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Anderson TJ, Hobart KD, Tadjer MJ, Koehler AD, Feygelson TI, Pate BB, Hite JK, Kub FJ, Eddy CR. Advances in Diamond Integration for Thermal Management in GaN Power HEMTs. ACTA ACUST UNITED AC 2014. [DOI: 10.1149/06407.0185ecst] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Hossain T, Wei D, Nepal N, Garces NY, Hite JK, Meyer HM, Eddy CR, Baker T, Mayo A, Schmitt J, Edgar JH. Insulating gallium oxide layer produced by thermal oxidation of gallium-polar GaN. ACTA ACUST UNITED AC 2014. [DOI: 10.1002/pssc.201300659] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Kühne P, Darakchieva V, Yakimova R, Tedesco JD, Myers-Ward RL, Eddy CR, Gaskill DK, Herzinger CM, Woollam JA, Schubert M, Hofmann T. Polarization selection rules for inter-Landau-level transitions in epitaxial graphene revealed by the infrared optical Hall effect. Phys Rev Lett 2013; 111:077402. [PMID: 23992081 DOI: 10.1103/physrevlett.111.077402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 05/07/2013] [Indexed: 06/02/2023]
Abstract
We report on the polarization selection rules of inter-Landau-level transitions using reflection-type optical Hall effect measurements from 600 to 4000 cm(-1) on epitaxial graphene grown by thermal decomposition of silicon carbide. We observe symmetric and antisymmetric signatures in our data due to polarization preserving and polarization mixing inter-Landau-level transitions, respectively. From field-dependent measurements, we identify that transitions in coupled graphene monolayers are governed by polarization mixing selection rules, whereas transitions in decoupled graphene monolayers are governed by polarization preserving selection rules. The selection rules may find explanation by different coupling mechanisms of inter-Landau-level transitions with free charge carrier magneto-optic plasma oscillations.
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Affiliation(s)
- P Kühne
- Department of Electrical Engineering and Center for Nanohybrid Functional Materials, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA.
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Nyakiti LO, Myers-Ward RL, Wheeler VD, Imhoff EA, Bezares FJ, Chun H, Caldwell JD, Friedman AL, Matis BR, Baldwin JW, Campbell PM, Culbertson JC, Eddy CR, Jernigan GG, Gaskill DK. Bilayer graphene grown on 4H-SiC (0001) step-free mesas. Nano Lett 2012; 12:1749-1756. [PMID: 22352833 DOI: 10.1021/nl203353f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We demonstrate the first successful growth of large-area (200 × 200 μm(2)) bilayer, Bernal stacked, epitaxial graphene (EG) on atomically flat, 4H-SiC (0001) step-free mesas (SFMs) . The use of SFMs for the growth of graphene resulted in the complete elimination of surface step-bunching typically found after EG growth on conventional nominally on-axis SiC (0001) substrates. As a result heights of EG surface features are reduced by at least a factor of 50 from the heights found on conventional substrates. Evaluation of the EG across the SFM using the Raman 2D mode indicates Bernal stacking with low and uniform compressive lattice strain of only 0.05%. The uniformity of this strain is significantly improved, which is about 13-fold decrease of strain found for EG grown on conventional nominally on-axis substrates. The magnitude of the strain approaches values for stress-free exfoliated graphene flakes. Hall transport measurements on large area bilayer samples taken as a function of temperature from 4.3 to 300 K revealed an n-type carrier mobility that increased from 1170 to 1730 cm(2) V(-1) s(-1), and a corresponding sheet carrier density that decreased from 5.0 × 10(12) cm(-2) to 3.26 × 10(12) cm(-2). The transport is believed to occur predominantly through the top EG layer with the bottom layer screening the top layer from the substrate. These results demonstrate that EG synthesized on large area, perfectly flat on-axis mesa surfaces can be used to produce Bernal-stacked bilayer EG having excellent uniformity and reduced strain and provides the perfect opportunity for significant advancement of epitaxial graphene electronics technology.
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Affiliation(s)
- L O Nyakiti
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA.
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Moustakas TD, Molnar RJ, Lei T, Menon G, Eddy CR. A Comparative Study of GaN Films Grown on Different Faces of Sapphire by ECR-Assisted MBE. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-242-427] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTGaN films were grown on c-plane (0001), a-plane (1120) and r-plane (1102) sapphire substrates by the ECR-assisted MBE method. The films were grown using a two-step growth process, in which a GaN buffer is grown first at relatively low temperatures and the rest of the film is grown at higher temperatures. RHEED studies indicate that this growth method promotes lateral growth and leads to films with smooth surface morphology. The epitaxial relationship to the substrate, the crystalline quality and the surface morphology were investigated by RHEED, X-ray diffraction and SEM studies.
