Three-dimensional S-wave velocity structure of oceanic core complexes at 13N on the Mid-Atlantic Ridge

13°N on the Mid-Atlantic Ridge is regarded as a type site for oceanic core complexes (OCCs). Within ~70 km along the spreading centre, it hosts four OCCs in different stages of their life cycle making this an ideal location to determine how OCCs are formed, and what drives the hydrothermal circulation that sustains the vent fields associated with them. Here we describe the results of S-wave seismic tomographic modelling within a 60 x 60 km footprint containing several OCCs, the spreading centre and both flanks. A grid of 17 wide-angle seismic refraction profiles was shot within this footprint and recorded by a network of 46 ocean-bottom seismographs (OBS). Approximately 6200 S-wave arrival travel times have been modelled, constraining primarily the velocity-depth structure of the upper-to-mid-crust. Depth slices through the resulting 3-D S-wave velocity (Vs) model reveal the OCCs located at 13°20’N and 13°30’N to each have a region of relatively low Vs (3 km s-1 ) in the inter-OCC basin and regions surrounding the detachments. Using the equivalent 3-D P-wave velocity (Vp) model of Simão et al. (2020), the corresponding Vp/Vs model is calculated to investigate lithology, permeability and the existence of any off-axis magmatic intrusions that may drive fluid flow. The Vp/Vs model clearly shows that the crust beneath the deep lava-floored inter-OCC basin is characteristically oceanic (Vp/Vs ratio of 1.85, suggesting that they formed under magma poor (tectonic) conditions. The Vp/Vs model also shows that the OCCs are not connected, at least to mid-crustal level. Alternatively, if the OCCs lie on the same detachment surface, that surface would have to undulate >3 km in amplitude over a distance of <20 km for these OCCs to appear to be unconnected. Our 3-D Swave and Vp/Vs models thus support MacLeod et al.’s (2009) model of localized OCC evolution. Our S-wave velocity model also suggests that the Irinovskoe (13°20’N) and Semyenov (13°30’N) vent fields have different hydrothermal circulation drivers, with the Semyenov field being driven by magma intrusion(s) and the Irinovskoe field being driven by the spreading centre thermal gradient and pervasive flow along open permeability within the detachment footwall, perhaps further opened by roll-over to lower dip angle as it exhumes at the seabed

The Timing of Application and Inclusion of a Surfactant Are Important for Absorption and Translocation of Foliar Phosphoric Acid by Wheat Leaves

Published: 22 November 2019Introduction: Foliar applied phosphorus (P) has the potential to provide a more tactical approach to P fertilization that could enhance P use efficiency. The aims of this study were to investigate the influence of adjuvant choice and application timing of foliar applied phosphoric acid on leaf wettability, foliar uptake, translocation, and grain yield of wheat plants. Materials and Methods: We measured the contact angles of water and fertilizers on wheat leaves, and the uptake, translocation and wheat yield response to isotopicallylabelled phosphoric acid in combination with five different adjuvants when foliar-applied to wheat at either early tillering or flag leaf emergence. Results: There was high foliar uptake of phosphoric acid in combination with all adjuvants that contained a surfactant, but only one treatment resulted in a 12% increase in grain yield and two treatments resulted in a decrease in grain yield. Despite the wettability of all foliar fertilizers being markedly different, foliar uptake was similar for all treatments that contained a surfactant. The translocation of phosphorus from foliar sources was higher when applied at a later growth stage than when applied at tillering despite the leaf surface properties that affect wettability being similar across all leaves at both growth stages. Discussion: Both the timing of foliar application and the inclusion of a surfactant in the formulation are important for absorption and translocation of phosphoric acid by wheat leaves, however high foliar uptake and translocation will not always translate to a yield increase.Courtney A. E. Peirce, Therese M. McBeath, Craig Priest and Michael J. McLaughli

Private Narratives and Infant Views: Iconizing 1970s Militancy in Contemporary Argentine Cinema

