Online rapid sampling microdialysis (rsMD) using enzyme-based electroanalysis for dynamic detection of ischaemia during free flap reconstructive surgery

We describe an enzyme-based electroanalysis system for real-time analysis of a clinical microdialysis sampling stream during surgery. Free flap tissue transfer is used widely in reconstructive surgery after resection of tumours or in other situations such as following major trauma. However, there is a risk of flap failure, due to thrombosis in the flap pedicle, leading to tissue ischaemia. Conventional clinical assessment is particularly difficult in such ‘buried’ flaps where access to the tissue is limited. Rapid sampling microdialysis (rsMD) is an enzyme-based electrochemical detection method, which is particularly suited to monitoring metabolism. This online flow injection system analyses a dialysate flow stream from an implanted microdialysis probe every 30 s for levels of glucose and lactate. Here, we report its first use in the monitoring of free flap reconstructive surgery, from flap detachment to re-vascularisation and overnight in the intensive care unit. The on-set of ischaemia by both arterial clamping and failure of venous drainage was seen as an increase in lactate and decrease in glucose levels. Glucose levels returned to normal within 10 min of successful arterial anastomosis, whilst lactate took longer to clear. The use of the lactate/glucose ratio provides a clear predictor of ischaemia on-set and subsequent recovery, as it is insensitive to changes in blood flow such as those caused by topical vasodilators, like papaverine. The use of storage tubing to preserve the time course of dialysate, when technical difficulties arise, until offline analysis can occur, is also shown. The potential use of rsMD in free flap surgery and tissue monitoring is highly promising.

The effects of streamline curvature and spanwise rotation on near-surface,turbulent boundary layers

A second moment closure model is used to study the mean fields and turbulence structure of spanwise rotating flows and flows with streamline curvature. The effects of flow stabilization and destabilization by rotation and/or curvature and their interpretation in terms of a Rayleigh instability mechanism are discussed in the context of the present model. When applied to the constant flux layer adjacent to a bounding surface, the model provides a similarity theory for flows with spanwise rotation and streamline curvature like that of Monin-Obukhov in the case of density stratified flows. In particular, it is shown that Bradshaw's empirical length scale correction can be derived in terms of the basic constants of the model determined in the absence of rotation and curvature. Also, direct comparisons with experimental data confirm the model predictions. The definitions of strong and mild curvature are discussed and a distinguishing criterion derived.

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Zusammenfassung Gemittelte Strömungsfelder und Turbulenzcharakteristiken werden bestimmt mittels eines numerischen Modelles mit Momenten zweiter Ordnung als Ciosure für lateral rotierende Strömungen und mit gekrümmten Stromlinien. Stabilisierungs- und Destabilisierungseffekte infolge Rotation und/oder Krümmung werden als Raleigh-Instabilitäten im Zusammenhang mit dem Modell diskutiert. Wenn angewandt auf die Konstant-Scherspannungszone in Grenzschichten, liefert das Modell eine Ähnlichkeitstheorie für Strömungen mit lateraler Rotation und Stromlinienkrümmung, vergleichbar dem Falle des Monin-Obukhov Modelles für geschichtete Strömungen. Es wird insbesondere gezeigt, dass Bradshaws empirische Längenkorrektur sich aus den Grundkonstanten des Modelles ergibt für den Grenzfall ohne Rotation und Krümmung. Direkter Vergleich mit experimentellen Daten bestätigt die Rechnungen. Die Definitionen von starker und schwacher Krümmung werden diskutiert und ein Unterscheidungskriterium eingeführt.

     

Monohydrates of cuprous chloride and argentous chloride: H2O⋅⋅⋅CuCl and H2O⋅⋅⋅AgCl characterized by rotational spectroscopy and ab initio calculations

Pure rotational spectra of the ground vibrational states of ten isotopologues of each of H(2)O???CuCl and H(2)O???AgCl have been measured and analyzed to determine rotational constants and hyperfine coupling constants for each molecule. The molecular structure and spectroscopic parameters determined from the experimental data are presented alongside the results of calculations at the CCSD(T) level. Both experiment and theory are consistent with structures that are nonplanar at equilibrium. The heavy atoms are collinear while the local C(2) axis of the water molecule intersects the axis defined by the heavy atoms at an angle, φ = 40.9(13)° for Cu and φ = 37.4(16)° for Ag. In the zero-point state, each molecule is effectively planar, undergoing rapid inversion between two equivalent structures where φ has equal magnitude but opposite sign. The equilibrium geometry has C(s) symmetry, however. The ab initio calculations confirm that the timescale of this inversion is at least an order of magnitude faster than that of rotation of the molecule in the lowest rotational energy levels. The molecular geometries are rationalized using simple rules that invoke the electrostatic interactions within the complexes. Centrifugal distortion constants, Δ(J) and Δ(JK), nuclear quadrupole coupling constants, χ(aa)(Cu), χ(aa)(Cl), (χ(bb) - χ(cc))(Cu), and (χ(bb) - χ(cc))(Cl), and the nuclear spin-rotation constant of the copper atom, C(bb)(Cu)+C(cc)(Cu), are also presented.     

