Binary Accelerated Particle Swarm Algorithm (BAPSA) for discrete optimization problems

The majority of Combinatorial Optimization Problems (COPs) are defined in the discrete space. Hence, proposing an efficient algorithm to solve the problems has become an attractive subject in recent years. In this paper, a meta-heuristic algorithm based on Binary Particle Swarm Algorithm (BPSO) and the governing Newtonian motion laws, so-called Binary Accelerated Particle Swarm Algorithm (BAPSA) is offered for discrete search spaces. The method is presented in two global and local topologies and evaluated on the 0–1 Multidimensional Knapsack Problem (MKP) as a famous problem in the class of COPs and NP-hard problems. Besides, the results are compared with BPSO for both global and local topologies as well as Genetic Algorithm (GA). We applied three methods of Penalty Function (PF) technique, Check-and-Drop (CD) and Improved Check-and-Repair Operator (ICRO) algorithms to solve the problem of infeasible solutions in the 0–1 MKP. Experimental results show that the proposed methods have better performance than BPSO and GA especially when ICRO algorithm is applied to convert infeasible solutions to feasible ones.     

Hierarchical organization of ferrocene-peptides

Hierarchical self-assembly of disubstituted ferrocene (Fc)-peptide conjugates that possess Gly-Val-Phe and Gly-Val-Phe-Phe peptide substituents leads to the formation of nano- and micro-sized assemblies. Hydrogen-bonding and hydrophobic interactions provide directionality to the assembly patterns. The self-assembling behavior of these compounds was studied in solution by using (1)H?NMR and circular dichroism (CD) spectroscopies. In the solid state, attenuated total reflectance (ATR) FTIR spectroscopy, single-crystal X-ray diffraction (XRD), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM) methods were used. Spontaneous self-assembly of Fc-peptides through intra- and intermolecular hydrogen-bonding interactions induces supramolecular assemblies, which further associate and give rise to fibers, large fibrous crystals, and twisted ropes. In the case of Fc[CO-Gly-Val-Phe-OMe](2) (1), molecules initially interact to form pleated sheets that undergo association into long fibers that form bundles and rectangular crystalline cuboids. Molecular offsets and defects, such as screw dislocations and solvent effects that occur during crystal growth, induce the formation of helical arrangements, ultimately leading to large twisted ropes. By contrast, the Fc-tetrapeptide conjugate Fc[CO-Gly-Val-Phe-Phe-OMe](2) (2) forms a network of nanofibers at the supramolecular level, presumably due to the additional hydrogen-bonding and hydrophobic interactions that stem from the additional Phe residues.     

Two polymorphs of tetraethylammonium [hydrogen tris(3,5‐dimethylpyrazolyl)borato]di‐μ2‐sulfido‐disulfido(η2‐tetrasulfido)ditungsten(V) with Z′ = 1 and 2

Two polymorphs of the title compound, (C₈H₂₀N)[W₂S₄(S₄)(C₁₅H₂₂BN₆)], have been obtained unexpectedly by attempted recrystallization of a mixed‐metal–sulfur cluster complex from different solvents. The dinuclear complex anion contains W^V in two different coordination environments, one of them distorted octahedral with a tris(pyrazolyl)borate anion, a terminal sulfide and two bridging sulfide ligands, the other distorted square‐pyramidal with a terminal sulfide, two bridging sulfide and a chelating tetrasulfide ligand. The three independent anions in the two polymorphs have essentially the same geometry. The central W₂S₂ ring is a slightly folded rhombus with acute angles at the S atoms, and the WS₄ chelate ring is an envelope with one noncoordinating S atom as the flap. The second polymorph, with Z′ = 2 and pseudo‐inversion symmetry relating the anions of the asymmetric unit, also displays pseudo‐translation features in its layer structure, and all examined crystals were found to be twinned, possibly as a consequence of this structural feature.     

A Facile Synthesis of 2‐Imino‐4‐methylene‐1,3‐dithiolanes

A one‐pot synthesis of 2‐imino‐4‐methylidene‐1,3‐dithiolanes via a three‐component reaction of propargyl bromide (=3‐bromoprop‐1‐yne), primary amines, and carbon disulfide (CS₂) is described.     

Extraction of aflatoxins from food samples using graphene‐based magnetic nanosorbents followed by high‐performance liquid chromatography: A simple solution to overcome the problems of immunoaffinity columns

In this research, magnetic graphene nanoparticles were prepared and used as adsorbents for preconcentrating the aflatoxins in rice, wheat, and sesame samples. For this purpose, graphene was synthesized by Hummer's method. Magnetically modified graphene formed by the deposition of magnetite (Fe₃O₄) on graphene was used for the separation of aflatoxins B₁, B₂, G₁, and G₂ from the samples. The extractants were subsequently analyzed with high‐performance liquid chromatography and fluorescence detection. Parameters affecting the efficiency of the method were thoroughly investigated. The measurements were done under the optimized conditions. For aflatoxins B₁, B₂, G₁, and G₂, limits of detection were 0.025, 0.05, 0.05, and 0.075 ng/g and limits of quantification were 0.083, 0.16, 0.16, and 0.23 ng/g, respectively. Accuracy was examined by the determination of the relative recovery of the aflatoxins. The relative recovery of aflatoxins B₁, B₂, G₁, and G₂ were quite satisfactory (between 64.38 and 122.21% for food samples). Relative standard deviations for within laboratory repeatability (n = 6) were in the range from 1.3 to 3.2. The application of this sorbent for the separation and concentration of the mentioned aflatoxins from food samples was examined.     

ZnO nanoparticles catalyzed efficient one-pot three-component synthesis of 2,3-disubstituted quinalolin-4(1H)-ones under solvent-free conditions

ZnO nanoparticles were prepared and applied as a favorable catalyst in three-component one-pot cyclocondensation reaction of isatoic anhydride with amines and aldehydes to afford the corresponding 2,3-disubstituted quinalolin-4(1H)-ones in good yields. Reactions occurred under solvent-free conditions in high atom economy.     

Synthesis and structural characterization of copper–molybdenum–sulfur and copper–tungsten–sulfur cluster complexes (n-Bu4N)[OMS3Cu3Br2L2] with heterocyclic thiones as ligands

Reaction of (NH₄)₂[WOS₃] or (NH₄)₂[MoO₂S₂], n-Bu₄NBr, CuCl and Imt in acetone solvent afforded air- and moisture-stable clusters (n-Bu₄N)[MOS₃Cu₃(Imt)₂Br₂] (M = W or Mo, Imt = imidazolidine-2-thione). These compounds have been characterized by IR, UV–Vis, ¹H and ¹³C NMR spectra and single-crystal X-ray diffraction. They are crystallographically isostructural, with Imt and [MOS₃]²⁻ acting as monodentate and bidentate S-donor ligands, respectively. In the anions, the three Cu atoms have different coordination environments, one being distorted tetrahedral with Imt and Br as terminal ligands, the other two being approximately trigonal planar with Imt as a terminal ligand for one and Br as a terminal ligand for the other. W and Mo have approximately tetrahedral coordination geometry, with a terminal O and three triply-bridging S atoms. The NH groups of the Imt ligands serve as donors in intramolecular N–H?Br and in intermolecular N–H?Br and N–H?O hydrogen bonds, linking the anions to form layers with the cations in cavities.