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Calibrated Langevin-dynamics simulations of intrinsically disordered proteins

Physical Review E 2014年第4期90卷 042709-042709页

作者： W. Wendell Smith Po-Yi Ho Corey S. O'Hern Department of Physics Yale University New Haven Connecticut 06520-8120 USA Integrated Graduate Program in Physical and Engineering Biology Yale University New Haven Connecticut 06520-8114 USA Department of Mechanical Engineering and Materials Science Yale University New Haven Connecticut 06520-8286 USA Department of Applied Physics Yale University New Haven Connecticut 06520-8267 USA Program in Computational Biology and Bioinformatics Yale University New Haven Connecticut 06520 USA

We perform extensive coarse-grained (CG) Langevin dynamics simulations of intrinsically disordered proteins (IDPs), which possess fluctuating conformational statistics between that for excluded volume random walks and collapsed globules. Our CG model includes repulsive steric, attractive hydrophobic, and electrostatic interactions between residues and is calibrated to a large collection of single-molecule fluorescence resonance energy transfer data on the interresidue separations for 36 pairs of residues in five IDPs: α−, β−, and γ-synuclein, the microtubule-associated protein τ, and prothymosin α. We find that our CG model is able to recapitulate the average interresidue separations regardless of the choice of the hydrophobicity scale, which shows that our calibrated model can robustly capture the conformational dynamics of IDPs. We then employ our model to study the scaling of the radius of gyration with chemical distance in 11 known IDPs. We identify a strong correlation between the distance to the dividing line between folded proteins and IDPs in the mean charge and hydrophobicity space and the scaling exponent of the radius of gyration with chemical distance along the protein.

关键词： LANGEVIN equations SIMULATION methods & models CONFORMATIONAL analysis MICROTUBULE-associated proteins HYDROPHOBIC compounds

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Optical properties of thin VO2-films at the phase transition: Design aspects for a fiber-optic thermometer

Optical properties of thin VO2-films at the phase transition...

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IEEE Instrumentation and Measurement Technology Conference

作者： L. Hermano C. L. A. M. N. Lima L. A. L. Almeida C. L. Ferreira H. Neff Graduate Program in Electrical Engineering - PpgEE Department of Electrical Engineering Universidade Federal de Campina Grande Brazil Universidade Federal de Campina Grande Campina Grande PB BR Universidade Federal do ABC Santo Andre SP BR Department of Materials Science Instituto Militar de Engenharia - IME Brazil

ISBN: (纸本)9781467363846

The pronounced variation of the optical reflectance R of nanometer thin VO 2 films with temperature T at the phase transition recently has triggered interest in the development of compact thermo-optical sensors that utilize optical fiber technology. Its immunity against electromagnetic interference effects makes this approach suited for an optical detection of local areas with increased temperature, i.e. so called hot spots, inside of high power transformers. Optical reflectance of thin VO 2 -films as function of T throughout the hysteretic phase transition is reported in this work. A modified version of the Preisach hysteresis model is utilized, and combined with experimental optical data. Suited VO 2 film thickness values and wavelengths range for optimum sensor operation can be extracted. The achievable temperature range, as confirmed by experimental observations, is consistent with requirements that apply for power transformers of the first group, according to NBR 5416 (ABNT).

关键词： Optical fiber sensors Mathematical model Reflectivity Equations Optical fibers Temperature sensors

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(Invited) Metal-Semiconductor-Metal Photocurrent Chip for Hydrogen Peroxide and Biomolecular Sensing with Chemiluminescence

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ECS Transactions 2014年第16期64卷

作者： Fu-Hsiang Ko Ching-Chang Lin Da-Shiuan Sun Tung-Ming Pan National Chiao Tung University Graduate Program for Nanotechnology Department of Materials Science and Engineering National Chiao Tung University Chang Gung University

