Pure mathematics in Australia

I.D. Macdonald argued in this journal in 1968 that there was an inadequate number of mathematicians teaching in Australian universities who were qualified by international standards to conduct honours courses and supervise research students..

Decision Problems for Nash Equilibria in Stochastic Games

We analyse the computational complexity of finding Nash equilibria in stochastic multiplayer games with $\omega$-regular objectives. While the existence of an equilibrium whose payoff falls into a certain interval may be undecidable, we single out several decidable restrictions of the problem. First, restricting the search space to stationary, or pure stationary, equilibria results in problems that are typically contained in PSPACE and NP, respectively. Second, we show that the existence of an equilibrium with a binary payoff (i.e. an equilibrium where each player either wins or loses with probability 1) is decidable. We also establish that the existence of a Nash equilibrium with a certain binary payoff entails the existence of an equilibrium with the same payoff in pure, finite-state strategies.Comment: 22 pages, revised versio

Modeling DNA Structure, Elasticity and Deformations at the Base-pair Level

We present a generic model for DNA at the base-pair level. We use a variant of the Gay-Berne potential to represent the stacking energy between neighboring base-pairs. The sugar-phosphate backbones are taken into account by semi-rigid harmonic springs with a non-zero spring length. The competition of these two interactions and the introduction of a simple geometrical constraint leads to a stacked right-handed B-DNA-like conformation. The mapping of the presented model to the Marko-Siggia and the Stack-of-Plates model enables us to optimize the free model parameters so as to reproduce the experimentally known observables such as persistence lengths, mean and mean squared base-pair step parameters. For the optimized model parameters we measured the critical force where the transition from B- to S-DNA occurs to be approximately $140{pN}$. We observe an overstretched S-DNA conformation with highly inclined bases that partially preserves the stacking of successive base-pairs.Comment: 15 pages, 25 figures. submitted to PR

Hypusination of Eif5a Regulates Cytoplasmic TDP-43 Aggregation and Accumulation in a Stress-Induced Cellular Model

TAR DNA-binding protein 43 (TDP-43) is a nuclear RNA/DNA binding protein involved in mRNA metabolism. Aberrant mislocalization to the cytoplasm and formation of phosphorylated/aggregated TDP-43 inclusions remains the hallmark pathology in a spectrum of neurodegenerative diseases, including frontotemporal disorders and Alzheimer\u27s disease. Eukaryotic Translation Initiation Factor 5A undergoes a unique post-translation modification of lysine to hypusine (K50), which determines eIF5A binding partners. We used a sodium arsenite-induced cellular stress model to investigate the role of hypusinated eIF5A (eIF5AHypK50) in governing TDP-43 cytoplasmic mislocalization and accumulation in stress granule. Our proteomics and functional data provide evidence that eIF5A interacts with TDP-43 in a hypusine-dependent manner. Additionally, we showed that following stress TDP-43 interactions with eIF5AHypK50 were induced both in the cytoplasm and stress granules. Pharmacological reduction of hypusination or mutations of lysine residues within the hypusine loop decreased phosphorylated and insoluble TDP-43 levels. The proteomic and biochemical analysis also identified nuclear pore complex importins KPNA1/2, KPNB1, and RanGTP as interacting partners of eIF5AHypK50. These findings are the first to provide a novel pathway and potential therapeutic targets that require further investigation in models of TDP-43 proteinopathies

Cocrystals of spironolactone and griseofulvin based on an in silico screening method

Cocrystal formation is considered as one of the most effective solid-state methods to alter the physicochemical properties of active pharmaceutical ingredients (APIs). In silico methods for cocrystal prediction are mostly based on structural and energetic considerations. We have developed a computational method that ranks the probability of cocrystal formation of APIs with large databases of crystal coformers (CCFs). This approach is based on using molecular electrostatic potential surfaces to assess molecular complementarity between two cocrystal components. The screening tool was applied to two low solubility drugs, namely griseofulvin and spironolactone. Promising coformer candidates were selected from a database of 310 pharmaceutically acceptable CCFs, and experimental screening was carried out. Novel solid forms were obtained by liquid-assisted grinding and were characterised by XRPD, DSC, TGA and IR. One new cocrystal of griseofulvin and two new cocrystals of spironolactone were identified, and the crystal structures were determined from the XRPD patterns. For these systems, phenols tend to act as successful H-bond donors in forming cocrystals, while carboxylic acids only give rise to physical mixtures of the two components

Determining the WIMP mass using the complementarity between direct and indirect searches and the ILC

We study the possibility of identifying dark matter properties from XENON-like 100 kg experiments and the GLAST satellite mission. We show that whereas direct detection experiments will probe efficiently light WIMPs, given a positive detection (at the 10% level for $m_{\chi} \lesssim 50$ GeV), GLAST will be able to confirm and even increase the precision in the case of a NFW profile, for a WIMP-nucleon cross-section $\sigma_{\chi-p} \lesssim 10^{-8}$ pb. We also predict the rate of production of a WIMP in the next generation of colliders (ILC), and compare their sensitivity to the WIMP mass with the XENON and GLAST projects.Comment: 32 pages, new figures and a more detailed statistical analysis. Final version to appear in JCA

An MPEG-7 scheme for semantic content modelling and filtering of digital video

Abstract Part 5 of the MPEG-7 standard specifies Multimedia Description Schemes (MDS); that is, the format multimedia content models should conform to in order to ensure interoperability across multiple platforms and applications. However, the standard does not specify how the content or the associated model may be filtered. This paper proposes an MPEG-7 scheme which can be deployed for digital video content modelling and filtering. The proposed scheme, COSMOS-7, produces rich and multi-faceted semantic content models and supports a content-based filtering approach that only analyses content relating directly to the preferred content requirements of the user. We present details of the scheme, front-end systems used for content modelling and filtering and experiences with a number of users

Leptospirosis as a cause of "white spot" kidneys in South African pig abattoirs

The incidence of isolation of Leptospira sp. from the kidneys of slaughter pigs with “white-spot" macroscopic lesions was determined. Histology and general bacteriology were performed. Leptospira pomona was isolated from 19/21 kidneys showing macroscopic lymphocytic lesions.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

Galactic-Centre Gamma Rays in CMSSM Dark Matter Scenarios

We study the production of gamma rays via LSP annihilations in the core of the Galaxy as a possible experimental signature of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which supersymmetry-breaking parameters are assumed to be universal at the GUT scale, assuming also that the LSP is the lightest neutralino chi. The part of the CMSSM parameter space that is compatible with the measured astrophysical density of cold dark matter is known to include a stau_1 - chi coannihilation strip, a focus-point strip where chi has an enhanced Higgsino component, and a funnel at large tanb where the annihilation rate is enhanced by the poles of nearby heavy MSSM Higgs bosons, A/H. We calculate the total annihilation rates, the fractions of annihilations into different Standard Model final states and the resulting fluxes of gamma rays for CMSSM scenarios along these strips. We observe that typical annihilation rates are much smaller in the coannihilation strip for tanb = 10 than along the focus-point strip or for tanb = 55, and that the annihilation branching ratios differ greatly between the different dark matter strips. Whereas the current Fermi-LAT data are not sensitive to any of the CMSSM scenarios studied, and the calculated gamma-ray fluxes are probably unobservably low along the coannihilation strip for tanb = 10, we find that substantial portions of the focus-point strips and rapid-annihilation funnel regions could be pressured by several more years of Fermi-LAT data, if understanding of the astrophysical background and/or systematic uncertainties can be improved in parallel.Comment: 33 pages, 12 figures, comments and references added, version to appear in JCA