1
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Yang F, Bai R, Zibrov AA, Joy S, Taniguchi T, Watanabe K, Skinner B, Goerbig MO, Young AF. Cascade of Multielectron Bubble Phases in Monolayer Graphene at High Landau Level Filling. Phys Rev Lett 2023; 131:226501. [PMID: 38101367 DOI: 10.1103/physrevlett.131.226501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Accepted: 10/23/2023] [Indexed: 12/17/2023]
Abstract
The phase diagram of an interacting two-dimensional electron system in a high magnetic field is enriched by the varying form of the effective Coulomb interaction, which depends strongly on the Landau level index. While the fractional quantum Hall states that dominate in the lower-energy Landau levels have been explored experimentally in a variety of two-dimensional systems, much less work has been done to explore electron solids owing to their subtle transport signatures and extreme sensitivity to disorder. Here, we use chemical potential measurements to map the phase diagram of electron solid states in N=2, N=3, and N=4 Landau levels in monolayer graphene. Direct comparison between our data and theoretical calculations reveals a cascade of density-tuned phase transitions between electron bubble phases up to two, three, or four electrons per bubble in the N=2, 3, and 4 Landau levels, respectively. Finite-temperature measurements are consistent with melting of the solids for T≈1 K.
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Affiliation(s)
- Fangyuan Yang
- Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106, USA
| | - Ruiheng Bai
- Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106, USA
| | - Alexander A Zibrov
- Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106, USA
| | - Sandeep Joy
- Department of Physics, Ohio State University, Columbus, Ohio 43210, USA
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Brian Skinner
- Department of Physics, Ohio State University, Columbus, Ohio 43210, USA
| | - Mark O Goerbig
- Laboratoire de Physique des Solides, CNRS UMR 8502, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - Andrea F Young
- Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106, USA
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2
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Hui A, Skinner B. Current Noise of Hydrodynamic Electrons. Phys Rev Lett 2023; 130:256301. [PMID: 37418728 DOI: 10.1103/physrevlett.130.256301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 05/04/2023] [Indexed: 07/09/2023]
Abstract
A resistor at finite temperature produces white noise fluctuations of the current called Johnson-Nyquist noise. Measuring the amplitude of this noise provides a powerful primary thermometry technique to access the electron temperature. In practical situations, however, one needs to generalize the Johnson-Nyquist theorem to handle spatially inhomogeneous temperature profiles. Recent work provided such a generalization for Ohmic devices obeying the Wiedemann-Franz law, but there is a need to provide a similar generalization for hydrodynamic electron systems, since hydrodynamic electrons provide unusual sensitivity for Johnson noise thermometry but they do not admit a local conductivity nor obey the Wiedemann-Franz law. Here we address this need by considering low-frequency Johnson noise in the hydrodynamic setting for a rectangular geometry. Unlike in the Ohmic setting, we find that the Johnson noise is geometry dependent due to nonlocal viscous gradients. Nonetheless, ignoring the geometric correction only leads to an error of at most 40% as compared to naively using the Ohmic result.
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Affiliation(s)
- Aaron Hui
- Department of Physics, Ohio State University, Columbus, Ohio 43202, USA
| | - Brian Skinner
- Department of Physics, Ohio State University, Columbus, Ohio 43202, USA
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3
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Falson J, Sodemann I, Skinner B, Tabrea D, Kozuka Y, Tsukazaki A, Kawasaki M, von Klitzing K, Smet JH. Competing correlated states around the zero-field Wigner crystallization transition of electrons in two dimensions. Nat Mater 2022; 21:311-316. [PMID: 34949813 DOI: 10.1038/s41563-021-01166-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 11/04/2021] [Indexed: 06/14/2023]
Abstract
The competition between kinetic energy and Coulomb interactions in electronic systems leads to complex many-body ground states with competing orders. Here we present zinc oxide-based two-dimensional electron systems as a high-mobility system to study the low-temperature phases of strongly interacting electrons. An analysis of the electronic transport provides evidence for competing correlated metallic and insulating states with varying degrees of spin polarization. Some features bear quantitative resemblance to quantum Monte Carlo simulation results, including the transition point from the paramagnetic Fermi liquid to Wigner crystal and the absence of a Stoner transition. At very low temperatures, we resolve a non-monotonic spin polarizability of electrons across the phase transition, pointing towards a low spin phase of electrons, and a two-order-of-magnitude positive magnetoresistance that is challenging to understand within traditional metallic transport paradigms. This work establishes zinc oxide as a platform for studying strongly correlated electrons in two dimensions.
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Affiliation(s)
- J Falson
- Max-Planck-Institute for Solid State Research, Stuttgart, Germany.
- Department of Applied Physics and Materials Science, California Institute of Technology, Pasadena, CA, USA.
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA, USA.
| | - I Sodemann
- Institut für Theoretische Physik, Universität Leipzig, Leipzig, Germany
- Max-Planck-Institute for the Physics of Complex Systems, Dresden, Germany
| | - B Skinner
- Department of Physics, Ohio State University, Columbus, OH, USA
| | - D Tabrea
- Max-Planck-Institute for Solid State Research, Stuttgart, Germany
| | - Y Kozuka
- Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science, Tsukuba, Japan
- PRESTO, JST, Kawaguchi, Japan
| | - A Tsukazaki
- Institute for Materials Research, Tohoku University, Sendai, Japan
| | - M Kawasaki
- Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
| | - K von Klitzing
- Max-Planck-Institute for Solid State Research, Stuttgart, Germany
| | - J H Smet
- Max-Planck-Institute for Solid State Research, Stuttgart, Germany
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4
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Waissman J, Anderson LE, Talanov AV, Yan Z, Shin YJ, Najafabadi DH, Rezaee M, Feng X, Nocera DG, Taniguchi T, Watanabe K, Skinner B, Matveev KA, Kim P. Electronic thermal transport measurement in low-dimensional materials with graphene non-local noise thermometry. Nat Nanotechnol 2022; 17:166-173. [PMID: 34782778 DOI: 10.1038/s41565-021-01015-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 09/22/2021] [Indexed: 06/13/2023]
Abstract
In low-dimensional systems, the combination of reduced dimensionality, strong interactions and topology has led to a growing number of many-body quantum phenomena. Thermal transport, which is sensitive to all energy-carrying degrees of freedom, provides a discriminating probe of emergent excitations in quantum materials and devices. However, thermal transport measurements in low dimensions are dominated by the phonon contribution of the lattice, requiring an experimental approach to isolate the electronic thermal conductance. Here we measured non-local voltage fluctuations in a multi-terminal device to reveal the electronic heat transported across a mesoscopic bridge made of low-dimensional materials. Using two-dimensional graphene as a noise thermometer, we measured the quantitative electronic thermal conductance of graphene and carbon nanotubes up to 70 K, achieving a precision of ~1% of the thermal conductance quantum at 5 K. Employing linear and nonlinear thermal transport, we observed signatures of energy transport mediated by long-range interactions in one-dimensional electron systems, in agreement with a theoretical model.
