56,923 research outputs found
Abstract Interpretation with Unfoldings
We present and evaluate a technique for computing path-sensitive interference
conditions during abstract interpretation of concurrent programs. In lieu of
fixed point computation, we use prime event structures to compactly represent
causal dependence and interference between sequences of transformers. Our main
contribution is an unfolding algorithm that uses a new notion of independence
to avoid redundant transformer application, thread-local fixed points to reduce
the size of the unfolding, and a novel cutoff criterion based on subsumption to
guarantee termination of the analysis. Our experiments show that the abstract
unfolding produces an order of magnitude fewer false alarms than a mature
abstract interpreter, while being several orders of magnitude faster than
solver-based tools that have the same precision.Comment: Extended version of the paper (with the same title and authors) to
appear at CAV 201
Identification of Non-Linear RF Systems Using Backpropagation
In this work, we use deep unfolding to view cascaded non-linear RF systems as
model-based neural networks. This view enables the direct use of a wide range
of neural network tools and optimizers to efficiently identify such cascaded
models. We demonstrate the effectiveness of this approach through the example
of digital self-interference cancellation in full-duplex communications where
an IQ imbalance model and a non-linear PA model are cascaded in series. For a
self-interference cancellation performance of approximately 44.5 dB, the number
of model parameters can be reduced by 74% and the number of operations per
sample can be reduced by 79% compared to an expanded linear-in-parameters
polynomial model.Comment: To be presented at the 2020 IEEE International Conference on
Communications (Workshop on Full-Duplex Communications for Future Wireless
Networks
Unfolding Quantum Computer Readout Noise
In the current era of noisy intermediate-scale quantum (NISQ) computers,
noisy qubits can result in biased results for early quantum algorithm
applications. This is a significant challenge for interpreting results from
quantum computer simulations for quantum chemistry, nuclear physics, high
energy physics, and other emerging scientific applications. An important class
of qubit errors are readout errors. The most basic method to correct readout
errors is matrix inversion, using a response matrix built from simple
operations to probe the rate of transitions from known initial quantum states
to readout outcomes. One challenge with inverting matrices with large
off-diagonal components is that the results are sensitive to statistical
fluctuations. This challenge is familiar to high energy physics, where
prior-independent regularized matrix inversion techniques (`unfolding') have
been developed for years to correct for acceptance and detector effects when
performing differential cross section measurements. We study various unfolding
methods in the context of universal gate-based quantum computers with the goal
of connecting the fields of quantum information science and high energy physics
and providing a reference for future work. The method known as iterative
Bayesian unfolding is shown to avoid pathologies from commonly used matrix
inversion and least squares methods.Comment: 13 pages, 16 figures; v2 has a typo fixed in Eq. 3 and a series of
minor modification
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Precise Measurement of the e+ e- --> pi+ pi- (gamma) Cross Section with the Initial-State Radiation Method at BABAR
A precise measurement of the cross section of the process
from threshold to an energy of 3GeV is obtained
with the initial-state radiation (ISR) method using 232fb of data
collected with the BaBar detector at center-of-mass energies near
10.6GeV. The ISR luminosity is determined from a study of the leptonic process
, which is found to agree with the
next-to-leading-order QED prediction to within 1.1%. The cross section for the
process is obtained with a systematic uncertainty
of 0.5% in the dominant resonance region. The leading-order hadronic
contribution to the muon magnetic anomaly calculated using the measured
cross section from threshold to 1.8GeV is .Comment: 58 pages, 56 figures, to be submitted to Phys. Rev.
Measurement of the charge asymmetry in top quark pair production in pp collisions at TeV using the ATLAS detector
We present a measurement of the charge asymmetry in top-antitop production
using data corresponding to an integrated luminosity of of
proton-proton collisions at TeV collected by the ATLAS detector.
The top pair events decaying semileptonically (lepton+jets channel) to either
an electron or muon, missing transverse energy and at least four jets are
selected. The reconstruction of the events was performed using a
kinematic likelihood approach. The difference of absolute values of top and
antitop rapidities is used to define the charge asymmetry: . To allow
comparisons with theory calculations, a Bayesian unfolding technique is applied
to correct the measured distributions for acceptance and detector
effects. The top charge asymmetry in both channels (e and mu) after correction
is measured to be: (e+jets
channel) and (+jets
channel) giving a combined result of : . These results are compatible with the Standard Model predictions
of .Comment: Presented at the 2011 Hadron Collider Physics symposium (HCP-2011),
Paris, France, November 14-18 2011, 3 pages, 4 figure
Biophysical characterization of the outer membrane polysaccharide export protein and the polysaccharide co-polymerase protein from Xanthomonas campestris
This study investigated the structural and biophysical characteristics of GumB and GumC, two Xanthomonas campestris membrane proteins that are involved in xanthan biosynthesis. Xanthan is an exopolysaccharide that is thought to be a virulence factor that contributes to bacterial in planta growth. It also is one of the most important industrial biopolymers. The first steps of xanthan biosynthesis are well understood, but the polymerization and export mechanisms remain unclear. For this reason, the key proteins must be characterized to better understand these processes. Here we characterized, by biochemical and biophysical techniques, GumB, the outer membrane polysaccharide export protein, and GumC, the polysaccharide co-polymerase protein of the xanthan biosynthesis system. Our results suggested that recombinant GumB is a tetrameric protein in solution. On the other hand, we observed that both native and recombinant GumC present oligomeric conformation consistent with dimers and higher-order oligomers. The transmembrane segments of GumC are required for GumC expression and/or stability. These initial results provide a starting point for additional studies that will clarify the roles of GumB and GumC in the xanthan polymerization and export processes and further elucidate their functions and mechanisms of action.Fil: Bianco, María Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Jacobs, Melisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Salinas, Silvina Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Salvay, Andrés Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; ArgentinaFil: Ielmini, M. V.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Ielpi, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentin
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