A novel (main chain) (side chain) polymeric peroxide: Synthesis and initiating characteristics of poly(alpha-(tert-butylperoxymethyl)styrene peroxide)

A novel (main chain)-(side chain) vinyl polyperoxide, poly(alpha-(tert-butylperoxymethyl)styrene peroxide) (MCSCPP), an alternating copolymer of alpha-(tert-butylperoxymethyl)styrene (TPMS) and oxygen, has been synthesized by the oxidative polymerization of TPMS. The MCSCPP was characterized by H-1 NMR, C-13 NMR, IR, DSC, EI-MS, and GC-MS studies. The overall activation energy (E(a)) for the degradation of MCSCPP was found to be 27 kcal/mol. Formaldehyde and alpha-(tert-butylperoxy)acetophenone (TPAP) were identified as the primary degradation products of MCSCPP; TPAP was found to undergo further degradation. The side chain peroxy groups were found to be thermally more stable than those in the main chain. Polymerization of styrene in the presence of MCSCPP as initiator, at 80 degrees C, follows classical kinetics. The presence of peroxy segments in the polystyrene chain was confirmed by both H-1 NMR and thermal decomposition studies. Interestingly, unlike other vinyl polyperoxides, the MCSCPP initiator shows an increase in molecular weight with conversion.

C-13 MAS NMR spectra of cis,cis-mucononitrile in liquid-crystalline media and in the solid state. Orientation of the carbon chemical-shift tensors

The spinning sidebands observed in the C-13 MAS NMR spectra of cis,cis-mucononitrile oriented in liquid-crystalline media and of the neat sample in the solid state are studied. There are differences in the sideband intensity patterns in the two cases. These differences arise because the order parameters which characterize the orientation of the solute in the liquid-crystalline media differ for different axes. It is shown that, in general, the relative intensities of the sidebands contain information on the sign and magnitude of an effective chemical-shift parameter which is a function of the sum of the products of the principal components of the chemical-shift tensor and the corresponding order parameters with respect to the director. A method for obtaining the orientation of the carbon chemical-shift tensor is proposed. The carbon chemical-shift tensors obtained from gauge-including atomic orbital calculations are also presented for comparison. (C) 1996 Academic Press, Inc.

Inter And Intramolecular Interactions Of Porphyrins With 5,5′-Dithiobis(2-Nitrobenzoic Acid)

meso-Tetraphenylporphyrin and its metal [zinc(II) and copper(II)] derivatives form both inter and intramolecular complexes with 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB). The nature of interaction is predominantly charge transfer (CT) in origin, with the porphyrin functioning as a II-donor and DTNB as an acceptor. Among the covalently linked intramolecular systems, the magnitude of CT interaction varies with the position (of one of the aryl groups of the porphyrin) to which DTNB is attached as ortho meta > para. Steady-state and time-resolved fluorescence studies revealed electron transfer to be the dominant pathway for the fluorescence quenching in these systems. Steady-state photolysis experiments probed using EPR and optical absorption studies have shown that electron transfer (from the excited singlet state of the porphyrin) to DTNB results in the formation of thiyl radical and production of free thiolate anion. It is found that the products of electrochemical reduction of covalently linked porphyrin-DTNB systems are different from those observed for the photochemical studies.

Nitrogen Derivatives Of C-60 And C-70 - Interaction Of Fullerenes With Nitrogen In Gas-Phase

Mass spectrometric studies show that contact-arc vaporization of graphite in a partial atmosphere of N2 or NH3 yields nitrogenous products tentatively assigned to species such as C70N2, C59N6, C59N4 and C59N2 involving addition of or substitution by nitrogen along with the species due to C2 and C4 losses. Mass spectrometry and other techniques have been employed to identify products of the nucleophilic addition of aliphatic amines to C60 and C70 in solution phase.

Microwave-assisted selective deoxygenation of layer- and chain-containing oxides

Very rapid (within 5 min), selective, single-step deoxygenation of layer- and chain-containing oxides, MoO3, CrO3, V2O5, alpha-VOPO4 . 2H(2)O and Ag6Mo10O33 has been accomplished using graphitic carbon in a microwave-assisted reaction. The products were found to be MoO2, Cr2O3, VO2, VPO4 and a mixture of (Ag + MoO2), respectively. Products were characterised by X-ray diffraction (XRD), differential scanning calorimetry (DSC), IR and electron paramagnetic resonance (EPR) spectroscopies. Although conventional methods of preparing these materials are tedious, the present method is simple, fast and yields very homogeneous products of good crystallinity. Our results reveal that while layer- and chain-containing oxides undergo rapid microwave-assisted carbothermal reduction, the non-layered materials do not. The high structural selectivity of these reactions is suggestive of the topochemical nature of the fast reduction process.

