Synthesis and characterization of new polyamides derived from di(4-cyanophenyl)isosorbide

New optically active polyamides were synthesized according to two ways: using a microwave-assisted polycondensation of an optically active isosorbide-derived diacylchloride with different aromatic diamines in NMP and using interfacial polymerization from an isosorbide-derived diamine with different diacylchlorides. The polymers are obtained with inherent viscosities in the range from 0.11 to 1.05 dL/g. The DSC and TGA measurements clearly demonstrate the high thermal stability of these polymers when considering the range of the melting points from 200 °C to 300 °C and the absence of decomposition till 350 °C.     

Highly Luminescent Colloidal Eu3+‐Doped KZnF3 Nanoparticles for the Selective and Sensitive Detection of CuII Ions

This article describes a green synthetic approach to prepare water dispersible perovskite‐type Eu³⁺‐doped KZnF₃ nanoparticles, carried out using environmentally friendly microwave irradiation at low temperature (85 °C) with water as a solvent. Incorporation of Eu³⁺ ions into the KZnF₃ matrix is confirmed by strong red emission upon ultraviolet (UV) excitation of the nanoparticles. The nanoparticles are coated with poly(acrylic acid) (PAA), which enhances the dispersibility of the nanoparticles in hydrophilic solvents. The strong red emission from Eu³⁺ ions is selectively quenched upon addition of Cu^II ions, thus making the nanoparticles a potential Cu^II sensing material. This sensing ability is highly reversible by the addition of ethylenediaminetetraacetic acid (EDTA), with recovery of almost 90 % of the luminescence. If the nanoparticles are strongly attached to a positively charged surface, dipping the surface in a Cu^II solution leads to the quenching of Eu³⁺ luminescence, which can be recovered after dipping in an EDTA solution. This process can be repeated for more than five cycles with only a slight decrease in the sensing ability. In addition to sensing, the strong luminescence from Eu³⁺‐doped KZnF₃ nanoparticles could be used as a tool for bioimaging.     

Vibro-acoustic response of orthogonally stiffened panels: The effects of finite dimensions

This paper investigates the effects of finite dimensions on the vibro-acoustic response of orthogonally stiffened panels. Three types of excitations are considered: acoustical excitation, point force excitation and random excitation by a turbulent boundary layer. In each case, a spatially windowed periodic model is compared with a Rayleigh-Ritz model where the modes of the un-stiffened panel are used as the basis functions. The latter model accounts for the reflected wave field generated at the boundaries by assuming that the panel is simply supported. On the contrary, the windowed periodic model only accounts for finiteness on sound radiation (the assumption of an infinite periodic structure is used to calculate the panel response). Numerical studies show that when the bending wavelength becomes comparable or smaller than the stiffener spacing, the periodic model is able to reproduce the results obtained with the Rayleigh-Ritz model. To complement the study, the developed models are compared with numerical simulations (finite element method) and with experimental results.     

A Nitrite Electrochemical Sensor Based on Boron‐Doped Diamond Planar Electrochemical Microcells Modified with a Monolacunary Silicotungstate Polyoxoanion

A new boron doped diamond microcells (BDD) was modified, for rapid, selective and highly sensitive determination of nitrite, using a coating film of polyoxometalates (POMs), formed by cyclic voltammetry on the molecular p‐phenylenediamine (PPD) functionalized BDD. The scanning electron microscopy (SEM) technique was used to examine the morphology of (PPD/SiW₁₁) modified (BDD) electrode. It was found that (SiW₁₁) layer was uniformly formed on the electrode surface. It was observed that (BDD/PPD/SiW₁₁) showed excellent electrocatalytic activities towards nitrite ion. Under the selected conditions, the anodic peak maximum at ?0.6 V was linear versus nitrite concentration in the 40 µM–4 mM range, and the detection limit obtained was 20 µM. The newly developed electrode has been successfully applied to the determination of nitrite content in real river water samples.     

Microwave-assisted polycondensation of aliphatic diols of isosorbide with aliphatic disulphonylesters via phase-transfer catalysis

Numerous polycondensations of aliphatic diol of isosorbide and 1,8-dimesyloctane or other aliphatic dibromo and disulphonated alkylating agent was performed under phase-transfer catalytic conditions. In order to check the possible specific non-thermal microwave (MW) effects, reactions were comparatively performed inside a thermostated oil bath (Δ) under similar conditions. The reactions conditions were varied to optimize both, the fraction insoluble in methanol (FP MeOH) and the molecular weight of polyethers. In all cases, it was found that microwave-assisted polycondensations proceeded more efficiently compared with conventional heating (the reaction time was reduced from 24 h to 30 min: ratio 1/50). The polycondensation under microwave yields 63% of polyethers precipitating in methanol with relatively high average-weight molecular weights (M_w up to approximately 7000). The polyethers were characterized by NMR (¹H, ¹³C) and FT-IR spectroscopy and SEC measurement and MALDI-TOF mass spectrometry.     

