Université d'Orléans
  • Orléans, Centre, France
Recent publications
The inhibiting effect on fuel ageing of 2,4-xylenol, a phenolic antioxidant that can be produced from biomass, was investigated experimentally in the liquid phase, while its impact on combustion was studied in the gas phase. The antioxidant effect of 2,4-xylenol in liquid phase has been examined in n-decane and in a surrogate, containing 65%vol. toluene and 35%vol. n-heptane. Experiments were performed in a PetroOxy at initial oxygen pressure 7 bar and temperature held at 180 °C. The impact of 2,4-xylenol on the gas-phase reactivity of the surrogate fuel was investigated on ignition delay times and laminar flame velocities. Ignition delay times were measured in the rapid compression machine at 10 bar, from 675 to 1000 K at two equivalence ratios, 0.5 and 1. Laminar flame velocity measurements were conducted in a heat flux burner at atmospheric pressure and an initial temperature of 398 K. For all experiments considered in this work, the doping level of 2,4-xylenol was kept below 1%mol. Results are compared to effect of other usual additives, EHN and ferrocene. Results show that 2,4-xylenol exhibits a remarkable antioxidant effect in liquid phase, without affecting the main combustion characteristics of the fuel.
A large inter‐individual variability of activation strategies is observed during hamstring strengthening exercises but their consequences remain unexplored. The objective of this study was to determine whether individual activation strategies is related to the distribution of damage across the hamstring muscle heads (semimembranosus, SM; semitendinosus, ST; biceps femoris, BF) after eccentric contractions. Twenty‐four participants performed 5 sets of 15 maximal eccentric contractions of knee flexors on a dynamometer, while activation of each muscle head was assessed using surface electromyography. Knee flexion maximal isometric strength was assessed before exercise and 48 hours afterwards. Shear modulus was measured using shear wave elastography before exercise and 30 min afterwards to quantify the distribution of damage across the hamstring muscle heads. At 48 h, maximal knee flexion torque had decreased by 15.9 ± 16.9% (P < 0.001). Although no differences between activation ratios of each muscle were found during the eccentric exercise (all P values > 0.364), we reported an heterogenous distribution of damage, with a larger change in shear modulus of ST/Hams than SM/Hams (+70.8%, P < 0.001) or BF/Hams (+50.3%, P < 0.001). A moderate correlation was found between the distribution of activation and the distribution of damage for ST/Hams (r = 0.69; P < 001). This study provides evidence that the distribution of activation during maximal eccentric contractions has mechanical consequences for synergist muscles. Further studies are needed to understand whether individual activation strategies influence the distribution of structural adaptations after a training program.
This study aims to investigate the persistent issue of the last few decades, that whether natural resources enhance economic performance or negatively affect it. To serve this purpose, this study examines panel data for the Group of Seven economies from 1990–2020. This study also explores the influence of renewable energy consumption, political risk index, and gross capital formation. Since this study is dealing with panel data, advanced panel data approaches are utilized that indicate slopes heterogeneity and cross-section dependence of the selected panel. The normality tests asserted that all the variables follow non-normal or non-parametric distribution, which lets this study to use the novel method of moments quantile regression. The empirical results asserted the asymmetric influence of natural resources on economic performance. Natural resources, a curse in the lower (Q0.25, Q0.50) quantiles, while blessings in the upper (Q0.75, Q0.90) quantiles. However, Renewable energy had a negative influences on the economic performance of the said region. Besides, political risk holds a weak link with economic performance across the quantiles. Yet, throughout the selected quantiles, the gross capital formation is found to the positive and significant factor in economic performance. These results are found robust, validated via Bootstrap quantile regression and quantile regression. Based on the empirical results, this study suggests, relevant policies to policy-makers regarding the sustainable use of clean energy investment, natural resources, stability of political system, and encouragement of the gross capital formation.
The paper examines the link between money and output in the U.S. by using wavelet analysis. The time span covers the period from 1960Q1 to 2021Q1. The main results evidence that money positively leads real output from the late 1960s to 1982, at medium frequency, with the interest rate playing an important role. In contrast, we reveal that real output negatively leads money, at the same medium frequency, but from the late 1990s to 2021. The COVID-19 pandemic generates significant co-movements in the short and medium frequencies, over the period from 2020 to 2021, with output negatively leading money. We underline that Federal Reserve monetary policy operating procedures play an essential role in explaining these findings. The results support using the federal funds rate operating procedure as countercyclical monetary policy measures and implementing unconventional monetary policy tools in times of the effective lower bound. Finally, no relationship between money and output is observed in the long term, while the short term (i.e. high frequency) reveals rather chaotic co-movements. The results remain robust to alternative wavelet tools, higher-frequency datasets, and a Hodrick–Prescott filtered quarterly sample.
