An X-ray absorption spectroscopic study at the mercury LIII edge on phenylmercury(II) oxygen species

The X-ray absorption spectra of the reference and model compounds HgCl2, PhHgCl, PhHgOAc and [(PhHg)2OH][BF4].H2O have been analysed in both the XANES and EXAFS regions, and the technique was extended to determine the structures of (PhHg)2O, PhHgOH, and the basic salts PhHgOH.PhHgNO3 and PhHgOH.(PhHg)2SO4, which were previously structurally uncharacterised. Results indicate that (PhHg)2O is a molecular species with Hg-O-Hg 135°, while PhHgOH contains the [(PhHg)2OH]+ cation and is better formulated as [(PhHg)2OH]OH. The same cation is also featured in the two basic salts. Electrospray mass spectral studies of PhHgOH in aqueous solutions show that [PhHgOH2]+, [(PhHg)2OH]+ and [(PhHg)3O]+ co-exist in solution in a pH-dependent equilibrium

Radio galaxies as large-scale cosmological probes

An all-sky sample of essentially all the radio galaxies within 30000 kms⁻¹ down to a flux-density limit of about 0.5 Jy at 1.4 GHz is assembled from the Parkes, Bologna, Jodrell Bank and Bonn surveys. The ease and uniformity with which this class of object can be selected render them as excellent statistical probes of the large-scale structure. This thesis is concerned with an application of the sample to study clustering and streaming motions in the universe on 10 - 100h⁻¹ Mpc scales.The observational database acquired the radio galaxies com prise spectroscopic redshifts and I band CCD frames, with additional ß frames for a few of the galaxies. These allow a simple distance indicator relation for the radio galaxies to be derived by fitting deVaucouleurs empirical r ¹/⁴ law to the azimuthally-averaged surface brightness profiles of the galaxies. This yields an effective size parameter rₑ and a distanceindependent surface-brightness /x for calibrating the ‘stan d ard ro d s’. In term s of rms scatte r, the μ-rₑ relation yields relative distance accurate to about 28%. This compares favourably with other distance indicators which incorporate velocity dispersions, yet it has the advantage that the photometric parameters μ and rₑ are very straightforward to measure.A useful parameter describing the richness of the environments of radio galaxies is the amplitude of the spatial cross-correlation function ßgr. Its calculation in the past has involved using full sets of galaxy counts, notably the Lick counts to do the cross-correlation. In the absence of such a set of galaxy counts, for declinations south of -23°, it is shown that the Abell cluster catalogue can be used to obtain a reasonable estimate of ß₉ᵣ. Considering the all-sky sample as a whole it is found that, on average, radio galaxies reside in systems of A bell richness R ≃ 0. A search for correlations between radio luminosity and ß₉ᵣ for the radio galaxies is performed but none are found. Similarly, no evidence is found for correlations between optical luminosity and ß₉ᵣ.T he 3-d correlation function for radio galaxies is calculated here for the first time. A strong signal is detected, although not as strong as some reports in the past of the cluster-cluster correlation function would have suggested. There is no trend for the clustering signal to show a systematic increase or decrease if radio galaxies in bands of radio luminosity are considered separately. No evidence is found to support the claim by Tully that rich clusters are aligned along the supergalactic plane and exhibit correlated structure on a scale 0.1c.Peculiar velocities are derived for the radio galaxies using the μ- rₑ relation and these are analysed in term s of simple dipole and quadrupole models for the motion of the Local Group. Large error bars on the dipole solution are traced to significant of diagonal elements in the error covariance matrix which tells us how the errors in each of the 6 free parameters in the non-linear least squares fit of the model to the data are coupled together. Monte-carlo simulations for an isotropised sky-distribution suggests that the large errors are a consequence of an anisotropic sky coverage - notably the sparse number of galaxies that were observed in the southern hemisphere relative to the north . A different technique for analysing peculiar velocities is to use the velocity autocorrelation tensor. Improvements are shown to exist over previous calculations - principally a better weighting function can be computed from the data itself and then fed iteratively back in to the calculation. These improvements are implemented here, although the overall effects they make to the solution are slight.A simple model for biased galaxy formation is considered in which the non-linear dark matter clumps are identified as sites for galaxy formation and their luminosity is assumed to be proportional to the product of some power of their mass and a power of the collapse redshift of the system . The implications of subjecting these systems to a long-wavelength density perturbation are examined. It turns out that the Faber-Jackson relation for elliptical galaxies should exhibit systematic offsets which correlate with the richness of their environments. This is a testable prediction. A large sample of elliptical galaxies with photometric and kinematic data are employed. No systematic offsets are found for either the Faber-Jackson relation or the Dn - δᵥ relation. Offsets are shown to exist for systems which typically inhabit extremely poor environments, such such as spiral bulges, and extremely rich environments such as radio galaxies and Brightest Cluster Members. Offsets are found and they are in the right sense for them to be attributed to the operation of bias. However, other more likely explanations are possible. At face value the data examined here seem to suggest that the distance indicator relations are effectively unbiased

