Impact of aquaculture and agriculture nutrient sources on macroalgae in a bioassay study

Eutrophication is a major threat to aquatic ecosystems, because excessive nutrient enrichment may result in the loss of ecosystem services. Fjord systems are specifically under pressure due to nutrient input from land (agriculture) and sea (aquaculture). In this bioassay study, we have analyzed the effect of different nutrient sources, as well as their combination, on growth, nutrient composition and recruitment of habitat-forming and ephemeral macrophytes. We found that agricultural fertilizer increased growth for all algae (except Fucus), while the fish farm effluents mainly increased growth of Ulva. The C:N ratio was hardly affected by the fish farm, but decreased significantly in all algae when agriculture fertilizer was added. Most interestingly, however, distance to the fish farm modulated the algal response to the fertilizer. Our results demonstrate the importance of studying effects of multiple stressors in aquatic ecosystems to sustainably manage the consequences of anthropogenic impacts.publishedVersio

What restricts generative rejuvenation of Calluna vulgaris in continental, dry heathland ecosystems: seed production, germination ability or safe site conditions?

A large-scale field experiment with different management options (free-range grazing, onetime cutting, additional disturbances and their interactions) was carried out in a continental, dry heathland. Within the framework of the experiment seed production and germination ability of over-aged Calluna individuals as well as specific safe site conditions were investigated to reveal restricting factors for the generative rejuvenation of Calluna. The calculated values of seed production and germination ability of over-aged Calluna individuals can be compared with those from literature or exceed the values reported there. Therefore, seed production andgermination ability are not the limiting factors for the generative rejuvenation of Calluna. Free-range grazing with large herbivores combined with onetime cutting of over-aged Calluna stands supports the generative rejuvenation, especially due to the creation of specific safe sites, which are crucial for a successful survival of Calluna seedlings. Particularly a light shadowing seems to be the restricting factor for a successful generative rejuvenation of Calluna in continental, dry heathlands

Building Clusters with Lower-Bounded Sizes

Classical clustering problems search for a partition of objects into a fixed number of clusters. In many scenarios however the number of clusters is not known or necessarily fixed. Further, clusters are sometimes only considered to be of significance if they have a certain size. We discuss clustering into sets of minimum cardinality k without a fixed number of sets and present a general model for these types of problems. This general framework allows the comparison of different measures to assess the quality of a clustering. We specifically consider nine quality-measures and classify the complexity of the resulting problems with respect to k. Further, we derive some polynomial-time solvable cases for k = 2 with connections to matching-type problems which, among other graph problems, then are used to compute approximations for larger values of k

Patienteninformierung - erste Ansätze auf dem Gebiet des Diabetes mellitus

An der Stoffwechselkrankheit Diabetes mellitus erkranken neuesten Erhebungen zufolge rund 5% der Gesamtbevölkerung Deutschlands - sie kann deshalb als Volkskrankheit bezeichnet werden. Betroffen sind davon die unterschiedlichsten Patientengruppen (Kinder, Jugendliche, junge und ältere Erwachsene, Schwangere). Eine erfolgreiche Therapie des Diabetes mellitus erfordert die aktive Mitarbeit des Patienten, eine umfassende Patienteninformierung ist dafür wichtige Voraussetzung. Mit Hilfe eines Fragebogens wurde von den Autoren der derzeitige Informierungsstand der Patienten erfasst. Die daraus abgeleiteten Anforderungen für den Informierungsprozess bilden u.a. die Grundlage für die Entwicklung erster Komponenten eines Patienteninformierungssystems (PIS)

Combinatorial Properties and Recognition of Unit Square Visibility Graphs

Unit square visibility graphs (USV) are described by axis-parallel visibility between unit squares placed in the plane. If the squares are required to be placed on integer grid coordinates, then USV become unit square grid visibility graphs (USGV), an alternative characterisation of the well-known rectilinear graphs. We extend known combinatorial results for USGV and we show that, in the weak case (i.e., visibilities do not necessarily translate into edges of the represented combinatorial graph), the area minimisation variant of their recognition problem is NP-hard. We also provide combinatorial insights with respect to USV, and as our main result, we prove their recognition problem to be NP-hard, which settles an open question.Peer Reviewe