Synthesis of chiral linear and macrocyclic candidates: II. Synthesis and investigation of 3,5-bis-linear and macrocyclic tetrapeptide Schiff base pyridine derivatives

Russian Journal of General Chemistry - A series of several linear and macrocyclic tetrapeptide derivatives based on N α-dinicotinoyl-bis[L-leucyl-L-phenylalaninyl] acid hydrazide as starting...     

Topology optimization of periodic Mindlin plates

Periodic structures exhibit unique dynamic characteristics that make them act as tunable mechanical filters for wave propagation. As a result, waves can propagate along the periodic structures only within specific frequency bands called the ‘pass bands’ and wave propagation is completely blocked within other frequency bands called the ‘stop bands’ or ‘band gaps’. The spectral width of these bands can be optimized using topology optimization. In this paper, topology optimization is used to maximize the fundamental natural frequency of Mindlin plates while enforcing periodicity. A finite element model for Mindlin plates is presented and used along with an optimization algorithm that accounts for the periodicity constraint in order to determine the optimal topologies of plates with various periodic configurations. The obtained results demonstrate the effectiveness of the proposed design optimization approach in generating periodic plates with optimal natural frequency and wide stop bands. The presented approach can be invaluable design tool for many structures in order to control the wave propagation in an attempt to stop/confine the propagation of undesirable disturbances.     

Synthesis of some novel 2-thioxoimidazolidin-4-one substituted glycosyl hydrazone derivatives

Russian Journal of General Chemistry - A series of novel 2-thioxoimidazolidine glycosides were prepared via reaction of the key intermediate...     

Erratum to: “Synthesis and Reactions of Novel Fused 1-(8-Hydroxy-7-iodoquinoline-5-sulfonyl)- 1H-pyrazolo-[3,4-d]pyrimidine-3-carbonitrile Derivatives” [Russian Journal of General Chemistry 88 (3), 560–563 (2018)]

Russian Journal of General Chemistry - The project was financially supported by King Saud University, Vice Deanship of Research Chairs.     

Synthesis and biological activity of some amino-4'-substituted phenyl(pyridine)androst-4-en-3-one candidates

Russian Journal of General Chemistry - A series of substituted androstanopyridine derivatives 2–5 were synthesized using 17-acetyl-...     

Preparation and characterization of uniform particles of flufenamic acid and its calcium and barium salts

Uniform fully dispersed particles of flufenamic acid, a widely used anti-inflammatory drug, were prepared by two different methods. In the first one, the drug solution in organic solvents was added to a non-solvent (water or aqueous solutions of stabilizers); while in the second procedure the drug was precipitated by acidifying its basic aqueous solutions. In addition calcium and barium salts of uniform spherical particles were obtained by precipitation in aqueous basic solutions of the drug. These salts are supposed to improve the drug reactivity. The prepared dispersions of the drug and its salts were examined by scanning electron microscopy, X-ray diffractometry and electrophoresis.     

Synthesis of some thiopyrimidine and thiazolopyrimidines starting from 2,6-dibenzylidene-3-methylcyclohexanone and its antimicrobial activities

A series of novel N-substituted arylidene, pyrazole, thioxopyrimidine and thiazolopyrimidine derivatives 2–7 were synthesized by initial reactions of 2-methyl-cyclohexanone with aromatic aldehydes to give 2,6-dibenzylidene-3-methylcyclohexanone 2. Some of the synthesized compounds were tested as antimicrobial agents. The detailed synthesis, spectroscopic data, and antimicrobial activities of the synthesized compounds were reported.     

Adaptive selection of heuristics for improving exam timetables

This paper presents a hyper-heuristic approach which hybridises low-level heuristic moves to improve timetables. Exams which cause a soft-constraint violation in the timetable are ordered and rescheduled to produce a better timetable. It is observed that both the order in which exams are rescheduled and the heuristic moves used to reschedule the exams and improve the timetable affect the quality of the solution produced. After testing different combinations in a hybrid hyper-heuristic approach, the Kempe chain move heuristic and time-slot swapping heuristic proved to be the best heuristic moves to use in a hybridisation. Similarly, it was shown that ordering the exams using Saturation Degree and breaking any ties using Largest Weighted Degree produce the best results. Based on these observations, a methodology is developed to adaptively hybridise the Kempe chain move and timeslot swapping heuristics in two stages. In the first stage, random heuristic sequences are generated and automatically analysed. The heuristics repeated in the best sequences are fixed while the rest are kept empty. In the second stage, sequences are generated by randomly assigning heuristics to the empty positions in an attempt to find the best heuristic sequence. Finally, the generated sequences are applied to the problem. The approach is tested on the Toronto benchmark and the exam timetabling track of the second International Timetabling Competition, to evaluate its generality. The hyper-heuristic with low-level improvement heuristics approach was found to generalise well over the two different datasets and performed comparably to the state of the art approaches.     

Every DFS Tree of a 3‐Connected Graph Contains a Contractible Edge

Tutte proved that every 3‐connected graph G on more than 4 vertices contains a contractible edge. We strengthen this result by showing that every depth‐first‐search tree of G contains a contractible edge. Moreover, we show that every spanning tree of G contains a contractible edge if G is 3‐regular or if G does not contain two disjoint pairs of adjacent degree‐3 vertices.