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  1. Free, publicly-accessible full text available December 31, 2023
  2. Abstract Sensitive dispersive readouts of single-electron devices (“gate reflectometry”) rely on one-port radio-frequency (RF) reflectometry to read out the state of the sensor. A standard practice in reflectometry measurements is to design an impedance transformer to match the impedance of the load to the characteristic impedance of the transmission line and thus obtain the best sensitivity and signal-to-noise ratio. This is particularly important for measuring large impedances, typical for dispersive readouts of single-electron devices because even a small mismatch will cause a strong signal degradation. When performing RF measurements, a calibration and error correction of the measurement apparatus must bemore »performed in order to remove errors caused by unavoidable non-idealities of the measurement system. Lack of calibration makes optimizing a matching network difficult and ambiguous, and it also prevents a direct quantitative comparison between measurements taken of different devices or on different systems. We propose and demonstrate a simple straightforward method to design and optimize a pi matching network for readouts of devices with large impedance, $$Z \ge 1\hbox {M}\Omega$$ Z ≥ 1 M Ω . It is based on a single low temperature calibrated measurement of an unadjusted network composed of a single L-section followed by a simple calculation to determine a value of the “balancing” capacitor needed to achieve matching conditions for a pi network. We demonstrate that the proposed calibration/error correction technique can be directly applied at low temperature using inexpensive calibration standards. Using proper modeling of the matching networks adjusted for low temperature operation the measurement system can be easily optimized to achieve the best conditions for energy transfer and targeted bandwidth, and can be used for quantitative measurements of the device impedance. In this work we use gate reflectometry to readout the signal generated by arrays of parallel-connected Al-AlOx single-electron boxes. Such arrays can be used as a fast nanoscale voltage sensor for scanning probe applications. We perform measurements of sensitivity and bandwidth for various settings of the matching network connected to arrays and obtain strong agreement with the simulations.« less
    Free, publicly-accessible full text available December 1, 2023
  3. Abstract The Southern Ocean paleoceanography provides key insights into how iron fertilization and oceanic productivity developed through Pleistocene ice-ages and their role in influencing the carbon cycle. We report a high-resolution record of dust deposition and ocean productivity for the Antarctic Zone, close to the main dust source, Patagonia. Our deep-ocean records cover the last 1.5 Ma, thus doubling that from Antarctic ice-cores. We find a 5 to 15-fold increase in dust deposition during glacials and a 2 to 5-fold increase in biogenic silica deposition, reflecting higher ocean productivity during interglacials. This antiphasing persisted throughout the last 25 glacial cycles. Dustmore »deposition became more pronounced across the Mid-Pleistocene Transition (MPT) in the Southern Hemisphere, with an abrupt shift suggesting more severe glaciations since ~0.9 Ma. Productivity was intermediate pre-MPT, lowest during the MPT and highest since 0.4 Ma. Generally, glacials experienced extended sea-ice cover, reduced bottom-water export and Weddell Gyre dynamics, which helped lower atmospheric CO 2 levels.« less
    Free, publicly-accessible full text available December 1, 2023
  4. Abstract The population-level distributions of the masses, spins, and redshifts of binary black holes (BBHs) observed using gravitational waves can shed light on how these systems form and evolve. Because of the complex astrophysical processes shaping the inferred BBH population, models allowing for correlations among these parameters will be necessary to fully characterize these sources. We hierarchically analyze the BBH population detected by LIGO and Virgo with a model allowing for correlations between the effective aligned spin and the primary mass and redshift. We find that the width of the effective spin distribution grows with redshift at 98.6% credibility. Wemore »determine this trend to be robust under the application of several alternative models and additionally verify that such a correlation is unlikely to be spuriously introduced using a simulated population. We discuss the possibility that this correlation could be due to a change in the natal black hole spin distribution with redshift.« less
    Free, publicly-accessible full text available June 1, 2023
  5. Free, publicly-accessible full text available May 3, 2023
  6. Hexacoordinate silicon pincer complexes using 2,6-bis(benzimidazol-2-yl)pyridine (bzimpy) ligands have been developed as a multifunctional, molecular electronic materials platform. We report the synthesis, characterization, and device application of a variety of Si(pincer) 2 complexes that exhibit tunable optoelectronic properties and excellent thermal stabilities. Promising, ambipolar charge carrier properties and excimeric electroluminescence were obtained from thermally deposited films using several device architectures. Incorporation of the complexes as a thin, interfacial contact and electron transport layer improved organic solar cell efficiencies by as much as 50%. The versatility and tailorability of this class of silicon complexes provides promising evidence for their future applicationmore »in molecular electronic devices.« less
    Free, publicly-accessible full text available March 8, 2023
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  8. Free, publicly-accessible full text available April 25, 2023
  9. Scientific instruments have long been a vital part of science, paving pathways to remarkable scientific advancements. Such advancements have changed the world both socially and culturally, especially in the past few decades. Students can be introduced to this idea through the concepts of nature of science (NOS): scientific observations are often filtered through apparatus, inferences can be made through observations, and science is a socially and culturally embedded practice. The curriculum often fails to emphasize the role of instruments in scientific practices, even in teaching laboratories. This study uses semistructured interviews to investigate the cognitive (thoughts) and affective (feelings) domainsmore »of first-year university students as they relate to scientific instrumentation, including students’ ideas of instruments. First, the study probed how general chemistry students conceptualize scientific instruments in relation to the three NOS notions. Second, students’ practices related to experimental data evaluation were investigated as data collection is a large part of psychomotor learning in laboratory. Third, students’ affective states toward learning about instruments were queried. The interview results suggested that a majority of participants acknowledge some ideas of NOS, while a few students displayed an advanced understanding when discussing scientific instruments and also tended to have higher interest and motivation toward learning about instruments.« less
    Free, publicly-accessible full text available December 13, 2022
  10. Free, publicly-accessible full text available March 1, 2023