Determination of chloroethenes in environmental biological samples using gas chromatography coupled with solid phase micro extraction

Summary An analytical method has been developed to determine the chloroethene series, tetrachloroethene (PCE), trichloroethene (TCE),cisdichloroethene (cis-DCE) andtransdichloroethene (trans-DCE) in environmental biotreatment studies using gas chromatography coupled with a solid phase micro extraction (SPME) technique. The volatile chlorinated compounds in aqueous solution can be analyzed directly without solvent extraction, purge and trap, or thermal heating. The calibration curves have demonstrated good linear relationships within 50.0 to 3000.0 g L^–1 concentration range. Detection limits are 18.0, 5.0, 25.0, and 42.0 g L^–1, for PCE, TCE,cis-DCE andtrans-DCE, respectively. Factors which affect the SPME process, such as sample adsorption time, thermal desorption time, and concentration of salt in the matrix, have also been evaluated.     

Equilibrium states of gravitational systems

We formulate the equilibrium correlation functions for local observables of an assembly of non-relativistic, neutral gravitating fermions in the limit where the number of particles becomes infinite, and in a scaling where the region , to which they are confined, remains fixed. We show that these correlation functions correspond, in the limit concerned, to states on the discrete tensor product , where the are copies of the gauge invariantC*-algebra of the CAR overL ²(R ³). The equilibrium states themselves are then given by , where , is the Gibbs state on for an infinitely extended ideal Fermi gas at density , and where ₀ is the normalised density function that minimises the Thomas-Fermi functional, obtained in [2], governing the equilibrium thermodynamics of the system.     

Two high-throughput techniques for determining wood properties as part of a molecular genetics analysis of hybrid poplar and loblolly pine

Two new high-through put techniques, computer tomography X-ray densitometry (CT scan) and pyrolysis molecular beam mass spectrometry (pyMBMS), coupled with quantitative trait loci (QTL) analysis, were tested as a means to overcome the time and cost associated with conventional characterization of biomass feedstock components. Applications of these two techniques were evaluated using hybrid poplar for the CT scan and loblolly pine for the pyMBMS. Segregating progeny from hybrid poplar varied in specific gravity, with individual mean estimates ranging from 0.21–0.41. Progeny from loblolly pine varied in lignin, α cellulose, and mannan contents, with individual mean estimates of lignin content ranging from 28.7–33.1%, α cellulose content from 28.8–43.5% and mannan content from 4.2–10.1%. QTL analysis of the loblolly pine data suggested that eleven QTLs were associated with individual feedstock characteristics and that two QTLs for several feedstock components were linked to the same position on the loblolly pine genetic map. Each QTL individually accounted for 7–13% of the total phenotypic variation in associated loblolly pine feedstock components.     

Structure related beam propagation

The general theory of a class of structure related (SR) non-orthogonal coordinate systems is introduced for the first time. Special cases of this type of coordinate system used separately or in combination can automatically follow the local geometry of many common optical waveguide designs, thereby facilitating the fast and accurate simulation of photonic circuits, when incorporated within a FD-BPM algorithm. Substantial savings in run time and memory are possible in comparison with standard FD-BPM in rectangular coordinates.     

Continuous flow analysis of iron in zinc electrowinning electrolyte using an iron chalcogenide glass ion-selective electrode Part I. Synthetic media

It is shown that the iron(III) chalcogenide glass membrane ion-selective electrode (ISE) can be calibrated in continuous flow analysis (CFA) using acidified iron(III) nitrate standards, yielding a 60+/-3 mV per decade change in activity of Fe(3+) response in the range 10(-7)-10(-2) M total iron(III). Extended ageing of the iron(III) ISE in 2 M zinc(II) sulphate did not alter the potentiometric response characteristics of the electrode. Furthermore, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy in the presence and absence of zinc(II) sulphate failed to detect a zinc(II) interference on the iron(III) ISE. CFA/ISE determined activities of Fe(3+) in synthetic zinc electrolyte containing 2x10(-3)-2x10(-1) M total iron(III) yielded results falling within +/-0.2logaFe(3+) unit of the corresponding iron speciation data calculated using the minteqa2 program.     

Dynamics of pulse propagation in phase-shifted fibre Bragg gratings: a numerical investigation

Fibre Bragg gratings (FBGs) are an integral component of optical fibre based communication systems for signal processing. Uniform FBGs and phase-shifted FBGs find major applications as add-drop filters in dense wavelength division multiplexing (DWDM) systems where these are used to filter out channels and to shape the signal spectrum. We investigate numerically the spatiotemporal deformation of pulses as they propagate through the gratings. In particular, the effect on the pulse dynamics of phase shift or defect present in the gratings, often introduced intentionally in a grating to generate a narrow transmission spike within the stopband, is studied in time domain. This study is of significance since the deformation in the pulse in time limits the maximum bit rate achievable, and hence the pulse duration and shape need to be analysed and controlled accurately. A time domain numerical tool based on the Transmission Line Modelling (TLM) method is developed to study the pulse dynamics. The results obtained give useful information about the signal dynamics in gratings with defects, including the signal oscillations trapped in the defect, to be considered in applications such as while designing spectral filters.     

Stability,equilibrium and metastability in statistical mechanics

We survey a body of work, containing some new material, concerning the characterisation of equilibrium and metastable states of large assemblies of particles in terms of a variety of stability conditions. The theory is formulated in the thermodynamic limit and is based on the premise that the former states are those that are stable against all dynamical and thermodynamical perturbations, whereas the latter ones are endowed with only limited stability, sufficing to guarantee their long lifetimes and good thermodynamical behaviour. The Kubo-Martin-Schwinger (KMS) fluctuation-dissipation conditions play a central role in the developments stemming from this viewpoint, since it turns out that these conditions represent stability against localised disturbances of both the dynamical and thermo-dynamical kinds. Consequently, the stability arguments invoked here lead us to the following principal conclusions: (1) The equilibrium states are those that minimise the free energy density of the system and also satisfy the KMS conditions. This substantiates Gibbs's hypothesis that these states correspond to the standard ensembles. (2) Metastable states are of two kinds, that we term “ideal” and “normal”. Those of the former type satisfy the KMS conditions but minimise only the restriction of the free energy density to some reduced state space: those of the latter type are characterised by a still lower grade of stability. (3) The conditions on the forces under which ideal metastable states can exist are very restrictive, and thus the normal ones generally correspond to those observed in nature.