Strain localization driven by thermal decomposition during seismic shear

Field and laboratory observations show that shear deformation is often extremely localized at seismic slip rates, with a typical deforming zone width on the order of a few tens of microns. This extreme localization can be understood in terms of thermally driven weakening mechanisms. A zone of initially high strain rate will experience more shear heating and thus weaken faster, making it more likely to accommodate subsequent deformation. Fault zones often contain thermally unstable minerals such as clays or carbonates, which devolatilize at the high temperatures attained during seismic slip. In this paper, we investigate how these thermal decomposition reactions drive strain localization when coupled to a model for thermal pressurization of in situ groundwater. Building on Rice et al. (2014), we use a linear stability analysis to predict a localized zone thickness that depends on a combination of hydraulic, frictional, and thermochemical properties of the deforming fault rock. Numerical simulations show that the onset of thermal decomposition drives additional strain localization when compared with thermal pressurization alone and predict localized zone thicknesses of ∼7 and ∼13 μm for lizardite and calcite, respectively. Finally we show how thermal diffusion and the endothermic reaction combine to limit the peak temperature of the fault and that the pore fluid released by the reaction provides additional weakening of ∼20–40% of the initial strength

CENP-meta, an essential kinetochore kinesin required for the maintenance of metaphase chromosome alignment in Drosophila.

CENP-meta has been identified as an essential, kinesin-like motor protein in Drosophila. The 257-kD CENP-meta protein is most similar to the vertebrate kinetochore-associated kinesin-like protein CENP-E, and like CENP-E, is shown to be a component of centromeric/kinetochore regions of Drosophila chromosomes. However, unlike CENP-E, which leaves the centromere/kinetochore region at the end of anaphase A, the CENP-meta protein remains associated with the centromeric/kinetochore region of the chromosome during all stages of the Drosophila cell cycle. P-element-mediated disruption of the CENP-meta gene leads to late larval/pupal stage lethality with incomplete chromosome alignment at metaphase. Complete removal of CENP-meta from the female germline leads to lethality in early embryos resulting from defects in metaphase chromosome alignment. Real-time imaging of these mutants with GFP-labeled chromosomes demonstrates that CENP-meta is required for the maintenance of chromosomes at the metaphase plate, demonstrating that the functions required to establish and maintain chromosome congression have distinguishable requirements

Natural history and outcome in systemic AA amyloidosis

BACKGROUND:Deposition of amyloid fibrils derived from circulating acute-phase reactant serum amyloid A protein (SAA) causes systemic AA amyloidosis, a serious complication of many chronic inflammatory disorders. Little is known about the natural history of AA amyloidosis or its response to treatment.METHODS:We evaluated clinical features, organ function, and survival among 374 patients with AA amyloidosis who were followed for a median of 86 months. The SAA concentration was measured serially, and the amyloid burden was estimated with the use of whole-body serum amyloid P component scintigraphy. Therapy for inflammatory diseases was administered to suppress the production of SAA.RESULTS:Median survival after diagnosis was 133 months; renal dysfunction was the predominant disease manifestation. Mortality, amyloid burden, and renal prognosis all significantly correlated with the SAA concentration during follow-up. The risk of death was 17.7 times as high among patients with SAA concentrations in the highest eighth, or octile, (greater/equal 155 mg per liter) as among those with concentrations in the lowest octile (< 4 mg per liter); and the risk of death was four times as high in the next-to-lowest octile (4 to 9 mg per liter). The median SAA concentration during follow-up was 6 mg per liter in patients in whom renal function improved and 28 mg per liter in those in whom it deteriorated (P < 0.001). Amyloid deposits regressed in 60% of patients who had a median SAA concentration of less than 10 mg per liter, and survival among these patients was superior to survival among those in whom amyloid deposits did not regress (P=0.04).CONCLUSIONS:The effects of renal dysfunction dominate the course of AA amyloidosis, which is associated with a relatively favorable outcome in patients with SAA concentrations that remain in the low-normal range (< 4 mg per liter)

