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showing 10 items of 10618 documents
Multiple positive normalized solutions for nonlinear Schrödinger systems
2018
We consider the existence of multiple positive solutions to the nonlinear Schr\"odinger systems sets on $H^1(\mathbb{R}^N) \times H^1(\mathbb{R}^N)$, \[ \left\{ \begin{aligned} -\Delta u_1 &= \lambda_1 u_1 + \mu_1 |u_1|^{p_1 -2}u_1 + \beta r_1 |u_1|^{r_1-2} u_1|u_2|^{r_2}, -\Delta u_2 &= \lambda_2 u_2 + \mu_2 |u_2|^{p_2 -2}u_2 + \beta r_2 |u_1|^{r_1} |u_2|^{r_2 -2} u_2, \end{aligned} \right. \] under the constraint \[ \int_{\mathbb{R}^N}|u_1|^2 \, dx = a_1,\quad \int_{\mathbb{R}^N}|u_2|^2 \, dx = a_2. \] Here $a_1, a_2 >0$ are prescribed, $\mu_1, \mu_2, \beta>0$, and the frequencies $\lambda_1, \lambda_2$ are unknown and will appear as Lagrange multipliers. Two cases are studied, the first …
Semi-natural Grassland Vegetation Database of Latvia
2012
The Semi-natural Grassland Vegetation Database of Latvia (GIVD ID EU-LV-001) was first developed in 1999 as part of the PhD Thesis on syntaxonomy and diversity of dry and mesic grasslands of Latvia. The database includes the original releves established by the author as early as 1997. The majority of releves belongs to the Filipendulo-Helictotrichion (Festuco-Brometea) and Arrhenatheretalia communities, but Molinietalia, Nardetalia, Caricion nigrae, Koelerion glaucae and Plantagini-Festucion are covered, as well. The total number of releves stored is 2,500 and there are approximately 700 releves to be digitised. Plot size varies from 1 to 125 m, the majority of releves are 4-9 m large. Rele…
The discovery of a Mycenaean-type tholos tomb in the Bronze Age necropolis of the Gazzi buried floodplain (Messina, Southern Italy): new geological a…
2019
This paper deals with a monument that is, up to this date, unique in Sicily and in the Italian peninsula: the Mycenaean-type tholos tomb of the Gazzi necropolis in Messina. A recent excavation in the alluvial deposits revealed extensive traces of a funerary area with a tholos tomb and several enchytrismos tombs with skeletal remains, presumably dated back to the end of the Early or the initial stage of the Middle(?) Bronze Age. The present multi-disciplinary investigation has been developed to analyse new data related to sediments, building stones and skeletal remains of this funerary area. The stratigraphic succession hosting the necropolis was formed by overbank sediments deposited on the…
Tetraploid European Salicornia species are best interpreted as ecotypes of multiple origin
2011
Abstract Salicornia procumbens and S. stricta are two tetraploid European salt marsh species of locally adjacent but ecologically differentiated distribution. Whereas S. procumbens grows in the lowest part of the salt marsh, it is replaced by S. stricta in the middle part (and diploid Salicornias in the upper part). Using AFLPs and a reciprocal transplantation experiment, we investigated whether the two species represent distinct evolutionary lineages. The analysis of AFLP variation clearly showed that both species are not monophyletic. Also, accessions do not cluster according to geographical origin. The transplantation experiment revealed that S. procumbens shows significantly reduced fit…
Habitat type and island identity as drivers of community assembly in an archipelago
2020
Aim: Ecoinformatics offer new opportunity to test islands as biogeographic and eco- logical models. In this paper we predicted three hypotheses: (1) plot-based data issu- ing from vegetation surveys can be used to predict Island Species-Area Relationships (ISARs) or island similarity; (2) the habitat area is an independent predictor of species richness patterns within island; (3) species richness and composition are more de- pendent on habitat type than island identity in land-bridge islands. Area: Tuscan Archipelago, Italy. Methods: We assembled a database of all the vegetation plots available for the archi- pelago. For the first hypothesis we calculated ISARs, using Arrhenius model, and B…
Vertical distribution and rotifer concentrations in the chemocline of meromictic lakes
1983
The vertical distribution of planktonic rotifers has been analysed in relation to season in several meromictic lakes; a coastal lagoon with sea-water intrusion and three dissolution lakes from two karstic systems. Two species, Filinia hofmanni and a form of Anuraeopsis fissa have been found to be more or less restricted to the chemocline or adjacent strata any time they occurred. Many species common in the upper water layers developed large populations near or in the chemocline and more strikingly in summer. Some species had two vertical maxima (one in the surface or the thermocline and another near the chemocline), while others successively shifted their maxima between the upper layers and…
Grasslands and Shrublands of Kazakhstan and Middle Asia
2020
Abstract Kazakhstan and Middle Asia comprise 4 million km2 of plains, uplands and tall mountain ranges in the core of the Eurasian continent. The region's semi-arid climate, grazing pressure by wild and domestic ungulates, and long pastoral tradition, have given rise to a variety of open habitat types and a distinct flora and fauna. Grasslands and shrublands are a natural and dominant vegetation type in the forest-steppe and steppe zone of northern and central Kazakhstan, as part of the Eurasian grassland biome. In Middle Asia, grasslands and shrublands are widespread habitat types in the Tian Shan, Pamir-Alai and Pamir—mountain systems that have been recently acknowledged as a global biodi…
Macro Element Content in Fertilized Forest Soils in Spruce (Picea Abies (L.) H. Karst.) Stands in Latvia
2012
The present paper provides an overview of analysis conducted with soil samples from depths up to 80 cm, obtained in the Klive area from a spruce stand owned by JSC “Latvijas Valsts meži”. Also test fertilization attempts were made with the use of ash- and potassium-based artificial fertilizers (K2SO4). The content of macro elements (K, Ca, N, and C) was determined in the soil samples in the course of the analysis. The obtained results indicate that the content of K and Ca decreases at greater horizontal depths of the soil. Nutrients are subsequently being leached away from the soil. A higher C/N ratio at the horizontal depth of up to 10 cm in the soil means a higher content of organic subst…
Spatial patterns of, and environmental controls on, soil properties at a riparianepaddock interface
2012
Abstract Riparian zones are prominent features of agricultural landscapes because they are the last point to intercept nutrients and sediments before they enter water bodies. We investigated the soil properties, nutrient dynamics and vegetation composition at the riparian–agriculture interface. Soil physicochemical and vegetation properties were spatially heterogeneous along the transition from the grazed paddock into the un-grazed and revegetated riparian zone. Soil C stocks varied considerably across the site, with values ranging from 2% in the paddock to 5% in the riparian zone. Using Bayesian model selection, a predictive model for total soil carbon was developed. By including soil mois…
Variable scale effects on hillslope soil erosion during rainfall-runoff processes
2021
Abstract The variation of soil erosion across scales remains a controversial issue. A theoretical framework, coupling the normalized Green-Ampt equation for infiltration, 1D kinematic wave model for overland flow, and WEPP erosion modeling approaches for soil erosion, was used to explain and quantify the direct effect of scale on the soil erosion process. The results show that the relation between interrill erosion and slope length accords with a power-law decreasing trend, while the relation of rill erosion versus slope length shows a power-law increasing trend. Moreover, the power-law scaling of interrill erosion becomes more prominent with an increase of rainfall duration and intensity b…