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  • American Institute of Physics (AIP)  (12)
  • 2010-2014  (6)
  • 2005-2009
  • 2000-2004  (5)
  • 1985-1989  (1)
  • 1
    Publikationsdatum: 2014-11-27
    Beschreibung: We investigate local phase transitions of the solvent in the neighborhood of a solvophobic polymer chain which is induced by a change of the polymer-solvent repulsion and the solvent pressure in the bulk solution. We describe the polymer in solution by the Edwards model, where the conditional partition function of the polymer chain at a fixed radius of gyration is described by a mean-field theory. The contributions of the polymer-solvent and the solvent-solvent interactions to the total free energy are described within the mean-field approximation. We obtain the total free energy of the solution as a function of the radius of gyration and the average solvent number density within the gyration volume. The resulting system of coupled equations is solved varying the polymer-solvent repulsion strength at high solvent pressure in the bulk. We show that the coil-globule (globule-coil) transition occurs accompanied by a local solvent evaporation (condensation) within the gyration volume.
    Print ISSN: 0021-9606
    Digitale ISSN: 1089-7690
    Thema: Chemie und Pharmazie , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2014-07-04
    Beschreibung: We present a statistical model of a dilute polymer solution in good solvent in the presence of low-molecular weight cosolvent. We investigate the conformational changes of the polymer induced by a change of the cosolvent concentration and the type of interaction between the cosolvent and the polymer. We describe the polymer in solution by the Edwards model, where the partition function of the polymer chain with a fixed radius of gyration is described in the framework of the mean-field approximation. The contributions of polymer-cosolvent and the cosolvent-cosolvent interactions in the total free energy are treated also within the mean-field approximation. For convenience we separate the system volume on two parts: the volume occupied by the polymer chain expressed through its gyration volume and the bulk solution. Considering the equilibrium between the two subvolumes we obtain the total free energy of the solution as a function of radius of gyration and the cosolvent concentration within gyration volume. After minimization of the total free energy with respect to its arguments we obtain a system of coupled equations with respect to the radius of gyration of the polymer chain and the cosolvent concentration within the gyration volume. Varying the interaction strength between polymer and cosolvent we show that the polymer collapse occurs in two cases—either when the interaction between polymer and cosolvent is repulsive or when the interaction is attractive. The reported effects could be relevant for different disciplines where conformational transitions of macromolecules in the presence of a cosolvent are of interest, in particular in biology, chemistry, and material science.
    Digitale ISSN: 1931-9223
    Thema: Chemie und Pharmazie , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2014-08-13
    Beschreibung: Functioning layout of a frequency comb-based subterahertz synthesizer is demonstrated. A primary subterahertz oscillator was phase-locked against the Ti:Sapphire femtosecond laser frequency comb down-converted to the subterahertz range by the semiconductor mixer. Synthesizer operation is demonstrated through Fabri-Perot resonator response curve recording experiment. Spectral purity of the synthesizer was estimated. The advantage of the comb-based synthesizer over the synthesizer based on the Agilent E8257D device was shown.
    Print ISSN: 0003-6951
    Digitale ISSN: 1077-3118
    Thema: Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    facet.materialart.
    Unbekannt
    American Institute of Physics (AIP)
    Publikationsdatum: 2014-06-11
    Beschreibung: The subject of this paper is solutions of an autoresonance equation. We look for a connection between the parameters of the solution bounded as t   →−∞, and the parameters of two two-parameter families of solutions as t   → ∞. One family consists of the solutions which are not captured into resonance, and another of those increasing solutions which are captured into resonance. In this way we describe the transition through the separatrix for equations with slowly varying parameters and get an estimate for parameters before the resonance of those solutions which may be captured into autoresonance.
    Print ISSN: 0022-2488
    Digitale ISSN: 1089-7658
    Thema: Mathematik , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Publikationsdatum: 2014-07-31
    Beschreibung: A single-electron tunneling (SET) device with a nanoscale central island that can move with respect to the bulk source- and drain electrodes allows for a nanoelectromechanical (NEM) coupling between the electrical current through the device and mechanical vibrations of the island. Although an electromechanical “shuttle” instability and the associated phenomenon of single-electron shuttling were predicted more than 15 years ago, both theoretical and experimental studies of NEM-SET structures are still carried out. New functionalities based on quantum coherence, Coulomb correlations and coherent electron-spin dynamics are of particular current interest. In this article we present a short review of recent activities in this area.
