The mode of abscisic acid （ABA） action, and its relations to drought adaptive responses in particular, has been a captivating area of plant hormone research for much over a decade. The hormone triggers stomatal clos...The mode of abscisic acid （ABA） action, and its relations to drought adaptive responses in particular, has been a captivating area of plant hormone research for much over a decade. The hormone triggers stomatal closure to limit water loss through transpiration, as well as mobilizes a battery of genes that presumably serve to protect the cells from the ensuing oxidative damage in prolonged stress. The signaling network orchestrating these various responses is, however, highly complex. This review summarizes several significant advances made within the last few years. The biosynthetic pathway of the hormone is now almost completely elucidated, with the latest identification of the ABA4 gene encoding a neoxanthin synthase, which seems essential for de novo ABA biosynthesis during water stress. This leads to the interesting question on how ABA is then delivered to perception sites. In this respect, regulated transport has attracted renewed focus by the unexpected finding of a shoot-to-root translocation of ABA during drought response, and at the cellular level, by the identification of a B-galactosidase that releases biologically active ABA from inactive ABA-glucose ester. Surprising candidate ABA receptors were also identified in the form of the Flowering Time Control Protein A （FCA） and the Chloroplastic Magnesium Protoporphyrin-IX Chelatase H subunit （CHLH） in chloroplast-nucleus communication, both of which have been shown to bind ABA in vitro. On the other hand, the protein（s） corresponding to the physiologically detectable cell-surface ABA receptor（s） is （are） still not known with certainty. Genetic and physiological studies based on the guard cell have reinforced the central importance of reversible phosphorylation in modulating rapid ABA responses. Sucrose Non-Fermenting Related Kinases （SnRK）, Calcium-Dependent Protein Kinases （CDPK）, Protein Phosphatases （PP） of the 2C and 2A classes figure as prominent regulators in this single-cell model. Identifying their direct in viv展开更多
Ultrasonic imaging is becoming the most popular medical imaging modality,owing to the low price per examination and its safety.However,blood is a poor scatterer of ultrasound waves at clinical diagnostic transmit freq...Ultrasonic imaging is becoming the most popular medical imaging modality,owing to the low price per examination and its safety.However,blood is a poor scatterer of ultrasound waves at clinical diagnostic transmit frequencies.For perfusion imaging,markers have been designed to enhance the contrast in B-mode imaging.These so-called ultrasound contrast agents consist of microscopically small gas bubbles encapsulated in biodegradable shells.In this review,the physical principles of ultrasound contrast agent microbubble behavior and their adjustment for drug delivery including sonoporation are described.Furthermore,an outline of clinical imaging applications of contrast-enhanced ultrasound is given.It is a challenging task to quantify and predict which bubble phenomenon occurs under which acoustic condition,and how these phenomena may be utilized in ultrasonic imaging.Aided by high-speed photography,our improved understanding of encapsulated microbubble behavior will lead to more sophisticated detection and delivery techniques.More sophisticated methods use quantitative approaches to measure the amount and the time course of bolus or reperfusion curves,and have shown great promise in revealing effective tumor responses to anti-angiogenic drugs in humans before tumor shrinkage occurs.These are beginning to be accepted into clinical practice.In the long term,targeted microbubbles for molecular imaging and eventually for directed anti-tumor therapy are expected to be tested.展开更多
Considering that even contaminated soils are a potential resource for agricultural production, it is essential to develop a set of cropping systems to allow a safe and sustainable agriculture on contaminated lands whi...Considering that even contaminated soils are a potential resource for agricultural production, it is essential to develop a set of cropping systems to allow a safe and sustainable agriculture on contaminated lands while avoiding any transfer of toxic trace elements to the food chain. In this review, three main strategies, i.e., phytoexclusion, phytostabilization, and phytoextraction, are proposed to establish cropping systems for production of edible and non-edible plants, and for extraction of elements for industrial use. For safe production of food crops, the selection of low-accumulating plants/cultivars and the application of soil amendments are of vital importance. Phytostabilization using non-food energy and fiber plants can provide additional renewable energy sources and economic benefit with minimum cost of agricultural measures. Phytoextracting trace elements （e.g., As, Cd, Ni, and Zn） using hyperaccumulator species is more suitable for slightly and moderately polluted sites, and phytomining of Ni from serpentine soils has shown a great potential to extract Ni-containing bio-ores of economic interests. We conclude that appropriate combinations of soil types, plant species/cultivars, and agronomic practices can restrict trace metal transfer to the food chain and/or extract energy and metals of industrial use and allow safe agricultural activities.展开更多
The synthesis of MnO2 powders by hydrothermal method with different oxidizing agents has been successfully achieved. The characterizations by scanning electron microscopy, energy-dispersive X-ray analyses, transmissio...The synthesis of MnO2 powders by hydrothermal method with different oxidizing agents has been successfully achieved. The characterizations by scanning electron microscopy, energy-dispersive X-ray analyses, transmission electron microscopy, and X-ray diffraction techniques confirm the synthesis of nanostructured γ-MnO2 powders. The electrochemical reactivity of these powders in 1 mol/l KOH is investigated by cyclic voltammetry and electrochemical impedance spectroscopy （EIS） by using microcavity electrode. The results reveal that the MnO2 synthesized with Na2S2O8 shows the highest electrochemical reactivity in the test medium. This is due both to its large expanded surface area and its crystallographic variety γ-MnO2 formed in the matrix of ramsdellite, which is largely used as cathodic material for primary batteries. However, the presence of pyrolusite in the structure of γ-MnO2 synthesized with （NH4）2S2O8 decreases its electrochemical reactivity due to its narrow 1×1 size tunnel, which hinders the protons insertion.展开更多
Desmodium adscendens is a plant in the Fabaceae family that is very important to man, both agronomically and medicinally. It is an important cover crop that contributes to improving soil fertility, reducing the risks ...Desmodium adscendens is a plant in the Fabaceae family that is very important to man, both agronomically and medicinally. It is an important cover crop that contributes to improving soil fertility, reducing the risks associated with crop pests and weeds. However, very little research has been carried out into its domestication for use as a cover crop in banana plantations in Côte d’Ivoire. The general objective of this study was to evaluate, under semi-controlled conditions, the effect of different levels of shade on the growth and development of Desmodium adscendens. The studies were carried out on the experimental site of the UP-Plant Physiology Laboratory. Four shading levels were evaluated: 0 (NO), 20% (N1), 40% (N2) and 60% (N3) light levels. The Desmodium adscendens cuttings used were collected from a 3-month nursery. For each treatment, 10 tubs containing sterilized soil were used, and 50 cuttings were planted. After planting, growth and development parameters were assessed weekly on 10 plants. In addition, yield and fresh and dry mass were measured. Finally, the reproductive cycle of Desmodium adscendens was determined. The results showed that plant growth and development were greatest in plants grown under the 40% shade level, followed by the 20% and 60% shade levels. In contrast, plants in full light showed poor growth and development. The 40% shade level was the most favorable for growing Desmodium adscendens cuttings, with a cycle length of 67 days. Growing Desmodium adscendens under shade with 20% and 40% light levels could be recommended to farmers.展开更多
