Opposing shear senses in a subdetachment mylonite zone: Implications for core complex mechanics

[1] Global studies of metamorphic core complexes and low‐angle detachment faults have highlighted a fundamental problem: Since detachments excise crustal section, the relationship between the mylonitic rocks in their footwalls and the brittle deformation in their hanging walls is commonly unclear. Mylonites could either reflect ductile deformation related to exhumation along the detachment fault, or they could be a more general feature of the extending middle crust that has been “captured ” by the detachment. In the first case we would expect the kinematics of the mylonite zone to mirror the sense of movement on the detachment; in the second case both the direction and sense of shear in the mylonites could be different. The northern Snake Range décollement (NSRD) is a classic Basin and Range detachment fault with a well‐documented top‐east of displacement. We present structural, paleo-magnetic, geochronological, and geothermometric evidence to suggest that the mylonite zone below the NSRD locally experienced phases of both east ‐ and west‐directed shear, inconsistent with movement along a single detachment fault. We therefore propose that the footwall mylonites represent a predetachment dis-continuity in the middle crust that separated localized deformation above from distributed crustal flow below (localized‐distributed transition (LDT)). The mylonites were subsequently captured by a moderately dipping brittle detachment that soled down to the middle crust and exhumed them around a rolling hinge into a subhorizontal orientation at the surface, produc-ing the present‐day NSRD. In this interpretation the brittle hanging wall represents a series of rotated upper crustal normal faults, whereas the mylonitic footwall represents one or more exhumed middl

The Effect of Mechanical Remoulding on the compression and strength characteristics of a Mercia Mudstone

A series of laboratory tests have been undertaken as part of a larger study into the effect of continuous flight auger pile installation on the soil-pile interface in the Mercia Mudstone Group [1]. This paper reports the results of stress path triaxial tests on bulk samples of the mudstone which have been subjected to varying amounts of mechanical remoulding representing the remoulding that occurs due to the action of the auger. In addition, the water content at which remoulding takes place has been varied. The tests were undertaken to investigate whether the silt sized aggregates of clay particles that exist [2] within this soil could be broken up by the mechanical remoulding and whether this would affect the compression and strength properties of the mudstone. It was found that both mechanical remoulding and the water content at which this is carried out affect the subsequent response of the soil

Remoulding of the Mercia Mudstone Group around CFA pile shafts

A field test has been undertaken to investigate changes to in situ Mercia Mudstone at the pile soil interface after installation of four 5.5 m long 350 mm diameter CFA piles. The test investigated whether a remoulded zone exists, the extent of the zone, changes caused by remoulding and the effect of the installation method. The piles and surrounding soil were excavated after installation to a depth of just under 2 m. The sections of pile and surrounding soil were returned to the laboratory where a variety of detailed observations at both micro and macroscopic scales were undertaken, together with chemical and mineralogical analysis. It was found that a remoulded zone existed in all piles but that this varied in thickness both laterally and vertically around a pile. Across all piles the maximum thickness observed was 55 mm. The average thickness, fabric and texture were all affected by installation method. A distinctive vertically orientated fabric was observed in which up to four vertically orientated layers could be distinguished. There was evidence of changes in texture/fabric, structure, colour, mineralogy and chemistry

Subcutaneous Neurotophin 4 Infusion Using Osmotic Pumps or Direct Muscular Injection Enhances Aging Rat Laryngeal Muscles

Laryngeal dysfunction in the elderly is a major cause of disability, from voice disorders to dysphagia and loss of airway protective reflexes. Few, if any, therapies exist that target age-related laryngeal muscle dysfunction. Neurotrophins are involved in muscle innervation and differentiation of neuromuscular junctions (NMJs). It is thought that neurotrophins enhance neuromuscular transmission by increasing neurotransmitter release. The neuromuscular junctions (NMJs) become smaller and less abundant in aging rat laryngeal muscles, with evidence of functional denervation. We explored the effects of NTF4 for future clinical use as a therapeutic to improve function in aging human laryngeal muscles. Here, we provide the detailed protocol for systemic application and direct injection of NTF4 to investigate the ability of aging rat laryngeal muscle to remodel in response to NTF4 application. In this method, rats either received NTF4 either systemically via osmotic pump or by direct injection through the vocal folds. Laryngeal muscles were then dissected and used for histological examination of morphology and age-related denervation

