297 research outputs found
On the role of chirality in structure-odor relationships
The influence of chirality on odors was studied on 16 enantiomeric pairs according to the dispersion/hydrogen bonding theory of receptor-odorant interaction. Comparisons of molecular structures were made by superimposition of optimized conformations, using the Alchemy II package. The quality of fit was assessed using the RMS parameter included in Alchemy II and a new index for hydrogen bonding: the angle between H-bonds in the two molecules. In the case of camphoraceous odorants where an interaction model was already known superimposition according to the model led to correct predictions of the high similarity of odors observed in enantiomeric pairs. For several urinous odorants comparisons were made using d-androstenone as a reference compound for the urinous odor. Correct predictions were obtained for l-androstenone, both enantiomers of androsta-4, 16-dienone, and (+)-2-methyl-4-(5,5,6-exo-trimethy1-2-exonorbornyl)-cyclobexane. The (−) enantiomer of the latter compound was correctly predicted only if it was assumed that its weak intensity is due to a partial interaction with the hydrophobic zone of the receptor. For ambergris odorants which have a complex odor (−)-Ambrox was selected as the reference compound. The odors of (+)-Ambrox and enantiomers of four other compounds (ambergris or woody) were correctly predicted by superimposition. For nootkatone and three derivatives which have a grapefruit note for one enantiomer and a woody note for the other no models or reference compounds were available. The superimpositions were made between grapefruit enantiomers, on the one hand, and woody enantiomers on the other hand. Woody and grapefruit characters were correctly predicted in all cases. The limits of this approach based on molecular modelling are discusse
Structure and diversity of shallow soft-bottom benthic macrofauna in the Gulf of Lions (NW Mediterranean).
14 páginas, 10 figuras, 4 tablas.Samples of soft-sediment macrobenthos from
92 sites between 10 and 50 m depth were used to assess (1)
the main soft-bottom macrofauna communities in the Gulf
of Lions, (2) the different components of the diversity of
benthic macrofauna in this area, and (3) the relevance of
the use of major taxonomic groups as surrogates for the
analysis of the structure and diversity of total macrofauna.
Three main communities were identified by cluster analysis
and associated procedures. These communities corresponded well to the assemblages recently identified on the
basis of polychaete composition. The a-diversity indices
were in accordance with those reported for similar communities in the Mediterranean. Conversely, the b-diversity
value was higher than the few other data available in the
literature for marine soft-bottom macrofauna. The total
number of species in the studied area estimated by the
‘‘total species accumulation curve’’ (TS) method was
2,319, which was only 10% higher than the number
obtained by extrapolation of the species–area curve. The
similarity matrix based on polychaetes correlated best with
the one based on total macrofauna. Polychaetes and crustaceans were also the best surrogates of total macrofauna
when assessing a-diversity (except in the case of D*).
Conversely, molluscs were the best surrogates of total
macrofauna b-diversity. Our results show that the choice of
an optimal surrogate for total benthic macrofauna depends
on the characteristic of the benthic macrofauna to be
studied. Moreover, this choice is also dependent on the
environment to be studiedThis work is part of the PhD thesis of Ce´line
Labrune. It was carried out within the EC Network of Excellence
MARBEF. Ce´line Labrune was supported by the SYSCOLAG project
run by the Re´gion Languedoc-Roussillon.Peer reviewe
Spring molybdenum enrichment in scallop shells: a potential tracer of diatom productivity in temperate coastal environments (Brittany, NW France)
Skeletal molybdenum/calcium ([Mo]/[Ca])<sub>shell</sub> ratios were examined in
shells of the Great Scallop <i>Pecten maximus</i> collected in temperate coastal environments of
Western Europe (42 to 49° N). These ratios were determined by
quantitative LA-ICP-MS analyses of daily striae taken every third day (i.e.
