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Search Results: 1 - 10 of 8454 matches for " Marie Sabbe "
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Isometric coactions of compact quantum groups on compact quantum metric spaces
Johan Quaegebeur,Marie Sabbe
Mathematics , 2010,
Abstract: We propose a notion of isometric coaction of a compact quantum group on a compact quantum metric space in the framework of Rieffel where the metric structure is given by a Lipnorm. We prove the existence of a quantum isometry group for finite metric quantum spaces, preserving a given state.
Philosophie der neuesten Musik-ein Versuch zur Extrapolation von Adornos 'Philosophie der neuen Musik'
H. Sabbe
Philosophica , 1971,
Abstract:
Paleolimnological studies of Laguna Chica of San Pedro (VIII Region): Diatoms, hydrocarbons and fatty acid records Estudio Paleolimnológico de Laguna Chica de San Pedro (VIII Región): Diatomeas, hidrocarburos y ácidos grasos
ROBERTO URRUTIA,SABBE KOEN,FABIOLA CRUCES,KARLA POZO
Revista chilena de historia natural , 2000,
Abstract: Diatom, hydrocarbons and fatty acid sedimentary records were used for reconstructing the recent (last 150 years) palaeolimnological history of Laguna Chica of San Pedro (Concepción, VIII Región, Chile). Cluster analyses (Constrained Incremental Sum of Squares) on the diatom data revealed three distinct periods. The first period (1883-1940's) showed a pronounced increase in sedimentation rate and a slight increase in organic matter accumulation. In this period, eutrophic species (Aulacoseira granulata and Staurosira construens) became increasingly dominant. From the 1940s until the 1970s the diatom signal is more equivocal: after the initial decrease in the relative abundance of A. granulata and S. construens their numbers fluctuate without a clear pattern. Sedimentation rates strongly fluctuate in this period. From 1978 onwards eutrophic species are in decline while indicators of oligotrophic conditions, such as Cyclotella stelligera and Aulacoseira distans, become more abundant. This shift in the lake trophic status could not be attributed to a reduction in the nutrient load from the catchment and we hypothesize that the invasion of the lake by the submersed macrophyte Egeria densa has altered nutrient availability to the plankton communities. This is in agreement with the hydrocarbons and fatty acid analyses which demonstrate a shift in carbon number distributions from short chain alkanes and alkanoic acids (typical for microalgae) to long chain molecules (characteristic for higher plants) in the upper layers of the lake sediment Se realizó la reconstrucción histórica de los últimos 150 a os de Laguna Chica de San Pedro (Concepción, VIII Región, Chile), a través de la utilización de los restos de diatomeas, hidrocarburos y ácidos grasos contenidos en la columna de sedimento. El análisis estratigráfico de las diatomeas reveló la presencia de tres períodos diferentes. El primer período (1883-1940's), mostró un marcado aumento de las tasas de sedimentación y un leve aumento en la acumulación de materia orgánica; en este período se registra un incremento de las especies eutróficas (Aulacoseira granulata y Staurosira construens). Desde los a os cuarenta hasta la década del setenta el cambio en la comunidad de diatomeas fue más evidente y las tasas de sedimentación variaron fuertemente. A partir de 1978 disminuyen las especies eutróficas y aumentan las indicadoras de condiciones oligotróficas (Cyclotella stelligera y Aulacoseira distans). El cambio en el estado trófico del lago, no se atribuye a una reducción de los aportes de nutrientes desde la cuenca, si
Individual and interacting effects of pCO2 and temperature on Emiliania huxleyi calcification: study of the calcite production, the coccolith morphology and the coccosphere size
C. De Bodt,N. Van Oostende,J. Harlay,K. Sabbe
Biogeosciences Discussions , 2009,
Abstract: The impact of ocean acidification and increased water temperature on marine ecosystems, in particular those involving calcifying organisms, has been gradually recognised. We examined the individual and combined effects of increased pCO2 (180 ppm V CO2, 380 ppm V CO2 and 750 ppm V CO2 corresponding to past, present and future CO2 conditions, respectively) and temperature (13°C and 18°C) during the calcification phase of the coccolithophore E. huxleyi using batch culture experiments. We showed that the cell abundance-normalized particulate organic carbon concentration (POC) increased from the present to the future CO2 treatments. A significant effect of pCO2 and of temperature on calcification was found, manifesting itself in a lower cell abundance-normalized particulate inorganic carbon (PIC) content as well as a lower PIC:POC ratio at future CO2 levels and at 18°C. Coccosphere-sized particles showed a size reduction trend with both increasing temperature and CO2 concentration. The influence of the different treatments on coccolith morphology was studied by categorizing SEM coccolith micrographs. The number of well-formed coccoliths decreased with increasing pCO2 while temperature did not have a significant impact on coccolith morphology. No interacting effect of pCO2 and temperature was observed on calcite production, coccolith morphology or on coccosphere size. Finally, our results suggest that ocean acidification might have a larger adverse impact on coccolithophorid calcification than surface water warming.
