1,844 research outputs found
A Quantitative Study of Java Software Buildability
Researchers, students and practitioners often encounter a situation when the
build process of a third-party software system fails. In this paper, we aim to
confirm this observation present mainly as anecdotal evidence so far. Using a
virtual environment simulating a programmer's one, we try to fully
automatically build target archives from the source code of over 7,200 open
source Java projects. We found that more than 38% of builds ended in failure.
Build log analysis reveals the largest portion of errors are
dependency-related. We also conduct an association study of factors affecting
build success
Evolution of populations expanding on curved surfaces
The expansion of a population into new habitat is a transient process that
leaves its footprints in the genetic composition of the expanding population.
How the structure of the environment shapes the population front and the
evolutionary dynamics during such a range expansion is little understood. Here,
we investigate the evolutionary dynamics of populations consisting of many
selectively neutral genotypes expanding on curved surfaces. Using a combination
of individual-based off-lattice simulations, geometrical arguments, and
lattice-based stepping-stone simulations, we characterise the effect of
individual bumps on an otherwise flat surface. Compared to the case of a range
expansion on a flat surface, we observe a transient relative increase, followed
by a decrease, in neutral genetic diversity at the population front. In
addition, we find that individuals at the sides of the bump have a dramatically
increased expected number of descendants, while their neighbours closer to the
bump's centre are far less lucky. Both observations can be explained using an
analytical description of straight paths (geodesics) on the curved surface.
Complementing previous studies of heterogeneous flat environments, the findings
here build our understanding of how complex environments shape the evolutionary
dynamics of expanding populations.Comment: This preprint has also been posted to http://www.biorxiv.org with
doi: 10.1101/406280. Seven pages with 5 figures, plus an appendix containing
3 pages with 1 figur
Co-based heterogeneous catalysts from well-defined Α-diimine complexes : Discussing the role of nitrogen
Ar-BIANs and related \uce\ub1-diimine Co complexes were wet impregnated onto Vulcan\uc2\uae XC 72 R carbon black powder and used as precursors for the synthesis of heterogeneous supported nanoscale catalysts by pyrolysis under argon at 800\uc2\ua0\uc2\ub0C. The catalytic materials feature a core-shell structure composed of metallic Co and Co oxides decorated with nitrogen-doped graphitic layers (NGr). These catalysts display high activity in the liquid phase hydrogenation of aromatic nitro compounds (110\uc2\ua0\uc2\ub0C, 50 bar H2) to give chemoselectively substituted aryl amines. The catalytic activity is closely related to the amount and type of nitrogen atoms in the final catalytic material, which suggests a heterolytic activation of dihydrogen
The maximum modulus of a trigonometric trinomial
Let Lambda be a set of three integers and let C_Lambda be the space of
2pi-periodic functions with spectrum in Lambda endowed with the maximum modulus
norm. We isolate the maximum modulus points x of trigonometric trinomials T in
C_Lambda and prove that x is unique unless |T| has an axis of symmetry. This
permits to compute the exposed and the extreme points of the unit ball of
C_Lambda, to describe how the maximum modulus of T varies with respect to the
arguments of its Fourier coefficients and to compute the norm of unimodular
relative Fourier multipliers on C_Lambda. We obtain in particular the Sidon
constant of Lambda
Templated self-assembly of gold nanoparticles in smectic liquid crystals confined at 3D printed curved surfaces
The fabrication of assembled structures of topological defects in liquid
crystals (LCs) has attracted much attention during the last decade, stemming
from the potential application of these defects in modern technologies. A range
of techniques can be employed to create large areas of engineered defects in
LCs, including mechanical shearing, chemical surface treatment, external
fields, or geometric confinement. The technology of 3D printing has recently
emerged as a powerful method to fabricate novel patterning topographies
inaccessible by other microfabrication techniques, especially confining
geometries with curved topographies. In this work, we show the advantages of
using 3D-printed curved surfaces and controlled anchoring properties to confine
LCs and engineer new structures of topological defects, whose structure we
elucidate by comparison with a novel application of Landau-de Gennes free
energy minimization to the smectic A-nematic phase transition. We also
demonstrate the ability of these defects to act as a scaffold for assembling
gold (Au) nanoparticles (NPs) into reconfigurable 3D structures. We discuss the
characteristics of this templated self-assembly (TSA) approach and explain the
relationship between NP concentrations and defect structures with insights
gained from numerical modeling. This work paves the way for a versatile
