One‐pot synthesis of primary 1‐aminophosphonates: Coupling reaction of carbonyl compounds,hexamethyldisilazane, and diethyl phosphite catalyzed by Al(OTf)3

Al(OTf)₃ has been utilized as a new and efficient catalyst for the selective synthesis of primary 1‐aminophosphonates by a one‐pot coupling reaction of various types of aldehydes/ketones, hexamethyldisilazane, and diethyl phosphite under solvent‐free conditions. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:109–115, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20517     

Experimental and computational study on the aqueous acidity constants of some new aminobenzoic acid compounds

The acidity constants of three new aminobenzoic acid derivatives were determined using potentiometric and spectrophotometric methods in 0.10 M aqueous potassium nitrate solution as supporting electrolyte. The potentiometric data and UV–Vis absorption spectra of solutions were recorded in the course of their pH-metric titration with a standard base solution. The protolytic equilibrium constants, concentration distribution diagrams and number of components involved have been calculated. The relative pK_a values for three acids were also calculated using ab initio quantum mechanical method at the HF/6-31G** level of theory in combination with CPCM continuum solvation method. The influence of substituents on the ionization constants of the studied molecular structures was investigated. The satisfactory agreement between the experimentally derived and theoretically calculated pK_a values provides solid support for the acid–base reactions proposed in this work.     

Tungstate sulfuric acid: preparation, characterization, and application in catalytic synthesis of novel benzimidazoles

Tungstate sulfuric acid (TSA) was prepared, characterized, and applied for direct synthesis of novel and known benzimidazoles through a condensation reaction of o-phenylenediamines with orthoesters under solvent-free conditions. TSA was characterized by powdered X-ray diffraction (XRD), X-ray fluorescence (XRF), and FTIR spectroscopy. This novel and eco-friendly method is very cheap and has many advantages such as excellent yields, recyclable and eco-friendly catalyst, and simple work-up procedure.     

Four‐component synthesis of disubstituted 1,3,4‐oxadiazole derivatives from cinnamaldehyde,an aromatic carboxylic acid,a secondary amine,and N‐isocyaniminotriphenylphosphorane

The iminium intermediate generated by the reaction between a secondary amine and cinnamaldehyde was reacted with N‐isocyanimino‐triphenylphosphorane in the presence of benzoic acid derivatives to form the corresponding iminophosphorane intermediate, whose intramolecular aza‐Wittig reaction led to disubstituted 1,3,4‐oxadiazole derivatives. The syntheses were completed under neutral conditions at room temperature to give excellent yields. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:315–321, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21013     

Free radical scavenging, antimicrobial and immunomodulatory activities of Orthosiphon stamineus

Orthosiphon stamineus is considered an important traditional folk medicine. In this study ethanol and aqueous extracts of O. stamineus were evaluated in vitro for their antioxidant, antimicrobial as well as for their immunomodulatory properties on human peripheral blood mononuclear cells (PBMCs). The DPPH radical scavenging method was used for the determination of antioxidant activity, while the antibacterial efficacy was investigated by both disc diffusion method and Minimum Inhibitory Concentration (MIC) against four bacterial strains (Gram-positive and Gram-negative). Furthermore, the immunomodulatory potential of the extracts was investigated through the MTT assay. Aqueous extract of O. stamineus exhibited significant free radical scavenging activity with IC?? 50 9.6 μg/mL, whereas the IC?? for the ethanol extract was 21.4 μg/mL. The best antimicrobial activity was shown by the aqueous extract of O. stamineus against Staphylococcus aureus, with inhibition zone of 10.5 mm and MIC value 1.56 mg/mL. Moreover, the results observed from the MTT assay showed that both plant extracts stimulated the PBMCs proliferation in vitro in a concentration-dependent manner, but the aqueous extract has remarkable activity against PBMCs. These findings indicate that O. stamineus showed high antioxidant activity and may be considered as an immunomodulatory agent.     

Extremal polyomino chains with respect to Zagreb indices

For a molecular graph, the first Zagreb index M₁ is equal to the sum of squares of the vertex degrees and second Zagreb index M₂ is equal to the sum of products of degree of pairs of adjacent vertices. In this paper, Zagreb indices of polyomino chains are computed. Also the extremal polyomino chains with respect to Zagreb indices are determined.     

Gain enhancement in two-stream free electron laser with a planar wiggler and an axial guide magnetic field

The theory for a two-stream free electron laser (FEL) consisting of a relativistic electron beam transported along the axis of a planar wiggler in the presence of an axial guiding magnetic field is proposed and investigated. The electron trajectories and the small signal gain are derived. The characteristic of the linear gain and the normalized maximum gain are studied numerically. The result shows that the normalized maximum gain is considerably enhanced in comparison with that of the single stream. The effect of the difference between the energies of the two beams in this configuration of FEL is also considered, and we find that the gain is affected by the energy differences between groups 1 and 2.     

Synchronization of different-order chaotic systems: Adaptive active vs. optimal control

In this paper, an adaptive algorithm is proposed for synchronization of chaotic systems with different orders. A modular adaptive control strategy is applied to make states of the slave system track those of the master, despite the unknown parameters. One of the most advantages of the modularity approach, which is applied for the first time in chaos synchronization, is its flexibility in choosing identification and control modules and designing them completely independently. In this paper, a modified recursive least square algorithm is used to identify the unknown parameters of the slave system, and the control module is designed by means of two different algorithms. First it is designed based on active control method, and then, in order to synchronize with a lower energy, we design an optimal controller. The two methods are applied on a practical case study, and the results are compared. Two different dimensional neuron models, the HR neuron model and the cable model of cylindrical cell, are considered as the master and slave systems, respectively. Simulation results confirm the effectiveness of the proposed method.     

Condensation of an ideal gas with intermediate statistics on the horizon

We consider a boson gas on the stretched horizon of the Schwartzschild and Kerr black holes. It is shown that the gas is in a Bose?CEinstein condensed state with the Hawking temperature T _c =T _H if the particle number of the system be equal to the number of quantum bits of space-time $N \simeq{A}/{l_{p}^{2}}$ . Entropy of the gas is proportional to the area of the horizon (A) by construction. For a more realistic model of quantum degrees of freedom on the horizon, we should presumably consider interacting bosons (gravitons). An ideal gas with intermediate statistics could be considered as an effective theory for interacting bosons. This analysis shows that we may obtain a correct entropy just by a suitable choice of parameter in the intermediate statistics.