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Affiliation(s)
- Jonah Waissman
- Department of Physics, Harvard University, Cambridge, MA, USA
| | | | - Artem V Talanov
- Department of Physics, Harvard University, Cambridge, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Zhongying Yan
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - Young J Shin
- Department of Physics, Harvard University, Cambridge, MA, USA
| | | | - Mehdi Rezaee
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Xiaowen Feng
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Daniel G Nocera
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Brian Skinner
- Department of Physics, The Ohio State University, Columbus, OH, USA
| | | | - Philip Kim
- Department of Physics, Harvard University, Cambridge, MA, USA.
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.
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5
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Abstract
A number of epidemics, including the SARS-CoV-1 epidemic of 2002-2004, have been known to exhibit superspreading, in which a small fraction of infected individuals is responsible for the majority of new infections. The existence of superspreading implies a fat-tailed distribution of infectiousness (new secondary infections caused per day) among different individuals. Here, we present a simple method to estimate the variation in infectiousness by examining the variation in early-time growth rates of new cases among different subpopulations. We use this method to estimate the mean and variance in the infectiousness, β, for SARS-CoV-2 transmission during the early stages of the pandemic within the United States. We find that σβ/μβ ≳ 3.2, where μβ is the mean infectiousness and σβ its standard deviation, which implies pervasive superspreading. This result allows us to estimate that in the early stages of the pandemic in the USA, over 81% of new cases were a result of the top 10% of most infectious individuals.
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Affiliation(s)
- Calvin Pozderac
- Department of Physics, Ohio State University, Columbus, Ohio, United States of America
| | - Brian Skinner
- Department of Physics, Ohio State University, Columbus, Ohio, United States of America
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6
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Tyne RL, Barry PH, Lawson M, Byrne DJ, Warr O, Xie H, Hillegonds DJ, Formolo M, Summers ZM, Skinner B, Eiler JM, Ballentine CJ. Rapid microbial methanogenesis during CO 2 storage in hydrocarbon reservoirs. Nature 2021; 600:670-674. [PMID: 34937895 PMCID: PMC8695373 DOI: 10.1038/s41586-021-04153-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Accepted: 10/14/2021] [Indexed: 01/04/2023]
Abstract
Carbon capture and storage (CCS) is a key technology to mitigate the environmental impact of carbon dioxide (CO2) emissions. An understanding of the potential trapping and storage mechanisms is required to provide confidence in safe and secure CO2 geological sequestration1,2. Depleted hydrocarbon reservoirs have substantial CO2 storage potential1,3, and numerous hydrocarbon reservoirs have undergone CO2 injection as a means of enhanced oil recovery (CO2-EOR), providing an opportunity to evaluate the (bio)geochemical behaviour of injected carbon. Here we present noble gas, stable isotope, clumped isotope and gene-sequencing analyses from a CO2-EOR project in the Olla Field (Louisiana, USA). We show that microbial methanogenesis converted as much as 13-19% of the injected CO2 to methane (CH4) and up to an additional 74% of CO2 was dissolved in the groundwater. We calculate an in situ microbial methanogenesis rate from within a natural system of 73-109 millimoles of CH4 per cubic metre (standard temperature and pressure) per year for the Olla Field. Similar geochemical trends in both injected and natural CO2 fields suggest that microbial methanogenesis may be an important subsurface sink of CO2 globally. For CO2 sequestration sites within the environmental window for microbial methanogenesis, conversion to CH4 should be considered in site selection.
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Affiliation(s)
- R. L. Tyne
- grid.4991.50000 0004 1936 8948Department of Earth Sciences, University of Oxford, Oxford, UK
| | - P. H. Barry
- grid.4991.50000 0004 1936 8948Department of Earth Sciences, University of Oxford, Oxford, UK ,grid.56466.370000 0004 0504 7510Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA USA
| | - M. Lawson
- grid.421234.20000 0004 1112 1641ExxonMobil Upstream Business Development, Spring, TX USA ,grid.497051.e0000 0004 5997 8548Present Address: Aker BP, Stavanger, Norway
| | - D. J. Byrne
- grid.29172.3f0000 0001 2194 6418CRPG-CNRS, Université de Lorraine, Nancy, France
| | - O. Warr
- grid.17063.330000 0001 2157 2938Department of Earth Sciences, University of Toronto, Toronto, Ontario Canada
| | - H. Xie
- grid.20861.3d0000000107068890Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA USA
| | - D. J. Hillegonds
- grid.4991.50000 0004 1936 8948Department of Earth Sciences, University of Oxford, Oxford, UK
| | - M. Formolo
- grid.421234.20000 0004 1112 1641ExxonMobil Upstream Integrated Solutions, Spring, TX USA
| | - Z. M. Summers
- ExxonMobil Research and Engineering Co., Virginia, NJ USA
| | - B. Skinner
- grid.421234.20000 0004 1112 1641ExxonMobil Upstream Integrated Solutions, Spring, TX USA
| | - J. M. Eiler
- grid.20861.3d0000000107068890Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA USA
| | - C. J. Ballentine
- grid.4991.50000 0004 1936 8948Department of Earth Sciences, University of Oxford, Oxford, UK
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7
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Han F, Andrejevic N, Nguyen T, Kozii V, Nguyen QT, Hogan T, Ding Z, Pablo-Pedro R, Parjan S, Skinner B, Alatas A, Alp E, Chi S, Fernandez-Baca J, Huang S, Fu L, Li M. Quantized thermoelectric Hall effect induces giant power factor in a topological semimetal. Nat Commun 2020; 11:6167. [PMID: 33268778 PMCID: PMC7710760 DOI: 10.1038/s41467-020-19850-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 11/03/2020] [Indexed: 11/24/2022] Open
Abstract
Thermoelectrics are promising by directly generating electricity from waste heat. However, (sub-)room-temperature thermoelectrics have been a long-standing challenge due to vanishing electronic entropy at low temperatures. Topological materials offer a new avenue for energy harvesting applications. Recent theories predicted that topological semimetals at the quantum limit can lead to a large, non-saturating thermopower and a quantized thermoelectric Hall conductivity approaching a universal value. Here, we experimentally demonstrate the non-saturating thermopower and quantized thermoelectric Hall effect in the topological Weyl semimetal (WSM) tantalum phosphide (TaP). An ultrahigh longitudinal thermopower \documentclass[12pt]{minimal}
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\begin{document}$$\sim 525 \, \mu \, {\mathrm{W}} \, {\mathrm{cm}}^{ - 1} \, {\mathrm{K}}^{ - 2}$$\end{document}~525μWcm−1K−2 are observed at ~40 K, which is largely attributed to the quantized thermoelectric Hall effect. Our work highlights the unique quantized thermoelectric Hall effect realized in a WSM toward low-temperature energy harvesting applications. Theories predict a large thermopower and a quantized thermoelectric Hall conductivity in topological semimetals. Here, the authors observe an ultrahigh longitudinal thermopower and a giant power factor attributed to the quantized thermoelectric Hall effect in a Weyl semimetal TaP.
