A novel synthetic approach towards 2-guanidinomethyl-4(5)-sulfamoylimidazoles

A library of 2-guanidinomethyl-4(5)-sulfamoylimidazoles was synthesised in a convergent manner by introducing a sulfonyl chloride group via a trianion electrophilic sulfinylation of suitably protected 2-guanidinomethyl imidazoles.     

Australian Sugar Mills Optimise Siding Rosters to Increase Profitability

Increasing cost/price ratios in sugarcane production and the pressure to remain internationally competitive have forced Australian sugar mills to reduce capital and operational costs. Increased utilisation of transport infrastructure through improved rostering of harvesting groups into sugarcane rail and road sidings provides an opportunity to reduce transport and harvesting costs. Generating and maintaining siding rosters manually also requires high labour costs because of the time-consuming effort to simultaneously balance limited capacities in the transportation facilities with costs of harvester movements as well as the social considerations of equity between growers. To address this complex socio-economic issue, participatory research was undertaken with a large sugar milling company in Australia to implement siding rosters that were optimised using a tabu search. This resulted in an original adoption of staff rosters produced using operations research techniques, which substantially reduced the up-front and on-going labour costs of planning and maintaining an effective roster throughout the 2002 harvest season.     

Adsorptive interaction between nitrogen compounds and organic and/or mineral phases in subsurface rocks. Models for compositional fractionation of pyrrolic nitrogen compounds in petroleum during petroleum migration

The results are reported of a range of laboratory chromatographic fractionation experiments with synthetic model compounds and a petroleum pyrrolic nitrogen fraction. Reversed phase separation of pyrrolic nitrogen compounds was governed mainly by the number of carbon atoms in the molecule, with little selectivity toward different positional isomers, whereas normal phase separation of the compounds could be explained in terms of steric effects related to alkylation position. Comparison of experimental results from model compounds with observations made previously using sets of natural samples taken from sedimentary basins clearly suggests adsorptive interactions between organic and mineral phases are involved in the compositional fractionation of pyrrolic nitrogen compounds in petroleum during migration. Detailed studies of the effects of petroleum migration on the molecular distribution of petroleum pyrrolic nitrogen compounds may provide useful, quantifiable, migration-related geochemical parameters.     

The smallest nontoroidal chiral maps

In this paper, we display those chiral maps which have fewest edges among those of genus greater than one. One of these is a branched covering of a regular map on the torus, and the other is its dual.     

A short proof of Chvátal's Watchman Theorem

This note contains a short proof of Chvátal's Watchman Theorem using the existence of a three-coloring of a triangulated polygon.     

Ultrahigh-bandwidth, on-chip all-optical pulse erasure using the χ(3) process in a nonlinear chalcogenide waveguide

We demonstrate on-chip all-optical pulse erasure based on four-wave mixing and cross-phase modulation in a dispersion engineered chalcogenide (As(2)S(3)) rib waveguide. We achieve an erasure efficiency of ~15 dB for picosecond pulses in good agreement with numerical simulations using the nonlinear Schr?dinger equation. The combined effect of the high instantaneous optical nonlinearity (γ = 9900 (W km)(-1)) and small group-velocity dispersion (D = 29 ps/nm km), which reduces pulse walk-off, will enable all-optical pulse erasure for ultrafast signal processing.     

Photonic generation of triangular-shaped pulses based on frequency-to-time conversion

An all-fiber approach to generate triangular-shaped pulses based on frequency-to-time conversion is proposed and demonstrated. Two filter modules that have sinusoidal spectral responses are cascaded to create a triangular-shaped optical spectrum. Through the frequency-to-time conversion in a dispersive fiber, periodic triangular pulses with the same shape as the optical spectrum are obtained. The repetition rate and pulse width of the generated signals can be tuned by adjusting the modulation rate and the dispersion value, respectively.     

On Partial Well-Order for Monotone Grid Classes of Permutations

A monotone grid class is a permutation class (i.e., a downset of permutations under the containment order) defined by local monotonicity conditions. We give a simplified proof of a result of Murphy and Vatter that monotone grid classes of forests are partially well-ordered.