621 research outputs found
A Multiwavelength Photometric Census of AGN and Star Formation Activity in the Brightest Cluster Galaxies of X-ray Selected Clusters
Despite their reputation as being âred and deadâ, the unique environment inhabited by brightest cluster galaxies (BCGs) can often lead to a self-regulated feedback cycle between radiatively cooling intracluster gas and star formation and active galactic nucleus (AGN) activity in the BCG. However the prevalence of âactiveâ BCGs, and details of the feedback involved, are still uncertain. We have performed an optical, UV and mid-IR photometric analysis of the BCGs in 981 clusters at 0.03 < z < 0.5, selected from the ROSAT All Sky Survey. Using Pan-STARRS PS1 3Ï, GALEX and WISE survey data we look for BCGs with photometric colours which deviate from that of the bulk population of passive BCGs â indicative of AGN and/or star formation activity within the BCG. We find that whilst the majority of BCGs are consistent with being passive, at least 14âperâcent of our BCGs show a significant colour offset from passivity in at least one colour index. And, where available, supplementary spectroscopy reveals the majority of these particular BCGs show strong optical emission lines. On comparing BCG âactivityâ with the X-ray luminosity of the host cluster, we find that BCGs showing a colour offset are preferentially found in the more X-ray luminous clusters, indicative of the connection between BCG âactivityâ and the intracluster medium
Book Reviews
Review of New Perspectives in Archeology, by Sally R. Binford and Lewis R. Binford, eds.; The Archaeology of Ancient China, by Kwang-chih Chang; Prehistoric Animals and Their Hunters, by I. W. Cornwall; Contes Malgaches en Dialecte Sakalava: Textes, Traduction, Grammaire et Lexique, by Otto Chr. Dahl; An Ethnographic Bibliography of New Guinea; Archaeology on the Island of Mo'orea, French Polynesia, by Roger C. Green, Kaye Green, Roy Rappaport, Ann Rappaport, and Janet Davidson; Polynesian Culture History: Essays in Honor of Kenneth P. Emory, by Genevieve A. Highland, et al.; Computer Analysis of Chronological Seriation, by Frank Hole and Mary Shaw; Prehistoric Japanese Arts: Jomon Pottery, by J. Edward Kidder and Teruya Esaka; A Selected and Annotated Bibliography of Korean Anthropology, by Eugene I. Knez and Chang-Su Swanson; Die Religionen der Sudsee und Australiens, by Hans Nevermann, Ernest A. Worms, and Helmut Petri; Geschichte und Sozialordnung der Sherpa, by Michael Oppitz; The Vermilion Bird: T'ang Images of the South, by Edward H. Schafer; Fijian Material Culture: A Study of Cultural Context, Function, and Change, by Alan Richard Tippett
A Generalized Fluctuation-Dissipation Theorem for Nonlinear Response Functions
A nonlinear generalization of the Fluctuation-Dissipation Theorem (FDT) for
the n-point Green functions and the amputated 1PI vertex functions at finite
temperature is derived in the framework of the Closed Time Path formalism. We
verify that this generalized FDT coincides with known results for n=2 and 3.
New explicit relations among the 4-point nonlinear response and correlation
(fluctuation) functions are presented.Comment: 34 pages, Revte
Endocrine disruptor compounds-a cause of impaired immune tolerance driving inflammatory disorders of pregnancy?
