Facilitated modelling in operational research

The traditional way of employing operational research in organisational interventions has been the expert mode. In this mode, the problem situation faced by the client is given to the operational research consultant, who then builds a model of the situation, solves the model to arrive at an optimal (or quasi-optimal) solution, and then provides a recommendation to the client based on the obtained solution. An alternative mode of engagement is to conduct the whole intervention together with the client: from structuring and defining the nature of the problem situation of interest, to supporting the evaluation of priorities and development of plans for subsequent implementation. In this latter mode, the operational researcher works throughout the intervention not only as an analyst, but also as a facilitator to the client. This paper discusses this latter mode of engagement with clients, with particular emphasis on the use of facilitated modelling as the intervention tool. Drawing on research scattered across a range of publications and domains, the review presented here provides a formal definition of facilitated modelling, together with a general framework that allows the conceptualisation of a wide variety of facilitated modelling approaches to organisational intervention. Design issues in facilitated modelling and their practical implication are discussed, and directions for future research identified.     

On the physical interpretation of asymptotically flat gravitational fields

A problem in general relativity is how to extract physical information from solutions to the Einstein equations. Most often information is found from special conditions, e.g., special vector fields, symmetries or approximate symmetries. Our concern is with asymptotically flat space–times with approximate symmetry: the BMS group. For these spaces the Bondi four-momentum vector and its evolution, found at infinity, describes the total energy–momentum and the energy–momentum radiated. By generalizing the simple idea of the transformation of (electromagnetic) dipoles under a translation, we define (analogous to center of charge) the center of mass for asymptotically flat Einstein–Maxwell fields. This gives kinematical meaning to the Bondi four-momentum, i.e., the four-momentum and its evolution which is described in terms of a center of mass position vector, its velocity and spin-vector. From dynamical arguments, a unique (for our approximation) total angular momentum and evolution equation in the form of a conservation law is found. Third Award in the 2008 Essay Competition of the Gravity Research Foundation.     

The unique carrier mobility of Janus MoSSe/GaN heterostructures

Heterostructure is an effective approach in modulating the physical and chemical behavior of materials. Here, the first-principles calculations were carried out to explore the structural, electronic, and carrier mobility properties of Janus MoSSe/GaN heterostructures. This heterostructure exhibits a superior high carrier mobility of 281.28 cm²·V⁻¹·s⁻¹ for electron carrier and 3951.2 cm²·V⁻¹·s⁻¹ for hole carrier. Particularly, the magnitude of the carrier mobility can be further tuned by Janus structure and stacking modes of the heterostructure. It is revealed that the equivalent mass and elastic moduli strongly affect the carrier mobility of the heterostructure, while the deformation potential contributes to the different carrier mobility for electron and hole of the heterostructure. These results suggest that the Janus MoSSe/GaN heterostructures have many potential applications for the unique carrier mobility.     

Physical properties of films made of copoly(ether-imide)s with long poly(ethylene oxide) segments

Polyimides having long poly(ethylene oxide), PEO, moieties in the main chain have been synthesized by a classical two-steps polycondensation method with good yield and high molecular weight. In contrast with previous works on this topic, essentially full conversion of the polyamic acid to polyimide was attained by heating at relatively low temperatures (around 160 °C).These copolyimides undergo an increase of phase separation between the PEO part and the polyimide one after a thermal annealing. This phase separation increases gas separation properties of membranes made up of these copolymers. An exhaustive study of polymer properties as a function of the thermal treatment has been carried out in order to figure out the origin of this behavior. The analysis performed included TGA, DSC, SAXS and mechanical testing.The polymers studied in this paper have medium thermal stability. In fact, degradation of the polyether chain under nitrogen takes place at temperatures above 300 °C. However, their thermal stabilities were much lower under oxidant atmosphere.     

A fractional order epidemic model for the simulation of outbreaks of influenza A(H1N1)

In this paper, we propose a nonlinear fractional order model in order to explain and understand the outbreaks of influenza A(H1N1). In the fractional model, the next state depends not only upon its current state but also upon all of its historical states. Thus, the fractional model is more general than the classical epidemic models. In order to deal with the fractional derivatives of the model, we rely on the Caputo operator and on the Grünwald–Letnikov method to numerically approximate the fractional derivatives. We conclude that the nonlinear fractional order epidemic model is well suited to provide numerical results that agree very well with real data of influenza A(H1N1) at the level population. In addition, the proposed model can provide useful information for the understanding, prediction, and control of the transmission of different epidemics worldwide. Copyright © 2013 John Wiley & Sons, Ltd.     