A new clustering algorithm Path-scan aiming at discovering natural partitions is proposed. It is based on the idea that a (k,ɛ) coreset of the original data base represented by core and support patterns can be path-connected via a density differential approach. The Path-scan algorithm is structured in two main parts producing a connectivity matrix where partitions can be extracted at different levels of granularity. The first one aims to identify and select core and support points while the second one extracts connected components of core points and clusters with the help of support points. A simulation experiment based on synthetic and real world data sets was conducted to show the effectiveness of the proposed method.
Background and Aims NOD2 has emerged as a critical player in the induction of both Th1- and Th2-responses for potentiation and polarization of antigen-dependent immunity. Loss-of-function mutations in the NOD2-encoding gene and deregulation of its downstream signaling pathway have been linked to Crohn’s disease. While it is well documented that NOD2 is capable of sensing bacterial muramyl dipeptide, it remains counterintuitive to link development of overt intestinal inflammation to a loss of bacterial-induced inflammatory response. We hypothesized that a T-helper bias could also contribute to an auto-immune like colitis different than inflammation that is fully fledged by Th1-type cells. Methods An edematous bowel wall with a mixed Th1/Th2 response was induced in mice by intrarectal instillation of the haptenating agent oxazolone. Survival and clinical scoring were evaluated. At several time-points after instillation, colonic damage was assessed by macroscopic and microscopic observations. To evaluate the involvement of NOD2 in immunochemical phenomena, quantitative PCR and flow cytometry analysis were performed. Bone-marrow chimera experiment allowed us to evaluate the role of hematopoietic/non-hematopoietic NOD2-expressing cells. Results Herein, we identified a key regulatory circuit whereby NOD2-mediated sensing of MDP by radio-resistant cells improves colitis with a mixed Th1/Th2 response that is induced by oxazolone. Genetic ablation of either Nod2 or Ripk2 precipitated oxazolone colitis that is predominantly linked to a lack of Interferon-gamma. Bone-marrow chimera experiments revealed that inactivation of Nod2 signaling in non-hematopoietic cells is causing a biased M1-M2 polarization of macrophages and a decreased frequency of splenic regulatory T cells that correlates with an impaired activation of CD4 + T cells within mesenteric lymph nodes. Mechanistically, mice were protected from oxazolone-induced colitis upon administration of MDP in an interleukin-1- and interleukin-23-dependent manner. Conclusions these findings indicate that Nod2 signaling may prevent pathologic conversion of T helper cells for maintenance of tissue homeostasis.
Background removal of an identity (ID) picture consists in separating the foreground (face, body, hair and clothes) from the background of the image. It is a necessary groundwork for all modern identity documents that also has many benefits for improving ID security. State of the art image processing techniques encountered several segmentation issues and offer only partial solutions. It is due to the presence of erratic components like hairs, poor contrast, luminosity variation, shadow, color overlap between clothes and background. In this paper, a knowledge infused approach is proposed that hybridizes smart image processing tasks and prior knowledge. The research is based on a divide and conquer strategy aiming at simulating the sequential attention of human when performing a manual segmentation. Knowledge is infused by considering the spatial relation between anatomic elements of the ID image (face feature, forehead, body and hair) as well as their “signal properties”. The process consists in first determining a convex hull around the person’s body including all the foreground while keeping very close to the contour between the background and the foreground. Then, a body map generated from biometric analysis associated to an automatic grab cut process is applied to reach a finer segmentation. Finally, a heuristic-based post-processing step consisting in correcting potential hair and fine boundary issues leads to the final segmentation. Experimental results show that the newly proposed architecture achieves better performances than tested current state-of-the-art methodologies including active contours, generalist popular deep learning techniques, and also two other ones considered as the smartest for portrait segmentation. This new technology has been adopted by an international company as its industrial ID foreground solution.
Individuals' health status is an essential indicator of the overall strength of a country. Existing literature has studied the determinants of individuals' health, but there is no direct evidence to date on the impact of mobile payment on health. To supplement relevant research and provide insightful policy suggestions to families, government and societies, based on data of 32,058 observations from the 2017 China Household Finance Survey, we estimate the effects of mobile payment on physical health using ordinary least squares and two-stage least squares strategy. This paper provides direct evidence that mobile payment has a positive impact on citizens' physical health. Heterogeneity analysis shows that mobile payment has a more profound impact on the health of citizens who are rural and less educated. Finally, further findings in this paper suggest that commercial insurance and leisure consumption are the mechanism through which the link between mobile payment and individuals' health operates.
