282 research outputs found
As above, so below: whole transcriptome profiling demonstrates strong molecular similarities between avian dorsal and ventral pallial subdivisions
Over the last two decades, beginning withthe Avian Brain Nomenclature Forum in2000, major revisions have been made to our understanding of the organization andnomenclature of the avian brain. However, there are still unresolved questions on avianpallial organization, particularly whether the cells above the vestigial ventricle representdistinct populations to those below it or similar populations. To test these two hypothe-ses, we profiled the transcriptomes of the major avian pallial subdivisions dorsal and ven-tral to the vestigial ventricle boundary using RNA sequencing and a new zebra finchgenome assembly containing about 22,000annotated, complete genes. We found thatthe transcriptomes of neural populations above and below the ventricle were remarkablysimilar. Each subdivision in dorsal pallium (Wulst) had a corresponding molecular counter-part in the ventral pallium (dorsal ventricularridge). In turn, each corresponding subdivi-sion exhibited shared gene co-expression modules that contained gene sets enriched infunctional specializations, such as anatomical structure development, synaptic transmis-sion, signaling, and neurogenesis. Thesefindings are more in line with the continuumhypothesis of avian brain subdivision organization above and below the vestigial ventriclespace, with the pallium as a whole consisting offour major cell populations (intercalatedpallium, mesopallium, hyper-nidopallium, andarcopallium) instead of seven (hyperpalliumapicale, interstitial hyperpallium apicale, intercalated hyperpallium, hyperpalliumdensocellare, mesopallium, nidopallium, and arcopallium). We suggest adopting a morestreamlined hierarchical naming system thatreflects the robust similarities in geneexpression, neural connectivity motifs, and function. These findings have important impli-cations for our understanding of overall vertebrate brain evolution
On-sky results of the adaptive optics MACAO for the new IR-spectrograph CRIRES at VLT
The adaptive optics MACAO has been implemented in 6 focii of the VLT
observatory, in three different flavors. We present in this paper the results
obtained during the commissioning of the last of these units, MACAO-CRIRES.
CRIRES is a high-resolution spectrograph, which efficiency will be improved by
a factor two at least for point-sources observations with a NGS brighter than
R=15. During the commissioning, Strehl exceeding 60% have been observed with
fair seeing conditions, and a general description of the performance of this
curvature adaptive optics system is done.Comment: SPIE conference 2006, Advances in adaptive optics, 12 pages, 11
figure
Optical response of small silver clusters
The time-dependent local density approximation is applied to the optical
response of the silver clusters, Ag_2, Ag_3, Ag_8 and Ag_9^+. The calculation
includes all the electrons beyond the closed-shell Ag^{+11} ionic core, thus
including for the first time explicitly the filled d-shell in the response. The
excitation energy of the strong surface plasmon near 4 eV agrees well with
experiment. The theoretical transition strength is quenched by a factor of 4
with respect to the pure s-electron sum rule in Ag_8 due to the d-electrons. A
comparable amount of strength lies in complex states below 6 eV excitation. The
total below 6 eV, about 50% of the s sum rule, is consistent with published
experiments.Comment: 13 pages RevTex and 9 Postscript figure
Artifcial neural network: a powerful tool in associating phenolic compounds with antioxidant activity of grape juices.
In vitro techniques are essential to assess the antioxidant potential of foods, although methods with diferent action mechanisms make troublesome data analysis. This article describes the use of artifcial neural network (ANN) to associate phenolic compounds with antioxidant activity in vitro (AOX) of grape juices. A multilayer perceptron (MLP) ANN was obtained with 28 phenolics quantifed, as input layers, and AOX measuring by DPPH, ABTS, FRAP, H2O2, and β-carotene/linoleic acid bleaching assay (βCLA) methods, as output layers. To improve discussion in food sciences, the ANN results were compared with Pearson?s correlation and principal component analysis (PCA), methods largely used in food studies. Pearson?s technique showed correlations between antioxidant methods and some of the phenolic compounds, but with limitations. PCA proved to be a more powerful method than Pearson?s correlation, as it positively associated 13 phenolics with four out of fve antioxidant methods. The MLP-ANN allowed simultaneous association of 19 individual phenolics, while a single hidden layer predicted 15 phenolics with simultaneous action in all AOX methods. The power of association was: ANN>PCA>Pearson. It was evidenced that ANN is a powerful tool for screening antioxidants in diferent AOX systems, which is applicable in health interests
Radial elasticity of multi-walled carbon nanotubes
We report an experimental and a theoretical study of the radial elasticity of
multi-walled carbon nanotubes as a function of external radius. We use atomic
force microscopy and apply small indentation amplitudes in order to stay in the
linear elasticity regime. The number of layers for a given tube radius is
inferred from transmission electron microscopy, revealing constant ratios of
external to internal radii. This enables a comparison with molecular dynamics
results, which also shed some light onto the applicability of Hertz theory in
this context. Using this theory, we find a radial Young modulus strongly
decreasing with increasing radius and reaching an asymptotic value of 30 +/- 10
GPa.Comment: 5 pages, 3 figure
Origin of Shifts in the Surface Plasmon Resonance Frequencies for Au and Ag Nanoparticles
Origin of shifts in the surface plasmon resonance (SPR) frequency for noble
metal (Au, Ag) nanoclusters are discussed in this book chapter. Spill out of
electron from the Fermi surface is considered as the origin of red shift. On
the other hand, both screening of electrons of the noble metal in porous media
and quantum effect of screen surface electron are considered for the observed
blue shift in the SPR peak position.Comment: 37 pages, 14 Figures in the submitted book chapter of The Annual
Reviews in Plasmonics, edited by Professor Chris D. Geddes. Springer Scinec
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