The intercalation reaction of pyridine with manganese thiophosphate, MnPS3

The intercalation of pyridine in the layered manganese thiophosphate, MnPS3, has been examined in detail by a variety of techniques. The reaction is interesting since none of the anticipated changes in optical and electrical properties associated with intercalation of electron donating molecules is observed. The only notable change in the properties of the host lattice is in the nature of the low-temperature magnetic ordering; while MnPS3 orders antiferromagnetically below 78 K, the intercalated compound shows weak ferromagnetism probably due to a canted spin structure. Vibrational spectra clearly show that the intercalated species are pyridinium ions solvated by neutral pyridine molecules. The corresponding reduced sites of the host lattice, however, were never observed. The molecules in the solvation shell are exchangeable. Although the reaction appears to be topotactic and reversible, from XRD, a more detailed analysis of the products of deintercalation reveal that it is not so. The intercalation proceeds by an ion exchange/intercalation mechanism wherein the intercalated species are pyridinium ions solvated by neutral molecules with charge neutrality being preserved not by electron transfer but by a loss of Mn2+ ions from the lattice. The experimental evidence leading to this conclusion is discussed and it is shown that this model can account satisfactorily for the observed changes (or lack of it) in the optical, electrical, vibrational, and magnetic properties.

Study of the reactions of pyridinium poly(hydrogen fluoride) with some ternary oxides

The products of the reaction of pyridinium poly(hydrogen fluoride), PPHF, with KIO3, Na2SnO3, NaBiO3, K2CrO4, Na2MoO4 and Na2WO4 were KIO2F2; Na2SnF6; NaHF2, BiF3; K3CrF6, KHF2, (PyH)(3)CrF6; NaHF2, (PyH)(2)MoO2F4.2NaHF(2); and (PyH)(2)WO2F4.2NaHF(2), respectively, while KClO3, KBrO3 and KlO(4) react with complete decomposition to form KHF2 as the fluorinated product. This differential reactivity and mode of reaction has been discussed in terms of the oxidation state of the central atom, the nature and strength of the bonds and the complex behaviour of the formed intermediate or fluorinated products that undergo complexation or solvation with pyridine and/or hydrogen fluoride.

Isomerisation of 4-aryl-4-methylhex-5-en-2-ones to 5-aryl-4-methylhex-5-en-2-ones by an intramolecular ene-retro ene reaction sequence

Acid-catalysed thermal rearrangement of 4-aryl-4-methylhex-5-en-2-ones (products of the Claisen rearrangement of beta-methylcinnamyl alcohols and 2-methoxypropene) to isomeric 5-aryl-4-methylhex-5-en-2-ones via an intramolecular ene reaction of the enol tautomer followed by a retro ene reaction of the resultant acetylcyclopropane is described. Formation of the known diketone 13 via the ozonolysis of the rearrangement product 10, confirmed the structures of the rearranged enones, whereas formation of the enone 15 containing an extra methyl group on the styrene double bond confirmed the proposed mechanism. Finally, the rearrangement has been extended to the formal synthesis of beta-cuparenone 20 via the enones 22 and 23.

Synthesis of metastable, wurzite-based zinc oxide-cobalt(II) oxide solid solutions by spray pyrolysis

Aqueous solutions of acetates and nitrates of zinc and cobalt have been spray decomposed to study the production of extended solid solutions in the ZnO-CoO system. Examination of the products of a variety of synthesis conditions indicates that up to 70% CoO may be retained in the solid solution in the wurzite phase, even though a comparison of the equilibrium solubility in the phase diagram might be expected to favor the formation of a rock-salt-based solid solution.

An interesting feature of the vapour pressure curve

There exists a maximum in the products of the saturation properties such as T(p(c) - p) and p(T-c - T) in the vapour-liquid coexistence region for all liquids. The magnitudes of those maxima on the reduced coordinate system provide an insight to the molecular complexity of the liquid. It is shown that the gradients of the vapour pressure curve at temperatures where those maxima occur are directly given by simple relations involving the reduced pressures and temperatures at that point. A linear relation between the maximum values of those products of the form [p(r)(1 - T-r)](max) = 0.2095 - 0.2415 [T-r(1 - p(r))](max) has been found based on a study of 55 liquids ranging from non-polar monatomic cryogenic liquids to polar high boiling point liquids.

Application of an evolutionary fuzzy system for the estimation of workforce deployment and cross-training in an assembly environment

Owing to the increased customer demands for make-to-order products and smaller product life-cycles, today assembly lines are designed to ensure a quick switch-over from one product model to another for companies' survival in market place. The complexity associated with the decisions pertaining to the type of training and number of workers and their exposition to the different tasks especially in the current era of customized production is a serious problem that the managers and the HRD gurus are facing in industry. This paper aims to determine the amount of cross-training and dynamic deployment policy caused by workforce flexibility for a make-to-order assembly. The aforementioned issues have been dealt with by adopting the concept of evolutionary fuzzy system because of the linguistic nature of the attributes associated with product variety and task complexity. A fuzzy system-based methodology is proposed to determine the amount of cross-training and dynamic deployment policy. The proposed methodology is tested on 10 sample products of varying complexities and the results obtained are in line with the conclusions drawn by previous researchers.