Oil recovery factor is one of the most important parameters in the development process of oil reservoir,especially in the low-permeability reservoir.In general,the determination of recovery factor can be obtained eith...Oil recovery factor is one of the most important parameters in the development process of oil reservoir,especially in the low-permeability reservoir.In general,the determination of recovery factor can be obtained either experimentally or numerically.Experimental method is often timeconsuming and expensive,while numerical method has been always confined to narrow range of application or relatively large error.Recently,an intelligent method has been proven as an efficient tool to model the complex and nonlinear phenomena.In this work,an intelligent model based on support vector machine in combination with the particle swarm optimization(PSO-SVM)technique was established to predict oil recovery factor in the low-permeability reservoir.Input variables of the proposed PSO-SVM model with the aid of a grey correlation analysis method are permeability,well spacing density,production-injection well ratio,porosity,effective thickness,crude oil viscosity and output parameter is oil recovery factor of low-permeability reservoir.The accuracy and reliability of the proposed model were evaluated through 34 data sets collected in the open literature and compared with PSO-BP neural network,empirical method from Oil and Gas Company.The results indicated that the PSO-SVM model gives the best results with average absolute relative deviation(AARD)of 3.79%,while AARDs for the PSO-BP neural network and empirical method are 9.18%and 10.0%,respectively.Furthermore,outlier detection was used on the basis of whole data sets to definite the valid domains of PSO-SVM and PSO-BP models by detecting the probable doubtful recovery factor data in the low-permeability reservoir.展开更多
The possibilities of combining the dissolution of short-range-order minerals （SROMs） like allophane and imogolite, by ammonium oxalate and a particle size distribution analysis performed by the pipette method were i...The possibilities of combining the dissolution of short-range-order minerals （SROMs） like allophane and imogolite, by ammonium oxalate and a particle size distribution analysis performed by the pipette method were investigated by tests on a soil sample from Reunion, a volcanic island located in the Indian Ocean, having a large SROMs content. The need to work with moist soil samples was again emphasized because the microaggregates formed during air-drying are resistant to the reagent. The SROM content increased, but irregularly, with the number of dissolutions by ammonium oxalate： 334 and 470 mg g-1 of SROMs were dissolved after one and three dissolutions respectively. Six successive dissolutions with ammonium oxalate on the same soil sample showed that 89% of the sum of oxides extracted by the 6 dissolutions were extracted by the first dissolution （mean 304 mg g-l）. A compromise needs to be found between the total removal of SROMs by large quantities of ammonium oxalate and the preservation of clay minerals, which were unexpectedly dissolved by this reagent. These tests enabled a description of the clay assemblage of the soil （gibbsite, smectite, and traces of kaolinite） in an area where such information was lacking due to the difficulties encountered in recuperation of the clay fraction.展开更多
Aims Invasive species,which recently expanded,may help understand how climatic niche can shift at the time scale of the current global change.Here,we address the climatic niche shift of an invasive shrub(common gorse,...Aims Invasive species,which recently expanded,may help understand how climatic niche can shift at the time scale of the current global change.Here,we address the climatic niche shift of an invasive shrub(common gorse,Ulex europaeus)at the world and regional scales to assess how it could contribute to increasing invasibility.Methods Based on a 28187 occurrences database,we used a combination of 9 species distribution models(SDM)to assess regional climatic niche from both the native range(Western Europe)and the introduced range in different parts of the world(North-West America,South America,North Europe,Australia and New Zealand).Important Findings Despite being restricted to annual mean temperature between 4℃ and 22℃,as well as annual precipitation higher than 300 mm/year,the range of bioclimatic conditions suitable for gorse was very large.Based on a native versus introduced SDM comparison,we highlighted a niche expansion in North-West America,South America and to a lesser degree in Australia,while a niche displacement was assessed in North Europe.These niche changes induced an increase in potential occupied areas by gorse by 49,111,202 and 283%in Australia,North Europe,North-West America and South America,respectively.On the contrary,we found no evidence of niche change in New Zealand,which presents similar climatic condition to the native environment(Western Europe).This study highlights how niche expansion and displacement of gorse might increase invasibility at regional scale.The change in gorse niche toward new climatic conditions may result from adaptive plasticity or genetic evolution and may explain why it has such a high level of invasibility.Taking into account the possibility of a niche shift is crucial to improve invasive plants management and control.展开更多
A tunable diode laser absorption spectrometer （TDLAS） for formaldehyde atmospheric measurements has been set up and validated through comparison experiments with a Fourier transform infrared spectrometer （FT-IR） i...A tunable diode laser absorption spectrometer （TDLAS） for formaldehyde atmospheric measurements has been set up and validated through comparison experiments with a Fourier transform infrared spectrometer （FT-IR） in a simulation chamber.Formaldehyde was generated in situ in the chamber from reaction of ethene with ozone.Three HCHO ro-vibrational line intensities （at 2909.71,2912.09 and 2914.46 cm-1） possibly used by TDLAS were calibrated by FT-IR spectra simultaneously recorded in the 1600–3200 cm-1 domain during ethene ozonolysis,enabling the on-line deduction of the varying concentration for HCHO in formation.The experimental line intensities values inferred confirmed the calculated ones from the updated HITRAN database.In addition,the feasibility of stratospheric in situ HCHO measurements using the 2912.09 cm-1 line was demonstrated.The TDLAS performances were also assessed,leading to a 2σ detection limit of 88 ppt in volume mixing ratio with a response time of 60 sec at 30 Torr and 294 K for 112 m optical path.As part of this work,the room-temperature rate constant of this reaction and the HCHO formation yield were found to be in excellent agreement with the compiled literature data.展开更多
This paper deals with a design approach of a gait training machine based on a quantitative gait analysis. The proposed training machine is composed of a body weight support device and a cable-driven parallel robot. Th...This paper deals with a design approach of a gait training machine based on a quantitative gait analysis. The proposed training machine is composed of a body weight support device and a cable-driven parallel robot. This paper is focused on the cable-driven robot, which controls the pose of the lower limb through an orthosis placed on the patient＇s leg. The cable robot reproduces a normal gait movement through the motion of the orthosis. A motion capture system is used to perform the quantitative analysis of a normal gait, which will be used as an input to the inverse dynamic model of the cable robot. By means of an optimization algorithm, the optimal design parameters, which minimize the tensions in the cables, are determined. Two constraints are considered, i.e., a non-negative tension in the cables at all times, and a free cable/end-effector collision. Once the optimal solution is computed, a power analysis is carried out in order to size the robot actuators. The proposed approach can be easily extended for the design study of a similar type of cable robots.展开更多
