On the discrepancy between two Zagreb indices

We examine the quantity

$S\left(G\right)=\sum _{uv\in E\left(G\right)}min(degu,degv)$

over sets of graphs with a fixed number of edges. The main result shows the maximum possible value of $S\left(G\right)$ is achieved by three different classes of constructions, depending on the distance between the number of edges and the nearest triangular number. Furthermore we determine the maximum possible value when the set of graphs is restricted to be bipartite, a forest, or to be planar given sufficiently many edges. The quantity $S\left(G\right)$ corresponds to the difference between two well studied indices, the irregularity of a graph and the sum of the squares of the degrees in a graph. These are known as the first and third Zagreb indices in the area of mathematical chemistry.     

Sorption of uranium on magnetite nanoparticles

Magnetite (Fe₃O₄) nanoparticle was synthesized using a solid state mechanochemical method and used for studying the sorption of uranium(VI) from aqueous solution onto the nanomaterial. The synthesized product is characterized using SEM, XRD and XPS. The particles were found to be largely agglomerated. XPS analysis showed that Fe(II)/Fe(III) ratio of the product is 0.58. Sorption of uranium on the synthesized nanomaterials was studied as a function of various operational parameters such as pH, initial metal ion concentration, ionic strength and contact time. pH studies showed that uranium sorption on magnetite is maximum in neutral solution. Uranium sorption onto magnetite showed two step kinetics, an initial fast sorption completing in 4–6 h followed by a slow uptake extending to several days. XPS analysis of the nanoparticle after sorption of uranium showed presence of the reduced species U(IV) on the nanoparticle surface. Fe(II)/Fe(III) ratio of the nanoparticle after uranium sorption was found to be 0.48, lower than the initial value indicating that some of the ferrous ion might be oxidized in the presence of uranium(VI). Uranium sorption studies were also conducted with effluent from ammonium diuranate precipitation process having a uranium concentration of about 4 ppm. 42% removal was observed during 6 h of equilibration.     

Synthesis and structure determination of 3β-hydroxyandrost-5-en-17-one (C19H28O2·CH3OH)

3-Hydroxyandrost-5-en-17-one (C₁₉H₂₈O₂.CH₃OH) has been prepared for undertaking its crystallographic analysis and to investigate the role of intra- and intermolecular interactions in steroids. The title compound crystallizes in the orthorhombic space group C222₁ with unit cell parameters a = 6.7892(17), b = 12.624(2), and c = 41.136(5) Å; V = 3525.7(12) ų and Z = 8. The three-dimensional structure has been solved by direct methods. The final reliability index for the computed structure is 0.050 for 1088 observed reflections. Ring A exist in chair conformation, Ring B in half-chair conformation, and the Ring C assumes a distorted chair conformation. The five-membered Ring D adopts half-chair conformation. The A/B ring junction is quasi-trans while as B/C and C/D are trans-fused. The oxygen atom of the solvent molecule (CH₃OH) is involved in O–H···O intermolecular interaction.     

Influence of Organic Additive on the Morphological, Electrical and Electrochromic Properties of Sol-Gel Derived WO3 Coatings

The WO₃ electrode is ubiquitous in an electrochromic device (ECD) and is a common choice as the electrochromic (EC) layer. EC films were deposited on different substrates by spin coating using peroxotungstic acid based precursor solutions followed by appropriate thermal treatment. Many properties of the films, including some of the EC properties dependant on microstructure of the films, were found to be modified by the addition of small amounts of organic acid to the precursor solution. A study of structural, electrical and electrochromic properties of films cast by using precursor solution comprising 0 to 10 wt% of oxalic acid dihydrate (OAD) was carried out in terms of surface morphology, electrical resistance, structure and EC response. The important findings are that the addition of oxalic acid to the precursor solution results in films with excellent EC properties, devoid of cracks and decreases their dc electrical resistance.     

Airline crew scheduling from planning to operations

Crew scheduling problems at the planning level are typically solved in two steps: first, creating working patterns, and then assigning these to individual crew. The first step is solved with a set covering model, and the second with a set-partitioning model. At the operational level, the (re) planning period is considerably smaller than during the strategic planning phase. We integrate both models to solve time critical crew recovery problems arising on the day of operations. We describe how pairing construction and pairing assignment are done in a single step, and provide solution techniques based on simple tree search and more sophisticated column generation and shortest-path algorithms.     

Metalloporphyrin and heteropoly acid catalyzed oxidation of CNOH bonds in an ionic liquid: biomimetic models of nitric oxide synthase

Water soluble iron(III) porphyrins and phosphotungstic acid in an ionic liquid are effective catalysts for the H₂O₂ mediated oxidation of the CNOH bond in N-hydroxyarginine and other oximes. The carbonyl compounds generated as the oxidation products can be easily isolated from the reaction media. These systems serve as biomimetic models of nitric oxide synthase (NOS) and the catalyst immobilized in an ionic liquid can be easily recycled and reused.     

EPR, UV-vis, magnetic, spectral studies and electrochemical behaviour of mononuclear transition metal complexes derived from novel hexa-aza-macrotricyclic ligand

Aza-macrocyclic complexes have gained importance because of their pharmacological properties. Hexa-aza-macrocycles containing glutarimide efficiently coordinate as hexa-dentate ligand, to give complexes of Cu(II) possessing tetragonal structure and Mn(II), Co(II) and Ni(II) metal ions that are essentially octahedral. Spectroscopic, and chemical characterizations of these systems are presented in this article. For Ni(II) complexes results on electron transfer processes measured by cyclic voltammetry and colourimetry have been studied.     

Mössbauer study of back co-ordination in some iron complexes of 1-(2-pyridylazo)-2-naphthol and 1-(2-pyridylazo)-2-phenanthrol

Mössbauer studies have been made on low-spin octahedral complexes of iron(II) and iron(III) formed with two terdentate ligands, viz., 1-(2-pyridylazo)-2-naphthol and 1-(2-pyridylazo)-2-phenanthrol. The data are suggestive of π-back bonding in the two iron(II) complexes.     

Synthesis and structure analysis of 2-(2′-propanonylthio)-3-(o-methyl phenyl) quinazol-4(3H)-one

The three-dimensional molecular and crystal structure of 2-(2'-propanonylthio)3-(o-methyl phenyl)quinazol-4(3H)-one has been determined by X-ray crystallographic methods. This compound crystallizes in the orthorhombic space group P_bca with unit cell parameters: a=9.649(5), b=30.102(10), c=11.403(9)Å. It has been solved by direct methods and refined to a residual index of 0.054. The magnitude of torsion along C16— C11— N3— C4 bond is 93.5(4)°. The dihedral angle between the plane comprising all the ring atoms of quinazoline moiety and the atoms of the methyl substituted phenyl ring is 94.12(1)°. The crystal structure is stabilized by one intramolecular C— HsO interaction and three intermolecular C— HsN contacts.