>Magister Scientiae - MSc / Electrochemical platforms were developed based on pencil graphite electrodes (PGEs) modified with electrochemically deposited graphene (EG) sheets and Nafion-graphene (NG) nanocomposites in conjunction with an in situ plated bismuth-film (EG-PG-BiE and NG-PG-BiE). The EG- and NG-PG-BiEs were used as sensing platforms for determining Zn2+, Cd2+ and Pb2+ by square wave anodic stripping voltammetry (SWASV). EG sheets were deposited onto pencil graphite electrodes by cyclic voltammetric reduction from a graphene oxide (GO) solution, while a dip coating method was used to prepare the NG-PG-BiE. The GO and graphene, with flake thicknesses of 1.78 (2 sheets) and 2.10 nm (5 sheets) respectively, was characterized using FT-IR, HR-SEM, HR-TEM, AFM, XRD and Raman spectroscopy. Parameters influencing the electroanalytical response of the EG-PG-BiE and NG-PG-BiE such as, bismuth ion concentration, deposition potential, deposition time and rotation speed were investigated and optimized. The EG-PG-BiE gave well-defined, reproducible peaks with detection limits of 0.19 μg L-1, 0.09 μg L-1 and 0.12 μg L-1 for Zn2+, Cd2+ and Pb2+ respectively, at a deposition time of 120 seconds. The NG-PG-BiE showed similar detection limits of 0.167 μg L-1, 0.098 μg L-1 and 0.125 μg L-1 for Zn2+, Cd2+ and Pb2+ respectively. For real sample analysis, the enhanced voltammetric sensor proved to be suitable for the detection and quantitation of heavy metals below the US EPA prescribed drinking water standards of 5 mg L-1, 5 μg L-1 and 15 μg L-1 for Zn2+, Cd2+ and Pb2+ respectively.

The following abstract is for a thesis submitted to the University of Manchester for the degree of Doctor in Philosophy by Omar AbdelRehim AbdelKerim in 2015.Anti-personnel (AP) mines remain a global problem that affects communities around the world, with 110 million active landmines still present. Landmines are a particularly callous and indiscriminate type of weapon detonating irrespective of presence of an enemy soldier or a child. Their devastating effect on communities has led to their ban through the 1997 Mine Ban Treaty. Current detectors used for mine clearance operations have an impeding weakness that has prompted this research; metal detectors used in humanitarian demining suffer from a high False Alarm Rate (FAR) prompting regular excavation of metallic clutter. The research presented aims to develop a detector capable of discriminating between metallic clutter and mines through the use of the magnetic polarizability dyadic tensor to reduce FARs, increase demining efficiency and improve deminer’s safety. A measurement apparatus was designed and constructed to perform spectroscopic magnetic measurements of small symmetrical metallic objects and produce for the first time unscaled accurate tensor values. The tensors deduced from the measurements were validated against analytical and simulated results and were found to be within 5% of measured tensors. The tensors of minimum metal AP mine surrogates and metallic clutter of symmetrical shape were measured and formed part of a tensor library to be used later by future research. This is in addition to a set of un-circulated US coinage which could be used as a calibration metric and a comparison piece for future work in this area. A detailed description of the coil design and manufacturing process is presented to develop a coil array capable of inverting buried metallic object tensors. The selection criterion was poised to identify an array that was best suited to perform the correct measurements in order to invert to an accurate tensor. The manufactured coil exhibited strong mutual coupling between the receive coils deeming it unfit for the portable detector; however, the findings of the work presented and the selection criterion developed has aided the future design of a suitable coil array. Expected signal levels from minimum metal mine detection were calculated and helped aide in the design of future detectors to ensure suitable SNR performance is achieved. A portable detector has been developed using the sensor head presented within this thesis. Work still lies ahead to achieve the complete detector capable of performing target characterisation and clutter elimination; however, significant advances have been made and are presented throughout this thesis.

No description available.