We introduce a paraconsistent modal logic KG2, based on Gödel logic with coimplication (bi-Gödel logic) expanded with a De Morgan negation ¬. We use the logic to formalise reasoning with graded, incomplete and inconsistent information. Semantics of KG2 is two-dimensional: we interpret KG2 on crisp frames with two valuations v1 and v2, connected via ¬, that assign to each formula two values from the real-valued interval [0, 1]. The first (resp., second) valuation encodes the positive (resp., negative) information the state gives to a statement. We obtain that KG2 is strictly more expressive than the classical modal logic K by proving that finitely branching frames are definable and by establishing a faithful embedding of K into KG2. We also construct a constraint tableau calculus for KG2 over finitely branching frames, establish its decidability and provide a complexity evaluation.
Mafic pegmatites have been reported from various geological environments, including ophiolites, layered magmatic intrusions, and volcanic arcs, but their petrogenesis stayed poorly constrained. This study brings new mineralogical and geochemical data obtained from unzoned and zoned gabbroic pegmatites hosted by the 1.8 Ga mafic-ultramafic Hamn intrusion, Northern Norway, with an aim to improve our understanding of the primary magmatic physicochemical factors that control the development of pegmatitic textures in mafic rocks. The unzoned mafic pegmatites in the Hamn intrusion are hosted in gabbronorite and gabbro. The pegmatites differ macroscopically from the gabbronorite only by grain size and the color of feldspars. The bulk chemical compositions, including REE concentrations and rock-forming mineral assemblages of both rocks, are identical. The mineral composition of the pegmatite and host gabbro overlap. However, the pegmatite experienced epidotization and scapolitization, suggesting that H2O- and chlorine were essential in the formation. Furthermore, the pyroxene of the pegmatite shows a more distinct negative Eu anomaly than the pyroxene of the host gabbronorite. Amphibole dyklets associated with the unzoned pegmatite pockets consist of Cl-rich pargasite and Cl-scapolite, indicating that the fluid pressure during crystallization of the unzoned pegmatites exceeded the confining pressure and resulted in the fracturing of host rocks and expulsion of a Cl- and H2O-rich fluid and residual melt that subsequently formed amphibole veins. The zoned pegmatites of the mafic-ultramafic Hamn intrusion are internally differentiated in terms of grain size, texture, and mineral composition. A characteristic comb-like diopside layering shows a change from numerous small to fewer larger grains from the rim towards the core of the pegmatite pocket. This textural change suggests that the pegmatite-forming melt experienced a transition from a high nucleation rate (N) vs. growth rate (G) ratio to a low N/G ratio. A decreasing degree of undercooling with continuous crystallization from the rim to the core of the pockets can explain this transition. Apart from the comb-like layering, the bifurcating texture of some of the diopside grains is another evidence that the pegmatite-forming melt experienced undercooling. The pegmatites could have formed from a remobilized intercumulus or fractionated melt that was emplaced as residual melt into the colder host rock. Fast heat diffusion towards the host rock could have caused undercooling of the pegmatite-forming melt, which led to the formation of the comb-like and partly extremely coarse-grained texture. In contrast to the unzoned pegmatites, the zoned pegmatites lack evidence of significant involvement of chlorine- and H2O. In contrast, the fluid inclusion study revealed that the pegmatite-forming melt was enriched in CO2. Microthermometry of the CO2-bearing inclusions indicates a minimum formation pressure of 647 to 734 MPa, and the titanium-in-quartz geothermometer yields a minimum formation temperature of 753 ± 34 °C for the quartz segregation.
The behavior of animals reflects their internal state. Changes in behavior, such as a lack of sleep, can be detected as early warning signs of health issues. Zoologists are often required to use video recordings to study animal activity. These videos are generally not sufficiently indexed, so the process is long and laborious, and the observation results may vary between the observers. This study looks at the difficulty of measuring elephant sleep stages from surveillance videos of the elephant bran at night. To assist zoologists, we propose using deep learning techniques to automatically locate elephants in each camera surveillance, then mapping the elephants detected onto the barn plan. Instead of watching all of the videos, zoologists will examine the mapping history, allowing them to measure elephant sleeping stages faster. Overall, our approach monitors elephants in their barn with a high degree of accuracy.