Linkage Mapping Identifies the Sex Determining Region as a Single Locus in the Pennate Diatom Seminavis robusta
Ives Vanstechelman, Koen Sabbe, Wim Vyverman, Pieter Vanormelingen, Marnik Vuylsteke
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0060132
Abstract: The pennate diatom Seminavis robusta, characterized by an archetypical diatom life cycle including a heterothallic mating system, is emerging as a model system for studying the molecular regulation of the diatom cell and life cycle. One of its main advantages compared with other diatom model systems is that sexual crosses can be made routinely, offering unprecedented possibilities for forward genetics. To date, nothing is known about the genetic basis of sex determination in diatoms. Here, we report on the construction of mating type-specific linkage maps for S. robusta, and use them to identify a single locus sex determination system in this diatom. We identified 13 mating type plus and 15 mating type minus linkage groups obtained from the analysis of 463 AFLP markers segregating in a full-sib family, covering 963.7 and 972.2 cM, respectively. Five linkage group pairs could be identified as putative homologues. The mating type phenotype mapped as a monogenic trait, disclosing the mating type plus as the heterogametic sex. This study provides the first evidence for a genetic sex determining mechanism in a diatom.
Marine Ostracod Provinciality in the Late Ordovician of Palaeocontinental Laurentia and Its Environmental and Geographical Expression
Mohibullah Mohibullah, Mark Williams, Thijs R. A. Vandenbroucke, Koen Sabbe, Jan A. Zalasiewicz
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0041682
Abstract: Background We examine the environmental, climatic and geographical controls on tropical ostracod distribution in the marine Ordovician of North America. Methodology/Principal Findings Analysis of the inter-regional distribution patterns of Ordovician Laurentian ostracods, focussing particularly on the diverse Late Ordovician Sandbian (ca 461 to 456 Ma) faunas, demonstrates strong endemicity at the species-level. Local endemism is very pronounced, ranging from 25% (e.g. Foxe basin) to 75% (e.g. Michigan basin) in each basin, a pattern that is also reflected in other benthic faunas such as brachiopods. Multivariate (ordination) analyses of the ostracod faunas allow demarcation of a Midcontinent Province and a southern Marginal Province in Laurentia. While these are most clearly differentiated at the stratigraphical level of the bicornis graptolite biozone, analyses of the entire dataset suggest that these provinces remain distinct throughout the Sandbian interval. Differences in species composition between the provinces appear to have been controlled by changes in physical parameters (e.g. temperature and salinity) related to water depth and latitude and a possible regional geographic barrier, and these differences persist into the Katian and possibly the Hirnantian. Local environmental parameters, perhaps operating at the microhabitat scale, may have been significant in driving local speciation events from ancestor species in each region. Conclusions/Significance Our work establishes a refined methodology for assessing marine benthic arthropod micro-benthos provinciality for the Early Palaeozoic.
GPs' perspectives of type 2 diabetes patients' adherence to treatment: A qualitative analysis of barriers and solutions
Johan Wens, Etienne Vermeire, Paul Van Royen, Bernard Sabbe, Joke Denekens
BMC Family Practice , 2005, DOI: 10.1186/1471-2296-6-20
Abstract: In a descriptive qualitative study, we explored the thoughts and feelings of general practitioners (GPs) on patients' compliance/adherence. Forty interested GPs could be recruited for focus group participation. Five open ended questions were derived on the one hand from a similar qualitative study on compliance/adherence in patients living with type 2 diabetes and on the other hand from the results of a comprehensive review of recent literature on compliance/adherence. A well-trained diabetes nurse guided the GPs through the focus group sessions while an observer was attentive for non-verbal communication and interactions between participants. All focus groups were audio taped and transcribed for content analysis. Two researchers independently performed the initial coding. A first draft with results was sent to all participants for agreement on content and comprehensiveness.General practitioners experience problems with the patient's deficient knowledge and the fact they minimize the consequences of having and living with diabetes. It appears that great confidence in modern medical science does not stimulate many changes in life style. Doctors tend to be frustrated because their patients do not achieve the common Evidence Based Medicine (EBM) objectives, i.e. on health behavior and metabolic control. Relevant solutions, derived from qualitative studies, for better compliance/adherence seem to be communication, tailored and shared care. GPs felt that a structured consultation and follow-up in a multidisciplinary team might help to increase compliance/adherence. It was recognized that the GP's efforts do not always meet the patients' health expectations. This initiates GPs' frustration and leads to a paternalistic attitude, which may induce anxiety in the patient. GPs often assume that the best methods to increase compliance/adherence are shocking the patients, putting pressure on them and threatening to refer them to hospital.GPs identified a number of problems with
Gain and loss of elongation factor genes in green algae
Ellen Cocquyt, Heroen Verbruggen, Frederik Leliaert, Frederick W Zechman, Koen Sabbe, Olivier De Clerck
BMC Evolutionary Biology , 2009, DOI: 10.1186/1471-2148-9-39
