Effects of NaCl on growth and activity of enzymes involved in carbon metabolism in leaves of tobacco (Nicotiana rustica)

The adverse effects of salt should not be the same in tobacco plants exposed to a permanent and transient high concentration of NaCl in its environment. Experiments were conducted in order to verify the hypothesis of reversibility of NaCl effects. The study of this reversibility is checked by monitoring a number of parameters in pre-stressed plants and then, replaced in normal conditions. Plants previously grown for 30 days on basic medium were treated for 7 days with 200 mM NaCl and then placed back on the basic culture without NaCl for 10 days. The results show that NaCl suppression leads to a resumption of growth with a decrease in the concentration of sodium (Na+) and chloride ions (Cl-). Hence, potassium content (K+) increases gradually in the leaves to reach the level obtained with unstressed plants. At the same time, there is a stimulation of the activities of phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase isoenzymes (NAD, NADP, NADH and NADPH-MDH) and isocitrate dehydrogenase (ICDH) after NaCl had been removed. Along with the boosting of the activity of these enzymes involved in the process of carbon assimilation, there is a gradual decrease in soluble sugars content, suggesting a resumption of the normal activity of photosynthetic assimilation process. All these results verify our hypothesis and can be explained by the ability of the plant to dilute the effects of Na+ and Cl- during the recovering period. An important result of this study is that a transient salinity is not necessarily followed by a significant depreciation in product yield or quality.Keywords: Tobacco, NaCl, reversibility, phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (MDH), isocitrate dehydrogenase (ICDH

Structure de verres de silicophosphate dopés europium : analyse par spectroscopie optique et simulation de dynamique moléculaire

National audienc

Europium site symmetry in sol gel silicophosphate glass : FLN spectroscopy and Molecular Dynamics simulation

International audienc

Time resolved and temperature dependence of the radiative properties of thiol-capped CdS nanoparticles films

In this work, we present the temperature-dependence and time-resolved photoluminescence (PL) of CdS nanoparticles capped independently with three different ligands thiophenol, thioglycerol, and l-cysteine over a broad temperature range from 10 to 300 K. The respective nanoparticles sizes in the three systems studied in this work are 1.5, 4, and 2 nm as determined from X-ray diffraction (XRD). From the analysis of AFM images, it was found that the lateral particle sizes of capped CdS nanoparticles are greater than those deduced from XRD or optical absorption measurements. The aim of this study is the investigation of the impact of the organic ligands on the radiative recombination dynamics in organically capped CdS nanoparticles. From the PL study and based on the temperature-dependence and time-resolved emission spectroscopy, we conclude that the emission of CdS QDs film originates from recombination of the delocalized carriers in the internal core states with a small contribution of the localized carriers at the interface. The PL decay reveals a biexponential behavior for the entire three samples at all temperatures. One of the two exponential components decays rapidly with a time τ(1) in the range 0.5–0.8 ns, whereas the other decays much more slowly, with a time τ(2) in the range 1–3 ns. The weak activation energy (32–37 meV) deduced from the temperature dependence of the PL intensity suggests the involvement of shallow traps. The analysis of the experimental results reveals a relatively narrow size distribution, an efficient surface passivation, and a satisfactory thermal stability of CdS nanocrystals

Optical and structural properties of Eu3+ doped silicophosphate glasses

National audienc

Examining parking choices of connected and autonomous vehicles

Raising parking charges is a measure that restricts the use of private vehicles. With the introduction of connected and autonomous vehicles (CAVs), the demand for parking has the potential to reduce as CAVs may not park at ‘pay to park’ areas as they are able to “cruise” or return home. However, it might not be financially feasible for them to return to their origin if the destination region is far away. Therefore, the question is: how could we develop parking policies in the CAVs era? To determine the best parking strategy for CAVs, four scenarios were tested in this paper: (i) enter and park within the destination area, (ii) enter, drop off, and return to the origin, (iii) enter, drop off, and return to outside parking and (iv) enter and drive around. Since real-world parking demand data for CAVs are not available, a simulation model of the road network in Santander (Spain) was employed to collect data on both CAV operations (e.g., conservative versus aggressive behaviors) and parking choices. Multinomial logistic regression model was used to identify the best parking option for CAVs. Performance indicators such as traffic, emissions, and safety were employed to compare the performance of a range of parking alternatives. It was found that the balanced scenario (i.e., combination of all parking choices) performs better with the greatest change in delay (around 32%). With 100% CAV market penetration, traffic crashes were reduced by 67%. This study will help local authorities formulate parking policies so that CAVs can park efficiently

Effect of CdS nanocrystals on the photoluminescence of Eu3+-doped silicophosphate sol gel glass

In this work, we investigate the effect of co-doping with CdS nanoparticles on the photoluminescence properties of Eu3+ doped silicophosphate glass prepared via the sol gel method. Infrared spectroscopy (FTIR) revealed the insertion of phosphorus within the silicate network. XRD and TEM analyses revealed the presence of CdS nanoparticles dispersed in the glass matrix. Based on the optical study and the effective mass theory for spherical quantum dots, it was found that CdS nanocrystals have a gap of nearly 3.53 eV and a size of 2.42 nm. The enhancement of Eu3+ emission induced by CdS nanocrystals and thermal annealing was assigned to either an energy transfer via defect states or structural alteration of the glass network around the rare earth ions

Investigation of the local environment of Eu3+ in a silicophosphate glass using site-selective spectroscopy and Molecular Dynamics simulations

Silicophosphate glasses (SiO2-P2O5) doped with Eu3+ ions were synthesized by the sol-gel process. Optical properties of these glasses were investigated by means of emission spectra and lifetime measurements. The Fluorescence Line Narrowing (FLN) technique was also used to explore the local structure around the Eu3+ ions in this host and to understand the role of phosphate as a codopant. As it is the case for aluminum, the ability of phosphate to avoid the rare earth clustering was investigated, and the role of this codopant in modifying the local order around the rare earth ion was evidenced. The analysis of the FLN spectra and lifetime measurements is consistent with this interpretation. Molecular Dynamics simulations were performed to evaluate and confirm these structural features. Two classes of europium sites were distinguished in agreement with the experimental characterization