Laboratoire National de Métrologie et d'Essais
Recent publications
A chemically vapor deposited MoS2 nanosheets (NSs) is aged in the laboratory at ambient and at 40% average humidity for ~36 months. Nanorods of few microns in length and few nanometers in diameter are found to grow from the MoS2 seeds. They have been growing as a result of the chemical reaction between the MoS2 NSs and ambient O2 and moisture, they exhibit an amorphous phase structure in the stoichiometric form of MoO3. Density functional theory simulations further reveal the role of H2O and O2 in the transformation of the MoS2 NSs. The adsorption energy of O2 molecules on the MoS2 sites is Ead = −1.09 eV as compared to lowest absolute Ead = −0.10 eV of H2O indicating the favorable adsorption of O2 and subsequent Mo oxidation. This study provides valuable insight into the aging phenomenon of MoS2 exposed to O2 and moisture which might limit their application.
The inspection of large mechanical parts manufacturing in real time camera-based scanning systems are increasingly adopted in industry 4.0. It leads to take preventive actions during the manufacturing process and then to fabricate mechanical parts right-first-time with respect to specified tolerances. Therefore, the use of camera-based scanners requests a preliminary calibration process. It consists on estimating the intrinsic and extrinsic parameters required to relate the 3D world point to its projection on the image plane. Since selection of the calibration grid poses affect the calibration quality, one approach-based machine learning (ML-approach) is proposed including the polynomial approximation of the reprojection errors function of 6 degree of freedom (DoF) combined with particle swarm optimization (PSO). Synthetic and experimental evaluations have been performed while assessing the performance of the proposed ML-approach. The synthetic evaluation reveals a better convergence of the intrinsic and extrinsic parameters in comparison to recent published calibration methods by Wizard (CW-method) and Rojtberg (R-method). The experimental evaluation of the ML-approach shows an average error RE < 12µm and a sub-micrometre repeatability, which confirm the benefit of using machine vision-based scanning systems for the inspection of large volume parts in real time.
Water-ethanol mixtures intended for specific purposes, such as bioethanol fuel, can be subject to national quality standards, including the measurement of pHe - a solvent-specific quantification of acidity. This work discusses the shortcomings of the use of pHe in these quality standards, including the lack of metrological traceability of pHe measurements made using combination pH electrodes calibrated using aqueous pH buffers. The feasibility of measuring the acidity of 50-50 wt% water-ethanol mixtures on a non-solvent-specific, unified pH scale, which is traceable to the conventional aqueous pH scale ( pH abs H 2 O ) is demonstrated. pH abs H 2 O measurements of buffered and un-buffered water-ethanol mixtures using two cell configurations, including the use of an ionic liquid salt bridge (ILSB), show good agreement. The cell configuration, consisting of a commercial glass (half-cell) electrode and a reference electrode incorporating an ILSB, can be readily adopted by measurement laboratories.
Tungsten disulfide nanosheets were successfully prepared by one-step chemical vapor deposition using tungsten oxide and thiourea in an inert gas environment. The size of the obtained nanosheets was subsequently reduced down to below 20 nm in width and 150 nm in length using high-energy ball milling, followed by 0.5 and 1 wt% graphene loading. The corresponding vibrational and structural characterizations are consistent with the fabrication of a pure WS2 structure for neat sampling and the presence of the graphene characteristic vibration modes in graphene@WS2 compounds. Additional morphological and crystal structures were examined and confirmed by highresolution electron microscopy. Subsequently, the investigations of the optical properties evidenced the high optical absorption (98%) and lower band gap (1.75 eV) for the graphene@WS2 compared to the other samples, with good band-edge alignment to water-splitting reaction. In addition, the photoelectrochemical measurements revealed that the graphene@WS2 (1 wt%) exhibits an excellent photocurrent density (95 �A/cm2 at 1.23 V bias) compared with RHE and higher applied bias potential efficiency under standard simulated solar illumination AM1.5G. Precisely, graphene@WS2 (1 wt%) exhibits 3.3 times higher performance compared to pristine WS2 and higher charge transfer ability, as measured by electrical impedance spectroscopy, suggesting its potential use as an efficient photoanode for hydrogen evolution reaction.
