601 research outputs found
Rare earth element fluorocarbonate minerals from the olympic dam Cu-U-Au-Ag deposit, South Australia
Olympic Dam is a world-class breccia-hosted iron-oxide copper-gold-uranium ore deposit located in the Gawler Craton, South Australia. It contains elevated concentrations of rare earth elements (REE) which occur as the REE minerals bastnäsite, synchysite, florencite, monazite, and xenotime. This is the first study to focus on the mineralogy and composition of the most abundant REE mineral at Olympic Dam, bastnäsite, and subordinate synchysite. The sample suite extends across the deposit and represents different sulfide mineralization styles (chalcopyrite-bornite and bornite-chalcocite) and breccias of various types, ranging from those dominated by clasts of granite, dykes, and hematite. The REE-fluorocarbonates (bastnäsite and synchysite) typically occur as fine-grained (<50 m) disseminations in Cu-Fe-sulfides and gangue minerals, and also within breccia matrix. They are also locally concentrated within macroscopic REE-mineral-rich pockets at various locations across the deposit. Such coarse-grained samples formed the primary target of this study. Three general textural groups of bastnäsite are recognized: matrix (further divided into disseminated, fine-grained, and stubby types), irregular (sulfide-associated), and clast replacement. Textures are largely driven by the specific location and prevailing mineral assemblage, with morphology and grain size often controlled by the associated minerals (hematite, sulfides). Major element concentration data reveal limited compositional variation among the REE-fluorocarbonates; all are Ce-dominant. Subtle compositional differences among REE-fluorocarbonates define a spectrum from relatively La-enriched to (Ce + Nd)-enriched phases. Granite-derived hydrothermal fluids were the likely source of F in the REE-fluorocarbonates, as well as some of the CO₂, which may also have been contributed by associated mafic-ultramafic magmatism. However, transport of REE by Cl-ligands is the most likely scenario. Stubby bastnäsite and synchysite may have formed earlier, coincident with hydrothermal alteration of granite releasing Ca from feldspars. Other categories of bastnäsite, notably those co-existing with sulfides, and reaching the top of the IOCG mineralization at Olympic Dam (chalcocite + bornite zone) are relatively younger. Such an interpretation is concordant with subtle changes in the REE patterns for the different categories. The common association of bastnäsite and fluorite throughout the deposit is typical of the hematite breccias and can be deposited from neutral, slightly acidic fluids (sericite stability) at T ≈ 300 °C.Danielle S. Schmandt, Nigel J. Cook, Cristiana L. Ciobanu, Kathy Ehrig, Benjamin P. Wade, Sarah Gilbert and Vadim S. Kamenetsk
A Radial Velocity Study of CTCV J1300-3052
We present time-resolved spectroscopy of the eclipsing, short period
cataclysmic variable CTCV J1300-3052. Using absorption features from the
secondary star, we determine the radial velocity semi-amplitude of the
secondary star to be K2 = 378 \pm 6 km/s, and its projected rotational velocity
to be v sin i = 125 \pm 7 km/s. Using these parameters and Monte Carlo
techniques, we obtain masses of M1 = 0.79 \pm 0.05 MSun for the white dwarf
primary and M2 = 0.198 \pm 0.029 MSun for the M-type secondary star. These
parameters are found to be in excellent agreement with previous mass
determinations found via photometric fitting techniques, supporting the
accuracy and validity of photometric mass determinations in short period CVs.Comment: Accepted for publication in MNRAS (24th January 2012). 10 pages, 9
figures (black and white
Variation in the SLC23A1 gene does not influence cardiometabolic outcomes to the extent expected given its association with L-ascorbic acid
Background: Observational studies showed that circulating L-ascorbic acid (vitamin C) is inversely associated with cardiometabolic traits. However, these studies were susceptible to confounding and reverse causation. Objectives: We assessed the relation between L-ascorbic acid and 10 cardiometabolic traits by using a single nucleotide polymorphism in the solute carrier family 23 member 1 (SLC23A1) gene (rs33972313) associated with circulating L-ascorbic acid concentrations. The observed association between rs33972313 and cardiometabolic outcomes was compared with that expected given the rs33972313-L-ascorbic acid and L-ascorbic acid-outcome associations. Design: A meta-analysis was performed in the following 5 independent studies: the British Women's Heart and Health Study (n = 1833), the MIDSPAN study (n = 1138), the Ten Towns study (n = 1324), the British Regional Heart Study (n = 2521), and the European Prospective Investigation into Cancer (n = 3737). Results: With the use of a meta-analysis of observational estimates, inverse associations were shown between L-ascorbic acid and systolic blood pressure, triglycerides, and the waist-hip ratio [the strongest of which was the waist-hip ratio (-0.13-SD change; 95% CI: -0.20-, -0.07-SD change; P = 0.0001) per SD increase in L-ascorbic acid], and a positive association was shown with high-density lipoprotein (HDL) cholesterol. The variation at rs33972313 was associated with a 0.18-SD (95% CI: 0.10-, 0.25-SD; P = 3.34 × 10⁻⁶) increase in L-ascorbic acid per effect allele. There was no evidence of a relation between the variation at rs33972313 and any cardiometabolic outcome. Although observed estimates were not statistically different from expected associations between rs33972313 and cardiometabolic outcomes, estimates for low-density lipoprotein cholesterol, HDL cholesterol, triglycerides, glucose, and body mass index were in the opposite direction to those expected.The nature of the genetic association exploited in this study led to limited statistical application, but despite this, when all cardiometabolic traits were assessed, there was no evidence of any trend supporting a protective role of L-ascorbic acid. In the context of existing work, these results add to the suggestion that observational relations between L-ascorbic acid and cardiometabolic health may be attributable to confounding and reverse causation.Kaitlin H Wade, Nita G Forouhi, Derek G Cook, Paul Johnson, Alex McConnachie, Richard W Morris, Santiago Rodriguez, Zheng Ye, Shah Ebrahim, Sandosh Padmanabhan, Graham Watt, K Richard Bruckdorfer, Nick J Wareham, Peter H Whincup, Stephen Chanock, Naveed Sattar, Debbie A Lawlor, George Davey Smith and Nicholas J Timpso