Photodetectors are generally the most promising, representative and widely-used type of detectors, and the applications of photodetectors are quite extensively. Photodetectors are made of photosensitive elements which are able to turn the light signal into electrical signal. Owing to the nature of fast responding speed and capability of large volume manufacturing, it provides photodetectors an advantageous future in biomedical sensing territory. This study focuses on fabrication method of the flexible photodetectors and application to biomolecule sensing through luminescence. The photosensitive element is based on silicon wafer which is treated with chemical etching process to achieve pliable characteristic. Then, the metal-semiconductor-metal structural flexible photodetectors are achieved after integrated with simple fabricating processes. The accomplished devices are handled with immobilization steps to fix the target enzyme which is able to catalyze the luminescent reaction. We provide a portable biomolecule sensor with outstanding flexible characteristic and high sensitivity and it exhibits illustrious stable consequence in various situations.

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Invited: Metal-Semiconductor-Metal Photocurrent Chip for Hydrogen Peroxide and Biomolecular Sensing with Chemiluminescence

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ECS Meeting Abstracts 2014年第45期MA2014-02卷

Photodetectors are generally the most promising, representative and widely-used type of detectors, and the applications of photodetectors are quite extensively[1-3]. Basically photodetectors are made of photosensitive elements which are able to turn the light signal into electrical signal. Nowadays, the detecting wavelength region is very broad and can be classified into infrared, visible light and ultraviolet zone; furthermore, the applications of each region are manifold especially in visible light region. Additionally owing to the nature of fast responding speed, it promises photodetectors an advantageous future in biomedical sensing territory[4-5]. This study is focus on fabrication method of the flexible[6-8] photodetectors and application to biomolecule sensing through luminescence. The photosensitive element is based on single crystalline silicon semiconductor material which is treated with chemical etching process to achieve pliable characteristic[9]. Then, the metal-semiconductor-metal[10-14]structural flexible photodetectors are achieved after integrated with simple fabricating processes. In detail, the accomplished devices are handled with immobilization steps to fix the target enzyme which is able to catalyze the luminescent reaction (Fig.1). Owing to only extremely stable sensor for biomedical use, it is necessary to ensure the operation function at any crucial conditions. In this study, we provide a portable biomolecule sensor with outstanding flexible characteristic and high sensitivity and it exhibits illustrious stable consequence in various situations. Figure *** diagram of immobilization process flow and luminescence detection. A pliable silicon chip measured under fifty micrometers in thickness is achieved through a simple method via alkaline etchant. The silicon chip with designed thickness is featured of great flexibility and relatively little fragility. A surface modification is applied to the flexible silicon chip with non-toxic and e

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Pueraria lobata (Kudzu) photosystem i improves the photoelectrochemical performance of silicon

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Industrial Biotechnology 2013年第1期9卷 37-41页

作者： Gunther, Darlene Leblanc, Gabriel Cliffel, David E. Kane Jennings, G. Interdisciplinary Materials Science Graduate Program Vanderbilt University Nashville TN United States Department of Chemistry Vanderbilt University Nashville TN United States Department of Chemical and Biomolecular Engineering Vanderbilt University 2301 Vanderbilt Place Nashville TN 37235 United States

Photosystem I (PSI), a protein complex found within the thylakoid membrane of green plants and some bacteria, drives nature's 90-terawatt solar energy conversion process known as photosynthesis. Kudzu (Pueraria lobata) is an invasive vine from eastern Asia that grows in the southern United States, spreading at ∼500 km2 per year and causing extensive environmental damage. This article reports the first integration of nature's optimized solar energy converter-PSI from the fast-growing, invasive leaves of kudzu-with the ubiquitous platform of integrated circuits-silicon-to prepare a "wet" photoelectrochemical cell. Herein, we report on the success of PSI films extracted from the kudzu leaf and deposited on boron-doped silicon (p-Si) to enhance photoelectrochemical current over p-Si alone. © 2013, Mary Ann Liebert, Inc.

