HAL-uB
Not a member yet
73989 research outputs found
Sort by
Spatio-temporal equilibrium thermodynamics of guided optical waves at positive and negative temperatures
No full textOptical thermalization has been recently studied theoretically and experimentally in the 2D spatial evolution of (quasi-)monochromatic light waves propagating in multimode fibers. In this work, we investigate the spatio-temporal equilibrium properties of incoherent multimode optical waves through the analysis of the (2+1)D Bose-Einstein thermal distribution and the corresponding classical Rayleigh-Jeans approximation. In the anomalous dispersion regime, the spatio-temporal equilibrium is characterized by positive temperatures. In this regime, we show that as the number of modes of the waveguide increases, the fundamental spatial mode becomes macroscopically populated, while its temporal spectrum undergoes significant narrowing, ultimately leading to complete (2+1)D spatio-temporal condensation in the thermodynamic limit. In the normal dispersion regime, the spatio-temporal equilibrium is characterized by negative temperature states that exhibit a hybrid character: the spatial equilibrium displays an inverted modal population, whereas the temporal spectrum remains peaked around the fundamental (carrier) optical frequency. In this regime, we predict that spatio-temporal light waves exhibit a phase transition to Bose-Einstein condensation at negative temperatures, which occurs by increasing the temperature above a negative critical value. Our work opens new avenues for future research, including the possibility for a dual spatio-temporal beam cleaning through full spatio-temporal light condensation, and lay the groundwork for the development of spatio-temporal optical thermodynamics
Roadmap on specialty optical fibers
No full textInternational audienceOptical fibers, long an enabling technology for telecommunications, are proving to play a central role in a growing number of modern applications, starting from high speed broad band internet to medical surgery and entering across the entire spectrum of scientific, military, industrial and commercial applications. Specialty optical fibers either special waveguide structure or novel material composition becomes heart of all fiber based advanced photonics devices and components. This rapidly evolving field calls on the expertise and skills of a broad set of different disciplines: materials science, ceramic engineering, optics, electrical engineering, physics, polymer chemistry, and several others. This roadmap on specialty optical fibers addresses different technologies and application areas. It is constituted by fourteen contributions authored by world-leading experts, providing insight into the current state-of-the-art and the challenges their respective fields face. Some articles address the area of multimode fibers, including the nonlinear effects occurring in them. Several other articles are dedicated to doped, plastic, and soft-glass fibers. Large mode area fibers, hollow-core fibers, and nanostructured fibers are also described in different sections. The use of some of such fibers for optical amplification and to realize several kinds of optical sources-including lasers, single photon sources and supercontinuum sources-is described in some other sections. Different approaches to satisfy applications at visible, infrared and terahertz spectra regions are also discussed. Throughout the roadmap there is an attempt to foresee and to suggest future directions in this particularly dynamic area of optical fiber technology
Structural and functional characteristics of β-lactoglobulin/Cphycocyanin/starch composite gels induced by pressure
No full textInternational audienceHigh-pressure processing (HPP) has emerged as a key sustainable green alternative for food treatment, effectively preserving food's sensory and nutritional properties. This study investigated the potential of HPP to develop β-lactoglobulin (BLG) gels in the presence of starch and the bioactive blue protein C-phycocyanin (C-PC). Various compositions of binary (BLG/C-PC and BLG/starch) and ternary (BLG/C-PC/starch) systems were subjected to high-pressure (HP) conditions at 4,500 bar. BLG, C-PC, and starch concentrations were maintained at 180, 10, and 5 g/L. HP-induced hydrogels preserve C-PC colour and partial preservation of secondary and tertiary structures, as evidenced by visible absorption and CD spectroscopy. SAXS data at the high-Q range revealed that C-PC induces the unfolding of BLG within binary system gels. In contrast, the ternary system gel maintained the BLG tertiary structure better. C-PC and starch affected the nano and microstructures of BLG HP-induced gels by increasing the pore size, as demonstrated by SAXS (at low Q-range) and SEM analysis. This increase in pore size further influenced the resulting gels' rheological behaviour and texture profile. C-PC enhanced the protein solubility and antioxidant activity of the HP-induced gels, potentially boosting the bioactive and nutritional value of the developed gels
Fokker-Planck Equations on Homogeneous Lie Groups and Probabilistic Counterparts
No full textInternational audienceWe address the well-posedness of subelliptic Fokker–Planck equations arising from stochastic control problems, as well as the properties of the associated diffusion processes. Here, the main difficulty arises from the possible polynomial growth of the coefficients, which is related to the growth of the family of vector fields generating the first layer of the associated Lie algebra. We prove the existence and uniqueness of the energy solution and its representation as the transition density of the underlying subelliptic diffusion process. Moreover, we show its Hölder continuity in time w.r.t. the Fortet–Mourier distance, where the Hölder seminorm depends on the degree of homogeneity of the vector fields. Finally, we provide a probabilistic proof of the Feyman–Kac formula as a consequence of the uniform boundedness in finite time intervals of all moments