platform of LC defect-templated assembly of a range of functional nanomaterials
useful in the field of energy technology.Comment: Main text: 30 pages, 6 figures. Supplementary Information: 5 pages, 4
figure
<i>In vitro</i> Characterization of Phenylacetate Decarboxylase, a Novel Enzyme Catalyzing Toluene Biosynthesis in an Anaerobic Microbial Community
Anaerobic bacterial biosynthesis of toluene from phenylacetate was reported more than two decades ago, but the biochemistry underlying this novel metabolism has never been elucidated. Here we report results of in vitro characterization studies of a novel phenylacetate decarboxylase from an anaerobic, sewage-derived enrichment culture that quantitatively produces toluene from phenylacetate; complementary metagenomic and metaproteomic analyses are also presented. Among the noteworthy findings is that this enzyme is not the well-characterized clostridial p-hydroxyphenylacetate decarboxylase (CsdBC). However, the toluene synthase under study appears to be able to catalyze both phenylacetate and p-hydroxyphenylacetate decarboxylation. Observations suggesting that phenylacetate and p-hydroxyphenylacetate decarboxylation in complex cell-free extracts were catalyzed by the same enzyme include the following: (i) the specific activity for both substrates was comparable in cell-free extracts, (ii) the two activities displayed identical behavior during chromatographic separation of cell-free extracts, (iii) both activities were irreversibly inactivated upon exposure to O2, and (iv) both activities were similarly inhibited by an amide analog of p-hydroxyphenylacetate. Based upon these and other data, we hypothesize that the toluene synthase reaction involves a glycyl radical decarboxylase. This first-time study of the phenylacetate decarboxylase reaction constitutes an important step in understanding and ultimately harnessing it for making bio-based toluene
Nonclassical correlations of phase noise and photon number in quantum nondemolition measurements
The continuous transition from a low resolution quantum nondemolition
measurement of light field intensity to a precise measurement of photon number
is described using a generalized measurement postulate. In the intermediate
regime, quantization appears as a weak modulation of measurement probability.
In this regime, the measurement result is strongly correlated with the amount
of phase decoherence introduced by the measurement interaction. In particular,
the accidental observation of half integer photon numbers preserves phase
coherence in the light field, while the accidental observation of quantized
values increases decoherence. The quantum mechanical nature of this correlation
is discussed and the implications for the general interpretation of
quantization are considered.Comment: 16 pages, 5 figures, final version to be published in Phys. Rev. A,
Clarifications of the nature of the measurement result and the noise added in
section I
From Einstein's Theorem to Bell's Theorem: A History of Quantum Nonlocality
In this Einstein Year of Physics it seems appropriate to look at an important
aspect of Einstein's work that is often down-played: his contribution to the
debate on the interpretation of quantum mechanics. Contrary to popular opinion,
Bohr had no defence against Einstein's 1935 attack (the EPR paper) on the
claimed completeness of orthodox quantum mechanics. I suggest that Einstein's
argument, as stated most clearly in 1946, could justly be called Einstein's
reality-locality-completeness theorem, since it proves that one of these three
must be false. Einstein's instinct was that completeness of orthodox quantum
mechanics was the falsehood, but he failed in his quest to find a more complete
theory that respected reality and locality. Einstein's theorem, and possibly
Einstein's failure, inspired John Bell in 1964 to prove his reality-locality
theorem. This strengthened Einstein's theorem (but showed the futility of his
quest) by demonstrating that either reality or locality is a falsehood. This
revealed the full nonlocality of the quantum world for the first time.Comment: 18 pages. To be published in Contemporary Physics. (Minor changes;
references and author info added
Direct observation of long-lived isomers in Bi
Long-lived isomers in 212Bi have been studied following 238U projectile
fragmentation at 670 MeV per nucleon. The fragmentation products were injected
as highly charged ions into the GSI storage ring, giving access to masses and
half-lives. While the excitation energy of the first isomer of 212Bi was
confirmed, the second isomer was observed at 1478(30) keV, in contrast to the
previously accepted value of >1910 keV. It was also found to have an extended
Lorentz-corrected in-ring halflife >30 min, compared to 7.0(3) min for the
neutral atom. Both the energy and half-life differences can be understood as
being due a substantial, though previously unrecognised, internal decay branch
for neutral atoms. Earlier shell-model calculations are now found to give good
agreement with the isomer excitation energy. Furthermore, these and new
calculations predict the existence of states at slightly higher energy that
could facilitate isomer de-excitation studies.Comment: published in PRL 110, 12250
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