Surgical site infection following surgery for hand trauma: a systematic review and meta-analysis
Surgical site infection is the most common healthcare-associated infection. Surgical site infection after surgery for hand trauma is associated with increased antibiotic prescribing, re-operation, hospital readmission and delayed rehabilitation, and in severe cases may lead to amputation. As the risk of surgical site infection after surgery for hand trauma remains unclear, we performed a systematic review and meta-analysis of all primary studies of hand trauma surgery, including randomized controlled trials, cohort studies, case-control studies and case series. A total of 8836 abstracts were screened, and 201 full studies with 315,618 patients included. The meta-analysis showed a 10% risk of surgical site infection in randomized control trials, with an overall risk of 5% when all studies were included. These summary statistics can be used clinically for informed consent and shared decision making, and for power calculations for future clinical trials of antimicrobial interventions in hand trauma
Tin-bearing magnetite with nanoscale Mg-Si defects: Evidence for the early stages of mineralization in a skarn system
Tin-bearing magnetite is reported from several types of magmatic-hydrothermal ore deposits. The question of whether tin is incorporated within solid solution, as Sn4+, or as nanoinclusions remains open, however. We report a micron- to nanoscale investigation of Sn (Mg, Si)-bearing magnetite from serpentinite in the Dulong Zn-Sn-In skarn, South China, with the dual aims of understanding the mechanisms involved in accommodating Sn and associated elements into the Fe-oxide, and the inferences that this carries for constraining the early stages of skarn formation. Magnetite preserves a range of textures that record the evolution of metasomatism during prograde growth of grain cores and retrograde rim replacement. Observations reveal the presence of chondrodite and sellaite (MgF2) as nanoscale inclusions preserved in magnetite. This implies initiation of the Dulong mineralizing system during a humite-bearing, magnesium skarn stage. Magnesium-Si defects, forming along (110) planes prior to Sn-enrichment, are recognized for the first time. Release of high volatile, F-rich fluids is interpreted to lead to precipitation of cassiterite inclusions along <111*> directions in magnetite
Magnetic Field Generation in Stars
Enormous progress has been made on observing stellar magnetism in stars from
the main sequence through to compact objects. Recent data have thrown into
sharper relief the vexed question of the origin of stellar magnetic fields,
which remains one of the main unanswered questions in astrophysics. In this
chapter we review recent work in this area of research. In particular, we look
at the fossil field hypothesis which links magnetism in compact stars to
magnetism in main sequence and pre-main sequence stars and we consider why its
feasibility has now been questioned particularly in the context of highly
magnetic white dwarfs. We also review the fossil versus dynamo debate in the
context of neutron stars and the roles played by key physical processes such as
buoyancy, helicity, and superfluid turbulence,in the generation and stability
of neutron star fields.
Independent information on the internal magnetic field of neutron stars will
come from future gravitational wave detections. Thus we maybe at the dawn of a
new era of exciting discoveries in compact star magnetism driven by the opening
of a new, non-electromagnetic observational window.
We also review recent advances in the theory and computation of
magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo
theory. These advances offer insight into the action of stellar dynamos as well
as processes whichcontrol the diffusive magnetic flux transport in stars.Comment: 41 pages, 7 figures. Invited review chapter on on magnetic field
generation in stars to appear in Space Science Reviews, Springe
A systematic review and meta-synthesis of the impact of low back pain on people's lives
Copyright @ 2014 Froud et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly credited.Background - Low back pain (LBP) is a common and costly problem that many interpret within a biopsychosocial model. There is renewed concern that core-sets of outcome measures do not capture what is important. To inform debate about the coverage of back pain outcome measure core-sets, and to suggest areas worthy of exploration within healthcare consultations, we have synthesised the qualitative literature on the impact of low back pain on people’s lives.
Methods - Two reviewers searched CINAHL, Embase, PsycINFO, PEDro, and Medline, identifying qualitative studies of people’s experiences of non-specific LBP. Abstracted data were thematic coded and synthesised using a meta-ethnographic, and a meta-narrative approach.
Results - We included 49 papers describing 42 studies. Patients are concerned with engagement in meaningful activities; but they also want to be believed and have their experiences and identity, as someone ‘doing battle’ with pain, validated. Patients seek diagnosis, treatment, and cure, but also reassurance of the absence of pathology. Some struggle to meet social expectations and obligations. When these are achieved, the credibility of their pain/disability claims can be jeopardised. Others withdraw, fearful of disapproval, or unable or unwilling to accommodate social demands. Patients generally seek to regain their pre-pain levels of health, and physical and emotional stability. After time, this can be perceived to become unrealistic and some adjust their expectations accordingly.
Conclusions - The social component of the biopsychosocial model is not well represented in current core-sets of outcome measures. Clinicians should appreciate that the broader impact of low back pain includes social factors; this may be crucial to improving patients’ experiences of health care. Researchers should consider social factors to help develop a portfolio of more relevant outcome measures.Arthritis Research U
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