Evolution of Quartz and Calcite Microstructures Exhumed From Deep Brittle-Ductile Shear Zones in the Southern Alps of New Zealand

Arrays of brittle-ductile shears exposed in the Southern Alps of New Zealand, have provided a superb natural laboratory for insight into the microstructural evolution of lower crustal shear zones during exhumation. Shears are exposed in the central section of the Southern Alps at Sam Peak, Chancellor Ridge, and Baumann Glacier in a zone ~2 km wide that is located 6–8 km structurally above the Alpine Fault. An array of systematically spaced shear zones that formed by embrittlement and faulting of quartzofeldspathic schist took place at the same time as ductile shearing of quartzcarbonate veins embedded within the schist. This study has used field-based structural mapping along with optical microscopy and universal stage measurements of crystallographic preferred orientations (CPO) to resolve the shear zone kinematics and rheology. On the basis of these data, the strain path can be reconstructed for the sheared veins during their progressive deformation. This began with their incidence as backshears at the base of the Alpine Fault ramp and ended with their subsequent recrystallisation, uplift, and exhumation. The near-vertical shear planes have mean orientation of 221@89 NW ± 1o (n = 780). They are inferred to have formed as backshears accommodating uplift of the Pacific Plate as it was translated onto the oblique footwall ramp of the Alpine Fault during late Cenozoic oblique convergence. Detailed fault offset transect surveys across the shears at Chancellor Ridge and Baumann Glacier reveal a mean spacing between the shear zones of 25 ± 5 cm (n = 410). Quartz-carbonate marker veins are displaced in a dextral west-sideup shear sense. Fault offset geometry and a consistent arrangement of mineral fibre lineations that decorate fault surfaces, indicate that the mean displacement vector pitches 35o SW in the shear plane (trend and plunge of: 262, 35 ± 7o). Ductilely deformed marker veins have been subject to a mean displacement of 9.9 ± 1.4 cm (n = 344) and a mean finite ductile shear strain of 4.8 ± 0.3 (n = 219). A strain-rate for the ductile deformation of the veins is estimated at 3 x 10-11 sec-1 based on the observed finite ductile shear strain, an escalator kinematic model, and assumptions about the width of the deforming zone. Five deformation phases have affected the sheared veins during their transport up the fault ramp: 1) initial brittle faulting and ductile shearing; 2) grain boundary sliding of mylonitic quartz in response to a post-ramping differential stress drop; 3) recrystallisation and grain growth; 4) renewed late-stage dislocation creep; and 5) semibrittle deformation and exhumation. In the schist, the shears initiated as planar brittle faults at lower crustal depths of ~21 km at a temperature of 450 ± 50oC. They developed in a zone of transiently high shear strain-rates near the base of the Alpine Fault ramp. Dislocation creep caused a CPO of quartz and calcite to develop in sheared veins. Using the flow law of Hirth et al. (2001) and the estimated strain-rate, a differential stress of ~165 MPa is inferred for ductile deformation of the veins. Near-lithostatic (λ = 0.85) fluid pressures would have caused the rocks to undergo brittle failure, a situation that is confirmed by a late component of brittle deformation that over prints the ductilely sheared veins. Syntectonic quartz-calcite veins infill the shear fractures, and these themselves have been sheared. The deformation of the veins was not a simple shear process but one with triclinic flow symmetry. This is inferred from discordance between the shear direction and the near-vertical principle extension direction that is revealed by the pattern and symmetry of quartz and calcite CPO fabrics. After the shears move away from the ramp-step, grain boundary sliding (GBS) accommodated by solid-state diffusion creep is inferred to have affected quartz veins. This deformation mechanism takes place because of 1) the small 8 μm grain size inherited from Phase 1; 2) the presence of fluid in the shear zone; and 3) a stress drop to ~22 MPa that followed the initial up-ramping. Quartz CPO fabrics in the sheared veins are remarkably weak considering their large shear strains. GBS is inferred to have been a chief deformation mechanism that caused the weakening of quartz CPO fabrics in the highly sheared sections of deformed veins. Calcite has also affected the quartz fabric strength as those veins containing >5% calcite have very weak quartz CPO fabrics. In contrast to quartz, the CPO fabrics for the co-existing calcite remained strong and continued to develop by dislocation creep. The third phase of deformation, a process that may have contributed to subsequent weakening of quartz CPO fabrics, was recrystallisation and grain growth to 126 μm and an equigranular-polygonal grain shape fabric. This fabric was overprinted by late-stage dislocation creep microstructures in the fourth deformation phase in response increased differential stress encountered by the rocks at lower temperatures in the upper crust. The final phase of deformation to affect the sheared veins was semibrittle deformation at differential stresses of <189 MPa and temperatures of 200–280oC as the rocks passed through the steady-state brittle-ductile transition zone at depths of 8–10 km before being exhumed at the surface