    Print ISSN: 1063-777X
    Digitale ISSN: 1090-6517
    Thema: Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Publikationsdatum: 2014-07-04
    Beschreibung: We present a statistical model of a dilute polymer solution in good solvent in the presence of low-molecular weight cosolvent. We investigate the conformational changes of the polymer induced by a change of the cosolvent concentration and the type of interaction between the cosolvent and the polymer. We describe the polymer in solution by the Edwards model, where the partition function of the polymer chain with a fixed radius of gyration is described in the framework of the mean-field approximation. The contributions of polymer-cosolvent and the cosolvent-cosolvent interactions in the total free energy are treated also within the mean-field approximation. For convenience we separate the system volume on two parts: the volume occupied by the polymer chain expressed through its gyration volume and the bulk solution. Considering the equilibrium between the two subvolumes we obtain the total free energy of the solution as a function of radius of gyration and the cosolvent concentration within gyration volume. After minimization of the total free energy with respect to its arguments we obtain a system of coupled equations with respect to the radius of gyration of the polymer chain and the cosolvent concentration within the gyration volume. Varying the interaction strength between polymer and cosolvent we show that the polymer collapse occurs in two cases—either when the interaction between polymer and cosolvent is repulsive or when the interaction is attractive. The reported effects could be relevant for different disciplines where conformational transitions of macromolecules in the presence of a cosolvent are of interest, in particular in biology, chemistry, and material science.
    Print ISSN: 0021-9606
    Digitale ISSN: 1089-7690
    Thema: Chemie und Pharmazie , Physik
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 7
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 41 (2000), S. 1934-1955 
    ISSN: 1089-7658
    Quelle: AIP Digital Archive
    Thema: Mathematik , Physik
    Notizen: Simple explicit solutions of the linear wave equation in three dimensions are presented which describe wave packets exponentially localized near a point moving with the wave speed. For large values of a certain free parameter these new solutions are localized in Gaussian manner with respect to longitudinal and transverse variables and time. This agrees with considerations by Babich–Ulin and Ralston who have presented an asymptotic description of solutions exhibiting such local behavior. Global estimates and large-time asymptotics of these solutions are given. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The paper deals with two projects of compact superconducting storage rings for industrial production of integrated circuits (IC) using x-ray lithography within the 8- to 20-A(ring) wavelengths range. The azimuthally symmetric superconducting storage ring Siberia-AS at an energy of 600 MeV is a superconducting analog of VEP-1, one of the earliest storage rings in the world intended for the purposes of high-energy physics. Unlike the conventional design, no iron yoke is used in the storage ring under consideration to form the magnetic field at the equilibrium orbit and to close the return magnetic flux—this is performed by some inner and outer superconducting windings. Such a scheme enables the size of the storage ring to be substantially reduced (a cylinder of 2 m in diameter and 2 m long), and as a result, its weight decreases, too (about 10 tons). The eight-magnet storage ring Siberia-SM is of four-order symmetry so that the periodicity element comprises two rectangular magnets and three lenses. Its basic component is a superconducting bending rectangular magnet at a 6-T magnetic field. Two variants of such magnets have been proposed: in the first, the iron yoke is utilized to form the magnetic field and to close the return flux, while the second is an ironless C-shaped magnet manufactured on the basis of original wedgelike coils.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 775-777 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We propose a semiconductor structure that can filter electron spin without using external magnetic fields. The structure consists of a T-shaped quasi-one-dimensional channel and an electrode placed near the channel intersection to control the spin-orbit interaction for electrons. Our calculations demonstrate that the proposed device can redirect electrons with opposite spins from an unpolarized source to left and right output leads, respectively, and, thus, serve as a spin filter. When the incident electron energy is in resonance with the quasilocalized zero-dimensional states at the intersection, polarization of the transmitted fluxes approaches 100%. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2857-2859 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In this letter, we develop optimal parameters for a structure which is suitable for the realization of a coherent quantum receiver. Conditions including predefined photon wavelength, strain, small Zeeman splitting of the electron levels, and large Zeeman effect for quantum-confined light holes are satisfied simultaneously for the structure based on the InGaAsP solid solutions. We are able to achieve designs with wavelengths of 1.3 and 1.55 μm that are desirable for optoelectronic applications. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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