65 research outputs found
Controls on the rheological properties of peridotite at a palaeosubduction interface: A transect across the base of the Oman-UAE ophiolite
Studies of experimentally deformed rocks and small-scale natural shear zones have
demonstrated that volumetrically minor phases can control strain localisation by limiting grain growth
and promoting grain-size sensitive deformation mechanisms. These small-scale studies are often used
to infer a critical role for minor phases in the development of plate boundaries. However, the role of
minor phases in strain localisation at an actual plate boundary remains to be tested by direct
observation. In order to test the hypothesis that minor phases control strain localisation at plate
boundaries, we conducted microstructural analyses of peridotite samples collected along a ~1 km
transect across the base of the Oman-United Arab Emirates (UAE) ophiolite. The base of the ophiolite
is marked by the Semail thrust, which represents the now exhumed contact between subducted
oceanic crust and the overlying mantle wedge. As such, the base of the ophiolite provides the
opportunity to directly examine a former plate boundary.
Our results demonstrate that the mean olivine grain size is inversely proportional to the
abundance of minor phases (primarily orthopyroxene, as well as clinopyroxene, hornblende, and
spinel), consistent with suppression of grain growth by grain-boundary pinning. Our results also
reveal that mean olivine grain size is proportional to CPO strength (both of which generally decrease
towards the metamorphic sole), suggesting that the fraction of strain produced by different
deformation mechanisms varied spatially. Experimentally-derived flow laws indicate that under the
inferred deformation conditions, the viscosity of olivine was grain-size sensitive. As such, grain size,
and thereby the abundance of minor phases, influenced viscosity during subduction-related
deformation along the base of the mantle wedge.
We calculate an order of magnitude decrease in the viscosity of olivine towards the base of
the ophiolite, which suggests strain was localized near the subduction interface. Our data indicate that
this rheological weakening was primarily the result of more abundant minor phases near the base of
the ophiolite. Our interpretations are consistent with those of previous studies on experimentally
deformed rocks and smaller-scale natural shear zones that indicate minor phases can exert the primary
control on strain localisation. However, our study demonstrates for the first time that minor phases can
control strain localisation at the scales relevant to a major plate boundar
Reconciling Himalayan midcrustal discontinuities: The Main Central thrust system
The occurrence of thrust-sense tectonometamorphic discontinuities within the exhumed Himalayan metamorphic core can be explained as part of the Main Central thrust system. This imbricate thrust structure, which significantly thickened the orogenic midcrustal core, comprises a series of thrust-sense faults that all merge into a single detachment. The existence of these various structures, and their potential for complex overprinting along the main detachment, may help explain the contention surrounding the definition, mapping, and interpretation of the Main Central thrust. The unique evolution of specific segments of the Main Central thrust system along the orogen is interpreted to be a reflection of the inherent basement structure and ramp position, and structural level of exposure of the mid-crust. This helps explain the variation in the timing and structural position of tectonometamorphic discontinuities along the length of the mountain belt
Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial
Background: The EMPA KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population. Methods: EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained â„40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110. Findings: Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5â2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62â0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16â1·59), representing a 50% (42â58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1). Interpretation: In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease. Funding: Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
Taxonomy of Ophiuroidea (Echinonermata) from the continental shelf and slope of the southern and southeastern Brazilian coast
Diet segregation in American bison (Bison bison) of Yellowstone National Park (Wyoming, USA)
Bad Behavior in Groups
Recent research shows the powerful impact of counterproductive behavior in teams. This study explores how team characteristics combine to influence bad behavior in groups. It builds upon recent work in organizational justice by exploring the relationship between overall justice climate and work groups\u27 deviant and political behavior. Findings suggest that the structure of the work itself, in the form of functional dependence, moderates this relationship. Specifically, it is argued that the relationship between injustice climate and deviant and political behavior will be strongest when functional dependence between employees is low. Results from a sample of 539 employees and 113 supervisors in 113 work units support the hypotheses. © The Author(s) 2013
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