455 research outputs found

    Post-earthquake recovery in Nepal

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    Interaction of in-plane Drude carrier with c-axis phonon in PdCoO2\rm PdCoO_2

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    We performed polarized reflection and transmission measurements on the layered conducting oxide PdCoO2\rm PdCoO_2 thin films. For the ab-plane, an optical peak near Ω\Omega ≈\approx 750 cm−1^{-1} drives the scattering rate γ∗(ω)\gamma^{*}(\omega) and effective mass m∗(ω)m^{*}(\omega) of the Drude carrier to increase and decrease respectively for ω\omega ≧\geqq Ω\Omega. For the c-axis, a longitudinal optical phonon (LO) is present at Ω\Omega as evidenced by a peak in the loss function Im[−1/εc(ω)-1/\varepsilon_{c}(\omega)]. Further polarized measurements in different light propagation (q) and electric field (E) configurations indicate that the Peak at Ω\Omega results from an electron-phonon coupling of the ab-plane carrier with the c-LO phonon, which leads to the frequency-dependent γ∗(ω)\gamma^{*}(\omega) and m∗(ω)m^{*}(\omega). This unusual interaction was previously reported in high-temperature superconductors (HTSC) between a non-Drude, mid-infrared band and a c-LO. On the contrary, it is the Drude carrier that couples in PdCoO2\rm PdCoO_2. The coupling between the ab-plane Drude carrier and c-LO suggests that the c-LO phonon may play a significant role in the characteristic ab-plane electronic properties of PdCoO2\rm PdCoO_2 including the ultra-high dc-conductivity, phonon-drag, and hydrodynamic electron transport.Comment: 4 figure

    Interaction of in-plane Drude carrier with c -axis phonon in PdCoO2

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    Funding: E.C. was supported by the NRF-2021R1A2C1009073 of Korea funded by the Ministry of Education. D.S. was partially supported by MOLIT as an Innovative Talent Education Program for Smart City. The work at Rutgers University is supported by the National Science Foundation’s DMR2004125 and the Army Research Office’s W911NF2010108. S.B.C. was supported by the National Research Foundation of Korea (NRF) grants funded by the Korean government (MSIT)(NRF-2023R1A2C1006144, NRF-2020R1A2C1007554, and NRF-2018R1A6A1A06024977). Research in Dresden benefits from the environment provided by the DFG Cluster of Excellence ct.qmat (EXC 2147, project ID 390858490). The work at HYU was supported by the NRF grant funded by the Korean government (MSIT) (2022R1F1A1072865), the BrainLink program funded by MSIT (2022H1D3A3A01077468), and the Quantum Simulator Development Project for Materials Innovation through the NRF funded by MSIT (2023M3K5A1094813).We performed polarized reflection and transmission measurements on the layered conducting oxide PdCoO2 thin films. For the ab-plane, an optical peak near Ω ≈ 750 cm−1 drives the scattering rate 1/τ(ω) and effective mass m*(ω) of the Drude carrier to increase and decrease respectively for ω ≧ Ω. For the c-axis, a longitudinal optical phonon (LO) is present at Ω as evidenced by a peak in the loss function Im[−1/εc(ω)]. Further polarized measurements in different light propagation (q) and electric field (E) configurations indicate that the Peak at Ω results from an electron-phonon coupling of the ab-plane carrier with the c-LO phonon, which leads to the frequency-dependent 1/τ(ω) and m*(ω). This unusual interaction was previously reported in high-temperature superconductors (HTSC) between a non-Drude, mid-infrared (IR) band and a c-LO. On the contrary, it is the Drude carrier that couples in PdCoO2. The coupling between the ab-plane Drude carrier and c-LO suggests that the c-LO phonon may play a significant role in the characteristic ab-plane electronic properties of PdCoO2, including the ultra-high dc-conductivity, phonon-drag, and hydrodynamic electron transport.Publisher PDFPeer reviewe

    Measurement of Two-Photon Exchange Effect by Comparing Elastic e ± p Cross Sections