a temporal resolution of 3 days) in 36 flat valves (2-years old; 3
shells/year). Variations of ([Mo]/[Ca])<sub>shell</sub> ratios were significant
and reproducible for scallops from the same population, from different years
(1998–2004) and temperate coastal locations (NW France). The
[Mo]/[Ca])<sub>shell</sub> ratios exhibit typical profiles characterized by a
background content, below the detection limit for this method
(<0.003 μmol/mol) for most of the shell growth period, which is punctuated by a
significant transient enrichment (0.031–2.1 μmol/mol) mainly occurring
from May to June. The Bay of Brest (France) was investigated in particular
because of its long term observations on scallop communities, environmental
variables, and high resolution analyses of dissolved Mo in bottom seawater
in 2000. In 2000, dissolved Mo exhibited a significant increase in
concentration just preceding the maximum ([Mo]/[Ca])<sub>shell</sub> ratio. Both
the intense monitoring survey in 2000 and over the 7-year period indicates
that the ([Mo]/[Ca])<sub>shell</sub> maximum is directly influenced by spring
changes of environmental conditions at the sediment water interface (SWI),
occurring subsequent to the intense and periodic spring bloom. Spring maxima
of ([Mo]/[Ca])<sub>shell</sub> ratios are closely correlated to the extent of
silicic acid and nitrate depletion in seawater between winter and late
spring (<i>r</i><sup>2</sup>=0.878 and 0.780, <i>p</i><0.05, <i>n</i>=6) that reflects diatom
uptake and productivity in the Bay of Brest. The Mo inputs in bottom waters
and subsequent shell enrichment are thus suggested to be directly or
indirectly influenced by such biogenic material input at the SWI. The
[Mo]/[Ca])<sub>shell</sub> records thus reveal unexpected biogeochemical cycles of
Mo influenced by coastal spring productivity, faithfully recorded in scallop
shells
Multipole analysis of cluster weak lensing shear in The Three Hundred project
Weak gravitational lensing is an important tool to estimate the masses of galaxy clusters, as it allows us to directly access their projected surface mass density along the line of sight in a manner largely independent of their dynamical state. Moreover, we can extract information on the projected shape of the cluster mass distribution. In this work, we generate mock catalogs of lensed background galaxies to measure the individual lensing properties of galaxy clusters from the simulation project The Three Hundred. By repeating the analysis for different projections of the same cluster, we find that the use of shear multipoles provides constraints on the ellipticity of the cluster projected mass density but does not have a significant impact on the cluster mass reconstruction compared to the standard approach
Natural enemies of armored scales (Hemiptera: Diaspididae) and soft scales (Hemiptera: Coccoidae) in Chile: molecular and morphological identification.
Scale insects (Hemiptera: Sternorrhyncha: Coccomorpha) are key pests of agricultural
crops and ornamental plants worldwide. Their populations are difficult to control, even with
insecticides, due to their cryptic habits. Moreover, there is growing concern over the use of
synthetic pesticides for their control, due to deleterious environmental effects and the emergence
of resistant populations of target pests. In this context, biological control may be an
effective and sustainable approach. Hymenoptera Chalcidoidea includes natural enemies of
scale insects that have been successfully used in many biological control programs. However,
the correct identification of pest scale species and their natural enemies is particularly
challenging because these insects are very small and highly specialized. Integrative taxonomy,
coupling DNA barcoding and morphological analysis, has been successfully used to
characterize pests and natural enemy species. In this study, we performed a survey of parasitoids
and predators of armored and soft scales in Chile, based on 28S and COI barcodes.
Fifty-three populations of Diaspididae and 79 populations of Coccidae were sampled over
the entire length of the country, from Arica (18˚S) to Frutillar (41˚S), between January 2015
and February 2016. The phylogenetic relationships obtained by Bayesian inference from
multilocus haplotypes revealed 41 putative species of Chalcidoidea, five Coccinellidae and
three Neuroptera. Species delimitation was confirmed using ABGD, GMYC and PTP model.
