9,214 research outputs found
Generating Predicate Callback Summaries for the Android Framework
One of the challenges of analyzing, testing and debugging Android apps is
that the potential execution orders of callbacks are missing from the apps'
source code. However, bugs, vulnerabilities and refactoring transformations
have been found to be related to callback sequences. Existing work on control
flow analysis of Android apps have mainly focused on analyzing GUI events. GUI
events, although being a key part of determining control flow of Android apps,
do not offer a complete picture. Our observation is that orthogonal to GUI
events, the Android API calls also play an important role in determining the
order of callbacks. In the past, such control flow information has been modeled
manually. This paper presents a complementary solution of constructing program
paths for Android apps. We proposed a specification technique, called Predicate
Callback Summary (PCS), that represents the callback control flow information
(including callback sequences as well as the conditions under which the
callbacks are invoked) in Android API methods and developed static analysis
techniques to automatically compute and apply such summaries to construct apps'
callback sequences. Our experiments show that by applying PCSs, we are able to
construct Android apps' control flow graphs, including inter-callback
relations, and also to detect infeasible paths involving multiple callbacks.
Such control flow information can help program analysis and testing tools to
report more precise results. Our detailed experimental data is available at:
http://goo.gl/NBPrKsComment: 11 page
Ratio of strange to non-strange quark condensates in QCD
Laplace transform QCD sum rules for two-point functions related to the
strangeness-changing scalar and pseudoscalar Green's functions and
, are used to determine the subtraction constants and
, which fix the ratio .
Our results are ,
, and . This implies corrections to
kaon-PCAC at the level of 50%, which although large, are not inconsistent with
the size of the corrections to Goldberger-Treiman relations in .Comment: Latex file, 14 pages including 3 figure
On dissociation of heavy mesons in a hot quark-gluon plasma
We compare two mechanisms for the dissociation of heavy mesons in an infinite
quark-gluon plasma: dynamic Debye screening and multiple scattering. Using the
uncertainty principle inspired by a Schrodinger-like equation, we find that the
criterion a_B\simeq1/\mu\simeq 1/(\alpha_{eff}^{1/2}T) with
\alpha_{eff}\equiv\alpha(N_c+{N_f\over2}) is parametrically true both for the
dissociation of fast moving heavy mesons with a size a_B due to dynamic Debye
screening as well as for mesons at rest in the medium. In contrast, we find
that the criterion for the dissociation of heavy mesons due to uncorrelated
multiple scattering is parametrically 1/a_B \simeq
[\gamma\alpha_{eff}\ln{1/\alpha_{eff}}]^{1/3}T. Therefore, multiple scattering
is a more efficient mechanism for the dissociation of heavy mesons in an
infinite hot plasma.Comment: 23 pages, 2 figures; minor changes, added references, accepted in
Nuclear Physics
Chiral corrections to the Gell-Mann-Oakes-Renner relation
The next to leading order chiral corrections to the
Gell-Mann-Oakes-Renner (GMOR) relation are obtained using the pseudoscalar
correlator to five-loop order in perturbative QCD, together with new finite
energy sum rules (FESR) incorporating polynomial, Legendre type, integration
kernels. The purpose of these kernels is to suppress hadronic contributions in
the region where they are least known. This reduces considerably the systematic
uncertainties arising from the lack of direct experimental information on the
hadronic resonance spectral function. Three different methods are used to
compute the FESR contour integral in the complex energy (squared) s-plane, i.e.
Fixed Order Perturbation Theory, Contour Improved Perturbation Theory, and a
fixed renormalization scale scheme. We obtain for the corrections to the GMOR
relation, , the value . This result
is substantially more accurate than previous determinations based on QCD sum
rules; it is also more reliable as it is basically free of systematic
uncertainties. It implies a light quark condensate . As a byproduct, the chiral perturbation theory (unphysical) low energy
constant is predicted to be , or .Comment: A comment about the value of the strong coupling has been added at
the end of Section 4. No change in results or conslusion
Phenomenological Analysis of a Dimension-Two Operator in QCD and its Impact on
Fits to the ARGUS data on hadronic decays of the tau-lepton, which determine
the vector and axial-vector spectral functions, are used in order to determine
the size of a dimension term in the Operator Product Expansion.
