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  1. Chaudhuri, Kamalika ; Jegelka, Stefanie ; Song, Le ; Szepesvari, Csaba ; Niu, Gang ; Sabato, Sivan (Ed.)
    We introduce a novel framework for optimization based on energy-conserving Hamiltonian dynamics in a strongly mixing (chaotic) regime and establish its key properties analytically and numerically. The prototype is a discretization of Born-Infeld dynamics, with a squared relativistic speed limit depending on the objective function. This class of frictionless, energy-conserving optimizers proceeds unobstructed until slowing naturally near the minimal loss, which dominates the phase space volume of the system. Building from studies of chaotic systems such as dynamical billiards, we formulate a specific algorithm with good performance on machine learning and PDE-solving tasks, including generalization. It cannot stop at a high local minimum, an advantage in non-convex loss functions, and proceeds faster than GD+momentum in shallow valleys. 
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  2. In this study, a suite of natural wastewater sources is tested to understand the effects of wastewater composition and source on electrochemically driven nitrogen and phosphorus nutrient removal. Kinetics, electrode behavior, and removal efficiency were evaluated during electrochemical precipitation, whereby a sacrificial magnesium (Mg) anode was used to drive precipitation of ammonium and phosphate. The electrochemical reactor demonstrated fast kinetics in the natural wastewater matrices, removing up to 54% of the phosphate present in natural wastewater within 1 min, with an energy input of only 0.04 kWh.m−3. After 1 min, phosphate removal followed a zero-order rate law in the 1 min - 30 min range. The zero-order rate constant (k) appears to depend upon differences in wastewater composition, where a faster rate constant is associated with higher Cl− and NH4+ concentrations, lower Ca2+ concentrations, and higher organic carbon content. The sacrificial Mg anode showed the lowest corrosion resistance in the natural industrial wastewater source, with an increased corrosion rate (vcorr) of 15.8 mm.y−1 compared to 1.9–3.5 mm.y−1 in municipal wastewater sources, while the Tafel slopes (β) showed a direct correlation with the natural wastewater composition and origin. An overall improvement of water quality was observed where important water quality parameters such as total organic carbon (TOC), total suspended solids (TSS), and turbidity showed a significant decrease. An economic analysis revealed costs based upon experimental Mg consumption are estimated to range from 0.19 $.m−3 to 0.30 $.m−3, but costs based upon theoretical Mg consumption range from 0.09 $.m−3 to 0.18 $.m−3. Overall, this study highlights that water chemistry parameters control nutrient recovery, while electrochemical treatment does not directly produce potable water, and that economic analysis should be based upon experimentally-determined Mg consumption data. 
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  3. In this work, we expand on the XENON1T nuclear recoil searches to study the individual signals of dark matter interactions from operators up to dimension eight in a chiral effective field theory (ChEFT) and a model of inelastic dark matter (iDM). We analyze data from two science runs of the XENON1T detector totaling1t×yrexposure. For these analyses, we extended the region of interest from[4.9,40.9]keVNRto[4.9,54.4]keVNRto enhance our sensitivity for signals that peak at nonzero energies. We show that the data are consistent with the background-only hypothesis, with a small background overfluctuation observed peaking between 20 and50keVNR, resulting in a maximum local discovery significance of1.7σfor theVectorVectorstrangeChEFT channel for a dark matter particle of70GeV/c2and1.8σfor an iDM particle of50GeV/c2with a mass splitting of100keV/c2. For each model, we report 90% confidence level upper limits. We also report upper limits on three benchmark models of dark matter interaction using ChEFT where we investigate the effect of isospin-breaking interactions. We observe rate-driven cancellations in regions of the isospin-breaking couplings, leading to up to 6 orders of magnitude weaker upper limits with respect to the isospin-conserving case.

