A Fast and Effective Algorithm for the Feedback Arc Set Problem

A divide-and-conquer approach for the feedback arc set is presented. The divide step is performed by solving a minimum bisection problem. Two strategies are used to solve minimum bisection problem: A heuristic based on the stochastic evolution methodology, and a heuristic based on dynamic clustering. Empirical results are presented to compare our method with other approaches. An algorithm to construct test cases for the feedback arc set problem with known optimal number of feedback arcs, is also presented.     

Reactions of 2‐amino‐3‐cyano‐4,5,6,7‐tetrahydrobenzo[b]thiophene and 2‐amino‐3‐cyano‐4,7‐diphenyl‐5‐methyl‐4H‐pyrano[2,3‐c] pyrazole with phenylisocyanate,carbon disulfide,and thiourea

2‐Amino‐3‐cyano‐4,5,6,7‐tetrahydrobenzo[b]thiophene 1a or 2‐amino‐3‐cyano‐4,7‐di‐ phenyl‐5‐methyl‐4H‐pyrano[2,3‐c]pyrazole 2a reacted with phenylisocyanate in dry pyridine to give 2‐(3‐phenylureido)‐3‐cyanobenzo[b]thiophene 1b or 2‐disubstituted amino‐3‐cyanopyranopyrazole 2b derivative. However, when 1a and 2a were refluxed with carbon disulfide in 10% ethanolic sodium hydroxide solution, they afforded the thieno[2,3‐d]pyrimidin‐2,4‐dithione derivative 5 in the former case, 2,4‐dicyano‐1,3‐bis(dithio carboxamino)cyclobuta‐1,3‐ diene 6 and pyrazolopyranopyrido[2,3‐d]pyrimidin‐ 2,4‐dithione derivative 7 in the latter one. Treatment of 2a with thiourea in refluxing ethanol in the presence of potassium carbonate gave 2,2′‐dithiobispyrimidine derivative 9 (major) in addition to pyranopyrazole derivative 10 and 2,2′‐dithiobis ethoxypyrimidine derivative 11 in minor amounts. The structures of all products were evidenced by microanalytical and spectral data. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:6–11, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20070     

Dependence of modulus of elasticity and thermal conductivity on reference temperature in generalized thermoelasticity for an infinite material with a spherical cavity

Introduction Thetheoryofgeneralizedthermoelasticitywithonerelaxationtimebasedonamodified Fourier’slawofheatconductionwasdevelopedbyLordandShulman[1].Thistheoryallowsfor theso_calledsecond_soundeffectsinsolids,hencethermaldisturbancespropagatewithfinite wavespeeds. Themathematicalmodelofthegeneralizedthermoelasticitytheoryisofacomplicatednature thathindersthepossibilityofderivingananalyticalsolution.Mostattemptsdealingwiththese equationsarebasedoneithershort_timesolution[2-4]. Modernstructur…     

New Ni(II), Pd(II) and Pt(II) complexes coordinated to azo pyrazolone ligand with a potent anti‐tumor activity: Synthesis,characterization, DFT and DNA cleavage studies

The absolute necessity to fight some class of tumor is perceived as serious health concerns, so the discovery and development of effective anticancer agents are urgently needed. (E)‐4‐((2‐hydroxyphenyl)diazenyl)‐3‐phenyl‐1H‐pyrazol‐5(4H)‐one, HL, and its Ni(II), Pd(II) and Pt(II) complexes were synthesized and the biological activity was evaluated for antitumor, antioxidant and antimicrobial activity as well as DNA cleavage. Their structures were assigned depending on the elemental analysis, conductivity, magnetic moment, spectral measurements (IR, ¹HNMR, mass and UV–Vis) and thermal analysis. 3D molecular modeling using DFT method confirmed that the geometrical structures agree well with the suggested experimental ones. The antitumor activity was evaluated against four different cell lines using MTT assay. The ligand HL showed a potent cytotoxic activity compared to 5‐fluorouracil as a reference drug. For metal complexes, the order of activity was: Pd(II) > Ni(II) > Pt(II). A remarkable antioxidant activity for the ligand HL was recorded. It was higher than that of the metal complexes. Results of antimicrobial experiments revealed that all compounds were moderate to highly active against selected bacterial strains but inactive as antifungal except Pd(II) which showed a moderate antifungal activity. Gel electrophoresis showed insignificant nucleases activity for the ligand or its metal complexes even in the presence of H₂O₂ providing protection of DNA from damage. The antitumor activity of our compounds may be not due to DNA cleavage but may be referred to a mechanism similar to that of 5‐fluorouracil which interfere with DNA replication. The present work suggests the use of this ligand in the design and development of new anticancer drugs.     

