Introduction: Occlusive arterial disease is usually multi-focal but the cumulative functional effect of multiple arterial stenoses is not fully understood. We tested the hypothesis that a non-linear pressure/flow model (DeltaP = k(1)Q + k(2)Q(2)) that has been validated for single stenoses is also valid for multiple stenoses arranged in series.Method: The pressure/flow characteristics of three dissimilar modelled stenoses were measured individually and in different combinations using a hydraulic flow rig. 2Results: The combined effect of multiple stenoses fitted the non-linear model accurately (R-2 = 0.99) and approximated to the sum of the k(1) and k(2) parameters for each individual stenosis. For multiple stenoses the cumulative k(1) was less than the predicted and the series order of the individual stenoses consistently altered the combined effect.Conclusions: A sequence of multiple stenoses is functionally equivalent to a single equivalent stenosis of greater functional severity and can be represented by a single viscous (k(1)) and inertial (k(2)) pressure loss coefficient. This finding allows the term I critical stenosis' to be defined precisely in terms of the functional effect rather than the anatomical appearance, particularly where disease is multi-focal.

AIM:To explore the learning possibilities of linking art and anatomy learning.METHOD AND RESULTS:First- and second-year medical students at Southampton University were offered the chance to take part in 3-hour life drawing classes with a life drawing tutor and an anatomist. Attempts were made by the anatomy tutor to link the muscles and bones of the living body in front of the students with their previous learning. The sessions were successful, and enjoyed by students.CONCLUSIONS:Whilst this type of learning cannot take the place of more formal instruction, there does seem to be value in increasing students' interest by providing new points of view and contexts for dry pre-clinical learning. A greater knowledge by the students of anatomy, physiology and clinical medicine at a later stage in their course might have provided further ways to exploit this learning opportunity.

A theoretical description of the kinetics of the passive transport of both lipophobic and lipophilic nonelectrolytes, weak acids, and weak bases through membranes of large unilamellar vesicles is discussed. Equations are derived which may be used to obtain permeability coefficients and predict the extent of LUV entrapment of permeant molecules. Theoretical curves are generated to illustrate the difference between lipophobic and lipophilic permeation. By applying a diffusional approach rather than a simple first order kinetic approach to the problem of passive transport, some of the inconsistencies observed in other works are corrected.

The transmembrane permeability coefficients of the environmentally sensitive arsenicals, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) have been measured for egg phosphatidylcholine large unilamellar vesicles. The determination of the vesicle concentration-independent first-order rate constants for membrane transport and the permeability coefficients were made using an NMR technique employing shift agents. The permeability coefficient of DMA was found to be two orders of magnitude greater than that of MMA. This is attributed to the presence of MMAs extra hydroxyl group. Both species are shown to permeate membranes in the neutral form. Both the temperature dependence and the dependence on cholesterol content were investigated for DMA. The activation energy and the Arrhenius preexponential factor were found to be dependent on the cholesterol content. A marked increase in both parameters was observed up to 20 mol.% cholesterol, with a further, small increase up to 60%. The significance of these results to our understanding of membrane transport is discussed. The importance of using permeability coefficients rather than n-octanol/water partition coefficients in determining bioavailability and bioaccumulation of environmentally sensitive compounds is also discussed.

The partial pyrolysis of gold(III) fluorosulfate, Au(SO3F)3, at temperatures below 145-degrees-C allows the generation of Au2+ defects in the solid residue by reductive elimination of SO3F. radicals. Solvated Au2+ is obtained by the reduction of Au(SO3F)3 in HSO3F solution by gold powder at 65-degrees-C. Both systems are studied by ESR and identical high g(iso) values of g = 2.360 are found. Hyperfine splitting due to Au-197, I = 3/2, is observed in frozen solutions of Au2+(solv). Pyrolysis of Br3[Au(SO3F)4] also gives partly pyrolyzed Au(SO3F)3, with a sufficiently high Au2+ ion concentration, to allow a magnetic susceptibility study between 100 and 295 K.