In industrial facilities handling or manufacturing hazardous materials, fires are one of the major hazards. Therefore, it is important to have tools to better understand the transport and deposition phenomenon of emitted particles in order to take into account their consequences on safety devices. For this purpose and due to the lack of quantitative soot deposition data under realistic fire conditions, an innovative method for soot quantification in experimental facilities devoted to fire research has been developed. This method is based on the quantification of gases emitted during regeneration of a resistive sensor surface and has a higher detection limit than the electrical conductance quantification method previously proposed and validated by (Kort et al., 2021). A proof of feasibility has been shown for two types of soot and a prediction curve has been proposed for deposited masses which vary between 16 and 350 μg (1304 mg.m⁻² and 28,525 mg.m⁻²). The applicability of this measurement method to realistic industrial fire situation is finally verified taking into account the mean deposition mass per surface area observed in this context.
In order to further improve the management of contaminated materials in nuclear facilities subject to a decommissioning programme, as well as during post-accidental site remediation and clearance, the definition and selection of the most appropriate intervention scenarios producing well-characterized radioactive waste for which storage and disposal routes are clearly identified is needed. As a step towards this accomplishment, we propose a methodology for the organization and analysis of coordinated interlaboratory comparisons (ILC) for the performance assessment and the uncertainty evaluation of available measurement techniques (methods and tools) of radioactive materials. This methodology is new for this type of comparison and demonstrated on the BR3 (Belgian Reactor 3, Belgian Nuclear Research Centre, Mol) case study from the H2020 INSIDER project (2017–2021), for which barium 133, cobalt 60 and europium 152 are analysed with gamma spectroscopy in ILC, based either on irradiated concrete from the BR3 bioshield or from spiked concrete certified reference material (CRM). On one hand, we show the advantage of organizing ILC on CRM for a more reliable uncertainty evaluation taking bias into account following ISO 21748:2017. But using CRM may be impossible due to their scarcity or too costly for performance assessment thus limiting the use of CRM in ILC in practice. On the other hand, we show that for performance evaluation and monitoring, ILC can be alternately performed on reference materials provided that laboratories’ uncertainties are reported and the most appropriate analysis of data is performed using dark uncertainty (excess variance) in the presence of inconsistent data.
Most of the methods for in situ measurement of the thermal resistance of building walls implement passive approaches requiring long measurement times and specific environmental conditions. In the literature, different active approaches have been studied but they remain limited in terms of applications and do not systematically lead to short identification times. This article that follows a previous numerical benchmark study presents a new measurement prototype using a lamp box which heats up one of the surfaces (typically the interior surface) of the wall to be characterized. The use of an aluminum plate placed in contact with the wall face subjected to thermal excitation enables the homogenization of the heat flux transmitted to the wall. Three inverse procedures are implemented to estimate the thermal resistance of the studied wall. The originality of this work comes from an exhaustive measurement campaign. On the one hand, four types of wall among the most common in France, i.e. Internal Insulation Wall, External Insulation Wall and Wood Frame Wall specially built for this study and a Single Concrete Wall located in a real building, were investigated. On the other hand, the use of different climatic chambers made it possible to generate many different environmental conditions (constant, variable and natural). The results highlight the possibilities offered by this in situ experimental device for estimating in a few hours (6 to 10 hours) the thermal resistance of the wall studied or of its first layers, as well as the limits depending on the type of wall and the environmental conditions. Some operational recommendations are also provided: avoiding thermal bridges, solar protection in case of strong sunlight on the exterior side of the wall and location of the device on the exterior side in the case of the External Insulation Wall.
Procalcitonin (PCT) is a widely used biomarker for rapid sepsis diagnosis and antibiotic stewardship. Variability of results in commercial assays has highlighted the need for standardization of PCT measurements. An antibody-free candidate reference measurement procedure (RMP) based on the isotope dilution mass spectrometry and protein calibration approach was developed and validated to quantify PCT in human serum. The method allows quantification of PCT from 0.25 to 13.74 μg/L (R > 0.998) with extension up to 132 μg/L after dilution of samples with PCT concentration above 13.74 μg/L. Intraday bias was between -3.3 and +5.7%, and interday bias was between -3.0 and -0.7%. Intraday precision was below 5.1%, and interday precision was below 4.0%. The candidate RMP was successfully applied to the absolute quantification of PCT in five frozen human serum pools. A recombinant PCT used as a primary calibrator was characterized by high-resolution mass spectrometry and amino acid analysis to establish traceability of the results to the SI units. This candidate RMP is fit to assign target values to secondary certified reference materials (CRMs) for further use in external quality assessment schemes to monitor the accuracy and comparability of the commercially available immunoassay results and to confirm the need for improving the harmonization of PCT assays. The candidate RMP will also be used to evaluate whether the correlation between the candidate RMP and immunoassays is sufficiently high. Overall, this candidate RMP will support reliable sepsis diagnosis and guide treatment decisions, patient monitoring, and outcomes.