Gas exchange during exercise in habitually active asthmatic subjects

We determined the relations among gas exchange, breathing mechanics, and airway inflammation during moderate- to maximum-intensity exercise in asthmatic subjects. Twenty-one habitually active (48.2 +/- 7.0 ml.kg(-1).min(-1) maximal O2 uptake) mildly to moderately asthmatic subjects (94 +/- 13% predicted forced expiratory volume in 1.0 s) performed treadmill exercise to exhaustion (11.2 +/- 0.15 min) at approximately 90% of maximal O2 uptake. Arterial O2 saturation decreased to < or =94% during the exercise in 8 of 21 subjects, in large part as a result of a decrease in arterial Po2 (PaO2): from 93.0 +/- 7.7 to 79.7 +/- 4.0 Torr. A widened alveolar-to-arterial Po2 difference and the magnitude of the ventilatory response contributed approximately equally to the decrease in PaO2 during exercise. Airflow limitation and airway inflammation at baseline did not correlate with exercise gas exchange, but an exercise-induced increase in sputum histamine levels correlated with exercise Pa(O2) (negatively) and alveolar-to-arterial Po2 difference (positively). Mean pulmonary resistance was high during exercise (3.4 +/- 1.2 cmH2O.l(-1).s) and did not increase throughout exercise. Expiratory flow limitation occurred in 19 of 21 subjects, averaging 43 +/- 35% of tidal volume near end exercise, and end-expiratory lung volume rose progressively to 0.25 +/- 0.47 liter greater than resting end-expiratory lung volume at exhaustion. These mechanical constraints to ventilation contributed to a heterogeneous and frequently insufficient ventilatory response; arterial Pco2 was 30-47 Torr at end exercise. Thus pulmonary gas exchange is impaired during high-intensity exercise in a significant number of habitually active asthmatic subjects because of high airway resistance and, possibly, a deleterious effect of exercise-induced airway inflammation on gas exchange efficiency

A multiple scales approach to crack front waves

Perturbation of a propagating crack with a straight edge is solved using the method of matched asymptotic expansions (MAE). This provides a simplified analysis in which the inner and outer solutions are governed by distinct mechanics. The inner solution contains the explicit perturbation and is governed by a quasi-static equation. The outer solution determines the radiation of energy away from the tip, and requires solving dynamic equations in the unperturbed configuration. The outer and inner expansions are matched via the small parameter L/l defined by the disparate length scales: the crack perturbation length L and the outer length scale l associated with the loading. The method is first illustrated for a scalar crack model and then applied to the elastodynamic mode I problem. The dispersion relation for crack front waves is found by requiring that the energy release rate is unaltered under perturbation. The wave speed is calculated as a function of the nondimensional parameter kl where k is the crack front wavenumber, and dispersive properties of the crack front wave speed are described for the first time. The example problems considered here demonstrate that the potential of using MAE for moving boundary value problems with multiple scales.Comment: 25 pages, 5 figure

Microwave edge modes on a metasurface with glide symmetry

This is the author accepted manuscript. The final version is available from the American Physical Society via the DOI in this record.In this work we study planar metasurfaces comprised of two layers of hexagonal arrays of circular metal patches. This two-layer geometry supports a bound surface wave that propagates along the x direction. In our study, each metasurface is infinitely periodic in one direction (x) but only a few periods wide in the orthogonal direction (y). Through experiments and modeling we find evidence of a localized edge mode whose existence is dependent on the relative alignment of the two layers. This edge mode is used to guide the propagation of electromagnetic energy around both triangular and hexagonal shapes.Engineering and Physical Sciences Research Council (EPSRC

Acoustic transmission through compound subwavelength slit arrays

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.The angular dependence of the transmission of sound in air through four types of 2D slit-arrays formed of aluminium slats is explored, both experimentally and numerically. For a simple, subwavelength periodic slit-array, it is well known that Fabry-Perot-like wave-guide resonances, supported by the slit-cavities, hybridising with bound acoustic surface waves, result in ‘Enhanced Acoustic Transmission’ at frequencies determined by the length, width and separation of each slit-cavity. We demonstrate that altering the spacing or width of some of the slits to form a compound array (i.e. an array having a basis comprised of more than one slit) results in sharp dips in the transmission spectra, that may have a strong angular dependence. These features correspond to ‘phase resonances’, which have been studied extensively in the electromagnetic case. This geometry allows for additional near-field configurations compared to the simple array, whereby the field in adjacent cavities can be out-of-phase. Several types of compound slit-array are investigated; one such structure is optimised to minimise the effect of boundary-layer loss mechanisms present in each slit cavity, thereby achieving a deep, sharp transmission minimum in a broad maximumThe authors would like to thank the UK Ministry of Defence’s Defence Science and Technology Laboratorty (DSTL) for their financial support and permission to publis