A comparison of human and pig decomposition rates and odour profiles in an Australian environment

© 2018, © 2018 Australian Academy of Forensic Sciences. Cadaver-detection dogs are trained to locate victim remains; however, their training is challenging owing to limited access to human remains. Animal analogues, such as pigs, are typically used as alternative training aids. This project aimed to compare the visual decomposition and volatile organic compound (VOC) profile of human and pig remains in an Australian environment, to determine the suitability of pig remains as human odour analogues for cadaver-detection dog training. Four human cadavers and four pig carcasses were placed in an outdoor environment at the Australian Facility for Taphonomic Experimental Research (AFTER) across two seasons. Decomposition was monitored progressively in summer and winter. VOCs were collected onto sorbent tubes and analysed using comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry. Visual observations highlighted the differences in decomposition rates, with pig remains progressing through all stages of decomposition, and human remains undergoing differential decomposition and mummification. Chemical and statistical analysis highlighted variations in the composition and abundance of VOCs over time between the odour profiles. This study concluded that the visual decomposition and VOC profile of pig and human remains was dissimilar. However, in cooler conditions the results from each species became more comparable, especially during the early stages of decomposition

Minimax Current Density Coil Design

'Coil design' is an inverse problem in which arrangements of wire are designed to generate a prescribed magnetic field when energized with electric current. The design of gradient and shim coils for magnetic resonance imaging (MRI) are important examples of coil design. The magnetic fields that these coils generate are usually required to be both strong and accurate. Other electromagnetic properties of the coils, such as inductance, may be considered in the design process, which becomes an optimization problem. The maximum current density is additionally optimized in this work and the resultant coils are investigated for performance and practicality. Coils with minimax current density were found to exhibit maximally spread wires and may help disperse localized regions of Joule heating. They also produce the highest possible magnetic field strength per unit current for any given surface and wire size. Three different flavours of boundary element method that employ different basis functions (triangular elements with uniform current, cylindrical elements with sinusoidal current and conic section elements with sinusoidal-uniform current) were used with this approach to illustrate its generality.Comment: 24 pages, 6 figures, 2 tables. To appear in Journal of Physics D: Applied Physic

Dependence of the LMXB population on stellar age

We investigate the dependence of the low-mass X-ray binary (LMXB) population in early-type galaxies on stellar age, by selecting 20 massive nearby early-type galaxies from the Chandra archive occupying a relatively narrow range of masses and spanning a broad range of ages, from 1.6 Gyr to more than 10 Gyrs, with the median value of 6 Gyrs. With the ~ 2000 X-ray point sources detected in total, we correlated the specific number of LMXBs in each galaxy with its stellar age and globular cluster (GC) content. We found a correlation between the LMXB population and stellar age: older galaxies tend to possess about ~50% more LMXBs (per unit stellar mass) than the younger ones. The interpretation of this dependence is complicated by large scatter and a rather strong correlation between stellar age and GC content of galaxies in our sample. We present evidence suggesting that the more important factor may be the evolution of the LMXB population with time. Its effect is further amplified by the larger GC content of older galaxies and correspondingly, the larger numbers of dynamically formed binaries in them. We also found clear evolution of the X-ray luminosity function (XLF) with age, that younger galaxies have more bright sources and fewer faint sources per unit stellar mass. The XLF of LMXBs in younger galaxies appears to extend significantly beyond E39 erg/s. Such bright sources seem to be less frequent in older galaxies. We found that 6 out of ~ 12 (ultra-) luminous sources are located in GCs.Comment: 13 pages, 8 figures, accepted by A&A on 03/08/201

iGPS capability study

This report presents the results of testing of the Metris iGPS system performed by the National Physical Laboratory (NPL) and the University of Bath (UoB), with the assistance of Metris, and Airbus at Airbus, Broughton in March 2008. The aim of the test was to determine the performance capability of the iGPS coordinate metrology system by comparison with a reference measurement system based on multilateration implemented using laser trackers. A network of reference points was created using SMR nests fixed to the ground and above ground level on various stands. The reference points were spread out within the measurement volume of approximately 10 m ´ 10 m ´ 2 m. The coordinates of each reference point were determined by the laser tracker survey using multilateration. The expanded uncertainty (k=2) in the relative position of these reference coordinates was estimated to be of the order of 10 µm in x, y and z. A comparison between the iGPS system and the reference system showed that for the test setup, the iGPS system was able to determine lengths up to 12 m with an uncertainty of 170 µm (k=2) and coordinates with an uncertainty of 120 µm in x and y and 190 µm in z (k=2)