A 3D cobalt corrole-based Zr-MOF for the selective adsorption of carbon monoxide
No full textInternational audienceTwo 3D MOFs based on a triphenylcorrole and their cobalt-metalated analogs (CoCorr-MOF) are presented. They show a hexagonal morphology, homogeneous particles size, and a microporosity with a specific area of 390 and 304 m² g-1, respectively. The CoCorr-MOF presents a better affinity for CO than for other interferents (N2, CO2 and O2). It demonstrates a CO sorption capacity of 7.2 cm3 g-1 with high selectivity
Promising in vitro results from bioinspired polyhydroxamic and picolinic chelators for actinide decorporation
No full textInternational audienceActinides (An = Th, U, Np, Pu, Am, Cm) are highly radiotoxic or chemotoxic elements that have been widely used over the past 75 years in civilian, industrial and military applications. In case of incidental or accidental internal contamination, An might induce cancerous and non-cancerous health effects once internalized. Furthermore, their tropism for specific organs such as bones and kidneys can lead to accumulation lasting from several days to several years. Decorporation via chemical chelation is the only specific strategy to address internal An contamination. Chelating agents bind actinides with high affinity, promoting their elimination via natural excretion pathways. Currently, the only decorporating treatment approved by health authorities is trisodium calcium/zinc pentetate (CaNa3-DTPA/ZnNa3-DTPA). Side effects, limited therapeutic efficacy, and inability to deplete U and Np underline the need for better treatments. Within the ActiDecorp research project (ANR-23-CE18-0046), we aim to assess the efficacy and safety of new synthetic compounds bearing cyclic hydroxamate or picolinate as bioinspired binding units. Ultrafiltration coupled with ICP-MS or alpha-spectrometry is used to assess the in vitro affinity of the candidate ligands for An. The selected filter device allows separating the light An complexes formed with the ligand from the heavier ones involving endogenous blood-serum proteins, which are retained by the filter. Among the four ligands tested for U, two have shown promising results with significant increases by 18 and 27% of the U content in the filtrate. Cytotoxicity of eight compounds is evaluated on renal hRPTEC-TERT1 cell model using necrosis, apoptosis, and viability tests. The safety of the ligands is then evaluated with calculated LC50 values that ranged from 100 to 625µM. Among the compounds analyzed up to now, the two most promising ligands for U have the highest LC50, therefore indicating a low cytotoxicity.These preliminary results obtained from in vitro affinity and in cellulo toxicity studies support the potential of cyclic hydroxamates as promising U decorporating agents. Further investigations are ongoing to determine their affinity for other An and to deepen the in cellulo toxicity assays, before considering in vivo studies for efficacy and safety assessment
Scientific Opinion of the French Agency for Food, Environmental and Occupational Health & Safety on the establishment of dietary guidelines for people following a diet that excludes some or all foods of animal origin (vegetarians)
No full textInternational audienceThis document presents the opinion of the French Agency for Food, Environmental and Occupational Health & Safety (ANSES), established from the work of its Working Group on Vegetarian diets and validated by its Expert Committee on Human Nutrition. ANSES issued an internal request to establish dietary guidelines for people who follow a diet that excludes some or all foods of animal origin. Firstly, ANSES conducted a systematic review of the scientific literature to identify epidemiological links between health and various types of vegetarian diets. This systematic review showed that the risk of developing type 2 diabetes is lower with vegetarian than with non‐vegetarian diets. With a lower level of evidence, vegetarians are less likely than non‐vegetarians to develop certain diseases, such as ischaemic heart disease, ovulation disorders, certain types of cancer (prostate, stomach, blood) and certain ophthalmological and gastro‐intestinal diseases. However, they are at greater risk of bone fractures and hypospadias (congenital malformation of the urethra). The epidemiological studies examined showed that vegetarians have a less favourable nutritional status in iron, iodine and vitamins B12 and D, and a poorer calcium and phosphorus balance than non‐vegetarians. Vegans also have a less favourable nutritional status in vitamin B2. ANSES then used dietary optimisation to identify combinations of food groups (state variables) enabling the set objectives to be met, i.e. to reduce nutritional and toxicological risks, while deviating as little as possible from current consumption habits. All the nutritional and toxicological constraints and the criteria (minimisations or maximisations) made it possible to take account of the risks associated with nutrient intakes or exposure to contaminants, as well as the expected nutritional benefits. The systematic review and establishment of dietary guidelines using an optimisation tool show that the lacto‐ovo‐vegetarian diet requires particular attention regarding certain nutrients for which requirements in terms of vitamin D and eicosapentaenoic and docosahexaenoic fatty acids may not be met. The risk of requirements not being met by the lacto‐ovo‐vegetarian diet is greater than that associated with the diet of non‐vegetarian populations. In addition, lacto‐ovo‐vegetarians limiting their intake of milk and fresh dairy products may not be able to cover their vitamin B12 requirements. Furthermore, with the vegan diet, which excludes all foods of animal origin, it is difficult to meet the dietary reference value for zinc in men
Paléoécologie et paléoenvironnement de Discosauriscus Kuhn, 1933 avec préservation exceptionnelle des moules de peau et d’intestin du Permien précoce de Franchesse (Allier, France).
