Université Bordeaux 1
  • Talence, France
Recent publications
The chemical pollution crisis severely threatens human and environmental health globally. To tackle this challenge the establishment of an overarching international science–policy body has recently been suggested. We strongly support this initiative based on the awareness that humanity has already likely left the safe operating space within planetary boundaries for novel entities including chemical pollution. Immediate action is essential and needs to be informed by sound scientific knowledge and data compiled and critically evaluated by an overarching science–policy interface body. Major challenges for such a body are (i) to foster global knowledge production on exposure, impacts and governance going beyond data-rich regions (e.g., Europe and North America), (ii) to cover the entirety of hazardous chemicals, mixtures and wastes, (iii) to follow a one-health perspective considering the risks posed by chemicals and waste on ecosystem and human health, and (iv) to strive for solution-oriented assessments based on systems thinking. Based on multiple evidence on urgent action on a global scale, we call scientists and practitioners to mobilize their scientific networks and to intensify science–policy interaction with national governments to support the negotiations on the establishment of an intergovernmental body based on scientific knowledge explaining the anticipated benefit for human and environmental health.
Concrete made with recycled concrete aggregates (RCA) presents particular properties that may lead to a specific behaviour under fire conditions, including the spalling risk. The spalling sensitivity of concrete made with RCA was evaluated through a campaign conducted in three concrete series: reference, direct replacement, and strength-based replacement. The last was designed to have the same performance as concrete made with natural aggregates (NA). Samples with different replacement rates of recycled coarse aggregates (0 %, 10 %, 20 %, 40 %, and 100 %) were exposed to the standard fire curve (ISO 834-1) with constant uniaxial loading (2.5 and 5 MPa). During the tests, the furnace temperature and spalling events were recorded. After the tests, digital photogrammetry was used to observe the spalling damage (volume and depth). Fire tests indicated that concrete made with RCA exhibited a higher spalling degree than concrete made with NA. Results also show that the replacement rate acts in different ways: in concrete with RCA replacement rates up to 40 %, the spalling damage increases, but a further increase does not lead to higher spalling. In addition, RCA changes the physical properties of concrete, which may trigger spalling, particularly water content.
Background: In HIV-medicine, the Veterans Aging Cohort Study (VACS) index is associated to some geriatric syndromes and has also been recently used as a proxy of frailty. However, using it as a proxy for the frailty phenotype may inadvertently interchange two different concepts. The purpose of this study was to evaluate to what extent the frailty phenotype may be explained by the index. Methods: Cross-sectional analysis including 393 participants with HIV aged 50 or older. Somers' delta (d) was calculated and a multinomial logistic regression model was run to determine to what extent the VACS index scores explained the probability of being pre-frail or frail. Results: Mean age 57.6 (SD 6.5) years, and 87.3% men. A weak, but positive association between the VACS 2.0 index score and the frailty phenotype was established (Somers' d= .120, P< .001). The multinomial logistic regression showed that pre-frail and frail participants had higher probabilities for greater VACS index scores (OR= 1.05, 95% CI 1.01-1.09; P=.006 and OR= 1.17, 95% CI 1.09-1.26; P < .001, respectively); however, VACS index only explained < 12% of the variability observed in the frailty phenotype. Conclusions: High VACS index scores were associated with a greater probability of being frail; however, with a weak association. Thus, we should be cautious when using the VACS index as a general proxy of frailty, particularly for the frailty phenotype. However, the VACS Index may be used as a means to identify persons who might benefit from further comprehensive geriatric assessment.
Optical generation of kilo-tesla scale magnetic fields enables prospective technologies and fundamental studies with unprecedentedly high magnetic field energy density. A question is the optimal configuration of proposed setups, where plenty of physical phenomena accompany the generation and complicate both theoretical studies and experimental realizations. Short laser drivers seem more suitable in many applications, though the process is tangled by an intrinsic transient nature. In this work, an artificial neural network is engaged for unravelling main features of the magnetic field excited with a picosecond laser pulse. The trained neural network acquires an ability to read the magnetic field values from experimental data, extremely facilitating interpretation of the experimental results. The conclusion is that the short sub-picosecond laser pulse may generate a quasi-stationary magnetic field structure living on a hundred picosecond time scale, when the induced current forms a closed circuit.