关键词： Solar energy

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Characterization of FeCr and FeCoCr alloy coatings of carbon steels for marine environment applications

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Applied Adhesion science 2013年第1期1卷 1-10页

作者： Antunes, Fernando José de Sá Brito, Vinícius Ribeiro dos Santos Bastos, Ivan Napoleão Costa, Hector Reynaldo Meneses Centro Federal de Educação Tecnológica Celso Suckow da Fonseca Graduate Program in Mechanical Engineering and Materials Technology Av. Maracanã 229 Rio de Janeiro RJ – 20271-110 Brazil Universidade do Estado do Rio de Janeiro Graduate Program in Materials Science and Technology Rua Bonfim 25 Nova Friburgo RJ – 28625-570 Brazil

This paper presents the adhesive strength results of FeCr and FeCoCr deposits produced by electric arc thermal spray process on carbon steel plates. Five chemical compositions were tested to give a large panel of possibility. Coatings were characterized by several methods to result in a performance screening. The main assessment of microstructural morphology was made by scanning electron microscopy (SEM). The mechanical strength of coatings was evaluated by standard pull-off test. The corrosion resistance was analyzed in salt-spray test. The morphology of coatings exhibits characteristics of lamellar microstructures with incompletely melted particles together with a distribution of similarly oriented oxides. The adhesive strength of FeCoCr alloy coatings was higher amongst all studied conditions. All sealed conditions presented low corrosion in salt-spray exposure. Additionally, a new FeCoCr alloy was studied to reduce pores and microcracks that are frequently found in traditional FeCr and FeCrNi alloys. Based on the performed characterizations, the findings suggested that the FeCoCr deposition, with an epoxy sealing, is suitable to be used as an efficient coating of carbon steel in aggressive marine environments. © 2013, Antunes et al.;licensee Springer.

关键词： Adhesion test Carbon steel FeCoCr coating Salt-spray test Thermal spray

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Mechanical Behavior of Yttria-Stabilized Zirconia Aqueous Cast Tapes and Laminates

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Journal of Ceramics 2014年第1期2014卷

作者： V. Moreno R. M. Bernardino D. Hotza Graduate Program on Materials Science and Engineering (PGMAT) Federal University of Santa Catarina 88040-900 Florianópolis SC Brazilufsc.br Department of Mechanical Engineering Federal University of Santa Catarina 88040-900 Florianópolis SC Brazilufsc.br Department of Chemical Engineering Federal University of Santa Catarina 88040-900 Florianópolis SC Brazilufsc.br

Aqueous tape casting was used to produce yttria-stabilized zirconia films for electrolyte-supported solid oxide fuel cell (SOFC). Tape casting slurries were prepared varying the binder content between 20 and 25 wt%. A commercial acrylic emulsion served as binder. Rheological measurements of the two slurries were performed. Both slurries showed a shear-thinning behavior. Tapes with 25 wt% binder exhibited adequate flexibility and a smooth and homogeneous surface, free of cracks and other defects. Suitable conditions of lamination were found and a theoretical density of 54% in the laminates was achieved. Laminated tapes showed higher tensile strength compared to single sheets. Tape orientation has a significant influence on the mechanical properties. Tensile strength, elongation to strain, and Young’s modulus measured in samples produced in the direction of casting showed higher property values.

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Existence of a Thermodynamic Spin-Glass Phase in the Zero-Concentration Limit of Anisotropic Dipolar Systems

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Physical Review X 2014年第4期4卷 041016-041016页

作者： Juan Carlos Andresen Helmut G. Katzgraber Vadim Oganesyan Moshe Schechter Theoretische Physik ETH Zurich CH-8093 Zurich Switzerland Department of Theoretical Physics Royal Institute of Technology SE-106 91 Stockholm Sweden Department of Physics and Astronomy Texas A&M University College Station Texas 77843-4242 USA Materials Science and Engineering Program Texas A&M University College Station Texas 77843 USA Santa Fe Institute 1399 Hyde Park Road Santa Fe New Mexico 87501 USA Department of Engineering Science and Physics College of Staten Island CUNY Staten Island New York 10314 USA Initiative for the Theoretical Sciences The Graduate Center CUNY New York New York 10016 USA Department of Physics Ben Gurion University of the Negev Beer Sheva 84105 Israel