Iron Pnictides: Superconductivity in Multi-Orbital Systems

This work focuses on the development and implementation of microscopic models as well as their numerical and analytical study to elucidate the properties of the iron pnictides. There are many first principle and phenomenological studies of these materials, but there is a need for unbiased numerical calculations following an approach similar to the one used in the study of the Hubbard and t-J models for the cuprates. First a two orbital model for the pnictides, focusing on two hybridized Fe-d orbitals (dxz and dyz) is formulated, including hoppings between nearest and next nearest neighbors as well as on site Coulomb interactions. This model is studied numerically on a tilted 8-site cluster. The magnetic tendencies and the pairing operators allowed by lattice and orbital symmetries are calculated including a study of which of these operators are favored in the model. Next, Heisenberg terms, deduced from a strong coupling expansion, are added to enhance magnetic order found experimentally as well as to increase carrier attraction. Superconducting pairing symmetries are studied in both the hole and electron doped cases. In both cases, many pairing symmetries compete (A1g, B2g, B1g) in the physical parameter regime suggesting that small changes in parameters may render any of these three channels stable. In the hole doped case, ground states with pseudocrystal momentum k=(pi,pi) in the unfolded Brillouin zone are found. In the two Fe-atom unit cell, this indicates that the ground state involves anti-bonding, rather than bonding, combinations of the orbitals. The lowest state with k=(0,0) has only a slightly higher energy and may become the favored state in some regions of parameter space. To investigate the role that degeneracy, hybridization and nesting play in the origin of magnetic order in the pnictides we introduce a phenomenological two orbital model composed of non-hybridized bands. Using a variety of techniques, in the weak coupling regime it is shown that only the model with hybridized bands develops magnetic order while the other does not have local magnetization. However, both models display similar insulating magnetic order in the strong coupling limit. These results indicate that nesting is a necessary but not sufficient condition for the development of ordered states with local magnetization in multi-orbital Hubbard systems; the additional requirement is that the nested portions of the bands have the same orbital flavor. This condition can be achieved via strong hybridization of the orbitals in the weak coupling limit or via Fermi surface reconstruction induced by Coulomb interactions in the strong coupling regime. Finally, a three orbital model is developed which, in addition to the Fe 3-dxz and dyz orbitals, takes into account the Fe 3-dxy orbital, which is found to have weight in a small region around the Fermi surface in bandstructure calculations. Mean field calculations are performed guided by the results of the two orbital model. The proceeds of this work include the discovery of four distinct magnetic phases in the model as well as the tabulation of a variety of pairing operators and their single particle spectral functions to be compared with experimental observations. Good agreement is found between both models for the magnetic tendencies and pairing symmetries

Comment on: "Technical note: Consistent calculation of aquatic gross production from oxygen triple isotope measurements" by Kaiser (2011)

