1,470 research outputs found
An efficient and scalable platform for java source code analysis using overlaid graph representations
© 2013 IEEE. Although source code programs are commonly written as textual information, they enclose syntactic and semantic information that is usually represented as graphs. This information is used for many different purposes, such as static program analysis, advanced code search, coding guideline checking, software metrics computation, and extraction of semantic and syntactic information to create predictive models. Most of the existing systems that provide these kinds of services are designed ad hoc for the particular purpose they are aimed at. For this reason, we created ProgQuery, a platform to allow users to write their own Java program analyses in a declarative fashion, using graph representations. We modify the Java compiler to compute seven syntactic and semantic representations, and store them in a Neo4j graph database. Such representations are overlaid, meaning that syntactic and semantic nodes of the different graphs are interconnected to allow combining different kinds of information in the queries/analyses. We evaluate ProgQuery and compare it to the related systems. Our platform outperforms the other systems in analysis time, and scales better to program sizes and analysis complexity. Moreover, the queries coded show that ProgQuery is more expressive than the other approaches. The additional information stored by ProgQuery increases the database size and associated insertion time, but these increases are significantly lower than the query/analysis performance gains obtained.Spanish Department of Science, Innovation and Universities under Project RTI2018-099235-B-I00
Structure stability in the simple element sodium under pressure
The simple alkali metal Na, that crystallizes in a body-centred cubic
structure at ambient pressure, exhibits a wealth of complex phases at extreme
conditions as found by experimental studies. The analysis of the mechanism of
stabilization of some of these phases, namely, the low-temperature Sm-type
phase and the high-pressure cI16 and oP8 phases, shows that they satisfy the
criteria for the Hume-Rothery mechanism. These phases appear to be stabilized
due to a formation of numerous planes in a Brillouin-Jones zone in the vicinity
of the Fermi sphere of Na, which leads to the reduction of the overall
electronic energy. For the oP8 phase, this mechanism seems to be working if one
assumes that Na becomes divalent metal at this density. The oP8 phase of Na is
analysed in comparison with the MnP-type oP8 phases known in binary compounds,
as well as in relation to the hP4 structure of the NiAs-type
A possible architecture of the planetary system HR 8799
HR8799 is a nearby A-type star with a debris disk and three planetary
candidates recently imaged directly. We undertake a coherent analysis of
various portions of observational data on all known components of the system.
The goal is to elucidate the architecture and evolutionary status of the
system. We try to further constrain the age and orientation of the system,
orbits and masses of the companions, as well as the location of dust. From the
high luminosity of debris dust and dynamical constraints, we argue for a rather
young system's age of <50Myr. The system must be seen nearly, but not exactly,
pole-on. Our analysis of the stellar rotational velocity yields an inclination
of 13-30deg, whereas i>20deg is needed for the system to be dynamically stable,
which suggests a probable inclination range of 20-30deg. The spectral energy
distribution is naturally reproduced with two dust rings associated with two
planetesimal belts. The inner "asteroid belt" is located at ~10AU inside the
orbit of the innermost companion and a "Kuiper belt" at >100AU is just exterior
to the orbit of the outermost companion. The dust masses in the inner and outer
ring are estimated to be ~1E-05 and 4E-02 M_earth, respectively. We show that
all three planetary candidates may be stable in the mass range suggested in the
discovery paper by Marois et al. 2008 (between 5 and 13 Jupiter masses), but
only for some of all possible orientations. Stable orbits imply a double
(4:2:1) mean-motion resonance between all three companions. We finally show
that in the cases where the companions themselves are orbitally stable, the
dust-producing planetesimal belts are also stable against planetary
perturbations.Comment: 12 pages, 14 figures, 4 tables, accepted to be published in Astronomy
& Astrophysics (May 20, 2009
Project overview and update on WEAVE: the next generation wide-field spectroscopy facility for the William Herschel Telescope
We present an overview of and status report on the WEAVE next-generation
spectroscopy facility for the William Herschel Telescope (WHT). WEAVE
principally targets optical ground-based follow up of upcoming ground-based
(LOFAR) and space-based (Gaia) surveys. WEAVE is a multi-object and multi-IFU
facility utilizing a new 2-degree prime focus field of view at the WHT, with a
buffered pick-and-place positioner system hosting 1000 multi-object (MOS)
fibres, 20 integral field units, or a single large IFU for each observation.
