Plastic pollution is widespread in ocean ecosystems worldwide, but it is unknown if plastic offers a unique habitat for bacteria compared to communities in the water column and attached to naturallyoccurring organic particles. The large set of samples taken during the Tara-Mediterranean expedition revealed for the rst time a clear niche partitioning be tween free-living (FL), orga nic particle-attached fi (PA) and the recently introduced plastic marine debris (PMD). Bacterial counts in PMD presented higher cell enrichment factors than generally observed for PA fraction, when compared to FL bacteria in the surrounding waters. Taxonomic diversity was also higher in the PMD communities, where higher evenness indicated a favorable environment for a very large number of species. were Cyanobacteria particularly overrepresented in PMD, together with essential functions for bio lm formation and fi maturation. The communit y distinction between the three habitats was consistent across the large-scale sampling in the Western Mediterranean basin. Plastic speci c bacteria recovered only on the PMD ' fi ' represented half of the OTUs, thus forming a distinct habitat that should be further considered for understanding microbial biodiversity in changing marine ecosystems.

Spin-lattice relaxation of the nuclear spin system in p-type GaAs is studied using a three-stage experimental protocol including optical pumping and measuring the difference of the nuclear spin polarization before and after a dark interval of variable length. This method allows us to measure the spin-lattice relaxation time T1 of optically pumped nuclei “in the dark,” that is, in the absence of illumination. The measured T1 values fall into the subsecond time range, being three orders of magnitude shorter than in earlier studied n-type GaAs. The drastic difference is further emphasized by magnetic-field and temperature dependencies of T1 in p-GaAs, showing no similarity to those in n-GaAs. This unexpected behavior finds its explanation in the spatial selectivity of the optical pumping in p-GaAs, that is only efficient in the vicinity of shallow donors, together with the quadrupole relaxation of nuclear spins, which is induced by electric fields within closely spaced donor-acceptor pairs. The developed theoretical model explains the whole set of experimental results.

Lead halide perovskites, used to produce photovoltaic devices, have been thesubject of a huge research effort these last years. This is due to the spectac-ular improvement of the conversion effciency results within a short amount oftime. However, some issues have been identified, which include stability, leaduse and cost of some precursors. It has recently been shown that low purity, lowcost PbI2 could be succesfully used in the synthesis of the MAPbI3 perovskite,provided that HCl is added during the synthesis to prevent solubility problems.Thus, it is of high interest to provide information pertaining to the materialquality, in relation with the HCl additions performed during synthesis. In thiswork, we have grown three sets of samples with different HCl to (PbI 2 + MAI)molar ratios (R HCl ), where PbI2 and methylamine iodide (MAI) are the precur-sors of the perovskite. We used RHCl = 0 (no HCl), 0.5 and 1.2 . We performedx-ray diffraction, transmittance and 77K photoluminescence experiments in or-der to assess the material structural and optoelectronic properties and foundthat an optimum HCl concentration must be used. HCl introduction clearlyhas a beneficial effect both on domain sizes and photoluminescence intensityat RHCl = 0.5, but lead to subsequent degradation of the perovskite quality athigher RHCl .

Casein micelle (CM), porous colloidal phosphoprotein-mineral complex, naturally present in milk to deliver minerals, also has several features, which could ensure its use as nanocarrier for bioactives. CM structure being not steady according to the physico-chemical conditions, its stability can be improved by intra-micellar cross-linking using transglutaminase (TGase) inducing a strengthened structure called casein nanogel. The aim of this research was to investigate the morphology and nanomechanics of casein nanogel particles cross-linked by TGase (TG-CM) using atomic force microscopy (AFM) in native-like liquid environment (lactose-free simulated milk ultrafiltrate, SMUF). Prior to AFM, TG-CM were captured by anti-phospho-Ser/Thr/Tyr monoclonal antibodies covalently bound to a gold-coated slide via carbodiimide chemistry. Surface topography and size properties evaluation revealed an increase in size of TG-CM compared to native CM, TG-CM being characterized by a mean width of 264 ± 7 nm and a mean height of 111 ± 5 nm. TG-CM displayed a relatively high contact angle (62°) indicating a limited flattening of these particles after adsorption on the substrate. The TG-CM elasticity was then evaluated applying low indentation forces on single TG-CM. The TGase treatment led to a significant modification of CM nanomechanics attributed to intramolecular rearrangements within the micellar structure. The elasticity distribution of TG-CM revealed three elasticity peaks centered at 219±14kPa, 536±14kPa and 711 ± 11 kPa. The lower elasticity peak is related to the native CM nanomechanical signature and the two stiffer peaks were attributed to the substantial changes in the TG-CM structure.

Dentin carious lesion is a dynamic process that involves de- mineralization and collagen denaturation. Collagen type I is the major protein in dentin and it has been investigated based on its optical properties. Multiphoton microscopy (MPM) is a nonlinear imaging technique that reveals the car- ies process using the collagen two-photon excitation fluo- rescence (2PEF) and its second-harmonic generation (SHG). Combining the histological and the International Caries De- tection and Assessment System (ICDAS) classifications with nonlinear optical spectroscopy (NLOS), 2PEF and SHG inten- sities of enamel and dentin were highly altered during the caries process. It has been proven that the ratio SHG/2PEF is a relevant indicator of the organic matrix denaturation [Ter- rer et al.: J Dent Res 2016;96:574–579]. In the present study, a series of measurable signals is made to detect early stages of carious lesion according to the ICDAS classification and to explore the relationship between these measures and theICDAS scale. Comparison of the efficiency of nonlinear opti- cal signals for caries detection with the ICDAS classification is essential to evaluate their potential for clinical applica- tion. In our study, the use of the NLOS measured by MPM allowed us to monitor a quantitative parameter (SHG/2PEF ratio) according to the dentin carious lesion state (ICDAS and histological examination). Three coherent new groups were defined (ICDAS 0/1; ICDAS 2/3; ICDAS 4/5/6), where the carious process can be clearly described with a statistically significant decrease of the SHG/2PEF ratio.

The understanding of interactions between electrons and phonons in atomically thin heterostructures is crucial for the engineering of novel two-dimensional devices. Electron–phonon (el–ph) interactions in layered materials can occur involving electrons in the same layer or in different layers. Here we report on the possibility of distinguishing intralayer and interlayer el–ph interactions in samples of twisted bilayer graphene and of probing the intralayer process in graphene/h-BN by using Raman spectroscopy. In the intralayer process, the el–ph scattering occurs in a single graphene layer and the other layer (graphene or h-BN) imposes a periodic potential that backscatters the excited electron, whereas for the interlayer process the el–ph scattering occurs between states in the Dirac cones of adjacent graphene layers. Our methodology of using Raman spectroscopy to probe different types of el–ph interactions can be extended to study any kind of graphene-based heterostructure.