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Affiliation(s)
- Fei Han
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
| | - Nina Andrejevic
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Thanh Nguyen
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Vladyslav Kozii
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Quynh T Nguyen
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.,Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Tom Hogan
- Quantum Design, Inc., San Diego, CA, 92121, USA
| | - Zhiwei Ding
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Ricardo Pablo-Pedro
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Shreya Parjan
- Department of Physics, Wellesley College, Wellesley, MA, 02481, USA
| | - Brian Skinner
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Ahmet Alatas
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Ercan Alp
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Songxue Chi
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Jaime Fernandez-Baca
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Shengxi Huang
- Department of Electrical Engineering, The Pennsylvania State University, State College, PA, 16802, USA
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
| | - Mingda Li
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
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8
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Zhang W, Wang P, Skinner B, Bi R, Kozii V, Cho CW, Zhong R, Schneeloch J, Yu D, Gu G, Fu L, Wu X, Zhang L. Observation of a thermoelectric Hall plateau in the extreme quantum limit. Nat Commun 2020; 11:1046. [PMID: 32098952 PMCID: PMC7042294 DOI: 10.1038/s41467-020-14819-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 01/30/2020] [Indexed: 11/09/2022] Open
Abstract
The thermoelectric Hall effect is the generation of a transverse heat current upon applying an electric field in the presence of a magnetic field. Here, we demonstrate that the thermoelectric Hall conductivity αxy in the three-dimensional Dirac semimetal ZrTe5 acquires a robust plateau in the extreme quantum limit of magnetic field. The plateau value is independent of the field strength, disorder strength, carrier concentration, or carrier sign. We explain this plateau theoretically and show that it is a unique signature of three-dimensional Dirac or Weyl electrons in the extreme quantum limit. We further find that other thermoelectric coefficients, such as the thermopower and Nernst coefficient, are greatly enhanced over their zero-field values even at relatively low fields.
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Affiliation(s)
- Wenjie Zhang
- State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Beijing Key Laboratory of Quantum Devices, Peking University, 100871, Beijing, China
| | - Peipei Wang
- Department of Physics, Southern University of Science and Technology, 518055, Shenzhen, China
| | - Brian Skinner
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- Department of Physics, Ohio State University, Columbus, OH, 43210, USA
| | - Ran Bi
- State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Beijing Key Laboratory of Quantum Devices, Peking University, 100871, Beijing, China
| | - Vladyslav Kozii
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- Department of Physics, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Chang-Woo Cho
- Department of Physics, Southern University of Science and Technology, 518055, Shenzhen, China
| | - Ruidan Zhong
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - John Schneeloch
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Dapeng Yu
- Department of Physics, Southern University of Science and Technology, 518055, Shenzhen, China
| | - Genda Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
| | - Xiaosong Wu
- State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Beijing Key Laboratory of Quantum Devices, Peking University, 100871, Beijing, China.
- Frontiers Science Center for Nano-optoelectronics and Collaborative Innovation Center of Quantum Matter, Peking University, 100871, Beijing, China.
| | - Liyuan Zhang
- Department of Physics, Southern University of Science and Technology, 518055, Shenzhen, China.
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9
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Lotfizadeh N, McCulley DR, Senger MJ, Fu H, Minot ED, Skinner B, Deshpande VV. Band-Gap-Dependent Electronic Compressibility of Carbon Nanotubes in the Wigner Crystal Regime. Phys Rev Lett 2019; 123:197701. [PMID: 31765201 DOI: 10.1103/physrevlett.123.197701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Indexed: 06/10/2023]
Abstract
Electronic compressibility, the second derivative of ground-state energy with respect to total electron number, is a measurable quantity that reveals the interaction strength of a system and can be used to characterize the orderly crystalline lattice of electrons known as the Wigner crystal. Here, we measure the electronic compressibility of individual suspended ultraclean carbon nanotubes in the low-density Wigner crystal regime. Using low-temperature quantum transport measurements, we determine the compressibility as a function of carrier number in nanotubes with varying band gaps. We observe two qualitatively different trends in compressibility versus carrier number, both of which can be explained using a theoretical model of a Wigner crystal that accounts for both the band gap and the confining potential experienced by charge carriers. We extract the interaction strength as a function of carrier number for individual nanotubes and show that the compressibility can be used to distinguish between strongly and weakly interacting regimes.
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Affiliation(s)
- Neda Lotfizadeh
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA
| | - Daniel R McCulley
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Mitchell J Senger
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Han Fu
- James Franck Institute, University of Chicago, Chicago, Illinois 60637, USA
| | - Ethan D Minot
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Brian Skinner
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Department of Physics, Ohio State University, Columbus, Ohio 43210, USA
| | - Vikram V Deshpande
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA
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10
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Skinner B, Song JCW. Polarity is a matter of perspective. Nat Mater 2019; 18:532-533. [PMID: 31114066 DOI: 10.1038/s41563-019-0373-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Affiliation(s)
- Brian Skinner
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Justin C W Song
- Division of Physics and Applied Physics, Nanyang Technological University, Singapore, Singapore.
- Institute of High Performance Computing, Agency for Science Technology and Research, Singapore, Singapore.
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11
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Liang S, Kushwaha S, Gao T, Hirschberger M, Li J, Wang Z, Stolze K, Skinner B, Bernevig BA, Cava RJ, Ong NP. A gap-protected zero-Hall effect state in the quantum limit of the non-symmorphic metal KHgSb. Nat Mater 2019; 18:443-447. [PMID: 30833782 DOI: 10.1038/s41563-019-0303-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 01/30/2019] [Indexed: 06/09/2023]
Abstract
A recurring theme in topological matter is the protection of unusual electronic states by symmetry, for example, protection of the surface states in Z2 topological insulators by time-reversal symmetry1-3. Recently, interest has turned to unusual surface states in the large class of non-symmorphic materials4-12. In particular, KHgSb is predicted to exhibit double quantum spin Hall states10. Here we report measurements of the Hall conductivity in KHgSb in a strong magnetic field B. In the quantum limit, the Hall conductivity is observed to fall exponentially to zero, but the diagonal conductivity is finite. A large gap protects this unusual zero-Hall state. We theoretically propose that, in this quantum limit, the chemical potential drops into the bulk gap, intersecting equal numbers of right- and left-moving quantum spin Hall surface modes to produce the zero-Hall state. The zero-Hall state illustrates how topological protection in a non-symmorphic material with glide symmetry may lead to highly unusual transport phenomena.
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Affiliation(s)
- Sihang Liang
- Department of Physics, Princeton University, Princeton, NJ, USA
| | - Satya Kushwaha
- Department of Chemistry, Princeton University, Princeton, NJ, USA
| | - Tong Gao
- Department of Physics, Princeton University, Princeton, NJ, USA
| | | | - Jian Li
- Department of Physics, Princeton University, Princeton, NJ, USA
- School of Science, Westlake University, Hangzhou, China
| | - Zhijun Wang
- Department of Physics, Princeton University, Princeton, NJ, USA
| | - Karoline Stolze
- Department of Chemistry, Princeton University, Princeton, NJ, USA
| | - Brian Skinner
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - B A Bernevig
- Department of Physics, Princeton University, Princeton, NJ, USA
| | - R J Cava
- Department of Chemistry, Princeton University, Princeton, NJ, USA
| | - N P Ong
- Department of Physics, Princeton University, Princeton, NJ, USA.
