6,908 research outputs found
Strong-coupling analysis of scanning tunneling spectra in BiSrCaCuO
We study a series of spectra measured in the superconducting state of
optimally-doped Bi-2223 by scanning tunneling spectroscopy. Each spectrum, as
well as the average of spectra presenting the same gap, is fitted using a
strong-coupling model taking into account the band structure, the BCS gap, and
the interaction of electrons with the spin resonance. After describing our
measurements and the main characteristics of the strong-coupling model, we
report the whole set of parameters determined from the fits, and we discuss
trends as a function of the gap magnitude. We also simulate angle-resolved
photoemission spectra, and compare with recent experimental results.Comment: Published versio
European cobalt sources identified in the production of Chinese Famille Rose porcelain
The blue pigments on 112 fragments or small objects of Qing Dynasty Chinese, 95 of underglaze blue and white and 17 overglaze enamelled porcelains were analysed by LA-ICPMS. The underglaze blues on both blue and white and polychrome objects were created with a cobalt pigment that was rich in manganese with lesser nickel and zinc. This suite of accessory elements is generally considered to be characteristic of local, Chinese, sources of pigments. However, the blue enamels were very different. The cobalt pigment here has low levels of manganese and instead is rich in nickel, zinc, arsenic and bismuth. No Chinese source of cobalt with these characteristics is known, but they closely match the elements found in the contemporary cobalt source at Erzgebirge in Germany. Textual evidence has been interpreted to suggest that some enamel pigment technologies were transferred from Europe to China, but this is the first analytical evidence to be found that an enamel pigment itself was imported. It is possible that this pigment was imported in the form of cobalt coloured glass, or smalt, which might account for its use in enamels, but not in an underglaze, where the colour might be susceptible to running. Furthermore, the European cobalt would have given a purer shade of blue than the manganese-rich Chinese cobalt
Generalized sum rules of the nucleon in the constituent quark model
We study the generalized sum rules and polarizabilities of the nucleon in the
framework of the hypercentral constituent quark model. We include in the
calculation all the well known and resonances and consider all the
generalized sum rules for which there are data available. To test the model
dependence of the calculation, we compare our results to the results obtained
in the harmonic oscillator CQM. We furthermore confront our results to the
model-independent sum rules values and to the predictions of the
phenomenological MAID model. The CQM calculations provide a good description of
most of the presented generalized sum rules in the intermediate region
(above GeV) while they encounter difficulties in describing these
observables at low , where the effects of the pion cloud, not included in
the present calculation, are expected to be important.Comment: 26 pages, 10 figure
Theory Support for the Excited Baryon Program at the Jlab 12 GeV Upgrade
This document outlines major directions in theoretical support for the
measurement of nucleon resonance transition form factors at the JLab 12 GeV
upgrade with the CLAS12 detector. Using single and double meson production,
prominent resonances in the mass range up to 2 GeV will be studied in the range
of photon virtuality up to 12 GeV where quark degrees of freedom are
expected to dominate. High level theoretical analysis of these data will open
up opportunities to understand how the interactions of dressed quarks create
the ground and excited nucleon states and how these interactions emerge from
QCD. The paper reviews the current status and the prospects of QCD based model
approaches that relate phenomenological information on transition form factors
to the non-perturbative strong interaction mechanisms, that are responsible for
resonance formation.Comment: 52 pages, 19 figures, White Paper of the Electromagnetic N-N*
Transition Form Factor Workshop at Jefferson Lab, October 13-15, 2008,
Newport News, VA, US
Flexible Power Modeling of LTE Base Stations
With the explosion of wireless communications in number of users and data rates, the reduction of network power consumption becomes more and more critical. This is especially true for base stations which represent a dominant share of the total power in cellular networks. In order to study power reduction techniques, a convenient power model is required, providing estimates of the power consumption in different scenarios. This paper proposes such a model, accurate but simple to use. It evaluates the base station power consumption for different types of cells supporting the 3GPP LTE standard. It is flexible enough to enable comparisons between state-of-the-art and advanced configurations, and an easy adaptation to various scenarios. The model is based on a combination of base station components and sub-components as well as power scaling rules as functions of the main system parameters
Imaging the essential role of spin-fluctuations in high-Tc superconductivity
We have used scanning tunneling spectroscopy to investigate short-length
electronic correlations in three-layer Bi2Sr2Ca2Cu3O(10+d) (Bi-2223). We show
that the superconducting gap and the energy Omega_dip, defined as the
difference between the dip minimum and the gap, are both modulated in space
following the lattice superstructure, and are locally anti-correlated. Based on
fits of our data to a microscopic strong-coupling model we show that Omega_dip
is an accurate measure of the collective mode energy in Bi-2223. We conclude
that the collective mode responsible for the dip is a local excitation with a
doping dependent energy, and is most likely the (pi,pi) spin resonance.Comment: 4 pages, 4 figure
Robust entanglement of a micromechanical resonator with output optical fields
We perform an analysis of the optomechanical entanglement between the
experimentally detectable output field of an optical cavity and a vibrating
cavity end-mirror. We show that by a proper choice of the readout (mainly by a
proper choice of detection bandwidth) one can not only detect the already
predicted intracavity entanglement but also optimize and increase it. This
entanglement is explained as being generated by a scattering process owing to
which strong quantum correlations between the mirror and the optical Stokes
sideband are created. All-optical entanglement between scattered sidebands is
also predicted and it is shown that the mechanical resonator and the two
sideband modes form a fully tripartite-entangled system capable of providing
practicable and robust solutions for continuous variable quantum communication
protocols
Systemic mastocytosis and essential thrombocythemia: Case report and literature overview
Case report of a patient with essential thrombocythemia and mastocytosis and overview of the literatur
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