The growth factor midkine （MK） is a cytokine that inhibits HIV infection in cell cultures in an autocrine and paracrine manner by blocking the attachment of HIV particles to permissive cells. MK mRNA is systematical...The growth factor midkine （MK） is a cytokine that inhibits HIV infection in cell cultures in an autocrine and paracrine manner by blocking the attachment of HIV particles to permissive cells. MK mRNA is systematically expressed in adult peripheral blood lymphocytes from healthy donors, while its expression becomes markedly but transiently increased upon in vitro treatment of lymphocytes with IL-2 or IFN-7 and activation of T lymphocytes by PHA or through the engagement of the CD28 antigen. The binding of MK to cells occurs specifically at a high and a low affinity binding site. This low affinity-binding site is the cell-surface expressed nucleolin, which is implicated in the mechanism of the initial attachment of HIV particles to cells. Accordingly, the nucleolin-binding HB-19 pseudopeptide has no effect on the MK binding to the high affinity binding site, whereas it prevents the binding of MK to the low affinity binding site, thus suggesting the low affinity receptor of MK is the cell-surface-expressed nucleolin. Confocal immunofluorescence laser microscopy revealed the colocalization of MK and the cell-surface-expressed nucleolin at distinct spots. The use of various deletion constructs of nucleolin then indicates that the extreme C-terminal end of nucleolin, containing repeats of the amino acid motif RGG, as the domain that binds MK. The specific binding of MK to the surface nucleolin is independent of heparan sulfate and chondroitin sulfate proteoglycans. After binding to cells, MK enters cells by an active process in which nucleolin and lipid rafts appear to be implicated. The potent and the distinct anti-HIV action of MK along with its enhanced expression in lymphocytes by various physiological stimuli, point out that MK is a cytokine that could be involved in HIV pathogenesis.展开更多
Rain-induced fruit cracking is a major problem in sweet cherry cultivation.Basic research has been conducted to disentangle the physiological and mechanistic bases of this complex phenomenon,whereas genetic studies ha...Rain-induced fruit cracking is a major problem in sweet cherry cultivation.Basic research has been conducted to disentangle the physiological and mechanistic bases of this complex phenomenon,whereas genetic studies have lagged behind.The objective of this work was to disentangle the genetic determinism of rain-induced fruit cracking.We hypothesized that a large genetic variation would be revealed,by visual field observations conducted on mapping populations derived from well-contrasted cultivars for cracking tolerance.Three populations were evaluated over 7–8 years by estimating the proportion of cracked fruits for each genotype at maturity,at three different areas of the sweet cherry fruit:pistillar end,stem end,and fruit side.An original approach was adopted to integrate,within simple linear models,covariates potentially related to cracking,such as rainfall accumulation before harvest,fruit weight,and firmness.We found the first stable quantitative trait loci(QTLs)for cherry fruit cracking,explaining percentages of phenotypic variance above 20%,for each of these three types of cracking tolerance,in different linkage groups,confirming the high complexity of this trait.For these and other QTLs,further analyses suggested the existence of at least two-linked QTLs in each linkage group,some of which showed confidence intervals close to 5 cM.These promising results open the possibility of developing marker-assisted selection strategies to select cracking-tolerant sweet cherry cultivars.Further studies are needed to confirm the stability of the reported QTLs over different genetic backgrounds and environments and to narrow down the QTL confidence intervals,allowing the exploration of underlying candidate genes.展开更多
This paper deals with an optimization approach to design a cable driven parallel robot intended for upper limb rehabilitation tasks. The cable driven parallel robots have characteristics that make them best candidate ...This paper deals with an optimization approach to design a cable driven parallel robot intended for upper limb rehabilitation tasks. The cable driven parallel robots have characteristics that make them best candidate for rehabilitation exercise purposes such as large workspace, re-configurable architecture, portability and cost effectiveness. Here, both the cable tensions that are needed to move a wristband as well as the workspace need to be carefully optimized for fulfilling the prescribed operation tasks. A specific case of study is addressed in this work by referring to LA RM wire driven exercising device (LAWEX), which is applied to upper limbs exercises. To that end, a motion capture system is used to collect quantitative data on the prescribed workspace of a human upper limb. A specific optimization problem is settled up for considering combining two optimization goals, namely, the smallest robot size reaching a prescribed workspace and the minimum cable tension distributions. A sequence of optimization steps is defined using Genetic Algorithms (GAs) applied to LAWEX robot. The proposed objective function is based on a mathematical formulation of the power of a point with respect to bounding surfaces in combination with a performance index to show the distributions of the minimum cable tensions.展开更多
Sugarcane bagasse is an agro-waste that could replace timber resources for the production of bio-composites.Composite boards such as particleboard offer an issue for the use and recycling of poor quality timber,and th...Sugarcane bagasse is an agro-waste that could replace timber resources for the production of bio-composites.Composite boards such as particleboard offer an issue for the use and recycling of poor quality timber,and these engineered products can overcome some solid wood limitations such as heterogeneity and dimension.Bagasse offers an alternative to wood chips for particleboard production but present some disadvantages as well,such as poor physico-mechanical properties.To address these issues,bagassefibers were treated with an innovative natural resin formulated with tannin and furfural.Impregnated particles with different concentrations of resin(5%,10%,and 15%m/m)were exposed to temperatures of 40℃,60℃,80℃,and 100℃ for resin curing.Various types of tannin-based adhesives,including tannin formaldehyde,tannin/formaldehyde-furfural,and tannin hex-amine,were utilized for bonding the treated bagasse particles.The resultant panels were assessed for their physical and mechanical properties and compared to those produced using Melamine-Urea-Formaldehyde(MUF)adhe-sive.The density of the panels varied from 650 to 730 kg/m^(3) depending on the resin concentration.The values for both modulus of elasticity and modulus of rupture increased as the resin concentration increased.The internal bonding values exhibited an increase with resin concentration up to a critical point,after which a decreasing trend was observed.The water absorption and thickness swelling were significantly reduced with an increase in resin concentration.However,the panels produced using MUF adhesive yielded the most favorable physico-mechanical properties.Additionally,the panels made with tannin-based adhesives met the minimum requirements specified in the standard EN 312(specifications for uncoated resin-bonded particleboards)for application in dry condi-tions.The analysis of formaldehyde emissions indicated that panels produced with tannin-based adhesives exhib-ited significantly lower emissions compared to those made with MUF.The tannin/furfural展开更多
Bio-silica issued from diatom, a microalgae, is attracted increasing attention in material science thanks to its peculiar nanoarchitecture and related properties with versatile applications. The present work is a deep...Bio-silica issued from diatom, a microalgae, is attracted increasing attention in material science thanks to its peculiar nanoarchitecture and related properties with versatile applications. The present work is a deep analysis on morphological and chemical properties of bio-silica issued from fossil origin (diatomaceous earth) and living one (algal paste). An optimization in purification protocol was performed to obtain multiparous bio-silica from its raw media with keeping its original shape entirely. Multiple characterization methods as scanning electronic microscopy (SEM), infrared spectroscopy, x-ray diffraction (DRX), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption and inverse gas chromatography (IGC), were used to check the purification protocol efficiency as well as to gather accurate information on morphology and chemical composition of diatom material obtained in large amount.展开更多
