Opinion: we need better data about the environmental persistence of plastic goods

Author Posting. © National Academy of Sciences, 2020. This article is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 117(26), (2020): 14618-14621, doi:10.1073/pnas.2008009117.Plastic pollution is one of the most visible and complex environmental issues today. Interested and concerned parties include researchers, governmental agencies, nongovernmental organizations, industry, media, and the general public. One key assumption behind the issue and the public outcry is that plastics last indefinitely in the environment, resulting in chronic exposure that harms animals and humans. But the data supporting this assumption are scant.We thank Briana Prado, Cassia Armstrong, and Anna Walsh for their help with the review, Kenneth Kostel, Katie Linehan, Daniel Ward, and Rose Cory for feedback on an earlier version of this piece, John Furfey for assistance with tracking down the original sources of the environmental lifetime estimates, and Natalie Reiner for help with Fig. 1. We acknowledge financial support from Woods Hole Oceanographic Institution (Woods Hole, MA) and the Seaver Institute (Los Angeles, CA).2020-12-1

Clues to Quasar Broad Line Region Geometry and Kinematics

We present evidence that the high-velocity CIV lambda 1549 emission line gas of radio-loud quasars may originate in a disk-like configuration, in close proximity to the accretion disk often assumed to emit the low-ionization lines. For a sample of 36 radio-loud z~2 quasars we find the 20--30% peak width to show significant inverse correlations with the fractional radio core-flux density, R, the radio axis inclination indicator. Highly inclined systems have broader line wings, consistent with a high-velocity field perpendicular to the radio axis. By contrast, the narrow line-core shows no such relation with R, so the lowest velocity CIV-emitting gas has an inclination independent velocity field. We propose that this low-velocity gas is located at higher disk-altitudes than the high-velocity gas. A planar origin of the high-velocity CIV-emission is consistent with the current results and with an accretion disk-wind emitting the broad lines. A spherical distribution of randomly orbiting broad-line clouds and a polar high-ionization outflow are ruled out.Comment: 5 Latex pages, 1 figure, accepted for publication in ApJ Letter

Improved TPB-coated Light Guides for Liquid Argon TPC Light Detection Systems

Scintillation light produced in liquid argon (LAr) must be shifted from 128 nm to visible wavelengths in light detection systems used for liquid argon time-projection chambers (LArTPCs). To date, LArTPC light collection systems have employed tetraphenyl butadiene (TPB) coatings on photomultiplier tubes (PMTs) or plates placed in front of the PMTs. Recently, a new approach using TPB-coated light guides was proposed. In this paper, we report on light guides with improved attenuation lengths above 100 cm when measured in air. This is an important step in the development of meter-scale light guides for future LArTPCs. Improvements come from using a new acrylic-based coating, diamond-polished cast UV transmitting acrylic bars, and a hand-dipping technique to coat the bars. We discuss a model for connecting bar response in air to response in liquid argon and compare this to data taken in liquid argon. The good agreement between the prediction of the model and the measured response in liquid argon demonstrates that characterization in air is sufficient for quality control of bar production. This model can be used in simulations of light guides for future experiments.Comment: 25 pages, 20 figure

Cu NMR evidence for enhanced antiferromagnetic correlations around Zn impurities in YBa2Cu3O6.7

Doping the high-Tc superconductor YBa2Cu3O6.7 with 1.5 % of non-magnetic Zn impurities in CuO2 planes is shown to produce a considerable broadening of 63Cu NMR spectra, as well as an increase of low-energy magnetic fluctuations detected in 63Cu spin-lattice relaxation measurements. A model-independent analysis demonstrates that these effects are due to the development of staggered magnetic moments on many Cu sites around each Zn and that the Zn-induced moment in the bulk susceptibility might be explained by this staggered magnetization. Several implications of these enhanced antiferromagnetic correlations are discussed.Comment: 4 pages including 2 figure

Intrinsic susceptibility and bond defects in the novel 2D frustrated antiferromagnet Ba2_{2}Sn2_{2}ZnCr7p_{7p}Ga10−7p_{10-7p}O22_{22}

