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Identification of hadronic tau lepton decays using a deep neural network
No full textA new algorithm is presented to discriminate reconstructed hadronic decays of tau leptons (τₕ) that originate from genuine tau leptons in the CMS detector against τₕ candidates that originate from quark or gluon jets, electrons, or muons. The algorithm inputs information from all reconstructed particles in the vicinity of a τₕ candidate and employs a deep neural network with convolutional layers to efficiently process the inputs. This algorithm leads to a significantly improved performance compared with the previously used one. For example, the efficiency for a genuine τₕ to pass the discriminator against jets increases by 10–30% for a given efficiency for quark and gluon jets. Furthermore, a more efficient τₕ reconstruction is introduced that incorporates additional hadronic decay modes. The superior performance of the new algorithm to discriminate against jets, electrons, and muons and the improved τₕ reconstruction method are validated with LHC proton-proton collision data at √s = 13 TeV
Cosmic shear in harmonic space from the Dark Energy Survey Year 1 Data: compatibility with configuration space results
No full textWe perform a cosmic shear analysis in harmonic space using the first year of data collected by the Dark Energy Survey (DES-Y1). We measure the cosmic weak lensing shear power spectra using the metacalibration catalogue and perform a likelihood analysis within the framework of CosmoSIS. We set scale cuts based on baryonic effects contamination and model redshift and shear calibration uncertainties as well as intrinsic alignments. We adopt as fiducial covariance matrix an analytical computation accounting for the mask geometry in the Gaussian term, including non-Gaussian contributions. A suite of 1200 lognormal simulations is used to validate the harmonic space pipeline and the covariance matrix. We perform a series of stress tests to gauge the robustness of the harmonic space analysis. Finally, we use the DES-Y1 pipeline in configuration space to perform a similar likelihood analysis and compare both results, demonstrating their compatibility in estimating the cosmological parameters S₈, σ₈, and Ωₘ. We use the DES-Y1 metacalibration shape catalogue, with photometric redshifts estimates in the range of 0.2−1.3, divided in four tomographic bins finding σ₈(Ωₘ/0.3)^(0.5) = 0.766 ± 0.033 at 68 per cent CL. The methods implemented and validated in this paper will allow us to perform a consistent harmonic space analysis in the upcoming DES data
X-ray absorption and reprocessing in the z ∼ 2.5 lensed quasar 2MASS J1042+1641
No full textWe present new broad-band X-ray observations of the z ∼ 2.5 lensed quasar 2MASS J1042+1641, combining XMM–Newton, Chandra, and NuSTAR to provide coverage of the X-ray spectrum over the 0.3–40 keV bandpass in the observed frame, corresponding to the ∼1–140 keV band in the rest frame of 2MASS J1042+1641. The X-ray data show clear evidence for strong (but still Compton-thin) X-ray absorption, NH ∼ 3–4 × 10²³ cm⁻², in addition to significant reprocessing by Compton-thick material that must lie away from our line of sight to the central X-ray source. We test two different interpretations for the latter: first that the reprocessing occurs in a classic active galactic nucleus torus, as invoked in unification models, and second that the reprocessing occurs in the accretion disc. Both models can successfully reproduce the observed spectra, and both imply that the source is viewed at moderately low inclinations (i < 50°) despite the heavy line-of-sight absorption. Combining the X-ray data with infrared (IR) data from WISE, the results seen from 2MASS J1042+1641 further support the recent suggestion that large X-ray and IR surveys may together be able to identify good lensed quasar candidates in advance of detailed imaging studies
¹⁷O Electron Nuclear Double Resonance Analysis of Compound I: Inverse Correlation between Oxygen Spin Population and Electron Donation
No full textAlthough the activation of inert C–H bonds by metal-oxo complexes has been widely studied, important questions remain, particularly regarding the role of oxygen spin population (i.e., unpaired electrons on the oxo ligand) in facilitating C–H bond cleavage. In order to shed light on this issue, we have utilized ¹⁷O electron nuclear double resonance spectroscopy to measure the oxygen spin populations of three compound I intermediates in heme enzymes with different reactivities toward C–H bonds: chloroperoxidase, cytochrome P450, and a selenolate (selenocysteinyl)-ligated cytochrome P450. The experimental data suggest an inverse correlation between oxygen spin population and electron donation from the axial ligand. We have explored the implications of this result using a Hückel-type molecular orbital model and constrained density functional theory calculations. These investigations have allowed us to examine the relationship between oxygen spin population, oxygen charge, electron donation from the axial ligand, and reactivity
Variational quantum optimization with multibasis encodings
No full textDespite extensive research efforts, few quantum algorithms for classical optimization demonstrate a realizable quantum advantage. The utility of many quantum algorithms is limited by high requisite circuit depth and nonconvex optimization landscapes. We tackle these challenges by introducing a variational quantum algorithm that benefits from two innovations: multibasis graph encodings using single-qubit expectation values and nonlinear activation functions. Our technique results in increased observed optimization performance and a factor-of-two reduction in requisite qubits. While the classical simulation of many qubits with traditional quantum formalism is impossible due to its exponential scaling, we mitigate this limitation with exact circuit representations using factorized tensor rings. In particular, the shallow circuits permitted by our technique, combined with efficient factorized tensor-based simulation, enable us to successfully optimize the MaxCut of the 512-vertex DIMACS library graphs on a single GPU. By improving the performance of quantum optimization algorithms while requiring fewer quantum resources and utilizing shallower, more error-resistant circuits, we offer tangible progress for variational quantum optimization
