Slotted microcavity ring resonators for optical storage applications

In this paper, slotted microcavity ring resonators based optical storage devices are proposed and analyzed by means of multiresolution time domain technique. The effect of the structure geometrical parameters on the coupling efficiency, normalized transmission spectra and quality factor has been thoroughly investigated and compared to that of the conventional no-slot microring resonator. The suggested slotted configurations increase the quality factor at a fixed gap size between the central ring and input/output waveguides. In addition, the desired compromise between the coupling efficiency and resonance effect inside the ring can be achieved by mere optimization of the slot geometrical characteristics.     

Spectral approximation in L(H)

We introduce the concept of numerical range approximant which is related to that of a spectral approximant. We obtain a variant of Bouldin result on spectral approximation of normal operators [3] and an analogous result for numerical range approximation . We also extend Maher's result on partially isometric approximation [9] and Halmos' on positive approximation [6].     

Simultaneous Determination of Naproxen and Diflunisal using Synchronous Luminescence Spectrometry

Binary mixtures of naproxen and diflunisal can be resolved by using zero-crossing first derivative emission spectrofluorimetry, first derivative constant wavelength synchronous luminescence spectrometry and first derivative constant energy synchronous luminescence spectrometry. These methods do not require any previous separation steps. The lowest quantitation limits for both drugs were obtained with first derivative constant wavelength synchronous luminescence spectrometry (0.002 and 0.015 μg ml⁻¹ for naproxen and diflunisal, respectively). The measurements were performed in 40% methanolic aqueous medium at pH 8.0 provided by adding 0.02 M phosphate buffer solution. The proposed methods were successfully applied to the simultaneous determination of naproxen and diflunisal in pharmaceuticals and human serum samples with high precision and accuracy. Linearity, accuracy, precision, limits of detection, limits of quantitation, and other aspects of analytical validation are included in the text.     

Graphene to graphite; a layer by layer experimental measurements and density function theory calculations of electric conductivity

ABSTRACT

We measured the electric conductivity of large (25?×?50?mm) graphene films as a function of number of layers in the range of 1–20 layers. We also calculated the energy gap for such samples using density function theory. Our results showed a conductivity slightly above that of ITO for monolayer graphene and an exponential decrease as the number of graphene layers increased. Both experimental and simulation results showed a convergence of graphene into graphite at as little as 18–20 layers.     

One-pot synthesis,spectroscopic characterization and DFT study of novel 8-azacoumarin derivatives as eco-friendly insecticidal agents

A series of sixteen 8-azacoumarin derivatives bearing aryl moieties at C-5 and C-7 was designed and synthesized by a concise and facile procedure utilizing grinding and ultrasound approaches. The efficient multi-component protocols proceeded smoothly and in the absence of solvent to furnish the target products in moderate to good yields. All the synthesized molecules were characterized via ¹HNMR, ¹³CNMR, IR, mass spectra, and elemental analyses. The density functional theory (DFT) was then used to discover the structural and electronic characteristics of such compounds. Finally, an insecticidal study against Plutella xylostella and Helicoverpa armigera on the synthesized compounds is reported. The bioassay results indicated that some of the tested compounds showed potency ranging from good to moderate. In particular, analogs 6i and 6l, among the tested compounds, showed even more potency than commercial chlorpyrifos. On the other hand, the rest of the tested compounds showed moderate to weak activities.     

Arylhydrazonals as the aldehyde component in Baylis-Hillman reactions

Arylhydrazonals were added to acrylonitrile or methyl vinyl ketone in the presence of DABCO or benzotriazole to yield the intermediate Baylis-Hillman adduct that cyclized under the reaction conditions with water elimination to yield dihydropyridazines. A pyridazine reacted with DMAD to yield a pyridine via a [4+2] Diels-Alder addition followed by retro Diels-Alder elimination of methylene aniline. Two pyridazines were condensed with DMFDMA to yield the corresponding enaminones that reacted with NH₂NH₂ to afford the pyrazolylpyridazines.     

Gas‐phase thermolysis of benzotriazole derivatives. Part 4. Pyrolysis of 1‐acylbenzotriazole phenylhydrazones. Interesting direct routes towards N‐aminobenzimidazoles

Flash vacuum pyrolysis (FVP) of 1‐acylbenzotriazole phenylhydrazones gave benzonitriles, aniline and 2‐arylbenzimidazole derivatives. Static pyrolysis of the same substrates at 180 °C gave exclusively the corresponding N‐anilino‐2‐arylbenzimidazole derivatives. Pyrolysis of the isomeric 2‐acylbenzotriazole phenylhydrazones gave similar products.     

Glucose-based surfactants with hydrogenated, fluorinated, or hemifluorinated tails: synthesis and comparative physical-chemical characterization

(Hemi)fluorinated hydrophobic chains have been found to minimize the denaturating propensity of surfactants toward membrane proteins. The work reported herein deals with the synthesis of a new series of non-ionic glucose-based surfactants endowed with a hybrid hemifluorocarbon chain. The convergent synthesis is based on a one-pot reduction/alkylation of hemifluorinated thioacetate and glucosylated trishydroxymethyl acrylamidomethane using NaBH4 in methanol. This "mild" alkylation was studied in order to improve yields and to pass up the use of an excess of commercially unavailable hemifluorinated thiols. The physical-chemical properties in aqueous solution of this novel series were studied by surface tension measurement and dynamic light scattering (DLS), as well as their behavior upon reverse-phase chromatography, and were compared with those of their hydrogenated and perfluorinated analogues. The atypical effect of the additional ethyl tip to the fluorinated chain was demonstrated by higher critical micellar concentration values and abnormal hydrophobicities measured by reverse-phase chromatography. Moreover, according to Israelachvili's concept, DLS studies showed that surfactants bearing bulkier polar head self-assemble into small and well-defined aggregates, suggesting the formation of spherical micelles rather than the cylindrical ones usually observed with classical fluorinated surfactants.     

Electrode Materials for Desalination of Water via Capacitive Deionization

Recent years have seen the emergence of capacitive deionization (CDI) as a promising desalination technique for converting sea and wastewater into potable water, due to its energy efficiency and eco-friendly nature. However, its low salt removal capacity and parasitic reactions have limited its effectiveness. As a result, the development of porous carbon nanomaterials as electrode materials have been explored, while taking into account of material characteristics such as morphology, wettability, high conductivity, chemical robustness, cyclic stability, specific surface area, and ease of production. To tackle the parasitic reaction issue, membrane capacitive deionization (mCDI) was proposed which utilizes ion-exchange membranes coupled to the electrode. Fabrication techniques along with the experimental parameters used to evaluate the desalination performance of different materials are discussed in this review to provide an overview of improvements made for CDI and mCDI desalination purposes