Heuristics to Schedule Service Engineers within Time Windows

This paper describes the development of a set of heuristics for tackling vehicle routeing problems with time windows (VRPTW) subject to uncertain demand where schedules are prepared interactively. Many public utility companies, e.g. gas, water, electricity, are now having to quote very specific times for visits to customers, both for regular service and emergency call-outs. The heuristics developed produce good tours by sequencing visits on the basis of closeness to existing visits. Tours are developed as and when demand occurs so that the customer is given an immediate appointment time, rather than waiting for a number of requests for service to be received. Simple methods to construct time windows will also be discussed.     

Measurement of the single-jet invariant cross section at Fermilab

In an experiment performed at Fermilab we have studied the production of high p_t hadron jets from 400 GeV/c pp interactions. A large solid-angle, towered calorimeter was used to trigger and reconstruct the jet events. We report results for inclusive single-jet production and compare those results with QCD predictions and results obtained at the ISR and the SPS Collider.     

Ovalling oscillations of thin circular cylindrical shells in cross flow—An experimental study

Experiments have been made to study the effect of a splitter-plate on the oscillation amplitudes, wake fluctuations and unsteady surface pressures of a shell undergoing ovalling oscillations in a cross flow in a wind tunnel. The results suggest that there is no major effect of the splitter-plate on these quantities and that periodic vortex shedding is probably the case of the ovalling.     

Determination of acesulfame and sucralose in oral electrolyte maintenance solution by liquid chromatography

A method was developed for the direct, simultaneous determination of acesulfame and sucralose in oral electrolyte maintenance solution (OEMS). Analyte separation and quantitation were achieved by gradient reversed-phase liquid chromatography (LC) and UV absorbance at 192 nm, respectively. Detection at a second wavelength, 214 nm, was used to check sucralose peak purity; 20 microL OEMS was injected without preparation or dilution. System linearity was demonstrated as 192 nm peak area versus analyte concentration at 80-120% OEMS sweetener fortification (r > 0.999, and all residuals < 0.5%, for both acesulfame and sucralose). Spike recoveries for OEMS samples prepared at 3 spiking levels (80, 100, and 120% sweetener fortification) ranged from 100.3 to 102.0% for acesulfame, and from 97.9 to 102.3% for sucralose. In a second assessment of method accuracy, the same spiked OEMS samples were tested by 2 alternative methods: acesulfame (LC/UV at 230 nm) and sucralose (anion exchange-pulsed amperometric detection). Results for the alternative acesulfame method were within 1.2%, and for the alternative sucralose method within 6.0%, of the corresponding results obtained by the 192 nm method. Repeatability and intermediate precision RSD values were < 1 % for acesulfame and < 3% for sucralose. The limits of quantitation were 1.6 and 32 mg/L for acesulfame potassium and sucralose, respectively. Despite the weak UV absorptivity of sucralose and the consequent small size of its LC peak, no evidence was found for sucralose interference in any of the commercial OEMS flavors.     

THE U.V. PHOTOCHEMISTRY OF CYTIDYLIC ACID

Abstract The ultraviolet (u.v.) irradiation of the 3' isomer of cytidylic acid (Cp) produces the hydrate (Cp*) with water added across the 5–6 double bond. The yield of this photo-product has been measured by, (a) separating the photoproduct by electrophoresis and (b) by observing the loss in absorbance. When corrections are made for reversal of the hydrate during the experiment, both methods gave the same result. Cross sections and quantum yields for the production of the hydrate were measured over the wavelength range 220 to 290 nm and over a pH range from 1 to 10. The quantum yield is markedly dependent on pH being higher by a factor of 6 to 10 for the neutral form. We have also demonstrated the existence of a very short lived photoproduct (half life 8–9 min) in both Cp3' and Cp5': The nature of this short lived product is not known.     

Chemoenzymatic Synthesis of Fluorinated Cellodextrins Identifies a New Allomorph for Cellulose-Like Materials**

Understanding the fine details of the self-assembly of building blocks into complex hierarchical structures represents a major challenge en route to the design and preparation of soft-matter materials with specific properties. Enzymatically synthesised cellodextrins are known to have limited water solubility beyond DP9, a point at which they self-assemble into particles resembling the antiparallel cellulose II crystalline packing. We have prepared and characterised a series of site-selectively fluorinated cellodextrins with different degrees of fluorination and substitution patterns by chemoenzymatic synthesis. Bearing in mind the potential disruption of the hydrogen-bond network of cellulose II, we have prepared and characterised a multiply 6-fluorinated cellodextrin. In addition, a series of single site-selectively fluorinated cellodextrins was synthesised to assess the structural impact upon the addition of one fluorine atom per chain. The structural characterisation of these materials at different length scales, combining advanced NMR spectroscopy and microscopy methods, showed that a 6-fluorinated donor substrate yielded multiply 6-fluorinated cellodextrin chains that assembled into particles presenting morphological and crystallinity features, and intermolecular interactions, that are unprecedented for cellulose-like materials.     

Mimicking Biological Recognition: Lessons in Binding Hydrophilic Guests in Water

Selective molecular recognition of hydrophilic guests in water plays a fundamental role in a vast number of biological processes, but synthetic mimicry of biomolecular recognition in water still proves challenging both in terms of achieving comparable affinities and selectivities. This Review highlights strategies that have been developed in the field of supramolecular chemistry to selectively and non-covalently bind three classes of biologically relevant molecules: nucleotides, carbohydrates, and amino acids. As several groups have systematically modified receptors for a specific guest, an evolutionary perspective is also provided in some cases. Trends in the most effective binding forces for each class are described, providing insight into selectivity and potential directions for future work.