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    Background: The electromagnetic form factors of the proton measured by unpolarized and polarized electron scattering experiments show a significant disagreement that grows with the squared four-momentum transfer (Q2) . Calculations have shown that the two measurements can be largely reconciled by accounting for the contributions of two-photon exchange (TPE). TPE effects are not typically included in the standard set of radiative corrections since theoretical calculations of the TPE effects are highly model dependent, and, until recently, no direct evidence of significant TPE effects has been observed. Purpose: We measured the ratio of positron-proton to electron-proton elastic-scattering cross sections in order to determine the TPE contribution to elastic electron-proton scattering and thereby resolve the proton electric form factor discrepancy. Methods: We produced a mixed simultaneous electron-positron beam in Jefferson Lab\u27s Hall B by passing the 5.6-GeV primary electron beam through a radiator to produce a bremsstrahlung photon beam and then passing the photon beam through a convertor to produce electron-positron pairs. The mixed electron-positron (lepton) beam with useful energies from approximately 0.85 to 3.5 GeV then struck a 30-cm-long liquid hydrogen (LH2) target located within the CEBAF Large Acceptance Spectrometer (CLAS). By detecting both the scattered leptons and the recoiling protons, we identified and reconstructed elastic scattering events and determined the incident lepton energy. A detailed description of the experiment is presented. Results: We present previously unpublished results for the quantity R2γ , the TPE correction to the elastic-scattering cross section, at Q2 ≈ 0.85 and 1.45 GeV2 over a large range of virtual photon polarization ɛ . Conclusions: Our results, along with recently published results from VEPP-3, demonstrate a nonzero contribution from TPE effects and are in excellent agreement with the calculations that include TPE effects and largely reconcile the form-factor discrepancy up to Q2 ≈ 2 GeV2 . These data are consistent with an increase in R2γ with decreasing ɛ at Q2 ≈ 0.85 and 1.45 GeV2 . There are indications of a slight increase in R2γ with Q2

    Reducing model bias in a deep learning classifier using domain adversarial neural networks in the MINERvA experiment

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    We present a simulation-based study using deep convolutional neural networks (DCNNs) to identify neutrino interaction vertices in the MINERvA passive targets region, and illustrate the application of domain adversarial neural networks (DANNs) in this context. DANNs are designed to be trained in one domain (simulated data) but tested in a second domain (physics data) and utilize unlabeled data from the second domain so that during training only features which are unable to discriminate between the domains are promoted. MINERvA is a neutrino-nucleus scattering experiment using the NuMI beamline at Fermilab. AA-dependent cross sections are an important part of the physics program, and these measurements require vertex finding in complicated events. To illustrate the impact of the DANN we used a modified set of simulation in place of physics data during the training of the DANN and then used the label of the modified simulation during the evaluation of the DANN. We find that deep learning based methods offer significant advantages over our prior track-based reconstruction for the task of vertex finding, and that DANNs are able to improve the performance of deep networks by leveraging available unlabeled data and by mitigating network performance degradation rooted in biases in the physics models used for training.Comment: 41 page

    How Accessible Was Information about H1N1 Flu? Literacy Assessments of CDC Guidance Documents for Different Audiences

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    We assessed the literacy level and readability of online communications about H1N1/09 influenza issued by the Centers for Disease Control and Prevention (CDC) during the first month of outbreak. Documents were classified as targeting one of six audiences ranging in technical expertise. Flesch-Kincaid (FK) measure assessed literacy level for each group of documents. ANOVA models tested for differences in FK scores across target audiences and over time. Readability was assessed for documents targeting non-technical audiences using the Suitability Assessment of Materials (SAM). Overall, there was a main-effect by audience, F(5, 82) = 29.72, P<.001, but FK scores did not vary over time, F(2, 82) = .34, P>.05. A time-by-audience interaction was significant, F(10, 82) = 2.11, P<.05. Documents targeting non-technical audiences were found to be text-heavy and densely-formatted. The vocabulary and writing style were found to adequately reflect audience needs. The reading level of CDC guidance documents about H1N1/09 influenza varied appropriately according to the intended audience; sub-optimal formatting and layout may have rendered some text difficult to comprehend
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