Weed problems in various tillage systems in the Nordic countries

There is an increasing use of various forms of reduced tillage or no-tillage in the Nordic countries. This will favour the growth of grass weed species and perennial species. Perennial creeping weeds like Elymus repens, Cirsium arvense, and Sonchus arvensis are important in all Nordic countries. Stationary weeds such as Taraxacum spp., Artemisia vulgaris and volunteer grassland species increase in areas with reduced tillage and especially no-tillage systems. Winter annual and biennial species such as Matricaria perforata, Poa annua, Alopecurus geniculatus and Stellaria media are frequently occuring weeds in reduced tillage systems in all countries, while Alopecurus myosuroides and Apera spica-venti are problems in Denmark and Southern parts of Sweden and Finland

A faster tree-decomposition based algorithm for counting linear extensions

We consider the problem of counting the linear extensions of an n-element poset whose cover graph has treewidth at most t. We show that the problem can be solved in time Õ(nt+3), where Õ suppresses logarithmic factors. Our algorithm is based on fast multiplication of multivariate polynomials, and so differs radically from a previous Õ(nt+4)-time inclusion–exclusion algorithm. We also investigate the algorithm from a practical point of view. We observe that the running time is not well characterized by the parameters n and t alone, fixing of which leaves large variance in running times due to uncontrolled features of the selected optimal-width tree decomposition. For selecting an efficient tree decomposition we adopt the method of empirical hardness models, and show that it typically enables picking a tree decomposition that is significantly more efficient than a random optimal-width tree decomposition. © Kustaa Kangas, Mikko Koivisto, and Sami Salonen; licensed under Creative Commons License CC-BY.Peer reviewe

Azimuthal asymmetry in ground-based GPS slant delay observations and their NWP model counterparts

International audienceThe ground-based measurements of the Global Positioning System (GPS) allow estimation of the tropospheric delay along the slanted signal paths through the atmosphere. The meteorological exploitation of such slant delay (SD) observations relies on the hypothesis of azimuthal asymmetry of the information content. This article addresses the validity of the hypothesis. The asymmetric properties of the SD observations and their model counterparts are investigated. In this study, the model counterparts are based on 3-h forecasts of a numerical weather prediction (NWP) model, run with four different horizontal resolutions. The SD observations are compared with their model counterparts with emphasis on cases of high asymmetry in order to see whether the observed asymmetry is a real atmospheric signature. The asymmetric delay component is found to be of the order of a few parts per thousand of the absolute SD value, thus barely exceeding the assumed standard deviation of the SD observation error. However, the observed asymmetric delay components show a statistically significant meteorological signal. Benefit of the asymmetric SD observations is therefore expected to be taken in future, when NWP systems will explicitly represent the small-scale atmospheric features revealed by the SD observations

Asymmetricity of ground-based GPS slant delay data

International audienceThe ground-based measurements of the Global Positioning System (GPS) allow estimation of the tropospheric delay along the slanted signal paths through the atmosphere. The meteorological exploitation of such slant delay (SD) observations relies on the hypothesis of azimuthal asymmetry of the information content. This article addresses the validity of the hypothesis. A new concept of asymmetricity is introduced for studying the SD observations and their model counterparts. The asymmetricity is defined as the ratio of the absolute asymmetric delay component to total SD. The model counterparts are determined from 3-h forecasts of a numerical weather prediction (NWP) model, run with four different horizontal resolutions. The SD observations are compared with their model counterparts with emphasis on cases of high asymmetricity in order to see whether the observed asymmetry is a real atmospheric signature. The asymmetricity is found to be of the order of a few parts per thousand. Thus, the asymmetric delay component barely exceeds the assumed standard deviation of the SD observation error. However, the observed asymmetric delay components show a statistically significant meteorological signal. Benefit of the asymmetric SD observations is therefore expected to be taken in future, when NWP systems will explicitly represent the small-scale atmospheric features revealed by the SD observations

Socioeconomic position, John Henryism, and incidence of acute myocardial infarction in Finnish men