A series of new transparent and magnetic barium gallogermanate glasses in the system (x) Gd2O3 – (100-x) [20BaO−15Ga2O3−65GeO2] with x = 0, 8, 14, 18, 22 and 25 mol% were synthesized. Their thermal, structural and magnetic properties were characterized. Based on the differential scanning calorimetry results, one determined the composition domain exhibiting the highest thermal stability toward crystallization and provided a detailed experimental fabrication method for the production of optical fibers. The local glass structure investigated using combined Raman and Infrared vibrational spectroscopies shows a progressive depolymerization of the 3D glass germanate network accompanied with an increase of non-bridging oxygens when increasing the Gd2O3 content. The incorporation of gadolinium ions tends to extend the IR transmission window. Thanks to the magnetic susceptibility measurements, the paramagnetic behavior was evidenced, and increases with the Gd³⁺ content. The combination of the optical, thermal and magnetic properties of Gd2O3 gallogermanate glasses as well as their ability to be shaped into optical fibers make them promising materials for their integration in MIR functional optical components.
Studying the Brownian motion of fibers and semi-flexible filaments in porous media is the key to understanding the transport and mechanical properties in a variety of systems. The motion of semi-flexible filaments in gel-like porous media including polymer networks and cell cytoskeleton has been studied theoretically and experimentally, whereas the motion of these materials in packed-colloid porous media, advanced foams, and rock-like systems has not been thoroughly studied. Here we use video microscopy to directly visualize the reptation and transport of intrinsically fluorescent, semiflexible, semiconducting single-walled carbon nanotubes (SWCNTs) in the sub-micron pores of packed colloids as fixed obstacles of packed-colloid porous media. By visualizing the filament motion and Brownian diffusion at different locations in the pore structures, we study how the properties of the environment, like the pore shape and pore structure of the porous media, affect SWCNT mobility. These results show that the porous media structure controls SWCNT reorientation during Brownian diffusion. In packed-colloid pores, SWCNTs diffuse along straight pores and bend across pores; conversely, in gel pores, SWCNTs consistently diffuse into curved pores, displaying a faster parallel motion. In both gel and packed-colloid porous media, SWCNT finite stiffness enhances SWCNT rotational diffusion and prevents jamming, allowing for inter-pore diffusion.
We study the prize-collecting job sequencing problem with one common and multiple secondary resources. In this problem, a set of jobs is given, each with a profit, multiple time windows for its execution, and a duration during which it requires the main resource. Each job also requires a preassigned secondary resource before, during, and after its use of the main resource. The goal is to select and schedule the subset of jobs that maximize the total profit. We present a new mixed integer linear programming formulation of the problem and a branch-cut-and-price algorithm as an exact solution method. We also introduce a heuristic algorithm to tackle larger instances. Extensive numerical experiments show that our exact algorithm can solve to optimality literature instances with up to 500 jobs for a particular dataset and up to 250 jobs for another dataset with different characteristics. Our heuristic builds high-quality solutions in a small computational time. It computes new best-known solutions for most of the larger instances.
We report the first high-precision mass measurements of the neutron-rich nuclei 74,75Ni and the clearly identified ground state of ⁷⁶Cu, along with a more precise mass-excess value of ⁷⁸Cu, performed with the double Penning trap JYFLTRAP at the Ion Guide Isotope Separator On-Line (IGISOL) facility. These new results lead to a quantitative estimation of the quenching for the N=50 neutron shell gap. The impact of this shell quenching on core-collapse supernova dynamics is specifically tested using a dedicated statistical equilibrium approach that allows a variation of the mass model independent of the other microphysical inputs. We conclude that the impact of nuclear masses is strong when implemented using a fixed trajectory as in the previous studies, but the effect is substantially reduced when implemented self-consistently in the simulation.