The aim of this thesis has been to investigate and interpret late Iron Ageand Early Medieval traces of non-ferrous metalworking on the islandGotland, Sweden. Gotland was not, based on the archaeological record, anintegrated part of the common Scandinavian culture. Instead a local,endemic cultural expression had developed; a seclusion which lasted forcenturies despite the islands central position in the Baltic Sea. In thepast, key elements for the understanding of local settlement- and burialpractices as well as the local material culture were mainly recovered andreported by local farmers. A specific category of such finds – so-called‘bronze slag’ is discussed and partly reinterpreted in the first study ofthis thesis. Two further studies treat different aspects of metalworkingand metalworkers – one discusses common archaeological notions ofScandinavian workshops, production sites and metalworkers from a criticalperspective while the other mainly focuses on the Gotlandic finds frommetal-detector surveys carried out over the last 35 years. Based on whereand to which extent, both from a quantitative and a qualitative point ofview, these finds occur a hierarchical classification into four sub groupsis presented – ordinary farm sites with traces of non-ferrous metalworking,workshop sites, potential workshop sites and last, extrovert harboursettlements. A fourth study presents an attempt to evaluate the usefulnessof magnetometry in delimiting extant traces of high-temperature crafts,such as metalworking. The last study of the thesis presents an attempt touse trace elements analysis of skeletal lead in human bone to identifypotential non-ferrous metalworkers. As the wearing of endemic Gotlandic jewellery appears to have been centralin the manifestation of the local identity it is argued that themetalworking artisans played a crucial role in defining how this identitywas signalled and displayed via the jewellery and dress-related metalobjects. It is further suggested that these artisans might have played animportant role in upholding the local economy before the advent of localminting. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 5: Manuscript.</p>

Recent terrorist attacks and the subsequently perceived threats to national security have meant that the demands of security networks are greater than ever before. The walkthrough metal detector (WTMD) is on the frontline of the personal security screening network and is used to check individuals for metallic threat objects such as knives or guns. In many operational conditions each positive identification of a metallic object is first considered to be a threat, however in many instances the source of the trigger does not necessarily constitute the detection of a threat object as many innocuous metallic items are allowed in certain secured zones, e.g. a mobile phone in an airport. Operators are often required to perform physical searches to confirm that the trigger was not due to a threat object. Often little or no positional information is provided, and as a result the time taken to conduct a physical search is often significant and causes delays to people waiting to be screened. A tomographic magnetic imaging system was designed and built with the intention of recovering detailed information about magnetic and/or conductive objects within the detector space, in addition to identifying the position of the detected object to a greater degree of accuracy than is possible with the current generation of WTMDs. The object-specific information that is recovered by the system is in the form of the magnetic polarisability dyadic tensor, which is considered to completely describe the behaviour of an object when it interacts with a magnetic field. The prototype system that has been produced is capable of inverting object tensors with a typical error of < 20%, and determines three-dimensional object location with an error of ±2 to ±3 cm. Given that both the inversion of an object tensor, and object location to this degree of accuracy have not been observed in the academic or commercial literature it is claimed that both of these factors represent original work. In order to achieve this level of performance a special 8-transmit, 8-receive coil array has been produced which is capable of minimising mutual coupling between all channels during background operation. This allows for greater detection of changes occurring as a result of the presence of the object, rather than from the excitation source. A procedure for modelling the response of this prototype coil array to a specified magnetic polarisability dyadic tensor is derived and tested by examining the response of the system to a ferrite sphere. This testing indicates that the measurements from the WTMD and simulated object response differ by less than 10% in almost all cases. Testing of the inversion algorithm has been conducted with six known objects, and the system has been shown to perform consistently, and to an acceptable degree of accuracy. The procedure for the inversion of an object tensor is based upon the response of the model, and consequently this error contains a portion of the error contained from the model. The detector system was tested in an airport environment where sensitivity was shown to be beyond the levels required for typical operation.

Hexavalent chromium is an extremely carcinogenic chemical that has been widely produced in the United States. This has led to major waste contamination and pollution throughout the country. According to the Environmental Working Group Hexavalent chromium has been found in 89% of city tap water. Most people believe they are safe using regular home filter systems however that is not true. A more expensive ion exchange water treatment unit is required. Therefore to protect yourselves from this carcinogenic metal a reliable test is required. In this study we have developed a Zinc Sulfide Manganese doped Quantum Rod technology to detect for presence of chromate and other harmful transitional metals in drinking water. Quantum Rods were synthesized using a hydrothermal reaction method. They were fully characterized using UV-visible absorption spectroscopy, fluorescence emission spectroscopy, X-ray Photoelectric Spectroscopy (XPS) and High Resolution Transmission Electron Microscopy (HRTEM). Quantum Rod metal detection studies were done with 28 different ions in a 96-well fluorescent plate reader. Results show that highest sensitivity to 8 ions including the toxic ions of chromate and mercury allowing us to create a sensor to detect these items.

No description available.