Solvent‐induced enantioselectivity reversal in a chiral metal organic framework

Solvent-induced enantioselectivity reversal is a rarely reported phenomenon in porous homochiral materials. Similar behavior has been studied in chiral high performance liquid chromatography, where minor modifications to the mobile phase can induce elution order reversal of two enantiomers on a chiral stationary phase column. We report the first instance of solvent-induced enantioselectivity reversal in a homochiral metal organic framework. Further, we highlight the complex enantioselectivity behavior of homochiral metal organic frameworks toward racemic mixtures in the presence of solvents through racemate-solvent enantioselectivity and loading experiments as well as enantiopure-solvent loading experiments. We hypothesize that this interesting selectivity reversal behavior is likely to be observed in other competitive adsorption, nonchiral selective processes involving a solvent

Infrared regulators and SCETII

We consider matching from SCETI, which includes ultrasoft and collinear particles, onto SCETII with soft and collinear particles at one loop. Keeping the external fermions off their mass shell does not regulate all IR divergences in both theories. We give a new prescription to regulate infrared divergences in SCET. Using this regulator, we show that soft and collinear modes in SCETII are sufficient to reproduce all the infrared divergences of SCETI. We explain the relationship between IR regulators and an additional mode proposed for SCETII.Comment: 9 pages. Added discussion about relationship between IR regulators and messenger mode

Qualification of a Null Lens Using Image-Based Phase Retrieval

In measuring the figure error of an aspheric optic using a null lens, the wavefront contribution from the null lens must be independently and accurately characterized in order to isolate the optical performance of the aspheric optic alone. Various techniques can be used to characterize such a null lens, including interferometry, profilometry and image-based methods. Only image-based methods, such as phase retrieval, can measure the null-lens wavefront in situ - in single-pass, and at the same conjugates and in the same alignment state in which the null lens will ultimately be used - with no additional optical components. Due to the intended purpose of a Dull lens (e.g., to null a large aspheric wavefront with a near-equal-but-opposite spherical wavefront), characterizing a null-lens wavefront presents several challenges to image-based phase retrieval: Large wavefront slopes and high-dynamic-range data decrease the capture range of phase-retrieval algorithms, increase the requirements on the fidelity of the forward model of the optical system, and make it difficult to extract diagnostic information (e.g., the system F/#) from the image data. In this paper, we present a study of these effects on phase-retrieval algorithms in the context of a null lens used in component development for the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission. Approaches for mitigation are also discussed

Mucus polymer concentration and in vivo adaptation converge to define the antibiotic response of Pseudomonas aeruginosa during chronic lung infection

