A method to quantify and account for the hygroscopic effect in stem diameter variations

Dendrometers recording stem diameter variations (SDV) at high-resolution are useful to assess trees' water relation since water reserves are stored in the elastic tissue of the bark. These tissues typically shrink during the day as they release water when evaporative demand is high and swell during the night as they are replenished when evaporative demand is low, generating the typical SDV profile known as the diel SDV cycle. However, similar SDV cycles have been observed on dead trees due to the hygroscopic shrinking and swelling of the dead bark tissues. In order to remove this hygroscopic effect of the bark, dendrometers are applied as close as possible to the living bark tissues by removing the outer dead layer, however with questionable success. In this study, we used SDV time series from 40 point dendrometers applied on dead-bark-removed mature trees to assess and quantify the remaining hygroscopic effect on individual trees. To do so, we checked SDV behavior in the cold season and explored the relation between the diel SDV cycle and changes in relative humidity (RH). Our results showed that (a) the hygroscopic effect in SDV can be well-detected based on the amplitude of the diel SDV cycle (diel SDVampl) and the correlation between SDV and RH during both the cold and the warm season; (b) the level of the hygroscopic effect varies strongly among individuals; (c) diel SDVampl is proportional to both changes in RH and transpiration so that the hygroscopic effect on the diel SDV cycle can be quantified using a linear model where (diel SDVampl) is a function of RH changes and transpiration. These results allow the use of the model to correct the amplitude of the diel SDV cycles and suggest that this method can be applied to other ecological relevant water-related SDV variables such as tree water deficit

Electron-Phonon Scattering in 2D Silver Nanotriangles

Electron-phonon energy exchanges are investigated in 2D silver nanotriangles of thickness ranging from 5 to 8 nm and lateral size ranging from 25 to 85 nm, using time-resolved femtosecond spectroscopy in the low-perturbation regime. The measured electron-phonon decay time is smaller in 2D nanotriangles than in bulk silver, and its value corresponds to the decay time measured in isolated nanospheres with a diameter equal to the thickness of the nanotriangles. These results show that the electron-phonon energy exchanges in 2D nanosystems are strongly accelerated by confinement and this acceleration is directly governed by the smallest dimension of the nano-object

Synthesis of Au-Ag nano-hybrids to investigate heat transfer

The modalities of energy transfer at the nanoscale strongly differ from those at the macroscopic scales because of the increased role played by interfaces..

Versatile template-directed synthesis of gold nanocages with a predefined number of windows

Highly symmetrical gold nanocages can be produced with a controllable number of circular windows of either 2, 3, 4, 6 or 12 via an original fabrication route. The synthetic pathway includes three main stages: the synthesis of silica/polystyrene multipod templates, the regioselective seeded growth of a gold shell on the unmasked part of the silica surface and the development of gold nanocages by dissolving/etching the templates. Electron microscopy and tomography provide evidence of the symmetrical features of the as-obtained nanostructures. The optical properties of nanocages with 4 and 12 windows were measured at the single particle level by spatial modulation spectroscopy and correlated with numerical simulations based on finite-element modeling. The new multi-step synthesis approach reported here also allows the synthesis of rattle-like nanostructures through filling of the nanocages with a guest nano-object. With the potential to adjust the chemical composition, size and geometry of both the guest particle and the host cage, it opens new routes towards the fabrication of hollow nanostructures of high interest for a variety of applications including sensing devices, catalytic reactors and biomedicine. New concepts We demonstrate a new concept for making hollow nanoscale structures which are central to the advances in many current and emerging areas of technology. Nanocages are hollow and porous nanostructures. The ones made of metal are needed for optics, catalysis, biomedicine, and sensing. But, they are difficult to make. In particular, it is difficult to yield precise nanoscale control of the porosity as well as the composition. We address this challenge by combining inorganic colloidal synthesis and metal deposition on biphasic sacrificial templates. The single-particle spectroscopy and simulation confirm that our approach affords tight control over the morphology and porosity at the nanoscale. Previous approaches to making metal nanocages rely on galvanic replacement reactions and siteselective deposition. They offer control over morphology, but limited control over composition, porosity and scaleup. Our approach provides a simple and general strategy to circumvent these issues. It can be applied to a wide range of materials, and with further developement to any nanorattle-like nanostructures.Towards Colloidal Molecules and Functional MaterialsAdvanced Materials by DesignInitiative d'excellence de l'Université de BordeauxNanoparticule hybride unique: synthèse et corrélation entre sa réponse optique et sa caractérisation par microscopie électronique analytique en 3D

Electron-Phonon Scattering in 2D Silver Nanotriangles

Electron-phonon energy exchanges are investigated in 2D silver nanotriangles of thickness ranging from 5 to 8 nm and lateral size ranging from 25 to 85 nm, using time-resolved femtosecond spectroscopy in the low-perturbation regime. The measured electron-phonon decay time is smaller in 2D nanotriangles than in bulk silver, and its value corresponds to the decay time measured in isolated nanospheres with a diameter equal to the thickness of the nanotriangles. These results show that the electron-phonon energy exchanges in 2D nanosystems are strongly accelerated by confinement and this acceleration is directly governed by the smallest dimension of the nano-object

Circular maps of the replicons encompassing the <i>P</i>. <i>veronii</i> 1YdBTEX2 genome.

