Dr Richard Smith

With the aim of characterizing polymer-based drug delivery systems a combination of Scanning MeV 3He microbeam Nuclear Reaction, Backscattering and Particle Induced X-ray Emission (PIXE) techniques has been developed. This, together with gravimetric and UV techniques has been applied to characterize both water infusion and drug effusion for three in-mouth polymer–drug systems. Preliminary results are presented from the exposure of polymers, containing drug at a level of 9% by weight of the dry polymer, to both pure water and a phosphate buffered saline solution at 37°C.

The use of in vitro reconstructed human epidermis (RHE) by the cosmetic and pharmaceutical industries is increasing because of its similar physiological mechanisms to native human skin. With the advent of ethic laws on animal experimentation, RHE provides an helpful alternative for the test of formulations. The aim of this study is to check that the RHE mineral status is comparable to that of human native skin by investigating the elemental distributions in the epidermis strata. In addition, possible deleterious effects of the transport on the epidermis ionic content were studied by nuclear microscopy.

Light-ion microbeams provide a unique opportunity to irradiate biological samples at the cellular level and to investigate radiobiological effects at low doses of high linear energy transfer ionizing radiation. Since 1998 a single-ion irradiation facility has been developed on the focused horizontal microbeam line of the CENBG 3.5 MV Van de Graaff accelerator. This setup delivers in air single protons and alpha particles of a few MeV onto cultured cells, with a spatial resolution of a few micrometers, allowing subcellular targeting. In this paper, we present results from the use of the GEANT4 toolkit to simulate cellular irradiation with the CENBG microbeam line, from the entrance to the microprobe up to the cellular medium. We show that a 3 MeV incident alpha particle may deliver a dose of 0.33 Gy to a typical cell nucleus.

In the framework of a systematic study on light ion (p, d) induced reaction on different targets of medical, industrial, etc. importance, natural cobalt has been investigated by using stacked-foil technique. In these measurements C-55,C-56,C-57,C-58,C-60 isotopes have been identified. Beyond the Cobalt isotopes we have also presented Ni-57 and Mn-52 from the proton experiment. For the above isotope the excitation functions in the measured energy range were determined and compared with the literature data and with the results of model calculations. The agreement with previous measurements was good and we have also measured new cross-section data.

The use of a 1/spl mu/m ion beam as a tomographic probe could constitute a powerful tool for displaying the 3D structure of samples a few tens or hundreds of micrometers thick in a nondestructive way. At the Centre d'Etudes Nucle/spl acute/aires de Bordeaux-Gradignan (CENBG), Gradignan, France, ion beam microtomography has been developed for biomedical applications at the cell level. The internal structure of cancer cells has been explored using scanning transmission ion microscopy (STIM) tomography, giving access to the 3D distribution of mass density (in g/cm/sup 3/) within the analyzed volume. The sole sample preparation required is cryofixation and freeze-drying, permitting under vacuum analysis. The combination of STIM and particle induced X-ray emission (PIXE) tomography is under progress with the aim of revealing the distributions and local concentrations of elements at the cell level.

Work is presented on the development of a retrospective/fortuitous accident dosimetry service using optically stimulated luminescence of resistors found in mobile phones to determine the doses of radiation to members of the public following a radiological accident or terrorist incident. The system is described and discussed in terms of its likely accuracy in a real incident.

In the framework of the EU-FP7 MULTIBIODOSE project, two protocols using OSL of resistors removed from the circuit board of mobile phones were developed with the aim to use the resistors as fortuitous dosimeters in the event of a large scale radiological accident. This paper presents the results of an inter-laboratory comparison carried out under the umbrella of EURADOS. The two aims of this exercise were the validation of the MULTIBIODOSE protocols by a large number of laboratories and the dissemination of the method with the objective of preparing the basis for a network that could increase Europe's response capacity in the case of a mass casualty radiological emergency. Twelve institutes from eleven European countries and one institute from the USA, with various degrees of expertise in OSL dosimetry, took part in the OSL inter-laboratory comparison. Generally, a good agreement within uncertainties was observed between estimated and nominal doses.