Slip-Squashing Factors as a Measure of Three-Dimensional Magnetic Reconnection

A general method for describing magnetic reconnection in arbitrary three-dimensional magnetic configurations is proposed. The method is based on the field-line mapping technique previously used only for the analysis of magnetic structure at a given time. This technique is extended here so as to analyze the evolution of magnetic structure. Such a generalization is made with the help of new dimensionless quantities called "slip-squashing factors". Their large values define the surfaces that border the reconnected or to-be-reconnected magnetic flux tubes for a given period of time during the magnetic evolution. The proposed method is universal, since it assumes only that the time sequence of evolving magnetic field and the tangential boundary flows are known. The application of the method is illustrated for simple examples, one of which was considered previously by Hesse and coworkers in the framework of the general magnetic reconnection theory. The examples help us to compare these two approaches; they reveal also that, just as for magnetic null points, hyperbolic and cusp minimum points of a magnetic field may serve as favorable sites for magnetic reconnection. The new method admits a straightforward numerical implementation and provides a powerful tool for the diagnostics of magnetic reconnection in numerical models of solar-flare-like phenomena in space and laboratory plasmas.Comment: 39 pages, 9 figures, corrected typos, to appear in ApJ, March 200

STATISTICAL ANALYSIS OF THE EFFECTS OF MIXING POTATO VARIETIES ON LATE BLIGHT

A field study in two regions of Peru was conducted to determine how host-diversity effects on potato late blight varied geographically. Foliar disease severity was evaluated separately for the potato varieties in mixtures as well as in the single-variety plots. The TAUDPC (truncated area under the disease progress curve) and RMR (relative mixture response) for each site were analyzed separately using SAS mixed effects model procedures. While there was little difference between the sites in the 1997-1998 season, host-diversity effects were generally greater near Huancayo than near Cajamarca in the 1998-1999 season. Estimates of host-diversity effects from studies in Oregon and Ecuador were also compared with results for Peru. Host-diversity effects for reduced disease were generally greater for sites where we predicted lower levels of outside inoculum

Relationship between eruptions of active-region filaments and associated flares and CMEs

To better understand the dynamical process of active-region filament eruptions and associated flares and CMEs, we carried out a statistical study of 120 events observed by BBSO, TRACE, and t(SOHO/EIT) from 1998 to 2007 and combined filament observations with the NOAA's flare reports, MDI magnetograms, and LASCO data, to investigate the relationship between active-region filament eruptions and other solar activities. We found that 115 out of 120 filament eruptions are associated with flares. 56 out of 105 filament eruptions are found to be associated with CMEs except for 15 events without corresponding LASCO data. We note the limitation of coronagraphs duo to geometry or sensitivity, leading to many smaller CMEs that are Earth-directed or well out of the plane of sky not being detected by near-Earth spacecraft. Excluding those without corresponding LASCO data, the CME association rate of active-region filament eruptions clearly increases with X-ray flare class from about 32% for C-class flares to 100% for X-class flares. The eruptions of active-region filaments associated with Halo CMEs are often accompanied by large flares. About 92% events associated with X-class flare are associated with Halo CMEs. Such a result is due to that the Earth-directed CMEs detected as Halo CMEs are often the larger CMEs and many of the smaller ones are not detected because of the geometry and low intensity. The average speed of the associated CMEs of filament eruptions increases with X-ray flare size from 563.7 km/s for C-class flares to 1506.6 km/s for X-class flares. Moreover, the magnetic emergence and cancellation play an important role in triggering filament eruptions. These findings may be instructive to not only in respect to the modeling of active-region filament eruptions but also in predicting flares and CMEs.Comment: 19 Pages, 7 figures, Accepted for publication in MNRA

The roles of apex dipoles and field penetration in the physics of charged, field emitting, single-walled carbon nanotubes

A 1 μm long, field emitting, (5, 5) single-walled carbon nanotube (SWCNT) closed with a fullerene cap, and a similar open nanotube with hydrogen-atom termination, have been simulated using the modified neglect of diatomic overlap quantum-mechanical method. Both contain about 80 000 atoms. It is found that field penetration and band bending, and various forms of chemically and electrically induced apex dipole play roles. Field penetration may help explain electroluminescence associated with field emitting CNTs. Charge-density oscillations, induced by the hydrogen adsorption, are also found. Many of the effects can be related to known effects that occur with metallic or semiconductor field emitters; this helps both to explain the effects and to unify our knowledge about FE emitters. However, it is currently unclear how best to treat correlation-and-exchange effects when defining the CNT emission barrier. A new form of definition for the field enhancement factor (FEF) is used. Predicted FEF values for these SWCNTs are significantly less than values predicted by simple classical formulae. The FEF for the closed SWCNT decreases with applied field; the FEF for the H-terminated open SWCNT is less than the FEF for the closed SWCNT but increases with applied field. Physical explanations for this behavior are proposed but the concept of FEF is clearly problematical for CNTs. Curved Fowler-Nordheim plots are predicted. Overall, the predicted field emission performance of the H-terminated open SWCNT is slightly better than that of the closed SWCNT, essentially because a C-H dipole is formed that reduces the height of the tunneling barrier. In general, the physics of a charged SWCNT seems much more complex than hitherto realized. © 2008 American Institute of Physics.published_or_final_versio