Spectre d'anneaux de polynômes sur une suite de modules

Sans résumé     

A new synthetic route to 1,3,4-oxadiazoles. Pharmacological study of some new derivatives

2-Substituted 1,3,4-oxadiazoles have been examined as possible prodrugs of antidepressant hydrazides. A new method of synthesis of this heterocycle from thionoester and five new oxadiazoles substituted at the 2-position by a 4-pyridyl or 4-aminophenyl group and at the 5-position by a phenyl group are described.     

Reactions of N , N -Disubstituted 5-Arylmethylidene-2-amino-thiazol-4(5 H )-ones with CH Acids

 N,N-Disubstituted 5-arylmethylidene-2-aminothiazol-4(5H)-ones reacted with diethyl malonate, ethyl benzoylacetate, acetylacetone, or cyclopentadiene in refluxing toluene and in presence of powdered sodium to give the respective 5-arylmethylidene-2′-amino-2,5′-bithiazolylidene-4,4′-dione derivatives in moderate yields. 5-Benzylidene-2-morpholin-4-yl-2-thiazol-4(5H)-one reacted with malononitrile in toluene and in presence of powdered sodium under mild conditions to afford the 1:1 adduct, benzylmalononitrile, and 2-morpholin-4-yl-2-thiazol-4(5H)-one. However, similar treatment of 5-(4-methoxyphenylmethylidene)-2-morpholin-4-yl-2-thiazol-4(5H)-one with malononitrile yielded the 2,5′-bithiazolylidene-4,4′-dione derivative together with 4-methoxyphenylmethylidene malononitrile. Treatment of 5-benzylidene- and 5-(4-methoxyphenylmethylidene)-2-morpholin-4-yl-2-thiazol-4(5H)-ones with 3-phenyl-4-oxo-2-thioxo-1,3-thiazolidine in refluxing toluene and in presence of powdered sodium produced 5-arylmethylidene-3-phenyl-4-oxo-2-thioxo-1,3-thiazolidines in good yields. The structures of all products were deduced from microanalytical and spectroscopic data, mechanistic details are discussed.     

Synthesis of [MnCl<Subscript>3</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>(Hatz)]·H<Subscript>2</Subscript>O and investigation of its structure via X-ray diffraction,spectroscopic measurements and DFT calculations

The 3-amino-1,2,4-triazole (atz)-based manganese complex was prepared and characterized through single-crystal X-ray diffraction, IR, EPR, and UV–visible spectroscopy. In the crystal structure, individual complex are interconnected through N(O)–H…Cl hydrogen bonds into 1D undulating chains running parallel to the [110] direction of the unit cell. Chains further grow into 2D supramolecular layers by way of the lattice water molecules of coordination and the chloride anions (O–H…Cl). Layers pack along the b-axis of the unit cell mediated by O–H…Cl(N) and N–H…O(Cl) hydrogen bonds forming a 3D supramolecular architecture. The theoretical calculations were also performed to optimize the structure of the complexes in the gas phase to confirm the structures proposed by X-ray crystallography. In addition, IR and UV–visible spectra of complex were calculated and compared with the corresponding experimental spectra to complete the experimental structural identification. The three-dimensional Hirshfeld surface (3D-HS) and their relative two-dimensional fingerprint plots (2D-FP) reveal that the structure is dominated by H…Cl/Cl…H (50.5%), H…O/O…H (11.3%) and N…O/O…N (10.2%) contacts.     

Simple synthesis of imidazo[1,2-A]pyridine derivatives bearing 2-aminonicotinonitrile or 2-aminochromene moiety

A simple and general method for the synthesis of new imidazopyridines bearing an aminopyridinyl, chromenyl, or quinolinyl moiety in the C2 position was developed. The Knoevenagel reaction between imidazo[1,2-a]pyridine-2-carbaldehyde 1 and malononitrile resulted in the formation of starting material 2. Subsequently, intramolecular cyclization between the cyano group of 2 and acetophenones, naphtols, hydroxyquinolines, or phenols, gave 3, 4, 5, and 6 compounds, respectively. This is a simple, reproducible, and environmentally friendly method of synthesizing substituted imidazopyridines using water as a solvent or under solvent-free conditions.