Mechanisms and recognition of hyper-extension at magma-poor rifted margins

Magma-poor rifted margins (MPRMs) are characterised by extreme crustal attenuation that increases ocean ward, serpentinised mantle, detachment fault systems and low volumes of syn-rift magmatism. An apparent “extension discrepancy” exists at MPRMs, whereby the amount of stretching accommodated by seismically observable faults is far less than that required to thin the entire crust to the extent observed on wide-angle seismic and gravity models. Unrecognised polyphase faulting can accommodate the required extension. High degrees of stretching require polyphase faulting (PPF), so that the extension discrepancy may simply be a failure to recognise multiple generations of faulting at MPRMs. The polyphase faulting hypothesis is tested through the consideration of the structural geometries likely to result, generation of synthetic seismic images from those geometries and comparison of synthetic images with reflection seismic data from the hyper-extended Porcupine Basin. From this comparison, I have identified at least two cross-cutting fault generations on the margins of the Porcupine Basin. The models demonstrate PPF can accommodate extremely high strain but is practically un-interpretable when β ≥ c.2.5, remaining hidden on hyper-extended crust. Crustal embrittlement is achievable over two fault generations (minimum) leading to hyper-extension and mantle serpentinisation, with the remaining extension likely accommodated by serpentinite detachment systems

Performance management in context: formative cross-functional performance monitoring for improvement and the mediating role of relational coordination in hospitals

Recent research suggests that to fully realise its potential, performance management should be bespoke to the social context in which it operates. Here we analyse factors supporting the use of performance data for improvement. The study purposively examines a developmentally oriented performance management system with cross-functional goals. We suggest that these system characteristics are significant in interdependent work contexts, such as healthcare. We propose and test that (a) relational coordination helps employees work effectively to resolve issues identified through formative and cross-functional performance monitoring and (b) that this contributes to better outcomes for both employees and patients. Based on survey data from management and care providers across Irish acute hospitals, the study found that perceptions of relational coordination mediated the link between formative cross-functional performance monitoring and employee outcomes and partially mediated the link between formative cross-functional performance monitoring and patient care respectively. Our findings signal potential for a more contextually driven and interdependent approach to the alignment of management and human resource management practices. While relational coordination is important in healthcare, we also note potential to identify other social drivers supporting productive responses to performance monitoring in different contexts

A review of the NE Atlantic conjugate margins based on seismic refraction data

The NE Atlantic region evolved through several rift episodes, leading to break-up in the Eocene that was associated with voluminous magmatism along the conjugate margins of East Greenland and NW Europe. Existing seismic refraction data provide good constraints on the overall tectonic development of the margins, despite data gaps at the NE Greenland shear margin and the southern Jan Mayen microcontinent. The maximum thickness of the initial oceanic crust is 40 km at the Greenland–Iceland–Faroe Ridge, but decreases with increasing distance to the Iceland plume. High-velocity lower crust interpreted as magmatic underplating or sill intrusions is observed along most margins but disappears north of the East Greenland Ridge and the Lofoten margin, with the exception of the Vestbakken Volcanic Province at the SW Barents Sea margin. South of the narrow Lofoten margin, the European side is characterized by wide margins. The opposite trend is seen in Greenland, with a wide margin in the NE and narrow margins elsewhere. The thin crust beneath the basins is generally underlain by rocks with velocities of >7 km s−1 interpreted as serpentinized mantle in the Porcupine and southern Rockall basins; while off Norway, alternative interpretations such as eclogite bodies and underplating are also discussed

Moho and basement depth in the NE Atlantic Ocean based on seismic refraction data and receiver functions

