341 research outputs found
The Growth of Black Holes and Bulges at the Cores of Cooling Flows
Central cluster galaxies (cDs) in cooling flows are growing rapidly through
gas accretion and star formation. At the same time, AGN outbursts fueled by
accretion onto supermassive black holes are generating X-ray cavity systems and
driving outflows that exceed those in powerful quasars. We show that the
resulting bulge and black hole growth follows a trend that is roughly
consistent with the slope of the local (Magorrian) relation between bulge and
black hole mass for nearby quiescent ellipticals. However, a large scatter
suggests that cD bulges and black holes do not always grow in lock-step. New
measurements made with XMM, Chandra, and FUSE of the condensation rates in
cooling flows are now approaching or are comparable to the star formation
rates, alleviating the need for an invisible sink of cold matter. We show that
the remaining radiation losses can be offset by AGN outbursts in more than half
of the systems in our sample, indicating that the level of cooling and star
formation is regulated by AGN feedback.Comment: 3 pages, 4 figures, to appear in the proceedings of "Heating vs.
Cooling in Galaxies and Clusters of Galaxies," edited by H. Boehringer, P.
Schuecker, G. W. Pratt, and A. Finogueno
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A Modeling Study Evaluating the Thermal-Hydrological Conditions In and Near Waste Emplacement Tunnels At Yucca Mountain
In heated tunnels such as those designated for emplacement of radioactive waste at the proposed geologic repository at Yucca Mountain, temperature gradients cause natural convection processes that may significantly influence the moisture conditions in the tunnels and in the surrounding fractured rock. Large-scale convection cells in the heated tunnels would provide an effective mechanism for turbulent mixing and axial transport of vapor generated from evaporation of pore water in the nearby formation. As a result, vapor would be transported from the elevated-temperature sections of the tunnels into cool end sections (where no waste is emplaced), would condense there, and subsequently drain into underlying rock units. To study these processes, we have developed a new simulation method that couples existing tools for simulating thermal-hydrological (TH) conditions in the fractured formation with a module that approximates turbulent natural convection in heated emplacement drifts. The new method simultaneously handles (1) the flow and energy transport processes in the fractured rock, (2) the flow and energy transport processes in the cavity, and (3) the heat and mass exchange at the rock-cavity interface. An application is presented studying the future TH conditions within and near a representative waste emplacement tunnel at Yucca Mountain. Particular focus is on the potential for condensation along the emplacement section, a possible result of heat output differences between individual waste packages
Maternal vitamin D deficiency and developmental origins of health and disease (DOHaD)
Vitamin D is an essential nutrient that is metabolized in the body to generate an active metabolite (1, 25(OH)2D) with hormone-like activity and highly diverse roles in cellular function. Vitamin D deficiency (VDD) is a prevalent but easily p reventable nutritional disturbance. Emerging evidence demonstrates the importance of s ufficient vitamin D concentrations during fetal life with deficiencies leading to long-term effects into adulthood. Here, we provide a detailed review and perspective of evidence for the role of maternal VDD in offspring long-term health, particularly as it relates to developmental origins of health and disease (DOHaD). We focus on the roles in neurobehavioral and cardiometabolic disorders in humans and highlight recent finding s from zebrafish and rodent models that probe potential mechanisms linking early life VDD to later life health outcomes. Moreover, we explore evidence implicating epigenetic mechanisms as a mediator of this link. Gaps in our current understanding of how maternal VDD might result in deleterious offspring outcomes later in life are also addressed
New species in Aspergillus section Terrei
Section Terrei of Aspergillus was studied using a polyphasic approach including sequence analysis of parts of the β-tubulin and calmodulin genes and the ITS region, macro- and micromorphological analyses and examination of extrolite profiles to describe three new species in this section. Based on phylogenetic analysis of calmodulin and β-tubulin sequences seven lineages were observed among isolates that have previously been treated as A. terreus and its subspecies by Raper & Fennell (1965) and others. Aspergillus alabamensis, A. terreus var. floccosus, A. terreus var. africanus, A. terreus var. aureus, A. hortai and A. terreus NRRL 4017 all represent distinct lineages from the A. terreus clade. Among them, A. terreus var. floccosus, A. terreus NRRL 4017 and A. terreus var. aureus could also be distinguished from A. terreus by using ITS sequence data. New names are proposed for A. terreus var. floccosus, A. terreus var. africanus, A. terreus var. aureus, while Aspergillus hortai is recognised at species level. Aspergillus terreus NRRL 4017 is described as the new species A. pseudoterreus. Also included in section Terrei are some species formerly placed in sections Flavipedes and Versicolores. A. clade including the type isolate of A. niveus (CBS 115.27) constitutes a lineage closely related to A. carneus. Fennellia nivea, the hypothesized teleomorph is not related to this clade. Aspergillus allahabadii, A. niveus var. indicus, and two species originally placed in section Versicolores, A. ambiguus and A. microcysticus, also form well-defined lineages on all trees. Species in Aspergillus section Terrei are producers of a diverse array of secondary metabolites. However, many of the species in the section produce different combinations of the following metabolites: acetylaranotin, asperphenamate, aspochalamins, aspulvinones, asteltoxin, asterric acid, asterriquinones, aszonalenins, atrovenetins, butyrolactones, citreoisocoumarins, citreoviridins, citrinins, decaturins, fulvic acid, geodins, gregatins, mevinolins, serantrypinone, terreic acid (only the precursor 3,6-dihydroxytoluquinone found), terreins, terrequinones, terretonins and territrems. The cholesterol-lowering agent mevinolin was found in A. terreus and A. neoafricanus only. The hepatotoxic extrolite citrinin was found in eight species: A. alabamensis, A. allahabadii, A. carneus, A. floccosus, A. hortai, A. neoindicus, A. niveus and A. pseudoterreus. The neurotoxic extrolite citreoviridin was found in five species: A. neoafricanus, A. aureoterreus, A. pseudoterreus, A. terreus and A. neoniveus. Territrems, tremorgenic extrolites, were found in some strains of A. alabamensis and A. terreus
Can forest management based on natural disturbances maintain ecological resilience?
Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance
Leveraging natural history biorepositories as a global, decentralized, pathogen surveillance network
The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic reveals a major gap in global biosecurity infrastructure: a lack of publicly available biological samples representative across space, time, and taxonomic diversity. The shortfall, in this case for vertebrates, prevents accurate and rapid identification and monitoring of emerging pathogens and their reservoir host(s) and precludes extended investigation of ecological, evolutionary, and environmental associations that lead to human infection or spillover. Natural history museum biorepositories form the backbone of a critically needed, decentralized, global network for zoonotic pathogen surveillance, yet this infrastructure remains marginally developed, underutilized, underfunded, and disconnected from public health initiatives. Proactive detection and mitigation for emerging infectious diseases (EIDs) requires expanded biodiversity infrastructure and training (particularly in biodiverse and lower income countries) and new communication pipelines that connect biorepositories and biomedical communities. To this end, we highlight a novel adaptation of Project ECHO’s virtual community of practice model: Museums and Emerging Pathogens in the Americas (MEPA). MEPA is a virtual network aimed at fostering communication, coordination, and collaborative problem-solving among pathogen researchers, public health officials, and biorepositories in the Americas. MEPA now acts as a model of effective international, interdisciplinary collaboration that can and should be replicated in other biodiversity hotspots. We encourage deposition of wildlife specimens and associated data with public biorepositories, regardless of original collection purpose, and urge biorepositories to embrace new specimen sources, types, and uses to maximize strategic growth and utility for EID research. Taxonomically, geographically, and temporally deep biorepository archives serve as the foundation of a proactive and increasingly predictive approach to zoonotic spillover, risk assessment, and threat mitigation
A Conformally Invariant Holographic Two-Point Function on the Berger Sphere
We apply our previous work on Green's functions for the four-dimensional
quaternionic Taub-NUT manifold to obtain a scalar two-point function on the
homogeneously squashed three-sphere (otherwise known as the Berger sphere),
which lies at its conformal infinity. Using basic notions from conformal
geometry and the theory of boundary value problems, in particular the
Dirichlet-to-Robin operator, we establish that our two-point correlation
function is conformally invariant and corresponds to a boundary operator of
conformal dimension one. It is plausible that the methods we use could have
more general applications in an AdS/CFT context.Comment: 1+49 pages, no figures. v2: Several typos correcte
The current status of species recognition and identification in Aspergillus
The species recognition and identification of aspergilli and their
teleomorphs is discussed. A historical overview of the taxonomic concepts
starting with the monograph of Raper & Fennell
(1965) is given. A list of
taxa described since 2000 is provided. Physiological characters, particularly
growth rates and the production of extrolites, often show differences that
reflect phylogenetic species boundaries and greater emphasis should be placed
on extrolite profiles and growth characteristics in species descriptions.
Multilocus sequence-based phylogenetic analyses have emerged as the primary
tool for inferring phylogenetic species boundaries and relationships within
subgenera and sections. A four locus DNA sequence study covering all major
lineages in Aspergillus using genealogical concordance theory
resulted in a species recognition system that agrees in part with phenotypic
studies and reveals the presence of many undescribed species not resolved by
phenotype. The use of as much data from as many sources as possible in making
taxonomic decisions is advocated. For species identification, DNA barcoding
uses a short genetic marker in an organism”s DNA to quickly and easily
identify it to a particular species. Partial cytochrome oxidase subunit 1
sequences, which are used for barcoding animal species, were found to have
limited value for species identification among black aspergilli. The various
possibilities are discussed and at present partial β-tubulin or
calmodulin are the most promising loci for Aspergillus
identification. For characterising Aspergillus species one
application would be to produce a multilocus phylogeny, with the goal of
having a firm understanding of the evolutionary relationships among species
across the entire genus. DNA chip technologies are discussed as possibilities
for an accurate multilocus barcoding tool for the genus
Aspergillus
Polyphasic taxonomy of Aspergillus section Fumigati and its teleomorph Neosartorya
The taxonomy of Aspergillus section Fumigati with its
teleomorph genus Neosartorya is revised. The species concept is based
on phenotypic (morphology and extrolite profiles) and molecular
(β-tubulin and calmodulin gene sequences) characters in a polyphasic
approach. Four new taxa are proposed: N. australensis N. ferenczii, N.
papuaensis and N. warcupii. All newly described and accepted
species are illustrated. The section consists of 33 taxa: 10 strictly
anamorphic Aspergillus species and 23 Neosartorya species.
Four other Neosartorya species described previously were not
available for this monograph, and consequently are relegated to the category
of doubtful species
Production and Decay of D_1(2420)^0 and D_2^*(2460)^0
We have investigated and final states and
observed the two established charmed mesons, the with mass
MeV/c and width MeV/c and
the with mass MeV/c and width
MeV/c. Properties of these final states, including
their decay angular distributions and spin-parity assignments, have been
studied. We identify these two mesons as the doublet predicted
by HQET. We also obtain constraints on {\footnotesize } as a function of the cosine of the relative phase of the two
amplitudes in the decay.Comment: 15 pages in REVTEX format. hardcopies with figures can be obtained by
sending mail to: [email protected]
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