The airway milieu of individuals with muco-obstructive airway diseases (MADs) is defined by the accumulation of dehydrated mucus due to hyperabsorption of airway surface liquid and defective mucociliary clearance. Pathological mucus becomes progressively more viscous with age and disease severity due to the concentration and overproduction of mucin and accumulation of host-derived extracellular DNA (eDNA). Respiratory mucus of MADs provides a niche for recurrent and persistent colonization by respiratory pathogens, including Pseudomonas aeruginosa, which is responsible for the majority of morbidity and mortality in MADs. Despite high concentration inhaled antibiotic therapies and the absence of antibiotic resistance, antipseudomonal treatment failure in MADs remains a significant clinical challenge. Understanding the drivers of antibiotic tolerance is essential for developing more effective treatments that eradicate persistent infections. The complex and dynamic environment of diseased airways makes it difficult to model antibiotic efficacy in vitro. We aimed to understand how mucin and eDNA concentrations, the two dominant polymers in respiratory mucus, alter the antibiotic tolerance of P. aeruginosa. Our results demonstrate that polymer concentration and molecular weight affect P. aeruginosa survival post antibiotic challenge. Polymer-driven antibiotic tolerance was not explicitly associated with reduced antibiotic diffusion. Lastly, we established a robust and standardized in vitro model for recapitulating the ex vivo antibiotic tolerance of P. aeruginosa observed in expectorated sputum across age, underlying MAD etiology, and disease severity, which revealed the inherent variability in intrinsic antibiotic tolerance of host-evolved P. aeruginosa populations. IMPORTANCE: Antibiotic treatment failure in Pseudomonas aeruginosa chronic lung infections is associated with increased morbidity and mortality, illustrating the clinical challenge of bacterial infection control. Understanding the underlying infection environment, as well as the host and bacterial factors driving antibiotic tolerance and the ability to accurately recapitulate these factors in vitro, is crucial for improving antibiotic treatment outcomes. Here, we demonstrate that increasing concentration and molecular weight of mucin and host eDNA drive increased antibiotic tolerance to tobramycin. Through systematic testing and modeling, we identified a biologically relevant in vitro condition that recapitulates antibiotic tolerance observed in ex vivo treated sputum. Ultimately, this study revealed a dominant effect of in vivo evolved bacterial populations in defining inter-subject ex vivo antibiotic tolerance and establishes a robust and translatable in vitro model for therapeutic development

Methane Emissions from Process Equipment at Natural Gas Production Sites in the United States: Liquid Unloadings

Methane emissions from liquid unloadings were measured at 107 wells in natural gas production regions throughout the United States. Liquid unloadings clear wells of accumulated liquids to increase production, employing a variety of liquid lifting mechanisms. In this work, wells with and without plunger lifts were sampled. Most wells without plunger lifts unload less than 10 times per year with emissions averaging 21 000–35 000 scf methane (0.4–0.7 Mg) per event (95% confidence limits of 10 000–50 000 scf/event). For wells with plunger lifts, emissions averaged 1000–10 000 scf methane (0.02–0.2 Mg) per event (95% confidence limits of 500–12 000 scf/event). Some wells with plunger lifts are automatically triggered and unload thousands of times per year and these wells account for the majority of the emissions from all wells with liquid unloadings. If the data collected in this work are assumed to be representative of national populations, the data suggest that the central estimate of emissions from unloadings (270 Gg/yr, 95% confidence range of 190–400 Gg) are within a few percent of the emissions estimated in the EPA 2012 Greenhouse Gas National Emission Inventory (released in 2014), with emissions dominated by wells with high frequencies of unloadings

Distinct Transcriptional and Anti-Mycobacterial Profiles of Peripheral Blood Monocytes Dependent on the Ratio of Monocytes: Lymphocytes.

The ratio of monocytes and lymphocytes (ML ratio) in peripheral blood is associated with tuberculosis and malaria disease risk and cancer and cardiovascular disease outcomes. We studied anti-mycobacterial function and the transcriptome of monocytes in relation to the ML ratio. Mycobacterial growth inhibition assays of whole or sorted blood were performed and mycobacteria were enumerated by liquid culture. Transcriptomes of unstimulated CD14 + monocytes isolated by magnetic bead sorting were characterised by microarray. Transcript expression was tested for association with ML ratio calculated from leucocyte differential counts by linear regression. The ML ratio was associated with mycobacterial growth in vitro (β = 2.23, SE 0.91, p = 0.02). Using sorted monocytes and lymphocytes, in vivo ML ratio (% variance explained R(2) = 11%, p = 0.02) dominated over in vitro ratios (R(2) = 5%, p = 0.10) in explaining mycobacterial growth. Expression of 906 genes was associated with the ML ratio and 53 with monocyte count alone. ML-ratio associated genes were enriched for type-I and -II interferon signalling (p = 1.2 × 10(− 8)), and for genes under transcriptional control of IRF1, IRF2, RUNX1, RELA and ESRRB. The ML-ratio-associated gene set was enriched in TB disease (3.11-fold, 95% CI: 2.28-4.19, p = 5.7 × 10(− 12)) and other inflammatory diseases including atopy, HIV, IBD and SLE. The ML ratio is associated with distinct transcriptional and anti-mycobacterial profiles of monocytes that may explain the disease associations of the ML ratio