We present microscopic and macroscopic magnetic properties of the highly frustrated antiferromagnet Ba$_{2}$Sn$_{2}$ZnCr$_{7p}$Ga$_{10-7p}$O$_{22}$, respectively probed with NMR and SQUID experiments. The $T$-variation of the intrinsic susceptibility of the Cr$^{3+}$ frustrated kagom\'{e} bilayer, $\chi_{kag}$, displays a maximum around 45 K. The dilution of the magnetic lattice has been studied in detail for $0.29 \leq p \leq0.97$. Novel dilution independent defects, likely related with magnetic bond disorder, are evidenced and discussed. We compare our results to SrCr$_{9p}$Ga$_{12-9p}$O$_{19}$. Both bond defects and spin vacancies do not affect the average susceptibility of the kagom\'{e} bilayers.Comment: Published in Phys. Rev. Lett. 92, 217202 (2004). Only minor changes as compared to previous version. 4 pages, 4 figure

The Effects of Dissolved Methane upon Liquid Argon Scintillation Light

In this paper we report on measurements of the effects of dissolved methane upon argon scintillation light. We monitor the light yield from an alpha source held 20 cm from a cryogenic photomultiplier tube (PMT) assembly as methane is injected into a high-purity liquid argon volume. We observe significant suppression of the scintillation light yield by dissolved methane at the 10 part per billion (ppb) level. By examining the late scintillation light time constant, we determine that this loss is caused by an absorption process and also see some evidence of methane-induced scintillation quenching at higher concentrations (50-100 ppb). Using a second PMT assembly we look for visible re-emission features from the dissolved methane which have been reported in gas-phase argon methane mixtures, and we find no evidence of visible re-emission from liquid-phase argon methane mixtures at concentrations between 10 ppb and 0.1%.Comment: 18 pages, 11 figures Updated to match published versio

Measuring microwave quantum states: tomogram and moments

Two measurable characteristics of microwave one-mode photon states are discussed: a rotated quadrature distribution (tomogram) and normally/antinormally ordered moments of photon creation and annihilation operators. Extraction of these characteristics from amplified microwave signal is presented. Relations between the tomogram and the moments are found and can be used as a cross check of experiments. Formalism of the ordered moments is developed. The state purity and generalized uncertainty relations are considered in terms of moments. Unitary and non-unitary time evolution of moments is obtained in the form of linear differential equations in contrast to partial differential equations for quasidistributions. Time evolution is specified for the cases of a harmonic oscillator and a damped harmonic oscillator, which describe noiseless and decoherence processes, respectively.Comment: 10 pages, 1 figure, to appear in Phys. Rev.

Normal State Magnetic Properties of Ni and Zn Substituted in YBa_{2}Cu_{3} O_{6+x}: Hole-Doping Dependence

We present SQUID susceptibility data on Zn and Ni substituted YBa_{2}Cu_{3}O_{6+x}. Cross-checks with NMR yield an unprecedented accuracy in the estimate of the magnetic susceptibility associated with the substituants, from the underdoped to the lightly overdoped case. This allows us to determine the Weiss temperature \theta for YBCO: its value is very small for all hole dopings n_h. Since in conventional metals, the Kondo temperature, $T_{K}<\theta$, magnetic screening effects would not be expected for $T\gg \theta$; in contrast, increasing n_h produces a reduction of the small moment induced by Zn^{2+} and a nearly constant effective moment for Ni^{2+} corresponding to a spin 1/2 rather than to a spin 1.Comment: 4 pages, 5 figures, to be published in Europhysics Letter

On homogenization of electromagnetic crystals formed by uniaxial resonant scatterers

Dispersion properties of electromagnetic crystals formed by small uniaxial resonant scatterers (magnetic or electric) are studied using the local field approach. The goal of the study is to determine the conditions under which the homogenization of such crystals can be made. Therefore the consideration is limited by the frequency region where the wavelength in the host medium is larger than the lattice periods. It is demonstrated that together with known restriction for the homogenization related with the large values of the material parameters there is an additional restriction related with their small absolute values. From the other hand, the homogenization becomes allowed in both cases of large and small material parameters for special directions of propagation. Two unusual effects inherent to the crystals under consideration are revealed: flat isofrequency contour which allows subwavelength imaging using canalization regime and birefringence of extraordinary modes which can be used for beam splitting.Comment: 16 pages, 12 figures, submitted to PR