A new data reduction software package has been developed at CENBG for scanning transmission ion microscopy tomography (STIM-T) data. This program, TomoRebuild, has been designed in Visual C++® in the Windows® environment. Fortran 77® routines from the Donner Library were translated to C++ for the reconstruction of 2D and 3D data using the filtered backprojection algorithm. Tomography images are stored as ASCII files to be displayed using a graphic interface. A graphic software based on the AMIRA® environment was developed to extract and display 3D structures according to their density. The whole program was designed to be interactive, simple to use and easily adjustable to different experimental conditions. 3D STIM-T was carried out on microcomposite materials, allowing determination of the density of a thin AlN layer deposited on a SiC microfibre.

N profiles of several GaAs1−xNx epitaxial layers with different N mole fractions in the range 0 < x < 0.14 were obtained by using (1) heavy-ion elastic recoil detection analysis (HI-ERDA) along with Rutherford backscattering spectrometry (RBS) using a 35 MeV Si6+ beam, and (2) nuclear reaction analysis (NRA) with the 14N(α, p)17O reaction, also with RBS, using a 3.7 MeV 4He+ beam. The results from the two techniques are compared and the advantages, disadvantages and capabilities are discussed.

AA2024 T3 alloy specimens have been anodised in tartaric acid/sulphuric media and tartaric acid/sulphuric media containing sodium molybdate; molybdate species were added to the anodising bath to enhance further the protection provided by the porous anodic film developed over the macroscopic alloy surface. Morphological characterisation of the anodic films formed in both electrolytes was undertaken using scanning electron and transmission electron microscopies; the chemical compositions of the films were determined by Rutherford backscattering spectroscopy that was complemented by elemental depth profiling using rf-glow discharge optical emission spectrometry. The electrochemical behaviour was evaluated using potentiodynamic polarisations and electrochemical impedance spectroscopy; the corrosion performance was examined after salt spray testing. The porous anodic film morphology was little influenced by the addition of molybdate salt, although thinner films were generated in its presence. Chemical composition of the anodic film was roughly similar; however, addition of sodium molybdate in the anodizing bath resulted in residues of molybdate species in the porous skeleton and improved corrosion resistance measured by electrochemical techniques that was confirmed by salt spray testing.

The Public Health England fortuitous dosimetry capability is reviewed, with particular attention focussed on the derivation of its energy and fading corrections, the Monte Carlo techniques used to generate the calibration factors between phone and body doses, and the procedures set in place to facilitate a reliable and effective service.

Irradiation of materials by heavy ions accelerated in MV tandem accelerators may lead to the production of latent ion tracks in many insulators and semiconductors. If irradiation is performed in a high resolution microprobe facility, ion tracks can be ordered by submicrometer positioning precision. However, full control of the ion track positioning can only be achieved by a reliable ion hit detection system that should provide a trigger signal irrespectively of the type and thickness of the material being irradiated. The most useful process that can be utilised for this purpose is emission of secondary electrons from the sample surface that follows the ion impact. The status report of the set-up presented here is based on the use of a channel electron multiplier (CEM) detector mounted on an interchangable sample holder that is inserted into the chamber in a close geometry along with the sample to be irradiated. The set-up has been tested at the Zagreb ion microprobe for different ions and energies, as well as different geometrical arrangements. For energies of heavy ions below 1 MeV/amu, results show that efficient (100%) control of ion impact can be achieved only for ions heavier than silicon. The successful use of the set-up is demonstrated by production of ordered single ion tracks in a polycarbonate film and by monitoring fluence during ion microbeam patterning of Foturan glass.

Water diffusion into cylindrical biodegradable monolithic depots fabricated from extruded mixtures of poly(dl-lactide) and a peptidic drug, goserelin, containing 20, 30 and 40% drug by weight has been studied using an ion beam analysis technique. A series of depots were immersed in a phosphate buffered saline/heavy water solution at 37 °C for times ranging from 1 h to 7 days. One-dimensional radial profiles showing the diffusion of water into the depots were produced at points along the length of the sample and, for some short immersion times, axial profiles were obtained for the cylinder ends. The changes in weight, radius, drug release and water uptake of the depots with time were also studied. Using the water uptake measurements the one-dimensional radial profiles were normalised. From appropriate one-dimensional profiles at the shorter times Fickian diffusion coefficients were obtained for initial water diffusion. The average radial diffusion coefficients were (1.07±0.22)×10−8 cm2 s−1 for the 20% drug-loaded depots, (1.54±0.27)×10−8 cm2 s−1 for the 30% drug-loaded depots and (2.00±0.83)×10−8 cm2 s−1 for the 40% drug-loaded depots—in the ratio of the drug loadings i.e. 2:3:4, implying the water associated with drug during its uptake into the monoliths. The axial diffusion coefficients were found to be of the same order of magnitude as the radial diffusion coefficients, in accord with this hypothesis. At longer times there is a subsequent non-Fickian increase in the water concentration profile. In the case of depots loaded with 40% by weight of goserelin, the substantial fraction of the hydrophilic drug released at times greater than one day is accompanied by a decrease in radius and a decrease in water concentration near the depot surface.

