Asymmetric Cipher Protocol Using Decomposition Problem

The asymmetric cipher protocol based on decomposition problem in matrix semiring M over semiring of natural numbers N is presented. The security parameters are defined and preliminary security analysis is presented.

Ag alloyed Pd single-atom catalysts for efficient selective hydrogenation of acetylene to ethylene in excess ethylene

Semihydrogenation of acetylene in an ethylene-rich stream is an industrially important process. Conventional supported monometallic Pd catalysts offer high acetylene conversion, but they suffer from very low selectivity to ethylene due to overhydrogenation and the formation of carbonaceous deposits. Herein, a series of Ag alloyed Pd single-atom catalysts, possessing only ppm levels of Pd, supported on silica gel were prepared by a simple incipient wetness coimpregnation method and applied to the selective hydrogenation of acetylene in an ethylene-rich stream under conditions close to the front-end employed by industry. High acetylene conversion and simultaneous selectivity to ethylene was attained over a wide temperature window, surpassing an analogous Au alloyed Pd single-atom system we previously reported. Restructuring of AgPd nanoparticles and electron transfer from Ag to Pd were evidenced by in situ FTIR and in situ XPS as a function of increasing reduction temperature. Microcalorimetry and XANES measurements support both geometric and electronic synergetic effects between the alloyed Pd and Ag. Kinetic studies provide valuable insight into the nature of the active sites within these AgPd/SiO2 catalysts, and hence, they provide evidence for the key factors underpinning the excellent performance of these bimetallic catalysts toward the selective hydrogenation of acetylene under ethylene-rich conditions while minimizing precious metal usage.

Highly selective hydrogenation of furfural over supported Pt nanoparticles under mild conditions

The selective liquid phase hydrogenation of furfural to furfuryl alcohol over Pt nanoparticles supported on SiO2, ZnO, γ-Al2O3, CeO2 is reported under extremely mild conditions. Ambient hydrogen pressure, and temperatures as low as 50 °C are shown sufficient to drive furfural hydrogenation with high conversion and >99% selectivity to furfuryl alcohol. Strong support and solvent dependencies are observed, with methanol and n-butanol proving excellent solvents for promoting high furfuryl alcohol yields over uniformly dispersed 4 nm Pt nanoparticles over MgO, CeO2 and γ-Al2O3. In contrast, non-polar solvents conferred poor furfural conversion, while ethanol favored acetal by-product formation. Furfural selective hydrogenation can be tuned through controlling the oxide support, reaction solvent and temperature.

Symmetric and Asymmetric Gaps in Some Fields of Formal Power Series

2000 Mathematics Subject Classification: 03E04, 12J15, 12J25.

Platinum-catalysed cinnamaldehyde hydrogenation in continuous flow

Platinum is one of the most widely used hydrogenation catalysts. Here we describe the translation of batch reactions to continuous flow, affording tunable C=O versus C=C hydrogenation over a Pt/SiO2 catalyst, resulting in high steady state activity and single-pass yields in the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol under mild conditions. Negligible catalyst deactivation occurs under extended flow operation due to removal of reactively-formed poisons from the reaction zone. Process intensification imparts a four-fold enhancement in cinnamyl alcohol productivity.

Performance evaluation of strongly filtered asymmetric 42.7 Gb/s coherent 50%RZ-BPSK system

We show, by numerical simulation, that the impact of tight optical filtering in high speed coherent 50% RZ-BPSK systems can be greatly reduced by offsetting the filter (equivalent to laser detuning). We show that by offsetting the filter by up to half the filter bandwidth, that system performance is improved by > 2.5 dB in the calculated 'Q' for an OSNR of 12 dB. © 2013 IEEE.

Asymmetric price transmission in EU petroleum markets

This research investigates the determinants of asymmetric price transmission (APT) in European petroleum markets. APT is the faster response of retail prices to cost increases than to cost decreases; resulting in a welfare transfer from consumers to fuel retailers. I investigate APT at 3 different levels: the EU, the UK and at the Birmingham level. First, I examine the incidence of asymmetries in the retail markets of six major EU countries; significant asymmetries are found in all countries except from the UK. The market share data suggest that asymmetries are more important in more concentrated markets; this finding supports the collusion theory. I extend the investigation to 12 EU countries and note that APT is greater in diesel markets. The cross-country analysis suggests that vertical and horizontal concentration at least partly explains the degree of asymmetry. I provide evidence justifying scrutiny over retail markets’ pricing and structure. Second daily data unveil the presence of APT in the UK fuel markets. I use break tests to identify segments with different pricing regimes. Two main types of periods are identified: periods of rising oil price exhibit significant asymmetries whilst periods of recession do not. Our results suggest that oligopolistic coordination between retailers generate excess rents during periods of rising oil price whilst the coordination fails due to price wars when oil prices are going downwards. Finally I investigate the pricing behaviour of petroleum retailers in the Birmingham (UK) area for 2008. Whilst the market structure data reveals that the horizontal concentration is higher than the national UK average, I find no evidence of APT. In contrast, I find that retail prices are sticky upwards and downwards and that firms with market power (majors and supermarkets) adjust their prices slower than other firms.