This is the author's accepted manuscript, made available with the permission of the publisher.This article analyses the connections between the subjective turn in the representation of militancy, iconicity, and historical examination in Infancia clandestina, a recent Argentine film that portrays the 1970s armed struggle through a child’s lens. Breaking with the leading interpretation that praises the movie because of its original exposition of left-leaning violence, I contend that this coming-of-age story fits within a version of militancy that originated in the mid-1990s and that has become quite common since the advent of the Kirchner administration in 2003. This particular version relies on a privatized and archaic image of activism that is at the core of the global iconization of 1970s militancy. An analysis of the filmic use of an infant perspective and of anime-style cartoons illuminates how contemporary Argentine cinema both registers and participates in this iconizing process

Research designs considerations for chronic pain prevention clinical trials: IMMPACT recommendations

Although certain risk factors can identify individuals who aremost likely to develop chronic pain, few interventions to prevent chronic pain have been identified. To facilitate the identification of preventive interventions, an IMMPACTmeeting was convened to discuss research design considerations for clinical trials investigating the prevention of chronic pain. We present general design considerations for prevention trials in populations that are at relatively high risk for developing chronic pain. Specific design considerations included subject identification, timing and duration of treatment, outcomes, timing of assessment, and adjusting for risk factors in the analyses.We provide a detailed examination of 4 models of chronic pain prevention (ie, chronic postsurgical pain, postherpetic neuralgia, chronic low back pain, and painful chemotherapy-induced peripheral neuropathy). The issues discussed can, inmany instances, be extrapolated to other chronic pain conditions. These examples were selected because they are representative models of primary and secondary prevention, reflect persistent pain resulting from multiple insults (ie, surgery, viral infection, injury, and toxic or noxious element exposure), and are chronically painful conditions that are treated with a range of interventions. Improvements in the design of chronic pain prevention trials could improve assay sensitivity and thus accelerate the identification of efficacious interventions. Such interventions would have the potential to reduce the prevalence of chronic pain in the population. Additionally, standardization of outcomes in prevention clinical trials will facilitate meta-analyses and systematic reviews and improve detection of preventive strategies emerging from clinical trials

The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set

Background Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables. Methods Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set. Results Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001). Conclusions The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy

The role of protein serine/threonine phosphatases in the regulation of human lung mast cell and basophil function

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN015464 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Structural variability of the Tonga-Kermadec forearc characterised using robustly constrained geophysical data

Subducting bathymetric anomalies enhance erosion of the overriding forearc crust. The deformation associated with this process is superimposed on pre-existing variable crustal and sedimentary structures developed as a subduction system evolves. Recent attempts to determine the effect and timescale of Louisville Ridge seamount subduction on the Tonga-Kermadec forearc have been limited by simplistic models of inherited overriding crustal structure that neglect along-strike variability. Synthesis of new robustly tested seismic velocity and density models with existing datasets from the region, highlight along-strike variations in the structure of the Tonga-Kermadec subducting and overriding plates. As the subducting plate undergoes bend-faulting and hydration throughout the trench-outer rise region, observed oceanic upper- and mid-crustal velocities are reduced by ∼1.0 km s−1 and upper mantle velocities by ∼0.5 km s−1. In the vicinity of the Louisville Ridge Seamount Chain (LRSC), the trench shallows by 4 km and normal fault throw is reduced by > 1 km, suggesting that the subduction of seamounts reduces plate deformation. We find that the extinct Eocene frontal arc, defined by a high velocity (7.0–7.4 km s−1) and density (3.2 g cm−3) lower-crustal anomaly, increases in thickness by ∼6 km, from 12 to > 18 km, over 300 km laterally along the Tonga-Kermadec forearc. Coincident variations in bathymetry and free-air gravity anomaly indicate a regional trend of northward-increasing crustal thickness that predates LRSC subduction, and highlight the present-day extent of the Eocene arc between 32° S and ∼18° S. Within this framework of existing forearc crustal structure, the subduction of seamounts of the LRSC promotes erosion of the overriding crust, forming steep, gravitationally unstable, lower-trench slopes. Trench-slope stability is most likely re-established by the collapse of the mid-trench slope and the trenchward side of the extinct Eocene arc, which, within the framework of forearc characterisation, implies seamount subduction commenced at ∼22° S