Abstract: Within the Chlorophyta, EF-1α is shown to be present in three ulvophycean orders (i.e., Dasycladales, Bryopsidales, Siphonocladales) and the genus Ignatius. Models describing gene gain-loss dynamics revealed that the presence of EF-1α, EFL or both genes along the backbone of the green plant phylogeny is highly uncertain due to sensitivity to branch lengths and lack of prior knowledge about ancestral states or rates of gene gain and loss. Model refinements based on insights gained from the EF-1α phylogeny reduce uncertainty but still imply several equally likely possibilities: a primitive EF-1α state with multiple independent EFL gains or coexistence of both genes in the ancestor of the Viridiplantae or Chlorophyta followed by differential loss of one or the other gene in the various lineages.EF-1α is much more common among green algae than previously thought. The mutually exclusive distribution of EF-1α and EFL is confirmed in a large sample of green plants. Hypotheses about the gain-loss dynamics of elongation factor genes are hard to test analytically due to a relatively flat likelihood surface, even if prior knowledge is incorporated. Phylogenetic analysis of EFL genes indicates misinterpretations in the recent literature due to uncertainty regarding the root position.Elongation factor-1 alpha (EF-1α) is a core element of the translation apparatus and member of the GTPase protein family. The gene has been widely used as a phylogenetic marker in eukaryotes; either to resolve their early evolution [e.g., [1,2]] or more recent phylogenetic patterns [e.g., [3-7]]. The evolutionary history of genes used for such inferences should closely match that of the organisms and not be affected by ancient paralogy or lateral gene transfer [8]. A gene related to but clearly distinguishable from EF-1α, called elongation factor-like (EFL), appears to substitute EF-1α in a scattered pattern: several unrelated eukaryote lineages have representatives that encode EFL and others that p
Paleolimnological studies of Laguna Chica of San Pedro (VIII Region): Diatoms, hydrocarbons and fatty acid records
URRUTIA,ROBERTO; KOEN,SABBE; CRUCES,FABIOLA; POZO,KARLA; BECERRA,JOSE; ARANEDA,ALBERTO; VYVERMAN,WIM; PARRA,OSCAR;
Revista chilena de historia natural , 2000, DOI: 10.4067/S0716-078X2000000400014
Abstract: diatom, hydrocarbons and fatty acid sedimentary records were used for reconstructing the recent (last 150 years) palaeolimnological history of laguna chica of san pedro (concepción, viii región, chile). cluster analyses (constrained incremental sum of squares) on the diatom data revealed three distinct periods. the first period (1883-1940's) showed a pronounced increase in sedimentation rate and a slight increase in organic matter accumulation. in this period, eutrophic species (aulacoseira granulata and staurosira construens) became increasingly dominant. from the 1940s until the 1970s the diatom signal is more equivocal: after the initial decrease in the relative abundance of a. granulata and s. construens their numbers fluctuate without a clear pattern. sedimentation rates strongly fluctuate in this period. from 1978 onwards eutrophic species are in decline while indicators of oligotrophic conditions, such as cyclotella stelligera and aulacoseira distans, become more abundant. this shift in the lake trophic status could not be attributed to a reduction in the nutrient load from the catchment and we hypothesize that the invasion of the lake by the submersed macrophyte egeria densa has altered nutrient availability to the plankton communities. this is in agreement with the hydrocarbons and fatty acid analyses which demonstrate a shift in carbon number distributions from short chain alkanes and alkanoic acids (typical for microalgae) to long chain molecules (characteristic for higher plants) in the upper layers of the lake sediment
Individual and interacting effects of pCO2 and temperature on Emiliania huxleyi calcification: study of the calcite production, the coccolith morphology and the coccosphere size
C. De Bodt, N. Van Oostende, J. Harlay, K. Sabbe,L. Chou
Biogeosciences (BG) & Discussions (BGD) , 2010,
Abstract: The impact of ocean acidification and increased water temperature on marine ecosystems, in particular those involving calcifying organisms, has been gradually recognised. We examined the individual and combined effects of increased pCO2 (180 ppmV CO2, 380 ppmV CO2 and 750 ppmV CO2 corresponding to past, present and future CO2 conditions, respectively) and temperature (13 °C and 18 °C) during the exponential growth phase of the coccolithophore E. huxleyi using batch culture experiments. We showed that cellular production rate of Particulate Organic Carbon (POC) increased from the present to the future CO2 treatments at 13 °C. A significant effect of pCO2 and of temperature on calcification was found, manifesting itself in a lower cellular production rate of Particulate Inorganic Carbon (PIC) as well as a lower PIC:POC ratio at future CO2 levels and at 18 °C. Coccosphere-sized particles showed a size reduction with both increasing temperature and CO2 concentration. The influence of the different treatments on coccolith morphology was studied by categorizing SEM coccolith micrographs. The number of well-formed coccoliths decreased with increasing pCO2 while temperature did not have a significant impact on coccolith morphology. No interacting effects of pCO2 and temperature were observed on calcite production, coccolith morphology or on coccosphere size. Finally, our results suggest that ocean acidification might have a larger adverse impact on coccolithophorid calcification than surface water warming.
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