Paul Christiaans's research works | The University of Western Ontario and other places

Cloud Base Height Correlation Between a Co-located Micro-Pulse LiDAR and a Lufft CHM15k Ceilometer

Chapter

July 2023

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Several large-scale networks using automated ceilometers and LiDARs now exist. Some networks, such as MPLNET, have developed algorithms that can be applied uniformly across all instruments. However, cross-network tools are not so readily available such as those used for cloud base height comparison. The London (CDN) node of the CANadian Micro-pulse LiDAR Network (MPLCAN) hosts both a miniHD MPL (MPLNET) and Lufft 15k ceilometer (European E-PROFILE network). Each has its own algorithm to estimate cloud base height. The MPL algorithm was developed by the NASA Langley MPLNET team, and the ceilometer has the manufacturers provided Sky Condition Algorithm. The cloud base should be in principle the same for these co-located instruments. Using the MPLNET vs. Lufft measurements for the first year of operation, the monthly correlation coefficient, R, varies between 0.45 and 0.97. This difference between instruments is mostly accounted for by a poor comparison below 1 km due to aerosols, precipitation, and overlap uncertainties. Applying a gradient-based algorithm (GBD) onto the measurements improves the worst comparison to greater than \(R = 0.9\). However, this GBD algorithm has low accuracy with decreased signal to noise. Thus, we can utilize this tool to help verify the overall agreement of measurements between these 2 instruments, and it offers a tool for standard processes of the 2 instruments.

In vitro electrical conductivity measurement (a) circuit diagram with waveform generator programmed to Vprog and internal impedance Z0, connected to the in vitro setup with impedance Z, voltage across the dish of Vmeas, and electric field map simulated from the (b) geometry of the in vitro setup.

Custom designed printed circuit board (PCB) including (a) three stimulating electrode wells labelled ‘Electrode A’, ‘Electrode B’ and ‘Electrode C’, and a Sham well. Each well is individually stimulated via the Signal In connector (white) or can be connected to other wells to provide identical stimulation using the corresponding links (A/B Link, A/C Link, B/C Link). Four platinum iridium wire electrodes are included in each well, located 6.3 mm from the center. (b) PCB fitted to the 24-well plate and connected to a 4-channel waveform generator with unique stimulation delivered to each electrode in well ‘Electrode A’. The A/B Link is connected in this case to provide identical stimulation to the top two wells. (c) The wire electrodes extend below the PCB, with a length that touches the bottom of the well.

of in vitro experiment designs, beginning with (a) 200 kHz rotating electric fields at magnitudes of 1, 1.5 and 2 V cm⁻¹, to determine the cell survival curve. Voltage and phase parameters were optimized for electric field coverage at the corresponding magnitude and homogeneity to the central 3 mm radius. Rotating fields were delivered with different voltage waveforms V(t)=Asin2πft−ϕn to each electrode (n = 1, 2, 3, 4), where A is the voltage amplitude, t is time, f is the frequency, and ϕn is the phase shift. Experiment (b) compares field rotation to no rotation by grounding ( G ) two adjacent electrodes and (c) compares a different rotating field frequency of 10 kHz, all with voltage configurations optimized to cover the central 3 mm radius with 1 V cm⁻¹. (d) Destructive interference configurations contain alternating ground ( G ) and stimulating electrodes: voltage matched (left) or power matched (right) to the rotating scenario, resulting in a field cancellation to 0 V cm⁻¹ in the center. See figure S3 for animation of this figure.

(a) Bioluminescence image after 3 d of 1.5 V cm⁻¹ average IMT electric fields to the top two wells. Bottom two wells were not stimulated, to provide two sham conditions. (b) The cell survival curve for increasing electric field magnitudes. Data is plotted as the mean ± standard error in blue, and the data was fit to a linear quadratic model S=Ae−αE+βE2−1+1 in black (R ² = 0.95).

Mean of the BLI peak signal normalized to sham ± standard error, proportional to the cell survival, for the cases of constructive interference 200 kHz rotating fields (0.53 ± 0.03, n = 12), 200 kHz non-rotating (0.55 ± 0.06, n = 12), 10 kHz rotating fields (0.49 ± 0.04, n = 12), and destructive interference 200 kHz voltage matched non-rotating fields (0.99 ± 0.02, n = 12).

Spatiotemporally dynamic electric fields for brain cancer treatment

April 2023

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1 Citation

Physics in Medicine & Biology

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Objective: The treatment of glioblastoma (GBM) using low intensity electric fields (~1 V/cm) is being investigated using multiple implanted bioelectrodes, which was termed intratumoral modulation therapy (IMT). Previous IMT studies theoretically optimized treatment parameters to maximize coverage with rotating fields, which required experimental investigation. In this study, we employed computer simulations to generate spatiotemporally dynamic electric fields, designed and purpose-built an IMT device for in vitro experiments, and evaluated the human GBM cellular responses to these fields. Approach: After measuring the electrical conductivity of the in vitro culturing medium, we designed experiments to evaluate the efficacy of various spatiotemporally dynamic fields: (a) different rotating field magnitudes, (b) rotating vs. non-rotating fields, (c) 200 kHz vs. 10 kHz stimulation, and (d) constructive vs. destructive interference. A custom printed circuit board (PCB) was fabricated to enable four-electrode IMT in a 24-well plate. Patient-derived GBM cells were treated and analyzed for viability using bioluminescence imaging. Main results: The optimal PCB design had electrodes placed 6.3 mm from the center. Spatiotemporally dynamic IMT fields at magnitudes of 1, 1.5, and 2 V/cm reduced GBM cell viability to 58%, 37% and 2% of sham controls respectively. Rotating vs. non-rotating, and 200 kHz vs. 10 kHz fields showed no statistical difference. The rotating configuration yielded a significant reduction (p<0.01) in cell viability (47±4%) compared to the voltage matched (99±2%) and power matched (66±3%) destructive interference cases. Significance: We found the most important factors in GBM cell susceptibility to IMT are electric field strength and homogeneity. Spatiotemporally dynamic electric fields have been evaluated in this study, where improvements to electric field coverage with lower power consumption and minimal field cancellations has been demonstrated. The impact of this optimized paradigm on cell susceptibility justifies its future use in preclinical and clinical trial investigations.

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Paul Christiaans's research while affiliated with The University of Western Ontario and other places

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