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Bed bugs (Cimex lectularius L.) are ectoparasitic wingless insects that feed on the blood of mammals, typically in residential settings. The objectives of this study were to establish a time-course of human DNA quantitation from bed bugs and to generate human DNA profile(s) of a host and/or multiple hosts from a bed bug that fed on human blood. Female human genomic DNA concentrations ranged from 18.370 to 0.195ng/bed bug at 0-108h post blood meal (PBM), male human genomic DNA concentrations ranged from 5.4 to 0.105ng/bed bug at 0-108h PBM, and pooled human female and male blood ranged from 5.49 to 0.135ng/bed bug at 0-96h PBM. Human autosomal STR complete profiles were obtained until 72h PBM for female, male, and pooled human blood. These results reveal that identification of multiple human hosts is possible from a single bed bug. However, the ratio of each contributor may be variable depending on the amount of blood ingested from each individual and the time difference of blood consumed from each subject. Average peak heights for three STR markers of low (D3S1358), medium (D13S317), and high molecular weight (D2S1338), were also compared over time. Peak heights were consistently higher for the low molecular weight marker over all time intervals. These data suggest that some markers can be successfully recovered more than three days PBM. Hence, bed bugs can serve as physical evidence in temporal and spatial predictions to match suspects and/or victims to specific locations in criminal investigations.

Current assessment methods within higher education (a focus on assessment measures at a single point in time) place expectations on students to be performing to a similar level – regardless of their educational background, or the skills and abilities they enter education with. Recent research argues this approach to assessment could be counterproductive in encouraging students’ motivation to learn. The addition of growth measures of assessment into current educational programs may offer those who find themselves performing below standard incentive and encouragement to perform to a higher standard, while challenging those currently performing to benchmarks to strive for even greater success.

A reversible solid oxide fuel cell (RSOFC) system, consisting of a RSOFC stack, heat store, and electrical inverters to convert DC to AC power, is shown by computer modeling to have the potential to efficiently store electrical energy. This paper describes the modeling of a single RSOFC, based on a proposed cell geometry, empirical data on the resistivities of the components, and calculation of activation and diffusion polarization resistances from electrochemical theory. Data from ac impedance spectroscopy measurements on symmetrical cells are used to model RSOFC impedance. A RSOFC stack is modeled by electrically linking the individual cells inside a pressurized vessel. A phase change heat store is added to improve energy storage efficiency. The model is implemented in MATLAB®/Simulink®. Two competing inverter control schemes are compared, trading off DC bus ripple against AC power quality. It is found that selection of appropriate DC bus capacitance is important in certain scenarios, with potential system cost implications. It is shown that the system can store electrical energy at an efficiency of 64% over a single discharge–charge cycle, i.e., hydrogen to electricity and heat to hydrogen.

Pressurised operation of solid oxide fuel cells (SOFC) has been shown to significantly improve their performance (Singhal, 2000) [ 1 ], however little work has been done on the effects of pressure on SOFC cathodes. The effect of pressurised oxygen on the area specific polarisation resistance (ASRp) of (La 0.8 Sr 0.2 ) 0.95 MnO 3–δ /8YSZ SOFC cathodes was determined by electrochemical impedance spectroscopy (EIS). Pellets of 8YSZ were pressed and sintered at 1350 °C, and screen printed layers of LSM/8YSZ cathode and LSM current collector were applied and sintered at 1300 °C and 1200 °C respectively. EIS was carried out between 1 and 3 bar oxygen at 800–1000 °C. One process dominated the spectra, and was identified as process C, (Jorgensen and Morgensen, 2001) [2] by comparison of measured and reference frequency maxima, the dependence of polarisation resistance on P O 2 , the capacitance, and the activation energy. It is suggested that this represents the physical process of dissociative adsorption of oxygen at the triple phase boundaries of the electrode. A second process, with a magnitude almost independent of P O 2 , is observed, which may be process B [2], related to transport of oxygen ions in the YSZ.

