Monochromatic triangles in three-coloured graphs

In 1959, Goodman determined the minimum number of monochromatic triangles in a complete graph whose edge set is two-coloured. Goodman also raised the question of proving analogous results for complete graphs whose edge sets are coloured with more than two colours. In this paper, we determine the minimum number of monochromatic triangles and the colourings which achieve this minimum in a sufficiently large three-coloured complete graph.Comment: Some data needed to verify the proof can be found at http://www.math.cmu.edu/users/jcumming/ckpsty

Microbial communities at a gasworks site: a marker gene- and cultivation-based approach to explore anaerobic aromatic compound degradation

Environmental pollutants such as BTEX (benzene, toluene, ethylbenzene, o-, m-, p-xylene) and other aromatic compounds are frequently detected at gasworks sites. The diversity and functioning of aromatic compound-degrading bacteria (ACDB) was investigated in the groundwater of a former Thuringian gasworks site by 16S rRNA and bamA marker gene analysis as well as by enrichment cultures. Nitrate-reducing ACDB (Betaproteobacteria) dominated the anaerobic aquifer. In a highly contaminated area of the plume, nitrate-reducing ACDB co-occurred with obligate anaerobic sulfate- and/or CO2-reducing ACDB (Deltaproteobacteria and Firmicutes), indicating an area of oxygen and nitrate depletion in which biodegradation is assumed to occur with limited rates. To explore to possibility of bioremediation with nitrate, the role of several nitrate dependent ACDB was investigated in more detail: Members of the genus Azoarcus were key players in the degradation of toluene, ethylbenzene and other monoaromatic compounds. They outcompeted co-occurring ACDB, presumably by the excretion of nitrite. Organisms related to Georgfuchsia toluolica were less abundant in the aquifer and involved in the degradation of the particularly recalcitrant compound p-xylene. The chemolithoautotrophic, sulfur-oxidizing bacterium Sulfuritalea hydrogenivorans sk43H was found to have an overlooked role in nitrate dependent degradation of aromatic carboxylic compounds. Sulfuritalea-related bacteria were also highly abundant in the aquifer and involved in the degradation of p-alkylated aromatic carboxylates. The conducted experiments comprise the first systematic analysis of 16S rRNA and bamA sequences using environmental samples in combination with enrichment cultures. Results from both marker genes were largely consistent and an implementation of bamA-sequencing as routine diagnostic tool to assess redox processes relevant for bioremediation is suggested

On the minimal monochromatic K4-density

We use Razborov's flag algebra method to show a new asymptotic lower bound for the minimal density $m_4$ of monochromatic $K_4$'s in any 2-coloring of the edges of the complete graph $K_n$ on $n$ vertices. The hitherto best known lower bound was obtained by Giraud, who proved that m_4>1/46, whereas the best known upper bound by Thomason states that m_41/35

Impact of estrogen receptor alpha on the tamoxifen resistance in breast cancer patients

Genetic aberrations and changes in the activity of estrogen receptors alpha (ERa[lpha]) play an important role in the endocrine sensitivity. The aim of this study was to examine the relationship between the ESR1 expression level, its polymorphic variants, and the distribution pattern of ER[alpha] expression with the prognosis and efficacy of tamoxifen treatment in breast cancer patients. Our data suggest that the ESR1 expression level, SNPs in the ESR1 gene and the distribution pattern of ERα expression can be a potential molecular marker of tamoxifen resistance in breast cancer patients

What drives growth responses of nitrogen and phosphorus (co-)limited primary producer communities?

The growth of autotroph communities is frequently (co-)limited by essential nutrients such as nitrogen (N) and phosphorus (P). Several mechanisms have been proposed to explain the observed co-limitation patterns at different levels of biological organization, especially at the biochemical level for individual species. When considering communities, the presence of different species and functional groups with contrasting physiologies and nutrient requirements leads to a more difficult understanding of the mechanisms involved in nutrient (co-)limitation. To investigate what drives co-limitation patterns and possible underlying mechanisms based on biomass responses in autotroph communities, we grew phytoplankton communities differing in species composition in experimental microcosms on three N:P ratios to impose different limiting conditions. Afterwards, N, P, both, or none were factorially supplied to the communities to test which nutrients were limiting growth. We measured the biovolume of single species in the communities to assess how they responded to nutrient additions and compared it to the response of the overall community biovolume. The types of nutrient (co-)limitation identified, i.e. the factorial limitation scenarios for community biomass were single N limitation or simultaneous co-limitation by N and P, and were strongly driven by the dominant species. The phytoplankton species in the communities responded differently to the nutrient addition treatments, i.e. they showed contrasting limitation outcomes and therefore likely different nutrient requirements. Our experiment indicates that phylogenetically distantly-related phytoplankton species grown in a community can have different resource use efficiencies and thus can be limited by different nutrients. We suggest that the dominance of species or groups with similar traits in nutrient requirements and acquisition is one of the leading mechanisms that determines the biomass pattern of nutrient (co-)limitation observed at the community level. This work also highlights the potential of predicting community growth limitation outcomes based on knowledge of nutrient use efficiencies of one or few dominant species, which can be a suitable tool for lake restoration and oligotrophication efforts

