1,332 research outputs found

    Imaging, simulation, and electrostatic control of power dissipation in graphene devices

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    We directly image hot spot formation in functioning mono- and bilayer graphene field effect transistors (GFETs) using infrared thermal microscopy. Correlating with an electrical-thermal transport model provides insight into carrier distributions, fields, and GFET power dissipation. The hot spot corresponds to the location of minimum charge density along the GFET; by changing the applied bias this can be shifted between electrodes or held in the middle of the channel in ambipolar transport. Interestingly, the hot spot shape bears the imprint of the density of states in mono- vs. bilayer graphene. More broadly, we find that thermal imaging combined with self-consistent simulation provides a non-invasive approach for more deeply examining transport and energy dissipation in nanoscale devices

    Dynamics of the Globular Cluster System Associated with M87 (NGC 4486). II. Analysis

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    We present a dynamical analysis of the globular cluster system associated with M87 (= NGC 4486), the cD galaxy near the dynamical center of the Virgo cluster. The analysis utilizes a new spectroscopic and photometric database which is described in a companion paper (Hanes et al. 2001). Using a sample of 278 globular clusters with measured radial velocities and metallicities, and new surface density profiles based on wide-field Washington photometry, we study the dynamics of the M87 globular cluster system both globally --- for the entire cluster sample --- and separately --- for the metal-rich and metal-poor globular cluster samples. This constitutes the largest sample of radial velocities for pure Population II tracers yet assembled for any galaxy. We discuss the implications of our findings for models for the formation of giant elliptical galaxies, globular cluster systems, and the Virgo cluster. (ABRIDGED)Comment: 28 pages, 19 postscript figures, 1 jpeg image. See http://www.physics.rutgers.edu/ast/ast-rap.html to download the manuscript with higher quality figures. Accepted for publication in the Astrophysical Journa

    Colon polyps in patients with short bowel syndrome before and after teduglutide: post hoc analysis of the STEPS study series

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    Background & aims: Teduglutide promotes intestinal growth and is approved for the treatment of short bowel syndrome and intestinal failure (SBS-IF). Based on the pharmacologic activity and preclinical findings, teduglutide can potentially induce proliferative colonic mucosal changes. The aim of this study is to report the occurrence of colorectal polyps in adult patients with SBS-IF who received teduglutide in clinical studies conducted to date. Methods: A post hoc analysis of the completed Study of Teduglutide Effectiveness in Parenteral Nutrition-Dependent Short Bowel Syndrome Subjects (STEPS) clinical study series (NCT00798967, EudraCT 2008-006193-15; NCT00930644, EudraCT 2009-011679-65; NCT01560403) evaluated electronic case report form data for baseline colonoscopies (performed before treatment) and for surveillance or end-of-study (performed after treatment with teduglutide 0.05 mg/kg/day for 24 and 36 months) post-exposure procedures. Results: In the STEPS studies, 73 patients treated with teduglutide had a baseline colonoscopy. No post-exposure colonoscopy was scheduled in STEPS. In STEPS-2/3, 50 of 65 patients with remnant colon (77%) underwent a protocol-mandated post-exposure colonoscopy. Colon polyps were reported at baseline in 12% (9/73) of patients and post-exposure in 18% (9/50) of patients. Two had polyps both at baseline and post-exposure. On histology, available for 7 patients, 5 had adenomas (1 serrated, 4 tubular) and none had malignancy or high-grade dysplasia. Conclusion: These data support recommendations for colonoscopic screening before teduglutide therapy and subsequent on-therapy colonoscopic surveillance for patients with SBS-IF. Further studies are required to assess the risk of polyp formation in patients with SBS-IF and the most appropriate colon polyp surveillance strategies

    'Round the Clock Observations of the Q0957+561 A,B Gravitationally Lensed Quasar

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    An observing campaign with 10 participating observatories has undertaken to monitor the optical brightness of the Q0957 gravitationally lensed quasar for 10 consecutive nights in January 2000. The resulting A image brightness curve has significant brightness fluctuations and makes a photometric prediction for the B image light curve for a second campaign planned for 12-21 March 2001. The ultimate purpose is to determine the gravitational lens time delay to a fraction of an hour, and to seek evidence for rapid microlensing.Comment: 8 pages, AASTeX 4.0, accepted by the Astrophysical Journa

    Extended phase space thermodynamics for charged and rotating black holes and Born-Infeld vacuum polarization

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    We investigate the critical behaviour of charged and rotating AdS black holes in d spacetime dimensions, including effects from non-linear electrodynamics via the Born-Infeld action, in an extended phase space in which the cosmological constant is interpreted as thermodynamic pressure. For Reissner-Nordstrom black holes we find that the analogy with the Van der Walls liquid-gas system holds in any dimension greater than three, and that the critical exponents coincide with those of the Van der Waals system. We find that neutral slowly rotating black holes in four space-time dimensions also have the same qualitative behaviour. However charged and rotating black holes in three spacetime dimensions do not exhibit critical phenomena. For Born-Infeld black holes we define a new thermodynamic quantity B conjugate to the Born-Infeld parameter b that we call Born-Infeld vacuum polarization. We demonstrate that this quantity is required for consistency of both the first law of thermodynamics and the corresponding Smarr relation.Comment: 23 pages, 32 figures, v2: minor changes, upgraded reference
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