Nanoengineering heterogeneous catalysts for the selective hydrogenation of key agrochemical derivatives

Rapidly rising world populations have sparked growing concerns over global food production to meet this increasing demand. Figures released by The World Bank suggest that a 50 % increase in worldwide cereal production is required by 2030. Primary amines are important intermediates in the synthesis of a wide variety of fine chemicals utilised within the agrochemical industry, and hence new 'greener' routes to their low cost manufacture from sustainable resources would permit significantly enhanced crop yields. Early synthetic pathways to primary amines employed stoichiometric (and often toxic) reagents via multi-step protocols, resulting in a large number of by-products and correspondingly high Environmental factors of 50-100 (compared with 1-5 for typical bulk chemicals syntheses). Alternative catalytic routes to primary amines have proven fruitful, however new issues relating to selectivity and deactivation have slowed commercialisation. The potential of heterogeneous catalysts for nitrile hydrogenation to amines has been demonstrated in a simplified reaction framework under benign conditions, but further work is required to improve the atom economy and energy efficiency through developing fundamental insight into nature of the active species and origin of on-stream deactivation. Supported palladium nanoparticles have been investigated for the hydrogenation of crotononitrile to butylamine (Figure 1) under favourable conditions, and the impact of reaction temperature, hydrogen pressure, support and loading upon activity and selectivity to C=C versus CºN activation assessed.

Price discrimination in asymmetric Cournot oligopoly

In this article we examine the eects of third degree price discrimination in asymmetric Cournot oligopolies. We show that the average price is not affected by the extent of price discrimination. We nd that the asymmetry between firms is reflected only by the output produced for the lowest-valuation consumers and firms produce equal quantities to the other consumer groups.

Price discrimination in asymmetric Cournot oligopoly

In this article we examine the eects of third degree price discrimination in asymmetric Cournot oligopolies. We show that the average price is not affected by the extent of price discrimination. We nd that the asymmetry between firms is reflected only by the output produced for the lowest-valuation consumers and firms produce equal quantities to the other consumer groups.

Endogenous timing of moves in an asymmetric price-setting duopoly

This paper adds to the growing literature on endogenous timing of decisions in duopolies. We show for a price-setting duopoly game with sufficiently asymmetric and strictly convex cost functions that the less efficient firm moves first while the more efficient moves second with a higher price than the less efficient firm.

Asymmetric syntheses of analogs of kainic acid

Kainic acid has been used for nearly 50 years as a tool in neuroscience due to its pronounced neuroexcitatory properties. However, the significant price increase of kainic acid resulting from the disruption in the supply from its natural source, the alga Digenea Simplex, as well as inefficient synthesis of kainic acid, call for the exploration of functional mimics of kainic acid that can be synthesized in a simpler way. Aza kainoids analog could be one of them. The unsubstituted aza analog of kainoids has demonstrates its ability as an ionotropic glutamate receptor agonist and showed affinity in the chloride dependent glutamate (GluCl) binding site. This opened a question of the importance of the presence of one nitrogen or both nitrogens in the aza kainoid analogs for binding to glutamate receptors. Therefore, two different pyrrolidine analogs of kainic acid, trans -4-(carboxymethyl)pyrrolidine-3-carboxylic acid and trans -2-carboxy-3-pyrrolidineacetic acid, were synthesized through multi-step sequences. The lack of the affinity of both pyrrolidine analogs in GluCl binding site indicated that both nitrogens in aza kainoid analogs are involved in hydrogen bonding with receptors, significantly enhancing their affinity in GluCl binding site. Another potential functional mimic of kainic acid is isoxazolidine analogs of kainoids whose skeleton can be constituted directly via a 1, 3 dipolar cycloaddition as the key step. The difficulty in synthesizing N-unsubstituted isoxazolidines when applying such common protecting groups as alkyl, phenyl and benzyl groups, and the requirement of a desired enantioselectivity due to the three chiral ceneters in kainic acid, pose great challenges. Hence, several different protected nitrones were studied to establish that diphenylmethine nitrone may be a good candidate as the dipole in that the generated isoxazolidines can be deprotected in mild conditions with high yields. Our investigations also indicated that the exo/endo selectivity of the 1, 3 dipolar cycloaddition can be controlled by Lewis acids, and that the application of a directing group in dipolarophiles can accomplish a satisfied enantioselectivity. Those results demonstrated the synthesis of isoxazoldines analogs of kainic acid is very promising.

Asymptotic Theory for Extended Asymmetric Multivariate GARCH Processes

The paper considers various extended asymmetric multivariate conditional volatility models, and derives appropriate regularity conditions and associated asymptotic theory. This enables checking of internal consistency and allows valid statistical inferences to be drawn based on empirical estimation. For this purpose, we use an underlying vector random coefficient autoregressive process, for which we show the equivalent representation for the asymmetric multivariate conditional volatility model, to derive asymptotic theory for the quasi-maximum likelihood estimator. As an extension, we develop a new multivariate asymmetric long memory volatility model, and discuss the associated asymptotic properties.

Asymmetric Synthesis and Absolute Configuration of (+)- and (–)-Perhexiline

Peer reviewed

Asymmetric Synthesis and Absolute Configuration of (+)- and (–)-Perhexiline

Peer reviewed