Intersection Matrices Revisited

Several intersection matrices of s‐subsets versus k‐subsets of a v‐set are introduced in the literature. We study these matrices systematically through counting arguments and generating function techniques. A number of new or known identities appear as natural consequences of this viewpoint; especially, use of the derivative operator and some related operators reveals some connections between intersection matrices and the “combinatorics of creation‐annihilation.” As application, the eigenvalues of several intersection matrices including some generalizations of the adjacency matrices of the Johnson scheme are derived; two new bases for the Bose–Mesner algebra of the Johnson scheme are introduced and the associated intersection numbers are obtained as well. Finally, we determine the rank of some intersection matrices. © 2012 Wiley Periodicals, Inc. J. Combin. Designs 20: 383–397, 2012     

Linear frequency-doubling in dual Mid-IR-wavelength quantum cascade laser active region

In this paper we have proposed a novel quantum cascade laser active region design to obtain a dual-mid-IR-wavelength laser which is capable of frequency-doubling (13.77–6.88 μm) without utilizing nonlinear processes in two coupled shallow and deep quantum well structures. Optimized design of the active region leads to higher dipole matrix elements and thus higher laser performances. This method can be used to design laser structures with different frequency ratios.     

A palladium complex immobilized onto mesoporous silica: a highly efficient and reusable catalytic system for carbon–carbon bond formation and anilines synthesis

A palladium complex supported on functionalized mesoporous silica MCM-41 proved to be a highly efficient, recoverable catalyst for C–C coupling reactions and amination of aryl halides to afford anilines. The nanocatalyst was characterized by FT-IR spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, N₂ adsorption–desorption isotherms and inductively coupled plasma analysis. The catalyst could be reused for several consecutive runs without significant loss of activity. The excellent yields of products, simple reaction procedures and short reaction times are the main advantages of this methodology.     

Solving Conic Systems via Projection and Rescaling

Mathematical Programming - We propose a simple projection and rescaling algorithm to solve the feasibility problem $$\begin{aligned} \text { find } x \in L \cap \Omega , \end{aligned}$$ where L and...     

Asymmetric synthesis of chiral oxindoles using isatin as starting material

Asymmetric synthesis plays an important role in the synthesis of therapeutics and natural products. Asymmetric oxindoles with a stereogenic quaternary carbon center are extensively present in various natural products and biologically active compounds. Several methods such as employing chiral auxiliaries or chiral catalysts were developed for asymmetric synthesis of spirooxindoles or 3,3-disubtituted oxindoles. In this review, we make a detailed overview of the latest developments in the use of isatin as starting material for the asymmetric synthesis of spirooxindoles and 3,3-disubstituted oxindoles during the period from 2015 to 2017.     

Boehmite silica sulfuric acid: as a new acidic material and reusable heterogeneous nanocatalyst for the various organic oxidation reactions

In this research, project boehmite silica sulfuric acid (Boehmite-SSA) has been applied as new acidic porous catalyst for the selective oxidation of sulfides to sulfoxides and oxidative coupling of thiols to corresponding disulfides using hydrogen peroxide as oxidizing agent. The products have been obtained in short reaction times and high yields. Boehmite nanoparticles was prepared, coated by silica and then reacted with chlorosulfuric acid to obtain Boehmite-SSA. This catalyst was characterized by FT-IR, TGA/DTA, XRD, TEM, SEM, EDS and BET techniques. BET curve of boehmite nanoparticles identified as a typical type IV isotherm (definition by IUPAC), which are the characteristics of mesoporous material. Nitrogen adsorption/desorption measurement indicated that boehmite nanoparticles had BET surface area of about 122.8 m²/g. The catalyst was easily separated and reused for the several runs without significant loss of its catalytic efficiency.     

