Datalog Programs with Arithmetical Constraints: Hierarchic, Periodic and Spiralling Least Fixpoints

We consider in this report Datalog programs with arithmetical constraints of the following form: p(x0 ; y0 ; z0 ): p(x + e; y + ; z + fl) / x 0; p(x; y; z): p(x + ¯; y + f; z + ffi) / y 0; p(x; y; z): p(x + ff; y + fi; z + g) / z 0; p(x; y; z): where x0 ; y0 ; z0 ; e; ; fl; ¯; f; ffi; ff; fi; g denote integer constants. The problem is to find an arithmetic formula f(x; y; z) equivalent to the relation p(x; y; z) defined by the above program. This characterization problem has useful applications in several fields, like the generation of lemmas for proving the termination of Prolog programs, the compilation of queries in Temporal Deductive Databases, or the verification of safety properties in parametric concurrent systems. We show here that programs of the above form are divided into three classes: the hierarchic, periodic and spiralling classes. More than 99% of the programs fall into the hierarchic and periodic classes and can be characterized by a linear arithmetic formula, un..

Multi-century reconstruction suggests complex interactions of climate and human controls of forest fire activity in a Karelian boreal landscape, North-West Russia

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A Decompositional Approach for Computing Least Fixed-Points of Datalog Programs with Z-Counters

We present a method for characterizing the least fixed-points of a certain class of Datalog programs in Presburger arithmetic. The method consists in applying a set of rules that transform general computation paths into "canonical" ones. We use the method for treating the problem of reachability in the field of Petri nets, thus relating together some unconnected results and extending them in several directions. R'esum'e Nous pr'esentons une m'ethode pour caract'eriser les plus petits points-fixes d'une certaine classe de programmes Datalog dans l'arithm'etique de Presburger. La m'ethode consiste `a appliquer un ensemble de r`egles qui transforment les chemins g'en'eraux de calcul en chemins "canoniques". Nous utilisons cette m'ethode pour traiter le probl`eme d'accessibilit'e dans le domaine des r'eseaux de Petri. Nous rapprochons ainsi des r'esultats consid'er'es jusqu'ici comme ind'ependendants, et nous les 'etendons dans plusieurs directions. A Decompositional Approach for Compu..

Discriminating males alter sperm production between species

Prezygotic reproductive isolation and its importance in speciation is traditionally approached from the viewpoint of those events that occur before mating. However, recent interest in sperm competition theory has shown that prezygotic isolation can be affected by mechanisms that occur after mating but before fertilization. One neglected aspect of these studies is how the cost of sperm production might play a role in species isolation. We examined differential sperm production in a species whose males are sexually parasitized by a unisexual gynogenetic species. Gynogens are clonal females that require sperm from males of closely related bisexual species to initiate embryogenesis. We tested for differential sperm production by male sailfin mollies (Poecilia latipinna) when they were in the presence of either a heterospecific, gynogenetic female (Poecilia formosa, Amazon molly) or a conspecific female. We found that previously demonstrated male mate choice for conspecific over heterospecific females also is revealed in sperm production. Males from both an allopatric and a sympatric population produce more sperm when in the presence of a conspecific female than when in the presence of a heterospecific female. We suggest that differential sperm production also could play a role in prezygotic reproductive isolation in bisexual species complexes that occur in sympatry

l-Kynurenine, an amino acid identified as a sex pheromone in the urine of ovulated female masu salmon

Many animals employ sex pheromones to find mating partners during their reproductive seasons. However, most sex pheromones of vertebrates remain to be identified. Over the past 20 years, steroids and prostaglandins have been identified as sex pheromones in several fishes. These pheromones are broadly termed “hormonal pheromones” because they or their precursors act as hormones in these fishes. Hitherto, no other type of sex pheromone has been unambiguously identified in teleost fish. Here we report the identification of a “nonhormonal pheromone” in teleost fish. The urine of the reproductively mature female masu salmon (Oncorhynchus masou) contains a male-attracting pheromone. Bioassay-guided fractionation yielded an active compound that was identical to l-kynurenine in spectral and chromatographic properties. l-Kynurenine is a major metabolite of l-tryptophan in vertebrates. This pheromone elicits a male-specific behavior at even picomolar concentrations; its electrophysiological threshold is 10(−14) M. l-Kynurenine is a reasonable substance for female masu salmon to advertise their readiness for mating

Surface sensing and adhesion of Escherichia coli controlled by the Cpx-signaling pathway

Bacterial adhesion is an important initial step in biofilm formation, which may cause problems in medical, environmental, and industrial settings. In spite of obvious phenotypic differences between attached and planktonic cells, knowledge about the genetic basis for these differences and how adhesion-induced changes are mediated is limited. The Cpx two-component signal transduction pathway responds specifically to stress caused by disturbances in the cell envelope and activates genes encoding periplasmic protein folding and degrading factors. Here, we address the role of the Cpx-signaling pathway in sensing and responding to the physical change occurring during adhesion of Escherichia coli to surfaces. We present evidence that the expression of Cpx-regulated genes is induced during initial adhesion of E. coli to abiotic surfaces. This induction is specifically observed upon attachment of stationary-phase cells to hydrophobic surfaces. Moreover, surface-induced activity of the Cpx response requires NlpE, an outer membrane lipoprotein, which has previously been shown to induce the Cpx system when overproduced. The importance of a functional Cpx response during adhesion is further supported by the fact that a dramatically lower number of cells attach to the surface and dynamic cell–surface interactions as measured by a quartz crystal microbalance technique are altered when the CpxRA pathway is disrupted. The defects in adhesion exhibited by the cpxR and nlpE mutants were strikingly similar to those of wild-type cells in which protein synthesis was inhibited, suggesting that the Cpx pathway plays a key role in the regulation of adhesion-induced gene expression

Self-fulfilling prophecies of the European <i>knowledge-based bio-economy</i>: the discursive shaping of institutional and policy frameworks in the bio-pharmaceuticals sector

Discourses matter. They help to shape institutions and policies. A new discourse has emerged in recent EU innovation policy centred on the idea of a knowledge-based bio-economy (KBBE). It is officially defined as ‘the sustainable, eco-efficient transformation of renewable biological resources into health, food, energy and other industrial products.’ The KBBE agenda links current problem diagnoses, research priorities, technological innovation, and societal benefits. In analysing the KBBE discourse, this paper draws on the sociology of technological expectations, which emphasises the performative, mobilising and self-fulfilling roles of such future-oriented visions. For example, the KBBE agenda shapes European research and innovation priorities in the bio-pharmaceutical sector. It frames socially relevant bio-knowledge in terms of pre-competitive research which can eventually facilitate new commercial products and patentable knowledge. Moreover, the agenda defines new institutional and policy frameworks necessary to realise societal benefits from these products and knowledge