The use of geoscience methods for aquatic forensic searches

There have been few publications on the forensic search of water and fewer still on the use of geoforensic techniques when exploring aqueous environments. Here we consider what the nature of the aqueous environment is, what the forensic target(s) may be, update the geoforensic search assets we may use in light of these, and provide a search strategy that includes multiple exploration assets. Some of the good practice involved in terrestrial searches has not been applied to water to-date, water being seen as homogenous and without the complexity of solid ground: this is incorrect and a full desktop study prior to searching, with prioritized areas, is recommended. Much experimental work on the decay of human remains is focused on terrestrial surface deposition or burial, with less known about the nature of this target in water, something which is expanded upon here, in order to deploy the most appropriate geoforensic method in water-based detection. We include case studies where detecting other forensic targets have been searched for; from metal (guns, knives) to those of a non-metallic nature, such as submerged barrels/packages of explosives, drugs, contraband and items that cause environmental pollution. A combination of the consideration of the environment, the target(s), and both modern and traditional search devices, leads to a preliminary aqueous search strategy for forensic targets. With further experimental research and criminal/humanitarian casework, this strategy will continue to evolve and improve our detection of forensic targets

Boundary value problems for the stationary axisymmetric Einstein equations: a disk rotating around a black hole

We solve a class of boundary value problems for the stationary axisymmetric Einstein equations corresponding to a disk of dust rotating uniformly around a central black hole. The solutions are given explicitly in terms of theta functions on a family of hyperelliptic Riemann surfaces of genus 4. In the absence of a disk, they reduce to the Kerr black hole. In the absence of a black hole, they reduce to the Neugebauer-Meinel disk.Comment: 46 page

Protic plastic crystal/PVDF composite membranes for Proton Exchange Membrane Fuel Cells under non-humidified conditions

Composite membranes based on the protic plastic crystal N,N-dimethylethylenediammonium triflate [DMEDAH][TFO] and poly(vinylidene fluoride) (PVDF) nanofibers have been developed for proton exchange membrane fuel cells (PEMFCs) under non-humidified conditions. The effect of addition of 5 mol% triflic acid or 5 mol% of the base N,N-dimethylethylenediamine on the thermal and transport properties of the material is discussed. The acid-doped plastic crystal reports more than double the ionic conductivity of the pure plastic crystal. The effects of doping the plastic crystal and the composites, with acid or base, on the ionic conductivity and fuel cell performance are reported. Composite membranes based on PVDF nanofibers and [DMEDAH][TFO] were tested in a single PEMFC. The results show the potential of these composite membranes to be used as electrolytes in this electrochemical application without external humidification.The authors acknowledge funding from the Australian Research Council (ARC) through its Centre of Excellence program, through the Australian Laureate Fellowship scheme for D.R.M and M.F, and Discovery Project DP140101535. In addition, M.D., A.O. and I.O acknowledge Spanish Ministry of Economy and Competitiveness for the project CTQ2015-66078-R (MINECO/FEDER, UE). M. D. is grateful to the Spanish Ministry of Education, Culture and Sport for the FPU2012-3721

The potential of discs from a "mean Green function"

By using various properties of the complete elliptic integrals, we have derived an alternative expression for the gravitational potential of axially symmetric bodies, which is free of singular kernel in contrast with the classical form. This is mainly a radial integral of the local surface density weighted by a regular "mean Green function" which depends explicitly on the body's vertical thickness. Rigorously, this result stands for a wide variety of configurations, as soon as the density structure is vertically homogeneous. Nevertheless, the sensitivity to vertical stratification | the Gaussian profile has been considered | appears weak provided that the surface density is conserved. For bodies with small aspect ratio (i.e. geometrically thin discs), a first-order Taylor expansion furnishes an excellent approximation for this mean Green function, the absolute error being of the fourth order in the aspect ratio. This formula is therefore well suited to studying the structure of self-gravitating discs and rings in the spirit of the "standard model of thin discs" where the vertical structure is often ignored, but it remains accurate for discs and tori of finite thickness. This approximation which perfectly saves the properties of Newton's law everywhere (in particular at large separations), is also very useful for dynamical studies where the body is just a source of gravity acting on external test particles.Comment: Accepted for publication in MNRAS, 11 page

