81 research outputs found

    Resistance of plant life forms of native and regenerated alpine plant communities to experimental trampling

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    Trampling of vegetation as a result of recreation can adversely affect natural habitats, leading to loss of vegetation and degradation of plant communities. Many studies indicated that intrinsic properties of plant communities appear to be the most important factors determining the response of vegetation to trampling disturbance. Specifically, the dominant life-form of a plant community accounts for more variation in the resistance of communities to trampling than the intensity of the trampling experienced, suggesting that simple assessments based on this trait could guide decisions on access to natural sites. We verify these claims in the Belianske Tatry National Nature Reserve in Slovakia, which has been closed since 1978 due to destruction by mass tourism, with the exception of one trail made accessible since 1993. In researching the resistance of communities according to dominant life forms we adjusted the number of passes according to the minimum (75 tourists) and maximum (225 tourists) daily visitation during the tourist season. The studied communities occur in close proximity to the trails on the saddles through which the open trail passes. Available evidence from our studies suggests that vegetation dominated by hemicryptophytes is more resistant to trampling and recovers from trampling to a greater extent than vegetation dominated by other life forms. Therefore, we selected three alpine communities dominated by hemicryptophytes. In the Juncetum trifidi community, they almost completely dominate, they are mainly composed of grasses. Although they dominate the Junco trifidi-Callunetum vulgaris community, the species, Calluna vulgaris has been added to the woody chamephytes, and thus the woody Chamaephytes achieve a higher cover than in the Juncetum trifidi community. Although in the community Seslerietum tatrae biscutelletosum laevigatae hemicryptophytes dominate, it consists of several plant life forms and its grasses reach greater heights than in previous communities. We found that it is not possible to estimate the resilience of communities to trampling by dominant life forms. Life forms within one community react very similarly, but this statement cannot be generalized globally for all communities. At the same time, we found that if we damage the native community, which subsequently regenerates, the life forms of the community behave differently when damaged repeatedly. More detailed research is needed worldwide, which would point out patterns of behaviour of alpine plant vegetation to trampling

    Analytical model of asymmetrical Mixed-Mode Bending test of adhesively bonded GFRP joint

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    This paper presents new analytical model of asymmetric mixed-mode bending (MMB) specimen of adhesively bonded pultruded GFRP joints. An easily applicable relationship for the calculation of the strain energy release rate of the asymmetric MMB specimens is proposed based on the beam theory. The model is capable to analyze stacking sequence as well as various crack propagation paths. In the paper the effect of the various fiber bridging length and different crack propagation paths is analyzed analytically and supported by experimental results. The methodology and results presented in this paper could be utilized for the design of both joint geometry and lay-up of the laminates constituting the joint or for the prediction of the fracture behavior of such structures

    On partial order semantics for SAT/SMT-based symbolic encodings of weak memory concurrency

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    Concurrent systems are notoriously difficult to analyze, and technological advances such as weak memory architectures greatly compound this problem. This has renewed interest in partial order semantics as a theoretical foundation for formal verification techniques. Among these, symbolic techniques have been shown to be particularly effective at finding concurrency-related bugs because they can leverage highly optimized decision procedures such as SAT/SMT solvers. This paper gives new fundamental results on partial order semantics for SAT/SMT-based symbolic encodings of weak memory concurrency. In particular, we give the theoretical basis for a decision procedure that can handle a fragment of concurrent programs endowed with least fixed point operators. In addition, we show that a certain partial order semantics of relaxed sequential consistency is equivalent to the conjunction of three extensively studied weak memory axioms by Alglave et al. An important consequence of this equivalence is an asymptotically smaller symbolic encoding for bounded model checking which has only a quadratic number of partial order constraints compared to the state-of-the-art cubic-size encoding.Comment: 15 pages, 3 figure

    Compositional Verification of Compiler Optimisations on Relaxed Memory

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    This paper is about verifying program transformations on an axiomatic relaxed memory model of the kind used in C/C++ and Java. Relaxed models present particular challenges for verifying program transformations, because they generate many additional modes of interaction between code and context. For a block of code being transformed, we define a denotation from its behaviour in a set of representative contexts. Our denotation summarises interactions of the code block with the rest of the program both through local and global variables, and through subtle synchronisation effects due to relaxed memory. We can then prove that a transformation does not introduce new program behaviours by comparing the denotations of the code block before and after. Our approach is compositional: by examining only representative contexts, transformations are verified for any context. It is also fully abstract, meaning any valid transformation can be verified. We cover several tricky aspects of C/C++-style memory models, including release-acquire operations, sequentially consistent fences, and non-atomics. We also define a variant of our denotation that is finite at the cost of losing full abstraction. Based on this variant, we have implemented a prototype verification tool and ap

    Finding flies in the mushroom soup : Host specificity of fungus-associated communities revisited with a novel molecular method

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    Fruiting bodies of fungi constitute an important resource for thousands of other taxa. The structure of these diverse assemblages has traditionally been studied with labour-intensive methods involving cultivation and morphology-based species identification, to which molecular information might offer convenient complements. To overcome challenges in DNA extraction and PCR associated with the complex chemical properties of fruiting bodies, we developed a pipeline applicable for extracting amplifiable total DNA from soft fungal samples of any size. Our protocol purifies DNA in two sequential steps: (a) initial salt-isopropanol extraction of all nucleic acids in the sample is followed by (b) an extra clean-up step using solid-phase reversible immobilization (SPRI) magnetic beads. The protocol proved highly efficient, with practically all of our samples-regardless of biomass or other properties-being successfully PCR-amplified using metabarcoding primers and subsequently sequenced. As a proof of concept, we apply our methods to address a topical ecological question: is host specificity a major characteristic of fungus-associated communities, that is, do different fungus species harbour different communities of associated organisms? Based on an analysis of 312 fungal fruiting bodies representing 10 species in five genera from three orders, we show that molecular methods are suitable for studying this rich natural microcosm. Comparing to previous knowledge based on rearing and morphology-based identifications, we find a species-rich assemblage characterized by a low degree of host specialization. Our method opens up new horizons for molecular analyses of fungus-associated interaction webs and communities.Peer reviewe

    Advances in Property-Based Testing for αProlog

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    α\alphaCheck is a light-weight property-based testing tool built on top of α\alphaProlog, a logic programming language based on nominal logic. α\alphaProlog is particularly suited to the validation of the meta-theory of formal systems, for example correctness of compiler translations involving name-binding, alpha-equivalence and capture-avoiding substitution. In this paper we describe an alternative to the negation elimination algorithm underlying α\alphaCheck that substantially improves its effectiveness. To substantiate this claim we compare the checker performances w.r.t. two of its main competitors in the logical framework niche, namely the QuickCheck/Nitpick combination offered by Isabelle/HOL and the random testing facility in PLT-Redex.Comment: To appear, Tests and Proofs 2016; includes appendix with details not in the conference versio

    Lethal lithium poisoning with sustained-release preparations

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