Structure-Property Relationships in Benzofurazan Derivatives: A Combined Experimental and DFT/TD-DFT Investigation

In this work we seek to understand and to quantify the reactivity of benzofurazan derivatives toward secondary cyclic amines, like pyrrolidine, piperidine and morpholine, acting as nucleophile groups in SNAr reactions. For this aim, physico-chemical and structural descriptors were determined experimentally and theoretically using the DFT/B3LYP/6-31+ g (d,p) methodology. Thus, different 4-X-7-nitrobenzofurazans (X = OCH3, OC6H5 and Cl) and products corresponding to the electrophilic aromatic substitution by pyrrolidine, piperidine and morpholine, were investigated. Particularly, the HOMO and LUMO energy levels of the studied compounds, determined by Cyclic Voltammetry (CV) and DFT calculations, were used to evaluate the electrophilicity index (ω). The latter was exploited, according to Parr’s approach, to develop a relationship which rationalizes the kinetic data previously reported for the reactions of the 4-X-7-nitrobenzofurazans with nucleophiles cited above. Moreover, the Parr’s electrophilicity index (ω) of these benzofurazans determined in this work were combined with their electrophilicity parameters (E), reported in preceding papers, was found to predict the unknown electrophilicity parameters E of 4-piperidino, 4-morpholino and 4-pyrrolidino-7-nitrobenzofurazan. In addition, the relationship between the Parr’s electrophilicity index (ω) and Hammett constants σ, has been used as a good model to predict the electronic effect of the nucleophile groups. Finally, we will subsequently compare the electrophilicity index (ω) and the electrophilicity parameters (E) of these series of 7-X-4-nitrobenzofurazans with the calculated dipole moment (μ) in order to elucidate general relationships between E, ω and μ

Assessment of the validity of self-reported smoking status among schoolchildren in Sousse, Tunisia

Introduction: Tobacco use, which begins in adolescence and childhood and continues in later life, is the major avoidable risk for non-communicable diseases and death in the world. Self-reports have frequently been used to estimate smoking prevalence and health consequences. This study explores the validity of self-reports of smoking behavior among schoolchildren in Tunisia. Materials and methods: This study was conducted in March 2014 among a sample of 147 schoolchildren randomly selected. Data concerning the smoking habit were collected by a questionnaire designed for the purposes of this work. Then, exhaled CO, a biochemical marker of smoke exposure, was measured using piCO+ Smokerlyzer® breath CO monitor among participants. Sensitivity and specificity of self-reports were calculated. Results: The prevalence of reported smoking was 9.5% with 16.7% and 1.7% respectively among boys and girls. Their mean age was 14.5±1.28 years old. When considering 4 ppm as the cut-off level of breath CO, sensitivity and specificity of self-reports were 100% and 93.7%, respectively. But at a breath CO cut-off of 3 ppm, self-reporting was 62.5% sensitive and 93.5% specific. Conclusion: According to our findings, we suggest that self-reports can be considered as a good tool to be used with a reasonable confidence to assess the smoking status

Theoretical analyses of the carrier localization effect on the photoluminescence of In-rich InGaAs layer grown on InP

The free buffer InGaAs/InP structure has been elaborated by Metal Organic Vapor Phase Epitaxy (MOVPE). High indium content is chosen to reduce the bandgap energy of the ternary material with direct bandgap to be pro-moted for Infrared optoelectronic devices. In this work, the temperature dependent photoluminescence (TDPL) analysis of In-rich InxGa1_xAs (x = 0.65: S-1, x = 0.661: S-2, and x = 0.667 S-3) samples is of the central focus. The S-shaped behavior recorded at low temperature range in the III-V ternary is quantitatively studied herein by Localized State Ensemble (LSE) model. A comparison between the semi-empirical evolution of luminescence versus temperature and our numerical simulation proves the adequacy of computational details, used in LSE model, in well reproducing the S-shape feature. The numerical simulation well matched with PL spectra proving that the localization phenomenon is stronger when increasing the Indium mole fraction. The clustering effect in In-rich structure seems to be beneficial for enhancing the carrier localization within InxGa1_xAs by localizing carriers from away extended defects that behave probably as non-radiative centers. This is indicative of the utmost importance of localization phenomenon in trapping carriers within localized states instead of dislocations and defects, owing to clustering of indium atoms