There is currently a great interest in the field of porous organosilica materials because of the high surface areas (> 1000 m²/g) and narrow pore size distributions which are beneficial for applications such as chromatography, chiral catalysis, sensing or selective adsorption. Periodic mesoporous organosilicas (PMOs) represent an interesting class of hybrid silica materials because of the wide variety of bridging organic groups which can be incorporated within the precursors [(OR)3Si-R-Si(OR)3] giving rise to materials with exceptional properties. We have synthesized and characterized various aromatic PMOs composed of supporting structural monomers (phenylene- or biphenylenebridged) and functional stilbene monomers (cis and trans) (1, 2). The effect of the different synthetic procedures and varying amounts of functional stilbene monomer on the properties of the materials was examined. The functional transstilbene component was determined to be well distributed in a phenylene-bridged PMO using P123 as a pore template from TEM techniques with Os staining. The trans-stilbene linkers were completely transformed to aryl aldehydes through ozonolysis with dimethylsulfide workup. Further transformation of the carbonyl functionality to an aryl imine showed a moderate level of success. Enantiomeric forms of a novel, chiral PMO precursor (CM) were synthesized and incorporated into biphenylene-bridged PMOs. Under basic pH conditions templated with C18TMACl, although very low levels of CM are incorporated, enantiomeric forms of chiral, porous materials are obtained as was verified by distinct mirror-image circular dichroism spectra. Powder XRD patterns suggest that a tightly packed asymmetric biphenylene arrangement may be necessary for the optical activity. Preliminary results using these materials as a chiral chromatographic phase are promising. Finally, a thin film morphology of an ethane-bridged PMO incorporating a thiol ligand, (3-mercaptopropyl)trimethoxysilane, was prepared on a fibre optic cable and used as a component in a heavy-metal sensing application. / Thesis (Ph.D, Chemistry) -- Queen's University, 2011-03-11 17:24:48.997

Magister Scientiae - MSc (Chemistry) / In this study, graphene oxide was synthesized by oxidizing graphite using the modified Hummer's method. The graphene oxide was characterized by Raman Spectroscopy, Fourier Transform Infrared Spectroscopy, High Resolution Transmission Electron Microscopy, Scanning Electron Microscopy and X-Ray Diffraction for structural and morphological properties. The graphene oxide was electrochemically reduced on a carbon paste electrode followed by the in situ deposition of mercury thin films to achieve electrochemically reduced graphene oxide modified carbon paste metal film electrodes (ERGO-CP-MEs). The experimental parameters (amplitude, deposition time, deposition potential, frequency and rotation speed) were optimized, and the applicability of the modified electrode was investigated towards the simultaneous and individual determination of TI1+ and In3+ at the low concentration levels (?g L-1) in 0.1 M acetate buffer (pH 4.6) using square wave anodic stripping voltammetry (SWASV). The detection limit values for individual analysis at electrochemically reduced graphene oxide modified carbon paste mercury film electrode (ERGO-CP-HgE ) was 2.4 and 1.1 ?g L-1 for TI1+ and In3+, respectively. The detection limit values for simultaneous analysis at ERGO-CPE was 1.32 and 1.33 ?g L-1 and individual analysis was 0.975 and 1.04 ?g L-1 for TI1+ and In3+, respectively.

Yes / Archaeological research at Stonehenge (UK) is increasingly aimed at understanding the dynamic of the wider archaeological landscape. Through the application of state-of-the-art geophysical techniques, unprecedented insight is being gathered into the buried archaeological features of the area. However, applied survey techniques have rarely targeted natural soil variation, and the detailed knowledge of the palaeotopography is consequently less complete. In addition, metallic topsoil debris, scattered over different parts of the Stonehenge landscape, often impacts the interpretation of geophysical datasets. The research presented here demonstrates how a single multi-receiver electromagnetic induction (EMI) survey, conducted over a 22 ha area within the Stonehenge landscape, offers detailed insight into natural and anthropogenic soil variation at Stonehenge. The soil variations that were detected through recording the electrical and magnetic soil variability, shed light on the genesis of the landscape, and allow for a better definition of potential palaeoenvironmental and archaeological sampling locations. Based on the multi-layered dataset, a procedure was developed to remove the influence of topsoil metal from the survey data, which enabled a more straightforward identification of the detected archaeology. The results provide a robust basis for further geoarchaeological research, while potential to differentiate between modern soil disturbances and the underlying sub-surface variations can help in solving conservation and management issues. Through expanding this approach over the wider area, we aim at a fuller understanding of the human–landscape interactions that have shaped the Stonehenge landscape.