Cemented mounds and hydrothermal sediments on the detachment surface at Kane Megamullion : a new manifestation of hydrothermal venting

Author Posting. © American Geophysical Union, 2013. 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 14 (2013): 3352–3378, doi:10.1002/ggge.20186.Long-lived detachment faults are now known to be important in tectonic evolution of slow-spreading mid-ocean ridges, and there is increasing evidence that fluid flow plays a critical role in development of detachment systems. Here we document a new manifestation of low-temperature hydrothermal venting associated with the detachment fault that formed Kane Megamullion ∼3.3–2.1 m.y. ago in the western rift-valley wall of the Mid-Atlantic Ridge. Hydrothermal effects on the detachment surface include (1) cemented mounds of igneous rock and chalk debris containing hydrothermal Mn oxides and Fe oxyhydroxides, and (2) layered deposits of similar Fe-Mn minerals ± interbedded chalks. Mounds are roughly conical, ∼1–10 m high, and contain primarily basalts with lesser gabbro, serpentinite, and polymict breccia. The layered Fe-Mn-rich sediments are flat-bedded to contorted and locally are buckled into low-relief linear or polygonal ridges. We propose that the mounds formed where hydrothermal fluids discharged through the detachment hanging wall near the active fault trace. Hydrothermal precipitates cemented hanging-wall debris and welded it to the footwall, and this debris persisted as mounds as the footwall was exhumed and surrounding unconsolidated material sloughed off the sloping detachment surface. Some of the layered Fe-Mn-rich deposits may have precipitated from fluids discharging from the hanging-wall vents, but they also precipitated from low-temperature fluids venting from the exposed footwall through overlying chalks. Observed natural disturbance and abnormally thin hydrogenous Fe-Mn crusts on some contorted, hydrothermal Fe-Mn-rich chalks on ∼2.7 Ma crust suggest diffuse venting that is geologically recent. Results of this study imply that there are significant fluid pathways through all parts of detachment systems and that low-temperature venting through fractured detachment footwalls may continue for several million years off-axis.NSF grant 0118445 supported data acquisition and processing for Knorr Cruise 180- 2. The Deep Ocean Exploration Institute at Woods Hole Oceanographic Institution supported research and analytical costs for this study.2014-03-0

A Recommitment Strategy for Long Term Private Equity Fund Investors

This paper develops a reinvestment strategy for private equity which aims to keep its portfolio weight equal to a desired strategic allocation, while taking into account the illiquid nature of private equity. Historical simulations (1980-2005) show that our dynamic strategy is capable of maintaining a stable investment level that is close to the target. This does not only hold for unrestricted portfolios, but also for investments limited to buyout or venture capital, a specific region, or management experience. This finding is of great importance for investors, because private equity funds have a finite lifetime and uncertain cash flows

NAVY EXPEDITIONARY ADDITIVE MANUFACTURING (NEAM) CAPABILITY INTEGRATION

This capstone report analyzes the current and future use of additive manufacturing (AM) technologies within the Department of Defense (DOD). This analysis provided the technical background necessary to develop the Additive Manufacturing Process and Analysis Tool (AMPAT). AMPAT will help stakeholders identify what AM equipment best serves warfighters and their missions in expeditionary environments. Furthermore, the tool can be used by stakeholders to identify the most advantageous dispersions of AM capabilities across the fleet and make decisions on how those capabilities should be integrated into the greater naval mission and larger DOD enterprise. A systems engineering (SE) approach was implemented to gather information on current and prospective AM methods in order to understand and define the AM system operational requirements. Additionally, an SE process was utilized to analyze alternative software options to build the tool, implement agile software development processes to develop the tool, and verify and validate that the tool met the project requirements. The study found that AMPAT successfully outputs a ranked list of AM systems recommendations based upon user-defined input parameters and weighting values. Recommendations for choosing AM equipment and developing dispersion plans for the fleet include using the AMPAT deliverable to conduct customized, iterative analysis with user-defined inputs that are tailored to specific expeditionary environments.Outstanding ThesisCivilian, Department of the NavyCivilian, Department of the NavyCivilian, Department of the NavyCivilian, Department of the ArmyCivilian, Department of the NavyApproved for public release. Distribution is unlimited

Mylonitic deformation at the Kane oceanic core complex : implications for the rheological behavior of oceanic detachment faults