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12
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Efetov DK, Shiue RJ, Gao Y, Skinner B, Walsh ED, Choi H, Zheng J, Tan C, Grosso G, Peng C, Hone J, Fong KC, Englund D. Fast thermal relaxation in cavity-coupled graphene bolometers with a Johnson noise read-out. Nat Nanotechnol 2018; 13:797-801. [PMID: 29892017 DOI: 10.1038/s41565-018-0169-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 05/15/2018] [Indexed: 05/13/2023]
Abstract
High sensitivity, fast response time and strong light absorption are the most important metrics for infrared sensing and imaging. The trade-off between these characteristics remains the primary challenge in bolometry. Graphene with its unique combination of a record small electronic heat capacity and a weak electron-phonon coupling has emerged as a sensitive bolometric medium that allows for high intrinsic bandwidths1-3. Moreover, the material's light absorption can be enhanced to near unity by integration into photonic structures. Here, we introduce an integrated hot-electron bolometer based on Johnson noise readout of electrons in ultra-clean hexagonal-boron-nitride-encapsulated graphene, which is critically coupled to incident radiation through a photonic nanocavity with Q = 900. The device operates at telecom wavelengths and shows an enhanced bolometric response at charge neutrality. At 5 K, we obtain a noise equivalent power of about 10 pW Hz-1/2, a record fast thermal relaxation time, <35 ps, and an improved light absorption. However the device can operate even above 300 K with reduced sensitivity. We work out the performance mechanisms and limits of the graphene bolometer and give important insights towards the potential development of practical applications.
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Affiliation(s)
- Dmitri K Efetov
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain.
| | - Ren-Jye Shiue
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Yuanda Gao
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Brian Skinner
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Evan D Walsh
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Hyeongrak Choi
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Jiabao Zheng
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Cheng Tan
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Gabriele Grosso
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Cheng Peng
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Kin Chung Fong
- Raytheon BBN Technologies, Quantum Information Processing Group, Cambridge, MA, USA
| | - Dirk Englund
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA
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13
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Choi YH, Zhang X, Tran C, Skinner B. Expression profiles of host immune response-related genes against HEV genotype 3 and genotype 1 infections in rhesus macaques. J Viral Hepat 2018; 25. [PMID: 29532615 PMCID: PMC8996335 DOI: 10.1111/jvh.12890] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Hepatitis E virus (HEV) genotype (gt) 3 infection is food-borne causing sporadic infections in older individuals and gt1 infection is waterborne, often causing epidemics affecting primarily young adults. Although HEV infection causes self-limited disease, gt3 induces chronic infection in immunocompromised individuals. Hepatic host gene expression against gt3 infection remains unknown. Host gene expression profiles for HEV gt1 (n = 3) and gt3 (n = 7) infections were analysed in the livers of experimentally infected rhesus macaques. HEV RNA was detected from 2 to 24 days after inoculation (DAI) in stool and serum, elevated alanine aminotransferase (ALT) activity was detected from 7 to 31 DAI, and anti-HEV antibody became detectable between 12 and 42 DAI. All 10 animals cleared the infection between 34 and 68 DAI. We found that 24%, 48% and 41% of hepatic immune response genes against gt3 infection were upregulated during the early, peak and decline phases of HEV RNA replication. For gt1 infection, 25% of hepatic immune response-related genes were downregulated during early viremia, but 6%, 34% and 37% of genes were upregulated at the early, peak and during decline of HEV RNA replication, respectively. Our study demonstrated distinct differences in the expression profiles of host immune response-related genes of HEV gt3 and gt1 infections in experimentally infected rhesus macaques.
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Affiliation(s)
- Y. H. Choi
- Laboratory Branch, Division of Viral Hepatitis, NCHHSTP, CDC, Atlanta, GA, USA
| | - X. Zhang
- Laboratory Branch, Division of Viral Hepatitis, NCHHSTP, CDC, Atlanta, GA, USA
| | - C. Tran
- Laboratory Branch, Division of Viral Hepatitis, NCHHSTP, CDC, Atlanta, GA, USA
| | - B. Skinner
- Comparative Medicine Branch, Division of Scientific Resources, NCEZID, CDC, Atlanta, GA, USA
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14
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Chowdhury D, Skinner B, Lee PA. Effect of Magnetization on the Tunneling Anomaly in Compressible Quantum Hall States. Phys Rev Lett 2018; 120:266601. [PMID: 30004777 DOI: 10.1103/physrevlett.120.266601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Indexed: 06/08/2023]
Abstract
Tunneling of electrons into a two-dimensional electron system is known to exhibit an anomaly at low bias, in which the tunneling conductance vanishes due to a many-body interaction effect. Recent experiments have measured this anomaly between two copies of the half-filled Landau level as a function of in-plane magnetic field, and they suggest that increasing spin polarization drives a deeper suppression of tunneling. Here, we present a theory of the tunneling anomaly between two copies of the partially spin-polarized Halperin-Lee-Read state, and we show that the conventional description of the tunneling anomaly, based on the Coulomb self-energy of the injected charge packet, is inconsistent with the experimental observation. We propose that the experiment is operating in a different regime, not previously considered, in which the charge-spreading action is determined by the compressibility of the composite fermions.
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Affiliation(s)
- Debanjan Chowdhury
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Brian Skinner
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Patrick A Lee
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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15
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Abstract
The thermoelectric effect is the generation of an electrical voltage from a temperature gradient in a solid material due to the diffusion of free charge carriers from hot to cold. Identifying materials with a large thermoelectric response is crucial for the development of novel electric generators and coolers. We theoretically consider the thermopower of Dirac/Weyl semimetals subjected to a quantizing magnetic field. We contrast their thermoelectric properties with those of traditional heavily doped semiconductors and show that, under a sufficiently large magnetic field, the thermopower of Dirac/Weyl semimetals grows linearly with the field without saturation and can reach extremely high values. Our results suggest an immediate pathway for achieving record-high thermopower and thermoelectric figure of merit, and they compare well with a recent experiment on Pb1-x Sn x Se.
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Affiliation(s)
| | - Liang Fu
- Corresponding author. (B.S.); (L.F.)
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16
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McPhee MJ, Walmsley BJ, Skinner B, Littler B, Siddell JP, Cafe LM, Wilkins JF, Oddy VH, Alempijevic A. Live animal assessments of rump fat and muscle score in Angus cows and steers using 3-dimensional imaging. J Anim Sci 2017; 95:1847-1857. [PMID: 28464097 DOI: 10.2527/jas.2016.1292] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The objective of this study was to develop a proof of concept for using off-the-shelf Red Green Blue-Depth (RGB-D) Microsoft Kinect cameras to objectively assess P8 rump fat (P8 fat; mm) and muscle score (MS) traits in Angus cows and steers. Data from low and high muscled cattle (156 cows and 79 steers) were collected at multiple locations and time points. The following steps were required for the 3-dimensional (3D) image data and subsequent machine learning techniques to learn the traits: 1) reduce the high dimensionality of the point cloud data by extracting features from the input signals to produce a compact and representative feature vector, 2) perform global optimization of the signatures using machine learning algorithms and a parallel genetic algorithm, and 3) train a sensor model using regression-supervised learning techniques on the ultrasound P8 fat and the classified learning techniques for the assessed MS for each animal in the data set. The correlation of estimating hip height (cm) between visually measured and assessed 3D data from RGB-D cameras on cows and steers was 0.75 and 0.90, respectively. The supervised machine learning and global optimization approach correctly classified MS (mean [SD]) 80 (4.7) and 83% [6.6%] for cows and steers, respectively. Kappa tests of MS were 0.74 and 0.79 in cows and steers, respectively, indicating substantial agreement between visual assessment and the learning approaches of RGB-D camera images. A stratified 10-fold cross-validation for P8 fat did not find any differences in the mean bias ( = 0.62 and = 0.42 for cows and steers, respectively). The root mean square error of P8 fat was 1.54 and 1.00 mm for cows and steers, respectively. Additional data is required to strengthen the capacity of machine learning to estimate measured P8 fat and assessed MS. Data sets for and continental cattle are also required to broaden the use of 3D cameras to assess cattle. The results demonstrate the importance of capturing curvature as a form of representing body shape. A data-driven model from shape to trait has established a proof of concept using optimized machine learning techniques to assess P8 fat and MS in Angus cows and steers.
