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We propose an AlGaAs microring resonator design for the generation of an optical frequency comb by means of the interplay between harmonic generation and Kerr effect. Modal phase matching imposes specific waveguide geometries and, consequently, it impacts the nonlinear efficiency of the system. We show the dynamics of χ(2) + χ(3) comb generation resulting from type-I modal phase matching.

We study how nanophotonic structures can be used for determining the position of a nearby nanoscale object with subwavelength accuracy. Through perturbing the near-field environment of a metasurface transducer consisting of nano-apertures in a metallic film, the location of the nanoscale object is transduced into the transducer’s far-field optical response. By monitoring the scattering pattern of the nanophotonic near-field transducer and comparing it to measured reference data, we demonstrate the two-dimensional localization of the object accurate to 24 nm across an area of 2 × 2 μm. We find that adding complexity to the nanophotonic transducer allows localization over a larger area while maintaining resolution, as it enables encoding more information on the position of the object in the transducer’s far-field response.

L'étude présentée a été réalisée dans le cadre du GMCL (Groupement Moteur Carburant Lubrifiant), organisme qui réunit des constructeurs d'automobiles, des raffineurs et des additiveurs, avec l'objectif d'examiner la sensibilité d'un moteur Diesel à injection directe d'automobile aux paramètres du gazole. Les partenaires de cette étude sont Elf, IFP, Octel, PSA, Renault et Total. Parmi les solutions technologiques permettant de disposer de convertisseurs d'énergie assurant de faibles niveaux d'émissions de polluants et de consommation, le moteur Diesel se place naturellement en bonne position. Dans ce contexte, on enregistre aujourd'hui l'émergence du moteur Diesel à injection directe pour les véhicules légers en raison de ses performances, notamment en regard de la consommation. Toutefois, cette technologie nécessite une technique d'injection performante, associée à la gestion électronique, demande de l'EGR et un catalyseur d'oxydation afin de régler les problèmes d'émissions polluantes et sonores. Il est donc de première importance de cerner avec précision la sensibilité du moteur Diesel à injection directe aux paramètres carburants afin de tirer le meilleur profit de cette technologie. À partir d'un ensemble de gazoles formulés pour faire varier la composition chimique, l'indice de cétane et la densité, un moteur Audi à injection directe de type 1Z a été testé au banc, dans des conditions standard de réglage (avance à l'injection et taux de gaz recyclés). Cet ensemble de résultats a ainsi permis de démontrer que l'accroissement de l'indice de cétane, la réduction de la densité et de la teneur en polyaromatiques ont une influence positive sensible sur les émissions de CO, d'hydrocarbures imbrûlés, des VOF. En ce qui concerne les émissions de particules, l'indice de cétane semble avoir une influence négative sur la fraction sèche dans certaines conditions. De plus, il apparaît que les particules totales sont plutôt dépendantes de la viscosité et des fractions légères des carburants. Les émissions sonores sont étroitement liées à l'indice de cétane. Par ailleurs, l'ensemble des résultats acquis semble indiquer que les paramètres pilotant le délai d'auto-inflammation sont importants sur ce type de convertisseur. Il serait cependant nécessaire de disposer de mesures directes des caractéristiques des jets d'injection (taille des gouttelettes, pénétration du spray) en fonction des différents carburants pour pouvoir quantifier l'effet des paramètres tels que la viscosité et la densité sur la partie physique du délai d'auto-inflammation. Among the technical solutions that can lead to energy converters with low pollutant emissions and low fuel consumption, diesel engines rank, by nature, in a good position. On this base, direct injection diesel engine has been developed and are now spreading in private passanger cars because of their performances, especially in terms of fuel consumption. However, this equipment requires an efficient injection system, electronically driven, needs EGR and an oxidation catalyst to improve the pollutant emissions and the noise level. Thus, it is a major concern to be able to assess precisely the sensitivity to fuel characteristics of direct injection engines as to take the best advantage of this technology. With a set of fuels formulated to cover a large range of chemical nature, viscosity, cetane number and density, an Audi direct injection engine (1Z model) was run at the test bench. The impact of the fuel characteristics on pollutant emissions, regulated or unregulated (PAH, aldehydes), and on noise levels was assessed either under standard tuning conditions, either by changing the EGR rate and the injection timing. The results obtained at the end of this program point out the main criteria that have an influence on emissions. They also allow a comparison between direct injection engines and their homologues with prechambers. The works this communication is dealing with have been conducted as part of the program of the Groupement Moteur Carburant Lubrifiant(GMCL), in collaboration with ELF, Octel, PSA, Renault and Total.

