341,784 research outputs found
Nature of well-defined conductance of amine anchored molecular junctions
Amine terminated molecules show well behaved conductance in the scanning
tunneling microscope break-junction experimental measurements. We performed
density functional theory based electron transport calculations to explain the
nature of this phenomenon. We find that amines can be adsorbed only on apex Au
atom, while thiolate group can be attached equally well to undercoordinated and
clean Au surfaces. Our calculations show that only one adsorption geo metry is
sterically and energetically possible for amine anchored junction whereas three
different adsorption geometries with very distinct transport pro perties are
almost equally probable for thiolate anchored junction. We calculated the
conductance as a function of the junction stretching when the molecules are
pulled by the scanning tunneling microscope tip from the Au electrode. Our
calculations show that the stretching of the thiolate anchored junction during
its formation is accompanied by significant electrode geometry distortio n. The
amine anchored junctions exhibit very different behavior -- the electrode
remains intact when the scan ning tunneling microscope tip stretches the
junction
Domain Wall and Periodic Solutions of Coupled phi4 Models in an External Field
Coupled double well (phi4) one-dimensional potentials abound in both
condensed matter physics and field theory. Here we provide an exhaustive set of
exact periodic solutions of a coupled model in an external field in
terms of elliptic functions (domain wall arrays) and obtain single domain wall
solutions in specific limits. We also calculate the energy and interaction
between solitons for various solutions. Both topological and nontopological
(e.g. some pulse-like solutions in the presence of a conjugate field) domain
walls are obtained. We relate some of these solutions to the recently observed
magnetic domain walls in certain multiferroic materials and also in the field
theory context wherever possible. Discrete analogs of these coupled models,
relevant for structural transitions on a lattice, are also considered.Comment: 35 pages, no figures (J. Math. Phys. 2006
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Integration, management and communication of heterogeneous design resources with WWW technologies
Recently, advanced information technologies have opened new pos-sibilities for collaborative designs. In this paper, a Web-based collaborative de-sign environment is proposed, where heterogeneous design applications can be integrated with a common interface, managed dynamically for publishing and searching, and communicated with each other for integrated multi-objective de-sign. The CORBA (Common Object Request Broker Architecture) is employed as an implementation tool to enable integration and communication of design application programs; and the XML (eXtensible Markup Language) is used as a common data descriptive language for data exchange between heterogeneous applications and for resource description and recording. This paper also intro-duces the implementation of the system and the encapsulating issues of existing legacy applications. At last, an example of gear design based on the system is il-lustrated to identify the methods and procedure developed by this research
Classification of Multipartite Entanglement via Negativity Fonts
Partial transposition of state operator is a well known tool to detect
quantum correlations between two parts of a composite system. In this letter,
the global partial transpose (GPT) is linked to conceptually multipartite
underlying structures in a state - the negativity fonts. If K-way negativity
fonts with non zero determinants exist, then selective partial transposition of
a pure state, involving K of the N qubits (K leq N) yields an operator with
negative eigevalues, identifying K-body correlations in the state. Expansion of
GPT interms of K-way partially transposed (KPT) operators reveals the nature of
intricate intrinsic correlations in the state. Classification criteria for
multipartite entangled states, based on underlying structure of global partial
transpose of canonical state, are proposed. Number of N-partite entanglement
types for an N qubit system is found to be 2^{N-1}-N+2, while the number of
major entanglement classes is 2^{N-1}-1. Major classes for three and four qubit
states are listed. Subclasses are determined by the number and type of
negativity fonts in canonical state.Comment: 5 pages, No figures, Corrected typo
Baryon enhancement in high-density QCD and relativistic heavy ion collisions
We argue that the collinear factorization of the fragmentation functions in
high energy nuclear collisions breaks down at transverse momenta due to high parton densities in the colliding hadrons and/or nuclei. We
find that gluon recombination dominates in that region. We calculate the
inclusive cross-section for meson and nucleon production using the low
energy theorems for the scale anomaly in QCD, and compare our quantitative
baryon-to-meson ratio to the RHIC data.Comment: 4 pages, 2 figure; Contribution to Quark Matter 2008 in Jaipur,
India; submitted to J. Phys.
Absence of Localization in Certain Field Effect Transistors
We review some experimental and theoretical results on the metal-to-insulator
transition (MIT) observed at zero magnetic field (B=0) in several
two-dimensional electron systems (2DES). Scaling of the conductance and
magnetic field dependence of the conductance provide convincing evidence that
the MIT is driven by Coulomb interactions among the carriers and is
dramatically sensitive to spin polarization of the carriers.Comment: 8 pages, LaTeX, figure label change
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