Despite notable progress in cancer therapy,metastatic diseases continue to be the primary cause of cancer-related mortality.Multi-walled carbon nanotubes(MWCNTs)can enter tissues and cells and interfere with the dynam...Despite notable progress in cancer therapy,metastatic diseases continue to be the primary cause of cancer-related mortality.Multi-walled carbon nanotubes(MWCNTs)can enter tissues and cells and interfere with the dynamics of the cytoskeletal nanofilaments biomimetically.This endows them with intrinsic anti-tumoral effects comparable to those of microtubule-binding chemotherapies such as Taxol®.In this study,our focus was on exploring the potential of oxidized MWCNTs in selectively targeting the vascular endothelial growth factor receptor(VEGFR).Our objective was to evaluate their effectiveness in inhibiting metastatic growth by inducing anti-proliferative,anti-migratory,and cytotoxic effects on both cancer and tumor microenvironment cells.Our findings demonstrated a significant reduction of over 80%in malignant melanoma lung metastases and a substantial enhancement in overall animal welfare following intravenous administration of the targeted biodegradable MWCNTs.Furthermore,the combination of these nanomaterials with the conventional chemotherapy agent Taxol®yielded a remarkable 90%increase in the antimetastatic effect.These results highlight the promising potential of this combined therapeutic approach against metastatic disease and are of paramount importance as metastasis is responsible for nearly 60,000 deaths each year.展开更多
For the first time,the mechanism of metal aluminum dissolution in NaF-ScF_(3) eutectic melts and the chemical interaction between the constituents of this mixture have been thoroughly studied by a combination of diffe...For the first time,the mechanism of metal aluminum dissolution in NaF-ScF_(3) eutectic melts and the chemical interaction between the constituents of this mixture have been thoroughly studied by a combination of differential thermal analysis(DTA),high temperature and solid-state nuclear magnetic resonance(NMR),and X-ray diffraction(XRD) coupled with the molecular dynamic simulations.The formation of an insoluble Al_(3)Sc alloy in molten(NaF-ScF_(3))_(eut)system was proven,and the chemical mechanism of this aluminothermic Al_(3)Sc alloy production was elucidated.Corresponding ex situ examinations bring to light the formation of NaScF_4 and solid solution of Na_(3)(Al,Sc)F_(6) in cooled bath.The molecular dynamics calculations of the bath allow us to construct the structural model and to predict viscosity,density and electrical conductivity of the reagent melt to help to optimize the conditions of the alloy synthesis.展开更多
Transparent Ce:lutetium aluminum garnet(Ce:Lu_(3)A_(l5)O_(12),Ce:LuAG)ceramics have been regarded as potential scintillator materials due to their relatively high density and atomic number(Zeff).However,the current Ce...Transparent Ce:lutetium aluminum garnet(Ce:Lu_(3)A_(l5)O_(12),Ce:LuAG)ceramics have been regarded as potential scintillator materials due to their relatively high density and atomic number(Zeff).However,the current Ce:LuAG ceramics exhibit a light yield much lower than the expected theoretical value due to the inevitable presence of LuAl antisite defects at high sintering temperatures.This work demonstrates a low-temperature(1100℃)synthetic strategy for elaborating transparent LuAG–Al_(2)O_(3) nanoceramics through the crystallization of 72 mol%Al_(2)O_(3)–28 mol%Lu_(2)O_(3)(ALu28)bulk glass.The biphasic nanostructure composed of LuAG and Al_(2)O_(3) nanocrystals makes up the whole ceramic materials.Most of Al_(2)O_(3) is distributed among LuAG grains,and the rest is present inside the LuAG grains.Fully dense biphasic LuAG–Al_(2)O_(3) nanoceramics are highly transparent from the visible region to mid-infrared(MIR)region,and particularly the transmittance reaches 82%at 780 nm.Moreover,LuAl antisite defect-related centers are completely undetectable in X-ray excited luminescence(XEL)spectra of Ce:LuAG–Al_(2)O_(3) nanoceramics with 0.3–1.0 at%Ce.The light yield of 0.3 at%Ce:LuAG–Al_(2)O_(3) nanoceramics is estimated to be 20,000 ph/MeV with short 1μs shaping time,which is far superior to that of commercial Bi_(4)Ge_(3)O_(12)(BGO)single crystals.These results show that a low-temperature glass crystallization route provides an alternative approach for eliminating the antisite defects in LuAG-based ceramics,and is promising to produce garnet-based ceramic materials with excellent properties,thereby meeting the demands of advanced scintillation applications.展开更多
Few layer graphene （FLG）, multi-walled carbon nanotubes （CNTs） and a nanotube-graphene composite （CNT-FLG） were used as supports for palladium nanoparticles. The catalysts, which were characterized by transmissi...Few layer graphene （FLG）, multi-walled carbon nanotubes （CNTs） and a nanotube-graphene composite （CNT-FLG） were used as supports for palladium nanoparticles. The catalysts, which were characterized by transmission electron microscopy, Raman spectroscopy and X-ray diffraction, were used as anodes in the electrooxidation of ethanol, ethylene glycol and glycerol in half cells and in passive direct ethanol fuel cells. Upon Pd deposition, a stronger interaction was found to occur between the metal and the nanotube-graphene composite and the particle size was significantly smaller in this material （6.3 nm）, comparing with nanotubes and graphene alone （8 and 8.4 nm, respectively）. Cyclic voltammetry experiments conducted with Pd/CNT, Pd/FLG and Pd/CNT-FLG in 10 wt% ethanol and 2 M KOH solution, showed high specific currents of 1.48, 2.29 and 2.51 mA-/zgp-d, respectively. Moreover, the results obtained for ethylene glycol and glycerol oxidation highlighted the excellent electrocatalytic activity of Pd/CNT-FLG in terms of peak current density （up to 3.70 mAgd for ethylene glycol and 1.84 mAfor glycerol, respectively）. Accordingly, Pd/CNT-FLG can be considered as the best performing one among the electrocatalysts ever reported for ethylene glycol oxidation, especially considering the low metal loading used in this work. Direct ethanol fuel cells at room temperature were studied by obtaining power density curves and undertaking galvanostatic experiments. The power density outputs using Pd/CNT, Pd/FLG and Pd/CNT-FLG were 12.1, 16.3 and 18.4 mW.cm-2, respectively. A remarkable activity for ethanol electrooxidation was shown by Pd/CNT-FLG anode catalyst. In a constant current experiment, the direct ethanol fuel cell containing Pd/CNT-FLG could continuously deliver 20 mA.cm-2 for 9.5 h during the conversion of ethanol into acetate of 30%, and the energy released from the cell was about 574 J.展开更多
The aim of the present work is to investigate the numerical modeling of interfacial cracks that may appear at the interface between two isotropic elastic materials. The extended finite element method is employed to an...The aim of the present work is to investigate the numerical modeling of interfacial cracks that may appear at the interface between two isotropic elastic materials. The extended finite element method is employed to analyze brittle and bi-material interfacial fatigue crack growth by computing the mixed mode stress intensity factors(SIF). Three different approaches are introduced to compute the SIFs. In the first one, mixed mode SIF is deduced from the computation of the contour integral as per the classical J-integral method,whereas a displacement method is used to evaluate the SIF by using either one or two displacement jumps located along the crack path in the second and third approaches. The displacement jump method is rather classical for mono-materials,but has to our knowledge not been used up to now for a bimaterial. Hence, use of displacement jump for characterizing bi-material cracks constitutes the main contribution of the present study. Several benchmark tests including parametric studies are performed to show the effectiveness of these computational methodologies for SIF considering static and fatigue problems of bi-material structures. It is found that results based on the displacement jump methods are in a very good agreement with those of exact solutions, such as for the J-integral method, but with a larger domain of applicability and a better numerical efficiency(less time consuming and less spurious boundary effect).展开更多
