High surface area nickel aluminate spinels prepared by a sol–gel method

The oxide spinel NiAl₂O₄ and spinel-type solid solutions Al₂O₃–NiAl₂O₄ (at Ni/Al=1:4, and Ni/Al=1:8) were prepared by controlled hydrolysis of mixed metal alkoxides, followed by calcination of the resulting gels. Powder X-ray diffraction showed that all samples prepared were single phase cubic materials having the spinel-type structure. The cubic lattice parameter, a_o, was found to decrease gradually with increasing aluminium content of the mixed metal oxides. The specific surface area (determined by nitrogen adsorption at 77 K) was found to be in the range of 200–300 m² g⁻¹. The materials were found to be basically mesoporous, the most frequent pore radius being in the range 3.2–6.4 nm. IR spectroscopy of CO adsorbed at liquid nitrogen temperature gave a main band at 2186–2195 cm⁻¹, which was assigned to the C---O stretching vibration of surface Al³⁺CO adducts where coordinatively unsaturated Al³⁺ ions act as Lewis acid centres.     

Inhibitory effects of lupene-derived pentacyclic triterpenoids from Bursera simaruba on HSV-1 and HSV-2 in vitro replication

The cytotoxicity and antiviral properties of Bursera simaruba against herpes simplex viruses (HSV-1 and HSV-2) were investigated through a bioactivity-guided isolation protocol. The plant material was fractionated using solvent-solvent partitioning, size-exclusion and thin-layer chromatography. The antiviral compounds present in the most active fractions were identified by means of LC-MS and NMR. Three different methods were compared during the evaluation of antiviral activity of samples. Four lupene-related pentacyclic triterpenes were found to be responsible for the anti-herpesvirus effects of B. simaruba and were isolated from this species for the first time. The selective indexes (SI) of B. simaruba-derived samples ranged from 7.7 to 201.9.     

3‐Formyl‐BODIPY Phenylhydrazone as a Chromo‐Fluorogenic Probe for Selective Detection of NO2 (g)

A new colorimetric and fluorogenic probe, based on a 3‐formyl boron dipyrromethene (BODIPY) phenylhydrazone, for the sensitive and selective detection NO₂ (g) has been prepared. The probe in solution experiences a remarkable hypsochromic shift of its absorption and fluorescence emission bands in the presence gaseous NO₂ (g), leading to limits of detection of few ppb. The probe also works in the solid phase, adsorbed on filter paper strips, or chemically immobilized on the surface of silica nanoparticles, with limits of detection to the naked eye of about 0.5 ppm.     

Calmness of the Argmin Mapping in Linear Semi-Infinite Optimization

This paper characterizes the calmness property of the argmin mapping in the framework of linear semi-infinite optimization problems under canonical perturbations; i.e., continuous perturbations of the right-hand side of the constraints (inequalities) together with perturbations of the objective function coefficient vector. This characterization is new for semi-infinite problems without requiring uniqueness of minimizers. For ordinary (finitely constrained) linear programs, the calmness of the argmin mapping always holds, since its graph is piecewise polyhedral (as a consequence of a classical result by Robinson). Moreover, the so-called isolated calmness (corresponding to the case of unique optimal solution for the nominal problem) has been previously characterized. As a key tool in this paper, we appeal to a certain supremum function associated with our nominal problem, not involving problems in a neighborhood, which is related to (sub)level sets. The main result establishes that, under Slater constraint qualification, perturbations of the objective function are negligible when characterizing the calmness of the argmin mapping. This result also states that the calmness of the argmin mapping is equivalent to the calmness of the level set mapping.     

New supramolecular liquid crystals induced by hydrogen bonding between pyridyl‐1,2,4‐oxadiazole derivatives and 2,5‐thiophene dicarboxylic acid

Supramolecular liquid crystalline complexes were obtained from binary mixtures of 3‐(4‐pyridyl)‐5‐(4‐n‐alkoxy)phenyl‐1,2,4‐oxadiazoles and 2,5‐thiophene dicarboxylic acid. Although the oxadiazole derivatives and the dicarboxylic acid are non‐mesomorphic, the H‐bonded complexes exhibit mesomorphism. Their liquid crystalline properties were investigated by differential scanning calorimetry and polarizing optical microscopy. The complexes exhibit enantiotropic nematic phases. A structural study involving AM1 semi‐empirical calculations is also described.     

Symmetric esters derived from 1,3,4-oxadiazole: synthesis,mesomorphic properties and structural study by semi-empirical calculations

Three homologous series of symmetric esters derived from 2-alkylthio-5-(p -hydroxy)phenyl-1,3,4-oxadiazole (series 3, 4 and 5) were synthesized and their liquid crystalline properties investigated by optical microscopy and differential scanning calorimetry. Depending on the chain length, nematic and smectic C phases were observed in the series 3 ; smectic A and smectic C phases in series 4. None of the homologues of series 5 shows mesomorphic properties. These three series are compared with other previously reported oxadiazoles. A structural study of AM1 semi-empirical calculations is also described.     

Synthesis and Characterization of Phenylene‐bis‐pyrazolones and Nitrosation Derivatives

Phenylene bis‐pyrazolone derivatives were obtained by condensation of two aromatic β‐diketo diesters with methyl‐, 2‐hydroxyethyl‐ and phenylhydrazines. The pyrazolone rings are connected to the central benzene ring by their C‐3 , leaving C‐4 free for further derivatization. Thus, and despite their low solubility, these compounds were successfully nitrosated in good yield providing new chelating dioximes.     

New approach to the Positron equation by means of the algebraic structure of the ideals

Starting from the electron Lagrangian density and expanding it with a more general idempotent than the one used by Hestenes, we achieve to show how the algebraic structure of the ideals draws a distinction between electrons and positrons without any need of the charge conjugation. A remarkable fact, consequence of the formalism used, is evidenced by the magnetization density discriminating the sign of the charge of the particles involved.