Oxo‐vanadium(IV) Schiff base complex supported on modified MCM‐41: a reusable and efficient catalyst for the oxidation of sulfides and oxidative S–S coupling of thiols

Oxo‐vanadium(IV) Schiff base complex supported on MCM‐41 as an organic–inorganic hybrid heterogeneous catalyst was synthesized with post‐grafting of MCM‐41 with 3‐aminoropropyltrimethoxysilane and subsequent reaction with 3,4‐dihydroxybenzaldehyde and then complexation with oxo‐vanadium acetylacetonate salt. The catalyst was analysed using a series of characterization techniques such as Fourier transform infrared spectroscopy, small‐angle X‐ray diffraction, nitrogen absorption isotherm, transmission electron microscopy and thermogravimetric analysis. The data collected provided evidence that the vanadium complex was anchored onto MCM‐41. High catalytic activity of this catalyst was observed in the oxidation of various sulfides and thiols (into sulfoxides and disulfides, respectively) with urea hydrogen peroxide as oxidant in high to excellent yields and selectivity under mild conditions. The heterogeneous catalyst could be recovered easily and reused several times without significant loss in catalytic activity and selectivity. Copyright © 2015 John Wiley & Sons, Ltd.     

Conformational Behaviors of 2-Substituted Cyclohexanone Oximes: An AB Initio,Hybrid Dft Study,and NBO Interpretation

Abstract

The impacts of the generalized anomeric effect (GAE) and gauche effect (GE) associated with donor–acceptor electron delocalizations and dipole–dipole interactions on the conformational properties of 2-methoxy- (1), 2-methylthio- (2), 2-methylseleno- (3), 2-fluoro- (4), 2-chloro- (5), and 2-bromocyclohexanone oxime (6) have been studied by means of hybrid density functional theory (B3LYP/6–311+G**) and ab initio molecular orbital (HF/6–311+G**)-based methods and natural bond orbital (NBO) interpretation. Both methods used showed that the above compounds exist predominantly in the axial chair conformation and the axial conformation stability increased from 2-methoxy- (1) to 2-methylselenocyclohexanone oxime (3) and also from 2-fluoro- (4) to 2-bromocyclohexanone oxime (6). The NBO analysis showed that the GAE increases from compound 1 to compound 3 and also from compound 4 to compound 6. GE does not have significant impact on the conformational behaviors of compounds 1–6 and GAE succeeds in accounting qualitatively for the increase of the axial preferences in both series of compounds.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: Table S1.

Supporting Information Available. The structures optimized and thermodynamic functions of the axial and equatorial conformations of compounds 1–6. This material is available free of charge via the Internet.     

Stereoselective synthesis of thiaerythrinanes based on an α-amidoalkylation/RCM approach

Parham cyclisation-intermolecular α-amidoalkylation and nucleophilic addition-intramolecular α-amidoalkylation sequences constitute diastereocomplementary routes to 1,10b-cis and trans thiazolo[4,3-a]isoquinolinones. These thiazolidinediones, that incorporate allyl groups at C-1 and C-10b, are efficient precursors of thiaerythrinanes by ring-closing metathesis reactions.     

Biodistribution and toxicity assessment of radiolabeled and DMSA coated ferrite nanoparticles in mice

DMSA-coated Fe₃O₄ nanoparticles were synthesized by wet-chemical method. The chemical interaction between Fe₃O₄ and DMSA were investigated by FTIR. They were directly radiolabeled with ^99mTc radioisotope (Fe₃O₄@DMSA–^99mTc) at room temperature in the presence of stannous solution as a reducing agent. Magnetic and structure properties of Fe₃O₄@DMSA–^99mTc nanoparticles were investigated by AGFM, TEM, and XRD. Biodistribution and toxicity assessment of Fe₃O₄@DMSA–^99mTc were studied in mice by intravenous and intraperitoneally injections, respectively. Blood, kidney, and liver factors were measured 4 days post injection and at the mean-while tissue sections were prepared from their kidney and liver. The results indicate that, the Fe₃O₄@DMSA–^99mTc nanoparticles were passed through the membrane of different cells but do not create any disorder in the kidney and liver function even in high doses such as 300 mg/kg.