Using an emittance technique with fast CO2 laser heating of glass samples, the high temperature absorption spectra in the near IR region of ultrapure and colored (Co‐, Cu‐, Mn‐ and Ni‐doped) glasses are measured. The effects of higher glass temperatures on these absorption spectra are explained in the framework of the ligand field theory. Thus, the temperature dependent absorption bands of the above transition metal ions are assigned to electronic transitions between the ligand field energy levels of these ions. In particular, spectral shifts, spectral broadening and changes in absorption strength are ascribed to changes in the structural symmetry of the ionic sites in the glass matrix and to changes of the ligand field strength at increasing temperatures. Besides, the temperature dependent Rosseland mean absorption of the sulfate fined soda lime silicate glass melts, colored with the above transition metal ions, are derived from the absorption spectra. Combining all the data, semi‐empirical correlations can be derived, which predict the Rosseland thermal radiation properties as a function of glass temperature and of glass redox chemistry, where the latter property involves the temperature dependent concentration of the specific valency of the coloring ions, determined independently by a Gibbs minimization redox calculation tool. This article is protected by copyright. All rights reserved
A combined experimental and kinetic modeling study is presented to improve the understanding of the formation of polycyclic aromatic hydrocarbons (PAHs) from neat cyclopentene and cyclopentene/acetylene mixtures. High-pressure experiments are conducted for the first time over a temperature range covering 930–1650 K using a single-pulse shock tube coupled to gas chromatography/gas chromatography-mass spectrometry (GC/GC–MS) techniques. Several updates and inclusions, mainly regarding the reactions involving C5 molecules and radicals, are made in our on-going PAH kinetic model, which shows satisfactory predictive performances for the speciation measurements obtained in the current work and in the literature. On the basis of the experimental observations and modeling analyses, the reaction pathways active during the pyrolysis of cyclopentene are illustrated and the effects of acetylene addition as co-reactant on the PAH chemistry are assessed. In all of the cases investigated, it is noted that the cyclopentadienyl radical largely participate in the formation of mono-aromatic hydrocarbons (benzene and styrene) and PAHs (indene, naphthalene and phenanthrene).
The composition of archaeological glass reflects the geochemical nature of its raw materials. To determine the origins and distribution of early Islamic glasses from Iran, a set of 169 glass samples from five different sites was analysed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of 58 elements. The glasses were classified into six different plant ash glass groups, three of which were attributed to a Mesopotamian origin, while three further groups are presumed to represent regional Iranian productions. The ratios of MgO/CaO and K2O/P2O5 of the different groups reflect variations in the plant ash component. Minor elements Cr, Ti, Zr, La and Th and their ratios proved effective in distinguishing the base glass types. Mapping their frequency across the Iranian plateau revealed the relative movement of glass and likely source areas. The decline in the frequency of glass types with elevated Cr/La ratios east of the Zagros Mountain range confirms that elevated Cr/La ratios together with an augmentation of the magnesium levels are features of Mesopotamian glass production apparently inherited from the geochemical environment of the Euphrates and Tigris river valleys. Some exceptionally clean Mesopotamian glasses made from a quartz-rich silica with low levels of accessory minerals are consistent with ninth-century glass from Samarra, which was evidently traded widely along the Silk Road network. No evidence of local glass production was detected in Nishapur. The Iranian groups were produced from a quartz-rich silica source, high in thorium but with different zirconium contents resulting in different Th/Zr ratios. Aluminium concentrations tend to increase from west to east, with the highest values found among glass assemblages from Central Asia.
A variety of clustering criteria have been applied as an objective function in Evolutionary Multi-Objective Clustering approaches (EMOCs). However, most EMOCs do not provide detailed analysis regarding the choice and usage of the objective functions. In general, the choice of the objective functions only considers the desired clustering properties, and most EMOCs present in the literature do not consider aspects of multi-objective optimization, such as the search direction, in their design. Aiming to support a better choice and definition of the objectives in the EMOCs, this paper proposes an analysis of the clustering criteria admissibility to examine the search direction and evaluate their potential in finding optimal results. We consider the fundamentals of the evaluation of a heuristic function to analyze the clustering criteria and demonstrate how they can influence the optimization. As a result, this study provides a detailed analysis of the main objective functions found in the literature and evaluates how the initialization interferes with their admissibility. Also, we highlight some common practices and issues found in some established EMOCs. Furthermore, we provide insights regarding how to combine and use the clustering criteria in the EMOCs.