The fibres are fed to a single spectrograph, with a pair of 8k(spectral) x 6k
(spatial) pixel cameras, located within the WHT GHRIL enclosure on the
telescope Nasmyth platform, supporting observations at R~5000 over the full
370-1000nm wavelength range in a single exposure, or a high resolution mode
with limited coverage in each arm at R~20000. The project is now in the final
design and early procurement phase, with commissioning at the telescope
expected in 2017.Comment: 11 pages, 11 Figures, Summary of a presentation to Astronomical
Telescopes and Instrumentation 201
Mitochondrial phylogeography and demographic history of the Vicuña: implications for conservation
The vicuña (Vicugna vicugna; Miller, 1924) is a conservation success story, having recovered from near extinction in the 1960s to current population levels estimated at 275 000. However, lack of information about its demographic history and genetic diversity has limited both our understanding of its recovery and the development of science-based conservation measures. To examine the evolution and recent demographic history of the vicuña across its current range and to assess its genetic variation and population structure, we sequenced mitochondrial DNA from the control region (CR) for 261 individuals from 29 populations across Peru, Chile and Argentina. Our results suggest that populations currently designated as Vicugna vicugna vicugna and Vicugna vicugna mensalis comprise separate mitochondrial lineages. The current population distribution appears to be the result of a recent demographic expansion associated with the last major glacial event of the Pleistocene in the northern (18 to 22°S) dry Andes 14â12 000 years ago and the establishment of an extremely arid belt known as the 'Dry Diagonal' to 29°S. Within the Dry Diagonal, small populations of V. v. vicugna appear to have survived showing the genetic signature of demographic isolation, whereas to the north V. v. mensalis populations underwent a rapid demographic expansion before recent anthropogenic impacts
The High-Acceptance Dielectron Spectrometer HADES
HADES is a versatile magnetic spectrometer aimed at studying dielectron
production in pion, proton and heavy-ion induced collisions. Its main features
include a ring imaging gas Cherenkov detector for electron-hadron
discrimination, a tracking system consisting of a set of 6 superconducting
coils producing a toroidal field and drift chambers and a multiplicity and
electron trigger array for additional electron-hadron discrimination and event
characterization. A two-stage trigger system enhances events containing
electrons. The physics program is focused on the investigation of hadron
properties in nuclei and in the hot and dense hadronic matter. The detector
system is characterized by an 85% azimuthal coverage over a polar angle
interval from 18 to 85 degree, a single electron efficiency of 50% and a vector
meson mass resolution of 2.5%. Identification of pions, kaons and protons is
achieved combining time-of-flight and energy loss measurements over a large
momentum range. This paper describes the main features and the performance of
the detector system
Study of decays to the final state and evidence for the decay
A study of decays is performed for the first time
using data corresponding to an integrated luminosity of 3.0
collected by the LHCb experiment in collisions at centre-of-mass energies
of and TeV. Evidence for the decay
is reported with a significance of 4.0 standard deviations, resulting in the
measurement of
to
be .
Here denotes a branching fraction while and
are the production cross-sections for and mesons.
An indication of weak annihilation is found for the region
, with a significance of
2.4 standard deviations.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-022.html,
link to supplemental material inserted in the reference
Study of J /Ï production in Jets
The production of J/Ï mesons in jets is studied in the forward region of proton-proton collisions using data collected with the LHCb detector at a center-of-mass energy of 13 TeV. The fraction of the jet transverse momentum carried by the J/Ï meson, z(J/Ï)âĄpT(J/Ï)/pT(jet), is measured using jets with pT(jet)>20 GeV in the pseudorapidity range 2.5<η(jet)<4.0. The observed z(J/Ï)distribution for J/Ï mesons produced in b-hadron decays is consistent with expectations. However, the results for prompt J/Ï production do not agree with predictions based on fixed-order nonrelativistic QCD. This is the first measurement of the pT fraction carried by prompt J/Ï mesons in jets at any experiment
Bose-Einstein correlations of same-sign charged pions in the forward region in pp collisions at âs=7 TeV
Bose-Einstein correlations of same-sign charged pions, produced in protonproton collisions at a 7 TeV centre-of-mass energy, are studied using a data sample collected
by the LHCb experiment. The signature for Bose-Einstein correlations is observed in the
form of an enhancement of pairs of like-sign charged pions with small four-momentum
difference squared. The charged-particle multiplicity dependence of the Bose-Einstein correlation parameters describing the correlation strength and the size of the emitting source
is investigated, determining both the correlation radius and the chaoticity parameter. The
measured correlation radius is found to increase as a function of increasing charged-particle
multiplicity, while the chaoticity parameter is seen to decreas
Chloramphenicol Selection of IS10 Transposition in the cat Promoter Region of Widely Used Cloning Vectors
The widely used pSU8 family of cloning vectors is based on a p15A replicon and a chloramphenicol acetyltransferase (cat) gene conferring chloramphenicol resistance. We frequently observed an increase in the size of plasmids derived from these vectors. Analysis of the bigger molecular species shows that they have an IS10 copy inserted at a specific site between the promoter and the cat open reading frame. Promoter activity from both ends of IS10 has been reported, suggesting that the insertion events could lead to higher CAT production. Insertions were observed in certain constructions containing inserts that could lead to plasmid instability. To test the possibility that IS10 insertions were selected as a response to chloramphenicol selection, we have grown these constructs in the presence of different amounts of antibiotic and we observed that insertions arise promptly under higher chloramphenicol selective pressure. IS10 is present in many E. coli laboratory strains, so the possibility of insertion in constructions involving cat-containing vectors should be taken into account. Using lower chloramphenicol concentrations could solve this problem
- âŠ