Microbially induced flotation of alumina, silica/calcite from haematite

Selective separation of haematite from alumina and silica/calcite was achieved through microbiologically induced flotation and flocculation in presence of Bacillus subtilis. Bacterial metabolites containing extracellular proteins were characterized from mineral-grown bacterial cell free extract. Bacteria can adhere to mineral surfaces and influence subsequent flotation of the minerals. Cells and metabolic products of bacteria were used in flotation, flocculation and adsorption studies on oxide minerals. Bacteria functions as a stronger depressant for haematite. Selective affinity of the bacterial cells towards the mineral surface was observed through adsorption studies. Bacterial byproduct like extracellular protein (EP) was isolated from bacteria. The protein profile of the EP of bacterial cells grown in presence and absence of minerals (haematite, corundum, quartz and calcite) was also studied. The role of such proteins in selective mineral separation was demonstrated through microbially induced selective flotation. This study has demonstrated the utility and amenability of microbially induced mineral beneficiation through the use of bacterially generated metabolic products and mineral-grown bacterial cells. (C) 2011 Elsevier B.V. All rights reserved.

Lubricant Degradation and Related Wear of a Steel Pin in Lubricated Sliding Against a Steel Disc

In lubricated sliding contacts, components wear out and the lubricating oil ages with time. The present work explores the interactive influence between lubricant aging and component wear. The flat face of a steel pin is slid against a rotating steel disk under near isothermal conditions while the contact is immersed in a reservoir of lubricant (hexadecane). The chemical changes in the oil with time are measured by vibrational spectroscopy and gas chromatography. The corresponding chemistry of the pin surface is recorded using X-ray photoelectron spectroscopy while the morphology of the worn pins; surface and subsurface, are observed using a combination of focused ion beam milling and scanning electron 5 microscopy. When compared to thermal auto-oxidation of the lubricant alone, steel on steel friction and wear are found to accentuate the decomposition of oil and to reduce the beneficial impact of antioxidants. The catalytic action of nascent iron, an outcome of pin wear and disk wear, is shown to contribute to this detrimental effect. Over long periods of sliding, the decomposition products of lubricant aging on their own, as well as in conjunction with their products of reaction with iron, generate a thick tribofilm that is highly protective in terms of friction and wear.

Topological analysis of general linear networks

A new method of network analysis, a generalization in several different senses of existing methods and applicable to all networks for which a branch-admittance (or impedance) matrix can be formed, is presented. The treatment of network determinants is very general and essentially four terminal rather than three terminal, and leads to simple expressions based on trees of a simple graph associated with the network and matrix, and involving products of low-order, usually(2 times 2)determinants of tree-branch admittances, in addition to tree-branch products as in existing methods. By comparison with existing methods, the total number of trees and of tree pairs is usually considerably reduced, and this fact, together with an easy method of tree-pair sign determination which is also presented, makes the new method simpler in general. The method can be very easily adapted, by the use of infinite parameters, to accommodate ideal transformers, operational amplifiers, and other forms of network constraint; in fact, is thought to be applicable to all linear networks.

Pleiotropic Roles of a Ribosomal Protein in Dictyostelium discoideum

The cell cycle phase at starvation influences post-starvation differentiation and morphogenesis in Dictyostelium discoideum. We found that when expressed in Saccharomyces cerevisiae, a D. discoideum cDNA that encodes the ribosomal protein S4 (DdS4) rescues mutations in the cell cycle genes cdc24, cdc42 and bem1. The products of these genes affect morphogenesis in yeast via a coordinated moulding of the cytoskeleton during bud site selection. D. discoideum cells that over-or under-expressed DdS4 did not show detectable changes in protein synthesis but displayed similar developmental aberrations whose intensity was graded with the extent of over-or under-expression. This suggested that DdS4 might influence morphogenesis via a stoichiometric effect - specifically, by taking part in a multimeric complex similar to the one involving Cdc24p, Cdc42p and Bem1p in yeast. In support of the hypothesis, the S. cerevisiae proteins Cdc24p, Cdc42p and Bem1p as well as their D. discoideum cognates could be co-precipitated with antibodies to DdS4. Computational analysis and mutational studies explained these findings: a C-terminal domain of DdS4 is the functional equivalent of an SH3 domain in the yeast scaffold protein Bem1p that is central to constructing the bud site selection complex. Thus in addition to being part of the ribosome, DdS4 has a second function, also as part of a multi-protein complex. We speculate that the existence of the second role can act as a safeguard against perturbations to ribosome function caused by spontaneous variations in DdS4 levels.