Initial steps towards automatic segmentation of the wire frame of stent grafts in CT data

For the purpose of obtaining a geometrical model of the wire frame of stent grafts, we propose three tracking methods to segment the stent's wire, and compare them in an experiment. A 2D test image was created by obtaining a projection of a 3D volume containing a stent. The image was modified to connect the parts of the stent's frame and thus create a single path. Ten versions of this image were obtained by adding different noise realizations. Each algorithm was started at the start of each of the ten images, after which the traveled paths were compared to the known correct path to determine the performance. Additionally, the algorithms were applied to 3D clinical data and visually inspected. The method based on the minimum cost path algorithm scored excellent in the experiment and showed good results on the 3D data. Future research will focus on establishing a geometrical model by determining the corner points and the crossings from the results of this method.\u

Concepts and Actors in Organic Livestock Husbandry in Bolivia

Traditional smallholder livestock production is expected to correspond widely with principles of organic livestock farming. Though, the real magnitude of livestock under organic and alike management is unknown. From stakeholder analysis and structured interviews with key persons in Bolivia it is deduced that similarities are widely given, whereas it is questioned whether a formal individual certification approach for livestock products will match the farmer interests and consumer demands

Two tone response of radiofrequency signals using the voltage output of a Superconducting Quantum Interference Filter

In the presence of weak time harmonic electromagnetic fields, Superconducting Quantum Interference Filters (SQIFs) show the typical behavior of non linear mixers. The SQIFs are manufactured from high-T_c grain boundary Josephson junctions and operated in active microcooler. The dependence of dc voltage output V_dc vs. static external magnetic field B is non-periodic and consists of a well pronounced unique dip at zero field, with marginal side modulations at higher fields. We have successfully exploited the parabolic shape of the voltage dip around B=0 to mix quadratically two external time harmonic rf-signals, at frequencies f_1 and f_2 below the Josephson frequency f_J, and detect the corresponding mixing signal at f_1-f_2. When the mixing takes place on the SQIF current-voltage characteristics the component at 2f_2 - f_1 is present. The experiments suggest potential applications of a SQIF as a non-linear mixing device, capable to operate at frequencies from dc to few GHz with a large dynamic range.Comment: 10 pages, 3 Figures, submitted to J. Supercond. (as proceeding of the HTSHFF Symposium, June 2006, Cardiff

Enhancement of the ferromagnetic order of graphite after sulphuric acid treatment

We have studied the changes in the ferromagnetic behavior of graphite powder and graphite flakes after treatment with diluted sulphuric acid. We show that this kind of acid treatment enhances substantially the ferromagnetic magnetization of virgin graphite micrometer size powder as well as in graphite flakes. The anisotropic magnetoresistance (AMR) amplitude at 300 K measured in a micrometer size thin graphite flake after acid treatment reaches values comparable to polycrystalline cobalt.Comment: 3.2 pages, 4 figure

Abundant Exotics and Cavalier Crafting: Obsidian Use and Emerging Complexity in the Northern Lake Titicaca Basin

Book Abstract: Using case studies from around the globe—including Mesoamerica, North and South America, Africa, China, and the Greco-Roman world—and across multiple time periods, the authors in this volume make the case that abundance provides an essential explanatory perspective on ancient peoples’ choices and activities. Economists frequently focus on scarcity as a driving principle in the development of social and economic hierarchies, yet focusing on plenitude enables the understanding of a range of cohesive behaviors that were equally important for the development of social complexity. Our earliest human ancestors were highly mobile hunter-gatherers who sought out places that provided ample food, water, and raw materials. Over time, humans accumulated and displayed an increasing quantity and variety of goods. In households, shrines, tombs, caches, and dumps, archaeologists have discovered large masses of materials that were deliberately gathered, curated, distributed, and discarded by ancient peoples. The volume’s authors draw upon new economic theories to consider the social, ideological, and political implications of human engagement with abundant quantities of resources and physical objects and consider how individual and household engagements with material culture were conditioned by the quest for abundance. Abundance shows that the human propensity for mass consumption is not just the result of modern production capacities but fulfills a longstanding focus on plenitude as both the assurance of well-being and a buffer against uncertainty. This book will be of great interest to scholars and students in economics, anthropology, and cultural studies. Contributors: Traci Ardren, Amy Bogaard, Elizabeth Klarich, Abigail Levine, Christopher R. Moore, Tito E. Naranjo, Stacey Pierson, James M. Potter, François G. Richard, Christopher W. Schmidt, Carol Schultze, Payson Sheets, Monica L. Smith, Katheryn C. Twiss, Mark D. Varien, Justin St. P. Walsh, María Nieves Zedeño Source: Publisherhttps://scholarworks.smith.edu/ant_books/1001/thumbnail.jp