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17
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McPhee MJ, Walmsley BJ, Skinner B, Littler B, Siddell JP, Cafe LM, Wilkins JF, Oddy VH, Alempijevic A. Live animal assessments of rump fat and muscle score in Angus cows and steers using 3-dimensional imaging. J Anim Sci 2017. [DOI: 10.2527/jas2016.1292] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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18
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Bhattacharya A, Skinner B, Khalsa G, Suslov AV. Spatially inhomogeneous electron state deep in the extreme quantum limit of strontium titanate. Nat Commun 2016; 7:12974. [PMID: 27680386 PMCID: PMC5056415 DOI: 10.1038/ncomms12974] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 08/23/2016] [Indexed: 11/09/2022] Open
Abstract
When an electronic system is subjected to a sufficiently strong magnetic field that the cyclotron energy is much larger than the Fermi energy, the system enters the extreme quantum limit (EQL) and becomes susceptible to a number of instabilities. Bringing a three-dimensional electronic system deeply into the EQL can be difficult however, since it requires a small Fermi energy, large magnetic field, and low disorder. Here we present an experimental study of the EQL in lightly-doped single crystals of strontium titanate. Our experiments probe deeply into the regime where theory has long predicted an interaction-driven charge density wave or Wigner crystal state. A number of interesting features arise in the transport in this regime, including a striking re-entrant nonlinearity in the current–voltage characteristics. We discuss these features in the context of possible correlated electron states, and present an alternative picture based on magnetic-field induced puddling of electrons. At sufficiently strong magnetic fields and low temperatures, electrons assume a quasi-one-dimensional quantum state that is challenging to observe. Here, Bhattacharya et al. report on electron transport in lightly-doped single crystals of SrTiO3 deep in this extreme quantum limit.
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Affiliation(s)
- Anand Bhattacharya
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Brian Skinner
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.,Massachusetts Institute of Technology, 77 Mass Ave, Cambridge, Massachusetts 02139, USA
| | - Guru Khalsa
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Alexey V Suslov
- National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr, Tallahassee, Florida 32310, USA
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19
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Skinner B. Mathematical toy model inspired by the problem of the adaptive origins of the sexual orientation continuum. R Soc Open Sci 2016; 3:160403. [PMID: 27703705 PMCID: PMC5043324 DOI: 10.1098/rsos.160403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 08/17/2016] [Indexed: 06/06/2023]
Abstract
Same-sex sexual behaviour is ubiquitous in the animal kingdom, but its adaptive origins remain a prominent puzzle. Here, I suggest the possibility that same-sex sexual behaviour arises as a consequence of the competition between an evolutionary drive for a wide diversity in traits, which improves the adaptability of a population, and a drive for sexual dichotomization of traits, which promotes opposite-sex attraction and increases the rate of reproduction. This trade-off is explored via a simple mathematical 'toy model'. The model exhibits a number of interesting features and suggests a simple mathematical form for describing the sexual orientation continuum.
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20
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Knaus SJ, Saum L, Cochard E, Prichard W, Skinner B, Medas R. Impact of Evidence-Based Guidelines on Outcomes of Hospitalized Patients With Clostridium difficile Infection. South Med J 2016; 109:144-50. [PMID: 26954650 DOI: 10.14423/smj.0000000000000428] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
OBJECTIVES Clostridium difficile infection (CDI) is the most common healthcare-associated infection in the United States. Clinical practice guidelines for the treatment of CDI were updated in 2010 by the Society for Healthcare Epidemiology of America and the Infectious Diseases Society of America. An institutional guideline for the classification and management of CDI in accordance with the 2010 Society for Healthcare Epidemiology of America/Infectious Diseases Society of America guideline was developed and provided to attending physicians and medical residents in multiple formats. METHODS We sought to determine the impact of an evidence-based guideline for the treatment of CDI at a community teaching hospital. A retrospective chart review was conducted to identify length of stay (LOS), readmission rates, direct cost, mortality, and physician adherence to guidelines in patients with International Classification of Diseases, Ninth Edition codes and laboratory confirmation of CDI between February 1, 2013 and January 31, 2014. Endpoints included LOS after diagnosis of CDI, 30-day readmission rates, direct cost after diagnosis of CDI, and mortality. RESULTS A total of 351 patient encounters were included in the study. Although not statistically significant, it was found that guideline-based therapy (n = 131) was associated with a lower median LOS (6 days vs 8 days; P = 0.06). Thirty-day hospital readmission (25.2% vs 29.5%; P = 0.39) and median cost after diagnosis of CDI ($7238.48 vs $8794.81; P = 0.10) also were lower but not statistically significant. Patients with mild-to-moderate infection were found to have a significantly lower median LOS (5 days vs 7 days; P = 0.03) and median cost after diagnosis ($5257.85 vs $7680.56; P = 0.03) when treated with guideline-based therapy. Overall physician adherence to guidelines was low, at 38%. CONCLUSIONS Treatment with guideline-based therapy for CDI was associated with a trend toward a significantly lower LOS and cost. Barriers to physician adherence to guidelines still exist, despite education and guideline availability. Electronic health record-based order sets or clinical decision tools may improve recognition of and adherence to guidelines.