No full textInternational audienceThe Carboniferous-Permian is a key period concerning the emergence and diversification of major tetrapod clades such as amphibians and amniotes. This is particularly the case of the Seymouriamorpha Watson, 1917. Some seymouriamorphs are well-known, such as Seymouria Broili, 1904 from North America and Germany, but the ecology of most taxa remains debated. This is the case of Discosauriscus Kuhn, 1933 from the early Permian of Europe. Here we provide a preliminary study of new specimens from the early Permian Lagerstätte of Franchesse (Allier, France) whose exceptionally well-preserved soft tissues including skin and intestinal casts provide valuable insights into the palaeoecology of Discosauriscus. We describe for the first time the complete skin external and histological features of a seymouriamorph indicating that juvenile discosauriscids already displayed epidermal scalation. This suggests a skin adapted towards terrestrial lifestyle in juvenile Discosauriscus. The recovery of an in situ cololite facilitates the identification of seymouriamorph coprolites found ex situ, and thus, future interpretations of the specific diet of this taxon. In order to better understand how these soft tissues have been preserved, we also conducted a taphonomic study including a stratigraphic and palaeoenvironmental analysis of the fossil layer deposits. Our results suggest that pronounced volcanic activity at work during the early Cisuralian of the Bourbon-l’Archambault Basin may be the cause of the multiple Permian mass mortality assemblages found at Franchesse, as well as the exceptional preservation of the fossil remains from this site.Le Carbonifère-Permien est une période clé en ce qui concerne l’émergence et la diversification des principaux clades de tétrapodes tels que les amphibiens et les amniotes. C’est notamment le cas des Seymouriamorpha Watson, 1917. Certains seymouriamorphes sont bien connus, comme Seymouria Broili, 1904 d’Amérique du Nord, mais l’écologie de la plupart des taxons reste débattue. C’est le cas de Discosauriscus Kuhn, 1933 du Permien inférieur d’Europe. Ici, nous étudions de manière préliminaire de nouveaux spécimens provenant du Lagerstätte du Permien inférieur de Franchesse (Allier, France) dont les tissus mous exceptionnellement bien conservés, y compris la peau et le moulage des intestins, permettent d’en apprendre davantage sur la paléoécologie de Discosauriscus. Nous décrivons pour la première fois la morphologie externe et interne de la peau d’un seymouriamorphe, indiquant que les discosauriscidés juvéniles présentaient des écailles épidermiques. Cela suggère une peau adaptée à un mode de vie terrestre chez les Discosauriscus juvéniles. La découverte d’un cololithe in situ facilite l’identification des coprolithes de seymouriamorphes trouvés ex situ et ainsi de futures interprétations sur le régime alimentaire de ce taxon. Afin de mieux comprendre comment ces tissus mous ont été préservés, nous avons également mené une étude taphonomique comprenant une analyse stratigraphique et paléoenvironnementale des dépôts des couches fossilifères. Nos résultats suggèrent qu’une activité volcanique marquée au cours du Cisuralien inférieur dans le bassin de Bourbon-l’Archambault pourrait être à l’origine des multiples assemblages de mortalité massive trouvés à Franchesse, ainsi que de la préservation exceptionnelle des restes fossiles de ce site
Can Excel® be used for gauge R&R study based on the analysis of variance (Anova)?
No full textInternational audienceThe Analysis of Variance (Anova) method, alongside the range method, is widely used to conduct Gauge Repeatability and Reproducibility (Gauge R&R) studies for measurement systems. While Anova provides more precise and robust statistical insights compared to the range-based approach, it is often perceived as more complex due to the necessity of calculating sum of squares, mean squares, and performing F-tests. Furthermore, this method can lead to misleading conclusions if the results-especially residuals-are not thoroughly and correctly analyzed. Despite its analytical complexity, the Anova method can be effectively implemented using spreadsheet tools such as Excel®. Excel® offers a flexible and accessible environment to perform rapid recalculations when input data are modified. In this paper, we demonstrate how to conduct a Gauge R&R study using the Anova approach within Excel®. The dual objective of this work is (i) to provide a user-friendly implementation within Excel®, and (ii) to enable rigorous and accurate interpretation of the statistical results produced.</div
Concluding remarks: Advanced imaging techniques in biomineralization research
No full textInternational audienceThese four half-days of Faraday Discussions highlighted the wide range of physical techniques available to image the diversity and complexity of biominerals, in several natural models and in vitro systems