manner. We begin by addressing subnuclear matter consisting of nucleons and a small admixture of light nuclei in the context of the excluded volume approach. We then turn our attention to supranuclear homogeneous matter as described by the Chiral Mean Field (CMF) formalism. Finally, we present results from realistic neutron-star-merger simulations performed using the CMF model that predict signatures for deconfinement to quark matter in gravitational wave signals.Comment: Contribution to the Special Issue "Compact Stars in the QCD Phase Diagram and in the Multi-Messenger Era of Astronomy" dedicated to the conference: Compact Stars in the QCD Phase Diagram VI

High-power CMOS current driver with accurate transconductance for electrical impedance tomography

Current drivers are fundamental circuits in bioimpedance measurements including electrical impedance tomography (EIT). In the case of EIT, the current driver is required to have a large output impedance to guarantee high current accuracy over a wide range of load impedance values. This paper presents an integrated current driver which meets these requirements and is capable of delivering large sinusoidal currents to the load. The current driver employs a differential architecture and negative feedback, the latter allowing the output current to be accurately set by the ratio of the input voltage to a resistor value. The circuit was fabricated in a 0.6-μ m high-voltage CMOS process technology and its core occupies a silicon area of 0.64 mm2. It operates from a ± 9 V power supply and can deliver output currents up to 5 mA p-p. The accuracy of the maximum output current is within 0.41% up to 500 kHz, reducing to 0.47% at 1 MHz with a total harmonic distortion of 0.69%. The output impedance is 665 kΩ at 100 kHz and 372 k Ω at 500 kHz

An Integrated Analog Readout for Multi-Frequency Bioimpedance Measurements

Bioimpedance spectroscopy is used in a wide range of biomedical applications. This paper presents an integrated analog readout, which employs synchronous detection to perform galvanostatic multi-channel, multi-frequency bioimpedance measurements. The circuit was fabricated in a 0.35-μm CMOS technology and occupies an area of 1.52 mm2. The effect of random dc offsets is investigated, along with the use of chopping to minimize them. Impedance measurements of a known RC load and skin (using commercially available electrodes) demonstrate the operation of the system over a frequency range up to 1 MHz. The circuit operates from a ±2.5 V power supply and has a power consumption of 3.4-mW per channel