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Affiliation(s)
- Stephen J Knaus
- From St Vincent Hospital & Health Services, Indianapolis, Indiana, and Butler University College of Pharmacy and Health Sciences, Indianapolis, Indiana
| | - Lindsay Saum
- From St Vincent Hospital & Health Services, Indianapolis, Indiana, and Butler University College of Pharmacy and Health Sciences, Indianapolis, Indiana
| | - Emily Cochard
- From St Vincent Hospital & Health Services, Indianapolis, Indiana, and Butler University College of Pharmacy and Health Sciences, Indianapolis, Indiana
| | - Wesley Prichard
- From St Vincent Hospital & Health Services, Indianapolis, Indiana, and Butler University College of Pharmacy and Health Sciences, Indianapolis, Indiana
| | - Brian Skinner
- From St Vincent Hospital & Health Services, Indianapolis, Indiana, and Butler University College of Pharmacy and Health Sciences, Indianapolis, Indiana
| | - Ryan Medas
- From St Vincent Hospital & Health Services, Indianapolis, Indiana, and Butler University College of Pharmacy and Health Sciences, Indianapolis, Indiana
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21
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Lim CS, Mowers EL, Mahnert N, Skinner B, Kamdar N, Morgan DM, As-Sanie S. Risk Factors for Conversion of Laparoscopic Hysterectomy. J Minim Invasive Gynecol 2015; 22:S61. [DOI: 10.1016/j.jmig.2015.08.164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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22
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23
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Mowers EL, Lim CS, Skinner B, Nichole M, Daniel M, As-Sanie S. Characteristics of Women Undergoing Hysterectomy for Chronic Pelvic Pain: Prevalence and Risk Factors for Endometriosis. J Minim Invasive Gynecol 2015; 22:S232. [PMID: 27679130 DOI: 10.1016/j.jmig.2015.08.816] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- E L Mowers
- Ob/Gyn, University of Michigan, Ann Arbor, Michigan
| | - C S Lim
- Ob/Gyn, University of Michigan, Ann Arbor, Michigan
| | - B Skinner
- Ob/Gyn, University of Michigan, Ann Arbor, Michigan
| | - M Nichole
- Ob/Gyn, University of Michigan, Ann Arbor, Michigan
| | - M Daniel
- Ob/Gyn, University of Michigan, Ann Arbor, Michigan
| | - S As-Sanie
- Ob/Gyn, University of Michigan, Ann Arbor, Michigan
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24
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Abstract
When many independent users try to route traffic through a network, the flow can easily become suboptimal as a consequence of congestion of the most efficient paths. The degree of this suboptimality is quantified by the so-called price of anarchy (POA), but so far there are no general rules for when to expect a large POA in a random network. Here I address this question by introducing a simple model of flow through a network with randomly placed congestible and incongestible links. I show that the POA is maximized precisely when the fraction of congestible links matches the percolation threshold of the lattice. Both the POA and the total cost demonstrate critical scaling near the percolation threshold.
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Affiliation(s)
- Brian Skinner
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
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25
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Mahnert N, Lim C, Skinner B, Quint E, As-Sanie S. Hysteroscopic Myomectomy of Multiple Submucosal Fibroids with Myosure Tissue Removal System. J Minim Invasive Gynecol 2015. [DOI: 10.1016/j.jmig.2014.12.136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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26
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Abstract
Human crowds often bear a striking resemblance to interacting particle systems, and this has prompted many researchers to describe pedestrian dynamics in terms of interaction forces and potential energies. The correct quantitative form of this interaction, however, has remained an open question. Here, we introduce a novel statistical-mechanical approach to directly measure the interaction energy between pedestrians. This analysis, when applied to a large collection of human motion data, reveals a simple power-law interaction that is based not on the physical separation between pedestrians but on their projected time to a potential future collision, and is therefore fundamentally anticipatory in nature. Remarkably, this simple law is able to describe human interactions across a wide variety of situations, speeds, and densities. We further show, through simulations, that the interaction law we identify is sufficient to reproduce many known crowd phenomena.
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Affiliation(s)
- Ioannis Karamouzas
- Department of Computer Science and Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Brian Skinner
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Stephen J Guy
- Department of Computer Science and Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
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27
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Affiliation(s)
- Brian Skinner
- Fine Theoretical Physics Institute, University of Minnesota, Minneapolis
| | - Brad Carlin
- Professor and head of the Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis
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28
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Abstract
As-grown topological insulators (TIs) are typically heavily doped n-type crystals. Compensation by acceptors is used to move the Fermi level to the middle of the band gap, but even then TIs have a frustratingly small bulk resistivity. We show that this small resistivity is the result of band bending by poorly screened fluctuations in the random Coulomb potential. Using numerical simulations of a completely compensated TI, we find that the bulk resistivity has an activation energy of just 0.15 times the band gap, in good agreement with experimental data. At lower temperatures activated transport crosses over to variable range hopping with a relatively large localization length.
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Affiliation(s)
- Brian Skinner
- Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA
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29
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Chen T, Skinner B, Shklovskii BI. Coulomb gap triptych in a periodic array of metal nanocrystals. Phys Rev Lett 2012; 109:126805. [PMID: 23005975 DOI: 10.1103/physrevlett.109.126805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Indexed: 06/01/2023]
Abstract
The Coulomb gap in the single-particle density of states (DOS) is a universal consequence of electron-electron interaction in disordered systems with localized electron states. Here we show that in arrays of monodisperse metallic nanocrystals, there is not one but three identical adjacent Coulomb gaps, which together form a structure that we call a "Coulomb gap triptych." We calculate the DOS and the conductivity in two- and three-dimensional arrays using a computer simulation. Unlike in the conventional Coulomb glass models, in nanocrystal arrays the DOS has a fixed width in the limit of large disorder. The Coulomb gap triptych can be studied via tunneling experiments.
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Affiliation(s)
- Tianran Chen
- Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, 55455, USA
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30
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Shankar S, Shaw M, Skinner B. Internal diameter marking on tracheal tube connectors. Anaesthesia 2012; 67:546-547. [DOI: 10.1111/j.1365-2044.2012.07126.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- S. Shankar
- University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - M. Shaw
- University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - B. Skinner
- University Hospital Southampton NHS Foundation Trust, Southampton, UK
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31
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Abstract
In basketball, every time the offense produces a shot opportunity the player with the ball must decide whether the shot is worth taking. In this article, I explore the question of when a team should shoot and when they should pass up the shot by considering a simple theoretical model of the shot selection process, in which the quality of shot opportunities generated by the offense is assumed to fall randomly within a uniform distribution. Within this model I derive an answer to the question “how likely must the shot be to go in before the player should take it?” and I show that this lower cutoff for shot quality depends crucially on the number of shot opportunities remaining (say, before the shot clock expires), with larger demanding that only higher-quality shots should be taken. The function is also derived in the presence of a finite turnover rate and used to predict the shooting rate of an optimal-shooting team as a function of time. The theoretical prediction for the optimal shooting rate is compared to data from the National Basketball Association (NBA). The comparison highlights some limitations of the theoretical model, while also suggesting that NBA teams may be overly reluctant to shoot the ball early in the shot clock.
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Affiliation(s)
- Brian Skinner
- Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota, United States of America.
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32
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Skinner B, Chen T, Loth MS, Shklovskii BI. Theory of volumetric capacitance of an electric double-layer supercapacitor. Phys Rev E Stat Nonlin Soft Matter Phys 2011; 83:056102. [PMID: 21728600 DOI: 10.1103/physreve.83.056102] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 03/30/2011] [Indexed: 05/31/2023]
Abstract
Electric double-layer supercapacitors are a fast-rising class of high-power energy storage devices based on porous electrodes immersed in a concentrated electrolyte or ionic liquid. As yet there is no microscopic theory to describe their surprisingly large capacitance per unit volume (volumetric capacitance) of ~100 F/cm(3), nor is there a good understanding of the fundamental limits on volumetric capacitance. In this paper we present a non-mean-field theory of the volumetric capacitance of a supercapacitor that captures the discrete nature of the ions and the exponential screening of their repulsive interaction by the electrode. We consider analytically and via Monte Carlo simulations the case of an electrode made from a good metal and show that in this case the volumetric capacitance can reach the record values. We also study how the capacitance is reduced when the electrode is an imperfect metal characterized by some finite screening radius. Finally, we argue that a carbon electrode, despite its relatively large linear screening radius, can be approximated as a perfect metal because of its strong nonlinear screening. In this way the experimentally measured capacitance values of ~100 F/cm(3) may be understood.