© The Author(s), 2011. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 8 (2011): 2993-2997, doi:10.5194/bg-8-2993-2011.Kaiser (2011) has introduced an improved method for calculating gross productivity from the triple isotopic composition of dissolved oxygen in aquatic systems. His equation avoids approximations of previous methodologies, and also accounts for additional physical processes such as kinetic fractionation during invasion and evasion at the air-sea interface. However, when comparing his new approach to previous methods, Kaiser inconsistently defines the biological end-member with the result of overestimating the degree to which the various approaches of previous studies diverge. In particular, for his base case, Kaiser assigns a 17O excess to the product of photosynthesis (17δP) that is too low, resulting in his result being ~30 % too high when compared to previous equations. When this is corrected, I find that Kaiser's equations are consistent with all previous study methodologies within about ±20 % for realistic conditions of metabolic balance (f) and gross productivity (g). A methodological bias of ±20 % is of similar magnitude to current uncertainty in the wind-speed dependence of the air-sea gas transfer velocity, k, which directly impacts calculated gross productivity rates as well. While previous results could and should be revisited and corrected using the proposed improved equations, the magnitude of such corrections may be much less than implied by Kaiser.This work was funded by the NOAA Global Carbon Cycle Program (NA 100AR4310093)

Intelligent Agents for Disaster Management

ALADDIN [1] is a multi-disciplinary project that is developing novel techniques, architectures, and mechanisms for multi-agent systems in uncertain and dynamic environments. The application focus of the project is disaster management. Research within a number of themes is being pursued and this is considering different aspects of the interaction between autonomous agents and the decentralised system architectures that support those interactions. The aim of the research is to contribute to building more robust multi-agent systems for future applications in disaster management and other similar domains

Environmental dispute resolution in Indonesia

In the last two decades, Indonesia has seen a dramatic proliferation of environmental disputes in a variety of sectors, triggered by intensified deforestation and large scale mining operations in the resource rich outer islands, together with rapid industrialisation in the densely populated inner island of Java. Whilst the emergence of environmental disputes has sometimes attracted political repression, attempts have also been made in recent times to explore more functional approaches to their resolution. The Environmental Management Act of 1997 created a legal framework for the resolution of environmental disputes through both litigation and mediation. This book is the first attempt to analyse the implementation of this framework in detail and to assess the effectiveness of litigation and mediation in resolving environmental disputes in Indonesia. It includes a detailed overview of the environmental legal framework and its interpretation by Indonesian courts in landmark court cases. The book features a number of detailed case studies of both environmental litigation and mediation and considers the legal and non-legal factors that have influenced the success of these approaches to resolving environmental disputes. David Nicholson graduated in Law (Hons) and Asian Studies from Murdoch University in 1995 and was admitted to legal practice in Western Australia in 1997. He subsequently undertook doctoral research on environmental dispute resolution in Indonesia as part of the Indonesia Netherlands Study of Environmental Law and Administration (INSELA) project, based at the Van Vollenhoven Institute at Leiden University, and was awarded a doctorate in law in 2005. Dr Nicholson has since returned to legal practice in Western Australia, specializing in environmental planning and local government law

STS-31 Space Shuttle mission report

The STS-31 Space Shuttle Program Mission Report contains a summary of the vehicle subsystem activities on this thirty-fifth flight of the Space Shuttle and the tenth flight of the Orbiter Vehicle Discovery (OV-103). In addition to the Discovery vehicle, the flight vehicle consisted of an External Tank (ET) (designated as ET-34/LWT-27), three Space Shuttle main engines (SSME's) (serial numbers 2011, 2031, and 2107), and two Solid Rocket Booster (SRB) (designated as BI-037). The primary objective of the mission was to place the Hubble Space Telescope (HST) into a 330 nmi. circular orbit having an inclination of 28.45 degrees. The secondary objectives were to perform all operations necessary to support the requirements of the Protein Crystal Growth (PCG), Investigations into Polymer Membrane Processing (IPMP), Radiation Monitoring Equipment (RME), Ascent Particle Monitor (APM), IMAX Cargo Bay Camera (ICBC), Air Force Maui Optical Site Calibration Test (AMOS), IMAX Crew Compartment Camera, and Ion Arc payloads. In addition, 12 development test objectives (DTO's) and 10 detailed supplementary objectives (DSO's) were assigned to the flight. The sequence of events for this mission is shown. The significant problems that occurred in the Space Shuttle Orbiter subsystems during the mission are summarized, and the official problem tracking list is presented. In addition, each of the Space Shuttle Orbiter problems is cited in the subsystem discussion