Universally signable graphs

In a graph, a chordless cycle of length greater than three is called a hole. Let be a {0, 1} vector whose entries are in one-to-one correspondence with the holes of a graphG. We characterize graphs for which, for all choices of the vector , we can pick a subsetF of the edge set ofG such that |F H| H (mod 2), for all holesH ofG and |F T| 1 for all trianglesT ofG. We call these graphsuniversally signable. The subsetF of edges is said to be labelledodd. All other edges are said to be labelledeven. Clearly graphs with no holes (triangulated graphs) are universally signable with a labelling of odd on all edges, for all choices of the vector . We give a decomposition theorem which leads to a good characterization of graphs that are universally signable. This is a generalization of a theorem due to Hajnal and Surányi [3] for triangulated graphs.This work was supported in part by NSF grants DMI-9424348 DMS-9509581 and ONR grant N00014-89-J-1063. Ajai Kapoor was also supported by a grant from Gruppo Nazionale Delle Ricerche-CNR. We also acknowledge the support of Laboratoire ARTEMIS, Université Joseph Fourier, Grenoble.     

Purification of americium from bulk quantities of plutonium loading effluent using trilaurylamine

Four litres of Am solution containing 81.5 mg/l Am and 0.6 mg/l Pu could be purified by a two-step procedure involving solvent extraction and extraction chromatography with trilaurylamine. The final product contained a maximum concentration of 9 g/l Pu.     

Studies on energetic compounds

Thermal and explosion characteristics of ring(mono) substituted arylammonium perchlorates (RSAP) are studied by DTA, impact and friction sensitivity measurements. Exothermic decomposition temperature (T _d) from DTA curves and impact sensitivity data (h _50%) were found to be linearly related to the Hammett substituent constant (σ⁺,σ^?) andpK _a values of the corresponding arylamines. A reaction scheme, based on the formation of reaction intermediates during decomposition and explosion, accounting for the products, is proposed which, involves proton transfer as the rate determining process and evolution of ammonia. It seems that oxidation-reduction reactions between the arylamine/substituted benzene and HClO₄ or its decomposition products cause explosion.     

Mixed ligand complexes of platinum(0) containing diphosphines

The reaction of PtCl₂L (L = diphosphine) with the appropriate diphosphine L′ in ethanol followed by reduction with aqueous sodium borohydride leads to either disproportionation to give mixtures of the bis(diphosphine) complexes PtL₂ and PtL′₂ or to the formation of the mixed ligand complex PtLL′ depending on the diphosphines. Mixed ligand complexes are obtained when L=Ph₂P(CH₂)₂PPh₂, L′ = Ph₂P(CH₂PPh₂cis-Ph₂PCH CHPPh₂, Ph₂P(CH₂)₂AsPh₂, Ph₂- P(CH₂)₄PPh₂, o-Ph₂PC₆H₄PPh₂; and L=(C₆H₁₁)₂P(CH₂₂P(C₆H₁₁)₂, L′= Ph₂P(CH₂)PPh₂, Ph₂P(CH₂)₂PPh₂cis-Ph₂PCHCHPPh₂, (2S,3S)-Ph₂PCH- (CH₃)CH(CH₃)PPh₂, (R)-Ph₂PCH(CH₃)CH₂PPh₂. When L=Ph₂P(CH₂)₄PPh₂ L′= Ph₂P(CH₂₃PPh₂ or cis-Ph₂PCHCHRPh₂ the mixed ligand complexes are obtained but extensive disproportionation also occurs.     

Thermogravimetric studies of dipyridinium complexes of cerium(IV), thorium(IV) and zirconium(IV)

The TG curves of dipyridinium complexes of Ce(IV), Th(IV) and Zr(IV) have been reported. The mode of decomposition of the cerium and thorium complexes is broadly comparable but the decomposition of Zr complex shows some variation.     

Voltammetric Study of Ferrocene/Ferricinium Ion Redox Reactions in Acetonitrile

Cyclic voltammetric and differential pulse voltammetric characteristics of the oxidation reaction of ferrocene in acetonitrile solvent have been evaluated using a glassy carbon indicator electrode. The redox couple ferrocene/ferricinium ion approaches thermodynamic reversibility in acetonitrile medium in only a low concentration range.     

