University of Maryland, Baltimore County

About: University of Maryland, Baltimore County is a education organization based out in Baltimore, Maryland, United States. It is known for research contribution in the topics: Population & Galaxy. The organization has 8749 authors who have published 20843 publications receiving 795706 citations. The organization is also known as: UMBC.

A new method for detecting and interpreting biodiversity and ecological community thresholds

Abstract: Summary 1 Existing methods for identifying ecological community thresholds are designed for univariate indicators or multivariate dimension-reduction of community structure Most are insensitive to responses of individual taxa with low occurrence frequencies or highly variable abundances, properties of the vast majority of taxa in community data sets We introduce Threshold Indicator Taxa ANalysis (TITAN) to detect changes in taxa distributions along an environmental gradient over space or time, and assess synchrony among taxa change points as evidence for community thresholds 2 TITAN uses indicator species scores to integrate occurrence, abundance and directionality of taxa responses It identifies the optimum value of a continuous variable, x, that partitions sample units while maximizing taxon-specific scores Indicator z scores standardize original scores relative to the mean and SD of permuted samples along x, thereby emphasizing the relative magnitude of change and increasing the contributions of taxa with low occurrence frequencies but high sensitivity to the gradient TITAN distinguishes negative (z−) and positive (z+) taxa responses and tracks cumulative responses of declining [sum(z−)] and increasing [sum(z+)] taxa in the community Bootstrapping is used to estimate indicator reliability and purity as well as uncertainty around the location of individual taxa and community change points 3 Using two simulated data sets, TITAN correctly identified taxon and community thresholds in more than 99% of 500 unique versions of each simulation In contrast, multivariate change-point analysis did not distinguish directional taxa responses, resulting in much wider confidence intervals that in one instance failed to capture thresholds in 38% of the iterations 4 Retrospective analysis of macroinvertebrate community response to a phosphorus gradient supported previous threshold estimates, although TITAN produced narrower confidence limits and revealed that several taxa declined at lower levels of phosphorus Re-analysis of macroinvertebrate responses to an urbanization gradient illustrated disparate change points for declining (0·81–3·3% urban land) and increasing (6·8–26·6%) taxa, whereas the published threshold estimate (20–30%) missed the declining-taxa threshold because it could not distinguish their synchronous decline from the gradual increase in ubiquitous taxa 5Synthesis and applications By deconstructing communities to assess synchrony of taxon-specific change points, TITAN provides a sensitive and precise alternative to existing methods for assessing community thresholds TITAN has tremendous potential to inform conservation of rare or threatened species, develop species sensitivity models, identify reference conditions and to support development of numerical regulatory criteria

Wind from the black-hole accretion disk driving a molecular outflow in an active galaxy

Abstract: Observations of an ultrafast accretion-disk wind in the X-ray spectrum of a nearby ultraluminous infrared galaxy support the theory that such winds affect the evolution of supermassive black holes and their host galaxies. Francesco Tombesi et al. report the detection of a powerful accretion-disk wind with a mildly relativistic velocity in the X-ray spectrum of IRAS F11119+3257, a nearby (z = 0.189) optically classified type 1 ultraluminous infrared galaxy hosting a powerful molecular outflow. The energetics of these winds are consistent with the suggestion that active galactic nuclei winds can provide an efficient way to transfer energy to the interstellar medium and support the theory that such winds affect the evolution of supermassive black holes and their host galaxies. Powerful winds driven by active galactic nuclei are often thought to affect the evolution of both supermassive black holes and their host galaxies, quenching star formation and explaining the close relationship between black holes and galaxies1,2. Recent observations of large-scale molecular outflows3,4,5,6,7,8 in ultraluminous infrared galaxies support this quasar-feedback idea, because they directly trace the gas from which stars form. Theoretical models9,10,11,12 suggest that these outflows originate as energy-conserving flows driven by fast accretion-disk winds. Proposed connections between large-scale molecular outflows and accretion-disk activity in ultraluminous galaxies were incomplete3,4,5,6,7,8 because no accretion-disk wind had been detected. Conversely, studies of powerful accretion-disk winds have until now focused only on X-ray observations of local Seyfert galaxies13,14 and a few higher-redshift quasars15,16,17,18,19. Here we report observations of a powerful accretion-disk wind with a mildly relativistic velocity (a quarter that of light) in the X-ray spectrum of IRAS F11119+3257, a nearby (redshift 0.189) optically classified type 1 ultraluminous infrared galaxy hosting a powerful molecular outflow6. The active galactic nucleus is responsible for about 80 per cent of the emission, with a quasar-like luminosity6 of 1.5 × 1046 ergs per second. The energetics of these two types of wide-angle outflows is consistent with the energy-conserving mechanism9,10,11,12 that is the basis of the quasar feedback1 in active galactic nuclei that lack powerful radio jets (such jets are an alternative way to drive molecular outflows).

Comparison of trypan blue dye exclusion and fluorometric assays for mammalian cell viability determinations

Abstract: A hemocytometer-based trypan blue dye exclusion cell quantitation and viability assay was compared with a similar assay using simultaneous fluorometric staining with fluorescein diacetate and propidium iodide. Viable and nonviable cell densities were measured, and culture viability was calculated both during the normal growth cycle of a murine hybridoma and in response to the application of millimolar concentrations of either tert-butyl hydroperoxide or ferrous iron. During the early phase of rapid hybridoma cell growth, assay-based differences in viable cell density were not significant. As the culture aged, the trypan blue dye exclusion assay significantly overestimated cell viability, thereby underestimating nonviable cell density and yielding an erroneous estimation of the overall viability of the culture. Because of its lack of ambiguity in the identification of stained, nonviable cells and its resulting increased accuracy in the estimation of culture viability, the fluorometric assay was considered a better choice for the evaluation of cell viability.

Trends in U.S. Burden of Clostridioides difficile Infection and Outcomes.

Abstract: Background Efforts to prevent Clostridioides difficile infection continue to expand across the health care spectrum in the United States. Whether these efforts are reducing the national bu...