In the present work we demonstrate the development of a thin layer activation (TLA) method to be able to measure micrometer wear or less by using radioactive tracing. In order to activate very swallow depths we decreased the bombarding energy to the “linear” region of the cross-section curve. The disadvantage of the method is that the wear curve will be “linear” near to the surface instead of “constant” as is the case with the usual (high energy) TLA. The advantage is that the activity of the sample will be much lower and it is concentrated in the swallower studied depth. The other possible method is irradiation under small angle (15 to 30° or even grazing incidence), which also causes a near-surface concentration of the activity produced. Both methods are demonstrated with the most suitable nuclear reactions and some commonly used industrial materials.

Nuclear reaction analysis (NRA) is a standard technique in compositional analysis of materials, including depth profiling of elements. It is particularly useful for the profiling of deuterium in polymers. However, the data analysis can be cumbersome and time-consuming. In this paper we present fully automated analysis of NRA data using the simulated annealing combinatorial optimization algorithm. The routine is general and can be used to analyse data from any reaction with known Q value and cross section. The shape of the cross section is taken into account, and hence depth profiling using reactions with non-flat cross sections can be done in a trivial way. Furthermore, the algorithm allows one to take into account the degradation of energy resolution with probing depth, which is shown to be crucial in analysing thin layers, where the depth resolution is a determining factor. We have also shown that we can calculate confidence limits on the depth profiles obtained by using Bayesian inference with the Markov chain Monte Carlo method. We present the application of the algorithm to the analysis of deuterated polystyrene samples.

The diffusion of water into the developmental drug-release polymer addition cured silicone has been investigated using {sup 3}He ion scanning micro-beam techniques developed at the University of Surrey. Polymer samples loaded with 15% by weight of the drug chlorohexidine diacetate were immersed in a water based phosphate buffered saline solution for times of 1 hour, 1 day, 1 week and 1 month. The results showed that as the water diffused into the polymer it associated with the drug allowing its release by diffusion through the network formed by water filled pores. Future improvements to the techniques are discussed including the use of an array of CdZnTe detectors.

Ensemble learning is a method of combining learners to obtain more reliable and accurate predictions in supervised and unsupervised learning. However, the ensemble sizes are sometimes unnecessarily large which leads to additional memory usage, computational overhead and decreased effectiveness. To overcome such side effects, pruning algorithms have been developed; since this is a combinatorial problem, finding the exact subset of ensembles is computationally infeasible. Different types of heuristic algorithms have developed to obtain an approximate solution but they lack a theoretical guarantee. Error Correcting Output Code (ECOC) is one of the well-known ensemble techniques for multiclass classification which combines the outputs of binary base learners to predict the classes for multiclass data. In this paper, we propose a novel approach for pruning the ECOC matrix by utilizing accuracy and diversity information simultaneously. All existing pruning methods need the size of the ensemble as a parameter, so the performance of the pruning methods depends on the size of the ensemble. Our unparametrized pruning method is novel as being independent of the size of ensemble. Experimental results show that our pruning method is mostly better than other existing approaches.

The molecular composition of polymer blend surfaces defines properties such as adhesion, wetting, gloss, and biocompatibility. The surface composition often differs from the bulk because of thermodynamic effects or modification. Mixtures of colloids and linear polymers in a common solvent are often used to deposit films for use in encapsulants, inks, coatings, and adhesives. However, means to control the nonequilibrium surface composition are lacking for these systems. Here we show how the surface composition and hydrophilicity of a film deposited from a bimodal mixture of linear polymers and colloids in water can be adjusted simply by varying the evaporation rate. Ion beam analysis was used to quantify the extent of stratification of the linear polymers near the surface, and the results are in agreement with a recent diffusiophoretic model. Because our approach to stratification relies solely on diffusiophoresis, it is widely applicable to any system deposited from colloids and nonadsorbing polymers in solution as a means to tailor surface properties.

