Arithmetic coding revisited

Over the last decade, arithmetic coding has emerged as an important compression tool. It is now the method of choice for adaptive coding on multisymbol alphabets because of its speed, low storage requirements, and effectiveness of compression. This article describes a new implementation of arithmetic coding that incorporates several improvements over a widely used earlier version by Witten, Neal, and Cleary, which has become a de facto standard. These improvements include fewer multiplicative operations, greatly extended range of alphabet sizes and symbol probabilities, and the use of low-precision arithmetic, permitting implementation by fast shift/add operations. We also describe a modular structure that separates the coding, modeling, and probability estimation components of a compression system. To motivate the improved coder, we consider the needs of a word-based text compression program. We report a range of experimental results using this and other models. Complete source code is available

A detailed X-ray investigation of zeta Puppis IV. Further characterization of the variability

Previously, the X-ray emission of zeta Puppis was found to be variable with light curves harbouring "trends" with a typical timescale longer than the exposure length. The origin of these changes was proposed to be linked to large-scale structures in the wind, but further characterization of the variability at high energies was needed. Since then, a number of new X-ray observations have become available. Furthermore, a cyclic behaviour with a 1.78d period was identified in long optical photometric runs, which is thought to be associated with the launching mechanism of large-scale wind structures. We analysed these new X-ray data, revisited the old data, and compared X-ray with optical data, including when simultaneous. We found that the behaviour in X-rays cannot be explained in terms of a perfect clock because the amplitude and shape of its variations change with time. For example, zeta Puppis was much more strongly variable between 2007 and 2011 than before and after this interval. Comparing the X-ray spectra of the star at maximum and minimum brightness yields no compelling difference beyond the overall flux change: the temperatures, absorptions, and line shapes seem to remain constant, well within errors. The only common feature between X-ray datasets is that the variation amplitudes appear maximum in the medium (0.6-1.2keV) energy band. Finally, no clear and coherent correlation can be found between simultaneous X-ray and optical data. Only a subgroup of observations may be combined coherently with the optical period of 1.78d, although the simultaneous optical behaviour is unknown. The currently available data do not reveal any obvious, permanent, and direct correlation between X-ray and optical variations. The origin of the X-ray variability therefore still needs to be ascertained, highlighting the need for long-term monitoring in multiwavelengths, i.e. X-ray, UV, and optical.Comment: accepted for publication by A&

The behaviour of flexible slabs on idealised and actual foundations

Due to a lack of contact between the disciplines of soil mechanics and structural engineering there is a tendency for flexible structures to be analysed under grossly simplified assumptions regarding the interaction between the structure and its soil foundation. For example, it is often assumed that the contact pressure on the base of a structure is uniform, or linearly varying. In the thesis it is proposed that the use of a digital computer enables a structure and its foundation to be analysed as a complete entity. The computer is essential because of the complexity of the mathematical formulation of the problem and because of the scale of the analysis involved. Most of the theoretical work concerns the finite element method for the analysis of structure and foundation, although some work on the finite difference method is also presented. The former method allows a more realistic approximation to be made to the inhomogeneity of soil deposits. An evaluation of current methods and some advances in the theory of the finite element method as applied to plate or slab structures are presented, culminating in an analysis incorporating the effect of transverse shear deformations on the bending of elastic plates. The theories are then applied to the evaluation of a set of experimental results obtained for circular plates bearing on a sand foundation and loaded with concentrated central loads. The classical idealisations of foundations are found to be inadequate and more realistic models are proposed for the particular plate structure and loading case examined

THE INVISIBLE MOATS OF THE MUN RIVER VALLEY, NE THAILAND: THE EXAMINATION OF WATER MANAGEMENT DEVICES AT MOUNDED SITES THROUGH GROUND PENETRATING RADAR (GPR)

The Mun River valley is well known for its moat-bound mounded archaeological sites that are usually associated with Iron Age occupation (~500BC- AD500).  The investigation of these sites has provided a wealth of information on the changing social and environmental conditions during prehistory.  In recent years, research has identified a greater diversity of site morphologies in the region, many of which, importantly, do not appear to have moats surrounding them.  This paper seeks to investigate whether the apparently ‘non-moated’ mound site of Non Klang (Nong Hua Raet village) was actually moated in the past, and if such, now in-filled features can be investigated through non-destructive Ground Penetrating Radar methodology.  Additionally, while large external moats can be observed in the modern day topography at sites such as Ban Non Wat, excavation has demonstrated that further, invisible, water management features exist beneath the surface within the current mound boundary of the site.  These are probably Iron Age precursors to the later more extensive and still visible moats.  This paper seeks to answer several fundamental questions: What application can GPR have at mounded sites in Southeast Asia?  Do invisible moats exist?  How will this affect our understanding of the broader prehistoric landscape in the Upper Mun River Valley? 