文摘The mode of abscisic acid （ABA） action, and its relations to drought adaptive responses in particular, has been a captivating area of plant hormone research for much over a decade. The hormone triggers stomatal closure to limit water loss through transpiration, as well as mobilizes a battery of genes that presumably serve to protect the cells from the ensuing oxidative damage in prolonged stress. The signaling network orchestrating these various responses is, however, highly complex. This review summarizes several significant advances made within the last few years. The biosynthetic pathway of the hormone is now almost completely elucidated, with the latest identification of the ABA4 gene encoding a neoxanthin synthase, which seems essential for de novo ABA biosynthesis during water stress. This leads to the interesting question on how ABA is then delivered to perception sites. In this respect, regulated transport has attracted renewed focus by the unexpected finding of a shoot-to-root translocation of ABA during drought response, and at the cellular level, by the identification of a B-galactosidase that releases biologically active ABA from inactive ABA-glucose ester. Surprising candidate ABA receptors were also identified in the form of the Flowering Time Control Protein A （FCA） and the Chloroplastic Magnesium Protoporphyrin-IX Chelatase H subunit （CHLH） in chloroplast-nucleus communication, both of which have been shown to bind ABA in vitro. On the other hand, the protein（s） corresponding to the physiologically detectable cell-surface ABA receptor（s） is （are） still not known with certainty. Genetic and physiological studies based on the guard cell have reinforced the central importance of reversible phosphorylation in modulating rapid ABA responses. Sucrose Non-Fermenting Related Kinases （SnRK）, Calcium-Dependent Protein Kinases （CDPK）, Protein Phosphatases （PP） of the 2C and 2A classes figure as prominent regulators in this single-cell model. Identifying their direct in viv
文摘Ultrasonic imaging is becoming the most popular medical imaging modality,owing to the low price per examination and its safety.However,blood is a poor scatterer of ultrasound waves at clinical diagnostic transmit frequencies.For perfusion imaging,markers have been designed to enhance the contrast in B-mode imaging.These so-called ultrasound contrast agents consist of microscopically small gas bubbles encapsulated in biodegradable shells.In this review,the physical principles of ultrasound contrast agent microbubble behavior and their adjustment for drug delivery including sonoporation are described.Furthermore,an outline of clinical imaging applications of contrast-enhanced ultrasound is given.It is a challenging task to quantify and predict which bubble phenomenon occurs under which acoustic condition,and how these phenomena may be utilized in ultrasonic imaging.Aided by high-speed photography,our improved understanding of encapsulated microbubble behavior will lead to more sophisticated detection and delivery techniques.More sophisticated methods use quantitative approaches to measure the amount and the time course of bolus or reperfusion curves,and have shown great promise in revealing effective tumor responses to anti-angiogenic drugs in humans before tumor shrinkage occurs.These are beginning to be accepted into clinical practice.In the long term,targeted microbubbles for molecular imaging and eventually for directed anti-tumor therapy are expected to be tested.
基金Supported by the Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, China and the Chinese Scholarship Council
文摘Considering that even contaminated soils are a potential resource for agricultural production, it is essential to develop a set of cropping systems to allow a safe and sustainable agriculture on contaminated lands while avoiding any transfer of toxic trace elements to the food chain. In this review, three main strategies, i.e., phytoexclusion, phytostabilization, and phytoextraction, are proposed to establish cropping systems for production of edible and non-edible plants, and for extraction of elements for industrial use. For safe production of food crops, the selection of low-accumulating plants/cultivars and the application of soil amendments are of vital importance. Phytostabilization using non-food energy and fiber plants can provide additional renewable energy sources and economic benefit with minimum cost of agricultural measures. Phytoextracting trace elements （e.g., As, Cd, Ni, and Zn） using hyperaccumulator species is more suitable for slightly and moderately polluted sites, and phytomining of Ni from serpentine soils has shown a great potential to extract Ni-containing bio-ores of economic interests. We conclude that appropriate combinations of soil types, plant species/cultivars, and agronomic practices can restrict trace metal transfer to the food chain and/or extract energy and metals of industrial use and allow safe agricultural activities.
基金The present work was carried out in the frame of French-Algerian cooperation project CMEP-PHC Tassili No.06MDU686
文摘The synthesis of MnO2 powders by hydrothermal method with different oxidizing agents has been successfully achieved. The characterizations by scanning electron microscopy, energy-dispersive X-ray analyses, transmission electron microscopy, and X-ray diffraction techniques confirm the synthesis of nanostructured γ-MnO2 powders. The electrochemical reactivity of these powders in 1 mol/l KOH is investigated by cyclic voltammetry and electrochemical impedance spectroscopy （EIS） by using microcavity electrode. The results reveal that the MnO2 synthesized with Na2S2O8 shows the highest electrochemical reactivity in the test medium. This is due both to its large expanded surface area and its crystallographic variety γ-MnO2 formed in the matrix of ramsdellite, which is largely used as cathodic material for primary batteries. However, the presence of pyrolusite in the structure of γ-MnO2 synthesized with （NH4）2S2O8 decreases its electrochemical reactivity due to its narrow 1×1 size tunnel, which hinders the protons insertion.
文摘Desmodium adscendens is a plant in the Fabaceae family that is very important to man, both agronomically and medicinally. It is an important cover crop that contributes to improving soil fertility, reducing the risks associated with crop pests and weeds. However, very little research has been carried out into its domestication for use as a cover crop in banana plantations in Côte d’Ivoire. The general objective of this study was to evaluate, under semi-controlled conditions, the effect of different levels of shade on the growth and development of Desmodium adscendens. The studies were carried out on the experimental site of the UP-Plant Physiology Laboratory. Four shading levels were evaluated: 0 (NO), 20% (N1), 40% (N2) and 60% (N3) light levels. The Desmodium adscendens cuttings used were collected from a 3-month nursery. For each treatment, 10 tubs containing sterilized soil were used, and 50 cuttings were planted. After planting, growth and development parameters were assessed weekly on 10 plants. In addition, yield and fresh and dry mass were measured. Finally, the reproductive cycle of Desmodium adscendens was determined. The results showed that plant growth and development were greatest in plants grown under the 40% shade level, followed by the 20% and 60% shade levels. In contrast, plants in full light showed poor growth and development. The 40% shade level was the most favorable for growing Desmodium adscendens cuttings, with a cycle length of 67 days. Growing Desmodium adscendens under shade with 20% and 40% light levels could be recommended to farmers.
基金This work was supported by National Natural Science Foundation of China(No.51404205)Open Fund(PLN 1207)of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Southwest Petroleum University)Innovation team project of Sichuan Provincial Department of Education(No.16TD0010).
