Arc–continent collision and the formation of continental crust : a new geochemical and isotopic record from the Ordovician Tyrone Igneous Complex, Ireland

Author Posting. © Geological Society of London, 2009. This is the author's version of the work. It is posted here by permission of Geological Society of London for personal use, not for redistribution. The definitive version was published in Journal of the Geological Society 166 (2009): 485-500, doi:10.1144/0016-76492008-102.Collisions between oceanic island-arc terranes and passive continental margins are thought to have been important in the formation of continental crust throughout much of Earth’s history. Magmatic evolution during this stage of the plate-tectonic cycle is evident in several areas of the Ordovician Grampian-Taconic Orogen, as we demonstrate in the first detailed geochemical study of the Tyrone Igneous Complex, Ireland. New U–Pb zircon dating yields ages of 493 ± 2 Ma from a primitive mafic intrusion, indicating intra-oceanic subduction in Tremadoc time, and 475 ± 10 Ma from a light-rare-earth-element (LREE)-enriched tonalite intrusion that incorporated Laurentian continental material by early Arenig time (Early Ordovician, Stage 2) during arc-continent collision. Notably, LREE enrichment in volcanism and silicic intrusions of the Tyrone Igneous Complex exceeds that of average Dalradian (Laurentian) continental material which would have been thrust under the colliding forearc and potentially recycled into arc magmatism. This implies that crystal fractionation, in addition to magmatic mixing and assimilation, was important to the formation of new crust in the Grampian-Taconic Orogeny. Because similar super-enrichment of orogenic melts occurred elsewhere in the Caledonides in the British Isles and Newfoundland, the addition of new, highly enriched melt to this accreted arc terrane was apparently widespread spatially and temporally. Such super-enrichment of magmatism, especially if accompanied by loss of corresponding lower crustal residues, supports the theory that arc-continent collision plays an important role in altering bulk crustal composition toward typical values for ancient continental crust.This work was supported by the University of Aberdeen. LA-MC-ICPMS dating was conducted at the Arizona LaserChron Center with the assistance of George Gehrels and Victor Valencia and was supported by NSF-EAR 0443387

A survey of tuberculosis infection control practices at the NIH/NIAID/DAIDS-supported clinical trial sites in low and middle income countries.

BACKGROUND: Health care associated transmission of Mycobacterium tuberculosis (TB) is well described. A previous survey of infection control (IC) practices at clinical research sites in low and middle income countries (LMIC) funded by the National Institute of Allergy and Infectious Diseases (NIAID) conducting HIV research identified issues with respiratory IC practices. A guideline for TB IC based on international recommendations was developed and promulgated. This paper reports on adherence to the guideline at sites conducting or planning to conduct TB studies with the intention of supporting improvement. METHODS: A survey was developed that assessed IC activities in three domains: facility level measures, administrative control measures and environmental measures. An external site monitor visited each site in 2013-2014, to complete the audit. A central review committee evaluated the site-level survey and results were tabulated. Fisher\u27s exact test was performed to determine whether there were significant differences in practices at sites that had IC officers versus sites that did not have IC officers. Significance was assessed at

Recommendations for the follow-up of study participants with breakthrough HIV infections during HIV/AIDS biomedical prevention studies.

CAPRISA_2013.Objective: To facilitate collection of cumulative data on longitudinal HIV disease outcomes during HIV prevention studies by developing recommendations for follow-up of the relatively few study participants with breakthrough infections. Design: We formed a working group to compare and contrast the various approaches taken in recent HIV prevention trials, to summarize the advantages and disadvantages associated with each, and to explore the feasibility of developing protocols for the long-term follow-up of seroconverters. Methods: We reviewed study designs, objectives, and assessments in 15 interventional studies that followed HIV seroconverters. Protocol team members joined discussions of the various approaches and developed recommendations. Results: Most HIV prevention clinical trials share a core set of objectives, including the description/comparison of virological, immunological, and clinical course of HIV, and sometimes a comparison of preseroconversion and postseroconversion behavior. Long-term follow-up of seroconverters can be conducted in separate studies if the transition from parent protocol is effectively managed. Conclusion: We recommend the development of harmonized seroconverter protocols. Although specific research questions in the postseroconversion period may differ depending on prevention modality, harmonizing key evaluations would create an opportunity to ask overarching questions that inform the prevention field with respect to design and implementation of future combination prevention studies. Follow-up immediately postseroconversion should be conducted in the parent protocol before roll over into a follow-up protocol. Development of specimen repositories with ample volumes for future assays, standardized definitions of infection, diagnosis and seroconversion dates, and harmonization of study objectives and sample collections at key time points are important