Intégrales orbitales sur les algèbres de Lie réductives

Sans résuméOblatum 28-I-1992 & 13-VII-1992     

Antifungal activity and phytochemical screening of extracts from Phoenix dactylifera L. cultivars

In this study, the rachis extracts of eight date palm Phoenix dactylifera L. cultivars were analysed by phytochemical screening and bioautography on Fusarium oxysporum f. sp. albedinis (Foa). The choice of cultivars was based on their reaction to Foa (resistant, tolerant and sensitive). Phytochemical screening was realised for flavonoids, tannins, alkaloids and coumarins. Antifungal effects were mostly represented by dichloromethanic extracts (seven out of nine inhibition zones). The best results were represented by the dichloromethanic extract of the cultivar 'Bent-Cherk' rachis (6.50?±?1.41?mm) and the ethyl acetate extract of the cultivar 'Rotbi' rachis (6.00?±?1.41?mm). The date palm cultivars presented some similarities concerning phytochemical screening results related to their resistance or sensibility to Foa. From the correlation between phytochemical screening and bioautography, it was observed that the majority of bioactive compounds against Foa seem to be polyphenols. Thus, the natural defence mechanism in vivo against Foa is probably related to the action of polyphenols. The difference between resistant, tolerant and sensitive cultivars is related to their mechanism of action.     

Dynamic and acoustic response of bidirectionally stiffened plates with eccentric stiffeners subject to airborne and structure-borne excitations

An analytical method based on the modal expansion technique was developed to predict the vibro-acoustic response of both unidirectionally and bidirectionally stiffened flat panel. This paper presents the response to diffuse acoustic field (DAF) and turbulent boundary layer (TBL) excitations in terms of their joint acceptance. Numerical results for the dynamic and acoustic responses are compared with finite element method (FEM) and boundary element (BEM) results for stiffened panel with complex and eccentrically shaped stiffeners subject to point force excitation. A theoretical prediction of the transmission loss (TL) is also compared with laboratory measurements conducted on flat panels representing aircraft models as well as with hybrid statistical energy analysis (SEA)-FEM periodic model. The results confirm that the stiffened panel has the same acoustic response as the skin without stiffeners at frequencies where the structural wavelengths are equal to the spacing between the stiffeners. In addition, the transmission loss is lowered by the presence of the stiffeners at some particular region of frequencies below the critical frequency with respect to the unstiffened panel.     

Combined static electromagnetic radiation and plant extract contribute to the biosynthesis of instable nanosilver responsible for the growth of microstructures

The instant biosynthesis of silver nanoparticles under static electromagnetic induction, its antibacterial activity and its post exposure monitoring were reported here. A mix of silver nitrate solution and Ruta chalepensis leaf extract was irradiated by a static electromagnetic field (SMF) of 200 mT. The characteristics and stability of the biosynthesized silver nanoparticles (Ag NPs) were determined. Compared to the non-irradiated exposure, the morphology and state of the obtained material change once the exposition to SMF is turned off. Shifting from 453 to 473 nm, the percentage of the needles shaped silver nanoparticles increased and continue to win and dominate the biomixture toward the spherical silver nanoparticles. TEM microscopy showed a wide range of silver materials designed in different nanoscale morphology and beyond where they undergo major changes affecting mainly the size, shape and form (dispersity) of nanosilver.     

Electrochemical Capacitive K+ EMIS Chemical Sensor Based on the Dibromoaza[7]helicene as an Ionophore for Potassium Ions Detection

A K⁺‐sensitive capacitive electrolyte‐membrane‐insulator‐semiconductor (EMIS) based on a novel dibromoaza[7]helicene ionophore has been developed. An ion‐sensitive membrane based on polyvinylchloride (PVC) doped with the ionophore was deposited on the Si₃N₄/SiO₂/Si‐p/Cu‐Al transducer. The properties of the K⁺‐EMIS chemical sensor were investigated by electrochemical impedance spectroscopy (EIS). All the developed devices upon being tested have shown good sensitivity and linearity responses within the range 10^?6 M to 10^?1 M of potassium activity, with good selectivity over a wide variety of other cations (Na⁺, Li⁺, Cu²⁺, Ca²⁺, and Mg²⁺). To our knowledge, this is the first time that a capacitive field‐effect sensor has been fabricated using helicene as a carrier for K⁺‐detection, combined with the structure: Si₃N₄/SiO₂/Si‐p/Cu‐Al as a transducer.