Stability Studies of Agrifood Reference Materials Under Different Conditions of Storage by Near-Infrared Spectroscopy

Reference materials (RM) play an increasingly important role for laboratories. The aim of this work is to compare different conditions of storage and assess the stability of agrifood external reference materials (ERM). These materials could be used as tools by laboratories notably for their quality control procedure. However, as the other RM, their stability must be assessed during stability studies. The determination of the limiting date of stability (LDS), defined as the period during which analytes called marker of stability are still considered as stable, is used on this purpose. The influences of the environmental factor were tested by the application of full experimental designs with two tested environmental factors: the temperature (storage at +4 °C or +20 ± 10 °C) and the composition of the atmosphere (absence or presence of gases in the packaging). Thus, the setting under vacuum increases clearly the stability for the studied analyte. Almost all ERM stored in the best conditions have a determined LDS higher than those stored in current condition of storage. Indeed, the bread wheat ERM LDS is higher than the current storage of 24 months     

3D Printing of a Thermo‐ and Solvatochromic Composite Material Based on a Cu(II)–Thymine Coordination Polymer with Moisture Sensing Capabilities

This work presents the fabrication of 3D‐printed composite objects based on copper(II) 1D coordination polymer ( CP1 ) decorated with thymine along its chains with potential utility as an environmental humidity sensor and as a water sensor in organic solvents. This new composite object has a remarkable sensitivity, ranging from 0.3% to 4% of water in organic solvents. The sensing capacity is related to the structural transformation due to the loss of water molecules that CP1 undergoes with temperature or by solvent molecules' competition, which induces significant change in color simultaneously. The CP1 and 3D printed materials are stable in air over 1 year and also at biological pHs (5–7), therefore suggesting potential applications as robust colorimetric sensors. These results open the door to generate a family of new 3D printed materials based on the integration of multifunctional coordination polymers with organic polymers.     

Variable‐temperature IR spectroscopic studies of CO adsorbed on Na‐ZSM‐5 and Na‐Y zeolites

CO interacts with extraframework alkali metal cations (M⁺=) of zeolites to form both M⁺CO and M⁺OC species. By using variabletemperature FTIR spectroscopy, these Cbonded and Obonded species were found to be in a temperaturedependent equilibrium. For the same cation, the difference in interaction energy depends upon the zeolite framework. Thus, for the equilibrium process ZNa⁺=CO ZNa⁺OC, where Z represents the zeolite framework, H ⁰ was found to take the values 3.8 and 2.4 kJ mol^– for CO/NaZSM5 and CO/NaY, respectively. The Cbonded species show always the highest cation–CO interaction energy.     

Coherence and localization in AC-driven quantum dots

We investigate the effects of an AC field on the dynamics of interacting electrons in quantum dots (QDs). We first consider a double QD containing two electrons. By mapping the system to an effective lattice model and employing Floquet theory we analyze the dynamics of the two-electron wavefunctions in the singlet space. This system presents a richer phenomenology than the case of a single electron in a double QD, displaying two distinct regimes of behaviour depending on whether the applied field strength or the inter-electron Coulomb repulsion is dominant. We then study the dynamics of two electrons in a 2D square QD in the limit of very low density, where the Coulomb interaction causes the electrons to become highly localized, forming a ‘Wigner molecule’. Using the same techniques we investigate how the AC field drives the dynamics of the Wigner states, and show how the parameters of the effective model may be measured in experiment.     

Prediction of the thermal conductivity of liquids and liquid mixtures including crude oil fractions

A new method based on the Effective Carbon Number is presented for the prediction of the thermal conductivity of liquids and liquid mixtures. The Effective Carbon Number for each substance of interest can be calculated from its thermal conductivity at a reduced temperature of 0.6. The thermal conductivities of isoalkanes, cycloalkanes, aro-matics, alkanes, carboxylic acids, ketones, esters and aldehydes over a range of temperatures were predicted using this method and the results were compared with experimental values. The thermal conductivities of defined mixtures were also predicted using a quadratic mixing rule for the Effective Carbon Number. Lastly, the thermal conductivities of undefined mixtures such as crude oil fractions were calculated by treating each fraction as a single pseudocompo-nent. In all cases studied, calculated results compared favorably with experimental values.     

Simple estimation of PV modules loss resistances for low error modelling

For practical purposes it can be assumed that the power delivered by a photovoltaic generator that is connected to an MPPT is always maximal. When studying the behaviour of a PV generator working in this way, the most interesting aspect is the evolution of the point of maximum power. So, the analysis of the I-V characteristic must be centred in the area of high voltages. In this situation the five parameter model is very appropriate for characterizing the PV generator.On the other hand, in the case of photovoltaic modules the information currently provided by manufacturers is insufficient to do modelling. Thus, to evaluate the loss resistances it is necessary to use any of the different methods that currently exist.The purpose of this paper is to present a new procedure, based on simplified equations, which allows the estimation of the loss resistances of any PV crystalline silicon module. By simulating the modules with the loss resistances calculated in this way highly accurate results are obtained. Especially in the surrounding of the maximum power point the error is always less than 0.5%.