A prospective study of hearing changes after beginning zidovudine or didanosine in HIV-1 treatment-naïve people

BACKGROUND: While hearing loss in HIV-infected people after beginning nucleoside reverse transcriptase inhibitors (NRTIs) has been reported, there have been no prospective studies that measured hearing changes longitudinally in treatment-naïve HIV-infected subjects following initiation of regimens containing NRTIs. The goal of this study was to conduct a prospective assessment of the contribution of zidovudine (ZDV) and didanosine (ddI) to hearing loss METHODS/DESIGN: A prospective observational pilot study to determine whether ZDV or ddI, alone or in combination, are associated with sensorineural hearing loss in HIV-infected persons. Changes in hearing levels at all frequencies and in low and high frequency pure tone averages were measured at baseline, 16, and 32 weeks after initiating antiretroviral therapy. DISCUSSION: Treatment with ZDV and ddI did not result in loss of hearing, even after taking into account noise exposure, immune status and age. The results of this prospective pilot study do not support the notion that treatment with nucleoside antiretrovirals damages hearing

Biomarkers Signal Contaminant Effects on the Organs of English Sole (Parophrys vetulus) from Puget Sound

Fish living in contaminated environments accumulate toxic chemicals in their tissues. Biomarkers are needed to identify the resulting health effects, particularly focusing on early changes at a subcellular level. We used a suite of complementary biomarkers to signal contaminant-induced changes in the DNA structure and cellular physiology of the livers and gills of English sole (Parophrys vetulus). These sediment-dwelling fish were obtained from the industrialized lower Duwamish River (DR) in Seattle, Washington, and from Quartermaster Harbor (QMH), a relatively clean reference site in south Puget Sound. Fourier transform–infrared (FT-IR) spectroscopy, liquid chromatography/mass spectrometry (LC/MS), and gas chromatography/mass spectrometry (GC/MS) identified potentially deleterious alterations in the DNA structure of the DR fish livers and gills, compared with the QMH fish. Expression of CYP1A (a member of the cytochrome P450 multigene family of enzymes) signaled changes in the liver associated with the oxidation of organic xenobiotics, as previously found with the gill. The FT-IR models demonstrated that the liver DNA of the DR fish had a unique structure likely arising from exposure to environmental chemicals. Analysis by LC/MS and GC/MS showed higher concentrations of DNA base lesions in the liver DNA of the DR fish, suggesting that these base modifications contributed to this discrete DNA structure. A comparable analysis by LC/MS and GC/MS of base modifications provided similar results with the gill. The biomarkers described are highly promising for identifying contaminant-induced stresses in fish populations from polluted and reference sites and, in addition, for monitoring the progress of remedial actions

Changes in Metabolic Syndrome Status After Initiation of Antiretroviral Therapy

Data on changes in metabolic syndrome (MetS) status in HIV-infected adults on antiretroviral therapy (ART) are limited

Seismicity of the Atlantis Massif detachment fault, 30°N at the Mid-Atlantic Ridge

Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 13 (2012): Q0AG11, doi:10.1029/2012GC004210.At the oceanic core complex that forms the Atlantis Massif at 30°N on the Mid-Atlantic Ridge, slip along the detachment fault for the last 1.5–2 Ma has brought lower crust and mantle rocks to the seafloor. Hydroacoustic data collected between 1999 and 2003 suggest that seismicity occurred near the top of the Massif, mostly on the southeastern section, while detected seismicity along the adjacent ridge axis was sparse. In 2005, five short-period ocean bottom seismographs (OBS) were deployed on and around the Massif as a pilot experiment to help constrain the distribution of seismicity in this region. Analysis of six months of OBS data indicates that, in contrast to the results of the earlier hydroacoustic study, the vast majority of the seismicity is located within the axial valley. During the OBS deployment, and within the array, seismicity was primarily composed of a relatively constant background rate and two large aftershock sequences that included 5 teleseismic events with magnitudes between 4.0 and 4.5. The aftershock sequences were located on the western side of the axial valley adjacent to the Atlantis Massif and close to the ridge-transform intersection. They follow Omori's law, and constitute more than half of the detected earthquakes. The OBS data also indicate a low but persistent level of seismicity associated with active faulting within the Atlantis Massif in the same region as the hydroacoustically detected seismicity. Within the Massif, the data indicate a north-south striking normal fault, and a left-lateral, strike-slip fault near a prominent, transform-parallel, north-facing scarp. Both features could be explained by changes in the stress field at the inside corner associated with weak coupling on the Atlantis transform. Alternatively, the normal faulting within the Massif might indicate deformation of the detachment surface as it rolls over to near horizontal from an initial dip of about 60° beneath the axis, and the strike-slip events may indicate transform-parallel movement on adjacent detachment surfaces.We thank the Deep Ocean Exploration Institute at WHOI, Director of Research at WHOI, WHOI’s Department of Geology and Geophysics, and the National Science Foundation for funding the data collection.2013-04-0

Metabolic Syndrome Before and After Initiation of Antiretroviral Therapy in Treatment-Naive HIV-Infected Individuals

Metabolic syndrome (MetS) is a cluster of risk factors for cardiovascular disease and diabetes, many of which are associated with HIV and antiretroviral therapy (ART). We examined prevalence and incidence of MetS, and risk factors for MetS in ART-naïve HIV-infected individuals starting ART

The Nontriviality of Trivial General Covariance: How Electrons Restrict 'Time' Coordinates, Spinors (Almost) Fit into Tensor Calculus, and 7/16 of a Tetrad Is Surplus Structure

It is a commonplace that any theory can be written in any coordinates via tensor calculus. But it is claimed that spinors as such cannot be represented in coordinates in a curved space-time. What general covariance means for theories with fermions is thus unclear. In fact both commonplaces are wrong. Though it is not widely known, Ogievetsky and Polubarinov (OP) constructed spinors in coordinates in 1965, helping to spawn nonlinear group representations. Locally, these spinors resemble the orthonormal basis or "tetrad" formalism in the symmetric gauge, but they are conceptually self-sufficient. The tetrad formalism is de-Ockhamized, with 6 extra fields and 6 compensating gauge symmetries. OP spinors, as developed nonperturbatively by Bilyalov, admit any coordinates at a point, but "time" must be listed first: the product of the metric components and the matrix diag(-1,1,1,1) must have no negative eigenvalues to yield a real symmetric square root function of the metric. Thus the admissible coordinates depend on the types and values of the fields. Apart from coordinate order and spinorial two-valuedness, OP spinors form, with the metric, a nonlinear geometric object, with Lie and covariant derivatives. Such spinors avoid a spurious absolute object in the Anderson-Friedman analysis of substantive general covariance. They also permit the gauge-invariant localization of the infinite-component gravitational energy in GR. Density-weighted spinors exploit the conformal invariance of the massless Dirac equation to show that the volume element is absent. Thus instead of a matrix with 16 components, one can use weighted OP spinors coupled to the 9-component symmetric unimodular square root of the conformal metric density. The surprising mildness of the restrictions on coordinates for the Schwarzschild solution is exhibited. (edited)Comment: Forthcoming in \textit{Studies in History and Philosophy of Modern Physics