Heating is a major concern for electrical measurements at cryogenic temperatures. In this study, the statics and dynamics of heating effects induced on a Si/SiO2 chip by the application of DC and AC power to an on-chip heating element are measured using on-chip cryogenic thermometers. It is found that large on chip temperatures, ∼ 100mK above cryostat temperature, and large on-chip thermal gradients, 100s of milliKelvins over ∼ 10μm distance, are generated at relatively small (∼ 0.1μW) input powers. As expected, the heating effects are larger at lower cryostat temperatures. With applied AC voltages, it is found that the average temperatures generated are similar in magnitude to the DC voltages, but the temperature gradients are smaller. The average temperatures reached on the surface of the chip increase with increasing frequency. At 5Hz frequency, the thermal dynamics are too slow to allow temperature oscillations following the input power, instead resulting in a steady state temperature increase.
Observing signatures of light-induced topological Floquet states in materials has been shown to be very challenging. Angle-resolved photoemission spectroscopy (ARPES) is well suited for the investigation of Floquet physics, as it allows to directly probe the dressed electronic states of driven solids. Depending on the system, scattering and decoherence can play an important role, hampering the emergence of Floquet states. Another challenge is to disentangle Floquet side bands from laser-assisted photoemission (LAPE), since both lead to similar signatures in ARPES spectra. Here, we investigate the emergence of Floquet state in the transition metal dichalcogenide 2H-WSe2, one of the most promising systems for observing Floquet physics. We discuss how the topological Floquet state manifests in characteristic features in the circular dichroism in photoelectron angular distributions (CDAD) that is determined by the transient band structure modifications and the associated texture of the orbital angular momentum. Combining highly accurate modeling of the photoemission matrix elements with an ab initio description of the light-matter interaction, we investigate regimes which can be realized in current state-of-the-art experimental setups. The predicted features are robust against scattering effects and are expected to be observed in forthcoming experiments. Direct observation of light-induced topological Floquet states can be challenging due to a number of obstacles such as laser-assisted photoemission which can complicate photoemission spectra. Here, the authors report a theoretical approach to the identification of topological Floquet states using circular dichroism in angle resolved photoemission spectroscopy.
Savanna ecosystems were the landscapes for human evolution and are vital to modern Sub-Saharan African food security, yet the fundamental drivers of climate and ecology in these ecosystems remain unclear. Here we generate plant-wax isotope and dust flux records to explore the mechanistic drivers of the Northwest African monsoon, and to assess ecosystem responses to changes in monsoon rainfall and atmospheric pCO 2. We show that monsoon rainfall is controlled by low-latitude insolation gradients and that while increases in precipitation are associated with expansion of grasslands into desert landscapes, changes in pCO 2 predominantly drive the C 3 /C 4 composition of savanna ecosystems.
Theoretically and experimentally, we study electroviscous phenomena resulting from charge-flow coupling in a nanoscale capillary. Our theoretical approach relies on Poisson-Boltzmann mean-field theory and on coupled linear relations for charge and hydrodynamic flows, including electro-osmosis and charge advection. With respect to the unperturbed Poiseuille flow, we define an electroviscous coupling parameter ξ, which turns out to be maximum where the film height h_{0} is comparable to the Debye screening length λ. We also present dynamic atomic force microscopy data for the viscoelastic response of a confined water film in sphere-plane geometry; our theory provides a quantitative description for the electroviscous drag coefficient and the electrostatic repulsion as a function of the film height, with the surface charge density as the only free parameter. Charge regulation sets in at even smaller distances.