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Affiliation(s)
- Brian Skinner
- Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA
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33
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Loth MS, Skinner B, Shklovskii BI. Anomalously large capacitance of an ionic liquid described by the restricted primitive model. Phys Rev E Stat Nonlin Soft Matter Phys 2010; 82:056102. [PMID: 21230540 DOI: 10.1103/physreve.82.056102] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Revised: 10/12/2010] [Indexed: 05/30/2023]
Abstract
We use Monte Carlo simulations to examine the simplest model of a room-temperature ionic liquid (RTIL), called the "restricted primitive model," at a metal surface. We find that at moderately low temperatures the capacitance of the metal-RTIL interface is so large that the effective thickness of the electrostatic double layer is up to three times smaller than the ion radius. To interpret these results we suggest an approach which is based on the interaction between discrete ions and their image charges in the metal surface and which therefore goes beyond the mean-field approximation. When a voltage is applied across the interface, the strong image attraction causes counterions to condense onto the metal surface to form compact ion-image dipoles. These dipoles repel each other to form a correlated liquid. When the surface density of these dipoles is low, the insertion of an additional dipole does not require much energy. This leads to a large capacitance C that decreases monotonically with voltage V, producing a "bell-shaped" curve C(V). We also consider what happens when the electrode is made from a semimetal rather than a perfect metal. In this case, the finite screening radius of the electrode shifts the reflection plane for image charges to the interior of the electrode, and we arrive at a "camel-shaped" C(V). These predictions seem to be in qualitative agreement with experiment.
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Affiliation(s)
- M S Loth
- Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA
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34
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Loth MS, Skinner B, Shklovskii BI. Non-mean-field theory of anomalously large double layer capacitance. Phys Rev E Stat Nonlin Soft Matter Phys 2010; 82:016107. [PMID: 20866689 DOI: 10.1103/physreve.82.016107] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Indexed: 05/29/2023]
Abstract
Mean-field theories claim that the capacitance of the double layer formed at a metal/ionic conductor interface cannot be larger than that of the Helmholtz capacitor, whose width is equal to the radius of an ion. However, in some experiments the apparent width of the double layer capacitor is substantially smaller. We propose an alternate non-mean-field theory of the ionic double layer to explain such large capacitance values. Our theory allows for the binding of discrete ions to their image charges in the metal, which results in the formation of interface dipoles. We focus primarily on the case where only small cations are mobile and other ions form an oppositely charged background. In this case, at small temperature and zero applied voltage dipoles form a correlated liquid on both contacts. We show that at small voltages the capacitance of the double layer is determined by the transfer of dipoles from one electrode to the other and is therefore limited only by the weak dipole-dipole repulsion between bound ions so that the capacitance is very large. At large voltages the depletion of bound ions from one of the capacitor electrodes triggers a collapse of the capacitance to the much smaller mean-field value, as seen in experimental data. We test our analytical predictions with a Monte Carlo simulation and find good agreement. We further argue that our "one-component plasma" model should work well for strongly asymmetric ion liquids. We believe that this work also suggests an improved theory of pseudocapacitance.
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Affiliation(s)
- M S Loth
- Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Skinner B, Loth MS, Shklovskii BI. Capacitance of the double layer formed at the metal/ionic-conductor interface: how large can it be? Phys Rev Lett 2010; 104:128302. [PMID: 20366568 DOI: 10.1103/physrevlett.104.128302] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Indexed: 05/29/2023]
Abstract
The capacitance of the double layer formed at a metal/ionic-conductor interface can be remarkably large, so that the apparent width of the double layer is as small as 0.3 A. Mean-field theories fail to explain such large capacitance. We propose an alternate theory of the ionic double layer which allows for the binding of discrete ions to their image charges in the metal. We show that at small voltages the capacitance of the double layer is limited only by the weak dipole-dipole repulsion between bound ions, and is therefore very large. At large voltages the depletion of bound ions from one of the capacitor electrodes triggers a collapse of the capacitance to the mean-field value.
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Affiliation(s)
- Brian Skinner
- Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Abstract
Recent experiments measuring the electrical conductivity of DNA molecules highlight the need for a theoretical model of ion transport along a charged surface. Here we present a simple theory based on the idea of unbinding of ion pairs. The strong humidity dependence of conductivity is explained by the decrease in the electrostatic self-energy of a separated pair when a layer of water (with high dielectric constant) is adsorbed to the surface. We compare our prediction for conductivity to experiment and discuss the limits of its applicability.
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Affiliation(s)
- Brian Skinner
- Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Nixon B, Skinner B, Aitken RJ. 137. ELUCIDATION OF THE MOLECULAR MECHANISMS THAT UNDERPIN CAPACITATION-ASSOCIATED SPERM SURFACE REMODELLING. Reprod Fertil Dev 2009. [DOI: 10.1071/srb09abs137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Recent research from our laboratory has provided evidence that sperm-egg interaction is mediated by a multimeric sperm receptor complex. Furthermore, we have demonstrated that this complex is assembled on the sperm surface during the final phase of their maturation, a process known as capacitation. The mechanisms underpinning this capacitation-associated surface remodelling remain poorly understood and are the subject of our current investigation. Specifically we have focused on whether this process is driven by vesicle mediated, intracellular trafficking of proteins. For this purpose we have examined the presence and physiological significance of a key part of the molecular machinery necessary for this form of trafficking, namely the enzyme dynamin. Our studies revealed that sperm are endowed with at least two isoforms of dynamin (1 and 2) both of which reside within the peri-acrosomal region of the sperm head, a location compatible with a role in sperm membrane remodelling. Consistent with this putative role, it was demonstrated that dynamin 1 was phosphorylated during capacitation, a post-translational modification that has been causally linked to both its activation and to the capacitation-associated surface remodelling of mouse spermatozoa. Furthermore, it was demonstrated that pharmacological inhibition of dynamin activity led to a concomitant reduction in the ability of spermatozoa to bind to the zona pellucida of homologous oocytes. This suppression was also correlated with reduced surface expression of a number of proteins including a subset of putative sperm-zona pellucida receptors. Collectively these data support the novel hypothesis that dynamin does participate indirectly in sperm membrane remodelling events by virtue of its ability to mediate intracellular trafficking.
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Skinner B. What works: financial application. One system fits all. Health Manag Technol 2001; 22:42-3. [PMID: 11766433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/17/2023]
Affiliation(s)
- B Skinner
- Prebysterian Healthcare Services Albuquerque, NM, USA.
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Nusbaum MR, Gamble G, Skinner B, Heiman J. The high prevalence of sexual concerns among women seeking routine gynecological care. J Fam Pract 2000; 49:229-232. [PMID: 10735482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
BACKGROUND Sexuality is an important part of health, quality of life, and general wellbeing. Studies indicate that less than half of patients' sexual concerns are known by their physicians, and physicians are unaware of how common these sexual concerns are in their practices. Our objective was to determine the prevalence and type of sexual concerns among women seeking routine gynecological care. METHODS We mailed the survey in waves. Of 1480 women seeking routine gynecological care from the departments of Family Practice and Obstetrics and Gynecology at Madigan Army Medical Center between August 1992 and January 1993, 964 responded. The main outcome measures were self-reported sexual concerns and their experiences with discussing these concerns with a physician. RESULTS A A total of 98.8% of the women we surveyed reported one or more sexual concerns. The most frequently reported concerns were lack of interest (87.2%), difficulty with orgasm (83.3%), inadequate lubrication (74.7%), dyspareunia (71.7%), body image concerns (68.5%), unmet sexual needs (67.2%), and needing information about sexual issues (63.4%). More than half reported concerns about physical or sexual abuse, and more than 40% reported sexual coercion at some point in their lives. CONCLUSIONS Our results suggest that sexual health concerns are prevalent for women seeking routine gynecological care. Sexual health inquiry should be a regular and important part of health care maintenance.