文摘Oil recovery factor is one of the most important parameters in the development process of oil reservoir,especially in the low-permeability reservoir.In general,the determination of recovery factor can be obtained either experimentally or numerically.Experimental method is often timeconsuming and expensive,while numerical method has been always confined to narrow range of application or relatively large error.Recently,an intelligent method has been proven as an efficient tool to model the complex and nonlinear phenomena.In this work,an intelligent model based on support vector machine in combination with the particle swarm optimization(PSO-SVM)technique was established to predict oil recovery factor in the low-permeability reservoir.Input variables of the proposed PSO-SVM model with the aid of a grey correlation analysis method are permeability,well spacing density,production-injection well ratio,porosity,effective thickness,crude oil viscosity and output parameter is oil recovery factor of low-permeability reservoir.The accuracy and reliability of the proposed model were evaluated through 34 data sets collected in the open literature and compared with PSO-BP neural network,empirical method from Oil and Gas Company.The results indicated that the PSO-SVM model gives the best results with average absolute relative deviation(AARD)of 3.79%,while AARDs for the PSO-BP neural network and empirical method are 9.18%and 10.0%,respectively.Furthermore,outlier detection was used on the basis of whole data sets to definite the valid domains of PSO-SVM and PSO-BP models by detecting the probable doubtful recovery factor data in the low-permeability reservoir.
基金Supported by the Center for International Cooperation in Agronomic Research for Developmentthe French Ministry of Overseas Departments and Territories+1 种基金the European Agricultural Guidance and Guarantee Fundthe Regional Direction of Environment,France
文摘The possibilities of combining the dissolution of short-range-order minerals （SROMs） like allophane and imogolite, by ammonium oxalate and a particle size distribution analysis performed by the pipette method were investigated by tests on a soil sample from Reunion, a volcanic island located in the Indian Ocean, having a large SROMs content. The need to work with moist soil samples was again emphasized because the microaggregates formed during air-drying are resistant to the reagent. The SROM content increased, but irregularly, with the number of dissolutions by ammonium oxalate： 334 and 470 mg g-1 of SROMs were dissolved after one and three dissolutions respectively. Six successive dissolutions with ammonium oxalate on the same soil sample showed that 89% of the sum of oxides extracted by the 6 dissolutions were extracted by the first dissolution （mean 304 mg g-l）. A compromise needs to be found between the total removal of SROMs by large quantities of ammonium oxalate and the preservation of clay minerals, which were unexpectedly dissolved by this reagent. These tests enabled a description of the clay assemblage of the soil （gibbsite, smectite, and traces of kaolinite） in an area where such information was lacking due to the difficulties encountered in recuperation of the clay fraction.
基金supported by the Centre Nationale de la Recherche Scientifique(CNRS)the MARIS Agence Nationale de la Recherche project(ANR grant ANR-14-CE03-0007-01)Institut National de la Recherche Agronomique(INRA Institute).
文摘Aims Invasive species,which recently expanded,may help understand how climatic niche can shift at the time scale of the current global change.Here,we address the climatic niche shift of an invasive shrub(common gorse,Ulex europaeus)at the world and regional scales to assess how it could contribute to increasing invasibility.Methods Based on a 28187 occurrences database,we used a combination of 9 species distribution models(SDM)to assess regional climatic niche from both the native range(Western Europe)and the introduced range in different parts of the world(North-West America,South America,North Europe,Australia and New Zealand).Important Findings Despite being restricted to annual mean temperature between 4℃ and 22℃,as well as annual precipitation higher than 300 mm/year,the range of bioclimatic conditions suitable for gorse was very large.Based on a native versus introduced SDM comparison,we highlighted a niche expansion in North-West America,South America and to a lesser degree in Australia,while a niche displacement was assessed in North Europe.These niche changes induced an increase in potential occupied areas by gorse by 49,111,202 and 283%in Australia,North Europe,North-West America and South America,respectively.On the contrary,we found no evidence of niche change in New Zealand,which presents similar climatic condition to the native environment(Western Europe).This study highlights how niche expansion and displacement of gorse might increase invasibility at regional scale.The change in gorse niche toward new climatic conditions may result from adaptive plasticity or genetic evolution and may explain why it has such a high level of invasibility.Taking into account the possibility of a niche shift is crucial to improve invasive plants management and control.
基金supported by the European Commission through the 7th Framework Programme under the grant agreement #228335 (EUROCHAMP-2 Project)by the French CNRS-INSU Programme National de Chimie Atmosphrique
文摘A tunable diode laser absorption spectrometer （TDLAS） for formaldehyde atmospheric measurements has been set up and validated through comparison experiments with a Fourier transform infrared spectrometer （FT-IR） in a simulation chamber.Formaldehyde was generated in situ in the chamber from reaction of ethene with ozone.Three HCHO ro-vibrational line intensities （at 2909.71,2912.09 and 2914.46 cm-1） possibly used by TDLAS were calibrated by FT-IR spectra simultaneously recorded in the 1600–3200 cm-1 domain during ethene ozonolysis,enabling the on-line deduction of the varying concentration for HCHO in formation.The experimental line intensities values inferred confirmed the calculated ones from the updated HITRAN database.In addition,the feasibility of stratospheric in situ HCHO measurements using the 2912.09 cm-1 line was demonstrated.The TDLAS performances were also assessed,leading to a 2σ detection limit of 88 ppt in volume mixing ratio with a response time of 60 sec at 30 Torr and 294 K for 112 m optical path.As part of this work,the room-temperature rate constant of this reaction and the HCHO formation yield were found to be in excellent agreement with the compiled literature data.
文摘This paper deals with a design approach of a gait training machine based on a quantitative gait analysis. The proposed training machine is composed of a body weight support device and a cable-driven parallel robot. This paper is focused on the cable-driven robot, which controls the pose of the lower limb through an orthosis placed on the patient＇s leg. The cable robot reproduces a normal gait movement through the motion of the orthosis. A motion capture system is used to perform the quantitative analysis of a normal gait, which will be used as an input to the inverse dynamic model of the cable robot. By means of an optimization algorithm, the optimal design parameters, which minimize the tensions in the cables, are determined. Two constraints are considered, i.e., a non-negative tension in the cables at all times, and a free cable/end-effector collision. Once the optimal solution is computed, a power analysis is carried out in order to size the robot actuators. The proposed approach can be easily extended for the design study of a similar type of cable robots.
文摘The growth factor midkine （MK） is a cytokine that inhibits HIV infection in cell cultures in an autocrine and paracrine manner by blocking the attachment of HIV particles to permissive cells. MK mRNA is systematically expressed in adult peripheral blood lymphocytes from healthy donors, while its expression becomes markedly but transiently increased upon in vitro treatment of lymphocytes with IL-2 or IFN-7 and activation of T lymphocytes by PHA or through the engagement of the CD28 antigen. The binding of MK to cells occurs specifically at a high and a low affinity binding site. This low affinity-binding site is the cell-surface expressed nucleolin, which is implicated in the mechanism of the initial attachment of HIV particles to cells. Accordingly, the nucleolin-binding HB-19 pseudopeptide has no effect on the MK binding to the high affinity binding site, whereas it prevents the binding of MK to the low affinity binding site, thus suggesting the low affinity receptor of MK is the cell-surface-expressed nucleolin. Confocal immunofluorescence laser microscopy revealed the colocalization of MK and the cell-surface-expressed nucleolin at distinct spots. The use of various deletion constructs of nucleolin then indicates that the extreme C-terminal end of nucleolin, containing repeats of the amino acid motif RGG, as the domain that binds MK. The specific binding of MK to the surface nucleolin is independent of heparan sulfate and chondroitin sulfate proteoglycans. After binding to cells, MK enters cells by an active process in which nucleolin and lipid rafts appear to be implicated. The potent and the distinct anti-HIV action of MK along with its enhanced expression in lymphocytes by various physiological stimuli, point out that MK is a cytokine that could be involved in HIV pathogenesis.