Systematic study of luminescent properties of new lanthanide complexes using crown ethers as ligand

This is a report on the synthesis, characterization and spectroscopic study of 24 lanthanide-crown ether coordination compounds, where Eu(III), Tb(III) and Gd(III) were complexes to 12-crown-4 (12C4), 15-crown-5 (15C5), 1,10-phenanthroline (phen) and 2,2′-dipyridyl (dipy). The compounds were synthesized in an ethanol/acetone solution at room temperature and analyzed using CHN elemental analysis and infrared, absorption and emission spectroscopies. The polarizability that the ligand exerts on the emission process was verified and found remarkable. The Eu-15C5-phen complex showed the highest quantum efficiency (71.6%) because of its low non-radiative rate and highest polarizability with reference to the ligands system.     

Development and validation of a fast isocratic liquid chromatography method for the simultaneous determination of norfloxacin,lomefloxacin and ciprofloxacin in human plasma

A simple and fast liquid chromatographic method coupled with fluorescence detection (LC‐FD) is reported, for the first time, for the simultaneous quantification of norfloxacin (NOR), ciprofloxacin (CIP) and lomefloxacin (LOM) in human plasma, using levofloxacin as internal standard (IS). Sample preparation consists of a single‐step precipitation of plasma proteins followed by vortex‐mixing and centrifugation. Chromatographic separation was achieved within 7 min on a reversed‐phase C₁₈ column with a mobile phase consisting of 0.1% aqueous formic acid (pH = 3.0, triethylamine)–methanol (82:18, v/v) pumped isocratically at 1.2 mL/min. The detector was set at excitation/emission wavelengths of 278/450 nm. Calibration curves were linear (r² ≥ 0.994) in the range of 0.02–5.0 µg/mL, and the limit of quantification was established at 0.02 µg/mL for all analytes (NOR, CIP and LOM). The overall precision did not exceed 8.19% and accuracy was within ±10.91%. NOR, CIP and LOM were extracted from human plasma with an overall mean recovery ranged from 90.1 to 111.5%. No interferences were observed at the retention times of the analytes and IS. This novel LC‐FD method enables the reliable determination of NOR, CIP and LOM in a single chromatographic run, which may be suitable to support human pharmacokinetic‐based studies with those antimicrobial agents. Copyright © 2010 John Wiley & Sons, Ltd.     

Polyisophthalamides with heteroaromatic pendent rings: Synthesis,physical properties,and water uptake

A set of novel aromatic polyamides containing pyridine pendent groups was prepared from aromatic diamines and new monomers that are 5‐substituted derivatives of isophthalic acid bearing nicotinamide, isonicotinamide, or picolinamide groups. The polymers were obtained in high yield and high molecular weight by the phosphorylation method of polycondensation. They were characterized by spectroscopic and chromatographic methods and several of their properties were investigated. All of the polymers were soluble in polar aprotic solvents and gave films of good mechanical properties. Glass transition temperatures were higher than that of the reference polymer, poly(m‐phenyleneisophthalamide) (IP‐MPD), while the thermal resistance, defined by the initial decomposition temperature observed by thermogravimetry, was in the range 370–420 °C, lower by 30–70 °C than that of IP‐MPD. The presence of a pendent pyridine group and an additional amide side group per repeat unit made the polymers essentially amorphous and greatly improved their abilities to absorb water in comparison with nonsubstituted polyamides. Water uptake values up to 15% were observed at 65% relative humidity. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5300–5311, 2005     

Direct Catalytic Enantio‐ and Diastereoselective Ketone Aldol Reactions of Isocyanoacetates

A catalytic asymmetric aldol addition/cyclization reaction of unactivated ketones with isocyanoacetate pronucleophiles has been developed. A quinine‐derived aminophosphine precatalyst and silver oxide were found to be an effective binary catalyst system and promoted the reaction to afford chiral oxazolines possessing a fully substituted stereocenter with good diastereoselectivities and excellent enantioselectivities.