Secondary metabolism responses in two Pisum sativum L. cultivars cultivated under Fe deficiency conditions

The present study was carried out to investigate the Fe deficiency effect on the secondary metabolism  responses in two Pisum sativum cultivars characterized by different tolerance to Fe deficiency. Previous study  investigating the physiological responses to Fe deficiency in these two pea cultivars showed that Kelvedon was  more tolerant than Lincoln. Both cultivars were grown in the absence or presence of Fe with the addition of bicarbonate for twelve days. Higher concentrations of phenols and flavonoids were observed in Fe-deficient  tissues of both cultivars; however, the increase was greater in the tolerant cultivar than in the susceptible  one. The activity of shikimate pathway enzymes tested was more enhanced in the tolerant cultivar. In  addition, lipid peroxidation and H2O2 concentrations were more increased in the susceptible cultivar when  compared with the tolerant one. Peroxidase activity was increased in the tolerant cultivar grown under  bicarbonate supply, while a considerable diminution was observed in the susceptible one, suggesting the  involvement of this antioxidant enzyme in the tolerance of pea to Fe deficiency. The lignifying peroxidases  activity was more decreased in Lincoln than in Kelvedon, especially in the presence of bicarbonate. Our data  suggest that the tolerance of Kelvedon was related to its ability to modulate the phenolic metabolism pathway and to enhance the antioxidant potentials.Key words: Iron deficiency, bicarbonate, phenolic metabolism, antioxidative enzymes, Pisum sativum

Radiative lifetime of localized excitons in transition metal dichalcogenides

Disorder derived from defects or strain in monolayer TMDs can lead to a dramatic change in the physical behavior of the interband excitations, producing inhomogeneous spectral broadening and localization; leading to radiative lifetime increase. In this study, we have modeled the disorder in the surface of the sample through a randomized potential in monolayer WSe2. We show that this model allows us to simulate the spectra of localized exciton states as well as their radiative lifetime. In this context, we give an in depth study of the influence of the disorder potential parameters on the optical properties of these defects through energies, density of states, oscillator strengths, photoluminescence (PL) spectroscopy and radiative lifetime at low temperature (4K). We demonstrate that localized excitons have a longer emission time than free excitons, in the range of tens of picoseconds or more, and we show that it depends strongly on the disorder parameter and dielectric environment. Finally, in order to prove the validity of our model we compare it to available experimental results of the literature.Comment: arXiv admin note: text overlap with arXiv:1409.3996 by other author

Accounting for localized deformation: a simple computation of true stress in micropillar compression experiments

Compression experiments are widely used to study the mechanical properties of materials at micro- and nanoscale. However, the conventional engineering stress measurement method used in these experiments neglects to account for the alterations in the material's shape during loading. This can lead to inaccurate stress values and potentially misleading conclusions about the material's mechanical behavior especially in the case of localized deformation. To address this issue, we present a method for calculating true stress in cases of localized plastic deformation commonly encountered in experimental settings: (i) a single band and (ii) two bands oriented in arbitrary directions with respect to the vertical axis of the pillar (either in the same or opposite directions). Our simple analytic formulas can be applied to homogeneous and isotropic materials and crystals, requiring only standard data (displacement-force curve, aspect ratio, shear band angle and elastic strain limit) obtained from experimental results and eliminating the need for finite element computations. Our approach provides a more precise interpretation of experimental results and can serve as a valuable and simple tool in material design and characterization.Comment: arXiv admin note: text overlap with arXiv:2012.1278

Effect of Piezoelectric Filed on the Optical Properties of (311) A and (311) B Oriented InAlAs/InP Heterostructures