A technical protocol for using ground penetrating radar and electrical resistivity tomography in the search for covert graves

The location of covert graves is an important but challenging part of missing persons investigations. Although traditional search techniques, such as foot searches and cadaver dogs, have proved successful, the incorporation of higher technology methods, such as geophysical techniques, can be used to increase the chances of locating covert graves. This article will present a field method for the use of two geophysical techniques, including ground penetrating radar and electrical resistivity tomography, which can successfully locate covert graves in an Australian environment. If the soil and climate conditions permit, this technical protocol can be applied to other clandestine grave search sites as well. Ultimately, by increasing chances of locating the covert grave, and by extension the missing person, a successful judicial outcome can be achieved and highly sought after answers can be provided to the family

Passive sampling: partition coefficients for a silicone rubber reference phase.

Silicone rubber sheeting can be used as a passive sampling device for hydrophobic organic contaminants in the environment to determine the available concentrations in water and sediments. Reliable sampler-water partition coefficients are required to determine the sampling rates and the dissolved contaminant concentrations in water and in sediment pore water. Log partition coefficients (logKsr,w) for silicone rubber-water have been estimated for 32 polycyclic aromatic hydrocarbons (PAHs), 2 deuterated PAH analogues and 32 chlorobiphenyls (CBs) using the cosolvent method, with methanol as cosolvent. Strong linear relationships were found with literature values for the corresponding log octanol-water partition coefficients (logKow) for both CBs and PAHs, confirming that partitioning into the silicone rubber is strongly determined by the hydrophobicity of the compounds, which suggests logKow is a good predictor of logKsr,w and that absorption is the main mechanism for accumulation of analytes into the silicone rubber polymer

PLAUR polymorphisms and lung function in UK smokers

<p>Abstract</p> <p>Background</p> <p>We have previously identified Urokinase Plasminogen Activator Receptor (<it>PLAUR</it>) as an asthma susceptibility gene. In the current study we tested the hypothesis that <it>PLAUR </it>single nucleotide polymorphisms (SNPs) determine baseline lung function and contribute to the development of Chronic Obstructive Pulmonary Disease (COPD) in smokers.</p> <p>Methods</p> <p>25 <it>PLAUR </it>SNPs were genotyped in COPD subjects and individuals with smoking history (n = 992). Linear regression was used to determine the effects of polymorphism on baseline lung function (FEV₁, FEV₁/FVC) in all smokers. Genotype frequencies were compared in spirometry defined smoking controls (n = 176) versus COPD cases (n = 599) and COPD severity (GOLD stratification) using logistic regression.</p> <p>Results</p> <p>Five SNPs showed a significant association (p < 0.01) with baseline lung function; rs2302524(Lys220Arg) and rs2283628(intron 3) were associated with lower and higher FEV₁respectively. rs740587(-22346), rs11668247(-20040) and rs344779(-3666) in the 5'region were associated with increased FEV₁/FVC ratio. rs740587 was also protective for COPD susceptibility and rs11668247 was protective for COPD severity although no allele dose relationship was apparent. Interestingly, several of these associations were driven by male smokers not females.</p> <p>Conclusion</p> <p>This study provides tentative evidence that the asthma associated gene <it>PLAUR </it>also influences baseline lung function in smokers. However the case-control analyses do not support the conclusion that <it>PLAUR </it>is a major COPD susceptibility gene in smokers. PLAUR is a key serine protease receptor involved in the generation of plasmin and has been implicated in airway remodelling.</p

Sampling Plants and Malacofauna in 87Sr/86Sr Bioavailability Studies : implications for isoscape mapping and reconstructing of past mobility patterns

Acknowledgments: We thank Annabell Reiner and Sven Steinbrenner (MPI-EVA) for technical and practical support with preparation and analysis of samples. We thank the La Ferrassie Team for support during field sampling and project development, especially Harold Dibble, Shannon McPherron (MPI-EVA), Teresa Steele (UC Davies), Vera Aldeias (MPI-EVA, University of Algarve), Paul Goldberg (University of Wollongong, University Tübingen), Dennis Sandgathe (Simon Fraser University, University of Pennsylvania), Alain Turq (Musée national de Préhistoire, CNRS), and Jean-Jacques Hublin (MPI-EVA), as well as Mike Richards (SFU). Special thanks to Daphne Katranides and Aaron Katranides. We also thank the editor (TP) and two reviewers whose constructive comments greatly improved this manuscript. Funding: This research was funded by the Max Planck Society and a Leverhulme Trust grant to KB (RPG-2017-410), with additional support from Australian Research Council Discovery grants DP0664144 and DP110101417 to RG. KJ thanks the ERC ARCHEIS 803676, and IM thanks Australian Research Council Discovery Early Career Award (DE160100703), for salary support during production of this manuscript.Peer reviewedPublisher PD