Untitled

Reynolds, C. S.; Irish, A.E.

doi:10.1023/a:1003020823129

Cited by 111 publications

(14 citation statements)

References 73 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In contrast, pure Type 1 objects have X-ray spectra that are almost unobscured by cold absorption material (e.g. Nandra & Pounds 1994;Schartel et al 1997;Reynolds 1997;Piconcelli et al 2005).…”

Section: Optical Classification and X-ray Absorptionmentioning

confidence: 99%

4U 1344-60: a bright intermediate Seyfert galaxy atz= 0.012 with a relativistic Fe K$\mathsf{\alpha}$ emission line

Piconcelli

Sánchez‐Portal

Guainazzi

et al. 2006

A&A

View full text Add to dashboard Cite

We present analysis of the optical and X-ray spectra of the low Galactic latitude bright (F 2−10 = 3.6 × 10 −11 erg cm −2 s −1 ) source 4U 1344−60. On the basis of the optical data we propose to classify 4U 1344−60 as an intermediate type Seyfert galaxy and we measure a value of z = 0.012 ± 0.001 for its redshift. From the XMM-Newton observation we find that the overall X-ray spectral shape of 4U 1344−60 is complex and can be described by a power-law continuum (Γ ≈ 1.55) obscured by two neutral absorption components (N f H ∼ 10 22 cm −2 and N p H ∼ 4 × 10 22 cm −2 ), the latter covering only the ∼50% of the primary X-ray source. The X-ray data therefore lend support to our classification of 4U 1344−60. It exhibits a broad and skewed Fe Kα line at ∼6.4 keV, which suggests the existence of an accretion disk that is able to reprocess the primary continuum down to a few gravitational radii. Such a line represents one of the clearest examples of a relativistic line observed by XMM-Newton so far. Our analysis has also revealed the marginal presence of two narrow line-like emission features at ∼4.9 and ∼5.2 keV.

show abstract

Section: Optical Classification and X-ray Absorptionmentioning

confidence: 99%

4U 1344-60: a bright intermediate Seyfert galaxy atz= 0.012 with a relativistic Fe K$\mathsf{\alpha}$ emission line

Piconcelli

Sánchez‐Portal

Guainazzi

et al. 2006

A&A

View full text Add to dashboard Cite

show abstract

“…It consists in grouping phytoplankton species that potentially and alternately may dominate or codominate in the system, according to their functional characteristics Reynolds 2006). In other words, a single functional groups combine dominant and co-dominant coexisting species with similar morphophysiological features, which increase and decrease simultaneously in the system under the same environmental conditions (Reynolds and Irish 1997). Furthermore, it is recognized that some species with different ecological strategies might be found under similar conditions because of their capability of adaptation (Weithoff 2003).…”

Section: Introductionmentioning

confidence: 99%

Phytoplankton Functional Groups in a Tropical Estuary: Hydrological Control and Nutrient Limitation

Costa

Huszar

Ovalle

2009

Estuaries and Coasts

105

View full text Add to dashboard Cite

Hydrology and nutrients have been indicated as the main driving factors acting on phytoplankton biomass and composition in estuarine systems, although grazing may occasionally have some influence. In order to identify these factors over temporal and spatial scales, we analyzed physical, chemical, and biological properties of a tropical river-dominated estuary during the dry and rainy seasons. As far as we know, this is the first time that the functional groups approach has been used to analyze the changes in phytoplankton composition in an estuary. This recent framework is based on the tolerances and sensitivities in relation to environmental conditions of groups of species, which are labeled by alpha-numeric codes (Reynolds et al., J. Pl. Res. 24:417-428, 2002). In the estuary of Paraíba do Sul River, all phytoplankton groups were represented by freshwater organisms, indicating the strong influence of the river. However, remarkable shifts in composition and biomass occurred from the low to high flushing seasons, due much more to the river discharge than to nutrient availability. The overall results showed no nitrogen, phosphorus, or silica limitation to phytoplankton growth (mean values: dissolved inorganic nitrogen=30.5 µM, soluble reactive phosphorus=1.45 µM, and silica=208.05 µM). The higher river flow supports a lower phytoplankton biomass composed mainly of nanoplankton (<20 µm) fast-growing functional groups, which are able to maintain biomass even in high flushing conditions (X 1 ), or large heavy organisms, such as some heavy diatoms of group P, which are able to be in suspension in shallow and turbulent systems. The lower river flow led to the coexistence of large organisms (>20 µm) of the groups P and F, which include slowgrowing populations typically found in mesotrophic lakes. Although the functional group approach was originally developed for temperate lakes, our data support this approach for a tropical estuarine environment.