The line width of the proton magnetic resonance spectrum (MRS) of the composite methylene and methyl resonances of plasma has been reported as a marker for the presence of malignancy. In this study, the contribution of very low density (VLDL), low density (LDL), and high density lipoproteins (HDL) to the MRS line width was determined. This was achieved by measuring the MRS line widths for the plasma from patients with primary disorders of lipoprotein metabolism and from normal individuals. A negative correlation between plasma trigylceride levels and the average line width was observed and this was confirmed in normal plasma to which pure VLDL was added. Also, computer simulations were employed to demonstrate how the line width varies in such complex mixtures of lipoproteins. We demonstrate that the line width is governed by the relative contribution of VLDL and HDL to the composite line shape. This is particularly important when the shoulder from the HDL line lies near the half-height of the VLDL line. As changes in VLDL/HDL ratio occur in patients with malignancy, we propose that this is the basis of the narrowed MRS lines observed in the proposed test for malignancy. However, any individual with elevated VLDL will be false positive in this test.

A combination of ESR lineshape studies and NMR relaxation time measurements permits the complete elucidation of the rotational diffusion tensor of a spin probe. The technique employs both paramagnetic (Cu(II)) and deuterated diamagnetic (Ni(II)) homologs of bis[pyrollidine-N-carbodithioato]metal(II) complexes. The lineshape and relaxation time measurements were analyzed in terms of spectral densities which in turn were inverted to give the principal elements of the diffusion tensor. The results obtained insights into the pitfalls of the commonly made assumption of isotropic rotational diffusion.

The errors arising from the approximations inherent in numerical integration are well known and are usually minimized by using large data densities. However, the relationship between the nature and magnitude of the errors and the data density has not been investigated in the context of magnetic resonance spectroscopy. This information is important if one is using spectra with an inherent low data density or if one wishes to trade off computation speed with accuracy. The relationship between data density and accuracy is especially pertinent to NMR and ESR spectroscopy where data densities are often low and the errors can become quite large. These errors are discussed in general and rule-of-thumb guidelines given.

The use of dispersion versus absorption (DISPA) plots in ESR spectroscopy is investigated. The utility of the method in detecting various lineshape distortions due to spectrometer or sample properties is discussed. The effects of saturation, dispersion leakage, inhomogeneous broadening, and overlapped resonances on DISPA plots are examined in detail using a radial difference plot. An interactive method of removing baseline drift, to which DISPA plots are sensitive, is introduced. The applicability of DISPA techniques to the field of spin-labeling polymers and biopolymers is also assessed.

The performance of quantitative analysis of 1D NMR spectra depends greatly on the choice of the NMR signal model. Complex least-squares analysis is well suited for optimizing the quantitative determination of spectra containing a limited number of signals (<30) obtained under satisfactory conditions of signal-to-noise ratio (>20). From a general point of view it is concluded, on the basis of mathematical considerations and numerical simulations, that, in the absence of truncation of the free-induction decay, complex least-squares curve fitting either in the time or in the frequency domain and linear-prediction methods are in fact nearly equivalent and give identical results. However, in the situation considered, complex least-squares analysis in the frequency domain is more flexible since it enables the quality of convergence to be appraised at every resonance position. An efficient data-processing strategy has been developed which makes use of an approximate conjugate-gradient algorithm. All spectral parameters (frequency, damping factors, amplitudes, phases, initial delay associated with intensity, and phase parameters of a baseline correction) are simultaneously managed in an integrated approach which is fully automatable. The behavior of the error as a function of the signal-to-noise ratio is theoretically estimated, and the influence of apodization is discussed. The least-squares curve fitting is theoretically proved to be the most accurate approach for quantitative analysis of 1D NMR data acquired with reasonable signal-to-noise ratio. The method enables complex spectral residuals to be sorted out. These residuals, which can be cumulated thanks to the possibility of correcting for frequency shifts and phase errors, extract systematic components, such as isotopic satellite lines, and characterize the shape and the intensity of the spectral distortion with respect to the Lorentzian model. This distortion is shown to be nearly independent of the chemical species, of the nature of the molecular site, and of the type of nucleus, but to vary significantly with the spectrometer. The potential of the method for accurate fast and fully automatic quantitative analysis is illustrated in the case of natural-abundance deuterium NMR spectra such as those of linalool and ethyl mandelate.

