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Fain B, Robert-Philip I, Beveratos A, David C, Wang ZZ, Sagnes I, Girard JC. Discretization of electronic states in large InAsP/InP multilevel quantum dots probed by scanning tunneling spectroscopy. Phys Rev Lett 2012; 108:126808. [PMID: 22540615 DOI: 10.1103/physrevlett.108.126808] [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: 11/03/2011] [Indexed: 05/31/2023]
Abstract
The topography and the electronic structure of InAsP/InP quantum dots are probed by cross-sectional scanning tunneling microscopy and spectroscopy. The study of the local density of states in such large quantum dots confirms the discrete nature of the electronic levels whose wave functions are measured by differential conductivity mapping. Because of their large dimensions, the energy separation between the discrete electronic levels is low, allowing for quantization in both the lateral and growth directions as well as the observation of the harmonicity of the dot lateral potential.
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Affiliation(s)
- B Fain
- Laboratoire de Photonique et de Nanostructures LPN-CNRS UPR20, Route de Nozay, 91460 Marcoussis, France
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Abstract
We present a novel technique of sampling the configurations of helical proteins. Assuming knowledge of native secondary structure, we employ assembly rules gathered from a database of existing structures to enumerate the geometrically possible three-dimensional arrangements of the constituent helices. We produce a library of possible folds for 25 helical protein cores. In each case, our method finds significant numbers of conformations close to the native structure. In addition, we assign coordinates to all atoms for four of the 25 proteins and show that this has a small effect on the number of near-native conformations. In the context of database driven exhaustive enumeration our method performs extremely well, yielding significant percentages of conformations (between 0.02% and 82%) within 6 A of the native structure. The method's speed and efficiency make it a valuable tool for predicting protein structure.
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Affiliation(s)
- B Fain
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
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Abstract
We examine the conformations of a model for a short segment of closed DNA. The molecule is represented as a cylindrically symmetric elastic rod with a constraint corresponding to a specification of the linking number. We obtain analytic expressions leading to the spatial configuration of a family of solutions representing distortions that interpolate between the circular form of DNA and a figure-eight form that represents the onset of interwinding. We are also able to generate knotted loops. We suggest ways to use our approach to produce other configurations relevant to studies of DNA structure. The stability of the distorted configurations is assessed, along with the effects of fluctuations on the free energy of the various configurations.
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Affiliation(s)
- B Fain
- Department of Physics, UCLA, Los Angeles, California 90095-1547, USA
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Liou HT, Huang KL, Fain B. Observing Population Transfer in a Two-Photon Dressed Field Three-Level System by Transient Stimulated Emission. J Phys Chem A 1997. [DOI: 10.1021/jp9710401] [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: 11/30/2022]
Affiliation(s)
- Huei Tarng Liou
- Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei, Taiwan, and School of Chemistry, Tel-Aviv University, Ramat-Aviv, Israel
| | - Kuang Lang Huang
- Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei, Taiwan, and School of Chemistry, Tel-Aviv University, Ramat-Aviv, Israel
| | - B. Fain
- Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei, Taiwan, and School of Chemistry, Tel-Aviv University, Ramat-Aviv, Israel
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Fain B, Lin SH, Khidekel V. Limitations of pump-probe femtosecond time-resolved experiments: Time-dependent absorption and dispersion line shapes. Phys Rev A 1993; 47:3222-3239. [PMID: 9909301 DOI: 10.1103/physreva.47.3222] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Alden R, Lin S, Xiao W, Fain B, Islampour R. Theory of femtosecond time-resolved infrared absorption spectroscopy with application to ligand dissociation in haemoglobin. Mol Phys 1992. [DOI: 10.1080/00268979200101051] [Citation(s) in RCA: 4] [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: 10/24/2022]
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Pines-Rojansky D, Fain B. Phonon-assisted energy-transfer process in a bottlenecked lattice. Phys Rev B Condens Matter 1990; 41:2704-2711. [PMID: 9994036 DOI: 10.1103/physrevb.41.2704] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Fain B, Lin S. General asymptotic behaviors for amplitude and frequency dependence of multiphoton ionization rates. Chem Phys Lett 1990. [DOI: 10.1016/0009-2614(90)85434-e] [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: 11/17/2022]
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Fain B, Lin SH, Hamer N. Two‐dimensional spectroscopy: Theory of nonstationary, time‐dependent absorption and its application to femtosecond processes. J Chem Phys 1989. [DOI: 10.1063/1.456786] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Fain B, Rojansky D. Mutual influence of energy transfer and lattice phonons. Phys Rev B Condens Matter 1986; 34:4323-4330. [PMID: 9940203 DOI: 10.1103/physrevb.34.4323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Boeglin A, Lin K, Lin S, Fain B. Theory of laser-stimulated phase transition kinetics in solids. Chem Phys Lett 1986. [DOI: 10.1016/0009-2614(86)80235-4] [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: 10/18/2022]
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Fain B, Vellet D, Hertzanu Y. Adult tethered cord syndrome. A case report. S Afr Med J 1985; 67:985-6. [PMID: 3890221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
A patient with adult onset of the tethered cord syndrome is described. The significance of the clinical presentation and the myelographic and computed tomographic findings are discussed.
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