In Chalcidoidea, 23 species were identified morphologically, resulting in new COI barcodes
for 12 species and new 28S barcodes for 14 species. Two predator species (Rhyzobius
lophantae and Coccidophilus transandinus) were identified morphologically, and two parasitoid
species, Chartocerus niger and Signiphora bifasciata, were recorded for the first time
in Chile
Abundance of Delta Resonances in 58Ni+58Ni Collisions between 1 and 2 AGeV
Charged pion spectra measured in 58Ni-58Ni collisions at 1.06, 1.45 and 1.93
AGeV are interpreted in terms of a thermal model including the decay of Delta
resonances. The transverse momentum spectra of pions are well reproduced by
adding the pions originating from the Delta-resonance decay to the component of
thermal pions, deduced from the high transverse momentum part of the pion
spectra. About 10 and 18% of the nucleons are excited to Delta states at
freeze-out for beam energies of 1 and 2 AGeV, respectively.Comment: 14 pages, LaTeX with 3 included figures; submitted to Physics Letters
Stopping and Radial Flow in Central 58Ni + 58Ni Collisions between 1 and 2 AGeV
The production of charged pions, protons and deuterons has been studied in
central collisions of 58Ni on 58Ni at incident beam energies of 1.06, 1.45 and
1.93 AGeV. The dependence of transverse-momentum and rapidity spectra on the
beam energy and on the centrality of the collison is presented. It is shown
that the scaling of the mean rapidity shift of protons established for AGS and
SPS energies is valid down to 1 AGeV. The degree of nuclear stopping is
discussed; the IQMD transport model reproduces the measured proton rapidity
spectra for the most central events reasonably well, but does not show any
sensitivity between the soft and the hard equation of state (EoS). A radial
flow analysis, using the midrapidity transverse-momentum spectra, delivers
freeze-out temperatures T and radial flow velocities beta_r which increase with
beam energy up to 2 AGeV; in comparison to existing data of Au on Au over a
large range of energies only beta_r shows a system size dependence
K^+ production in the reaction at incident energies from 1 to 2 AGeV
Semi-inclusive triple differential multiplicity distributions of positively
charged kaons have been measured over a wide range in rapidity and transverse
mass for central collisions of Ni with Ni nuclei. The transverse
mass () spectra have been studied as a function of rapidity at a beam
energy 1.93 AGeV. The distributions of K^+ mesons are well described by a
single Boltzmann-type function. The spectral slopes are similar to that of the
protons indicating that rescattering plays a significant role in the
propagation of the kaon. Multiplicity densities have been obtained as a
function of rapidity by extrapolating the Boltzmann-type fits to the measured
distributions over the remaining phase space. The total K^+ meson yield has
been determined at beam energies of 1.06, 1.45, and 1.93 AGeV, and is presented
in comparison to existing data. The low total yield indicates that the K^+
meson can not be explained within a hadro-chemical equilibrium scenario,
therefore indicating that the yield does remain sensitive to effects related to
its production processes such as the equation of state of nuclear matter and/or
modifications to the K^+ dispersion relation.Comment: 24 pages Latex (elsart) 7 PS figures to be submitted to Nucl. Phys
Long-term (1998–2010) large-scale comparison of the ecological quality status of gulf of lions (NW Mediterranean) benthic habitats
12 páginas, 4 tablas, 8 figuras.A comprehensive Mediterranean data set has been used to address 3 questions associated with the use of sensitivity/tolerance
based biotic indices to infer the Ecological Quality status (EcoQs) of benthic habitats. Our results
showed: (1) a significant effect of the reference database on derived sensitivity/tolerance measure (ES500.05) as
well as associated Benthic Quality Index values and derived EcoQs; (2) a lack of correlation neither between BQI
and AZTI Marine Biotic Index values nor between BQI and Multivariate-AZTI Marine Biotic Index values; (3) a lack
of correlation between the values of the Benthic Habitat Quality Index (index derived from Sediment Profile Imagery)
and those of either of the 3 tested biotic indices; and (4) a general agreement between the 3 tested biotic
indices in describing the lack of global trend for the EcoQs of the Gulf of Lions despite the occurrence of significant
changes in benthic macrofauna composition between 1998 and 2010.This study has been carried out with financial support from the French National
Research Agency (ANR) in the frame of the Investments for the future
Programme, within the Cluster of Excellence COTE (ANR-10-LABX-45).Peer reviewe
From the Idea of a basic income to the political movement in Europe
Volume: 71Start Page: 289End Page: 30
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