Endocrine disrupting compounds (EDCs) are prevalent and ubiquitous in our environment and have substantial potential to compromise human and animal health. Amongst the chronic health conditions associated with EDC exposure, dysregulation of reproductive function in both females and males is prominent. Human epidemiological studies demonstrate links between EDC exposure and infertility, as well as gestational disorders including miscarriage, fetal growth restriction, preeclampsia, and preterm birth. Animal experiments show EDCs administered during gestation, or to either parent prior to conception, can interfere with gamete quality, embryo implantation, and placental and fetal development, with consequences for offspring viability and health. It has been presumed that EDCs operate principally through disrupting hormone-regulated events in reproduction and fetal development, but EDC effects on maternal immune receptivity to pregnancy are also implicated. EDCs can modulate both the innate and adaptive arms of the immune system, to alter inflammatory responses, and interfere with generation of regulatory T (Treg) cells that are critical for pregnancy tolerance. Effects of EDCs on immune cells are complex and likely exerted by both steroid hormone-dependent and hormone-independent pathways. Thus, to better understand how EDCs impact reproduction and pregnancy, it is imperative to consider how immune-mediated mechanisms are affected by EDCs. This review will describe evidence that several EDCs modify elements of the immune response relevant to pregnancy, and will discuss the potential for EDCs to disrupt immune tolerance required for robust placentation and optimal fetal development.John E. Schjenken, Ella S. Green, Tenuis S. Overduin, Chui Yan Mah, Darryl L. Russell and Sarah A. Robertso
The stone adze and obsidian assemblage from the Talasiu site, Kingdom of Tonga
Typological and geochemical analyses of stone adzes and other stone tools have played a significant role in identifying directionality of colonisation movements in early migratory events in the Western Pacific. In later phases of Polynesian prehistory, stone adzes are important status goods which show substantial spatial and temporal variation. However, there is a debate when standardisation of form and manufacture appeared, whether it can be seen in earliest populations colonising the Pacific or whether it is a later development. We present in this paper a stone adze and obsidian tool assemblage from an early Ancestral Polynesian Society Talasiu site on Tongatapu, Kingdom of Tonga. The site shows a wide variety of adze types; however, if raw material origin is taken into account, emerging standardisation in adze form might be detected. We also show that Tongatapu was strongly connected in a network of interaction to islands to the North, particularly Samoa, suggesting that these islands had permanent populations
Chiral unitary approach to S-wave meson baryon scattering in the strangeness S=0 sector
We study the S-wave interaction of mesons with baryons in the strangeness S=0
sector in a coupled channel unitary approach. The basic dynamics is drawn from
the lowest order meson baryon chiral Lagrangians. Small modifications inspired
by models with explicit vector meson exchange in the t-channel are also
considered. In addition the pi pi N channel is included and shown to have an
important repercussion in the results, particularly in the isospin 3/2 sector.Comment: 23 pages, LaTeX, 21 figure
Mitochondriotropic lanthanide nanorods : implications for multimodal imaging
Organelles such as mitochondria, lysosome, and nucleus, are essential for controlling basic cellular operations and metabolism. Because mitochondria play a critical role in energy production and programmed cell death, they act as prime therapeutic targets for various diseases and dysfunctional states. In this study, a multifunctional nanoplatform based on lanthanide upconverting nanorods is developed for concurrent mitochondria-targeted fluorescence imaging and preclinical MRI. This study provides critical insights into the spectral profiles of mitochondria and paves the way to developing novel, multimodal nanoprobes for mitochondria-targeted theranostics
Lepton Flavor Non-Conservation
In the present work we review the most prominent lepton flavor violating
processes (\mu \ra e\gamma, \mu \ra 3e, conversion,
oscillations etc), in the context of unified gauge theories. Many currently
fashionable extensions of the standard model are considered, such as: {\it i)}
extensions of the fermion sector (right-handed neutrino); {\it ii)} minimal
extensions involving additional Higgs scalars (more than one isodoublets,
singly and doubly charged isosinglets, isotriplets with doubly charged members
etc.); {\it iii)} supersymmetric or superstring inspired unified models
emphasizing the implications of the renormalization group equations in the
leptonic sector. Special attention is given to the experimentaly most
interesting conversion in the presence of nuclei. The relevant
nuclear aspects of the amplitudes are discussed in a number of fashionable
nuclear models. The main features of the relevant experiments are also
discussed, and detailed predictions of the above models are compared to the
present experimental limits.Comment: (IOA-300/93, review article, 83p, 6 epsf figures , available upon
request from [email protected])
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Research and theory for nursing and midwifery: Rethinking the nature of evidence
Background and Rationale: The rise in the principles of evidence-based medicine in the 1990s heralded a re-emerging orthodoxy in research methodologies. The view of the randomised controlled trial (RCT) as a âgold standardâ for evaluation of medical interventions has extended recently to evaluation of organisational forms and reforms and of change in complex systemsâwithin health care and in other human services. Relatively little attention has been given to the epistemological assumptions underlying such a hierarchy of research evidence.
Aims and Methods: Case studies from research in maternity care are used in this article to describe problems and limitations encountered in using RCTs to evaluate some recent policy-driven and consumer-oriented developments. These are discussed in relation to theory of knowledge and the epistemological assumptions, or paradigms, underpinning health services research. The aim in this discussion is not to advocate, or to reject, particular approaches to research but to advocate a more open and critical engagement with questions about the nature of evidence.
Findings and Discussion: Experimental approaches are of considerable value in investigating deterministic and probabilistic cause and effect relationships, and in testing often well-established but unevaluated technologies. However, little attention has been paid to contextual and cultural factors in the effects of interventions, in the culturally constructed nature of research questions themselves, or of the data on which much research is based. More complex, and less linear, approaches to methodology are needed to address these issues. A simple hierarchical approach does not represent the complexity of evidence well and should move toward a more cyclical view of knowledge development
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