Optical and structural properties of In-rich InxGa1−xAs epitaxial layers on (1 0 0) InP for SWIR detectors

International audienceIn-rich InxGa1−xAs epitaxial layers were grown on InP (1 0 0) substrates by a metalorganic vapor phase epitaxy (MOVPE) technique. The effect of Indium (In) composition on the crystalline quality and optical properties are investigated. High resolution X-ray diffraction (HR-XRD) measurement and Raman scattering spectrum are used to evaluate the crystalline quality, the residual strain and dislocation density property. The number of dislocations in the epitaxial layers is found to increase by increasing the Indium content in order to release the stresses due to the epitaxial clamping. Photoluminescence (PL) measurement is used to characterize the optical properties. At 10 K, PL measurements show that the InGaAs band gap redshifts with the indium content. Moreover, the asymmetry at the low-energy side of the PL peak has been attributed to the presence of localized excitons. In all samples, a blue shift of PL peaks is evidenced by increasing the excitation power density, which is in line with the presence of carrier’s localization and non-idealities in this system. Moreover, the temperature-dependence of the PL peak energy displays an unusual red-blue-red shift (S-shaped) behavior when raising the temperature. These observations can be related to the inhomogeneous distribution of indium which gives rise to the appearance of dislocations and other defects which serve as traps for charge carriers. Interestingly, those highly In-content InxGa1−xAs epitaxial layers show PL emission located between 1637 and 1811 nm (depending on In content) and thus might be suitable for in the design of novel heterostructure devices such as short wave infrared (SWIR) detectors

Structural, vibrational and optical properties of a new organic–inorganic material: (C 5 H 8 N 3 ) 2 [BiCl 5 ]

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A blockchain-based security system with light cryptography for user authentication security

International audienceNowadays, the Internet of Things (IoT) enables the creation of a wide range of new services, including smart cities, agriculture, energy, technology, healthcare, and other security concerns. Safety concerns currently limit the development of this advanced technology. On the other hand, traditional security protocols and existing solutions cannot be used for IoT because most of them cannot guarantee good performance. Furthermore, they are often severely limited in terms of storage, computing power, and performance. The aim of the proposed research is to introduce a secure verification framework for user authentication, with a special focus on the communication between access points and node databases. The main goal is to increase the level of security within the proposed approach, ensuring the confidentiality, integrity, and availability of the image verification system during the authentication process. To achieve this goal, three phases were implemented. First, a new hybrid biometric pattern is proposed that merges image and password features to enhance the security of user authentication. Second, lightweight Encryption and Blockchain technologies are also utilized to ensure secure communication of patterns between the access point and the node database. Finally, in order to verify authenticity, a new proposed matching process involves comparing image and password features with the database records. The experimental analysis has been carried out in terms of accuracy, False Rejection Rate (FRR), False Acceptance Rate (FAR), and error rate. The proposed approach attained an accuracy of 98%, FAR of 0.1, FRR of 0.992, and an error rate of 0.017

Sea-blue histiocytes syndrome: Case report and review of literature

Partant de la constatation qu’aucune tentative n’a été faite pour expliquer l’absence d’une historiographie officielle sous les Mongols de la Horde d’or, en termes d’histoire culturelle, l’auteur tente de replacer le développement de l’historiographie dans l’empire mongol et dans les États qui lui ont succédé dans un cadre global. Le texte le plus ancien de l’historiographique mongole, l’« Histoire secrète des Mongols », pour lequel l’auteur donne deux dates possibles, 1228 ou 1240 (il faut r..

Challenges and results of a school-based intervention to manage excess weight among school children in Tunisia 2012-2014

Obesity is a serious health issue and predisposes individuals to an increased risk of morbidity and mortality. Its prevalence in children has increased worldwide