Constraints from the first Weinberg sum rule (in the chiral limit) are enforced
in order to reduce the uncertainty of this determination. Results for the
operator are consistent with a quadratic dependence on . The
impact of this term on the extraction of is assessed.Comment: 7 pages and 4 figures (not included). LATEX fil
Is there evidence for dimension-two corrections in QCD two-point functions?
The ALEPH data on the (non-strange) vector and axial-vector spectral
functions, extracted from tau-lepton decays, is used in order to search for
evidence for a dimension-two contribution, , to the Operator Product
Expansion (other than quark mass terms). This is done by means of a
dimension-two Finite Energy Sum Rule, which relates QCD to the experimental
hadronic information. The average is
remarkably stable against variations in the continuum threshold, but depends
rather strongly on . Given the current wide spread in the values
of , as extracted from different experiments, we would
conservatively conclude from our analysis that is consistent with zero.Comment: A misprint in Eq. (14) has been corrected. No other changes. Paper to
appear in Phys. Rev.
Direct Instanton Effects in Current-Current Correlators
We compute the effect of small-size instantons on the coefficient function of
the chiral condensate in the operator product expansion of current-current
correlators. Furthermore, we also compute the instanton corrections associated
with four-quark and six-quark operators in the factorization approximation. We
discuss the phenomenological implications of our result.Comment: 24 pages, Late
Studying feeding behavior in the Xenopus laevis tadpole animal model
This poster was presented at the 2022 Undergraduate Research Opportunity Program (UROP) Symposium, held at Boston University on October 21, 2022 at GSU Metcalf Ballroom.Xenopus laevis is an emerging model organism for neurodevelopmental diseases. We are using Xenopus to model a rare genetic disorder known as Okur-Chung Neurodevelopmental Syndrome (OCNDS). Patients with OCNDS exhibit eating difficulties and intestinal issues such as constipation and acid reflux. Our objective is to establish a baseline feeding behavioral assay in Xenopus laevis to investigate the mechanisms of OCNDS. Additionally, we used whole mount immunofluorescence to test neuronal and skeletal muscle markers. We manipulated the amount of food that stage 45-50 tadpoles received (6, 7, or 8 mg) and we observed their buccal pumping rates, time of digestion, feces length, and survival rates (about 26-38 embryos, 10 cm plates). The buccal pumping rate did not change prior and post feeding. The average first excretion happened 44.3 minutes after feeding. The aggregate feces length varied between 3.034 cm for younger embryos and 0.279 cm for older embryos (reproducing previously published data). The survival rate was the same for each group. We also found that skeletal muscle antibody (12/101) and the neuronal antibodies (Xen1 and E7) specifically stained stage 49 tadpoles. We now know how to perform the baseline feeding procedures and have antibodies to investigate neuronal and muscular changes. Further experimentation is required to determine the optimal amount of food and once established, we will launch feeding experiments to determine behavioral and morphological differences in embryos expressing CSNK2A1 variants, which would help us better understand the mechanisms of OCNDS
Issues in determining alpha_s from hadronic tau decay and electroproduction data
We discuss some key issues associated with duality-violating and
non-perturbative OPE contributions to the theoretical representations of light
quark current-current two-point functions and relevant to precision
determinations of alpha_s from hadronic tau decay and electroproduction
cross-section data. We demonstrate that analyses with an explicit
representation of duality-violating effects are required to bring theoretical
errors in such extractions under control, motivating the accompanying paper in
these proceedings, which presents the results of such an analysis.Comment: 5 pages, 4 figures. Prepared for the Proceedings of the International
Workshop on e+e- collisions from Phi to Psi (PHIPSI11), Sep. 19-22, 2011,
BINP, Novosibirsk, Russi
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