X-ray Observations of the Compact Source in CTA 1

The point source RX J0007.0+7302, at the center of supernova remnant CTA 1, was studied using the X-Ray Multi-mirror Mission. The X-ray spectrum of the source is consistent with a neutron star interpretation, and is well described by a power law with the addition of a soft thermal component that may correspond to emission from hot polar cap regions or to cooling emission from a light element atmosphere over the entire star. There is evidence of extended emission on small spatial scales which may correspond to structure in the underlying synchrotron nebula. No pulsations are observed. Extrapolation of the nonthermal spectrum of RX J0007.0+7302 to gamma-ray energies yields a flux consistent with that of EGRET source 3EG J0010+7309, supporting the proposition that there is a gamma-ray emitting pulsar at the center of CTA 1. Observations of the outer regions of CTA 1 with the Advanced Satellite for Cosmology and Astrophysics confirm earlier detections of thermal emission from the remnant and show that the synchrotron nebula extends to the outermost reaches of the SNR.Comment: 5 pages, including 4 postscript figs.LaTex. Accepted for publication by Ap

Chandra Observation of the Magellanic Cloud Supernova Remnant 0454-672 in N9

A Chandra observation has defined the extent of the SNR B 0454-692 in the LMC H II region N9. The remnant has dimension 2.3" x 3.6" and is elongated in the NS direction. The brightest emission comes from a NS central ridge which includes three bright patches. There is good agreement between X-ray and [O III] and [S II] morphology. The remnant is old enough so that optical data give more information about dynamics than do the X-ray data. The SN energy release was >= 4 x 10^50 ergs and the age is ~3 x 10^4 years. There are several unresolved sources nearby but none are clearly associated with the remnant. The X-ray spectrum is soft and indicates enhanced Fe abundance in the central region, consistent with a Type Ia SN origin, but a Type II origin cannot be ruled out.Comment: AASTeX, 20 pages including 5 figures. Accepted for publication in The Astrophysical Journal. Figures have been reduced in resolution for space requirements; full-resolution figures may be requested by email to [email protected]

X-Ray Light Curves of Gamma-ray Bursts Detected with the All-Sky Monitor on RXTE

We present X-ray light curves (1.5-12 keV) for fifteen gamma-ray bursts (GRBs) detected by the All-Sky Monitor on the Rossi X-ray Timing Explorer. We compare these soft X-ray light curves with count rate histories obtained by the high-energy (>12 keV) experiments BATSE, Konus-Wind, the BeppoSAX Gamma-Ray Burst Monitor, and the burst monitor on Ulysses. We discuss these light curves within the context of a simple relativistic fireball and synchrotron shock paradigm, and we address the possibility of having observed the transition between a GRB and its afterglow. The light curves show diverse morphologies, with striking differences between energy bands. In several bursts, intervals of significant emission are evident in the ASM energy range with little or no corresponding emission apparent in the high-energy light curves. For example, the final peak of GRB 970815 as recorded by the ASM is only detected in the softest BATSE energy bands. We also study the duration of bursts as a function of energy. Simple, singly-peaked bursts seem consistent with the E^{-0.5} power law expected from an origin in synchrotron radiation, but durations of bursts that exhibit complex temporal structure are not consistent with this prediction. Bursts such as GRB 970828 that show many short spikes of emission at high energies last significantly longer at low energies than the synchrotron cooling law would predict.Comment: 15 pages with 20 figures and 2 tables. In emulateapj format. Accepted by ApJ