1,634 research outputs found
Low temperature electron transfer in strongly condensed phase
Electron transfer coupled to a collective vibronic degree of freedom is
studied in strongly condensed phase and at lower temperatures where quantum
fluctuations are essential. Based on an exact representation of the reduced
density matrix of the electronic+reaction coordinate compound in terms of path
integrals, recent findings on the overdamped limit in quantum dissipative
systems are employed. This allows to give for the first time a consistent
generalization of the well-known Zusman equations to the quantum domain.
Detailed conditions for the range of validity are specified. Using the Wigner
transform these results are also extended to the quantum dynamics in full phase
space. As an important application electronic transfer rates are derived that
comprise adiabatic and nonadiabatic processes in the low temperature regime
including nuclear tunneling. Accurate agreement with precise quantum Monte
Carlo data is observed.Comment: 16 pages, 6 figures, revised version with minor change
TEMP-2--A ONE DIMENSIONAL TRANSIENT THERMAL STRESS PROGRAM FOR THE IBM 704
An IBM-704 computer program for the solution of transient thermal stress problems in one dimension is described. For given boundary and initial conditions the transient temperature distribution and stresses are computed. Spherical, cylindrical, and slab geometeries can be treated by this program. (auth
Divergence alone cannot guarantee stable sparse activity patterns if connections are dense
No description supplie
Electron Transfer in Donor-Acceptor Systems: Many-Particle Effects and Influence of Electronic Correlations
We investigate electron transfer processes in donor-acceptor systems with a
coupling of the electronic degrees of freedom to a common bosonic bath. The
model allows to study many-particle effects and the influence of the local
Coulomb interaction U between electrons on donor and acceptor sites. Using the
non-perturbative numerical renormalization group approach we find distinct
differences between the electron transfer characteristics in the single- and
two-particle subspaces. We calculate the critical electron-boson coupling
alpha_c as a function of and show results for density-density correlation
functions in the whole parameter space. The possibility of many-particle
(bipolaronic) and Coulomb-assisted transfer is discussed.Comment: 4 pages, 4 figure
Detection of liquid xenon scintillation light with a Silicon Photomultiplier
We have studied the feasibility of a silicon photomultiplier (SiPM) to detect
liquid xenon (LXe) scintillation light. The SiPM was operated inside a small
volume of pure LXe, at -95 degree Celsius, irradiated with an internal Am-241
alpha source. The gain of the SiPM at this temperature was estimated to be 1.8
x 10^6 with bias voltage at 52 V. Based on the geometry of the setup, the
quantum efficiency of the SiPM was estimated to be 22% at the Xe wavelength of
178 nm. The low excess noise factor, high single photoelectron detection
efficiency, and low bias voltage of SiPMs make them attractive alternative UV
photon detection devices to photomultiplier tubes (PMTs) for liquid xenon
detectors, especially for experiments requiring a very low energy detection
threshold, such as neutralino dark matter searches
The Rational Overhauser: an Interpolating Rational Cubic Curve.
A rational interpolating cubic curve which implicitly maintains first order geometric continuity in splines has been developed. The curve is formed by blending two rational quadratic curves. Since the blending method used was originally introduced by Overhauser, this curve is referred to as the Rational Overhauser (Rover) curve. The curve formulation utilizes four shape factors to provide control of the curve. A geometrical and analytical interpretation of these shape factors and their relationship to each other is discussed. Procedures for representing conic sections using the rational Overhauser curve are presented. Also included are techniques for mapping between the Rover curve and rational forms of the Hermite, Bezier, and B-Spline curves
Playing "America" on Nineteenth-Century Stages; Or, Jonathan in England and Jonathan at Home
"Playing America," prepared towards the completion of a Ph.D. in Theatre and Performance Studies at the University of Pittsburgh, examines "Yankee Theatre" in America and London through a post-colonial lens from 1787 to 1855. Actors under consideration include: Charles Mathews, James Hackett, George Hill, Danforth Marble and Joshua Silsbee. These actors were selected due to their status as iconic performers in "Yankee Theatre."The Post-Revolutionary period in America was filled with questions of national identity. Much of American culture came directly from England. American citizens read English books, studied English texts in school, and watched English theatre. They were inundated with English culture and unsure of what their own civilization might look like. A post-colonial crisis, in other words, gripped the new nation. This dissertation attempts to explain "Yankee Theatre," a performance tradition popular from the mid-1820s to the mid-1850s, within this complex, transatlantic, sociopolitical situation. It begins with a discussion of early Yankee plays and explains how they were written against the "empire," distinguishing the new citizen from the English subject. It examines ways early Yankee Theatre actors expressed their American identity and discusses the pressures these actors faced in fighting for international success. "Yankee Theatre" was not only popular in America. Several American actors also traveled across the Atlantic to perform it on London stages. Thus, this dissertation also encompasses how the English understood the Yankee, how an imperial standard was established overseas, why English audiences were unhappy with the first American Yankee actors they witnessed, and how future Yankee actors were caught in this web of criterion and taste for years to come. "Playing America" asserts that "Yankee Theatre" addressed specific problems, issues, and questions arising from America's post-colonial status. When the post-colonial crisis passed, Yankee Theatre also ended. By the mid-to late-1850s, the minstrel replaced Jonathan as the symbol of the nation. An examination of "Yankee Theatre" allows for a greater understanding of circum-Atlantic performance as well as issues of nationalism and national identity in the theatre. Research methodologies include historical and textual analysis as well as post-colonial, literary, and dramatic theory
Self-assembled guanine ribbons as wide-bandgap semiconductors
We present a first principle study about the stability and the electronic
properties of a new biomolecular solid-state material, obtained by the
self-assembling of guanine (G) molecules. We consider hydrogen-bonded planar
ribbons in isolated and stacked configurations. These aggregates present
electronic properties similar to inorganic wide-bandgap semiconductors. The
formation of Bloch-type orbitals is observed along the stacking direction,
while it is negligible in the ribbon plane. Global band-like conduction may be
affected by a dipole-field which spontaneously arises along the ribbon axis.
Our results indicate that G-ribbon assemblies are promising materials for
biomolecular nanodevices, consistently with recent experimental results.Comment: 7 pages, 3 figures, to be published in Physica
- …