基金the INRAE sweet cherry breeding program,which is supported by INRAE BAP division and by INRAE’s private partner,CEP Innovation.
文摘Rain-induced fruit cracking is a major problem in sweet cherry cultivation.Basic research has been conducted to disentangle the physiological and mechanistic bases of this complex phenomenon,whereas genetic studies have lagged behind.The objective of this work was to disentangle the genetic determinism of rain-induced fruit cracking.We hypothesized that a large genetic variation would be revealed,by visual field observations conducted on mapping populations derived from well-contrasted cultivars for cracking tolerance.Three populations were evaluated over 7–8 years by estimating the proportion of cracked fruits for each genotype at maturity,at three different areas of the sweet cherry fruit:pistillar end,stem end,and fruit side.An original approach was adopted to integrate,within simple linear models,covariates potentially related to cracking,such as rainfall accumulation before harvest,fruit weight,and firmness.We found the first stable quantitative trait loci(QTLs)for cherry fruit cracking,explaining percentages of phenotypic variance above 20%,for each of these three types of cracking tolerance,in different linkage groups,confirming the high complexity of this trait.For these and other QTLs,further analyses suggested the existence of at least two-linked QTLs in each linkage group,some of which showed confidence intervals close to 5 cM.These promising results open the possibility of developing marker-assisted selection strategies to select cracking-tolerant sweet cherry cultivars.Further studies are needed to confirm the stability of the reported QTLs over different genetic backgrounds and environments and to narrow down the QTL confidence intervals,allowing the exploration of underlying candidate genes.
文摘This paper deals with an optimization approach to design a cable driven parallel robot intended for upper limb rehabilitation tasks. The cable driven parallel robots have characteristics that make them best candidate for rehabilitation exercise purposes such as large workspace, re-configurable architecture, portability and cost effectiveness. Here, both the cable tensions that are needed to move a wristband as well as the workspace need to be carefully optimized for fulfilling the prescribed operation tasks. A specific case of study is addressed in this work by referring to LA RM wire driven exercising device (LAWEX), which is applied to upper limbs exercises. To that end, a motion capture system is used to collect quantitative data on the prescribed workspace of a human upper limb. A specific optimization problem is settled up for considering combining two optimization goals, namely, the smallest robot size reaching a prescribed workspace and the minimum cable tension distributions. A sequence of optimization steps is defined using Genetic Algorithms (GAs) applied to LAWEX robot. The proposed objective function is based on a mathematical formulation of the power of a point with respect to bounding surfaces in combination with a performance index to show the distributions of the minimum cable tensions.
基金This work was supported by the office of vice-president for research and technology,University of Tehran,Gundishapur project 1584/45227SG,and Campus France.
文摘Sugarcane bagasse is an agro-waste that could replace timber resources for the production of bio-composites.Composite boards such as particleboard offer an issue for the use and recycling of poor quality timber,and these engineered products can overcome some solid wood limitations such as heterogeneity and dimension.Bagasse offers an alternative to wood chips for particleboard production but present some disadvantages as well,such as poor physico-mechanical properties.To address these issues,bagassefibers were treated with an innovative natural resin formulated with tannin and furfural.Impregnated particles with different concentrations of resin(5%,10%,and 15%m/m)were exposed to temperatures of 40℃,60℃,80℃,and 100℃ for resin curing.Various types of tannin-based adhesives,including tannin formaldehyde,tannin/formaldehyde-furfural,and tannin hex-amine,were utilized for bonding the treated bagasse particles.The resultant panels were assessed for their physical and mechanical properties and compared to those produced using Melamine-Urea-Formaldehyde(MUF)adhe-sive.The density of the panels varied from 650 to 730 kg/m^(3) depending on the resin concentration.The values for both modulus of elasticity and modulus of rupture increased as the resin concentration increased.The internal bonding values exhibited an increase with resin concentration up to a critical point,after which a decreasing trend was observed.The water absorption and thickness swelling were significantly reduced with an increase in resin concentration.However,the panels produced using MUF adhesive yielded the most favorable physico-mechanical properties.Additionally,the panels made with tannin-based adhesives met the minimum requirements specified in the standard EN 312(specifications for uncoated resin-bonded particleboards)for application in dry condi-tions.The analysis of formaldehyde emissions indicated that panels produced with tannin-based adhesives exhib-ited significantly lower emissions compared to those made with MUF.The tannin/furfural
文摘Bio-silica issued from diatom, a microalgae, is attracted increasing attention in material science thanks to its peculiar nanoarchitecture and related properties with versatile applications. The present work is a deep analysis on morphological and chemical properties of bio-silica issued from fossil origin (diatomaceous earth) and living one (algal paste). An optimization in purification protocol was performed to obtain multiparous bio-silica from its raw media with keeping its original shape entirely. Multiple characterization methods as scanning electronic microscopy (SEM), infrared spectroscopy, x-ray diffraction (DRX), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption and inverse gas chromatography (IGC), were used to check the purification protocol efficiency as well as to gather accurate information on morphology and chemical composition of diatom material obtained in large amount.
基金funded by ISCIII Projects ref.PI19/00349,PI22/00030,PI23/00261 co-funded by ERDF/ESF,“Investing in your future”,Ministerio de Ciencia e Innovación ref.TED2021-129248B-100the Agence Nationale de la Recherche(ANR)through the LabEx project Chemistry of Complex Systems(ANR-10-LABX-0026_CSC)+1 种基金funding from the European Union’s Horizon Europe Research and Innovation Program(Marie Skłodowska-Curie Actions-Doctoral Networks)under the grant agreement 101073025(Melomanes)LGH thanks the Ministry of Innovation and Science of Spain for her Juan de la Cierva Incorporación grant(IJC2020-043746-I).
文摘Despite notable progress in cancer therapy,metastatic diseases continue to be the primary cause of cancer-related mortality.Multi-walled carbon nanotubes(MWCNTs)can enter tissues and cells and interfere with the dynamics of the cytoskeletal nanofilaments biomimetically.This endows them with intrinsic anti-tumoral effects comparable to those of microtubule-binding chemotherapies such as Taxol®.In this study,our focus was on exploring the potential of oxidized MWCNTs in selectively targeting the vascular endothelial growth factor receptor(VEGFR).Our objective was to evaluate their effectiveness in inhibiting metastatic growth by inducing anti-proliferative,anti-migratory,and cytotoxic effects on both cancer and tumor microenvironment cells.Our findings demonstrated a significant reduction of over 80%in malignant melanoma lung metastases and a substantial enhancement in overall animal welfare following intravenous administration of the targeted biodegradable MWCNTs.Furthermore,the combination of these nanomaterials with the conventional chemotherapy agent Taxol®yielded a remarkable 90%increase in the antimetastatic effect.These results highlight the promising potential of this combined therapeutic approach against metastatic disease and are of paramount importance as metastasis is responsible for nearly 60,000 deaths each year.