show abstract

“…The probability of a cell dividing within a given time step is calculated based on a growth rate (kg, /d) in the same manner as advection is calculated above. The model uses a constant growth rate of 0.53 /d based on estimates for phytoplankton in freshwater (Reynolds & Irish, 1997). The death rate is assigned to simulate a constant population size in each segment.…”

Section: Growth and Deathmentioning

confidence: 99%

“…A growth rate of 0.53/d was assigned based on estimates of in situ growth rates of phytoplankton in freshwater (Reynolds & Irish, 1997). A constant mutation rate is used throughout the model, as described in the main paper.…”

Section: Great Lakesmentioning

confidence: 99%

“…This would require estimates of growth and mutation rates. The growth rate we use is a general estimate for freshwater phytoplankton (Reynolds & Irish, 1997), but the mutation rate is specific to Microcystis aeruginosa (using m from E. coli and r / m for Microcystis aeruginosa). Estimates of r / m for 48 bacteria and archaea are available from Vos and Didelot (2009), but Microcystis aeruginosa is the only free living, freshwater cyanobacteria in this database.…”

Section: Relation To Other Species and Systemsmentioning

confidence: 99%

See 1 more Smart Citation

Neutral Evolution and Dispersal Limitation Produce Biogeographic Patterns in Microcystis aeruginosa Populations of Lake Systems

Shirani

Hellweger

2017

Microb Ecol

View full text Add to dashboard Cite

Molecular observations reveal substantial biogeographic patterns of cyanobacteria within systems of connected lakes. An important question is the relative role of environmental selection and neutral processes in the biogeography of these systems. Here we quantify the effect of genetic drift and dispersal limitation by simulating individual cyanobacteria cells using an agent-based model (ABM). In the model, cells grow (divide), die and migrate between lakes. Each cell has a full genome that is subject to neutral mutation (i.e. the growth rate is independent of the genome). The model is verified by simulating simplified lake systems, for which theoretical solutions are available. Then, it is used to simulate the biogeography of the cyanobacterium Microcystis aeruginosa in a number of real systems, including the Great Lakes, Klamath River, Yahara River and Chattahoochee River. Model output is analyzed using standard bioinformatics tools (BLAST, MAFFT). The emergent patterns of nucleotide divergence between lakes are dynamic, including gradual increases due to accumulation of mutations and abrupt changes due to population takeovers by migrant cells (coalescence events). The model predicted nucleotide divergence is heterogeneous within systems and for weakly connected lakes it can be substantial. For example, Lakes Superior and Michigan are predicted to have an average genomic nucleotide divergence of 8,200 bp or 0.14%. The divergence between more strongly connected lakes is much lower. Our results provide a quantitative baseline for future biogeography studies. They show that dispersal limitation can be an important factor in microbe biogeography, which is contrary to the common belief, and could affect how a system responds to environmental change.iii ACKNOWLEDGMENTSWe thank Steve Chapra for providing the Great Lakes model and Euan Reavie for cyanobacteria concentration data in the Great Lakes. Peter Furth and Haris Koutsopoulos provided advice on the theoretical aspect. Haiwei Luo helped with the mutation rates. Three anonymous reviewers provided constructive criticism.

show abstract

Untitled

Cited by 111 publications

References 73 publications

4U 1344-60: a bright intermediate Seyfert galaxy atz= 0.012 with a relativistic Fe K$\mathsf{\alpha}$ emission line

4U 1344-60: a bright intermediate Seyfert galaxy atz= 0.012 with a relativistic Fe K$\mathsf{\alpha}$ emission line

Phytoplankton Functional Groups in a Tropical Estuary: Hydrological Control and Nutrient Limitation

Neutral Evolution and Dispersal Limitation Produce Biogeographic Patterns in Microcystis aeruginosa Populations of Lake Systems

Contact Info

Product

Resources

About