The synthesis of functionalized pyranophenalenones

Abstract  Protonation of the highly reactive 1:1 intermediate produced in the reaction between alkyl or aryl isocyanides and electron-deficient acetylenic esters with 3-hydroxy-1H-phenalene-1-one leads to a vinylisonitrilium cation, which undergoes an addition reaction with the conjugate base of the 3-hydroxy-1H-phenalene-1-one to produce biologically interesting dialkyl 10-(alkyl or arylamino)-7-oxo-7H,8H-naphtho[1,8-gh]chromene-8,9-dicarboxylates in moderate to fairly good yields at room temperature. Graphical abstract        

Theoretical study on thermal behavior of passively Q-switched microchip Nd:YAG laser

This study deals with the thermal characterization of a continuous wave (CW-) and end-pumped passively Q-switched microchip Nd:YAG laser crystal by solving the rate and heat transfer equations in the laser cavity. In this approach, a parametric study has been performed to investigate the influence of the pumping parameters, cooling metal dimension and also the crystal dimension and doping concentration on the thermal behavior of the laser crystal. Obtained results reveal a closed correlation between the mentioned parameters and the thermal behavior of the crystal indicating that a proper selection of the laser parameters is essential to control the crystal's temperature and improve the performance of the laser accordingly.     

Transient bioelectronics: Electronic properties of silver microparticle‐based circuits on polymeric substrates subjected to mechanical load

Transient soft bioelectronics are capable of forming conformal contacts with curvilinear surfaces of biological host tissues and organs. Such systems are often subject to continuous static and dynamic loads from the biological host. In this article, we present investigation of electronic attributes of transient soft bioelectronic circuits subjected to mechanical force and influence of substrate's transiency on the transiency of the whole device; also, characterize and quantify loss of functionality in triggered devices. Variations in the electrical conductivity of circuits as a function of applied mechanical load was used as a means to deduce electronic characteristics under stress. The experimental results suggest that there exists a correlation between electronic properties of circuits and applied mechanical strain; no clear correlation was, however, observed between electronic properties of circuits and frequency of the applied dynamic load. Control over transiency rate of identical circuits utilizing the transiency characteristics of the poly(vinyl alcohol)l‐based substrates is also studied and demonstrated. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1603–1610     

Highly efficient oxidative cleavage of alkenes and cyanosilylation of aldehydes catalysed by magnetically recoverable MIL‐101

The catalytic activity of magnetically recoverable MIL‐101 was investigated in the oxidation of alkenes to carboxylic acids and cyanosilylation of aldehydes. MIL‐101 was treated with Fe₃O₄ and the prepared catalyst was characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, N₂ adsorption measurements, field emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and inductively coupled plasma analysis. The catalytic active sites in this heterogeneous catalyst are Cr³⁺ nodes of the MIL‐101 framework. This heterogeneous catalyst has the advantages of excellent yields, short reaction times and reusability several times without significant decrease in its initial activity and stability in both oxidation and cyanosilylation reactions. Its magnetic property allows its easy separation using an external magnetic field.     

Highly efficient protection of alcohols and phenols catalysed by tin porphyrin supported on MIL‐101

The catalytic activity of 5,10,15,20‐tetrakis(4‐aminophenyl)porphyrinatotin(IV) trifluoromethanesulfonate, [Sn^IV(TNH₂PP)(OTf)₂], supported on chloromethylated MIL‐101, was investigated in the trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) and also their tetrahydropyranylation with 3,4‐dihydro‐2H‐pyran. Excellent yields, mild reaction conditions, short reaction times and reusability of the catalyst without significant decrease in its initial activity are noteworthy advantages of this supported catalyst. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of pulsed laser parameters on in-situ TiC synthesis in laser surface treatment

Commercial titanium sheets pre-coated with 300-μm thick graphite layer were treated by employing a pulsed Nd:YAG laser in order to enhance surface properties such as wear and erosion resistance. Laser in-situ alloying method produced a composite layer by melting the titanium substrate and dissolution of graphite in the melt pool. Correlations between pulsed laser parameters, microstructure and microhardness of the synthesized composite coatings were investigated. Effects of pulse duration and overlapping factor on the microstructure and hardness of the alloyed layer were deduced from Vickers micro-indentation tests, XRD, SEM and metallographic analyses of cross sections of the generated layer. Results show that the composite cladding layer was constituted with TiC intermetallic phase between the titanium matrix in particle and dendrite forms. The dendritic morphology of composite layer was changed to cellular grain structure by increasing laser pulse duration and irradiated energy. High values of the measured hardness indicate that deposited titanium carbide increases in the conditions with more pulse duration and low process speed. This occurs due to more dissolution of carbon into liquid Ti by heat input increasing and positive influence of the Marangoni flow in the melted zone.     

[Cu(bpdo)2·2H2O]2+-supported SBA-15 nanocatalyst for efficient one-pot synthesis of benzoxanthenone and benzochromene derivatives

A novel [Cu(bpdo)₂·2H₂O]²⁺-supported SBA-15 catalyst (bpdo = 2,2′-bipyridine,1,1′-dioxide) was prepared by the impregnation method. The catalyst was characterized by XRD, TEM, and BET nitrogen adsorption–desorption method, FT-IR, UV–vis, and chemical analysis. XRD patterns and TEM analysis of [Cu(bpdo)₂·2H₂O]²⁺/SBA-15 showed highly ordered hexagonal mesoporous silica, even after immobilization. Also, nitrogen adsorption–desorption isotherms exhibited type-IV isotherms and H1 hysteresis loops according to the IUPAC classification of mesoporous materials. This green support was tested for the synthesis of benzoxanthenone and benzochromene derivatives under solvent-free conditions, with high yield of products via a simple experimental and work-up procedure.     

Attack on Han et al.’s ID-based confirmer (undeniable) signature at ACM-EC’03

In ACM conference on electronic commerce (EC’03), Han et al. [Identity-based confirmer signatures from pairings over elliptic curves, in: Proceedings of ACM Conference on Electronic Commerce Citation 2003, San Diego, CA, USA, June 09–12, 2003, pp. 262–263] proposed an ID-based confirmer signature scheme using pairings (the scheme is in fact an ID-based undeniable signature scheme). In this paper, we show that this signature scheme is not secure and the signer can deny any signature, even if it is a valid signature, and any one can forge a valid confirmer signature of a signer with identity ID on an arbitrary message and confirm this signature to the verifier.     

The Dynamic Nature of CO Adlayers on Pt(111) Electrodes

CO adlayers on Pt(111) electrode surfaces are an important electrochemical system and of great relevance to electrocatalysis. The potential‐dependent structure and dynamics of these adlayers are complex and still controversial, especially in the CO pre‐oxidation regime. We here employ in situ high‐speed scanning tunneling microscopy for studying the surface phase behavior in CO‐saturated 0.1 m H₂SO₄ on the millisecond time scale. At potentials near the onset of CO pre‐oxidation local fluctuations in the (2×2)‐CO adlayer are observed, which increase towards more positive potentials. Above 0.20 V (vs. Ag/AgCl), this leads to an adlayer where CO_ad apparently reside on every top site, but still exhibit a (2×2) superstructure modulation. We interpret this observation as a dynamic effect, caused by a small number of highly mobile point defects in the (2×2)‐CO adlayer. As shown by density functional theory calculations, the CO lattice near such defects relaxes into a local (1×1) arrangement, which can rapidly propagate across the surface. This scenario, where a static (2×2) CO_ad sublattice coexists with a highly dynamic sublattice of partially occupied top sites, explains the pronounced CO_ad surface mobility during electrooxidation.