Preliminary soilwater conductivity analysis to date clandestine burials of homicide victims

This study reports on a new geoscientific method to estimate the post-burial interval (PBI) and potential post-mortem interval (PMI) date of homicide victims in clandestine graves by measuring decomposition fluid conductivities. Establishing PBI/PMI dates may be critical for forensic investigators to establish time-lines to link or indeed rule out suspects to a crime. Regular in situ soilwater analysis from a simulated clandestine grave (which contained a domestic buried pig carcass) in a semi-rural environment had significantly elevated conductivity measurements when compared to background values. A temporal rapid increase of the conductivity of burial fluids was observed until one-year post-burial, after this values slowly increased until two years (end of the current study period). Conversion of x-axis from post-burial days to 'accumulated degree days' (ADDs) corrected for both local temperature variations and associated depth of burial and resulted in an improved fit for multiple linear regression analyses. ADD correction also allowed comparison with a previous conductivity grave study on a different site with a different soil type and environment; this showed comparable results with a similar trend observed. A separate simulated discovered burial had a conductivity estimated PBI date that showed 12% error from its actual burial date. Research is also applicable in examining illegal animal burials; time of burial and waste deposition. Further research is required to extend the monitoring period, to use human cadavers and to repeat this with other soil types and depositional environments

A study of the affect of seasonal climatic factors on the electrical resistivity response of three experimental graves

Electrical resistivity surveys have proven useful for locating clandestine graves in a number of forensic searches. However, some aspects of grave detection with resistivity surveys remain imperfectly understood. One such aspect is the effect of seasonal changes in climate on the resistivity response of graves. In this study, resistivity survey data collected over three years over three simulated graves were analysed in order to assess how the graves' resistivity anomalies varied seasonally and when they could most easily be detected. Thresholds were used to identify anomalies, and the ‘residual volume’ of grave-related anomalies was calculated as the area bounded by the relevant thresholds multiplied by the anomaly's average value above the threshold. The residual volume of a resistivity anomaly associated with a buried pig cadaver showed evidence of repeating annual patterns and was moderately correlated with the soil moisture budget. This anomaly was easiest to detect between January and April each year, after prolonged periods of high net gain in soil moisture. The resistivity response of a wrapped cadaver was more complex, although it also showed evidence of seasonal variation during the third year after burial.We suggest that the observed variation in the graves' resistivity anomalies was caused by seasonal change in survey data noise levels, which was in turn influenced by the soil moisture budget. It is possible that similar variations occur elsewhere for sites with seasonal climate variations and this could affect successful detection of other subsurface features. Further research to investigate how different climates and soil types affect seasonal variation in grave-related resistivity anomalies would be useful

Comparison of Time-lapse GPR and Resistivity over Simulated Clandestine Graves

Forensic geophysics should be an invaluable tool to assist search teams to detect and locate clandestine graves of buried murder victims. At present however, geophysics is under-utilised and currently used techniques may not be optimal for specific targets or sites. There is a need for geophysical datasets to be collected over known burial sites for varying time periods post-burial. A study site was created with a naked and wrapped pig cadaver. The dimensions are based on available statistics of discovered burials. Monthly surveys using resistivity, Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) were performed post-burial. Resistivity results show low anomalies over the naked pig and a smaller high anomaly over the wrapped pig with respect to background values. ERT time-lapse data shows optimum survey periods for the naked and wrapped pigs to be 9 and 3 months respectively. GPR 2D profiles detected both burials, with the wrapped pig exhibiting stronger reflection events. Lower frequency (110 MHz) antennae were found to be the optimal frequency to detect pig burials

Development of Novel Alloy Electrocatalysts for the Hydrogen Oxidation Reaction in Alkaline Media and their Application to Low Temperature Fuel Cells

Fuel cells represent a promising technology for alternative electricity generation in both automotive and stationary applications. However, at present, cost and durability of the materials employed in fuel cells are barriers to commercial ubiquity. One of the main sources of cost in fuel cells is the platinum or platinum based catalysts used in the electrodes, particularly at the cathode where the sluggish oxygen reduction reaction (ORR) kinetics require high loading of precious metals. An alternative to the more widely studied polymer electrolyte membrane (PEM) acidic fuel cell is the alkaline anion exchange membrane (AAEM) fuel cell. Though the alkaline membranes are less developed than the acidic membranes used in PEM fuel cells, AAEMs are seen as a promising route to cost reduction due to the more facile ORR kinetics in alkaline media. This allows the employment of non-noble metals at the cathode, significantly reducing the amount of precious metals required in the fuel cell. However, the hydrogen oxidation reaction (HOR) kinetics (an often neglected area of study in acidic PEM fuel cells due to the negligible activation losses on the anode) in alkaline are an order of magnitude slower and thus, in order to unlock the potential of cheaper cathode catalysts, more active anode catalysts must be developed before AAEMs can be seen as a true alternative to the more established PEM technology. This thesis describes the synthesis, characterisation and electrochemical activity of a novel carbon-supported PdIr catalyst for the HOR in alkaline media. Initial synthesis methods showed the catalyst to have comparable activity with platinum through electrochemical testing, and on increasing the surface area with improved synthesis a two-fold increase in exchange current density was achieved The catalyst has been characterised with a variety of methods including SEM, HR-TEM, XRD, EXAFS and LEIS, and initial in-situ fuel cell polarisation curves are also presented

High-power nitrided TiO2 carbon felt as the negative electrode for all-vanadium redox flow batteries

This work describes the design of an electrode with enhanced performance applied to all-vanadium redox flow batteries (VRFBs). This new electrode consists of a structural porous carbon felt decorated with TiO2 rutile nanoparticles, which has been nitrided using ammonolysis at 900 °C. An outstanding charge and mass transfer over the electrode-electrolyte interface was observed as a consequence of the synergetic effect of N- and O-functionalization over carbon felt (CF) and the partial formation of TiN (metallic conductor) phase. Moreover, this material has not only improved in terms of catalysis towards the V3+/V2+ redox reaction (k0 = 1.6 × 10−3 cm s−1), but also inhibited the hydrogen evolution reaction (HER), which is one of the main causes of imbalances that lead to battery failure. This led to an impressive high-power peak output value up to 700 mW cm−2, as well as work at high current density in galvanostatic conditions (i.e. 150 mA cm−2), exhibiting low ohmic losses (overpotential) and great redox single cell reversibility, with a superior energy efficiency of 71%. An inexpensive, earth abundant and scalable synthesis method to boost VRFBs technology based on nitrided CF@TiO2 is presented, being able to overcome certain constrains, and therefore to achieve high energy and power densities