Productivity in the Barents Sea - Response to recent climate variability

The temporal and spatial dynamics of primary and secondary biomass/production in the Barents Sea since the late 1990s are examined using remote sensing data, observations and a coupled physical-biological model. Field observations of mesozooplankton biomass, and chlorophyll a data from transects (different seasons) and large-scale surveys (autumn) were used for validation of the remote sensing products and modeling results. The validation showed that satellite data are well suited to study temporal and spatial dynamics of chlorophyll a in the Barents Sea and that the model is an essential tool for secondary production estimates. Temperature, open water area, chlorophyll a, and zooplankton biomass show large interannual variations in the Barents Sea. The climatic variability is strongest in the northern and eastern parts. The moderate increase in net primary production evident in this study is likely an ecosystem response to changes in climate during the same period. Increased open water area and duration of open water season, which are related to elevated temperatures, appear to be the key drivers of the changes in annual net primary production that has occurred in the northern and eastern areas of this ecosystem. The temporal and spatial variability in zooplankton biomass appears to be controlled largely by predation pressure. In the southeastern Barents Sea, statistically significant linkages were observed between chlorophyll a and zooplankton biomass, as well as between net primary production and fish biomass, indicating bottom-up trophic interactions in this region

Size-fractioned zooplankton biomass in the Barents Sea: macroecological patterns across biogeography, climate, and varying ecosystem state (1989-2020)

The zooplankton community in the Barents Sea was monitored during autumn cruises from 1989-2020, with biomass determined as the depth-integrated dry weight (g m-2) of 3 size fractions (>2 mm, 1-2 mm, <1 mm). A large data set of 4543 sampling stations encompassing a subdivision of the Barents Sea was spatially averaged into 15 polygons based on topography. The resulting data set is used to describe relationships between the biomass of size fractions as expressions of the size structure of the zooplankton communities. Each of the 3 size fractions was positively related to the total zooplankton biomass (sum of fractions). The medium size fraction, which contained on average 48% of the total biomass, showed a strong linear correlation with total biomass (R2 ≈ 0.8). The medium fraction contained the older copepodite stages of Calanus species (C. finmarchicus and C. glacialis), which are dominant species interpreted to drive the overall changes in zooplankton biomass. The biomass of the small size fraction decreased with decreasing total biomass, but less so than the medium fraction. Thus, the small/medium biomass ratio increased as the total biomass decreased. This trend was most pronounced for shallow and central polygons, which coincide with the core feeding area of the large Barents Sea stock of capelin Mallotus villosus. The change in the small/medium biomass ratio is interpreted to reflect a shift from Calanus to smaller zooplankton in response to predation by capelin and other planktivorous predators, and possibly also by warming due to climate change.publishedVersio

Producing interventions for AIDS-affected young people in Lesotho's schools: Scalar relations and power differentials

This is the post-print version of the final paper published in Geoforum. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2009 Elsevier B.V.Children and youth are a key target group for interventions to address southern Africa’s AIDS pandemic. Such interventions are frequently implemented through schools, and are often complex products of negotiation between a range of institutional actors including international agencies, NGOs, government departments and individual schools. These institutions not only stand in different (horizontally scaled) spatial relationships to students in schools; they also appear to operate at different hierarchical levels. Empirical research with policy makers and practitioners in Lesotho, however, reveals how interventions are produced through flows of knowledge, funding and personnel within and between institutions that make it difficult to assert that any intervention is manifestly more international or more local than any other. Scale theory offers the metaphor of a network or web which usefully serves to move attention away from discrete organisations, sectors and scalar positionings and onto the relationships and flows between them. Nevertheless, organisations and development interventions are often partly structured in scalar hierarchical ways that express substantive power differentials and shape the forms of interaction that take place, albeit not binding them to strict binaries or nested hierarchies. A modified network metaphor is useful in aiding understanding of how particular interventions are produced through intermeshing scales and diverse fluid interactions, and why they take the form they do.RGS-IB

Individualisierung im Phonetikunterricht. Die Arbeit mit Portfolios zur Unterstützung des Ausspracheerwerbs

Der Ausspracheerwerb ist ein vielschichtiger und sich individuell sehr verschieden vollziehender Prozess. Ausgehend von der Grundannahme, dass der Ausspracheerwerb im Phonetikunterricht durch Individualisierung unterstützt werden kann, werden in diesem Beitrag Möglichkeiten aufgezeigt, den Unterricht so zu gestalten, dass die einzelne Person entsprechend ihren individuellen Lernbedürfnissen selbststeuernd aktiv werden kann. Anhand der Ergebnisse einer Befragung unter polnischen Studierenden der Germanistik wird verdeutlicht, worin die Besonderheiten und die Individualisierungspotentiale der Arbeit mit Portfolios im Phonetikunterricht bestehen. Darüber hinaus werden eigene Tonaufnahmen, die individuelle Lernberatung und Lernverträge als weitere Ansätze zur Individualisierung im Phonetikunterricht besprochen. Der Beitrag wird mit einem Plädoyer für methodische Vielfalt im Phonetikunterricht abgeschlossen