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Affiliation(s)
- M R Nusbaum
- Department of Family Medicine, University of North Carolina at Chapel Hill, 27599-7595, USA.
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Lynch T, Skinner B. Changing the guard: how the Mewburn Veterans Centre received new owners. Leadersh Health Serv 1994; 3:20-3. [PMID: 10136715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
The consolidation of programs and services is currently of great interest in Canadian health care. This article describes the process that was used to transfer a 146-bed continuing care centre from one hospital organization to another. Leadership, team work, structure and communication were found to be the keys to success in dealing with the many problems and complexities of a facility transfer.
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Curtis P, Skinner B, Varenholt JJ, Addison L, Resnick J, Kebede M. Papanicolaou smear quality assurance: providing feedback to physicians. J Fam Pract 1993; 36:309-312. [PMID: 8454978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
BACKGROUND The effective management of Papanicolaou (Pap) smears depends on the reliability and accuracy of obtaining and interpreting the specimen. Provider sampling error is one of the important factors contributing to inadequate specimens. Feedback on provider performance may be an effective way to improve the quality of Pap smears. METHODS A pilot study in a university-based residency program involving resident and faculty physicians was initiated to assess the impact of feedback on performance of Pap smears. After establishing adequacy and inadequacy criteria and recording adequacy rates for 3 months, individual and group feedback was implemented. No formal educational intervention on Pap smear technique was undertaken. RESULTS The quality of 836 Pap smears performed by 9 faculty and 13 resident physicians showed continued improvement in both sampling and slide preparation to 90% adequacy over a 9-month period. This improvement, though clinically useful, was not statistically significant owing to the relatively small numbers of smears performed by each physician. This form of feedback may be useful in both practice and educational settings. CONCLUSIONS Feedback without any formal educational intervention led to a clinically useful trend of improvement in the quality of Pap smears, which has been sustained since the study began. This type of simple feedback may be useful in practice settings and particularly valuable in pinpointing areas for improvement for learners in residency programs.
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Affiliation(s)
- P Curtis
- Department of Family Medicine, School of Medicine, University of North Carolina, Chapel Hill 27599
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Nou X, Skinner B, Braaten B, Blyn L, Hirsch D, Low D. Regulation of pyelonephritis-associated pili phase-variation in Escherichia coli: binding of the PapI and the Lrp regulatory proteins is controlled by DNA methylation. Mol Microbiol 1993; 7:545-53. [PMID: 8096319 DOI: 10.1111/j.1365-2958.1993.tb01145.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Expression of pyelonephritis-associated pili (Pap) in Escherichia coli is under a phase-variation control mechanism in which individual cells alternate between pili+ (ON) and pili- (OFF) states through a process involving DNA methylation by deoxyadenosine methylase (Dam). Methylation of two GATC sites (GATC1028 and GATC1130) within the pap regulatory region is differentially inhibited in phase ON and phase OFF cells. The GATC1028 site of phase ON cells is non-methylated and the GATC1130 site is fully methylated. Conversely, in phase OFF cells the GATC1028 site is fully methylated whereas the GATC1130 site is non-methylated. Two transcriptional activators, PapI and Lrp (leucine-responsive regulatory protein), are required for this specific methylation inhibition. DNA footprint analysis using non-methylated pap DNAs indicates that Lrp binds to a region surrounding the GATC1130 site, whereas PapI does not appear to bind to pap regulatory DNA. However, addition of Lrp and PapI together results in an additional DNaseI footprint around the GATC1028 site. Moreover, Dam methylation inhibits binding of Lrp/PapI near the GATC1028 site and alters binding of Lrp at the GATC1130 site. Our results support a model in which Dam and Lrp/PapI compete for binding near the GATC1028 site, regulating the methylation state of this GATC site and, consequently, the pap transcription state.
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Affiliation(s)
- X Nou
- Department of Pathology, University of Utah Medical Center, Salt Lake City 84132
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Curtis P, Varenholt JJ, Skinner B, Addison L, Resnick J, Kebede M. Development of a Pap smear quality-assurance system in family practice. Fam Med 1993; 25:135-9. [PMID: 8458544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
BACKGROUND AND OBJECTIVES To improve the effectiveness of cervical cancer screening, quality assurance programs can be designed to ensure that normal Pap smear results are dealt with appropriately and that Pap smears yielding inadequate specimen material are brought to a physician's attention. The objective of this study was to use a new Pap Smear Quality Assurance (PAPQA) system to determine and monitor the performance of physicians in a family practice over a two-year period. METHODS We developed a PAPQA system designed to gather data and report on: 1) Pap smear adequacy, 2) reporting of abnormal results to physicians, and 3) follow-up of patients who had abnormal Pap smear results. We followed these parameters for two years. RESULTS Over a two-year period, 2,771 cervical Pap smears were performed, of which 64% were normal. The percentage of Pap smears that yielded adequate specimen material improved from 82% to 91%, an improvement we attributed to feedback the system provided to physicians. Overall, Pap smear results and follow-up appeared in the medical record of 94% of patients who had abnormal findings. However, during the second year, the quality assurance system detected a deterioration in documentation of results and follow-up plans that coincided with moving the practice to a new facility. The operating cost for this program was approximately $950 per year. CONCLUSIONS Quality assurance programs can effectively monitor physicians' performance in dealing with abnormal Pap smears, can detect deteriorations in performance, and can improve some aspects of performance through feedback reporting to physicians.
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Affiliation(s)
- P Curtis
- Department of Family Medicine, University of North Carolina, Chapel Hill
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Abstract
The study on which this article is based was conducted at the University of North Carolina's Family Practice Center to analyze the content of teaching that occurred in the face-to-face chart review sessions. Data were collected from a sample of 276 chart reviews and processed by a microcomputer program that compiled reports of types of problems encountered by residents, topics of discussion pertinent to those problems, and learning needs defined as a result of those discussions. Reports were generated for faculty members nad residents, and summary reports were produced for the teaching encounters. This system of computerized data analysis can be used to identifying learning needs of residents and areas of teaching emphasis for faculty. The information can be used for educational planning and faculty development.
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Lisbona R, Leger J, Stern J, Derbekyan V, Skinner B. Observations on Tc-99m-erythrocyte venography in normal subjects and in patients with deep vein thrombosis. Clin Nucl Med 1981; 6:305-9. [PMID: 7237876 DOI: 10.1097/00003072-198107000-00005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Blood pool imaging of the lower limbs with Tc-99m-erythrocytes demonstrates the deep venous channels of the leg. The radionuclide image of deep vein thrombosis, by this method, appears sufficiently distinctive to suggest that Tc-99m-erythrocyte venography may be a useful screening examination for deep vein patency.
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