Search results for "Zone"
showing 10 items of 2029 documents
From clear lakes to murky waters – tracing the functional response of high-latitude lake communities to concurrent ‘greening’ and ‘browning’
2019
Climate change and the intensification of land use practices are causing widespread eutrophication of subarctic lakes. The implications of this rapid change for lake ecosystem function remain poorly understood. To assess how freshwater communities respond to such profound changes in their habitat and resource availability, we conducted a space-for-time analysis of food-web structure in 30 lakes situated across a temperature-productivity gradient equivalent to the predicted future climate of subarctic Europe (temperature +3 degrees C, precipitation +30% and nutrient +45 mu g L-1 total phosphorus). Along this gradient, we observed an increase in the assimilation of pelagic-derived carbon from…
How diffusivity, thermocline and incident light intensity modulate the dynamics of Deep Chlorophyll Maximum in Tyrrhenian Sea
2015
During the last few years theoretical works have shed new light and proposed new hypotheses on the mechanisms which regulate the spatio-temporal behaviour of phytoplankton communities in marine pelagic ecosystems. Despite this, relevant physical and biological issues, such as effects of the time- dependent mixing in the upper layer, competition between groups, and dynamics of non-stationary deep chlorophyll maxima, are still open questions. In this work, we analyze the spatio-temporal behaviour of five phytoplankton populations in a real marine ecosystem by using a one-dimensional reaction-diffusion-taxis model. The study is performed, taking into account the seasonal variations of environm…
Middle Miocene foraminifera from Canals (Valencia, western Mediterranean). Biostratigraphic and palaeoenvironmental aspects
2020
The age and the palaeoenvironmental conditions of the tap marls outcroppings near the locality of Canals in the south of the Valencia Province (E Spain) are discussed. Based on the planktonic foraminifera assemblages, mainly the species Globorotalia praemenardii , these tap marls are dated as Serravallian in age (middle Miocene). The analysis of the foraminiferal assemblages suggests a relatively well-ventilated uppermiddle bathyal environment, with only a moderate oxygen deficiency throughout most of the studied section. The rather cool waters indicated by the planktonic foraminifera (e.g. Globigerina bulloides ) are compatible with the decreasing temperatures trend during the middle Mioce…
Genome-wide DNA profiling of marginal zone lymphomas identifies subtype-specific lesions with an impact on the clinical outcome
2011
Abstract Marginal zone B-cell lymphomas (MZLs) have been divided into 3 distinct subtypes (extranodal MZLs of mucosa-associated lymphoid tissue [MALT] type, nodal MZLs, and splenic MZLs). Nevertheless, the relationship between the subtypes is still unclear. We performed a comprehensive analysis of genomic DNA copy number changes in a very large series of MZL cases with the aim of addressing this question. Samples from 218 MZL patients (25 nodal, 57 MALT, 134 splenic, and 2 not better specified MZLs) were analyzed with the Affymetrix Human Mapping 250K SNP arrays, and the data combined with matched gene expression in 33 of 218 cases. MALT lymphoma presented significantly more frequently gain…
Hybrid DFT calculations of the atomic and electronic structure for ABO3 perovskite (001) surfaces
2005
Abstract We present the results of first-principles calculations on two possible terminations of the (0 0 1) surfaces of SrTiO3, BaTiO3, and PbTiO3 perovskite crystals. Atomic structure and the electronic configurations were calculated for different 2D slabs, both stoichiometric and non-stoichiometric, using hybrid (B3PW) exchange-correlation technique and re-optimized basis sets of atomic (Gaussian) orbitals. Results are compared with previous calculations and available experimental data. The electronic density distribution near the surface and covalency effects are discussed in details for all three perovskites. Both SrTiO3 and BaTiO3 (0 0 1) surfaces demonstrate reduction of the optical …
Biochronological and paleoenvironmental interest of foraminifera lived in restricted environments: application to the study of the western Mediterran…
2002
As a consequence ofthe Flandrian transgression, numerous littoral lakes were f since roughly 6000 BP in the western Mediterranean coast. This kind of environment is colonized, among other groups, by specialized forms of foraminifera. Some species arose in the Upper Tertiary, some others in the Pleistocene and others are exclusively Holocene. Two kinds ofenvironment are proposed in the colonization: one with very low salinity waters where agglutinated test species prevail and another one with brackish waters, dominated by calcareous test species. In addition, Trichohyalus aguayoi can be considered as an acmezone within the Holocene. We propose a cenozone formed by the following assemblage: A…
Calcareous nannofossil response to Late Cretaceous climate change in the eastern Tethys (Zagros Basin, Iran)
2020
Abstract Coniacian to Maastrichtian changes in calcareous nannofossil assemblages have been investigated in the eastern Tethyan Shahneshin section (central Zagros Basin, Iran). The nannofossil assemblages are mainly composed of Watznaueria spp. (avg. 54%), Retecapsa spp (avg. 7.9%), Cribrosphaerella ehrenbergii (avg. 7.7%) and Micula spp. (avg. 5.7%). Throughout the late Campanian, there is a trend to lower abundances in Watznaueria spp. together with increasing abundances of C. ehrenbergii and Arkhangelskiella cymbiformis, which are considered in this basin as the main cool-water taxa. Our results reveal that, despite a diagenetic impact on calcareous nannoflora, a number of primary paleoe…
On thrusting, regional unconformities and exhumation of high-grade greenstones in Neoarchean orogens. The case of the Waroonga Shear Zone, Yilgarn Cr…
2017
Abstract During the Neoarchean, the dominant tectonic style progressively changed from an episodic-overturn/stagnant-lid regime to modern-style plate tectonics. The Neoarchean strengthening of continental lithosphere changed the style of deformation of orogenic belts. The case study presented here provides insights into how such transition in tectonic style occurred, a matter that is generally controversial. We present structural and metamorphic data from the c. 2660 Ma Waroonga Shear Zone (WSZ) in the Neoarchean Yilgarn orogen (Western Australia). The WSZ contains a syntectonic pluton and older, high-grade greenstones. The tectonic fabric in the pluton developed during melt-present thrusti…
Intertidal epilithic bacteria diversity changes along a naturally occurring carbon dioxide and pH gradient.
2014
Intertidal epilithic bacteria communities are important components of coastal ecosystems, yet few studies have assessed their diversity and how it may be affected by changing environmental parameters. Submarine CO2 seeps produce localised areas of CO2-enriched seawater with reduced pH levels. We utilised the seawater pH/CO2 gradient at Levante Bay (Italy) to test the hypothesis that epilithic bacteria communities are modified by exposure to seawater with the varying chemical parameters. Biofilms were sampled from three sites exposed to seawater with different pH/CO2 levels and diversity determined using high-throughput sequencing of 16S rRNA genes. Seawater pCO2 concentrations were increase…
Neural Stem Cell Regulation by Adhesion Molecules Within the Subependymal Niche
2019
In the mammalian adult brain, neural stem cells persist in neurogenic niches. The subependymal zone is the most prolific neurogenic niche in adult rodents, where residing stem cells generate large numbers of immature neurons that migrate into the olfactory bulb, where they differentiate into different types of interneurons. Subependymal neural stem cells derive from embryonic radial glia and retain some of their features like apico-basal polarity, with apical processes piercing the ependymal layer, and a basal process contacting blood vessels, constituting an epithelial niche. Conservation of the cytoarchitecture of the niche is of crucial importance for the maintenance of stem cells and fo…