We present an innovative hydrogeophysical approach for non-invasive quantification of the unsaturated water flow. For the water content measurements, we apply the Magnetic Resonance Soundings (MRS) method in the time-lapse mode. For inversion of MRS measurements, we approximate the subsurface by a horizontally stratified media. Laterally, the MRS estimated water content is averaged over the area below the measuring setup. During this study, we used a square loop of 75 m side-length. The time-lapse inversion allows visualizing variations in the water content in the vadose zone down to twenty meters. We tested our approach at the Villamblain test site (France). For that, we carried out the MRS monitoring in 1999-2000 and 2020-2021. During these two observation windows, MRS shows seasonal variations of the water content but also a strong dependence of the water content on the rainfall that was different between two data sets. Comparison of MRS results with the rainfall records shows a good correspondence in-between. For measuring and processing MRS data, we used commercially available MRS instrument and interpretation software.
Chronic pulmonary inflammation and chronic obstructive pulmonary disease (COPD) are major health issues largely due to air pollution and cigarette smoke (CS) exposure. The role of the innate receptor NLRP3 (nucleotide-binding domain and leucine-rich repeat containing protein 3) orchestrating inflammation through formation of an inflammasome complex in CS-induced inflammation or COPD remains controversial. Using acute and subchronic CS exposure models, we found that Nlrp3-deficient mice or wild-type mice treated with the NLRP3 inhibitor MCC950 presented an important reduction of inflammatory cells recruited into the bronchoalveolar space and of pulmonary inflammation with decreased chemokines and cytokines production, in particular IL-1β demonstrating the key role of NLRP3. Furthermore, mice deficient for Caspase-1/Caspase-11 presented also decreased inflammation parameters, suggesting a role for the NLRP3 inflammasome. Importantly we showed that acute CS-exposure promotes NLRP3-dependent cleavage of gasdermin D in macrophages present in the bronchoalveolar space and in bronchial airway epithelial cells. Finally, Gsdmd-deficiency reduced acute CS-induced lung and bronchoalveolar space inflammation and IL-1β secretion. Thus, we demonstrated in our model that NLRP3 and gasdermin D are key players in CS-induced pulmonary inflammation and IL-1β release potentially through gasdermin D forming-pore and/or pyroptoctic cell death.
The effect of polypyridyl Ru(II) complexes on the ability of cancer cells to migrate and invade, two features important in the formation of metastases, is evaluated. In vitro studies are carried out on breast cancer cell lines, MDA-MB-231 and MCF-7, as well as melanoma cell lines A2058 and A375. Three Ru(II) complexes comprising two 4,7-diphenyl-1,10-phenanthroline (dip) ligands and as a third ligand 2,2'-bipyridine (bpy), or its derivative with either 4-[3-(2-nitro-1H-imidazol-1-yl)propyl] (bpy-NitroIm), or 5-(4-{4'-methyl-[2,2'-bipyridine]-4-yl}but-1-yn-1-yl)pyridine-2-carbaldehyde semicarbazone (bpy-SC) moiety attached are examined. The low sub-toxic doses of the studied compounds greatly affected the cancer cells by inhibiting cell detachment, migration, invasion, transmigration, and re-adhesion, as well as increasing cell elasticity. The molecular studies revealed that the Ru(II) polypyridyl complexes impact the activity of the selected integrins and upregulate the expression of focal adhesion components such as vinculin and paxillin, leading to an increased number of focal adhesion contacts.
Energy is essential to achieving economic growth, yet the production of energy results in the emission of carbon dioxide, the primary factor in the deterioration of the environment and the acceleration of climate change. In this sense, the diversity of energy sources can contribute to achieving both environmentally sustainable development. This study investigates the relationship between energy diversification and economic growth in Nordic nations by employing a unique measure of energy diversity. The Nonlinear Panel Autoregressive Distributed Lag (NPARDL) approach is utilized in the research, and it looks at data from 1998 through 2018. According to our results, these nations experience favorable economic growth when there is an increase in the long-term diversity of their energy sources. However, in the near term, they have seen negative economic development due to the diversification of their energy sources. According to these findings, energy diversification benefits Nordic economic growth; however, further research is required for developing economies. As a result, further preventative actions must be implemented while simultaneously diversifying energy sources.
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2,179 members
Eva Kovacevic
  • Groupe de Recherches sur l'Energétique des Milieux Ionisés (GREMI)
Cem Ertur
  • Laboratoire d'Economie d'Orléans
François Bernard
  • Laboratoire de Physique et Chimie de l'Environnement et de l'Espace LPC2E
sébastien Limet
  • Laboratoire d'Informatique Fondamentale d'Orléans (LIFO)
Gisèle Krysztofiak Tong
  • Département de Chimie
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Université d'Orléans - Rue de Chartres BP6759, 45067, Orléans, Centre, France
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http://www.univ-orleans.fr/fr
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+33 (0) 2 38 41 71 71
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