Author Posting. © American Geophysical Union, 2013. 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 14 (2013): 3085–3108, doi:10.1002/ggge.20184.The depth extent, strength, and composition of oceanic detachment faults remain poorly understood because the grade of deformation-related fabrics varies widely among sampled oceanic core complexes (OCCs). We address this issue by analyzing fault rocks collected from the Kane oceanic core complex at 23°30′N on the Mid-Atlantic Ridge. A portion of the sample suite was collected from a younger fault scarp that cuts the detachment surface and exposes the interior of the most prominent dome. The style of deformation was assessed as a function of proximity to the detachment surface, revealing a ∼450 m thick zone of high-temperature mylonitization overprinted by a ∼200 m thick zone of brittle deformation. Geothermometry of deformed gabbros demonstrates that crystal-plastic deformation occurred at temperatures >700°C. Analysis of the morphology of the complex in conjunction with recent thermochronology suggests that deformation initiated at depths of ∼7 km. Thus we suggest the detachment system extended into or below the brittle-plastic transition (BPT). Microstructural evidence suggests that gabbros and peridotites with high-temperature fabrics were dominantly deforming by dislocation-accommodated processes and diffusion creep. Recrystallized grain size piezometry yields differential stresses consistent with those predicted by dry-plagioclase flow laws. The temperature and stress at the BPT determined from laboratory-derived constitutive models agree well with the lowest temperatures and highest stresses estimated from gabbro mylonites. We suggest that the variation in abundance of mylonites among oceanic core complexes can be explained by variation in the depth of the BPT, which depends to a first order on the thermal structure and water content of newly forming oceanic lithosphere.Knorr Cruise 180-2 data and sample acquisition was supported by NSF grant 0118445.2014-02-2

Plutonic foundation of a slow-spreading ridge segment : oceanic core complex at Kane Megamullion, 23°30′N, 45°20′W

Author Posting. © American Geophysical Union, 2008. 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 9 (2008): Q05014, doi:10.1029/2007GC001645.We mapped the Kane megamullion, an oceanic core complex on the west flank of the Mid-Atlantic Ridge exposing the plutonic foundation of a ∼50 km long, second-order ridge segment. The complex was exhumed by long-lived slip on a normal-sense detachment fault at the base of the rift valley wall from ∼3.3 to 2.1 Ma (Williams, 2007). Mantle peridotites, gabbros, and diabase dikes are exposed in the detachment footwall and in outward facing high-angle normal fault scarps and slide-scar headwalls that cut through the detachment. These rocks directly constrain crustal architecture and the pattern of melt flow from the mantle to and within the lower crust. In addition, the volcanic carapace that originally overlay the complex is preserved intact on the conjugate African plate, so the complete internal and external architecture of the paleoridge segment can be studied. Seafloor spreading during formation of the core complex was highly asymmetric, and crustal accretion occurred largely in the footwall of the detachment fault exposing the core complex. Because additions to the footwall, both magmatic and amagmatic, are nonconservative, oceanic detachment faults are plutonic growth faults. A local volcano and fissure eruptions partially cover the northwestern quarter of the complex. This volcanism is associated with outward facing normal faults and possible, intersecting transform-parallel faults that formed during exhumation of the megamullion, suggesting the volcanics erupted off-axis. We find a zone of late-stage vertical melt transport through the mantle to the crust in the southern part of the segment marked by a ∼10 km wide zone of dunites that likely fed a large gabbro and troctolite intrusion intercalated with dikes. This zone correlates with the midpoint of a lineated axial volcanic high of the same age on the conjugate African plate. In the central region of the segment, however, primitive gabbro is rare, massive depleted peridotite tectonites abundant, and dunites nearly absent, which indicate that little melt crossed the crust-mantle boundary there. Greenschist facies diabase and pillow basalt hanging wall debris are scattered over the detachment surface. The diabase indicates lateral melt transport in dikes that fed the volcanic carapace away from the magmatic centers. At the northern edge of the complex (southern wall of the Kane transform) is a second magmatic center marked by olivine gabbro and minor troctolite intruded into mantle peridotite tectonite. This center varied substantially in size with time, consistent with waxing and waning volcanism near the transform as is also inferred from volcanic abyssal-hill relief on the conjugate African plate. Our results indicate that melt flow from the mantle focuses to local magmatic centers and creates plutonic complexes within the ridge segment whose position varies in space and time rather than fixed at a single central point. Distal to and between these complexes there may not be continuous gabbroic crust, but only a thin carapace of pillow lavas overlying dike complexes laterally fed from the magmatic centers. This is consistent with plate-driven flow that engenders local, stochastically distributed transient instabilities at depth in the partially molten mantle that fed the magmatic centers. Fixed boundaries, such as large-offset fracture zones, or relatively short segment lengths, however, may help to focus episodes of repeated melt extraction in the same location. While no previous model for ocean crust is like that inferred here, our observations do not invalidate them but rather extend the known diversity of ridge architecture.NSF Grants OCE-0118445, OCE-0624408 and OCE-0621660 supported this research. B. Tucholke was also supported by the Henry Bryant Bigelow Chair in Oceanography at Woods Hole Oceanographic Institution

The metabolic enzyme hexokinase 2 localizes to the nucleus in AML and normal haematopoietic stem and progenitor cells to maintain stemness