Seismic refraction data and results from receiver functions were used to compile the depth to the basement and Moho in the NE Atlantic Ocean. For interpolation between the unevenly spaced data points, the kriging technique was used. Free-air gravity data were used as constraints in the kriging process for the basement. That way, structures with little or no seismic coverage are still presented on the basement map, in particular the basins off East Greenland. The rift basins off NW Europe are mapped as a continuous zone with basement depths of between 5 and 15 km. Maximum basement depths off NE Greenland are 8 km, but these are probably underestimated. Plate reconstructions for Chron C24 (c. 54 Ma) suggest that the poorly known Ammassalik Basin off SE Greenland may correlate with the northern termination of the Hatton Basin at the conjugate margin. The most prominent feature on the Moho map is the Greenland–Iceland–Faroe Ridge, with Moho depths >28 km. Crustal thickness is compiled from the Moho and basement depths. The oceanic crust displays an increased thickness close to the volcanic margins affected by the Iceland plume

Structure of an Early Intermediate in the M-State Phase of the Bacteriorhodopsin Photocycle

AbstractThe structure of an early M-intermediate of the wild-type bacteriorhodopsin photocycle formed by actinic illumination at 230K has been determined by x-ray crystallography to a resolution of 2.0Å. Three-dimensional crystals were trapped by illuminating with actinic light at 230K, followed by quenching in liquid nitrogen. Amide I, amide II, and other infrared absorption bands, recorded from single bacteriorhodopsin crystals, confirm that the M-substate formed represents a structure that occurs early after deprotonation of the Schiff base. Rotation about the retinal C13—C14 double bond appears to be complete, but a relatively large torsion angle of 26° is still seen for the C14—C15 bond. The intramolecular stress associated with the isomerization of retinal and the subsequent deprotonation of the Schiff base generates numerous small but experimentally measurable structural changes within the protein. Many of the residues that are displaced during the formation of the late M (MN) substate formed by three-dimensional crystals of the D96N mutant (Luecke et al., 1999b) are positioned, in early M, between their resting-state locations and the ones which they will adopt at the end of the M phase. The relatively small magnitude of atomic displacements observed in this intermediate, and the well-defined positions adopted by nearly all of the atoms in the structure, may make the formation of this structure favorable to model (simulate) by molecular dynamics

Agricultural Land Use Planning and Groundwater Quality

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75123/1/j.1468-2257.1983.tb00394.x.pd

Lower mitochondrial energy production of the thigh muscles in patients with low-normal ankle-brachial index

Background--Lower muscle mitochondrial energy production may contribute to impaired walking endurance in patients with peripheral arterial disease. A borderline ankle-brachial index (ABI) of 0.91 to 1.10 is associated with poorer walking endurance compared with higher ABI. We hypothesized that in the absence of peripheral arterial disease, lower ABI is associated with lower mitochondrial energy production. Methods and Results--We examined 363 men and women participating in the Baltimore Longitudinal Study of Aging with an ABI between 0.90 and 1.40. Muscle mitochondrial energy production was assessed by post-exercise phosphocreatine recovery rate constant (kPCr) measured by phosphorus magnetic resonance spectroscopy of the left thigh. A lower post-exercise phosphocreatine recovery rate constant reflects decreased mitochondria energy production.The mean age of the participants was 71\uc2\ub112 years. A total of 18.4% had diabetes mellitus and 4% were current and 40% were former smokers. Compared with participants with an ABI of 1.11 to 1.40, those with an ABI of 0.90 to 1.10 had significantly lower post-exercise phosphocreatine recovery rate constant (19.3 versus 20.8 ms-1, P=0.015). This difference remained significant after adjusting for age, sex, race, smoking status, diabetes mellitus, body mass index, and cholesterol levels (P=0.028). Similarly, post-exercise phosphocreatine recovery rate constant was linearly associated with ABI as a continuous variable, both in the ABI ranges of 0.90 to 1.40 (standardized coefficient=0.15, P=0.003) and 1.1 to 1.4 (standardized coefficient=0.12, P=0.0405). Conclusions--An ABI of 0.90 to 1.10 is associated with lower mitochondrial energy production compared with an ABI of 1.11 to 1.40. These data demonstrate adverse associations of lower ABI values with impaired mitochondrial activity even within the range of a clinically accepted definition of a normal ABI. Further study is needed to determine whether interventions in persons with ABIs of 0.90 to 1.10 can prevent subsequent functional decline