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Creators/Authors contains: "Sheng, Z"

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  1. Abstract The Scintillating Bubble Chamber (SBC) collaboration purchased 32 Hamamatsu VUV4 silicon photomultipliers (SiPMs) for use in SBC-LAr10, a bubble chamber containing 10 kg of liquid argon. A dark-count characterization technique, which avoids the use of a single-photon source, was used at two temperatures to measure the VUV4 SiPMs breakdown voltage (VBD), the SiPM gain (gSiPM), the rate of change ofgSiPMwith respect to voltage (m), the dark count rate (DCR), and the probability of a correlated avalanche (PCA) as well as the temperature coefficients of these parameters. A Peltier-based chilled vacuum chamber was developed at Queen's University to cool down the Quads to 233.15 ± 0.2 K and 255.15 ± 0.2 K with average stability of ±20 mK. An analysis framework was developed to estimate VBDto tens of mV precision and DCR close to Poissonian error. The temperature dependence of VBDwas found to be 56 ± 2 mV K-1, andmon average across all Quads was found to be (459 ± 3(stat.)±23(sys.))× 103e-PE-1V-1. The average DCR temperature coefficient was estimated to be 0.099 ± 0.008 K-1corresponding to a reduction factor of 7 for every 20 K drop in temperature. The average temperature dependence of PCAwas estimated to be 4000 ± 1000 ppm K-1. PCAestimated from the average across all SiPMs is a better estimator than the PCAcalculated from individual SiPMs, for all of the other parameters, the opposite is true. All the estimated parameters were measured to the precision required for SBC-LAr10, and the Quads will be used in conditions to optimize the signal-to-noise ratio. 
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  2. High-frequency irreversible electroporation (H-FIRE) is a technique that uses pulsed electric fields that have been shown to ablate malignant cells. In order to evaluate the clinical potential of H-FIRE to treat glioblastoma (GBM), a primary brain tumor, we have studied the effects of high-frequency waveforms on therapy-resistant glioma stem-like cell (GSC) populations. We demonstrate that patient-derived GSCs are more susceptible to H-FIRE damage than primary normal astrocytes. This selectivity presents an opportunity for a degree of malignant cell targeting as bulk tumor cells and tumor stem cells are seen to exhibit similar lethal electric field thresholds, significantly lower than that of healthy astrocytes. However, neural stem cell (NSC) populations also exhibit a similar sensitivity to these pulses. This observation may suggest that different considerations be taken when applying these therapies in younger versus older patients, where the importance of preserving NSC populations may impose different restrictions on use. We also demonstrate variability in threshold among the three patient-derived GSC lines studied, suggesting the need for personalized cell-specific characterization in the development of potential clinical procedures. Future work may provide further useful insights regarding this patient-dependent variability observed that could inform targeted and personalized treatment. 
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