<p>(A) Chromosome 1 (chr1) with indication of possible genomic islands (GEI) and prophages (pf). The outermost circles show the location and orientation of predicted coding regions (blue and cyan), followed by tRNA (olive green) and rRNA genes (black), predicted regions of genome plasticity (blue-green-brown) islands and prophages (grey). The inner circles represent BLASTN comparisons with the close relatives <i>P</i>. <i>fluorescens</i> SBW25 (red, Acc. No. AM181176.4), <i>P</i>. <i>trivialis</i> strain IHBB745 (deep pink, CP011507.1), <i>P</i>. <i>syringae</i> pv. syringae B728a (dark purple, CP000075.1), <i>P</i>. <i>putida</i> KT2440 (light purple, AE015451.1) and <i>P</i>. <i>knackmussii</i> B13 (persian green, HG322950). GC skew (dark magenta and yellow green) is shown in the most central circle. (B) As A, but for the chromosome 2 replicon (chr2). Inner circles, from outwards to inwards, predicted transposons (dark purple) and <i>tra</i> genes (green), regions of genome plasticity (blue-green-brown) and prophages (grey), followed by BLASTN comparisons to <i>P</i>. <i>fluorescens</i> SBW25 plasmid pQB103 (red, AM235768.1, NC_009444.1), <i>Pseudomonas stutzeri</i> strain 19SMN4 plasmid pLIB119 (deep pink, CP007510.1), <i>Pseudomonas mandelii</i> JR-1 plasmid (dark purple, CP005961.1) and <i>Pseudomonas resinovorans</i> NBRC 106553 plasmid pCAR1.3 (Persian green, AP013069.1). (C) As B, but for the plasmid replicon. The inner circles represent the BLASTN comparisons with <i>P</i>. <i>putida</i> S12 plasmid pTTS12 (red, CP009975.1), and <i>Pseudomonas</i> sp. VLB120 plasmid pSTY (purple, CP003962.1). Plots generated with DNAPlotter [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0165850#pone.0165850.ref046" target="_blank">46</a>].</p

Overview of denitrification capacity of <i>P</i>. <i>veronii</i> 1YdBTEX2.

<p>(A) Overnight growth of <i>P</i>. <i>veronii</i> 1YdBTEX2 wild type (WT) and the Δ<i>nar</i> mutant in presence (+O₂, left) or absence of air but with 15 mM nitrate supplemented medium (+NO₃,–O₂, right panel) conditions. Note the gas formation in the right panel of the WT incubation. (B) Gene regions predicted for denitrification in the <i>P</i>. <i>veronii</i> 1YdBTEX2 chromosome 1 with trivial gene names indicated. Black bar represents the deleted region in <i>P</i>. <i>veronii</i> Δ<i>nar</i>.</p

Genome-wide gene expression differences in <i>P</i>. <i>veronii</i> 1YdBTEX2 after 1 h exposure to different carbon sources or growth environment.

<p>(A) Two-dimensional Principal Component Analysis of quadruplate global RNA-sequencing data sets of <i>P</i>. <i>veronii</i> 1YdBTEX2 incubated in liquid medium with succinate (Li-Su), or toluene (Li-To), or in sand with succinate (Sa-Su) or with toluene (Sa-To). (B) Venn diagram with the number of unique and common genes significantly differentially expressed (2-way ANOVA, ²log-fold-change [logFC] >1, false-discovery rate [FDR] <0.05, <i>P</i> <0.01) as result of change of carbon source (succinate to toluene) or environment (liquid to sand). (C) Smear-plot of global gene expression intensity (²log CPKM) versus expression changes (²log fold change) compared between cells incubated with toluene (Li-To) versus succinate (Li-Su); in grey, genes not statistically differentially expressed (logFC<1, FDR>0.05, <i>P</i> >0.01); magenta, genes with lower, and dark purple, genes with higher expression in presence of toluene (+). Blue, <i>ipb</i> genes; yellow, <i>dmp</i> genes; green, <i>ttg</i> genes (toluene efflux pump). (D) Gene expression changes as an effect of carbon source (succinate versus toluene, left) or of environment (liquid versus sand, right), and plotted as function of genomic location (chromosome 1, chr1; chromosome 2, chr2 and plasmid, plm; organized according to locus_tag number). Bars indicate ²log-fold change. Dark purple, statistically significantly higher expressed genes in presence of toluene (+, left) or sand (+, right); cyan, lower expressed genes in pink. Positions of the <i>ipb</i>, <i>dmp</i> and <i>ttg</i> genes are highlighted.</p

Comparison of catabolic gene transcription involved in toluene or <i>meta-</i>cleavage metabolism by <i>P</i>. <i>veronii</i> 1YdBTEX2 in liquid culture with succinate (Li-Su) or toluene (Li-To).

<p>(A) Normalized read counts across the <i>ipb</i> gene cluster (PVE_r2g0739-0753). Note the decrease as a result of the transposon insertion (white arrow). (B) Expression level (reads per kilobase per million, RPKM, ¹⁰log scale) of the <i>ipb</i> cluster genes (numbers refer to PVE_r2g loci). (C) as B, for the <i>dmp</i> cluster genes (PVE_r2g0708-0719), and the proposed gene encoding for the dihydrodiol dehydrogenase (PVE_r2g0805). (D) as B, for the <i>nah</i> cluster genes (PVE_r2g0834-0847).</p