A new and efficient one-pot synthesis of 2-hydroxy-1,4-dihydrobenzoxazines via a three-component Petasis reaction

The secondary amines synthesized by the reaction between 2-aminophenols and aromatic aldehydes, via the reduction of the corresponding imines, were employed in the synthesis of new 2-hydroxy-2H-1,4-benzoxazine derivatives through a one-pot Petasis multicomponent reaction in good to excellent yields.     

A taxonomy of multicast data origin authentication: Issues and solutions

Multicasting is an efficient communication mechanism for group-oriented applications such as videoconferencing, broadcasting stock quotes, interactive group games, and video on demand. The lack of security obstructs a large deployment of this efficient communication model. This limitation motivated a host of research works that have addressed the many issues relating to securing the multicast, such as confidentiality, authentication, non-repudiation, integrity, and access control. Many applications, such as broadcasting stock quotes and video-conferencing, require data origin authentication of the received traffic. Hence, data origin authentication is an important component in the multicast security architecture. Multicast data origin authentication must take into consideration the scalability and the efficiency of the underlying cryptographic schemes and mechanisms, because multicast groups can be very large and the exchanged data is likely to be heavy in volume (streaming). Besides, multicast data origin authentication must be robust enough against packet loss because most multicast multimedia applications do not use reliable packet delivery. Therefore, multicast data origin authentication is subject to many concurrent and competitive challenges, when considering these miscellaneous application-level requirements and features. In this article we review and classify recent works dealing with the data origin authentication problem in group communication, and we discuss and compare them with respect to some relevant performance criteria.     

Structural,electronic, optical and thermodynamic properties of NaxRb1−xH and NaxK1−xH alloys

A theoretical study of the structural, electronic, optical and thermodynamic properties of Na_xRb_1?xH and Na_xK_1?xH ternary alloys in NaCl phase has been carried out using the first-principles method. We modeled the alloys at some selected compositions with ordered structures described in terms of periodically repeated supercells. The dependences on the composition of the lattice constant, band gap, dielectric constant, refractive index, Debye temperature, mixing entropy and heat capacities were analyzed for x=0, 0.25, 0.50, 0.75 and 1. The lattice constants of Na_xRb_1?xH and Na_xK_1?xH exhibit a marginal deviation from Vegard's law. A strong deviation of the bulk modulus from linear concentration dependence was observed for both alloys. We found that the composition dependence of the energy band gap is highly non linear and the large bowing coefficient for Na_xRb_1?xH is sensitive to the composition. Using the approach of Zunger and co-workers, the microscopic origins of the gap bowing were detailed and explained. The thermodynamic stability of these alloys was investigated by calculating the phase diagram. The thermal effect on some macroscopic properties was investigated using the quasi-harmonic Debye model. There is a good agreement between our results and the available experimental data for the binary compounds, which is a support for those of the ternary alloys that we report for the first time.     

Radiation and Resonant Frequency of Superconducting Annular Ring Microstrip Antenna on Uniaxial Anisotropic Media

In this work, the full-wave method is used for computing the resonant frequency, the bandwidth, and radiation pattern of High temperature superconductor, or an imperfectly conducting annular ring microstrip, which is printed on uniaxial anisotropic substrate. Galerkin’s method is used in the resolution of the electric field integral equation. The TM set of modes issued from the cavity model theory are used to expand the unknown currents on the patch. Numerical results concerning the effect of the anisotropic substrates on the antenna performance are presented and discussed. It is found that microstrip superconducting could give high efficiency with high gain in millimeter wavelengths. Results are compared with previously published data and are found to be in good agreement.     

Delamination and Wrinkling of Flexible Conductive Polymer Thin Films

Polymer based conductive and transparent thin films are an important class of functional materials at the heart of flexible organic electronic devices. These flexible films are prone to degradation and to mechanical instability leading to the formation of blisters, wrinkles, and cracks. This is detrimental to their use especially in the case of multilayer devices. Here, it is shown that a simple water or solvent drop deposited on such films gives rise to a buckling instability and the formation of several folds due to the tendency of these films to swell in contact with the solvent. A phase diagram of the instability portraying its domain of existence, and thus the means to inhibit it, is proposed. By depositing drops on such films and observing the instability, material parameters such as the elastic modulus of the thin films or their energy of adhesion to the substrate can be estimated reliably. Further, the instability can be harnessed to pattern surfaces at low cost giving rise to percolated and more conductive pathways in the conductive polymer films under scrutiny.     

An efficient one-step synthesis of 1,4-dihydropyridines via a triphenylphosphine-catalyzed three-component Hantzsch reaction under mild conditions

An efficient one-step synthesis of 1,4-dihydropyridines in good to excellent yields via the triphenylphosphine-catalyzed Hantzsch three-component reaction of an aromatic aldehyde, ethyl acetoacetate and ammonium acetate is described.     

In Situ Synthesis and Characterization of Nano ZnO on Wool: Influence of Nano Photo Reactor on Wool Properties

This study has been carried out to synthesize nano ZnO on wool fabric and also to investigate influences of nano photo reactors on wool fabric characteristics. Zinc acetate has been used as a precursor and the synthesis process has been done in water and water/ethanol media. The treated wool fabrics were heated at 80°C for 10 h to dehydrate Zn(OH)₂ obtaining ZnO. The fabric samples were then subjected to daylight for 7 days to examine the influence of nano ZnO photo reactor on the fabric properties. SEM images revealed the embedding of ZnO nanoparticles on the fabrics and X‐ray diffraction verified the nanoparticles composition. The Yellowness Index (YI) of the fabrics was measured with Color Eye XTH that has been reduced with increasing pH, Zn(CH₃COO)₂ concentration, ethanol and heating. The lower water contact angle and time of water absorption confirmed higher hydrophilic properties of the treated fabrics. Interestingly, a higher tensile strength obtained on the wool fabrics proved the interaction of ZnO with protein chains of wool, which was verified through lower alkali solubility of treated fabric with nano ZnO and confirmed more benefits of the in situ synthesis process.     

A silver nanoparticles-catalyzed efficient three-component synthesis of polysubstituted 4H-chromenylphosphonates and their antioxidant activity

Abstract

A simple and efficient protocol for one-pot three-component synthesis of structurally diverse dialkyl 2-amino-3-cyano-4H-chromen-4-ylphosphonates from the condensation of salicylaldehydes, malononitrile, and trialkyl phosphite using silver nanoparticles as catalyst in ethanol at reflux has been developed. Selected new compounds were evaluated for their antioxidant activity by free radical screening using 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. Among the compounds employed, 5a, 5?b, and 5?h showed promising DPPH radical scavenging activities compared to the experimental standards at low concentration (100?µg/mL) after 24?h incubation.