Tetrachlorosilane-Zinc Chloride as a New Potent Binary Reagent for One-Pot,Three-Component Synthesis of Mannich-Type Products

A combination of tetrachlorosilane and zinc chloride in dichloromethane as an efficient and ambient binary reagent to promote a one-pot amidoalkylation reaction of enolizable ketones, aromatic aldehydes with acetonitriles, or benzonitrile have been developed. The newly synthesized β-acetamidoketones 3 and β-benzamidoketones 5 were obtained in good yields.     

The Effect of Lateral Guiding Mechanism on Noise Characteristics in Semiconductor Lasers

A comparison between intensity noise spectra and also the line shapes of gain-guided, weakly-index-guided, and strongly-index-guided semiconductor lasers are made using numerical solution of Maxwell-Bloch equations including spontaneous emission noise.     

Analysis of MPN, MHN and Phase Noise of a Two-Mode Semiconductor Laser

Intensity noise including Mode Partition Noise (MPN) and Mode Hopping Noise (MHN), and Phase/Frequency Noise Spectrum (FNS) are calculated for a two-mode semiconductor laser. RIN is derived considering of MPN and MHN effect.     

Essential Norm of Weighted Composition Operators From $$H^\infty $$ H ∞ to nth Weighted Type Spaces

Mediterranean Journal of Mathematics - This work is concerned with the existence and uniqueness of positive solutions to a nonlinear boundary value problem with fractional q-derivative:...     

Quasi-Armendariz rings relative to a monoid

For a monoid M, we introduce M-quasi-Armendariz rings which are a generalization of quasi-Armendariz rings, and investigate their properties. The M-quasi-Armendariz condition is a Morita invariant property. The class of M-quasi-Armendariz rings is closed under some kinds of upper triangular matrix rings. Every semiprime ring is M-quasi-Armendariz for any unique product monoid and any strictly totally ordered monoid M. Moreover, we study the relationship between the quasi-Baer property of a ring R and those of the monoid ring R[M]. Every quasi-Baer ring is M-quasi-Armendariz for any unique product monoid and any strictly totally ordered monoid M.     

Ultra trace level square wave anodic stripping voltammetric sensing of mercury(II) ions in environmental samples using a Schiff base-modified carbon paste electrode

ABSTRACT

In this approach, a new carbon paste electrode modified with N,N′-bis(5-bromo-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine Schiff base ligand (L) was synthesised for selective and effective determination of Hg²⁺ ions in aqueous environmental samples using cyclic and square wave anodic stripping voltammetric methods. First, the selective detection of mercury ion was confirmed by evaluating the stability constants of metal complexes formed between the Schiff base ligand (L) and some desired cations by conductometric measurements. Afterwards, by preparing an effective carbon paste electrode modified with L, the experimental and instrumental parameters affecting the performance of modified electrode were investigated. Square wave anodic stripping voltammograms were obtained after applying an accumulation potential ?0.5 V and accumulation time 150 s in Britton–Robinson buffer solution at pH 2.0. The optimal square wave parameters found are pulse amplitude 75 mV, frequency 50 Hz and step potential 6 mV. The procedure exhibited linear range from 0.4 to 120 μg L^?1 Hg²⁺ with a limit of detection of 0.042 μg L^?1. The proposed electrode was proved to be highly selective in the presence of various cations and anions and was successfully used for determination of mercury in tobacco and several water samples.     

A Novel Three Component Reaction: The Synthesis of Stable,Highly Functionalized 1,4-Diionic Nitrogen Betaines

The protonation of a highly reactive 1,4-dipole generated in the reaction between pyridine or isoquinoline and dialkyl acetylenedicarboxylates by the acidic C-H group of (ethoxycarbonylmethyl) triphenylphosphonium bromide leads to a vinyl pyridinium cation derivatives, which undergo a carbon-centered Michael type addition with the conjugate base of the CH-acid to produce highly functionalized stable 1,4-diionic nitrogen betaines.     

Biosynthesis of Fe3O4-magnetic nanoparticles using clover leaf aqueous extract: Green synthesis of 1,3-benzoxazole derivatives

In this research, magnetic Fe₃O₄-NP nanoparticles were synthesized employing a green biosynthetic procedure by reduction of ferric chloride solution with clover leaf water extract. The nanoparticles prepared via this biosynthesis method can potentially be valuable for different purposes such as organic synthesis. In this research, 1,3-benzoxazole derivatives were generated via a multicomponent reaction of α-bromo ketones, isothiocyanate, and propiolate in the presence of a catalytic amount of bio-Fe₃O₄ MNPs and sodium hydride in water at 50°C in good yields. The catalyst was reused five times with a minor decrease in its catalytic activity.     

Serial Femtosecond Zero Dose Crystallography Captures a Water-Free Distal Heme Site in a Dye-Decolorising Peroxidase to Reveal a Catalytic Role for an Arginine in FeIV=O Formation

Obtaining structures of intact redox states of metal centers derived from zero dose X-ray crystallography can advance our mechanistic understanding of metalloenzymes. In dye-decolorising heme peroxidases (DyPs), controversy exists regarding the mechanistic role of the distal heme residues aspartate and arginine in the heterolysis of peroxide to form the catalytic intermediate compound I (Fe^IV=O and a porphyrin cation radical). Using serial femtosecond X-ray crystallography (SFX), we have determined the pristine structures of the Fe^III and Fe^IV=O redox states of a B-type DyP. These structures reveal a water-free distal heme site that, together with the presence of an asparagine, imply the use of the distal arginine as a catalytic base. A combination of mutagenesis and kinetic studies corroborate such a role. Our SFX approach thus provides unique insight into how the distal heme site of DyPs can be tuned to select aspartate or arginine for the rate enhancement of peroxide heterolysis.