Previous cross-sectional studies examining whether John Henryism (JH), or high-effort coping with socioeconomic adversity, potentiates the inverse association between socioeconomic position (SEP) and cardiovascular health have focused mainly on hypertension in African Americans. We conducted the first longitudinal test of this hypothesis on incident acute myocardial infarction (AMI) using data from the Kuopio Ischemic Heart Disease Risk Factor Study in Finland (N = 1405 men, 42-60 years). We hypothesized that the expected inverse gradient between SEP and AMI risk would be stronger for men scoring high on JH than for those scoring low. John Henryism was measured by a Finnish version of the JH Scale for Active Coping. Four different measures of SEP were used: childhood SEP, education, income, and occupation. AMI hazard ratios (HR) by SEP and JH were estimated using COX proportional hazard models, before and after adjustment for study covariates. 205 cases of AMI occurred over a median of 14.9 years. Men employed in lower rank (farmer, blue-collar) occupations who scored high on JH had significantly higher age-adjusted risks of AMI than men in higher rank (white-collar) occupations (HR = 3.14, 95% CI: 1.65-5.98 for blue collar; HR = 2.33, 95% Cl: 1.04-5.22 for farmers) who also scored high on JH. No socioeconomic differences in AMI were observed for men who scored low on JH (HR = 136, 95% CI: 0.74 2.47 for blue collar; HR = 0.93, 95% CI: 0.59-1.48 for farmers; p = 0.002 for the SEP x JH interaction). These findings persisted after adjustment for sociodemographic, behavioral, and biological factors. Results for other SEP measures were in the same direction, but did not reach statistical significance. Repetitive high-effort coping with adversity (John Henryism) was independently associated with increased risk for AMI in Finnish men, underscoring the potential relevance of the John Henryism hypothesis to CVD outcomes other than hypertension and to populations other than African Americans. (C) 2016 Published by Elsevier Ltd.Peer reviewe

Metabarcoding successfully tracks temporal changes in eukaryotic communities in coastal sediments

Metabarcoding is a method that combines high-throughput DNA sequencing and DNA-based identification. Previously, this method has been successfully used to target spatial variation of eukaryote communities in marine sediments, however, the temporal changes in these communities remain understudied. Here, we follow the temporal changes of the eukaryote communities in Baltic Sea surface sediments collected from two coastal localities during three seasons of two consecutive years. Our study reveals that the structure of the sediment eukaryotic ecosystem was primarily driven by annual and seasonal changes in prevailing environmental conditions, whereas spatial variation was a less significant factor in explaining the variance in eukaryotic communities over time. Therefore, our data suggests that shifts in regional climate regime or large-scale changes in the environment are the overdriving factors in shaping the coastal eukaryotic sediment ecosystems rather than small-scale changes in local environmental conditions or heterogeneity in ecosystem structure. More studies targeting temporal changes are needed to further understand the long-term trends in ecosystem stability and response to climate change. Furthermore, this work contributes to the recent efforts in developing metabarcoding applications for environmental biomonitoring, proving a comprehensive option for traditional monitoring approaches.Peer reviewe

Arresting bubble coarsening: A two-bubble experiment to investigate grain growth in presence of surface elasticity

Many two-phase materials suffer from grain-growth due to the energy cost which is associated with the interface that separates both phases. While our understanding of the driving forces and the dynamics of grain growth in different materials is well advanced by now, current research efforts address the question of how this process may be slowed down, or, ideally, arrested. We use a model system of two bubbles to explore how the presence of a finite surface elasticity may interfere with the coarsening process and the final grain size distribution. Combining experiments and modelling in the analysis of the evolution of two bubbles, we show that clear relationships can be predicted between the surface tension, the surface elasticity and the initial/final size ratio of the bubbles. We rationalise these relationships by the introduction of a modified Gibbs criterion. Besides their general interest, the present results have direct implications for our understanding of foam stability

Comparison of the levels of organic, elemental and inorganic carbon in particulate matter in six urban environments in Europe