基金Financial supports from the IR INFRANALYTICS FR2054from Slovak grant agency (VEGA 2/0046/22)+1 种基金ITMS project (with code 313021T081) supported by Research and Innovation Operational program funded by the ERDFthe Kazan Federal University Strategic Academic Leadership Program》 (Priority-2030)。
文摘For the first time,the mechanism of metal aluminum dissolution in NaF-ScF_(3) eutectic melts and the chemical interaction between the constituents of this mixture have been thoroughly studied by a combination of differential thermal analysis(DTA),high temperature and solid-state nuclear magnetic resonance(NMR),and X-ray diffraction(XRD) coupled with the molecular dynamic simulations.The formation of an insoluble Al_(3)Sc alloy in molten(NaF-ScF_(3))_(eut)system was proven,and the chemical mechanism of this aluminothermic Al_(3)Sc alloy production was elucidated.Corresponding ex situ examinations bring to light the formation of NaScF_4 and solid solution of Na_(3)(Al,Sc)F_(6) in cooled bath.The molecular dynamics calculations of the bath allow us to construct the structural model and to predict viscosity,density and electrical conductivity of the reagent melt to help to optimize the conditions of the alloy synthesis.
基金supported by the National Natural Science Foundation of China (No.51972304)Beijing Municipal Science&Technology Commission,Administrative Commission of Zhongguancun Science Park (No.Z221100006722022)+1 种基金the Project of Scientific Experiment on Chinese Manned Space Station,Chinese Academy of Sciences President’s International Fellowship Initiative for 2021 (No.2021VEA0012)the Fundamental Research Funds for the Central Universities.
文摘Transparent Ce:lutetium aluminum garnet(Ce:Lu_(3)A_(l5)O_(12),Ce:LuAG)ceramics have been regarded as potential scintillator materials due to their relatively high density and atomic number(Zeff).However,the current Ce:LuAG ceramics exhibit a light yield much lower than the expected theoretical value due to the inevitable presence of LuAl antisite defects at high sintering temperatures.This work demonstrates a low-temperature(1100℃)synthetic strategy for elaborating transparent LuAG–Al_(2)O_(3) nanoceramics through the crystallization of 72 mol%Al_(2)O_(3)–28 mol%Lu_(2)O_(3)(ALu28)bulk glass.The biphasic nanostructure composed of LuAG and Al_(2)O_(3) nanocrystals makes up the whole ceramic materials.Most of Al_(2)O_(3) is distributed among LuAG grains,and the rest is present inside the LuAG grains.Fully dense biphasic LuAG–Al_(2)O_(3) nanoceramics are highly transparent from the visible region to mid-infrared(MIR)region,and particularly the transmittance reaches 82%at 780 nm.Moreover,LuAl antisite defect-related centers are completely undetectable in X-ray excited luminescence(XEL)spectra of Ce:LuAG–Al_(2)O_(3) nanoceramics with 0.3–1.0 at%Ce.The light yield of 0.3 at%Ce:LuAG–Al_(2)O_(3) nanoceramics is estimated to be 20,000 ph/MeV with short 1μs shaping time,which is far superior to that of commercial Bi_(4)Ge_(3)O_(12)(BGO)single crystals.These results show that a low-temperature glass crystallization route provides an alternative approach for eliminating the antisite defects in LuAG-based ceramics,and is promising to produce garnet-based ceramic materials with excellent properties,thereby meeting the demands of advanced scintillation applications.
基金supported by the MATTM (Italy) for the PIRODE Project No 94the MSE for the PRIT Project Industria 2015the MIUR (Italy) for the FIRB 2010 Project RBFR10J4H7 002 and HYDROLAB2
文摘Few layer graphene （FLG）, multi-walled carbon nanotubes （CNTs） and a nanotube-graphene composite （CNT-FLG） were used as supports for palladium nanoparticles. The catalysts, which were characterized by transmission electron microscopy, Raman spectroscopy and X-ray diffraction, were used as anodes in the electrooxidation of ethanol, ethylene glycol and glycerol in half cells and in passive direct ethanol fuel cells. Upon Pd deposition, a stronger interaction was found to occur between the metal and the nanotube-graphene composite and the particle size was significantly smaller in this material （6.3 nm）, comparing with nanotubes and graphene alone （8 and 8.4 nm, respectively）. Cyclic voltammetry experiments conducted with Pd/CNT, Pd/FLG and Pd/CNT-FLG in 10 wt% ethanol and 2 M KOH solution, showed high specific currents of 1.48, 2.29 and 2.51 mA-/zgp-d, respectively. Moreover, the results obtained for ethylene glycol and glycerol oxidation highlighted the excellent electrocatalytic activity of Pd/CNT-FLG in terms of peak current density （up to 3.70 mAgd for ethylene glycol and 1.84 mAfor glycerol, respectively）. Accordingly, Pd/CNT-FLG can be considered as the best performing one among the electrocatalysts ever reported for ethylene glycol oxidation, especially considering the low metal loading used in this work. Direct ethanol fuel cells at room temperature were studied by obtaining power density curves and undertaking galvanostatic experiments. The power density outputs using Pd/CNT, Pd/FLG and Pd/CNT-FLG were 12.1, 16.3 and 18.4 mW.cm-2, respectively. A remarkable activity for ethanol electrooxidation was shown by Pd/CNT-FLG anode catalyst. In a constant current experiment, the direct ethanol fuel cell containing Pd/CNT-FLG could continuously deliver 20 mA.cm-2 for 9.5 h during the conversion of ethanol into acetate of 30%, and the energy released from the cell was about 574 J.
文摘The aim of the present work is to investigate the numerical modeling of interfacial cracks that may appear at the interface between two isotropic elastic materials. The extended finite element method is employed to analyze brittle and bi-material interfacial fatigue crack growth by computing the mixed mode stress intensity factors(SIF). Three different approaches are introduced to compute the SIFs. In the first one, mixed mode SIF is deduced from the computation of the contour integral as per the classical J-integral method,whereas a displacement method is used to evaluate the SIF by using either one or two displacement jumps located along the crack path in the second and third approaches. The displacement jump method is rather classical for mono-materials,but has to our knowledge not been used up to now for a bimaterial. Hence, use of displacement jump for characterizing bi-material cracks constitutes the main contribution of the present study. Several benchmark tests including parametric studies are performed to show the effectiveness of these computational methodologies for SIF considering static and fatigue problems of bi-material structures. It is found that results based on the displacement jump methods are in a very good agreement with those of exact solutions, such as for the J-integral method, but with a larger domain of applicability and a better numerical efficiency(less time consuming and less spurious boundary effect).
