Differing preferences of Antarctic soil nematodes for microbial prey

We tested the preferences of three nematode taxa, Geomonhystera villosa, Plectus spp. and Teratocephalus spp., extracted from moss at Signy Island in the Maritime Antarctic, for two microalgae, three microfungi and six heterotrophic bacteria, each also from soils at Signy Island. Choice test experiments on water agar medium, in which nematodes were enumerated in wells containing microbes at 24 and 48 h, indicated that there were differing preferences between nematodes for distinct prey. G. villosa was significantly attracted to the alga Chlorella cf. minutissima and the fungus Mortierella hyalina, and was more attracted to all algae and fungi than either of the other two nematodes. Both G. villosa and Teratocephalus spp. were attracted to an actinobacterium. Plectus spp. were significantly attracted to the alga Stichococcus bacillaris and bacteria with close taxonomic affinities to Arthrobacter, Pseudomonas and Polaromonas. Experiments using 0.5 μm diameter fluorescent beads indicated significantly increased ingestion by nematodes in the presence of each of these microbes compared with controls, except by Plectus spp. in the presence of S. bacillaris. We conclude that complex trophic interactions may occur in apparently simple Antarctic soil food webs

Optimal agricultural policy and PSE measurement: an assessment and application to Norway

The producer support estimate calculated by the OECD is widely misused as an indicator of distortions created by agricultural policies. In this paper we demonstrate rigorously that a change in the relative (percentage) PSE is not an accurate indicator of the implications of policy reform for domestic welfare or for trade distortions. If there are positive externalities linked to agricultural inputs (e.g., land), we demonstrate that replacing output subsidies by optimal Pigouvian subsidies may result in an increase or a reduction in relative PSE depending on the parameters of the production function. Using the example of Norway we show that an increase in the relative PSE is likely if the focus of agricultural policies shifts from income support to the provision of public goods.Agricultural policy; trade distortion; domestic support; producer support estimate PSE).

Erhaltung und Wiederansiedlung des Kleinen Rohrkolbens ( Typha minima ) - Vegetationsaufnahmen, Monitoring und genetische Herkunftsanalysen

Abstract.: Galeuchet D. J. and Holderegger R. 2005. Conservation and re-introduction of Dwarf Bulrush (Typha minima) - vegetation surveys, monitoring and genetic analysis of origin. Bot. Helv. 115: 15-32. Typha minima was formerly widespread along fast flowing alpine rivers but is now red-listed as critically endangered. To assess its conservation perspectives, we surveyed the few remaining natural populations along the alpine part of the River Rhine from 1997 to 2002 and determined their genetic diversity using isozyme electrophoresis. Six of the populations became extinct or extremely small, probably due to shading by taller plants and trampling, while six other populations remained stable or increased, partly due to habitat restoration measures. The largest populations, with areas of more than 10'000 m2, are found in secondary habitats which are regularly disturbed due to water regime management. Of the 19 investigated isozyme loci, only six were polymorphic. Allelic diversity (1.4-1.8) was low in all populations, and the number of multilocus genotpyes (1-18) was low for 11 of 13 investigated populations. Genetic diversity was also studied for ex-situ cultivations of T. minima in Swiss botanical gardens and reintroduced stands.These artificial populations (each with 1-3 multilocus genotypes) were genetically similar to natural populations (average genetic distance 0.094). For two ex-situ cultivations with unknown origin, the likely origin could genetically be defined. Hybridisation between two ex-situ cultivations of different origin (i.e. a potential risk of genetic introgression) was detected in one botanical garden. It is concluded that the long-term conservation of T. minima requires both the restoration of regularly disturbed, sparsely vegetated river margins and the re-introduction of plants from ex-situ cultivations with appropriate origi