International audienceA series of 7-week sampling campaigns were conducted in urban background sites in the six European cities as follows: Duisburg 4 October?21 November 2002 (autumn), Prague 29 November 2002?16 January 2003 (winter), Amsterdam 24 January?13 March 2003 (winter), Helsinki 21 March?12 May 2003 (spring), Barcelona 28 March?19 May 2003 (spring) and Athens 2 June?21 July 2003 (summer). The campaigns were scheduled to include seasons of local public health concern due to high PM concentrations or findings in previously conducted epidemiological studies. Aerosol samples were collected in parallel with two identical virtual impactors (VI), which divide air PM into two size fractions, PM2.5 and PM2.5-10. The filter samples were analysed with a microbalance, an energy dispersive X-ray fluorescence (ED-XRF), an ion chromatograph (IC) and a thermo-optical carbon analyser (TOA). The PM2.5 and PM2.5-10 campaign means ranged 8.3?29.6 µg m-3 and 5.4?28.7 µg m-3, respectively. The ''wet and cool'' seasons favoured low coarse PM concentration and high fine PM concentration, whereas the spring and summer led to low fine and high coarse PM concentrations. The contribution of particulate organic matter (POM) to PM2.5-10 was highest (27%) in Prague and the lowest (10%) in Barcelona, while those to PM2.5 were generally higher, ranging from 21% in Barcelona to 54% in Prague. The contribution of elemental carbon (EC) to PM2.5-10 were relatively low (1?6%) in all the six European cities but it contributed somewhat higher (5?9%) to PM2.5. The differences are most likely due to variable contributions of local emission sources and seasonal factors such as domestic heating, vehicle exhausts and photochemical reactions. Carbonate, which interferes with carbon analysis by evolving stage at 900°C, was detected in the coarse particles of Athens and Barcelona and it could be separated reliably from OC by a simple integrating method. The calcium carbonate in Athens and Barcelona accounted for 56% and 11% of coarse PM masses, respectively. Carbonate was not found in other cities or in PM2.5. The mean PM2.5 mass portions of five OC thermal fractions (OC1, OC2, OC3, OC4 and OCP) varied in the range 26?33%, 6?10%, 7?10%, 9?22% and 29?50%, respectively, in six cities. The differences in the mass portion profiles were relatively small between the cities

Organic, elemental and inorganic carbon in particulate matter of six urban environments in Europe

International audienceA series of 7-week sampling campaigns were conducted in urban background sites of six European cities as follows: Duisburg (autumn), Prague (winter), Amsterdam (winter), Helsinki (spring), Barcelona (spring) and Athens (summer). The campaigns were scheduled to include seasons of local public health concern due to high particulate concentrations or findings in previously conducted epidemiological studies. Aerosol samples were collected in parallel with two identical virtual impactors that divide air particles into fine (PM2.5) and coarse (PM2.5-10) size ranges. From the collected filter samples, elemental (EC) and organic (OC) carbon contents were analysed with a thermal-optical carbon analyser (TOA); total Ca, Ti, Fe, Si, Al and K by energy dispersive X-ray fluorescence (ED-XRF); As, Cu, Ni, V, and Zn by inductively coupled plasma mass spectrometry (ICP/MS); Ca2+, succinate, malonate and oxalate by ion chromatography (IC); and the sum of levoglucosan+galactosan+mannosan (?MA) by liquid chromatography mass spectrometry (LC/MS). The campaign means of PM2.5 and PM2.5-10 were 8.3-29.6 µg m-3 and 5.4-28.7 µg m-3, respectively. The contribution of particulate organic matter (POM) to PM2.5 ranged from 21% in Barcelona to 54% in Prague, while that to PM2.5-10 ranged from 10% in Barcelona to 27% in Prague. The contribution of EC was higher to PM2.5 (5-9%) than to PM2.5-10 (1-6%) in all the six campaigns. Carbonate (C(CO3), that interferes with the TOA analysis, was detected in PM2.5-10 of Athens and Barcelona but not elsewhere. It was subtracted from the OC by a simple integration method that was validated. The CaCO3 accounted for 55% and 11% of PM2.5-10 in Athens and Barcelona, respectively. It was anticipated that combustion emissions from vehicle engines affected the POM content in PM2.5 of all the six sampling campaigns, but a comparison of mass concentration ratios of the selected inorganic and organic tracers of common sources of organic material to POM suggested also interesting differences in source dominance during the campaign periods: Prague (biomass and coal combustion), Barcelona (fuel oil combustion, secondary photochemical organics) and Athens (secondary photochemical organics). The on-going toxicological studies will clarify the health significance of these findings