Introduction: Hearing loss is a rare manifestation in giant cell arteritis. The different types of deafness are possible with a predominance of sensorineural deafness. Case report: We report a 75-year-old woman who presented with typical manifestations of giant cell arteritis associated concomitantly with the occurrence of bilateral mixed hearing loss confirmed on the audiogram. Corticosteroids allowed a rapidly favorable clinical and biological outcome. The follow-up audiogram at 3 months was markedly improved and showed a decrease in sensorineural hearing loss and disappearance of conductive hearing loss. Conclusion: Any rapid onset deafness in an inflammatory context in the elderly should lead to a search for giant cell arteritis. The diagnosis can be difficult in the absence of other typical manifestations, especially since the biopsy of the temporal artery most often comes back negative. Corticosteroids are usually effective.
In the present study, the selective sublimation of the p-GaN cap layer of Al(Ga)N/GaN HEMTs is developed to replace the commonly used dry etching with no risk of damage in the barrier layer in order to fabricate enhanced mode transistors. Thanks to this approach, enhancement-mode transistors are fabricated with a threshold voltage between 0V and +1.5V depending on the barrier layer aluminum molar fraction and thickness. Furthermore, we show the benefit of the combination of selective sublimation with the regrowth of AlGaN to reduce access resistance in these transistors which can be co-integrated with depletion-mode devices fabricated in the same process in areas where p-GaN has been totally evaporated.
Foam injection is a promising option for soil remediation applications. However, predicting how it will propagate in highly permeable aquifers under groundwater flow is challenging. Here, we have studied pressure and saturation variations during foam propagation. A 2D tank packed with 1 mm glass beads was used to study foam injection in highly permeable porous media under lateral flow. Specifically, we evaluated the efficiency of pressure and time-domain reflectometer (TDR) sensors to predict foam propagation using an imaging technique. A numerical model coupling two-phase flow and surfactant transport was developed to simulate the experimental results. This model takes into account the effect of non-Newtonian behavior of foam, surfactant concentration, and critical capillary pressure through the definition of the mobility reduction factor (MRF). The experimental results show that the foam injection pressure first increases with a logarithmic law and then stabilizes. This pressure stabilization can be related to the state of pseudo-equilibrium between foam generation and destruction. We observed an asymmetrical foam propagation due to water lateral flow. Comparisons of the liquid saturation fields calculated by analysis of TDR probes and estimated by imaging show that the TDR sensors monitor foam propagation well in saturated porous media. They can predict the shape of the injected foam. Contrary to pressure sensors, it is possible to capture weak foam behavior using TDR sensors. Finally, the numerical model we have developed correctly captures the shape of foam propagation and its ability to divert water flows. This model produces the propagation of the strong foam well and predicts the saturation and pressure fields with good precision.
In this paper, the behavior of foam in a porous medium is studied in order to understand the effect of the fluid velocity on foam properties. This aspect is crucial during foam injection, as due to radial effects the foam velocity largely decreases around the injection well. The foam properties are detailed through the use of a new local equilibrium foam model parameter estimation approach using an improved new shear function and based on the most widely used STARS model developed by the Computer Modeling Group (CMG). A new mode of calculation of the STARS model parameters is then presented in order to allow both a semiautomated fitting of several quality scan pressure curves and a consideration of the role of the total velocity. The approach is tested through column experiments done at various velocities and gas fractions. Furthermore, the proposed model is also tested on literature results in order to validate it for very different experimental conditions. This study and the fitted results are then used to understand, on both our column experiments and the literature data, the existence of two shear effects and their origins.
