4,910 research outputs found
Evidence for Factorization in Three-body Decays
Motivated by experimental results on , we use a
factorization approach to study these decays. Two mechanisms concerning kaon
pair production arise: current-produced (from vacuum) and transition (from the
meson). The kaon pair in the decays can be
produced only by the vector current (current-produced), whose matrix element
can be extracted from processes via isospin relations. The
decay rates obtained this way are in good agreement with experiment. The
decays involve both current-produced and transition
processes. By using QCD counting rules and the measured decay rates, the measured decay spectra can be understood.Comment: 3 pages, 6 figures. Talk presented at EPS2003 Conference, Aachen,
Germany, July 200
InGaN nano-ring structures for high-efficiency light emitting diodes
A technique based on the Fresnel diffraction effect for the fabrication of nano-scale site-controlled ring structures in InGaN/GaN multi-quantum well structures has been demonstrated. The ring structures have an internal diameter of 500 nm and a wall width of 300 nm. A 1 cm-1 Raman shift has been measured, signifying substantial strain relaxation from the fabricated structure. The 9 nm blueshift observed in the cathodoluminescence spectra can be attributed to band filling and/or screening of the piezoelectric field. A light emitting diode based on this geometry has been demonstrated
Evidence for Factorization in Three-body B --> D(*) K- K0 Decays
Motivated by recent experimental results, we use a factorization approach to
study the three-body B --> D(*) K- K0 decay modes. Two mechanisms are proposed
for kaon pair production: current-produced (from vacuum) and transition (from B
meson). The Bbar0 --> D(*)+ K- K0 decay is governed solely by the
current-produced mechanism. As the kaon pair can be produced only by the vector
current, the matrix element can be extracted from e+ e- --> K Kbar processes
via isospin relations. The decay rates obtained this way are in good agreement
with experiment. Both current-produced and transition processes contribute to
B- --> D(*)0 K- K0 decays. By using QCD counting rules and the measured B- -->
D(*)0 K- K0 decay rates, the measured decay spectra can be understood.Comment: 17 pages, 6 figure
Memory difference control of unknown unstable fixed points: Drifting parameter conditions and delayed measurement
Difference control schemes for controlling unstable fixed points become
important if the exact position of the fixed point is unavailable or moving due
to drifting parameters. We propose a memory difference control method for
stabilization of a priori unknown unstable fixed points by introducing a memory
term. If the amplitude of the control applied in the previous time step is
added to the present control signal, fixed points with arbitrary Lyapunov
numbers can be controlled. This method is also extended to compensate arbitrary
time steps of measurement delay. We show that our method stabilizes orbits of
the Chua circuit where ordinary difference control fails.Comment: 5 pages, 8 figures. See also chao-dyn/9810029 (Phys. Rev. E 70,
056225) and nlin.CD/0204031 (Phys. Rev. E 70, 046205
Structural Characterization of Rapid Thermal Oxidized Si\u3csub\u3e1−x−y\u3c/sub\u3eGe\u3csub\u3ex\u3c/sub\u3eC\u3csub\u3ey\u3c/sub\u3e Alloy Films Grown by Rapid Thermal Chemical Vapor Deposition
The structural properties of as-grown and rapid thermal oxidized Si1−x−yGexCy epitaxial layers have been examined using a combination of infrared, x-ray photoelectron, x-ray diffraction, secondary ion mass spectroscopy, and Raman spectroscopy techniques. Carbon incorporation into the Si1−x−yGexCy system can lead to compressive or tensile strain in the film. The structural properties of the oxidized Si1−x−yGexCy film depend on the type of strain (i.e., carbon concentration) of the as-prepared film. For compressive or fully compensated films, the oxidation process drastically reduces the carbon content so that the oxidized films closely resemble to Si1−xGex films. For tensile films, two broad regions, one with carbon content higher and the other lower than that required for full strain compensation, coexist in the oxidized films
The Neutrino Magnetic Moment Induced by Leptoquarks
Allowing leptoquarks to interact with both right-handed and left-handed
neutrinos (i.e., ``non-chiral'' leptoquarks), we show that a non-zero neutrino
magnetic moment can arise naturally. Although the mass of the non-chiral vector
leptoquark that couples to the first generation fermions is constrained
severely by universality of the leptonic decays and is found to be
greater than 50 TeV, the masses of the second and third generation non-chiral
vector leptoquarks may evade such constraint and may in general be in the range
of TeV. With reasonable input mass and coupling values, we find
that the neutrino magnetic moment due to the second generation leptoquarks is
of the order of while that caused by the
third generation leptoquarks, being enhanced significantly by the large top
quark mass, is in the range of .Comment: 11 pages, 3 eps figures, uses revte
The Fourth Element: Characteristics, Modelling, and Electromagnetic Theory of the Memristor
In 2008, researchers at HP Labs published a paper in {\it Nature} reporting
the realisation of a new basic circuit element that completes the missing link
between charge and flux-linkage, which was postulated by Leon Chua in 1971. The
HP memristor is based on a nanometer scale TiO thin-film, containing a
doped region and an undoped region. Further to proposed applications of
memristors in artificial biological systems and nonvolatile RAM (NVRAM), they
also enable reconfigurable nanoelectronics. Moreover, memristors provide new
paradigms in application specific integrated circuits (ASICs) and field
programmable gate arrays (FPGAs). A significant reduction in area with an
unprecedented memory capacity and device density are the potential advantages
of memristors for Integrated Circuits (ICs). This work reviews the memristor
and provides mathematical and SPICE models for memristors. Insight into the
memristor device is given via recalling the quasi-static expansion of Maxwell's
equations. We also review Chua's arguments based on electromagnetic theory.Comment: 28 pages, 14 figures, Accepted as a regular paper - the Proceedings
of Royal Society
Myeloperoxidase As a Multifaceted Target for Cardiovascular Protection
SIGNIFICANCE: Myeloperoxidase (MPO) is a heme peroxidase that is primarily expressed by neutrophils. It has the capacity to generate several reactive species, essential for its inherent antimicrobial activity and innate host defense. Dysregulated MPO release however, can lead to tissue damage, as seen in several diseases. Increased MPO levels in circulation is therefore, widely associated with conditions of increased oxidative stress and inflammation. Recent Advances: Several studies have shown a strong correlation between MPO and cardiovascular disease (CVD), whereby elevated levels of circulating MPO are linked to poor prognosis with increased risk of CVD-related mortality. Accordingly, circulating MPO is considered a 'high-risk' biomarker for patients with acute coronary syndrome, atherosclerosis, heart failure, hypertension and stroke, thereby implicating MPO as a multifaceted target for cardiovascular protection. Consistently, recent studies that target MPO in animal models of CVD have demonstrated favorable outcomes with regard to disease progression. CRITICAL ISSUES: Although most of these studies have established a critical link between circulating MPO and worsening cardiac outcomes, the mechanisms by which MPO exerts its detrimental effects in CVD remain unclear. FUTURE DIRECTIONS: Elucidating the mechanisms by which elevated MPO leads to poor prognosis and conversely, investigating the beneficial effects of therapeutic MPO inhibition on alleviating disease phenotype, will facilitate future MPO-targeted clinical trials for improving CVD-related outcomes
Interacting classical and quantum particles
We apply Hall and Reginatto's theory of interacting classical and quantum
ensembles to harmonically coupled particles, with a view to understanding its
experimental implications. This hybrid theory has no free parameters and makes
distinctive predictions that should allow it to be experimentally distinguished
from quantum mechanics. It also bears on the questions of quantum measurement
and quantum gravity.Comment: 7 pages, 6 figure
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