Injection by Programmed Temperature Vaporization Injection (PTV) of Gaseous Samples for Gas Chromatography – Atomic Emission Spectrometry (GC-AED)

Programmed temperature vaporization injection (PTV) coupled to gas chromatography and atomic emission detector (AED) has been studied for large volume injection of gaseous samples. As examples of the effectiveness of the technique, the results of the analysis of a series of headspace samples of foods such as garlic and onion, and of landfill gases are presented. The volumes of gaseous samples reconcentrated varied from a few milliliters up to liters depending on analyte dilution, through focusing onto a sorbent trap, then rapid liberation into the GC-AED system by programmed thermal desorption. Despite the high carrier gas flow rates associated with direct PTV-GC, AED performance and sensitivity were unaffected. The detailed elemental information obtained from the PTV-GC-AED analyses was confirmed using a PTV coupled to a gas chromatograph with ion trap detector mass spectrometer as detector (PTV-GC-ITD/MS).     

Dopant type dependency of domain development in rare-earth-doped ceria: An explanation by computer simulation of defect clusters

Defect clusters in several rare-earth-doped ceria (doped with Y, Sm, Gd, Dy and Yb) containing up to four oxygen vacancies and eight dopant cations have been simulated and compared. In all doped ceria systems, the binding energy of the clusters increases with increasing cluster size and the oxygen vacancies tend to form curved chains in the clusters. Moreover, the capability of the growth of defect cluster is affected by dopant type, which can explain the dopant type dependency of domain development with increasing doping concentration in heavily doped ceria.     

SEM imaging of liquid jets

We present a technique for the study of liquid jets in an environmental scanning electron microscope (ESEM). By using a two-fluid stream consisting of a water inner core and a co-flowing outer gas sheath, we are able to produce liquid streams of sufficiently low flow rate to be compatible with ESEM vacuum requirements. We have recorded ESEM images of water jets down to 700 nm diameter. Details of the jet structure, such as the point of jet breakup and size and shape of the jet cone, can be measured with ESEM to far greater accuracy than with optical microscopy. ESEM imaging of liquid jets offers a valuable research tool for the study of aerosol production, combustion processes, ink-jet generation, and many other attributes of micro- and nanojet systems.     

The Benzyne Aza‐Claisen Reaction

Adding an aryne to a tertiary allylamine affords o‐allylaniline products of an aza‐Claisen rearrangement. The aryne simultaneously provides the π component for the rearrangement and the quaternization event that lowers the activation energy for the sigmatropic shift. The reaction was applied to the synthesis of medium‐ring benzannulated amines (see scheme).

     

Spectroscopic characterization of copper(II) binding to the immunosuppressive drug mycophenolic acid

Mycophenolic acid (MPA) is a drug that has found widespread use as an immunosuppressive agent which limits rejection of transplanted organs. Optimal use of this drug is hampered by gastrointestinal side effects which can range in severity. One mechanism by which MPA causes gastropathy may involve a direct interaction between the drug and gastric phospholipids. To combat this interaction we have investigated the potential of MPA to coordinate Cu(II), a metal which has been used to inhibit gastropathy associated with use of the NSAID indomethacin. Using a range of spectroscopic techniques we show that Cu(II) is coordinated to two MPA molecules via carboxylates and, at low pH, water ligands. The copper complex formed is stable in solution as assessed by mass spectrometry and 1H NMR diffusion experiments. Competition studies with glycine and albumin indicate that the copper-MPA complex will release Cu(II) to amino acids and proteins thereby allowing free MPA to be transported to its site of action. Transfer to serum albumin proceeds via a Cu(MPA)(albumin) ternary complex. These results raise the possibility that copper complexes of MPA may be useful in a therapeutic situation.     

Monitoring erythrocytes in a microchip channel that narrows uniformly: towards an improved microfluidic-based mimic of the microcirculation

The release of adenosine triphosphate (ATP) from red blood cells (RBCs) flowing through PDMS microchannels has been determined as a function of channel cross-sectional area using a design containing a channel that narrows uniformly. ATP, released from the RBCs in response to the mechanical deformation of their cell membranes, increased as the channel cross-section decreased. One sample of rabbit RBCs released 1.16 +/- 0.11, 1.92 +/- 0.14 and 2.09 +/- 0.10 microM ATP as the median cross-sectional area decreased from 4314 to 3192 to 2052 microm(2), respectively. Numerous samples (n = 6) displayed the same trend. Incubating a sample of RBCs with diamide, a substance known to stiffen cell membranes without harming the cell cytosol, provided evidence that no cell lysis occurred in the microchip device. This novel use of lab-on-a-chip technology allows for channel designs that enable an in vitro study of physiological events that occur in the microcirculation.     