A swath sounding system is under development which is capable of being towed from ships of opportunity. The principle on which it is based is an acoustic interferometer to which a vernier has been added to resolve the ambiguity of phase ramp identification. The ‘fish’ is equipped with both rotational and translational attitude sensors, though no attempt is made to stabilize it. This is in the interest of size and hence of both instrumental and deployment economy. The paper, which was presented at Oceanology International 1982 at Brighton, proposes a novel method to permit replication of the swath depth measurements, and also to provide an independent means of ground scale correction, which may obviate the need to deploy a positioning network for deep-water high-resolution swath surveys.

The reorientational correlation times (τ2) of spin probe molecules based on 63Cu dithiocarbonates have been determined by line width analysis. The dependence of τ2 on (η/T) has been investigated and it is found that at low values of (η/T) the hydrodynamic lip boundary condition holds. At higher values of (η/T) an increase in the degree of stickiness of the interaction between the probe molecule and the solvent occurs.

Plots of dispersion versus absorption (DISPA) in NMR have previously been shown to provide an extremely sensitive test for deviations from Lorentzian lineshape. In this paper, the experimental absorption derivative EPR spectrum of peroxylamine disulfonate (PADS) is digitized during field-sweep detection and numerically integrated to give an absorption spectrum, which is then numerically Hilbert transformed to yield a dispersion spectrum, and in turn a DISPA plot. The effect of field modulation is demonstrated both theoretically and experimentally to produce an EPR DISPA curve whose displacement outside its reference circle is directly related to the strength of the modulating field. The modulating field strength can thus be determined without external calibration, using a single DISPA plot. In addition, DISPA detection of small lineshape distortions resulting from field sweep at rates faster than are appropriate to the time constant of the phase-sensitive detector is demonstrated experimentally. Finally, the circular DISPA plot for PADS at high concentration readily illustrates the homogeneous nature of the line broadening, again from a single EPR spectrum. These results show that the DISPA technique can be used, even when only the absorption spectrum is experimentally available.

Electron spin resonance (ESR) has been used to study the reorientational correlation times (τ2) of a series of bis(dialkyldithiocarbamato)63 Cu(II) spin probes, in toluene, as a function of temperature. It has been found that the linear relationship τ2=C(η/T)+τ02 is obeyed over most of the temperature range studied, but at high temperatures some evidence of nonlinearity exists for the smaller spin probes. The value of C observed is intermediate between the value calculated using slip and stick boundary conditions of hydrodynamic theory. The magnitude of C is indicative of moderate non-hard-core interactions.

We have built a low-cost stand-alone digital data logging system, designed around a Fairchild F-8 microprocessor, interfaced to an EPR spectrometer. The general block diagram, some hardware details and the software concepts of the system are presented together with the operational procedure. The data acquired are processed off-line at a central computer to provide calibrated EPR spectra or the absolute values of line positions and linewidths.

Current UK Building Regulations specify the installation of radon-proofing, typically by means of an impermeable membrane, in new homes constructed in Radon Affected Areas. Radon levels were measured in 64 recently-constructed dwellings in the village of Brixworth, Northamptonshire, an area designated as a Radon Affected Area in 1992, all of which were known to have had radon-proof membranes installed during construction. 11% of the dwellings surveyed were found to have radon levels in excess of the Action Level, compared with the 17% average for all homes in the area, radon-proofed or not. The results suggest that, in some 60% of the homes surveyed, installation of a membrane has not resulted in reduction of mean annual radon concentrations to below the Action Level. It is recommended that mandatory testing be introduced for all new homes in Affected Areas.