A Pyridine Dearomatization Approach to the Matrine-Type Lupin Alkaloids
No full text(+)-Matrine and (+)-isomatrine are tetracyclic alkaloids isolated from the plant Sophora flavescens, the roots of which are used in traditional Chinese medicine. Biosynthetically, these alkaloids are proposed to derive from three molecules of (−)-lysine via the intermediacy of the unstable cyclic imine Δ1-piperidine. Inspired by the biosynthesis, a new dearomative annulation reaction has been developed that leverages pyridine as a stable surrogate for Δ1-piperidine. In this key transformation, two molecules of pyridine are joined with a molecule of glutaryl chloride to give the complete tetracyclic framework of the matrine alkaloids in a single step. Using this dearomative annulation, isomatrine is synthesized in four steps from inexpensive commercially available chemicals. Isomatrine then serves as the precursor to additional lupin alkaloids, including matrine, allomatrine, isosophoridine, and sophoridine
Listening to the seafloor with optical fibers
No full textMeasurements of seismic ground motion at the seafloor provide critical insights into earthquake and tsunami hazards, deep-Earth structure, plate tectonics, submarine volcanism, and interactions between the ocean and solid Earth. Yet ocean-bottom seismometers (OBSs) and observatories are exceedingly scarce: Although about 70% of Earth’s surface is covered by water, less than 1% of the global network of permanent broadband seismic stations is installed at the seafloor (see “Deploying seismometers where they’re needed most: Underwater,” Physics Today online, 24 May 2019).
The emerging field of fiber-optic seismology offers a promising new paradigm for ocean-bottom instrumentation: distributed sensing rather than point sensing. Submarine fiber-optic cables for intercontinental telecommunications and power transmission traverse the global oceans and can be harnessed for distributed sensor networks. As seismic and ocean waves stretch and compress optical fibers at the seafloor, the light traveling through them encodes valuable information. With distributed acoustic sensing (DAS) and other new fiber-seismic methods, that information can be exploited for geophysical monitoring (see Physics Today, March 2018, page 24). This Quick Study explains how
Dust in the wind with resonant drag instabilities – I. The dynamics of dust-driven outflows in GMCs and Hɪɪ regions
No full textRadiation-dust driven outflows, where radiation pressure on dust grains accelerates gas, occur in many astrophysical environments. Almost all previous numerical studies of these systems have assumed that the dust was perfectly coupled to the gas. However, it has recently been shown that the dust in these systems is unstable to a large class of 'resonant drag instabilities' (RDIs) which de-couple the dust and gas dynamics and could qualitatively change the non-linear outcome of these outflows. We present the first simulations of radiation-dust driven outflows in stratified, inhomogeneous media, including explicit grain dynamics and a realistic spectrum of grain sizes and charge, magnetic fields and Lorentz forces on grains (which dramatically enhance the RDIs), Coulomb and Epstein drag forces, and explicit radiation transport allowing for different grain absorption and scattering properties. In this paper, we consider conditions resembling giant molecular clouds (GMCs), Hɪɪ regions, and distributed starbursts, where optical depths are modest (≲1), single-scattering effects dominate radiation-dust coupling, Lorentz forces dominate over drag on grains, and the fastest-growing RDIs are similar, such as magnetosonic and fast-gyro RDIs. These RDIs generically produce strong size-dependent dust clustering, growing non-linear on time-scales that are much shorter than the characteristic times of the outflow. The instabilities produce filamentary and plume-like or 'horsehead' nebular morphologies that are remarkably similar to observed dust structures in GMCs and Hɪɪ regions. Additionally, in some cases they strongly alter the magnetic field structure and topology relative to filaments. Despite driving strong micro-scale dust clumping which leaves some gas 'behind,' an order-unity fraction of the gas is always efficiently entrained by dust
Public Goods Under Financial Distress
No full textI study the effect of financial crises on local public good provision using novel archival panel data on U.S. cities and municipal bonds during the 1920s and 1930s. Cities issue debt to fund infrastructure projects and provide important public services to residents. However, when a financial crisis occurs, financially leveraged cities can suffer distress and curtail public spending, which may lead to long-term consequences for urban growth. In this paper, I estimate the effect of financial leverage on spending and investment during the Great Depression, a time of little federal support and intergovernmental transfers. I find that distressed cities significantly lowered public expenditure: roughly 20 percent of the drop in public investment is explained through a reallocation of budgets towards debt repayment. In response, I find suggestive evidence that households subsequently relocated away from distressed cities
Mergers, Entry, and Consumer Welfare
No full textWe analyze mergers and entry in oligopoly models of differentiated-products price competition. Under logit or constant elasticity of substitution demands, entry that restores pre-merger consumer surplus renders merger unprofitable. Thus, by revealed preference, it can be appropriate to infer entry barriers in merger review. The result extends to nested and random coefficients demand systems unless the entrant is a distant competitor of the merging firms. We develop modeling frameworks to guide empirical analysis in settings where theory is not dispositive. Applying these to the T-Mobile/Sprint merger, we find the Court may have erred in treating DISH as a merger-induced entrant