    <supplementary-material><permissions><copyright-statement>Published by the American Physical Society</copyright-statement><copyright-year>2024</copyright-year></permissions></supplementary-material></sec> </div> <a href='#' class='show open-abstract' style='margin-left:10px;'>more »</a> <a href='#' class='hide close-abstract' style='margin-left:10px;'>« less</a> <div class="actions" style="padding-left:10px;"> <span class="reader-count"> Free, publicly-accessible full text available June 1, 2025</span> </div> </div><div class="clearfix"></div> </div> </li> <li> <div class="article item document" itemscope itemtype=""> <div class="item-info"> <div class="title"> <a href="" itemprop="url"> <span class='span-link' itemprop="name">Chromosome Structural Mechanics Dictates the Local Spreading of Epigenetic Marks</span> </a> </div> <div> <strong> <a class="misc external-link" href="" target="_blank" title="Link to document DOI">  <span class="fas fa-external-link-alt"></span></a> </strong> </div> <div class="metadata"> <span class="authors"> <span class="author" itemprop="author">Sandholtz, Sarah H.</span> <span class="sep">; </span><span class="author" itemprop="author">Kannan, Deepti</span> <span class="sep">; </span><span class="author" itemprop="author">Beltran, Bruno G.</span> <span class="sep">; </span><span class="author" itemprop="author">Spakowitz, Andrew J.</span> </span> <span class="year">( <time itemprop="datePublished" datetime="2020-10-01">October 2020</time> , Biophysical Journal) </span> </div> <span class="editors"> <span class="editor" itemprop="editor">null</span> (Ed.) </span> <div class="actions" style="padding-left:10px;"> <span class="reader-count"> <a class="misc external-link" href="" target="_blank" title="Link to document DOI" data-ostiid="10290263"> Full Text Available <span class="fas fa-external-link-alt"></span> </a> </span> </div> </div><div class="clearfix"></div> </div> </li> <li> <div class="article item document" itemscope itemtype=""> <div class="item-info"> <div class="title"> <a href="" itemprop="url"> <span class='span-link' itemprop="name">Design and performance of the field cage for the XENONnT experiment</span> </a> </div> <div> <strong> <a class="misc external-link" href="" target="_blank" title="Link to document DOI">  <span class="fas fa-external-link-alt"></span></a> </strong> </div> <div class="metadata"> <span class="authors"> <span class="author" itemprop="author">Aprile, E</span> <span class="sep">; </span><span class="author" itemprop="author">Abe, K</span> <span class="sep">; </span><span class="author" itemprop="author">Ahmed_Maouloud, S</span> <span class="sep">; </span><span class="author" itemprop="author">Althueser, L</span> <span class="sep">; </span><span class="author" itemprop="author">Andrieu, B</span> <span class="sep">; </span><span class="author" itemprop="author">Angelino, E</span> <span class="sep">; </span><span class="author" itemprop="author">Angevaare, J R</span> <span class="sep">; </span><span class="author" itemprop="author">Antochi, V C</span> <span class="sep">; </span><span class="author" itemprop="author">Antón_Martin, D</span> <span class="sep">; </span><span class="author" itemprop="author">Arneodo, F</span> <span class="sep">; </span><span class="author">et al</span></span> <span class="year">( <time itemprop="datePublished" datetime="2024-02-08">February 2024</time> , The European Physical Journal C) </span> </div> <div style="cursor: pointer;-webkit-line-clamp: 5;" class="abstract" itemprop="description"> <title>Abstract

    The precision in reconstructing events detected in a dual-phase time projection chamber depends on an homogeneous and well understood electric field within the liquid target. In the XENONnT TPC the field homogeneity is achieved through a double-array field cage, consisting of two nested arrays of field shaping rings connected by an easily accessible resistor chain. Rather than being connected to the gate electrode, the topmost field shaping ring is independently biased, adding a degree of freedom to tune the electric field during operation. Two-dimensional finite element simulations were used to optimize the field cage, as well as its operation. Simulation results were compared to$${}^{83\textrm{m}}\hbox {Kr }$$83mKrcalibration data. This comparison indicates an accumulation of charge on the panels of the TPC which is constant over time, as no evolution of the reconstructed position distribution of events is observed. The simulated electric field was then used to correct the charge signal for the field dependence of the charge yield. This correction resolves the inconsistent measurement of the drift electron lifetime when using different calibrations sources and different field cage tuning voltages.

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    Free, publicly-accessible full text available February 8, 2025
  4. null (Ed.)
  5. Abstract

    Xenon dual-phase time projections chambers (TPCs) have proven to be a successful technology in studying physical phenomena that require low-background conditions. With$$40\,\textrm{t}$$40tof liquid xenon (LXe) in the TPC baseline design, DARWIN will have a high sensitivity for the detection of particle dark matter, neutrinoless double beta decay ($$0\upnu \upbeta \upbeta $$0νββ), and axion-like particles (ALPs). Although cosmic muons are a source of background that cannot be entirely eliminated, they may be greatly diminished by placing the detector deep underground. In this study, we used Monte Carlo simulations to model the cosmogenic background expected for the DARWIN observatory at four underground laboratories: Laboratori Nazionali del Gran Sasso (LNGS), Sanford Underground Research Facility (SURF), Laboratoire Souterrain de Modane (LSM) and SNOLAB. We present here the results of simulations performed to determine the production rate of$${}^{137}$$137Xe, the most crucial isotope in the search for$$0\upnu \upbeta \upbeta $$0νββof$${}^{136}$$136Xe. Additionally, we explore the contribution that other muon-induced spallation products, such as other unstable xenon isotopes and tritium, may have on the cosmogenic background.

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  6. Free, publicly-accessible full text available October 1, 2024