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Affiliation(s)
- C. R. Eddy
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA
| | - D. K. Gaskill
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA
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Parashar UD, Dow L, Fankhauser RL, Humphrey CD, Miller J, Ando T, Williams KS, Eddy CR, Noel JS, Ingram T, Bresee JS, Monroe SS, Glass RI. An outbreak of viral gastroenteritis associated with consumption of sandwiches: implications for the control of transmission by food handlers. Epidemiol Infect 1998; 121:615-21. [PMID: 10030711 PMCID: PMC2809569 DOI: 10.1017/s0950268898001150] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although food handlers are often implicated as the source of infection in outbreaks of food-borne viral gastroenteritis, little is known about the timing of infectivity in relation to illness. We investigated a gastroenteritis outbreak among employees of a manufacturing company and found an association (RR = 14.1, 95% CI = 2.0-97.3) between disease and eating sandwiches prepared by 6 food handlers, 1 of whom reported gastroenteritis which had subsided 4 days earlier. Norwalk-like viruses were detected by electron microscopy or reverse transcriptase-polymerase chain reaction (RT-PCR) in stool specimens from several company employees, the sick food handler whose specimen was obtained 10 days after resolution of illness, and an asymptomatic food handler. All RT-PCR product sequences were identical, suggesting a common source of infection. These data support observations from recent volunteer studies that current recommendations to exclude food handlers from work for 48-72 h after recovery from illness may not always prevent transmission of Norwalk-like viruses because virus can be shed up to 10 days after illness or while exhibiting no symptoms.
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Affiliation(s)
- U D Parashar
- Epidemic Intelligence Service, Epidemiology Program Office, Centers for Disease Control and Prevention, Atlanta, GA, USA
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Narasimhulu S, Eddy CR, Dibartolomeis M, Kowluru R, Jefcoate CR. Adrenal microsomal hydroxylating system: purification and substrate binding properties of cytochrome P-450C-21. Biochemistry 1985; 24:4287-94. [PMID: 3931675 DOI: 10.1021/bi00337a006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The substrate-cytochrome P-450C-21 binding reaction has been investigated in detail by using the purified cytochrome. The apparent substrate dissociation constant (KDapp) depended on the enzyme concentration, indicating that the binding reaction does not follow simple two-component mass action equilibrium. However, the binding data fit reasonably well to a model in which the P-450C-21 exists in a monomer-dimer equilibrium and the substrate does not bind to the dimer. The intrinsic dissociation constant (K1) and the dissociation constant for the dimerization reaction (K2) were calculated from the titration data by a pattern search procedure. K1 and K2 were found to be essentially independent of the enzyme concentration, indicating the appropriateness of the assumed model. In the present study, all factors that increased the dissociation of the dimer, as indicated by an increase in K2, decreased KDapp so that it approached the intrinsic constant K1. These results suggest that there is mutual interaction of the substrate binding and self-association reactions of cytochrome P-450C-21 in the purified preparation.
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Abstract
The results of the present study indicate first that in the microsomal preparation, the components of the P-450 reduction system are heterogeneously distributed, comprising dissociable and nondissociable parts. Second, the P-450 reduction curve can be adequately described by a sum of two exponential functions, indicating two concurrent first-order reactions. Third, the two phases can be altered independently. The addition of the substrate increased the extent of the fast phase while it had little or no effect on that of the slow phase. Changes in the interaction of the dissociable and nondissociable components affected the extent of the slow phase while they were without effect on that of the fast phase. Experiments with different steroids indicated that the independence of the two phases is not due to functionally different P-450's and that the cytochrome reduced in both phases is essentially P-450C-21. The results are interpreted as follows: Transformation of P-450 from the low- to the high-spin state controls the total P-450 reduced. The rate and the biphasicity of the reduction are functions of the interaction of P-450 and the reductase.
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Lerner J, Martin V, Eddy CR, Taylor MW. Some additional characteristics of methionine transport in the chicken intestine. Experientia 1968; 24:1103-4. [PMID: 5721124 DOI: 10.1007/bf02147782] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Abstract
X-ray powder diffraction data are reported for 15 normal long-chain esters. The compounds represent all combinations of acid and alcohol where the acid portion is n-tetradecanoic, n-hexadecanoic, or n-octadecanoic acid, and the alcohol portion is n-tetradecanol, n-pentadecanol, n-hexadecanol, n-heptadecanol, or n-octadecanol. The individual compounds can be identified and distinguished by the diffraction data. Several of the esters have long spacings that are a linear function of the number of carbon atoms in the molecule and are consistent with a similar function for ethyl esters of long-chain acids. The remainder of the compounds crystallize in other polymorphic forms and therefore do not follow this function.
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Affiliation(s)
- D A Lutz
- Eastern Regional Research Laboratory, Philadelphia, Pennsylvania
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Rodebush WH, Eddy CR, Eubank LD. Dielectric Polarization in Solution II. The Polarization of Some Alcohols as a Function of Concentration and Temperature. J Chem Phys 1940. [DOI: 10.1063/1.1750600] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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