InAlAs alloy was grown by MOCVD on an InP (311) substrate with different polarities. Measurements of photoluminescence (PL) and photoreflectance (PR) were performed to study the impact of the V/III flux ratio. It is discovered that the PL line was shifted to a greater energy side with the increasing excitation power density, and no saturation was observed of its related PL intensity. It is a fingerprint of type II transition emission. However, the recombination of the type II interface showed a powerful dependence on AsH3 overpressure and substrate polarity. In fact, we have noted an opposite behavior of type II energy transition shift from A to B polarity substrate in respect to V/III ratio variation. PR signals corresponding to Franz-Keldysh Oscillation (FKO) were observed. The analysis of their period has allowed one to assess the value of the PZ field in the samples. PL-luminescence measurements were performed out as a function of temperature. PL peak energy, PL intensity, and half maximum full width show anomalous behaviors. Indicating the existence of localized carriers, they were ascribed to the energy potential modulation associated with the indium cluster formation and PZ field

Gold octahedra nanoparticles (Au_0.03 and Au_0.045): Synthesis and impact on marine clams Ruditapes decussatus

The increased use of gold nanoparticles (AuNPs) in several applications has led to a rise in concerns about their potential toxicity to aquatic organisms. In addition, toxicity of nanoparticles to aquatic organisms is related to their physical and chemical properties. In the present study, we synthesize two forms of gold octahedra nanoparticles (Au_0.03 and Au_0.045) in 1.3-propandiol with polyvinyl-pyrrolidone K30 (PVPK30) as capping agent using polyol process. Shape, size and optical properties of the particles could be tuned by changing the molar ratio of PVP K30 to metal salts. The anisotropy in nanoparticles shape shows strong localized surface plasmon resonance (SPR) in the near infrared region of the electromagnetic spectrum. Environmental impact of Oct-AuNPs was determined in the marine bivalve, Ruditapes decussatus exposed to different concentrations of Au_0.03 and Au_0.045. The dynamic light scattering showed the stability and resistance of Au_0.03 and Au_0.045 in the natural seawater. No significant modification in vg-like proteins, MDA level and enzymatic activities were observed in treated clams with Au_0.03 even at high concentration. In contrast, Au_0.045 induced superoxide dismutase (SOD), catalase (CAT), glutathione transferase (GST) activities, in a concentration dependent manner indicating defense against oxidative stress. Enhanced lipid peroxidation represented by malondialdehyde content confirmed oxidative stress of Au_0.045 at high concentration. These results highlight the importance of the physical form of nanomaterials on their interactions with marine organisms and provide a useful guideline for future use of Oct-AuNPs. In addition, Vitellogenin is shown not to be an appropriate biomarker for Oct-AuNPs contamination even at high concentration. We further show that Oct-AuNPs exhibit an important antioxidant response without inducing estrogenic disruption

Caracterisation et purification de molecules apparentees a la gastrine/cholecystokinine chez une Annelide Polychete, Nereis diversicolor

SIGLEINIST T 73251 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

The Influence of the Calcination Time on Synthesis of Nanomaterials with Small Size, High Crystalline Nature and Photocatalytic Activity in the TiO2 Nanoparticles Calcined at 500 °C

The development of new materials with diverse applications that fit well in the context of the current economy, where energy issues abound, is paramount. The goal of this study was to generate materials with high photocatalytic properties, at low cost and with less energy, and without health and ecological risks. Such materials would allow for a form of sustainable development that respects nature. This study investigated the influence of calcination time on titanium dioxide nanoparticles (TiO2 NPs) produced by green synthesis using Aloe vera leaf extract under a constant temperature of 500 °C. The interaction between synthesis conditions like calcination time and the size of nanoparticles produced in relation to changes in photocatalytic activity were analyzed and discussed. The results showed that when calcination was increased at 500 °C, the synthesis of small-diameter nanoparticles was promoted. TiO2 were 23 ± 2 nm (D1) and 83 ± 5 nm (D2) after 5 h and 1 h of calcination, respectively. Moreover, the calcination duration promoted an increase in crystalline nature. In the same way, the level of reduction of azo dye Remazol Red Brilliant F3B (RR180) increased when calcination time increased, and therefore, changed the optic and photo-catalytic properties of the TiO2 nanomaterial. In addition, TiO2 nanopowders (size 23 ± 2 nm) had the higher efficiency in photodegradation (100%) of dye RR180 under visible light irradiation for 60 min for up to one hour duration, but TiO2 NPs (83 ± 5 nm) had the higher efficiency (100%) for up to two hours duration