Dynamic impact to the water environment of deicing salt application at a major highway (motorway) interchange in the UK is quantitatively evaluated for two recent severe UK winters. The contaminant transport pathway studied allowed controls on dynamic highway runoff and storm-sewer discharge to a receiving stream and its subsequent leakage to an underlying sandstone aquifer, including possible contribution to long-term chloride increases in supply wells, to be evaluated. Logged stream electrical-conductivity (EC) to estimate chloride concentrations, stream flow, climate and motorway salt application data were used to assess salt fate. Stream loading was responsive to salt applications and climate variability influencing salt release. Chloride (via EC) was predicted to exceed the stream Environmental Quality Standard (250 mg/l) for 33% and 18% of the two winters. Maximum stream concentrations (3500 mg/l, 15% sea water salinity) were ascribed to salt-induced melting and drainage of highway snowfall without dilution from, still frozen, catchment water. Salt persistance on the highway under dry-cold conditions was inferred from stream observations of delayed salt removal. Streambed and stream-loss data demonstrated chloride infiltration could occur to the underlying aquifer with mild and severe winter stream leakage estimated to account for 21 to 54% respectively of the 70 t of increased chloride (over baseline) annually abstracted by supply wells. Deicing salt infiltration lateral to the highway alongside other urban/natural sources were inferred to contribute the shortfall. Challenges in quantifying chloride mass/fluxes (flow gauge accuracy at high flows, salt loading from other roads, weaker chloride-EC correlation at low concentrations), may be largely overcome by modest investment in enhanced data acquisition or minor approach modification. The increased understanding of deicing salt dynamic loading to the water environment obtained is relevant to improved groundwater resource management, highway salt application practice, surface-water - ecosystem management, and decision making on highway drainage to ground.

A standard reformed biogas composition, based on a 63% CH4 37% CO2 input biogas, was defined by calculation. It is designed to resemble the composition of biogas that would enter a real SOFC stack, assuming 80% fuel utilization, and 25% recirculation of the anode off-gas. It is thermodynamically impervious to coking above 720°C. This gas composition was then used to test the catalytic reforming performance of nickel powder and La0.8Ce0.1Ni0.4Ti0.6O3-δ at 900°C in the standard reformed biogas. No coking was seen on the powder samples by visual inspection after this test. The La0.8Ce0.1Ni0.4Ti0.6O3-δ is designed to exsolve Ni nanoparticles when reduced. SEM pictures of the post-test sample show some small particles that may be exsolved nanoparticles, but further investigation is needed to confirm this. Ni powder was the better reforming catalyst, but sintered extensively in the 3 h test. The La0.8Ce0.1Ni0.4Ti0.6O3-δ also showed reforming capability, and much better microstructural stability in the standard reformed biogas.

One way to increase the value of renewable energy is to use a high efficiency reversible solid oxide fuel cell (SOFC) as an energy storage device. The utilization of SOFC for distributed generation (DG) requires the development of inverters that convert variable DC power into AC power. This paper addresses the integration of the SOFC with a power electronic inverter as a distributed generation device. The SOFC model and power inverter blocks are implemented in MATLAB/Simulink with three competing inverter control schemes. Hardware tests are required in the future and the purpose of this research is to verify a stable SOFC power system.

Polymer electrolytes have been studied extensively because uniquely they combine ionic conductivity with solid yet flexible mechanical properties, rendering them important for all-solid-state devices including batteries, electrochromic displays and smart windows. For some 30 years, ionic conductivity in polymers was considered to occur only in the amorphous state above Tg. Crystalline polymers were believed to be insulators. This changed with the discovery of Li(+) conductivity in crystalline poly(ethylene oxide)(6):LiAsF(6). However, new crystalline polymer electrolytes have proved elusive, questioning whether the 6:1 complex has particular structural features making it a unique exception to the rule that only amorphous polymers conduct. Here, we demonstrate that ionic conductivity in crystalline polymers is not unique to the 6:1 complex by reporting several new crystalline polymer electrolytes containing different alkali metal salts (Na(+), K(+) and Rb(+)), including the best conductor poly(ethylene oxide)(8):NaAsF(6) discovered so far, with a conductivity 1.5 orders of magnitude higher than poly(ethylene oxide)(6):LiAsF(6). These are the first crystalline polymer electrolytes with a different composition and structures to that of the 6:1 Li(+) complex.