Construction and subduction of the Louisville Ridge, SW Pacific—insights from wide-angle seismic data modelling

The Louisville Ridge is a ca. 4000 km-long chain of seamounts in the SW Pacific that is currently being subducted at the Tonga-Kermadec trench. The Pacific Plate, on which the chain sits, is subducting obliquely beneath the Indo-Australian Plate. Combined with the oblique strike of the chain relative to the margin, this results in the southward migration of the ridge-trench intersection and leads to significant along-trench variation in forearc morphology as a result of tectonic erosion processes. To understand how the subduction of such large-scale plate topography controls forearc deformation, knowledge of the structure of the seamounts themselves and the crust upon which they lie, and how these seamounts are deformed prior to and on entering the trench is required. The TOTAL (Tonga Thrust earthquake Asperity at Louisville Ridge) project aimed to address these questions by undertaking a multidisciplinary geophysical study of the ridge-trench intersection and surrounding region, as part of which multichannel and wide-angle seismic, gravity and swath bathymetry data were acquired along a ∼750 km-long profile extending along the Louisville Ridge and into the adjacent Tonga forearc

Evolution and properties of young oceanic crust: constraints from Poisson's ratio

The seismic velocity of the oceanic crust is a function of its physical properties that include its lithology, degree of alteration, and porosity. Variations in these properties are particularly significant in young crust, but also occur with age as it evolves through hydrothermal circulation and is progressively covered with sediment. While such variation may be investigated through P-wave velocity alone, joint analysis with S-wave velocity allows the determination of Poisson’s ratio, which provides a more robust insight into the nature of change in these properties. Here we describe the independent modelling of P- and S-wave seismic datasets, acquired along an ~330 km-long profile traversing new to ~8 Myr-old oceanic crust formed at the intermediate-spreading Costa Rica Rift (CRR). Despite S-wave data coverage being almost four-times lower than that of the P-wave dataset, both velocity models demonstrate correlations in local variability and a long-wavelength increase in velocity with distance, and thus age, from the ridge axis of up to 0.8 and 0.6 km s-1, respectively. Using the Vp and Vs models to calculate Poisson’s ratio (s), it reveals a typical structure for young oceanic crust, with generally high values in the uppermost crust that decrease to a minimum of 0.24 by 1.0-1.5km sub-basement, before increasing again throughout the lower crust. The observed upper crustal decrease in s most likely results from sealing of fractures, which is supported by observations of a significant decrease in porosity with depth (from ~15 to 0.31) is observed throughout the crust of the north flank of the CRR axis and, whilst this falls within the ‘serpentinite’ classification of lithological proxies, morphological evidence of pervasive surface magmatism and limited tectonism suggests, instead, that the cause is porosity in the form of pervasive fracturing and, thus, that this is the dominant control on seismic velocity in the newly formed CRR crust. South of the CRR, the values of Poisson’s ratio are representative of more typical oceanic crust, and decrease with increasing distance from the spreading centre, most likely as a result of mineralisation and increased fracture infill. This is supported by borehole observations and modelled 3-D seismic anisotropy. Crustal segments formed during periods of particularly low half-spreading rate (<35 mm yr-1) demonstrate high Poisson’s ratio relative to the background, indicating the likely retention of increased porosity and fracturing associated with the greater degrees of tectonism at the time of their formation. Across the south flank of the CRR, we find that the average Poisson’s ratio in the upper 1 km of the crust decreases with age by ~0.0084 Myr1 prior to the thermal sealing of the crust, suggesting that, to at least ~7 Myr, advective hydrothermal processes dominate early CRR-generated oceanic crustal evolution, consistent with heat flow measurements