Living envelopes, such as biological skins and structures built by animals, are functional and sustainable designs resulting from years of evolution, conditioned by biological and physical pressures from the environment. When building a home, animals demonstrate inspiring strategies to protect themselves from predator threats and external climatic conditions. As for human buildings, temperature, humidity, air quality, light, are some of the various factors they have to manage for optimal conditions. Facing the climate emergency, growing efforts to build durable designs have led designers to search for more efficient or alternative solutions by observing Nature. The emerging field of bioinspiration including animal architecture has already brought few but rare exemplary innovations that were integrated into building designs. Data on animal architecture are scattered among various biological domains, from observation of species habitats by zoologists such as entomologists or ornithologists, to bioindicator studies by climatologists. Data collected by scientists is available in eclectic idioms, a challenge to be fully comprehended by building designers. This chapter presents a characterization of living envelopes aiming at facilitating the transposition of some relevant biological features into innovative and sustainable architectural designs. The approach is architecture and engineer oriented, assessing biological functions and strategies, using criteria that are meaningful to building designers: functional and temporal analyses of spaces and materials, physical factors regulated through envelopes, behaviors, and interactions of species. Applied to a sample of species and animal-built structures, the characterized biological role models put forwards multi-functionality and efficiency through relevant construction techniques, the use of local resources, as well as behavioral adaptation. Examples of applications inspired from the characterized species are described, from theoretical proposals to a very practical application of an adaptive envelope skin inspired by the Morpho butterfly.
Mitochondria are the major organelles of energy production; however, active mitochondria can decline their energetic role and show a dysfunctional status. Mitochondrial dysfunction was induced by high non-physiological level of L-galactone-1,4-lactone (L-GalL), the precursor of ascorbate (AsA), in plant mitochondria. The dysfunction induced by L-GalL was associated with the fault in the mitochondrial electron partition and reactive oxygen species (ROS) over-production. Using mitochondria from RNAi-plant lines harbouring silenced L-galactone-1,4-lactone dehydrogenase (L-GalLDH) activity, it was demonstrated that such dysfunction is dependent on this enzyme activity. The capacity of alternative respiration was strongly decreased by L-GalL, probably mediated by redox-inactivation of the alternative oxidase (AOX) enzyme. Although, alternative respiration was shown to be the key factor that helps support AsA synthesis in dysfunctional mitochondria. Experiments with respiratory inhibitors showed that ROS formation and mitochondrial dysfunction were more associated with the decline in the activities of COX (cytochrome oxidase) and particularly AOX than with the lower activities of respiratory complexes I and III. The application of high L-GalL concentrations induced proteomic changes that indicated alterations in proteins related to oxidative stress and energetic status. However, supra-optimal L-GalL concentration was not deleterious for plants. Instead, the L-GalLDH activity could be positive. Indeed, it was found that wild type plants performed better growth than L-GalLDH-RNAi plants in response to high non-physiological L-GalL concentrations.
We recently assisted in a revolution in the realm of fluorescence microscopy triggered by the advent of super-resolution techniques that surpass the classic diffraction limit barrier. By providing optical images with nanometer resolution in the far field, super-resolution microscopy (SRM) is currently accelerating our understanding of the molecular organization of bio-specimens, bridging the gap between cellular observations and molecular structural knowledge, which was previously only accessible using electron microscopy. SRM mainly finds its roots in progress made in the control and manipulation of the optical properties of (single) fluorescent molecules. The flourishing development of novel fluorescent nanostructures has recently opened the possibility of associating super-resolution imaging strategies with nanomaterials’ design and applications. In this review article, we discuss some of the recent developments in the field of super-resolution imaging explicitly based on the use of nanomaterials. As an archetypal class of fluorescent nanomaterial, we mainly focus on single-walled carbon nanotubes (SWCNTs), which are photoluminescent emitters at near-infrared (NIR) wavelengths bearing great interest for biological imaging and for information optical transmission. Whether for fundamental applications in nanomaterial science or in biology, we show how super-resolution techniques can be applied to create nanoscale images “in”, “of” and “with” SWCNTs.
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Vincent Lepetit
  • UMR LaBRI - Laboratoire Bordelais de Recherche en Informatique
Breysse Denys
  • Département de Génie Civil et Environnemental (GCE)
Bernard Veyret
  • UMR IMS - Laboratoire d'Integration du Materiau au Système (IMS)
Stéphane Arbault
  • UMR ISM - Institut des Sciences Moléculaires
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  • UMR PACEA - Laboratoire de la Préhistoire à l'Actuel : Culture, Environnement et Anthropologie
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