Combination treatment to improve mucociliary transport of Pseudomonas aeruginosa biofilms

People with muco-obstructive pulmonary diseases such as cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) often have acute or chronic respiratory infections that are difficult to treat due in part to the accumulation of hyperconcentrated mucus within the airway. Mucus accumulation and obstruction promote chronic inflammation and infection and reduce therapeutic efficacy. Bacterial aggregates in the form of biofilms exhibit increased resistance to mechanical stressors from the immune response (e.g., phagocytosis) and chemical treatments including antibiotics. Herein, combination treatments designed to disrupt the mechanical properties of biofilms and potentiate antibiotic efficacy are investigated against mucus-grown Pseudomonas aeruginosa biofilms and optimized to 1) alter biofilm viscoelastic properties, 2) increase mucociliary transport rates, and 3) reduce bacterial viability. A disulfide bond reducing agent (tris(2-carboxyethyl)phosphine, TCEP), a surfactant (NP40), a biopolymer (hyaluronic acid, HA), a DNA degradation enzyme (DNase), and an antibiotic (tobramycin) are tested in various combinations to maximize biofilm disruption. The viscoelastic properties of biofilms are quantified with particle tracking microrheology and transport rates are quantified in a mucociliary transport device comprised of fully differentiated primary human bronchial epithelial cells. The combination of the NP40 with hyaluronic acid and tobramycin was the most effective at increasing mucociliary transport rates, decreasing the viscoelastic properties of mucus, and reducing bacterial viability. Multimechanistic targeting of biofilm infections may ultimately result in improved clinical outcomes, and the results of this study may be translated into future in vivo infection models

Seasonal variability of lotic macroinvertebrate communities at the habitat scale demonstrates the value of discriminating fine sediment fractions in ecological assessments

Despite lotic systems demonstrating high levels of seasonal and spatial variability, most research and biomonitoring practices do not consider seasonality when interpreting results and are typically focused at the meso-scale (combined pool/riffle samples) rather than considering habitat patch dynamics. We therefore sought to determine if the sampling season (spring, summer and autumn) influenced observed macroinvertebrate biodiversity, structure and function at the habitat unit scale (determined by substrate composition), and if this in turn influenced the assessment of fine sediment (sand and silt) pressures. We found that biodiversity supported at the habitat level was not seasonally consistent with the contribution of nestedness and turnover in structuring communities varying seasonally. Habitat differences in community composition were evident for taxonomic communities regardless of the season but were not seasonally consistent for functional communities, and, notably, season explained a greater amount of variance in functional community composition than the habitat unit. Macroinvertebrate biodiversity supported by silt habitats demonstrated strong seasonal differences and communities were functionally comparable to sand habitats in spring and to gravel habitats in autumn. Sand communities were impoverished compared to other habitats regardless of the season. Silt habitats demonstrated a strong increase in Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa and functional richness from spring into autumn, while vegetation habitats displayed a peak in EPT abundance in summer. Only silt and sand habitats demonstrated temporal variability in functional evenness suggesting that these habitats are different in terms of their resource partitioning and productivity over time compared to other habitats. Gravel and vegetation habitats appeared to be more stable over time with functional richness and evenness remaining consistent. To accurately evaluate the influence of fine sediment on lotic ecosystems, it is imperative that routine biomonitoring and scientific research discriminate between sand and silt fractions, given they support different biodiversity, particularly during summer and autumn months