991 research outputs found
A conceptual approach to gene expression analysis enhanced by visual analytics
The analysis of gene expression data is a complex task for biologists wishing to understand the role of genes in the formation of diseases such as cancer. Biologists need greater support when trying to discover, and comprehend, new relationships within their data. In this paper, we describe an approach to the analysis of gene expression data where overlapping groupings are generated by Formal Concept Analysis and interactively analyzed in a tool called CUBIST. The CUBIST workflow involves querying a semantic database and converting the result into a formal context, which can be simplified to make it manageable, before it is visualized as a concept lattice and associated charts
Electronic excited states of benzene in interaction with water clusters : influence of structure and size
This work is dedicated to the theoretical investigation of the influence of
water clusters' organisation and size on the electronic spectrum of an
interacting benzene (Bz) molecule using both TD-DFT and CASPT2 approaches. Two
series of geometries, namely and were extracted from
two Bz-hexagonal ice configurations leading to maximum and minimum ionization
energies respectively. An appropriate basis set containing atomic diffuse and
polarisation orbitals and describing the Rydberg states of Bz was determined.
The TD-DFT approach was carefully benchmarked against CASPT2 results for the
smallest systems.Despite some discrepancies, the trends were found to be
similar at both levels of theory: the positions and intensities of the main
transitions were found slightly split due to
symmetry breaking. For the smallest systems, our results clearly show the
dependence of the electronic transitions on the clusters' structures. Of
particular interest, low energy transitions of non negligible oscillator
strength from a Bz orbital to a virtual orbital of Rydberg character,
also involving atomic diffuse functions and partially expanded on the water
cluster, were found for the series. The energies of such
transitions were determined to be more than 2\,eV below the ionization
potential of Bz. When the cluster's size increases, similar transitions were
found for all structures, the virtual orbitals becoming mainly developed on the
H atoms of the water molecules at the edge of the cluster. Given their nature
and energy, such transitions could play a role in the photochemistry of
aromatic species in interaction with water clusters or ice, such processes
being of astrophysical interest.Comment: 37 pages, 15 figures, 7 table
Robust Measurement Feedback Control of an Inclined Cable
International audienceConsidering the partial differential equation model of the vibrations of an inclined cable, we are interested in applying robust control technics to stabilize the system with measurement feedback when it is submitted to external disturbances. This paper focuses indeed on the construction of a standard linear infinite dimensional state space system and an H_infinity feedback control of vibrations with partial observation of the state. The control and observation are performed using an active tendon
PAH chemistry at eV internal energies. 1. H-shifted isomers
The PAH family of organic compounds (polycyclic aromatic hydrocarbons),
involved in several fields of chemistry, has received particular attention in
astrochemistry, where their vibrational spectroscopy, thermodynamic, dynamic,
and fragmentation properties are now abundantly documented. This survey aims at
drawing trends for low spin-multiplicity surfaces of PAHs bearing internal
energies in the range 1-10 eV. It addresses some typical alternatives to the
ground-state regular structures of PAHs, making explicit possible
intramolecular rearrangements leading to high-lying minima. These
isomerisations should be taken into consideration when addressing PAH
processing in astrophysical conditions. The first part of this double-entry
study focuses on the hydrogen-shifted forms, which bear both a carbene center
and a saturated carbon. It rests upon DFT calculations mainly performed on two
emblematic PAH representatives, coronene and pyrene, in their neutral and mono
and multi-cationic states. Systematically searched for in neutral species,
these H-shifted minima are lying 4-5 eV above the regular all-conjugated forms,
and are separated by barriers of about one eV. General hydrogen-shifting is
found to be easier for cationic species as the relative energies of their
H-shifted minima are 1-1.5 eV lower than those for neutral species. As much as
possible, classical knowledge and concepts of organic chemistry such as
aromaticity and Clar's rules are invoked for result interpretation.Comment: 35 pages, accepted by Molecular Astrophysic
PAH chemistry at eV internal energies. 2. Ring alteration and dissociation
Recognized as important interstellar constituents, polycyclic aromatic
hydrocarbons (PAHs) have been intensively studied in astrochemistry and their
spectroscopy, thermodynamics, dynamics, and fragmentations are now amply
documented. There exists typical alternatives to the ground-state regular
planar structures of PAHs, as long as they bear internal energies in the range
1-10 eV. Resulting from intramolecular rearrangements, such high-lying minima
on the potential- energy surfaces should be taken into consideration in the
