14,753 research outputs found
Probing Pauli Blocking Factors in Quantum Pumps with Broken Time-Reversal Symmetry
A recently demonstrated quantum electron pump is discussed within the
framework of photon-assisted tunneling. Due to lack of time-reversal symmetry,
different results are obtained for the pump current depending on whether or not
final-state Pauli blocking factors are used when describing the tunneling
process. Whilst in both cases the current depends quadratically on the driving
amplitude for moderate pumping, a marked difference is predicted for the
temperature dependence. With blocking factors the pump current decreases
roughly linearly with temperature until k_B T ~ \hbar\omega is reached, whereas
without them it is unaffected by temperature, indicating that the entire Fermi
sea participates in the electronic transport.Comment: 4 pages in RevTex4 (beta4), 6 figures; status: to appear in PR
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extensible Markup Language (XML) for Competitive Advantage
extensible Markup Language (XML) has received much attention in the popular press lately as a new technology designed to facilitate information sharing among business entities. One of the biggest problems that companies are experiencing today with XML is that many executives do not understand what XML is and why it is important, nor do they understand what its potential impact on their information strategy might be. In this paper, we present an overview of XML and a framework for generating IS strategic alternatives, which was introduced in its original form in the 1980s. This framework is adapted to suit the properties of XML and its usage is illustrated with XML cases. Finally, considerations for developing XML applications that are identified by the framework are presented
Disorder-induced melting of the charge order in thin films of Pr0.5Ca0.5MnO3
We have studied the magnetic-field-induced melting of the charge order in
thin films of Pr0.5Ca0.5MnO3 (PCMO) films on SrTiO3 (STO) by X-ray diffraction,
magnetization and transport measurement. At small thickness (25 nm) the films
are under tensile strain and the low-temperature melting fields are of the
order of 20 T or more, comparable to the bulk value. With increasing film
thickness the strain relaxes, which leads to a strong decrease of the melting
fields. For a film of 150 nm, with in-plane and out-of-plane lattice parameters
closer to the bulk value, the melting field has reduced to 4 T at 50 K, with a
strong increase in the hysteretic behavior and also an increasing fraction of
ferromagnetic material. Strain relaxation by growth on a template of
YBa2Cu3O(7-delta) or by post-annealing yields similar results with an even
stronger reduction of the melting field. Apparently, strained films behave
bulk-like. Relaxation leads to increasing suppression of the CO state,
presumably due to atomic scale disorder produced by the relaxation process.Comment: 7 pages, 4 fig
Electromagnetic Dipole Strength in Transitional Nuclei
Electromagnetic dipole absorption cross-sections of transitional nuclei with
large-amplitude shape fluctuations are calculated in a microscopic way by
introducing the concept of Instantaneous Shape Sampling. The concept bases on
the slow shape dynamics as compared to the fast dipole vibrations. The
elctromagnetic dipole strength is calculated by means of RPA for the
instantaneous shapes, the probability of which is obtained by means of IBA.
Very good agreement with the experimental absorption cross sections near the
nucleon emission threshold is obtained.Comment: 4 pages, 4 figure
Charge pumping in a quantum wire driven by a series of local time-periodic potentials
We develop a method to calculate electronic transport properties through a
mesoscopic scattering region in the presence of a series of time-periodic
potentials. Using the method, the quantum charge pumping driven by
time-periodic potentials is studied. Jumps in the pumped current are observed
at the peak positions of the Wigner delay time. Our main results in both the
weak pumping and strong pumping regimes are consistent with experimental
results. More interestingly, we also observed the nonzero pumping at the phase
difference phi=0 and addressed its relevance to the experimental result.Comment: 5 page
Graphenylene, a unique two-dimensional carbon network with nondelocalized cyclohexatriene units
Over many years chemists have established the general principle that two-dimensional chemical structures constructed with pure sp2-carbon atoms will definitely form an aromatic system with delocalized electron density. However, based on a recently proposed chemical structure, graphenylene, this rule may finally be broken. Herein, we predict the properties of a new two-dimensional sp2- carbon network known as graphenylene, which is the first example of a non-delocalized sp2-carbon structure composed of cyclohexatriene units with two quite distinct CâC bonds within a C6 ring. In addition, theoretical calculations demonstrate that graphenylene has periodic pores of 3.2 Ă
in diameter and is a semiconductor with a narrow direct band gap, making it promising for various applications, such as electronic devices and efficient hydrogen separation. This study provides a new perspective on carbon allotropes, leading to a better understanding of [N]phenylene based organic frameworks, as well as clarifying the relationship between benzene and cyclohexatriene
Fv antibodies to aflatoxin B1 derived from a pre-immunized antibody phage display library system
The production and characterization of recombinant antibodies to aflatoxin B[SUB1] (AFB[SUB1]), a potent mycotoxin and carcinogen is described. The antibody fragments produced were then applied for use in a surface plasmon resonance-based biosensor (BIAcore), which measures biomolecular interactions in 'real-time'. Single chain Fv (scFv) antibodies were generated to aflatoxin B1 from an established phage display system, which incorporated a range of different plasmids for efficient scFv expression. The scFv's were used in the development of a competitive ELISA, and also for the development of surface plasmon resonance (SPR)-based inhibition immunoassays. They were found to be suitable for the detection of AFB[SUB1], in this format, with the assays being sensitive and reproducible
Medium Effects in Kaon and Antikaon Production in Nuclear Collisions at Subthreshold Beam Energies
Production cross sections of K and K mesons have been measured in C+C
collisions at beam energies per nucleon below and near the nucleon-nucleon
threshold. At a given beam energy, the spectral slopes of the K mesons are
significantly steeper than the ones of the K mesons. The excitation
functions for K and K mesons nearly coincide when correcting for the
threshold energy. In contrast, the K yield exceeds the K yield by a
factor of about 100 in proton-proton collisions at beam energies near the
respective nucleon-nucleon thresholds.Comment: Accepted for publication in Phys. Rev. Let
A Relativistic-Plasma Compton Maser
A relativistic pair-plasma which contains a high excitation of electrostatic
turbulence could produce intense radiation at brightness temperature in excess
of 10^22 K by stimulated scattering. Important relativistic effects would
include the broadband frequency response of the plasma and Compton-boosting of
the scattered radiation. In radio-frequency relativistic plasma, the optical
depth can be as small as hundreds of meters. When the plasma wave excitation
and particle distributions are one-dimensional, the frequency-dependent angular
distribution of the emission exhibits characteristics of pulsar emission.Comment: 13 pages, 4 figures; to appear in ApJ 559 (Sept 01
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