Determination of Teucrium chamaedrys volatiles by using direct thermal desorption-comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry

The direct qualification and quantification of the volatile components of Teucrium chamaedrys was studied using a direct thermal desorption (DTD) technique with comprehensive two-dimensional (2D) gas chromatography-time-of-flight mass spectrometry (GC x GC-TOF/MS). The GC x GC separation chromatographically resolved hundreds of components within this sample, and with the separation coupled with TOF/MS for detection, high probability identifications were made for 68 compounds. The quantitative results were determined through the use of internal standards and the desorption of differing amounts of raw material in the injector. The highest yield of volatile compounds (0.39%, w/w) was obtained at 150 degrees C thermal desorption temperature using 1.0mg of dried sample placed in a glass injector liner when studied over the range 1.0-7.0mg. Lowest yield of 0.33% (w/w) was found for the largest sample size of 7.0mg. Relative standard deviation (RSD) for 10 replicates at each size sample were in the range 3.9-21.6%. The major compounds identified were beta-pinene, germacrene D, alpha-pinene, alpha-farnesene, alpha-gurjunene, gamma-elemene and gamma-cadinene. All identified compounds were quantified using total ion chromatogram (TIC) peak areas. DTD is a promising method for quantitative analysis of complex mixtures, and in particular for quantitative analysis of plant samples, which can yield data without the traditional obligation for costly and time-consuming extraction techniques.     

Spectroscopic analysis of bacterial biological warfare simulants and the effects of environmental conditioning on a bacterial spectrum

The ability to distinguish bacteria from mixed samples is of great interest, especially in the medical and defence arenas. This paper reports a step towards the aim of differentiating pathogenic endospores in situ, to aid any required response for hazard management using infrared spectroscopy combined with multivariate analysis. We describe a proof-of-principle study aimed at discriminating biological warfare simulants from common environmental bacteria. We also report an evaluation of multiple pre-processing techniques and subsequent differences in cross-validation of two pattern recognition models (Support Vector Machines and Principal Component–Linear Discriminant Analysis) for a six-class classification (bacterial classification). These classifications were possible with an average sensitivity of 88.0 and 86.9?%, and an average specificity of 97.6 and 97.5?% for the SVM and the PC-LDA models, respectively. Most spectroscopic models are built upon spectra from bacteria that have been specifically prepared for analysis by a particular method; this paper will comment upon the differences in the bacterial spectrum that occur between specific preparations when the bacteria have spent 30?days in the simulated weather conditions of a hot dry climate.

Formalising the Pathways to Life Using Assembly Spaces

Assembly theory (referred to in prior works as pathway assembly) has been developed to explore the extrinsic information required to distinguish a given object from a random ensemble. In prior work, we explored the key concepts relating to deconstructing an object into its irreducible parts and then evaluating the minimum number of steps required to rebuild it, allowing for the reuse of constructed sub-objects. We have also explored the application of this approach to molecules, as molecular assembly, and how molecular assembly can be inferred experimentally and used for life detection. In this article, we formalise the core assembly concepts mathematically in terms of assembly spaces and related concepts and determine bounds on the assembly index. We explore examples of constructing assembly spaces for mathematical and physical objects and propose that objects with a high assembly index can be uniquely identified as those that must have been produced using directed biological or technological processes rather than purely random processes, thereby defining a new scale of aliveness. We think this approach is needed to help identify the new physical and chemical laws needed to understand what life is, by quantifying what life does.     

On a separation theorem for generalized eigenvalues and a problem in the analysis of sample surveys

We obtain usable bounds for the asymptotic percentage points of chi-squared tests of fit for log-linear models fitted to contingency tables estimated from survey data, by applying some new separation inequalities for the generalized eigenvalues of a matrix X′AX with respect to a matrix X′BX, when both the matrices A and B are nonnegative definite. We also present some historical remarks on the Poincaré separation theorem for eigenvalues from which our new inequalities are shown to follow.