Hamilton cycles in hypergraphs below the Dirac threshold

We establish a precise characterisation of $4$-uniform hypergraphs with minimum codegree close to $n/2$ which contain a Hamilton $2$-cycle. As an immediate corollary we identify the exact Dirac threshold for Hamilton $2$-cycles in $4$-uniform hypergraphs. Moreover, by derandomising the proof of our characterisation we provide a polynomial-time algorithm which, given a $4$-uniform hypergraph $H$ with minimum codegree close to $n/2$, either finds a Hamilton $2$-cycle in $H$ or provides a certificate that no such cycle exists. This surprising result stands in contrast to the graph setting, in which below the Dirac threshold it is NP-hard to determine if a graph is Hamiltonian. We also consider tight Hamilton cycles in $k$-uniform hypergraphs $H$ for $k \geq 3$, giving a series of reductions to show that it is NP-hard to determine whether a $k$-uniform hypergraph $H$ with minimum degree $\delta(H) \geq \frac{1}{2}|V(H)| - O(1)$ contains a tight Hamilton cycle. It is therefore unlikely that a similar characterisation can be obtained for tight Hamilton cycles.Comment: v2: minor revisions in response to reviewer comments, most pseudocode and details of the polynomial time reduction moved to the appendix which will not appear in the printed version of the paper. To appear in Journal of Combinatorial Theory, Series

Statistical Image Reconstruction for High-Throughput Thermal Neutron Computed Tomography

Neutron Computed Tomography (CT) is an increasingly utilised non-destructive analysis tool in material science, palaeontology, and cultural heritage. With the development of new neutron imaging facilities (such as DINGO, ANSTO, Australia) new opportunities arise to maximise their performance through the implementation of statistically driven image reconstruction methods which have yet to see wide scale application in neutron transmission tomography. This work outlines the implementation of a convex algorithm statistical image reconstruction framework applicable to the geometry of most neutron tomography instruments with the aim of obtaining similar imaging quality to conventional ramp filtered back-projection via the inverse Radon transform, but using a lower number of measured projections to increase object throughput. Through comparison of the output of these two frameworks using a tomographic scan of a known 3 material cylindrical phantom obtain with the DINGO neutron radiography instrument (ANSTO, Australia), this work illustrates the advantages of statistical image reconstruction techniques over conventional filter back-projection. It was found that the statistical image reconstruction framework was capable of obtaining image estimates of similar quality with respect to filtered back-projection using only 12.5% the number of projections, potentially increasing object throughput at neutron imaging facilities such as DINGO eight-fold

Effects of homeopathic and antibiotic mastitis treatment considering mediumterm parameters in an organic dairy herd

Introduction: Homeopathic treatment is a common method against bovine mastitis in organic herds. In a study conducted in a large biodyn farm in Brandenburg (D) considering 261 cases of acute or chronical mastitis, we used four different combinations of homeopathic remedies depending on clinical state of the mastitis (e.g. general findings, pain, swelling or secretion). The remedies were administrated orally. The control group was treated with antibiotics intracisternally for three days at minimum until the cow was clinically cured or defined as therapy failure. While the cure rate was calculated from clinical and laboratory data (bacterial findings and somatic cell count), the further development of the treated cows during the lactation was confirmed using monthly provided somatic cell counts of cows, mastitis and culling data. Results: We found an overall cure rate (complete healing) after administration of homeopathic remedies (H) of 21.7 % compared to 35.8 % in the antibiotically treated control group (A). Though there was an obviously poor treatment success in the homeopathy group, we found no remarkable depression of general udder health in the herd. So it was fair to assume that there must exist positive mediumterm effects of homeopathic remedies. We compared the parameters "Remain in Lactation (RIL)", "Acceptable Cell Count (ACC; < 200.000/ ml)" and analysed the reasons of culling or leaving production by other reasons. We found that there were no differences in RIL (H: 26 % vs. A: 24 %) and ACC (14 % vs. 10 %) in general six month after treatment. The risk of unsuccessful homeopathic treatment during the observing time only was higher in cases of Staph. aureus mastitis and in cows in second lactation. The most important fact was that treated cows which were classified as- subclinical infected 3 weeks after treatment- (n = 35) showed the best relative mediumterm results in the homeopathatic treatment group (ACC: 10 % vs. 0 %; RIL: 29 % vs. 7 %). We conclude that maybe the time frame of 3 weeks after treatment is not suitable to describe the effects of regulatory (homeopathic) mastitis treatment. The mediumterm effects at least six months after treatment are comparable to those after antibiotic administration. We suppose that it is possible to keep the udder health standard in a herd avoiding antibiotics

