Acyloxylactonisations mediated by lead tetracarboxylates

The reaction of lead(IV) tetracarboxylates with carboxylic acids containing unsaturated side chains has been found to give acyloxy lactone products in a diastereoselective process; the reaction can be extended to lead(IV) tetrazolates to give the analogous outcome. Mechanistic implications of these results are discussed.     

Retention and progression of engineering students with diverse mathematical backgrounds

There are increasing concerns about the mathematics abilityof students entering higher education. This situation appearsto be as a result of the perceived lowering standards of A Levels,a reduction in entry requirements on some courses with a strongmathematical component and the wide-ranging educational backgroundsof many of the students. With Additional Student Numbers (ASN) funding, a pre-sessionalcourse has been introduced at Loughborough University as a collaborationbetween the Engineering Centre for Excellence in Teaching andLearning (engCETL) and the Mathematics Education Centre (MEC),also a designated Centre for Excellence. The 4 day, residential,pre-sessional course targets engineering students with diversemathematical backgrounds just before the start of the firstyear of their degree course. Due to possible gaps in their mathematicalknowledge, students with non-traditional mathematics backgroundsare at risk of struggling in traditional lectures where a certainlevel of knowledge is assumed. The pre-sessional course, calledFlying Start, aims both to reinforce the need for mathematicalcompetency and to raise awareness of and to encourage studentsto engage with the support facilities available to them oncethey start at University. The main constituents of the FlyingStart course are mathematics and engineering key skills workshops.Flying Start was introduced in 2003, growing from a pilot of11 Electrical Engineering students to 24 students from Electrical,Manufacturing and Materials Engineering in 2005. Following eachcourse, the performance of the Electrical Engineering studentsis monitored throughout the first year. This article examinesthe Flying Start students’ academic performance in lightof their mathematical background and their uptake of the additionalsupport on offer. Student feedback suggests that the pre-sessionalcourse offers the additional benefit of aiding the studentsin their transition into higher education. The implicationsof the feedback and the student performance data are also discussed.     

Controlling the action of chlorine radical: from lab to environment

The strength of Bz-Cl˙ complexation has been explored using density functional theory (DFT) calculations, including dispersion-corrected (DFT-D) calculations. Of the methods tested, the ωB97X-D method seems the best performing, along with the previously tested MPW1K method. The effect of substituent (X = NO(2), F, Cl, Br, H, CH(3), OCH(3), OH, NH(2) and N(CH(3))(2)) on the stabilities of the Ar-Cl˙π-like intermediates show a good correlation with the linear free energy relationships used experimentally, but this is not the case for Ar-Cl˙σ-complexes, suggesting the transition state of abstraction as being π-like in nature. The role of PAH and lignin derivatives in mediating chlorination reactions in nature is explored. Stable π-complexes were identified for lignin derivatives, indicating humic substances may mediate chlorine atom reactivity at the marine boundary layer, in addition to forming chlorolignins.     

Simultaneous quantitative analysis of polyphenolic compounds in human plasma by liquid chromatography tandem mass spectrometry

A diet rich in polyphenolic compounds has recognized health benefits, and as such is routinely monitored as part of dietary intervention studies. A method for the simultaneous determination of 36 phenolic compounds, including phenolic acids and flavonoids, using liquid chromatography and tandem mass spectrometry is described here. The target analytes were quantified based on their specific mass spectral fragments using a selected reaction monitoring approach. A C18 column with embedded aromatic functionality ensured separation of all phenolic compounds studied which included several pairs of isomers. Sample preparation involved the use of β‐glucuronidase to release the phenolic compounds from their conjugated forms. The intra‐day and inter‐day precision and accuracy was less than 7% for all phenolic compounds studied. Recoveries, where plasma was spiked with three different concentrations of the analytes, ranged from 95–115%. The limits of detection and quantification were 0.23–3.89 and 1.15–7.79 nM, respectively. The method was successfully applied to real samples and the range reported for each phenolic compound, with the exception of hydroferulic acid, nordihydroguaiaretic acid, methylgallate, and m‐coumaric acid, was at least an order of magnitude higher than the limit of quantification for the method.     

Temperature dependence of the penetration depth in Sr2RuO4: evidence for nodes in the gap function

We report measurements of the magnetic penetration depth in single crystals of Sr2RuO4 down to 0.04 K using a tunnel-diode based, self-inductive technique. We observe a power law temperature dependence below 0.8 K, with no sign of a second phase transition nor of a crossover predicted for a multiband superconductor. A power law dependence suggests that the gap function has nodes, inconsistent with candidate p-wave states. We argue that nonlocal effects, rather than impurity scattering, can explain the observed T2 dependence instead of the T-linear behavior expected for line nodes.     

The onset of coulomb explosions in polyatomic molecules

With the development of high intensity femtosecond lasers, the ionisation and dissociation dynamics of molecules has become an area of considerable interest. Using the technique of femtosecond laser mass spectrometry (FLMS), the molecules carbon disulphide, pyrimidine, toluene, cyclohexanone and benzaldehyde are studied with pulse widths of 50 fs in the near infrared (IR) wavelength region (790 nm). Results are presented and contrasted for laser beam intensities around 10(15) and 10(16) W cm(-2). For the lower intensities, the mass spectra yield dominant singly charged parent ions. Additionally, the appearance of doubly charged parent ions is evident for carbon disulphide, toluene and benzaldehyde with envelopes of doubly charged satellite species existing in these local regions. Carbon disulphide also reveals a small triply charged component. Such atomic-like features are thought to be a strong fingerprint of FLMS at these intensities. However, upon increasing the laser intensity to approximately 10(16) W cm(-2), parent ion dominance decreases and the appearance of multiply charged atomic species occurs, particularly carbon. This phenomenon has been attributed to Coulomb explosions in which the fast absorption of many photons may produce transient highly ionised parent species which can subsequently blow apart. Copyright 1999 John Wiley & Sons, Ltd.     

Uniform molecular analysis using femtosecond laser mass spectrometry

The potential of femtosecond laser time-of-flight mass spectrometry (FLMS) for uniform quantitative analysis of molecules has been investigated. Various samples of molecular gases and vapours have been studied, using ultra-fast ( approximately 50 fs) laser pulses with very high intensity (up to 1.6 x 10(16) Wcm(-2)) for non-resonant multiphoton ionisation/tunnel ionisation. Some of these molecules have high ionisation potentials, requiring up to ten photons for non-resonant ionisation. The relative sensitivity factors (RSF) have been determined as a function of the laser intensity and it has been demonstrated that for molecules with very different masses and ionisation potentials, uniform ionisation has been achieved at the highest laser intensities. Quantitative laser mass spectrometry of molecules is therefore a distinct possibility. Copyright 1999 John Wiley & Sons, Ltd.     

How the choice of data reduction can strongly influence uncertainty assessment: A re-analysis of Mn-bath experiments

The Mn-bath technique is widely used, especially by standardization laboratories, for the absolute determination of neutron emission rates. Understanding the limitations of the technique, and in particular the total measurement uncertainty, is crucial if quality results, fit for purpose, are to be reported. In this work, we show that the way in which the acquired data is analyzed can strongly influence the uncertainty assessment. We take a carefully performed set of Mn-bath measurements from the literature as our example and show that the same data when reanalyzed can be used to justify an uncertainty smaller by about an order of magnitude than was originally reported. This finding should caution all those involved in radiation measurements to critically assess their approach to data analysis and to perform a careful uncertainty analysis taking into account possible alternatives.