Exact Mean Computation in Dynamic Time Warping Spaces

Dynamic time warping constitutes a major tool for analyzing time series. In particular, computing a mean series of a given sample of series in dynamic time warping spaces (by minimizing the Fr\'echet function) is a challenging computational problem, so far solved by several heuristic and inexact strategies. We spot some inaccuracies in the literature on exact mean computation in dynamic time warping spaces. Our contributions comprise an exact dynamic program computing a mean (useful for benchmarking and evaluating known heuristics). Based on this dynamic program, we empirically study properties like uniqueness and length of a mean. Moreover, experimental evaluations reveal substantial deficits of state-of-the-art heuristics in terms of their output quality. We also give an exact polynomial-time algorithm for the special case of binary time series

Influence of steel fibers on the fatigue behavior of high-performance concretes under cyclic loading

Due to the advancement of high-performance concretes, the development of filigree constructions has been improved in the last decades. However, as the demand to create more filigree designs increases, the vulnerability to fatigue loads of such structures has also become a decisive factor. Various construction projects, such as wide-span bridges or wind turbines, are exposed to fatigue loads. Especially wind turbines are permanently subjected to wind and wave loads of several hundred million load cycles during their service life. At present, the fatigue behavior of high-performance concretes under cyclic loading is still unknown. In a worst-case scenario, the significantly lower ductility can lead to a sudden failure of the entire structure. In this case, the addition of steel fibers could be advantageous, as they significantly improve the ductility of concretes. However, it is still undetermined how the material fatigue is influenced by steel fibers. Hence, systematic investigations on the fatigue behavior of various high-strength concretes with steel fibers were conducted. Since the crack-bridging effect of fibers is relevant for tensile stresses, predominantly cyclic bending tests were performed on concrete beams with different steel fiber variations. To accomplish the investigations, a test setup has been developed which allows the simultaneous testing of a total of six specimens. Based on the predetermined static concrete strengths, the specimens were subjected to cyclic loads with a defined lower stress level and various upper stress levels. During these cyclic tests, the cycles-to-failure as well as the degradation within the microstructure were detected

Perfectly Secure Steganography: Capacity, Error Exponents, and Code Constructions

An analysis of steganographic systems subject to the following perfect undetectability condition is presented in this paper. Following embedding of the message into the covertext, the resulting stegotext is required to have exactly the same probability distribution as the covertext. Then no statistical test can reliably detect the presence of the hidden message. We refer to such steganographic schemes as perfectly secure. A few such schemes have been proposed in recent literature, but they have vanishing rate. We prove that communication performance can potentially be vastly improved; specifically, our basic setup assumes independently and identically distributed (i.i.d.) covertext, and we construct perfectly secure steganographic codes from public watermarking codes using binning methods and randomized permutations of the code. The permutation is a secret key shared between encoder and decoder. We derive (positive) capacity and random-coding exponents for perfectly-secure steganographic systems. The error exponents provide estimates of the code length required to achieve a target low error probability. We address the potential loss in communication performance due to the perfect-security requirement. This loss is the same as the loss obtained under a weaker order-1 steganographic requirement that would just require matching of first-order marginals of the covertext and stegotext distributions. Furthermore, no loss occurs if the covertext distribution is uniform and the distortion metric is cyclically symmetric; steganographic capacity is then achieved by randomized linear codes. Our framework may also be useful for developing computationally secure steganographic systems that have near-optimal communication performance.Comment: To appear in IEEE Trans. on Information Theory, June 2008; ignore Version 2 as the file was corrupte

German Merger Control: A European Approach to Anticompetitive Takeovers

European free-market countries recently have begun to enact more laws regulating mergers and joint-ventures, with Germany at the forefront. In this article, Messrs. Belke and Braun intensively analyze the German merger control law, including the criteria that necessitate a report to the German Cartel Office, its application of the substantive merger control rules, and possible exceptions to an anti-merger ruling. They also explore the impact of the German law on international mergers and joint-ventures. Finally, they discuss in detail the first two German Supreme Court decisions that construed the substantive rules and contrast them with similar American cases