A 119Sn Mössbauer study of the thermal degradation of organotin stabilisers in PVC

^119mSn Mössbauer studies of the thermal degradation of PVC containing the stabilisers dibutyltinbis ($\text{iso}$octylthioglycollate) (1.2% by weight of the polymer), dioctyltinbis ($\text{iso}$octylthioglycollate (4% by weight of the polymer) and dibutyltinbis ($\text{iso}$octylmaleate) (2% by weight of the polymer) indicate that in each case the stabiliser is converted into the dialkylmonochlorotin ester R₂SnCl(X) (X  SCH₂CO₂C₈H₁₇ or O₂C.CH  CHCO₂C₈H₁₇), and not into the dialkyltin dichloride, R₂SnCl₂, as recently suggested by other workers. Comparison of the Mössbauer data for organotin-stabilised PVC samples prepared by both hot-milling and room temperature solvent casting processes indicates that there is little degradation of the polymer (and stabiliser) during the initial hot-milling process.     

Site distribution in resin beads as determined by confocal Raman spectroscopy

Scanning confocal Raman spectroscopy was used to study the distribution of reactive sites within a resin bead used for solid-phase synthesis. The distribution of NH2 groups in aminomethylated polystyrene resin (APS) was determined by doping with varying amounts of 4-cyanobenzoic acid. The extent of loading was determined by both elemental analysis and ninhydrin assays. The spatial distribution of the coupled 4-cyanobenzamide within the bead was determined to an in-plane resolution of 1 microm and depth resolution of about 4 microm, using the strong Raman CN stretching vibrational transition at 2230 cm(-1). Dry and swollen beads were studied and the distribution was found to be essentially uniform throughout the bead in all cases.     

Turbulent boundary layers with large streamline curvature effects

It has been shown that turbulent flows are greatly affected by streamline curvature. In spite of this and the fact that curved shear flows are frequently encountered in engineering applications, the predictions of such flows are relatively less developed than the predictions of two-dimensional plane flows. Recently, various attempts were made by different investigators; however, their methods are only successful when the product of the boundary layer thickness to the local surface curvature |k| is 0.05. The present paper investigates the more general case where 0.1|k|0.5. Results show that the calculated boundary-layer characteristics for arbitrary free stream conditions are in good agreement with measurements.

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Zusammenfassung Es ist gezeigt worden, dass turbulente Strömungen durch eine stromlinienförmige Krümmung stark beeinflusst werden. Trotzdem und trotz der Tatsache, dass gekrümmte Randströmungen häufig bei technischen Anwendungen gefunden werden, sind die Vorhersagen solcher Strömungen verhältnismässig weniger entwickelt als die Vorhersagen zweidimensionaler ebener Strömungen. In letzter Zeit sind von verschiedenen Forschern Versuche in dieser Richtung unternommen worden; jedoch waren ihre Methoden nur dann erfolgreich, wenn das Verhältnis der Grenzschichtdicke zur bestimmten örtlichen Oberflächenkrümmung |k|0,05 ist. Die vorgelegte Arbeit untersucht den allgemeineren Fall, bei dem 0,1|k|0,5 ist. Die Resultate zeigen, dass sich die berechneten Grenzschichteigenschaften für beliebig freie Strömungsbedingungen in befriedigender Uebereinstimmung mit den Messungen befinden.

     

Low-pressure membrane filtration of secondary effluent in water reuse: Pre-treatment for fouling reduction

Fouling in the low-pressure membrane filtration of secondary effluent for water reuse can be severe due to the complex nature of the components in the water. Pre-filtration, coagulation and anion exchange resin were investigated as pre-treatments for reducing fouling of microfiltration (MF) and ultrafiltration (UF) membranes in the treatment of activated sludge-lagoon effluent. The key fouling components were determined using several analytical techniques to detect differences in the organic components between the feed and permeate.Pre-filtration (1.5 μm) enhanced the permeate flux for MF by removing particulates, but had little effect for UF. Marked flux improvement was obtained by coagulation pre-treatment at 5 mg L⁻¹ Al³⁺ with internal membrane fouling being substantially alleviated. Anion exchange resin removed >50% of effluent organic matter but did not improve the flux or reduce irreversible membrane fouling. These results, together with detailed organic compositional analyses, showed that the very high-molecular weight organic materials (40–70 kDa) comprised of hydrophilic components such as soluble microbial products, and protein-like extracellular matter were the major cause of membrane fouling.     

Complexation of L-lactate with boronic acids: a solution and holographic analysis

Boronic acids have been used as receptors for the detection of diols and alpha-hydroxy acids. The incorporation of 3-acrylamide phenyl boronic acid (3-APB) into a hydrogel generates a suitably responsive and fully reversible holographic sensor for L-lactate. However, it was also found that the use of 3-APB resulted in the sensor being responsive towards a number of other compounds containing two hydroxy groups. This report details the further investigation into the reaction between L-lactate and three boronic acid-based receptors, both in the holograms and in solution, in order to establish the mechanism of binding. A novel boronate receptor is proposed based on this understanding.     

The Physical Tourist¶Historical Sites of Physical Science in Copenhagen

We provide a physical tour of Copenhagen focusing particularly on the sites associated with five great Danish scientists: Tycho Brahe (1546-1601), Niels Steensen (1638-1686), Ole Rømer (1644-1710), Hans Christian Ørsted (1777-1851), and Niels Bohr (1885-1962). We also point out the cemetery where prominent scientists are buried, and we note the location of the Carlsberg Honorary Residence.