Potential Role of Native Bush in the Chaco for Mitigation of Dryland Salinity in Grassland

There is a zone of some 3.000.000 ha with an elevated dryland salinity risk in the Paraguayan Chaco due to a shallow saline ground water table. Evidence is shown of the crucial role native bush seems to play in keeping the water table at a low level and reducing therefore the risk of soil salinisation. In this paper a planned field experiment is outlined to define the tolerable level of deforestation and pasture establishment for a sylvopastoral production system in the Chacoan zone prone to dryland salinity

Amphicarpic Legumes for Tropical Pasture Persistence

Amphicarpy, by which a plant produces underground seeds in addition to aerial fruits, is found in many plant families and in species of at least 15 legume genera. First studies on the tropical Centrosema rotundifolium and subtropical Macroptilium panduratum revealed for both species, besides their stoloniferous growth habit, two important mechanisms for survival under unfavorable conditions: (1) Underground meristems and reserve organs, and (2) regeneration from a soil seed reserve based on underground, aerial-flowering independent, seed production. Underground seed production was for both species particularly high on very sandy soils, but amphicarpy enables the plants to exhibit a plasticity response to unfavourable soil conditions by changing resource allocation from underground to above-ground reproduction. The latter, which seems to be influenced by cross-pollination and thus aids gene-recombination, favours spreading of plant populations whereas underground reproduction ensures population survival on-site. Preliminary information on the agronomic potential of both species is given and several research needs are highlighted

\u3cem\u3eCanavalia brasiliensis\u3c/em\u3e: A Multipurpose Legume for the Sub-Humid Tropics

Canavalia brasiliensis Mart. ex Benth. ( Brazilian jackbean ) is a weakly perennial, prostrate to twining herbaceous legume with a wide natural distribution in the New World tropics and subtropics. In comparison with C. ensiformis ( jackbean ), research reports on C. brasiliensis are scattered and restricted to studies done in Latin America. The species develops a dense and extensive, deep-reaching root system and subsequently tolerates a 5-6 month dry period. Based on studies that generally were done with only one genotype, it is adapted to a wide range of soils, including very acid, low-fertility soils. Its main use is as green manure, for fallow improvement and erosion control. Due to medium biomass decomposition, nutrient release of C. brasiliensis green manure has the potential to synchronise well with the nutrient demand of the succeeding crop and may lead to high N recovery rates. Whereas the high concentration, in Canavalia seeds, of antinutritive substances such as toxic amino acids (e.g., canavanin), lectins (e.g., concanavalin Br) and trypsin inhibitors, there is little information on the nutritive value of the herbage of this species (Schloen et al., 2004). In order to develop multipurpose legume germplasm for smallholder systems in the sub-humid tropics, we initiated a C. brasiliensis germplasm screening experiment and engaged with farmers in Central America to integrate this legume into local maize-bean production systems. First promising results are reported

Measuring rhizosphere hydraulic properties: impact of root mucilage on soil hydraulic conductivity and water retention curve

Roots are hypothesized to alter rhizosphere hydraulic properties by release of mucilage. This mechanism is expected to have strong implications for root water uptake under drought conditions. Direct measurement of rhizosphere hydraulic properties is hindered by the dynamic nature of the components involved; root hydraulics change with ontology; mucilage production, composition and diffusion are not constant; soil water content changes. An experimental approach was developed which enables to simultaneously measure hydraulic conductivity and apparent water retention curve in a radial flow setup, mimicking the flow geometry around roots. The method consists of extracting water at constant suction via a suction cup, which is centrally placed in a soil filled cylinder and recording water outflow and soil matric potential. In the past, the setup was tested for homogeneous distribution of a model substance (calcium-polygalacturonic acid) frequently used to mimic the properties of root mucilage. Now the system has been applied to investigate the impact of plant root mucilage collected from white lupine. As the system allows a local placement of mucilage treated soil around the suction cup to simulate a ‘rhizosphere’ between bulk soil and suction cup, it can be set up with the limited quantity of natural plant root mucilage available from direct collection. Quartz sand has been treated with lupine root mucilage by mixing liquid mucilage with dry sand at a concentration of 2 mg mucilage per gram soil. Treated sand has been placed as a circular layer with 3.75 mm thickness around the suction cup, which has a radius of 1.25 mm. All around this layer, the device has been filled up with untreated sand. The radius of the whole device was 25 mm. To determine soil hydraulic conductivity we inversely fitted the outflow curves and soil matric potential by solving the Richards’ equation in radial coordinates. Water outflow curves show a significant impact of lupine mucilage on water flow rate – it slows water flow from bulk soil to suction cup. Currently modelling is in process to determine soil hydraulic conductivity and water retention curves. Decreasing hydraulic conductivities and increasing water retention due to lupine mucilage treatment are expected