Branching processes, the max-plus algebra and network calculus

Branching processes can describe the dynamics of various queueing systems, peer-to-peer systems, delay tolerant networks, etc. In this paper we study the basic stochastic recursion of multitype branching processes, but in two non-standard contexts. First, we consider this recursion in the max-plus algebra where branching corresponds to finding the maximal offspring of the current generation. Secondly, we consider network-calculus-type deterministic bounds as introduced by Cruz, which we extend to handle branching-type processes. The paper provides both qualitative and quantitative results and introduces various applications of (max-plus) branching processes in queueing theory

Shape-Based Models for Interactive Segmentation of Medical Images

Accurate image segmentation is one of the key problems in computer vision. In domains such as radiation treatment planning, dosimetrists must manually trace the outlines of a few critical structures on large numbers of images. Considerable similarity can be seen in the shape of these regions, both between adjacent slices in a particular patient and across the spectrum of patients. Consequently we should be able to model this similarity and use it to assist in the process of segmentation. Previous work has demonstrated that a constraint-based 2D radial model can capture generic shape information for certain shape classes, and can reduce user interaction by a factor of three over purely manual segmentation. Additional simulation studies have shown that a probabilistic version of the model has the potential to further reduce user interaction. This paper describes an implementation of both models in a general-purpose imaging and graphics framework and compares the usefulness of the models on several shape classes

Some competition and consumer issues in the Indigenous visual arts industry

This paper focuses on how competition and consumer protection issues might be relevant to the Indigenous visual arts industry. The structure of the industry is complex: the majority of producers reside in remote localities; there are a variety of functional levels; the industry encompasses both the 'fine' and 'tourist' art markets and includes works made in collaboration with non-Indigenous people. There is an emphasis in the paper on government funded community art centres which collect, document and market Indigenous art. However, the objectives of most art centres are mixed and the roles that they play in remote communities extend well beyond these tasks. Perhaps most importantly, art centres act as cultural mediators between artists and the market. If they are to act in the artists' best interests, art centres may operate most effectively as monopolies. This is primarily because of market failure associated with remoteness, their small size, dispersed artist populations and the poor track record of private dealers. Notwithstanding the fact that a few art centres have exclusive access to some geographically defined art styles, the nature of competition within the industry appears healthy. However, there is concern about competition from imported as well as locally produced 'fakes' in the tourist market. Authorship and issues of authenticity emerge as considerations with potential for future industry impacts, though labelling and other documentation strategies by art centres and other outlets have improved markedly in recent years. Those sections of the Trade Practices Act 1974 that may be relevant to the industry include unconscionable conduct, no and misleading representation and coercion or harassment. A significant amount of anecdotal evidence has emerged in the course of research in relation to the unethical practices of some private dealers. The production of a producer and consumer education charter is put forward as a strategy which may be of benefit to this growing industry

Heuristic Refinement Method for the Derivation of Protein Solution Structures: Validation on Cytochrome B562

A method is described for determining the family of protein structures compatible with solution data obtained primarily from nuclear magnetic resonance (NMR) spectroscopy. Starting with all possible conformations, the method systematically excludes conformations until the remaining structures are only those compatible with the data. The apparent computational intractability of this approach is reduced by assembling the protein in pieces, by considering the protein at several levels of abstraction, by utilizing constraint satisfaction methods to consider only a few atoms at a time, and by utilizing artificial intelligence methods of heuristic control to decide which actions will exclude the most conformations. Example results are presented for simulated NMR data from the known crystal structure of cytochrome b562 (103 residues). For 10 sample backbones an average root-mean-square deviation from the crystal of 4.1 A was found for all alpha-carbon atoms and 2.8 A for helix alpha-carbons alone. The 10 backbones define the family of all structures compatible with the data and provide nearly correct starting structures for adjustment by any of the current structure determination methods

Heating Houses Electrically

More and more Iowa homes are being heated with electricity. Electrical house heating differs from other heating systems in several respects. Here\u27s a situation report on this relatively new house-heating method

Microscopic thickness determination of thin graphite films formed on SiC from quantized oscillation in reflectivity of low-energy electrons

Low-energy electron microscopy (LEEM) was used to measure the reflectivity of low-energy electrons from graphitized SiC(0001). The reflectivity shows distinct quantized oscillations as a function of the electron energy and graphite thickness. Conduction bands in thin graphite films form discrete energy levels whose wave vectors are normal to the surface. Resonance of the incident electrons with these quantized conduction band states enhances electrons to transmit through the film into the SiC substrate, resulting in dips in the reflectivity. The dip positions are well explained using tight-binding and first-principles calculations. The graphite thickness distribution can be determined microscopically from LEEM reflectivity measurements.Comment: 7 pages, 3 figure

Interference between independent fluctuating condensates

We consider a problem of interference between two independent condensates, which lack true long range order. We show that their interference pattern contains information about correlation functions within each condensate. As an example we analyze the interference between a pair of one dimensional interacting Bose liquids. We find universal scaling of the average fringe contrast with system size and temperature that depends only on the Luttinger parameter. Moreover the full distribution of the fringe contrast, which is also equivalent to the full counting statistics of the interfering atoms, changes with interaction strength and lends information on high order correlation functions. We also demonstrate that the interference between two-dimensional condensates at finite temperature can be used as a direct probe of the Kosterlitz-Thouless transition. Finally, we discuss generalization of our results to describe the intereference of a periodic array of independent fluctuating condensates.Comment: 7 pages, 3 figures, published versio