Towards a New Standard Model for Black Hole Accretion

We briefly review recent developments in black hole accretion disk theory, emphasizing the vital role played by magnetohydrodynamic (MHD) stresses in transporting angular momentum. The apparent universality of accretion-related outflow phenomena is a strong indicator that large-scale MHD torques facilitate vertical transport of angular momentum. This leads to an enhanced overall rate of angular momentum transport and allows accretion of matter to proceed at an interesting rate. Furthermore, we argue that when vertical transport is important, the radial structure of the accretion disk is modified at small radii and this affects the disk emission spectrum. We present a simple model demonstrating how energetic, magnetically-driven outflows modify the emergent disk emission spectrum with respect to that predicted by standard accretion disk theory. A comparison of the predicted spectra against observations of quasar spectral energy distributions suggests that mass accretion rates inferred using the standard disk model may severely underestimate their true values.Comment: To appear in the Fifth Stromlo Symposium Proceedings special issue of ApS

Stability of circular orbits of spinning particles in Schwarzschild-like space-times

Circular orbits of spinning test particles and their stability in Schwarzschild-like backgrounds are investigated. For these space-times the equations of motion admit solutions representing circular orbits with particles spins being constant and normal to the plane of orbits. For the de Sitter background the orbits are always stable with particle velocity and momentum being co-linear along them. The world-line deviation equations for particles of the same spin-to-mass ratios are solved and the resulting deviation vectors are used to study the stability of orbits. It is shown that the orbits are stable against radial perturbations. The general criterion for stability against normal perturbations is obtained. Explicit calculations are performed in the case of the Schwarzschild space-time leading to the conclusion that the orbits are stable.Comment: eps figures, submitted to General Relativity and Gravitatio

An enrichment method for temperature-sensitive and auxotrophic mutants of yeast

An enrichment procedure that exploits the difference in heat-sensitivity between exponentially growing and stationary phase cells has been developed for the isolation of yeast mutants. Enrichments of up to 12-fold for temperature-sensitive lethal mutants and of up to 15-fold for auxotrophs have been obtained with single cycles of selection. Still higher enrichments (to frequencies of greater than 90% and 80% for temperature-sensitive lethals and auxotrophs, respectively) have been obtained with multiple cycles of selection. The method requires no special parent strain, and seems adaptable to the selection of a wide variety of types of mutants.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47545/1/438_2004_Article_BF00274022.pd

C-axis lattice dynamics in Bi-based cuprate superconductors

We present results of a systematic study of the c axis lattice dynamics in single layer Bi2Sr2CuO6 (Bi2201), bilayer Bi2Sr2CaCu2O8 (Bi2212) and trilayer Bi2Sr2Ca2Cu3O10 (Bi2223) cuprate superconductors. Our study is based on both experimental data obtained by spectral ellipsometry on single crystals and theoretical calculations. The calculations are carried out within the framework of a classical shell model, which includes long-range Coulomb interactions and short-range interactions of the Buckingham form in a system of polarizable ions. Using the same set of the shell model parameters for Bi2201, Bi2212 and Bi2223, we calculate the frequencies of the Brillouin-zone center phonon modes of A2u symmetry and suggest the phonon mode eigenvector patterns. We achieve good agreement between the calculated A2u eigenfrequencies and the experimental values of the c axis TO phonon frequencies which allows us to make a reliable phonon mode assignment for all three Bi-based cuprate superconductors. We also present the results of our shell model calculations for the Gamma-point A1g symmetry modes in Bi2201, Bi2212 and Bi2223 and suggest an assignment that is based on the published experimental Raman spectra. The superconductivity-induced phonon anomalies recently observed in the c axis infrared and resonant Raman scattering spectra in trilayer Bi2223 are consistently explained with the suggested assignment.Comment: 29 pages, 13 figure

Low-Luminosity Accretion in Black Hole X-ray Binaries and Active Galactic Nuclei

At luminosities below a few percent of Eddington, accreting black holes switch to a hard spectral state which is very different from the soft blackbody-like spectral state that is found at higher luminosities. The hard state is well-described by a two-temperature, optically thin, geometrically thick, advection-dominated accretion flow (ADAF) in which the ions are extremely hot (up to $10^{12}$ K near the black hole), the electrons are also hot ($\sim10^{9-10.5}$ K), and thermal Comptonization dominates the X-ray emission. The radiative efficiency of an ADAF decreases rapidly with decreasing mass accretion rate, becoming extremely low when a source reaches quiescence. ADAFs are expected to have strong outflows, which may explain why relativistic jets are often inferred from the radio emission of these sources. It has been suggested that most of the X-ray emission also comes from a jet, but this is less well established.Comment: To appear in "From X-ray Binaries to Quasars: Black Hole Accretion on All Mass Scales" edited by T. Maccarone, R. Fender, L. Ho, to be published as a special edition of "Astrophysics and Space Science" by Kluwe