studies of PAH processing in astrophysical conditions. Resting upon DFT
calculations mainly performed on two emblematic PAH representatives, coronene
and pyrene, in their neutral and mono and multi-cationic states, this second
survey addresses the following alternatives: (1) opened forms containing
ethynyl or 2- butynyl groups, (2) vinylidene isomers, in which phenanthrene
patterns are reorganized into dibenzofulvene ones, (3) twisted forms, where
external CH=CH bonds can be partly twisted, and (4) bicyclobutane forms, in
which the latter are integrated in saturated bicyclic forms. A few scenarios
for elimination of fragments H, H2, C2H2 and C2H4 are explored. As far as
possible, familiar concepts of organic chemistry, such as aromaticity or Clar's
rules, are invoked for interpretations.Comment: 65 pages, accepted by Molecular Astrophysic
Lithium conducting solid electrolyte Li1.3Al0.3Ti1.7(PO4)3 obtained via solution chemistry
NaSICON-type lithium conductor Li1.3Al0.3Ti1.7(PO4)3 (LATP) is synthesized with controlled grain size and composition using solution chemistry. After thermal treatment at 850 C, sub-micronic crystallized powders with high purity are obtained. They are converted into ceramic through Spark Plasma Sintering at 850â1000 C. By varying the processing parameters, pellet with conductivities up to 1.6 * 10â4 S/cm with density of 97% of the theoretical density have been obtained. XRD, FEG-SEM, ac-impedance and Vickers indentation were used to characterize the products. The influence of sintering parameters on pellet composition, microstructure and conductivity is discussed in addition to the analysis of the mechanical behavior of the grains interfaces
Gestion Publique ou PrivĂ©e ? Un benchmarking des services dâeau en France
Nous utilisons une mĂ©thode dâAnalyse par Enveloppe de DonnĂ©es (DEA) ainsi quâune mĂ©thode dâAnalyse par FrontiĂšre Stochastique (SFA) pour mesurer lâefficacitĂ© relative de 177 services dâeau en France, en 2009. Ces services peuvent ĂȘtre gĂ©rĂ©s directement par les communes (rĂ©gies) ou ĂȘtre dĂ©lĂ©guĂ©s Ă des opĂ©rateurs privĂ©s. Lâutilisation de ces deux outils de benchmarking nous permet de distinguer la part de lâinefficience relative des services provenant de lâinefficience managĂ©riale, du contexte opĂ©rationnel et des bruits statistiques. Nos rĂ©sultats indiquent tout dâabord que les opĂ©rateurs privĂ©s opĂšrent dans des environnements plus difficiles. AprĂšs correction de cet environnement dâexploitation, les services dâeau dĂ©lĂ©guĂ©s demeurent, en moyenne, trĂšs lĂ©gĂšrement moins efficients en comparaison des rĂ©gies. Cependant, cette faible diffĂ©rence se dissipe lorsque les performances relatives sont mesurĂ©es Ă©conomĂ©triquement.This paper uses a Data Envelopment Analysis (DEA) and a Stochastic Frontier Analysis (SFA) to assess the relative technical efficiency of 177 decision making units in the water supply sector in France in 2009. Water utilities can be directly managed by the local authorities or contracted out and then managed by a private operator. The use of a three-stage model mixing DEA and SFA enables us to dissociate managerial inefficiencies from the structural inefficiencies and statistical noise. Our results show that private managers face more difficult environment. After having taken into account the environmental variables, private management remains on average slightly less efficient than public management. However, this small difference dissipates when relative performance is econometrically measured
Hydrogenation of C carbon clusters : structural diversity and energetic properties
This work aims at exploring the potential energy surfaces of
CH{n=0,6,12,18,24} up to 20-25\,eV using the genetic algorithm in
combination with the density functional based tight binding (DFTB) potential.
The structural diversity of the non fragmented structures was analysed using
order parameters which were chosen as the number of 5 or 6 carbon rings and the
asphericity constant . The most abundant and lowest energy population
was found to correspond to a flakes population, constituted of isomers of
variable shapes possessing a large number of 5 or 6-carbon rings. This
population is characterized by a larger number of spherical isomers when
increases. Simultaneously, the fraction of the pretzels population
constituted of spherical isomers possessing fewer 5 or 6 carbon ring cycles
increases. For all hydrogenation rates, the fraction of cages population
remains extremely minor while the branched population is the highest energy
population for all ratios. For all CH{n=0,6,12,18,24}
clusters, a detailed study of the evolution of the carbon ring size
distribution as a function of energy clearly shows that the stability is
correlated to the number of 6-carbon rings. A similar study for hybridization
(n=1-3) shows that the number of carbon atoms increases with
energy while globally the number of carbon atoms increases with
. The average values of the ionization potentials of all populations
were found to decrease when increases, ranging from 7.9\,eV down to
6.4\,eV that we correlated to carbon atoms hybridization (n=1-3). These
results are of astrophysical interest as they should be taken into account in
astrophysical models especially regarding the role of carbonaceous species in
the gas ionization.Comment: 37 pages, 13 figure
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