The measurement of the Seebeck coefficient of thin film (100 nm) amorphous germanium telluride containing~31% oxygen under dark conditions and when exposed to monochromatic light in the 400 nm to 1800 nm wavelength region is reported. Exposure of the films to light is found to reduce the absolute value of the Seebeck coefficient compared to that measured in the dark. Furthermore, the magnitude of this reduction displays a distinctive spectral dependence over the wavelength range covered. The observed behaviour suggests that these measurements provide a method determining the optical bandgap of thin amorphous chalcogenide films. Further analysis of the data, along with that of X-ray photoelectron spectroscopy and photoconductivity studies, is used to determine the presence of sub-bandgap defect states and their role in determining the optical response of the Seebeck coefficient.

The distribution of surfactants in waterborne colloidal polymer films is of significant interest for scientific understanding and defining surface properties in applications including pressure-sensitive adhesives and coatings. Because of negative effects on appearance, wetting, and adhesion, it is desirable to prevent surfactant accumulation at film surfaces. The effect of particle deformation on surfactant migration during film formation was previously investigated by Gromer et al. through simulations, but experimental investigations are lacking. Here, we study deuterium-labeled sodium dodecyl sulfate surfactant in a poly(butyl acrylate) latex model system. The particle deformability was varied via cross-linking of the intraparticle polymer chains by differing extents. The cross-linker concentration varied from 0 to 35 mol % in the copolymer, leading to a transition from viscoelastic to elastic. Ion beam analysis was used to probe the dry films and provide information on the near-surface depth distribution of surfactant. Films of nondeformable particles, containing the highest concentration of cross-linker, show no surfactant accumulation at the top surface. Films from particles partially deformed by capillary action show a distinct surfactant surface layer (ca. 150 nm thick). Films of coalesced particles, containing little or no cross-linker, show a very small amount of surfactant on the surface (ca. 20 nm thick). The observed results are explained by considering the effect of cross-linking on rubber elasticity and applying the viscous particle deformation model by Gromer et al. to elastically deformed particles. We find that partially deformed particles allow surfactant transport to the surface during film formation, whereas there is far less transport when skin formation acts as a barrier. With elastic particles, the surfactant is carried in the water phase as it falls beneath the surface of packed particles. The ability to exert control over surfactant distribution in waterborne colloidal films will aid in the design of new high-performance adhesives and coatings.

In this paper a new technique is introduced for automatically building recognisable moving 3D models of individual people. A set of multi-view colour images of a person are captured from the front, side and back using one or more cameras. Model-based reconstruction of shape from silhouettes is used to transform a standard 3D generic humanoid model to approximate the persons shape and anatomical structure. Realistic appearance is achieved by colour texture mapping from the multi-view images. Results demonstrate the reconstruction of a realistic 3D facsimile of the person suitable for animation in a virtual world. The system is low-cost and is reliable for large variations in shape, size and clothing. This is the first approach to achieve realistic model capture for clothed people and automatic reconstruction of animated models. A commercial system based on this approach has recently been used to capture thousands of models of the general public.

Nuclear reaction analysis (NRA) and elastic recoil detection (ERD) are commonly used for the elemental depth profiling of materials in fields ranging from biological to the semiconductor industry. This article introduces both techniques and explains the theory and principles of them along with the instrumentation and experimental apparatus that is required for their use. Several applications are also described such as their use in hydrogen analysis, depth profiling deuterium-labeled molecules (including deuterated hair dye into hair), the investigation of nitrogen and their use with an external beam. Lastly, some of the available computer programs for the analysis of NRA and ERD data are briefly described.

The thin layer activation (TLA) technique is being used to measure the continuous wear of piston rings and cylinder liners in the nm to μm range. The procedure, effectively using a radioisotope tracer, involves two main steps. Firstly the surface of interest is activated using a charged particle beam and secondly its wear characteristics are tested using a special tribometer set-up. The whole procedure will be discussed along with technical factors to be considered (including the different nuclear reactions used to study different elements) and its limitations. Other known and potential applications will also be described.