Thomas, Egan et al. report that hexokinase 2 localizes to the nucleus of leukaemic and normal haematopoietic cells to maintain stemness by interacting with nuclear proteins and modulating chromatin accessibility independently of its kinase activity. Mitochondrial metabolites regulate leukaemic and normal stem cells by affecting epigenetic marks. How mitochondrial enzymes localize to the nucleus to control stem cell function is less understood. We discovered that the mitochondrial metabolic enzyme hexokinase 2 (HK2) localizes to the nucleus in leukaemic and normal haematopoietic stem cells. Overexpression of nuclear HK2 increases leukaemic stem cell properties and decreases differentiation, whereas selective nuclear HK2 knockdown promotes differentiation and decreases stem cell function. Nuclear HK2 localization is phosphorylation-dependent, requires active import and export, and regulates differentiation independently of its enzymatic activity. HK2 interacts with nuclear proteins regulating chromatin openness, increasing chromatin accessibilities at leukaemic stem cell-positive signature and DNA-repair sites. Nuclear HK2 overexpression decreases double-strand breaks and confers chemoresistance, which may contribute to the mechanism by which leukaemic stem cells resist DNA-damaging agents. Thus, we describe a non-canonical mechanism by which mitochondrial enzymes influence stem cell function independently of their metabolic function

Crustal Evolution of the Mid-Atlantic Ridge near the Fifteen-Twenty Fracture Zone in the last 5 Ma

Author Posting. © American Geophysical Union, 2003. 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 4 (2003): 1024, doi:10.1029/2002GC000364.The Mid-Atlantic Ridge around the Fifteen-Twenty Fracture Zone is unique in that outcrops of lower crust and mantle rocks are extensive on both flanks of the axial valley walls over an unusually long distance along-axis, indicating a high ratio of tectonic to magmatic extension. On the basis of newly collected multibeam bathymetry, magnetic, and gravity data, we investigate crustal evolution of this unique section of the Mid-Atlantic Ridge over the last 5 Ma. The northern and southern edges of the study area, away from the fracture zone, contain long abyssal hills with small spacing and fault throw, well lineated and high-amplitude magnetic signals, and residual mantle Bouguer anomaly (RMBA) lows, all of which suggest relatively robust magmatic extension. In contrast, crust in two ridge segments immediately north of the fracture zone and two immediately to the south is characterized by rugged and blocky topography, by low-amplitude and discontinuous magnetization stripes, and by RMBA highs that imply thin crust throughout the last 5 Ma. Over these segments, morphology is typically asymmetric across the spreading axis, indicating significant tectonic thinning of crust caused by faults that have persistently dipped in only one direction. North of the fracture zone, however, megamullions are that thought to have formed by slip on long-lived normal faults are found on both ridge flanks at different ages and within the same spreading segment. This unusual partitioning of megamullions can be explained either by a ridge jump or by polarity reversal of the detachment fault following formation of the first megamullion.This work was completed while T. Fujiwara was a Guest Investigator at Woods Hole Oceanographic Institution with funding from Japan Marine Science and Technology Center (JAMSTEC), National Science Foundation, and the JAMSTEC Research Overseas Program. J. Lin’s contributions to this research were supported by NSF Grant OCE-9811924. B. E. Tucholke’s contributions were supported by NSF Grant OCE-9503561 and by the Andrew W. Mellon Endowment Fund for Innovative Research and the Henry Bryant Bigelow Chair at Woods Hole Oceanographic Institution

Tuberculosis Incidence in Prisons: A Systematic Review

A systematic review by Iacopo Baussano and colleagues synthesizes published research to show that improved tuberculosis (TB) control in prisons could significantly reduce the burden of TB both inside and outside prisons

The Toronto prehospital hypertonic resuscitation-head injury and multi organ dysfunction trial (TOPHR HIT) - Methods and data collection tools

<p>Abstract</p> <p>Background</p> <p>Clinical trials evaluating the use of hypertonic saline in the treatment of hypovolemia and head trauma suggest no survival superiority over normal saline; however subgroup analyses suggest there may be a reduction in the inflammatory response and multiorgan failure which may lead to better survival and enhanced neurocognitive function. We describe a feasibility study of randomizing head injured patients to hypertonic saline and dextran vs. normal saline administration in the out of hospital setting.</p> <p>Methods/Design</p> <p>This feasibility study employs a randomized, placebo-controlled design evaluating normal saline compared with a single dose of 250 ml of 7.5% hypertonic saline in 6% dextran 70 in the management of traumatic brain injuries. The primary feasibility endpoints of the trial were: 1) baseline survival rates for the treatment and control group to aid in the design of a definitive multicentre trial, 2) randomization compliance rate, 3) ease of protocol implementation in the out-of-hospital setting, and 4) adverse event rate of HSD infusion.</p> <p>The secondary objectives include measuring the effect of HSD in modulating the immuno-inflammatory response to severe head injury and its effect on modulating the release of neuro-biomarkers into serum; evaluating the role of serum neuro-biomarkers in predicting patient outcome and clinical response to HSD intervention; evaluating effects of HSD on brain atrophy post-injury and neurocognitive and neuropsychological outcomes.</p> <p>Discussion</p> <p>We anticipate three aspects of the trial will present challenges to trial success; ethical demands associated with a waiver of consent trial, challenging follow up and comprehensive accurate timely data collection of patient identifiers and clinical or laboratory values. In addition all the data collection tools had to be derived de novo as none existed in the literature.</p> <p>Trial registration number</p> <p>NCT00878631</p