Micro/nanoplastics (MNPs), which are widely spread in the environment, have gained attention because of their ability to enter the human body mainly through ingestion, inhalation, and skin contact, thus representing a serious health threat. Several studies have reported the presence of MNPs in lung tissue and the potential role of MNP inhalation in triggering lung fibrosis and tumorigenesis. However, there is a paucity of knowledge regarding the cellular response to MNPs composed of polyethylene (PE), one of the most common plastic pollutants in the biosphere. In this study, we investigated the effects of low/high concentrations of PE MNPs on respiratory epithelial cell viability and migration/invasion abilities, using MTT, scratch, and transwell assays. Morphological and molecular changes were assessed via immunofluorescence, Western blot, and qRT-PCR. We demonstrated that acute exposure to PE MNPs does not induce cellular toxicity. Instead, cells displayed visible morphological changes also involving actin cytoskeleton reorganization. Our data underlined the role of epithelial–mesenchymal transition (EMT) in triggering this process. Moreover, a remarkable increase in migration potential was noticed, in absence of a significant alteration of the cell's invasive capacity. The present study highlights the potential impact of PE MNPs inhalation on the human respiratory epithelium, suggesting a possible role in carcinogenesis. [ABSTRACT FROM AUTHOR]

Adipose-derived mesenchymal stem cells (ASCs) represent a valid therapeutic option for clinical application in several diseases, due to their ability to repair damaged tissues and to mitigate the inflammatory/immune response. A better understanding of the underlying mechanisms regulating ASC biology might represent the chance to modulate their in vitro characteristics and differentiation potential for regenerative medicine purposes. Herein, we investigated the effects of the demethylating agent 5-azacytidine (5-aza) on proliferation, clonogenicity, migration, adipogenic differentiation and senescence of ASCs, to identify the molecular pathways involved. Through functional assays, we observed a detrimental effect of 5-aza on ASC self-renewal capacity and migration, accompanied by actin cytoskeleton reorganization, with decreased stress fibers. Conversely, 5-aza treatment enhanced ASC adipogenic differentiation, as assessed by lipid accumulation and expression of lineage-specific markers. We analyzed the involvement of the Akt/mTOR, MAPK and Wnt/β-catenin pathways in these processes. Our results indicated impairment of Akt and ERK phosphorylation, potentially explaining the reduced cell proliferation and migration. We observed a 5-aza-mediated inhibition of the Wnt signaling pathway, this potentially explaining the pro-adipogenic effect of the drug. Finally, 5-aza treatment significantly induced ASC senescence, through upregulation of the p53/p21 axis. Our data may have important translational implications, by helping in clarifying the potential risks and advantages of using epigenetic treatment to improve ASC characteristics for cell-based clinical approaches.

This paper provides an experimental investigation of the effect of Thermally Expandable Particle (TEP) adhesive additive on the mechanical and reversibility performance of epoxy-bonded load single lap joints (SLJs). Joint substrates are made of aluminum 6061 and woven carbon fiber reinforced plastic 0/90/0 substrates. TEP additive is used for modifying the structural epoxy adhesive used in this study. An electrically charged RF coil is placed around the joint bond area; generated electromagnetic field would heat the aluminum substrate which would in turn heat the modified adhesive. Very large volumetric expansion of the hollow spherical Thermally Expandable Particles (TEPs) would significantly reduce adhesive strength and lead to joint debonding under a minimal load of 100 N. Various weight concentrations of the TEP in the range of 5% to 25% with particulate size from 6 to 16 µm are used for investigating the effect on joint static and fatigue strength as well as the reversibility performance. Measured time to achieve full debonding of the joint (under charged RF coil), is used for assessing the reversibility performance.

Abstract In this paper, we report the effect of optical trapping on the enhancement factor for Raman spectroscopy, using a dielectric metasurface. It was found that a higher enhancement factor (up to 275%) can be obtained in a substrate immersed in water, where particles are freee to move, compared to a dried substrate, where the particles (radius $$r=9$$ r = 9 nm, refractive index $$n=1.58$$ n = 1.58 ) are fixed on the surface. The highest enhancement is obtained at low concentrations because, this case, the particles are trapped preferentially in the regions of highest electric field (hotspots). For high concentrations, it was observed that the hotspots become saturated with particles and that additional particles are forced to occupy regions of lower field. The dielectric metasurface offers low optical absorption compared to conventional gold substrates. This aspect can be important for temperature-sensitive applications. The method shows potential for applications in crystal nucleation, where high solute supersaturation can be achieved near the high-field regions of the metasurface. The high sensitivity for SERS (surface-enhanced Raman spectroscopy) at low analyte concentrations makes the proposed method highly promising for detection of small biological particles, such as proteins or viruses.

The large retail chains represent the main distribution channel for wine sales in Italy. Retailers, therefore, define the wine supply of their points-of-sale based on their own commercial strategies, taking into account evolving consumer demand, producer characteristics, and product types. Wine bottles from different producers with varying characteristics, sales performances, and commercial trends can be found on shelves next to each other. The aim of this study is to investigate the performance of various producers whose wines were sold in large retail chains in Italy before the pandemic. This analysis enabled us to observe market trends without disruptions. We focused on the two most sold Protected Designation of Origin (PDO) wines, Chianti DOCG and Montepulciano d'Abruzzo DOC. For this purpose, cluster segmentation was implemented using variables related to sales (value of sales, number of labels, average price, discount units, discount percentage, units sold above a certain price), and sales trends of each producer present in large retail chains with these products. The results show that, although there are different trends and commercial strategies among the producers of each of the two denominations of origin, there are similarities between the clusters of the two different denominations. In particular, in the domain of large-scale retail, wine sales are dominated by a few wineries with a strategy based on high sales volume, a wide range of labels, low prices, and promotional sales. The remaining sales refer to wines from producers with different characteristics that record positive sales trends and producers characterised by the declining value of sales. The identified results provide valuable insights for a better understanding of the dynamics of the large retail chain in Italy. [ABSTRACT FROM AUTHOR]