Analytical aspects of organic acids

Summary Phenyl acetic acid has been found to be a selective reagent for the estimation of zirconium. The acid gives a white crystalline precipitate which is quantitative between pH values of 3.00 to 5.40. As the composition of the precipitate varies somewhat, direct weighing is not possible and the compound is ignited to the oxide. The ions Be²⁺, Ca²⁺, Sr²⁺, Zn²⁺, Hg²⁺, Pb²⁺, Mg²⁺, Ni²⁺, and Co²⁺ do not interfere, whereas the ions Fe³⁺, UO₂ ²⁺, Cr³⁺, Ba²⁺, Au⁺, Al³⁺, V₂O₄ ²⁺, Ti⁴⁺, Sn²⁺, and Ba²⁺ cause interferences in the estimation.

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Zusammenfassung Zur gravimetrischen Bestimmung von Zirkonium wird Phenylessigsäure empfohlen. Die weiße, kristalline Fällung ist im pH-Bereich 3,00–5,40 quantitativ. Infolge schwankender Zusammensetzung des Niederschlages ist eine direkte Wägung nicht möglich; er wird daher zum Oxid verglüht. Folgende Ionen stören nicht: Be²⁺, Ca²⁺, Sr²⁺, Zn²⁺, Hg²⁺, Pb²⁺, Mg²⁺, Ni²⁺ und Co²⁺; dagegen verursachen Fe³⁺, UO₂ ²⁺, Cr³⁺, Ba²⁺, Au⁺, Al³⁺, V₂O₄ ²⁺, Ti⁴⁺, Sn²⁺ und Ba²⁺ Störungen bei der Bestim mung.

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Part VI: See Z. analyt. Chem. 175, 29 (1960).     

AluminiumkomplexeSchiffscher Basen

Reactions of Aluminium isopropoxide with monofunctional bidentateSchiff bases, such as salicylidene-o-toluidine, salicylidene-p-toluidine, 2-hydroxy-1-naphthylmethylidene-p-toluidine and 2-hydroxy-1-naphthylmethylidene-p-toluidine in different stoichiometric ratios have yielded products of the type Al(OPr ⁱ)₂(SB), Al(OPr ⁱ)(SB)₂, and Al(SB)₃ (whereSB ^– is the anion of the correspondingSchiff base,SBH). Bifunctional tetradentateSchiff bases in 11 and 23 molar ratios [Al(OPr ⁱ)₃:SBH₂] yielded insoluble derivatives of the type Al(OPr ⁱ)SB and Al₂(SB)₃ (whereSB ^– represents the anion of theSchiff baseSBH₂ andSBH₂=bis-salicylaldehyde-o-phenylene-diamine or bis-salicylaldehyde-p-phenylenediamine). The newSchiff base derivatives have been characterized by elemental analyses, infrared spectroscopy and molecular weight determinations.     

Structural relation properties of hydrothermally stable functionalized mesoporous organosilicas and catalysis

The surfactant assistant syntheses of sulfonic acid functionalized periodic mesoporous organosilicas with large pores are reported. A one-step condensation of tetramethoxysilane (TMOS) with 1,2-bis(trimethoxysilyl)ethane (BTME) and 3-mercaptopropyltrimethoxysilane (MPTMS) in highly acidic medium was performed in the presence of triblock copolymer Pluronic P123 and inorganic salt as additive. During the condensation process, thiol (-SH) group was in situ oxidized to sulfonic acid (-SO(3)H) by hydrogen peroxide (30 wt % H(2)O(2)). X-ray diffraction studies along with nitrogen and water sorption analyses reveal the formation of stable, highly hydrophobic, and well-ordered hexagonal mesoscopic structures in a wide range of -CH(2)CH(2)- concentrations in the mesoporous framework. The resultant materials were also investigated by (29)Si MAS and (13)C CP MAS NMR, thermogravimetric analyses, UV-Raman spectroscopy, and FT-IR spectroscopy. The role of the bridged organic group on the hydrothermal stability of the mesoporous materials was established, which revealed an enhancement in hydrothermal stability of the materials with incorporation of the bridged organic groups in the network. The catalytic performance of -SO(3)H functionalized mesoporous materials was investigated in the esterification of ethanol with acetic acid, and the results demonstrate that the ethane groups incorporated in the mesoporous framework have a positive influence on the catalytic behavior of the materials.