Geochemistry of volcanic rocks from the Woodlark Basin

EGU2011-12864 The Woodlark Basin east of Papua New Guinea represents one of the few places on Earth where a spreading axis propagates into continental crust. This special tectonic setting allows insights into the evolution of magma composition as continental extension and break-up changes to the formation of ocean crust. We report here geochemical results on samples collected in 2009 from the four segments closest to the continental breakup, from segment 1 which abuts the detachment fault responsible for continental extension on Moresby Seamount in the West, to segment 4, representing mature oceanic crust in the East. A total of 208 glass samples have been analyzed for their major (EMPA) and trace element (LA-ICPMS) compositions. The data show strong E-W variations. Samples ranging from tholeiitic basalt and basaltic andesite to andesite and rhyolite are found on Segment 1. They have generally high alkali values and a wide range of trace element contents and ratios. Segments 2 to 4 magmas in contrast only comprise tholeiitic basalt with lower alkali contents and a more restricted range of trace element chemistry. The geochemical differences between the segments cannot be attributed to differentiation processes alone, and different sources are required. High Ba/La, (La/Sm)N, Rb/Sr, and Th/La on Segment 1 suggest a derivation from an enriched mantle source, while low Nd/Pb and Nb/U suggest that some of the enrichment may also reflect the influence of continental crust during magma genesis. Whether this continental signature is present in the form of recycled material in the mantle or as rafted continental blocks in the axial region is at present unclear. In contrast to rocks from segment 1, trace element compositions of volcanic glasses from segments 2 to 4 show a stronger MORB signature, presumably reflecting more mature spreading in this part of the basin. The influence of continental material appears to be minimal, suggesting that uncontaminated asthenosphere quickly flows into the rift and/or that continental blocks are not retained in the axial region for long time periods following the rifting-spreading transition

Using Inhabitation in Bounded Combinatory Logic with Intersection Types for Composition Synthesis

We describe ongoing work on a framework for automatic composition synthesis from a repository of software components. This work is based on combinatory logic with intersection types. The idea is that components are modeled as typed combinators, and an algorithm for inhabitation {\textemdash} is there a combinatory term e with type tau relative to an environment Gamma? {\textemdash} can be used to synthesize compositions. Here, Gamma represents the repository in the form of typed combinators, tau specifies the synthesis goal, and e is the synthesized program. We illustrate our approach by examples, including an application to synthesis from GUI-components.Comment: In Proceedings ITRS 2012, arXiv:1307.784

Weaving Solidarity

In the Global South, Indigenous and Native people continue to live under colonial relations within formally independent nation-states. Sebastian Garbe offers a critical perspective on contemporary expressions of international solidarity and transnational advocacy. He combines approaches from critical race and decolonial studies with an activist ethnography on networked spaces of encounters created through solidarity activism by Mapuche and non-Mapuche actors. Departing from those experiences, this book not only presents potential pitfalls of transnational advocacy but suggests new ways of understanding and practicing solidarity

Nutrient acquisition and metabolic adaptation in the context of Candida albicans virulence

Candida albicans is an opportunistic human fungal pathogen. Normally a harmless commensal and part of the microbiota of healthy humans, it can cause superficial to life-threatening systemic infections under distinct circumstances. Central for this switch is a variety of fungal pathogenicity mechanisms. Amongst them is a remarkable metabolic plasticity, which is intricately linked with other central fungal virulence traits like the yeast-to-hyphae switch. The chief aim of this thesis was to investigate three different aspects of these connections. The first part focused on nutrient acquisition on the example of proline – not only an especially valuable nutrient source for C. albicans but also a potent morphogenetic stimulus. In this study Gnp2 was identified as a specialized proline permease. Further analysis revealed an essential role for this permease for proline-induced morphogenesis and fungal resistance against macrophage killing and exposure to reactive oxygen species. In the second part a combinatorial approach of transcriptional and metabolic profiling was utilized to examine the metabolic adaptation of C. albicans to varying degrees of amino acid availability. Thereby, a repressive activity of the central amino acid metabolism regulator Stp2 was found on a metabolic gene cluster, which is required for the assimilation of hydroxybenzenes. Together with subsequent phenotypical analyses these findings suggested a so far unknown link between the metabolism of aromatic amino acids and hydroxybenzenes in C. albicans. Lastly, metabolic changes associated with the fungal switch from yeast to hyphal growth were investigated. A variety of morphotype-specific activities of metabolic pathways was identified, most notably including a stimulus-independent activation of the de novo sphingolipid biosynthesis in C. albicans hyphae. Further, by the pharmacological inhibition of this pathway its essential role for proper filamentation was verified