The nature of ordering in dilute dipolar interacting systems dates back to the work of Debye and is one of the most basic, oldest and as-of-yet unsettled problems in magnetism. While spin-glass order is readily observed in several RKKY-interacting systems, dipolar spin glasses are the subject of controversy and ongoing scrutiny, e.g., in LiHoxY1−xF4, a rare-earth randomly diluted uniaxial (Ising) dipolar system. In particular, it is unclear if the spin-glass phase in these paradigmatic materials persists in the limit of zero concentration or not. We study an effective model of LiHoxY1−xF4 using large-scale Monte Carlo simulations that combine parallel tempering with a special cluster algorithm tailored to overcome the numerical difficulties that occur at extreme dilutions. We find a paramagnetic to spin-glass phase transition for all Ho+ ion concentrations down to the smallest concentration numerically accessible, 0.1%, and including Ho+ ion concentrations that coincide with those studied experimentally up to 16.7%. Our results suggest that randomly diluted dipolar Ising systems have a spin-glass phase in the limit of vanishing dipole concentration, with a critical temperature vanishing linearly with concentration. The agreement of our results with mean-field theory testifies to the irrelevance of fluctuations in interactions strengths, albeit being strong at small concentrations, to the nature of the low-temperature phase and the functional form of the critical temperature of dilute anisotropic dipolar systems. Deviations from linearity in experimental results at the lowest concentrations are discussed.

关键词： Computational physics Condensed matter physics Magnetism

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Fabrication of graphene by electrochemical exfoliation in alkaline electrolytes

Fabrication of graphene by electrochemical exfoliation in al...

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作者： Chang, Li-Chung Hsieh, Yu-Chi Chen, Yong-Min Wu, Pu-Wei Lee, Jyh-Fu Graduate Program for Science and Technology of Accelerator Light Source China Department of Materials Science and Engineering National Chiao Tung University Hsin-Chu 30010 Taiwan Taiwan National Synchrotron Radiation Research Center Hsin-Chu 30076 Taiwan Taiwan

ISBN: (纸本)9781607685395

Fabrication of graphene was demonstrated by electrochemical exfoliation of graphite in an ammonium hydroxide solution. The processing parameter of applied voltage was optimized to accomplish graphene productivity and desired chemical composition. Images from the atomic force microscopy showed graphene sheets with lateral sizes of several hundred nanometers. Images from the transmission electron microscopy indicated the existence of stacked graphene sheets with thickness of a few graphene layers. Raman spectroscopy confirmed variation of assynthesized graphene and bulk graphite. X-ray photoemission spectroscopy suggested the formation of graphene oxide at large voltage. © 2014 The Electrochemical Society.

关键词： Graphene

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Deformation of porous, nanostructured silver at room temperature and 150C°

Deformation of porous, nanostructured silver at room tempera...

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2012 MRS Fall Meeting

作者： Noiseau, Guillaume Becker, Michael F. Keto, John W. Kovar, Desiderio Materials Science and Engineering Graduate Program University of Texas at Austin Austin TX 78712-1591 United States Department of Electrical and Computer Engineering University of Texas Austin TX United States Department of Physics University of Texas Austin TX United States Department of Mechanical Engineering University of Texas Austin TX United States

ISBN: (纸本)9781632661067

Porous, nanostructured silver samples were produced using a direct-write method where a nanoparticle aerosol consisting of particles with a mean size of approximately 5 nm were accelerated to speeds of approximately 1000 m/sec and impacted onto a translating substrate [1]. The impacting particles have sufficient energy to stick to the substrate, allowing patterned thick films to be directly written from the aerosol without a mask. Unlike other low temperature processing routes for achieving patterned films, no organics are added that can interfere with post-deposition processing. Typical films are 5-100 μm thick, up to several centimeters long, and have an as-deposited relative densities as high as 70% of bulk Ag. Compression tests were carried out in steps at room temperature and at 150°C under constant displacement rates. Local strain and densification were measured by optical profilometry between each compression step. The results can be used as a starting point to better understand the mechanisms that govern plasticity, creep, and sintering in nanostructured, porous silver at low processing temperatures. © 2013 materials Research Society.

关键词： Room temperature

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