Biogas is a potentially widely available fuel derived from the anaerobic digestion of biological materials such as animal waste. The nature of this fuel source predicates its availability to areas of a more rural nature and as such can be a valuable resource in remote areas where supply of other energy vectors (such as an electricity grid) can create significant logistical issues. Where Biogas is currently utilised it is often burnt in a reciprocating engine to drive a generator for the supply of electricity. This is a low efficiency method of energy conversion and much of the energy content of the fuel is lost in the process. A better method would be direct electrochemical conversion, taking the higher conversion efficiencies offered by solid oxide fuel cells to improve the utilisation of biogas and provide an efficient source of electricity for remote or off grid locations. Biogas is mainly a mixture of carbon dioxide and methane, however the ratio of the two gases in many cases is not enough to prevent carbon formation if used directly in a nickel based cermet anode. This is compounded by the presence of hydrogen sulphide as a significant impurity in biogas, which is of course well known to poison SOFC Ni cermets. To look to tackle these issues University of St Andrews has been part of a collaborative UK-India research programme jointly funded by EPSRC (UK ) and DST (India) on improving bigas utilisation in SOFC, other partners are Imperial College London and University of Strathclyde from the UK and CGCRI (Kolkata) and IMMT (Bhubaneswar) from India. In this paper some of the recent activities at St Andrews to improve anode robustness through catalyst impregnation and exsloution are discussed. Two approaches are described here, in the case of the impregnation, a proton conducting oxide, BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BCZYYb) was impregnated into the Ni-YSZ anode of a thin electrolyte, anode supported cell at various levels up to 1.6wt%. For the exsloution based structures, both Sr and Ca doped lanthanum titanate perovskites were doped with various catalyst materials such as Ni, Ce, Mg, and Rh. These perovskites were A-site deficient so that on reduction the catalyst materials were exsolved onto the surface as fine metallic particles with a typical size in the 10’snm. All anodes were tested on a standard reformed biogas mixture developed as part of the project. This represented the product of a 63:37 methane:CO2 input biogas exposed to 25% recirculation of an 80% utilised fuel to result in a gas mixture of 36% CH4, 26% CO2, 20% H2O, 4% H2 and 4% CO. For impurity testing H2S was added to this mixture at levels of 4-10ppm. Catalyst function was assessed by both cell testing and reforming activity. For the impregnated specimens, microstructures revealed coarser, more concentrated distribution of impregnated particles on the surface of the anode as the level of impregnation increased. All of the BCZYYb impregnations improved cell performance, however the optimum performance was at the lowest level of impregnation (0.6wt%) (-2 at 0.8V at 800°C) with performance dropping towards the non impregnated value (around 0.6 Acm-2 at 0.8V at 800°C) as impregnation levels increased to 1.6wt%. Short term steady state durability was good with initial performances proving stable over the first 50 hours of operation at 1.25 Acm-2 at 0.8V at 750°C. However poisoning effects were observed on the introduction of H2S with a performance drop of the order of 60-70% over 20 hours of exposure. Recovery was observed on return to a non-poisoned biogas mixture, however perfomance was still significantly lower than initial levels. Changing to steam/hydrogen mixtures helped bring performances back to initial levels. The doped perovskites showed various levels of metallic particle exsolution depending on the dopant type and level. These have been tested for reforming activity, with all showing activity for reformation of the standard biogas mixture, however they also all exhibited rapid degradation on introduction of H2S. Only the Rh catalyst retained some catalytic activity in the presence of hydrogen suphide, although all specimens showed recovery when the this was removed from the gas stream. A comparison was carried out between exsolved and impregnated nickel, with the former showing greater resistance to initial particle coarsening and carbon deposition. This demonstrates that it is not just the catalyst material itself which is important but also the nature and morphology of the catalyst particle. These results show that both approaches continue to be of great interest in the continued development of robust anodes for challenging fuel environments.