Wildlife is increasingly exposed to environmental pollution, but data illustrating to what extent this exposure can impact health and survival of endangered species is missing. In humans, hair matrix analysis is a reliable tool for assessing cumulative exposure to organic pollutants such as pesticides but has rarely been used in other primates for this purpose. LC/MS-MS and GC/MS-MS multi-residue methods were used to screen the presence of 152 organic pollutants and their metabolites belonging to 21 different chemical families in hair samples from our closest relative, the chimpanzee. Samples were collected from 20 wild chimpanzees in Sebitoli, Kibale National Park, Uganda and 9 captive chimpanzees in the Réserve Africaine de Sigean, France. In total, 90 chemicals were detected, 60 in wild chimpanzees and 79 in captive chimpanzees. The median concentrations of detected chemicals in captive individuals were significantly higher than those in wild chimpanzees. Hair from the captive individuals at RAS was sampled a second time after 6 months in an environment of reduced exposure to these pollutants (diet of organic food, decreased use of plastic food and water containers). The number of chemicals detected in captive chimpanzees reduced from 79 to 63, and their concentrations were also significantly reduced. In the present study we report for the first time the use of hair analysis to detect organic pollutants in primate hair. We conclude that both wild and captive chimpanzees are exposed to a large range of different chemicals through their diet. Our study provides surprising and alarming evidence that besides the direct threats of poaching, deforestation and diseases, wild chimpanzees might be endangered by indirect consequences of anthropic activities. As chimpanzees are our closest relatives, our results should be considered as an alert for human health as well.
The efficient monitoring of the environment is currently gaining a continuous growing interest in view of finding solutions for the global pollution issues and their associated climate change. In this sense, two-dimensional (2D) materials appear as one of highly attractive routes for the development of efficient sensing devices due, in particular, to the interesting blend of their superlative properties. For instance, graphene (Gr) and graphitic carbon nitride g-C3N4 (g-CN) have specifically attracted great attention in several domains of sensing applications owing to their excellent electronic and physical-chemical properties. Despite the high potential they offer in the development and fabrication of high-performance gas-sensing devices, an exhaustive comparison between Gr and g-CN is not well established yet regarding their electronic properties and their sensing performances such as sensitivity and selectivity. Hence, this work aims at providing a state-of-the-art overview of the latest experimental advances in the fabrication, characterization, development, and implementation of these 2D materials in gas-sensing applications. Then, the reported results are compared to our numerical simulations using density functional theory carried out on the interactions of Gr and g-CN with some selected hazardous gases’ molecules such as NO2, CO2, and HF. Our findings conform with the superior performances of the g-CN regarding HF detection, while both g-CN and Gr show comparable detection performances for the remaining considered gases. This allows suggesting an outlook regarding the future use of these 2D materials as high-performance gas sensors.
The role of an External Quality Assurance (EQA) program is generally seen as providing a service to routine laboratories that their analytical performance is satisfactory and stimulating corrective action in the event of poor results. It is recognised that an ideal EQA program uses materials that are commutable with patient samples and have values assigned by higher-order reference methods. Despite this, most routine EQA programs use materials without verified commutability and use consensus means (based on either peer group or all laboratories) as target values. We propose an ongoing role for EQA programs using non-commutable materials and consensus targets to support the measurement services of routine laboratories. This is provided the relevant comparators supplied by the laboratory, e.g. reference intervals and clinical decision points, are based on the same or equivalent measurement system as is used by the laboratory. Materials without verified commutability often have certain practical advantages, which may include the range of analyte concentrations, verified stability, replicate samples and, significantly, lower costs. Laboratories using such programs need to be aware of the limitations, especially comparing results from different measurement systems. However, we also recognise that as well as individual laboratories, data from EQA programs informs manufacturers, professional organisations, clinical guideline writers and other medical bodies For consideration beyond an individual laboratory, proper assessment of differences between measurement systems (results harmonization) and demonstration of correct implementation of metrological traceability (methods trueness) become vital, and for that purpose, commutability of EQA materials and traceability of target values are required.
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136 members
François Ziade
  • Electrical High Frequency Department
François-Xavier Ouf
  • Department of Metrology and Industrial Systems
G. Labarraque
  • biomedical and inorganic chemistry
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